Carburetor and two-cycle engine with carburetor

Abstract

The invention relates to a carburettor and to a two-stroke engine with a carburettor, the carburettor having a carburettor body in which an air intake channel section is configured. A throttle flap for controlling the free flow cross-section of the air intake channel section is pivotably supported in the carburettor body on a throttle shaft. The air intake channel section has a first longitudinal centre axis in the region of the throttle shaft. The throttle flap has a first end position and a second end position, in which the throttle flap releases a greater flow cross-section of the air intake channel section than in the first end position. Arranged upstream of the throttle shaft is a partition wall section, against which the throttle flap lies in the second end position. Upstream of the partition wall section is provided a choke flap, which can be pivoted between a first end position and a second end position. The throttle flap and the choke flap overlap in the direction of the first longitudinal centre axis in their second end positions. The carburettor is provided for a two-stroke engine.

Description

TECHNICAL FIELD

[0001] The invention relates to a carburettor and to a two-stroke engine having a carburettor. BACKGROUND

[0002] A carburettor is known from US 2007 / 00257379 A1, which has a throttle valve and a choke valve for controlling the flow cross-section of an air passage. Between the throttle valve shaft and the choke valve shaft there is arranged a partition wall section, which separates the air passage and the mixture passage in the carburettor from one another.

[0003] Such a carburettor can be used in a two-stroke engine in a hand-guided work appliance, such as for example a motor saw, an outdoor trimmer, a hedge trimmer, a separator, a blowing appliance or the like. In such a work appliance, a small weight and a small construction size are desirable in order to achieve an ergonomic work. At the same time, the two-stroke engine should also have a smooth running behaviour in operation when the work appliance is swung. SUMMARY

[0004] The invention is based on the task of creating a carburettor of this type, which has a small weight and a small construction size with a good running behaviour of the two-stroke engine operated with the carburettor. A further task of the invention is to create a two-stroke engine having a carburettor, which has a good running behaviour and a small construction size.

[0005] The task with regard to the carburettor is solved by a carburettor having a carburettor body, in which a air passage section is configured, wherein a throttle valve for controlling the free flow cross-section of the air passage section is pivotably supported in the carburettor body on a throttle valve shaft, wherein the air passage section has a first longitudinal centre axis in the region of the throttle valve shaft, wherein the throttle valve has a first end position and a second end position, wherein the throttle valve releases a greater flow cross-section of the air passage section in the second end position than in the first end position, wherein in the air passage section upstream of the throttle valve shaft there is arranged a partition wall section, which divides the air passage section into a mixture passage section and an air passage section, wherein the throttle valve in the second end position rests against the partition wall section, wherein in the air passage section upstream of the partition wall section there is arranged a choke valve, which can be pivoted between a first end position and a second end position, wherein the choke valve releases a greater flow cross-section in its second end position than in its first end position, wherein the throttle valve and the choke valve in their second end positions overlap in the direction of the first longitudinal centre axis of the air passage section.

[0006] The task relates to a carburettor which is also solved by a carburettor with a carburettor body in which an air inlet channel section is configured, wherein a throttle flap for controlling the free flow cross section of the air inlet channel section is swingably supported in the carburettor body on a throttle flap axis, wherein the air inlet channel section has a first longitudinal centre axis in the region of the throttle flap axis, wherein the throttle flap has a first end position and a second end position, wherein the throttle flap releases a greater flow cross section of the air inlet channel section in the second end position than in the first end position, wherein a partition wall section is arranged in the air inlet channel section upstream of the throttle flap axis, which divides the air inlet channel section into a mixture channel section and an air channel section, wherein the throttle flap rests against the partition wall section in the second end position, wherein a choke flap is arranged in the air inlet channel section upstream of the partition wall section, which can be swung between a first end position and a second end position, wherein the choke flap releases a greater flow cross section in its second end position than in its first end position, wherein the first longitudinal centre axis of the air inlet channel section and the second longitudinal centre axis of the air inlet channel section have a misalignment relative to one another in the region of the choke flap axis, which is measured parallel to the swing axis of the throttle flap.

[0007] With regard to two-stroke engines, the task is solved by a two-stroke engine having a carburettor, wherein the carburettor has a carburettor body, in which a gas inlet channel section is configured, wherein a throttle flap for controlling the free flow cross section of the gas inlet channel section is swingably supported in the carburettor body on a throttle shaft, wherein the gas inlet channel section has a first longitudinal centre axis in the region of the throttle shaft, wherein the throttle flap has a first end position and a second end position, wherein the throttle flap releases a greater flow cross section of the gas inlet channel section in the second end position than in the first end position, wherein a partition wall section is arranged in the gas inlet channel section upstream of the throttle shaft, which divides the gas inlet channel section into a mixture channel section and an air channel section, wherein the throttle flap in the second end position rests against the partition wall section, wherein a choke flap is arranged in the gas inlet channel section upstream of the partition wall section, which can be swung between a first end position and a second end position, wherein the choke flap releases a greater flow cross section in its second end position than in its first end position, wherein the throttle flap and the choke flap in their second end positions overlap in the direction of the first longitudinal centre axis of the gas inlet channel section, wherein the gas inlet channel section of the carburettor forms one section of the gas inlet channel of the two-stroke engine, wherein the gas inlet channel is divided downstream of the carburettor into a mixture channel and an air channel, wherein the mixture channel section of the carburettor is coupled at the mixture channel and the air channel section of the carburettor is coupled at the air channel, wherein the two-stroke engine has a cylinder body, in which a combustion chamber is configured, wherein the combustion chamber is bounded by a piston which is supported in the cylinder body for back-and-forth movement, wherein the piston rotationally drives a crankshaft which is supported in a crankcase, wherein the mixture channel opens via a mixture inlet into a crankcase interior space of the crankcase and wherein the air channel can be connected to at least one overflow channel of the two-stroke engine.

