Working device, throttle arrangement, internal combustion engine and method for operating an internal combustion engine

Abstract

A working device comprises a tool and an internal combustion engine (A-11) for driving the tool. The internal combustion engine (A-11) comprises an intake duct (A-14), in which a throttle element (A-16) is pivotably mounted. The internal combustion engine (A-11) comprises an air duct (A-13), in which an air-control element (A-20) is pivotably mounted. An operator-control element (A-5) is provided for adjusting the throttle element (A-16) in an opening direction (A-42). The internal combustion engine (A-11) has a speed-limiting device (A-100). The speed-limiting device (A-100) comprises an actuator, which is designed to adjust the throttle element (A-16) for the purpose of reducing the free flow cross section of the intake duct (A-14) in a closing direction (A-44). The working device (A-1) has a load-free state, in which the tool is driven by the internal combustion engine (A-11) and is not engaging a workpiece. The position of the air-control element (A-20) is coupled to the position of the throttle element (A-16) by way of a coupling device (A-58). The coupling device (A-58) has an idle path (A-ε), which allows pivoting of the throttle element (A-16) in relation to the air-control element (A-20). The idle path (A-ε) is dimensioned such that, in the load-free state, the air-control element (A-20) is in its closed position (A-104) irrespective of the position of the operator-control element (A-5).

Description

[0001] Working device throttle arrangement, internal combustion engine and method for operating an internal combustion engine

[0002] The invention relates to a working device of the type specified in the preamble of claim 1.

[0003] US 2021 / 0254566 A1 discloses a work tool with a speed limiting device. The control for limiting the speed is provided to act on both the air control element and the throttle element. This is comparatively complex, since two throttle elements must be controlled.

[0004] The invention is based on the object of creating a working device of the generic type which is of simple construction and which enables a good speed limitation in a simple manner.

[0005] This object is achieved by a working device having the features of claim 1.

[0006] The position of the air control element is coupled to the position of the throttle element via a coupling device. This requires only one actuator for the throttle element and no additional actuator for the air control element. This results in a simplified design. The coupling device enables adjustment of the throttle element relative to the air control element.

[0007] The throttle element can therefore be pivoted relative to the air control element until the air control element is driven along by the coupling device. Within the adjustment range in which the throttle element is movable relative to the air control element and does not drive the air control element, a sensitive adjustment of the air volume supplied to the combustion engine is possible. The free travel is dimensioned such that the air control element remains in its closed position in the unloaded state, regardless of the position of the control element.

[0008] The no-load state is a quasi-stationary state. In the no-load state, a constant speed and a constant position of the throttle element have been established. The constant position of the throttle element is established when the implement is operating in the no-load state, in particular after a certain period of time. The position of the throttle element then remains constant under constant ambient conditions and no longer changes. The period of time depends in particular on the implement and can be, for example, 5 seconds. The ambient conditions and inertia of a tool under which the maximum adjustment angle of the throttle element from the closed towards the fully open position is established can vary from implement to implement.

[0009] When an operator operates the control element when the tool is not engaged with a workpiece, the throttle element pivots, and the speed increases. If the speed increases excessively, the actuator of the speed limiting device is activated and adjusts the throttle element in the closing direction to limit the speed. In the no-load state, this adjusts the throttle element from the closed position toward the fully open position.

[0010] The free travel is dimensioned such that the air control element is in its closed position in the no-load state, even if an operator activates the control element, for example, applies full throttle, and the throttle element has been adjusted by the adjustment angle from the closed towards the fully open position. The free travel is dimensioned such that the air control element is in its closed position in the no-load state regardless of the position of the control element. The actuator therefore only acts on the throttle element from the closed position of the throttle element up to the position of the throttle element that corresponds to the no-load state. Adjusting the throttle element only changes the free flow cross-section of the intake duct and does not change the free flow cross-section of the air duct. This enables sensitive adjustment of the supplied air volume in the no-load state.The speed can be easily adjusted and thus easily limited in the no-load state.

[0011] The adjustment angle corresponds, in particular, to at most the free travel. The implement is designed in particular such that the throttle element is movable relative to the air control element at least until the position corresponding to the no-load state is reached. When the throttle element is adjusted from the closed position toward the fully open position, the air control element is not moved via the coupling device at least until the position of the throttle element associated with the no-load state is reached when the position of the throttle element is changed.

[0012] The throttle element has, in particular, a closed position and a fully open position. In the load-free state, the throttle element is pivoted, in particular, by a maximum adjustment angle from the closed position toward the fully open position. The coupling device enables, in particular, an adjustment of the throttle element relative to the air control element by a differential angle. The differential angle corresponds, in particular, to the free travel. The adjustment angle corresponds, in particular, at most, to the differential angle.

[0013] The adjustment angle can vary, in particular, depending on ambient conditions and the inertia of a tool of the work device. The adjustment angle remains constant and does not change under constant ambient conditions. The adjustment angle is adjusted, in particular, by the intervention of the speed limiting device, which acts on the position of the throttle element via the actuator. The coupling device is, in particular, a mechanical coupling device. This results in a simple design.

[0014] The free travel is, in particular, a maximum of 30°. In particular, the free travel is at least 15°. The free travel is, in particular, at least 2°, and in particular at least 3°, greater than the adjustment angle. This allows for sensitive speed limitation even when the throttle element is opened by 2°, and in particular by 3°, beyond the position assigned to the adjustment angle. Because the free travel is greater than the adjustment angle, sensitive adjustment of the desired speed is possible even with unfavorable manufacturing tolerances.

[0015] In particular, the internal combustion engine comprises a fuel valve for supplying fuel. The fuel valve is in particular controlled by a control device. In particular, the control device also controls the actuator of the speed-limiting device. In particular, a control device is provided that controls the actuator, the fuel valve, and an ignition device of the internal combustion engine. Alternatively, it can be provided that the control device only controls the actuator of the speed-limiting device, while other elements are provided for supplying fuel. A design with multiple control devices, which in particular communicate with one another and control different devices of the implement, such as the fuel supply device, actuator, ignition device, and / or optionally other devices of the implement, can also be advantageous.

[0016] A simple design results if the throttle element is a throttle valve. The throttle element is in particular pivotally mounted with a throttle shaft. The air control element is in particular pivotally mounted with an air control shaft. In an alternative embodiment, the throttle element and / or the air control element can be designed as a control roller. In particular, an operating element for operation by an operator is provided, via which the position of the throttle shaft can be adjusted. The operating element is coupled, in particular via a transmission device, to an adjustable stop element for the throttle shaft. In particular, the stop element limits the possible position of the throttle element to a range that extends from the closed position to the position predetermined by the stop element. If the actuator is not active, the throttle element assumes in particular the position predetermined by the stop element.In particular, a closing spring is provided that preloads the stop element in a closing direction of the throttle shaft. The operator can adjust the stop element via the control element, counter to the force of the closing spring, toward the position corresponding to the fully open position of the throttle element.

[0017] In particular, an opening spring is provided which preloads the throttle shaft in an opening direction towards the stop element. The throttle arrangement is preferably designed such that, when the operating element and the transmission device are not actuated, the torque exerted by the closing spring on the throttle shaft is greater than the torque exerted by the opening spring on the throttle shaft. This ensures that the throttle element is closed by the closing spring when the transmission device is not actuated, i.e. when the operator does not actuate the operating element. The actuator is advantageously designed, in particular, to release the throttle shaft from the stop element against the force of the opening spring and to adjust the throttle element in a closing direction.

[0018] In particular, the opening spring and the coupling device act on the same end section of the throttle shaft. This allows for a compact design.

[0019] The coupling device comprises, in particular, a coupling element that is non-rotatably connected to the throttle shaft. The movement of the throttle shaft can be easily transmitted to the air control element via the coupling element, in particular by means of additional elements.

[0020] In particular, the opening spring rests on the coupling element at one end and the base body at the other. This results in a simple and compact design and a space-saving arrangement of the opening spring.

[0021] The motor acts in particular on a first end section of the throttle shaft, and the coupling device acts on a second end section of the throttle shaft. The first end section and the second end section are arranged in particular on opposite sides of the intake duct. This enables a compact design.

[0022] The coupling device comprises, in particular, a coupling rod that connects a coupling element that is connected in a rotationally fixed manner to the throttle shaft and a coupling element that is connected in a rotationally fixed manner to the air control shaft. The connection of the coupling rod to at least one of the coupling elements has, in particular, an elongated hole that allows a limited relative movement of the coupling rod to the coupling element. This results in a simple structural design. The elongated hole is, in particular, designed to allow a relative movement of the throttle element relative to the air control element by the free travel.

[0023] The working device is in particular a cutting grinder and the tool is a cutting disc.

[0024] Embodiments of the invention are explained below with reference to the drawings. They show:

[0025] Fig. A1 is a schematic side view of a hand-held implement, Fig. A-2 is a schematic representation of a two-stroke engine operating with a scavenging reservoir,

[0026] Fig. A-3 is a side view of a throttle arrangement for a two-stroke engine according to Fig. A-2,

[0027] Fig. A-4 is an exploded perspective view of parts of the

[0028] Throttle arrangement from Fig. A-3,

[0029] Fig. A-5 is a perspective view of the throttle assembly,

[0030] Fig. A-6 is a side view of an alternative embodiment of the coupling device of the throttle arrangement in the direction of arrow VI in Fig. A-3,

[0031] Fig. A-7 is a sectional view of the throttle assembly,

[0032] Fig. A-8 to Fig. A-10 are partial sectional views of the throttle arrangement in different sectional planes,

[0033] Fig. Al 1 is a perspective view of the throttle assembly with the engine removed,

[0034] Fig. A-12 a partial view corresponding to Fig. A1 1 with additionally removed connection element for the motor,

[0035] Fig. A1 3 to Fig. A1 5 are schematic representations of the function of the throttle arrangement, Fig. A-16 is an alternative embodiment of the throttle arrangement in a sectional view,

[0036] Fig. A-17 and Fig. A-18 are partial perspective views of the throttle arrangement from Fig. A-16 with the cover element removed in different positions of the transmission device.

[0037] Fig. A1 shows a schematic illustration of an exemplary embodiment of a hand-held working device AL. In the exemplary embodiment, the working device AL is a cut-off machine. The working device AL is, in particular, portable and hand-held during operation. The working device AL has a rear handle A-3 and a handlebar A-4. An operating element A-5 and a locking element A-6 for the operating element A-5 are arranged on the rear handle A-3. The working device AL has a cutting disk A-7 as a tool. A drive motor A11 drives the cutting disk A-7. Another working device AL with a different tool can also be provided. In the exemplary embodiment, the drive motor A-11 is a two-stroke engine. The drive motor A11 is preferably a single-cylinder engine. In the exemplary embodiment, the drive motor A11 is a two-stroke engine operating with a scavenging reservoir.The drive motor Al 1 is, in particular, a mixture-lubricated engine, in particular a two-stroke engine or a mixture-lubricated four-stroke engine. In the illustrated embodiment, the drive motor Al 1 is to be started manually. A starter handle A-9 is used for this purpose.

[0038] The drive motor Al 1 has an air filter A-12 through which air is drawn in during operation. An air duct Al 3 and an intake duct A-14 serve to supply air. It can be provided that the air duct A-13 and intake duct A-14 supply clean air. Alternatively, it can be provided that fuel is supplied to the intake duct A-14, so that a fuel / air mixture is supplied via the intake duct A-14. However, a different design of the drive motor Al 1, in particular a design without the air duct A-13, can also be advantageous.

[0039] Fig. A-2 shows the drive motor Al 1 in a schematic sectional view. As Fig. A-2 shows, the drive motor Al 1 has a throttle arrangement Al 5, which serves to control the amount of air supplied. In the exemplary embodiment, the throttle arrangement Al 5 comprises a throttle element Al 6, which serves to control the amount of air flowing through the intake duct A-14. The throttle arrangement A-15 also has an air control element A-20, which serves to control the amount of air flowing through the air duct A-13. In the exemplary embodiment, a choke element Al 8 is arranged upstream of the throttle element A-16. In an advantageous alternative embodiment, the choke element Al 8 can also be omitted or designed differently. In the exemplary embodiment, the throttle element Al 6, the choke element Al 8 and the air control element A-20 are each pivotally mounted. The throttle element A-16 is pivotally mounted with a throttle shaft Al 7.The choke element A-18 is pivotally mounted on a choke shaft A-9. The air control element A-20 is mounted on an air control shaft A-21. In the exemplary embodiment, the throttle element A-16, the choke element A-18, and the air control element A-20 are designed as flaps. However, another design, for example, as rollers with an air passage opening running perpendicular to the rotational axis, may also be advantageous. It may also be provided that the drive motor A-11 does not have a choke element A-8.

[0040] The drive engine A1 1 comprises a cylinder A-22 in which a combustion chamber A-23 is formed. A piston A-25 is reciprocatingly mounted in the cylinder A-22. The piston A-25 drives a crankshaft A-27, which is rotatably mounted in a crankcase A-24, via a connecting rod A-26. The crankshaft A-27 is shown only schematically in Fig. A-2. The crankshaft A-27 is rotatably mounted about a rotational axis A-28.

[0041] In the area of ​​the bottom dead center of piston A-25 shown in Fig. A-2, the interior of the crankcase A-24 is fluidly connected to the combustion chamber A-23 via transfer ports A-29. The transfer ports A-29 open into the combustion chamber A-23 via transfer ports A-30. The transfer ports A-30 are controlled by the piston A-25. A spark plug A-34 extends into the combustion chamber A-23 and serves to ignite the fuel / air mixture in the combustion chamber A-23. An outlet A-35, controlled by the piston A-25, leads from the combustion chamber A-23.

[0042] The intake port A-14 opens into the bore of cylinder A-22 via an intake port inlet A-32. The intake port inlet A-32 is controlled by piston A-25. The intake port inlet A-32 is connected to the interior of the crankcase A-24 in the area of ​​top dead center of piston A-25. The air port A-13 opens into the bore of cylinder A-22 via one or more air inlets A-33. The piston A-25 has one or more piston pockets A-31 on its piston skirt. The piston pocket A-31 connects the air inlet A-33 to one or more transfer ports A-30 in the area of ​​top dead center of piston A-25. This air can be pre-stored in the transfer ports A-29 via the air port A-13, which serves to scavenge the combustion chamber A-23.

[0043] For supplying fuel, the throttle assembly A-15 may include a carburetor. A fuel valve A-63 may also be provided for supplying fuel. The fuel valve A-63 may, for example, supply the fuel to the interior of the crankcase A-24. Alternatively, a fuel valve A-63' may be provided, which supplies fuel to the intake port A-14.

[0044] The working device A1 comprises a control device A-10. The control device A-10 serves to control the fuel valve A-63, A-63'. In particular, the control device A-10 determines the opening time and opening duration of the fuel valve A-63, A-63' and controls the fuel valve A-63, A-63' accordingly.

[0045] The throttle assembly A-15 comprises a base body A-36. An intake duct section A-37 of the intake duct A-14 is formed in the base body A-36. The base body A-36 is, in particular, a cast metal part. The air control element A-20 is mounted in an air duct section A-75. In the arrangement shown in Fig. A-2, the air duct section A-75 is formed in a separate body of the throttle assembly A-15.

[0046] The following figures show an advantageous embodiment in which the intake duct section A-37 and the air duct section A-75 are formed in the base body A-36. The base body A-36 is a single-piece, particularly a cast part. The single-piece design results in a simple structure.

[0047] As Fig. A-3 shows, the position of the air control element A-20 is coupled to the position of the throttle element A-16 via a coupling device A-58. For this purpose, in the exemplary embodiment, the throttle shaft A-17 and the air control shaft A-21 are coupled to one another on one side of the base body A-36, which is shown on the left in Fig. A-3. The coupling device A-58 is provided for coupling the throttle shaft A-17 and the air control shaft A-21. The air control shaft A-21 is preloaded by an air closing spring A-64 towards the closed position of the air control element A-20. The air closing spring A-64 is designed as a leg spring. The air closing spring A-64 extends around an end of the air control shaft A-21 protruding from the base body A-36. A coupling element A-65 is fixed to this end of the air control shaft A-21. The coupling element A-65 can be designed, for example, as a lever or as a disc.

[0048] An end section of the throttle shaft A-17, not visible in Fig. A-3, is provided with a coupling element A-59, which can be designed, for example, as a disc or a lever. The coupling element A-59 and the coupling element A-65 are coupled via a coupling rod A-66. The air control shaft A-21 is pivotally mounted about a rotational axis A-55. The throttle shaft A-17 is pivotally mounted about a rotational axis A-54. The coupling rod A-66 is connected to the coupling elements A-65 and A-59 at a distance from the rotational axis A-54 of the throttle shaft A-17 and from the rotational axis A-55 of the air control shaft A-21. In particular, the coupling element A-59 is connected in a rotationally fixed manner to the throttle shaft A-17. The coupling element A-65 is in particular connected in a rotationally fixed manner to the air control shaft A-21.

[0049] As shown in Fig. A-4, in the exemplary embodiment, the coupling element A-65 is designed as a lever. The coupling element A-59 is designed as a disc having a plurality of openings A-84.

[0050] As shown in Figs. A-3 and A-4, the throttle assembly A-15 has an opening spring A-41. The opening spring A-41 biases the throttle shaft A-17 toward the fully open position of the throttle element A-16. The opening spring A-41 is designed as a leg spring. The opening spring A-41 extends around the axis of rotation A-54 of the throttle shaft A-17 and is arranged outside the base body A-36. A first end A-71 of the opening spring A-41 is connected to the coupling element A-59. For this purpose, the first end A-71 is suspended in one of the openings A-84. By suitably selecting one of the openings A-84, tolerances of the opening spring A-41 can be easily compensated. A second end A-72 of the opening spring A-41 is supported in particular on the base body A-36, as shown in Fig. A-6.

[0051] On the side of the base body A-36 opposite the coupling device A-58, a housing A-57 is formed, which is shown in Fig. A-3. The housing A-57 is delimited by a housing shell A-60 and a cover element A-48. In the exemplary embodiment, the housing shell A-60 is formed integrally with the base body A-36. A motor A-45 is arranged on the side of the housing A-57 opposite the base body A-36. The motor A-45 serves to move the throttle element A-16 in a closing direction and thereby reduce the free flow cross-section in the intake duct section A-37. The motor A-45 forms the actuator of a speed limiting device A-100 (Fig. A-5).

[0052] For the control of the throttle element A-16 by the operator, a transmission device A-38 is provided, which transmits a position of the control element A-5, only partially shown in Fig. A-3, to the rotational position of the throttle shaft A-17. The transmission device A-38 comprises a transmission rod A-39.

[0053] As shown in Fig. A-5, the transmission rod A-39 has a first end A-61 that is attached to the control element A-5. The transmission rod A-39 has a second end A-62 that is attached to a throttle lever A-49.

[0054] The operating element A-5 has an actuating section A-2, which preferably protrudes from a housing of the work device A1 and at which an operator can actuate the operating element A-5. In the exemplary embodiment, the operating element A-5 is pivotally mounted about a pivot axis A-73. An operator can actuate the actuating section A-2 in the direction of an arrow A-67. This pivots the operating element A-5 about its pivot axis A-73 and moves the first end A-61 of the transmission rod A-39 in the direction of an arrow A-68. In the illustration in Fig. A-5, the arrow A-68 points downward. The transmission rod A-39 is rigid. The movement of the first end A-61 in the direction of the arrow A-68 causes a movement of the second end A-62 in the direction of the arrow A-69. The arrow A-69 also points downward in Fig. A-5.The engagement of the second end A-62 of the transmission rod A-39 on the throttle lever A-49 causes—when the motor A-45 is not acting on the assembly—a movement of the throttle element A-16 in an opening direction A-42. In Fig. A-5, the throttle element A-16 is arranged in a closed position A-85. The throttle element A-16 assumes the closed position A-85 when the control element A-5 is not actuated by the operator. The air control element A-20 is in a closed position A-04.

[0055] A movement of the throttle element A-16 in the opening direction A-42 causes—after overcoming a free travel As described in detail below—a movement of the air control element A-20 in an opening direction A-86 due to the coupling device A-58. In the exemplary embodiment, the opening direction A-86 is directed in the same direction as the opening direction A-42 of the throttle element A-16.

[0056] A movement of the throttle element A-16 in the opening direction A-42 causes an increase in the free flow cross-section of the intake duct A-14 (Fig. A-2). A movement of the air control element in the opening direction A-86 causes an increase in the free flow cross-section of the air duct A-13 (Fig. A-2).

[0057] Fig. A-6 shows a view of a coupling device A-58. In the embodiment according to Fig. A-6, the coupling element A-65 on the air control shaft A-21 is designed, unlike in the previous figures, as a disc with a plurality of openings A-99 for attaching the air closing spring A-64. The further design of the embodiment according to Fig. A-6 can correspond to the design of the previous figures.

[0058] As shown in Fig. A-6, the coupling element A-59 has an elongated hole A-87 in which the coupling rod A-66 is suspended. If the throttle element A-16 is adjusted in the opening direction A-42, the coupling element A-59, which is connected in a rotationally fixed manner to the throttle shaft A-17, rotates with it. Due to the elongated hole A-87, the coupling element A-59 rotates without moving the coupling rod A-66. Therefore, when the coupling rod A-66 moves from the closed position A-85, it does not initially transmit the movement of the throttle element A-16 to the coupling element A-65 and the air control element A-20. This corresponds to an actuation of the actuating section A-2 of the control element A-5 by the operator.

[0059] The coupling rod A-66 has, in particular, a pin A-103 which projects into the elongated hole A-87 and which moves in the elongated hole A-66 when the coupling element A-59 moves. The throttle element A-16 can be adjusted over an idle travel As from the closed position A-85 towards a fully open position A-106 (Fig. A-14) without the movement of the throttle element A-16 being transmitted to the air control element A-20 via the coupling device A-58. The air control element A-20 remains at least in its closed position A-104 until the throttle element A-16 has been adjusted from its closed position A-85 by the idle travel As in the opening direction A-42. In particular, the idle travel As is at most 30°. In particular, the idle travel As is at least 15°. However, a smaller idle travel As can also be advantageous.

[0060] Both motor A-45 and control element A-5 can act on throttle shaft A-17. Control element A-5 acts on throttle shaft A-17 in the opening direction A-42 via throttle lever A-49. Motor A-45 acts on throttle shaft A-17 in the closing direction A-44. This is illustrated in detail in Figs. A-7 to A-9.

[0061] As shown in Fig. A-7, the throttle lever A-49 is fixed to a bearing shaft A-76, which is rotatably mounted in the housing A-57. The throttle lever A-49 is arranged outside the housing A-57. The bearing shaft A-76 projects through an opening A-88 in the housing A-57. A seal A-77 is arranged in the opening A-88, which seals the interior of the housing A-57 from the environment. The bearing shaft A-76 and the seal A-77 are also visible in the perspective view in Fig. A-4, in which the housing A-57 is shown open. The seal A-77 can be designed, for example, as a shaft seal or as an O-ring. As shown in Fig. A-7, a seal A-78 is arranged between the housing shell A-60 and the cover element A-48 of the housing A-57. The seal A-78 can be designed separately from the housing parts of the housing A-57. The seal A-78 can be designed, for example, as a felt element, paper seal, formed ring, sealing cord or O-ring.In an alternative design, the seal A-78 can be molded onto the housing shell A-60 or the cover element A-48 of the housing A-57. The seal A-78 can be, for example, a liquid seal, preferably made of silicone. In a further alternative design, the housing shell A-60 and the cover element A-48 of the housing A-57 can be sealingly connected to one another without the interposition of a seal, for example, by welding. The housing shell A-60 and the cover element A-48 can be sealingly connected to one another, for example, by hot gas welding or friction welding.

[0062] The housing shell A-60 is formed in one piece with the base body A-36 of the throttle assembly A-15. This is particularly evident in Fig. A-8.

[0063] As Fig. A-7 shows, the bearing shaft A-76 is rotatably mounted about an axis A-79. A gear wheel A-74 of a gearbox A-56 (Fig. A-8) is arranged on the outer circumference of the bearing shaft A-76. The gear wheel A-74 is connected in a rotationally fixed manner to the bearing shaft A-76. For this purpose, the bearing shaft A-76 has a non-circular cross-section, as Fig. A-4 shows. An external toothing A-95 of the gear wheel A-74 extends only over part of the axial length of the gear wheel A-74. In the length section in which no external toothing is arranged, a closing spring A-43 extends on the outer circumference of the gear wheel A-74. The closing spring A-43 counteracts a movement of the throttle lever A-49 in the direction of the arrow A-69 (Fig. A-5). If the operating element A-5 is not actuated by the operator, the closing spring A-43 returns the throttle element A-16 to the closed position A-85 shown in Fig. A-5 and A-7.The opening spring A-41 and the closing spring A-43 are designed such that the torque exerted by the closing spring A-43 on the throttle shaft A-17 in the closing direction A-44 is greater than the torque exerted by the opening spring A-41 in the opening direction A-42. When not actuated, the throttle shaft A-17 is therefore moved to the closed position A-85 by the closing spring A-43.

[0064] Fig. A-8 shows the arrangement in a sectional plane containing the axis A-79 of the gear wheel A-74 and the rotational axis A-54 of the throttle shaft A-17. As Fig. A-8 shows, a bearing journal A-70 is formed on the base body A-36 coaxial with the throttle shaft A-17 and projects into the interior of the housing A-57. The bearing journal A-70 is also shown in Fig. A-4. A driver A-46 is rotatably mounted on the bearing journal A-70, as shown in Fig. A-8. The driver A-46 carries an external toothing A-94 over part of its circumference, which is also shown in Fig. A-9. The external toothing A-94 of the driver A-46 engages with the external toothing A-95 of the gear wheel A-74, as shown in Fig. A-9. The external gears A-94 and A-95 form the gear unit A-56. In the illustrated example, the gear unit A-56 is a single-stage spur gear unit. A different design of the gear unit A-56 is also possible.

[0065] In the exemplary embodiment, the motor A-45 has an output shaft A-50 which can act on the throttle shaft A-17 via a connecting element A-89. The housing A-57 has an opening A-53 through which the drive connection of the motor A-45 to the throttle shaft A-17 protrudes. In the exemplary embodiment, the output shaft A-50 protrudes through the opening A-53. However, another design may also be advantageous. The housing of the motor A-45 is sealingly connected to the housing A-57 outside the opening A-53. Because the moving parts protrude through the opening A-53 arranged within the seal, sealing of the moving parts is not necessary. As Fig. A-8 shows, in the exemplary embodiment, a seal A-83 is arranged between the cover element A-48 and the motor A-45. The seal A-83 is also shown in Fig. A-4. In the exemplary embodiment, the seal A-83 is an O-ring.The seal A-83 can alternatively be designed, for example, as a felt element, paper seal, molded ring, or sealing cord. In an alternative design, the seal A-83 can be molded onto the cover element A-48 of the housing A-57 or onto the housing of the motor A-45. The seal A-83 can in particular be a liquid seal, preferably made of silicone. The seal A-83 prevents the ingress of contaminants into the housing A-57 and the escape of lubricant, in particular lubricating grease, from the housing A-57. If the tool is a cut-off grinder, the seal A-83 prevents, in particular, the ingress of mineral dust and water into the housing A-57.

