JPH0278764A - Air-fuel ratio controller for internal combustion engine of automobile - Google Patents

Abstract

PURPOSE:To prevent overheat of catalyser and improve drivability by controlling movement of an air bleed controller, according to difference between the present position and the target position of the air bleed controller and increasing (variation) ratio of an engine speed, when a specified high speed of the engine is judged. CONSTITUTION:A computing and control unit 8 transmits an output signal 10 to an air bleed controller 4 mounted on a fuel supply device 3, and controls air-fuel ratio of an internal combustion engine 1, based on input signals such as an air-fuel ratio signal 9 from an oxygen concentration sensor 5 fitted on an exhaust pipe 2 and an engine speed signal 7 detected from an ignition device 6. Further, a catalysis device 11 is arranged and provided on the exhaust pipe 2. In this case, when the engine speed reaches the specified high speed, moving speed of the air bleed controller 4 is controlled, according to difference between the present position and the target position of the air bleed controller 4 and variation ratio of the engine speed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an air-fuel ratio control device for an internal combustion engine for an automobile.

[Conventional technology]

An air-fuel ratio control device that senses the exhaust composition of an automobile internal combustion engine equipped with a carburetor and controls the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine to a substantially constant level is disclosed in Japanese Patent Publication No. 57-59905. There is.

By installing a solenoid valve in the air passage connected to the fuel passage, or by providing a bypass in the fuel passage and installing a solenoid valve in this bypass, this product can be operated at a temperature higher than the set temperature and a load lower than the set rotation speed. The above solenoid valve is turned on and off by air-fuel ratio feedback within the range,
It is possible to purify exhaust gas and improve fuel efficiency within the operating range, and to stop feedback control outside the operating range, and to open or close a part of the air passage or fuel passage that is opened and closed by the solenoid valve when the solenoid valve is stopped. This is an air-fuel ratio control device that increases the amount of fuel to produce a rich mixture.

[Problem to be solved by the invention]

In this conventional air-fuel ratio control device, when a high engine speed is detected and the solenoid valve is turned on or off in the direction of changing the air-fuel ratio to 'a' mixture.

The shock was 11 and the drivability deteriorated due to the rapid fluctuation of the air-fuel mixture due to the positional movement of the solenoid valve. Also, to prevent this shock, if the moving speed of the solenoid valve is slowed down,
It took a long time to create a rich mixture, which caused the inconvenience of overheating the catalyst device.

Therefore, the present applicant proposed a technique for feedback controlling the air flow rate to the slow system and main system of the carburetor using a stepping motor as shown in Japanese Patent Laid-Open No. 149558/1983. With this technology, an ideal air-fuel ratio can be obtained at all times, improving the performance of exhaust gas purification devices and improving drivability.

However, even in the above air-fuel ratio control device, it is necessary to enrich the air-fuel ratio to prevent overheating of the catalyst device, and feedback control is performed based on the air-fuel ratio signal from the exhaust composition sensor. If it is determined that the engine speed is high due to the input of one ignition signal,
The air-fuel ratio control device moves and stops the actuator to a position where a rich mixture is obtained. At this time, if there is a large difference between the actuator position immediately before the actuator moves to the stop position and the stop position, the sudden change in the air-fuel ratio due to actuator movement will cause a shock when the vehicle is running, worsening drivability and causing engine damage. When the rate of change (increase) in rotational speed is small, shocks and deterioration of drivability become noticeable.

Therefore, if the movement of the actuator was slowed down to prevent shock, since the amount of movement was large, it took time to move to the target position, and catalyst overheating became a problem.

SUMMARY OF THE INVENTION Therefore, the present invention provides an air-fuel ratio control device that can prevent overheating of the medium and improve drivability during high engine speeds.

[Means to solve the problem]

The air-fuel ratio control device for an automobile internal combustion engine of the present invention includes a fuel supply device that supplies a mixture of fuel and intake air to an automobile internal combustion engine, a needle valve that supplies air to the fuel supply device, and a needle valve. The difference between the current position of the actuator and the target position of the air bleed control device equipped with the actuator to be operated, the circuit that determines that the engine speed has reached the specified (set) high rotation speed, and the air bleed control device. A circuit that calculates and compares the difference with the specified (set) difference, and a circuit that calculates the rate of change in engine speed when the engine speed reaches the specified (set) high rotation speed,
The air bleed controller is equipped with circuits for comparing the magnitude of the rate of change with the set rate of change, and an arithmetic control device that outputs a control signal for the moving speed of the actuator of the air bleed control device in accordance with the output signals of these circuits.

