JPH0569974B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine idle speed control device that controls the engine speed by adjusting the amount of intake air to the engine during idling. be.

(Prior art) A conventional engine idle speed control device is
In general, a bypass passage for intake air is formed to bypass the throttle valve of the engine, and an air amount adjustment means (electromagnetic valve) is installed in this bypass passage to adjust the intake air amount in the minimum opening state (idle state) of the throttle valve. The engine is configured to operate at an idle target rotation speed by controlling the air amount adjusting means in a feedback manner according to the deviation between the actual rotation speed of the engine and a predetermined target rotation speed. .

However, in such a configuration, only the engine speed is considered as the control parameter that is the reference for feedback control of the engine speed, so in the idling state,
When the compressor for the air conditioner, which causes engine load, is turned on, or when the shift lever of the transmission in an automatic vehicle is switched from the park or neutral state to the drive state, the engine load suddenly changes without any feedback control being performed. As a result, the engine speed suddenly drops temporarily, resulting in a rough idle that gives the driver a sense of discomfort. In some cases, it may also cause engine stall.

Therefore, in order to eliminate such drawbacks, the above-mentioned load fluctuations are detected by a load switch, and the detection signal is used to operate the air amount adjusting means to adjust the intake air amount to the engine within a predetermined period of time. There is a known device in which the increase in amount is controlled (see, for example, Japanese Patent Laid-Open No. 54-98413).

Further, the control of the rotation speed in the above-mentioned idle operating state is feedback control in which the control system is closed loop, whereas the control in the non-idle region is open loop control in which the control value is constant. Therefore, if you start driving immediately after starting in a cold state without performing sufficient warm-up operation, the control system will be fixed at a large open-loop control value (final value during feedback) as soon as driving starts. As a result, if the vehicle is returned to the idling state after the warm-up by driving is completed, the control value is large even though the warm-up has been completed, so that the idle speed temporarily increases abnormally.

Therefore, in order to eliminate these drawbacks, the control duty, which determines the basic intake air amount for open loop control immediately after engine startup, is set in relation to the engine coolant temperature, and this set value can be manually adjusted. , depending on the automatic transmission, or depending on the range of the automatic transmission, or turning on the air conditioner,
It is also known that the control value is corrected to an appropriate control value depending on the OFF state (load amount), and control is performed using this correction value (see, for example, Japanese Patent Laid-Open No. 156230/1983).

In the case of any of these known techniques, the control value (control duty) on the intake air amount reduction side (when reducing the intake air amount) of the above-mentioned feedback control in the idling state is generally determined by the overshoot. In order to prevent engine stall, the lower limit value (minimum value) is set at a predetermined value or higher.

However, the lower limit set as above is generally set based on the normal idling state (no load) and corresponds only to the load amount, so the following occurs in relation to the intake air amount. A problem arises. That is, as shown in the above two known technologies, when the engine load of air conditioning equipment, etc. is input in the idling operating state, in addition to the original feedback control value, a predetermined intake air amount is also adjusted accordingly. Since the amount of intake air is corrected to increase, the overall amount of intake air becomes considerably large.

By the way, in this case, the relationship between the intake air amount of the engine and the engine torque is generally expressed as
As shown in the figure, it is known to exhibit a quadratic characteristic, and from the point when the intake air amount V increases to a certain value _V1 or more, the ratio of torque change to the ratio of intake air amount change increases. become much larger. This means that even if the amount of change in the amount of intake air is constant, if the amount of intake air is increased above the certain value V ₁ (V ₁ to V ₂ ) and if it is not (V ₁
(below), the rate of change in torque is different; in the former case, it means a sudden change. As a result, if the accelerator pedal is placed while the engine load is input as described above and the amount of intake air is increased above the normal feedback control value, if the accelerator pedal is suddenly removed from this condition, Feedback control on the intake air amount reduction side, which attempts to reduce the intake air amount that is currently increasing, will continue to operate at the set lower limit value, just like when idling in a normal no-load state. This causes a sudden and large decrease in torque, resulting in rough idling and engine stall.

