JPH0236929Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a supercharged engine that is mainly used in a vehicle such as an automobile.

[Conventional technology]

As a prior art related to this type of supercharged engine, as shown in Japanese Patent Application Laid-Open No. 55-164741, a turbo supercharger is provided upstream of the carburetor, and the turbo supercharger pressurizes the fuel. Some engines are designed to supply air to the engine body through the carburetor. In order to eliminate the inconvenience that the amount of fuel to be ejected from the main nozzle of the carburetor is reduced due to the push-back effect of the supercharging pressure, the supercharging pressure is transferred to the supercharging pressure guide path. Countermeasures are being taken such as guiding the water into the float chamber via the float.

[The problem that the idea aims to solve]

However, with just this, for example,
When the throttle valve is suddenly closed to enter a deceleration mode from full-throttle running or a state close to full-throttle running, problems tend to occur in the carburetor section. That is, if the throttle valve is suddenly closed while the supercharger is operating at full capacity, the pressure in the intake manifold will correspondingly decrease (see broken line a), as shown in FIG. The pressure in the surge tank, for example, on the upstream side of the throttle valve will temporarily rise to a considerably high value, exceeding the full-load normal pressure (see solid line b), and the pressure in the float chamber will also rise rapidly. A rise occurs. As a result, problems may occur with the sealing performance of the carburetor, resulting in poor durability; fuel may be forced out of the main nozzle, causing the mixture to become too rich, resulting in catalyst overheating, poor drivability, or air pollution due to unforeseen gas emissions. This can easily lead to other inconveniences.

Note that one possible solution to this inconvenience is to improve the accuracy of the blow-off valve and shift its opening set pressure to a lower value. In other words, a normal blow-off valve opens when the supercharging pressure becomes abnormally high due to a malfunction of the waste gate valve, etc., and diverts a portion of the charge air discharged from the supercharger to the supercharger. It is like a relief valve that can be opened to the suction side or to the atmosphere, and has a simple configuration with large variations in valve opening setting pressure. Therefore, if the opening setting pressure of the blow-off valve is set to a low enough value to prevent the boost pressure from increasing during sudden deceleration as described above,
The blow-off valve may open at an unnecessary time, making it difficult to maintain an appropriate normal supercharging pressure P. Therefore, in order to solve the above-mentioned disadvantages using this method, a high-quality blow-off valve that accurately detects the boost pressure and operates delicately is required. However, in order to improve the quality of the blow-off valve, it is essential to increase the length of the valve-closing spring used. Therefore, there is a problem in that the blow-off valve becomes expensive and large in size.

Another method is to install a supercharger upstream of the carburetor and transfer the pressure of the air discharged from the supercharger to the float of the carburetor via the boost pressure guide path. In an engine in which air is introduced into the float chamber, an engine has been considered in which, when a throttle valve is closed, the introduction of air supply pressure into the float chamber is cut off, and atmospheric air is introduced into the float chamber.

However, when the throttle valve is closed to rapidly decelerate, it is difficult to sufficiently eliminate the above-described overrichness during deceleration simply by cutting off the introduction of supply pressure into the float chamber. In other words, in the case where the pressure of supply air is introduced into the float chamber during supercharging to increase the pressure, in order to maintain the pressurizing effect in the float chamber during supercharging, the fuel passage returning from the float chamber to the fuel tank is Supply air pressure is also introduced into the diaphragm chamber of the provided regulator, and in addition to the spring force, this pressure urges the valve body of the regulator in the closing direction, thereby closing the fuel passage. However, with such a configuration, if only the supply air pressure to the float chamber is cut off during sudden deceleration, in other words, the regulator is connected independently to a surge tank, etc., and during deceleration However, if the introduction of pressure to the regulator is not shut off, when the supply air pressure increases due to sudden deceleration, the pressure introduced to the regulator will increase, and the return of fuel from the float chamber to the fuel tank will continue to be prohibited. As a result, the oil level in the float chamber will rise, and even if the introduction of supply pressure to the float chamber is cut off, the rising oil level will cause fuel to leak from the main system of the carburetor and from the slow system. This results in an increase in fuel consumption, and it is difficult to completely eliminate the problem of overload during sudden deceleration.

The present invention aims to eliminate such problems.

