JPH0567766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle engine equipped with an exhaust purifying catalyst in the exhaust system, and particularly to a structure for preventing deterioration of the catalyst when the engine misfires.

In an engine equipped with a catalyst in the exhaust system, a large amount of unburned mixed gas flows into the exhaust system when the engine misfires, and there is a risk that this unburned mixed gas will come into contact with a high-temperature catalyst, burn it, and melt the catalyst.

The present invention can immediately stop engine operation when a misfire occurs, prevent thermal deterioration of the catalyst due to unburned mixed gas, and prevent the engine from running at full throttle by suddenly opening the throttle valve wide. ,
If the exhaust temperature rises due to a cause other than a misfire,
It is possible to continue supplying fuel to the intake passage for a certain period of time, prevent thermal deterioration of the catalyst due to air discharged into the exhaust system, and continue to operate the engine for a certain period of time to stop the vehicle. To provide an exhaust gas purification device for a vehicle engine that can quickly travel to a suitable location.

That is, in order to achieve the above object, the present invention provides a detector for detecting whether the exhaust temperature downstream of the catalyst is at an abnormal temperature exceeding a set value indicating a misfire state of the engine. a negative pressure-responsive on-off valve that is provided in a fuel supply passage connecting a float chamber of the carburetor and a fuel tank and that is opened in response to intake negative pressure downstream of the throttle valve of the carburetor;
A return pump is provided in the fuel return passage connecting the float chamber of the carburetor and the fuel tank, and is driven by the vibration of the intake negative pressure downstream of the throttle valve of the carburetor, and the detector detects the exhaust gas. When an abnormality in temperature is detected, the negative pressure responsive on/off valve is closed by cutting off the supply of intake negative pressure to the negative pressure responsive on/off valve, thereby supplying fuel from the fuel tank to the float chamber of the carburetor. When an abnormality in the exhaust temperature is detected by the detector, the intake negative pressure is introduced into the return pump to drive the return pump, and the fuel in the float chamber is stopped. It is characterized by being equipped with a drive mechanism for sucking out fuel toward the fuel tank.

An embodiment of the present invention will be described below based on a motorcycle engine shown in FIG. . engine 1
The intake passage 2 guides air introduced from the air cleaner 3 to the cylinders, and on the way, the air is mixed with fuel from the carburetor 4, and this mixed gas is controlled by the throttle valve 5. Combustion gas burned in the cylinder is released into the atmosphere through an exhaust pipe 6 and a muffler 7. An oxidation catalyst 8 is provided downstream of the exhaust pipe 6 to purify the exhaust gas.

The float chamber 9 of the carburetor 4 is connected to the fuel tank 10,
They are communicated via a fuel supply passage 11. This fuel supply passage 11 is opened and closed by a negative pressure responsive on-off valve 12 . The negative pressure-responsive on-off valve 12 is configured to open in response to negative intake pressure in the intake passage 2.
Therefore, this negative pressure responsive on-off valve 12 is connected to the negative pressure introduction path 1.
3. The intake passage 2 is communicated with the downstream side of the throttle valve 5 through the first electromagnetic three-way switching valve 14 and the negative pressure outlet hole 15 . The first electromagnetic three-way switching valve 14 normally has a negative pressure outlet hole 15 and a negative pressure introduction path 1.
However, as will be described later, when an electric signal is applied, the negative pressure introduction path 1 is connected by electromagnetic switching action.
3 is communicated with the atmosphere opening port 16, and thereby operates so as not to apply negative intake pressure to the negative pressure responsive on-off valve 12. When negative pressure does not act on the negative pressure responsive on-off valve 12, the negative pressure responsive on-off valve 12 opens the fuel supply passage 11 and drains the fuel from the fuel tank 10 to the float chamber 9.
Do not supply fuel to.

The bottom of the float chamber 9 is connected to a fuel tank 10 via a fuel return passage 18. A negative pressure responsive return pump 19 is provided in the fuel return passage 18 . This return pump 19 is driven by the pulsation of the intake negative pressure, and normally the intake negative pressure does not act on it, but it is activated by the intake negative pressure in an emergency, which will be described later. That is, the return pump 19 is communicated with the intake passage 2 on the downstream side of the throttle valve 5 via the negative pressure conduit 20, the second electromagnetic three-way switching valve 21, and the negative pressure outlet hole 22. The second electromagnetic three-way switching valve 21 normally opens the negative pressure conduit 20 to the atmosphere opening 23, thereby stopping the return pump 19, but an electric signal described later is applied. If the negative pressure passage 20 is connected to the negative pressure outlet hole 22 by electromagnetic switching, the return pump 19 is thereby driven.

A temperature-sensitive detector 25 is provided in the muffler 7 near the downstream side of the catalyst 8.
is composed of, for example, a thermocouple, and transmits an electrical signal to the controller 26 when it detects that the exhaust gas temperature has exceeded a predetermined value. controller 26
is composed of, for example, an electromagnetic relay or other microcomputer, and based on the signal from the detector 25, it energizes the first and second electromagnetic three-way switching valves 14 and 21 to perform electromagnetic switching operations, respectively. .

In the embodiment with such a configuration, during normal operation of the engine 1, the negative pressure responsive on-off valve 12 receives negative pressure in the intake passage 2 through the first electromagnetic three-way switching valve 14 and the negative pressure outlet hole 15. The fuel supply passage 11 is opened to supply fuel from the fuel tank 10 to the float chamber 9 of the carburetor 4. In this case, since the second electromagnetic three-way switching valve 21 opens the negative pressure passage 20 to the atmosphere opening 23, the return pump 19
has been stopped.

