JPH07189812A - Starting aid for engine for gaseous fuel - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a start assist device for an engine for gaseous fuel, which improves startability and prevents fuel from being diffused to the outside when the engine is stopped. A venturi portion 3 is formed in the intake passage 2, and a gas passage 5 for guiding a gaseous fuel such as CNG is communicated with the venturi portion 3, and the inside of the intake passage 2 is downstream of the venturi portion 3. A throttle valve 4 is provided on the intake passage 2 upstream of the venturi portion 3.
In addition, an intake passage shutoff valve 12 that is closed when the engine 1 is stopped and is opened when the engine 1 is started and operated.
Is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine starting assist device using a gaseous fuel such as CNG or LPG, and more particularly,
The present invention relates to a start assist device for a gas fuel engine, which improves startability and prevents fuel from being diffused to the outside when the engine is stopped.

[0002]

2. Description of the Related Art A general gas fuel engine using a gas fuel such as CNG or LPG is shown in FIG. The engine 1 has an intake passage 2, a venturi portion (mixer) 3 is formed in the intake passage 2, and a throttle valve 4 is provided in the intake passage 2 downstream of the venturi portion 3. The venturi section 3 is connected to a gas passage 5 for guiding low-pressure gaseous fuel, like a carburetor. During engine operation, the high-pressure gaseous fuel sent from the high-pressure gas passage 6 is depressurized by the regulator 7 to be almost atmospheric pressure, and then introduced into the venturi portion 3 through the gas passage 5. The gas fuel is the air cleaner 8
After being mixed with the negative pressure air sucked in from the combustion chamber 9 at a predetermined mixing ratio, it is burned in the combustion chamber 9.

[0003]

By the way, in the case of such an engine, the gas passage 5 is provided when the engine is stopped.
The gaseous fuel remaining inside gradually diffuses, passes through the gap of the throttle valve 4 and stays in the combustion chamber 9 or the exhaust passage 10, or diffuses from the air cleaner 8 to the outside.

Therefore, there is a problem that the supply of the gaseous fuel is delayed at the time of starting the engine and it takes a long time to start the engine, and when the engine is stopped, odor is given to the outside to cause discomfort or danger.

Therefore, an object of the present invention, which was devised to solve the above problems, is to provide a start assisting device for a gas fuel engine, which improves the startability and prevents the fuel from being diffused to the outside when the engine is stopped. It is in.

[0006]

In order to achieve the above object, the present invention forms a venturi portion in an intake passage and connects the vent passage portion with a gas passage for guiding a gaseous fuel such as CNG. A throttle valve is provided in the intake passage downstream of the venturi portion, and an intake passage is closed in the intake passage upstream of the venturi portion when the engine is stopped and opened when the engine is started or operated. It is provided with a stop valve. ... Further, a bypass passage is provided which bypasses the throttle valve and communicates the intake passages on the upstream side and the downstream side, and the bypass passage is provided with a bypass passage closing valve which is opened at least when the engine is started. It has been done. The intake passage stop valve has an electric opening / closing means, and the electric opening / closing means is connected to a delay circuit for opening the intake passage stop valve after a lapse of a predetermined time from the start of the engine start. It is a thing. …

[0007]

According to the structure of [Operation], when the engine is stopped,
The intake passage upstream of the venturi portion is closed. Therefore, the gaseous fuel remaining in the gas passage can be sent to the combustion chamber without being emitted to the outside, and the startability can be improved. At the same time, the problem of odor can be solved.

Further, according to the above construction, since the intake air is made through the bypass passage at the time of starting the engine, the air-fuel mixture can be promptly sent into the combustion chamber and the startability can be further improved.

With the above construction, only the gaseous fuel can be sent to the combustion chamber between the start of the engine start and the opening of the intake passage stop valve, and the choke effect further enhances the startability.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a side sectional view showing such a starting assist device for a gas fuel engine. As in the prior art, a venturi portion 3 is formed in the intake passage 2, and a throttle valve 4 is provided in the intake passage 2 downstream of the venturi portion 3. The venturi portion 3 is communicated with a gas passage 5 for introducing a gas fuel having a substantially atmospheric pressure. The intake passage 2 shown here is specifically defined by an intake manifold 11.

