JPH08135511A - Fuel supply device for gas fuel engine - Google Patents

Abstract

PURPOSE: To increase durability by preventing damage to a pilot valve of a fuel cut-off valve. CONSTITUTION: A fuel cut-off valve 50 is provided in a pipe 27 through which high pressure compressed natural gas stored in a gas container is led, after decompression, to the intake system of an engine main body, and the fuel cut-off valve 50 is provided with a pilot valve 54 and a main valve 53 which open and close automatically by the energization and deenergization of a coil 62 when an engine is operated and stopped, respectively. Also the pilot valve 54 is provided with multiple small injection holes 52e interconnected to a gas downstream side inside a main valve body 53b and a pilot valve body 54b with small pressure receiving area on the gas upstream side which opens and closes the injection holes 2e by connecting it to the main valve body 53b so that it can be moved independently. Then a rubber sheet 54c is installed at the top of the pilot valve body 54b so that multiple injection holes 52e are opened and closed and, in addition, enclosed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for a gas fuel engine using compressed natural gas as a fuel, and more particularly to preventing damage to a rubber seal of a fuel cutoff valve.

[0002]

2. Description of the Related Art In recent years, natural gas has been revisited as a clean energy source with less oil pollution and less air pollution, and a natural gas vehicle using this natural gas as a fuel for automobiles has been put to practical use and spread. Natural gas is a gas containing methane as a main component, and its advantage as a fuel for automobiles is that the emission of harmful substances such as NOx, CO, and HC is very small, and the octane number is high and the compression ratio is increased. You can In addition, it has excellent knocking resistance, is suitable for a large-diameter, multi-cylinder engine, is capable of lean combustion, and has good startability at low temperatures due to gaseous fuel. The disadvantage is that the storage volume efficiency is poor because the fuel is a gas and the fuel is sucked in a gas state,
The intake air amount decreases and the engine output decreases somewhat.

Therefore, as a fuel storage system, a natural gas vehicle is generally stored in a gas container with high volumetric efficiency in the state of compressed natural gas (CNG) and used. In this respect, it is called a CNG vehicle. ing. This CNG car is
The high-pressure gas in the gas container is decompressed by the decompression valve to near atmospheric pressure by the fuel supply device, and the fuel of this low-pressure gas is mixed well with air by the mixer and supplied to the intake system of the engine body. Further, a pipe for guiding the high pressure gas is provided with a fuel cutoff valve or the like that automatically shuts off the high pressure gas when the engine is stopped.

The fuel cutoff valve is provided on the gas container side of the pipe and is configured to inactivate the pressure reducing valve and the like when the engine is stopped and to keep the valve closed by using high pressure gas. It is necessary to overcome the force of high pressure gas and open the valve. Therefore, the fuel cutoff valve has a double valve structure in which a pilot valve is arranged inside the main valve.

Conventionally, the pilot valve and the main valve of the fuel cutoff valve are as shown in FIG. That is,
A main valve chamber 53a is formed in the valve main body 52 of the fuel cutoff valve 50, and an upstream inlet port 52a into which high-pressure compressed natural gas is introduced is provided on a side portion of the main valve chamber 53a. 52b is provided. The main valve 53 is provided in the main valve chamber 53a, and the pilot valve 54 is provided inside the main valve 53. Main valve 53
Is configured so that the main valve body 53b moves up and down in the main valve chamber 53a to open and close the outlet port 52b, and the ring-shaped rubber seal 53c at the tip of the main valve body 53b seals the outlet port 52b when the valve is closed. Is.

In the pilot valve 54, a pilot valve chamber 54a and a pilot port 52c communicating with the outlet port 52b are formed in the main valve body 53b.
A pilot valve body 54b having a small pressure receiving area is inserted in a so as to be vertically movable. In the pilot valve body 54b, the pin 55 inserted in the radial direction of the pilot valve body 54b is provided in the elongated hole 56 of the main valve body 53b.
And the pilot valve body 54b can be independently moved upward by an amount corresponding to the gap S between the pin 55 and the elongated hole 56.