(Objective of the Invention) The present invention has been made to improve the above-mentioned problems, and by variably correcting the lower limit value of the conventionally set feedback control according to the intake air amount at that time, it is possible to It is an object of the present invention to provide an engine idle speed control device that prevents occurrence of rough idle or engine stall due to changes, stabilizes control characteristics, and improves drivability.

(Means for Achieving the Object) In order to achieve the above object, the present invention includes an intake air amount detection means for detecting the amount of intake air into the engine, and a detection value based on the detected value of the intake air amount detection means. the idle speed of the engine is adjusted by controlling the air amount adjusting means according to the rotation speed deviation between the actual engine speed and the idle target speed; An engine idle speed control device, wherein the engine idle speed is adjusted to match the target idle speed,
A lower limit value of the engine intake air amount reduction side control amount is set in the feedback control amount according to the rotation speed deviation between the idle target rotation speed and the actual rotation speed supplied to the air amount adjusting means, and A lower limit value correcting means is provided to vary the lower limit value to a smaller value as the amount of intake air increases.

(Function) According to the above means, the lower limit value of the feedback control during idling is always set to the optimum value corresponding to the intake air amount at that time and with little change in torque. Therefore, at idle,
Even when a predetermined engine load is input and the amount of intake air increases by more than a certain amount, smooth control can be performed without rough idle or engine stall, resulting in good drivability. You can get yi.

(Embodiment) First, FIGS. 1 to 5 show an engine idle speed control device according to an embodiment of the present invention, and FIG. 1 shows the configuration of the main part of the present invention. 2 is a system schematic diagram of the above embodiment device, FIG. 3 is a flowchart explaining the operation of the above embodiment device, and FIG. 4 is a throttle valve opening degree explaining the control operation in the above embodiment device. Figure 5 is a characteristic graph showing the relationship between (TVO) and engine speed (rpm). It is a characteristic graph showing the relationship with the intake air amount V.

First, the outline of the system according to the embodiment of the present invention will be explained with reference to FIG. 2, and then the control of the main parts will be explained.

In Fig. 2, reference numeral 1 is the engine body, where intake air is taken in from the outside via an air cleaner, and then supplied to each cylinder via an air flow meter 2 and a throttle chamber 3, and fuel is sent to an ECU 9 (described later). The fuel is injected by a fuel injector 5 which is controlled by the fuel injector 5. The amount of air taken into the cylinder is controlled by a throttle valve 6 provided in the throttle chamber 3, and the amount is detected by an air flow meter 2. Throttle valve 6
is operated in conjunction with the accelerator pedal, and is maintained in an almost closed state (fully closed opening degree) in the idling state.

On the other hand, the throttle chamber 3 is provided with a bypass passage 7 that bypasses the throttle valve 6, and this bypass passage 7 is provided with an electromagnetic valve that serves as an air amount adjusting means for controlling the engine speed during idling. A valve (throttle valve) 8 is provided. Therefore, in the idling state, the intake air that has passed through the air flow meter 2 is supplied to each cylinder via the bypass passage 7, and the amount of intake air is regulated by the solenoid valve 8. This solenoid valve 8 is connected to an engine control unit (hereinafter referred to as
Its opening/closing state is controlled by the duty ratio (hereinafter referred to as a control value) of a control pulse signal (hereinafter simply referred to as a control signal) supplied from the ECU (hereinafter simply referred to as a control signal).

ECU9 is, for example, a microprocessor (CPU)
It is centered around , and includes memory (ROM and RAM) and interface (I/O) circuits. The interface circuit of this ECU 9 includes, for example, a detection signal of the cooling water temperature of the engine body 1 detected by a thermistor, an opening signal (TVO) of the throttle valve 6 detected by a potentiometer, and an air flow meter 2. The intake air amount detection signals detected by are inputted respectively.

Note that the reference numeral 10 indicates an exhaust pipe equipped with a three-way catalytic converter 11.

Next, the control operation of the above control device will be explained in detail with reference to FIG.

When the control operation is first started, the various input information described above, namely the actual engine speed and the opening degree (TVO) of the throttle valve 6, are read at predetermined time intervals (step S ₁ ), and then Based on this information, it is determined whether the current operating state is in the idle operating region as shown in FIG. 4 (step S ₂ ). That is, engine speed
(N) is below a predetermined value (N _EXT ) and the opening degree of the throttle valve 6 is in the fully closed (minimum opening) state (TVOmin), it is determined to be in the idle operating region, and on the other hand, when the number of engines mentioned above is higher than the predetermined value (N _EXT );
The opening degree of throttle valve 6 is fully closed (TVOmin)
When the value is greater than a predetermined value, it is determined that the vehicle is in the non-idling operation region.

