JPH0684736B2 - Air-fuel ratio controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device, and in particular, during deceleration operation of an internal combustion engine, an air-fuel ratio correction value corresponding to a predetermined engine speed range. Is changed to a predetermined value, and the air-fuel ratio correction value is used to control the operation of the control valve to adjust the supply amount of bleed air to improve the operating performance during re-acceleration after deceleration, and to improve the exhaust purification performance and The present invention relates to an air-fuel ratio control device that can improve fuel efficiency.

[Prior Art] In an internal combustion engine for a vehicle, the fluctuations in the running speed of the vehicle, that is, the engine speed and the load are extremely large, and in various operating states in which these two fluctuation factors are combined, low fuel consumption and low harmful emissions are produced. Performance of gas etc. is required. Therefore, it is necessary to appropriately control the air-fuel ratio of the internal combustion engine in various operating states of the internal combustion engine.

In order to properly control this air-fuel ratio, a solenoid valve that is a control valve should be used to adjust the bleed air supply amount by the air-fuel ratio correction value determined by the output signal state from the exhaust sensor that detects the components in the exhaust gas. A feedback type air-fuel ratio control device is used that controls the air-fuel ratio by adjusting the bleed air adjustment amount in order to obtain the best combustion state for the above-mentioned various operating states by controlling the operation. There is.

An example of such an air-fuel ratio control device is disclosed in JP-A-60
-111033. The one described in this publication is provided with a main passage and a slow passage that communicate with the float chamber of the carburetor, and a main system solenoid valve that is a control valve that adjusts the amount of bleed air supplied to the main passage and the slow passage. Slow solenoid valves are provided, solenoids for operating these solenoid valves are provided, and the solenoid valves are operated and controlled by the air-fuel ratio correction signal voltage which is the air-fuel ratio correction value determined by the output signal state of the exhaust sensor. Feedback control of the air-fuel ratio. The above air-fuel ratio correction value is the duty ratio to the solenoid. This duty ratio is in the range of 0% to 100%. When the duty ratio is 0%, the solenoid closes the main air bleed passage and the slow air bleed passage completely. Also, fully open the slow air bleed passage.

Further, the carburetor is provided with a fuel cut device during deceleration. This fuel cut device has a cut solenoid valve that opens and closes the slow port, and temporarily shuts off the slow port by the cut solenoid valve at the time of deceleration to stop the supply of the slow system fuel. The cut solenoid valve is installed on the downstream side of the solenoid that adjusts the supply amount of the bleed air, that is, on the intake passage side.

Further, as an air-fuel ratio control device, there is one disclosed in Japanese Patent Publication No. 59-16090. In the one described in this publication, the integral value of the integrating means is held in the set specific operating state of the internal combustion engine, and the integral value is reduced by the first amount when the internal combustion engine is in the deceleration state or the idling state. While the value is generated as an integrated output, a value obtained by increasing the integrated value by the second amount is generated as an integrated output in the acceleration state, and the air-fuel ratio is controlled according to the integrated output.

[Problems to be Solved by the Invention] In a conventional air-fuel ratio control device, a control signal value for operating a cut solenoid valve and an air-fuel ratio correction value for operating a solenoid valve are used during deceleration operation of an internal combustion engine. Was clamped (held) to a constant value to control the air-fuel ratio. At this time, when the air-fuel ratio correction value is set to a large value, that is, when it is clamped to the 100% side, the generation of CO and THC, which are exhaust harmful components, is reduced and the fuel consumption rate is reduced.

However, even if the engine speed is constantly lowered and the fuel cut is released, as shown in FIGS. 6 and 7, a fuel following delay occurs at the time of reacceleration after deceleration due to factors such as shift up, and the fuel supply is reduced. Since the amount of fuel consumed decreases and the air-fuel ratio shifts to the lean side, there is a problem that a malfunction such as an engine stall occurs and driving performance deteriorates.

In order to prevent the deterioration of the driving performance, the air-fuel ratio correction value may be clamped to a small value, that is, to the 0% side, but the exhaust purification performance or the fuel consumption deteriorates as described above, and conflicting inconveniences occur. Therefore, improvement was desired.

