WO2015199011A1

WO2015199011A1 - Gas fuel injection control device

Info

Publication number: WO2015199011A1
Application number: PCT/JP2015/067833
Authority: WO
Inventors: 和雅末廣
Original assignee: スズキ株式会社
Priority date: 2014-06-26
Filing date: 2015-06-22
Publication date: 2015-12-30
Also published as: JP6265064B2; JP2016008597A

Abstract

　A gas fuel injection control device with which it is possible to inject an amount of gas fuel suitable for the operating state of an internal combustion engine, the gas fuel injection control device having: a gas fuel supply tube (73) for connecting a pressure regulator (75) and a gas fuel injector (71), the gas fuel supply tube (73) being provided with a pressure adjustment valve (74) for opening and closing the gas fuel supply tube (73) between fully open and fully closed states; and a pressure adjustment unit (301) for reducing the opening degree of the pressure adjustment valve (74) in increments of a preset opening degree adjustment value until the air/fuel ratio reaches a target air/fuel ratio, when the air/fuel ratio is determined to have deviated from the target air/fuel ratio and the drive time of the gas fuel injector (71) is determined to be shorter than a minimum drive time.

Description

Gas fuel injection control device

The present invention relates to an injection control device for gas fuel of an engine provided with an injector for injecting gas fuel.

An internal combustion engine that operates by supplying liquid fuel such as gasoline and gaseous fuel such as CNG (Compressed Natural Gas) or LPG (Liquefied Petroleum Gas) as a fuel to be supplied to the combustion chamber is installed in the vehicle. It is known to use as a drive source.

In vehicles equipped with such a bi-fuel engine, gaseous fuel is generally used as the main fuel from the viewpoint of air pollution control and resource saving. However, with a bi-fuel engine, it is possible to run with liquid fuel even when there is no gaseous fuel, and it is unlikely that the user will care about the remaining amount of gaseous fuel. There is a risk of being done. When traveling in such a low residual pressure state, the fuel is not sufficiently supplied, and the durability of the internal combustion engine, the exhaust gas treatment catalyst, etc. is adversely affected by the occurrence of overlean combustion and misfire.

In order to deal with such a problem, Japanese Patent No. 4300511 (Patent Document 1) describes the remaining amount of gas fuel, and when it is determined that the shortest gas fuel supply station cannot be reached from the current location, the driver In addition, it is described that the fuel is automatically switched when the fuel is not switched from the gaseous fuel to the liquid fuel even after a predetermined time has elapsed.

Japanese Patent No. 4300511

However, among the gaseous fuels, the composition ratio of methane, hydrocarbons, and nitrogen may vary greatly among CNG fuels depending on the production area. For this reason, there is a difference in the included combustion components, and if the included combustion components are small, even if the remaining amount of CNG is sufficient, the combustion components may be insufficient, resulting in lean combustion. . For example, at a high flow rate such as when traveling with the throttle opening fully open, there is a problem that lean combustion occurs even if the maximum flow rate of fuel is supplied.

In order to perform proper fuel control at high flow rates, it is conceivable to increase the fuel pressure in order to increase the maximum flow rate. However, if the fuel pressure is increased to increase the maximum flow rate, the minimum flow rate at which fuel can be injected accurately increases. End up. This is because the maximum valve opening time and the minimum valve opening time during which the injector can inject fuel with high accuracy are determined as the single unit performance of the injector. For this reason, if the fuel pressure is increased in order to perform proper fuel control at a high flow rate, the injector is driven to open in a time shorter than the minimum valve opening time of the injector when the required fuel amount is small such as during idling. Control becomes unstable.

Therefore, an object of the present invention is to provide a gas fuel injection control device capable of injecting an appropriate amount of gas fuel in accordance with the operating state of the internal combustion engine.

One aspect of the invention of an injection control device for a gas fuel that solves the above problems includes an engine including a gas fuel injector that injects the gas fuel, a gas fuel tank that stores the gas fuel, and a gas fuel that is supplied from the gas fuel tank A gas fuel injection control device for a vehicle, comprising: a pressure regulator for reducing the pressure of the exhaust gas; and an oxygen sensor for detecting richness or leanness of an air-fuel ratio based on an oxygen concentration in exhaust gas flowing in an exhaust pipe. A pressure adjustment valve for reducing the pressure of the gas fuel supplied to the gas fuel injector is arranged in the pipe connecting the regulator and the gas fuel injector, and when it is determined that the air / fuel ratio deviates from the target air / fuel ratio, A pressure adjusting unit that closes the pressure adjusting valve until the air-fuel ratio becomes the same.