If the hole diameter of the pilot port 52c is reduced, the valve body 54b can be easily opened even if the differential pressure of the gas upstream and downstream of the pilot valve 54 is large, so that the main valve 53 can be opened. It will be possible. Therefore, a valve seat 54d is provided at the center of the bottom of the pilot valve chamber 54a, and a single small-diameter injection hole 52 communicating with the pilot port 52c is formed.
d is formed, and a thick rubber seal 54c is attached to the tip of the pilot valve body 54b so as to face the injection hole 52d. The rubber seal 54c is configured to open and close the injection hole 52d. Further, a portion corresponding to the inlet port 52a of the main valve body 53b is formed in a stepped shape so that high pressure gas is constantly supplied to the main valve chamber 53a, the valve body 52 and the valve body 53.
It can be introduced into the pilot valve chamber 54a or the like through a gap between b and 54b.

With this construction, when the engine is stopped, both valve bodies 53b and 54b of the main valve 53 and the pilot valve 54 are pushed down by springs or the like as shown in FIG. Therefore, in the case of the main valve 53, the main valve body 53b
Then, the outlet port 52b is closed and sealed by the rubber seal 53c. Further, in the case of the pilot valve 54, the rubber seal 54c at the tip of the pilot valve body directly contacts the valve seat 54d to close the injection hole 52d, thereby sealing the injection hole 52d. As a result, the high-pressure gas in the inlet port 52a is automatically shut off, and at this time the high-pressure gas acts on both valve bodies 53b and 54b and is kept shut.

When the engine is operating, the pilot valve 54b and its rubber seal 5 are first subjected to electromagnetic force generated by energization of the coil.
4c is pulled up by the gap S between the pin 55 and the long hole 56 as shown in (b) to open the injection hole 52d. Therefore, the high pressure gas on the upstream side of the main valve 53 gradually flows to the outlet port 52b via the injection hole 52d and the pilot port 53d,
The pressure difference between the ports 52a and 52b is reduced. Then, when the electromagnetic force of the coil overcomes the differential pressure, both the valve bodies 53b and 54b are pulled up together by the pin 55, so that the main valve 53 is also opened and the high pressure gas of the inlet port 52a directly flows to the outlet port 52b. Thus, compressed natural gas fuel is supplied.

[0010]

By the way, in the above-mentioned prior art, the pilot valve 5 of the fuel cutoff valve 50 is used.
4 has a single injection hole 52d having a small diameter, and a pilot valve body 54
Since the rubber seal 54c of b is configured so as to closely face the injection hole 52d and directly open and close, the following problems occur. That is, the high speed and high pressure gas flow of the small diameter injection hole 52d, the impact at the time of valve closing, and the suction force due to the relative negative pressure on the downstream side act on the rubber seal 54c at the same position. Since the number of the injection holes 52d is one, the gas flow and various forces described above are concentrated in one place in the center of the rubber seal 54c, and become a great destructive force. Therefore, when used for a long period of time, the rubber in the central portion of the rubber seal 54c is gradually shaved and a cutting hole H as shown in FIG. 6 is formed, which results in poor sealing and deterioration due to the penetration of high-pressure gas into the rubber. There is a risk of causing damage early.

In view of the above points, the present invention has an object to prevent damage to the pilot valve of the fuel cutoff valve and improve durability.

[0012]

In order to achieve this object, a fuel supply system for a gas fuel engine according to claim 1 of the present invention uses a high pressure compressed natural gas stored in a gas container as an intake system for an engine body. A fuel cutoff valve is provided in the pipe that is depressurized to and led to.The fuel cutoff valve has a pilot valve and a main valve that automatically open and close by energizing and de-energizing the coil during engine operation and stop. A small diameter injection hole that communicates with the gas downstream side inside the main valve body, a pilot valve body with a small pressure receiving area on the gas upstream side that opens and closes the injection hole by connecting independently to the main valve body, and a valve closing Sometimes, a rubber seal for sealing the injection holes is provided, and the pilot valve of the fuel cutoff valve has a plurality of small-diameter injection holes, so that the pilot valve body has a plurality of injection holes which can be opened and closed and sealed. Rubber seal on Give characterized by comprising.