[Object of the invention] Therefore, an object of the present invention is to eliminate the above-mentioned inconveniences.
A throttle switch that turns on by detecting the open / closed state of the throttle valve during deceleration operation of the internal combustion engine is provided, and the engine speed becomes the set engine speed from the start of deceleration operation of the internal combustion engine when the throttle switch is turned on. In the first rotation range until it decreases, the air-fuel ratio correction value is kept constant at a value before the start of deceleration operation of the internal combustion engine, the control valve is operated, and the engine speed drops below the set engine speed. The air-fuel ratio correction value is held in the rotation range so as to be gradually changed to a smaller value in response to the lowering state of the engine rotation speed, and the control valve is operated so that the engine rotation speed is the second rotation speed.
In the third rotation range which is lower than the rotation range and higher than the idling speed, a control unit for operating the control valve by holding the air-fuel ratio correction value at a preset set air-fuel ratio correction value at which engine stall does not occur is provided. By providing this, it is possible to avoid the occurrence of a fuel following delay at the time of reacceleration after deceleration, prevent malfunctions such as engine stalls, improve operating performance, and improve exhaust purification performance and fuel efficiency. It is to realize a fuel ratio control device.

[Means for Solving Problems] In order to achieve this object, the present invention provides a main passage and a slow passage that communicate with the carburetor float chamber, and supplies the bleed air to the main passage and the slow passage. In the air-fuel ratio control device for controlling the air-fuel ratio by controlling the air-fuel ratio by the air-fuel ratio correction value determined by the output signal state of the exhaust sensor, a control valve for adjusting the A throttle switch is provided which is turned on by detecting the open / closed state of the throttle valve. The first time from the start of deceleration operation of the internal combustion engine when the throttle switch is turned on until the engine speed drops to the set engine speed. In the rotation range, the air-fuel ratio correction value is kept constant at a value before the start of deceleration operation of the internal combustion engine to operate the control valve, and the engine speed falls below the set engine speed. In the second rotation range, the air-fuel ratio correction value is held so as to gradually change to a smaller value in response to the lowering state of the engine rotation speed, and the control valve is operated to change the engine rotation speed to the second rotation speed. A control unit for operating the control valve by holding the air-fuel ratio correction value at a predetermined set air-fuel ratio correction value at which engine stall does not occur in the third rotation range which is lower than the range and higher than the idling speed. Is provided.

[Operation] According to the configuration of the present invention, during deceleration operation of the internal combustion engine,
Since the air-fuel ratio correction value to the control valve is changed to a predetermined value in accordance with the predetermined first, second, and third rotation speed regions of the engine speed to adjust the supply amount of bleed air, Always adjust the mixing amount according to the predetermined engine speed range,
At the time of reacceleration after deceleration, fuel is supplied to the intake passage with an appropriate amount of air mixed in, thereby avoiding the occurrence of fuel following delay and preventing malfunctions such as engine stalls and improving operating performance. At the same time, it is possible to improve exhaust gas purification performance and fuel efficiency.

Embodiments Embodiments of the present invention will be described in detail and specifically below with reference to the drawings.

1 to 8 show an embodiment of the present invention. In the figure, 2 is an air-fuel ratio control device, 4 is an internal combustion engine, 6 is a carburetor, 8 is an intake passage, 10 is a throttle valve, and 12 is a three-way catalyst. The air-fuel mixture supplied to the internal combustion engine 4 is adjusted by the carburetor 6. The adjustment of the air-fuel mixture in the vaporizer 6 is
Solenoid valves 16 and 16 which are control valves whose operation is controlled by a control unit 14 mainly including a CPU (central processing unit) 24 described later.
Done through.

The control unit 14 includes a comparison circuit 20 that compares an output signal input from the exhaust sensor 18 provided in the exhaust system with a reference value, an input circuit 22 that receives signals from various sensors that detect the engine operating state as inputs, and CPU24 which processes the signal input from the input circuit 22 and the solenoid valves 16, 16 based on the processing of this CPU24.
And a drive circuit 26 for outputting an air-fuel ratio correction value which is an air-fuel ratio correction signal of the control unit 14.