[0008] With regard to two-stroke engines, the task is also solved by a two-stroke engine having a carburettor, wherein the carburettor has a carburettor body, in which a gas inlet channel section is configured, wherein a throttle flap for controlling the free flow cross section of the gas inlet channel section is swingably supported in the carburettor body on a throttle flap axis, wherein the gas inlet channel section has a first longitudinal centre axis in the region of the throttle flap axis, wherein the throttle flap has a first end position and a second end position, wherein the throttle flap releases a greater flow cross section of the gas inlet channel section in the second end position than in the first end position, wherein a partition wall section is arranged in the gas inlet channel section upstream of the throttle flap axis, which divides the gas inlet channel section into a mixture channel section and an air channel section, wherein the throttle flap abuts against the partition wall section in the second end position, wherein a choke flap is arranged in the gas inlet channel section upstream of the partition wall section, which can be swung between a first end position and a second end position, wherein the choke flap releases a greater flow cross section in its second end position than in its first end position, wherein the first longitudinal centre axis of the gas inlet channel section and the second longitudinal centre axis of the gas inlet channel section have a misalignment relative to one another in the region of the choke flap axis, measured parallel to the swing axis of the throttle flap, wherein the gas inlet channel section of the carburettor forms a section of a gas inlet channel of the two-stroke engine, wherein the gas inlet channel is divided downstream of the carburettor into a mixture channel and an air channel, wherein the mixture channel section of the carburettor is coupled at the mixture channel and wherein the air channel section of the carburettor is coupled at the air channel, wherein the two-stroke engine has a cylinder body, in which a combustion chamber is configured, wherein the combustion chamber is bounded by a piston which is supported in the cylinder body for back-and-forth movement, wherein the piston drives a crankshaft supported in a crankcase in rotation, wherein the mixture channel opens via a mixture inlet into a crankcase interior space of the crankcase and wherein the air channel can be connected to at least one overflow channel of the two-stroke engine.

[0009] The throttle valve and the choke valve of the carburettor each have a first end position and a second end position. The flow cross section of the intake channel section released by the throttle valve or the choke valve is respectively larger in the second end position of the throttle valve and the choke valve than in the first end position. Upstream of the throttle valve shaft a partition wall section is arranged in the intake channel section, which divides the intake channel section into a mixture channel section and an air channel section. In their second end position the throttle valve and the choke valve overlap in the direction of the first longitudinal centre axis of the intake channel section. Thereby, the distance between the rotational axes of the throttle valve and the choke valve can be reduced. A reduced construction length of the carburettor body and thereby also a reduced weight of the carburettor is produced. By means of the partition wall section arranged between the throttle valve and the choke valve a desired separation between the intake channel section and the air channel section can be achieved. Depending on the design of the partition wall section a transfer of the mixture from the mixture channel section into the air channel section or a pressure equalisation can be achieved with the throttle valve partially open. If the partition wall section leads up to the throttle valve shaft, a very great or complete separation of the air channel section and the mixture channel section in the carburettor can be achieved.

[0010] In the region in which the throttle valve and the choke valve overlap, the partition wall section is arranged between the throttle valve and the choke valve as a result of the throttle valve and the choke valve abutting at the partition wall section. Thus, in the second end position of the throttle valve and the choke valve the throttle valve, the choke valve and the partition wall section are arranged in a length section of the carburettor. In this region, a comparatively large thickness of the arrangement between the air channel section and the mixture channel section is thereby achieved. It has been shown, however, that as a result of the usual dimensions of the choke valve shaft this region is largely or completely in the wind shadow of the choke valve shaft and thereby only slightly influences the flow characteristics in the carburettor and thereby also the air quantity and the mixture quantity supplied to the internal combustion engine and the mixture composition. Thereby, the desired operating behaviour can be achieved with a reduced carburettor size and a reduced weight.

[0011] Advantageously, the ratio of the length of the carburettor body measured in the direction of the first longitudinal centre axis to the diameter of the throttle valve is at most 1.5. Advantageously, a ratio of at most 1.4, in particular preferably at most 1.3, is provided. Thereby, a relatively small length of the carburettor body with regard to the diameter of the throttle valve, which also determines the size of the intake channel section in the region of the throttle valve, is obtained. The length section of the carburettor, in which not only the throttle valve but also the choke valve extends in its second end position, advantageously has a length measured parallel to the longitudinal centre axis, which is at least 10%, in particular at least 15%, of the diameter of the throttle valve. The relatively large length of the length section, in which not only the throttle valve but also the choke valve extends, in which the choke valve and the throttle valve thus overlap in their second end positions along the first longitudinal centre axis of the intake channel section, enables a small length of the carburettor body. Here advantageously not only the throttle valve but also the choke valve is supported in the carburettor body.

[0012] Advantageously, the choke valve also abuts at the partition wall section in its second end position. Thereby, the thickness of the region between the air channel section and the mixture channel section in the second end positions of the throttle valve and the choke valve can be reduced, so that a sufficiently large air flow for the two-stroke engine is produced even in the case of full load. Thereby, the diameter of the intake channel section can be kept relatively small, so that a small construction size of the carburettor is produced. It is also possible, however, for the choke valve not to abut at the partition wall section in its second end position. The second end position of the choke valve can in this case be determined by other means, for example by a stopper.

[0013] In order to influence the flow as little as possible, it is provided that, when the choke valve is in its second end position, the throttle valve in its second end position is covered by the choke valve in the projection in the direction of the first longitudinal centre axis in the viewing direction from the choke valve axis towards the throttle valve axis. The throttle valve thus does not protrude beyond the corridor behind the choke valve axis in the flow direction. The throttle valve is thereby in the lee of the choke valve axis and influences the flow in the intake channel section at most slightly. The intake channel section has the second longitudinal centre axis of the intake channel section in the region of the choke valve axis.

