JPH1047108A - Idling rotation control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an unstable condition of idling rotational speed in the case where an air conditioner is stopped by detecting the magnitude of the load of the air conditioner on the basis of the cycle of the change of a temperature in relation to an evaporator, and controlling the air flow rate of a bypass passage. SOLUTION: A fuel injection valve 15 is arranged in an intake system 11, and it is controlled together with a flow rate control valve 14 by an electronical control device 4 for controlling engine rotational speed at the time of idle operation, namely, for controlling idle rotational speed so as to correct the intake air flow rate of a bypass passage 13 by detecting the load of an air conditioner 5 on the basis of the cycle of the change of a temperature in relation to the temperature of an evaporator 5a for gasifying a refrigerant and also controlling the flow rate control valve 14 on the basis of a detected load. It is thus possible to converge the idle rotational speed to a target rotational speed in the case where the air conditioner 5 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idle rotation control method when an air conditioner (hereinafter, abbreviated as "air conditioner") serving as a room temperature adjusting device for an internal combustion engine for an automobile is turned on.

[0002]

2. Description of the Related Art Conventionally, in this kind of idle rotation control method for an internal combustion engine, the temperature of an evaporator for vaporizing a refrigerant of an air conditioner is detected and detected as disclosed in Japanese Patent Application Laid-Open No. 6-101515. The amount of change in the temperature of the evaporator per predetermined time is detected, and the heat load is detected based on the detected amount of change.If the detected heat load is small, the idle speed is set even when the compressor of the air conditioner is in the refrigerant discharge state. There is known a configuration in which the increase in fuel consumption is prohibited to improve fuel efficiency. In the control of the idle rotation when the air conditioner is turned on, that is, when the air conditioner is turned on, the intake air amount when the air conditioner is turned on is corrected through a passage that bypasses a throttle valve of the intake system so that the target air speed is converged. The air amount to be corrected is increased or decreased.
The amount of air to be corrected is usually determined by the cooling water temperature of the engine, and as the outside air temperature increases,
It is set to be large.

[0003]

The load on the air conditioner depends on the outside air temperature, the temperature inside the vehicle, the strength of the blower of the air conditioner, and the air introduction system, that is, whether the outside air is introduced or the inside air is circulated. It fluctuates each time. As a result, the load of the air conditioner applied to the engine also varies, and if the correction amount of the intake air amount is set based on the cooling water temperature, the correction amount may not be appropriate.

For example, when the outside air temperature is low and the cooling water temperature is high, the load on the air conditioner is reduced. On the other hand, the correction amount of the intake air amount, that is, the air conditioner load correction amount DSET increases because the cooling water temperature is high, but the engine speed NE becomes higher than the target speed during idle operation because the air conditioner as the load is light. . This state is shown in FIG. For this reason, the increased engine speed
The air-fuel ratio is detected from the exhaust gas during idling operation, and the correction is made by reducing the correction intake air amount, that is, the feedback correction amount DFB, which is set so that the air-fuel ratio becomes the stoichiometric air-fuel ratio. The control is performed so as to converge to the target rotation speed.

However, when the engine rotation increased by the air conditioner load correction amount DSET is corrected by the feedback correction amount DFB, when the air conditioner is turned off, the engine rotation is reduced in accordance with the reduced feedback correction amount DFB. It may be lower than the target speed in the case of OFF. Conversely, when the air conditioner as a load is heavy, even if the cooling water temperature is high, the amount of correction required for the heavy load increases, but the air conditioner load correction amount DSET based on the cooling water temperature may be insufficient. . In this case, as shown in FIG. 8B, when the engine speed does not rise to the target speed, and this is compensated for by the feedback correction amount DFB, the engine speed increases when the air conditioner is turned off. The DFB may increase in proportion to the increased amount.

As described above, there are cases where the idle speed cannot be sufficiently controlled only by the air conditioner load correction amount DSET based on the cooling water temperature. In such a case, when the feedback correction amount DFB acts, the engine rotation may become unstable when the air conditioner is turned off. An object of the present invention is to solve such a problem.

