JPH062619A - Gas fuel supply system of engine - Google Patents

Abstract

PURPOSE:To promote an improvement in accelerating performance and prevention against any deterioration in an exhaust state by inducting a proper quantity of gas fuel into an intake air passage so responsively at the transient driving of an engine. CONSTITUTION:A secondary valve 13 of a gas fuel pressure regulator 5 is regulated by an actuator 21 in an opening-stepless manner. This actuator 21 forcibly opens the secondary valve 13 at a time when an intake air quantity in an engine 9 is suddenly increased for accleration, and it heightens the extent of gas fuel pressure at the outlet side, thereby increasing the flow rate according to the intake air quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for supplying a gaseous fuel such as LPG or CNG to a spark ignition type engine, and more particularly to a device having excellent fuel supply responsiveness during transient engine operation.

Gas fuels such as LPG and CNG are available at a lower cost than gasoline, which is a liquid fuel, and have many advantages such as a small amount of carbon dioxide in the exhaust gas.
It is well known that G is used as fuel for commercial vehicles.

In the current commercial vehicles, as is well known, the high pressure LPG filled in the pombe is decompressed and adjusted to a pressure of about atmospheric pressure by a pressure regulator (vaporizer).
The LPG is supplied to the engine by a system in which this is introduced into the intake passage by sucking it into the engine intake air flow.

On the other hand, in addition to this widely used system, as disclosed in JP-A-59-82556, a high pressure LPG is controlled by a pressure regulator (pressure control valve) to a constant level considerably higher than atmospheric pressure. A system has been proposed in which the positive pressure is adjusted to a positive pressure, which is introduced into the intake passage by the injection valve and supplied to the engine. Further, the gaseous fuel is introduced into the intake passage in a positive pressure state without being gasified or gasified. In order to put the system to practical use
It is also well known that various improvement proposals have been proposed as seen in Japanese Patent Laid-Open No. 8860 and Japanese Patent Laid-Open No. 63-16160.

Most of these pressure regulators for adjusting the gaseous fuel to a constant pressure have a structure in which the fuel pressure is controlled with the atmospheric pressure as a reference pressure, and the fuel economy in the steady operation of the engine in the partial load range is achieved. It is possible to perform control so as to maintain an optimum air-fuel ratio that makes exhaust measures and engine drivability good.

However, during transient operation such as acceleration or under high load, a higher concentration of air-fuel mixture than in steady operation is required. Therefore, in the system for adjusting the gaseous fuel to almost atmospheric pressure, the secondary valve of the vaporizer is used. Japanese Patent Publication No. 61-12106 proposes that a valve closing spring and a valve opening spring are actuated to reduce the spring force of the valve opening spring by negative pressure of the intake manifold during steady operation and increase by atmospheric pressure during acceleration or high load. Has been done.

However, according to this technique, the spring force of the valve opening spring uniformly increases due to the atmospheric pressure at the time of acceleration or high load to make the secondary valve opening constant, so that the degree of acceleration or the state of high load is increased. Accordingly, it is not possible to increase the amount of gaseous fuel by an appropriate amount, and there is a disadvantage that the maximum amount is always increased and the exhaust condition is often deteriorated.

On the other hand, in the system for adjusting the gaseous fuel to a constant positive pressure, the amount of the gaseous fuel increased at the time of acceleration or high load is downstream from the pressure regulator as in the technique disclosed in Japanese Patent Laid-Open No. 59-82556. When the auxiliary passage provided with the adjusting valve that operates based on the electric signal according to the engine operating state is branched, the opening of the adjusting valve is increased, and the above-mentioned Japanese Utility Model Laid-Open No. 61-138860 and the special feature. When a fuel injection valve that opens and closes based on an electric signal according to the engine operating state is provided as in the technique disclosed in Japanese Laid-Open Patent Publication No. 63-16160, the opening of the fuel injection valve is increased to cope with the problem. Is possible.

[0009]

However, in this technique, since it is intended to increase the flow rate of the gaseous fuel adjusted to a constant positive pressure, it is difficult to increase the flow rate in a large flow rate range as scheduled, and a response delay easily occurs. Therefore, there is a disadvantage that the acceleration performance and the exhaust state are easily deteriorated.

[0010]

The problem to be solved by the present invention is that there was no system capable of introducing a proper amount of gaseous fuel in response to the operating condition into the intake passage in a responsive manner during transient operation of the engine. That is the point.

[0011]

In order to solve the above-mentioned problems, the present invention adjusts the opening of a control valve in a pressure regulator having a control valve for adjusting the gas fuel introduced into the intake passage of an engine to a constant pressure. An actuator for controlling the opening of the control valve is continuously adjusted so as to adjust the pressure of the gaseous fuel introduced into the intake passage according to the intake air amount of the engine. In any system in which the pressure is adjusted to be introduced into the intake passage by suction or injection, the objective of introducing an appropriate amount of gaseous fuel in response to the operating state into the intake passage during transient operation of the engine is achieved. It was possible to introduce an appropriate amount of gaseous fuel into the intake passage with good response even at high output.

