JP2009215975A - Acceleration pump mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration pump mechanism included in a fuel supply system of an engine which secures excellent engine restartability by preventing fuel from leaking out into an intake passage through an acceleration nozzle from engine stop until the time immediately before restart. <P>SOLUTION: An acceleration pump mechanism 1A includes an acceleration fuel chamber 20a for introducing fuel for acceleration from a constant fuel chamber 3 to be stored therein, a fuel pressurization means for pressurizing fuel in the acceleration fuel chamber 20a in synchronization with engine acceleration operation, and an acceleration fuel passage 29 for feeding pressurized fuel to an acceleration nozzle 23 of an intake passage 4, and additionally supplies fuel for acceleration at engine acceleration, wherein a cutoff valve 130 for blocking the circulation of fuel by being closed at engine stop is provided to the acceleration fuel passage 29. At least from engine stop until the time immediately before restart, fuel is prevented from leaking out into the intake passage 4 through the acceleration nozzle 23. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an acceleration pump mechanism, and more particularly to an acceleration pump mechanism having a function of avoiding an overrich at the time of engine restart due to fuel flowing out from an acceleration nozzle into an intake passage when the engine is stopped.

  In a general-purpose engine or the like that uses a carburetor for fuel supply, the fuel supplied from the carburetor may be insufficient at the time of acceleration accompanied by a sudden throttle opening operation, which may impair the operability of the engine. In order to solve this fuel shortage, an acceleration pump mechanism 2B described in Japanese Utility Model Laid-Open No. 6-1754 and shown in FIG. 4 is widely adopted.

  The acceleration pump mechanism 2B rotates the lever 6 attached thereto by opening the throttle valve 5, and slides the rod 21 downward with the rod 7 and the link lever 27 to push down the plunger 22. Thus, the valve spring 24b is compressed and seated by the valve body 24a, and the check valve 24 closes the inlet from the float chamber 3.

  The fuel stored in the pressurized fuel chamber 20 formed inside the main body 20 and below the plunger 22 is pressurized by the lowering operation of the plunger 22, passes through the acceleration fuel passage 29 along the arrow, and the valve body. The fuel passes through the check valve 25 including the valve seat 25c and the valve seat 25c, and the fuel is injected from the acceleration nozzle 23 opened in the intake passage 4 toward the intake manifold.

  In the fuel supply system provided with the acceleration pump mechanism 2B having such a configuration, after the engine is stopped, the inlet side and the outlet side of the acceleration fuel chamber 20a are closed by the check valves 24 and 25, and the fuel is sealed between them. Become. However, since the vicinity is heated by the residual heat of the engine after the engine is stopped, the fuel stored inside starts to expand and vaporize.

Then, the fuel that has been filled up to just before the check valve 25 in the acceleration fuel passage 29 pushes open the valve body 25a and flows out from the acceleration nozzle 23 into the intake passage 4 as the pressure rises. For this reason, the fuel accumulated in the intake passage 4 at the time of restarting the engine enters the combustion chamber excessively, resulting in over-riching of the supplied fuel, resulting in deterioration of engine restartability.
Japanese Utility Model Publication No. 6-1754

  The present invention is intended to solve the above-described problems. In the acceleration pump mechanism provided in the fuel supply system of the engine, the fuel is sucked from the acceleration nozzle to the intake passage between the stop of the engine and immediately before the restart. It is an object of the present invention to ensure good engine restartability by preventing the engine from flowing out.

  Accordingly, the present invention provides an acceleration fuel chamber that introduces and stores fuel for acceleration from a constant fuel chamber, fuel pressurizing means that pressurizes fuel in the acceleration fuel chamber in conjunction with an engine acceleration operation, and pressurized fuel. In an acceleration pump mechanism for supplying additional fuel for acceleration when accelerating the engine, the valve is closed when the engine is stopped to shut off the fuel flow A valve is provided in the acceleration fuel passage, and at least from the time when the engine is stopped until immediately before restarting, the fuel is prevented from flowing out from the acceleration nozzle into the intake passage.

  Thus, by closing the acceleration fuel passage when the engine is stopped, it becomes possible to avoid the fuel from flowing out of the acceleration nozzle into the intake passage immediately before the engine restart. It is possible to reliably prevent over-richness during engine restart.

