Hand-held tool

Abstract

Hand-held working device with an internal combustion engine (4) for driving a tool, wherein the internal combustion engine (4) has an ignition device, a device for supplying fuel and a control device (31), wherein the control device (31) upon reaching an engagement speed (n E1 , n E2 ) to limit the speed (n) of the internal combustion engine (4), characterized in that the working device has an operating element for adjusting the engagement speed (n E2 ) by the operator.

Description

[0001] The invention relates to a hand-held working device of the type specified in the preamble of claim 1.

[0002] From DE 10 2008 064 008 A1 an internal combustion engine for a hand-held working device is known in which the speed is limited when an engagement speed is reached.

[0003] DE 100 03 486 C1 discloses a hand-held implement with automatic speed adjustment. Sensor elements are located in the handle areas of the implement. An increase in speed above a safety speed is possible if the operator holds the handle with both hands.

[0004] DE 10 2006 031 695 A1 discloses a hand-held working device with a mechanical speed controller for the combustion engine.

[0005] DE 10 2007 046 603 A1 discloses a work tool with a speed reduction function. When the operator lifts the work tool by a handle, the throttle valve can only be opened to a partial load position.

[0006] DE 10 2007 046 111 A1 discloses a hand-held harvesting device with counter-rotating balancing masses.

[0007] DE 198 34 443 A1 discloses a working device in which the speed of the combustion engine is limited to a safety speed when a special operating condition is detected.

[0008] For hand-held implements, continuous operation at reduced speed, i.e. a speed below full load, can be advantageous. This is the case, for example, with harvesting equipment, where adjusting the speed depending on the ripeness of the fruit to be harvested and the thickness of the branches to be shaken is advantageous. Operation at reduced speed can also be desirable to reduce noise. Until now, the operator has had to set the desired speed by partially pressing the throttle trigger. This is unpleasant for the operator, as the throttle trigger has to be held partially depressed continuously. It is also known to fix the throttle trigger in selected positions.

[0009] The invention is based on the object of creating a hand-held working device of the generic type in which the speed can be adjusted in a simple manner.

[0010] This object is achieved by a hand-held working device having the features of claim 1.

[0011] The engagement speed of the internal combustion engine is the speed at which the control device intervenes to limit the speed of the internal combustion engine. The speed can rise above the engagement speed during operation. Above the engagement speed, however, the control device takes measures to limit the speed. The fact that the engagement speed can be changed by the operator to set the speed of the internal combustion engine makes it easy to adjust the speed. The throttle lever usually acts on a throttle valve that controls the amount of combustion air supplied. If the throttle lever is only half operated, the throttle valve is also only half open. In part-load operation, i.e. when the throttle valve is only partially open, speed fluctuations occur when the load changes. It is therefore desirable to operate the internal combustion engine at full throttle, i.e. with the throttle valve completely open.

[0012] Because the operator can adjust the engagement speed, continuous operation at full throttle, i.e. with the throttle element fully open, is possible even at reduced speeds. The throttle trigger can be held fully depressed by the operator for a comfortable working experience. Adjusting the engagement speed shifts the upper branch of the engine characteristic curve. This results in the same engine behavior at each set engagement speed. This engine behavior corresponds to the behavior of an internal combustion engine at the usually fixed engagement speed. Because the engine is operated at full throttle, changes in load result in only comparatively small fluctuations in speed, resulting in comfortable and effective operation. Load changes are compensated for by the control system, which regulates the engine less at higher loads and more at lower loads.However, it may also be desirable to limit the engine speed at half throttle, i.e., with the throttle element partially open. This can be particularly advantageous for noise reduction.

[0013] The implement has a control element for adjusting the engagement speed. The control element can, for example, be a selector element such as a rotary switch or the like acting on a rotary potentiometer, via which the desired speed can be easily set. However, a switch can also be provided that can be used to switch between two engagement speeds. The control element is easy to operate by the operator. Even when the combustion engine is switched off, the set engagement speed can be retained, eliminating the need to readjust the speed every time the engine is started. The engagement speed is, in particular, continuously adjustable.The engagement speed can also be set similarly to a cruise control system in motor vehicles, for example, by the operator setting a desired speed by operating the throttle lever and then setting this as the engagement speed by operating a control element. A further control element or a predefined sequence of operating steps can be provided, for example, to change or delete the specified engagement speed.

