Patent Publication Number: US-11391248-B2

Title: Fuel supply device

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a fuel supply device, in particular a carburetor, with a housing in which an intake channel section is formed, wherein at least one fuel supply port opens into the intake channel section, wherein the fuel supply device comprises at least one fuel channel in which a valve is arranged, wherein the valve comprises a valve plate. The valve comprises an open position and comprises a closed position, wherein the valve plate contacts a valve seat in the closed position. The valve plate carries out a valve stroke between the open position and the closed position. 
     U.S. Pat. No. 6,149,138 discloses a membrane carburetor comprising a main nozzle with a check valve. At idle, the check valve closes off the main nozzle path so that pressure pulsations in the intake channel cannot act through the main nozzle path on the control chamber. 
     CN 202690251 U discloses a carburetor which comprises a screen in the idle fuel path; in this way, impurities are to be filtered out of the fuel and deposits of impurities at the idle port are to be avoided in this way. 
     It has been found that functional impairments, for example, unsatisfactory starting behavior or rough running of an internal combustion engine in operation, may be encountered in internal combustion engines whose fuel supply device comprises at least one valve. 
     The invention has the object to provide a fuel supply device with which functional impairments of an internal combustion engine are prevented. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, this is achieved by a fuel supply device that is characterized in that at least one annular gap is formed in the fuel channel, wherein the gap width of the annular gap is matched to the valve stroke of the valve plate of the valve such that the gap width is not larger than twice a length of the valve stroke, wherein the flow cross section of the annular gap is larger than the flow cross section of the valve. 
     It is provided that in the fuel channel, in which the valve is arranged, an annular gap is formed wherein the gap width of the annular gap is matched to the valve stroke of the valve plate of the valve such that the gap width is not larger than twice the length of the valve stroke. The flow cross section of the annular gap is larger than the flow cross section of the valve. The flow cross sections are advantageously cross-sectional areas in this context. 
     The annular gap is advantageously not delimited by the valve plate of the valve. The annular gap is in particular embodied separate from the valve plate of the valve. The annular gap is advantageously embodied to be spaced apart from the valve plate. 
     It has been found that rough running of an internal combustion engine may be the result of an unsuitable fuel supply action. This unsuitable fuel supply action may result when dirt such as cuttings or chips, which may result from the production of the fuel supply device, is positioned between the valve plate and a stop for the valve plate. These dirt particles prevent that the valve plate reaches the closed position. The function of the fuel supply device is impaired by this. Also, an unsatisfactory starting behavior may be caused by dirt particles at a valve, namely a valve of a fuel pump, in particular of a purge pump. 
     By matching the gap width of the annular gap to the length of the valve stroke of the valve plate, the annular gap retains dirt particles such as cuttings or chips or the like and ensures in this way that the valve plate can reach the closed position. It has been found that already with a gap width that is not larger than twice the length of the valve stroke of the valve plate blocking or prevention of movement of the valve plate can be prevented to the greatest possible extent. The flow cross section of the annular gap is in this context larger than the flow cross section of the valve. The annular gap is thus not a significantly limiting factor for the flow volume through the fuel channel. 
     The gap width of the annular gap is advantageously fixedly set by construction. The gap width of the annular gap is preferably not changeable or not adjustable. 
     Preferably, the gap width is not larger than the length of the valve stroke (amounts to at most 100% of the length of the valve stroke). Only dirt particles that are not larger than the length of the valve stroke of the valve plate can pass through the annular gap. These dirt particles are however not retained at the valve plate due to the sufficiently large valve stroke of the valve plate and can pass the valve plate in operation. In this way, blockage or preventing of movement of the valve plate by dirt particles is prevented. 
     The valve can be, for example, the valve of a fuel nozzle or a valve in a pump of the fuel supply device. It can be provided that the valve is a check valve or a solenoid valve with a valve plate. In case of a check valve, the movement of the valve plate between the open position and the closed position is realized due to the pressure conditions at the valve plate. In case of a solenoid valve, the valve plate is moved as a function of the current flow through a solenoid. 
     Preferably, the gap width of the annular gap is smaller than the length of the valve stroke of the valve plate. Particularly preferred, the gap width amounts to at most 80% of the length of the valve stroke. In this way, it can be reliably prevented that dirt particles can pass through the annular gap to the valve, get lodged between valve plate and stop, and thus prevent closing of the valve. Dirt particles that are smaller than the length of the valve stroke can pass between valve plate and stop and are then flushed away by the fuel so that these dirt particles do not cause any functional impairment. 
