JPH11141369A - Idle speed control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the fluctuation width of engine speed when a compressor for an air-conditioner is brought into ON/OFF during idle of an internal combustion engine. SOLUTION: An ECU 15 calculates the magnitude of the load of an air- conditioner from the ON time and the OFF time of a compressor 52 for an air-compressor and based on the magnitude of the load of the air-conditioner, an ON delay time t1 and an OFF delay time t2 are read from a map. When, during idle of an internal combustion engine 1, the compressor 52 is operated, the compressor 52 is operated after a lapse of the ON delay time t1 corresponding to the magnitude of the load of the air-conditioner and starting from the start of control of the idle speed such that engine speed is adjusted to second target idle engine speed NI2 . In a stop of the compressor 52, the compressor 52 is stopped after a lapse of an OFF delay time t2 corresponding to the magnitude of the load of the air-conditioner and starting from the start of idle speed control such that the engine speed is adjusted to first target idle speed NI1 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Generally, an internal combustion engine for a vehicle is provided with a so-called idle speed control device for adjusting an intake air amount so that the engine speed becomes a target idle speed at the time of idling. When an air conditioner (hereinafter, abbreviated as air conditioner or A / C) is operated during idle speed control by the idle speed control device,
Compressor constituting a part of the refrigeration cycle in the air conditioner (hereinafter, sometimes abbreviated as COMP) is set higher also than the target idle speed NI ₁ when the target idle speed NI ₂ in the OFF state when the ON state Japanese Unexamined Patent Publication No. Hei 8-3 discloses performing idle speed control (hereinafter referred to as idle-up control, sometimes abbreviated as IUC).
It is known from, for example, JP-A-34048.

[0003] The reason why the idle-up control is performed when the compressor is ON is to stabilize the operation of the internal combustion engine. That is, since the compressor normally uses the internal combustion engine as a power source, the load on the internal combustion engine increases as the compressor is driven. If such a load is originally applied at the time of idling with a small engine output, it causes a decrease in idle speed and a stall of the engine. Therefore, if it is necessary to operate the compressor at the time of idling, the problem is prevented from occurring by increasing the target idle speed.

By the way, the compressor is turned on from OFF.
When the target idle speed is increased from NI ₁ to NI ₂ by the execution of the idle-up control with switches, the expected deterioration idle speed immediately after the compressor ON, delayed from the start of the idle-up control the predetermined time period and it is ON compressor Te (hereinafter, this delay time of ON delay time t _a). On the other hand, when lowering the target idle speed to stop the idle-up control with switching OFF the compressor from ON from NI ₂ to NI _1, the expected idle speed increase of just after the compressor OFF, idle-up control Compressor OF
And then F (hereinafter, the delay time of OFF delay time t _b).

[0005]

The decrease in the idle speed immediately after the compressor is turned on is small when the load on the air conditioner is small and large when the load on the air conditioner is large. In addition, the increasing range of the idle speed immediately after the compressor is turned off is small when the load on the air conditioner is small, and large when the load on the air conditioner is large.

In the conventional idle speed control device,
Regardless of the size of the air conditioner load, the ON delay time t _a was constant, and the OFF delay time t _b was also constant. Therefore, as shown in FIG. 14, when executing the idle-up control, when the air conditioning load is small, the idle speed after the compressor ON exceeds the target idle rotation speed NI _2, may called overshoot phenomenon , Controllability was bad.

On the other hand, as shown in FIG. 15, when executing the idle-up control, when the air conditioning load is large, the idle speed right after the compressor ON is lower than the target idle rotational speed NI _1, the so-called undershoot phenomenon It occurs when there is, also, like it takes time to reach a target idle speed NI ₂ after undershoot, also controllability was poor.

Further, as shown in FIG. 16, when the user stops the idle-up control, when the air conditioning load is small, the idle speed right after the compressor OFF exceeds the target idle rotational speed NI _2, a so-called overshoot phenomenon In some cases, controllability was poor.

On the other hand, as shown in FIG. 17, when the user stops the idle-up control, when the air conditioning load is large, the idle speed before the compressor OFF falls below the target idle rotational speed NI _1, the so-called undershoot phenomenon In some cases, controllability was poor.

