KR910008911B1 - Air-fuel ratio control method for liquid gas - Google Patents

Abstract

opening and closing sub- fuel path (5) driven by feed back solenoid for engine control unit (15) in accordance with input signal from temperature sensor (10) and oxygen sensor (14), and the fuel cut-off valve (7) and feed back solenoid (9) which is opened and closed in proportion to temperature of cooling water. The space of vaporizer (2) and mixer (3) is formed to main fuel path (4) which is controlled by control screw (6), and sub-fuel path (5) for supplying the proper amount of fuel.

Description

Air-fuel ratio control method of liquefied gas engine

1 is a schematic configuration diagram of an engine showing an embodiment of the present invention.

2 is a side sectional view showing a preferred example of the coolant water temperature sensing valve in the present invention, in which FIG. 2a is an operating state in the low speed region, and FIG. 2b is an operating state diagram in the high speed region.

3 is a comparison graph of the air-fuel ratio curve according to the present invention and the prior art.

* Explanation of symbols for main parts of the drawings

1: Pressure-resistant container 2: Vaporizer

3: Mixer 4: Main fuel passage

5: auxiliary fuel passage 7: fuel shutoff valve

8: Temperature sensing valve 9: Feed back solenoid

10: temperature sensor

The present invention relates to an air-fuel ratio control method for a liquefied gas engine, and more particularly, to an air-fuel ratio control method for a liquefied gas engine for a vehicle.

Engines using liquefied gas as fuel have the same ignition system and combustion as gasoline engines, but by reducing the liquefied gas through a vaporizer before introducing the liquefied gas into the cylinder by mixing the liquefied gas with air, It is a fuel system that obtains the proper air-fuel ratio in the mixer.

However, in the above fuel system, since the vaporizer controls the entire operating range of the engine by the secondary valve that opens and closes the gas cylinder from the primary chamber to the secondary chamber, the idling operation becomes unstable, and moreover, the liquefaction as is well known. The gas has a large difference in vaporization pressure depending on the components, and this pressure varies with temperature. Therefore, the decompression vaporization of liquefied gas is performed from the start after a long stop or the start of cold air to the warming up of the engine. With the high concentration, there is a problem that causes engine relief and harmful gas emissions.

To solve this problem, vaporizers have been put into practice by introducing the engine coolant into the vaporizer to promote the reduced pressure of the liquefied fuel by the water temperature of the coolant. However, the vaporizer was able to improve the stable state during idling operation. Engine instability up to warm-up and emissions of harmful gases are not resolved.

On the other hand, an air passage provided with an air control valve is separately installed in the intake system of the engine, and the coolant temperature detection valve possessed by the intake system is opened and closed in accordance with the coolant temperature indicating the state of the engine warming up and down, and thus a large amount of the intake system is provided. By introducing air, an air-fuel ratio control method for preventing high concentration of the mixer in the initial operating state before engine warm-up has been disclosed in Japanese Patent Laid-Open No. 63-36056.

This air-fuel ratio control method is greatly noticed in that it presented the possibility to solve the engine by-products and harmful gas emissions appearing from the initial start up to the engine warm-up, but it is expected to be as effective as controlling the air supply to the fuel It does not represent.

In other words, the air-fuel ratio control method described above is a method of introducing a large amount of air into a high concentration of mixed gas supplied through the choke circuit of the mixer at the beginning of the start to reduce the concentration of the mixed gas, thereby essentially matching the air-fuel ratio appropriate to the operating state of the engine. Will not get.

In view of the foregoing, the present inventors have studied the air-fuel ratio control method in earnest, and have therefore proposed an air-fuel ratio control method for a liquefied gas engine in which the engine is operated in a stable state immediately after starting and there is no emission of harmful gases.

Accordingly, an object of the present invention is to provide an air-fuel ratio control method of a liquefied gas engine while the engine is stably driven by the supply of a mixer according to the appropriate air-fuel ratio from the beginning of the start-up.