[Effect]

When determining the high rotation speed specified by the arithmetic and control unit,
The current position of the actuator of the air bleed control device,
The difference between the position of the actuator that supplies the amount of air to obtain the target mixture (target position) and the rate of increase (change) in engine speed are calculated, and the amount of movement of the actuator to the target position is specified. is greater than or equal to the value of
Also, when the rate of increase in engine speed is large, shocks caused by changes in the air-fuel mixture do not pose a problem for vehicle operation.
It sends an output signal to the air bleed control device to move the actuator at high speed, rapidly changing the amount of air supplied to the fuel supply device, and rapidly changing the air-fuel ratio. Furthermore, under the same conditions, when the rate of increase in engine speed is small, the engine is sensitive to shocks caused by changes in the air-fuel mixture, so an output signal that moves the actuator at a low speed is output to change the air-fuel ratio at a low speed.

〔Example〕

An embodiment of the air-fuel ratio control 'A tn of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of the overall configuration of an automobile internal combustion engine,
The arithmetic control device 8 that controls the air-fuel ratio of the internal combustion engine 1 receives an air-fuel ratio signal 91 from the oxygen concentration sensor 5 attached to the exhaust pipe 2.
Based on input signals such as an engine rotational speed signal 7 detected from the ignition device 6, an output signal 10 is sent to the air bleed control device 4 attached to the fuel supply device 3 of the internal combustion engine 1;
Controls the air-fuel ratio of the internal combustion engine 1. Further, the exhaust pipe 2 is provided with a catalyst bag "y111" for purifying exhaust gas.

FIG. 2 is a sectional view showing details of the fuel supply device 3 and the air bleed control device 4. As shown in FIG.

The fuel supply device 3 includes an intake passage 31 that communicates with the air cleaner.
A choke valve 32 and a throttle valve 35 provided on a shaft 33 that rotates in response to the amount of depression of the accelerator pedal are disposed in the intake passage 31.

A large bench lily 34a and a small bench lily 34b are provided inside the intake passage 31, and the tip of the main nozzle 36 is opened inside the small bench lily 34b. The other end of the main nozzle 36 communicates with a fuel float chamber 37, and an amount of fuel corresponding to the amount of intake air passing through the small bench lily 34b, which changes depending on the opening degree of the throttle valve 35, is sucked out from the main nozzle 36.

The mixture becomes a mixture and is supplied to the engine 1.

An upper slow port 38b and a lower slow port 38a are opened in the vicinity of the throttle valve 35 of the intake passage 31, and supply fuel for the air-fuel mixture when the engine 1 is idling. This lower slow port 38a is provided with a throw adjustment screw 38c having a needle 38d at its tip, and the opening degrees of the lower slow ports 1 to 38a are adjusted by moving the needle back and forth.

The air bleed control device 4 has two needle valves inside and is covered with an airtight case 48.
The ends of the air passages 41a and 41b that communicate with the air cleaner are open to the case 48, and the air passages 44 and 45, which have one end open to the case 48, are communicated within the case 48, and are connected to the air inflow passages 42a and 43a. Become.

Inside the case 48, two needles 42 and 43 are disposed while being supported by a holder 46. Needle 4
2.43 are air flow passages 42a, 43a depending on their positions.
The opening area with the inlet is adjusted to adjust the amount of air flowing into the air passages 44, 45.

On the other hand, the outlet side of the air flow passage 42 a controlled by the needle 42 communicates with an air passage 44 , and the other end of the air passage 44 communicates with the main nozzle 36 . Therefore, an amount of air corresponding to the position of the needle 42 is sent to the main nozzle 36. That is, the mixture created by the intake air passing through the small bench lily 34b and the fuel from the main nozzle 36 is set to be a rich mixture, and the air (air bleed) is sent from the air bleed control device to the main nozzle 36. By controlling the amount of , it is possible to ensure the optimum air-fuel ratio for the operating condition of the engine 1.

Similarly, the outlet of the air flow passage 43a controlled by the needle 43 also communicates with the upper slow port 38b and the lower slow port 38a via the air passage 45.
The amount of air sent to 8a and 38b is controlled to ensure an optimal air-fuel ratio.

Figure 3 shows the details of the air bleed control device.
The book needles 42, 43 are supported by a holder 46, and a shaft 47 is rotatably inserted into the center of the holder 46. The shaft 47 is a rotating shaft of an actuator that moves the needles 42, 43 in the axial direction, and in the present invention, a stepping motor 49 is used as the actuator.

The stepping motor 49 is a known type whose rotation direction and rotation angle are controlled according to the input signal 10 from the arithmetic and control unit 8, and the rotation of the motor is controlled by a worm 491 provided on the rotation shaft.
The shaft 47, which is integrated with the worm 491, rotates and moves in the axial direction.

In response to this movement, the two needles 42 and 43 supported by the holder 46 move simultaneously in the axial direction.

As described above, the rotational movement speed of the stepping motor 49, which is an actuator that opens and closes the needle valve that controls the amount of air sent to the engine, requires a certain level of speed in order to improve the responsiveness of air-fuel ratio control.

