Fuel supply device

Abstract

A fuel supply device (1) has a housing (2) in which an intake channel section (3) is formed. At least one fuel opening (11, 12) opens into the intake channel section (3). The fuel supply device (1) has at least one fuel channel (26, 27, 28) in which a valve (23, 24, 25) is arranged. The valve (23, 24, 25) has a valve plate (29, 30, 31). The valve (23, 24, 25) has a closed position (41), in which the valve plate (29, 30, 31) rests against a valve seat (32, 33, 34), and an open position (42). The valve plate (29, 30, 31) travels one valve stroke (h) between the open position (42) and the closed position (41).In the fuel channel (26, 27, 28) an annular gap (28, 39, 40, 49) is formed, wherein the gap width (b) of the annular gap (38, 39, 40, 49) is matched to the stroke (a) of the valve plate (29, 30, 31) of the valve (23, 24, 25) such that the gap width (b) is not greater than twice the stroke (a) and wherein the flow cross-section of the annular gap (40) is larger than the flow cross-section of the valve (23, 24, 25).

Description

[0001] The invention relates to a fuel supply device of the type specified in the preamble of claim 1.

[0002] DE 297 22 869 U1 describes a diaphragm carburetor featuring a main jet with a check valve. The check valve closes the main jet path at idle, preventing pressure pulsations in the intake port from affecting the control chamber via the main jet path.

[0003] CN 202690251 U describes a carburetor with a strainer in the idle fuel path. This is designed to filter out contaminants from the fuel and prevent the buildup of contaminants at the idle opening.

[0004] DE 101 42 247 A1 discloses a carburetor with a fuel path in which a high-speed needle valve, a check valve and a high-speed nozzle are arranged.

[0005] It has been shown that in internal combustion engines whose fuel supply system has at least one valve, functional impairments can occur, for example unsatisfactory starting behavior or uneven running of an internal combustion engine during operation.

[0006] The invention is based on the object of specifying a fuel supply device with which functional impairments of an internal combustion engine are avoided.

[0007] This object is achieved by a fuel supply device having the features of claim 1.

[0008] It is provided that an annular gap is formed in the fuel channel in which the valve is arranged, the gap width being matched to the stroke of the valve plate of the valve in such a way that the gap width is not greater than twice the stroke. The flow cross-section of the annular gap is larger than the flow cross-section of the valve. In this case, the flow cross-sections are surface cross-sections.

[0009] In a first variant of claim 1, the annular gap is not delimited by the valve plate of the valve. The annular gap is formed separately from the valve plate of the valve. The annular gap is advantageously formed at a distance from the valve plate. The annular gap is delimited by an inner wall and an outer wall. A simple construction of the fuel supply device results from the fact that the valve seat and the inner wall of the annular gap are formed on the same component. Therefore, no additional components are required to form the annular gap.

[0010] In a second variant of claim 1, a main fuel nozzle having a valve opens into the intake duct section. The main fuel nozzle is the nozzle through which the majority of the fuel is supplied when an internal combustion engine is operating at full load. The main fuel nozzle is arranged in a bore of the fuel supply device. The main fuel nozzle is advantageously pressed into a bore of the fuel supply device. In an alternative design, it can also be provided that the main fuel nozzle is screwed into the bore or is held in the bore by means of an elastic element, for example by means of an O-ring. A simple construction results from the fact that the annular gap is formed between the wall of the bore and the outer circumference of the main fuel nozzle. Therefore, no additional components are required to form the annular gap.Only the dimensions of the bore and the outer circumference of the main fuel nozzle need to be coordinated. The annular gap preferably runs between a first annular channel and a second annular channel. Fuel supply and fuel removal can occur via the two annular channels. Advantageously, the first annular channel, the annular gap, and the second annular channel are bounded by the wall of the bore and the outer circumference of the main fuel nozzle.

[0011] It has been shown that rough running of an internal combustion engine can be due to an unsuitable fuel supply. This unsuitable fuel supply can occur when contaminants, such as chips that may originate from the production of the fuel supply device, are located between the valve plate and a stop for the valve plate. This contaminant prevents the valve plate from reaching the closed position. This impairs the function of the fuel supply device. Inadequate starting behavior can also be due to contamination on a valve, namely a fuel pump valve, especially a purger.