[0010] The present invention has been made in view of the above-described problems, and has been described in connection with the following description.
An object of the present invention is to improve the controllability of idle speed control by changing a delay time or an OFF delay time from a stop of idle-up control to a compressor OFF in accordance with a load on an air conditioner.

[0011]

The present invention employs the following means in order to solve the above-mentioned problems. That is, at the time of idling of the internal combustion engine, when the compressor forming a part of the air conditioner refrigeration cycle is stopped, feedback control is performed so that the engine speed becomes the first target idle speed, and the compressor is operated. Feedback control is performed so that the engine speed becomes a second target idle speed higher than the first target idle speed, and when the compressor is operated, the engine speed becomes the second target idle speed. The compressor is operated after the ON delay time has elapsed since the start of the idle speed control so as to attain the idle speed. When the compressor is stopped, the engine speed is set to the first target idle speed. After starting the idle speed control,
An idle speed control device for an internal combustion engine that performs control so as to stop the compressor after the elapse of the F delay time. In the idle speed control device for the internal combustion engine, an air conditioner load detecting means for detecting a magnitude of a load on the air conditioner; According to the size of the load, at least the ON
And delay time changing means for changing any one of the delay time and the OFF delay time.

In the idle speed control device for the internal combustion engine thus configured, the air conditioner load detecting means detects the magnitude of the load of the air conditioner, and the delay time changing means detects the air conditioner load detected by the air conditioner load detecting means. Either one or both of the ON delay time and the OFF delay time is changed according to the magnitude of the load.

When the compressor for the air conditioner is operated, the control of the idle speed is started so that the engine speed becomes the second target idle speed.
After the ON delay time set in accordance with the size of the air conditioner load has elapsed, the compressor is operated, and when the compressor is stopped, the idle speed is set so that the engine speed becomes the first target idle speed. After starting the control, the OFF set according to the size of the air conditioner load
After the delay time has elapsed, stop the compressor.

By performing such processing, the compressor for the air conditioner is turned on / off when the internal combustion engine is idling.
The fluctuation range of the idling speed that occurs when the FF is performed is reduced, and even when the load of the air conditioner is of any magnitude, the occurrence of overshoot or undershoot when the compressor is turned ON / OFF is prevented, and the load of the air conditioner is reduced. , The deviation from the target idle speed can be reduced.

It is preferable that the delay time changing means changes the ON delay time to a longer time and the OFF delay time to a shorter time as the load on the air conditioner increases.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an internal combustion engine idle speed control apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 to which an idle speed control device for an internal combustion engine is applied. The internal combustion engine 1 shown in FIG. 1 is a four-cycle gasoline engine for an automobile. The internal combustion engine 1 includes a cylinder block 1a in which a plurality of cylinders 2 are formed, and a cylinder head 1b fixed to an upper portion of the cylinder block 1a.

Each cylinder 2 of the cylinder block 1a is loaded with an axially slidable piston 3, and this piston 3 is connected to a crankshaft 4 which is an engine output shaft. Above the piston 3, a combustion chamber 5 surrounded by the top surface of the piston 3 and the cylinder head 1b is formed.

An ignition plug 6 is attached to the cylinder head 1b so as to face the combustion chamber 5, and the open ends of the intake port 7 and the exhaust port 8 are formed so as to face the combustion chamber 5. Further, the cylinder head 1b includes:
An intake valve 9 and an exhaust valve 10 for opening and closing the open ends of the intake and exhaust ports 7 and 8 are supported to be able to move forward and backward, and an intake camshaft 11 and an exhaust camshaft for driving the intake and exhaust valves 9 and 10 to open and close. 12 are rotatably supported.

The intake camshaft 11 and the exhaust camshaft 12 are connected to the crankshaft 4 via a timing belt (not shown).
The rotational force of the crankshaft 4 is transmitted to the intake camshaft 11 and the exhaust camshaft 12 via the timing belt.

The internal combustion engine 1 has a crankshaft 4
Is provided with a crank position sensor 13 that outputs an electric signal each time the motor rotates a predetermined angle (for example, 10 degrees). Further, a water temperature sensor 14 that outputs an electric signal corresponding to the temperature of the cooling water flowing in the cooling water flow path 1c formed in the cylinder block 1a is attached to the cylinder block 1a.

