JPH10115246A - Idle speed control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate insufficiency of warm-up performance due to a decrease of engine cooling water temperature and provide compatibly a warm up characteristic, quietness and fuel consumption. SOLUTION: A maximum value of engine cooling water temperature after starting is detected, by this value and the present cooling water temperature TWN, a cooling water temperature decrease amount is calculated, when it is a prescribed amount or more, a decrease of cooling water temperature is decided, by a left warming up target rotational speed RPMST1 with warm up acceleration as an object, a target rotational speed RPMSET is set (S24, S29). On the other hand, when the decrease is not decided, in the case of detecting a running condition not even once after starting, by the left warming up target rotational speed, the target rotational speed is set (S28, S29), in the case of detecting the running condition, thereafter by a running warming up target rotational speed RPMST2 with quietness and fuel consumption as an object, a target rotational speed is set (S25, S27). At idle time, in accordance with a comparing result of the target rotational speed with an engine speed NE, duty ratio of a drive signal as a controlled variable relating to an idle speed control, valve is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine idling speed control device for ensuring engine warm-up performance.

[0002]

2. Description of the Related Art Conventionally, an idle speed control valve (ISC valve) is provided in a bypass passage that bypasses a throttle valve, and a target speed is set by an electronic control unit in accordance with the temperature of engine cooling water. An idle speed control device that controls the valve opening of the ISC valve so that the speed converges to the target speed is employed.

As disclosed in Japanese Patent Application Laid-Open No. Hei 5-171975, a relatively high target rotation speed is set in a low water temperature range in order to accelerate the rise of the cooling water temperature and promote the warm-up of the engine. At the same time, in the normal temperature range where engine warm-up is completed, a relatively low target speed is set in order to improve quietness by reducing engine noise and improve fuel efficiency.
During the warming-up of the engine from the low water temperature range to the normal temperature range, the value of the target rotation speed is sequentially reduced in accordance with the rise of the engine cooling water temperature.

In this idle speed control of the engine, the target speed is set between a target speed for standing warm-up for improving the engine warm-up promotion and a target speed for running warm-up with emphasis on quietness. The target rotation speed for traveling warm-up is set to be lower than the target rotation speed for leaving warm-up, which is set separately for two types.

If the running state of the vehicle has not been detected even once after the engine is started, it is determined that the vehicle is in a warm-up state, and a higher target rotational speed is set to the target rotational speed for the warm-up period, and the running state is detected. In this case, it is determined that the vehicle is running warm, and thereafter,
A low target speed is set according to the target speed for traveling warm-up, and the engine speed during idling (idling speed)
The control amount of the ISC valve is set so as to converge to the target rotational speed, and the valve opening of the ISC valve is controlled so that both the engine warm-up characteristic and the quietness are achieved.

[0006] Here, the determination of the warming-up during the standing and the warming-up of the traveling is performed by detecting the vehicle speed, the throttle opening, the neutral state, and the like, and by determining whether or not the vehicle can be determined to be traveling. When it comes to running warm-up, it does not return to neglected warm-up,
The idle speed control is performed based on the target speed for traveling warm-up, and the speed remains low.

[0007]

However, in the above prior art, after the detection of the running state of the vehicle, the idle speed remains low due to the target speed for warming up the vehicle, and the use of a cold region or the like is difficult.
When the outside air temperature is low, the warm-up function is insufficient at low idling speed, which emphasizes quietness due to the target speed for running warm-up. There is a risk of doing this.

Further, in vehicles such as automobiles, the engine cooling water is also used for heating the interior of the vehicle, and the heating effect deteriorates due to a decrease in the temperature of the cooling water.

[0009] In particular, in a vehicle having a layout in which the engine is arranged at the rear of the vehicle and the radiator is located at the front of the vehicle,
The length of the radiator hose for sending the cooling water between the engine and the radiator becomes long, and the cooling water is easily cooled, and the above-mentioned inconvenience becomes significant.