[0007]

In order to achieve the above object, the present invention takes the following measures. That is, the idle rotation control method for the internal combustion engine according to the present invention has a configuration in which the magnitude of the load on the air conditioner is detected based on the cycle of temperature change related to the evaporator, and the air flow rate in the bypass passage is controlled. is there. Therefore, when the air conditioner stops, the idling rotation can be prevented from becoming unstable due to the influence of another correction amount.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine capable of driving a room temperature adjusting device, wherein a control valve is provided in a bypass passage bypassing a throttle valve provided in an intake system, and the control valve is controlled in an idle operation state. A control method for controlling the engine speed so as to attain a predetermined target speed, wherein the room temperature adjusting device is based on a cycle of a temperature change correlated with a temperature of an evaporator for vaporizing a refrigerant. The idle rotation control method for an internal combustion engine is characterized in that a load of the internal combustion engine is detected and a control valve is controlled based on the detected load to correct an intake air amount.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. The engine 100 schematically shown in FIG. 1 is for an automobile, and its intake system 11 is provided with a throttle valve 12 that opens and closes in response to an accelerator pedal (not shown) and bypasses the throttle valve 12. A bypass passage 13 is provided, and a flow control valve 14 for controlling the idle speed is provided in the bypass passage 13. The flow control valve 14 is of an electronic opening and closing type, abbreviated as a large flow rate VSV, and calculates a duty ratio of a drive voltage, which is a control value applied to a terminal 14a, based on various correction amounts. The opening degree per unit time can be changed by controlling with the calculation duty ratio DISC, whereby the air flow rate in the bypass passage 13 can be adjusted. In other words, a set of the bypass passage 13 and the flow control valve 14 unifies a single bypass passage provided for each correction item in the feedback control during idling. The calculation duty ratio DISC includes those items, and includes, for example, correction items such as a start-time correction amount DSTA, a water temperature correction amount DAAV, a feedback correction amount DFB, an electric load correction amount DSET, and a power steering correction amount DPST. The variable range is limited so that they do not become extremely large or small when added together. The calculation duty ratio DISC is calculated by the following equation. DISC (%) = DSTA + DAAV + DSET + DPST + DFB

The load correction amount DSET is calculated based on various electric loads,
For example, they are set according to the air conditioner 5, headlights, turn signal lights, hazard lamps, radiator fans, wipers, and the like. In this embodiment, the air conditioner 5
The control is performed by stopping the operation of the compressor 5b for compressing the refrigerant based on the temperature of the evaporator 5a, that is, the temperature of the air coming out of the evaporator 5a (hereinafter, abbreviated as evaporator temperature) so that the inside of the vehicle compartment does not drop too much. Is done. The air conditioner is turned off when the compressor 5b is stopped due to the temperature of the air, and the air conditioner is turned on when the compressor 5b is operating. Air conditioner load correction amount D for this air conditioner 5
SETAC is calculated from an amount based on the cooling water temperature THW and an amount based on the evaporator temperature. Note that the temperature correlated with the temperature of the evaporator 5a may be the temperature of the refrigerant itself directly measured by the temperature sensor.

The intake system 11 is further provided with a fuel injection valve 15.
Is controlled by an electronic control unit (ECU) 4. The electronic control unit 4 is mainly configured by a microcomputer system including a central processing unit 4a, a storage unit 4b, an input interface 4c, and an output interface 4d. The input interface 4c has an intake pressure signal a output from an intake pressure sensor 17 for detecting the pressure in the surge tank 16 and a rotational speed output from a rotational speed sensor 18 for detecting the engine rotational speed NE. A signal b, a vehicle speed signal c output from a vehicle speed sensor 19 for detecting the vehicle speed, an LL signal d output from an idle switch 20 for detecting the open / closed state of the throttle valve 12, and an engine coolant temperature THW are detected. Temperature signal e output from a water temperature sensor 21 for the operation, a reference position signal f output from a crank angle reference position sensor 23 built in the distributor 22, and an air conditioner switch 5 for controlling the operation of the air conditioner 5.
c and signals ss1 and ss2 of the blower switch 6a for turning on and off the blower 6 are input. Although not shown, an output signal that changes according to the air-fuel ratio is input to the input interface 4c from an O ₂ sensor provided in the exhaust system, and feedback control is performed based on the output signal. It is.