Thus, according to one aspect of the present invention, it is possible to inject an appropriate amount of gas fuel in accordance with the operating state of the internal combustion engine.

FIG. 1 is a conceptual block diagram showing a gas fuel injection control apparatus according to a first embodiment of the present invention. FIG. 2 is a view showing the gas fuel injection control device according to the first embodiment of the present invention, and is a flowchart for explaining the injector drive time diagnosis process. FIG. 3 is a diagram showing the gas fuel injection control device according to the first embodiment of the present invention, and is a flowchart for explaining the pressure adjustment valve reset processing. FIG. 4 is a diagram illustrating an injection control device for gas fuel according to the second embodiment of the present invention, and is a flowchart for explaining the excessive fuel control process.

Hereinafter, a gas fuel injection control device according to a first embodiment of the present invention will be described in detail with reference to the drawings.

(First embodiment)
As shown in FIG. 1, a vehicle 1 equipped with a gas fuel injection control device according to this embodiment includes an internal combustion engine type engine 2 and an ECU (Electronic Control Unit) 3.

The engine 2 performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston 10 makes two reciprocations within the cylinder 11, and performs four ignition cycles during the compression stroke and the expansion stroke. It is composed by the engine.

In this embodiment, the engine 2 is assumed to be an in-line 4-cylinder engine. However, in the present invention, an in-line 6-cylinder engine, a V-type 6-cylinder engine, a V-type 12-cylinder engine, or a horizontally opposed 6-cylinder engine. You may be comprised by various types of engines, such as an engine. The engine 2 shown in FIG. 1 shows one cylinder 11 out of four cylinders arranged in series.

The piston 10 accommodated in each cylinder 11 is connected to a crankshaft 13 via a connecting rod 12. The connecting rod 12 converts the reciprocating motion of the piston 10 into the rotational motion of the crankshaft 13.

Therefore, the engine 2 causes the piston 10 to reciprocate by burning a mixture of fuel and air in the combustion chamber 14 in the cylinder 11, and rotates the crankshaft 13 via the connecting rod 12, thereby A driving force for driving the is generated.

The intake port 30 of the engine 2 is provided with an intake manifold 31 for introducing air into the combustion chamber 14. The intake manifold 31 is connected to an intake pipe 32 for sucking outside air. That is, the intake manifold 31 communicates the intake pipe 32 and the intake port 30 of each cylinder 11.

The intake pipe 32 is provided with a throttle valve 33 for adjusting the intake air amount of the engine 2. The throttle valve 33 adjusts the intake air amount of the engine 2 by controlling the throttle opening degree according to a command signal from the ECU 3. The throttle valve 33 is provided with a throttle opening sensor 34 for detecting the opening of the throttle valve 33 (hereinafter simply referred to as “throttle opening”).

The exhaust port 40 of the engine 2 is provided with an exhaust manifold 41 for discharging exhaust gas generated by combustion of the air-fuel mixture in the combustion chamber 14 to the outside of the vehicle. The exhaust manifold 41 is connected to the exhaust pipe 42. That is, the exhaust manifold 41 communicates the exhaust pipe 42 and the exhaust port 40 of each cylinder 11.

The exhaust pipe 42 is provided with a three-way catalyst 43, an upstream oxygen sensor 44, and a downstream oxygen sensor 45. The three-way catalyst 43 purifies exhaust gas discharged from the combustion chamber 14 of the engine 2, that is, burned gas.

The upstream oxygen sensor 44 is provided upstream of the three-way catalyst 43 in the exhaust direction, which is the direction in which exhaust gas is discharged. The downstream oxygen sensor 45 is provided downstream of the three-way catalyst 43 in the exhaust direction. The upstream oxygen sensor 44 and the downstream oxygen sensor 45 output a signal whose output changes suddenly between the rich side and the lean side with respect to the air / fuel ratio based on the stoichiometric air / fuel ratio based on the oxygen concentration in the exhaust gas. It is an oxygen sensor.

Further, the engine 2 includes an intake valve 50 for controlling the introduction of air from the intake manifold 31 to the combustion chamber 14 and an exhaust valve 51 for controlling the discharge of exhaust gas from the combustion chamber 14 to the exhaust manifold 41. And a spark plug 52 for igniting the air-fuel mixture in the combustion chamber 14.

