JPH0777076A - Air-fuel ratio control device for gaseous fuel engine - Google Patents

Abstract

PURPOSE:To make improvement of drivability compatible with improvement of emission of exhaust gas when lean combustion is effected during light load running and theoretical air-fuel ratio combustion is carried out at other region than the above, in an internal combustion engine which is provided in an exhaust gas passage with a three-WAY catalyst for purifying exhaust gas and an air-fuel sensor. CONSTITUTION:The opening of a fuel control valve 4 operated through an acceleration wire proportions the opening of an accelerator. A lever 16 interlocking with a fuel control valve 4 through a link 17 is loosely engaged with the throttle valve stem 10 of an intake passage 2. When, during light load running, the lever 16 is rotated in linkage with the fuel control valve 4, a throttle valve 9 is opened through a lever 11. When an engine is brought into specified load or more running, a motor 13 is energized, a throttle valve 9 is operated in a closing direction, and an air amount is reduced. In this case, feedback control is performed so that an air-fuel ratio is adjusted to a theoretical air-fuel ratio.

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 system for a vehicle gas fuel engine.

[0002]

2. Description of the Related Art A system for improving fuel efficiency by performing lean combustion at light load is disclosed in Japanese Patent Laid-Open No. 165852/1984. This air-fuel ratio control device for a gas fuel engine is equipped with a three-way catalyst for purifying exhaust gas in the exhaust path, while at the time of light load below the rated load operation, a lean air-fuel mixture is formed by the gas mixer. In order to detect the air-fuel ratio while burning the air-fuel mixture and adjusting the main jet needle of the gas mixer in the valve opening opening direction to correct the air-fuel ratio to near the stoichiometric air-fuel ratio during overload operation. It is directly connected to a step motor which is operated to advance and retreat in response to a signal emitted from the air-fuel ratio sensor of. In this way, lean combustion is performed at light load, ideal air-fuel ratio combustion is performed in other regions, and the air-fuel ratio of the air-fuel mixture becomes a predetermined value based on the signal from the air-fuel ratio sensor during ideal air-fuel ratio combustion. It has feedback control.

[0003]

SUMMARY OF THE INVENTION In the above conventional technique,
The lean air-fuel ratio is achieved by reducing the fuel flow rate at light load, and the stoichiometric air-fuel ratio is achieved by increasing the fuel flow rate at overload. Therefore, in order to mitigate the drivability problem that the accelerator opening and the fuel flow rate are not proportional and the engine output desired by the driver cannot be obtained, and the acceleration shock at the time of transition from the lean air-fuel ratio to the theoretical air-fuel ratio. In addition, there is a problem in exhaust emission that the air-fuel ratio region with poor exhaust emission must be used for a long time by gradually increasing the fuel, and it is difficult to achieve both drivability and exhaust emission. Therefore, it is an object of the present invention to provide an air-fuel ratio control device for a gas fuel engine that can solve both of these problems and achieve both drivability and exhaust emission.

[0004]

In order to achieve the above object, the first invention comprises a three-way catalyst for purifying exhaust gas and an air-fuel ratio sensor in an exhaust passage, and lean combustion is performed at a light load. In the region other than that, ideal air-fuel ratio combustion is performed, and at least during ideal air-fuel ratio combustion, feedback control is performed so that the air-fuel mixture becomes a predetermined air-fuel ratio by the signal from the air-fuel ratio sensor. In a fuel ratio control device, a fuel passage (3) having a fuel control valve (4) for controlling a fuel flow rate to a value proportional to an accelerator opening operated by a driver, and intake air linked with the fuel control valve (4). A throttle valve (9) for controlling the amount and an electric actuator (13) for limiting the opening of the throttle valve (9) are provided, and the throttle valve (9) is used to control the fuel when the load is light. In conjunction with the valve (4), the intake air amount is controlled to a lean air-fuel ratio within a range where exhaust emission is below the regulation value and does not cause misfire, and when the lean air-fuel ratio makes it impossible to travel, the load range is reached. The electric actuator (13) is operated by a signal from the air-fuel ratio sensor to limit the opening of the throttle valve (9) to control the air-fuel mixture to a stoichiometric air-fuel ratio.

