JPS6213753A - Idle rotational speed control device in engine - Google Patents

Abstract

PURPOSE:To make it possible to prevent engine stalls, by stopping feed-back control to hold the control amount of an engine if the actual rotational speed of the engine exceeds a desired idle rotational speed in such a condition that the volume of intake-air is increased by a load compensating means. CONSTITUTION:When an engine control device 9 determines that the operation of an engine is in an idle running range in accordance with the rotational speed N of the engine and the opening degree of a throttle valve 6, and obtains a desired idle rotational speed Ne in accordance with the temperature of cooling water to carry out the feed-back control of the engine by means of a solenoid valve 8. Further, when a signal from a load such as, for example, an air- conditioning device is delivered, the control device 9 adds a compensating value in accordance with the amount of load, to a duty control signal fed to the solenoid valve 8 in order to increase the volume of intake-air. In this condition, if N>Ne, the feed-back control is stopped to hold the feed-back control amount until then. Then, even if the external load is cut off, not so great drop in the rotational speed of the engine occurs due to the negative side feed-back control at that time, thereby it is possible to prevent an engine stall from occurring.

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 generally forms a bypass passage for intake air to bypass the throttle valve of the engine, and also sets the throttle valve in the minimum opening state (idle state) in this bypass passage. An air amount adjustment means (Ti magnetic valve) is provided to adjust the amount of intake air at 1iEl! according to the deviation of the engine speed between the actual engine speed and the set predetermined speed. The engine is configured to operate at the target idle rotation speed by feedback controlling the adjustment means.

However, in such a configuration, only the engine speed is considered as the control parameter that serves as the reference for feedback control of the engine speed, so in the idling state, the air conditioner compressor, which is the engine load, is turned on. When the shift lever of an automatic transmission is switched from the park or neutral state to the drive state, the engine load changes suddenly without any feedback control, and the engine speed may suddenly suddenly increase. This results in a rough idle, which gives the driver a sense of discomfort. In some cases, this may 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 increase the amount of intake air to the engine within a predetermined period. There is a known device that performs load correction (for example, see Japanese Patent Laid-Open No. 54-98413).

However, according to this prior art, when the above-mentioned external load is applied, the engine speed is sufficiently increased by the load correction amount, and the actual engine speed is adjusted to the target speed corresponding to the load amount at that time. If the external load exceeds this value and increases further (for example, when the external load is smaller than the load correction amount), feedback control on the negative side comes into play. Therefore, if the external load is cut in this state, the engine speed will temporarily drop significantly due to the influence of the negative side feedback control when the external load is cut. If this decrease is extremely large, there is a problem that sometimes the engine stalls.

(Object of the Invention) The present invention has been made to improve the above problem, and when the actual engine speed is higher than the idle target speed while an external load is applied as described above, It is an object of the present invention to provide an engine idle speed control device that can more reliably prevent engine stalling by stopping the feedback control described above.

(Means for Achieving the Object) In order to achieve the above object, the engine idle speed control device of the present invention controls the amount of intake air into the engine, as illustrated in FIGS. 1 and 2, for example. and a load correction means that controls the air amount adjusting means to increase a predetermined amount of intake air in accordance with the engine load, the actual idle speed of the engine being equal to the target idle speed. In an engine idle speed control device that performs feedback control to converge, a comparison means for comparing the actual engine speed and the idle target speed, and an intake air amount are increased by the load correction means. feedback that stops the feedback control and bolds the feedback control amount up to that point when the actual engine speed is larger than the idle target speed according to the comparison value compared by the comparison means in parentheses. The control stop means is also provided.

(IIc IT+) According to the above means, when the feedback control acts on the negative side when an external load is applied to the engine, that is, when the actual engine speed is higher than the idle target speed, the feedback control is Control will now be automatically stopped. Therefore, even if the external load is cut in the above state, a large drop in engine speed due to the effect of negative feedback at the time of the cut will not occur, and the occurrence of engine stall can be reliably prevented. It becomes like this.

(Example) First, Fig. 1 and Fig. 2 show an engine idle speed control device according to an embodiment of the present invention, and Fig. 1 is a schematic diagram of a control system of the above-mentioned embodiment device; FIG. 2 is a flowchart explaining the operation of the above embodiment device, and FIG. 3 is a flowchart showing the throttle valve opening (TVO) and engine rotation speed (r
pm) is a characteristic graph showing the relationship with pm).