[Means to solve the problem]

The present invention takes the following measures to achieve the above objectives.

That is, the supercharged engine according to the present invention is
A supercharger is disposed upstream of the carburetor, and the pressure of supply air discharged from the supercharger is guided to a float chamber of the carburetor and a regulator through a boost pressure guide path, In the engine, the valve body of the regulator is biased in the closing direction by the pressure of the air supply, and the fuel passage returning from the float chamber to the fuel tank is closed. The present invention is characterized in that a switching valve is provided to block the pressure from being transmitted to the float chamber and the regulator.

[Effect]

With such a configuration, when the supply air pressure increases rapidly due to sudden deceleration, the switching valve switches to cut off the supercharging pressure guide path, so that the supply air pressure is no longer transmitted to the float chamber. Therefore,
It is possible to prevent the pressure in the float chamber from increasing. Moreover, when the switching valve is switched,
Since the pressure of the air supply is no longer transmitted to the regulator, the effect of urging the valve body of the regulator in the closing direction by the pressure of the air supply disappears. Therefore,
Fuel is allowed to return from the float chamber to the fuel tank, and the oil level in the float chamber does not rise unduly. Therefore, it is possible to simultaneously prevent an excessive pressure rise in the float chamber and an unreasonable rise in oil level during sudden deceleration, and effectively eliminate the above-mentioned disadvantage of the mixture becoming too rich during sudden deceleration. be able to.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a system explanatory diagram of the supercharged engine according to the present invention, in which 1 is the engine body, 2 is the carburetor, 3 is the throttle valve of this carburetor 2, and 4
5 is a main nozzle, and 5 is a float chamber communicating with this main nozzle 4. This float chamber 5 is connected to a fuel tank 8 via a fuel passage 7 having a fuel pump 6. Further, 9 is a surge tank provided upstream of the carburetor 2, 10 is a compressor portion of an exhaust turbo supercharger 11 provided upstream of this surge tank 9, 12 is a turbine portion of the same supercharger 11, and 13 is a This is an air cleaner provided upstream of the compressor section 10. Further, 14 is a supercharging pressure guide path that communicates the surge tank 9 and the float chamber 5, and 15 is this supercharging pressure guide path 1.
This branch path 15 is connected to a diaphragm chamber 16a of a regulator 16 interposed in the middle of the fuel passage 7. The regulator 16 includes the diaphragm chamber 1
6a and a fuel chamber 16b forming a part of the fuel passage 7.
and is partitioned by a diaphragm 16c, and a fuel return pipe 17 that communicates the fuel chamber 16b with the fuel tank 8 can be opened and closed by a valve body 16d held by the diaphragm 16c. .

In such a device, a switching valve 18 is provided upstream of a portion of the boost pressure guide path 14 to which the branch path 15 is connected.
The switching valve 18 has a first port 18a that communicates with the surge tank 9, a second port 18b that communicates with the float chamber 5, and a third port that is open to the atmosphere.
The first port 18a and the second port 18b are normally in communication, and the third port 18c is closed. Then, only while the switching signal α is input to the input terminal 18d, the first port 1
8a is closed, and the second port 18b and the third port 18c are switched to communicate with each other. The control means 19 for switching and controlling the switching valve 18 includes, for example, a pressure switch 21, a throttle switch 22, and an AND gate 23 for processing signals from both of these switches 21 and 22. Become. The pressure switch 21 is configured to be turned on only when the pressure in the surge tank 9 exceeds a set value (for example, +430 mmHg) that is slightly higher than the full load normal pressure (for example, +400 mmHg). . Further, the throttle switch 22 is configured to be turned on only when the opening degree of the throttle valve falls below a set value, which is set to be, for example, 10 degrees closer than fully open (for example, 80 degrees). has been done. When both switches 21 and 22 are turned on, a switching signal α is output from the AND gate 23 to the switching valve 18.

