JPH0777092A - Method and device for controlling air-fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE:To shorten a response time and to perform stable control close to target value by a method wherein when a fluctuation in the load of an internal combustion engine is produced, and before a lapse of a set time, a control distance is shortened to control an air-fuel ratio and meanwhile, after a lapse of the set time, the control distance is lengthened to control air-fuel ratio. CONSTITUTION:A gas passage 2, an air passage 3, and a mixer 17 are disposed in the feed passage 1 of a gas engine E to drive a load L, and a bypass valve 5 is disposed in the bypass passage 4 of the mixer 17. In this case, a load sensor 7 is disposed to the gas engine E and a rotation pickup 9 is disposed on an output shaft 8. The bypass valve 5 is driven by a control unit 10 through an actuator 5a based on each detecting signal to control an air-fuel ratio. Namely, in a CPU 11, when a fluctuation in a detecting load is produced, before a lapse of a set time stored at a map 12, a control distance is shortened and an air-fuel ratio is controlled. Meanwhile, after a lapse of the set time, the control distance is lengthened to control an 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 method and apparatus for an internal combustion engine such as a gas engine or a diesel engine.

[0002]

2. Description of the Related Art Conventional air-fuel ratio control of a gas engine is mainly open control in which the air-fuel ratio is systematically set based on a preset map or the like when the load changes. In the feedback control, the control interval and the proportional gain are kept constant.

[0003]

However, if the control interval is kept constant, the following problems occur. That is,
When the control interval is shortened, the response speed becomes faster, but there is a problem that hunting occurs after reaching the numerical value (target value) corresponding to the changed load. On the contrary,
If the control interval is lengthened, as shown in FIG. 5, it stabilizes after reaching the numerical value (target value) corresponding to the changed load, but the response time TR from the current value VM to the target value VT becomes long. . Further, when the current value VM exceeds the target value VT, it takes time to return to the target value, so the response time becomes longer.

Further, if the proportional gain is made constant, the following problems occur. That is, if the proportional gain is increased, the response speed is increased because the control amount for one time is increased, but hunting occurs after reaching the numerical value (target value) corresponding to the changed load. On the other hand, when the proportional gain is small, the control amount stabilizes after reaching the target value, but since the control amount for one time is small, it takes a long time to reach the target value.

The present invention has been proposed in view of the above-mentioned problems of the prior art, and provides an air-fuel ratio control method for an internal combustion engine and an apparatus therefor which can shorten response time and perform stable control near a target value. It is intended to be provided.

[0006]

SUMMARY OF THE INVENTION An air ratio control method for an internal combustion engine according to the present invention includes a step of detecting a load of the internal combustion engine and a control interval shortened before a set time elapses when the detected load fluctuates. And a step of controlling the air-fuel ratio, and a step of controlling the air-fuel ratio by increasing the control interval after the set time.

Further, the air-fuel ratio control apparatus for an internal combustion engine according to the present invention uses load detecting means for detecting the load of the internal combustion engine, a bypass valve for changing the air-fuel ratio of the internal combustion engine, and a load detecting signal from the load detecting means. On the basis of the load fluctuation, the control interval is shortened up to the set time to control the air-fuel ratio, and the control interval is increased after the set time to control the air-fuel ratio.

Further, the air-fuel ratio control method for an internal combustion engine according to the present invention includes a step of detecting the load of the internal combustion engine, and if the detected load fluctuates, the air-fuel ratio is increased by increasing the proportional gain before the set time elapses. And a step of controlling the air-fuel ratio by reducing the proportional gain after the set time.

The air-fuel ratio control system for an internal combustion engine according to the present invention uses load detection means for detecting the load of the internal combustion engine, a bypass valve for changing the air-fuel ratio of the internal combustion engine, and a load detection signal from the load detection means. Based on the above, when there is a load change, the control unit includes a control means for increasing the proportional gain to control the air-fuel ratio before the set time elapses and for reducing the proportional gain after the set time to control the air-fuel ratio.