The spark plug 52 is a known spark plug having an electrode made of platinum or an iridium alloy. The spark plug 52 is discharged when the electrode is energized by the ECU 3 and ignites the air-fuel mixture in the combustion chamber 14.

The intake valve 50 is opened and closed so as to communicate or block the intake port 30 and the combustion chamber 14. The intake valve 50 is opened and closed by an intake camshaft (not shown).

The exhaust valve 51 is opened and closed so as to communicate or block the exhaust port 40 and the combustion chamber 14. The exhaust valve 51 is opened and closed by an exhaust camshaft (not shown).

This engine 2 is supplied by selecting one of two types of fuel, that is, liquid fuel gasoline and gas fuel CNG (or LPG) as fuel to be injected into the combustion chamber 14. The engine 2 includes a gasoline supply system 60 that supplies gasoline stored in the gasoline tank 65 into the combustion chamber 14, and a gas fuel supply system 70 that supplies CNG stored in the gas fuel tank 78 at high pressure into the combustion chamber 14. And.

The gasoline supply system 60 includes a gasoline injector 61, a gasoline fuel rail 62, a liquid fuel supply pipe 63, a fuel pump 64, and a gasoline tank 65.

The fuel pump 64 sucks gasoline stored in the gasoline tank 65 at normal pressure and pumps it to the gasoline fuel rail 62 via the liquid fuel supply pipe 63. A plurality of gasoline injectors 61 corresponding to each cylinder 11 of the engine 2 are connected to the fuel rail 62 for gasoline. Each gasoline injector 61 injects gasoline into the intake port 30.

The gasoline fuel rail 62 stores the gasoline pumped from the fuel pump 64 while maintaining the pressure. The gasoline stored in the gasoline fuel rail 62 is injected when the gasoline injector 61 is opened. The gasoline injector 61 is connected to the ECU 3 and under the control of the ECU 3, the injection timing of gasoline into each corresponding intake port 30 is individually adjusted.

The gas fuel supply system 70 includes a gas fuel injector 71, a gas fuel fuel rail 72, a gas fuel supply pipe 73, a pressure adjustment valve 74, a pressure regulator 75, a regulator shutoff valve 76, and a main valve 77. And a gas fuel tank 78.

A gas fuel tank 78 is connected to one end of the gas fuel supply pipe 73, and a gas fuel fuel rail 72 is connected to the other end of the gas fuel supply pipe 73. A main valve 77 is provided between the gas fuel tank 78 and the gas fuel supply pipe 73. The original valve 77 is a normally closed electromagnetic valve whose opening and closing is controlled by the ECU 3. When the main valve 77 is closed, the gas fuel tank 78 is hermetically sealed.

Further, a regulator shut-off valve 76, a pressure regulator 75, and a pressure adjusting valve 74 are provided in this order downstream from the main valve 77 in the supply direction, which is the direction in which CNG is supplied from the gas fuel supply pipe 73. Yes.

The opening and closing of the regulator shutoff valve 76 is controlled by the ECU 3. When the main valve 77 and the regulator shut-off valve 76 are open, the CNG in the gas fuel tank 78 is supplied to the gas fuel fuel rail 72 via the gas fuel supply pipe 73. When the regulator shut-off valve 76 is closed, CNG is not supplied to the fuel rail 72 for gas fuel.

The pressure regulator 75 reduces the pressure of the CNG supplied from the gas fuel tank 78, that is, the fuel pressure. The pressure regulator 75 operates so that CNG having a prescribed fuel pressure is supplied to the fuel rail 72 for gas fuel. The fuel rail 72 for gas fuel stores CNG supplied from the pressure regulator 75 while maintaining the pressure.

A plurality of gas fuel injectors 71 corresponding to each cylinder 11 of the engine 2 are connected to the fuel rail 72 for gas fuel. Each gas fuel injector 71 injects CNG into the intake manifold 31. The gas fuel fuel rail 72 is provided with a pressure sensor 79 for detecting the pressure in the gas fuel fuel rail 72. The reason why CNG is injected into intake manifold 31 is to mix a large amount of CNG with intake air in intake manifold 31 having a large volume.

