JP2009215974A - Overrich prevention mechanism at restart of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure excellent engine restartability even in the state where fuel leaks out into an intake passage from an acceleration pump after engine stop. <P>SOLUTION: The overrich prevention mechanism includes an outside air introducing passage 11 for communicating an air side to an intake passage, a temperature sensing type valve opening/closing means for closing a first cutoff valve 12 arranged in the outside air introducing passage 11 through the deformation thereof by a valve element supporting member 12b at a designated temperature or higher, and a complete explosion diaphragm 13 taken as a boost pressure sensing type valve opening/closing means for closing a second cutoff valve 130 arranged in the outside air introducing passage 11 when introduced engine boost pressure exceeds a prescribed level. At engine restart in a state where fuel in an acceleration pump mechanism leaks out into an intake passage after engine stop, the overrich state is avoided through the introduction of outside air into the intake passage by leaving the outside air introducing passage 11 open until the engine boost pressure exceeds a prescribed level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an overrich prevention mechanism at the time of engine restart, and in particular, an overrich prevention mechanism for preventing the fuel from leaking from an acceleration pump to an intake passage after the engine is stopped to fall into an overrich at the time of engine restart. About.

  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, and the operability of the engine may be impaired. In order to eliminate this fuel shortage, an acceleration pump mechanism 2 as described in Japanese Utility Model Laid-Open No. 6-1754 and shown in FIG. 2 is widely adopted.

  The acceleration pump mechanism 2 opens the throttle valve 5 to rotate the lever 6 attached thereto, operates the rod 21 with the link lever 27 to push down the plunger 22, compresses the valve spring 24b, and compresses the seat with the valve body 24a. By doing so, the check valve 24 closes the inlet from the float chamber 3. As a result, the fuel in the cylinder 20 is pressurized and passed through the acceleration fuel passage 29 through the check valve 25 including the valve body 25a and the valve spring 25b. The fuel is injected toward the manifold.

  In such a fuel supply system provided with the acceleration pump mechanism 2, after the engine is stopped, the check valve 24, 25 of the acceleration pump mechanism 2 closes the inlet side and the outlet side, and the fuel is sealed therebetween. . However, since the vicinity is heated by the residual heat of the engine and becomes high after the engine is stopped, the temperature in the acceleration fuel passage 29 of the acceleration pump mechanism 2 rises and the fuel starts to vaporize.

The fuel filled up to the front of the check valve 25 pushes open the valve body 25a as the pressure rises, and leaks into the intake passage 4 from the acceleration nozzle 23. Therefore, when the engine is restarted, the fuel that has flowed out and accumulated in the intake passage 4 enters the combustion chamber excessively, resulting in deterioration of the restartability of the engine due to over-riching.
Japanese Utility Model Publication No. 6-1754

  The present invention is intended to solve the above-described problems, and is capable of ensuring good engine restartability even in a situation where fuel leaks from the acceleration pump to the intake passage after the engine is stopped. Let it be an issue.

  Therefore, the present invention is an overrich prevention mechanism at the time of engine restart provided in the fuel supply system of the engine together with the acceleration pump mechanism, and includes an outside air introduction path that communicates the atmosphere side with the intake passage, and the outside air introduction path. An engine boost pressure that introduces a temperature-sensitive valve opening / closing means that opens and closes the provided first shut-off valve by deformation accompanying a change in temperature of the valve body support member, and a second shut-off valve disposed in the outside air introduction path Boost pressure-sensitive valve opening / closing means that opens and closes when the engine changes, and when the engine is restarted in a state where fuel in the acceleration pump mechanism leaks into the intake passage after the engine is stopped, the engine boost pressure In order to avoid over-riching by opening the outside air introduction path and introducing outside air into the intake passage until the air temperature exceeds a predetermined level. It was.