[0012] By matching the gap width of the annular gap to the valve plate stroke, the annular gap retains contaminants such as chips and the like, thus ensuring that the valve plate can reach the closed position. It has been shown that a gap width no larger than twice the valve plate stroke can largely prevent blockage or obstruction of the valve plate's movement. The flow cross-section of the annular gap is larger than the flow cross-section of the valve. Therefore, the annular gap does not significantly limit the flow rate through the fuel channel.

[0013] The gap width of the annular gap is preferably fixed by design. The gap width of the annular gap is preferably not variable or adjustable.

[0014] Preferably, the gap width is not larger than the stroke. Only contaminants that are no larger than the stroke of the valve disc can pass through the annular gap. However, due to the sufficiently large stroke of the valve disc, these contaminants are not retained by the valve disc and can pass through the valve disc during operation. This prevents contaminants from blocking or impeding the movement of the valve disc.

[0015] The valve can, for example, be the valve of a fuel nozzle or a valve in a pump of the fuel supply system. The valve can be a check valve or an electromagnetic valve with a valve plate. In a check valve, the movement of the valve plate between the open and closed positions occurs due to the pressure conditions at the valve plate. In an electromagnetic valve, the valve plate is moved by an electromagnet depending on the current flow.

[0016] Preferably, the gap width of the annular gap is smaller than the stroke of the valve plate. Particularly preferably, the gap width is at most 80% of the stroke. This reliably prevents contaminants from entering the valve through the annular gap, which could become trapped between the valve plate and the stop, thus preventing the valve from closing. Contaminants smaller than the valve stroke can penetrate between the valve plate and the stop and are flushed away by the fuel, thus preventing any functional impairment.

[0017] The open position of the valve is, in particular, a position in which the valve plate rests against a stop. The stop and the valve seat thus mechanically define the two end positions of the valve plate.

[0018] Advantageously, at least one annular gap is arranged upstream of the valve. The term "upstream" refers to a flow direction from a fuel tank to an internal combustion engine, i.e., the usual flow direction during operation of the fuel supply device. It can also be provided that, additionally or alternatively, at least one annular gap is arranged downstream of the valve. An annular gap arranged downstream of the valve prevents contaminants from reaching the valve in the event of back pulsations in the fuel system. This can be the case, for example, when the internal combustion engine is pivoted during operation, for example, in a hand-held tool, or when the internal combustion engine is switched off and fuel flows back to the fuel tank.

[0019] Advantageously, at least one throttle is arranged upstream of the annular gap. The throttle can be a fixed throttle. The throttle is, in particular, a part-load fixed nozzle. It can also be provided that the at least one throttle is adjustable. An adjustable throttle can, in particular, be a full-load adjusting screw if the valve is formed on a main fuel nozzle. Advantageously, the flow cross-section of the annular gap is larger than the flow cross-section of the throttle. As a result, the annular gap does not limit the flow. In an advantageous embodiment, at least one adjustable throttle and at least one fixed throttle are provided.

[0020] The fuel supply device advantageously comprises a purger as a manually operated fuel pump. The purger has a pump chamber. A first valve is advantageously arranged upstream of the pump chamber and a second valve downstream of the pump chamber. An annular gap is also advantageous for valves on a purger to ensure that the valve plate opens and closes reliably and is not impeded in its movement by contamination. This ensures the long-term function of the purger. The fuel system is reliably flooded when the purger is operated, resulting in good starting behavior of an internal combustion engine operated by the fuel supply device.

[0021] Embodiments of the invention are explained below with reference to the drawings. They show: Fig. 1 a schematic sectional view through a fuel supply device, Fig. 2 a schematic, enlarged view of the main fuel nozzle of the carburettor from Fig. 1 , Fig. 3 a schematic sectional view through a check valve of the purger of the carburettor from Fig. 1 , Fig. 4 a variant of the main fuel nozzle from Fig. 2 , Fig. 5 to 7 enlarged views of variants of the annular gap.