Next, the intake port 7 communicates with an intake branch pipe 16 attached to the cylinder head 1b, and the intake branch pipe 16 is connected to a surge tank 17. The surge tank 17 is connected to an air cleaner box 19 via an intake pipe 18.

The intake pipe 18 is provided with a throttle valve 20 for opening and closing an intake passage in the intake pipe 18 in conjunction with an accelerator pedal (not shown).
At 0, a throttle position sensor 21 that outputs an electric signal corresponding to the opening of the throttle valve 20 is attached.

The intake pipe 1 upstream of the throttle valve 20
8, an air flow meter 2 for outputting an electric signal corresponding to the mass of fresh air flowing through the intake pipe 18 (mass of intake air);
2 is attached.

Further, a bypass pipe 23 for bypassing the throttle valve 20 is connected to the intake pipe 18.
An idle speed control valve (ISCV) 24 for adjusting the flow rate of fresh air flowing in the bypass pipe 23 is attached to the bypass pipe 23.

When the internal combustion engine 1 is idling (when the throttle valve 20 is fully closed), the ISCV 24 opens the flow path of the bypass pipe 23 and supplies the intake air of an amount required for the internal combustion engine 1 to rotate at idle. Bypass from upstream to downstream.

A fuel injection valve 25 is attached to the intake branch pipe 16 such that its injection hole faces the intake port 7. This fuel injection valve 25 is connected to a drive circuit 38,
The valve opens when a drive current from the drive circuit 38 is applied, and fuel is injected into the intake branch pipe 16.

The exhaust port 8 communicates with an exhaust branch pipe 26 attached to the cylinder head 1b, and the exhaust branch pipe 26 is connected to an exhaust pipe 27. The exhaust pipe 27 is connected to a muffler (not shown).

Next, as shown in FIG. 2, the automobile of this embodiment is provided with an air conditioner 50 for cooling and dehumidifying the air in the passenger compartment. The air conditioner 50 includes an evaporator (evaporator) 51, a compressor (compressor) 52,
A refrigeration cycle including a condenser (condenser) 53, a receiver 54, an expansion valve 55, etc., a fan 56 for blowing air outside the vehicle or inside the vehicle to the evaporator 51 and supplying cool air to the vehicle interior, and air to the evaporator 51. An inlet temperature sensor 57 that outputs an electrical signal corresponding to the temperature of the air, and a blowout temperature sensor 58 that outputs an electrical signal corresponding to the temperature of the air that is cooled by the evaporator 51 and blown into the vehicle interior are provided.

The drive shaft of the compressor 52 is a belt 27
And is connected or disconnected by a magnet clutch 29 to a rotation shaft of a pulley 28 that is driven to rotate by the crankshaft 4 via the.

The air conditioner 50 can be automatically operated or stopped by turning on / off an air conditioner switch 59 installed in the vehicle interior. Cooling in the vehicle interior is performed by circulating a refrigerant according to the refrigeration cycle. That is, when the liquid refrigerant passes through the evaporator 51 and evaporates, the heat of the surrounding air is deprived, and the cooled air is blown into the vehicle interior by the fan 56. The refrigerant gas vaporized by the evaporator 51 is sucked into the compressor 52 and then compressed to a high temperature. This refrigerant gas is cooled and liquefied when passing through the condenser 53. The refrigerant liquefied by the condenser 53 is temporarily stored in the receiver 54. The high-temperature and high-pressure liquid refrigerant that has passed through the receiver 54 is expelled from the small holes of the expansion valve 55 to rapidly expand in volume and becomes a low-temperature and low-pressure mist-like refrigerant. This mist-like refrigerant is evaporated again by the evaporator 51.

In the air conditioner 50, the temperature in the vehicle compartment is controlled to a set temperature by turning on / off the compressor 52. When the load on the air conditioner 50 is large, the ON time of the compressor 52 becomes longer and the OF
When the F time is short and the load on the air conditioner 50 is small, the ON time of the compressor 52 is short and the OFF time is long.

Next, the crank position sensor 1
3. Various sensors such as the water temperature sensor 14, the throttle position sensor 21, the air flow meter 22, the inlet temperature sensor 57, and the outlet temperature sensor 58 are connected to an electronic control unit (Electronic) for engine control via electric wiring. Control Unit: ECU)
15 and the output signal of each sensor is
To be entered.