A second aspect of the present invention is provided with a three-way catalyst for purifying exhaust gas and an air-fuel ratio sensor in the exhaust passage, performs lean combustion at light load and ideal air-fuel ratio combustion in other regions, and at least In the ideal air-fuel ratio combustion, the signal from the air-fuel ratio sensor is used to perform feedback control so that the air-fuel mixture becomes a predetermined air-fuel ratio.In an air-fuel ratio control device for an internal combustion engine that uses gaseous fuel, it is proportional to the accelerator opening operated by the driver. A fuel passage (3) having a fuel control valve (4) for controlling the fuel flow rate to a predetermined value, a throttle valve (9) for controlling the intake air amount of the intake passage (2), and driving the throttle valve (9). And an electric actuator (13A) for controlling the intake air amount to a predetermined lean air-fuel ratio and stoichiometric air-fuel ratio in accordance with a signal from the air-fuel ratio sensor according to the load state of the engine. Ku is characterized in that so as to operate the electric actuator.

[0006]

In the first aspect of the invention, the electric actuator is de-energized when the load is light, the fuel control valve (4) is opened by the accelerator operation, and the fuel from the fuel passage (3) is sucked into the intake air (2). It is mixed and supplied to the engine. At this time, the throttle valve (9) of the intake passage (2) controls the intake air amount in conjunction with the fuel control valve (4), so that the exhaust emission falls below the regulation value and the lean air-fuel ratio within the range where misfire does not occur. To be slightly higher than the stoichiometric air-fuel ratio requires. Then, when the accelerator is further depressed to reach a load range where traveling with a lean air-fuel ratio is impossible, the electric actuator (3) is energized, and the electric actuator (1) is activated by the signal from the air-fuel ratio sensor (21).
3) is operated to limit the opening of the throttle valve (9) to reduce the air amount, and the air-fuel mixture is feedback-controlled to the stoichiometric air-fuel ratio.

In the second aspect of the invention, first, similarly to the first aspect of the invention, the fuel flow rate is controlled by the fuel control valve (4) to a value proportional to the accelerator opening operated by the driver. The throttle valve (9) in the intake passage (2) is driven by the electric actuator (13) under all operating conditions, unlike the case of the first invention. Lean air-fuel ratio at light load,
Further, except when the load is light, the electric actuator (13) is operated so that the stoichiometric air-fuel ratio is controlled and the intake air amount is controlled by the signal of the air-fuel ratio sensor (21).

[0008]

1 to 5 show a first embodiment of the present invention, which corresponds to the first invention. 1 is a gas mixer, 2 is an intake passage,
A fuel passage 3 includes a fuel control valve 4. The fuel control valve 4 is attached to a rotatable shaft 5, and a lever 6 is connected to one end of the shaft 5 (in front of FIG. 1B).
Reference numeral 7 denotes a spring which constantly urges the lever 6 in the direction in which the fuel control valve 4 is closed. An accelerator wire (not shown) interlocking with an accelerator pedal is connected to the lever 6, and the movable end of the lever 6 moves in the direction of arrow A according to the accelerator opening operated by the driver, and the fuel control valve opens the accelerator opening. It is configured to open in proportion to. In addition, 8 is a stopper, which engages with one end 6a of the lever 6 and is connected to the fuel control valve 4
Determine the fully closed position of.

Reference numeral 9 denotes a throttle valve provided in the intake passage 2, which is attached to a rotatable shaft 10 and controls the intake air amount. A lever 11 is coupled to one end (front side of FIG. 1B) of the shaft 10, and a sector gear 12 shown in FIG. 1C is coupled to the other end (rear end) thereof. 13 is an electric actuator (motor) attached to the body of the gas mixer 1,
A pinion 14 mounted on the rotary shaft of this electric actuator meshes with the sector gear 12. Reference numeral 15 is a spring, which constantly biases the lever 11 in the direction in which the throttle valve 9 opens. Reference numeral 16 is a lever loosely fitted to the one end of the shaft 10, and its movable end is connected to the lever 1 via a link 17.
6 is connected to one end 6a. Further, the other end 16a of the lever 16 engages with the movable end of the lever 11, and the movable end of the lever 11 is moved by the spring 15 as shown in FIG.
Thus, it is restricted to try to rotate clockwise about the shaft 10. In other words, the fuel control valve 4 opens in proportion to the throttle opening operated by the driver, and the lever 16 is moved through the link 17 and in conjunction with the fuel control valve 4.
When rotated clockwise in (b), the other end 16 of the lever 16 is rotated.
Following a, the lever 11 moves by the force of the spring 15 to open the throttle valve 9 to an opening corresponding to the accelerator opening.
At this time, when the engine is in a light load state, the electric actuator 13 is de-energized and rotates following the opening of the throttle valve 9 by the force of the spring 15. The urging force of the spring 15 is set to be smaller than the urging force of the spring 7 in the direction of closing the fuel control valve 4.