     The open position of the valve is in particular a position in which the valve plate contacts a stop. The stop and the valve seat define thereby mechanically the two end positions of the valve plate. 
     Advantageously, at least one annular gap is arranged upstream of the valve. The term “upstream” refers in this context to a flow direction from a fuel tank to an internal combustion engine, i.e., the usual flow direction in operation of the fuel supply device. However, it can also be provided that, in addition or as an alternative, at least one annular gap is arranged downstream of the valve. An annular gap which is arranged downstream of the valve prevents in case of back pulsations in the fuel system that dirt particles reach the valve. This can be the case, for example, when the internal combustion engine of a hand-guided work apparatus is pivoted in operation or when the internal combustion engine is turned off and fuel returns to the fuel tank. 
     Advantageously, the annular gap is delimited by an inner wall and an outer wall. A simple configuration of the fuel supply device results when the valve seat and the inner wall of the annular gap are embodied at the same component. Accordingly, no additional components are required for the configuration of the annular gap. 
     Advantageously, a main fuel nozzle opens into the intake channel section and comprises a valve. The main fuel nozzle is in this context the nozzle through which the main portion of the fuel is supplied at full load of an internal combustion engine. The main fuel nozzle is advantageously arranged in a bore of the fuel supply device. The main fuel nozzle is advantageously press-fit into a bore of the fuel supply device. In an alternative configuration, 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 configuration results when the annular gap is formed between the wall of the bore and the outer circumference of the main fuel nozzle. In this way, no additional components are required for embodying the annular gap. It is only necessary to match the dimensions of bore and outer circumference of the main fuel nozzle to each other. Particularly preferred, the annular gap extends between a first annular channel and a second annular channel. The fuel supply and the fuel discharge can be realized by the two annular channels. Advantageously, the first annular channel, the annular gap, and the second annular channel are delimited by the wall of the bore and by the outer circumference of the main fuel nozzle. 
     Advantageously, upstream of the annular gap at least one throttle is arranged. The throttle can be a fixed throttle in this context. The throttle is in particular a partial load fixed nozzle. It can also be provided that the at least one throttle is adjustable. An adjustable throttle can be in particular a full load adjusting screw when the valve is provided at a main fuel nozzle. Advantageously, the flow cross section of the annular gap is larger than the flow cross section of the throttle. In this way, the annular gap does not limit the flow. In an advantageous configuration, at least an adjustable throttle and at least one fixed throttle are provided. 
     Advantageously, the fuel supply device comprises a purge pump as a manually actuated fuel pump. The purge pump comprises a pump chamber. Advantageously, a first valve is arranged upstream of the pump chamber and a second valve is arranged downstream of the pump chamber. For valves at a purge pump, an annular gap is also advantageous in order to ensure that the valve plate opens reliably and closes reliably and is not impaired in its movement by dirt particles. In this way, the permanent function of the purge pump can be ensured. Upon actuation of the purge pump, the fuel system is reliably purged so that a good starting behavior of an internal combustion engine operated with the fuel supply device is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Embodiments of the invention will be explained in the following with the aid of the drawings. 
         FIG. 1  is a schematic section illustration of a fuel supply device. 
         FIG. 2  is a schematic enlarged illustration of the main fuel nozzle of the carburetor of  FIG. 1 . 
         FIG. 3  is a schematic section illustration of a check valve of the purge pump of the carburetor of  FIG. 1 . 
         FIG. 4  is an embodiment variant of the main fuel nozzle of  FIG. 2 . 
         FIG. 5  is an enlarged illustration of an embodiment variant of the annular gap. 
         FIG. 6  is an enlarged illustration of another embodiment variant of the annular gap. 