And if it is in the idle operation region (YES)
Next, the process moves to the calculation operation of the control value duty ratio for the control signal for controlling the idle rotation speed, and first, the basic characteristics determined in response to the detection signal of the cooling water temperature from the engine are first calculated. The value (basic term of the duty ratio calculation formula) D _B is calculated (step S ₃ ).

On the other hand, if the engine speed (N) is above a predetermined value (N _EXT ) and the opening degree (TVO) of the throttle valve 6 is greater than the fully closed opening degree by a predetermined value or more, it is determined that the engine is in the non-idle region (NO). However, it is recognized that feedback control is unnecessary, and the control operation is shifted to open loop control and the control operation according to the flow shown in FIG. 3 is ended (END).

On the other hand, when the calculation of the basic characteristic value D _B is completed in step _S3 , in the idle operating state,
For example, the input status of engine loads such as air conditioners and shift ranges of automatic vehicles can be checked using load switches.
Judgment is made based on ON or OFF (step
S ₄ ), if the load switch is ON, then a correction value _DL (load correction term in the duty ratio calculation formula) is calculated according to those loads (step S ₅ ),
Then, the process moves to an operation of reading the intake air amount V of the engine at that time (step _S6 ). Then, the control lower limit value (LL _FB ) of the feedback control according to the intake air amount in the idling state is determined.
The calculation is performed (step _S7 ). This lower control limit value (LL _FB ) is calculated, for example, in accordance with the characteristics shown in FIG. 5 read from the lookup table. Therefore, in the range (V ₁ to V ₂ ) where the intake air amount V is above a certain constant value V ₁ in FIG. 6 (in this case, the load is also large), the intake air amount increases (V _{1 .about.V2} ), the control lower limit value ( _LLFB ) on the engine intake air amount reduction side is variably set in _the smaller direction ( _{LLFB1.about.LLFB2} ).

On the other hand, in step _S4 above, if the load switch is OFF and the load switch is in the idling state with no load (NO), the calculation of the load correction value _DL (step
S ₅ ), without reading the intake air amount (step S ₆ ), proceed to step S ₈ and calculate (read) the normal control lower limit value (D _FB ) regardless of the characteristics shown in Fig. 5. Proceed to step _S9 .

In step _S9 , the target rotation speed (No) is calculated based on the lower limit value (LL _FB ) or (D _FB ) of the feedback control calculated in step S ₇ or step S ₈ , and then this target rotation speed is calculated. Number of rotations (No)
The actual rotational speed (N) of the engine is compared with the value obtained by adding a predetermined dead value (α) (No+α) as a reference (step S ₁₀ ). As a result, if the actual rotation speed (N) is below the above reference value (NO), the actual rotation speed (N) will be further increased.
It is determined whether or not is less than the reference value (No - α), that is, the value obtained by subtracting the dead value (α) from the target rotation speed (No) (step S ₁₁ ).

As a result, the actual rotation speed (N) is the above reference value (No - α)
If the following is true (YES), perform a calculation to increase the feedback correction value (D _FB ) by (△ _FB ) in order to increase the amount of intake air (D _FB ← D _FB + △ _FB )
(Step _S12 ). On the other hand, as a result of the above judgment, if the actual rotation speed (N) is larger than the above reference value (No - α) (No), it is recognized that it approximately matches the target rotation speed, and step _S15 is performed. Let's move on to the calculation operation for the final output.

On the other hand, in step S ₁₀ above, if the actual engine speed (N) is equal to or higher than the reference value (No + α) (YES), feedback control on the engine intake air amount reduction side operates to reduce the engine intake air amount. I will let you do it.