Prior to the step of controlling the air-fuel ratio by shortening the control interval or the step of controlling the air-fuel ratio by increasing the proportional gain when the control method of the present invention is performed, a map set in advance is set. It is preferable to execute the step (planning step) of setting the air-fuel ratio systematically based on the above.

In implementing the control device of the present invention,
Before the set time elapses, the control interval is shortened to control the air-fuel ratio or the proportional gain is increased to control the air-fuel ratio, and then the air-fuel ratio is set systematically based on a preset map etc. Preferably, means are included.

Further, as the internal combustion engine of the present invention, for example, a gas engine or the like is preferable.

[0013]

According to the present invention having the above-mentioned structure,
When the load fluctuates and the control target value fluctuates, first,
Until the set time elapses, the control interval is shortened or the proportional gain is increased to greatly change the control amount in a short time. Here, when the control interval is short or the proportional gain is large, the current value reaches the newly set target value in a short time, but hunting occurs or control becomes unstable after approaching the target value. There is a problem that becomes. Therefore, in the present invention, the control is changed after the set time elapses to increase the control interval or decrease the proportional gain. This stabilizes the control after the controlled variable approaches the target value.

In addition to this, it is more effective to change the control interval and the control gain together.

Thus, according to the present invention, the set time (preset on a case-by-case basis: the same applies hereinafter)
Since the control interval or the proportional gain changes before and after the passage of, the shortening of the target value reaching time and the stabilization of the control after reaching the target value can be achieved at the same time, which are not compatible with the conventional technique.

In the present invention, before the set time elapses, the control interval is shortened to control the air-fuel ratio, or the proportional gain is increased to control the air-fuel ratio. If the air-fuel ratio is set automatically (configured to execute the planning step), when the load fluctuates, first, it is possible to approach the target value within the safe side range using the map, etc.
It is possible to further shorten the time to reach the target value.
After executing such a planning step, the actuated state of the actuator is kept for a predetermined time to stabilize the rotation of the internal combustion engine.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. In the illustrated embodiment, feedback control uses the method disclosed in Japanese Patent Application No. 5-156684, that is, the method of controlling the air-fuel ratio based on the rotation fluctuation amount.

FIG. 1 shows an apparatus for carrying out the first and second methods.

A gas supply passage 1 of a gas engine E for driving a load L is connected to a gas supply passage 2 for a gas G, an air supply passage 3 for an air A, and a mixer 17 for mixing these. There is. A bypass passage 4 for bypassing the mixer 17 from the supply passage 2 is provided, a bypass valve 5 for adjusting the air-fuel ratio is provided for the bypass passage 4, and the intake passage 1 is provided with an engine speed. A throttle valve 6 for adjusting is provided.

On the other hand, the engine E is provided with a load sensor 7 as load detecting means, and the output shaft 8 is provided with a rotary pickup 9. And the rotary pickup 9
Is connected to the throttle valve 6 and, together with the load sensor 7, is connected to a control unit 10 which is a control means. Note that instead of detecting the load from the engine E, it is also possible to detect from the load side.

The control unit 10 is provided with a central processing unit (CPU) 11, a map 12 for intentionally setting an air-fuel ratio in the initial stage of control, and an actuator controller 13. The controller 13 drives the bypass valve 5. It is connected to the actuator 5a.

Next, the control mode will be described with reference to FIGS. 3 and 4.

The control unit 10 is provided with a map 12 for setting a planned air-fuel ratio in the initial stage of control in advance, and the central processing unit 11 stores a control interval and a set time To for changing the proportional gain. .

For control, the control unit 10
Detects the engine load from the load detection signal from the load sensor 7 during operation (step S1) (step S1).
2) Detect whether or not the load fluctuates (step S
3).

If there is no change in the load, the process returns to step S2. On the other hand, if the load fluctuates, map 1
2 outputs a control signal to the actuator 5a to control the opening of the bypass valve 5 and systematically approaches the target value VT within the safe side range (step S4: FIGS. 3 and 4). Next, after the opening degree of the bypass valve 5 is kept and waiting is made until the rotation of the internal combustion engine becomes stable (step S5:
3 and 4), the feedback control will be described.