[0014] The control element for adjusting the engagement speed can be operated without tools. The control element for adjusting the engagement speed can be operated particularly when the combustion engine is running. This allows the engagement speed to be adjusted during operation. The operator advantageously sets the desired speed during operation using the throttle lever. If the implement is a harvester, for example, the operator regulates the speed with the throttle lever to achieve the desired shaking frequency of the harvester. If the control element for adjusting the engagement speed, e.g., a button or similar, is then actuated, the current speed is advantageously set as the engagement speed.

[0015] It can also be provided that means for adjusting the engagement speed are formed by a predetermined manner of operating the implement. Advantageously, the implement has a control device that automatically adjusts the engagement speed when the operator operates the implement in the predetermined manner. This can be achieved, for example, by operating the implement at a constant speed for a predetermined period of time. This constant speed is advantageously defined as the engagement speed. Changing an engagement speed, once set, can also be achieved by a predetermined manner of operation, for example, by performing a predetermined sequence of operating steps.

[0016] To enable the operator to operate the control element for adjusting the engagement speed while the internal combustion engine is operating, the control element for adjusting the engagement speed is arranged on the handle or directly adjacent to the handle. The arrangement of the control element for adjusting the engagement speed should be such that the operator can hold the handle and use the handle to support the weight of the implement while simultaneously operating the control element for adjusting the engagement speed. Advantageously, two handles are provided, with the throttle lever for operating the internal combustion engine being arranged on one of the handles. In particular, the control element for adjusting the engagement speed is arranged on the handle or directly adjacent to the handle on which the throttle lever is also arranged.The control element for adjusting the engagement speed is arranged in particular such that an operator can simultaneously hold the handle, operate the throttle trigger, and operate the control element for adjusting the engagement speed with one hand. Advantageously, the control element for adjusting the engagement speed is arranged adjacent to the throttle trigger. It may also be advantageous to arrange the control element for adjusting the engagement speed on a housing of the implement adjacent to the throttle trigger. The arrangement is advantageously such that an operator can simultaneously operate the throttle trigger and the control element for adjusting the engagement speed with one hand.

[0017] The control device advantageously acts on the ignition device to limit the speed. The control device can suspend the ignition for at least some of the engine cycles, i.e., clock the engine out. The term “clocking out” refers to the operation of the internal combustion engine in which the internal combustion engine is deliberately controlled by suspending the ignition so that combustion does not take place in every engine cycle. One engine cycle corresponds to one revolution of the crankshaft in a two-stroke engine and two revolutions of the crankshaft in a four-stroke engine. Additionally or alternatively, the control device can adjust the ignition timing. In this case, adjusting the ignition timing “advance” or “retard” can be advantageous.

[0018] The control device advantageously also controls the amount of fuel supplied. To limit the engine speed, it is particularly provided that the control device changes the amount of fuel supplied. In this case, enriching or leaning the supplied mixture can be advantageous for limiting the engine speed. It can also be advantageous to interrupt the fuel supply for one or more engine cycles and thus regulate the engine. The term “regulation” refers to any measure to reduce or limit the engine speed, in particular interrupting the ignition, adjusting the ignition timing, interrupting the fuel supply, changing the amount of fuel supplied and any combination of these measures. In particular, a combination of the aforementioned measures is provided for limiting the engine speed.

[0019] Above the engagement speed, different speed ranges can also be provided, in which different throttle control measures are taken. In particular, above the engagement speed, as the speed continues to rise, the ignition is initially clocked out in a first speed range. Ignition therefore does not occur in every engine cycle, and accordingly combustion does not occur in every engine cycle. As the speed continues to rise, it is advantageous to also switch off the fuel supply in a second speed range above the first speed range. With all of the aforementioned measures to limit the speed, the position of the throttle valve remains unchanged. If the engine load changes at full throttle, i.e. while the engine is operating above the engagement speed, the throttle control of the combustion engine is automatically adjusted accordingly by the control unit.For example, the exhaust rate, the amount of fuel supplied, or the ignition timing are changed so that the engine speed can be kept essentially constant. The exhaust rate is the ratio of engine cycles without ignition in a period of time divided by the total number of engine cycles in that period. At partial load, the engine does not usually throttle down below the engagement speed, so the throttle position must be changed if the load changes. However, with simple combustion engines, such as those used in hand-held implements, this is usually only possible by the operator and not automatically.