The electronic control unit 4 determines the opening time of the fuel injection valve using the signal from the intake pressure sensor 17 and the signal from the rotation speed sensor 18 as main information, and controls the fuel injection valve 15 based on the determination. A program for injecting fuel corresponding to the engine load from the fuel injection valve 15 to the intake system 11 is incorporated. Further, in order to control the engine speed during idling, that is, the idling speed, the electronic control unit 4 controls the load on the air conditioner 5 based on the cycle of temperature change correlated with the temperature of the evaporator 5a that vaporizes the refrigerant. A program is incorporated which detects and controls the flow control valve 14 based on the detected load to correct the intake air amount.

The outline of the idle speed control (ISC) program is as shown in FIGS. In this idle speed control, the ISC routine is repeatedly executed, for example, every 5 msec.
The respective correction amount subroutines for calculating the SC are sequentially executed (steps S1, 2,... N, n + 1,
…).

In the calculation routine of the load correction amount DSET,
A load correction amount DSET for various electric loads other than the air conditioner 5 and for the automatic transmission and the like is calculated (step S21). In step S22, a basic air conditioner load correction amount DSETACB is calculated from the cooling water temperature THW. The basic air conditioner load correction amount DSETACB is calculated based on the cooling water temperature T.
The lower the HW, the smaller the HW. Step S23
Then, an evaporation temperature correction calculation routine described later is executed. In step S24, the calculated basic air conditioner load correction amount D
SETACB and the air temperature correction amount DSETEV are added to calculate the air conditioner load correction amount DSETAC. It should be noted that the EVA temperature correction amount DSETEV is not added to the basic air conditioner load correction amount DSETACB during the EVA temperature cut. It is added in the case. During the evaporator temperature cut, the evaporator temperature correction amount DSET previously set
The EV is stored, and is erased when either the air conditioner switch 5c or the blower switch 6a is turned off.

In this embodiment, the evaporation temperature correction amount DSETEV is calculated every 80 msec, and is set in advance with a map for the evaporation temperature cut cycle EVAV. As shown in FIG. 6, the evaporation temperature correction amount DSETEV increases as the time calculated by the on-time EVON and the off-time EVOF, which is the on-off period of the air conditioner 5 based on the evaporator temperature, is reduced. It is set to increase.

In this calculation routine, first, in step S3
In step 1, it is determined whether the air conditioner flag XACSW indicating whether the air conditioner switch 5c is on is set (= 1). In step S32, it is determined whether or not the blower flag XBLW indicating whether or not the blower switch 6a is on is set (= 1). In step S33, it is determined whether or not the evaporator temperature is being cut based on whether or not the evaporator temperature cut flag XEVCUT is set (= 1). In step S34, it is determined whether or not the air conditioner off flag XACONOFF is set (= 1), that is, whether or not the compressor 5b of the air conditioner 5 has been turned off (cut) from on.

In step S35, the result of measuring the time during which the switch is on due to the temperature of the evaporator, that is, the count value C80 of the counter, is obtained.
EVON is set as the ON time EVON. In step S36, the count value C80EVOF of the counter for counting the off time EVOF is incremented (+1).
In step S37, the counter of the ON time EVON is reset to set the count value C80EVON to zero. In step S38, based on the ratio of the ON time EVON to the total time of the OFF time EVOF and the ON time EVON,
The evaporator temperature cut cycle EVAV is calculated by the following equation. EVAV = [EVAV + {EVON / (EVOF + EVON)}] / 2 In step S39, the ECU 50 searches for and determines an evaporation temperature correction amount DSETEV from the evaporation temperature cut cycle EVAV.