In the feedback control, until the elapsed time T reaches the set time To (NO in step S6), the control interval Tc is set to the short control interval Tco, and the proportional gain K is set to the large proportional gain Ko. It is quickly changed to approach the target value VT (step S7: FIG. 3).
As shown in FIG. 4), the opening degree of the bypass valve 5 is controlled (step S10). When the time T reaches the set time To (YES in step S6), the control interval Tc is set to the long control interval Tc1, and the proportional gain K is set to the small proportional gain K1 to stabilize the control to the target value VT. (Step S9: FIG. 3 and FIG. 4), the bypass valve opening is controlled correspondingly (step S10), and then the process returns.

That is, when the current value VM of the rotation fluctuation amount is in a range apart from the target value VT, a planning step (step S4) is performed, and in addition, the control interval Tc is shortened and the proportional gain K is increased. By doing so, the current value VM approaches the target value VT as quickly as possible. Then, after the set time (in this embodiment, the total time from step S4 to step S6 YES) has elapsed, the control interval Tc is lengthened and the gain K is reduced to suppress hunting. It achieves stable control.

It should be noted that the illustrated embodiments are merely examples and are not intended to limit the technical scope of the present invention. For example, in the illustrated embodiment, only the gas engine is shown as the internal combustion engine, but it is also applicable to a diesel engine and other internal combustion engines.

[0029]

As described above, according to the present invention, the time required for the current value to reach the target value can be shortened, and stable control can be performed after reaching the target value. As a result, stable operation control is achieved even if the load on the internal combustion engine fluctuates.

Further, it is possible to suppress the rotational fluctuation of the internal combustion engine caused by changing the air-fuel ratio.

Further, when controlling the air-fuel ratio or the like by the rotational fluctuation, it is possible to prevent malfunction due to the fluctuation caused by changing the air-fuel ratio.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a signal for detecting a rotation speed.

FIG. 3 is a control flowchart.

FIG. 4 is a control timing chart.

FIG. 5 is a view corresponding to FIG. 4 according to a conventional method.

[Explanation of symbols]

 E ... Gas engine L ... Load LP ... Load detection signal To ... Set time VM ... Current value 1 ... Intake passage 2 ... Gas supply passage 3 ... Air supply passage 4 ... Bypass path 5 ... Bypass valve 5a ... Actuator 6 ... Throttle valve 7 ... Load sensor 8 ... Output shaft 9 ... Rotary pickup 10 ... Control unit 11 ...・ Central processing unit 12 ・ ・ ・ Map 13 ・ ・ ・ Actuator controller 17 ・ ・ ・ Mixer

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Claims (4)

[Claims] 1. A step of detecting a load of an internal combustion engine, a step of controlling an air-fuel ratio by shortening a control interval before a set time elapses when the detected load fluctuates, and a control after the set time. And a step of controlling the air-fuel ratio by increasing the interval, and a method of controlling the air-fuel ratio of the internal combustion engine. 2. A load detection means for detecting the load of the internal combustion engine, a bypass valve for changing the air-fuel ratio of the internal combustion engine, and a load detection signal from the load detection means. An air-fuel ratio control device for an internal combustion engine, comprising: a control means for controlling the air-fuel ratio by shortening the control interval and for controlling the air-fuel ratio by lengthening the control interval after the set time. 3. A step of detecting the load of the internal combustion engine, a step of increasing the proportional gain to control the air-fuel ratio before the set time elapses when the detected load fluctuates, and a step of proportionally after the set time. And a step of controlling the air-fuel ratio by reducing the gain, and a method of controlling an air-fuel ratio of an internal combustion engine. 4. A load detection means for detecting a load of an internal combustion engine, a bypass valve for changing an air-fuel ratio of the internal combustion engine, and a load change based on a load detection signal from the load detection means before a set time elapses. And a control means for controlling the air-fuel ratio by increasing the proportional gain and reducing the proportional gain after the set time to control the air-fuel ratio.