CNG stored in the fuel rail 72 for gas fuel is injected when the gas fuel injector 71 is opened. The gas fuel injector 71 is connected to the ECU 3, and the injection timing of CNG into the corresponding intake manifolds 31 is individually controlled by the control of the ECU 3. The time during which the gas fuel injector 71 is open is referred to as the drive time, and the ECU 3 controls the drive time of the gas fuel injector 71 to adjust the CNG injection amount.

The pressure adjusting valve 74 opens and closes the gas fuel supply pipe 73 between fully open and fully closed. The pressure adjusting valve 74 is electrically connected to the ECU 3. The pressure adjusting valve 74 is configured to adjust the pressure of the CNG supplied to the gas fuel fuel rail 72 by controlling the valve opening degree according to a command signal from the ECU 3. The opening degree of the pressure adjusting valve 74 is expressed by a ratio [%] of the opening area to the opening area when the pressure adjusting valve 74 is fully opened, and the opening degree can be adjusted in units of 1 [%].

In the present embodiment, the operating state of the engine 2 configured as described above is controlled by the ECU 3. The ECU 3 includes, for example, a microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an input / output interface, and the like. The CPU has a temporary storage function of the RAM. The signal processing is performed according to a program that is used and stored in advance in the ROM. Various control constants and various maps are stored in advance in the ROM.

In addition, various sensors and switches such as the throttle opening sensor 34, the upstream oxygen sensor 44, the downstream oxygen sensor 45, the pressure sensor 79, and the fuel changeover switch 80 are connected to the input side of the ECU 3. . The fuel changeover switch 80 performs a changeover operation of the fuel to be manually used by the driver or the like according to the operation state such as when warming up or accelerating.

On the output side of the ECU 3, various devices such as the throttle valve 33, the spark plug 52, the gasoline injector 61, the fuel pump 64, the gas fuel injector 71, the pressure adjusting valve 74, the regulator shut-off valve 76, the main valve 77, etc. It is connected.

The ECU 3 appropriately switches the fuel to be supplied into the combustion chamber 14 from gasoline to CNG or from CNG to gasoline so as to selectively switch between liquid fuel and gas fuel having different properties and supply them to the combustion chamber 14 of the engine 2. It is supposed to switch.
For example, the ECU 3 switches to the operation mode of the engine 2 such as a manual switching operation by the fuel changeover switch 80, a fuel outage detection in the gasoline tank 65 or the gas fuel tank 78, or a warm-up operation or a steady operation or acceleration. The fuel to be used is switched accordingly.
As a method of selecting the fuel according to the operation mode of the engine 2, there are a method of selecting an inexpensive CNG during warm-up operation or steady operation, and a method of selecting gasoline at the time of acceleration or climbing that requires torque. .

Furthermore, the ECU 3 includes a pressure adjustment unit 301. When the pressure adjusting unit 301 determines that the air-fuel ratio deviates from the target air-fuel ratio, the pressure adjusting unit 301 controls the pressure adjusting valve 74 described above to adjust the pressure of the CNG supplied to the gas fuel injector 71, so that the target Make the air-fuel ratio.

The pressure adjustment unit 301 determines whether or not the air-fuel ratio deviates from the target air-fuel ratio based on the detection signal from the upstream oxygen sensor 44. The pressure adjustment unit 301 monitors the time interval between the inversion of the detection signal of the upstream oxygen sensor 44 from the rich side to the lean side or the inversion from the lean side to the rich side as the rich lean inversion time.
The pressure adjustment unit 301 determines whether the air-fuel ratio deviates from the target air-fuel ratio based on whether the rich lean inversion time is longer than a preset abnormality diagnosis time. The abnormality diagnosis time is experimentally obtained in advance and stored in the ROM of the ECU 3. The abnormality diagnosis time may be stored, for example, as a map whose value is determined by the engine speed, and the abnormality diagnosis time may be set shorter as the engine speed is higher.

Further, the pressure adjustment unit 301 determines whether or not the gas fuel injector 71 performs proper fuel injection based on whether or not the driving time of the gas fuel injector 71 is shorter than a preset minimum driving time. The minimum drive time is a value determined from the design value of the gas fuel injector 71 and is stored in the ROM of the ECU 3.