[0012]

In the steady operation of the engine in the partial load range, the actuator does not act on the control valve, and the pressure regulator regulates the gas fuel to a constant pressure and introduces it into the intake passage. The actuator adjusts the opening of the control valve in response to a sudden increase in the intake air amount of the engine during acceleration to increase the pressure of the gaseous fuel and increase the flow rate of the gaseous fuel introduced into the intake passage. Even at high output, the amount of gaseous fuel is increased according to the intake air amount.

[0013]

[First Embodiment] An example in which the present invention is applied to a system in which a gas fuel is adjusted to an atmospheric pressure and introduced into an intake passage will be described with reference to FIG. 1. From a cylinder 2 filled with LPG, which is a gas fuel, in a liquid state. Mixer 7 installed in intake passage 8 of engine 9
In the fuel passage 1 up to, there are a manual opening / closing valve 3, an electromagnetically driven shutoff valve 4 that opens when the engine is operating and closes when the engine is stopped, a pressure regulator 5, and an electromagnetically driven control valve 6 that changes the fuel flow rate according to the composition. They are provided in order.

The pressure regulator 5 includes a primary valve 11 and a primary chamber 12 for depressurizing the high-pressure gaseous fuel in the cylinder 1 to a pressure slightly higher than the atmospheric pressure, and a secondary valve 13 for depressurizing the primary chamber 12 to a pressure substantially equal to the atmospheric pressure. And a secondary chamber 14, and when air flows into the intake passage 8 and a negative pressure is generated in the venturi 23 of the mixer 7, the gaseous fuel in the secondary chamber 14 is sucked and the secondary diaphragm 15 is attached to the secondary chamber. The structure is such that the secondary valve 13 is opened by displacing it toward 14 and rotating the lever 16, which is nothing but an ordinary vaporizer.

In the atmosphere chamber 18 facing the secondary chamber 14 with the secondary diaphragm 15 of the pressure regulator 5 interposed therebetween,
A spring opening 19 is loaded with a valve opening spring 20 composed of a coil spring supported in a cantilever manner.
A spring bearing 19 is attached to the tip of the output shaft 22 of the.

The stepping motor 21 is an actuator that opens the secondary valve 13, which is an embodiment of the control valve of the present invention, against the spring force of the valve closing spring 17, and linearly moves with a stroke proportional to the number of rotations thereof. In addition, the output shaft 22 that moves forward and backward depending on the rotation direction causes the valve opening spring 20 to act on the secondary diaphragm 15 to forcefully open the secondary valve 13, or separates from the secondary diaphragm 15 and causes the secondary valve 13 to move. Allows normal opening and closing operations.

That is, during the steady operation of the engine 9 in the partial load range, the output shaft 22 is retracted to the position where the valve opening spring 20 is separated from the secondary diaphragm 15, and the gas flow rate is proportional to the intake air amount. Fuel is introduced into the intake passage 8.
At the time of acceleration when the intake air amount suddenly increases, the output shaft 22 moves forward to press the valve opening spring 20 against the secondary diaphragm 15 and forcefully displace it toward the secondary chamber 14, so that the opening degree is adjusted according to the intake air amount. By opening the secondary valve 13 and causing the gaseous fuel in the primary chamber 12 to flow into the secondary chamber 14, the gaseous fuel pressure in the secondary chamber 14 is increased. Therefore, a large amount of gaseous fuel is introduced into the intake passage 8 and it is possible to deal with the intake air rapidly increasing without delay.

The operating state of the engine 9 is an electric signal generated by the opening sensor 25 of the throttle valve 24 of the mixer 7, the negative pressure sensor 26 of the intake passage 8, the rotation speed sensor 27 of the engine 9, and the oxygen sensor 28 of the exhaust passage 10. Is transmitted to the stepping motor 21 so that the secondary valve 13 is opened according to the intake air amount when the acceleration operation is determined. Using this system, it is possible to increase the amount of fuel at the time of high output according to the intake air amount, and the intake air amount may be detected by a flow meter such as an air flow meter.

[0019]

[Embodiment 2] Next, an example in which the present invention is applied to a system in which gaseous fuel is adjusted to a constant positive pressure and introduced into an intake passage is shown in FIG.
In the fuel passage 31 from the cylinder 32 filled with LPG, which is a gaseous fuel in a liquid state, to the electromagnetically driven injection valve 37 installed in the intake passage 38 of the engine 39, a manual opening / closing valve 33, which is opened when the engine is operating, will be described. An electromagnetically driven shutoff valve 34 that is closed when the valve is stopped, a fuel pump 35 that is driven only when the engine is operating, and a fuel sump 36 are sequentially provided.

On the other hand, a return passage 41 extending from the fuel reservoir 36 of the fuel passage 31 and the injection valve 37 to the cylinder 32 is provided. In the return passage 41, a diaphragm type pressure regulator 42 and an electromagnetically driven stop valve 43 are provided. Are provided in order.