[0020] Advantageously, the tool has a carburetor in which a throttle element is arranged, in particular rotatably mounted, wherein the fuel is supplied to the carburetor via at least one fuel opening. The supplied fuel quantity can be easily controlled by supplying the fuel via a metering valve controlled by the control system. In this case, the supplied fuel quantity can be controlled precisely according to the engine cycle. Especially when fuel is supplied directly into the crankcase or into a transfer port of the internal combustion engine, fuel metering precisely according to the engine cycle is easily possible.

[0021] The internal combustion engine advantageously has a throttle element for controlling the amount of combustion air supplied. The control element for adjusting the engagement speed advantageously also acts on the throttle element. This is particularly advantageous for automatically achieving a predetermined operating state by actuating the control element for adjusting the engagement speed. This is particularly an operating state for quiet operation, in which the throttle element is only partially open. To limit the speed, the ignition timing is advantageously adjusted to "advance" or "retard." In this case, it is advantageous to only set a fixed engagement speed for quiet operation.It can be provided that a first control element is provided for setting several engagement speeds by the operator and a second control element is provided for setting a special engagement speed for quiet operation, when actuated, the throttle element is adjusted at the same time and when actuated, the speed limitation is only effected by adjusting the ignition timing and not by balancing or changing the amount of fuel supplied.

[0022] The work device advantageously has a housing. The control element for adjusting the engagement speed is advantageously arranged outside the housing. This allows the operator to conveniently operate the control element for adjusting the engagement speed. Advantageously, the operator can operate the control element for adjusting the engagement speed without having to remove their hand, for example, from a handle on which an actuating element, in particular a throttle lever, for the combustion engine is arranged. This results in an ergonomic arrangement. The control element for adjusting the engagement speed advantageously protrudes beyond the outer contour of the housing. This makes the control element for adjusting the engagement speed easily accessible for the operator.

[0023] An embodiment of the invention is explained below with reference to the drawings. They show: Fig. 1 a schematic representation of a harvesting device, Fig. 2 a schematic representation of the combustion engine of the harvester from Fig. 1, Fig. 3 a diagram showing the ignition timing versus the engine speed, Fig. 4 a schematic representation of the speed adjustment process, Fig. 5 a diagram showing the engine power as a function of the amount of fuel supplied at a constant ignition point and Fig. 6 a diagram showing the course of the engine power over the ignition timing with a constant amount of fuel supplied.

[0024] Fig. Figure 1 shows a harvesting device 1, namely an olive shaker, as an exemplary embodiment of a hand-held implement. However, a speed adjustment can also be advantageous for other hand-held implements, such as power cutters, brush cutters, hedge trimmers, chainsaws, or blowers, to adapt to the respective tool and / or application.

[0025] The harvesting device 1 has a housing 2 on which a handle 3 is arranged. During operation, the harvesting device 1 is advantageously guided via the handle 3 shown and another handle, not shown. A throttle lever 32 is pivotally mounted on the handle 3. An internal combustion engine 4, which is designed as a two-stroke engine, is arranged in the housing 2. However, the internal combustion engine 4 can also be a four-stroke engine, in particular a mixture-lubricated four-stroke engine. The internal combustion engine 4 is a single-cylinder engine. The internal combustion engine 4 has a piston 12 that rotates a crankshaft 5. The crankshaft 5 drives a vibrating rod 8 back and forth in the direction of arrow 10 via a clutch 11, a gear 6, and a crank drive 7. The clutch 11 is in particular a centrifugal clutch.A hook 9 is arranged on the shaking rod 8, which forms the tool of the harvesting device and can be used to grip branches of a tree or shrub to be harvested. When harvesting olives, for example, it is advantageous to adapt the shaking frequency to the ripeness of the fruit to be shaken and the thickness of the branch. A switch 13 is provided for this purpose. In the exemplary embodiment, the switch 13 is arranged on the handle 3, in the immediate spatial proximity of the throttle lever 32. The arrangement of the switch 13 is advantageously such that the switch 13 can be operated, for example, with the thumb, while the throttle lever 32 is operated by the index finger. This allows the operator to operate the switch 13 and simultaneously guide the harvesting device 1 with both hands. The switch 13 can advantageously act on a rotary potentiometer or be designed as a button.In particular, the operator uses the throttle lever 32 to set a desired speed, which, for example, generates a desired frequency for shaking a tree. When the desired speed is reached, the operator actuates switch 13. Advantageously, the current speed of the combustion engine 4 is set as the engagement speed when switch 13 is actuated. The engagement speed is the speed above which a control device of the implement intervenes to limit the speed. The speed can therefore rise above the engagement speed during operation, but the combustion engine 4 is throttled down above the engagement speed. In order to delete an engagement speed once it has been set, a further switch can be provided. Alternatively, a predetermined sequence of operating steps can cause a set engagement speed to be deleted.