[0014] It is possible for the throttle valve and the choke valve to extend parallel to the first longitudinal centre axis in their second end positions. In an advantageous alternative arrangement, it is provided that the choke valve in its second end position is inclined at an angle of at least 2° with respect to the first longitudinal centre axis. The partition wall section is preferably constructed such that it is covered by the choke valve axis in the projection in the direction of the longitudinal centre axis in the viewing direction from the choke valve axis towards the throttle valve axis. Thereby, the partition wall section does not influence or only slightly influences the flow in the case of full load, even when the choke valve and the throttle valve are in their second end positions.

[0015] The throttle valve is preferably covered by the choke valve in its second end position in the projection in the direction of the first longitudinal center axis in the viewing direction from the choke valve axis towards the throttle valve axis. The throttle valve is advantageously in the leeward region of the choke valve axis. At least the section of the throttle valve which is downstream of the choke valve axis in terms of the flow direction from the choke valve axis towards the throttle valve axis advantageously does not protrude beyond the choke valve axis in the direction of the first longitudinal center axis in its second end position. The section of the throttle valve is thus in the leeward region of the choke valve axis. Thereby, the flow in the intake passage section through the throttle valve in its second end position is only slightly impeded or not impeded.

[0016] The throttle valve can extend parallel to the first longitudinal center axis in its second end position. In an alternative advantageous design, it is provided that the throttle valve is inclined in its second end position by an angle of at least 2° with respect to the first longitudinal center axis. If both the throttle valve and the choke valve are inclined by at least 2° with respect to the first longitudinal center axis, a relatively large overlap of the throttle valve and the choke valve can be achieved with a sufficient thickness of the partition wall section, so that the overall construction size of the carburetor can be further reduced.

[0017] Preferably, the first longitudinal center axis extends through the partition wall section. The first longitudinal center axis thus intersects the partition wall section. Advantageously, the upstream main fuel opening of the choke valve opens into the mixture passage section.

[0018] An independent concept of the present application relates to a carburetor in which the first longitudinal center axis of the intake passage section and the second longitudinal center axis of the intake passage section have a misalignment relative to each other measured parallel to the oscillation axis of the throttle valve in the region of the choke valve axis. Thereby, a compact arrangement and a small construction size of the carburetor are achieved.

[0019] The misalignment of the first and second longitudinal center axes measured parallel to the oscillation axis of the throttle valve is particularly advantageous when different flow cross sections of the intake passage section are provided in the region of the choke valve axis and in the region of the throttle valve axis. Advantageously, the throttle valve and the choke valve have a circular shape, and the intake passage section has a circular cross section in the region of the choke valve axis and a circular cross section in the region of the throttle valve axis. The misalignment of the first longitudinal center axis and the second longitudinal center axis is preferably at least one millimeter. Alternatively or additionally, it can be provided that the choke valve axis and the oscillation axis of the throttle valve have a high misalignment in the direction perpendicular to the first longitudinal center axis and perpendicular to the oscillation axis of the throttle valve axis. Preferably, the throttle valve axis and the choke valve axis are parallel to each other, so that the oscillation axes of the throttle valve and the choke valve extend parallel to each other.

[0020] It is advantageous for a two-stroke engine having a carburettor according to the application to be provided in that the intake channel section of the carburettor forms a section of the intake channel of the two-stroke engine, wherein the intake channel is divided downstream of the carburettor into a mixture channel and an air channel. Here it is advantageous for the mixture channel section of the carburettor to be coupled at the mixture channel and for the air channel section of the carburettor to be coupled at the air channel. The two-stroke engine advantageously has a cylinder in which a combustion chamber is configured, wherein the combustion chamber is bounded by a piston which is supported in the cylinder for movement to and fro. The piston drives a crankshaft which is supported in a crankcase in rotation. The mixture channel opens via a mixture inlet into a crankcase interior of the crankcase and the air channel can be connected to at least one overflow channel of the two-stroke engine. BRIEF DESCRIPTION OF DRAWINGS

[0021] An embodiment of the application is explained below with the aid of the drawings. In the drawings:

[0022] Figure 1 A schematic cross-sectional view through a two-stroke engine is shown;

[0023] Figure 2 A cross-sectional view of the carburettor of the two-stroke engine in Figure 1 is shown in an enlarged cross-sectional view, wherein the throttle valve and the choke valve are in their second end positions;

[0024] Figure 3 A cross-sectional view of the carburettor in Figure 2 is shown with the air filter and the connecting piece shown in part, wherein the throttle valve and the choke valve are in their first end positions;

[0025] Figure 4 A cross-sectional view corresponding to Figure 3 is shown, wherein the choke valve is in its second end position and the throttle valve is in its first end position;

[0026] Figures 5 to 7 A cross-sectional view through a further embodiment of the carburettor is shown, wherein the throttle valve and the choke valve are in their second end positions;

[0027] Figure 8 A cross-sectional view through a further embodiment of the carburettor is shown, in which the first and second longitudinal centre axes have a misalignment relative to one another. DETAILED DESCRIPTION

[0028] Figure 1A two-stroke engine 1 is shown, which can be used, for example, in a hand-guided work appliance, such as a motor saw, a separator, an outdoor trimmer, a hedge trimmer, a blower appliance or the like. The two-stroke engine 1 is an engine which operates with stratified scavenging. The two-stroke engine 1 is a single-cylinder engine. The two-stroke engine 1 has a cylinder block 2 in which a combustion chamber 3 is configured. The combustion chamber 3 is delimited by a piston 5 which is supported in the cylinder block 2 in a reciprocating manner and which is provided with at least one piston recess 12. The piston 5 is driven via a connecting rod 6 on a crankshaft 7 which is rotatably supported in a crankcase 4. The crankshaft 7 serves to drive a tool of the work appliance. Figure 1 The piston 5 is shown schematically in dashed lines in the lower dead center. The piston 5 drives, via the connecting rod 6, the crankshaft 7 which is rotatably supported in the crankcase 4. The crankshaft 7 serves to drive a tool of the work appliance.