The intake passage 2 upstream of the venturi portion 3 is provided with an intake passage stop valve 12 for opening and closing the intake passage 2. In this embodiment, the intake passage stop valve 12 is the intake manifold 11
A butterfly valve whose valve shaft is rotatably attached is used, but a shutter that moves in and out of the intake passage 2 or an air flow sensor may be used. A diaphragm 13 is connected to the intake passage shutoff valve 12 via a rod 14. An intake negative pressure derivation unit 15 is provided in the intake passage 2 downstream of the throttle valve 4, and the intake negative pressure derivation unit 15 and the diaphragm 13 are connected by a vacuum hose 16. Intake passage shutoff valve 12
Is closed when the engine is stopped, that is, when the intake negative pressure is not generated, and is opened when the engine is started and operated.

A throttle valve 4 is provided in the intake passage 2.
A bypass passage 17 is provided that bypasses and connects the upstream side and the downstream side. The bypass passage 17 is provided with a bypass passage closing valve 18 for opening and closing the bypass passage 17, which is specifically constituted by a solenoid valve 19. The bypass passage shutoff valve 18 is connected to the start position of the ignition switch 20, and when not energized, its valve body 21 projects into the bypass passage 17 and closes it.

Next, the operation of the embodiment will be described.

FIG. 1 shows the engine stopped, FIG. 2 shows its start, and FIG. 3 shows its operation.

First, as shown in FIG. 1, the intake passage stop valve 12 and the bypass passage valve 18 are closed when the engine is stopped. Accordingly, the intake passage 2 and the bypass passage 17
Is completely closed, and the gaseous fuel remaining in the gas passage 5 passes through the slight gap around the throttle valve 4 to the combustion chamber 9
Sent to. Therefore, these gaseous fuels can be used for the next engine start, and the startability can be improved.
Further, since the gaseous fuel cannot leak outside, the problem of odor can be solved at the same time.

Next, when the engine shown in FIG. 2 is started, the intake passage shut-off valve 1 is operated by the intake negative pressure generated by cranking.
2 is opened, and at the same time, the bypass passage 17 is also opened.
At this time, since the gaseous fuel is sent from the gas passage 5, the mixture of the gaseous fuel and the intake air formed in the venturi portion 3 is promptly passed through the bypass passage 17 to the combustion chamber 9
It is possible to further improve the startability.

Further, during operation of the engine shown in FIG.
Although the intake passage shutoff valve 12 remains open, the bypass passage 17 is closed because the ignition switch 20 moves from the start position to the on position. This puts the engine in normal throttle control.

Next, a modified embodiment will be described.

As shown in FIG. 4, in this embodiment, the intake passage shutoff valve 12 is electrically controlled to open and close. As in the above-described embodiment, the intake passage shutoff valve 12 is a butterfly valve, and its valve shaft 22 is rotatably attached to the intake manifold 11. One end of the valve shaft 22 is urged to rotate it in the closing direction. Return spring 2
3 is attached, and a step motor 25 as an electric opening / closing means 24 is connected to the other end. In this way, the intake passage shutoff valve 12 is controlled to be opened and closed together with the bypass passage shutoff valve 18 by the control circuit described later.

FIG. 5 shows a control circuit for opening and closing the intake passage shutoff valve 12 and the bypass passage shutoff valve 18, and FIG. 6 is a table showing the control modes thereof. In FIG. 6, the bypass passage shutoff valve 18 is opened when the engine is stopped, unlike the above-described embodiment.

In the control circuit shown in FIG. 5, the step motor 25 of the intake passage closing valve 12 operates in the opening direction when energized, and the solenoid valve 19 forming the bypass passage closing valve 18 also operates in the closing direction. When the ignition switch 20 is off, or when it is switched from off to on, they do not operate and are in the state shown in FIG.

When the ignition switch 20 is switched to start, the power from the battery 26 is supplied from both the start and on terminals. The electric power supplied from the start terminal rotates the starter and acts on the first relay 27 to turn it on. The power of the ON terminal is branched into two, one of which is used as a signal and the other is used as an operating power supply. The signals are the first relay 27 and the delay circuit 28.
Is input to the microcomputer 29 via. Further, the operating power source is directly sent to the microcomputer 29. The microcomputer 29 operates the step motor 25 in response to the input of the signal. At this time, the solenoid valve 19
Is not energized and remains open.