[0013]

Therefore, according to the first aspect of the present invention, when the engine is stopped, the pilot valve of the fuel cutoff valve and the main valve are hermetically closed by the rubber seal by deenergizing the coil,
The compressed natural gas stored in the gas container is automatically shut off to prevent leakage. When the coil of the fuel cutoff valve is energized during engine operation, the pilot valve body of the pilot valve first moves and opens independently due to the small diameter injection hole and the small pressure receiving area, whereby high pressure gas gradually flows to the downstream side,
When the pressure difference between upstream and downstream becomes small, the main valve also opens. Then, the compressed natural gas in the gas container is decompressed and supplied to the intake system of the engine body, thus operating the engine with the fuel of the compressed natural gas.

On the other hand, the pilot valve of the fuel cutoff valve is constructed such that it is directly opened and closed by the rubber seal at the tip of the pilot valve body. However, in the present invention, by providing a plurality of injection holes,
The high-speed, high-pressure gas flow in the injection hole portion gives an impact when the tip rubber seal is opened / closed and the suction force due to the relative negative pressure on the downstream side is dispersed and acts on the rubber seal at multiple points to destroy it. The force is greatly reduced, which reliably prevents damage such as rubber cutting.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the overall configuration of the CNG engine system will be described. A fuel supply device 30 having an ignition type engine body 1 similar to a gasoline engine and a container unit 20 provided in the engine body, an air-fuel ratio control device 4
0 is provided.

The engine body 1 is inserted into a cylinder 2 so that a piston 3 reciprocates, and an intake port 6 having an intake valve 5 and an exhaust port 8 having an exhaust valve 7 are provided in a combustion chamber 4 at the top of the piston 3. A spark plug 9 is provided. An exhaust pipe 10 from the exhaust port 8 is provided with a three-way catalyst 11 that removes harmful components in the exhaust. As an intake system, an air cleaner 12 communicates with a mixer 13 having a mixer type venturi section 14, and the mixer 13 communicates with an intake port 6 via a throttle valve 15 and an intake pipe 16.

The container unit 20 includes a gas container 21 having a large capacity and housed in a luggage carrier or the like at the rear of the vehicle, and the collective pipe 2.
2 Then, from the collecting pipe 22 to each of the plurality of gas containers 21 through the container valve 23, and to the filling port 26 through the filling pipe 24 having the fuel filling valve 25,
It communicates with a CNG pipe 27 for taking out high-pressure gas, and further communicates with a pressure gauge 31 in the driver's seat. Therefore, at the filling station, the filling port 26
Is connected to a gas filling facility so that the compressed natural gas in the gas container 21 is filled and stored at a high pressure of, for example, 200 kg / cm @ 2. As a safety mechanism,
An overflow prevention valve 23a for preventing a large amount of gas outflow due to pipe damage or the like is built in the container main valve 23, and a check valve 28 for preventing the release of fuel from the gas container 21 is provided in the filling pipe 24. An emergency shutoff valve 29 that shuts off the fuel in an emergency is provided at 27.

A CNG pipe 27 extending from the container unit 20 is extended to the front of the vehicle and a fuel supply device 30 is provided. In the fuel supply device 30, a fuel cutoff valve 50, a high pressure reducing valve 34, a pressure increasing prevention switch 35, and a low pressure reducing valve 36 are sequentially arranged in the CNG pipe 27 from the upstream side. Fuel cutoff valve 50
Is connected to a battery 33 through a switch 32 that works in conjunction with an ignition switch, and when the engine is stopped, the coil 62 is de-energized to close the valve to shut off fuel, and when the engine is running, the coil 62 is energized to open the valve. And supply fuel. The high-pressure pressure reducing valve 34 stores, for example, 4 kg of 200 kg / cm 2 of high-pressure gas stored in the gas container 21.
Reduce the pressure to / cm2. Low pressure reducing valve 36 is 4 kg / cm
The gas pressure of 2 is further reduced to a low pressure gas near atmospheric pressure, and the natural gas compressed and stored in this manner is gradually reduced in pressure to be usable.