[0022] Fig. 1 shows a schematic sectional view of a fuel supply device 1. The fuel supply device 1 in Fig. 1 In the exemplary embodiment, a carburetor is used, i.e., a fuel supply device in which the fuel is sucked in due to negative pressure. Another type of fuel supply device can also be provided, for example, a fuel supply device with a fuel valve that delivers the fuel under pressure and thereby injects it into the intake duct. The fuel supply device 1 has a housing 2 in which an intake duct section 3 is formed. The intake duct section 3 is advantageously connected to the mixture inlet of an internal combustion engine, not shown. Combustion air is usually sucked into the intake duct section 3 via an air filter. In the intake duct section 3, a throttle element 7, in the exemplary embodiment a throttle valve, is mounted with a throttle shaft 8 so as to be pivotable about a rotation axis 9. Upstream of the throttle element 7, a choke element 4 is arranged in the intake duct section 3.It can also be provided that the fuel supply device 1 does not have a choke element 4. In the exemplary embodiment, the choke element 4 is a choke flap that is pivotally mounted about a rotation axis 6 by a choke shaft 5. The throttle element 7 and the choke element 4 serve to control the free flow cross-section of the intake duct section 3.

[0023] In the exemplary embodiment, the fuel supply device 1 is designed to supply both a fuel / air mixture to a mixture channel and air to an air channel. For this purpose, the intake channel section 3 is divided by a partition wall section 10 into a mixture channel section 51 and an air channel section 52. When the choke element 4 and throttle element 7 are fully open, they lie in the same plane as the partition wall section 10. This achieves a substantial separation of the mixture channel section 51 and the air channel section 52.

[0024] Several secondary fuel openings 12 and a main fuel opening 11 open into the intake duct section 3, namely into the mixture duct section 51 of the intake duct section 3. The secondary fuel openings 12 are arranged in the region of the throttle element 7. In the exemplary embodiment, the main fuel opening 11 is arranged in the region of the partition wall section 10 and upstream of the throttle element 7.

[0025] In the exemplary embodiment, the fuel supply device 1 is designed as a diaphragm carburetor to which fuel is supplied via a fuel pump 16. The fuel pump 16 is preferably driven by the fluctuating pressure in a crankcase of an internal combustion engine. The fuel pump 16 delivers the fuel via a fuel valve (not shown) into a control chamber 17 of the fuel supply device 1. The control chamber 17 is separated from a compensation chamber 19 by a control diaphragm 18. Depending on the position of the control diaphragm 18, i.e. depending on the pressure conditions in the control chamber 17 and the compensation chamber 19, an inlet valve in the control chamber 17 is opened or closed in a known manner, so that fuel can flow into the control chamber 17 in a controlled manner.

[0026] The secondary fuel openings 12 are fed by an idle chamber 53, which is connected to the control chamber 17 via an idle check valve 54 and an idle throttle 55.

[0027] The main fuel opening 11 is formed on a main fuel nozzle 13, which is connected to the control chamber 17 via a fuel channel 28, schematically shown with a dashed line. A throttle 45 is arranged in the fuel channel 28. The throttle 45 can be a fixed throttle, for example, a part-load fixed nozzle. However, the throttle 45 can also be adjustable. The throttle 45 can, in particular, be an adjusting screw. In an advantageous alternative design, a fixed throttle and an adjustable throttle can be provided instead of the throttle 45.

[0028] The main fuel nozzle 13 is arranged in a bore 14 of the housing 2. In the exemplary embodiment, the fuel channel 56 opens at the circumference of the bore 14. The main fuel opening 11 opens into the intake channel section 3 in the region of a venturi 15. The main fuel nozzle 13 has a valve 25 which is designed as a check valve. The valve 25 comprises a valve plate 31. The valve plate 31 is located in the Fig. 1 In the closed position 41 shown, it rests against a valve seat 34. In the open position, the valve plate 31 rests against a stop 37 in the exemplary embodiment.

[0029] The fuel supply device 1 has a purger 20. The purger 20 is a manually operated fuel pump that pumps fuel from the control chamber 17 into a fuel tank. The resulting negative pressure in the fuel system causes fuel to be sucked from the fuel tank into the fuel system, thereby flooding the fuel system. Any air present in the fuel system is pumped back into the fuel tank. The purger 20 has a purger bellows 21, which the operator presses to pump fuel. A pump chamber 22 is formed in the purger bellows 21. A fuel channel 26 opens into the pump chamber 22 via a valve 23. The fuel channel 26 connects the pump chamber 22 to the control chamber 17. A valve 24 leads from the pump chamber 22 and can be connected to the fuel tank via a fuel channel 27. The valves 23 and 24 are designed as check valves in the exemplary embodiment.