[0066] Due to the seals A-78, A-83 and A-77, the interior of the A-57 housing is completely sealed from the environment.

[0067] As Fig. A-8 also shows, the opening spring A-41 is arranged on the outer circumference of a bearing element A-97 which is mounted on the throttle shaft A-17. As Fig. A-9 shows, when the bearing shaft A-76 and gear wheel A-74 move in the direction of arrow A-69 (see also Fig. A-5), the driver A-46 is moved in the opening direction A-42. As Fig. A-8 shows, the throttle shaft A-17 carries a connecting part A-80. The connecting part A-80 comprises a stop A-81 which projects into an opening A-96 in the driver A-46. The opening A-96 and the arrangement of the stop A-81 in the opening A-96 are shown in the sectional view in Fig. A-9. In Figs. A-9 and A-10, the unactuated position of the connecting part A-80 is shown by a dashed line. In this position, the stop A-81' rests against a stop element A-40 of the driver A-46. In the illustrated embodiment, the stop element A-40 is formed by an end face of the opening A-96.A different design of the stop element A-40 and the stop A-81 may also be advantageous. If the driver A-46 is actuated in the opening direction A-42, the stop element A-40 drives the throttle shaft A-17 via the stop A-81 in the opening direction A-42.

[0068] The throttle lever A-49 therefore acts on the throttle shaft A-17 via the gear A-56. In the illustrated embodiment, the gear A-56 has a gear ratio of A-1. However, a different gear ratio may also be advantageous.

[0069] As shown in Figs. A-8 and A-12, the connecting part A-80 has a stop A-82 projecting towards the cover element A-48. The stop A-82 interacts with a connecting element A-89, which is provided for connecting the output shaft A-50 of the motor A-45. This is shown in Fig. A-10. The motor A-45 is shown only schematically in the figures and can have any conventional design. When the motor A-45 is actuated accordingly, the output shaft A-50 (Fig. A-8) is rotated in the closing direction A-44 (Fig. A-10). This rotates the connecting element A-89 in the closing direction A-44 about the rotational axis A-54 of the throttle shaft A-17. The connecting element A-89 takes the stop A-82 of the connecting part A-80 with it in the closing direction A-44. Due to the elongated design of the opening A-96 as a slot running around the rotation axis A-54, the stop A-81 can move relative to the driver A-46 in the closing direction A-44.Even though the operator actuates control element A-5 and the driver A-46 has been moved to the position for a fully open throttle element A-16, the connecting part A-80 can be moved by the motor A-45 in such a way that the throttle element A-16 moves in the closing direction A-44. This reduces the free flow cross-section of the intake port A-14.

[0070] Adjustment of the throttle element A-16 by the motor A-45 is possible when the throttle element A-16 is open, i.e. the stops A-81 and A-82 are in the positions shown in Fig. A-9 and A-10 with a solid line. When the throttle element A-16 is closed or only partially open, the motor A-45 only moves the connecting element A-89 relative to the connecting part A-80. The position at which adjustment of the throttle element A-16 in the closing direction A-44 is possible by the motor A-45 can be predetermined by a suitable design of the connecting element A-89.

[0071] As shown in Fig. A-10, two stops A-91 and A-92 are provided on the housing A-57. These define the end positions of the connecting element A-89. Fig. A-10 shows the arrangement with the connecting element A-89 at the stop A-92, which defines the fully open position. The connecting element A-89 can be adjusted in the closing direction A-44 until it rests against the further stop A-91. The stops A-91 and A-92 determine the maximum travel over which the motor A-45 can close the throttle element A-16.

[0072] Fig. A1 1 shows an alternative design for the connecting element A-89. In this embodiment, the connecting element A-89 has a lug A-93, which interacts with the stops A-91 and A-92 and thus determines the maximum adjustment range for the connecting element A-89. As Fig. A1 1 also shows, connecting arms A-47 are arranged on the cover element A-48 of the throttle assembly A-15. These arms secure the motor A-45 to the base body A-36 via the cover element A-48. This allows the comparatively heavy weight of the motor A-45 to be effectively supported.

[0073] As shown in Fig. A-8, the throttle shaft A-17 has a first end section A-51 and a second end section A-52. The first end section A-51 projects into the housing A-57. The second end section A-52 projects from the base body A-36. The end sections A-51 and A-52 project from the base body A-36 on opposite sides of the intake duct section A-37. The connecting part A-80 is fixed to the first end section A-51. The operator acts on the first end section A-51 via the transmission device A-38, the throttle lever A-49, the gear A-56, the driver A-46 with the stop element A-40, and the connecting part A-80. The motor A-45 also acts on the first end section A-51. The closing spring A-43 preloads the gear wheel A-74 and acts via the gear A-56 on the first end section A-51. The opening spring A-41 acts on the second end section A-52. The second end section A-52 acts on the coupling device A-58 (Fig. A-7).

[0074] As Fig. A-8 also shows, the output shaft A-50 of the motor A-45 is arranged coaxially with the throttle shaft A-17. The throttle lever A-49 is pivotally mounted about the axis A-79. The axis of rotation A-54 of the throttle shaft A-17 and the axis A-79, about which the throttle lever A-49 is pivotally mounted, are spaced a distance a from each other. The axis of rotation A-54 and the axis A-79 run parallel to each other. In the exemplary embodiment, the gear A-56 is designed as a single-stage gear, and the two gears of the gear A-56 are each aligned coaxially with one of the axes. As Fig. A-8 also shows, the gear A-56 is also arranged in the sealed housing A-57.

[0075] Figs. A-13 to A-15 schematically illustrate the operation of the throttle assembly A-15. In Fig. A-15, the throttle element A-16 is shown in the closed position A-85. In the closed position A-85, the throttle element A-16 rests, in particular, against an idle stop (not shown). The opening spring A-41 (Fig. 8) biases the throttle element A-16 in the opening direction A-42, and the closing spring A-43 (Fig. A-8) biases the throttle element A-16 in the closing direction A-44, as shown schematically in Fig. A-13.

[0076] In this position, stop A-82 (Fig. A-10) is not engaged with connecting element A-89 and therefore does not act on throttle element A-16. Stop A-82 is located in position A-82', shown by the dashed line in Fig. A-10.

[0077] As shown in Fig. A-13, when the throttle element A-16 is in the closed position, the air control element A-20 is in its closed position A-104.

[0078] Fig. A-14 schematically shows the positions of the elements when the operator has actuated the operating element A-5. The operator moves the throttle shaft A-17 and the throttle element A-16 in the opening direction A-42 via the transmission device A-38 and the gear A-56 (Fig. A-8). The operator actuates the operating element A-5 against the force of the closing spring A-43 in the opening direction A-42 in order to adjust the throttle element A-16 in the opening direction A-42. Fig. A-14 shows a position A-105 of the throttle element A-16 which corresponds to the load-free state. The throttle element A-16 assumes position A-105 when the tool of the work device A1 is not in engagement with a workpiece and the operator actuates the operating element A-5, for example, fully actuates it.

[0079] To limit the speed, motor A-45 adjusts driver A-46 (Fig. A-9) in the closing direction A-44 until the speed corresponds to the desired speed in the no-load state, in particular the desired maximum speed of the combustion engine A-11. For this purpose, the speed limiting device A-100 controls motor A-45 via control device A-10, so that motor A-45 rotates output shaft A-50 (Fig. A-8) in the closing direction A-44. Motor A-45 moves connecting part A-80 with stop A-82 in the closing direction A-44 via connecting element A-89 (Figs. A-9 and A-10). Fig. A-9 shows this arrangement before motor A-45 has become active. If the motor A-45 now moves the connecting part A-80 over the stop A-82 in the closing direction A-44, the stop A-81 moves into the opening A-96. The operator can continue to keep the control element A-5 fully actuated, thus maintaining the position of the driver A-46 with the stop element A-40.The motor A-45 acts directly on the throttle shaft A-17 via the connecting element A-89 and the connecting part A-80 and adjusts the throttle element A-16 in the closing direction A-44. In the process, the connecting part A-80 is adjusted relative to the driver A-46, as shown schematically in Fig. A-15. In the no-load state, the cutting wheel A-7 is not in engagement with a workpiece. The operator holds down the control element A-5. To limit the speed, the speed limiting device A-100 intervenes and, by controlling the motor A-45, causes the throttle element A-16 to close. If the speed drops too sharply, the throttle element A-16 is subsequently opened again by adjusting the motor A-45 in the opposite direction. The position of the throttle element A-16 and thus the desired speed are set by adjusting the throttle element A-16 using appropriate control.If the desired speed for the no-load condition is set, the throttle element A-16 is in position A-105. The no-load condition is a quasi-stationary condition. The position of the throttle element A-16 is no longer changed by the speed limiting device A-100, in particular as long as the ambient conditions do not change. The free travel As is designed such that the throttle element A-16, in the no-load, quasi-stationary condition, is adjusted by a maximum of the free travel As from the closed position A-85 towards the fully open position A-106. The fully open position A-106 is shown in Fig. A-14 with a dashed line.

[0080] In position A-105, the throttle element A-16 is adjusted by an adjustment angle A-5 in the opening direction A-42 compared to the closed position A-85. The adjustment angle A-5 is the maximum adjustment angle A-5 that can be achieved in the no-load state of the work tool A1 depending on the ambient conditions. The adjustment angle A-5 is matched to the free travel As. The adjustment angle A-5 corresponds at most to the free travel As. In particular, the free travel As is at least 2°, especially at least 3° greater than the adjustment angle A-5.

[0081] The air control element A-20 is in the closed position Al 04 when the throttle element Al 6 is in the position Al 05. The adjustment angle A-5 of the throttle element A-16 corresponds at most to the free travel As. An adjustment of the throttle element A-16 from the position Al 05 in the closing direction A-44 therefore only causes a change in the free flow cross-section of the intake duct A-14, but not a change in the free flow cross-section of the air duct A-13.

[0082] Fig. A1 5 shows the arrangement when the throttle element A-16 is adjusted by more than the free travel As from the fully closed position A-85. When adjusted by more than the free travel As, the air control element A-20 is driven via the coupling device A-58 and adjusted together with the throttle element A-16.

[0083] Figs. A-16 to A-18 show an alternative embodiment of the arrangement. In this embodiment, the opening spring A-41 and the closing spring A-43 are arranged coaxially with the rotational axis A-54 of the throttle shaft A-17. The closing spring A-43 is arranged outside the housing A-57. The driver A-46 is mounted on the throttle shaft A-17. The motor A-45 acts via a gear A-90, which in this embodiment is designed as a two-stage spur gear, on the connecting part A-80, which in turn acts on the driver A-46. The function of the arrangement according to Figs. A-16 to A-18 corresponds to the function described for the previous figures.

[0084] Fig. A1 7 shows the arrangement when the operator actuates control element A-5 and throttle element A-16 is fully open. In Fig. A1 8, motor A-45 has moved connecting part A-80 and thus throttle shaft A-17 relative to the position in Fig. A-17, closing throttle element A-16. In doing so, a gear wheel A-98 of gear A-90 has moved connecting part A-80.

[0085] The invention further relates to a throttle arrangement of the type specified in the preamble of claim 20 and to a hand-held working device with a throttle arrangement of the type specified in the preamble of claim 36.

[0086] DE 37 11 779 A1 describes a throttle valve that can be controlled mechanically and electrically. The mechanical control specifies a maximum opening position for the throttle valve. The electrical control can further close the throttle valve relative to this position.

[0087] The invention is based on the object of providing a throttle assembly of the generic type with a simple and robust design. A further object of the invention is to provide a hand-held implement with an advantageous design.

[0088] This object is achieved with respect to the throttle assembly by a throttle assembly having the features of claim 20. With respect to the hand-held implement, the object is achieved by a hand-held implement having the features of claim 36.

[0089] In order to achieve a simple design of the throttle assembly, the stop element is formed on a rotatably mounted driver. To ensure the function of the assembly even when used in dirty environments, as occurs, for example, with hand-held tools such as cut-off grinders, chainsaws or the like, the driver is arranged in a housing that is sealed off from the environment. In particular, the transmission device comprises a shaft that enters the housing, wherein the shaft is sealed by a seal. In particular, the adjustment movement that the operator exerts on the control element is transmitted via the shaft. Sealing the shaft is easy due to the rotary movement of the shaft. The complex sealing of a translationally moving component of the transmission device can be avoided.

[0090] In particular, the motor is arranged in a sealed manner at an opening in the housing. This protects the opening and the elements protruding through the opening from contamination. In particular, an element driven by the motor, for example, a motor output shaft, protrudes through the opening. In particular, no direct sealing is provided for the motor-driven element. This avoids sealing moving parts. This reduces wear on the sealing elements. The seal also protects the motor output shaft and the point where the motor output shaft enters the motor housing from contamination.

[0091] The stop element can be adjusted by the operator, particularly via the transmission device, against the force of the closing spring. The throttle assembly is preferably designed such that, when the transmission device is not actuated, the torque exerted by the closing spring on the throttle shaft is greater than the torque exerted by the opening spring on the throttle shaft. This ensures that the throttle element is closed by the closing spring when the transmission device is not actuated, i.e., when the operator does not actuate the transmission device.

[0092] Since the closing spring exerts a greater torque on the throttle shaft than the opening spring, the closing spring is particularly larger than the opening spring. To minimize the housing's installation space and thus achieve a compact design of the overall assembly, the closing spring is arranged outside the housing. In particular, the closing spring extends helically around the rotational axis of the driver. The rotational axis of the driver corresponds in particular to the rotational axis of the throttle element.

[0093] A simple design of the arrangement results when the housing is defined by the base body and at least one cover element. To seal the housing, one or more seals are arranged, in particular, between the base body and the cover element. Shafts or the like leading outward are also mounted in the housing in a sealed manner.

[0094] A simple and compact design results if the throttle shaft has two end sections that run on opposite sides of the intake duct section. At least one end section protrudes in particular from the base body. In particular, one end section protrudes from the base body into the housing. In particular, the motor and the transmission device act on the throttle shaft at a first end section of the throttle shaft. The opening spring and the closing spring act on the throttle shaft in particular at different end sections of the throttle shaft. In particular, it is provided that the closing spring acts on the end section of the throttle shaft on which the stop element acts. In an alternative embodiment, it can be provided that the opening spring acts on the end section of the throttle shaft on which the stop element acts.

[0095] An arrangement of the closing spring outside the housing is particularly provided when the closing spring is arranged coaxially with the driver and, in particular, coaxially with the rotational axis of the throttle element. In an alternative embodiment, the closing spring can be arranged helically around an axis that is spaced from the rotational axis of the throttle shaft. In this case, an arrangement of the closing spring inside the housing can also be advantageous. In one embodiment, the driver is mounted on an end section of the throttle shaft that protrudes from the base body. This results in a simple and compact design.

[0096] To ensure proper mounting of the driver, an alternative design variant provides for the stop element to be mounted on the base body. The intake duct section is formed in the base body. This achieves small tolerances between the position of the throttle element and the driver.

[0097] In particular, the transmission device comprises a shear-resistant transmission rod, which is suspended from a throttle lever arranged outside the housing and connected to the driver. The throttle lever can be connected to the driver in a rotationally fixed manner and can pivot with it about the same axis. In an alternative embodiment, the throttle lever is pivotably mounted about a rotational axis that is spaced apart from the axis of the throttle shaft. In this embodiment, it is particularly provided that an output shaft of the motor is arranged coaxially with the throttle shaft.

[0098] In particular, it is provided that the transmission device comprises a gear, in particular a spur gear. This is particularly provided when the throttle lever is pivotably mounted about an axis of rotation which is at a distance from the axis of the throttle shaft. If the throttle lever is pivotably mounted about the axis of the throttle shaft, it is particularly provided that the motor is coupled to the throttle shaft via a gear, in particular a spur gear. The motor is arranged in particular in the base body. The housing of the motor is formed by the base body. This results in a simple and compact design. The gear is arranged in particular in the sealed housing. This also protects the gear from contamination.

[0099] For a hand-held tool with at least one tool and a drive motor for driving the at least one tool, it is advantageously provided, in particular, that the drive motor is a two-stroke engine operating with a scavenging system, which has an intake duct and an air duct, and which has a throttle arrangement. An air control element is provided, which is pivotally mounted in the air duct with an air control shaft. The position of the air control shaft is coupled, in particular, via a coupling device, to the position of the throttle shaft. The motor and the coupling device act on the throttle shaft, in particular at different end sections of the throttle shaft.

[0100] In particular, the throttle shaft has a coupling element that is non-rotatably connected to the throttle shaft, via which the position of the air control shaft is coupled to the position of the throttle shaft. The opening spring is supported, in particular, at one end on the coupling element and at the other end on the base body. This results in a simple and compact design and a space-saving arrangement of the opening spring.

[0101] Embodiments of the invention are explained below with reference to the drawings. They show:

[0102] Fig. Bl is a schematic side view of a hand-held implement,

[0103] Fig. B-2 is a schematic representation of a two-stroke engine operating with a scavenging reservoir, Fig. B-3 is a side view of a throttle arrangement for a two-stroke engine according to Fig. B-2,

[0104] Fig. B-4 is an exploded perspective view of parts of the

[0105] Throttle arrangement from Fig. B-3,

[0106] Fig. B-5 is a perspective view of the throttle assembly,

[0107] Fig. B-6 is a side view of an alternative embodiment of the coupling device of the throttle arrangement in the direction of arrow VI in Fig. B-3,

[0108] Fig. B-7 is a sectional view of the throttle assembly,

[0109] Fig. B-8 to Fig. B-10 are partial sectional views of the throttle arrangement in different sectional planes,

[0110] Fig. Bl 1 is a perspective view of the throttle assembly with the engine removed,

[0111] Fig. B-12 a partial view corresponding to Fig. Bl 1 with additionally removed connection element for the motor,

[0112] Fig. B-13 to Fig. B-15 are schematic representations of the function of the throttle arrangement,

[0113] Fig. B-16 shows an alternative embodiment of the throttle arrangement in a sectional view, Fig. B-17 and Fig. B-18 show partial perspective views of the throttle arrangement from Fig. B-16 with the cover element removed in different positions of the transmission device.

[0114] Fig. B1 shows a schematic illustration of an exemplary embodiment of a hand-held work tool BL. In the exemplary embodiment, the work tool BL is a chainsaw. The work tool BL is, in particular, portable and hand-held during operation. The work tool BL has a rear handle B-3 and a handlebar B-4. An operating element B-5 and a locking element B-6 for the operating element B-5 are arranged on the rear handle B-3. The work tool BL has a saw chain B-8 which is driven in rotation on a guide rail B-7. A drive motor B1 serves to drive the saw chain B-8. In the exemplary embodiment, the drive motor B1 is a two-stroke engine. The drive motor B1 is preferably a single-cylinder engine. In the exemplary embodiment, the drive motor B1 is a two-stroke engine operating with a scavenging reservoir. The drive motor B1 is, in particular, a mixture-lubricated engine, in particular a two-stroke engine or a mixture-lubricated four-stroke engine.In this example, the drive motor B1 is to be started manually. A starter handle B-9 is used for this purpose. The implement B1 has a hand guard B-10, which serves in particular to trigger a braking device (not shown) for the saw chain B-8.

[0115] The drive motor B1 has an air filter B-12 through which air is drawn in during operation. An air duct B-13 and an intake duct B-14 serve to supply air. It can be provided that the air duct B-13 and intake duct B-14 supply clean air. Alternatively, it can be provided that fuel is supplied to the intake duct B-14, so that a fuel / air mixture is supplied via the intake duct B-14.

[0116] However, a different design of the drive motor Bl 1, in particular a design without an air duct B-13, can also be provided. Fig. B-2 shows the drive motor Bl 1 in a schematic sectional view. As Fig. B-2 shows, the drive motor Bl 1 has a throttle arrangement Bl 5, which serves to control the amount of air supplied. In the exemplary embodiment, the throttle arrangement B-15 comprises a throttle element B-16, which serves to control the amount of air flowing through the intake duct B-14. The throttle arrangement B-15 also has an air control element B-20, which serves to control the amount of air flowing through the air duct Bl 3. In the exemplary embodiment, a choke element Bl 8 is arranged upstream of the throttle element B-16. In an alternative embodiment, the choke element Bl 8 can also be omitted or designed differently. In the exemplary embodiment, the throttle element B-16, the choke element B-18 and the air control element B-20 are each pivotably mounted.For this purpose, the throttle element B-16 has a throttle shaft B-17. The choke element B-18 is pivotally mounted by a choke shaft B-9. The air control element B-20 is mounted by an air control shaft B-21. In the exemplary embodiment, the throttle element B-16, choke element B-18, and air control element B-20 are designed as flaps. However, a different design, for example, as rollers with an air passage opening running perpendicular to the axis of rotation, can also be provided. It can also be provided that the drive motor B-11 does not have a choke element B-18.

[0117] The drive engine B-1 comprises a cylinder B-22 in which a combustion chamber B-23 is formed. A piston B-25 is reciprocatingly mounted in the cylinder B-22. The piston B-25 drives a crankshaft B-27, which is rotatably mounted in a crankcase B-24, via a connecting rod B-26. The crankshaft B-27 is shown only schematically in Fig. B-2. The crankshaft B-27 is rotatably mounted about a rotational axis B-28.

[0118] In the area of ​​the bottom dead center of piston B-25, shown in Fig. B-2, the interior of the crankcase B-24 is connected to the combustion chamber B-23 via transfer ports B-29. The transfer ports B-29 open into the combustion chamber B-23 via transfer ports B-30. The transfer ports B-30 are controlled by the piston B-25. A spark plug B-34 extends into the combustion chamber B-23 and serves to ignite the fuel / air mixture in the combustion chamber B-23. An outlet B-35, also controlled by the piston B-25, leads from the combustion chamber B-23.

[0119] The intake port B-14 opens into the bore of cylinder B-22 via an intake port inlet B-32. The intake port inlet B-32 is also controlled by piston B-25 and is connected to the interior of the crankcase B-24 in the area of ​​top dead center of piston B-25. The air port B-13 opens into the bore of cylinder B-22 via one or more air inlets B-33. The piston B-25 has one or more piston pockets B-31 on its piston skirt. The piston pocket B-31 connects the air inlet B-33 to one or more transfer ports B-30 in the area of ​​top dead center of piston B-25. This allows air to be pre-stored in the transfer ports B-29 via the air port B-13, which serves to scavenge the combustion chamber B-23.

[0120] For supplying fuel, the throttle assembly B-15 may include a carburetor. A fuel valve B-63 may also be provided for supplying fuel. The fuel valve B-63 may, for example, supply the fuel to the interior of the crankcase B-24. Alternatively, a fuel valve B-63' may be provided, which supplies fuel to the intake port B-14.

[0121] The throttle assembly B-15 comprises a base body B-36. An intake duct section B-37 of the intake duct B-14 is formed in the base body B-36. The base body B-36 is, in particular, a cast metal part. In the arrangement shown in Fig. B-2, the air control element B-20 is mounted in an air duct section B-75, which is formed in a separate body of the throttle assembly B-15.

[0122] The following figures show a design in which the intake duct section B-37 and the air duct section B-75 are formed in the base body B-36. The base body B-36 is a single piece and, in particular, a cast part. The single-piece design results in a simple structure.

[0123] As Fig. B-3 shows, the throttle shaft B-17 and the air control shaft B-21 are coupled to one another on one side of the base body B-36, which is shown on the left in Fig. B-3. A coupling device B-58 is provided for coupling the throttle shaft B-17 and the air control shaft B-21. The air control shaft B-21 is preloaded by an air closing spring B-64 toward the closed position of the air control element B-20. The air closing spring B-64 is designed as a leg spring. The air closing spring B-64 extends around an end of the air control shaft B-21 protruding from the base body B-36. A coupling element B-65 is fixed to this end of the air control shaft B-21. The coupling element B-65 can be designed, for example, as a lever or as a disc.

[0124] An end section of the throttle shaft B-17, not visible in Fig. B-3, is provided with a coupling element B-59, which can be designed, for example, as a disc or a lever. The coupling element B-59 and the coupling element B-65 are coupled via a coupling rod B-66. The air control shaft B-21 is pivotally mounted about a rotational axis B-55. The throttle shaft B-17 is pivotally mounted about a rotational axis B-54. The coupling rod B-66 is connected to the coupling elements B-65 and B-59 at a distance from the rotational axis B-54 of the throttle shaft B-17 and from the rotational axis B-55 of the air control shaft B-21. In particular, the coupling element B-59 is connected in a rotationally fixed manner to the throttle shaft B-17. The coupling element B-65 is in particular connected in a rotationally fixed manner to the air control shaft B-21.

[0125] As Fig. B-4 shows, in the exemplary embodiment the coupling element B-65 is designed as a lever. The coupling element B-59 is designed as a disk in the exemplary embodiment which has a plurality of openings B-84. As Figs. B-3 and B-4 show, the throttle arrangement B-15 has an opening spring B-41. The opening spring B-41 biases the throttle shaft B-17 towards the fully open position of the throttle element B-16. The opening spring B-41 is designed as a leg spring. The opening spring B-41 extends around the axis of rotation B-54 of the throttle shaft B-17 and is arranged outside the base body B-36. A first end B-71 of the opening spring B-41 is connected to the coupling element B-59. For this purpose the first end B-71 is hooked into one of the openings B-84. By appropriately selecting one of the openings B-84, tolerances of the opening spring B-41 can be easily compensated.A second end B-72 of the opening spring B-41 is supported in particular on the base body B-36, as shown in Fig. B-6.

[0126] On the side of the base body B-36 opposite the coupling device B-58, a housing B-57 is formed. The housing B-57 is delimited by a housing shell B-60 and a cover element B-48. In the exemplary embodiment, the housing shell B-60 is formed integrally with the base body B-36. A motor B-45 is arranged on the side of the housing B-57 opposite the base body B-36. This motor serves to move the throttle element B-16 in a closing direction and thereby reduce the free flow cross-section in the intake duct section B-37.

[0127] For the operator to control the throttle element B-16, a transmission device B-38 is provided, which transmits the position of the control element B-5 (only partially shown in Fig. B-3) to the rotational position of the throttle shaft B-17. The transmission device B-38 comprises a transmission rod B-39.