The input circuit 22 has a throttle switch 28 which is turned on by detecting the open / closed state of the throttle 10 during deceleration operation of the internal combustion engine 4.
And the ignition coil 30 that detects the engine speed. The throttle switch 28 functions as an idle switch, and turns on when the throttle valve 10 is in the idle opening state, and turns off when the throttle valve 10 is at the idle opening or more. It should be noted that the input circuit 22 can be connected to a detection means for detecting another engine operating state.

When the internal combustion engine 4 is in the decelerating operation, the control unit 14 causes the solenoid valve 16 to correspond to predetermined first, second, and third engine speed ranges of the engine speed.
The air-fuel ratio correction value is clamped (held) to a predetermined value.

The air-fuel ratio correction value for the solenoid valve 16 described above is determined by the output signal state of the exhaust sensor 18, and is a duty ratio for operating the solenoid valve 16. This duty ratio is in the range of 0% to 100% as shown in FIG.
The solenoid valve 16 fully closes the main system bleed passage (not shown) and the slow system air bleed passage (not shown), and the solenoid valve 16 sets the solenoid valve 16 to 100%. Fully open the bleed passage. In this way, the operation of the solenoid valve 16 is controlled by the air-fuel ratio correction value (duty ratio),
The amount of bleed air supplied to the main passage 34 and the slow passage 36 is adjusted. However, when the duty ratio is 100%, the solenoid valve 1
Even if 6 is activated and the above-mentioned main and slow air bleed passages are fully open, the main passage 34 and the slow passage
The amount of fuel from 36 does not become zero, but a predetermined amount of fuel is supplied to the intake passage 8. This fuel amount is, for example, the 8th
As shown in the figure, the setting can be changed.

Further, the carburetor 6 is provided with a fuel cut device (not shown) for deceleration. This fuel cut device has a cut solenoid valve that opens and closes the slow port, and temporarily shuts off the slow port by the cut solenoid valve at the time of deceleration to stop the supply of the slow system fuel. The cut solenoid valve is installed on the downstream side of the solenoid valve 16 for adjusting the supply amount of the bleed air, that is, on the intake passage 8 side. This fuel cut device
A slow port (not shown) is fully closed when fuel is cut. At this time, fuel does not flow into the main passage 34 because the throttle valve 10 is fully closed. However, the fuel flows into the intake passage 8 though a little from the slow port.

In the control unit 14, as shown in the attached table, the "high speed range" is the first speed range from the start of deceleration operation of the internal combustion engine 4 with the throttle switch 28 turned on until the engine speed falls to the set engine speed. In the case of “,” the air-fuel ratio correction value is kept constant (clamped) at a value before deceleration start of the internal combustion engine 4 (shown in a of FIG. 5), the solenoid valve 16 is operated, and the engine speed is changed. Is the second speed range, which is lower than the set engine speed, "medium"
In the case of, the air-fuel ratio correction value is held linearly (collinearly) with the engine speed, that is, to be gradually changed to a value (indicated by b in FIG. 5) corresponding to the state of decrease in the engine speed. Then, the solenoid valve 16 is actuated, and when the engine speed is "low" which is the third speed range lower than the second speed range and higher than the idling speed, engine stall does not occur. Set air-fuel ratio correction value (shown in Fig. 5c)
That is, that is, the solenoid valve 16 is operated with the air-fuel ratio correction value held at 0% as shown in FIGS.

Further, as shown in FIG. 3, the vaporizer 6 has a float chamber 32. In the float chamber 32, the main passage 34 and the slow passage 36 are provided in communication with each other. The front ends of the main passage 34 and the slow passage 36 face the intake passage 8. In FIG. 2, reference numeral 38 is an ignition switch, 40 is a fuse, and 42 is a battery.

Next, the operation of this embodiment will be described based on the flowchart of FIG.

When the program of the control unit 14 starts (step 102) during deceleration operation of the internal combustion engine 4, first, the ON / OFF state of the throttle switch 28 is detected (step 10).
Four).