[0030] The valve 23 comprises a valve plate 29. The valve plate 29 is between the Fig. 1 shown closed position 41 and an open position. In the closed position 41, the valve plate 29 rests against a valve seat 32 and thereby separates the fuel channel 26 from the pump chamber 22. The valve plate 29 is preloaded by a spring 57, which in the exemplary embodiment is designed as a compression spring, in the direction of the valve seat 32, i.e. in the direction of the closed position 41. If a negative pressure develops in the pump chamber 22, the valve plate 29 is lifted off the valve seat 32 once the force applied by the spring 57 is exceeded. A stop 35 for the valve plate 29 is formed in the housing 2, which stop defines the open position of the valve 23 and limits the stroke of the valve plate 32. Alternatively, the block length of the spring 57 can also form a stop for the valve plate 29. The forces acting on the valve plate 29 during operation can also define the open position of the valve 23.

[0031] The valve 24, which leads from the pump chamber 22 into the fuel channel 27, has a valve plate 30 which is arranged in the Fig. 1 The valve plate 30 is biased toward the closed position 41 by a spring 58, in this embodiment a compression spring. A stop 36 is formed in the housing 2, which limits the maximum stroke of the valve plate 30. Alternatively, the block length of the spring 58 can limit the stroke of the valve plate 30.

[0032] During the manufacture of the housing 2 of the fuel supply device 1, chips are generated by machining the metal housing 2. Contaminants may also be present in the fuel. Such contaminants, especially chips, can impede the movement of the valve plates 29, 30, 31. The contaminants can become lodged between the valve plates 29, 30, 31 and the valve seat 32, 33, and 34, or between the valve plates 29, 30, 31 and the stops 35, 36, 37, thus blocking or impeding the movement of the valve plates 29, 30, 31.

[0033] In order to prevent contaminants from entering the area of ​​the valves 23, 24, 25, an annular gap is provided. In the direction of flow from the control chamber 15 to the pump chamber 22, an annular gap 38 is arranged upstream of the valve 23. The annular gap 38 is at a distance from the valve plate 29 of the valve 23 in the direction of flow. In the direction of flow from the pump chamber 22 to the fuel channel 27, an annular gap 39 is arranged upstream of the valve 24. The annular gap 39 is at a distance from the valve plate 30 of the valve 24 in the direction of flow. In the direction of flow from the fuel channel 56 to the main fuel opening 11, an annular gap 40 is arranged upstream of the valve 25 in the direction of flow. The annular gap 40 is at a distance from the valve plate 31 of the valve 25 in the direction of flow. The annular gaps 38, 39 and 40 are each formed separately from the valve plate 29, 30, 31.The annular gaps 38, 39 and 40 do not extend along the outer circumference of a valve plate 29, 30 or 31. The annular gaps 38, 39 and 40 are each arranged at a distance from the valve plates 29, 30, 31.

[0034] In Fig. 2 The main fuel nozzle 13 is shown schematically enlarged. The valve 25 is in its open position 42. In the open position 42, the valve plate 31 has a Fig. 1 The valve plate 31 has traveled a stroke a in the closed position 41 shown. The valve plate 31 rests against the stop 37. The valve plate 31 is located at a distance from the valve seat 34 that corresponds to the stroke a. The stroke a can be, for example, from 0.05 mm to 1 mm. The main fuel nozzle 13 has a base body 50 that has a substantially cylindrical shape. The base body 50 is pressed into the bore 14 of the housing 2. In an alternative design, the base body 50 can also be screwed into the bore 50 or held in the bore 50 by means of an elastic element such as an O-ring or the like.

[0035] In Fig. 2 The throttle 45 is schematically shown as an adjustable throttle with a valve needle 46. Via the throttle 45, the fuel channel 28 opens into a first annular channel 43, which is formed between the base body 50 of the main fuel nozzle 13 and the wall of the bore 14. In the exemplary embodiment, the first annular channel 43 is formed by a circumferential groove on the base body 50. A second annular channel 44 is arranged at a distance from the first annular channel 43 and is also delimited by the base body 50 and the wall of the bore 14. The second annular channel 44 is also formed by a circumferential groove on the outer circumference of the base body 50. The annular gap 40 extends between the annular channels 43 and 44. The annular gap 40 is delimited by an inner wall 47 and an outer wall 48. The inner wall 47 is formed by the outer circumference of the base body 50. The outer wall 48 is the wall of the bore 14.