[0029] In the cylinder block 2, an overflow channel 8 is configured which opens into the combustion chamber 3 with an overflow window 9. The overflow channel 8 connects, in the region of the lower dead center of the piston 5, a crankcase interior space 43 of the crankcase 4 with the combustion chamber 3. A mixture inlet 10 which is controlled by the piston 5 opens in at the cylinder block 2. Furthermore, at least one air inlet 11 which is controlled by the piston 5 opens in at the cylinder block 2. The piston 5 has at least one piston recess 12. The at least one piston recess 12 is shown in dashed lines in the upper dead center. The at least one piston recess 12 fluidically connects the at least one air inlet 11 in the region of the upper dead center of the piston 5 with the at least one overflow window 9. Thereby, air from the air channel 16 can be pre-stored in the overflow channel 8. In this embodiment, two air inlets 11 are provided which are advantageously arranged symmetrically in the sectioning plane in the Figure 1 Figure 1 The air inlets 11 connect respectively with two overflow channels 8. The air channel 16 opens in at the cylinder bore 50 of the cylinder block 2 with the at least one air inlet 11. A discharge 13 which is controlled by the piston 5 leads out of the combustion chamber 3.

[0030] The two-stroke engine 1 has an intake channel 14 via which the two-stroke engine 1 is supplied with air and fuel in operation. The intake channel 14 is divided into a mixture channel 15 and an air channel 16. The air channel 16 opens in at the cylinder bore 50 with the at least one air inlet 11. The mixture channel 15 opens in at the cylinder bore 50 with the mixture inlet 10. The supply of fuel takes place in a carburettor 20. A main fuel opening 18 opens in the carburettor 20 into the mixture channel 15. The mixture channel 15 is supplied with fuel via the main fuel opening 18. A further, secondary fuel opening can be provided which opens into the mixture channel. The main fuel opening 18 is advantageously arranged in the region of a Venturi 17 which is configured in the carburettor 20.

[0031] ​The carburettor 20 is connected to the cylinder block 2 in this embodiment via a connecting pipe 19. The connecting pipe 19 is preferably a flexible connecting pipe, so that relative movements between different components of the hand-guided work implement can be compensated via the flexible connecting pipe 19. An air filter 39 is arranged upstream of the carburettor 20, through which air is drawn into the intake channel 14 in operation.

[0032] A fuel / air-mixture is drawn into the crankcase interior space 43 via the mixture channel 15 in the upward stroke of the piston 5 in operation. Once the piston recess 12 connects the at least one air inlet 11 with the at least one overflow window 9, air from the air channel 16 is pre-stored in the overflow channel 8. In the downward stroke of the piston 5, the fuel mixture is compressed in the crankcase interior space 43. Once the overflow window 9 opens towards the combustion chamber 3, the air pre-stored in the overflow channel 8 flows first into the combustion chamber 3 and sweeps the exhaust gas from the previous engine cycle out through the drain 13. Then the fuel / air-mixture flows from the crankcase interior space 43 via the overflow channel 8 into the combustion chamber 3. In the upward stroke of the piston 5 the mixture is compressed in the combustion chamber 3 and ignited in the region of the top dead centre of the piston 5 by the spark plug 60. Thereby, the piston 5 is accelerated in the direction of the crankcase 4. Once the drain 13 is opened by the piston 5, the exhaust gas flows out of the combustion chamber 3 through the drain 13. Once the overflow window 9 opens, the exhaust gas still present in the combustion chamber 3 is swept out through the drain 13. Then, fresh fuel / air-mixture flows from the crankcase interior space 43 into the combustion chamber 3.

[0033] As Figure 2 is shown, the carburettor 20 has a carburettor body 21 in which an intake channel section 22 is configured as a through-opening. In the carburettor body 21, a throttle valve 23 is swingably supported about a swivel axis 25 by means of a throttle valve shaft 24. Furthermore, in the carburettor body 21 a choke valve 28 is swingably supported about a swivel axis 30 by means of a choke valve shaft 29. In Figure 2 the throttle valve 23 is shown in a second end position 27 in which the throttle valve 23 is fully open. The choke valve 28 is likewise shown in a second end position 32 in which the choke valve 28 is fully open. Upstream of the throttle valve shaft 24, in the region between the throttle valve shaft 24 and the choke valve shaft 29, a partition wall section 33 is arranged. The partition wall section 33 separates the intake channel section 22 into a mixture channel section 34 and an air channel section 35. The mixture channel section 34 forms a section of the mixture channel 15 of the two-stroke engine 1. The air channel section 35 forms a section of the air channel 16 of the two-stroke engine 1.

[0034] In this embodiment, a second partition wall section 46 is arranged downstream of the throttle shaft 24, which separates the mixture channel section 34 and the air channel section 35 or the mixture channel 15 and the air channel 16 downstream of the carburettor 20 from one another. As Figure 2 indicated, the main fuel opening 18 is arranged in the region of the Venturi 17 upstream of the throttle shaft 24.

[0035] In this embodiment, the second partition wall section 46 is configured at a ring 45 which is pushed, preferably pressed, into the carburettor body 21. The second partition wall section 46 can be configured in one piece with the ring 45 here. The throttle 23 advantageously bears against the partition wall section 33 in its second end position 27. The throttle 23 can also bear against the second partition wall section 46 in its second end position 27.