Then, in step 106, the throttle switch 28
Judge whether or not is ON.

If step 106 is NO, it means that the operation is other than idle operation, and therefore the process returns to step 104.

If YES at step 106, the internal combustion engine 4 is decelerated.
Becomes the idle operation state, and the engine speed (Ne) is detected by the signal state of the ignition coil 30 (step 10
8). During the idle operation of the internal combustion engine 4, the air-fuel ratio feedback control is stopped and the fuel cut is executed.

Then, it is determined whether the engine speed is equal to or higher than the set engine speed Nα (step 110).

If YES at step 110, at step 112, the air-fuel ratio correction value is constantly clamped to the same a value as the DL value before the start of deceleration operation of the internal combustion engine 4 (the first rotation range in FIG. 5). Rotation range A).

As a result, as shown in FIG. 6, conventionally, for example, during deceleration for a short time such as shift-up, that is, during re-acceleration after deceleration, a fuel following delay (shown by a broken line) occurs and the air-fuel ratio is increased. However, there was a problem that the operating performance was deteriorated due to a shift to the lean side, a low engine speed, and an engine stall.

However, according to this embodiment, the air-fuel ratio correction value is clamped to the value a before the start of deceleration operation of the internal combustion engine 4, and the solenoid valve 16 is operated to adjust the bleed air supply amount. Since the amount of air mixed in the slow passage 36 on the upstream side of the cut solenoid valve is adjusted in the first rotation range A of the engine speed, when the fuel is re-accelerated after deceleration, the fuel is introduced in an appropriate amount in the intake passage. Supply to 8
At the time of re-acceleration after deceleration, as shown in Fig. 6, the occurrence of a fuel following delay is avoided, engine stalls and other problems are prevented, and driving performance is improved, while exhaust gas purification performance and fuel efficiency are improved. Can be planned.

When step 110 is NO, it is determined whether or not the engine speed Nβ is lower than the set engine speed Nα (step 114).

If step 114 is YES, the air-fuel ratio correction value is clamped so as to be changed to a value b that is linear to the engine speed, that is, a value that gradually decreases in response to the state of decrease in the engine speed, and the solenoid valve 16 is changed. It is operated to adjust the supply amount of bleed air (step 116). That is, b = α × Ne (2 in FIG. 5)
The rotation range B, which is the rotation range, is shown). In this step 116, the air-fuel ratio correction value is clamped to the engine speed and the linear b value, so that when the engine speed is high, the air-fuel ratio correction value is made large (duty ratio 100% side) and the solenoid valve 16 is operated. In addition to improving exhaust purification performance and fuel efficiency,
When the engine speed is low, the solenoid valve 16 is operated with the air-fuel ratio correction value set to a small value (duty ratio 0% side) to prevent the occurrence of problems such as engine stall.

When step 114 is NO, the engine speed N
It is determined whether or not the engine speed Nγ is lower than β and higher than the idling speed N _ID (step 118).

If step 118 is YES, in step 120, the air-fuel ratio correction value is clamped to a c value which is a predetermined set air-fuel ratio correction value at which engine stall does not occur, for example, a duty ratio of 0% (fifth ratio). (Indicated by rotation range C, which is the third rotation range in the figure).

If step 118 is NO, the idling feedback (ID F / B) control of the air-fuel ratio is performed in step 122, and the process jumps to step 104 to set the air-fuel ratio correction value L during idling operation (see FIG. 5). .

As described above, in the decelerating operation state of the internal combustion engine 4, the feedback control is stopped, the fuel is cut, the air-fuel ratio correction value is changed corresponding to the predetermined engine rotation range, and the solenoid valve 16 is operated and controlled. By adjusting the amount of bleed air and controlling the air-fuel ratio, the air-fuel ratio correction value is controlled to a large value in order to improve the exhaust gas purification performance in the high engine speed and medium speed regions, which greatly contributes to the exhaust gas purification performance. Further, in the low rotation speed range, the air-fuel ratio correction value can be set to 0%, for example, to prevent the occurrence of troubles such as engine stall.