According to the above-described object, the present invention provides a fuel-fuel ratio control method for supplying fuel from a vaporizer to an engine in a vaporizer, in which a liquefied gas of an internal pressure vessel is heated with cooling water of an engine to be depressurized and supplied to an engine through an intake machine. The system consists of a main fuel passage equipped with a fuel shutoff mechanism and an auxiliary fuel passage equipped with a feedback solenoid, and the fuel shutoff mechanism of the main fuel passage described above is connected to a coolant temperature sensing valve to indicate that the engine is in a warm-up state. By operating the fuel shutoff mechanism in the coolant low temperature zone, the main fuel passage is blocked and the auxiliary fuel passage is developed to supply the appropriate amount of fuel to the engine warm-up state, and the coolant temperature is increased by the warm-up of the engine. When the temperature rises above a certain level, the electric coolant water temperature detection valve is used to proportionally shut off the fuel Sikkim room and at the same time blocking the secondary fuel path to be characterized in that it allows the fuel is supplied in an amount that make the proper air-fuel ratio before the warming up of the engine until warm eophu.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic configuration diagram of an engine showing an embodiment of the present invention, in which liquefied gas is supplied from a pressure vessel 1 to a normal vaporizer 2, vaporized under reduced pressure, and then adjusted to a constant pressure slightly lower than atmospheric pressure. It is intended to be sent to the mixer 3.

Between the vaporizer 2 and the mixer 3, the main fuel passage 4, which normally supplies fuel after warming up the engine, and the auxiliary fuel, which continuously supplies quantitatively controlled fuel to suit the operating state of the engine. The passage 5 is formed, and the basic fuel amount supplied from the main fuel passage 4 described above is constantly adjusted by the adjusting screw 6.

In addition, between the vaporizer 2 and the main fuel passage 4, there is an upper open fuel cutoff valve 7 which is always opened by the elasticity of the spring, and the fuel cutoff valve 7 has a coolant temperature sensing valve ( 8), the opening and closing is controlled according to the cooling water temperature as described later. On the other hand, the auxiliary fuel passage 5 also has a feed back solenoid 9 for opening and closing the passage.

In contrast to the fuel shutoff valve 7 described above, which is an open valve, the feedback solenoid 9 is an upper-closed valve that opens the passage with an opening corresponding to the excitation force.

In addition to the configuration of each part between the vaporizer 2 and the mixer 3, the coolant temperature sensor 10, the throttle position sensor 11, the idle switch 12, and the exhaust manifold 13 side for checking the operation state of the engine. An oxygen sensor 14 is provided.

These sensors are those conventionally applied to automobiles and are controlled by the electronic engine control unit 15.

The engine control unit 15 includes a control program and a ROM including a fuel supply system and a supply amount related to an air-fuel ratio suitable for a state after a warm-up before the engine warm-up as computer information, and output values and control amounts of the sensors. An electronic control device comprising a RAM for temporarily storing the result of calculation and an input / output device for outputting the output values and control signals of the above sensors, wherein the throttle opening and the coolant temperature sensor in the throttle position sensor 11 are included. The amount of fuel through the auxiliary fuel passage 5 is controlled by driving the feedback solenoid 9 according to the coolant temperature value from (10).

2 is a side cross-sectional view showing the structure of the cooling water temperature sensing valve 8 described above. The common port 80 is connected to the fuel shutoff valve 7 of the main fuel passage 5, and the negative pressure port 81 is connected. Is communicated to the lower side of the throttle in the carburetor (3) to introduce the negative pressure caused by the movement of the piston to the common port 80, the open port 82 is open to the air, when communicating with the common common port 80 The negative pressure will be released.

An annular valve element 84 pressurized by a spring 83 is housed inside the cooling water temperature sensing valve 8, and the annular valve element 84 is always provided between the common port 80 and the negative pressure port 81. It is preserved in a position to communicate.

The upper end of the annular valve element 84 is provided with a valve body 85 for closing the negative pressure port 81, while the lower end portion is attached with a temperature sensing means 86 which contracts and expands in accordance with the temperature of the cooling water.

The temperature sensing means 86 may use a conventional bimetal or a material having a high coefficient of thermal expansion. When the cooling water temperature rises in the illustrated state and the temperature sensing means 86 expands, the annular valve body 84 may have a spring ( 83, the negative pressure port 81 is closed by the valve body 85 as shown in FIG. 2A while the common port 81 is in communication with the open port 82 as shown by the arrow. do.

Referring to the air-fuel ratio control process according to the present invention.

When the engine is started with the switch in place, all of the engine's electrical controls and sensors are energized to perform their unique functions.

In this state, when the temperature of the coolant is a low temperature region indicating that the engine is before warming up, the engine control unit 15 is input from the coolant temperature sensor 10, the throttle position sensor 11, and the oxygen sensor 14. In response to the signal, an appropriate fuel supply amount is read out and the feedback solenoid 9 is opened to a corresponding degree.