In step S40, the evaporator temperature A at this time point
It is determined whether DEV is equal to or greater than an ON determination value KEVON.
In step S41, the air conditioner on flag XACOFF
It is determined whether or not ON is set (= 1), that is, whether or not the air conditioner 5 has been turned on from off. In step S42, the time measurement result of the time in which the battery is turned off due to the temperature of the evaporator, that is, the count value C80EVOF of the counter is calculated as the
Set as In step S43, the count value C80EVON of the counter is incremented (+1). In step S44, the counter is reset to count value C80.
Set EVOF to 0. In step S45, the evaporator temperature cut cycle EVAV is set by its upper limit average value EVAVMAX. In step S46, the ON count value C80E
The VON and OFF count values C80EVOF are both reset.

In such a configuration, the engine 100
During idle operation, the ISC routine is executed at predetermined intervals, the intake air amount is corrected based on various correction amounts, and control is performed so that the engine speed NE converges to the target speed. Here, in the DSET calculation routine for calculating the correction amount based on the load, the air conditioner correction amount DSETAV changes depending on the size of the load of the air conditioner 5, and the change basically depends on the air temperature correction amount DSETEV. is there.

Specifically, the air conditioner 5 is not used, that is, the air conditioner switch 5c and the blower switch 6a
Are turned off, the air conditioner flag XACSW and the blower flag XBLW are reset. Therefore, the control proceeds from step S31 → S32 → S46,
Without setting the evaporation temperature correction amount DSETEV, the load correction amount DSET is set to the basic air conditioner load correction amount DSETAC.
B. In the summer, when the outside air temperature is high, the basic air conditioner load correction amount DSETACB is set to compensate for the water temperature correction amount DAAV, and the idling speed is maintained relatively high.

Next, when the air conditioner 5 and the blower 6 are turned on for the first time after starting, the outside temperature is high.
May be higher than the ON determination value KEVON. In this case, when the air conditioner switch 5c and the blower switch 6a are turned on, the air conditioner flag XACSW and the blower flag XBLW are set, so that the control is performed in steps S31 → S32 → S33 → S40 → S45 → S3.
9 and the evaporator temperature correction amount DSETEV is increased to the upper limit average value EV.
It is set based on the evaporator temperature cut cycle EVAV set by AVMAX. Therefore, the evaporation temperature correction amount DSET
EV increases, and as a result, the duty ratio DISC increases, the flow control valve 14 is greatly opened, the intake air amount increases, and the engine speed NE increases (FIG. 7).

Thereafter, as the air conditioner 5 operates continuously, the air temperature ADEV decreases and the on-judgment value KEVON
If the temperature is less than the temperature of the evaporator temperature cut, the evaporator temperature is not being cut, and the control proceeds from step S31 to S
The process proceeds from 32 to S33 to S40 to S41. At this time, until the air-conditioner ON flag XACOFFON is set, the control proceeds to steps S43 → S38 → S39,
A time during which the air conditioner 5 is on, that is, an on-time EVON during which the compressor 5b operates to load the engine 100 is measured. Then, as the operation of the air conditioner 5 continues, the evaporator temperature ADEV further decreases, the evaporator temperature cut flag XEVCUT is set, and immediately after that, the air conditioner off flag XACONOFF is set.
The process proceeds to S33 → S34 → S35 → S37 → S38 → S39, and the evaporation temperature correction amount DS is calculated based on the measured ON time EVON.
Calculate ETEV.

Here, the ratio of the on-time EVON to one cycle of the air-conditioner is turned on and off is calculated as the evaporator temperature cut cycle EVAV, so that the evaporator heat cut cycle EVAV indicates the magnitude of the load. And the ON time EVO
When N is long, the evaporator temperature cut cycle EVAV becomes longer, so that the evaporator temperature correction amount DSETEV is increased accordingly. Therefore, since the electric load correction amount DSET is increased and corrected by the temperature of the engine, the idle rotation speed can be maintained at the target rotation speed in consideration of the outside air temperature and the indoor temperature. Therefore, an excessive increase or an insufficient increase in the engine speed NE is unlikely to occur, and control for further correcting the engine speed NE with the feedback correction amount DFB is not performed. An abnormal rise can be prevented. Further, since the feedback correction amount DFB is not changed, the current correction content can be reflected when the air conditioner is turned on next time.