Reference numeral 18 denotes a stopper which engages with the movable end of the lever 11 to determine the fully closed position of the throttle valve 9. FIG. 2 shows a state in which the fuel control valve 4 is opened to a certain extent in proportion to the accelerator opening degree, and the throttle valve 9 is opened to a certain extent in conjunction with this. 1 shows the fuel control valve 4
Both the throttle valve 9 and the throttle valve 9 are closed.

The electric actuator 13 is not energized during a light load, that is, during the period shown in FIGS. 1 and 2, but is operated by the controller (microcomputer) 19 shown in FIG. It In FIG. 1 (d),
The controller 19 includes a rotation sensor 20 that rotates to convert the engine speed into an electric signal, a fuel control valve opening sensor 21 that converts the opening of the fuel control valve 4 into an electric signal, and an air-fuel ratio provided in the exhaust passage of the engine. Sensor (O ₂ sensor) 2
2, and signals from the engine cooling water temperature sensor 27 and the like are input to operate the electric actuator (motor) 13 according to the operating conditions of the engine. A not-shown engine exhaust passage is provided with a well-known three-way catalyst for purifying exhaust gas, and when the air-fuel ratio of the combined air-fuel mixture supplied from the gas mixer 1 to the engine is the theoretical air-fuel ratio. Purifies exhaust gas most effectively.

As described above, when the load is light, the controller 19 does not energize the electric actuator 13. The throttle valve 9 is linked to the fuel control valve 4 via the link 17. In this state, the lever ratio between the levers 6 and 16 is set so that the throttle valve 9 opens more than the opening required for the air-fuel ratio of the air-fuel mixture supplied to the engine to become the stoichiometric air-fuel ratio. By doing so, the intake air amount of the intake passage 2 is controlled so that the air-fuel mixture has a lean air-fuel ratio in a range that is below the exhaust emission regulation value and does not cause misfire.

FIG. 5 shows that the controller 19 determines the lean burn region as the region below the curve B. Then, from the state of FIG. 2, when the accelerator opening becomes larger, the fuel control valve 4 opens to the opening shown in FIG. 3, and when the vehicle is in a load operation state above a certain level where traveling with a lean air-fuel ratio is impossible, From the signals of the fuel control valve opening sensor 21 and the rotation sensor 20 at this time, the controller 1 indicates that the operating condition of the engine has moved above curve B in FIG.
9 makes a judgment and energizes the electric actuator 13 to operate the throttle valve 9 in the closing direction against the spring 15. That is, the opening of the throttle valve 9 is limited to reduce the intake air amount. Then, the intake air amount is feedback-controlled by the signal of the air-fuel ratio sensor (O ₂ sensor) 22 to maintain the air-fuel mixture at the stoichiometric air-fuel ratio.

As described above, the lever 11 is connected to the throttle valve 9
From the fully closed state (Fig. 1 (b)), the operating angle θ of the lever 16
It is operable between. 2 (a) and 2 (b) show a lean air-fuel ratio state with the accelerator open, and FIGS. 3 (a) and 3 (b) show a stoichiometric air-fuel ratio state with the accelerator open. 4A and 4B show the stoichiometric air-fuel ratio state when the accelerator is fully opened.

FIGS. 6A, 6B and 7 show a second embodiment of the present invention, which corresponds to the second invention. In this second embodiment, the electric actuator 13A directly operates the throttle valve 9 in all load regions of the engine. Therefore, unlike the first embodiment, no link or lever 16 for interlocking the fuel control valve 4 and the throttle valve 9 is provided. The rotary shaft of the electric actuator 13A is the shaft 10 of the throttle valve 9.
It is directly connected to. As shown in FIG. 7, the controller (microcomputer) 19A has a rotation sensor 20, a fuel control valve opening sensor 21, an air-fuel ratio sensor (O ₂ sensor) 22, and an engine cooling water temperature, as in the first embodiment. Although the signals of the sensor 27 and the like are input, the operation of operating the electric actuator (motor) 13A by determining the operating conditions of the engine according to these input signals is somewhat different from that of the first embodiment.

First, the controller 19A determines whether the engine load condition corresponds to the lean burn region or the stoichiometric air-fuel ratio region with the curve B of FIG. 5 as a boundary, which is similar to the first embodiment. However, as a result of the determination, in both the lean combustion and stoichiometric air-fuel ratio combustion regions, the air amount is adjusted by the throttle valve 9 so that a predetermined air-fuel ratio is achieved by the signal from the air-fuel ratio sensor (O ₂ sensor) 22. The air-fuel ratio is feedback-controlled by controlling.