[0026] Instead of the switch 13 on the handle 3, a switch 13' can be arranged on the housing 2. The switch 13 is arranged on the outside of the housing 2 in the immediate vicinity of the handle 3 and the throttle lever 32, so that the switch 13 can be conveniently operated by the operator. The switch 13' is advantageously also arranged so that the operator can hold the handle 3 with one hand and simultaneously operate the throttle lever 32 and the switch 13'. The switch 13, 13' can also be arranged so that it can be operated with the other hand, which is not located on the handle 3.

[0027] The switch 13, 13' can, for example, be designed as a rotary switch that acts on a rotary potentiometer and with which the engagement speed can be adjusted continuously or in design-specified detent increments. However, the switch 13, 13' can also have only two detent positions, so that the switch 13, 13' can be used to switch between two engagement speeds, advantageously a maximum engagement speed and a reduced engagement speed. The switch 13, 13' projects beyond the outer contour of the housing 2 and can be operated from the outside without tools, i.e., without a screwdriver or the like.

[0028] Fig. Figure 2 shows the structure of the internal combustion engine 4 in detail. The internal combustion engine 4 has a cylinder 14 in which the piston 12 is reciprocating. The cylinder 14 and the piston 12 define a combustion chamber 18 into which a spark plug 19 projects. An outlet 21 for exhaust gases leads from the combustion chamber 18. The piston 12 drives the crankshaft 5 via a connecting rod 16. The crankshaft 5 is rotatably mounted in a crankcase 15. The crankshaft 5 is advantageously connected in a rotationally fixed manner to a flywheel 30 on which one or more pole groups are arranged, which in Fig. 2 are not shown. The flywheel 30 can also be designed as a fan wheel. An ignition module 20 is arranged on the outer circumference of the flywheel 30. The ignition module has at least one coil in which the pole groups on the flywheel 30 induce a voltage that is used to ignite the spark plug 19. The ignition module 20 is connected to a control device 31 that controls or regulates the ignition timing.

[0029] The internal combustion engine 4 has an intake duct 24, which opens into the crankcase 15 via an inlet 25 controlled by the piston 12. The intake duct 24 draws in combustion air via an air filter 29. Part of the intake duct 24 is formed in a carburetor 23. A throttle valve 26 is pivotally mounted in the carburetor 23. In addition, a choke valve (not shown) can be provided upstream of the throttle valve 26. In the area of ​​the throttle valve 26, fuel openings 27 open into the intake duct 24, through which fuel is drawn into the intake duct 24 depending on the negative pressure prevailing in the area of ​​the throttle valve 26. The amount of fuel supplied to the fuel openings 27 is controlled by a metering valve 28, which is actuated by the control device 31.Instead of supplying the fuel to the carburetor 23, a direct fuel supply can also be provided via a metering valve 28' into the crankcase 15 or via a metering valve 28" into a transfer channel 22. The transfer channel 22 connects the crankcase 15 in the region of the bottom dead center of the piston 12 to the combustion chamber 18.

[0030] During operation, a fuel / air mixture is drawn into the crankcase 15 near the top dead center of the piston 12 and compressed in the crankcase 15 during the downward stroke of the piston 12. Near the bottom dead center of the piston 12, the fuel / air mixture flows from the crankcase 15 through one or more transfer channels 22 into the combustion chamber 18, where it is ignited by the spark plug 19 near the top dead center of the piston 12. During the downward stroke of the piston 12, the exhaust gases leave the combustion chamber 18 through the outlet 21.

