JPH07332132A - Post-start idle speed control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To establish a control method which can prevent the engine speed from heightening too much temporarily immediately after the start of engine, eliminates risk of generation of undershoot thereafter, and ensures stable behavior of the engine speed after the start. CONSTITUTION:When the engine speed NE becomes over the specified value (500rpm) after the starting operation (Step 46), the specified amount CIRED is determined (Step 54) to decrease the bypass suction amount according to the engine temp. THW, and also the specified period CTCUT for decreasing is determined (Step 55), and the bypass suction amount is decreased by this amount CIRBD for the period CTCUT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the idle speed of an internal combustion engine after starting.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 60-19937 describes a method for controlling the idle speed of an internal combustion engine after starting. According to this method, the idle speed control valve ISCV is started depending on the elapsed time from the start. Although the method of reducing the amount of increase is adopted, in this method, when the internal combustion engine temperature is high, the rotational speed immediately after starting tends to be high (flare) as shown in 1 of FIG. There may be a problem depending on the internal combustion engine.

As a countermeasure against this, the case where the increase in the amount of ISCV after starting is eliminated is 2 in FIG. 1. However, although the flare is reduced less, an undershoot after that occurs,
This also feels strange.

[0004]

As described above, according to the above-mentioned prior art, since the engine generated torque at the time of starting when the internal combustion engine temperature is high, the engine speed temporarily becomes too high immediately after starting (flare). There are cases. But,
In the conventional technology, the amount of air immediately after starting cannot be controlled only to reduce flare, so the amount of air immediately after starting is less effective for flare reduction, but after that, an under short circuit occurs and it is difficult to achieve both. there were.

Therefore, the present invention sufficiently exerts the flare reduction effect, does not cause the undershoot thereafter, and exhibits a stable engine speed behavior after starting as shown by 3 in FIG. The purpose is to provide.

[0006]

SUMMARY OF THE INVENTION Therefore, according to the present invention, the amount of intake air in the intake bypass passage of the internal combustion engine is adjusted to control the idle speed of the internal combustion engine. In this case, there is provided a method for controlling a post-start idle speed of an internal combustion engine, characterized in that the bypass intake air amount is decreased by a predetermined amount for a predetermined period according to the temperature of the internal combustion engine.

[0007]

As a result, when the predetermined engine speed is reached after the start operation, the bypass intake air amount is reduced by a predetermined amount for a predetermined period according to the engine temperature.

[0008]

FIG. 2 shows the configuration of one embodiment of the present invention. The electronic control unit ECU 10 outputs the output of the water temperature sensor 11 for detecting the engine cooling water temperature via the A / D converter 12.
Further, the output of the rotation angle sensor 13 attached to the engine camshaft is input to the CPU 15 via the I / O port 14 to calculate the fuel amount and ignition timing required by the internal combustion engine (engine) to calculate the output stage. The actuator 18 and the like are driven via the transistor 16 and the like to control fuel and ignition timing. The actuator 18 and the like are injectors (not shown),
Such as an igniter.

On the other hand, the idle speed control valve ISCV19 for controlling the idle speed is installed in the bypass passage 20 that bypasses the throttle valve 23 of the intake pipe 22.
Amount of air taken into the cylinder 21 of the engine 24 by controlling the area of the bypass passage 20 by causing a current to flow through the solenoid coil 19a in the valve 19 through the transistor 17 of the output stage based on the calculation result of the CPU 15. To control the idle speed.