[0036] In an alternative design, the throttle 23 does not bear against the partition wall section 33 and / or the partition wall section 46 in its second end position 27. The throttle 23 can be advantageously positioned in this embodiment by other means, such as for example by a stop.

[0037] The choke 28 advantageously bears against the partition wall section 33 in its second end position 32 shown in Figure 2 here. The second end position 32 is accordingly a position in which the throttle 23 or the choke 28 minimally reduces the flow cross section in the intake channel section 22. The choke 28 can alternatively be positioned in its second end position 32 in another way, for example by means of at least one stop.

[0038] The intake channel section 22 has a first longitudinal centre axis 37 in the region of the throttle shaft 24. The intake channel section 22 has a second longitudinal centre axis 38 in the region of the choke shaft 29. The first longitudinal centre axis 37 and the second longitudinal centre axis 38 can coincide in a sectional view perpendicular to the swivel axis 25 of the throttle shaft 24 as shown.

[0039] As Figure 2As shown, the throttle valve 23 and the choke valve 28 overlap in the direction of the longitudinal center axis 37 of the intake passage section 22 in their second end positions 27, 32. The carburettor 20 has a length section 42 in which not only the choke valve 28 and the throttle valve 23 but also the partition wall section 33 extend. The length section 42 of the carburettor 20 is here the section which is limited by the planes 51, 52 which extend perpendicular to the first longitudinal center axis 37. The length section 42 is thus an imaginary disc of the carburettor 20 through which the intake passage section 22 extends. The length section 42 has a length b which is measured parallel to the first longitudinal center axis 37. The length b is advantageously at least 5%, in particular at least 10%, preferably at least 15% of the diameter d of the throttle valve 23. But also a significantly smaller length b can be advantageous, in particular in the case of a smaller diameter d of the throttle valve 23. Due to the overlap of the throttle valve 23 and the choke valve 28, the carburettor 20 can be constructed with a relatively small length a. The length a is here the length of the carburettor body 21 in the direction of the first longitudinal center axis 37. The length a is advantageously at most 1.5 times the diameter d of the throttle valve 23. But also a larger ratio of the length a to the diameter d can be advantageous.

[0040] In the intake passage section 22, air and fuel flow in a flow direction 53 which points from the choke valve axis 29 toward the throttle valve axis 24. When the choke valve 28 is in its second end position 32, the throttle valve 23 is covered by the choke valve axis 29 in the projection in the direction of the first longitudinal center axis 37 in the viewing direction from the choke valve axis 29 toward the throttle valve axis 24 in its second end position 27. The throttle valve 23 is thus in the lee of the choke valve axis 29. Advantageously at least the section of the throttle valve 23 which is downstream of the throttle valve axis 24 with respect to the flow direction 53 is covered by the throttle valve axis 24 in the flow direction 53. This section of the throttle valve 23 is advantageously in the lee of the throttle valve axis 24. In the Figure 2 The passage 47 is drawn in dashed lines in Fig. 4. The passage is limited by a first limiting line 48 and a second limiting line 49, which are each shown in dashed lines. The spacing of the limiting lines 48 and 49 corresponds to the diameter of the choke valve axis 29. As shown, the throttle valve axis 23 lies completely within the passage 47 in its second end position 27. The partition wall section 33 also lies within the passage 47 and thus in the lee of the choke valve axis 29. Figure 2

[0041] In the second projection direction 54, which is in the opposite direction to the projection direction 44, the choke valve 28 is covered by the throttle valve axis 24. In the second projection direction 54, the lee is formed by the throttle valve axis 24. The throttle valve axis 24 constructs a passage 47'. The choke valve 28 lies completely within the passage 47' in its first end position 31. The partition wall section 33 also lies within the passage 47' and thus in the lee of the throttle valve axis 24. Figure 2 ​The arrangement shown in Fig. 6 is not extended from the passage 47' in this embodiment. In this embodiment, the choke valve 28 is parallel to the longitudinal center axes 37 and 38 and next to the longitudinal center axes 37 and 38. The choke valve 28 thus also does not impede or only slightly impedes the flow in the intake passage section 22 in its second end position 32. The section of the throttle valve shaft 23 upstream of the throttle valve shaft 24 with respect to the flow direction 53 is covered by the throttle valve shaft 24 in the second projection direction 54 and is completely in the passage 47'.

[0042] In this embodiment, the passages 47 and 47' overlap. It is also possible to provide that the passages 47 and 47' only partially overlap.

[0043] The throttle valve 23 is inclined to the first longitudinal center axis 37 in its second end position 32 in this embodiment. The angle β by which the throttle valve 23 is inclined with respect to the first longitudinal center axis 37 is preferably at least 2°. A compact construction of the carburettor 20 can thus be achieved with sufficient thickness of the partition wall section 33.

[0044] As Figure 2 It is also shown that the throttle valve 23 is in the first recess 40 of the partition wall section 33 in its second end position 27. The first recess 40 is so dimensioned deep that the section of the periphery of the throttle valve 23 facing the choke valve 28 is advantageously completely in the first recess 40 in the shown cross-sectional view perpendicular to the axes of oscillation 25 and 30. The choke valve 28 is in the second recess 41 of the partition wall section 33 in its second end position 32. The periphery of the choke valve 28 also does not extend from the second recess 41 at the side facing the throttle valve 23 downstream of the choke valve shaft 29. The first longitudinal center axis 37 intersects the partition wall section 33, as Figure 2 is shown.

[0045] Figure 3 The arrangement in Fig. 5 is shown in part Figure 1 , in which the throttle valve 23 is in its first end position 26 and the choke valve 28 is in its first end position 31. The air filter 39 and the connecting piece 19 are only partially shown. In addition to the remaining cross section, the throttle valve 23 closes the intake passage section 22 in the first end position 26. In addition to the remaining cross section, the choke valve 28 also closes the intake passage section 22 when the choke valve is in its first end position 31. The remaining cross section is determined by the opening 57 in the throttle valve 23 and the opening 58 in the choke valve 28. Preferably, the valves abut with their periphery at the passage wall of the intake passage section 22. The free flow cross section in the first end positions 26 and 31 is significantly smaller than the free flow cross section in the second end positions 27 or 32.