[0128] As shown in Fig. B-5, the transmission rod B-39 has a first end B-61 that is attached to the control element B-5. The transmission rod B-39 has a second end B-62 that is attached to a throttle lever B-49.

[0129] The operating element B-5 has an actuating section B-2, which preferably projects from a housing of the work device B1 and at which an operator can actuate the operating element B-5. In the exemplary embodiment, the operating element B-5 is pivotally mounted about a pivot axis B-73. An operator can actuate the actuating section B-2 in the direction of an arrow B-67. This causes the operating element B-5 to pivot about its pivot axis B-73 and move the first end B-61 of the transmission rod B-39 in the direction of an arrow B-68. In the illustration in Fig. B-5, the arrow B-68 points downwards. The transmission rod B-39 is rigid. The movement of the first end B-61 in the direction of the arrow B-68 causes a movement of the second end B-62 in the direction of the arrow B-69. The arrow B-69 is also pointed downwards in Fig. B-5.The engagement of the second end B-62 on the throttle lever B-49 causes—when the motor B-45 is not actuated—a movement of the throttle element B-16 in an opening direction B-42. In Fig. B-5, the throttle element B-16 is arranged in a closed position B-85. The throttle element B-16 assumes the closed position B-85 when the control element B-5 is not actuated by the operator.

[0130] A movement of the throttle element B-16 in the opening direction B-42 causes a movement of the air control element B-20 in an opening direction B-86 due to the coupling device B-58. In the exemplary embodiment, the opening direction B-86 is directed in the same direction as the opening direction B-42 of the throttle element B-16.

[0131] Fig. B-6 shows a view of the coupling device B-58, wherein the coupling element B-65 on the air control shaft B-21 is designed, unlike in the previous figures, as a disc with a plurality of openings for suspending the air closing spring B-64.

[0132] As shown in Fig. B-6, the coupling element B-59 has an elongated hole B-87 into which the coupling rod B-66 is suspended. If the throttle element B-16 is adjusted in the opening direction B-42, the coupling element B-59, which is non-rotatably connected to the throttle shaft B-17, rotates with it. Due to the elongated hole B-87, the coupling element B-59 rotates without moving the coupling rod B-66. Therefore, the coupling rod B-66 does not initially transmit the movement of the throttle element B-16 to the coupling element B-65 and the air control element B-20 when moving from the closed position B-85.

[0133] The coupling rod B-66 has, in particular, a pin B-103 which projects into the elongated hole B-87 and which moves in the elongated hole B-66 when the coupling element B-59 moves. The throttle element B-16 can be adjusted over an idle travel Bs from the closed position B-85 towards a fully open position B-106 (Fig. B-14) without the movement of the throttle element B-16 being transmitted to the air control element B-20 via the coupling device B-58. The air control element B-20 remains at least in its closed position B-104 until the throttle element B-16 has been adjusted from its closed position B-85 by the idle travel Bs in the opening direction B-42. In particular, the idle travel Bs is at most 30°. In particular, it is provided that the idle travel Bs is at least 15°. However, a smaller idle travel Bs can also be provided.

[0134] As shown in Fig. B-7, the throttle lever B-49 is fixed to a bearing shaft B-76, which is rotatably mounted in the housing B-57. The throttle lever B-49 is arranged outside the housing B-57. The bearing shaft B-76 projects through an opening B-88 in the housing. A seal B-77 is arranged in the opening B-88, which seals the interior of the housing B-57 from the environment. The bearing shaft B-76 and the seal B-77 are also visible in the perspective view in Fig. B-4, in which the housing B-57 is shown open. The seal B-77 can be designed, for example, as a shaft seal or as an O-ring. As shown in Fig. B-7, a seal B-78 is arranged between the housing shell B-60 and the cover element B-48 of the housing B-57. The seal B-78 can be designed separately from the housing parts of the housing B-57. The B-78 seal can be designed, for example, as a felt element, paper seal, molded ring, sealing cord or O-ring.In an alternative design, the seal B-78 can be molded onto the housing shell B-60 or the cover element B-48 of the housing B-57. The seal B-78 can be, for example, a liquid seal, preferably made of silicone. In a further alternative design, the housing shell B-60 and the cover element B-48 of the housing B-57 can be sealingly connected to one another without the interposition of a seal, for example, by welding. The housing shell B-60 and the cover element B-48 can be sealingly connected to one another, for example, by hot gas welding or friction welding.

[0135] The housing shell B-60 is formed in one piece with the base body B-36 of the throttle assembly B-15. This is particularly evident in Fig. B-8.

[0136] As Fig. B-7 shows, the bearing shaft B-76 is mounted so as to be rotatable about an axis B-79. A gear wheel B-74 of a gear B-56 ​​(Fig. B-8) is arranged on the outer circumference of the bearing shaft B-76. The gear wheel B-74 is connected in a rotationally fixed manner to the bearing shaft B-76. For this purpose, the bearing shaft B-76 has a non-circular cross-section, as Fig. B-4 shows. An external toothing B-95 of the gear wheel B-74 extends only over part of the axial length of the gear wheel B-74. In the length section in which no external toothing is arranged, a closing spring B-43 extends on the outer circumference of the gear wheel B-74. The closing spring B-43 counteracts a movement of the throttle lever B-49 in the direction of the arrow B-69 (Fig. B-5). If the operating element B-5 is not operated by the operator, the closing spring B-43 returns the throttle element B-16 to the closed position B-85 shown in Fig. B-5 and B-7.The opening spring B-41 and the closing spring B-43 are designed such that the torque exerted by the closing spring B-43 on the throttle shaft B-17 in the closing direction B-44 is greater than the torque exerted by the opening spring B-41 in the opening direction B-42. When not actuated, the throttle shaft B-17 is therefore moved to the closed position B-85 by the closing spring B-43.

[0137] Fig. B-8 shows the arrangement in a sectional plane containing the axis B-79 of the gear wheel B-74 and the rotational axis B-54 of the throttle shaft B-17. As Fig. B-8 shows, a bearing journal B-70 is formed on the base body B-36 coaxial with the throttle shaft B-17 and projects into the interior of the housing B-57. The bearing journal B-70 is also shown in Fig. B-4. A driver B-46 is rotatably mounted on the bearing journal B-70, as shown in Fig. B-8. The driver B-46 carries an external toothing B-94 over part of its circumference, which is also shown in Fig. B-9. The external toothing B-94 of the driver B-46 engages with the external toothing B-95 of the gear wheel B-74, as shown in Fig. B-9. The external gears B-94 and B-95 form the gear B-56. In the illustrated example, the gear B-56 ​​is a single-stage spur gear. A different design of the gear B-56 ​​is also possible.

[0138] In the exemplary embodiment, the motor B-45 has an output shaft B-50 which can act on the throttle shaft B-17 via a connecting element B-89. The housing B-57 has an opening B-53 through which the drive connection of the motor B-45 to the throttle shaft B-17 protrudes. In the exemplary embodiment, the output shaft B-50 protrudes through the opening B-53. The housing of the motor B-45 is sealingly connected to the housing B-57 outside the opening B-53. Because the moving parts protrude through the opening B-53 arranged within the seal, sealing of the moving parts is not necessary. As Fig. B-8 shows, in the exemplary embodiment, a seal B-83 is arranged between the cover element B-48 and the motor B-45. The seal B-83 is also shown in Fig. B-4. In the exemplary embodiment, the seal B-83 is an O-ring. The B-83 seal can alternatively be designed as a felt element, paper seal, shaped ring or sealing cord.In an alternative design, the seal B-83 can be molded onto the cover element B-48 of the housing B-57 or onto the motor housing B-45. The seal B-83 can, in particular, be a liquid seal, preferably made of silicone. The seal B-83 prevents the ingress of contaminants into the housing B-57 and the escape of lubricant, particularly grease, from the housing B-57. If the tool is a power cutter, the seal B-83 prevents, in particular, the ingress of mineral dust and water into the housing B-57.

[0139] Thanks to the seals B-78, B-83, and B-77, the interior of the housing B-57 is completely sealed from the environment. As Fig. B-8 also shows, the opening spring B-41 is located on the outer circumference of a bearing element B-97, which is mounted on the throttle shaft B-17.

[0140] As Fig. B-9 shows, when the bearing shaft B-76 and gear wheel B-74 move in the direction of arrow B-69 (see also Fig. B-5), the driver B-46 is moved in the opening direction B-42. As Fig. B-8 shows, the throttle shaft B-17 carries a connecting part B-80. The connecting part B-80 includes a stop B-81 that projects into an opening B-96 in the driver B-46. The opening B-96 and the arrangement of the stop B-81 in the opening B-96 are shown in the sectional view in Fig. B-9. In Figs. B-9 and B-10, the unactuated position of the connecting part B-80 is shown with a dashed line. In this position, the stop B-81' rests against a stop element B-40 of the driver B-46. In the exemplary embodiment, the stop element B-40 is formed by a front side of the opening B-96. A different design of the stop element B-40 and the stop B-81 can also be provided.If the driver B-46 is actuated in the opening direction B-42, the stop element B-40 takes the throttle shaft B-17 via the stop B-81 in the opening direction B-42.

[0141] The throttle lever B-49 therefore acts on the throttle shaft B-17 via the gear B-56. In the illustrated embodiment, the gear B-56 ​​has a gear ratio of B-1. A different gear ratio may also be provided.

[0142] As shown in Figs. B-8 and B-12, the connecting part B-80 has a stop B-82 directed towards the cover element B-48. The stop B-82 interacts with a connecting element B-89, which is provided for connecting the output shaft B-50 of the motor B-45. This is shown in Fig. B-10. The motor B-45 is shown only schematically in the figures and can have any conventional design. When the motor B-45 is activated, the output shaft B-50 (Fig. B-8) is set in rotation in the closing direction B-44 (Fig. B-10). This rotates the connecting element B-89 in the closing direction B-44 about the rotation axis B-54 of the throttle shaft B-17. The connecting element B-89 takes the stop B-82 of the connecting part B-80 with it in the closing direction B-44. Due to the elongated design of the opening B-96 as a slot running around the rotation axis B-54, the stop B-81 can move relative to the driver B-46 in the closing direction B-44.Although the operator actuates the control element B-5 and the driver B-46 has been moved to the position for a fully open throttle element B-16, the connecting part B-80 can be moved by the motor B-45 in such a way that the throttle element B-16 is adjusted in the closing direction B-44.

[0143] Adjustment of the throttle element B-16 by the motor B-45 is possible when the throttle element B-16 is open, i.e. the stops B-81 and B-82 are in the positions shown in Fig. B-9 and B-10 with a solid line. When the throttle element B-16 is closed or only partially open, the motor B-45 only moves the connecting element B-89 relative to the connecting part B-80. The position at which the throttle element B-16 can be adjusted in the closing direction B-44 by the motor B-45 can be predetermined by a suitable design of the connecting element B-89.

[0144] As shown in Fig. B-10, two stops B-91 and B-92 are provided on the housing B-57. These define the end positions of the connecting element B-89. Fig. B-10 shows the arrangement with the connecting element B-89 at the stop B-92, which defines the fully open position. The connecting element B-89 can be adjusted in the closing direction B-44 until it rests against the further stop B-91. The stops B-91 and B-92 determine the maximum travel over which the motor B-45 can close the throttle element B-16.

[0145] Fig. Bl 1 shows an alternative design for the connecting element B-89. In this version, the connecting element B-89 has a nose B-93, which interacts with the stops B-91 and B-92 and thus determines the maximum adjustment range for the connecting element B-89.

[0146] As Fig. Bl 1 also shows, connecting arms B-47 are arranged on the cover element B-48 of the throttle assembly B-15, with which the motor B-45 is fixed to the base body B-36 via the cover element B-48. This allows the comparatively large weight of the motor B-45 to be effectively supported.

[0147] As shown in Fig. B-8, the throttle shaft B-17 has a first end section B-51 and a second end section B-52. The first end section B-51 projects into the housing B-57. The second end section B-52 projects from the base body B-36. The end sections B-51 and B-52 project from the base body B-36 on opposite sides of the intake duct section B-37. The connecting part B-80 is fixed to the first end section B-51. The operator acts on the first end section B-51 via the transmission device B-38, the throttle lever B-49, the gear B-56, the driver B-46 with the stop element B-40, and the connecting part B-80. The motor B-45 also acts on the first end section B-51. The closing spring B-43 preloads the gear wheel B-74 and acts via the gear B-56 ​​on the first end section B-51. The opening spring B-41 acts on the second end section B-52. The second end section B-52 acts on the coupling device B-58 (Fig. B-7).

[0148] As Fig. B-8 also shows, the output shaft B-50 of the motor B-45 is arranged coaxially with the throttle shaft B-17. The throttle lever B-49 is pivotally mounted about the axis B-79. The axis of rotation B-54 of the throttle shaft B-17 and the axis B-79, about which the throttle lever B-49 is pivotally mounted, are spaced a distance a from each other. The axis of rotation B-54 and the axis B-79 run parallel to each other. In the exemplary embodiment, the gear B-56 ​​is designed as a single-stage gear, and the two gears of the gear B-56 ​​are each aligned coaxially with one of the axes. As Fig. B-8 also shows, the gear B-56 ​​is also arranged in the sealed housing B-57. Figs. B-13 to B-15 schematically show the operation of the throttle assembly B-15. In Fig. B-15, the throttle element B-16 is shown in the closed position B-85. In the closed position B-85, the throttle element B-16 rests against an idle stop (not shown). The opening spring B-41 (Fig.8) preloads the throttle element B-16 in the opening direction B-42 and the closing spring B-43 (Fig. B-8) preloads the throttle element B-16 in the closing direction B-44, as shown schematically in Fig. B-13.

[0149] In this position, stop B-82 (Fig. B-10) is not engaged with connecting element B-89 and therefore does not act on throttle element B-16. Stop B-82 is located in position B-82', shown by the dashed line in Fig. B-10.

[0150] As shown in Fig. B-13, when the throttle element B-16 is in the closed position, the air control element B-20 is in its closed position B-104.

[0151] Fig. B-14 schematically shows the positions of the elements when the operator has actuated the operating element B-5. The operator moves the throttle shaft B-17 and the throttle element B-16 in the opening direction B-42 via the transmission device B-38 and the gear B-56 ​​(Fig. B-8). The operator actuates the operating element B-5 against the force of the closing spring B-43 in the opening direction B-42 in order to adjust the throttle element B-16 in the opening direction B-42. Fig. B-14 shows a position B-105 of the throttle element B-16 which corresponds to the load-free state. The throttle element B-16 assumes position B-105 when the tool of the work device B1 is not in engagement with a workpiece and the operator actuates the operating element B-5, for example, fully actuates it.

[0152] To limit the speed, motor B-45 adjusts driver B-46 (Fig. B-9) in the closing direction B-44 until the speed corresponds to the desired speed in the no-load state, in particular the desired maximum speed of the combustion engine B-11. For this purpose, speed limiting device B-100 controls motor B-45 via control device B-10, so that motor B-45 rotates output shaft B-50 (Fig. B-8) in the closing direction B-44. Motor B-45 moves connecting part B-80 with stop B-82 in the closing direction B-44 via connecting element B-89 (Figs. B-9 and B-10). Fig. B-9 shows this arrangement before motor B-45 has become active. If the motor B-45 now moves the connecting part B-80 over the stop B-82 in the closing direction B-44, the stop B-81 moves into the opening B-96. The operator can continue to keep the control element B-5 fully actuated, thus maintaining the position of the driver B-46 with the stop element B-40.The motor B-45 acts directly on the throttle shaft B-17 via the connecting element B-89 and the connecting part B-80 and adjusts the throttle element B-16 in the closing direction B-44. In this process, the connecting part B-80 is adjusted relative to the driver B-46, as shown schematically in Fig. B-15. In the no-load state, the cutting wheel B-7 is not in engagement with a workpiece. The operator presses the control element B-5. To limit the speed, the speed limiting device B-100 intervenes and, by controlling the motor B-45, causes the throttle element B-16 to close. If the speed drops too sharply, the throttle element B-16 is subsequently opened again by adjusting the motor B-45 in the opposite direction. The position of the throttle element B-16 and thus the desired speed are set by adjusting the throttle element B-16 using appropriate control.If the desired speed for the no-load condition is set, the throttle element B-16 is in position B-105. The no-load condition is a quasi-stationary condition. The position of the throttle element B-16 is no longer changed by the speed limiting device B-100, in particular as long as the ambient conditions do not change. The free travel Bs is designed such that in the no-load, quasi-stationary condition the throttle element B-16 is adjusted by a maximum of the free travel Bs from the closed position B-85 towards the fully open position B-106. The fully open position B-106 is shown in Fig. B-14 with a dashed line. In position B-105 the throttle element B-16 is adjusted by an adjustment angle B-5 in the opening direction B-42 compared to the closed position B-85.The adjustment angle B-5 is the maximum adjustment angle B-5 that can be achieved in the unloaded state of the work tool B1, depending on the ambient conditions. The adjustment angle B-5 is coordinated with the free travel Bs. The adjustment angle B-5 corresponds at most to the free travel Bs. In particular, the free travel Bs is at least 2°, and especially at least 3°, greater than the adjustment angle B-5.

[0153] When the throttle element B-16 is in position B-105, the air control element B-20 is in the closed position B-104. The adjustment angle B-5 of the throttle element B-16 corresponds at most to the free travel Bs. Adjusting the throttle element B-16 from position B-105 in the closing direction B-44 therefore only changes the free flow cross-section of the intake duct B-14, but not the free flow cross-section of the air duct B-13.

[0154] Fig. B-15 shows the arrangement when the throttle element B-16 is adjusted by more than the free travel Bs from the fully closed position B-85. When adjusted by more than the free travel Bs, the air control element B-20 is driven via the coupling device B-58 and adjusted together with the throttle element B-16.

[0155] Figs. B-16 to B-18 show an alternative embodiment of the arrangement. In this embodiment, the opening spring B-41 and the closing spring B-43 are arranged coaxially with the rotational axis B-54 of the throttle shaft B-17. The closing spring B-43 is arranged outside the housing B-57. The driver B-46 is mounted on the throttle shaft B-17. The motor B-45 acts via a gear B-90, which in the exemplary embodiment is designed as a two-stage spur gear, on the connecting part B-80, which in turn acts on the driver B-46. The function of the arrangement according to Figs. B-16 to B-18 corresponds to the function described for the previous figures. Fig. B-17 shows the arrangement when the operator actuates the control element B-5 and the throttle element B-16 is fully open. In Fig. B-18, the motor B-45 has moved the connecting part B-80 and thus the throttle shaft B-17 relative to the position in Fig. B-17 and closed the throttle element B-16.A gear wheel B-98 of the gearbox B-90 moved the connecting part B-80.

[0156] The invention further relates to a method for operating an internal combustion engine of the type specified in the preamble of claim 38, as well as a method for operating an internal combustion engine of the type specified in the preamble of claim 40, as well as an internal combustion engine.

[0157] From DE 196 09 536 A1, it is known to adjust a throttle element via a geared motor, thereby limiting the speed of the combustion engine. A sensor is provided to detect the current speed. The throttle element is adjusted in the direction of closing depending on the sensor signal.

[0158] The invention is based on the object of providing a method for operating an internal combustion engine that achieves improved engine performance. A further object of the invention is to provide an internal combustion engine with improved operating performance.

[0159] This object is achieved with respect to the method by a method having the features of claim 38. This object is also achieved with respect to the method by a method having the features of claim 40. With respect to the internal combustion engine, the object is achieved by an internal combustion engine having the features of claim 49.

[0160] It has been shown that the adjustment of the throttle element in particular takes place comparatively slowly, since otherwise the control system may tend to oscillate. Internal combustion engines often have a maximum speed at which the control device intervenes to limit the speed of the internal combustion engine, and an intervention speed above which the speed should not increase during operation in order to avoid damage to the internal combustion engine. Depending on the boundary conditions, the speed change brought about by the comparatively slow adjustment of the throttle element may be too small to prevent the speed from rising above the intervention speed. The present invention now provides for the throttle element to be controlled in the closing direction in different ways. This occurs depending on whether a first limit value or a second limit value of a speed criterion is exceeded.It is provided that the actuator is controlled in the closing direction of the throttle element, taking into account a speed criterion of the actual speed of the combustion engine as an input variable, when a first limit value of a speed criterion is exceeded. If a second limit value of the speed criterion is exceeded, it is provided that the actuator is controlled in the closing direction of the throttle element without taking into account the actual speed of the combustion engine as an input variable, over at least a partial angle range of the adjustment angle range.

[0161] By controlling the actuator in the closing direction of the throttle element without taking the actual speed of the combustion engine into account as an input variable when the second limit value of the speed criterion is exceeded, a comparatively rapid adjustment of the throttle element in the closing direction can be achieved. This makes it easy to avoid oscillations in the control loop when adjusting to a maximum speed, and also prevents the speed from rising above the intervention speed. Indirect consideration of the actual speed of the combustion engine, for example, by considering the behavior of a speed-dependent control system such as an ignition spark timing control, is also not provided for.

[0162] A speed criterion is, in particular, a speed of the internal combustion engine, in particular the actual speed or an average value of the actual speed, for example, the average value of the speed over several engine cycles, or a speed gradient of a speed of the internal combustion engine, for example, the speed gradient of the actual speed over a specified period of time. Other speed criteria can also be provided.

[0163] In particular, the first speed criterion is a first speed of the internal combustion engine, and the second speed criterion is a second speed of the internal combustion engine. The second speed is, in particular, higher than the first speed.

[0164] The actual speed is, in particular, the current speed of the internal combustion engine. The actual speed can be determined in a suitable manner based on a sub-range of a revolution, based on one revolution, or based on several revolutions of the internal combustion engine.

[0165] In particular, the actuator is controlled according to a first control method in the closing direction of the throttle element when a first limit value of a speed criterion is exceeded. The actuator is controlled, in particular, in the closing direction of the throttle element without taking the actual speed of the combustion engine into account as an input variable over at least a partial angle range of the adjustment angle range according to a second control method when a second limit value of a speed criterion is exceeded.

[0166] In particular, the throttle element is adjusted more quickly in the closing direction when the actuator is controlled according to the second control method than when the actuator is controlled according to the first control method. The faster control of the actuator in the closing direction according to the second control method represents an independent inventive concept that solves the stated problem regardless of whether the actual speed of the internal combustion engine is taken into account in the first and / or the second control method. Faster control of the actuator in the closing direction according to the second control method can be achieved, for example, by not taking the actual speed of the internal combustion engine into account as an input variable when controlling the actuator.Alternatively, different adjustment speeds can be achieved, for example, by different time elements in the control methods, by different predetermined adjustment speeds or by other suitable measures.

[0167] In the event of a load drop from full load to below 30% of full load, the throttle element is adjusted in the closing direction, particularly over a partial angle range of at least 5°, in particular of at least 25°, when the actuator is controlled according to the second control method. In the event of a significant load drop and control according to the second control method, the throttle element is therefore adjusted over a comparatively large partial angle range. This allows a quick, effective reduction in the speed to be achieved in a simple manner.

[0168] In particular, it is provided that the first control method and the second control method are carried out independently of the position of the throttle element. The position of the throttle element is therefore not an input variable for the control of either the first control method or the second control method. The control methods can be open-loop or closed-loop control methods. Closed-loop control methods are control methods in which the output variable is fed back and continuously influences itself during the control cycle. In contrast, no feedback occurs in a control method.

[0169] It can be provided that the actuator is designed only to control the throttle element in the closing direction of the throttle element. Alternatively, it can be provided that the actuator is designed to control the throttle element in both the closing direction and the opening direction of the throttle element.

[0170] In particular, the actuator for limiting the speed of the internal combustion engine is controlled according to the first control method and according to the second control method. Accordingly, both the first control method and the second control method preferably serve to limit the speed of the internal combustion engine. Alternatively or additionally, the first control method and the second control method can be used for other purposes, for example, to prevent the internal combustion engine from remaining in an engagement speed range of a centrifugal clutch and thus preventing excessive clutch wear.

[0171] The actuator is controlled by the control device to close the throttle element, in particular until at least one termination criterion is reached. In particular, the at least one termination criterion is also a speed criterion. However, it can also be provided that a termination criterion is a different criterion, for example a position of the throttle element being reached or the expiration of a predetermined time. A termination criterion for controlling the actuator according to the first control method is, in particular, the second speed criterion being exceeded. An alternative or supplementary termination criterion after the first limit value of the speed criterion has been exceeded is, in particular, the first speed criterion being undershot. A termination criterion after the second limit value of the speed criterion has been exceeded is, in particular, the second limit value of the second speed criterion being undershot.

[0172] It can be provided that the internal combustion engine has means for detecting the position of the throttle element. During operation of the internal combustion engine, in particular the position of the throttle element is determined. After the second limit value of the speed criterion is exceeded, it can be provided in particular that the throttle element is adjusted by a predetermined partial angular range or until a termination criterion is reached. Alternatively, it can be provided that the throttle element is adjusted to a predetermined position if the second limit value of the speed criterion is exceeded. The predetermined position of the throttle element is in particular a position of the throttle element that was stored during a controlled operation of the internal combustion engine in which the first speed criterion or the second speed criterion is not exceeded.Control mode is, in particular, operation of the internal combustion engine in which less than 50% of the maximum load is applied to the internal combustion engine. In particular, the throttle element is adjusted to the specified position when the second limit value of the speed criterion is exceeded. The specified position is therefore the position stored in control mode to which the throttle element is adjusted. However, it can also be provided that the specified position is permanently stored in the control device or that a specified position is stored in the control device according to other criteria.

[0173] In particular, the control device controls an ignition device of the internal combustion engine such that the ignition point is retarded after the second speed criterion is exceeded until a termination criterion is met. Alternatively or additionally, the control device can control the ignition device of the internal combustion engine such that the ignition is suspended in individual engine cycles after the second speed criterion is exceeded until a termination criterion is met. The termination criterion can be, for example, the second speed criterion being undershot or the speed falling below a certain speed. Because the control device, in addition to controlling the throttle element, also controls the ignition device of the internal combustion engine to reduce the speed of the internal combustion engine, an increase in the speed above an intervention speed can be avoided.

[0174] In one embodiment, the first speed criterion and the second speed criterion are a maximum speed and an engagement speed. The maximum speed is in particular lower than the engagement speed. Alternatively, the speed criteria can be speed gradients. A combination of speed and speed gradient can also be provided as a speed criterion. If the speed criteria are a maximum speed and an engagement speed, the engagement speed can in particular be less than 2,000 rpm, in particular less than 1,000 rpm, higher than the maximum speed. In particular when the engagement speed and the maximum speed are comparatively close to one another, for example less than 2,000 rpm, a second control method is provided which enables rapid adjustment of the throttle element and thus a rapid reduction in the speed.