[0010] To cope with this, if the target rotation speed for traveling warm-up is increased in consideration of the use of cold regions, the quietness deteriorates,
There is no merit to separate the target rotation speed for leaving warm-up from the target rotation speed for running warm-up, and it is not possible to achieve both engine warm-up characteristics, quietness, and fuel efficiency.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention solves the problem of insufficient engine warm-up performance due to a decrease in the temperature of engine cooling water, and at the same time, idle rotation of an engine capable of achieving both engine warm-up characteristics, quietness, and fuel efficiency. It is an object to provide a numerical control device.

[0012]

In order to achieve the above object, the invention according to the first aspect of the present invention promotes engine warm-up when the vehicle running state is not detected even once after the engine is started, and increases the temperature of the engine cooling water. The target rotation speed is set based on the target rotation speed for the leaving warm-up that sequentially decreases, and when the vehicle traveling state is detected, the traveling warm-up having a value on the way of warming-up that is lower than the target rotation speed for the leaving warm-up after that is detected. The target engine speed is set according to the target engine speed, and at idle, the control amount for the engine speed control valve is set according to the result of comparison between the target engine speed and the engine speed to control the engine idle speed. In the rotation speed control device, as shown in the basic configuration diagram of FIG. 1, a target warm-up rotation speed setting unit for setting the target warm-up rotation speed based on the engine coolant temperature, Target rotation speed setting means for setting the target rotation speed for traveling warming based on the engine cooling water temperature, and cooling water temperature maximum value detection means for detecting the maximum value of the engine cooling water temperature after the engine is started. Calculating the amount of cooling water temperature decrease from the maximum value of the cooling water temperature and the current engine cooling water temperature, and when the amount of cooling water temperature decrease is equal to or more than a predetermined amount,
Water temperature drop determining means for determining that the cooling water temperature is low, and at the time of determining the cooling water temperature, a target rotation speed is set based on the target rotation speed for leaving and warming up.On the other hand, when it is not determined that the cooling water temperature is low, once after starting the engine, If the vehicle running state is not detected, the target rotation speed is set based on the target warm-up rotation speed, and if the vehicle running state is detected, the target rotation speed is set based on the target warm-up rotation speed. And a control amount setting means for setting a control amount for the idle speed control valve according to a result of comparison between the target speed and the engine speed during idling. .

According to a second aspect of the present invention, in the first aspect of the present invention, the cooling water temperature maximum value detecting means cannot actually have the cooling water temperature maximum value until a predetermined time has elapsed after the start of the engine. It is characterized in that it is fixed at a preset low water temperature value.

According to a third aspect of the present invention, in the first aspect of the present invention, the cooling water temperature maximum value detecting means is provided when the engine cooling water temperature is equal to or higher than a warming-up completion water temperature at which it is determined that the warming-up of the engine is completed. The cooling water temperature maximum value is set based on the warm-up completion water temperature.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the water temperature drop determining means is configured to determine that the cooling water temperature drop is equal to or more than a predetermined amount and the engine cooling water temperature at this time is equal to or higher than a set value. At this time, it is characterized that it is determined that the cooling water temperature is low.

According to a fifth aspect of the present invention, in the first or the fourth aspect of the present invention, the water temperature drop determining means includes:
When the engine coolant temperature becomes equal to or higher than the warm-up completion water temperature at which it is determined that the engine warm-up is completed after the coolant temperature decrease is determined, the cooling water temperature decrease determination is released.