Next, in the state where the evaporator temperature cut is continued, the control is performed in steps S31 → S32 → S33 → S3.
The procedure proceeds from 4 to S36 to S38 to S39, and the time while the air conditioner 5 is off is measured. This off time EVOF
Is longer when the outside air temperature is high or when the indoor temperature, that is, when the inside air is high. Then, as described above, when the evaporator temperature cut is continued, the evaporator temperature rises. When the evaporator temperature cut is not performed below the upper limit value KEVON, the control proceeds to step S.
31 → S32 → S33 → S40 → S41 → S42 → S4
4 → S38 → S39, the air conditioner 5 is switched from off to on due to the temperature of the air, and the off time EVO
Completion of timing of F, and calculated EVA temperature cut cycle EVAV
Is used to retrieve and set the evaporation temperature correction amount DSETEV. Thereafter, the control is performed in steps S31 → S32 → S33 → S40 until the evaporator temperature drops and the evaporator temperature is being cut.
→ S41 → S43 → S38 → S39 are repeated to count the ON time EVON.

As described above, the air conditioner load correction amount is determined by the basic air conditioner load correction amount DSETACB defined by the cooling water temperature THW and the evaluation temperature correction amount DSETEV set based on the magnitude of the load detected from the cycle of the change of the evaluation temperature. DSE
Since the TAC is set, the duty ratio DISC can be set according to the change in the load while the air conditioner 5 is in use, and the idle speed can converge to the target speed. Therefore, the feedback correction amount DF is not controlled to be increased or decreased to converge on the target rotation speed by increasing or decreasing the feedback amount DFB, and when the use of the air conditioner 5 is stopped (the air conditioner switch 5c or the blower switch 6a is turned off).
It is possible to suppress the idling speed from rising or dropping unstably due to B.

The present invention is not limited to the embodiment described above. In the above embodiment, the evaporator temperature cut cycle EVAV is calculated based on the on time EVON for the on / off cycle of the air conditioner 5 based on the evaporator temperature. However, the off time EVOF may be used instead of the on time EVON. EVAV = [EVAV + {EVOF / (EVOF + EVON)}] / 2

Alternatively, the ON time EVON and the OFF time E
Any one of the VOF and the average value may be used. As an example, a calculation formula in the case of 1/2 smoothing is shown. EVAV = (EVAV + EVOF) / 2 EVAV = (EVAV + EVON) / 2 In addition, the configuration of each unit is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0028]

As described above, according to the present invention, the magnitude of the load on the room temperature controller is detected based on the period of the temperature change correlated with the temperature of the evaporator to correct the intake air amount. Therefore, the necessity of correction by another correction element is eliminated, and the idle speed can converge to the target speed. In addition, since the correction based on the feedback correction amount is not performed, when the air conditioner is turned off, the rotation does not fluctuate due to the feedback correction amount, and a stable idle rotation can be maintained regardless of whether the air conditioner is on or off.

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory view showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is a flowchart showing a control procedure of the embodiment.

FIG. 4 is a flowchart showing a control procedure of the embodiment.

FIG. 5 is a flowchart showing a control procedure of the embodiment.

FIG. 6 is a graph showing a relationship between an evaporator temperature cut cycle and an evaporator temperature correction amount according to the embodiment.

FIG. 7 is an operation explanatory view of the embodiment.

FIG. 8 is an operation explanatory view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 4 ... Electronic control device 4a ... Central processing unit 4b ... Storage device 4c ... Input interface 4d ... Output interface 5 ... Air conditioner 5a ... Evaporator 11 ... Intake system 12 ... Throttle valve 13 ... Bypass passage 14 ... Flow control valve 100 ... Engine

Claims (1)

[Claims] In an internal combustion engine capable of driving a room temperature adjusting device, a control valve is provided in a bypass passage that bypasses a throttle valve provided in an intake system, and the control valve is controlled in an idle operation state to control a preset target. An idle rotation control method for an internal combustion engine that controls an engine rotation speed so as to be a rotation speed, wherein a load of a room temperature adjustment device is detected based on a period of a temperature change correlated with a temperature of an evaporator that vaporizes a refrigerant, An idle rotation control method for an internal combustion engine, wherein a control valve is controlled based on a detected load to correct an intake air amount.