[0046] As Figure 3The oscillation axes 30 and 25 of the choke valve shaft 29 and the throttle valve shaft 24 have a spacing f measured in the direction of the first longitudinal center axis 37. The spacing f is smaller than the sum of half the diameter g of the choke valve 28 and half the diameter d of the throttle valve 23. This results in an overlap of the throttle valve 23 and the choke valve 28 in their second end positions 27 and 32, as shown in Figure 2

[0047] Figure 4 The choke valve 28 in its second end position 32 and the throttle valve 23 in its first end position 26 are shown. These valve positions are generally associated with an idling operation.

[0048] Figure 5 An embodiment of the carburettor 20 is shown. Identical reference numerals denote corresponding elements in all the figures. Reference is made to the description of the above figures for elements which are not described in detail again below. The carburettor 20 has a choke valve 28 which is inclined by an angle a with respect to the first longitudinal center axis 37 in the second end position 32 shown in Figure 5 The angle a is advantageously at least 2°.

[0049] In an embodiment variant, the choke valve 28 abuts in the second end position 32 at the partition wall section 33. The position of the choke valve 28 in its second end position 32 can also be fixed in alternative embodiments by other means, for example by a stop. The first longitudinal center axis 37 and the second longitudinal center axis 38 coincide in the shown sectional view. The throttle valve 23 runs in its shown second end position 27 parallel to the first longitudinal center axis 37 and abuts not only at the partition wall section 33 but also at the partition wall section 46.

[0050] In the embodiment shown in Figure 6 The choke valve 28 is inclined to the first longitudinal center axis 37 in its second end position 32. The angle a with which the choke valve 28 is clamped to the first longitudinal center axis 37 is at least 2°. The throttle valve 23 is inclined in its second end position 27 by an angle β of at least 2° with respect to the first longitudinal center axis 37. The choke valve 28 and the throttle valve 23 abut at the partition wall section 33. In addition, the throttle valve 23 can abut at the second partition wall section 46.

[0051] In the embodiment according to Figure 7 ​In an embodiment of the throttle valve 23 and the choke valve 28 extend parallel to each other in their two end positions 27, 32 and parallel to the longitudinal center axes 37 and 38. The choke valve advantageously abuts at the partition wall section 33 and the throttle valve advantageously abuts not only at the partition wall section 33 but also at the partition wall section 46. The pivot axes 25 and 30 have a high positional offset e from each other measured in the direction perpendicular to the longitudinal center axis 37 and perpendicular to the pivot axes 25 and 30. In the projection direction 44, the pivot axes 30 and 25 thus do not lie on top of each other but are placed at a distance from each other corresponding to the high positional offset e.

[0052] Figure 8 The arrangement of the longitudinal center axes 37 and 38 can be advantageous for all of the above-explained embodiments. The longitudinal center axes 37 and 38 have a positional offset c from each other. The positional offset c is measured parallel to the pivot axes 25 and 30 and perpendicular to the first longitudinal center axis 37. The positional offset c is preferably at least one millimeter. The throttle valve 23 and the choke valve 28 are advantageously configured circularly. Due to the positional offset c of the longitudinal center axes 37 and 38, the side walls 55 and 56 of the intake passage section 22 are not mirror-symmetrically configured from each other in the cut plane Figure 8 schematically shown in the cut plane. In this embodiment, the side wall 56 extends straight and the side wall 55 extends bent. The Venturi section is not shown here in Figure 8 . Figure 8 The cross section is shown in a cut plane which contains at least the pivot axis 25 of the throttle valve 23 and extends parallel to the pivot axis 30 or which also contains the pivot axis 30. The positional offset c forms a separate idea of the invention which can be advantageous independently of the overlap of the throttle valve 23 and the choke valve 28.

Claims

1. A vaporizer having a vaporizer body (21) in which an air intake passage section (22) is constructed, wherein, A throttle valve (23) for controlling the free flow cross-section of the intake passage section (22) is pivotally supported in the carburetor body (21) about a throttle valve shaft (24) about a pivot axis (25) of the throttle valve shaft (24), wherein the intake passage section (22) has a first longitudinal central axis (37) in the region of the throttle valve shaft (24), wherein the throttle valve (23) has a first terminal position (26) and a second terminal position (27), wherein the throttle valve (23) releases a larger flow cross-section of the intake passage section (22) in the second terminal position (27) than in the first terminal position (26), wherein a partition wall section is arranged upstream of the throttle valve shaft (24) in the intake passage section (22). (33) The partition wall section divides the intake passage section (22) into a mixture passage section (34) and an air passage section (35), wherein the throttle valve (23) is abutted against the partition wall section (33) in the second terminal position (27), wherein a choke valve (28) is arranged upstream of the partition wall section (33) in the intake passage section (22), the choke valve being able to swing between the first terminal position (31) and the second terminal position (32), wherein the choke valve (28) is oscillatingly supported by a choke valve shaft (29) about the swing axis (30) of the choke valve (28), wherein the choke valve (28) releases a larger flow cross-section in its second terminal position (32) than in its first terminal position (31). The throttle valve (23) and the choke valve (28) overlap at their second terminal positions (27, 32) along the first longitudinal central axis (37) of the intake passage section (22), such that at the second terminal positions (27, 32) of the throttle valve (23) and the choke valve (28), the throttle valve (23), the choke valve (28), and the partition wall section (33) are arranged in the length section (42) of the carburetor (20), wherein the carburetor... The length segment (42) of the device (20) is a segment limited by planes (51, 52) that extend perpendicular to the first longitudinal central axis (37), wherein the swing axis (30) of the choke shaft (29) and the swing axis (25) of the throttle shaft (24) have a distance (f) measured along the first longitudinal central axis (37), the distance (f) being less than half the diameter (g) of the choke (28) and half the diameter (d) of the throttle (23).