[0036] In an alternative embodiment, the inner wall 47 can be formed by a thickened portion molded onto the base body 50. It can also be provided that the inner wall 47 is formed by the outer circumference of a ring 60 held on the base body 50. This is shown in Fig. 2 indicated schematically with a dashed line.

[0037] The annular gap 40 has a gap width b that is matched to the stroke a of the valve 25. The gap width b corresponds to the distance between the inner wall 47 and the outer wall 48. The gap width b is not greater than twice the stroke a. In particular, the gap width b is not greater than the stroke a. Advantageously, the gap width b is smaller than the stroke a. Preferably, the gap width b is at most 80% of the stroke a. The gap width b is advantageously at least 30%, in particular at least 50% of the stroke a. This simplifies production. The gap width b can be, for example, from 0.04 mm to 2 mm, in particular 0.04 mm to 1.6 mm, advantageously 0.05 mm to 1.5 mm. The stroke a can be, for example, from 0.05 mm to 1.0 mm. The chips typically generated are usually significantly larger than the gap width b, so even a gap width b that is larger than the stroke a can largely retain the chips that occur. The gap width b is fixed by design.The gap width b is not adjustable and cannot be changed by the user.

[0038] The flow cross-section of the annular gap 40 is larger than the flow cross-section of the valve 25. Therefore, the annular gap 40 does not limit the flow rate. The flow cross-section of the annular gap 40 is advantageously larger than the flow cross-section of the throttle 45. If the throttle 45 is adjustable, the flow cross-section of the annular gap 40 is preferably larger than the largest flow cross-section adjustable with the throttle 45.

[0039] The annular gap 40 has a gap length c. The gap length c is advantageously comparatively small. The gap length c is advantageously less than half the gap width b. The gap length c is advantageously 0.02 mm to 1.5 mm, in particular 0.02 mm to 1.0 mm, preferably 0.1 mm to 0.5 mm.

[0040] The valve plate 31 is in its closed position 41 ( Fig. 1 ) is applied to the valve seat 34 over a valve seat width d. For a flat valve seat 34 (as shown), the valve seat width d is the difference between the outer valve seat radius and the inner valve seat radius. For a valve with a flat valve seat 34, the gap length c is advantageously less than twice the width d. For a valve with a round valve seat 34 (not shown), the gap length c is advantageously less than twice the valve plate thickness e.

[0041] The gap width of the annular gaps 38 and 39 ( Fig. 1 ) is correspondingly matched to the stroke of the valve plates 29 and 30 of the valves 23 and 24 of the purger 20.

[0042] Fig. 3 shows an embodiment of a valve 24 of the purger 20, in which an annular gap 39 is arranged upstream of the valve 24 in the direction of flow. A second annular gap 49 is arranged downstream of the valve 24 in the direction of flow. The annular gap 49 protects the valve 24 from contamination that reaches the valve 24 during a flow in the opposite direction. This can occur, for example, when the combustion engine is switched off, when fuel still in the fuel system drains back into the fuel tank. In the embodiment, the annular gaps 39 and 49 are formed on inserts 59 that are inserted into the fuel channel 27 downstream and upstream of the valve 24.

[0043] In the example according to Fig. 4 The check valve and the annular gap 40 are formed on separate components. The check valve is formed on the base body 50. The annular gap 40 is delimited by a component 61. The component 61 is pressed into the bore 14 separately from the base body 50. The component 61 has the first annular channel 43, into which the fuel channel 28 opens. The inner wall 47 delimiting the annular gap 40 is also formed on the component 61.

[0044] The Figuren 5 bis 7 show different design variants for the annular gap 40. The annular gaps 38, 39 and 49 can be designed accordingly.

[0045] In the example according to Fig. 5 The inner wall 47 is formed with an outwardly tapered cross-section, in particular with a triangular cross-section. The gap length c is thereby minimized. The outer wall 48 is cylindrical.