Next, the operation of this embodiment will be explained. first,
When the throttle valve 3 is opened and the engine speed increases, the pressure of the air supply discharged from the compressor section 10 of the exhaust turbo supercharger 11, that is, the supercharging pressure increases. The supercharging pressure is also guided to the float chamber 5 via the supercharging pressure guide path 14, and the pressure within the float chamber 5 also increases. At the same time, the boost pressure passes through the branch path 15 to the regulator 16.
act on the diaphragm chamber 16a, the diaphragm 16c is pushed down, the valve body 16d closes the open end of the fuel return pipe 17, and the pressure of the fuel fed to the float chamber 5 is increased. Therefore, even if the supply air pressure increases, the amount of fuel jetted from the main nozzle 4 will not be insufficient, and the air-fuel ratio will be maintained at an appropriate value. If the throttle valve 3 suddenly closes and the engine enters a deceleration mode while continuing full throttle driving in this way, the throttle switch 22 turns ON.
Switch to state. At the same time, surge tank 9
Since the internal pressure is about to rise above the full load normal pressure, the pressure switch 21 is also switched to the ON state. Therefore, a switching signal α is output from the AND gate 23 to the switching valve 18, and the switching valve 18 is switched to prevent the supercharging pressure from being transmitted to the float chamber 5. That is, the first port 18a of the switching valve 18 is closed, the second port 18b and the third port 18c communicate with each other, and the float chamber 5 is opened to the atmosphere. Therefore, even if sudden deceleration is performed, the pressure within the float chamber 5 will not rise suddenly.

Moreover, when the switching valve 18 is switched, the supply air pressure no longer acts on the diaphragm chamber 16a of the regulator 16. the result,
The force pressing the valve body 16d of the regulator 16 in the closing direction is deenergized, the valve body 16d is separated from the open end of the fuel return pipe 17, and the float chamber 5 and the fuel tank 8 are connected via the fuel passage 7. It becomes connected. Therefore, the oil level in the float chamber 5 will not rise unduly. Therefore, it is possible to effectively eliminate the problem of fuel leaking from the main nozzle 4 during sudden deceleration, resulting in an excessively rich mixture.

It should be noted that the switching valve is of course not limited to the structure described above, and may be of the type shown in FIG. 3, for example. That is, in the one shown in FIG. 3, a diaphragm mechanism 24 operated directly by the pressure inside the surge tank 9 drives a valve body 25 interposed in the supercharging pressure guide path 14. When the pressure in the surge tank 9 acting on the diaphragm chamber 24a of the diaphragm mechanism 24 exceeds a set value, the diaphragm 24b is deflected by a required distance in the direction of arrow X, causing the valve body 25 to move to the path blocking position. It is becoming more and more popular. However, in the case shown in FIG. 2, when the boost pressure is cut off, the float chamber 5 is opened to the atmosphere to actively reduce the pressure inside the float chamber 5, so the structure shown in FIG. In comparison, leakage of fuel from the main nozzle 4 can be more reliably prevented.

[Effect of idea]

Since the present invention has the above-mentioned configuration, when the throttle valve is suddenly closed to decelerate from full-throttle running or a state close to it, the pressure in the float chamber of the carburetor installed downstream of the supercharging air is reduced. It is possible to eliminate the inconvenience of a sudden rise or an unreasonable rise of the oil level in the float chamber. Therefore, it is possible to reliably solve the problem of the durability of the carburetor being impaired or fuel leaking out from the main nozzle due to an excessive pressure rise in the float chamber.

Furthermore, since the switching valve is simply provided in the middle of the boost pressure guide path, the structure is relatively simple and implementation is easy. Moreover, since the supercharging pressure guide path is a much finer air passage than the blow-off path, etc., highly accurate control can be performed without increasing the size of the devices.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram for explaining the change characteristics of supercharging pressure, Fig. 2 is a system explanatory diagram showing one embodiment of the present invention, and Fig. 3 is an explanatory diagram showing another embodiment of the present invention. be. 2... Carburetor, 3... Throttle valve, 4...
... Main nozzle, 5 ... Float chamber, 11 ... Supercharger (exhaust turbo supercharger), 14 ... Supercharging pressure guide path, 18 ... Switching valve.

Claims (1)

[Scope of utility model registration request] A supercharger is disposed upstream of the carburetor, and the pressure of supply air discharged from the supercharger is guided to a float chamber of the carburetor and a regulator through a boost pressure guide path, In the engine, the valve body of the regulator is biased in the closing direction by the pressure of the air supply, and the fuel passage returning from the float chamber to the fuel tank is closed. A supercharged engine characterized in that a switching valve is provided to block the pressure from being transmitted to the float chamber and the regulator.