[0175] For an internal combustion engine, it is provided in particular that a first control method for the actuator is stored in the control device of the internal combustion engine, which is designed to control the actuator to close the throttle element when a first limit value of a speed criterion is exceeded, and that a second control method is stored in the control device, which is designed to control the actuator in such a way that the throttle element is adjusted in the closing direction over at least a partial angular range of an adjustment angle range without taking into account the actual speed of the internal combustion engine as an input variable, and that the control device is designed to control the actuator according to the second control method when a second limit value of a speed criterion is exceeded.

[0176] The throttle element can be easily controlled and adjusted if the actuator includes an electric motor.

[0177] Advantageously, the internal combustion engine comprises a fuel valve for supplying fuel, which is controlled by the control device.

[0178] In particular, the internal combustion engine has an exhaust silencer with a catalytic converter. Especially with exhaust silencers with catalytic converters, effective speed limitation must be ensured to prevent overheating and thus damage to the catalytic converter during operation. This can be easily achieved by providing two different control methods for limiting the speed.

[0179] Embodiments of the invention are explained below with reference to the drawings. Fig. 11 shows a schematic representation of a hand-held implement with an internal combustion engine,

[0180] Fig. C-2 is a schematic representation of the combustion engine of the

[0181] Tool from Fig. Cl,

[0182] Fig. C-3 is a schematic representation of a throttle element in an intake duct,

[0183] Fig. C-4 is a schematic representation of a first control method,

[0184] Fig. C-5 is a schematic representation of an exemplary curve of the load on the internal combustion engine and the associated possible curve of the speed and the position of the throttle element when actuated according to the first actuation method shown in Fig. C-4,

[0185] Fig. C-6 is a schematic representation of the air mass flow through the combustion engine versus the speed for the curve of the position of the throttle element shown in Fig. C-5,

[0186] Fig. C-7 is a schematic representation of a second control method,

[0187] Fig. C-8 is a schematic representation of an exemplary curve of the load on the combustion engine and the associated possible curve of the speed and the position of the throttle element when controlled according to the first and second control methods,

[0188] Fig. C-9 is a schematic, exemplary representation of the air mass flow rate through the combustion engine over the speed for the curve of the position of the throttle element shown in Fig. C-8,

[0189] Fig. C-10 is a flowchart for a method for controlling a

[0190] internal combustion engine.

[0191] Fig. C1 schematically shows a hand-held tool C-25. In Fig. C1, a chainsaw is depicted as the hand-held tool C-25. However, the hand-held tool C-25 can also be another tool, for example a power cutter, a brush cutter, a lawnmower, or the like. The hand-held tool C-25 has a housing C-26 in which an internal combustion engine C1 is arranged. To guide the tool C-25, a handle C-27 with operating elements C-28 is attached to the housing C-26, in particular via vibration-damping elements. In particular, one of the operating elements C-28 is a throttle lever which acts on a throttle lever C-30 via an actuating device C-29. The throttle lever C-30 is coupled in particular to a throttle element C-17. The throttle element C-17 (Fig. C-2) can be adjusted by an operator via this operating element C-28 and the actuating device C-29.In the exemplary embodiment, a carburetor C-15 is provided as the fuel supply device, and the throttle element C-17 is arranged in the carburetor C-15. However, a different type of fuel supply may also be provided.

[0192] The internal combustion engine C-1 has an intake port C-14. The throttle element C-17 is located in a section of the intake port C-14. Using the control element C-28, an operator can control the free flow cross-section of the intake port C-14.

[0193] The internal combustion engine C-1 has a cylinder C-2 in which a piston C-5 is mounted in a reciprocating manner. The piston C-5 delimits a combustion chamber C-3 formed in the cylinder C-2. The piston C-5 drives a crankshaft C-7, which is mounted in a crankcase C-4 such that it can rotate about a rotational axis C-8, via a connecting rod C-6. The rotational axis C-8 is shown in Fig. C-2. The intake port C-14 opens at the cylinder C-2 with an inlet opening C-9, which is controlled by the piston C-5. The inlet opening C-9 opens into the crankcase C-4 in the region of the top dead center of the piston C-5. An exhaust opening C-10, which is formed in the cylinder bore and controlled by the piston C-5, leads from the combustion chamber C-3.

[0194] As shown in Fig. C1, an exhaust port C-33 adjoins the exhaust port C-10, which leads into an exhaust silencer C-23. In this exemplary embodiment, the exhaust silencer C-23 includes a catalyst C-24 for exhaust gas aftertreatment. The catalyst C-24 has at least a partial catalytic coating. Instead of the catalyst C-24, or in addition to it, a particulate filter, for example in the form of a washcoat-coated or uncoated wire body, can also be provided.

[0195] Fig. C-2 shows the internal combustion engine C-1 in detail. At least one transfer channel C-12 with at least one transfer window C-13 opens into the combustion chamber C-3. The transfer channel C-12 connects the crankcase C-4 in the region of the bottom dead center of the piston C-5 with the combustion chamber C-3. The internal combustion engine C-1 draws in air via an air filter C-16 and the intake channel C-14. A section of the intake channel C-14 is formed in a carburetor C-15. Instead of the carburetor C-15, another type of fuel supply device can also be provided. In the exemplary embodiment, the carburetor C-15 comprises a valve C-19 for controlling the supplied fuel quantity. The valve C-19 is connected to fuel openings C-18 opening into the intake channel C-14. It may be provided that the entire amount of fuel supplied to the intake port C-14 is controlled by the valve C-19. Alternatively, only a portion of the supplied amount of fuel may be controlled by the valve C-19.The valve C-19 is in particular an electromagnetic valve.

[0196] Valve C-19 is controlled by a control device C-20. The internal combustion engine C-1 has a spark plug C-11 extending into the combustion chamber C-3. The energy for generating the spark at the spark plug C-11 is generated by an ignition device C-22. The control device C-20 can be integrated into the ignition device C-22 or formed separately from it.

[0197] During operation of the internal combustion engine C-1, air is sucked into the intake duct C-14 through the air filter C-16 in the region of top dead center of piston C-5. In the exemplary embodiment, fuel is fed to the air in the carburetor C-5. The fuel / air mixture thus formed is sucked into the interior of the crankcase C-4 via the inlet opening C-9. During the downward stroke of the piston C-5, the fuel / air mixture in the crankcase C-4 is compressed. During the downward stroke, the piston C-5 opens at least one transfer window C-13. As soon as the transfer window C-13 is open, a fuel / air mixture flows from the crankcase C-4 into the combustion chamber C-3. The fuel / air mixture in the combustion chamber C-3 is compressed by the upwardly moving piston C-5. In the region of top dead center of the piston C-5, the mixture is ignited by the spark plug C-11. The subsequent combustion accelerates the piston C-5 towards the crankcase C-4.As soon as the exhaust port C-10 is opened by the descending piston C-5, the exhaust gases flow from the combustion chamber C-3 through the exhaust port C-33 into the exhaust silencer C-23 and from there into the environment.

[0198] In the exemplary embodiment, the internal combustion engine C1 is a two-stroke engine having only one intake port. Alternatively, the internal combustion engine C1 can be a two-stroke engine operating with a scavenging pre-filter, which, in addition to the intake port, has at least one air port for supplying scavenging pre-filter air, or whose intake port is divided downstream of the throttle element C-17 into at least one air port and one mixture port.

[0199] To influence the speed of the internal combustion engine Cl, the internal combustion engine Cl has an actuator C-21 which can adjust the position of the throttle element C-17. The actuator C-21 can pivot the throttle element C-17 at least in a closing direction C-32. When the throttle element C-17 is pivoted in the closing direction C-32, the free flow cross-section of the intake channel C-14 is reduced. To adjust the throttle element C-17, the actuator C-21 in the exemplary embodiment has an electric motor C-31. In addition, it can be provided that the actuator C-21 can control the throttle element C-17 in an opening direction C-34 opposite to the closing direction. When the throttle element C-17 is pivoted in the opening direction C-34, the free flow cross-section of the intake channel C-14 increases.

[0200] A first control method C-41 and a second control method C-42 are stored in the control device C-20, as schematically illustrated in Fig. C-2. The illustration in Fig. C-2 is schematic and simplified. The separate illustration of the first control method C-41 and the second control method C-42 merely indicates that the program code stored in the control device C-20 is designed to control the actuator C-21 according to the first control method C-41 and, if no control occurs according to the first control method C-41, according to the second control method C-42. However, the first control method C-41 and the second control method C-42 do not have to be spatially separated or stored separately from one another in the program code.

[0201] Fig. C-3 shows the arrangement of the throttle element C-17 in the intake duct C-14 in detail. Fig. C-3 shows the position of the throttle element C-17 in the fully closed position with a solid line. The position y of the throttle element C-17 is specified as the pivot angle from the fully open position of the throttle element C-17. The fully open position is shown with a dashed line. From the closed to the fully open position, the throttle element C-17 can be adjusted within an adjustment angle range Ca. Typically, the adjustment angle range Ca is less than 90° and is, for example, approximately 75°. In order to achieve rapid closing of the throttle element C-17, the throttle element is preferably closed by a partial angle range C-ß according to the second control method C-42, which partial angle range is at least 5°, in particular at least C-25°.These partial angle ranges C-ß refer to a load drop from maximum load C-Pmax to less than 30% of the maximum load C-Pmax. 30% of the maximum load C-Pmax can, for example, be the minimum load on the combustion engine C1. The load drop refers in particular to when a tool of the C-25 work device is brought out of engagement with a workpiece from maximum load, for example when a saw chain of the C-25 work device leaves the cut from full load. The position of the throttle element C-17 after an adjustment by the partial angle range C-ß from the fully open position is shown in Fig. C-3 with a dotted line.

[0202] Fig. C-4 shows a schematic of the first control method C-41. The control method C-41 has a reference variable Cw(t). The reference variable Cw(t) is constant in the exemplary embodiment. In the exemplary embodiment, the reference variable Cw(t) is a maximum speed nl. Alternatively, the reference variable Cw(t) can also be another speed criterion, for example a speed gradient. If a first limit value C-gl of a speed criterion is exceeded, the actuator C-21 is controlled according to the first control method C-41 and counteracts any deviation of the reference variable Cw(t) from its setpoint. The control deviation Ce(t) forms the input variable for the control device C-20. The control deviation Ce(t) is determined as the difference between the reference variable Cw(t) and the speed Cn(t). The speed Cn(t) corresponds to the actual speed Cn at the respective point in time. Other influencing variables can also be taken into account for determining the control deviation Ce(t).The control device C-20 determines a manipulated variable Cu(t), for example, a partial angle range C-ß of the adjustment angle range Ca, by which the throttle element C-17 is to be adjusted. The throttle element C-17 is then adjusted by this partial angle range C-ß in a control system C-35. A disturbance variable Cd(t), for example, a change in the load CP on the combustion engine Cl, can also be taken into account in the control system C-35.

[0203] The throttle element C-17 is adjusted in particular in the closing direction C-32 (Fig. C-2) until a termination criterion is met. The termination criterion can be, for example, reaching a predetermined position C-yl of the throttle element C-17, adjustment by the predetermined partial angle range C-ß, falling below a first limit value g1 of a speed criterion, or exceeding a second limit value g2 of a speed criterion. The output variable Cy(t) of the controlled system C-35 is a controlled variable, for example the actual speed n of the combustion engine C1. In the first control method C-41, the actual speed n of the combustion engine C1 is taken into account as an input variable for the reference variable Cw(t), as shown in Fig. C-3. The actual speed n is fed back. The first control method C-41 is therefore a control method.

[0204] Fig. C-5 shows the curve of actual speed Cn, throttle valve angle Ca and load CP over time Ct in the exemplary sequence of the first control method C-41 shown in Fig. C-5. The control method is activated in particular when the actual speed n exceeds an activation speed C-n3. Up to a time C-tl, the load CP is the maximum load C-Pmax, as curve C-38 shows. At time C-tl, the load CP drops from the maximum load C-Pmax to a load C-Pmin, in the exemplary embodiment to the minimum load. As curve C-37 shows, the throttle element C-17 is maximally open at time C-tl. The position Cy (Fig. C-4) of the throttle element C-17 corresponds to a pivot angle of 0° to the fully open position. The actual speed Cn is below the first limit value C-gl of the first speed criterion, in the exemplary embodiment below the maximum speed C-nl.The load drop at time C-tl can result, for example, from the saw chain of a chainsaw or the cutting wheel of a power cutter being moved out of the cut. This results in a sudden drop in the load CP from the maximum load C-Pmax to the minimum load Pmin. This sudden load drop results in an increase in speed, as shown in curve C-36.

[0205] In the exemplary embodiment, the first limit value C-gl of the first speed criterion, in the exemplary embodiment below the maximum speed C-nl

[0206] At time C-t2, the first speed criterion C-gl, in the exemplary embodiment the maximum speed C-nl, is exceeded. The control device C-20 then begins to control the actuator C-21 according to the first control method C-41 and to close the throttle element C-17 according to the curve C-37. The actual speed n is taken into account in each case, as shown in Fig. C-4. Because the actual speed n is taken into account, the throttle element C-17 closes gradually and comparatively slowly. The speed Cn(t) initially continues to rise until it reaches a plateau and begins to fall at time C-t3. Only at time t4 has the actual speed Cn reached the maximum speed C-nl. At every time t, the speed is below the intervention speed n2.The intervention speed n2 is in particular the speed at which the control device C-20 begins to retard the ignition timing of the spark plug Cl 1 and / or to suspend the ignition during individual engine cycles in order to prevent a further increase in the speed.

[0207] In the exemplary embodiment, the first limit value C-gl of the first speed criterion and the second limit value g2 of the first speed criterion are speed values, namely the maximum speed C-nl and the intervention speed C-n2. If the limit values ​​C-gl and C-g2 are speed values, the first limit value C-gl is in particular smaller than the second limit value C-g2. Alternatively, the speed criterion can also be another value derived from the speed, for example a speed gradient. In particular, the control of the actuator C-21 is not always active. In particular, the control of the actuator C-21 is only active within predetermined speed limits. Outside of these speed limits, the position of the throttle element C-17 is determined in particular solely by the position specified by the operator via the control element C-28.

[0208] In the exemplary embodiment, the control of the actuator C-21 is activated when an activation speed C-n3 is exceeded. In particular, the control of the actuator C-21 is deactivated when a deactivation speed C-n4 is undershot. The activation speed C-n3 and the deactivation speed C-n4 can be the same speed. If the first speed criterion C-gl is a speed, the activation speed C-n3 and the deactivation speed n4 are in particular below the first speed criterion C-gl, in particular below the maximum speed C-nl. If the second speed criterion C-g2 is a speed, the activation speed C-n3 and the deactivation speed n4 are in particular below the second speed criterion C-g2, in particular below the intervention speed C-n2.

[0209] If the activation speed C-n3 and the deactivation speed C-n4 are different, it is provided that the activation speed C-n3 is greater than the deactivation speed C-n4. Instead of the activation speed C-n3 and the deactivation speed n4, other speed criteria C-g3 and C-g4 can also be provided for activating and deactivating the control of the actuator C-21.

[0210] Fig. C-6 shows the curve of the air mass flow m as a function of the speed C-n(t). Curve C-39 shows the curve of the air mass flow m over the speed C-n(t) at full load. The maximum power CL is delivered at a speed which is slightly below the maximum speed nl. When the maximum speed C-nl is reached, the control device C-20 begins to close the throttle element C-17. This reduces the air mass flow m along curve C-40. The speed Cn remains below the intervention speed C-n2 and drops to the maximum speed C-nl as the air mass flow m drops. As soon as the maximum speed C-nl is reached, the first control process C-41 can be terminated. Alternatively, instead of reaching the maximum speed C-nl, other termination criteria can also be used as termination criteria for terminating the first control process C-41.Other termination criteria may include, for example, reaching a predefined speed gradient or reaching another speed, such as falling below the intervention speed C-n2 or falling below a deactivation speed C-n4 that is below the maximum speed C-n1. In the exemplary embodiment, it is provided that the control of the actuator C-21 is deactivated when the deactivation speed C-n4 is undershot until the activation speed C-n3 is exceeded again.

[0211] If the speed Cn(t) increases up to an intervention speed C-n2, a second control method C-42, which is shown schematically in Fig. C-7, becomes active. The second control method C-42 causes the throttle element C-17 to close very quickly. For this purpose, it is provided that the second control method C-42 does not take the actual speed Cn of the combustion engine C1 into account as an input variable. The second control method C-42 is therefore a control method. The maximum speed C-n1 also forms the reference variable Cw(t) in the second control method C-42. The reference variable Cw(t) can also be a different speed criterion in the second control method.

[0212] The reference variable Cw(t) forms the input signal for the control device C-20. The control device C-20 derives a manipulated variable Cu(t) from the reference variable Cw(t). The manipulated variable Cu(t) can, for example, be an angle by which the throttle element C-17 is to be adjusted, or a predetermined end position of the throttle element C-17. The throttle element C-17 is adjusted accordingly in the control path C-43, possibly taking into account other disturbance variables Cd(t) such as a change in load. The output variable Cy(t), i.e. the control variable, is not taken into account when determining the intended adjustment of the throttle element C-17. There is no feedback of the output variable Cy(t). Figs. C-8 and C-9 show the resulting curves C-36 to C-39. The designations partially correspond to those for Figs. C-5 and C-6.At a first time C-tl, the load CP is reduced from a maximum load C-Pmax to a minimum load C-Pmin, as shown by curve C-38. The actual speed Cn then increases to a maximum speed C-nl. The maximum speed C-nl is reached at a second time t2. At this second time C-t2, the control device C-20 begins to close the throttle element C-17 according to the first control method C-41. Since the closing movement of the throttle element C-17 occurs comparatively slowly, the actual speed n can continue to increase and reaches an engagement speed C-n2 at a time C-t3. The control device C-20 then begins to close the throttle element C-17 according to the second control method C-42 without taking the actual speed Cn into account. As a result, the closing movement of the throttle element C-17 can occur very quickly.The speed at which the throttle element C-17 is closed is greater when the actuator C-21 is controlled according to the second control method C-42 than when the actuator C-21 is controlled according to the first control method C-41. In particular, the throttle element C-17 is closed at maximum speed when the actuator is controlled according to the second control method C-42.

[0213] As Fig. C-8 clearly shows, the adjustment speed of the throttle element C-17 when controlled according to the second control method C-42, i.e. between the third time t3 and the fourth time C-t4, is significantly greater than the adjustment speed when controlled according to the first control method C-41, i.e. between the second time C-t2 and the third time C-t3. Due to the rapid closing of the throttle element C-17, the air mass flow m through the intake duct C-14 decreases considerably and the speed Cn(t) cannot increase any further. To support this, the spark plug C11 can be controlled in such a way that the ignition timing is retarded or the ignition is suspended in individual engine cycles in order to additionally limit the speed Cn(t). At the fourth time C-t4, the throttle element C-17 was adjusted to a predetermined position C-yl, as shown in Fig. C-8.At this time C-t4, the control of the actuator C-21 is terminated according to the second control method C-42. Reaching a predetermined position or adjusting by a predetermined partial angle range C-ß of the adjustment angle range Ca can be the termination criterion for the second control method C-42. Subsequently, in the exemplary embodiment, the throttle element C-17 continues to be controlled according to the first control method C-41 until the termination criterion for the first control method C-41 is reached. In the exemplary embodiment, this is the drop in the actual speed Cn to the maximum speed nl at a fifth time t5.

[0214] Fig. C-9 shows the course of the air mass flow m during the process according to Fig. C-8. At the second time t2, the throttle element C-17 is closed. Above the maximum speed nl, the air mass flow m does not continue according to curve C-39, but decreases according to curve C-40. At the third time t3, the intervention speed n2 is reached and the throttle element C-17 closes very quickly until the fourth time t4. As a result, the actual speed n does not increase any further. At the fourth time t4, the second control method C-42 is ended. The throttle element C-17 continues to be closed until the fifth time t5, namely by controlling the actuator C-21 according to the first control method C-41, until the maximum speed nl is reached.The termination criterion for the second control method C-42 is selected in particular such that the throttle element C-17 is closed to such an extent when the second control method C-42 is terminated that no further increase in speed above the intervention speed C-n2 can occur.

[0215] Fig. C-10 shows a flowchart for the procedure. In method step C-51, a check is carried out to determine whether the actual speed Cn or a speed gradient C-An or another speed criterion exceeds a limit value C-gl for this speed criterion. If the limit value C-gl is exceeded, the control device C-20 begins, in method step C-52, to control the actuator C-21 to close the throttle element C-17 according to the first control method C-41. While the first control method C-41 is being carried out, a continuous check is carried out in method step C-53 to determine whether the actual speed Cn, the speed gradient An or another speed criterion falls below the first limit value C-gl. As soon as the actual speed n or the speed gradient An falls below the first limit value C-gl, method step C-51 is carried out and a check is carried out to determine whether the speed n or the speed gradient C-An exceeds the first limit value C-gl again.

[0216] In process step C-54, which is executed if the speed Cn or the speed gradient C-An remains above the first limit value C-gl, a check is made to determine whether the speed n or the speed gradient C-An exceeds a second limit value C-g2. If this is not the case, process step C-52, i.e., the first control method C-41 for controlling the actuator C-21, is executed. If the actual speed Cn or the speed gradient C-An rises above the second limit value C-g2, the second control method C-42 for controlling the actuator C-21 is executed in process step C-55, and the throttle element C-17 is closed at maximum speed.In process step C-56, a check is made to determine whether a termination criterion has been met, for example, whether the actual speed n or the speed gradient C-An falls below the second limit value C-g2 of the engagement speed C-n2, or alternatively, whether a specified position of the throttle element C-17 has been reached or the throttle element C-17 has been adjusted by a specified partial angle range C-ß. If the termination criterion is met, the process returns to process step C-51.

[0217] The invention further relates to a method for operating an internal combustion engine of the type specified in the preamble of claim 51 and to a working device with an internal combustion engine.

[0218] US 2021 / 0254566 A1 discloses a work device having a speed limiting device. To limit the speed, a controller acts on both an air control element and a throttle element. The throttle element and the air control element can be opened or closed by the controller depending on the engine's operating point to set a desired speed.

[0219] The invention is based on the object of providing an improved method for operating an internal combustion engine. A further object of the invention is to provide a work device with an improved internal combustion engine.

[0220] This object is achieved with respect to the method by a method having the features of claim 51. With respect to the working device, the object is achieved by a working device having the features of claim 55.

[0221] Such internal combustion engines can be used, for example, in hand-held tools such as chainsaws, cut-off machines, or the like. If the load on the engine is low, for example, when a tool driven by the internal combustion engine is not in the cut, and the operator fully operates an actuating device, such as a throttle lever, the speed limiter, in particular, is active. The actuator closes the throttle element relative to the position set by the operator in order to regulate the speed to the desired target final speed. If the load taken off the internal combustion engine increases, for example, because the tool penetrates a workpiece, the speed of the internal combustion engine can drop below the target final speed. The actuator will then reopen the throttle element as long as the operator operates the actuating device accordingly. This is the case at least in part of the adjustment angle range.The partial angle range includes, in particular, at least one opening angle at which the throttle element is largely or completely closed. Opening the throttle element is intended to cause the engine speed to increase again.

[0222] If the throttle element is largely closed, the combustion engine reacts very sensitively to changes in the throttle element's opening angle. A largely closed throttle element, i.e., a very small opening angle of the throttle element, occurs at a speed close to the target maximum speed, especially when only a small load is being taken off the combustion engine. This can be particularly the case with hand-held tools when the tool is not engaging a workpiece and the operator fully activates the actuating device, for example, by fully pressing a throttle lever.

[0223] If the load taken from the combustion engine increases from this state, the speed drops sharply and the actuator counteracts this by adjusting the throttle element in the opening direction in order to increase the speed again. This is particularly the case as long as the opening angle of the throttle element remains below the throttle angle specified by the operator via the actuating device. If this adjustment of the throttle element occurs very slowly and at the same time the load on the combustion engine increases comparatively sharply, the speed of the combustion engine can drop undesirably sharply. This sharp drop in speed is undesirable. The sharp drop in speed is particularly undesirable if the actuator is only active in a speed range below the target speed and the speed leaves the range in which the actuator is active.This can cause the throttle element to be abruptly adjusted to the larger opening angle specified by the operator. Opening the throttle element again leads to an increase in the released power, whereupon the combustion engine accelerates abruptly and returns to the speed range in which the actuator is active. This leads to rough running of the combustion engine and severe speed fluctuations.

[0224] It is provided that the adjustment speed of the throttle element when adjusted by the actuator in the opening direction after falling below a first speed limit is at least twice as high as the adjustment speed of the throttle element when adjusted by the actuator in the opening direction above the first speed limit. The invention therefore provides two different adjustment speeds for adjusting the throttle element when adjusted by the actuator in the opening direction of the throttle element. A first, lower adjustment speed is provided for adjusting the throttle element in the opening direction between the target final speed and the first speed limit. A second, higher adjustment speed is provided after falling below the first speed limit.

[0225] The adjustment speed of the throttle element during adjustment by the actuator in the opening direction of the throttle element after the first speed limit has been undershot is, in particular, 2 to 10 times the adjustment speed of the throttle element during adjustment by the actuator in the opening direction above the first speed limit. In particular, the adjustment speed after the first speed limit has been undershot is 3 to 0 times the adjustment speed above the first speed limit.

[0226] In particular, when a second speed limit is undershot, the actuator is put into an inactive state, so that the throttle element is adjusted to a position corresponding to the opening angle set by the operator via the actuating device, wherein the second speed limit is below the first speed limit. Below the second speed limit, the speed of the combustion engine is therefore not regulated by the actuator. The resulting speed results in particular from the position of the throttle element set by the operator and the load applied to the combustion engine. The first speed limit is in particular 500 rpm to 3,000 rpm, in particular 500 rpm to 2,000 rpm below the target final speed of the combustion engine.

[0227] The internal combustion engine has a control device for controlling the actuator. The control device is connected to means for detecting the rotational speed of the internal combustion engine. The control device can also control other components of the internal combustion engine, for example, a fuel valve, the ignition device, or the like. The control device can be connected to other sensors, for example, a pressure sensor for detecting a pressure of the internal combustion engine, in particular the crankcase pressure, and / or a temperature sensor for detecting a temperature of the internal combustion engine, for example, the temperature in the crankcase and / or the ambient temperature. The target final rotational speed of the internal combustion engine is, in particular, a rotational speed stored in a control device of the internal combustion engine.

[0228] The method is particularly intended for a two-stroke engine. It can be provided that the internal combustion engine has only a single intake port. Alternatively, it can be provided that the internal combustion engine has, in addition to the intake port in which the throttle element is arranged, a further intake port, which is provided in particular for supplying purge air to at least one transfer port of the internal combustion engine.