Then, the ECU 15 determines the operating state of the internal combustion engine 1 using the output signals from the various sensors as parameters, and in accordance with the operating state, the ignition plug 6,
Various controls of the ISCV 24, the drive circuit 38, the fan 56, and the like are performed, and on / off control (connection / disconnection of the magnet clutch 29) of the compressor 52, which is the gist of the present invention, is performed.

Here, as shown in FIG. 3, the ECU 15 is connected to a CP which is interconnected by a bidirectional bus 39.
U40, a ROM 41, a RAM 42, an input port 43, and an output port 44.
A / D converter (A / D) 45 connected to the

The input port 43 receives signals from the throttle position sensor 21, the crank position sensor 13, and the air conditioner switch 59, and sends these signals to the CPU 40 or the RAM 42. Further, the input port 43 inputs signals from the water temperature sensor 14, the air flow meter 22, the inlet temperature sensor 57, and the outlet temperature sensor 58 via the A / D converter 45, and transmits these signals to the CPU 40 or the RAM 42. I do.

The output port 44 sends a control signal from the CPU 40 to the ignition plug 6, the ISCV 24,
8. Output to the magnet clutch 29 or the fan 56.

The ROM 41 includes a fuel injection amount control routine for determining the fuel injection amount, a fuel injection timing control routine for determining the fuel injection timing, an ignition timing control routine for determining the ignition timing, and a target of the ISCV 24. ISCV control routine for determining opening, air conditioner 5
An application program such as an idle speed control routine for controlling the idle speed by changing the ON / OFF timing of the compressor 52 according to the load of 0, and various control maps are stored.

The control map includes, for example, a fuel injection amount control map showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection amount, and a fuel injection timing control showing the relationship between the operating state of the internal combustion engine 1 and the fuel injection timing. A map, an ignition timing control map showing the relationship between the operating state of the internal combustion engine 1 and the ignition timing, a target idle speed control map showing the relationship between the operating state of the compressor 52 and the target idle speed, and the magnitude of the load of the air conditioner 50. An ON delay time control map (FIG. 7) or an OFF delay time control map (FIG. 8) showing the relationship between the ON delay time and the OFF delay time for the compressor 52 is shown.

Subsequently, the RAM 42 stores the output signals from the respective sensors, the calculation results of the CPU 40, and the like. The calculation result is, for example, an engine speed calculated from an output signal of the crank position sensor 13. The output signal from each sensor, the calculation result of the CPU 40, and the like are rewritten to the latest data every time the crank position sensor 13 outputs a signal.

Next, the CPU 40 reads the ROM 41
Operates in accordance with the application program stored in the CPU, determines the operating state of the internal combustion engine 1 from the output signal of each sensor, and determines the fuel injection amount,
The fuel injection timing, ignition timing, ISCV opening, and the like are calculated.
Then, the CPU 40 determines the drive circuit 3 according to the calculated fuel injection amount, fuel injection timing, ignition timing, and ISCV opening.
8. Control the ignition plug 6 and the ISCV 24.

The idle speed control is performed by a signal indicating the fully closed state of the throttle valve 20 from the throttle position sensor 21 or an O signal from an idle switch (not shown).
When the N signal is input to the CPU 40, the CPU 40
This is realized by executing an idle speed control routine of the OM 41. At that time, first, the CPU 40 calculates the target idle speed by using the operating state of the compressor 52 of the air conditioner 50 as a parameter. That is, when the compressor 52 is OFF, the target idle speed is set to the first idle speed.
Of the target idle rotation speed NI _1, the compressor 52 is the target idle speed NI ₂ the number of rotation target idle of the first second greater than the target idle speed NI ₁ when the _{ON (NI 2> NI 1)} , Next, a control value of the ISCV 24 corresponding to the target idle speed is calculated, and the control value is transmitted to the ISCV 24 via the output port 44. Subsequently, the CPU 70 calculates the actual engine speed based on the output signal of the crank position sensor 13, and determines the control amount of the ISCV 24 in accordance with the difference between the target idle speed and the actual engine speed, a so-called "so-called". Feedback control is performed so that the actual engine speed becomes the target idle speed.