The control state and the rotational speed behavior of the present invention are shown in FIG. When the starter switch is turned on (31 in FIG. 3) to perform cranking, fuel is supplied to the engine 24, and ignition is executed, combustion occurs, the engine speed increases, and the engine speed increases to a predetermined value (see FIG. 3). 32), the opening of the ISCV 19 is delayed for a short period of time (36 in FIG. 3) for a predetermined period (34 in FIG. 3) and a predetermined amount (33 in FIG. 3) from the current opening toward the closing direction. Controlled. As a result, compared to the case without this control, the combustion torque when the engine speed increases and the flare of the engine speed immediately after the start is decreased by 35 in FIG. 3, and the start feeling is comfortable. Becomes

The flow chart of this embodiment will be described below with reference to FIG. This control is executed by the CPU 15 in the ECU 10 from step 41 every 64 ms. From step 42 to step 47, the flag XCSTEM for start determination
This is a part for controlling S, and the state X after starting is determined in step 42.
When CSTEMS = 1, in step 43 the engine speed NE
Is less than 300 rpm, the routine proceeds to step 44, where XCSTEMS = 0 and the starting state is judged. on the other hand,
If the engine speed NE is 500 rpm or more in step 46 when the engine is in the starting state in step 42, the process proceeds to step 47, in which XCSTEMS = 1 is set and the post-starting state determination is performed.

Next, in step 51, the XCSTE
If MS = 1, the routine proceeds to step 52, where the elapsed time counter CSTART after starting is counted up by 64 ms.
Next, in step 53, the elapsed time CSTART after the start is 256
When the time is longer than ms, the routine proceeds to step 54, where the flare correction value CIRED of ISCV19 is set according to the water temperature THW (water temperature TW).
When HW becomes equal to or larger than a predetermined value, the flare correction value CIRED is determined so as to increase linearly according to the increase in water temperature. Next, at step 55, flare correction value cut time C
Similarly, TCUT is determined according to the water temperature (when the water temperature THW becomes a predetermined value or more, the CTCUT decreases linearly according to the increase of the water temperature). Here, the flare correction value CIRED is not set (the CIRED is kept at 0) for a short time of less than 256 ms after the start-up elapsed time CAST is because the engine speed is excessively reduced due to the reduction of the bypass intake amount immediately after the start. This is to prevent

In the next steps 56 and 57, the flare correction value CIRED becomes 0 if the post-start elapsed time CAST exceeds CTCUT + 256 ms. Next step 5
In 8, the drive final duty CIOPA of the ISCV19 is obtained by subtracting the flare correction value CIRED from the other coefficient a (learning value, increase after starting, increase in warm-up, etc.), and the ISCV19 is driven by this drive final duty CIOPA. The amount of intake air flowing through the bypass passage 20 is controlled. Here, among the other coefficients a, the amount of increase after the start is disclosed in JP-A-60-19.
Similarly to the one described in Japanese Patent No. 937, the bypass air amount is increased in accordance with the water temperature during the engine starting operation, and after the engine is started (the engine speed NE is 500 rpm or more), the bypass air amount is increased by a predetermined amount each time a predetermined time elapses. The amount of air thus made is reduced to the target amount of air.

In the post-startup rotation speed flare control method described above, flare correction is performed according to atmospheric pressure because flare is reduced at high altitudes due to a decrease in combustion torque with a decrease in intake air weight. By decreasing the operation period and the amount of the value CIRED, more precise flare correction can be performed. Specifically, as shown in FIG. 5, steps 65 and 66 are added after step 54 to correct the operation amount of the flare correction value CIRED by the atmospheric pressure PMHAC.
The operation is performed so that the lower the atmospheric pressure, the smaller the operating amount of CIRED. Further, after step 55, step 6
9, 70 are added, and the operating period correction of the flare correction value CIRED by the atmospheric pressure PMHAC is performed so that the operating period CTCUT becomes shorter as the atmospheric pressure becomes lower.

Further, in the above-described rotational speed flare control method after starting, the flare becomes large because the combustion torque increases as the intake air weight increases at a low intake temperature, so the flare increases depending on the intake temperature. By increasing the operation period and amount of the correction value CIRED, more precise flare correction can be performed. Specifically, as shown in FIG. 6, steps 85 and 86 are added after step 54 to correct the operation amount of the flare correction value CIRED by the intake air temperature THA so that the operation amount of the CIRED becomes larger as the intake air temperature becomes lower. To implement. Furthermore, steps 89 and 90 are added after step 55, and the operating period correction of the flare correction value CIRED with the intake temperature THA is performed so that the operating period CTCUT becomes longer as the intake temperature becomes lower.