That is, in that case, first in step _S13 ,
The control value (D _FB ) of the feedback control at that time is compared with the control lower limit value (LL _FB ) determined based on the characteristics shown in FIG. 5 in accordance with the above-mentioned intake air amount at that time. As a result, if the control value (D _FB ) is larger than the lower limit value (LL _FB ), the above (△D _FB ) is subtracted from the control value (D _FB ) in the next step _S14 , and ( D _FB −△D _FB ) is calculated as the control value and the final output calculation operation is performed (step S ₁₅ ).
Move to.

On the other hand, as a result of the comparison in step _S13 above, (D _FB )
If LL FB is smaller than (LL _FB ) (No), the process directly proceeds to the final output calculation operation (step S ₁₅ ).

In step _S15 , the calculation data for each control operation described above is input, the final control value (duty ratio) (D _T ) is calculated based on the following formula (1), and corrected according to the intake air amount. The final feedback control output is determined and output (step _S16 ).

D _T =D _B +D _L +D _FB (1) The above control flow is performed at a predetermined period, for example, every rotation of the engine.

In the above embodiment, the solenoid valve 8 is provided in the bypass passage 7 that bypasses the throttle valve 6, and the opening and closing of the solenoid valve is controlled. However, the present invention is not limited to this, and for example, the throttle valve 6 may be directly controlled. The amount of intake air may be adjusted by doing so.

(Effects of the Invention) As described above, the present invention includes an intake air amount detection means for detecting the intake air amount to the engine, and an intake air amount of the engine based on the detected value of the intake air amount detection means. The idle speed of the engine is adjusted to the idle speed by controlling the air amount adjusting means according to the rotation speed deviation between the actual engine speed and the idle target speed. The engine idle rotation speed control device is configured to control the engine intake air at a feedback control amount according to a rotation speed deviation between the idle target rotation speed and the actual rotation speed supplied to the air amount adjusting means. The present invention is characterized in that a lower limit value correction means is provided for setting a lower limit value of the control amount on the side of reducing the amount of air, and for varying the lower limit value in a direction that decreases as the amount of intake air to the engine increases.

Therefore, according to the present invention, in an idling operating state, when the engine load of an air conditioner or the like is input and the intake air amount is increased to a predetermined amount or more, feedback on the intake air amount reduction side that reduces the intake air amount is provided. Even if the control is performed, the lower limit value of the feedback amount is variably set to a value smaller by a predetermined amount than the originally set lower limit value (at no load) depending on the intake air amount at that time. Therefore,
Even when the amount of intake air is in a range larger than a certain value, a sudden drop in engine torque does not occur, and occurrences of rough idle, engine stall, etc., which are conventional, can be prevented. Furthermore, being able to control the torque change itself to a small value in response to the amount of intake air simultaneously makes the control characteristics themselves stable and improves drivability.

[Brief explanation of drawings]

FIG. 1 is a claim correspondence diagram showing the configuration of essential parts of the present invention, FIG. 2 is a system schematic diagram of an engine idle speed control device according to an embodiment of the present invention, and FIG. 3 is a diagram corresponding to the claims described above. Flowchart for explaining the control operation in the illustrated embodiment device, No. 4
The figure is a characteristic diagram showing the relationship between the throttle valve opening and the engine speed in the control operation of Figure 3, and Figure 5.
The figure is a characteristic diagram showing the relationship between the lower limit value of feedback control (LL _FB ) and the intake air amount in the control operation shown in FIG. It is a characteristic diagram showing a relationship. 1...Engine body, 2...Air flow meter,
3... Throttle chamber, 6... Throttle valve, 7... Bypass passage, 8... Solenoid valve, 9...
Engine control unit.

Claims (1)

[Claims] 1. An intake air amount detection means for detecting the amount of intake air into the engine, and an air amount adjustment means for adjusting the intake air amount of the engine based on the detected value of the intake air amount detection means, and the actual rotational speed of the engine. An engine idle speed control device that controls the air amount adjusting means according to a rotation speed deviation between the engine speed and the idle target speed, so that the idle speed of the engine matches the idle target speed. A lower limit value of the engine intake air amount reduction side control amount in the feedback control amount according to the rotational speed deviation between the idle target rotational speed and the actual rotational speed supplied to the air amount adjusting means is set, and 1. An engine idle speed control device comprising lower limit value correcting means that varies the lower limit value in a direction that decreases as the amount of air taken into the engine increases.