When the pressure adjusting unit 301 determines that the rich lean inversion time is longer than the abnormality diagnosis time and determines that the driving time of the gas fuel injector 71 is shorter than the minimum driving time, the pressure adjusting unit 301 sets the opening degree of the pressure adjusting valve 74 to the opening degree. The opening adjustment value set in advance, for example, 1 [%] is closed, and this is repeated until the rich lean inversion time becomes equal to or less than the abnormality diagnosis time. The opening adjustment value is experimentally obtained in advance and stored in the ROM of the ECU 3.

The injector drive time diagnosis process by the gas fuel injection control device according to the present embodiment configured as described above will be described with reference to FIG. The injector drive time diagnosis process described below is started simultaneously with the start of the operation of the ECU 3, and is repeatedly executed at a preset time interval. In addition, the pressure adjustment unit 301 performs detection of the rich lean inversion time in parallel as another process, and the detected rich lean inversion time is stored in the RAM of the ECU 3 and can be referred to during the injector driving time diagnosis processing. It has become.

First, the pressure adjustment unit 301 determines whether gas fuel is being used as the fuel supplied to the engine 2 (step S11). If it is determined that the gas fuel is not in use, the pressure adjustment unit 301 ends the process.

When it is determined that the gas fuel is being used, the pressure adjustment unit 301 determines whether or not the rich lean inversion time is longer than the abnormality diagnosis time (step S12). If it is determined that the rich lean inversion time is not longer than the abnormality diagnosis time, the pressure adjustment unit 301 ends the process.

When it is determined in step S12 that the rich lean inversion time is longer than the abnormality diagnosis time, the pressure adjustment unit 301 determines whether the driving time of the gas fuel injector 71 is shorter than the minimum driving time (step S13). When it is determined that the driving time of the gas fuel injector 71 is not shorter than the minimum driving time, the pressure adjusting unit 301 ends the process.

When it is determined in step S13 that the driving time of the gas fuel injector 71 is shorter than the minimum driving time, the pressure adjusting unit 301 closes the opening of the pressure adjusting valve 74 by the opening adjustment value (step S14). Next, the pressure adjustment unit 301 determines whether or not the rich lean inversion time is equal to or shorter than the abnormality diagnosis time (step S15).

If it is determined in step S15 that the rich lean inversion time is not less than or equal to the abnormality diagnosis time, the pressure adjustment unit 301 repeats the process of step S14. When the rich lean determination time is equal to or less than the abnormality diagnosis time, the pressure adjustment unit 301 ends the process.

In this way, when the air-fuel ratio deviates from the target air-fuel ratio and the driving time of the gas fuel injector 71 is shorter than the minimum driving time, the pressure adjustment valve 74 supplies the gas fuel injector 71 to the gas fuel injector 71. The pressure of the CNG is reduced. For this reason, the minimum flow rate of the gas fuel injector 71 can be lowered, and an appropriate amount of fuel can be injected.

Further, the pressure adjusting unit 301 is configured to open the opening of the pressure adjusting valve 74 to the maximum opening when the intake air amount to the engine 2 is larger than a predetermined intake air amount. The pressure adjusting unit 301 increases the intake air amount to the engine 2 from a predetermined intake air amount depending on whether or not the throttle opening detected by the throttle opening sensor 34 is larger than a preset throttle opening determination value. It is determined whether or not. That is, the throttle opening sensor 34 constitutes an intake air amount detection unit in the present invention. The throttle opening determination value is experimentally obtained in advance and stored in the ROM of the ECU 3. The throttle opening determination value is an upper limit value of the throttle opening at which the shortage of fuel does not occur.

When the pressure adjustment unit 301 determines that the throttle opening detected by the throttle opening sensor 34 is larger than the throttle opening determination value, the opening of the pressure adjustment valve 74 is set to a predetermined opening adjustment value, for example, 1% is opened, and this is repeated until the opening of the pressure adjusting valve 74 is fully opened. The opening adjustment value may be different from the value at the time of adjusting the air-fuel ratio described above.

A pressure adjustment valve reset process by the gas fuel injection control device according to the present embodiment configured as described above will be described with reference to FIG. The pressure adjustment valve reset process described below is started simultaneously with the start of the operation of the ECU 3, and is repeatedly executed at a preset time interval.

First, the pressure adjustment unit 301 determines whether or not the throttle opening detected by the throttle opening sensor 34 is larger than a throttle opening determination value (step S21). When it is determined that the throttle opening is not greater than the throttle opening determination value, the pressure adjustment unit 301 ends the process.