[0031] The carburetor 23 has one or more adjustment devices, such as adjusting screws, with which the supplied fuel quantity can be adjusted. The adjustment of the carburetor 23 is a preset that is made during manufacture or service. Adjustment by the operator may also be possible. The adjustment of the carburetor 23 is performed using tools, in particular a screwdriver or special tools.

[0032] Fig. 3 shows the curve of the ignition timing ZZP and the power P of the internal combustion engine 4 over the speed n. The ignition timing ZZP is changed, as the curves 41, 42 and 43 show, depending on the speed n of the internal combustion engine 4. In Fig. 3, the ignition timing ZZP is given in degrees of crankshaft angle before top dead center. Typically, the speed n is controlled by the control device 31 in the range of an engagement speed n E1, which in the example is approximately 9,000 revolutions per minute. For this purpose, the ignition timing ZZP is set above the engagement speed n E1 towards the top dead center, i.e. "late", as shown in curve 41. The speed can be adjusted via the engagement speed n E1 out into the above the engagement speed n E1 The intervention speed n E1 is the speed at which the control device 31 intervenes to prevent an excessive increase in the speed. Additionally or alternatively, above the intervention speed n E1It may also be provided to suspend the ignition, for example, according to a predetermined timing pattern for individual engine cycles. The term "timing pattern" refers to the pattern with which engine cycles with ignition and engine cycles without ignition follow one another. A complete ignition shutdown may also be provided. The power P resulting from controlling the ignition timing ZZP according to curve 41 is shown in curve 44. The maximum power P max results at a speed n Pmax which are below the engagement speed n E1 lies.

[0033] The engagement speed n can be set via switch 13, 13' E1 be adjusted, for example to the Fig. 3 marked engagement speed n E2 . The adjustment is possible over a wide operating range, as indicated schematically by the double arrow 33. The adjustment of the engagement speed n E1causes the control device 31 to already at a lower engagement speed below the engagement speed n E1 , which corresponds to the maximum engagement speed, intervenes to limit the speed. If the engagement speed n E1 for example, to the lower engagement speed n E2 adjusted, the control device 31 already intervenes at the engagement speed n E2 to limit the engine speed. The maximum engagement speed corresponds to the engagement speed usually set for speed limitation in combustion engines whose engagement speed is not adjustable. The maximum engagement speed is also the maximum adjustable engagement speed. For regulation, the ignition timing ZZP is controlled according to curve 42. The throttle lever 32 can be moved by the operator at the engagement speed n E2remain fully pressed, so that the throttle valve 26 is fully open, thus operating the combustion engine 4 at full throttle. The setting of the engagement speed n E1 , n E2 , n E3 can be done during operation and without tools and is to be distinguished from the adjustment of the carburetor 23, which is a basic setting and cannot be done during operation. The adjustment of the carburetor 23 acts on the carburetor itself and directly influences the amount of fuel supplied, while the adjustment of the engagement speed n E1 , n E2 , n E3 acts on the control device 31 and the intervention speed n stored in the control device E1 The change in the engagement speed advantageously only causes a change in the control of the combustion engine 4 above the engagement speed.

[0034] If the engagement speed n is exceeded E2the speed n is regulated by the control device 31 in a predetermined manner. In the range above the engagement speed n E2 Within the cut-off range, the combustion engine 4 is controlled by adjusting the ignition timing ZZP or suspending the ignition and / or changing the supplied fuel quantity x or interrupting the fuel supply so that the speed n does not rise beyond the cut-off range. Curve 45 shows the power P curve when the ignition timing is controlled according to curve 42, i.e., above the intervention speed n E2 is adjusted to “late”. The power P drops above the engagement speed n E2 more than when the ignition timing ZZP is controlled according to curve 41. Since the engagement speed n E2 above the speed n Pmax , at which the maximum power P is reached, the maximum power P is also achieved when the ignition timing ZZP is controlled according to curve 42. maxreached.