[0229] The internal combustion engine, in particular, has a fuel supply device. The fuel supply device can be a carburetor. The fuel can be metered solely based on the negative pressure in the intake port. Alternatively, the carburetor can be provided with a fuel valve, in particular an electromagnetically actuated valve. In a carburetor with an electromagnetic valve, the supplied fuel quantity can be influenced via the control device of the internal combustion engine in addition to the negative pressure in the intake port.

[0230] Instead of a carburetor, the fuel supply can be via a fuel valve, in particular an electromagnetically operated fuel valve. The fuel valve can supply the fuel, for example, to the intake port, the crankcase interior, or one or more transfer ports of the internal combustion engine. The fuel valve is, in particular, a fuel valve operating with a slight overpressure of less than 5 bar. The throttle element can be a throttle flap. Alternatively, the throttle element can also be a control cylinder. This is particularly provided when the fuel supply is via a carburetor designed as a cylinder carburetor.

[0231] The internal combustion engine is, in particular, the drive motor in a hand-held, especially hand-carried, tool. The internal combustion engine is, in particular, the drive motor in a chainsaw, a power cutter, or the like.

[0232] For a working device, it is provided that the working device has an internal combustion engine that is designed to be controlled according to the method according to the invention. The working device is, in particular, a cut-off machine.

[0233] The actuator comprises, in particular, an electric motor. In particular, the electric motor is designed to pivot the throttle element in the opening and closing directions.

[0234] In particular, the throttle element is a throttle valve. Especially with throttle valves, the change in the free flow cross-section in the closed position of the throttle element is comparatively large, even with a slight pivoting of the throttle element. Therefore, a slow adjustment of the position in the closed position and / or in the slightly open position is provided, particularly for a throttle element designed as a throttle valve.

[0235] Embodiments of the invention are explained below with reference to the drawings. They show:

[0236] Fig. Dl is a schematic sectional view of a working device,

[0237] Fig. D-2 is a schematic representation of an internal combustion engine, Fig. D-3 is a schematic representation of a throttle element arranged in the intake duct and schematically illustrated exemplary possible angular positions of the throttle element,

[0238] Fig. D-4 is a diagram which schematically and exemplarily shows the course of speed, load and opening angle of the throttle element over time when carrying out the method,

[0239] Fig. D-5 is a flow chart of the process.

[0240] Fig. D1 schematically shows a working device D-225. In the illustrated embodiment, the working device D-225 is a chainsaw. The working device D-225 can also be another working device, for example, a power cutter or the like. In the illustrated embodiment, the working device D-225 has a guide bar D-235 on which a saw chain D-236 is arranged circumferentially. The saw chain D-236 is the tool of the working device D-225. If the working device D-225 is a power cutter, the tool is a rotating cutting disc.

[0241] The working device D-225 has a housing D-226 to which at least one handle is attached. In the exemplary embodiment, a handle D-227 is provided, which is designed as a rear handle. An upper handle and / or a handle tube can also be provided. Operating elements D-228 are provided on the handle D-227. The working device D-225 has an internal combustion engine D-201. The internal combustion engine D-201 is arranged in particular in the housing D-226.

[0242] A control element D-228 is designed as a throttle lever and forms part of an actuating device D-229 for controlling the internal combustion engine D-201. In the exemplary embodiment, the internal combustion engine D-201 is designed as a two-stroke engine. The internal combustion engine D-201 has a cylinder D-202 in which a combustion chamber D-203 is formed. A piston D-205 is reciprocatingly mounted in the cylinder D-202. The piston D-205 drives a crankshaft D-207 via a connecting rod D-206. The crankshaft D-207 is rotatably mounted about a rotational axis D-208 in a crankcase D-204 of the internal combustion engine D-201.

[0243] The internal combustion engine D-201 has an inlet port D-209 leading into the crankcase D-204. The inlet port D-209 is controlled in particular by the piston D-205. The internal combustion engine D-201 has an outlet port D-210 leading from the combustion chamber D-203. The outlet port D-210 is controlled in particular by the piston D-205. A spark plug D-211 extends into the combustion chamber D-203. Transfer channels D-212 with transfer windows D-213 open into the combustion chamber D-203. The transfer channels D-212 fluidly connect the interior of the crankcase D-204 with the combustion chamber D-203 in the region of the bottom dead center of the piston D-205. The bottom dead center of piston D-205 is the end position of piston D-205 closest to crankcase D-204.

[0244] The exhaust port D-210 is connected to an exhaust duct D-233, which can lead into an exhaust silencer D-223. The exhaust silencer D-223 can be provided with a catalytic converter D-224. It can also be provided that the exhaust silencer D-223 does not have a catalytic converter D-224.

[0245] An intake duct D-214 opens into the intake port D-209. The free flow cross-section of the intake duct D-214 is determined by the opening angle y of the throttle element D-217.

[0246] Fig. D-2 shows the structure of the internal combustion engine D-201 in detail. As Fig. D-2 shows, the intake duct D-214 is connected to an air filter D-216. During operation, air is drawn in via the air filter D-216. The internal combustion engine D-201 comprises a carburetor D-215. In the exemplary embodiment, fuel openings D-218 in the carburetor D-215 open into the intake duct D-214. The throttle element D-217 is pivotally mounted in the intake duct D-214, in the exemplary embodiment in the carburetor D-215. Instead of via a carburetor D-215, the fuel can also be supplied in another way, for example via a fuel valve. In this case, the throttle element D-217 is also mounted in the intake duct D-214.

[0247] To increase the free flow cross-section, the throttle element D-217 must be pivoted in an opening direction D-234. To decrease the free flow cross-section, the throttle element D-217 must be pivoted in a closing direction D-232.

[0248] The actuating device D-229 actuates the throttle element D-217 in the opening direction D-234. In the closing direction, actuation occurs primarily via a spring device. The throttle element D-217 is shown schematically in Fig. D-2. The position of the throttle element D-217 is coupled to the position of a throttle lever D-230, which can be adjusted via the actuating device D-229.

[0249] The amount of fuel supplied through at least one fuel port D-218 is controlled by a valve D-219 and also depends on the negative pressure in the intake port D-214. The valve D-219 is connected to a control device D-220 of the internal combustion engine D-201, which opens and closes the valve D-219.

[0250] Alternatively, the fuel supply can also be effected via a schematically illustrated fuel valve D-219' directly into the interior of the crankcase D-204 or at another location in the internal combustion engine D-201.

[0251] An actuator D-221 is provided for the throttle element D-217. The actuator D-221 can adjust the throttle element D-217 in the opening direction D-234 and in the closing direction D-232. The actuator D-221 comprises an electric motor D-231 for adjusting the throttle element D-217. The actuator D-221 is connected to the control device D-220. To provide the power for the control device D-220 and the spark plug D-211, an ignition device D-222 is provided in the exemplary embodiment. Alternatively, the combustion engine D-201 can also have a generator for providing the ignition energy.

[0252] The structure of the D-201 combustion engine is described only as an example and shown schematically.

[0253] The internal combustion engine D-201 can also be a two-stroke engine operating with a scavenging air supply. In this case, an additional air duct is provided next to the intake duct D-214 for supplying scavenging air. The air duct can be controlled by the throttle element D-217 or another throttle element. In this case, the position of the additional throttle element can be coupled to the position of the throttle element D-217 for the intake duct D-214.

[0254] Fig. D-3 schematically shows the positions of a throttle element D-217 for a throttle element D-217 designed as a throttle valve. A throttle element D-217 designed as a roller has corresponding positions. A throttle element designed as a roller has, in particular, an approximately cylindrical base body that has at least one transverse bore, wherein the transverse bore forms an intake duct section of the intake duct D-214.

[0255] The position of the throttle element D-217 is specified as the opening angle Dy. The opening angle Dy is measured relative to an intake duct longitudinal axis D-237. The intake duct longitudinal axis D-237 is aligned in a main flow direction of the intake duct D-214. In a closed position D-243 of the throttle element D-217, the throttle element D-217 encloses an opening angle D-y2 with the intake duct longitudinal axis D-237. In the closed position D-243 of the throttle element D-217, the free flow cross-section of the intake duct D-214 is minimal. In the closed position D-243, the throttle element D-217 is shown in Fig. D-3 with a solid line. In an intermediate position D-244, shown in Fig. D-3 with a dotted line, the throttle element D-217 forms an opening angle D-yl with the intake duct longitudinal axis D-237. The opening angle D-yl is smaller than the opening angle D-y2.In the fully open position D-245, the throttle element D-217 in the exemplary embodiment encloses an opening angle Dy of 0° with the intake duct longitudinal axis D-237. In this position, the throttle element D-217 lies parallel to the intake duct longitudinal axis D-237. The free flow cross-section of the intake duct D-214 is at its maximum in this position of the throttle element D-217. In the exemplary embodiment, it is provided that the actuator D-221 is not active over the entire adjustment angle range of the throttle element D-217. The actuator D-221 is active in particular in the range between the intermediate position D-244 and the fully closed position D-243.

[0256] If the throttle element D-217 is close to the fully open position D-245 while the speed Dn is in the range of the target final speed D-nsoll or below the target final speed D-nsoll, the load is removed from the tool. The tool is in cutting. If the throttle element D-217 is close to the closed position D-243 when the target final speed D-nsoll is reached, the load is not removed from the tool. The proposed method is provided in particular for this case. In the exemplary embodiment, it is provided that the method is carried out in particular in a partial angular range D-g2 between the intermediate position D-244 and the fully closed position D-243 of the throttle element D-217. To detect the position of the throttle element D-217, a throttle sensor D-238, shown schematically in Fig. D-3, for example, is provided, which detects the rotational position of the throttle element D-217.

[0257] Fig. D-4 shows the curves for speed Dn, load DL and opening angle Dy over time Dt for an exemplary process sequence. Curve D-240 in diagram (Da) shows the curve for speed Dn. Curve D-242 in diagram (Db) shows an exemplary curve for load DL, for which the illustrated speed curve can arise. Curve D-241 in diagram (Dc) shows the curve for opening angle Dy, which can arise with this curve for load DL. Up to time D-t0, a control of the position of throttle element D-217 is shown schematically for an exemplary speed curve, not according to the invention. Speed ​​Dn fluctuates greatly. Accordingly, actuator D-221 (Fig. D-2) is alternately controlled to open and close throttle element D-217. This results in an irregular speed curve. From the time D-tO, the throttle element D-217 is adjusted only very slowly.This results in a uniform decrease of the speed n below the target final speed D-nsoll at the time D-tl (diagram (Da)).

[0258] At time D-tl, the target speed D-nsoll is undershot. The throttle element D-217 is then continuously opened at a low adjustment speed. The opening of the throttle element D-217 occurs so slowly that the speed Dn can drop comparatively sharply if the load on the tool increases, for example, because an operator moves the tool into a workpiece. The increase in load DL is shown schematically in diagram (Db) starting at time D-t2.

[0259] At time D-t3, a first speed limit D-nl is undershot (diagram (D-a). The first speed limit D-nl is below the target final speed D-nsoll.

[0260] Curve sections D-246 (diagram (Da)) and D-247 (diagram (Dc)) schematically show the course of speed Dn and throttle angle Dy when the throttle element is further adjusted at the same speed. This results in a very strong drop in speed between times D-t4 and D-t5, as curve section D-246 in diagram (Da) shows.

[0261] To prevent this sharp drop in speed, the adjustment speed for the throttle element D-217 is increased after the first speed limit D-nl is undershot. This is shown by the curve D-241 shown by the solid line in diagram (Dc). Due to the faster adjustment of the throttle element D-217 in the opening direction D-234 (Fig. D-2), the very sharp drop in speed can be prevented. In the exemplary embodiment, the speed Dn remains above a second speed limit D-n2, as shown by the solid line in diagram (Da).

[0262] When the second speed limit D-n2 is undershot, the actuator D-221 is in particular placed in an inactive state. In this inactive state, the position of the throttle element D-217 is determined solely by the position specified by the operator via the actuating device D-229. In the exemplary embodiment, the operator has fully actuated the control element D-228, designed as a throttle lever, so that the throttle element D-217 would be moved to the fully open position D-245 at time D-t4 with a speed profile according to the curve section D-246. The activation of the actuator D-221 is reset in particular after the first speed limit D-n1 is exceeded again. Other speed limits can also be provided for the activation and deactivation of the actuator D-221.

[0263] Fig. D-5 schematically shows the process flow. In a first process step D-251, as long as the speed n is above the target final speed D-nset, the throttle element D-217 is moved in the closing direction D-232 to regulate the speed Dn.

[0264] If the speed n drops below the target final speed D-nsoll, the throttle element D-217 is moved in the opening direction D-234 in process step D-252, specifically at a first adjustment speed D-vl. If the speed then rises above the target final speed D-nsoll again, process step D-251 is executed again.

[0265] If the speed Dn drops further below a first speed limit D-nl, for example because the load is removed from the tool, the throttle element D-217 is adjusted in the opening direction D-234 at a higher adjustment speed D-v2 in process step D-253. The second adjustment speed D-v2 is at least twice, in particular 2 to 10 times, the first adjustment speed vl. In particular, the second adjustment speed D-v2 is 3 to 10 times the first adjustment speed D-vl.

[0266] If the speed continues to drop below a second speed limit D-n2, actuator D-221 is set to an inactive state in process step D-254. The position of throttle element D-217 is determined solely by the position specified by the operator. Only when the speed Dn exceeds the first speed limit D-nl again is actuator D-221 set back to the active state, and the speed is adjusted to the target final speed D-nsetpoint, as described above.

[0267] In particular, the actuator D-221 is controlled in such a way that the opening angle Dy of the throttle element D-217 can never be smaller than the opening angle Dy specified by the operator. Therefore, the actuator D-221 cannot open the throttle element D-217 further than specified by the operator. The adjustment toward the fully open position D-245 is limited by the operator's command.

[0268] The actuator D-221 is controlled, in particular, via a PI controller. In order to achieve the different adjustment speeds D-vl and D-v2 of the throttle element D-217, it can be provided, for example, that the P and I components of the controller are designed to be speed-dependent. Alternatively or additionally, it can be provided to provide speed-dependent control of the actuator D-221 in addition to the PI controller. A PI controller with small P and I components is intended in particular for tools with a comparatively high mass inertia. If no load is removed from the tool with these tools, the throttle element D-217 must be moved very far towards the fully closed position D-243 to set the target final speed.Changes in the position—in this example, the rotational position—of the throttle element D-217 by a few degrees lead to very large changes in the free flow cross-section of the intake port D-214 and thus to very large speed fluctuations. By slowly adjusting the throttle element D-217 between the target final speed D-nsoll and the first speed limit D-nl and quickly adjusting it between the first speed limit D-nl and the second speed limit D-n2, stable operation of the internal combustion engine D-201 can be achieved.

[0269] The invention further relates to a method for operating an internal combustion engine of the type specified in the preamble of claim 60 and to an internal combustion engine.

[0270] From WO 2020 / 027708 A1, an internal combustion engine is known whose control device is designed to adjust a throttle element arranged in the intake duct in order to set a desired speed of the internal combustion engine.

[0271] From DE 10 2009 023 964 B4 a carburettor for operating an internal combustion engine is known, in which it is determined whether combustion takes place in the combustion chamber during each engine cycle.

[0272] The invention is based on the object of creating a method for operating an internal combustion engine that enables advantageous control of the internal combustion engine. A further object of the invention is to provide an internal combustion engine for implementing the method.

[0273] With regard to the method, this object is achieved by a method having the features of claim 60. With regard to the internal combustion engine, the object is achieved by an internal combustion engine having the features of claim 70. Whether combustion takes place in every engine cycle in an internal combustion engine depends on the fuel / air ratio in the combustion chamber. If the fuel / air mixture in the combustion chamber is too rich or too lean, combustion cannot take place in every engine cycle. To remedy this undesirable situation, the amount of fuel supplied must be increased if combustion does not take place in the combustion chamber because the mixture is too lean. If combustion does not take place because the mixture is too rich, the amount of fuel supplied must be reduced.

[0274] To detect whether combustion is not occurring due to a mixture that is too rich or too lean in the combustion chamber, the present invention provides for reducing the amount of fuel supplied if it is determined that an engine cycle has taken place without combustion in the combustion chamber. To distinguish between the possible causes of the combustion failure—i.e., a mixture that is too rich or too lean in the combustion chamber—the reaction of an actuator is evaluated.

[0275] The actuator is designed to adjust the throttle element in a closing direction and an opening direction to set a desired speed. The actuator adjusts the throttle element in the closing direction to decrease the speed and in the opening direction to increase the speed.

[0276] To set a desired speed, the actuator must adjust the throttle element in the closing direction if the current speed is greater than the desired speed to reduce the current speed to the desired speed. If the current speed is lower than the desired speed, the actuator must adjust the throttle element in the opening direction to increase the current speed to the desired speed.

[0277] When the amount of fuel supplied is reduced, the engine speed changes depending on whether the mixture in the combustion chamber is too rich or too lean. If the mixture is too rich, the engine speed increases as a result of a reduction in the amount of fuel supplied. If the mixture is too lean, the engine speed decreases as a result of a reduction in the amount of fuel supplied.

[0278] If the actuator adjusts the throttle element in the opening direction in response to the reduction in the supplied fuel quantity, the actuator counteracts a reduction in engine speed. Since the engine speed has decreased in response to the reduction in the supplied fuel quantity, the fuel / air mixture in the combustion chamber is too lean. The resulting lambda value in the combustion chamber is therefore significantly greater than 1.0. In this case, the method provides for increasing the supplied fuel quantity. This can counteract engine cycles without combustion in the combustion chamber.

[0279] If the actuator adjusts the throttle element in the closing direction in response to the reduction in the supplied fuel quantity, the actuator counteracts an increase in engine speed. Since the engine speed has increased in response to the reduction in the supplied fuel quantity, the fuel / air mixture in the combustion chamber is too rich. The lambda value established in the combustion chamber is therefore significantly less than 1.0. Reducing the supplied fuel quantity in response to a detected engine cycle without combustion in the combustion chamber was therefore the correct response to counteract further engine cycles without combustion. Therefore, no further change in the fuel quantity is necessary until the next detected engine cycle without combustion.

[0280] By evaluating the reaction of the actuator, an undesirable operating state of the internal combustion engine, in which combustion does not take place in the combustion chamber during every engine cycle, can be easily avoided or counteracted by using the actuator that is already present. The method is repeated in particular after each detection of an engine cycle without combustion. If the internal combustion engine is in an operating state in which engine cycles without combustion take place in the combustion chamber due to an excessively rich mixture in the combustion chamber, the supplied fuel quantity is further reduced each time the method is carried out, since it is not detected that the actuator is adjusting the opening direction of the throttle element in response to the reduction in the supplied fuel quantity. As a result, the mixture is increasingly leaned out until no more engine cycles without combustion in the combustion chamber are detected.If an engine cycle occurs without combustion in the combustion chamber due to an excessively lean mixture in the combustion chamber, the amount of fuel supplied is increased because it is detected that the actuator adjusts the throttle element in the opening direction in response to the reduction in the amount of fuel supplied.

[0281] In particular, the fuel quantity is increased to a fuel quantity that is greater than the fuel quantity supplied before the reduction in the supplied fuel quantity in the previous step of the method. Overall, the supplied fuel quantity is thus increased during one run of the method.

[0282] In particular, the internal combustion engine is a two-stroke engine. Based on the engine cycles during which no combustion with the combustion chamber occurred, it is determined whether the two-stroke engine operates in four-stroke mode. This is the case if no combustion occurs in the combustion chamber during every second engine cycle.

[0283] Four-stroke operation can be easily detected by evaluating the pressure in the crankcase. In particular, the fluctuation in the pressure in the crankcase can be evaluated. Another method of evaluating the pressure in the crankcase can also be provided. To detect four-stroke operation, the engine speed can be evaluated alternatively or additionally. Another method of determining whether combustion has taken place in the combustion chamber and / or whether the two-stroke engine is operating in four-stroke mode can also be provided.

[0284] In particular, the two-stroke engine is designed so that a fuel / air mixture is present in the crankcase. The fuel present in the crankcase can thus serve to lubricate the moving parts in the crankcase. The fuel is supplied, in particular, to an intake port or a crankcase of the two-stroke engine. A supply to a transfer port of the two-stroke engine can also be provided.

[0285] In particular, the internal combustion engine comprises a control device. The control device determines, in particular, whether an engine cycle has occurred without combustion in the combustion chamber. The control device can, in particular, be a control device that monitors engine parameters and controls the amount of fuel to be supplied and / or the actuator and / or an ignition device of the internal combustion engine. Other components of the internal combustion engine can also be controlled by the control device.

[0286] To evaluate the actuator's response, it is sufficient to distinguish whether the actuator adjusts the throttle element in the opening or closing direction. It can be provided that the direction of rotation of the actuator is detected when evaluating the actuator's response to the reduction in the supplied fuel quantity. Alternatively or additionally, the position of the throttle element can be detected when evaluating the actuator's response in step (c). For this purpose, for example, a rotational position sensor can be arranged on a throttle shaft of the throttle element. Any other type of detection of the position of the throttle element can also be provided.

[0287] An internal combustion engine which is designed to carry out the method has in particular a cylinder in which a combustion chamber is formed, and an intake duct for supplying air, wherein a throttle element is arranged in the intake duct, wherein an actuator is provided which is designed to adjust the throttle element in an opening direction to increase the free flow cross-section of the intake duct and in a closing direction to reduce the free flow cross-section of the intake duct in order to set a desired speed, wherein a device for supplying fuel is provided.

[0288] The internal combustion engine has, in particular, a control device designed to control the actuator. In particular, the control device is also designed to determine whether an engine cycle has taken place without combustion in the combustion chamber. To do so, the control device can, for example, evaluate signals from a pressure sensor that measures the pressure in the crankcase and / or the speed of the internal combustion engine. In particular, the controller is designed to change the supplied fuel quantity. The control device serves, in particular, to specify the ignition timing. In particular, the control device is also provided to evaluate the reaction of the actuator when the supplied fuel quantity has been changed.

[0289] In particular, the internal combustion engine is a two-stroke engine. The combustion chamber is defined in particular by a piston, which rotates a crankshaft mounted in a crankcase of the internal combustion engine. The intake duct supplies air, in particular, into the crankcase. The crankcase is fluidly connected to the combustion chamber in at least one predetermined position of the piston. The internal combustion engine has, in particular, a pressure sensor for determining the pressure in the crankcase. The device for supplying fuel supplies the fuel, in particular, to the intake duct or to the crankcase. For supplying fuel, a fuel valve, in particular an electromagnetic valve controlled by a control device, is provided.

[0290] Embodiments of the invention are explained below with reference to the drawings. In the drawings: Fig. 11 shows a schematic sectional view of a hand-held implement,

[0291] Fig. E-2 is a schematic representation of the combustion engine of the

[0292] Tool from Fig. El,

[0293] Fig. E-3 is a schematic representation of the throttle element of the internal combustion engine in different positions,

[0294] Fig. E-4 is a schematic representation of a diagram showing the

[0295] throttle angle as a function of the lambda value of the fuel / air mixture in the combustion chamber for a constant speed curve,

[0296] Fig. E-5 and Fig. E-6 are schematic representations of possible sequences of the method,

[0297] Fig. E-7 is a diagram showing the course of an average

[0298] crankcase pressure and individual measured pressure values ​​over time.

[0299] Fig. E-1 shows a schematic diagram of a work tool E-25. In Fig. E-1, a chainsaw is shown as an exemplary embodiment of a work tool E-25, the structure of which is explained below by way of example. The work tool E-25 is preferably a hand-held, in particular a hand-carried work tool. The work tool E-25 can also be another work tool, for example a cut-off grinder, a blower or a brush cutter. The work tool E-25 comprises a housing E-26, on which a handle E-27 is arranged for guiding and carrying the work tool E-25 during operation. Control elements E-28 are arranged on the handle E-27. At least one of the control elements E-28 serves to control an internal combustion engine E-1 of the work tool E-25. In the exemplary embodiment, the control element E-28 acts on a throttle lever E-30 via an actuating device E-29. To control the amount of combustion air supplied to the internal combustion engine E-1, a control element E-28 shown in Fig.E-2 schematically depicts the throttle element E-17, which is mounted in a throttle housing E-15 shown in Fig. E-1. The throttle housing E-5 can be a carburetor, for example. The throttle element E-17 is coupled to the throttle lever E-30. An operator can open the throttle element E-17 via the throttle lever E-30. The throttle element E-17 is typically reset via a return spring (not shown).

[0300] The internal combustion engine E-1 comprises a cylinder E-2 in which a combustion chamber E-3 is formed. The combustion chamber E-3 is delimited by a piston E-5, which, via a connecting rod E-6, drives a crankshaft E-7 rotatably mounted in a crankcase E-4. As shown in Fig. E-2, the crankshaft E-7 is rotatably mounted about a rotational axis E-8. The internal combustion engine E-1 comprises an intake duct E-14 for supplying combustion air. The intake duct E-14 opens with an inlet opening E-9 at a cylinder bore of the cylinder E-2. An exhaust opening E-10 leads from the combustion chamber E-3. The inlet opening E-9 and the exhaust opening E-10 are controlled by the piston E-5 in the exemplary embodiment. As shown in Fig. E1, a spark plug E11 projects into the combustion chamber E-3. The spark plug E11 is supplied with energy by an ignition device E-22 shown schematically in Fig. E-2.

[0301] In the exemplary embodiment, the internal combustion engine E-1 is a two-stroke engine. The internal combustion engine E-1 is, in particular, a single-cylinder engine. The internal combustion engine E-1 has transfer channels E-12, which open into the combustion chamber E-3 via transfer windows E-13. Fig. E-2 shows a schematic illustration of one of the transfer channels E-12. In the region of the bottom dead center of the piston E-5, the transfer channels E-12 fluidly connect the interior of the crankcase E-4 with the combustion chamber E-3. The transfer windows E-13 are controlled by the piston E-5. As Fig. E-1 shows, the exhaust opening E-10 opens into an exhaust silencer E-23 via an exhaust channel E-33. A catalytic converter E-24 or another device for exhaust gas aftertreatment can be arranged in the exhaust silencer E-23.

[0302] Fig. E-2 shows the structure of the internal combustion engine E-1 in detail. The intake duct E-14 draws in ambient air via an air filter E-16. In the throttle body E-5, in the exemplary embodiment, at least one fuel opening E-18 opens into the intake duct E-14. The fuel opening E-18 is controlled in the exemplary embodiment by a valve E-19. The valve E-19 is in particular an electrically controllable valve, in particular an electromagnetic valve. It can also be provided that the valve E-19 supplies fuel directly into the interior of the crankcase E-14. Fig. E-2 schematically shows a valve E-19' on the crankcase E-4, with which fuel can be supplied directly into the interior of the crankcase E-4 as an alternative to the valve E-19.