In the following description, in this idle speed control, setting the target idle speed to the second target idle speed NI ₂ and controlling the idle speed is referred to as idle-up control. execution of the idle-up control means to set the rotational speed target idle to the second target idle speed NI _2, stop of the idle-up control is set a rotational speed target idle the first target idle speed NI ₁ Shall mean.

The CPU 40 is provided with the air conditioner switch 5
When an ON signal is input from the air conditioner 9 (that is, when the air conditioner 50 is automatically operated), as shown in FIG. It comes to T ₁ or more,
First, perform the idle-up control is (are displayed in ON in the figure), then, ON the compressor 52 from the idle-up control is started after the ON delay time t ₁ has elapsed (i.e., the magnetic clutch 29 ON) to, balloon When the temperature falls below the compressor OFF temperature T _2, first, the idle-up control is stopped (in the figure are displayed at OFF), then, OFF from the idle-up control stop
Turn off compressor 52 after delay time t _{2 has} elapsed
(That is, the magnet clutch 29 is turned off).

The CPU 40 calculates the load of the air conditioner 50, and calculates the ON delay time t ₁ and the OFF delay time t ₂ from the maps of FIGS. 7 and 8 according to the magnitude of the load.

The operation and effect of the internal combustion engine idle speed control device according to the present embodiment will be described below. The CPU 40 of the ECU 15 includes an air conditioner switch 59
When the ON signal is input from the throttle position sensor 21 and a signal indicating the fully closed state of the throttle valve 20 is input, or when the ON signal is input from an idle switch (not shown), 5
And an idle speed control routine shown in FIG. This idle speed control routine is executed every predetermined time (for example, several ms).

First, the CPU 40 calculates the load on the air conditioner 50 in step 100. The load on the air conditioner 50 is obtained by the following equation. A / C load (%) = [(COMP.ON time) / ｛(COMP.ON time)
+ (COMP.OFF time)｝] × 100 Here, the compressor ON time (COMP.ON time) or the compressor OFF time (COMP.OFF time) is determined in step 109 or step 118 when this control routine was executed last time. The updated compressor ON time or compressor OFF time is used.

Next, the CPU 40 proceeds to step 101, reads out the ON delay time t ₁ corresponding to the air conditioner load with reference to the ON delay time map shown in FIG. 7, and further proceeds to step 102, which is shown in FIG. with reference to the OFF delay time map reading the OFF delay time t ₂ in accordance with the air conditioning load. The ON delay time t ₁ is small when the air conditioner load is small, gradually increases as the air conditioner load increases, and is set to a maximum at 100% air conditioner load. On the other hand, the OFF delay time t ₂ is maximum when the air conditioner load is zero, gradually decreases as the air conditioner load increases, and is set to a minimum at 100% air conditioner load.

Next, at step 103, the CPU 4
0 determines whether or not the compressor 52 of the air conditioner 50 is in the ON state. In addition, turn on the air conditioner switch 59
In the first execution of the present control routine immediately after the execution, steps 100 to 102 are not performed.
Referring to another map (not shown) in which the evaporator inlet temperature corresponds to the ON delay time t ₁ or the OFF delay time T ₂ , the ON delay time t ₁ and the OFF delay time based on the output signal from the inlet temperature sensor 57. t ₂
Is set, and the routine proceeds to step 103.

At step 103, the compressor 52 is turned on.
If it is determined that the state is in the state, the CPU 40 proceeds to step 1
Advances to 04, air temperature T is equal to or less OFF temperature T _2.

When it is determined that the blow-out temperature T is equal to or lower than the OFF temperature T ₂ , the CPU 40 proceeds to step 105, stops the idle-up control, and sets the actual engine speed to the first target idle speed NI _1. Control so that

[0052] Subsequently, CPU 40 proceeds to step 106, it is determined whether the OFF delay timer OFF delay time t ₂ or more read out in step 102. If OFF delay timer is determined to not OFF delay time t ₂ or more, CPU 40, the step 10
7, the OFF delay timer is counted up, and idle-up control is stopped.
The delay time until 2 is turned off is integrated.

Subsequently, the CPU 40 proceeds to step 108, counts up the compressor ON time timer, accumulates the ON time of the compressor 52, and ends the execution of this control routine.