When it is determined in step S21 that the throttle opening is larger than the throttle opening determination value, the pressure adjustment unit 301 opens the opening of the pressure adjustment valve 74 by the opening adjustment value (step S22). Next, the pressure adjusting unit 301 determines whether or not the opening degree of the pressure adjusting valve 74 is fully opened (step S23).

If it is determined in step S23 that the opening of the pressure adjusting valve 74 is not fully opened, the pressure adjusting unit 301 repeats the process of step S22. When the opening degree of the pressure adjusting valve 74 is fully opened, the pressure adjusting unit 301 ends the process.

In this way, when the throttle opening is larger than the throttle opening determination value and the required fuel amount is large, the pressure adjusting valve 74 is fully opened. For this reason, the gas fuel with the maximum flow rate of the gas fuel injector 71 can be supplied, and an appropriate amount of fuel can be injected.

Thus, in the above-described embodiment, the pressure adjustment valve 74 for reducing the pressure of the CNG supplied to the gas fuel injector 71 is provided between the pressure regulator 75 and the gas fuel injector 71 so that the air-fuel ratio is less than the target air-fuel ratio. A pressure adjustment unit 301 is provided that closes the pressure adjustment valve 74 until the target air-fuel ratio is reached when it is determined that the air-fuel ratio is off.

Thus, the pressure of the CNG supplied to the gas fuel injector 71 can be reduced, the minimum flow rate of the gas fuel injector 71 can be reduced, and an appropriate amount of fuel can be injected.

In addition, when the driving time of the gas fuel injector 71 is shorter than the minimum driving time, the pressure adjusting unit 301 closes the pressure adjusting valve 74 until the target air-fuel ratio is reached.
Thereby, when the drive time of the gas fuel injector 71 is shorter than the minimum drive time, the pressure of the CNG supplied to the gas fuel injector 71 can be reduced, and the minimum flow rate of the gas fuel injector 71 can be lowered. Therefore, it is possible to accurately and appropriately perform fuel injection.

In addition, a throttle opening sensor 34 for detecting the intake air amount to the engine 2 is provided, and the pressure adjustment unit 301 fully opens the pressure adjustment valve 74 when the intake air amount to the engine 2 is larger than a predetermined intake air amount. Open up to.

Thereby, when the intake air amount to the engine 2 is larger than the predetermined intake air amount, the pressure adjusting valve 74 is fully opened, and the gas fuel with the maximum flow rate of the gas fuel injector 71 can be supplied. Fuel injection can be performed.

(Second Embodiment)
Next, a gas fuel injection control apparatus according to a second embodiment of the present invention will be described. Here, since this embodiment is configured in substantially the same manner as the above-described first embodiment, the same reference numerals are given to the same configurations using the drawings, and the characteristic portions will be described.

1 is configured to reduce the pressure of the CNG supplied from the gas fuel tank 78 using the negative pressure of the intake manifold 31 (negative pressure applied to the intake pipe 32).

In the pressure regulator 75 that reduces the pressure of the CNG using the negative pressure of the intake pipe 32, the pressure regulator 75 can adjust the pressure when the throttle opening degree changes abruptly, for example, when it is fully opened to fully closed. There is a possibility of excessive fuel without catching up with fluctuations in air volume.

For this reason, if the pressure adjustment unit 301 determines that the reduction rate of the throttle opening detected by the throttle opening sensor 34 (a reduction with respect to time) is equal to or greater than a preset reduction threshold, the pressure adjustment valve 74 The opening is closed to a preset adjustment opening.

Specifically, the pressure adjustment unit 301 refers to the throttle opening detected by the throttle opening sensor 34 at a preset time interval. The pressure adjusting unit 301 sets the opening of the pressure adjusting valve 74 in advance if the amount of decrease in the current throttle opening is greater than or equal to the reduction threshold from the previous throttle opening stored in the RAM of the ECU 3. Close to adjusted opening. In addition, the pressure adjustment unit 301 stores the throttle opening referred this time in the RAM of the ECU 3 for reference during the next processing.

Here, the reduction threshold is a lower limit value of the reduction amount of the throttle opening that causes excessive fuel, is experimentally obtained, and is stored in the ROM of the ECU 3. The adjustment opening is the opening of the pressure adjusting valve 74 that can avoid excessive fuel, is experimentally determined, and is stored in the ROM of the ECU 3.