Further, a gas flow rate control valve 37 is provided in the venturi section 14 of the mixer 13 of the engine main body intake system, and a pipeline 38 downstream of the low pressure reducing valve 36 is provided in the gas flow rate control valve 37.
Communicate with Then, the low-pressure gas is subjected to flow rate control by the gas flow rate control valve 37 and is supplied to the venturi section 14 to supply the mixer 1
3 is mixed with air and the mixture of this gas and air is sucked into the combustion chamber 4 of the engine body 1.

The air-fuel ratio control device 40 is provided in the exhaust pipe 10 and has an O2 sensor 41 for detecting the air-fuel ratio, a controller 4 for inputting signals such as engine speed and throttle opening.
2 The controller 42 judges the engine operating state, the air-fuel ratio rich or lean based on these signals, and outputs an electric signal to the gas flow rate control valve 37 to appropriately control the gas flow rate.

The overall construction of the fuel cutoff valve 50 will be described with reference to FIG. The fuel cutoff valve 50 is an electromagnetic type,
It is roughly divided into a valve portion 51 and a coil portion 60 having a double valve structure. The valve portion 51 includes a valve body 52, a main valve chamber 53, and a main valve chamber 53.
The inlet port 52a on the gas upstream side is connected to the side of the main valve chamber 53a, and the outlet port 52b on the downstream side is connected to the center of the bottom. The main valve 53 is provided in the main valve chamber 53a, and the pilot valve 54 is provided inside the main valve 53. The main valve 53 is a main valve chamber 53.
The main valve body 53b moves up and down to a and the outlet port 52b
Is opened and closed, and a ring-shaped rubber seal 53c at the tip of the main valve body 53b is used to close the outlet port 52 when the valve is closed.
This is a structure for sealing b.

The pilot valve 54 has a pilot valve chamber 54a formed in a main valve body 53b and a pilot port 52c communicating with the outlet port 52b.
The pilot valve body 54b having a small pressure receiving area a is inserted so as to be vertically movable. In the pilot valve body 54b, the pin 55 inserted in the radial direction of the pilot valve body 54b is provided in the elongated hole 56 of the main valve body 53b.
And the pilot valve body 54b can be independently moved upward by an amount corresponding to the gap S between the pin 55 and the elongated hole 56.

If the hole diameter of the pilot port 52c is reduced, the valve body 54b can be easily opened even if the differential pressure of the gas upstream and downstream of the pilot valve 54 is large, and the main valve 53 can be opened. It will be possible. Also, it is not necessary to limit the number of injection holes to one, and the higher the number, the faster
A force such as a high-pressure gas flow can be dispersed and act on the rubber seal 54c.

Therefore, as shown in FIGS. 3 and 4, four small diameter injection holes 52e communicating with the pilot port 52c are formed by projecting a valve seat 54d at the center of the bottom of the pilot valve chamber 54a. A thick rubber seal 54c is attached to the tip of the pilot valve body 54b so as to face the injection hole 52e, and the rubber seal 54c is configured to simultaneously open and close the four injection holes 52e. 4 injection holes 5
The hole diameter of 2e is set smaller than that of the conventional single injection hole. A total flow rate of the four injection holes 52e ensures a necessary flow rate at which the pilot valve 54 can be opened. Further, a portion of the main valve body 53b corresponding to the inlet port 52a is formed in a stepped shape so that high pressure gas is constantly supplied to the main valve chamber 53a and the valve body 52 and the valve bodies 53b and 54b.
It can be introduced into the pilot valve chamber 54a or the like through the gap or the like.