Further, other factors such as the post-start increase and the warm-up increase may not be necessary depending on the engine model, and the decrease of the predetermined amount by the predetermined amount for a predetermined period according to the engine temperature of the bypass intake air amount depends on the water temperature. Accordingly, only one of the predetermined period and the predetermined amount may be changed, and the bypass intake amount may be reduced only when the water temperature is equal to or higher than the predetermined value while the predetermined amount is set to a constant value for the predetermined period. May be.

[0017]

As described above, according to the present invention, there is an excellent effect that the increase in rotational speed (flare) immediately after starting can be improved as follows. It is possible to suppress the increase in engine speed by reducing the bypass intake air amount for a predetermined period after the start to reduce the engine generated torque immediately after the start. Since it is limited, undershoot does not occur after the engine speed increases. Also, by reducing the period and amount of reducing the bypass intake air amount at high altitudes and increasing the period and amount of reducing the bypass intake air amount at low intake air temperature, a more precise engine rotation immediately after starting can be performed. It is possible to control the increase of the number.

[Brief description of drawings]

FIG. 1 is a time chart showing the ISCV opening after starting and the engine speed according to the related art and the present invention.

FIG. 2 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 3 is a time chart showing the ISCV opening after starting and the engine speed in the above embodiment.

FIG. 4 is a flowchart showing an embodiment of a control flow of the present invention.

FIG. 5 is a flowchart showing an embodiment of a control flow in the case of considering atmospheric pressure according to the present invention.

FIG. 6 is a flow chart showing an embodiment of a control flow when the intake air temperature of the present invention is taken into consideration.

[Explanation of symbols]

 10 Electronic Control Unit (ECU) 11 Water Temperature Sensor 15 CPU 19 ISCV 20 Bypass Passage 22 Intake Pipe 23 Throttle Valve 24 Engine

Claims (7)

[Claims] 1. An engine for controlling an idle speed of an internal combustion engine by adjusting an intake air amount of an intake bypass passage of the internal combustion engine, wherein when a predetermined engine speed is reached after a starting operation, the temperature of the internal combustion engine is changed according to a temperature of the internal combustion engine. Then, the bypass intake air amount is decreased by a predetermined amount for a predetermined period, and a post-start idle speed control method for an internal combustion engine. 2. The predetermined period, or the predetermined amount when the bypass intake air amount is decreased by a predetermined period, a predetermined amount,
The post-start idle speed control method according to claim 1, wherein the lower the atmospheric pressure, the shorter or the smaller the atmospheric pressure is set. 3. The predetermined period, or the predetermined amount when the bypass intake air amount is decreased by a predetermined period, a predetermined amount,
3. The post-start idle speed control method according to claim 1, wherein the lower the intake air temperature of the internal combustion engine, the longer or more the intake air temperature is set. 4. The predetermined period when the bypass intake amount is reduced by a predetermined amount for a predetermined period, the predetermined period is set to decrease in accordance with an increase in engine temperature.
Alternatively, the post-startup idle speed control method described in 3 above. 5. The predetermined amount for decreasing the bypass intake air amount by a predetermined amount for a predetermined period is set so as to increase in accordance with the increase in the engine temperature. The method for controlling idle speed after starting as described in. 6. The post-startup according to claim 1, wherein the reduction of the bypass intake air amount by the predetermined amount during the predetermined period is substantially prohibited when the engine temperature is below a predetermined value. Idle speed control method. 7. The reduction of the bypass intake amount by the predetermined amount during the predetermined period is delayed for a short period after reaching the predetermined engine speed, and executed. Idle speed control method after starting.