That is, according to the first aspect of the present invention, the value of the target rotation speed for leaving warm-up, which has a high value of warm-up for the purpose of promoting engine warm-up, and the value of warm-up, which emphasizes quietness and fuel efficiency, are: The low target rotation speed for running warm-up is set based on the engine coolant temperature, and the maximum value of the engine coolant temperature after the engine is started is detected, and the maximum value of the coolant temperature and the current engine coolant temperature are determined. The cooling water temperature decrease amount is calculated, and when the cooling water temperature decrease amount is equal to or more than a predetermined amount, it is determined that the cooling water temperature decrease. At the time of cooling water temperature drop determination, a target rotation speed is set based on the target rotation speed for idle warm-up, which has a high value on the way to warm up. The control amount for the rotation speed control valve is set, and the engine warm-up performance due to the decrease in the cooling water temperature is controlled even when the vehicle is running at idle and the idle speed is lower than the target speed for running warm-up. If the engine speed is insufficient, the process proceeds to the setting of the target rotation speed based on the target rotation speed for leaving warm-up, the idle rotation speed is increased, and the promotion of warm-up of the engine is improved. Further, when it is not determined that the cooling water temperature is low, if the vehicle running state is not detected even once after the engine is started, the target rotation speed is set by the above-mentioned target rotation speed for warming-up, which has a high value on the way to warm up, and this target rotation speed is set. The control amount for the idle speed control valve is set in accordance with the result of the comparison between the engine speed at idle and the engine speed at idle, and the idle speed during engine warm-up is controlled to be higher to promote warming of the engine, When the vehicle running state is detected, the target rotation speed is set based on the target rotation speed for traveling warm-up, which has a low value on the warming-up process with emphasis on quietness and fuel efficiency, and the idle rotation speed is set in accordance with the target rotation speed. By controlling
Improves quietness and fuel efficiency.

When detecting the maximum value of the cooling water temperature,
According to the second aspect of the present invention, the maximum value of the cooling water temperature is fixed to a preset low water temperature value that cannot actually exist until a predetermined time has elapsed after the engine is started.
In the described invention, when the engine cooling water temperature is equal to or higher than the warm-up completion water temperature at which it is determined that the engine warm-up is completed, the cooling water temperature maximum value is set by the warm-up completion water temperature.

Further, when determining the decrease in the coolant temperature, in the invention according to the fourth aspect, when the amount of decrease in the coolant temperature is not less than a predetermined amount and the engine coolant temperature at this time is not less than a set value, it is determined that the coolant temperature is decreased. . In the invention according to claim 5, when the engine cooling water temperature becomes equal to or higher than the warm-up completion water temperature at which it is determined that the engine warm-up is completed after the cooling water temperature is determined to decrease, the cooling water temperature decrease determination is canceled. .

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

First, the schematic structure of the engine will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes an engine for a vehicle such as an automobile (an in-line multi-cylinder engine in the figure), and an intake port 2a and an exhaust port 2b are formed in a cylinder head 2 corresponding to each cylinder. .

In the intake system of the engine 1, an intake manifold 3 communicates with each intake port 2a, and a throttle chamber 5 communicates with the intake manifold 3 via an air chamber 4 in which intake passages of respective cylinders gather. An air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6, and the air cleaner 7 is connected to the air intake chamber 8.

The throttle chamber 5 is provided with a throttle valve 5a linked to an accelerator pedal. The intake pipe 6 is connected to a bypass passage 9 that bypasses the throttle valve 5a.
In addition, an idle speed control valve (ISC valve) 10 for controlling the idle speed by adjusting the amount of bypass air flowing through the bypass passage 9 according to the valve opening degree, and bypass air by opening when the air conditioner operates. A FICD valve 11 for increasing the amount and increasing the idle speed is interposed in parallel.

The above ISC valve 10 and FICD valve 11
Is controlled by an electronic control unit (ECU) 40. In this embodiment, the ISC valve 10 increases the valve opening degree as the duty ratio of the drive signal output from the ECU 40 increases, increases the bypass air amount, and increases the idle speed. The engine speed is increased, and as the duty ratio decreases, the valve opening decreases, and the idle air speed decreases due to a decrease in the amount of bypass air.