[0303] In the exemplary embodiment, the throttle element E-17 is designed as a throttle valve. The throttle element E-17 is adjustable between a closed position E-56, which is shown in Fig. E-2 with a solid line, and an open position E-57, shown in Fig. E-2 with a dashed line. To adjust the throttle element E-17 from the closed position E-56 towards the open position E-57, the throttle element must be pivoted in an opening direction E-34. To adjust it from the open position E-57 towards the closed position E-56, the throttle element E-17 must be pivoted in a closing direction E-32. In the closing direction E-32, the throttle element E-17 is preloaded by a closing spring (not shown).

[0304] The open position E-57 of the throttle element E-17 is a position in which the throttle element E-17 largely opens the flow cross-section in the intake port E-14. In the closed position E-56, the throttle element E-17 closes the flow cross-section of the intake port E-14 except for a predetermined residual cross-section. The flow cross-section of the intake port E-14 is therefore larger in the open position E-57 of the throttle element E-17 than the flow cross-section of the intake port E-14 in the closed position E-56 of the throttle element E-17.

[0305] The internal combustion engine E-1 comprises a control device E-20. The control device E-20 controls the ignition device E-22 and specifies the ignition point for the spark plug E-11. The control device E-20 also controls the valve E-19, 19' and thus the amount of fuel supplied to the interior of the crankcase E-4 via the intake port E-14. In the exemplary embodiment, the control device E-20 also controls an actuator E-21. The actuator E-21 is designed to adjust the throttle element E-17 in the closing direction E-32 and in the opening direction E-34. In the exemplary embodiment, the actuator E-21 comprises an electric motor E-31 for this purpose. However, a differently designed actuator for adjusting the position of the throttle element E-17 can also be provided.

[0306] Fig. E-3 shows a schematic view of the arrangement of the throttle element E-17 in the intake duct E-14. The closed position E-56 is shown as a solid line, the open position E-57 as a dashed line, and an intermediate position E-58 as a dotted line. The throttle element E-17 can be adjusted over an adjustment angle range a between the closed position E-56 and the open position E-57. The position of the throttle element E-17 can be specified via a throttle angle y, with the fully closed position E-56 corresponding to a throttle angle y of E-0°. The fully open position E-57 can, for example, correspond to a throttle angle y of E-50° to E-80°.

[0307] The throttle angle y can be determined, for example, via a throttle shaft sensor E-35, as shown schematically in Fig. E-3. The control device E-20 is designed to set a desired speed for at least one operating state. Such an operating state can be, for example, a no-load final speed state. For this purpose, the control device E-20 can change the throttle angle y via the actuator E-21 and thus adjust the amount of air supplied to the combustion engine E1. Fig. E-4 shows a curve E-60 of constant speed as a function of the throttle angle y and the air ratio in the combustion chamber. The maximum power for this operating state occurs at point E-59. In a two-stroke engine, the maximum power occurs at an air ratio in the combustion chamber E-3 of slightly below E1. This corresponds to a throttle element E17 that is comparatively widely closed for this operating state.If the throttle element E-17 is moved further in the closing direction E-32 from the position at point E-59, the speed drops below the speed set at curve E-60.

[0308] In range E-37, four-stroke operation does not normally occur. In ranges E-38 and E-39, the internal combustion engine E1 can fall into four-stroke operation, in which no combustion takes place in the combustion chamber during every other engine cycle. Such an operating state should be avoided. The control device E-20 can determine such an operating state, for example, by evaluating the pressure Ep in the crankcase E-4, which is shown schematically in Fig. E-7, or by evaluating the speed of the internal combustion engine E1. The ranges E-40 designate intermediate ranges in which four-stroke operation can occur.

[0309] If four-stroke operation or an engine cycle without combustion in the combustion chamber E-3 is detected, the control device E-20 initially assumes that the fuel / air mixture in the combustion chamber E-3 is too rich. In this case, the internal combustion engine E1 can, for example, be at point E-45 on curve E-60, as shown in Fig. E-4. The sequence of the method in this case is shown in Fig. E-5. If it is determined at this operating point in a method step E-41 (Fig. E-5) that an engine cycle without combustion has taken place in the combustion chamber E-3, the supplied fuel quantity is to be reduced in a subsequent method step E-42, i.e. the fuel / air mixture in the combustion chamber E-3 is to be leaned out. In the exemplary embodiment, a leaning out up to a point E-46 in Fig. E-4 is provided as an example.Leaning the mixture with a rich mixture in the combustion chamber E-3 leads to an increase in the speed of the internal combustion engine EL. The control device E-20 will therefore adjust the actuator E-21 in the closing direction E-32 up to a point E-47 in order to reduce the speed back to the desired speed. Accordingly, reducing the supplied fuel quantity was the correct response to prevent engine cycles without combustion in the combustion chamber E-3 in this operating state of the internal combustion engine EL. The method therefore starts again by determining whether an engine cycle has taken place without combustion in the combustion chamber. If another engine cycle has taken place without combustion, the supplied fuel quantity is reduced again, for example up to point E-48.In response to the reduction in the supplied fuel quantity, actuator E-21 adjusts throttle element E-7 further in the closing direction E-32 to counteract the increase in speed resulting from the reduction in the fuel quantity, for example, up to point E-49. At point E-49, the combustion engine E-1 is in a range of the air ratio where four-stroke cycles do not normally occur.

[0310] If an engine cycle without combustion in the combustion chamber E-3 takes place at a point E-50, at which the internal combustion engine E-1 is operated with a lean fuel / air mixture in the combustion chamber E-3, i.e. an air / fuel ratio of significantly more than E-1.0, the supplied fuel quantity is also initially reduced, for example, down to point E-51. This takes place in a method step E-41 shown in Fig. E-6. In response to this reduction in the supplied fuel quantity, the speed of the internal combustion engine E-1 drops. The actuator E-21 then adjusts the throttle element E-17 in the opening direction E-34 in order to increase the speed back to the desired value. This can take place, for example, up to point E-52. If it is detected in method step E-42 that the actuator E-21 has adjusted the throttle element E-17 in the opening direction E-34 in response to the reduction in the supplied fuel quantity, then in method step E-43 (Fig.E-6) increases the supplied fuel quantity, for example up to point E-53 in Fig. E-4. The supplied fuel quantity is increased in particular to a fuel quantity that is greater than the fuel quantity that was supplied before the supplied fuel quantity was reduced in method step E-41. This results in an overall increase in the supplied fuel quantity compared to the initial state at point E-50, as Fig. E-4 also shows. Due to the increase in the supplied fuel quantity, the speed increases and the actuator E-21 adjusts the throttle element E1 7 in the closing direction E-32 until the curve E-60 is reached. This is the case in the exemplary embodiment at point E-54. The point E-54 is located in the area E-37, in which four-stroke operation does not normally take place.

[0311] By evaluating the reaction of actuator E-21 to a reduction in the supplied fuel quantity, it is easy to determine whether the internal combustion engine E-1 in the diagram in Fig. E-4 is operating on the left branch or the right branch of curve E-60, i.e., with a lean mixture in combustion chamber E-3 or with a rich mixture in combustion chamber E-3. The supplied fuel quantity can be adjusted accordingly until no more engine cycles occur without combustion in combustion chamber E-3. This is when the richness of the mixture in combustion chamber E-3 is in the range E-37.

[0312] Fig. E-7 shows exemplary measured values ​​of the crankcase pressure p during consecutive engine cycles. Based on the crankcase pressure p, it can be determined whether combustion takes place during each engine cycle. Fig. E-7 shows individual measured pressure values ​​for the crankcase pressure Ep over time Et. The pressure values ​​for the crankcase pressure p initially fluctuate greatly. From time E-t3, the pressure values ​​are at an approximately constant level. Before time E-t3, the internal combustion engine E1 is operated in four-stroke mode, i.e., combustion only occurs in the combustion chamber E-3 every other engine cycle. The pressure value E-pi represents the crankcase pressure Ep at a time E-ti, after combustion has taken place in the combustion chamber E-3. The pressure value E-p2 represents the pressure Ep in the crankcase E-4 at a time t2 after an engine cycle in which no combustion has taken place in the combustion chamber E-3. In Fig.E-7 is also an average Ep. M for the crankcase pressure Ep. To determine whether combustion has taken place in the combustion chamber E-3 or whether the two-stroke engine is operating in four-stroke mode, a pressure difference E-Api is measured between the pressure value E-pi and the mean value Ep M Corresponding pressure differences E-Ap2 and E-Ap3 are determined for the pressure values ​​E-p2 and E-p3. If combustion does not occur in the combustion chamber E-3 during every engine cycle, the difference E-Ap b E-Ap2 is comparatively large. If combustion occurs in combustion chamber E-3 during every engine cycle, the difference E-Ap3 is comparatively small. By evaluating the fluctuation in crankcase pressure Ep, it is easy to determine whether an engine cycle has occurred without combustion in combustion chamber E-3.

[0313] If combustion has occurred in combustion chamber E-3, piston E-5 and thus also the crankshaft E-4 are accelerated comparatively strongly. By evaluating the engine speed n, the acceleration of the crankshaft E-4 between top and bottom dead center of piston E-5 can be used to determine whether combustion has occurred in combustion chamber E-3 or not. Other methods for determining whether combustion has occurred in combustion chamber E-3 can also be provided.

[0314] The invention further relates to a carburetor with a carburetor housing and a throttle valve, wherein the throttle valve is mounted on a rotatably mounted throttle valve shaft. The throttle valve assumes an idle position in a first rotational position and an end position corresponding to a full-load position in a second rotational position. In the full-load position, the throttle valve is aligned in the direction of combustion air flow. A switch is provided to detect the position of the throttle valve in the full-load position; this switch emits an output signal when the throttle valve is in a predetermined rotational position.

[0315] The throttle valve's end position is determined by a mechanical stop. The switch is mounted at a rotational position relative to the throttle valve shaft so that, at a given rotational position, it emits an output signal that corresponds to the full-throttle position of the throttle valve.

[0316] The output signal of the switch is fed to a control electronics which, by processing the output signal and other parameters and boundary conditions given at the respective time from the environment, determines a metering of the fuel in the full load position of the throttle valve in order to supply an internal combustion engine with a rich mixture corresponding to the full load position via an intake duct of the carburettor whose flow cross-section is controlled by the throttle valve.

[0317] The stop for the throttle valve's end position is subject to tolerances, and the switch's contact elements are subject to wear during operation. This can lead to the carburetor being so worn after extended operation that the switch indicating the throttle valve's full-throttle position is no longer reliably activated. As a result, the control unit fails to detect a full-throttle condition, so that the controlled variable, such as the ignition timing, is incorrectly selected and / or the fuel quantity is insufficient. An internal combustion engine equipped with a carburetor, especially a two-stroke engine, can experience significant performance losses.

[0318] The invention is based on the object of designing a carburetor with a switch for detecting the rotational position of the throttle valve in such a way that, even after a prolonged period of operation and the associated wear, a reliable output signal for detecting a full-throttle position is generated. This object is achieved according to the features of claim 73.

[0319] According to the invention, the switch is actuated in a predetermined rotational position of the throttle valve and an output signal is generated which indicates the full load position. According to the invention, the predetermined rotational position of the throttle valve is within a rotational angle range of 5° to 12° before the end position of the throttle valve. It is provided that an output signal for the full load position of the throttle valve is emitted at least once before the throttle valve reaches its actual end stop. A structurally predetermined mechanical end stop of the throttle valve corresponds to the structural full load position of the throttle valve. The switching instant of the switch provided according to the invention is within a predetermined wear zone in degrees of rotational angle before an end position of the throttle valve or the throttle valve shaft. In the predetermined rotational position before the end position of the throttle valve, the output signal for the full load position of the throttle valve is emitted at least once.It may be advantageous to provide a continuous output signal in the specified rotation angle range.

[0320] It was determined that early activation of the switch and the indication of a full-load position before the throttle valve actually reaches its design limit does not adversely affect the operation of a carbureted two-stroke engine. Rather, early activation of the switch and the transmission of the output signal for a full-load position in a rotation angle range of 5° to 12° before the throttle valve's design limit, in particular, ensures reliable detection of the full-load position even after extended periods of operation, and thus reliable calculation of the controlled variable by the control unit in the full-load case.

[0321] In a further development of the invention, the output signal for the full-load position of the throttle valve is emitted at least once at a rotation angle between 7° and 10° before the end position of the throttle valve. Preferably, the switch is actuated and the output signal for the full-load position is emitted in a rotation angle range between 8° and 9° before the nominal end position of the throttle valve. The mechanical end position of the throttle valve is at a tolerance of 90° + / -3°, i.e., at a nominal 90°. The switching time for emitting the output signal is independent of this and is expediently specified at a preset 81.5° with a tolerance of approximately 0.5°.

[0322] The rotatable throttle valve shaft with the throttle valve fixed to it in a rotationally fixed manner is conveniently mounted in the carburettor housing, with the switch for detecting the specified rotational position of the throttle valve being held on the carburettor housing.

[0323] The switch is advantageously designed as a "normally open" contact, with a closing contact that closes when the throttle valve reaches its predetermined rotational position. It may be advantageous to design the switch as a "normally closed" contact, i.e., with an opening contact that opens when the throttle valve reaches its predetermined rotational position.

[0324] In a specific embodiment of the switch, it has a first electrical contact element and a second electrical contact element. One of the contact elements is formed by the throttle valve shaft, in particular by an end section of the throttle valve shaft. It may be expedient to form the contact element by an element attached to the throttle valve shaft, for example, by an element attached to the end section of the throttle valve shaft.

[0325] In a further development of the switch, the first electrical contact element is held in a component to be attached to the carburetor housing. A shaft section of the throttle valve shaft, in particular an end section of the throttle valve shaft, projects into this component, with the shaft section of the throttle valve shaft projecting into the component forming the second electrical contact element. A switch constructed in this way operates more reliably than commercially available switches.

[0326] To form the second electrical contact element, a control edge is formed on the shaft section of the throttle valve shaft. The control edge is designed, in particular, as an edge of a flattened portion of the throttle valve shaft. The control edge interacts with the first electrical contact element held in the component. The control edge is advantageously designed in the form of a chamfer attached to the throttle valve shaft. The design of the chamfer can reduce wear.

[0327] The switch is designed so that in the specified rotational position of the throttle valve shaft, the control edge of the throttle valve shaft rests against the first contact element located in the component and closes the electrical contact of the switch.

[0328] In a special embodiment of the invention, the throttle valve shaft itself is designed as an electrical conductor. In particular, the throttle valve shaft is made of an electrically conductive material.

[0329] The carburetor housing, in which the throttle valve shaft is rotatably mounted, is advantageously designed as an electrical conductor. In particular, the carburetor housing is made of an electrically conductive material.

[0330] If the throttle valve shaft is designed as an electrical conductor and rotatably mounted in the carburetor housing made of an electrically conductive material, electrical contact with the switch is easily possible. The first contact element of the switch is held in an insulated manner in the component held on the carburetor housing, wherein the component is formed from an electrically non-conductive material, in particular an electrically insulating material. The material of the component is advantageously plastic. The carburetor with the full-load switch is arranged in particular on a two-stroke engine. The ignition of a mixture sucked into the combustion chamber of the two-stroke engine and / or the fuel metering into the intake channel to the combustion chamber of the two-stroke engine is advantageously carried out by a control unit to which the output signal of the switch is fed.Irrespective of tolerances and the occurring mechanical wear, the teaching according to the invention ensures that a full-load position of the throttle valve is reliably detected over a long operating period of the carburettor and that the control unit of the internal combustion engine can determine control variables associated with the operating state in order to ensure ignition and fuel metering appropriate to the load state of the internal combustion engine, in particular a two-stroke engine.

[0331] In a further development of the invention or as an independent invention, a carburetor is provided comprising a carburetor housing, an intake port formed in the carburetor housing, and a throttle valve arranged in the intake port and held on a throttle valve shaft. A switch is provided which, when the throttle valve is in a predetermined rotational position, closes an electrical contact between a first electrical contact element and a second electrical contact element. The first contact element is connected to a leading signal line via at least one diode. The first contact element is held in a plug-in receptacle, and at least one electrical connecting wire of the diode is held in a further plug-in receptacle.The plug receptacles are adjacent to one another and overlap geometrically such that a connecting wire held in one plug receptacle makes electrical contact with the contact element located in the other plug receptacle in the overlapping area. A secure electrical contact between the diode and the contact element is achieved in a simple manner. The connecting wire is round, in particular cylindrical. The plug receptacle for the connecting wire is designed accordingly, in particular cylindrical. In a further development of the invention, two diodes inserted into diode receptacles are held in a housing of the switch, the connecting wires of which are located at the bottom of the plug receptacles make electrical contact with one another.

[0332] In a further development of the invention or as an independent invention, a circuit arrangement for a switch arranged on a carburetor is further provided. An intake duct is formed in a carburetor housing of the carburetor. An electrically controlled fuel valve is also provided, which supplies fuel to the internal combustion engine, preferably opening into the intake duct. A choke valve is arranged in the intake duct and is held on a choke valve shaft. A first switch emits an output signal as a position signal when the choke valve is in a predetermined rotational position. The first switch is arranged in a first electrical parallel branch to the electrical fuel valve. In the first electrical parallel branch, a diode is connected in series with the switch, which diode is in particular electrically connected in the blocking direction. A throttle valve is arranged in the intake duct and is held on a throttle valve shaft.A second switch outputs a position signal as a position signal when the throttle valve is in a predetermined rotational position. The second switch is located in a second electrical parallel branch to the electric fuel valve. A first diode and a second diode are connected in series with the second switch in the second electrical parallel branch. In particular, one diode is electrically connected in the reverse direction, and the other diode is electrically connected in the forward direction. Diodes of various designs are arranged in the parallel branches, in particular a Zener diode, a Schottky diode, an LED diode, a rectifier diode, or a similar diode.

[0333] Further features of the invention emerge from further claims, the description, and the drawings. The features disclosed in the exemplary embodiment are alternative or supplementary features to the teaching stated in claim 73. The features disclosed in the claims, the description, and the drawings can be combined with one another as desired within the scope of the invention. The drawings show: Fig. F1 shows, by way of example, a schematic representation of a carburetor with a choke valve, a throttle valve, and a control device,

[0334] Fig. F-2 is a perspective view of a structurally designed carburettor with a switch according to the invention for detecting a full-load position of the throttle valve,

[0335] Fig. F-3 is a perspective view of a throttle shaft,

[0336] Fig. F-4 is a perspective view of a component for holding a first contact element of the switch for detecting a full load position,

[0337] Fig. F-4a is a detailed enlargement of Fig. F-4,

[0338] Fig. F-5 is a perspective view of the component for holding the first contact element with a projecting shaft section of the throttle valve shaft in an idle position or partial load position,

[0339] Fig. F-6 is a perspective view of the component for holding the first contact element with a projecting shaft section of the throttle valve shaft in a full load position,

[0340] Fig. F-7 is a schematic diagram of switching times occurring over the angle of rotation of the throttle valve shaft, Fig. F-8 is a schematic overview of a circuit arrangement with several switches in parallel branches to the fuel valve.

[0341] The schematic representation according to Fig. F1 shows a carburetor F1 with a carburetor housing F-10. An intake duct F-2 is formed in the carburetor housing F-10, in which intake duct F-2 at least one throttle valve F-4 is arranged. The throttle valve F-4 is held on a throttle valve shaft F-3 which is rotatably mounted. In the exemplary embodiment shown, the throttle valve shaft F-3 is rotatably held in the carburetor housing F-10. The throttle valve shaft F-3 and / or the carburetor housing F-10 are preferably designed as electrical conductors. The throttle valve shaft F-3 and / or the carburetor housing F-10 are made of an electrically conductive material, in particular of metal or a metal alloy.

[0342] The carburetor F-1 shown as an example further includes a choke valve F-6, which is mounted on a choke valve shaft F-5. The choke valve shaft F-5 is rotatably mounted. In the illustrated embodiment, the choke valve shaft F-5 is rotatably mounted in the carburetor housing F-10 of the carburetor F-1.

[0343] In the flow direction F-40 of the incoming combustion air, choke valve F-6 and throttle valve F-4 are arranged one behind the other. Advantageously, choke valve F-6 in its open position F-16 and throttle valve F-4 in its full-load position F-14 are approximately in the same plane. Preferably, throttle valve F-4 in the full-load position F-14 and choke valve F-6 in its open position F-16 are located on the longitudinal center axis F-7 of intake duct F-2.

[0344] An electromagnetic fuel valve F-8, which is controlled by a control unit F-9, opens into the intake port F-2. The control unit F-9 determines the opening time of the fuel valve F-8 and thus the amount of fuel supplied to the intake port F-2. The combustion air flowing in the direction of flow F-40 creates a vacuum in the intake port F-2, so that when the fuel valve F-8 is open, fuel escapes into the intake port F-2. The resulting fuel / air mixture F-41 is fed to a combustion chamber F-22 of an internal combustion engine F-20, in particular a two-stroke engine. The combustion chamber F-22 is delimited by a reciprocating piston F-23, which drives a crankshaft (not shown in detail) of the internal combustion engine F-20 via a connecting rod F-25. When the piston F-23 moves upwards, the fuel / air mixture F-41 present in the combustion chamber F-22 is compressed and ignited by a spark plug F-21.Combustion drives piston F-23 downward, which rotates the crankshaft.

[0345] The ignition spark triggered at spark plug F-21 to ignite the compressed fuel / air mixture F-41 in combustion chamber F-22 is triggered by control unit F-9 depending on the crankshaft angle. Depending on the load condition of the combustion engine F-20 (idling, partial load, full load), spark plug F-21 is triggered at different crankshaft angles to trigger an ignition spark.

[0346] Switches F-1 and F-17 are provided to signal the rotational position of the choke valve F-6 and / or the throttle valve F-4 to the control unit F-9. A switch F-1 or F-17 transmits an output signal F-12 or F-18 to the control unit F-9 via a signal line F-13 or F-19. The control unit F-9 processes the output signal F-12 or F-18 and accordingly controls, for example, the fuel valve F-8 to meter fuel into the intake port F-2 and / or the spark plug F-21 to trigger an ignition spark depending on the rotational position of the crankshaft of the internal combustion engine F-20.

[0347] As Fig. F-2 shows, the switch F-11 assigned to the choke valve F-6 is attached to the carburetor body F-10. The switch F-17 assigned to the throttle valve F-4 is fixed to the carburetor body F-10 of the carburetor F-10 with a fastening screw F-15. The switch F-17 is composed of a housing F-30, which is in particular made up of two parts (F-30). The housing F-30 consists of a first component F-31, which is closed by a second component F-32. The second component F-32 forms a housing cover. Figs. F-4 to F-6 show the first component F-31 attached to the carburetor body F-10 in more detail.

[0348] The throttle valve shaft F-3 is rotatably mounted in the carburetor housing F-10 and pivots the throttle valve F-4 arranged in the intake duct F-2. The throttle valve shaft F-3 has a preferably central fastening section F-26 to which the throttle valve F-4 is fastened in a rotationally fixed manner. The fastening section F-26 lies between two bearing sections F-27 of the throttle valve shaft F-3. At the ends F-28 and F-29 of the throttle valve shaft F-3, holding devices for levers (not shown in detail) are provided. The end F-28 of the throttle valve shaft F-3, which is preferably located on the side of the switch F-17, projects axially out of the switch F-17 (Fig. F-2). Fig. F-2 shows that a lever F-45 is mounted on the end F-28 of the throttle valve shaft F-3 in a rotationally fixed manner and is expediently fastened by a fastening screw F-44, a rivet connection or another type of fastening such as e.g. B. is secured by gluing.Between the bearing section F-27 and the end F-28 lies a shaft section F-33 of the throttle valve shaft F-3. Formed in the shaft section F-33 is a flattened portion F-34, the bottom F-35 of which, as shown in Fig. F-5, forms a secant to the circular diameter of the throttle valve shaft F-3. At least one of the edges extending axially to the throttle valve shaft F-3 forms a control edge F-37 of a second electrical contact element F-61. Advantageously, the control edge F-37 is chamfered, so that the control edge F-37 itself is formed by a chamfer.

[0349] The first component F-31 of the housing F-30 of the switch F-17 is shown in Fig. F-4. In the bottom of the housing there is a through-opening F-36 which is adapted to the diameter D of the throttle valve shaft F-3. The throttle valve shaft F-3 is inserted through the through-opening F-36 into the first component F-31 of the housing F-30. In the first component F-31 there is held a first contact element F-51 which projects with a contact section F-52 into the diameter circle F-39 with a diameter D of the through-opening F-36. The throttle valve shaft F-3, preferably the shaft section F-33 of the throttle valve shaft forms a second contact element F-61 which together with the first contact element F-51 forms the switch F-17.

[0350] Furthermore, a connection terminal F-42 with a suitably sleeve-shaped end F-57 is held in the first component F-31. A signal line F-19 is connected to the connection terminal F-42, via which the state of the switch F-17 is reported. Electronic components F-48 and F-49 are arranged in electrical contact between the connection terminal F-42 and the first contact element F-51, which is designed in particular as a leaf spring, and via which an electrical connection is established between the connection terminal F-42 and the first contact element F-51. The electronic components F-48 and F-49 are preferably connected in series. The connection wires F-46 and F-47 of the electronic components F-48 and F-49 are round. The connection wire F-46 and F-47 has a particularly cylindrical shape of a predetermined length. The plug-in receptacle F-50 for the connection wire F-46, F-47 is designed accordingly, in particular cylindrical.

[0351] The special design of the electrical connection is a further, independent invention independent of the technical teaching mentioned in the claims or is to be combined with the technical teaching mentioned in the claims as a further development of the latter.

[0352] For the electrical connection of the electronic components F-48 and F-49, it is provided in particular that a connecting wire F-46 of the electronic component F-48 is inserted into a particularly cylindrical plug-in receptacle F-50. The cylindrical plug-in receptacle F-50 is expediently formed in the first component F-31. The diameter of the cylindrical plug-in receptacle F-50 is designed to precisely match the diameter of the connecting wire F-46. The term "precise fit" means that the connecting wire F-46 can be inserted flush into the cylindrical plug-in receptacle F-50 and is held therein, in particular, securely. This second plug-in receptacle F-50 is located adjacent to a further, first plug-in receptacle F-59, which can in particular have the shape of a receiving slot F-54. According to an inventive teaching, it is provided that the plug-in receptacles F-50 and F-59 are located adjacent to one another and overlap geometrically.The overlap is designed such that a connecting wire F-46 held in one plug-in receptacle F-50 makes electrical contact in the overlap region F-53 with the contact element F-51 located in the adjacent plug-in receptacle F-59, which is designed in particular as a receiving slot F-54. In Fig. F-4a, this is schematically shown using the example of the overlap F-53 between the second plug-in receptacle F-50 and the receiving slot F-54 as the first plug-in receptacle F-59. The receiving slot F-54 for receiving the first contact element F-51, which is designed in particular as a leaf spring, is designed as a part-circular receiving slot F-54. Other courses of the receiving slot F-54 are expedient. The plug-in receptacle F-50 for the connecting wire F-46 of the electronic component F-48 is provided in such a way that its diameter circle F-55 lies in a partial circumference in the receiving slot F-54 or the first plug-in receptacle F-59, as shown in Fig.4 by dash-dotted lines.This results in an overlap F-53 of the second plug-in receptacle F-50 with the first plug-in receptacle F-59 or the receptacle slot F-54.

