JPH0510212A - Air-fuel ratio control device of lpg engine car - Google Patents

Abstract

PURPOSE:To construct an air-fuel ratio control device for LPG engine car having a large width of air fuel ratio control, which functions well with eventual deviation of the base air-fuel ratio to a great extent. CONSTITUTION:A main fuel passage 9 is equipped with a flow control valve 22. A sensing signal from an oxygen sensor 13 is fed to a controller 14, which gives a drive signal for controlling the aux. fuel injecting amount to an injector 16. The injector 16 makes aux. fuel injection so that the air-fuel ratio becomes the proper value. If the proper value is not obtainable with this injection amount control, the controller 14 emits drive signal to actuator 24 of the flow control valve 22. The actuator 24 controls the opening of the valve 22 to correct the base air-fuel ratio so that it approaches the proper air-fuel ratio zone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an LPG engine mounted on an industrial vehicle such as a forklift, and more particularly to an air-fuel ratio control device implemented as part of exhaust gas purification measures.

[0002]

2. Description of the Related Art Conventionally, in a forklift equipped with an LPG engine, the air-fuel ratio is controlled so as to be near an appropriate air-fuel ratio as a measure for exhaust gas. There is one as shown in 5. As shown in the drawing, the air taken in from the opening of the head guard pillar 1 is
It flows into the carburetor 6 through the air cleaner 3, the hose 4, and the air connector 5. On the other hand, the fuel sent from an LPG cylinder (not shown) to the LPG regulator 8 via the fuel pipe 7 passes through the main fuel supply pipe 9 to the carburetor 6
Is flowed into. Then, a mixture of air and fuel agitated and mixed in the carburetor 6 (hereinafter, the mixture at this time is referred to as a base mixture, and its air-fuel ratio is referred to as a base air-fuel ratio) passes through the intake manifold 10 and the engine 11
Sent to and burned.

Therefore, the exhaust manifold 12
Is provided with an oxygen sensor 13 for detecting the oxygen concentration in the exhaust gas, and a detection signal from the oxygen sensor 13 is input to the controller 14. Based on this detected value, the controller 14 then injects the auxiliary fuel by the LPG injector 16 (injection time) so that the air-fuel ratio becomes close to the appropriate air-fuel ratio (theoretical air-fuel ratio with good purification characteristics of the three-way catalyst). To control. 12a is a three-way catalyst muffler. In short, the air-fuel ratio feedback control shown in FIG. 5 attempts to bring the air-fuel ratio close to the appropriate air-fuel ratio by controlling the injection amount of the auxiliary fuel with respect to the base mixture, and if the air-fuel ratio is lean, Increase the injection amount of auxiliary fuel and decrease the injection charge when it is rich,
The LPG injector 16 is controlled (see the characteristic diagram shown in FIG. 7A). The auxiliary fuel is introduced from the LPG regulator 8 to the LPG injector 16 via the auxiliary fuel supply pipe 15, and is injected into the intake manifold 10 by the injector 16.

FIG. 6 is a detailed view of the main fuel supply portion of the carburetor 8. The main fuel introduced through the main passage 9a is the power adjust screw 17
It is fixed by. When the engine has a high load, the negative pressure of the intake manifold 10 decreases, so the negative pressure acting on the diaphragm chamber 19 via the negative pressure introducing pipe 18 also decreases, and the spring 20 returns to open the power valve 21. .. Due to this, the main passage 9a
In addition to the above, the sub passage 9b is secured, the main fuel is increased, the concentration of the air-fuel mixture is increased, and the required output is secured.