[0035] The engagement speed n E can also be used up to an exemplary engagement speed n B3 be adjusted below the speed n Pmax at maximum engine power. At the engagement speed n E3 the ignition timing ZZP is not yet fully advanced, which would cause the engine speed n to continue to rise. If the engagement speed were set to a higher value, the ignition timing ZZP would be further advanced as the engine speed n continues to rise. If the engagement speed n E3 to a speed below the speed n Pmax set at maximum power, the maximum engine power P max is not reached, but the power decreases according to curve 46 as soon as the engagement speed n E3is achieved. Even at partial load, i.e. partially open throttle valve 26, the setting of a lower intervention speed n E2 , n B3 be advantageous, for example, to influence the noise development of the combustion engine 4. The control range extends from the respectively set intervention speed n E1 , n E2 , n E3 up to the assigned maximum speed n max1 , n max2 , n max3 . The maximum speed n max1 , n max2 , n max3 is the speed of the combustion engine 4, over which the speed at the respectively set intervention speed n E1 , n E2 , n E3 cannot increase. The maximum speeds n max1 , n max2 , n max3 can, as in Fig. 3. However, it can also be provided that the speeds n max1 , n max2 , n max3are equal, so that regardless of the set engagement speed n E1 , n E2 , n E3 the same maximum speed n max1 , n max2 , n max3 This can be achieved by using different characteristics between the engagement speeds n E1 , n E2 , n E3 and the associated maximum speeds n max1 , n max2 , n max3 can be achieved.

[0036] Fig. Figure 4 schematically illustrates the effect of adjusting the engagement speed. In process step 38, the operator sets an engagement speed n via switch 13. E2 This engagement speed n E2 is transmitted in method step 39 to the control device 31, which in method step 40 controls the spark plug 19 and / or the metering valve 28 so that the speed n above the intervention speed n set by the operator E2The engagement speed n E2 therefore does not indicate the maximum engine speed, but rather the speed at which the control device 31 intervenes to limit the speed. The control device 31 can interrupt the fuel supply for individual engine cycles, completely shut off the fuel supply, or increase or decrease the supplied fuel quantity x per engine cycle. A combination of these measures, for example interrupting the fuel supply for some engine cycles and supplying a reduced or increased fuel quantity for other engine cycles, can also be provided. Additionally or alternatively, the ignition point ZZP can be adjusted and / or the ignition can be interrupted for individual engine cycles, i.e. the ignition can be de-clocked, so that the internal combustion engine 4 is throttled down.

[0037] Fig. Figure 5 shows schematically the curve of the engine power P over the supplied fuel quantity x. The power P is in the form of a downwardly opening parabolic curve 34. The curve 34 has a maximum corresponding to the maximum power P max By increasing or decreasing the supplied fuel quantity, the power P and thus also the speed n of the combustion engine 14 can be reduced. The possible control range 36 is in Fig. 5 is also entered. Curve 34 shows the power P curve at a constant ignition timing ZZP.

[0038] Fig. Figure 6 shows the power P curve for a constant fuel quantity x and a changed ignition timing ZZP using a curve 35. Curve 35 has a maximum. At later ignition timings ZZP, the power P is reduced. The possible adjustment of the ignition timing ZZP is shown as control range 37. Control range 37 extends from the ignition timing ZZP at the maximum power P max to earlier ignition timings ZZP. Therefore, the engine power P and thus the speed n of the combustion engine 4 can also be changed by changing the ignition timing ZZP.

[0039] It may be advantageous to adjust the engagement speed n simultaneously with the adjustment of the engagement speed n E2also adjust the position of the throttle valve 26. This can be particularly advantageous for setting a quiet operating mode. Using the switch 13, 13', the operator can select a quiet operating mode in which the throttle valve is only partially open and in which the engine speed is already at an engagement speed n E2 which is below the maximum speed n A1 of the combustion engine 4. The adjustment of the throttle valve 26 is advantageously carried out by actuating the switch 13, 13'. This is shown schematically in Fig.2. It may also be advantageous to provide several switches 13, 13', wherein one of the switches 13, 13' is provided for setting a quiet operation, which merely allows switching between normal operation and quiet operation. This switch 13, 13' also advantageously acts on the throttle valve 26 and prevents the throttle valve 26 from opening completely. At the same time, for quiet operation, limiting the speed by simply adjusting the ignition timing to "advance" or "retard" is advantageous. Clocking out, i.e., interrupting the ignition, or changing the amount of fuel supplied is not provided for this operating mode. The engagement speed n E2 variable, especially continuously adjustable.