         FIG. 7  is an enlarged illustration of yet another embodiment variant of the annular gap. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows schematically a fuel supply device  1  in section illustration. In the embodiment, the fuel supply device  1  in  FIG. 1  is a carburetor, i.e., a fuel supply device in which the fuel is sucked in by vacuum. A different kind of fuel supply device, for example, a fuel supply device with a fuel valve that conveys the fuel under pressure and injects the fuel into the intake channel in this way, can also be provided. The fuel supply device  1  comprises a housing  2  in which an intake channel section  3  is formed. The intake channel section  3  is advantageously connected to a mixture inlet of an internal combustion engine, not illustrated. Combustion air is usually sucked in through an air filter into the intake channel section  3 . In the intake channel section  3 , a throttle element  7 , in the embodiment a throttle flap, is supported by means of a throttle shaft  8  so as to be pivotable about an axis of rotation  9 . Upstream of the throttle element  7 , a choke element  4  is arranged in the intake channel section  3 . It can also be provided that the fuel supply device  1  does not comprise a choke element  4 . The choke element  4  in the embodiment is a choke flap which is supported by means of a choke shaft  5  so as to be pivotable about an axis of rotation  6 . The throttle element  7  and the choke element  4  serve to control the open flow cross section of the intake channel section  3 . 
     In the embodiment, the fuel supply device  1  is provided to supply a fuel/air mixture into a mixture channel as well as air into 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 the throttle element  7  are completely open, they are positioned in a common plane with the partition wall section  10 . In this way, a separation as complete as possible of mixture channel section  51  and air channel section  52  is achieved. 
     A plurality of auxiliary fuel ports  12  as well as a main fuel port  11  open into the intake channel section  3 , namely into the mixture channel section  51  of the intake channel section  3 . The auxiliary fuel ports  12  are arranged in the region of the throttle element  7 . In the embodiment, the main fuel port  11  is arranged in the region of the partition wall section  10  and upstream of the throttle element  7 . 
     In the embodiment, the fuel supply device  1  is embodied as a membrane carburetor to which fuel is supplied by means of the 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  conveys the fuel by means of a fuel valve, not illustrated, into a control chamber  17  of the fuel supply device  1 . The control chamber  17  is separated by a control membrane  18  from a compensation chamber  19 . As a function of the position of the control membrane  18 , i.e., as a function of the pressure conditions in the control chamber  17  and in the compensation chamber  19 , an inlet valve in the control chamber  17  is opened or closed, as is well known, so that the fuel can flow in a controlled fashion into the control chamber  17 . 
     The auxiliary fuel ports  12  are supplied from an idle chamber  53  which is connected by means of an idle check valve  54  and an idle throttle  55  to the control chamber  17 . 
     The main fuel port  11  is formed at a main fuel nozzle  13  that is connected by means of a fuel channel  28 , shown schematically in dashed line, to the control chamber  17 . A throttle  45  is arranged in the fuel channel  28 . The throttle  45  can be a fixed throttle, for example, a partial load fixed nozzle. However, the throttle  45  can be adjustable also. The throttle  45  can be in particular an adjusting screw. In an advantageous alternative configuration, a fixed throttle and an adjustable throttle can be provided in place of the throttle  45 . 
     The main fuel nozzle  13  is arranged in a bore  14  of the housing  2 . In the embodiment, the fuel channel  28  opens at the circumference of the bore  14 . The main fuel port  11  opens in the region of a venturi section  15  into the intake channel section  3 . The main fuel nozzle  13  comprises a valve  25  that is configured as a check valve. The valve  25  comprises a valve plate  31 . In the closed position  41  illustrated in  FIG. 1 , the valve plate  31  contacts a valve seat  34 . In the embodiment, the valve plate  31  contacts a stop  37  in the open position. 
     The fuel supply device  1  comprises a purge pump  20 . The purge pump  20  is a manually actuated fuel pump that conveys fuel from the control chamber  17  into a fuel tank. The vacuum which is produced in this way in the fuel system has the effect that fuel is sucked from the fuel tank into the fuel system and the fuel system is purged thereby. In doing so, air contained in the fuel system is returned to the fuel tank. The purge pump  20  comprises a purge pump bulb  21  which is to be compressed by the operator for conveying fuel. A pump chamber  22  is provided in the purge pump bulb  21 . A fuel channel  26  opens into the pump chamber  22  through a valve  23 . The fuel channel  26  connects the pump chamber  22  to the control chamber  17 . A valve  24  leads out of the pump chamber  22  and is connectable by means of a fuel channel  27  to the fuel tank. The valves  23  and  24  are embodied as check valves in the embodiment. 