[0005]

However, in the above-described conventional air-fuel ratio control system, the flow characteristics of the carburetor are different depending on the type of engine, or the intake system and the fuel system are different depending on the type of engine and the flow characteristics are different. When the base air-fuel ratio deviates and exceeds the air-fuel ratio control range due to variations, etc., or because the air density is low in high-altitude areas, and it is not possible to control to a predetermined appropriate air-fuel ratio. There is a problem in that there is. Figure 7 (b)
This is an example of this situation, where the base air-fuel ratio deviates significantly from the proper air-fuel ratio range to the lean side, and the air-fuel ratio does not enter the proper air-fuel ratio range when the auxiliary fuel injection amount control is performed. It cannot be controlled. That is, the conventional method of controlling the injection amount of the auxiliary fuel has a limit in its control width, and there is a problem that it is not possible to cope with a large deviation of the base air-fuel ratio caused by the above variation.

In view of the above-mentioned conventional problems, the present invention provides an air-fuel ratio control device having a wide air-fuel ratio control range capable of coping with a large deviation of the base air-fuel ratio.
It is a technical issue to be solved.

[0007]

In order to solve the above problems, the present invention is configured as follows. That is, the present invention is an air-fuel ratio control device for an LPG engine vehicle, which includes an LPG regulator and a main fuel passage for guiding fuel from the LPG regulator to a carburetor.
An auxiliary fuel passage for guiding the fuel from the LPG regulator to the intake manifold, a flow control valve for adjusting the flow rate provided in the main fuel passage, an actuator for adjusting the opening of the flow control valve, and the auxiliary. The injector for auxiliary fuel injection provided in the fuel passage, the oxygen sensor installed to detect the air-fuel ratio, and the detection signal of the oxygen sensor are input, and the air-fuel ratio is in the proper air-fuel ratio range based on this signal. To output an operation command for controlling the injection amount of the auxiliary fuel by the injector so as to enter, and a controller for outputting an operation command for correcting the base air-fuel ratio to the actuator of the flow control valve. It has a feature.

[0008]

In the air-fuel ratio control system for an LPG engine vehicle according to the present invention constructed as described above, since the base air-fuel ratio is largely deviated from the proper air-fuel ratio range, the auxiliary fuel injection amount control by the injector is performed. If the air-fuel ratio cannot be controlled to an appropriate air-fuel ratio, the actuator of the flow control valve is operated to adjust the opening of the flow control valve to increase or decrease the main fuel supplied to the carburetor to increase the base fuel. Correct the air-fuel ratio. That is, it is possible to control the air-fuel ratio to an appropriate air-fuel ratio by bringing the base air-fuel ratio close to a range where the air-fuel ratio control by the injection amount control of the auxiliary fuel is possible.

[0009]

Embodiments of the present invention will be specifically described below with reference to FIGS. FIG. 1 shows an LP according to an embodiment of the present invention.
FIG. 6 is a configuration diagram of an air-fuel ratio control device for a G engine vehicle, and the same components as those in the conventional art are denoted by the same reference numerals as those in the conventional art shown in FIG.

As shown in the figure, a flow control valve 22 for controlling the flow rate of the main fuel supplied to the carburetor 6 is provided in the main fuel supply pipe 9 which is the main fuel passage.
Is provided. This flow control valve 22
As shown in FIG. 2, the needle valve 23 is linearly moved forward and backward to adjust the opening of the main passage, the motor 24 as an actuator for driving the needle valve 23, and the rotation of the motor 24. A worm gear 25 as a motion direction conversion mechanism that converts the motion into a linear motion and transmits the motion to the needle valve 23. The motor 24 has its rotation direction and rotation angle controlled based on a drive signal output from the controller 14. ..

Further, the intake manifold 10 includes
A negative pressure sensor 26 is installed, and its detection signal is input to the controller 14. That is, the controller 14
A signal from the oxygen sensor 13 installed in the exhaust manifold 12 and a signal from the negative pressure sensor 26 are input to the controller 14, and the controller 14 determines the flow control valve 22 for the main fuel based on these signals.
Motor 24 and injector 16 for auxiliary fuel injection
Control the operation of.

