JPH0341657B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine idle speed control device.

[Conventional technology]

Normally, vehicle engines use liquid fuel such as gasoline as the fuel to be supplied to the engine. For example, in a carburetor engine, the liquid fuel is vaporized and atomized using a ventilator negative pressure, and a fuel injection type Engines inject liquid fuel into the intake air stream, creating a mixture from the liquid fuel to ensure combustibility.
Liquid fuel evaporates within the fuel supply system, which may cause problems such as percolation, resulting in poor drivability and engine stalling.

Therefore, in addition to the normal liquid fuel supply system, conventional vehicle engines are equipped with a gaseous fuel supply system that supplies gaseous fuel such as LPG, as shown in Japanese Patent Application Laid-open No. 57-18446. By making it possible to switch between fuel and gaseous fuel, this prevents deterioration in drivability and engine stalling caused by fuel evaporation when using liquid fuel, and also prevents the occurrence of engine stalls caused by the small number of gaseous refueling stations. There are some devices designed to solve the difficulty of gaseous fuel replenishment.

In conventional vehicle engines of this type, if the compression ratio of the engine is set high, knocking is likely to occur due to this high compression ratio when using liquid fuel, so the compression ratio is set to a level that does not cause knocking. The reality is that it is.

[Problem that the invention seeks to solve]

However, in this case, since the gaseous fuel is supplied to the intake system as a gas, the amount of intake air is smaller than when using liquid fuel under the same operating conditions, and as mentioned above, the compression ratio is too high. Without it, combustibility deteriorates, and especially during idling, the number of rotations decreases, causing a problem in that idling stability is impaired.

SUMMARY OF THE INVENTION In view of these problems, it is an object of the present invention to provide an engine idle speed control device that can prevent the idle speed from decreasing when using gaseous fuel.

[Means for solving problems]

Therefore, the engine idle speed control device according to the present invention is provided with a discriminating means for determining whether gaseous fuel or liquid fuel is being used, and at least when idling and when using gaseous fuel, the intake speed is higher than when using liquid fuel. This is provided with intake air amount correction means for increasing the amount of air mixture.

[Effect]

In this invention, when the gaseous fuel is used at idle, the intake passage area is increased by the intake air amount correction means, thereby increasing the filling efficiency of the air-fuel mixture and ensuring good combustibility at idle. It is something.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an engine idle speed control device according to an embodiment of the present invention. In the figure, 1 is an intake passage, and in the middle of the intake passage 1 is a partition wall 2.
The intake passage is divided into a primary intake passage 3 and a secondary intake passage 4, and throttle valves 5 and 6 are provided in the middle of both intake passages 3 and 4, and ventilated portions 7 and 8 are formed upstream of the throttle valves 5 and 6. Further, a choke valve 9 is provided upstream of the ventilate portion 7 of the primary intake passage 3, and the upstream end of the intake passage 1 reaches an air cleaner 11.

Also, the ventilary part 7 of the primary intake passage 3
A main nozzle 12b of the vaporizer 12 is disposed in the vaporizer 12, one end of a liquid fuel feed passage 13 is connected to the vaporizer 12 in communication with the float chamber 12a, and the other end of the liquid fuel feed passage 13 is connected to the vaporizer 12 in communication with the float chamber 12a. is connected to the gasoline tank 14, and a filter 15, a pump 16, and a gasoline cut valve 17 are interposed in the middle of the liquid fuel supply passage 13, and the liquid fuel supply system 18 is configured as described above. There is.

Also, on the upstream side of the intake passage valve 9,
An LPG mixer 10 is formed, and the LPG mixer 10
One end of the LPG feeding passage 19 is connected to the LPG feeding passage 19, the other end of the feeding passage 19 is connected to the LPG cylinder 20,
Also, a filter 21 is installed in the middle of the LPG feeding passage 19,
An LPG cut valve 22 and a vapor riser 23 are interposed, and the gaseous fuel supply system 24 is configured as described above.

In the figure, 25 is the battery, 26 is the ignition switch, and 27 is the gasoline cut valve 17.
and a fuel selector switch 28 for switching the operation of the LPG cut valve 22 is a timer, and the fuel selector switch 27 serves as a determining means for determining whether gaseous fuel or liquid fuel is used.