[0353] As shown in Fig. F-4, the contact element F-51, in particular a leaf spring-shaped one, is inserted into the plug-in receptacle F-59, which is in particular designed as a receiving slot F-54, for fixing in the component F-31 of the housing F-30. Since the second plug-in receptacle F-50 has a geometric overlap F-53 with the receiving slot F-54 of the first plug-in receptacle F-59, the contact element F-51 lies with a contact section F-56 in the diameter circle F-55 of the receiving sleeve F-50. If a connecting wire F-46 of an electronic component F-48 is now inserted into the plug-in receptacle F-50, the connecting wire F-46, in particular a cylindrical one, is clamped between the contact section F-56 of the contact element F-51 and the plug-in receptacle F-50, whereby a secure electrical contact is established between the connecting wire F-46 of the electronic component F-48 and the first contact element F-51.This electrical plug-in connection is particularly useful for easy assembly of the electronic components F-48 and F-49.

[0354] In the same way, the connecting wire F-47 of the electronic component F-49 can be electrically contacted by inserting it into a cylindrical plug-in receptacle F-50 with the sleeve-shaped end of the connecting terminal F-42.

[0355] The electronic components are in particular diodes F-101, F-102 and Fl 12, whereby two geometrically identical diodes are expediently used, which in particular have different electrical forward voltages. The diodes are inserted axially into diode receptacles F-124, F-125 of component F-31, with the connecting wire F-46 or F-47 being inserted into the corresponding plug-in receptacle F-50. The connecting wires (not shown in detail) on the other connection side of a diode F-101, F-102 and Fl 12 lie in intersecting channels, whereby electrical contact between the other connecting wires is ensured at the intersection point. Two diode receptacles F-124 and F-125 are formed in the same component F-31, each of which contains a plug-in diode Fl 12, F-122. The connecting wires Fl 14, F- 115 located at the bottom of the diode holders F-124 and F-125 cross each other, thereby achieving electrical contact.Diodes Fl 11, Fl 12, F-122 of different designs can be used, in particular a Zener diode, a Schottky diode, an LED diode, a rectifier diode or similar diodes.

[0356] Fig. F-5 shows the idle position F-24 of the throttle valve F-4, with the throttle valve shaft inserted into the component F-31 of the housing F-30. The axial position of the throttle valve shaft F-3 is such that the flattened portion F-34 of the shaft section F-33 is opposite the contact portion F-52 of the first contact element F-51. In particular, the flattened portion F-34 in the shaft section F-33 has a width B that is at least slightly wider than the leaf spring-shaped, first contact element F-51 in the component F-31. The contact portion F-52 projecting into the diameter circle D is guided in the axial direction of the throttle valve shaft F-3 between the shoulders F-38 of the flattened portion F-34. As Fig. F-5 shows, the bottom F-35 of the flattening F-34 is located at a sufficient distance from the contact section F-52 of the first contact element F-51 so that the shaft section F-33 or the flattening F-34 does not touch the contact section F-52.There is no electrical contact between the throttle valve shaft F-3 and the contact section F-52 of the first contact element F-51. The switch F-17 is open.

[0357] If the throttle valve shaft F-3 is rotated in the direction of rotation F-43 and the throttle valve F-4 is pivoted from the idle position shown in Fig. F-5 towards a full-load position, the control edge F-37 rotates in the direction of the contact section F-52. If the throttle valve F-4 approaches an end position associated with the full-load position, the control edge F-37 comes into contact with the contact section F-52 of the first contact element F-51, as shown in Fig. F-6. The closing of the electrical contact between the first contact element F-51 and the throttle valve shaft F-3 as the second contact element F-61 is provided to indicate a full-load position of the throttle valve F-4.

[0358] According to the invention, an output signal F-18 is output via switch F-17 in a predetermined rotational position of throttle valve F-4, which can be fed, in particular, to a control unit F-9. The predetermined rotational position lies in a range of 5° to 12° before the design end position of throttle valve F-4 corresponding to a full-load position F-14.

[0359] This is shown schematically in Fig. F-7. Assuming a full-load position of the throttle valve F-4 at a 90° rotation angle (DW), the invention provides for actuating switch F-17 at a predetermined rotational position of the throttle valve at a rotation angle of 5 to 12°, in particular 8° to 9°, before the full-load position of 90° in order to emit an output signal indicating a full-load position. Fig. F-7 uses curve F-70 to show how the switching time is limited by the adjustment process of switch F-17 in the new state. As shown, with a bandwidth of preferably only 1° rotation angle of the throttle valve shaft F-3, reliable switching of switch F-17 and thus a precise output signal F-18 is ensured. If the wear is less, the tolerance bandwidth can also be up to 2°. The switching range in the new state is then in a rotation angle range of 81° to 83°.

[0360] Fig. F-7, curve F-80 shows the statistical distribution of the position of the throttle shaft stop for the full-throttle position across a variety of carburetors. In the example shown in curve 80, the mechanical end position of the throttle valve is within a tolerance of 90° + / -2°, i.e., at a nominal 90°.

[0361] With the inventive arrangement of switch F-17 for generating an output signal F-18 and actuating switch F-17 within a range of 5° to 12° of rotation angle before the nominal end position of the throttle valve, a reliable output signal for the full-load position of the throttle valve is achieved over a long operating period. The distribution of the switch's switching points in the new condition is represented by curve F-70. Due to wear, the switching point of switch F-17, when new, shifts from a rotation angle of the throttle valve shaft of 81° to 82° to a maximum rotation angle of 88°.

[0362] Preferably, the rotation angle range according to the invention is 80° to 83° rotation angle of the throttle valve shaft F-3, in particular 81° to 82° rotation angle of the throttle valve shaft F-3.

[0363] As can be seen from curve F-70 in Fig. F-7, the switching instant of switch F-17 occurs before the mechanical or design end position of throttle valve shaft F-3 of nominally 90°. Between possible switching instants of a switch F-17 in the area of ​​the design end position of throttle valve shaft F-3 of 90° according to curve F-80 and the switching instant of switch F-17 according to the invention, there is a wear zone FV. Even if the switching instant of curve F-70 selected according to the invention shifts due to mechanical wear, an output signal F-18 of switch F-17 indicating a full-load position is still guaranteed.

[0364] Fig. F-8 shows a circuit arrangement for switches F1 and F-17 arranged on a carburetor F1. The circuit arrangement indicates a further inventive teaching, which in itself represents an independent invention or, in combination with the other disclosed features of the above inventions, discloses the subject matter of a further invention.

[0365] As shown in Fig. F1, switches F11 and F17 indicate preset rotational positions of the choke valve F-6 and the throttle valve F-4, respectively. An electrically controlled fuel valve F-8 is provided on the carburetor body F-10. The fuel valve F-8 is controlled by the control unit F-9 to supply the required amount of fuel for the operation of the internal combustion engine.

[0366] The control unit F-9 is connected to a short-circuit switch F-75, which is designed in particular as a push-button. If the short-circuit switch F-75 is closed, the control unit F-9 stops the operation of the combustion engine. The first switch Fl 1 is used to detect a predetermined rotational position of the choke valve F-6, which can in particular correspond to a closed position of the choke valve F-6. The first switch F- 11 is connected in series with a diode Fl 11 in a parallel branch Fl 01 to the fuel valve F-8. The diode Fl 11 and the switch Fl 1 are located in a common switch housing F-92. The diode Fl 11 is electrically connected in the reverse direction, so that when the switch Fl 1 is closed, electrical control of the fuel valve F-8 is possible. The diode Fl 11 can be a Zener diode, a Schottky diode, an LED diode, a rectifier diode or similar diode. In the embodiment shown, the diode Fl 11 is a Zener diode.The circuit arrangement F-100 shown has a second parallel branch F-102 connected to the fuel valve F-8. The second parallel branch is formed by the second switch F-17 in series with a first diode F-112 and a second diode F-122. The first diode F-112 is electrically connected in the reverse direction, so that the fuel valve F-8 can be controlled. An opening signal (current pulse, voltage pulse) applied to the fuel valve F-8 is not short-circuited by either the first parallel branch F-101 or the second parallel branch F-102.

[0367] The second diode F-122, which can preferably be a Zener diode, is forward-biased. The second parallel branch F-102, consisting of the switch F-17 and the diodes F-112 and F-122, is located in a common switch housing F-94.

[0368] The F-8 fuel valve is an electromagnetic fuel valve that operates with a pulse sequence. The electromagnetic actuator of the F-8 fuel valve is switched on and off via the pulse sequence, with an induced voltage occurring each time the valve is switched off, which can also be referred to as a counter voltage. To protect such electromagnetic actuators, the counter voltage is usually suppressed by a diode.

[0369] In the illustrated embodiment, when switch Fl 1 is closed, the voltage induced across diode Fl 11 when fuel valve F-8 is turned off will drop, so that the forward voltage of diode Fl 11 is present at input F-96 of control unit F-9. The forward voltage present at input F-96 depends on the diode Fl 11 used. Diode Fl 11 has a predetermined first forward voltage.

[0370] If the switch Fl 1 is open and the switch F-17 indicating the rotational position of the throttle valve F-4 is closed, the series circuit from the

[0371] Switch F-17 and the oppositely polarized diodes F-12 and F-122. Diode F-122 is reverse-biased, while diode F-12 is forward-biased. The breakdown voltage of diode F-122, preferably designed as a Zener diode, is thus added to the forward voltage of diode F-12, which conducts the reverse voltage, so that a voltage level is present at input F-96 that is greater than the forward voltage of diode F-11 in switch housing F-92 of the first switch F-1.

[0372] A first signal voltage is present at input F-96 when switch Fl 1 is closed and a second signal voltage is present when switch F-17 is closed. Since two diodes Fl 12 and F-122 are provided in switch housing F-94, their forward voltages add up to form the second signal voltage. Only one diode Fl 11 is provided in switch housing F-92, and its forward voltage forms the first signal voltage. Control unit F-9 detects the signal voltages present at signal input F-96 and can use their analog value to distinguish whether switch Fl 1 of choke valve F-5 or switch F-17 of throttle valve F-4 is closed. Control unit F-9 controls fuel valve F-8 depending on the detected signal voltage.

[0373] The F-96 input of the control unit is preferably a control / diagnosis connection to which an external diagnostic device F-98 can also be connected.

[0374] The invention further relates to a switch for detecting a rotational position of a shaft, in particular a predetermined rotational position of a shaft, having a control edge moved with the shaft, preferably a cam or the like, for actuating an electrical contact. The electrical contact is arranged in a switch housing of the switch, wherein the switch housing is mounted so as to be adjustably about a pivot axis. To adjust the rotational position of the switch housing relative to the rotational position of the shaft, a stationary, adjustable stop is provided, which also serves to fix the position of the pivotable switch housing. Such a switch can be provided, for example, as a throttle valve switch on a carburetor for an internal combustion engine. The switch generates a switching signal which is fed to a controller such as an electronic system to control the fuel supply. The switching signal can, for example, indicate the full load position of the throttle valve.To achieve this, the throttle valve shaft actuates the switch's electrical contact when the full-load position is reached. When installing the switch, its rotational position relative to the throttle valve shaft must be adjusted and secured in such a way that, regardless of installation tolerances, the switching signal is reliably triggered and made available to the combustion engine control unit when the throttle valve is in the full-load position.

[0375] When installing the switch, it is swiveled to the stop and a stop screw is screwed in or out until the switch housing is positioned in such a way that the switching signal is reliably triggered when the throttle shaft is in the full load position.

[0376] The invention is based on the object of specifying a simple position adjustment of the switch housing of a switch for detecting a particularly predetermined rotational position of a shaft, which ensures a simple and precise adjustment of the switch for the purpose of triggering a switching signal.

[0377] The problem is solved according to claim 88 in that a spring-elastic element engages the switch housing. The spring-elastic element is preloaded and applies a preload force to the switch housing. Due to the preload force, the switch housing is held against the stop without play, so that for precise adjustment of the switch, only one stop screw of the stop needs to be screwed in or out.

[0378] According to a preferred embodiment of the invention, the resilient element is designed as a spring, for example as a spiral spring, tension spring, but in particular as a leg spring. I ll

[0379] Advantageously, the pivot axis is at least parallel to the shaft's rotational axis; in particular, the pivot axis of the switch housing is coaxial with the shaft's rotational axis. This ensures easy adjustment.

[0380] In an embodiment of the invention, the shaft carries a flap of a carburettor, wherein the shaft is rotatably mounted in a carburettor housing of the carburettor and the flap lies in a flow channel of the carburettor housing and controls its effective channel cross-section.

[0381] In a particular application of the invention, the shaft is the throttle valve shaft of a carburetor, and the valve is a throttle valve of a carburetor. The switch can thus precisely detect the full-throttle position of the throttle valve. When the throttle valve is in the full-throttle position, the switch contact closes, so that when the throttle valve shaft is in a precisely adjustable rotational position, a switching signal is transmitted to the control unit of an internal combustion engine.

[0382] A spring engages the throttle valve shaft. The throttle valve shaft can be adjusted against the spring force of the spring into an open position of the throttle valve. Preferably, the applied preload force of the spring-elastic element is greater than the spring force acting on the throttle valve shaft.

[0383] The pivotable switch housing can be fixed in a rotationally fixed manner using a fastening screw. The fastening screw is first loosened so that the elastic element, in particular a leg spring, presses the switch housing against the stop with a preload force. Once the precise adjustment of the rotational position of the switch has been completed by screwing the stop screw in or out, the fastening screw is tightened and the switch housing is fixed in a rotationally fixed manner in the correctly set pivot position. The fastening screw engages in particular in the carburetor housing. According to an inventive method for adjusting a switch for detecting a full-load position of a throttle valve shaft of a carburetor with a control edge that moves with the throttle valve shaft for actuating a contact, it is provided that the contact is arranged in a switch housing of the switch, and the switch housing is mounted so as to be adjustably about a pivot axis.When assembling the switch housing, it is first pivoted against a stationary, adjustable stop to fix the position of the pivoting switch housing. To adjust the rotational position of the switch housing when it is resting against the stop, a stop screw is screwed in or out. The stop screw is screwed in or out until the switch housing is positioned such that the switching signal is reliably triggered when the throttle shaft is in the full load position. To secure the adjusted switch housing against the stop, a spring-elastic element can engage the switch housing. This element is preloaded and applies a preload force to the switch housing. Once the switch housing is adjusted in its rotational position, it is held against the stop by the preload force.

[0384] Further features of the invention emerge from the claims, the description, and the drawings. The features mentioned in the individual claims, as well as those mentioned in the description and illustrated in the drawings, can be combined individually to further define the subject matter of the invention. The features can also be combined in any desired manner into feature groups.

[0385] The invention generally relates to the arrangement of a switch on a shaft to trigger a contact in a predetermined rotational position of the shaft in order to transmit a switching signal to a control system. This general concept is described in the exemplary embodiment using a throttle valve shaft as an example.

[0386] An embodiment of the invention is illustrated in the drawings and will be described in detail below. Fig. 1 shows a perspective view of a carburetor with a throttle valve mounted on a throttle valve shaft and a choke valve mounted on a choke shaft,

[0387] Fig. G-2 a side view of the carburettor with a switch arranged on the throttle shaft,

[0388] Fig. G-3 a front view of the mixture channel of one connection side of the carburettor,

[0389] Fig. G-4 is a side view of the carburetor corresponding to Fig. G-2 with the throttle switch removed.

[0390] In the figures, reference symbol G-1 generally denotes a carburetor comprising a carburetor housing G-2 with a flow channel G-3 formed therein. The carburetor is a diaphragm carburetor with a fuel pump located beneath a housing cap G-4, to which fuel is supplied via a connecting piece G-5. On the side of the carburetor housing G-2 opposite the fuel pump, a control chamber is formed, the dry side of which has a connection G-6 for the ambient pressure, in particular for the clean air side of an air filter.

[0391] A choke valve G-7 and a throttle valve G-9 are arranged in the flow channel G-3 of the carburetor housing G-2 (Fig. G-4). The choke valve G-7 is held on a choke valve shaft G-8. The throttle valve G-9 is held on a throttle valve shaft G-10. The throttle valve shaft G-10 represents, by way of example, a general shaft G-50. The invention is not limited to the arrangement of a switch G-20 on a throttle valve shaft G-10, but generally relates to the arrangement of a switch G-20 on a shaft G-50. The choke valve shaft G-8 and the throttle valve shaft G-10 protrude from the carburetor housing G-2 on both sides. On one side of the carburetor, their ends carry levers G-47, G-48, which form part of an automatic starter G-49 (not further described).

[0392] The switch G-20 is located on the shaft G-50, in this example the throttle valve shaft G-10. The switch G-20 is located on an end section of the shaft G-50. The shaft G-50 preferably extends through the switch housing G-21 of the switch G-20.

[0393] The switch G-20 is designed as a position sensor, preferably formed by an electrical contact. The electrical contact is located within the switch housing G-21. The position sensor can also be an optical sensor, a capacitive sensor, or an inductive sensor.

[0394] A control edge G-22 (Fig. G-4) of the shaft G-50, e.g. a cam or the like, not shown in detail, is located within the switch housing G-21 and actuates the electrical contact in the switch housing G-21 in a predetermined rotational position of the shaft G-50, in the embodiment of the throttle valve shaft G-10.

[0395] According to the invention, a spring-elastic element G-30 (Fig. G-3, G-4) engages the switch housing G-21 and applies a preload force G-35 to the switch housing G-21 in the direction of arrow G-33 (Fig. G1). The preload force G-35 of the spring-elastic element G-30 causes the switch housing G-21 and thus the switch G-20 to rest against a preferably stationary stop G-40, in particular against a stop G-40 fixed to the housing. For this purpose, the switch housing G-21 can be pivoted about a pivot axis G-23 in the direction of arrow G-32. The pivot axis G-23 of the switch housing G-21, i.e. the pivot axis G-23 of the switch G-20, lies at least parallel to the rotation axis G1 1 of the shaft G-50, in the exemplary embodiment the throttle valve shaft G-10. Preferably, the pivot axis G-23 of the switch G-20 and the rotation axis Gl 1 of the throttle valve shaft G-10 are coaxial (Fig. G-3).In a special embodiment, the shaft G-50, in the exemplary embodiment the throttle valve shaft G-10, projects through the switch housing G-21, so that the switch housing G-21 can be pivoted about the rotation axis Gl 1 of the throttle valve shaft G-10.

[0396] A spring Gl 2 acts on the throttle valve shaft G-10. The throttle valve shaft G-10 can be adjusted against the spring force of the spring G-12 into an open position of the throttle valve G-9. The spring can be a spiral spring G-12 held on the throttle valve shaft G-10, the spring force of which acts in the open position of the throttle valve G-10. The preload force applied to the switch housing G-21 via the spring-elastic element G-30 is greater than the spring force of a spring acting in the opposite direction on the throttle valve shaft. This ensures that the spring force acting on the throttle valve shaft G-10 does not cancel out the preload force G-35 of the elastic spring element G-30.

[0397] In the illustrated embodiment, a leg spring G-31 is shown as the spring-elastic element G-30. One spring end of the spring is supported on the carburetor housing G-2 and the other spring end G-37 engages behind the switch housing G-21 of the switch G-20. As a result, as shown in Fig. G-4, a preload force G-35 is applied to the switch housing G-21 in the direction of arrow G-33 (Fig. G-2). The preload force G-35 applied to the switch housing G-21 in the direction of arrow G-33 causes the switch housing G-21 or the switch G-20 to be pressed against the stop G-40 in the direction of arrow G-32.

[0398] Preferably, a tab G-25 is provided on the switch housing G-21, which is opposite the stop G-40. An adjusting screw G-41 is held in the stop G-40. By screwing the adjusting screw G-41 in or out, the pivot position of the switch G-20 relative to the shaft G-50, in the exemplary embodiment to the throttle valve shaft G-10, is changed in the direction of arrow G-32 or against the direction of arrow G-32. In this way, the pivot position of the switch G-20 can be adjusted so precisely that the contact in the switch housing G-21 is actuated and a switching signal is generated precisely at a predetermined rotational position of the shaft G-50, in the exemplary embodiment the throttle valve shaft G-10. When the switch according to the invention is used on a carburetor G-11, the adjustment can be made such that a switching signal is emitted precisely at the full load position of the throttle valve G-9.

[0399] As shown schematically in Fig. 11, the fastening screw G-28 passes through a slot G-27 in the switch housing G-21. After loosening the fastening screw G-28, the switch housing G-21 can be moved in the direction of arrow G-32 and against the direction of arrow G-32 without the fastening screw G-28 having to be completely unscrewed. Once the adjustment of the switch G-21 is completed by correspondingly correcting its pivoting position relative to the predetermined rotational position of the shaft G-50, in this embodiment the throttle valve shaft G-10, the fastening screw G-28 is tightened and the switch G-20 is fixedly fastened against rotation. In the embodiment shown in Figure 11, after tightening the fastening screw G-28, the switch housing G-21 is firmly connected to the carburetor housing G-2.

Claims

Claims 1. A working device with a tool and with an internal combustion engine (Al 1) for driving the tool, wherein the internal combustion engine (Al 1) comprises an intake duct (Al 4) in which a throttle element (Al 6) is pivotably mounted, and wherein the internal combustion engine (Al 1) comprises an air duct (A-13) in which an air control element (A-20) is pivotably mounted, with an operating element (A-5) for adjusting the throttle element (A-16) in an opening direction (A-42), wherein the internal combustion engine (Al 1) has a speed limiting device (A-100), wherein the speed limiting device (A-100) comprises an actuator which is designed to adjust the throttle element (A-16) in a closing direction (A-44) to reduce the free flow cross-section of the intake duct (A-14), and wherein the working device (A-1) has a load-free state in which the tool is driven by the combustion engine (Al 1) and is not in engagement with a workpiece,characterized in that the position of the air control element (A-20) is coupled to the position of the throttle element (A-16) via a coupling device (A-58), wherein the coupling device (A-58) has an idle travel (As) which enables pivoting of the throttle element (A-16) relative to the air control element (A-20), and that the idle travel (As) is dimensioned such that the air control element (A-20) is in its closed position (A-104) in the load-free state, regardless of the position of the control element (A-5).

2. Working device according to claim 1, characterized in that the coupling device (A-58) is a mechanical coupling device (A-58).

3. Tool according to claim 1, characterized in that the free travel (As) is at most 30°.

4. Tool according to claim 1, characterized in that the free travel (As) is at least 15°.

5. Tool according to one of claims 1 to 4, characterized in that the free travel (As) is at least 2° greater than the adjustment angle (A-5).

6. Working device according to one of claims 1 to 5, characterized in that the internal combustion engine (Al 1) comprises a fuel valve (A-63, A-63') for supplying fuel, which is controlled by a control device (A-10).

7. Working device according to claim 6, characterized in that the control device (A-10) controls the actuator of the speed limiting device (Al 00).

8. Tool according to one of claims 1 to 7, characterized in that the throttle element (A-16) is a throttle valve.

9. Tool according to one of claims 1 to 8, characterized in that the throttle element (A-16) is pivotally mounted with a throttle shaft (A1 7) and that the air control element (A-20) is pivotally mounted with an air control shaft (A-21).

10. Tool according to claim 9, characterized in that the position of the throttle shaft (A-17) can be adjusted via the operating element (A-5), wherein the operating element (A-5) has a Transmission device (A-38) is coupled to an adjustable stop element (A-40) for the throttle shaft (A-17), wherein the stop element (A-40) specifies the maximum open position of the throttle element (A-16).

11. Tool according to claim 10, characterized in that a closing spring (A-43) is provided which pretensions the stop element (A-40) in a closing direction (A-44) of the throttle shaft (A-17).

12. Tool according to claim 10 or 11, characterized in that an opening spring (A-41) is provided which pretensions the throttle shaft (A-17) in an opening direction (A-42) towards the stop element (A-40).

13. Tool according to claim 12, characterized in that the actuator is designed to release the throttle shaft (A-17) from the stop element (A-40) against the force of the opening spring (A-41) and to adjust the throttle element (A-16) in the closing direction (A-44).

14. Tool according to claim 12 or 13, characterized in that the opening spring (A-41) and the coupling device (A-58) act on the same end section (A-52) of the throttle shaft (A-17).

15. Tool according to claim 14, characterized in that the coupling device (A-58) comprises a coupling element (A-59) connected in a rotationally fixed manner to the throttle shaft (A-17), and in that the opening spring (A-41) is supported with one end (A-71) on the coupling element (A-59) and with the other end (A-72) on the base body (A-36).

16. Tool according to one of claims 9 to 15, characterized in that the motor (A-45) acts on a first end portion (A-51) of the throttle shaft (A-17) and that the coupling device (A-58) acts on a second end portion (A-52) of the throttle shaft (A-17), the first end portion (A-51) and the second end portion (A-52) being arranged on opposite sides of the intake duct (A-14).

17. Tool according to one of claims 9 to 16, characterized in that the coupling device (A-58) comprises a coupling rod (A-66) which connects a coupling element (A-59) connected in a rotationally fixed manner to the throttle shaft (A-17) and a coupling element (A-65) connected in a rotationally fixed manner to the air control shaft (A-21).

18. Tool according to claim 17, characterized in that the connection of the coupling rod (A-66) to at least one of the coupling elements (A-59, A65) has an elongated hole which enables a limited relative movement of the coupling rod (A-66) to the coupling element (A-59, A-65).

19. Tool according to one of claims 1 to 18, characterized in that the tool (A1) is a cutting machine and the tool (A-7) is a cutting disc.