The pressure regulator 42 is a diaphragm 44.
A return valve 41 is connected to the fuel chamber 45 in the two chambers partitioned by and a discharge valve 47 for adjusting the opening degree of the outlet 46 is attached to the diaphragm 44.
A valve closing spring 49 that pushes the diaphragm 44 is installed in the atmosphere chamber 48. When the discharge pressure of the fuel pump 35, that is, the pressure of the gaseous fuel in the fuel chamber 45, becomes higher, the diaphragm 44 is displaced toward the atmosphere chamber 48 and the opening degree of the outlet 46 is increased to increase the return amount of the gaseous fuel to the cylinder 32. As a result, the pressure is reduced, and when the pressure of the gaseous fuel is reduced, the diaphragm 44 is displaced toward the fuel chamber 45 and the outlet 4
The pressure is increased by decreasing the opening degree of 6.
As a result, the gaseous fuel adjusted to a constant positive pressure is introduced into the intake passage 38.

A valve closing spring 49 of the pressure regulator 42.
A spring receiver 50 sandwiching the shaft with the diaphragm 44 is attached to the tip of the output shaft 52 of the stepping motor 51. The stepping motor 51 is an actuator that adjusts the spring force of the valve closing spring 49 of the discharge valve 47, which is an embodiment of the control valve of the present invention. The stepping motor 51 linearly moves with a stroke proportional to the number of rotations of the discharge valve 47 and responds to the rotation direction. The output shaft 52 that moves forward and backward adjusts the spring force of the valve closing spring 49 to adjust the discharge valve 47.
The opening degree of the outlet 46 is changed.

That is, during the steady operation of the engine 39 in the partial load range, the output shaft 52 holds the spring bearing 50 at a predetermined distance from the diaphragm 44 so that the outlet 46 has an appropriate opening and the flow rate proportional to the intake air amount. Gas fuel of the intake passage 38
Have been introduced. During acceleration in which the intake air amount suddenly increases, the output shaft 52 moves forward to increase the spring force of the valve closing spring 49 to forcibly reduce the opening degree of the outlet 46 and reduce the return amount of the gaseous fuel to the cylinder 32. By making the injection valve 37
Increase the pressure of the gaseous fuel sent to. For this reason, a large amount of gaseous fuel is introduced into the intake passage 38, and it is possible to cope with the intake air that rapidly increases and is not delayed.

As in the previous embodiment, the operating state of the engine 39 includes the opening sensor 25 of the throttle valve 53, the negative pressure sensor 26 of the intake passage 38, the rotation speed sensor 27 of the engine 39, and the oxygen sensor 28 of the exhaust passage 40. It is determined by processing the electric signal emitted by the electronic control unit 54, and when it is determined that the operation is accelerated, a drive signal is sent to the stepping motor 51 so as to move the discharge valve 47 in the valve closing direction according to the intake air amount. Using this system, it is possible to increase the amount of fuel at high output in accordance with the intake air amount, and the intake air amount may be detected by a flow meter such as an air flow meter. Is the same as.

In the two embodiments, the secondary valve 13 and the discharge valve 4 are used.
The output shaft 22 as an actuator for adjusting the opening degree of 7,
Although 52 uses the stepping motors 21 and 51 that linearly reciprocate, it is also possible to use a stepping motor whose output shaft rotates to convert its rotation into linear motion with a cam, a link, or the like, and a proportional solenoid or the like as an actuator. Can be used.

[0026]

The present invention has a structure in which the pressure of the gaseous fuel introduced into the intake passage of the engine is adjusted steplessly to a value according to the intake air amount of the engine by the control valve opening of the pressure regulator. Depending on the degree, the pressure of the gaseous fuel can be raised and the appropriate amount of it can be introduced into the intake passage with good responsiveness and even in the large flow rate range, and it can exhibit excellent acceleration performance and does not deteriorate the exhaust state. Is.

Further, by utilizing this system, a proper amount of gaseous fuel corresponding to the intake air amount can be supplied with good response even at the time of high output.

[Brief description of drawings]

FIG. 1 is a layout diagram of a first embodiment of the present invention.

FIG. 2 is a layout diagram of a second embodiment of the present invention.

[Explanation of symbols]

1, 31 Fuel passage, 2, 32 cylinder, 5, 42 Pressure regulator, 8, 38 Intake passage, 9, 39 Engine, 13 Secondary valve, 21, 51 Stepping motor,
30, 54 Electronic control device, 47 Release valve,

Claims (1)

[Claims] 1. A pressure regulator having a control valve for adjusting a pressure of gaseous fuel introduced into an intake passage of an engine to a constant pressure is provided with an actuator for adjusting an opening of the control valve, and the actuator is an intake air amount of the engine. A gas fuel supply apparatus for an engine, wherein the opening of the control valve is adjusted steplessly so as to adjust the pressure of the gas fuel introduced into the intake passage in accordance with the above.