JPH06264799A - Idle engine speed control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent rise of idle engine speed due to a supplementary air flow rate by an FICD valve becoming excessive in the case when a variable capacity type compressor is used and others. CONSTITUTION:At the time of idle driving, idle engine speed is controlled by feedback control of an AAC valve (step 3), and when a compressor for an air conditioner works, in principle, an FICD valve is switched ON (step 9). In the case when an actual external load is small against a fixed supplementary air flow rate of the FICD valve, as real engine speed Ne excessively rises, when the state of more than judgement value continues for more than ten seconds (step 4), the FICD valve is switched OFF (steps 7, 10). In the same way, when a feedback control value against the AAC valve becomes less than ten % for more than a specified period of time (step 5), the FICD valve is switched OFF, too.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idle speed control device for feedback controlling the idle speed of an internal combustion engine.

[0002]

2. Description of the Related Art An actual idle speed of an internal combustion engine is detected by a crank angle sensor or the like, and the idle speed is set to a target speed by controlling an opening degree of an auxiliary air control valve provided by bypassing a throttle valve. An idle speed control device that performs feedback control is known (see, for example, Japanese Patent Laid-Open No. 62-13753).

There are various methods of this feedback control. For example, a digital type flow control valve is used as an auxiliary air control valve, and its ON duty ratio is proportional to the deviation between the target rotation speed and the actual rotation speed. It is determined by integral control or the like, and the flow rate of auxiliary air is controlled.

On the other hand, in the internal combustion engine for automobiles, the compressor for cooling the vehicle compartment, the hydraulic pump for power steering, etc. are driven by the engine output. Therefore, when these external loads act on the internal combustion engine, the internal combustion engine remains as it is. The idle speed of the engine fluctuates greatly. In addition, the target idle speed itself may be set higher than the normal time in order to secure the cooling capacity. Therefore, conventionally, in addition to the above-described auxiliary air control valve for feedback control, an auxiliary air control valve for an external load is provided in parallel, and when an external load is applied, a predetermined amount of the auxiliary air control valve for the external load is provided. Some have also introduced auxiliary air. As the auxiliary air control valve for the external load, for example, a simple open / close type solenoid valve is used. In this way, the auxiliary air control valve for the external load is provided separately from the feedback control auxiliary air control valve. As a result, the capacity of the feedback control auxiliary air control valve can be made relatively small.

[0005]

The auxiliary air control valve for an external load as described above is, of course, the O of the external load.
Opening / closing is controlled in conjunction with N and OFF. For example, an auxiliary air control valve, a so-called FICD valve, provided as an external load for a compressor for an air conditioner is always kept open while the compressor is operating, and introduces a predetermined amount of auxiliary air. However, in the case of the variable displacement compressor that has been widely adopted in recent years, the compressor is
Even in the N state, the external load actually acting on the internal combustion engine may be very small. In this case, the auxiliary air flow rate of the above-described auxiliary air control valve for feedback control is feedback-controlled in a decreasing direction, but since the auxiliary air flow rate of the FICD valve is a fixed value, the feedback control may be performed depending on the outside temperature and the like. Even if the flow rate of the auxiliary air control valve for the vehicle is at a minimum, the total auxiliary air flow rate may be too large for the load, and the idle rotation speed is kept higher than the target rotation speed. There was a chance

[0006]

Therefore, according to the present invention,
Even when the external load is working, the auxiliary air control valve for the external load is closed according to the magnitude of the actual external load.

That is, as shown in FIG. 1, the idle speed control device for an internal combustion engine according to the present invention variably controls the auxiliary air flow rate of the internal combustion engine according to the magnitude of the feedback control value. 1, a rotation speed detection means 2 for detecting an actual rotation speed of the internal combustion engine, a feedback control means 3 for setting the feedback control value according to a deviation between the detected rotation speed and a target rotation speed, and a specific external A second auxiliary air control valve 4 provided individually corresponding to the load and introducing a predetermined amount of auxiliary air when the corresponding external load is turned on, and when the second auxiliary air control valve 4 is turned on,
And a high idle prevention means 5 for turning off the second auxiliary air control valve 4 when the deviation between the engine speed and the target speed is greater than or equal to a predetermined value or the feedback control value is less than or equal to a predetermined value. Is characterized by.

[0008]

When the external load is not acting, the second auxiliary air control valve 4 is in the OFF state, and the auxiliary air is introduced only through the first auxiliary air control valve 1. This first
The auxiliary air control valve 1 variably controls the auxiliary air flow rate according to the magnitude of the feedback control value set by the feedback control means 3 according to the deviation between the actual rotation speed and the target rotation speed. As a result, the actual engine speed is kept near the target speed.

On the other hand, when the external load such as the air conditioner compressor is turned on, the second auxiliary air control valve 4 is turned on accordingly, and a predetermined amount of auxiliary air is introduced. That is, the auxiliary air is introduced through both the first and second auxiliary air control valves 1 and 4.