  In this case, the shut-off valve is opened and closed by a diaphragm device that is operated by displacement of the membrane member due to the variation of the introduced intake pipe pressure. Assuming that the valve opening state is maintained when the intake pipe pressure exceeds a predetermined level due to rotation, the accelerating fuel passage can be reliably closed at least when the engine is stopped to effectively prevent fuel from flowing out. .

  Alternatively, the shut-off valve may be opened and closed by an electric valve driving means, and the valve closing state may be maintained when the engine power is turned off and the valve opening state may be maintained when the engine power is turned on. It is possible to effectively prevent the outflow of fuel to the fuel cell.

  Furthermore, if the carburetor is characterized by integrally including the acceleration pump mechanism described above, the carburetor can be accommodated only by arranging the carburetor in the fuel supply system of the engine while meeting the space-saving requirements. In addition to the function / acceleration pump function, it can exhibit an overrich prevention function when the engine is restarted.

  According to the present invention in which the acceleration fuel passage is closed while the engine is stopped, fuel is prevented from flowing out from the acceleration nozzle to the intake passage from the time when the engine is stopped until immediately before restarting, thereby ensuring good engine restartability. It is something that can be done.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 shows a vertical cross-sectional view of a portion of an engine fuel supply system centering on an acceleration pump mechanism 2A of the present embodiment. In the present embodiment, it is assumed that the acceleration pump mechanism 2A is disposed in the engine fuel supply system in a state of being integrally provided in a carburetor (not shown).

  In this acceleration pump mechanism 2A, a plunger 22 is slidably arranged in a cylindrical main body 20 constituting a cylinder, and an acceleration fuel chamber 20a is formed in a lower space thereof. A fuel pipe from the constant fuel chamber 3 is connected to the acceleration fuel chamber 20a, and a check valve 24 for pressing a ball-shaped valve body 24a against a valve seat 24c by a valve spring 24b is provided at the inlet portion. Is provided.

  Further, the acceleration fuel passage 24 extends from the acceleration fuel chamber 20 a to the acceleration nozzle 23 that opens to the intake passage 4, and the ball-shaped valve body 25 a is connected to the valve spring in the middle of the acceleration fuel passage 29. A check valve 25 is provided by being pressed against the valve seat 25 c by 25 b, and acceleration fuel is held between the check valve 25 and the check valve 24.

  Further, the plunger 22 constituting the top wall of the accelerating fuel chamber 20a is connected to a downward rod 21, which is connected in order of the throttle valve 5, the lever 6, the rod 7, and the link lever 27. Thus, it can slide up and down, and these constitute the fuel pressurizing means.

  In the acceleration pump mechanism 2A having such a configuration, the plunger 22 is pushed down in conjunction with the operation of opening the throttle valve 5, the valve spring 24b is compressed, and the check valve 24 closes the inlet from the float chamber 3 for acceleration. The fuel in the fuel chamber 20a is pressurized, passes through the acceleration fuel passage 29, passes through the check valve 25, and is injected from the acceleration nozzle 23 opened in the intake passage 4 toward the intake manifold. The above configuration is common to the conventional acceleration pump mechanism 2B shown in FIG.

  In the present embodiment, FIG. 2 is enlarged on the downstream side of the check valve 25 in the middle of the acceleration fuel passage 29 centering on a shutoff valve 130 that closes and seals fuel flow while the engine is stopped. Referring to FIG. 2, the shutoff valve 130 that exhibits such a function includes a valve seat 132 and a valve body 131 that closes the passage and closes the passage.

  Further, the shut-off valve 130 is a valve body with a valve rod 134 extended from the diaphragm device 13 in which a pipe 135 for introducing intake pipe pressure is connected to the back pressure chamber side partitioned by a membrane member (diaphragm) 133. The opening / closing operation is performed by moving 131 up and down. That is, during normal times when the engine does not rotate and intake pipe negative pressure is not applied, the valve body 131 is pressed against the valve seat 132 and the shut-off valve 130 is closed, and the engine is started and the intake pipe pressure (negative pressure is negative). When the pressure) exceeds a predetermined level, the membrane member 133 is displaced, and the valve body 131 is lifted through the valve rod 134 to open the valve.