The secondary intake passage 4 is provided with an idle bypass passage 29 that bypasses the throttle valve 6.
In other words, the air intake port of the passage is located upstream of the throttle valve 6 and downstream of the LPG mixer 10, and the air outlet of the passage is located downstream of the throttle valve 6, and the idle bypass passage 29
is provided with a bypass solenoid valve 30 that opens and closes the bypass passage 29 in conjunction with the operation of the LPG cut valve 22.As described above, at idle, when using gaseous fuel, the suction is lower than when using liquid fuel. An intake air amount correction means 31 is configured to increase the amount of air.

Next, the operation will be explained.

When gasoline is used as fuel, the ignition switch 26 is turned on to operate the engine, and the fuel selector switch 27 is turned to the gasoline side to close the LPG cut valve 22 and open the gasoline cut valve 17. Then, the gasoline in the tank 14 is supplied to the float chamber 12a of the carburetor 12 through the filter 15 and the gasoline cut valve 17 by the action of the pump 16, and the gasoline in the float chamber 12a is supplied to the main nozzle 12b by the action of the ventilary negative pressure. The air is supplied to the intake passage 3 from the air, and is drawn into the engine as a mixture together with intake air in an amount corresponding to the opening degree of the throttle valves 5 and 6.

In order to switch the fuel to LPG in such a state, the fuel changeover switch 27 can be turned to the LPG side. Then immediately open the gasoline cut valve 17.
is closed and the supply of gasoline to the float chamber 12a of the carburetor 12 is stopped, and at the same time the timer 28 is activated, and after all the remaining gasoline in the carburetor 12 is supplied into the intake passage 3, the LPG cut valve is closed. 22 is opened, and the LPG in the tank 20 passes through the filter 21 and the LPG cut valve 22, is vaporized and metered by the vapor riser 23, is guided to the LPG mixer 10, is supplied from there to the intake passage 1, and is inhaled into the engine together with intake air. be done.

At this time, in the intake air amount correction means 31, the bypass solenoid valve 30 opens in response to the signal from the timer 28, and thereby the throttle valves 5, 6
In addition to the amount of intake air determined by the opening degree of the engine, intake air is supplied to the engine via the idle bypass passage 29, and thus the amount of intake air is increased compared to when gasoline is used.

In the device of this embodiment as described above, when LPG is used as fuel, the air intake port is
By opening the bypass passage 29, which is provided between the LPG mixer 10 and the throttle valve 4 and having its outlet located downstream of the throttle valve 4, and increasing the area of the intake passage 1, the amount of intake air and fuel can be increased. By increasing the intake air-fuel mixture amount compared to when using liquid fuel, the simple structure increases charging efficiency even at a constant air-fuel ratio, improves combustibility, and improves combustibility when switching fuels. No shock or the like occurs, and as a result, it is possible to prevent a drop in the idle rotation speed and guarantee idle stability.

In addition, this device delays the start of LPG supply when switching from gasoline to LPG, which prevents the fuel air-fuel ratio from becoming overbalanced and ensures good drivability.

In the above-mentioned embodiment, the intake air amount correcting means is constituted by the idle bypass passage and the bypass solenoid valve, but this may be one that increases the intake air amount by adjusting the opening degree of the throttle valve. Further, the opening/closing control of the bypass solenoid valve may be performed only in the idling operation region rather than in the entire operating region.

〔Effect of the invention〕

As described above, according to the engine idle speed control device according to the present invention, when gaseous fuel is used during idling operation, the intake passage area is increased to increase the intake air-fuel mixture amount. , improves combustibility by increasing the filling efficiency of the air-fuel mixture when using gaseous fuel at a constant air-fuel ratio with a simple structure, and also prevents a drop in idle speed without causing shock when switching fuel. There is.

[Brief explanation of drawings]

The drawing is a schematic configuration diagram of an engine idle speed control device according to an embodiment of the present invention. 4, 5...throttle valve, 10...LPG mixer (gaseous fuel supply device), 12...carburizer (liquid fuel supply device), 29...idle bypass passage,
30...Bypass solenoid valve, 31...Intake amount correction means.

Claims (1)

[Scope of Claims] 1. In an engine capable of switching between liquid fuel and gaseous fuel, a discriminating means for determining whether gaseous fuel or liquid fuel is being used is provided, and
At least when idling and when gaseous fuel is used, intake air amount correction means is provided to increase the intake air mixture amount compared to when liquid fuel is used. The idle speed of the engine is characterized by being arranged downstream of the gaseous fuel supply device and its outlet downstream of the throttle valve, so that when gaseous fuel is used, the intake air-fuel mixture amount is increased to increase the filling rate. Number control device.