First, the outline of the control system according to the embodiment of the present invention will be explained with reference to FIG. 1, and then the control of the main parts will be explained.

In FIG. 1, reference numeral l indicates 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.Fuel is controlled by an ECU 9, which will be described later. The fuel is injected by a fuel injector 5.

The amount of intake air 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. The throttle valve 6 is operated in conjunction with the accelerator pedal, and is maintained at a minimum opening state in an idling state.

On the other hand, the throttle chamber 3 is provided with a bypass passage 7 that bypasses the throttle valve 6.
In this bypass passage 7, a solenoid valve (throttle valve) 8 serves as a means for adjusting the air ff1l for controlling the engine speed during idling.
is provided. Therefore, in an 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. The solenoid valve 8 opens and closes depending on 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 an engine control unit (hereinafter referred to as ECU) 9. state or controlled.

The ECU 9 is configured to include, for example, a microprocessor (CPU) at its core, a memory (ROM and RAM), and an interface (T10) circuit. The interface circuit of the ECU 9 includes, for example, a detection signal of the cooling water temperature of the engine body I detected by a thermistor, an opening signal (TVO) of the throttle valve 6 detected by a potentiometer, and a signal detected by the air flow meter 2. The intake air amount detection signal, load signals for the cooler, power steering, etc. are manually input.

Moreover, the symbol 1O indicates an exhaust pipe provided with a three-way catalytic converter 11.

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

When the control operation is first started, the various input information described above, that is, the actual engine speed (N) and the opening degree (TVO) of the throttle valve 6, are read at predetermined time intervals (step S, ), and then, based on this information, it is determined whether the current operating state is in the idle operating region as shown in FIG. 3 (step S). That is, when the engine speed (N) is below the predetermined value (N ext), the opening degree of the throttle valve 6 is at the minimum opening degree, @ (TvOm
When r n
), and the opening degree of the throttle valve 6 is higher than the minimum opening degree (T
When it is larger than V Om1n by a predetermined value or more, it is determined that the vehicle is in the non-idling operation region.

Then, 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 speed, and first, the basic characteristic value (duty ratio) determined in response to the detection signal of the cooling water temperature from the engine is first calculated. - Basic term of ratio calculation formula) Da
is calculated (step S3).

On the other hand, if the engine speed (N) is equal to or higher than the predetermined value (Next) and the opening degree (TVO) of the throttle valve 6 is greater than the minimum opening degree by a predetermined value or more, the engine is in the non-idle region (No).
After determining that the feedback control in steps S3 to S+4 is unnecessary, the oven loop control is started, and the predetermined standby is performed by setting the amount DEXT and outputting the final output. (Step S8).

On the other hand, when the calculation of the basic characteristic value DB is completed in step S, in the idling state, for example, the human power state of the engine load such as air conditioning equipment, power steering, shift range of an automatic car, etc. is changed by turning on the load switch.
or OFF' as a reference step S4),
If the load switch is ON (YES), then a correction value DL (load correction term in the duty ratio calculation formula) is calculated according to the load amount (step S5).

Then, the actual engine rotation speed N in the load ON state is compared with the idle target rotation speed No + α (α is a dead value for control) at that time (step S6).
is smaller than the target rotational speed No+α (YES), the feedback control in steps S8 to Sl, which will be described later, is stopped and the process moves to step S15 to calculate the final output (duty ratio), and correct the feedback control up to that point. value(
(previous DFB) is held. On the other hand, if the actual engine rotation speed N is less than or equal to the target rotation speed No+α (NO),
Based on the value of the feedback loop load correction value DL in steps 89 to S13, the idle target rotation speed No. in the load state is calculated (step SS).

On the other hand, - in step S4 above, the load switch is turned OFF.
4 in idle operation state with no load, which is FF
In the case (No), the process moves to step S7 without calculating the load correction value DL (step S5), and the load correction value D is calculated.
After setting L to 0, the process moves to step S9.