2. The vaporizer according to claim 1, characterized in that, The ratio of the length (a) of the carburetor body (21) measured along the first longitudinal central axis (37) to the diameter (d) of the throttle valve (23) is at most 1.

5.

3. The vaporizer according to claim 1, characterized in that, The length segment (42) of the carburetor (20) has a length (b) measured parallel to the first longitudinal central axis (37), in which not only the throttle valve (23) but also the choke valve (28) extends in its second terminal position (27, 32), the length being at least 10% of the diameter (d) of the throttle valve (23).

4. The vaporizer according to claim 1, characterized in that, The length segment (42) of the carburetor (20) has a length (b) measured parallel to the first longitudinal central axis (37), in which not only the throttle valve (23) but also the choke valve (28) extends in its second terminal position (27, 32), the length being at least 15% of the diameter (d) of the throttle valve (23).

5. The vaporizer according to claim 1, characterized in that, The air choke (28) is abutted against the partition wall section (33) at its second terminal position (32).

6. The vaporizer according to claim 1, characterized in that, When the choke (28) is in its second terminal position (32), the throttle (23) in its second terminal position (27) is covered by the choke shaft (29) in the projection along the first longitudinal central axis (37) in the direction of observation from the choke shaft (29) toward the throttle shaft (24).

7. The vaporizer according to claim 1, characterized in that, The air choke (28) is tilted at an angle (α) of at least 2° relative to the first longitudinal central axis (37) in its second terminal position (32).

8. The vaporizer according to claim 1, characterized in that, The partition section (33) is covered by the choke shaft (29) in the projection along the first longitudinal central axis (37) in the viewing direction from the choke shaft (29) toward the throttle shaft (24).

9. The vaporizer according to claim 1, characterized in that, The throttle valve (23) in its second terminal position (27) is covered by the throttle valve shaft (29) in the projection along the first longitudinal central axis (37) in the viewing direction from the throttle valve shaft (29) toward the throttle valve shaft (24).

10. The vaporizer according to claim 1, characterized in that, The throttle valve (23) is tilted at an angle (β) of at least 2° relative to the first longitudinal central axis (37) in its second terminal position (27).

11. The vaporizer according to claim 1, characterized in that, The first longitudinal central axis (37) extends through the partition wall section (33).

12. The vaporizer according to claim 1, characterized in that, The main fuel opening (18) extends upstream of the throttle shaft (24) into the mixture passage section (34).

13. A vaporizer having a vaporizer body (21) in which an air intake passage section (22) is constructed, wherein, A throttle valve (23) for controlling the free flow cross-section of the intake passage section (22) is pivotally supported in the carburetor body (21) about a throttle valve shaft (24) about a pivot axis (25) of the throttle valve shaft (24), wherein the intake passage section (22) has a first longitudinal central axis (37) in the region of the throttle valve shaft (24), wherein the throttle valve (23) has a first terminal position (26) and a second terminal position (27), wherein the throttle valve (23) releases a larger flow cross-section of the intake passage section (22) in the second terminal position (27) than in the first terminal position (26), wherein a partition wall section is arranged upstream of the throttle valve shaft (24) in the intake passage section (22). (33) The partition wall section divides the intake passage section (22) into a mixture passage section (34) and an air passage section (35), wherein the throttle valve (23) is abutted against the partition wall section (33) in the second terminal position (27), wherein a choke valve (28) is arranged upstream of the partition wall section (33) in the intake passage section (22), the choke valve being able to swing between the first terminal position (31) and the second terminal position (32), wherein the choke valve (28) is oscillatingly supported by a choke valve shaft (29) about the swing axis (30) of the choke valve (28), wherein the choke valve (28) releases a larger flow cross-section in its second terminal position (32) than in its first terminal position (31). The characteristic feature is that the first longitudinal central axis (37) of the intake passage section (22) and the second longitudinal central axis (38) of the intake passage section (22) have a misalignment (c) relative to each other in the region of the throttle shaft (28) that is parallel to the swing axis (25) of the throttle shaft (24), and the throttle (23) and the throttle (28) overlap in their second terminal positions (27, 32) along the direction of the first longitudinal central axis (37) of the intake passage section (22), so that in the second terminal positions (27, 32) of the throttle (23) and the throttle (28), the throttle ( 23) The choke (28) and the partition wall section (33) are arranged in the length section (42) of the carburetor (20), wherein the length section (42) of the carburetor (20) is a section limited by a plane (51, 52) extending perpendicular to the first longitudinal central axis (37), wherein the swing axis (30) of the choke shaft (29) and the swing axis (25) of the throttle shaft (24) have a distance (f) measured along the direction of the first longitudinal central axis (37), the distance (f) being less than half the diameter (g) of the choke (28) and half the diameter (d) of the throttle (23).

14. The vaporizer according to claim 13, characterized in that, The misalignment (c) between the first longitudinal centerline (37) and the second longitudinal centerline (38) is at least 1 mm.