  Next, the function of this acceleration pump mechanism 2A will be described in detail. As described above, after the engine is stopped, the temperature around the carburetor becomes high due to the remaining heat of the engine. Therefore, the temperature of the fuel enclosed between the acceleration fuel chamber 20a of the acceleration pump mechanism 2A and the check valve 25 is high. As it rises, it expands and vaporizes, increasing the pressure.

  At this time, the engine is stopped and the pressure in the intake passage 4 does not change from the atmospheric pressure, and the negative pressure from the intake pipe is not applied. Therefore, the diaphragm device 13 does not operate in the valve opening direction. Therefore, the shutoff valve 130 remains closed to block the acceleration fuel passage 29, so that fuel flows out from the acceleration nozzle 23 into the intake passage 4 at least from the stop of the engine to immediately before restarting. Prevents over-riching of the supplied fuel and ensures good engine restartability.

  FIG. 3 shows an application example of this embodiment. Instead of opening / closing the shut-off valve 130 described above with the diaphragm device 13 for introducing the intake pipe pressure, the solenoid 14 as an electric valve driving means is disposed in the acceleration fuel passage 29, whereby the engine is stopped by the operation of the solenoid 14. The figure shows the case where the valve closed state is maintained and the valve opened state is interlocked with the engine start operation.

  In other words, the electromagnetically driven solenoid 14 connected to a power wiring from a battery (not shown) causes the valve rod 134 to protrude when the engine power is off and presses the valve element 131 against the valve seat 132 to Keep the valve closed. When the engine power is turned on for starting, the solenoid 14 is activated by energization, pulls the valve rod 134 to lift the valve body 131, and opens the shut-off valve 130. By performing such an operation, it is possible to prevent the fuel from flowing out from the acceleration nozzle 23 into the intake passage 4 between the stop of the engine and immediately before the restart in the same manner as described above, thereby avoiding over-richness, which is favorable. Ensure engine restartability.

  As described above, the acceleration pump mechanism provided in the fuel supply system of the engine is good according to the present invention as that the fuel does not flow from the acceleration nozzle to the intake passage at least from the stop of the engine to immediately before restart. Engine restartability can be ensured.

The longitudinal cross-sectional view which shows embodiment of this invention. FIG. 2 is an enlarged partial view centering on an acceleration fuel passage portion of FIG. 1. FIG. 3 is an enlarged partial view showing an application example of FIG. 2. The longitudinal cross-sectional view which shows a prior art example.

Explanation of symbols

2A Acceleration pump mechanism, 4 intake passage, 5 throttle valve, 13 diaphragm device, 14 solenoid, 20 body body, 20a acceleration fuel chamber, 22 plunger, 23 acceleration nozzle, 24, 25 check valve, 130 shut-off valve, 24a, 25a 131 Valve body, 24b, 25b, 132 Valve seat, 134 Valve rod

Claims (4)

  An acceleration fuel chamber that introduces and stores fuel for acceleration from the constant fuel chamber, a fuel pressurizing unit that pressurizes fuel in the acceleration fuel chamber in conjunction with an engine acceleration operation, and an acceleration nozzle in the intake passage for the pressurized fuel An acceleration pump mechanism for supplying additional fuel for acceleration when the engine is accelerated, and a shutoff valve that closes when the engine is stopped and seals the flow of fuel. The acceleration pump mechanism is characterized in that fuel is prevented from flowing out from the acceleration nozzle into the intake passage at least from the time when the engine is stopped until immediately before restarting.   The shut-off valve is opened and closed by a diaphragm device that is operated by displacement of the membrane member due to the variation of the introduced intake pipe pressure. The shut-off valve is kept closed when the engine is stopped, and the intake air is 2. The acceleration pump mechanism according to claim 1, wherein the valve opening state is maintained in a state where the pipe pressure exceeds a predetermined level.   The said shut-off valve is opened and closed by an electric valve driving means, and maintains a closed state when the engine power is turned off and maintains a valve opened state when the engine power is turned on. Acceleration pump mechanism. A carburetor comprising the acceleration pump mechanism according to claim 1, 2 or 3 integrally.

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