  When the engine is restarted in a temperature situation in which fuel leaks from the acceleration pump when the engine is stopped, the temperature-sensitive valve opening and closing means open in this way to open the outside air introduction path, so that the excess content due to the leaked fuel can be exposed to the outside air. The engine restarts while avoiding excessive leaning after starting the engine by diluting and closing the outside air introduction path with the boost pressure sensitive valve opening and closing means at the timing when the idle speed stabilizes after starting the engine Over-riching at the time can be effectively prevented.

  In this case, if the complete explosion diaphragm is used as the boost pressure sensitive valve opening / closing means, the existing parts can be used as they are, and the engine restart overrich prevention mechanism is provided with a choke chamber ASSY or an acceleration pump. It can also be integrated with a vaporizer.

  Furthermore, in the above-described over-rich prevention mechanism at the time of restarting the engine, accurate operation is realized at low cost by using a bimetal that deforms the valve body support member of the first shut-off valve at a predetermined temperature and bends in the valve opening direction. can do.

  Furthermore, in the above-described overrich prevention mechanism at the time of restart, the boost pressure sensitive valve opening / closing means is closed when the engine boost pressure is -50 mmHg to -200 mmHg or less, and the outside air introduction path is closed. By setting in this way, the dilution function of the air-fuel mixture can be easily finished at an appropriate timing.

  In addition, if the carburetor with an acceleration pump, which is integrally provided with the above-described over-rich prevention mechanism at the time of restarting the engine, a small arrangement space is required, and this is used as a fuel supply system for the engine. By simply disposing, the above-described overrich prevention function can be exhibited in addition to the function of the vaporizer.

  In a situation where the engine is likely to be overrich when the engine is restarted, the temperature-sensitive valve opening / closing means and the boost pressure-sensitive valve opening / closing means open the outside air introduction path and introduce outside air into the intake passage to dilute the mixture. According to the present invention, it is possible to ensure good engine restartability even in a situation where fuel leaks from the acceleration pump to the intake passage after the engine is stopped.

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

  FIG. 1 shows a longitudinal sectional view of the overrich prevention mechanism 1 when the engine is restarted according to the present embodiment. In this embodiment, the over-rich prevention mechanism 1 at the time of engine restart is provided in a carburetor with an acceleration pump (not shown) provided with an acceleration pump mechanism as shown in FIG. It is assumed to be installed in the system.

  The over-rich prevention mechanism 1 at the time of restarting the engine is such that an outside air introduction path 11 having an inlet 11a opened to the atmosphere side and an outlet side opened into the intake passage 4 passes through the body 10, and the atmosphere side and the intake passage 4 side A first bypass passage 11 is closed to the outside air introduction passage 11 with a rubber valve body 12a provided at the tip of a bimetallic valve body support member 12b. The valve body support member 12b is operated by a temperature change to constitute a temperature sensitive valve opening / closing means for opening and closing the inlet 11a.

  The bimetal constituting the support member 12b is formed by laminating two different types of metals into a thin plate / strip shape, and has a characteristic of bending to a non-expanding side when one metal expands in a predetermined temperature range. In this embodiment, after the engine stops, it expands due to the residual heat of the engine, and when the fuel in the acceleration pump reaches a temperature range that flows out to the intake passage 4, it is deformed to the valve opening side, The valve body 12a that has blocked the inlet 11a is opened to introduce outside air into the intake passage 4.

  The outside air introduction path 11 is provided with a second shut-off valve 130 comprising a rubber valve body 131 and a valve seat 132 in the middle thereof, and an engine boost pressure is connected to the back surface of the body 10 through a pipe 135. The complete explosion diaphragm 13 introduced to the pressure chamber side is provided, and the internal diaphragm is displaced by the fluctuation of the engine boost pressure, and the valve rod 133 supporting the valve element 131 is operated by extending the inner diaphragm to introduce the outside air. The path 11 is opened and closed.

  This complete explosion diaphragm 13 is generally used for the purpose of appropriately maintaining the choke valve opening during the choke operation from the start to the completion of warming up. In the present embodiment, the complete explosion diaphragm 13 is used. Thus, the second shut-off valve 130 is opened and the outside air introduction path 11 is opened. When the engine speed increases and the engine boost pressure exceeds a predetermined level, the second shut-off valve 130 is closed to perform normal operation. It has a function to switch between.