When the engine 1 misfires, a large amount of unburned mixed gas flows into the exhaust pipe 6. This unburned gas is the catalyst 8
If it touches and burns, the exhaust temperature on the downstream side of the catalyst 8 will rise, so the temperature sensor 25 detects this, and when the detected temperature reaches the set temperature or higher, the controller 26 acts to Then, the second electromagnetic three-way switching valves 14 and 21 are operated. Since the first switching valve 14 prevents the transmission of negative pressure to the negative pressure responsive on-off valve 12, the fuel supply passage 11 is closed. Further, since the second switching valve 21 connects the negative pressure conduction 20 to the negative pressure outlet hole 22, the pulsation of the intake negative pressure acts on the return pump 19, causing the return pump 19 to perform a pumping action, and inside the float chamber 9. of fuel is sucked up into the fuel tank 10. Therefore, in the event of a misfire, not only is the fuel supply to the carburetor 4 stopped, but the fuel remaining in the float chamber 9 of the carburetor 4 is quickly suctioned and removed. Compared to simply stopping the fuel supply to the carburetor 4, the engine 1 stops immediately. From this, it is possible to prevent the catalyst 8 from being eroded.

Also, when sudden acceleration is required while the engine 1 is running, the throttle valve 5 is wide open and a rich air-fuel mixture is temporarily supplied to the cylinders of the engine 1. Exhaust temperature may increase. This rise in exhaust temperature is detected by the temperature sensor 2.
5, even though the throttle valve 5 is wide open, the fuel supply to the carburetor 4 is stopped as described above, and the intake negative pressure is activated in the return pump 19. , the fuel in the float chamber 9 will be sucked out, and there is a possibility that a large amount of air flowing through the intake passage 2 will be supplied to the catalyst 8.

However, when the throttle valve 5 is suddenly opened to a large extent to shift to full-open running, the negative intake pressure in the intake passage 2 temporarily decreases, so the pulsation of the negative intake pressure acting on the return pump 19 also decreases. , the fuel siphoning capacity becomes smaller.

Therefore, if the exhaust temperature rises due to a cause other than a misfire, the fuel remaining in the float chamber 9 will not be sucked up all at once. will continue to be supplied. Therefore, a large amount of air is not supplied to the catalyst 8 when the vehicle shifts to full-throttle running, and overheating of the catalyst and accompanying thermal deterioration can be prevented. At the same time, since the fuel in the float chamber 9 does not suddenly become empty, the engine 1 can continue to operate for a certain period of time.
The motorcycle can be driven to a suitable place to stop.

According to the present invention described in detail above, when the engine misfires, the fuel supply to the carburetor is stopped, and at the same time, the fuel remaining in the float chamber of the carburetor is quickly suctioned and removed. Therefore, compared to simply stopping the fuel supply, the engine can be stopped immediately, and catalyst melting and thermal deterioration can be prevented.

Moreover, when the throttle valve is suddenly opened wide and the mode shifts to full-open driving, the intake negative pressure in the intake passage temporarily decreases, and the pulsation of the intake negative pressure acting on the return pump also decreases, which reduces the fuel flow. Suction capacity decreases. Therefore, if the exhaust temperature rises due to a cause other than a misfire, such as when the engine moves to full-throttle driving, the fuel remaining in the float chamber will not be sucked up all at once; Fuel will continue to be supplied to the intake passage. Therefore, when moving to full throttle driving,
A large amount of air is not supplied to the catalyst, and overheating of the catalyst and accompanying thermal deterioration can be prevented. At the same time, since the fuel in the float chamber does not become empty, it is possible to continue operating the engine for a certain period of time, and the advantage is that the vehicle can quickly travel to a suitable place to stop.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention. 1...Engine, 2...Intake passage, 4...Carburetor,
6, 7...Exhaust system (exhaust pipe, muffler), 8...Catalyst,
9... Float chamber, 10... Fuel tank, 11... Fuel supply passage, 12... Negative pressure responsive on-off valve, 14... Fuel supply stop mechanism (electromagnetic three-way switching valve), 18... Fuel return passage, 19... Return pump, 21... Drive mechanism (electromagnetic three-way switching valve), 25... Detector.

Claims (1)

[Claims] 1. In a vehicle engine in which a catalyst is provided in the exhaust system, the exhaust temperature downstream of the catalyst in the exhaust system is
A detector is installed in the fuel supply passage connecting the float chamber of the carburetor and the fuel tank, and is installed in the fuel supply passage connecting the float chamber of the carburetor and the fuel tank. A negative pressure-responsive opening/closing valve that is opened in response to intake negative pressure downstream of the throttle valve, and a fuel return passage connecting the float chamber of the carburetor and the fuel tank; The return pump is driven by the pulsation of the intake negative pressure on the downstream side, and when an abnormality in the exhaust temperature is detected by the detector, the supply of intake negative pressure to the negative pressure responsive on-off valve is cut off. a fuel supply stop mechanism for closing the negative pressure response valve and stopping the fuel supply from the fuel tank to the float chamber of the carburetor; , a drive mechanism for introducing the intake negative pressure into a return pump to drive the return pump and sucking out fuel in a float chamber toward a fuel tank; Device.