In short, the air-fuel ratio control system of the present embodiment constructed as described above, in short, controls the injection amount of the auxiliary fuel by the injector 16 and the main fuel by the flow control valve 22 based on the detection signal to the oxygen sensor 13. The air-fuel ratio control is performed by the flow control of the flow rate of the main fuel, and the flow control valve 22 controls the flow rate of the main fuel for the high engine load based on the detection signal of the negative pressure sensor 26. This will be described based on the flowchart of FIG.

Now, when the control shifts to step 31,
The position P of the flow control valve 22 is the initial position P0.
Is set to. Next, the routine proceeds to step 32, where it is judged if the negative pressure V of the intake manifold 10 detected by the negative pressure sensor 26 is smaller (lower) than the high output required negative pressure VPWR. And when it ’s small,
It is determined that high output is required, and the process proceeds to step 33,
Set the position P of the flow control valve 22 to the high output position P.
Move to PWR. That is, the needle valve 23 is moved to the high output position PPWR through the motor 24 so that the opening of the main passage corresponds to the high output required negative pressure VPWR. Therefore, the amount of main fuel is increased to form an air-fuel mixture having a high base air-fuel ratio, and a required high output can be obtained. The injection time T of the auxiliary fuel by the injector 16 at this time is controlled to T = 0. That is, the fuel injection by the injector 16 is stopped.

On the other hand, if the determination result in step 32 is NO, that is, if the negative pressure V of the intake manifold 10 is larger (higher) than the high output required negative pressure VPWR, the routine proceeds to step 34, where the current air-fuel ratio λ is the proper air-fuel ratio λ. It is determined whether it is greater than or equal to the fuel ratio λ0. And YE
If S, it is determined that the current air-fuel ratio is lean, and the routine proceeds to step 35, where it is determined whether the injection time T of the injector 16 is the maximum injection time Tmax. If it is not the maximum, go to step 36 to control T = T + 1,
That is, after the injection time T of the injector 16 is extended, the process returns to step 32. Thereafter, the control for sequentially extending the injection time T is repeated until the air-fuel ratio enters the proper air-fuel ratio range.

In this way, the control for making the air-fuel ratio close to the proper air-fuel ratio is executed by controlling the injection amount of the auxiliary fuel supplied to the base air-fuel mixture. Even if T is repeated until the maximum injection time Tmax is reached, as shown in the characteristic diagram of FIG. 3 (a), when the air-fuel ratio does not fall within the proper air-fuel ratio range, the base air-fuel ratio changes from the proper air-fuel ratio range to the lean side. It is determined that there is a large deviation from, and the following control is performed.

That is, in step 35, if the injection time T is the maximum injection time Tmax, step 37
Then, it is determined whether or not the duration S (or the repetition time) of the maximum injection time Tmax exceeds the reference time S0 (the time when it is judged that the injector 16 cannot completely control). When the continuation time S exceeds the reference time S0, the routine proceeds to step 38, where P = P + 1 control, that is, the control for advancing the position P of the flow control valve 22 to the opening increasing side, and then to step 32. After returning, the control for sequentially increasing the opening degree of the flow control valve 22 is repeated. By performing this control, the main fuel is increased, the concentration of the base air-fuel mixture is increased, and the base air-fuel ratio is corrected to the rich side. as a result,
As shown in FIG. 3B, the air-fuel ratio of the air-fuel mixture supplied with the auxiliary fuel can be put in the proper air-fuel ratio range.

On the other hand, if it is determined in step 34 that the current air-fuel ratio λ is greater than or equal to the proper air-fuel ratio λ0, the result is NO, it is determined that the current air-fuel ratio is rich. Then, the routine proceeds to step 39, where it is judged whether or not the injection time T of the injector 16 is the minimum injection time 0. Then, if NO, the routine proceeds to step 40, where T = T-1 is controlled, that is, the injection time T of the injector 16 is shortened, and then the routine returns to step 32.
Thereafter, the control for sequentially shortening the injection time T is repeated until the air-fuel ratio enters the proper air-fuel ratio range.