If it is determined in step 104 that the blowing temperature T is not lower than the OFF temperature T ₂ ,
U40 proceeds to step 108 where the compressor 52
And the compressor ON time timer is counted up.

In step 106, the OFF
Ray timer is OFF delay time t _TwoIt is judged that it is more than
If so, the CPU 40 proceeds to step 109 and
At step 108 of the executed control routine,
The value of the compressor ON time timer
In the RAM 42 of the ECU 15 as the Lesser ON time
Update. The updated compressor ON time is
The next time this control routine is executed, step 100
The air-conditioner load read from the RAM 42
Used for calculation.

Next, the CPU 40 proceeds to step 110, turns off the compressor 52, and further proceeds to step 1
Proceeding to 11, the compressor ON time timer is cleared, and proceeding to step 112, the OFF delay timer is cleared, and the execution of this control routine ends.

If it is determined in step 103 that the compressor 52 is not in the ON state, the CPU
In step 40, the process proceeds to step 113, and the blowing temperature T is turned on.
Determining whether a temperature above T _1.

[0058] If the air temperature T is determined to be ON temperature above T _1, CPU 40 proceeds to step 114, by performing the idle-up control, the actual engine speed second target idle speed NI ₂ Control so that

Subsequently, the CPU 40 proceeds to step 115 and determines whether or not the ON delay timer is equal to or longer than the ON delay time t ₁ read in step 101.
If the ON delay timer is determined not to be ON delay time t ₁ or more, CPU 40, the program proceeds to a step 116, increments the ON delay timer, the delay time from the start of the idle-up control until ON the compressor 52 Is multiplied.

Subsequently, the CPU 40 proceeds to step 117, counts up the compressor OFF time timer, accumulates the OFF time of the compressor 52, and ends the execution of this control routine.

If it is determined in step 113 that the blowing temperature T is not higher than the ON temperature T ₁ ,
The PU 40 proceeds to step 117, where the compressor 5
2 and the compressor OFF time timer is counted up.

If it is determined in step 115 that the ON delay timer is equal to or longer than the ON delay time t ₁ , the CPU 40 proceeds to step 118 and executes the compressor OFF time timer counted up in step 117 of the present control routine executed last time. Is updated in the RAM 42 of the ECU 15 as the compressor OFF time. When the updated compressor OFF time is executed next time, this control routine is executed.
At 00, it is read from the RAM 42 and used for calculating the air conditioner load.

Next, the CPU 40 proceeds to step 119, turns on the compressor 52, and further proceeds to step 12
The routine proceeds to 0, the compressor OFF time timer is cleared, the routine proceeds to step 121, the ON delay timer is cleared, and the execution of this control routine is terminated.

As described above, by executing the idle speed control routine of the ROM 41, the CPU 40 realizes the air conditioner load detecting means and the delay time changing means according to the present invention.

Here, a specific control example of the idle speed control device for the internal combustion engine according to the present embodiment will be described with reference to FIGS. 9 to 12. 9 and 10, air temperature T rises to the ON temperature above T _1, shows a case of switching to ON the compressor 52 from the OFF, when the air temperature T is turned ON temperature above T _1, first, idle up control is executed (IUC start), the actual engine speed rises to approach the first target idle speed NI ₁ to the second target idle speed NI _2. When the ON delay time t ₁ elapses from the start of the idle-up control, the compressor 52 is turned on, and the air conditioner 50 performs cooling.

FIG. 9 shows a case where the load on the air conditioner is small. At this time, the ON delay time t _{1 is set.}
Is set short. Thus, to set short ON delay time t ₁ when air conditioning load is small, in order to prevent an overshoot phenomenon. That is, conventionally, when the air conditioner load is small, the overshoot phenomenon occurs as shown in FIG. 14 because the ON delay time is too long and the engine speed becomes the second target idle speed NI
_This is because the compressor is turned on when approaching ₂ . Incidentally, when the air conditioning load is small, so that small drop in the engine speed due to the compressor 52 to ON, undershoot phenomenon does not occur even set a short ON delay time t ₁ in this way.