In the air-fuel ratio control device configured as described above.

In the normal operating state of the engine 1, the arithmetic and control unit 8
Based on the air-fuel ratio signal 9 sent from the oxygen concentration sensor 5, the air bleed control device 4 is feedback-controlled to obtain the air-fuel ratio most suitable for the operating condition of the engine 1 at that time.

As described above, when the rotational speed of the engine 1 increases due to depressing the accelerator pedal or changing the engine load from the operating state of the engine 1.

The temperature of the catalyst device 11 for purifying exhaust gas of the engine 1 increases. In order to prevent the catalyst device 11 from overheating, it is necessary to make the air-fuel ratio of the air-fuel mixture rich (rich mixture ratio).

Therefore, when the arithmetic control unit 8 detects that the rotation speed of the doubler 7 from the ignition device 9 which detects the rotation speed of the engine 1 is higher than a certain specified rotation speed, the arithmetic and control unit 8 stops feedback control and controls the air flow so that the air-fuel ratio becomes rich. A signal 10 is sent to the stepping motor 49 of the bleed control device 4, and the stepping motor 49 is moved to adjust the opening degree of the needle valve to hold the stepping motor 49 at a position where the air-fuel ratio is rich (rich mixture ratio). .

At this time, the stepping motor which is the actuator
When the amount of movement of the stepping motor 9 is small, the movement speed of the stepping motor 49 can remain high without causing any inconvenience to the driving performance. However, when the amount of movement of the stepping motor 49 is large, moving the stepping motor 51 at high speed will cause a problem, especially in the engine rotation speed. If the rate of increase (change) is small, a shock may occur due to the rapid change in the air-fuel ratio, which may deteriorate drivability.

To prevent this shock, the stepping motor 4
If the moving speed of the stepping motor 49 is large and the rate of increase in engine speed is large, if the moving speed of the stepping motor 49 is set to a low speed, the stepping motor 49 will step to the target position to move the needles 42 and 43 to the optimum air bleed adjustment position. The disadvantage is that it takes a long time for the motor 49 to reach the motor 49, and that the catalyst is exposed to overheating conditions for a long time.

Therefore, in the present invention, the arithmetic and control device 8 is configured to instruct the air bleed control device 4 to determine the optimum moving speed of the stepping motor 49 based on the amount of movement of the stepping motor 49 and the rate of increase in engine speed.

Next, the arithmetic and control device 8 of the present invention will be explained.

The signals that enter the ECU (Electric Control Unit) of the arithmetic and control unit 8 are the engine rotation speed and the air-fuel ratio signal from the oxygen concentration sensor.

These are the vehicle speed, the position of the stepping motor, etc., and the rotational speed and moving speed of the stepping motor are determined based on these signals.

Figure 4 shows the relationship between the rate of increase in engine speed and the target position (hold position) of the stepping motor and the current position when the stepper motor position for obtaining the target mixture is set as the target position or hold position. This is a graph representing

Here, curve A in graphs (1), (2), and (3) is
Line B represents the engine rotation speed over time, and line B represents the moving position of the stepping motor over time.
b is a target position at which the stepping motor 49 is held under control. In each curve A, the engine speed reaches the speed determined by the ECU as a high engine speed NEHI, and the speed is still increasing.

When the difference ST between the position b1 of the stepping motor at the time when the judgment engine rotation speed NEHI is reached and the position ST of the target stepping motor is smaller than a certain set value (STC) [as shown in Fig. 4 (1)] → Stepping motor moves to the target position at high speed.

This is a case where the difference ST between the position b2 of the stepping motor at the time when the judgment engine speed is reached and the position of the target stepping motor is greater than a certain set value (STC), and there is an increase rate ΔNe2 of the engine speed. Set increase rate Δ
If it is larger than NE [as shown in FIG. 4 (2)] → the stepping motor moves to the target position at high speed.

When the difference ST3 between the position of the stepping motor at the time when the judgment engine speed is reached and the position of the J standard stepping motor is larger than a certain setting value (STC), and the rate of increase in engine speed ΔNe is greater than NE to a certain set rate of increase [as shown in Figure 4 (3)] -> The stepping motor moves to the target position at low speed.

That is, when the arithmetic and control device 8 determines that the engine speed is high, the difference between the current position of the stepping motor 49 and the target position for hold control, and the increase (change) in the engine speed.
When the amount of movement of the stepping motor 49 to the target position is above a certain value, and when the rate of increase in the engine speed is large, shocks due to changes in the air-fuel mixture will not cause problems in vehicle operation. In addition, the stepping motor 4 will rotate at a higher speed and the catalyst will become overheated.
9 at high speed to rapidly enrich the air-fuel ratio. When the rate of increase in engine speed is small, the vehicle is sensitive to shocks during operation, and there is plenty of time before the catalyst is exposed to overheating conditions, so even if the stepping motor 49 is rotated at a low speed, You can avoid shock in time.