Next, when the ignition switch 20 is turned back on from the start, the second relay 30 is turned on this time by the power generation of the alternator, and the signal is transmitted to the second relay 30.
Is directly input to the microcomputer 29 without passing through the delay circuit 28. Therefore, the step motor 25 is held open. The third relay 31 is also turned on by the power generated by the alternator, and the solenoid valve 19 is closed by the electric power sent through the third relay 31.

The delay circuit 28 outputs a signal after a predetermined time has elapsed from the time when the signal was input to it. By providing the delay circuit 28, the intake passage shutoff valve 12 is opened after a predetermined time has passed from the start of the engine, that is, the moment when the ignition switch 20 is started, so that the gas passage 5 inside the gas passage 5 is opened during that time. The gaseous fuel and the air in the intake passage 2 form a rich air-fuel mixture, which is quickly sucked out from the bypass passage 17 and sent to the combustion chamber, and the choke effect can further improve the startability. This delay time is set to about 0.5 seconds.

FIG. 7 and FIG. 8 are circuit diagrams showing an example of the delay circuit and the change state of the signal thereof. The rectangular wave input signal is branched in the A section, and one of the branched signals directly enters the AND circuit 32. In the other case, the waveform is smoothly converted between AB and then enters the inverter 33, and the delay time t from the rectangular wave of the portion A
The same rectangular wave accompanied by is entered into the AND circuit 32. AND
The signals are processed in the circuit 32, and as a result, the output is delayed by the time t from the time of input of the signals.

However, since it is not necessary to control the delay time very accurately, the delay circuit 28 may be a simple one as shown in FIG. This is a switch circuit in which the heater 34 heated by energization operates the bimetal 35. This also delays the opening of the intake passage shutoff valve 12, and the same effect as described above can be achieved. At the same time, it is very effective for cost reduction.

[0028]

The present invention exhibits the following excellent effects.

(1) The residual gaseous fuel can be effectively utilized at the time of starting, and the startability can be remarkably improved.

(2) The fuel is prevented from being dissipated to the outside when the engine is stopped, and the odor causing discomfort or danger is not given to the outside.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a starting assist device for a gas fuel engine according to the present invention, showing a state when the engine is stopped.

FIG. 2 is a side sectional view showing a state when the engine of the starting auxiliary device shown in FIG. 1 is started.

FIG. 3 is a side cross-sectional view showing a state of the starting assist device shown in FIG. 1 during engine operation.

FIG. 4 is a side sectional view showing a modified embodiment, showing an intake passage shutoff valve.

5 is a diagram showing a control circuit of the intake passage stop valve shown in FIG. 4. FIG.

FIG. 6 is a table showing control modes of the control circuit shown in FIG.

FIG. 7 is a diagram illustrating an example of a delay circuit.

8 is a diagram showing a signal change state in the delay circuit of FIG. 7. FIG.

FIG. 9 is a diagram showing a modification of the delay circuit.

FIG. 10 is a side sectional view showing a conventional gas fuel engine.

[Explanation of symbols]

 1 Engine 2 Intake Passage 3 Venturi Part 4 Throttle Valve 5 Gas Passage 12 Intake Passage Stop Valve 17 Bypass Passage 18 Bypass Passage Stop Valve 24 Electric Opening / Closing Means 28 Delay Circuit

Claims (3)

[Claims] 1. A venturi portion is formed in the intake passage, a gas passage for guiding a gaseous fuel such as CNG is communicated with the venturi portion, and a throttle valve is provided in the intake passage downstream of the venturi portion. An intake passage closing valve is provided in the intake passage upstream of the venturi portion, the intake passage closing valve being closed when the engine is stopped and opened when the engine is started and operated. Auxiliary device. 2. A bypass passage closing valve, which bypasses the throttle valve and connects the upstream and downstream intake passages to each other, and which is opened at least when the engine is started. The starting assist device for the gas fuel engine according to claim 1, further comprising: 3. The intake passage closing valve has an electric opening / closing means, and the electric opening / closing means is provided with a delay circuit for opening the intake passage closing valve after a predetermined time has elapsed from the start of starting the engine. The starting aid device for an engine for gaseous fuel according to claim 1, which is connected.