FIG. 10 shows a case where the air conditioner load is large. At this time, the ON delay time t ₁ is set long. Thus, to set a longer ON delay time t ₁ when a large air conditioning load, and to prevent the undershoot phenomenon, is to reduce the drop engine speed when the compressor 52 is turned ON . Conventionally, the undershoot phenomenon occurs as shown in FIG. 15 when the load of the air conditioner is large, because the undershoot phenomenon occurs when the load of the air conditioner is large despite the large decrease in the engine speed when the compressor is turned on.
Because paddle delay time is short, there is a reason to ON the compressor before the engine speed approaches the second target idle speed NI _2. Therefore, when the air-conditioner load is large, the ON delay time t ₁ is lengthened so that the engine speed becomes equal to the second target idle speed N
And from close to the I ₂ such that the compressor 52 to ON. Further, since the engine speed is in the ON compressor 52 from approaching the second target idle speed NI _2, becomes relatively small engine speed drop due to the compressor 52 is turned ON, then Second
Even faster convergence to the target idle speed NI _2.

FIGS. 11 and 12 show that the blowing temperature T is O
Lowered to FF temperature T ₂ less, ON the compressor 52
Shows a case where switching to OFF from the outlet temperature T falls below OFF temperature T _2, first, the idle-up control is stopped (IUC stop), the actual engine speed second target idle speed NI ₂ first decreases to approach the target idling rotational speed NI ₁ from. When the OFF delay time t ₂ has elapsed since the stop of the idle-up control, the compressor 52 is turned off, and the air conditioner 50 is turned off.
Is stopped.

FIG. 11 shows a case where the load on the air conditioner is small. In this case, the OFF delay time t ₂ is set to be long. Thus, the to set long OFF delay time t ₂ when air conditioning load is small, and in order to prevent an overshoot phenomenon caused by turning OFF the compressor 52, the compressor 52 O
This is to reduce the increase in the engine speed when the FF is set. Conventionally, when the load of the air conditioner is large, the overshoot phenomenon occurs as shown in FIG. 16 because the OFF delay time is short, so that the compressor is turned off when the engine speed is not so low, This is because the compressor is turned off when the engine speed is high, and the increase in the engine speed becomes large. Therefore, when the air conditioning load is small, by increasing the OFF delay time t _2, the engine speed is from close enough to the first target idle speed NI _1, so that the compressor 52 to OFF. Since the compressor 52 is turned off when the engine speed is low, the increase in the engine speed when the compressor 52 is turned off is small, and the overshoot phenomenon does not occur.

FIG. 12 shows a case where the load of the air conditioner is large. In this case, the OFF delay time t ₂
Is set short. Thus, the to set short OFF delay time t ₂ when air conditioning load is large, in order to prevent the undershoot phenomenon. Conventionally, the undershoot phenomenon occurs as shown in FIG. 17 when the air-conditioner load is large because when the idle-up control is stopped when the air-conditioner load is large, the speed at which the engine speed decreases is large. Idle speed NI ₁
It is because there is a cause that it falls below. Therefore, when the air conditioning load is large, by shortening the OFF delay time t _2, while the engine speed is not Kira fall too far from the second target idle speed NI _2, and so that the compressor 52 to OFF. Incidentally, when the air conditioning load is large, since it is relatively greater increase in the engine speed due to the compressor 52 to OFF, setting the OFF delay time t ₂ as overshoot phenomenon does not occur after OFF of the compressor 52 An OFF delay time control map (FIG. 8) is created in advance so as to be executed.

As described above, according to the idle speed control device for the internal combustion engine, regardless of the magnitude of the load on the air conditioner 50, the compressor 52 is turned ON or OFF.
When setting to FF, the fluctuation range of the engine speed becomes smaller,
Since the overshoot phenomenon and the undershoot phenomenon do not occur, the controllability of the idle speed control is improved, and the stability of the idle speed is improved.

FIG. 13 shows an internal combustion engine idling speed control device according to the present invention and a conventional idling speed control device (that is, an on / off control regardless of the load of the air conditioner).
FIG. 9 is a diagram illustrating controllability in a case where a delay time and an OFF delay time are set to a fixed time. In this figure, the horizontal axis is the load of the air conditioner, and the vertical axis is the deviation from the target idle speed. In the case of the idle speed control device of the present invention shown by the solid line, while the load falls within the target deviation range in the entire range of the load of the air conditioner,
In the case of the conventional idle speed control device shown by the broken line,
It can be seen that the target deviation is exceeded in a small range and a large range of the load of the air conditioner.