Even if the above control is repeated until the injection time T by the injector 16 reaches the minimum injection time 0, if the air-fuel ratio does not fall within the proper air-fuel ratio range, the base air-fuel ratio increases from the proper air-fuel ratio range to the rich side. It is determined that there is a deviation, and at this time, the routine proceeds from step 39 to step 41, where it is determined whether the duration S of the minimum injection time 0 exceeds the reference time S0. When the continuation time S exceeds the reference time S0, the routine proceeds to step 42, where P = P-1 control, that is, the control for advancing the position P of the flow control valve 22 to the opening decrease side, and then the step Returning to step 32, the opening degree reduction control of the flow control valve 22 is repeated. By performing this control, the main fuel is reduced, the concentration of the base mixture is reduced, and the base air-fuel ratio is corrected to the lean side. The position P of the flow control valve 22 after the above control is executed is stored in the controller 14 as the initial position P0.

As described above, according to the air-fuel ratio control system of the present embodiment, when the injection air amount control of the auxiliary fuel by the injector 16 cannot control the proper air-fuel ratio, the air-fuel ratio is corrected by correcting the main fuel supply amount. The fuel ratio can be controlled to an appropriate air-fuel ratio, and when the engine has a high load, the main fuel can be increased to obtain the required high output.

[0020]

As described above in detail, the LP according to the present invention
In the air-fuel ratio control device for G engine vehicles, the control range of the air-fuel ratio can be expanded by controlling the opening of the flow control valve to directly control the flow rate of the main fuel. It is possible to control the air-fuel ratio to an appropriate air-fuel ratio even if the base air-fuel ratio deviates significantly from the appropriate air-fuel ratio range due to variations in the carburetor flow rate characteristics, intake system, fuel system variations, etc. With
An appropriate air-fuel ratio can be obtained by correcting the base air-fuel ratio even when enriched by lean air at high altitudes. Also,
The demand for high output under heavy load can be met by controlling the opening of the flow control valve to increase the amount of main fuel, so the complicated power passage mechanism inside the carburetor, which was necessary in the past, was eliminated. There is also an advantage.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an air-fuel ratio control device for an LPG engine vehicle according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main fuel supply system.

FIG. 3 is a characteristic diagram.

FIG. 4 is a flowchart of a control system.

FIG. 5 is a configuration diagram of an air-fuel ratio control device for a conventional LPG engine vehicle.

FIG. 6 is a sectional view of an LPG carburetor (main fuel supply unit).

FIG. 7 is a characteristic diagram.

[Explanation of symbols]

6 ... Carburetor 8 ... LPG regulator 9 ... Main fuel supply pipe 10 ... Intake manifold 13 ... Oxygen sensor 14 ... Controller 15 ... Auxiliary fuel supply pipe 16 ... Injector 22 ... Flow control valve 24 ... Motor 26 ... Negative pressure sensor

Claims (1)

Claim: What is claimed is: 1. An LPG regulator, a main fuel passage for introducing fuel from the LPG regulator to a carburetor, and an auxiliary fuel passage for introducing fuel from the LPG regulator to an intake manifold. A flow control valve for adjusting the flow rate provided in the main fuel passage, an actuator for adjusting the opening of the flow control valve, an injector for auxiliary fuel injection provided in the auxiliary fuel passage, and an air-fuel ratio detection An oxygen sensor installed for the purpose of inputting a detection signal of the oxygen sensor, and based on this signal, an operation command for controlling the injection amount of the auxiliary fuel by the injector so that the air-fuel ratio falls within an appropriate air-fuel ratio range. Is output to the actuator of the flow control valve. Air-fuel ratio control system for an LPG engine vehicle equipped with a capital and a controller for outputting an actuation command for correcting the air-fuel ratio.