15. A two-stroke engine having a carburetor (20), wherein, The carburetor (20) has a carburetor body (21) in which an intake passage section (22) is constructed. A throttle valve (23) for controlling the free flow cross-section of the intake passage section (22) is pivotally supported in the carburetor body (21) about a throttle valve shaft (24) about a pivot axis (25) of the throttle valve shaft (24). The intake passage section (22) has a first longitudinal central axis (37) in the region of the throttle valve shaft (24). The throttle valve (23) has a first terminal... The throttle (23) has two terminal positions (26 and 27), wherein the throttle (23) in the second terminal position (27) releases a larger flow cross-section of the intake passage section (22) than in the first terminal position (26), wherein a partition wall section (33) is arranged upstream of the throttle shaft (24) in the intake passage section (22), the partition wall section dividing the intake passage section (22) into a mixture passage section (34) and an air passage section (35), wherein the throttle (23) in the second terminal position... The air intake passage section (22) is located abutting against the partition wall section (33), wherein an air choke (28) is arranged upstream of the partition wall section (33) in the air intake passage section (22). The air choke is swayable between a first terminal position (31) and a second terminal position (32). The air choke (28) is swayably supported by an air choke shaft (29) about the swing axis (30) of the air choke (28). The air choke (28) releases a greater amount of air in its second terminal position (32) than in its first terminal position (31). The flow cross section, wherein the throttle valve (23) and the choke valve (28) overlap at their second terminal positions (27, 32) along the first longitudinal central axis (37) of the intake passage section (22), such that at the second terminal positions (27, 32) of the throttle valve (23) and the choke valve (28), the throttle valve (23), the choke valve (28) and the partition wall section (33) are arranged in the length section (42) of the carburetor (20), wherein the length section (42) of the carburetor (20) is through the plane (51,52) A restricted section, the plane extending perpendicular to the first longitudinal central axis (37), wherein the swing axis (30) of the choke shaft (29) and the swing axis (25) of the throttle shaft (24) have a distance (f) measured along the first longitudinal central axis (37), the distance (f) being less than half the diameter (g) of the choke (28) and half the diameter (d) of the throttle (23), wherein the intake passage section (22) of the carburetor (20) forms a section of the intake passage (14) of the two-stroke engine (1), wherein the intake passage (14) is divided into a mixture passage (15) and an air passage (16) downstream of the carburetor (20), wherein the mixture passage of the carburetor (20) Section (34) is connected to the mixture passage (15), and wherein the air passage section (35) of the carburetor (20) is connected to the air passage (16), wherein the two-stroke engine (1) has a cylinder block (2) in which a combustion chamber (3) is constructed, wherein the combustion chamber (3) is limited by a piston (5) supported reciprocally in the cylinder block (2), wherein the piston (5) rotatably drives a crankshaft (7) supported in a crankcase (4), wherein the mixture passage (15) extends into the crankcase interior space (43) of the crankcase (3) via a mixture inlet (10), and wherein the air passage (16) is connectable to at least one overflow passage (8) of the two-stroke engine (1).

16. A two-stroke engine having a carburetor (20), wherein, The carburetor (20) has a carburetor body (21) in which an intake passage section (22) is constructed, wherein a throttle valve (23) for controlling the free flow cross-section of the intake passage section (22) is pivotally supported in the carburetor body (21) about a throttle valve shaft (24) about a swing axis (25) of the throttle valve shaft (24), wherein the intake passage section (22) has a first longitudinal central axis (37) in the region of the throttle valve shaft (24), wherein the throttle valve (23) has a first end position (26) and a second end position (27), wherein the throttle valve ( 23) A larger flow cross-section of the intake passage section (22) is released in the second terminal position (27) than in the first terminal position (26), wherein a partition wall section (33) is arranged upstream of the throttle shaft (24) in the intake passage section (22), the partition wall section dividing the intake passage section (22) into a mixture passage section (34) and an air passage section (35), wherein the throttle (23) is abutted against the partition wall section (33) in the second terminal position (27), wherein a barrier is arranged upstream of the partition wall section (33) in the intake passage section (22). A valve (28) is oscillating between a first terminal position (31) and a second terminal position (32), wherein the valve (28) is oscillatingly supported by a valve shaft (29) about an oscillation axis (30) of the valve (28), wherein the valve (28) releases a larger flow cross-section in its second terminal position (32) than in its first terminal position (31), wherein the first longitudinal central axis (37) of the intake passage section (22) and the second longitudinal central axis (38) of the intake passage section (22) are parallel to each other in the region of the valve shaft (28). The misalignment (c) measured at the swing axis (25) of the throttle shaft (24), wherein the throttle (23) and the choke (28) overlap in their second end positions (27, 32) along the first longitudinal central axis (37) of the intake passage section (22), such that in the second end positions (27, 32) of the throttle (23) and the choke (28), the throttle (23), the choke (28) and the partition wall section (33) are arranged in the length section (42) of the carburetor (20), wherein the length section (42) of the carburetor (20) is through the plane (51,52) A restricted section, the plane extending perpendicular to the first longitudinal central axis (37), wherein the swing axis (30) of the choke shaft (29) and the swing axis (25) of the throttle shaft (24) have a distance (f) measured along the first longitudinal central axis (37), the distance (f) being less than half the diameter (g) of the choke (28) and half the diameter (d) of the throttle (23), wherein the intake passage section (22) of the carburetor (20) forms a section of the intake passage (14) of the two-stroke engine (1), wherein the intake passage (14) is divided into a mixture passage (15) and an air passage (16) downstream of the carburetor (20), wherein the mixture passage of the carburetor (20) Section (34) is connected to the mixture passage (15), and wherein the air passage section (35) of the carburetor (20) is connected to the air passage (16), wherein the two-stroke engine (1) has a cylinder block (2) in which a combustion chamber (3) is constructed, wherein the combustion chamber (3) is limited by a piston (5) supported reciprocally in the cylinder block (2), wherein the piston (5) rotatably drives a crankshaft (7) supported in a crankcase (4), wherein the mixture passage (15) extends into the crankcase interior space (43) of the crankcase (3) via a mixture inlet (10), and wherein the air passage (16) is connectable to at least one overflow passage (8) of the two-stroke engine (1).

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