Here, if the auxiliary air flow rate introduced from the second auxiliary air control valve 4 is too large as compared to the actual external load, the auxiliary air flow rate of the first auxiliary air control valve 1 is very small. Even then, the actual rotation speed tends to exceed the target rotation speed. Therefore, in this case, the second auxiliary air control valve 4 is turned off by the high idle prevention means 5, and the auxiliary air flow rate is suppressed to match the actual load. In addition, as described above, when the auxiliary air flow rate by the second auxiliary air control valve 4 is excessive, the first auxiliary air control valve 1
Since the feedback control value given to is extremely small, the second auxiliary air control valve 4 is similarly turned off by the determination based on this.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a structural explanatory view showing a mechanical structure of an idle speed control device according to the present invention. A throttle valve 13 is provided in an intake passage 12 of an internal combustion engine 11 and the throttle valve 13 is provided. The first bypass passage 14 and the second bypass passage 15 so as to bypass the valve 13.
Are formed in parallel. In the first bypass passage 14,
An AAC valve 16 which is an appropriate digital flow control valve is interposed as the first auxiliary air control valve, and the second auxiliary air control valve is provided.
The bypass passage 15 has O as a second auxiliary air control valve.
A FICD valve 17, which is an N, OFF type solenoid valve, is interposed. It should be noted that the AAC valve 16 uses the O of the drive pulse signal given as the feedback control value.
The flow rate of the auxiliary air is controlled according to the N duty ratio. The FICD valve 17 has a fixed flow rate that can sufficiently offset the load of the air conditioner compressor (not shown).

The throttle valve 13 is provided with an idle switch 18 which issues an ON signal when the throttle valve 13 is in a substantially fully closed position, that is, at an idle opening.

Then, the throttle valve 13 in the intake passage 12
An air flow meter 19 for detecting the entire engine intake air flow rate including the auxiliary air is disposed on the upstream side. The fuel injection valve 20 is provided for each cylinder on the downstream side of the intake passage 12.
Is provided.

Reference numeral 21 denotes a water temperature sensor for detecting the cooling water temperature of the internal combustion engine 11, and 22 denotes an air-fuel ratio sensor for detecting the richness of the air-fuel ratio from the residual oxygen concentration in the exhaust gas.

Further, the internal combustion engine 11 is provided with a crank angle sensor 23, which rotates in synchronization with the engine crankshaft and generates a pulse signal at every constant crank angle, as rotation speed detecting means.

Reference numeral 24 is an air conditioner switch operated by a driver, and 25 is an air conditioner relay for turning on and off an electromagnetic clutch for a compressor (not shown).

A control unit 26 controls the auxiliary air flow rate by the AAC valve 16 and the FICD valve 17 and the injection amount in the fuel injection valve 20 based on the detection signals of the above-mentioned sensors, and feedback-controls the idle speed. Is shown. The control unit 26 is composed of a digital microcomputer system including a CPU, a RAM, a ROM and an I / O port, and controls idle speed according to a predetermined program.

In the structure of the above embodiment, when the idle switch 18 detects the fully closed state of the throttle valve 13, that is, the idle state, the deviation between the actual rotational speed detected by the crank angle sensor 23 and the target rotational speed. According to AA
The C valve 16 is feedback-controlled. Specifically, the feedback control value corresponding to the ON duty ratio of the drive pulse signal of the AAC valve 16 is calculated by the proportional-plus-integral control based on the deviation, and the first bypass passage 14 is opened depending on the magnitude of the feedback control value. It is designed to increase or decrease the flow rate of auxiliary air passing through.

On the other hand, when the air conditioner compressor, which is a representative of the external load, operates, the FICD valve 17 is turned on so as to cancel the external load, and the predetermined amount of auxiliary air is increased.

The flow chart of FIG. 3 shows the contents of control of the FICD valve 17 with respect to the operation of the air conditioner compressor, which will be described below. It should be noted that this process is repeatedly executed at regular intervals.

First, in steps 1 and 2, it is determined whether the air conditioner switch 24 is in the on state or the off state, and if it is in the on state, the compressor (not shown) is turned on via the air conditioner relay 25. Next, step 3
Then, it is determined whether or not the feedback control of the idle speed using the AAC valve 16 is being performed. If the idle speed feedback control is being executed, the routine proceeds to steps 4 and 5, where it is determined whether the engine is in the so-called high idle state. That is, in step 4, the actual rotational speed Ne and the determination reference value (Nset +
d), the actual rotation speed Ne is determined by the determination reference value (Nset).
It is determined whether or not the state of + d) or more continues for 10 seconds or more. The Nset indicates the target rotation speed at that time, and as shown in FIG. 4, the determination reference value is set higher than the target rotation speed Nset by a predetermined amount d. Further, in step 5, the feedback control value given to the AAC valve 16 is a predetermined judgment reference value (for example, 1
It is determined whether or not the state of being 0% or less has continued for 20 seconds. If the determinations at step 4 and step 5 are both NO, go to step 6,
Set the flag to 1. If YES in either step 4 or step 5, the process proceeds to step 7 and the flag is set to 0.