20. Throttle arrangement comprising a base body (B-36) in which an intake duct section (B-37) is formed, wherein in the intake duct section (B-37) a throttle element (B-16) with a throttle shaft (B-17) is pivotally mounted, wherein an operating element (B-5) for operation by an operator is provided, which is coupled via a transmission device (B-38) to an adjustable stop element (B-40) for the throttle shaft (B-17), wherein the stop element (B-40) specifies the maximum open position of the throttle element (B-16), and wherein an opening spring (B-41) is provided, which pretensions the throttle shaft (B-17) in an opening direction (B-42) towards the stop element (B-40), wherein a closing spring (B-43) is provided, which pretensions the stop element (B-40) in a closing direction (B-44) of the throttle shaft (B-17), and wherein a motor (B-45) is provided which is designed toto release the throttle shaft (B-17) from the stop element (B-40) against the force of the opening spring (B-41) and to adjust the throttle element (B-16) in the closing direction (B-44), characterized in that the stop element (B-40) is formed on a rotatably mounted driver (B-46) which is arranged in a housing (B-57) sealed from the environment.

21. Throttle assembly according to claim 20, characterized in that the transmission device (B-38) comprises a shaft entering the housing (B-57), the shaft being sealed by a seal (B-77).

22. Throttle arrangement according to claim 20 or 21, characterized in that the motor (B-45) is arranged sealingly at an opening (B-53) of the housing (B-57), wherein an element driven by the motor (B-45) projects through the opening (B-53).

23. Throttle arrangement according to one of claims 20 to 22, characterized in that the stop element (B-40) can be adjusted by the operator via the transmission device (B-38) against the force of the closing spring (B-43).

24. Throttle arrangement according to one of claims 20 to 23, characterized in that the throttle arrangement (B-15) is designed such that in the unactuated state of the transmission device (B-38), the torque exerted by the closing spring (B-43) on the throttle shaft (B-17) is greater than the torque exerted by the opening spring (B-41) on the throttle shaft (B-17).

25. Throttle arrangement according to one of claims 20 to 24, characterized in that the closing spring (B-43) is arranged outside the housing (B-57) and extends helically around an axis of rotation of the driver (B-46).

26. Throttle arrangement according to one of claims 20 to 25, characterized in that the housing (B-57) is delimited by the base body (B-36) and at least one cover element (B-48).

27. Throttle arrangement according to one of claims 20 to 26, characterized in that the throttle shaft (B-17) has two end sections (B-51, B52) which run on opposite sides of the intake duct section (B-37), that the motor (B-45) and the transmission device (B-38) act on the throttle shaft (B-17) at a first end section (B-51) of the throttle shaft (B-17), and that the opening spring (B-41) and the closing spring (B-43) act on the throttle shaft (B-17) at different end sections (B-51, B52) of the throttle shaft (B-17).

28. Throttle arrangement according to claim 27, characterized in that the closing spring (B-43) acts on the end portion (B-51) of the throttle shaft (B-17) on which the stop element (B-40) acts.

29. Throttle arrangement according to one of claims 20 to 28, characterized in that the driver (B-46) is mounted on an end section (B-51) of the throttle shaft (B-17) projecting from the base body (B-36).

30. Throttle arrangement according to one of claims 20 to 28, characterized in that the driver (B-46) is mounted on the base body (B-36).

31. Throttle arrangement according to one of claims 20 to 30, characterized in that the transmission device (B-38) comprises a shear-resistant transmission rod (B-39) which is suspended from a throttle lever (B-49) arranged outside the housing (B-57) and connected to the driver (B-46).

32. Throttle arrangement according to one of claims 20 to 31, characterized in that the transmission device (B-38) comprises a gear (B-56), in particular a spur gear.

33. Throttle arrangement according to one of claims 20 to 32, characterized in that the motor (B-45) is coupled to the throttle shaft (B-17) via a gear (B-90).

34. Throttle arrangement according to claim 32, characterized in that the motor (B-45) is arranged in the base body (B-36).

35. Throttle arrangement according to claim 32 or 33, characterized in that the gear (B-56, B-90) is arranged in the sealed housing (B-57).

36. Hand-held tool with at least one tool and a drive motor (Bl 1) for driving the at least one tool, wherein the drive motor (Bl 1) is a two-stroke engine operating with a scavenging system and having an intake duct (B-14) and an air duct (B-13), with a throttle arrangement (Bl 5) according to one of claims 20 to 35, with an air control element (B-20) which is pivotally mounted in the air duct (B-13) with an air control shaft (B-21), wherein the position of the air control shaft (B-21) is coupled to the position of the throttle shaft (B-17) via a coupling device (B-58), and wherein the motor (B-45) and the transmission device (B-38) act on the throttle shaft (B-17) at different end sections (B-51, B-52) of the throttle shaft (B-17).

37. Hand-held tool according to claim 36, characterized in that the throttle shaft (B-17) has a coupling element (B-59) which is formed in a rotationally fixed manner with the throttle shaft (B-17), via which coupling element the position of the air control shaft (B-21) is coupled to the position of the throttle shaft (B-17), and in that the opening spring (B-41) is supported with one end (B-71) on the coupling element (B-59) and with the other end (B-72) on the base body (B-36).

38. Method for operating an internal combustion engine, - wherein the internal combustion engine (Cl) has an intake duct (C-14) in which a throttle element (Cl 7) is pivotally mounted in an adjustment angle range (Ca), - wherein the position (Cy) of the throttle element (Cl 7) in the adjustment angle range (Ca) can be adjusted by an operator via an actuating device (C-29), and - wherein an actuator (C-21) is provided to pivot the throttle element (C-17) in a closing direction (C-32) to reduce a free flow cross-section of the intake duct (C-14), - with a control device (C-20) which is designed to control the actuator (C-21), - wherein the actuator (C-21) is controlled in the closing direction (C-32) of the throttle element (C-17) taking into account a speed criterion of the actual speed (Cn) of the combustion engine (Cl) as an input variable when a first limit value (C-gi) of a speed criterion is exceeded, - wherein the actuator (C-21) is controlled in the closing direction (C-32) of the throttle element (C-17) without taking into account the actual speed (Cn) of the internal combustion engine (Cl) as an input variable over at least one partial angle range (C-ß) of the adjustment angle range (Ca) when a second limit value (C-g2) of a speed criterion is exceeded.

39. Method according to claim 38, characterized in that the actuator (C-21) is controlled taking into account a speed criterion of the actual speed (Cn) of the internal combustion engine (Cl) as an input variable in the closing direction (C-32) of the throttle element (C-17) according to a first control method (C-41) when a first limit value (C-gi) of a speed criterion is exceeded and that the actuator (C-21) in the closing direction (C-32) of the throttle element (C-17) without taking into account the actual speed (Cn) of the internal combustion engine (Cl) as an input variable via at least at least one partial angle range (C-ß) of the adjustment angle range (Ca) is controlled according to a second control method (C-42) when a second limit value (C-g2) of a speed criterion is exceeded.

40. Method for operating an internal combustion engine, - wherein the internal combustion engine (Cl) has an intake duct (C-14) in which a throttle element (Cl 7) is pivotally mounted in an adjustment angle range (Ca), - wherein the position (Cy) of the throttle element (Cl 7) in the adjustment angle range (Ca) can be adjusted by an operator via an actuating device (C-29), and - wherein an actuator (C-21) is provided to pivot the throttle element (C-17) in a closing direction (C-32) to reduce a free flow cross-section of the intake duct (C-14), - with a control device (C-20) which is designed to control the actuator (C-21), - wherein the actuator (C-21) is controlled in the closing direction (C-32) of the throttle element (C-17) according to a first control method (C-41) when a first limit value (C-gl) of a speed criterion is exceeded, - wherein the actuator (C-21) is controlled in the closing direction (C-32) of the throttle element (C-17) over at least a partial angle range (C-ß) of the adjustment angle range (Ca) according to a second control method (C-42) when a second limit value (C-g2) of a speed criterion is exceeded, wherein the throttle element (C-17) is adjusted more quickly in the closing direction (C-32) when the actuator (C-21) is controlled according to the second control method (C-42) than when the actuator (C-21) is controlled according to the first control method (C-41).

41. Method according to claim 39 or 40, characterized in that the throttle element (C-17) is of maximum load (CP max ) to less than 30% of the maximum load (CP max ) is adjusted over a partial angle range (C-ß) of at least 5°, in particular at least 25° in the closing direction (C-32) when the actuator (C-21) is controlled according to the second control method (C-42).

42. Method according to one of claims 39 to 41, characterized in that the first control method (C-41) and the second control method (C-42) are carried out independently of the position of the throttle element (C-17).

43. Method according to one of claims 39 to 42, characterized in that the actuator (C-21) is also provided to pivot the throttle element (C-17) in an opening direction (C-34) to increase a free flow cross-section of the intake duct (C-14) and that the actuator (C-21) is controlled according to the first control method (C-41) in order to regulate a desired speed (C-ni) of the internal combustion engine (Cl) by pivoting the throttle element (C-17) in the opening direction (C-34) and in the closing direction (C-32).

44. Method according to claim 43, characterized in that the control is deactivated according to the first control method (C-41) when the rotational speed falls below a deactivation speed (C-n4).

45. Method according to one of claims 38 to 44, characterized in that the actuator (C-21) is controlled by the control device (C-20) to close the throttle element (C-17) until at least one termination criterion is reached, wherein a termination criterion after exceeding the second limit value (C-g2) of the speed criterion is the undershooting of the second limit value (C-g2) of the speed criterion.

46. ​​Method according to one of claims 38 to 45, characterized in that the internal combustion engine (Cl) has means for detecting the position (Cy) of the throttle element (Cl 7), wherein the position (Cy) of the throttle element (Cl 7) is detected and the throttle element (Cl 7) is adjusted to a predetermined position (C-yi) when the second limit value (C-g2) of the speed criterion is exceeded.

47. Method according to claim 46, characterized in that in a control operation of the internal combustion engine (Cl), in which the first speed criterion (C-gi) and the second speed criterion (C-g2) are not exceeded, the current position (Cy) of the throttle element (Cl 7) is stored as a predetermined position (Cy) and that the throttle element (C-17) is adjusted to the predetermined position (C-yi) when the second limit value (C-g2) of the speed criterion is exceeded.

48. Method according to one of claims 38 to 47, characterized in that the first speed criterion (C-gi) is a maximum speed (C-ni) and the second speed criterion (C-g2) is an engagement speed (C-n2), that the maximum speed (C-ni) is less than the engagement speed (C-n2) and that the engagement speed (C-n2) is less than 2,000 rpm, in particular less than 1,000 rpm, above the maximum speed (C-ni).

49. Internal combustion engine with an intake duct (C-14) in which a throttle element (C-17) is pivotally mounted in an adjustment angle range (Ca), wherein an actuating device (C-29) is provided for adjusting the position (Cy) of the throttle element (C-17) in the adjustment angle range (Ca) by an operator, with an actuator (C-21) which is designed to actuate the throttle element (C-17) to reduce a free flow cross-section of the intake duct (C-14) in a closing direction (C-32), with a control device (C-20) which is designed to control the actuator (C-21), wherein a first control method (C-41) for the actuator (C-21) is stored in the control device (C-20), wherein the first control method (C-41) is designed to control the actuator (C-21) to close the throttle element (C-17) when a first limit value (C-gi) of a speed criterion is exceeded, wherein the first control method (C-41) is designed to take into account a speed criterion of the actual speed (Cn) of the internal combustion engine (Cl) as an input variable, characterized in that a second control method (C-42) is stored in the control device (C-20), wherein the second control method (C-42) is designed to control the actuator (C-21) so to control,that the throttle element (C-17) is adjusted in the closing direction (C-32) over at least a partial angle range (C-ß) of its adjustment angle range (Ca) without taking into account the actual speed (Cn) of the internal combustion engine (Cl) as an input variable, wherein the control device (C-20) is designed to control the actuator (C-21) according to the second control method (C-42) when a second limit value (C-g2) of a speed criterion is exceeded.

50. Internal combustion engine according to claim 49, characterized in that the actuator (C-21) comprises an electric motor (C-31) and / or that the internal combustion engine (C1) has an exhaust silencer (C-23) with a catalyst (C-24).

51. Method for operating an internal combustion engine, - wherein the internal combustion engine (D-201) has an intake duct (D-214) in which a throttle element (D-217) is pivotally mounted in an adjustment angle range (Da), - wherein the opening angle (Dy) of the throttle element (D-217) can be adjusted in the adjustment angle range (Da) by an operator via an actuating device (D-229), and - wherein an actuator (D-221) is provided to pivot the throttle element (D-217) in a closing direction (D-232) to reduce a free flow cross-section of the intake duct (D-214) and to pivot the throttle element (D-217) in an opening direction (D-234) to increase a free flow cross-section of the intake duct (D-214), - with a control device (D-220) which is designed to control the actuator (D-221), - whereby the actuator (D-221) is above a target speed (Dn so n) is controlled to close the throttle element (D-217) in order to achieve the target final speed (Dn so n) to regulate, - wherein the actuator (D-221) is controlled in the opening direction (D-234) of the throttle element (D-217) over at least a partial angle range (D-ß) of the adjustment angle range (Da) when the target final speed (Dn so n) is exceeded, - wherein the adjustment speed of the throttle element (D-217) during adjustment by the actuator (D-221) in the opening direction (D-234) of the throttle element (D-217) after falling below a first speed limit (D-nö) is at least twice as high as the adjustment speed of the throttle element (D-217) during adjustment by the actuator (D-221) in the opening direction (D-234) above the first speed limit (D-ni).

52. Method according to claim 51, characterized in that the adjustment speed of the throttle element (D-217) during adjustment by the actuator (D-221) in the opening direction (D-234) of the throttle element (D-217) after falling below the first speed limit (D-nö) is 2 times to 10 times the adjustment speed of the throttle seielements (D-217) when adjusted by the actuator (D-221) in the opening direction (D-234) is above the first speed limit (D-ni).

53. Method according to claim 51 or 52, characterized in that the actuator (D-221) is put into an inactive state when a second speed limit (D-n2) is undershot, so that the throttle element (D-217) is adjusted to a position which corresponds to the opening angle (Dy) which was set by the operator via the actuating device (D-229), the second speed limit (D-n2) being below the first speed limit (D-ni).

54. Method according to one of claims 51 to 53, characterized in that the first speed limit (D-ni) is 500 rpm to 3,000 rpm, in particular 500 rpm to 2,000 rpm below the target final speed (Dn so n) of the combustion engine.

55. A working device with an internal combustion engine which is designed to be controlled according to one of claims 51 to 54.

56. Tool according to claim 55, characterized in that the tool is a cutting machine.

57. Working device according to claim 55 or 56, characterized in that the actuator (D-221) comprises an electric motor (D-231).

58. Tool according to one of claims 55 to 57, characterized in that the throttle element (D-217) is a throttle valve.

59. Working device according to one of claims 55 to 58, characterized in that the target final speed (Dn son) is stored in a control device (D-220) of the internal combustion engine (D-201).

60. A method for operating an internal combustion engine (E-1) having a cylinder (E-2), wherein a combustion chamber (E-3) is formed in the cylinder (E-2), having an intake duct (E-4) for supplying air, having a throttle element (E-7) arranged in the intake duct (E-4), having an actuator (E-21) designed to adjust the throttle element (E-17) in an opening direction (E-32) to increase the free flow cross-section of the intake duct (E-14) and in a closing direction (E-34) to reduce the free flow cross-section of the intake duct (E-14) in order to set a desired speed, and having a device for supplying fuel, the method comprising the following steps: (Ea) Determine whether an engine cycle has taken place without combustion in the combustion chamber (E-3) (Eb) reducing the amount of fuel supplied when a non-combustion engine cycle has been detected, (Ec) Evaluate the reaction of the actuator (E-21) (Ed) Increasing the amount of fuel supplied when the actuator (E-21) adjusts the throttle element (E-17) in the opening direction (E-34) in response to the reduction in the amount of fuel supplied.

61. Method according to claim 60, characterized in that the amount of fuel is increased in step (Ed) to a fuel amount which is greater than the amount of fuel which was supplied before the amount of fuel supplied was reduced in step (Eb).

62. Method according to claim 60 or 61, characterized in that the internal combustion engine (El) is a two-stroke engine.

63. Method according to claim 62, characterized in that on the basis of the determined engine cycles during which no combustion has taken place in the combustion chamber (E-3), it is determined whether the two-stroke engine operates in four-stroke operation.

64. Method according to claim 63, characterized in that the pressure (E-p) in the crankcase (E-4) is evaluated to detect the four-stroke operation.

65. Method according to claim 64, characterized in that the speed of the internal combustion engine (El) is evaluated to detect the four-stroke operation.

66. Method according to one of claims 60 to 65, characterized in that the fuel is fed into the intake duct (El 4) or into a crankcase (E-4) of the two-stroke engine.

67. Method according to one of claims 60 to 66, characterized in that the internal combustion engine (E1) comprises a control device (E-20) and that in step (Ea) the control device (E-20) determines whether an engine cycle without combustion in the combustion chamber (E-3) has taken place.

68. Method according to one of claims 60 to 67, characterized in that the direction of rotation of the actuator (E-21) is detected during the evaluation of the reaction of the actuator (E-21) in step (Eb).

69. Method according to one of claims 60 to 68, characterized in that the position of the throttle element (E-17) is detected during the evaluation of the reaction of the actuator (E-21) in step (Eb).

70. Internal combustion engine with a cylinder (E-2), wherein a combustion chamber (E-3) is formed in the cylinder (E-2), with an intake duct (E-14) for supplying air, with a throttle element (E-17) arranged in the intake duct (E-14), with an actuator (E-21) which is designed to adjust the throttle element (E-17) in an opening direction (E-32) to increase the free flow cross-section of the intake duct (E-14) and in a closing direction (E-34) to reduce the free flow cross-section of the intake duct (E-14) in order to set a desired speed, with a device for supplying fuel, wherein the internal combustion engine is designed to carry out the method according to one of claims 60 to 69.

71. Internal combustion engine according to claim 70, characterized in that the internal combustion engine (E-1) comprises a control device (E-20) which is designed to control the actuator (E-21).

72. Internal combustion engine according to claim 70 or 71, characterized in that the internal combustion engine (E-1) is a two-stroke engine, wherein the combustion chamber (E-3) is delimited by a piston (E-5) which drives a crankshaft (E-7) mounted in a crankcase (E-4) of the internal combustion engine (E-1), wherein the intake duct (E-14) supplies air into the crankcase (E-4), wherein the crankcase (E-4) is fluidically connected to the combustion chamber (E-3) in at least one predetermined position of the piston (E-5), wherein the internal combustion engine (E-1) has a pressure sensor (E- 36) for determining the pressure (Ep) in the crankcase (E-4), and wherein the device for supplying fuel supplies the fuel into the intake duct (E-14) or into the crankcase (E-4).

73. Carburettor comprising a carburettor body (F-10) and a throttle valve (F-4), • wherein the throttle valve (F-4) is held on a rotatably mounted throttle valve shaft (F-3), • and the throttle valve (F-4) assumes an idle position (F-14) in a first rotational position and an end position in a second rotational position, • and with a switch (F-17) which is suitable for emitting at least one output signal (F-18) to a full load position (F-24) of the throttle valve (F-4) in a predetermined rotational position of the throttle valve (F-4), characterized in that • that the specified rotational position of the throttle valve (F-4) is before the end position of the throttle valve (F-4), • that the specified rotational position with a rotation angle (F-DW) of 5° to 12° before the end position of the throttle valve (F-4), • and that in the specified rotational position before the end position of the throttle valve (F-4) the output signal (F-18) for the full load position (F-24) of the throttle valve (F-4) is emitted at least once.

74. Carburettor according to claim 73, characterized in that at a rotation angle (F-DW) between 7° and 10° before the end position of the throttle valve (F-4) the output signal (F-18) for the full load position (F-24) of the throttle valve (F-4) is emitted at least once, in particular at a rotation angle (F-DW) between 8° and 9°.

75. Carburettor according to one of claims 73 to 74, characterized in that the throttle valve shaft (F-3) is mounted in the carburettor housing (F-10) and the switch (F-17) is held on the carburettor housing (F-10).

76. Carburettor according to one of claims 73 to 75, characterized in that the switch (F-17) has a closing contact consisting of two contact elements (F-51, 61).

77. Carburettor according to one of claims 73 to 76, characterized in that the switch (F-17) is formed from a first electrical contact element (F-51) and a second electrical contact element (F-61), one contact element (F-61) being formed by the throttle valve shaft (F-4).

78. Carburettor according to claim 77, characterized in that the first electrical contact element (F-51) is held in a component (F-31) to be attached to the carburettor housing (F-10), into which a shaft section (F-33) of the throttle valve shaft (F-3) projects, and the shaft section (F-33) of the throttle valve shaft (F-3) projecting into the component (F-31) forms the second electrical contact element (F-61).

79. Carburettor according to claim 78, characterized in that the throttle valve shaft (F-4) has a control edge (F-37) which forms the second mechanical contact element (F-61).

80. Carburettor according to claim 79, characterized in that the control edge (F-37) is formed by a chamfer attached to the throttle valve shaft (F-3).

81. Carburettor according to claim 79 or 80, characterized in that in the predetermined rotational position of the throttle valve shaft (F-3), the control edge (F-37) of the throttle valve shaft (F-3) bears against the first contact element (F-51) located in the component (F-31) and closes the electrical contact of the switch (F-17).

82. Carburettor according to one of claims 73 to 81, characterized in that the throttle valve shaft (F-3) and / or the carburettor housing (F-10) is designed as an electrical conductor.

83. Carburettor, in particular according to one of claims 73 to 82, comprising a carburetor housing (F-10) and an intake duct (F-2) with a throttle valve (F-4) held on a throttle valve shaft (F-3), and with a switch (F-17) which is suitable for closing an electrical contact between a first contact element (F-51) and a second contact element (F-61) in a predetermined rotational position of the throttle valve (F-4), wherein the first contact element (F-51) is connected to a leading signal line (F-19) via at least one diode (F112, F-122), and the first contact element (F-51) is held in a plug-in receptacle (F-59) and at least one electrical connecting wire (F-46) of the diode (F112) is held in a further plug-in receptacle (F-50), wherein the plug-in receptacles (F-50, F59) are adjacent to each other and overlap geometrically, such thatthat a connecting wire (F-46) held in one plug-in receptacle (F-50) makes electrical contact with the contact element (F-51) located in the other plug-in receptacle (F-59) in the overlapping area.

84. Carburettor according to claim 83, characterized in that in a housing (F-30) of the switch (F-17) two diodes (Fl 12, Fl 22) inserted into diode receptacles (Fl 24, Fl 25) are whose connecting wires located at the bottom of the plug-in receptacles (F-124, F125) make electrical contact with each other.

85. Circuit arrangement for switches (Fl 1, F17) arranged on a carburetor, in particular on a carburetor according to one of claims 73 to 84, comprising a carburetor housing (F-10) and an intake duct (F-2) and an electrically controlled fuel valve (F-8) which opens into the intake duct (F-2), and with a choke valve (F-6) held in the intake duct (F-2) by a choke valve shaft (F-5), and with a first switch (Fl 1) which is suitable for indicating a predetermined rotational position of the choke valve (F-6), wherein the first switch (Fl 1) is arranged in a first electrical parallel branch (F-101) to the electrical fuel valve (F-8), and in the first electrical parallel branch (F-101) in series with the switch (Fl 1), a diode (Fl 11) is provided, as well as with a diode (Fl 11) arranged in the intake duct (F-2) arranged throttle valve (F-4), wherein the throttle valve (F-4) is held on a throttle valve shaft (F-3), and with a second switch (F-17) which is suitableto indicate a predetermined rotational position of the throttle valve (F-4), wherein the second switch (F-17) is arranged in a second electrical parallel branch (Fl 02) to the electrical fuel valve (F-8), and in the second electrical parallel branch (Fl 02) in series with the second switch (F-17) a first diode (F-, 112) and a second diode (F-122) is provided.

86. Circuit arrangement according to claim 85, characterized in that diodes (F-111, F-112, F-122) of different construction are arranged in the parallel branches (F-101, F-102), in particular a Zener diode, a Schottky diode, an LED diode, a rectifier diode or similar diode.

87. Two-stroke engine with a carburettor according to any one of claims 73 to 86.

88. Switch for detecting a rotational position of a shaft (G-50), with a control edge (G-22) moved with the shaft (G-50) for actuating a contact, wherein the contact is arranged in a switch housing (G-21) of the switch (G-20), and the switch housing (G-21) is mounted so as to be adjustable about a pivot axis (G-23), and with a stationary, adjustable stop (G-40) for fixing the position of the pivotable switch housing (G-21), characterized in that a spring-elastic element (G-30) acts on the switch housing (G-21), that the spring-elastic element (G-30) is prestressed and applies a prestressing force (G-35) to the switch housing (G-21), and the switch housing (G-21) is held on the stop (G-40) with the prestressing force (G-35).

89. Switch according to claim 88, characterized in that the spring-elastic element (G-30) is a spring, in particular a leg spring (G-31).

90. Switch according to claim 88 or 89, characterized in that the pivot axis (G-23) of the switch housing is the rotation axis (G-1) of the shaft (G-50).

91. Switch according to one of claims 88 to 90, characterized in that the shaft (G-50) carries a flap (G-9) of a carburetor (Gl), that the shaft (G-50) is rotatably mounted in a carburetor housing (G-2) of the carburetor (Gl), and the flap (G-9) lies in a flow channel (G-3) of the carburetor (Gl) and controls a channel cross-section of the flow channel (G-3).

92. Switch according to claim 91, characterized in that the shaft (G-50) is a throttle valve shaft (G-10) and the flap is a throttle valve (G-9) of the carburettor (Gl).

93. Switch according to claim 91 or 92, characterized in that a spring (G-12) acts on the throttle valve shaft (G-10), and the throttle valve shaft (G-10) is adjustable against a spring force of the spring (G-12) into an open position of the throttle valve (G-9).

94. Switch according to claim 93, characterized in that the applied pretensioning force (G-35) of the spring-elastic element (G-30) is greater than the spring force acting on the throttle valve shaft (G-10) by the spring (G-12).

95. Switch according to claim 88, characterized in that the switch housing (G-21) can be fixed in a rotationally fixed manner by means of a fastening screw (G-28).

96. Method for adjusting a switch for detecting a full-load position of a throttle valve shaft (G-50) of a carburetor (G-1), with a control edge (G-22) moved with the throttle valve shaft (G-50) for actuating a contact, wherein the contact is arranged in a switch housing (G-21) of the switch (G-20), and the switch housing (G-21) is mounted so as to be adjustable about a pivot axis (G-23), and with a stationary, adjustable stop (G-40) for fixing the position of the pivotable switch housing (G-21), characterized in that during assembly of the switch housing (G-21), it is first pivoted to the stop (G-40), that a stop screw (G-41) is screwed in or out to adjust the rotational position of the switch housing (G-21) resting against the stop (G-40), that the stop screw (G-41) is screwed in or out until the Switch housing (G-21) is positioned in such a waythat the switching signal is reliably triggered in the full load position of the throttle valve shaft (G-50).

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