This control form will be explained with reference to the control flowchart in FIG.

Starting from step 100, it is determined at step 110 whether a high engine speed has been reached.

If it is determined that the high engine speed has not been reached, No
Proceed to the circuit and finish with 145 steps.

If a high engine speed is determined, the process proceeds to step 120.

The current position of the stepping motor and [1
Determine whether the difference from the target position is larger or smaller than the set value. If it is smaller than the set value, the process goes to the No circuit, and the stepping motor issues a command to move at high speed in 140 steps.
Step #r.

If the difference between the current position and the target position of the stepping motor is larger than the set value at the 120th step, the step goes to Yesl path, and the step goes to 1.
The rate of increase in engine speed is determined in 30 steps. If the rate of increase is greater than the set rate of increase, the process goes to the Yes circuit and 14
At step 0, a command to move the stepping motor at high speed is issued, and the process ends at step 145.

If the rate of increase in engine speed is smaller than the set rate of increase at step 130, the program proceeds through the No circuit, and at step 150 a command is issued to move the stepping motor at a low speed, and the process ends at step 155.

The arithmetic and control device 8, which incorporates the control circuit as described above, converts the command from the control circuit into a signal 1o and sends it to the actuator of the air bleed control device. The actuator moves at low or high speed to a position where a specified air-fuel ratio is obtained.

When the rotation speed of the engine 1 becomes lower than the set rotation speed, normal feedback control is resumed.

〔Effect of the invention〕

The air-fuel ratio control device of the present invention can freely control the air-fuel ratio in stages, compared to conventional air-fuel ratio control devices that use electromagnetic valves to adjust the amount of air sent to the engine on and off.

In addition, the actuator that controls the air amount moves at a certain high speed in order to improve the responsiveness of air-fuel ratio control, but when the amount of movement of the actuator to the target position is large, the accuracy rate of the engine rotation speed decreases. If the actuator is small, changing the actuator at high speeds may deteriorate drivability due to shocks caused by sudden changes in the air-fuel ratio, and reducing the actuator speeds slowly to prevent shocks may cause catalyst overheating. Since the air-fuel ratio control device of the present invention determines the movement speed of the actuator in relation to the amount of movement of the actuator up to the 11 mark position and the rate of increase in engine speed, it simultaneously improves drivability and prevents catalyst overheating. It can be achieved.

That is, when the amount of movement of the actuator to the target position is large and the rate of increase in engine speed is large, overheating of the catalyst can be prevented by moving the actuator at high speed and rapidly enriching the air-fuel mixture. Furthermore, when the rate of increase in engine speed is small, shock is prevented by changing the air-fuel mixture at low speeds, thereby improving drivability.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the overall configuration of an automobile internal combustion engine. FIG. 2 is a sectional view of the fuel supply device and air bleed control device, FIG. 3 is a sectional view of the main part of the air bleed control device, and FIG. 4 is a graph showing the engine rotation speed and the step position of the stepping motor. FIG. 5 is a control flowchart. 1...... Internal combustion engine, 3...
・・・・・・Fuel supply device, 4・・・・・・・・・・・・
・Air bleed control device, 5...
Oxygen concentration sensor, 6... Ignition device, 7... Engine rotation sensor, 8
・・・・・・・・・・・・ Arithmetic control unit, 41.42・
・・・・・・・・・・・・Needle, 49・・・・・・・
...Stepping motor, 491...
... Warm. Patent applicant Aisan Kogyo Co., Ltd. Agent Patent attorney Yasuaki Suzuki (2 others) Figure 4

Claims (1)

[Claims] (1) a fuel supply device that supplies a mixture of fuel and intake air to an automobile internal combustion engine; an air bleed control device that includes a needle valve that supplies air to the fuel supply device; and an actuator that operates the needle valve; An engine rotation sensor installed in the engine's ignition system detects the rotation speed, an oxygen concentration sensor installed in the exhaust pipe, and an actuator is sent to the air bleed control device based on the input signal from the engine rotation sensor and the oxygen concentration sensor. In an air-fuel ratio control device for an internal combustion engine for an automobile, which includes an arithmetic and control device that outputs a control signal, the arithmetic and control device includes a circuit that determines that the engine speed has reached a specified high rotational speed, and an air bleed device. A circuit that calculates the difference between the current position of the actuator and the target position and compares the difference with a specified difference, and a circuit that calculates the rate of change in engine speed when the engine speed reaches a specified high speed. , an air-fuel ratio control for an internal combustion engine for an automobile, comprising circuits for comparing the magnitude with a prescribed rate of change, and controlling the moving speed of the actuator of the air bleed control device according to the output signals of these circuits. Device.