In the coil portion 60, a coil 62 is attached to the outside of a coil body 61 with a cover 63, and a guide 64 is bolted to the inside thereof. Then, with the pilot valve body 54b fitted in the guide 64, the coil body 61 is coupled to the upper portion of the valve body 52 by the fastening metal fitting 66, and the electromagnetic force generated by the coil 62 energizes both valve bodies 53.
It is possible to open the valve by pulling up b and 54b. Further, a spring 65 is urged between the guide 64 and the pilot valve body 54b so as to push down both valve bodies 53b and 54b to close the valve.

Next, the operation of this embodiment will be described. First, when the container valve 23 of the gas container 21 of the container unit 20 is opened, the high-pressure compressed natural gas stored in the gas container 21 is taken out to the CNG pipe 27 through the central pipe 22. This high-pressure gas is introduced into the pressure gauge 31 in the driver's seat through the emergency cutoff valve 29, and the main valve 53 of the fuel cutoff valve 50 of the fuel supply device 30 and both valve chambers 53 of the pilot valve 54.
a, 54a.

Therefore, when the engine is stopped, the switch 32 is turned off, the coil 62 of the fuel cutoff valve 50 is de-energized, and the valve bodies 53b and 54b of the main valve 53 and the pilot valve 54 are both turned on.
Is pushed down by the spring 65. Therefore, in the case of the main valve 53, the main valve body 53b is used for the outlet port 52b.
Is closed and sealed by the rubber seal 53c. Further, in the case of the pilot valve 54, the rubber seal 54c at the tip of the pilot valve body directly contacts the valve seat 54d to close the injection hole 52e, thereby sealing the four injection holes 52e. As a result, the high-pressure gas in the gas container 21 is automatically shut off so as not to leak, and at this time, the high-pressure gas acts on both valve bodies 53b and 54b and is kept shut.

At this time, the high pressure gas in the gas container 21 is introduced into the pressure gauge 31 in the driver's seat to display the gas filling state.
When the amount of gas becomes low, the filling equipment is connected to the filling port 26 at the filling station and the fuel filling valve 25 is opened to open the natural gas with the engine stopped and the fuel cutoff valve 50 closed as described above. Is compressed and filled in the gas container 21. As a result, the gas container 21 is sufficiently filled with gaseous natural gas as compressed natural gas with high volume efficiency.

When the engine is in operation, the switch 32 is turned on to energize the coil 62 of the fuel cutoff valve 50, and the electromagnetic force thereof causes the valve bodies 53b and 54 of the main valve 53 and the pilot valve 54 to operate.
acts on b. Here, the pilot valve body 54b is easily pulled up by electromagnetic force because the suction force is small due to the small diameter injection hole 52e and the pressure receiving area of the high pressure gas is small. Therefore, first, the pilot valve body 54b and its rubber seal 54c are pulled up by the gap S between the pin 55 and the elongated hole 56 to open the four injection holes 52e. Therefore, the high-pressure gas on the upstream side gradually flows through the four injection holes 52e and the pilot port 52c to the outlet port 52b, and both ports 52e
The differential pressure between a and 52b decreases. When the electromagnetic force of the coil 62 overcomes the differential pressure, the pin 55 causes the valve elements 53
b and 54b are pulled up together, so that the main valve 5
3 is also opened and the high pressure gas at the inlet port 52a flows directly to the outlet port 52b.