  Next, the operation of the overrich prevention mechanism 1 when the engine is restarted will be described in detail. After the engine is stopped, the ambient temperature around the carburetor becomes high due to the residual heat of the engine, so the fuel sealed in the cylinder of the acceleration pump mechanism 1 is vaporized and expanded and accelerated through the check valve on the outlet side. The air leaks from the nozzle and accumulates in the intake passage 4.

  At this time, the valve body 12a that has blocked the inlet 11a of the outside air introduction path 11 is set so that the valve body support member 12b that supports the valve body 12a is deformed at a temperature higher than the temperature at which the fuel in the acceleration pump leaks. The valve is lifted in the valve opening direction, and the inlet 11a is opened. On the other hand, the complete explosion diaphragm 13 maintains the open state of the second shut-off valve 130 until the engine boost pressure becomes a predetermined level or less, and the outside air introduction path 11 is connected between the intake passage 4 and the atmosphere side. It is in a state of communication.

  When the engine is restarted in this state, the outside air is taken into the intake passage 4 via the open outside air introduction passage 11 and leaks from the acceleration pump mechanism to remove the excess concentration due to the fuel accumulated in the intake passage 4. Dilute to avoid over-richness when the engine is restarted to achieve an appropriate air / fuel ratio.

  Then, after the engine is started, when the idle boost pressure introduced to the back pressure chamber side becomes −50 mmHg to −200 mmHg or less, the complete explosion diaphragm 13 is actuated to close the second shutoff valve 130 and open the outside air introduction path 11. When closed and shifted to normal operation, the air-fuel mixture will not become excessively lean.

  As described above, since the outside air is mixed with the air containing the fuel leaked from the acceleration pump at the time of starting the engine, over-riching is effectively avoided and the engine restartability is improved. In addition, the intake air amount suitable for normal operation can be made by closing the outside air introduction passage when the idle speed is stabilized after the engine is started.

  As described above, even when the fuel leaks from the acceleration pump to the intake passage after the engine is stopped, the present invention can ensure good engine restartability.

The longitudinal cross-sectional view which shows embodiment of this invention. FIG. 2 is a layout view showing a part of an engine fuel supply system centering on an acceleration pump mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Overrich prevention mechanism at the time of engine restart, 2 Acceleration pump mechanism, 4 Intake passage, 5 Throttle valve, 10 Body, 11 Outside air introduction path, 12, 130 Shut-off valve, 12a, 131 Valve body, 12b Valve body support member 13 Complete explosion diaphragm, 23 nozzle for acceleration

Claims (4)

  An over-rich prevention mechanism at the time of engine restart provided in an engine fuel supply system together with an acceleration pump mechanism, and an external air introduction path that communicates the air side with an intake passage, and a first shut-off disposed in the external air introduction path A temperature-sensitive valve opening / closing means for opening and closing the valve by deformation accompanying a temperature change of the valve body support member, and a boost for opening / closing by a change in engine boost pressure introducing a second shut-off valve disposed in the outside air introduction path Until the engine boost pressure exceeds a predetermined level when the engine is restarted with fuel in the acceleration pump mechanism leaking into the intake passage after the engine is stopped. The engine is characterized in that over-riching is avoided by opening the outside air introduction path and introducing outside air into the intake passage. Starting at the time of the over-rich prevention mechanism.   The over-rich prevention mechanism at the time of engine restart according to claim 1, wherein the boost pressure sensitive valve opening / closing means is a complete explosion diaphragm.   3. The overrich prevention mechanism at the time of engine restart according to claim 1, wherein the valve body support member of the first shut-off valve is made of a bimetal that is deformed at a predetermined temperature and bends in a valve opening direction. 2. The boost pressure responsive valve opening / closing means is set to close when the engine boost pressure becomes −50 mmHg to −200 mmHg or less to close the outside air introduction path. , 2 or 3, an over-rich prevention mechanism at the time of engine restart.

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