Further, in the idle speed control device for an internal combustion engine according to the present invention, the deviation from the target idle speed is reduced, so that the quietness at the time of idling is improved. further,
Eliminating the overshoot phenomenon improves the fuel efficiency during idling and reduces the amount of CO ₂ emissions during idling.

[0074]

As described above, according to the idle speed control apparatus for an internal combustion engine according to the present invention, at least one of the ON delay time and the OFF delay time is set according to the load of the air conditioner. Since it can be changed, the fluctuation range of the engine speed when the air conditioner compressor is turned on / off when the internal combustion engine is idling can be reduced, and overshoot and undershoot can be prevented.

As a result, the stability of the idling speed and the controllability of the idling speed control are improved, and the quietness at the time of idling, the fuel efficiency, and the CO ₂ emission are reduced. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an idle speed control device for an internal combustion engine according to the present invention is applied;

FIG. 2 is a diagram showing a schematic configuration of an air conditioner;

FIG. 3 is a diagram showing a configuration of an ECU.

Fig. 4 Blow-off temperature and ON / OFF of compressor
And idle timing control ON / OFF timing chart

FIG. 5 is a flowchart showing an idle speed control routine (part 1);

FIG. 6 is a flowchart showing an idle speed control routine (part 2);

FIG. 7 is a map showing a relationship between an A / C load and an ON delay time.

FIG. 8 is a map showing a relationship between an A / C load and an OFF delay time.

FIG. 9 is a view showing a change in engine speed when the idle speed is controlled by the idle speed control device for the internal combustion engine according to the present invention, wherein the compressor is turned from OFF to ON when the A / C load is small. Diagram showing switching to

FIG. 10 is a diagram corresponding to FIG. 9 when the compressor is switched from OFF to ON when the A / C load is large in the present invention.

11 is a diagram corresponding to FIG. 9 when the compressor is switched from ON to OFF when the A / C load is small in the present invention.

FIG. 12 is a diagram corresponding to FIG. 9 when the compressor is switched from ON to OFF when the A / C load is large in the present invention.

FIG. 13 is a diagram for explaining the deviation of the idle speed by comparing the present invention with the conventional art.

FIG. 14 is a diagram showing a change in the engine speed when the idle speed is controlled by the idle speed control device for the internal combustion engine according to the related art, in which the compressor is changed from OFF to ON when the A / C load is small. Diagram showing switching

FIG. 15 shows a conventional case where the compressor is switched from OFF to ON when the A / C load is large.
Figure corresponding to 4

FIG. 16 shows a conventional case where the compressor is switched from ON to OFF when the A / C load is small.
Figure corresponding to 4

FIG. 17 shows a conventional case where the compressor is switched from ON to OFF when the A / C load is large.
Figure corresponding to 4

[Explanation of symbols]

1: Internal combustion engine 15: ECU 24: Idle speed control valve (IS
CV) 40: CPU 41: ROM 42: RAM 50: Air conditioner 52: Compressor 58: Blow-out temperature sensor

Claims (2)

[Claims] When an internal combustion engine is idling, a feedback control is performed so that an engine speed becomes a first target idle speed when a compressor forming a part of a refrigeration cycle for an air conditioner is stopped. During operation, feedback control is performed so that the engine speed becomes a second target idle speed higher than the first target idle speed, and when the compressor is operated, the engine speed becomes the second target idle speed. The compressor is operated after the ON delay time has elapsed since the start of the control of the idle speed so as to reach the target idle speed of 2 and the engine speed is reduced to the first speed when the compressor is stopped.
In the idle speed control device for the internal combustion engine, which controls to stop the compressor after the OFF delay time has elapsed since the start of the idle speed control to reach the target idle speed of the air conditioner, the load of the air conditioner is reduced. Air conditioner load detecting means for detecting, and a delay time changing means for changing at least one of the ON delay time and the OFF delay time in accordance with the load of the air conditioner detected by the air conditioner load detecting means. An idle speed control device for an internal combustion engine, comprising: 2. The delay time changing means according to claim 1, wherein the ON delay time is changed to a long time and the OFF delay time is changed to a short time as the load on the air conditioner increases. An idle speed control device for an internal combustion engine.