     The valve  23  comprises a valve plate  29 . The valve plate  29  is movable between a closed position  41 , illustrated in  FIG. 1 , and an open position. In the closed position  41 , the valve plate  29  contacts a valve seat  32  and separates in this way the fuel channel  26  from the pump chamber  22 . The valve plate  29  is pretensioned by a spring  57 , embodied in the embodiment as a pressure spring, in the direction toward the valve seat  32 , i.e., in the direction toward the closed position  41 . When a vacuum is produced in the pump chamber  22 , the valve plate  29  is thus lifted off the valve seat  32  when the force applied by the spring  57  is surpassed. A stop  35  for the valve plate  29  is formed in the housing  2  and defines the open position of the valve  23  and delimits the valve stroke of the valve plate  32 . Alternatively, the block length of the spring  57  can also form a stop for the valve plate  29 . Also, the forces which are acting in operation at the valve plate  29  can define the open position of the valve  23 . 
     The valve  24  which leads away from the pump chamber  22  into the fuel channel  27  comprises a valve plate  30  which in the closed position  41 , illustrated in  FIG. 1 , contacts a valve seat  33 . The valve plate  30  is pretensioned by a spring  58 , in the embodiment a pressure spring, in the direction toward the closed position  41 . In the housing  2 , a stop  36  is formed that delimits the maximum valve stroke of the valve plate  30 . Alternatively, the block length of the spring  58  can delimit the valve stroke of the valve plate  30 . 
     When manufacturing the housing  2  of the fuel supply device  1 , cuttings or chips are produced by machining the metallic housing  2 . Impurities can be contained also in the fuel. Such impurities, in particular cuttings or chips, can impair the movement of the valve plates  29 ,  30 ,  31 . The impurities can become lodged between valve plate  29 ,  30 ,  31  and valve seat  32 ,  33  and  34  or between valve plate  29 ,  30 ,  31  and stop  35 ,  36 ,  37  and thereby block or make difficult movement of the valve plate  29 ,  30 ,  31 . 
     In order to prevent that impurities can reach the region of the valves  23 ,  24 ,  25 , the arrangement of an annular gap is provided. In the flow direction from the control chamber  17  to the pump chamber  22 , an annular gap  38  is arranged upstream of the valve  23 . In flow direction, the annular gap  38  is positioned at a distance from the valve plate  29  of the valve  23 . In flow direction 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 positioned at a distance from the valve plate  30  of the valve  24  in flow direction. In flow direction from the fuel channel  28  to the main fuel port  11 , an annular gap  40  is arranged upstream of the valve  25  in the flow direction. The annular gap  40  is positioned at a distance from the valve plate  31  of the valve  25  in flow direction. The annular gaps  38 ,  39 , and  40  are embodied to be separate from the valve plates  29 ,  30 ,  31 , respectively. The annular gaps  38 ,  39  and  40  do not extend along the outer circumference of the 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 , respectively. 
     In  FIG. 2 , the main fuel nozzle  13  is illustrated schematically at an enlarged scale. The valve  25  is in its open position  42 . In the open position  42 , the valve plate  31  has carried out a valve stroke a relative to the closed position  41  illustrated in  FIG. 1 . The valve plate  31  contacts the stop  37 . The valve plate  31  is positioned at a distance from the valve seat  34  corresponding to the length of the valve stroke a. The length of the valve stroke a can be, for example, 0.05 mm to 1 mm. The main fuel nozzle  13  comprises a base body  50  that has a substantially cylindrical shape. The base body  50  is press-fit into the bore  14  of the housing  2 . In an alternative embodiment, the base body  50  can also be screwed into the bore  14  or can be held in the bore  14  by means of an elastic element such as an O-ring or the like. 
     In  FIG. 2 , the throttle  45  is schematically illustrated as an adjustable throttle with a valve needle  46 . By means of 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 embodiment, the first annular channel  43  is formed by a circumferentially extending groove at the base body  50 . A second annular channel  44  is arranged at a distance to 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 circumferentially extending groove at 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 . 
     In an alternative embodiment, the inner wall  47  can be formed by an enlarged portion which is extruded 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 at the base body  50 . This is indicated schematically with a dashed line in  FIG. 2 . 