When the fuel cutoff valve 50 is opened in this way, the high pressure gas in the gas container 21 is introduced into the high pressure pressure reducing valve 34 through the CNG pipe 27 to reduce the pressure, and then is introduced into the low pressure pressure reducing valve 36 to reduce the pressure to near atmospheric pressure. To be done. The flow rate of the low-pressure gas is controlled by the gas flow rate control valve 37 to be supplied to the intake system of the engine body 1, and the mixer 13 efficiently mixes it with a large amount of air. Then, the air-fuel mixture is drawn into the combustion chamber 4 of the engine body 1, ignited by the ignition plug 9, and satisfactorily combusts at a low temperature and a lean air-fuel ratio. In this way, the engine is operated by the fuel of compressed natural gas, and in this case, a large amount of compressed natural gas is stored in the gas container 21, so that it is possible to continuously operate the engine for a long time and travel a long distance. Further, although the emission of harmful components is originally small due to the characteristics of natural gas, the harmful components in the exhaust gas are purified by the three-way catalyst 11, resulting in further cleanliness.

On the other hand, the pilot valve 54 of the fuel cutoff valve 50
Has a configuration in which it is directly opened and closed by a rubber seal 54c at the tip of the pilot valve body 54b as in the conventional case.
Four e are provided. Therefore, the suction force due to the high speed and high pressure gas flow in the injection hole 52e, the impact at the time of valve closing, and the relative negative pressure on the downstream side is equal to that of the rubber seal 54c.
It acts in a distributed manner at the points, and the destructive force at one point is reduced to 1/4 or less, and it becomes possible to withstand the rigidity of rubber. Therefore, the rubber seal 54c is reliably prevented from damage such as rubber cutting and deterioration due to gas permeation, and its durability is significantly increased. As a result, good sealing performance is ensured even after long-term use.

Although the embodiments of the present invention have been described above, the present invention can be applied to all solenoid valves that are used in a conduit for high-pressure fluid and that open and close a small diameter hole with a rubber seal. The number of injection holes of the pilot valve of the fuel cutoff valve may be plural other than four.

[0033]

As described above, in the fuel supply system for a gas fuel engine according to claim 1 of the present invention, the pilot valve of the fuel cutoff valve has a plurality of small injection holes, and Since the rubber seal is attached to the tip so as to open and close and seal the plurality of injection holes, it is possible to reliably prevent the rubber seal of the pilot valve from being damaged and improve the durability. Therefore, the life of the fuel cutoff valve is extended, the frequency of replacement and the leakage of compressed natural gas are reduced, and the practical effect is great. Since only the number of injection holes of the pilot valve is increased, there is no need to change the structure and the machining is easy.

[Brief description of drawings]

FIG. 1 is a system diagram showing an overall configuration of a gas fuel engine according to the present invention.

FIG. 2 is a cross-sectional view showing the overall configuration of a fuel cutoff valve.

FIG. 3 is a sectional view showing a main part of an embodiment of the present invention.

4 is a sectional view taken along line AA of FIG.

FIG. 5 shows a conventional example, (a) is a sectional view of a main valve and a pilot valve in a closed state, and (b) is a sectional view of a pilot valve in an open state.

FIG. 6 is a bottom view showing a damaged state of a conventional rubber seal.

[Explanation of symbols]

 1 Engine Main Body 21 Gas Container 27 CNG Piping 50 Fuel Cutoff Valve 53 Main Valve 53b Main Valve Body 54 Pilot Valve 54b Pilot Valve Body 54c Rubber Seal 52e Injection Hole 62 Coil

Claims (1)

[Claims] 1. A fuel cutoff valve is provided in a pipe for decompressing high-pressure compressed natural gas stored in a gas container to an intake system of an engine main body, and the fuel cutoff valve is a coil cutoff valve during engine operation and stop. It has a pilot valve and a main valve that automatically open and close by energizing and de-energizing, and the pilot valve is connected to a small diameter injection hole that communicates with the gas downstream side inside the main valve body and independently movable with respect to the main valve body. In a fuel supply device for a gas fuel engine, which includes a pilot valve body having a small pressure receiving area on the upstream side of the gas that opens and closes the injection hole and a rubber seal that seals the injection hole when the valve is closed, the pilot valve of the fuel cutoff valve has a small diameter. Has multiple injection holes,
A fuel supply device for a gas fuel engine, wherein a rubber seal is attached to a tip of a pilot valve body so as to open and close and seal the plurality of injection holes.