Next, when the target rotation speed No. is calculated in step S8, the value NO obtained by adding a predetermined dead value α to the target rotation speed NO is calculated.
+α is compared with the actual engine rotation speed N (steps S, o). As a result, if the actual rotational speed N is less than the above reference value (NO), the actual rotational speed N is further reduced to NO.
-α is less than the reference value, that is, the value obtained by subtracting the dead value α from the target rotation speed No. (Step 511
).

As a result, if the actual rotation speed N is below the reference value No = α (YES), a calculation is performed to increase the feedback correction value DF8 by △DFB in order to increase the intake air amount (D Fe + D FB + △ DFB) is performed (step 512). On the other hand, if the result of the above judgment is that the actual rotational speed N is larger than the reference value NO-α (No), it is recognized that the actual rotational speed substantially matches the target rotational speed, and the final output is calculated in step S14. Move on to action.

On the other hand, ``Step S,'' above. In this case, when the actual engine speed N is equal to or higher than the reference value NO+α (YES), feedback on the negative side acts to reduce the amount of intake air.

That is, in that case, in the next step S13, a predetermined value △DFB is subtracted from the control value DFB, and DFEI−△
DF[l is calculated as a feedback correction value and the process moves to the final output calculation operation (step S, 4).

In step S14, the calculation data for each control operation described above is input, and the final control value (
(duty ratio) DT is calculated, and a final feedback control output corrected in accordance with the load amount and the intake air amount at that time is determined and output (step 515).

D T = D B ”, D L + △DFB ・・
- (1) The above control flow is performed at a predetermined period, for example, every revolution 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, but the present invention is not limited to this.
It goes without saying that the amount of intake air may be adjusted by directly controlling the throttle valve 6, for example.

According to the above configuration, the ON state of the external load (step S
4), in the judgment operation of step S, if the actual rotation speed N is larger than the idle target rotation speed NO+α, the feedback control of steps S to Sll is stopped. Therefore, even if the external load is cut in this state, negative feedback control is not performed and the engine speed does not decrease significantly.

(Effects of the Invention) As described above, the engine idle speed control device of the present invention includes an air ff1l adjusting means for adjusting the amount of intake air to the engine and a predetermined amount of intake air in accordance with the engine load. and a load correction means for controlling the air amount adjusting means to increase the amount of air, the engine idle speed control device performing feedback control so that the actual idle speed of the engine converges to the idle target speed. A comparison means for comparing the actual engine speed with the target idle speed, and a comparison value compared by the comparison means in parentheses when the intake air amount has been increased by the load correction means. The present invention is characterized in that a feedback control stopping means is provided for stopping the feedback control and holding the feedback control amount up to that point when the rotation speed is higher than the idle target rotation speed.

Therefore, according to the present invention, when the feedback control acts on the negative side when an external load is applied to the engine, that is, when the actual engine speed is higher than the idle target speed, the corresponding Feedback control will now be automatically stopped. Therefore, even if the external load is cut in the above state, the engine speed will not decrease significantly due to the effect of negative feedback at the time of the cut, and it is possible to reliably prevent engine stalling. It becomes like this.

[Brief explanation of drawings]

FIG. 1 is a control system diagram of an engine idle speed control device according to an embodiment of the present invention, FIG. 2 is a flowchart for explaining the control operation in the embodiment device of FIG. 1, and FIG. 2 is a characteristic diagram showing the relationship between the throttle valve opening and the engine rotation speed in the control operation shown in FIG. 2. FIG. 1...Engine body 2...Air flow meter 6...Throttle valve 7...Bypass port 8...Solenoid valve 9...Q Engine control unit/ ...
・Engine body 2・・・Air flow meter

Claims (1)

[Claims] 1. The engine is equipped with an air amount adjusting means for adjusting the amount of intake air into the engine, and a load correcting means for controlling the air amount adjusting means to increase a predetermined amount of intake air in accordance with the engine load, An engine idle speed control device that performs feedback control so that the idle speed converges to a target idle speed, comprising a comparison means for comparing the actual engine speed and the target idle speed, and a load correction means. In a state where the amount of intake air has been increased, and when the actual rotation speed of the engine is larger than the idle target rotation speed according to the comparison value compared by the comparison means, the feedback control is stopped. 1. An engine idle speed control device, comprising: feedback control stopping means for holding a feedback control amount.