The reason why the air-fuel ratio correction value is controlled to a value b that is linear with the engine speed in the middle speed range of the engine speed is as follows. That is, if the speed is made constant by the integral control and the speeds do not match depending on the operating conditions, for example,
As shown in FIG. 7, when racing (high-speed idling) occurs, a fuel following delay occurs, and a problem such as engine stall occurs, so that this problem is prevented. Therefore, in this embodiment, when the internal combustion engine is in the decelerating operation state, the air-fuel ratio correction value is changed corresponding to the predetermined first, second, and third engine speed regions of the engine speed, and the exhaust gas purification performance and It is possible to improve fuel efficiency and driving performance.

[Effects of the Invention] As is apparent from the above detailed description, according to the present invention,
A throttle switch that turns on by detecting the open / closed state of the throttle valve during deceleration operation of the internal combustion engine is provided, and the engine speed becomes the set engine speed from the start of deceleration operation of the internal combustion engine when the throttle switch is turned on. In the first rotation range until it decreases, the air-fuel ratio correction value is kept constant at a value before the start of deceleration operation of the internal combustion engine, the control valve is operated, and the engine speed drops below the set engine speed. In the rotation range, the control valve is operated by keeping the air-fuel ratio correction value gradually changing to a smaller value in response to the lowering state of the engine rotation speed, and the engine rotation speed is lower than the second rotation range. In the third rotation speed region higher than the idling speed, the control unit that operates the control valve by holding the air-fuel ratio correction value at a predetermined set air-fuel ratio correction value at which engine stall does not occur is provided. The amount of air The engine speed is adjusted according to a predetermined rotation range, and when re-accelerating after deceleration, the fuel is supplied to the intake passage with an appropriate amount of air mixed in, thereby avoiding the occurrence of a fuel following delay, It is possible to prevent malfunctions such as stalls and improve driving performance, and also improve exhaust purification performance and fuel efficiency.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention, FIG. 1 is a system configuration diagram of an air-fuel ratio control device, FIG. 2 is a block configuration diagram of the air-fuel ratio control device, and FIG. 3 is a schematic sectional view of a carburetor. FIG. 4 is a flow chart of the air-fuel ratio control, FIGS. 5 to 7 are time charts of the air-fuel ratio control, and FIG. 8 is a diagram showing the relationship between the air-fuel ratio correction value and the air-fuel ratio. In the figure, 2 is an air-fuel ratio control device, 4 is an internal combustion engine, 6 is a carburetor, 8 is an intake passage, 10 is a throttle valve, 14 is a control unit, 16 is an electromagnetic valve, 18 is an exhaust sensor, 24 is a CPU, 28 Is a throttle switch, 30 is an ignition switch, 32 is a float chamber,
34 is the main passage and 36 is the slow passage.

Claims (1)

[Claims] 1. A main passage and a slow passage communicating with a carburetor float chamber are provided, and a control valve for adjusting the amount of bleed air supplied to the main passage and the slow passage is provided, which is determined by an output signal state of an exhaust sensor. An air-fuel ratio control device for controlling the air-fuel ratio by operating the control valve according to the air-fuel ratio correction value to be provided, is provided with a throttle switch that is turned on by detecting the open / closed state of the throttle valve during deceleration operation of the internal combustion engine. , The air-fuel ratio correction value is set in the deceleration operation of the internal combustion engine in the first rotation range from the start of the deceleration operation of the internal combustion engine when the throttle switch is turned on until the engine speed decreases to the set engine speed. The control valve is operated with the value before the start being kept constant, and the second rotation speed range in which the engine speed is lower than the set engine speed is set in correspondence with the state of decrease of the engine speed. The control valve is operated by holding the air-fuel ratio correction value so as to be gradually changed to a smaller value, and the engine rotation speed is lower than the second rotation speed range and higher than the idling speed in the third rotation speed range. An air-fuel ratio control device comprising: a control unit for operating the control valve by holding an air-fuel ratio correction value at a preset set air-fuel ratio correction value at which engine stall does not occur.