The fuel excess control process by the gas fuel injection control device according to the present embodiment configured as described above will be described with reference to FIG. The excessive fuel control process described below is started simultaneously with the start of the operation of the ECU 3, and is repeatedly executed at a preset time interval.

First, the pressure adjusting unit 301 determines whether or not the throttle opening detected by the throttle opening sensor 34 has been fully closed from the fully open at the previous detection (step S31). When it is determined that the throttle opening is not fully opened to fully closed, the pressure adjustment unit 301 ends the process.

When it is determined in step S31 that the throttle opening has been fully opened, the pressure adjusting unit 301 closes the opening of the pressure adjusting valve 74 by the opening adjustment value (step S32). Next, the pressure adjusting unit 301 determines whether or not the opening degree of the pressure adjusting valve 74 has reached the adjusted opening degree (step S33).

If it is determined in step S33 that the opening of the pressure adjusting valve 74 is not the adjusted opening, the pressure adjusting unit 301 repeats the process of step S32. On the other hand, when the opening degree of the pressure adjusting valve 74 becomes the adjusted opening degree, the pressure adjusting unit 301 ends the process.

In this way, when the throttle opening is fully opened to fully closed and there is a high possibility of excessive fuel, the opening of the pressure adjusting valve 74 is set to the adjusted opening. For this reason, the amount of gas fuel supplied from the gas fuel injector 71 can be reduced, and an appropriate amount of fuel can be injected.

Thus, in the second embodiment described above, the throttle opening sensor 34 that detects the amount of intake air to the engine 2 is provided, and the pressure adjusting unit 301 reduces the amount of intake air to the engine 2 per hour. When the amount of decrease is larger than a preset reduction amount, the pressure adjustment unit 301 closes the pressure adjustment valve 74 to the adjustment opening degree.

As a result, when the amount of reduction of the intake air amount to the engine 2 per time is greater than a preset amount of reduction, the pressure adjustment valve 74 is closed to the adjustment opening, and the amount of gas fuel supplied from the gas fuel injector 71 is reduced. It is possible to reduce the amount of fuel, and an appropriate amount of fuel can be injected.

Although embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that changes may be made without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 Vehicle 2 Engine 3 ECU
30 Intake Port 31 Intake Manifold 32 Intake Pipe 33 Throttle Valve 34 Throttle Opening Sensor (Intake Air Volume Detection Unit)
44 Upstream oxygen sensor 70 Gas fuel supply system 71 Gas fuel injector 72 Gas fuel fuel rail 73 Gas fuel supply pipe 74 Pressure adjusting valve 75 Pressure regulator 76 Regulator shutoff valve 77 Main valve 78 Gas fuel tank 79 Pressure sensor 301 Pressure Adjustment section

Claims

An engine comprising a gas fuel injector for injecting gas fuel;
A gas fuel tank for storing the gas fuel;
A pressure regulator for reducing the pressure of the gas fuel supplied from the gas fuel tank;
An oxygen sensor for detecting rich or lean air-fuel ratio based on the concentration of oxygen in exhaust gas flowing through an exhaust pipe, and a fuel injection control device for a vehicle gas fuel comprising:
In a pipe connecting the pressure regulator and the gas fuel injector, a pressure adjusting valve for reducing the pressure of the gas fuel supplied to the gas fuel injector is disposed,
A gas fuel injection control device comprising: a pressure adjusting unit that closes the pressure adjusting valve until the air / fuel ratio reaches the target air / fuel ratio when it is determined that the air / fuel ratio deviates from the target air / fuel ratio.
When it is determined that the air-fuel ratio deviates from the target air-fuel ratio, the pressure adjusting unit adjusts the pressure-adjusting valve until the target air-fuel ratio is reached when the driving time of the gas fuel injector is shorter than the minimum driving time. The injection control apparatus of the gas fuel of Claim 1 which closes.
An intake air amount detection unit for detecting an intake air amount to the engine;
3. The gas fuel injection control device according to claim 1, wherein the pressure adjusting unit opens the pressure adjusting valve to a maximum opening degree when it is determined that the intake air amount is larger than a preset intake air amount. .
An intake air amount detection unit for detecting an intake air amount to the engine;
The pressure adjusting unit closes the pressure adjusting valve to a preset opening degree when it is determined that the reduction amount per hour of the intake air amount is equal to or more than a preset reduction amount. 2. An injection control device for gas fuel described in 1.