[0040] It can also be provided that the intervention speed can be set by the operator according to the speed setting in a cruise control system in motor vehicles. The operator sets a desired speed, for example, using the throttle lever 32 and then actuates a control element, for example a switch 13, 13', control knob, or button, while the internal combustion engine 4 is running. This sets the current speed as the intervention speed. The speed can be released, for example, by another control element, by repeatedly actuating the control element for setting the intervention speed, by executing a predetermined sequence of operating steps, or the like.

[0041] The operating element, for example the switch 13, 13', a control knob or button, is advantageously arranged so that the operator can hold the handle 3 with one hand and simultaneously operate the throttle lever 32 and the operating element with this hand.

[0042] Alternatively, electronics can be provided which - conveniently integrated into the control unit 31 - automatically adjusts the engagement speed n E If, for example, the user operates a working device such as harvester 1 over a specified period of time at a largely constant speed, the electronics causes this same speed to be stored as the intervention speed n E .

[0043] The automatic adjustment of the engagement speed n Ecan be continuously active. If the user operates the harvesting device 1 for a predetermined period of time at a different working speed, the electronics again initiates the adoption of the current engine speed as the new intervention speed n E . The speed can be released by actuating an operating element, for example a switch 13, 13', a button, a control knob or the like, or by carrying out a predetermined sequence of operating steps.

[0044] The automatic adjustment of the engagement speed n E and / or the deletion of a set intervention speed n E can alternatively or additionally be carried out depending on the signal from a sensor, for example depending on the signal from a yaw rate sensor, pressure sensor, temperature sensor, capacitive and / or inductive sensor or the like.

Claims

[1] Hand-held working device with an internal combustion engine (4) for driving a tool, wherein the internal combustion engine (4) has an ignition device, a device for supplying fuel and a control device (31), wherein the control device (31) upon reaching an engagement speed (n E1 , n E2 ) intervenes to limit the speed (n) of the internal combustion engine (4), characterized by that the implement has a control element for adjusting the engagement speed (n E2 ) by the operator. [2] Working device according to claim 1, characterized by that the control element for setting the engagement speed (n E2 ) can be operated without tools. [3] Working device according to claim 1 or 2, characterized by that the control element for setting the engagement speed (n E2 ) can be actuated during operation of the internal combustion engine (4). [4] Working device according to claim 3, characterized bythat when the control element for setting the engagement speed (n E2 ) the instantaneous speed as engagement speed (n E2 ) is determined. [5] Working device according to one of claims 1 to 4, characterized by that the working device has at least one handle (3) for holding the working device during operation and that the control element for adjusting the engagement speed (n E2 ) are arranged on the handle (3) or immediately adjacent to the handle (3). [6] Working device according to one of claims 1 to 5, characterized by that the working device has a throttle lever (32) and that the means for adjusting the engagement speed (n E2 ) are arranged adjacent to the throttle lever (32). [7] Working device according to claims 1 to 6, characterized by that the control device (31) acts on the ignition device to limit the speed (n). [8] Working device according to claim 7, characterized bythat the control device (31) suspends the ignition during at least part of the engine cycles. [9] Working device according to claim 7 or 8, characterized by that the control device (31) adjusts the ignition timing (ZZP). [10] Working device according to one of claims 1 to 9, characterized by that the control device (31) controls the supplied fuel quantity (x), and that the control device (31) changes the supplied fuel quantity (x) to limit the speed (n). [11] Working device according to claim 10, characterized by that the working device has a carburettor (23), wherein the fuel in the carburettor (23) is supplied via at least one fuel opening (27). [12] Working device according to claim 10 or 11, characterized by that the fuel is supplied via a metering valve (28, 28', 28'') which is controlled by the control device (31). [13] Working device according to one of claims 1 to 12, characterized bythat the internal combustion engine (4) has a throttle element for controlling the amount of combustion air supplied, and that the control element for adjusting the engagement speed (n E2 ) acts on the throttle element. [14] Working device according to one of claims 1 to 13, characterized by that the working device has a housing (2), wherein the control element for adjusting the engagement speed (n E2 ) is arranged outside the housing (2). [15] Working device according to one of claims 1 to 14, characterized by that the control element for setting the engagement speed (n E2 ) protrudes beyond the outer contour of the housing (2).

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