Then, in step 8, the flag is judged. If the flag is 1, the process proceeds to step 9 and the FICD
The valve 17 is turned on. That is, the auxiliary air is introduced through the FICD valve 17. If the flag is 0 in step 8, the process proceeds to step 10 and the FICD valve 17 is turned off. That is, the introduction of the auxiliary air via the FICD valve 17 is stopped.

That is, when the air conditioner compressor is in the ON state in the idle state, in principle, F
When the ICD valve 17 is turned on, but the actual rotation speed Ne remains above the judgment reference value (Nset + d) for 10 seconds or longer, or the feedback control value of the AAC valve 16 falls below 10%. If it continues for 20 seconds or more, the flag becomes 0 (step 7) to avoid the high idle state, and the FICD valve 17 becomes O.
The FF state is set (step 10).

If the air conditioner switch 24 is OFF in step 1, the process proceeds to step 11, the flag is set to 1, and the process proceeds to step 12.
The FICD valve 17 is kept in the OFF state. Therefore, when the air conditioner switch 24 is ON and in the non-idle state (step 3), the flag is 1 in principle, and the auxiliary air is introduced through the FICD valve 17.

FIG. 4 shows changes in engine speed at the start of air conditioner operation based on the above flow chart.
When the air conditioner switch 24 is turned on as shown in (a), the air conditioner relay 25 is interlocked as shown in (b) to start driving the compressor (not shown), and (c).
The FICD valve 17 is turned on as shown in FIG. As a result, a predetermined amount of auxiliary air is introduced through the second bypass passage 15, so that the engine speed reduction shown in (d) is prevented. In particular, in this embodiment, in order to secure the cooling capacity of the idle value, the target rotation speed Nset is set to be high at the same time when the air conditioner is turned on. Therefore, after a slight delay, the engine rotation speed Ne is It rises as shown in (d). On the other hand, the feedback control value given to the AAC valve 16 temporarily increases as the target rotation speed Nset increases, but the actual rotation speed Ne is equal to the target rotation speed Ns.
When it exceeds et, it gradually decreases.

When the actual compressor load is relatively smaller than the auxiliary air flow rate by the FICD valve 17 in a variable displacement compressor or the like, the actual rotation speed Ne is the target rotation speed as shown in (d). A state in which Nset, and further, the determination reference value (Nset + d) set higher than this, is exceeded continues for a long time. Therefore, when this state continues for a predetermined time, specifically, 10 seconds, the FICD valve 17 is turned off as shown in FIG. 4C based on the determination in step 4 of the above-mentioned flowchart. This allows
The actual idle speed Ne can be reduced to near the target speed Nset.

When the actual rotation speed Ne continues to exceed the target rotation speed Nset in this way, the feedback control value gradually decreases as shown in (e) and reaches the minimum value of 10% or less. . Therefore, this feedback control value is 1
Even when the state of 0% or less continues for a predetermined time, specifically, 20 seconds or more, the FICD valve 17 is turned off.

As described above, the FICD valve 17 is turned off.
After that, the idle speed control is performed only by the feedback control of the AAC valve 16 including the load of the compressor.

Although the embodiment in which the present invention is applied to the control of the FICD valve 17 corresponding to the load of the air conditioner compressor has been described above, the present invention is not limited to this, and another power steering oil pump is provided. The same can be applied to the case where the second auxiliary air control valve is provided for external loads such as.

[0031]

As is apparent from the above description, according to the idle speed control device for an internal combustion engine according to the present invention, the idle speed is excessively increased even when the external load actually acting on the internal combustion engine is small. It is possible to perform more appropriate idle speed control without increasing the temperature. In particular, it is not necessary to strictly match the magnitude of the external load with the flow rate of the second auxiliary air control valve for the external load, which is suitable when a variable displacement compressor is used as the external load.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of the present invention.

FIG. 2 is a structural explanatory view showing an embodiment of an idle speed control device according to the present invention.

FIG. 3 is a flowchart showing control of a FICD valve in this embodiment.

FIG. 4 is a time chart showing changes in engine speed and the like at the start of air conditioner operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st auxiliary air control valve 2 ... Rotation speed detection means 3 ... Feedback control means 4 ... 2nd auxiliary air control valve 5 ... High idle prevention means

Claims (1)

[Claims] 1. A first auxiliary air control valve for variably controlling an auxiliary air flow rate of an internal combustion engine according to the magnitude of a feedback control value, a rotation speed detecting means for detecting an actual rotation speed of the internal combustion engine, and a detected rotation. Feedback control means for setting the feedback control value in accordance with the deviation between the number of revolutions and the target speed, and a specific amount of auxiliary air provided when the external load is turned on. When the deviation between the engine speed and the target speed is greater than or equal to a predetermined value or the feedback control value is less than or equal to a predetermined value when the second auxiliary air control valve to be introduced and the second auxiliary air control valve are turned on, An idle speed control device for an internal combustion engine, comprising: a high idle prevention means for turning off a second auxiliary air control valve.