As the air-fuel ratio sensor used in the above embodiment, a normal O ₂ sensor which reacts stepwise near the stoichiometric air-fuel ratio is the most suitable in the first embodiment, but in the second embodiment. It is preferable to use a sensor that linearly detects the oxygen concentration in the exhaust gas corresponding to the air-fuel ratio over the range from the lean air-fuel ratio to the stoichiometric air-fuel ratio. As this type of sensor, an O ₂ sensor (lean-mixture sensor) is well known in which a voltage is applied to a zirconia solid electrolyte to promote the movement of oxygen ions inside, and the oxygen ions are detected as a change in current.

[0018]

Since the air-fuel ratio control system for a gas fuel engine according to the present invention is constructed as described above, the accelerator opening and the fuel amount are proportional to each other, so that the acceleration force desired by the driver can be obtained. Since the air amount does not affect the drivability, the degree of opening of the second throttle valve (5) is suddenly changed at the time of acceleration to suddenly change the air-fuel mixture from the lean air-fuel ratio to the stoichiometric air-fuel ratio, thereby preventing deterioration of exhaust emission. it can.
As a result, both drivability and exhaust emission can be improved.

[Brief description of drawings]

FIG. 1 is a first embodiment of the present invention, (a) is a longitudinal sectional view of a gas mixer, (b) is a front view of the gas mixer, (c).
Is a view of a part of the gas mixer shown in FIG.
(D) is a block diagram of an electric system.

2A is a view showing a different aspect of the front view of FIG. 1B, and FIG. 2B is a view of a part of FIG.

FIG. 3A is a view showing a different aspect of the front view of FIG. 1B, and FIG. 3B is a view of a part of FIG.

4A is a view showing a different aspect of the front view of FIG. 1B, and FIG. 4B is a view of a part of FIG.

FIG. 5 is a diagram showing the relationship between the engine speed and the opening of the fuel flow rate control valve 4, for explaining the switching between the lean burn region and the stoichiometric air-fuel ratio region in the present invention.

6 (a) is a vertical sectional view of the gas mixer, and FIG. 6 (b) is a front view of the gas mixer according to the second embodiment of the present invention.

FIG. 7 is a block diagram of an electric system according to a second embodiment of the present invention.

[Explanation of symbols]

2 ... Intake passage, 3 ... Fuel passage, 4 ... Fuel control valve, 9 ... Throttle valve, 13, 13A ... Electric actuator, 22
… Air-fuel ratio sensor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location F02M 21/02 301 J 311 D

Claims (2)

[Claims] 1. A three-way catalyst for purifying exhaust gas and an air-fuel ratio sensor are provided in an exhaust passage to perform lean combustion at light load, ideal air-fuel ratio combustion in other regions, and at least ideal air-fuel ratio combustion. At times, in an air-fuel ratio control device for an internal combustion engine that uses a gaseous fuel to perform feedback control so that an air-fuel mixture has a predetermined air-fuel ratio by a signal from the air-fuel ratio sensor, the fuel is adjusted to a value proportional to the accelerator opening operated by the driver. A fuel passage having a fuel control valve for controlling the flow rate, a throttle valve for controlling the intake air amount in conjunction with the fuel control valve, and an electric actuator for limiting the opening of the throttle valve are provided, and at the time of light load By interlocking the throttle valve with the fuel control valve, the intake air amount is controlled to a lean air-fuel ratio in a range where exhaust emission is below a regulation value and does not cause misfire. At the same time, when the vehicle is in a load range where traveling with a lean air-fuel ratio is impossible, an electric actuator is operated by a signal from the air-fuel ratio sensor to limit the opening of the throttle valve to control the air-fuel mixture to the stoichiometric air-fuel ratio. An air-fuel ratio control device for a gas fuel engine, characterized in that 2. A three-way catalyst for purifying exhaust gas and an air-fuel ratio sensor are provided in the exhaust passage to perform lean combustion at light load, ideal air-fuel ratio combustion in other regions, and at least ideal air-fuel ratio combustion. At times, in an air-fuel ratio control device for an internal combustion engine that uses a gaseous fuel to perform feedback control so that an air-fuel mixture has a predetermined air-fuel ratio by a signal from the air-fuel ratio sensor, the fuel is adjusted to a value proportional to the accelerator opening operated by the driver. A fuel passage having a fuel control valve for controlling the flow rate, a throttle valve for controlling the intake air amount in the intake passage, and an electric actuator for driving the throttle valve are provided, and the air-fuel ratio is adjusted according to the load state of the engine. The electric actuator is operated to control the intake air amount to a predetermined lean air-fuel ratio and stoichiometric air-fuel ratio by a signal from the sensor. Air-fuel ratio control system of the gaseous fuel engine according to symptoms.