[0046] In the example according to Fig. 6 The inner wall 47 and outer wall 48 are designed with a tapered, particularly pointed, cross-section. This also results in a minimum gap length c.

[0047] In the example according to Fig. 7 The inner wall 47 is designed with a tapered cross-section. However, the inner wall 47 does not taper to a point, but is rounded. The outer wall 48 is cylindrical.

[0048] Any combination of the aforementioned designs of inner wall 47 and outer wall 48 may also be advantageous.

[0049] The flow cross-sections in this case are advantageously surface cross-sections.

Claims

1. Fuel-supply device, in particular a carburettor, having a housing (2) in which there is formed an intake-channel section (3) into which at least one fuel opening (11, 12) opens out, wherein the fuel-supply device (1) has at least one fuel channel (26, 27, 28) in which a valve (23, 24, 25) is arranged, wherein the valve (23, 24, 25) has a valve plate (29, 30, 31), wherein the valve (23, 24, 25) has a closed position (41) in which the valve plate (29, 30, 31) abuts against a valve seat (32, 33, 34), and wherein the valve (23, 24, 25) has an open position (42), wherein the valve plate (29, 30, 31) covers a valve stroke (h) between the open position (42) and the closed position (41), wherein at least one annular gap (38, 39, 40, 49) is formed in the fuel channel (26, 27, 28), wherein the gap width (b) of the annular gap (38, 39, 40, 49) is matched to the stroke (a) of the valve plate (29, 30, 31) of the valve (23, 24, 25) in such a way that the gap width (b) is not greater than twice the stroke (a), and wherein the flow cross section of the annular gap (40) is larger than the flow cross section of the valve (23, 24, 25), wherein the flow cross sections are area cross-sections, and characterized - in that the annular gap (38, 39, 40, 49) is formed separately from the valve plate (29, 30, 31) and does not extend along the outer periphery of the valve plate (29, 30, 31), in that the annular gap (38, 39, 40, 49) is delimited by an inner wall (47) and an outer wall (48), and in that the valve seat (32, 33, 34) and the inner wall (47) of the annular gap (38, 39, 40, 49) are formed on the same component, or - in that a main fuel nozzle (13) having a valve (25) opens out into the intake-channel section (3), in that the main fuel nozzle (13) is arranged in a bore (14), and in that the annular gap (40) is formed between the wall of the bore (14) and the outer periphery of the main fuel nozzle (13).

2. Fuel-supply device according to Claim 1, characterized in that the gap width (b) is at most 100%, preferably at most 80%, of the stroke (a).

3. Fuel-supply device according to Claim 1 or 2, characterized in that, in the open position (42), the valve plate (29, 30, 31) abuts against a stop (34, 35, 36).

4. Fuel-supply device according to one of Claims 1 to 3, characterized in that at least one annular gap (38, 39, 40) is arranged upstream of the valve (23, 24, 25).

5. Fuel-supply device according to one of Claims 1 to 4, characterized in that at least one annular gap (49) is arranged downstream of the valve (24).

6. Fuel-supply device according to one of Claims 1 to 5, characterized in that the annular gap (40) is formed between the wall of the bore (14) and the outer periphery of the main fuel nozzle (13), and in that the annular gap (40) extends between a first annular channel (43) and a second annular channel (44).

7. Fuel-supply device according to Claim 6, characterized in that the first annular channel (43), the annular gap (40) and the second annular channel (44) are delimited by the wall of the bore (14) and the outer periphery of the main fuel nozzle (13).

8. Fuel-supply device according to one of Claims 1 to 7, characterized in that at least one throttle (45) is arranged upstream of the annular gap (40).

9. Fuel-supply device according to Claim 8, characterized in that the at least one throttle (45) is adjustable.

10. Fuel-supply device according to Claim 8 or 9, characterized in that the flow cross section of the annular gap (38, 39, 40, 49) is larger than the flow cross section of the throttle (45).

11. Fuel-supply device according to one of Claims 1 to 10, characterized in that the fuel-supply device has a purger (20), wherein the purger (20) has a pump chamber (22), wherein a first valve (23) is arranged upstream of the pump chamber (22) and a second valve (24) is arranged downstream of the pump chamber.

12. Fuel-supply device according to one of Claims 1 to 11, characterized in that the at least one valve (23, 24, 25) is a check valve.

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