Accordingly, the auxiliary fuel passage 5 can supply the amount of fuel capable of obtaining the most desirable air-fuel ratio in the state before the engine warm-up, and at the same time, the temperature sensing means 86 contracted by the coolant in the low temperature region is 2a. As shown in the figure, the annular valve body 84 is lowered so that the valve body 85 is spaced apart from the inlet of the sub-arm port 81, and thus, between the common port 80 and the negative pressure port 81 as shown by the arrow. To be placed in a communicating position.

As a result, the negative pressure on the cylinder side caused by the operation of the engine is applied to the fuel shutoff valve 7 of the main fuel passage 4 via the common passage 80 so that the main fuel passage 4 is shut off. It is supplied only through the auxiliary fuel passage 5 which is constantly controlled by the engine control unit 15.

As the engine warms up, of course, the temperature rises to the coolant temperature. Accordingly, the signal value transmitted from the temperature sensor 10 is also changed at a time, and the temperature sensing means 86 starts to expand to open the negative pressure port 81. It is closed.

Due to this process, as the engine warms up, the engine control unit 15 controls the feedback solenoid 9 to the closed side, and as the temperature sensing means 86 expands, as shown in FIG. 84 is raised to the fuel cutoff valve 7 as the valve body 85 opens the common port 80 and the open port 82 side as shown by the arrow to block the inlet of the sub-arm port 81. As the negative pressure is blocked, the main fuel passage 4 is opened, and the engine control unit 15 generates a control signal suitable for the operation state to open and control the feedback solenoid 9 installed in the auxiliary fuel cylinder 5. Normal operation will be achieved.

On the other hand, when the engine is warmed up and the engine is warmed up, the temperature sensing means 86 is expanded and the signals of the temperature sensing sensor 10 and the throttle position sensor 11 input to the engine control unit 15 are expanded. Indicates that the coolant is a high temperature zone, the main fuel passage (4) is opened because no negative pressure is applied to the fuel shutoff valve (7), and the feedback solenoid (10) is connected to the signal output from the engine control unit (15). Opening and closing is controlled.

Therefore, starting in the engine warmed-up state is that fuel is supplied via the main fuel passage 4 as in the normal operation.

3 is a graph comparing air-fuel ratio curves between the present invention and the prior art, wherein a dotted line is an air-fuel ratio curve (prior art) of a conventional liquefied gas engine which does not have a means to prepare for an operating defect before warm-up. The air-fuel ratio curve of the improved liquefied gas engine (prior art 2) obtained by adjusting the air supply amount beforehand to obtain a suitable air-fuel ratio, and the solid line is the air-fuel ratio curve according to the present invention.

The prior art 1 shows a problem that the air-fuel ratio becomes lower as the coolant temperature is lower than the cooling water temperature of 60 ° C., that is, before the warm-up state. However, the instability of the cooling water temperature 604C _F immediately before the end of warming up is shown.

However, the present invention has shown the result that the engine is operated at the most suitable air-fuel ratio which forms a gentle curve from the initial start state before the warm up state to the state after the warm up state.

As described above, the present invention is to supply the amount of fuel supplied to the mixer while controlling continuously at a moment-by-minute through the separate supply line, the amount which becomes the most preferable air-fuel ratio for the engine operating state from the start of the engine before the warm-up to the warm-up after the warm-up. It will fundamentally solve the operation stability and the harmful gas emission before warming up which are the problems of the gas engine.

Claims (3)

In the vaporizer, an air-fuel ratio control method in which a liquefied gas of an internal pressure vessel is heated with cooling water of an engine and vaporized under reduced pressure, is supplied to the engine through a mixer of an intake system, and the fuel supply system from the vaporizer 2 to the engine is connected to a fuel shutoff valve. The fuel shutoff valve (7) of the main fuel passage (4) provided with (7) is connected with the coolant temperature sensing valve (8) so that the fuel shutoff valve (7) blocks the main fuel passage (4) in the coolant low temperature region. At the same time, the engine control unit 15 drives the feedback solenoid 9 in response to the signals input from the temperature sensor 10, the throttle position sensor 11, and the oxygen sensor 14 to open the auxiliary fuel passage 5. And closing and opening the fuel cutoff valve (7) when the coolant temperature rises and the auxiliary fuel passage (5) is controlled according to the operating state. 2. A method according to claim 1, wherein the fuel shutoff valve (7) and the feedback solenoid (9) are opened and closed in proportion to the temperature of the cooling water, respectively. According to claim 1, the temperature sensing valve (8) is opened to the coolant low temperature zone port (81), and as the coolant temperature rises, the common port (80) communicated to the open port (82) and at the same time negative pressure port ( 81) is closed, the air-fuel ratio control method of a liquefied gas engine.

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