     The annular gap  40  comprises a gap width b which is matched to the length of the valve stroke a of the valve  25 . The gap width b corresponds to the distance between inner wall  47  and outer wall  48 . The gap width b is not larger than twice the length of the valve stroke a. The gap width b is in particular not larger than the length of the valve stroke a. Advantageously, the gap width b is smaller than the length of the valve stroke a. Preferably, the gap width b amounts to at most 80% of the length of the valve stroke a. The gap width B amounts advantageously to at least 30%, in particular at least 50%, of the length of the valve stroke a. In this way, manufacture is simplified. The gap width b can be, for example, 0.04 mm to 2 mm, in particular 0.04 mm to 1.6 mm, advantageously 0.05 mm to 1.5 mm. The length of the valve stroke a can amount to, for example, 0.05 mm to 1.0 mm. The usually occurring chips or cuttings are mostly significantly larger than the gap width b so that a gap width b that is larger than the length of the valve stroke a is also able to mostly retain the occurring cuttings. The gap width b is constructively fixedly predetermined. The gap width b is not adjustable and cannot be changed by the user. 
     The flow cross section of the annular gap  40  is greater than the flow cross section of the valve  25 . In this way, 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 . When the throttle  45  is adjustable, the flow cross section of the annular gap  40  is preferably larger than the largest flow cross section that can be adjusted by the throttle  45 . 
     The annular gap  40  comprises a gap length c. The gap length c is advantageously comparatively small. The gap length c amounts advantageously to less than half of the gap width b. The gap length c amounts advantageously to 0.02 mm to 1.5 mm, in particular 0.02 mm to 1.0 mm, preferably 0.1 mm to 0.5 mm. 
     In its closed position  41  ( FIG. 1 ), the valve plate  31  contacts the valve seat  34  across a valve seat width d. The valve seat width d in case of a flat valve seat  34  (as illustrated) is the difference between the valve seat outer radius and the valve seat inner radius. The gap length c is advantageously smaller than 2 times the width d for a valve with a flat valve seat  34 . In case of a valve with a round valve seat  34  (not illustrated), the gap length c is advantageously smaller than 2 times the valve plate thickness e. 
     The gap width of the annular gaps  38  and  39  ( FIG. 1 ) is matched in a corresponding manner to the length of the valve stroke of the valve plates  29  and  30  of the valves  23  and  24  of the purge pump  20 . 
       FIG. 3  shows an embodiment of a valve  24  of the purge pump  20  in which an annular gap  39  is arranged in flow direction upstream of the valve  24 . A second annular gap  49  is arranged in flow direction downstream of the valve  24 . The annular gap  49  protects the valve  24  from dirt which may reach the valve  24  in case of a flow in opposite direction. This can be the case, for example, when turning off the internal combustion engine when fuel still contained in the fuel system drains into the fuel tank. In the embodiment, the annular gaps  39  and  49  are embodied at insertion parts  59  which are inserted into the fuel channel  27  upstream and downstream of the valve  24 . 
     In the embodiment according to  FIG. 4 , the check valve and the annular gap  40  are embodied at separate components. The check valve is embodied at the base body  50 . The annular gap  40  is delimited by a component  61 . The component  61  is separate from the base body  50  and press-fit into the bore  14 . The component  61  comprises the first annular channel  43  into which the fuel channel  28  opens. The inner wall  47  which delimits the annular gap  40  is moreover embodied at the component  61 . 
       FIGS. 5 through 7  show different embodiment variants for the annular gap  40 . The annular gaps  38 ,  39 , and  49  can be designed in a corresponding manner. 
     In the embodiment according to  FIG. 5 , the inner wall  47  is embodied with an outwardly tapering cross section, in particular with a triangular cross section. The gap length c is thereby minimized. The outer wall  48  is cylindrically embodied. 
     In the embodiment according to  FIG. 6 , the inner wall  47  and the outer wall  48  are embodied with tapering, in particular pointedly tapering, cross section. This also results in a minimal gap length c. 
     In the embodiment according to  FIG. 7 , the inner wall  47  is embodied with tapering cross section. The inner wall  47  however does not taper to a point but is rounded. The outer wall  47  is cylindrically embodied. 
     Arbitrary combination of the aforementioned configurations of inner wall  47  and outer wall  48  may be advantageous also. 
     Advantageously, the flow cross sections are cross-sectional areas in the invention. 
     The specification incorporates by reference the entire disclosure of European priority document 19 200 476.0 having a filing date of Sep. 30, 2019. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.