The exhaust system of the engine 1 includes:
An exhaust pipe 13 communicates with a collection portion of the exhaust manifold 12 that communicates with each exhaust port 2b of the cylinder head 2, and a catalytic converter 14 is interposed in the exhaust pipe 13 and communicates with a muffler 15.

On the other hand, an injector 16 is located just upstream of each intake port 2a of the intake manifold 3. Further, for each cylinder of the cylinder head 2, a spark plug 17 for exposing the discharge electrode at the tip to the combustion chamber is provided.
The ignition plug 17 is connected to a secondary side of an ignition coil 19 via a distributor 18 connected to a camshaft of the engine 1, and a primary side of the ignition coil 19 is connected to an igniter 20. .
Then, an ignition switch (I in FIG. 12)
(Indicated by G), the ECU 40 is started by turning on the power supply relay 21, the ignition timing is calculated by the ECU 40 according to the engine operating state, and an ignition signal corresponding to this ignition timing is sent from the electronic control unit 40. When output to the igniter 20, the primary side of the ignition coil 19 is turned on and off by the igniter 20, and the high voltage induced on the secondary side of the ignition coil 19 is distributed to the ignition plug 17 of the ignition target cylinder via the distributor 18. The ignition plug 17 of the corresponding cylinder is ignited.

Further, various sensors for detecting the operating state of the engine are provided. These sensors will be described. The throttle valve 5a is turned on when the throttle opening sensor 22a and the throttle valve 5a are fully closed. Throttle sensor 2 incorporating idle switch 22b
2 are connected in series. Further, an intake air temperature sensor 23 faces the air chamber 4 and an intake pipe pressure sensor 2 for detecting an intake pipe pressure downstream of the throttle valve 5a by an absolute pressure.
4 are attached.

The cylinder block 1a of the engine 1
A knock sensor 25 is attached to the cooling water passage 2 c formed in the cylinder head 2, and a cooling water temperature sensor 26 faces the cooling water passage 2 c.
A sensor 27 is provided.

In the distributor 18,
A signal rotor 28 connected to the camshaft and a crank angle sensor 29 provided for the signal rotor 28 for detecting a crank angle and determining a cylinder are incorporated.

As shown in FIG. 13, the signal rotor 28 has, on its outer periphery, an angle discriminating projection 28a for discriminating the crank angle, and compression top dead center of the # 1, # 3, # 4, and # 2 cylinders. It is formed at 90 ° intervals at the front (BTDC) θ1 position, and a cylinder discrimination projection 28b is formed at a position after the compression top dead center (ATDC) θ2 of the # 1 cylinder. In the present embodiment, θ1 = BTDC10 ° CA,
θ2 = ATDC20 ° CA.

Then, the camshaft rotates with the operation of the engine 1, and the signal rotor 28 rotates with the rotation of the camshaft. Each of the projections of the signal rotor 28 is formed of a magnetic sensor (such as an electromagnetic pickup). 29, the crank angle sensor 29 sends the signal to the ECU 40 as shown in the time chart of FIG.
The θ1 pulse from the angle determining projection 28a is
Output every two rotations (every 180 ° CA), the θ of cylinder # 1
Between the one pulse and the θ1 pulse of the # 3 cylinder, a θ2 pulse is output by the cylinder discrimination projection 28b.

As will be described later, the ECU 40 calculates the engine speed NE based on the input interval time Tθ of the θ1 pulse output from the crank angle sensor 29, and receives the next compression top dead by inputting the θ2 pulse. The # 3 cylinder reaching the point is determined, and the combustion stroke order of each cylinder (# 1 cylinder → #
The cylinders such as the fuel injection target cylinders are determined based on (3 cylinders → # 4 cylinders → # 2 cylinders).

The above ISC valve 10, FICD valve 11,
The ECU 40 performs calculation of control amounts for actuators such as the injector 16 and the igniter 20 and output of a drive signal corresponding to the control amounts, that is, engine control such as idle speed control, fuel injection control, and ignition timing control. .

The ECU 40, as shown in FIG.
CPU 41, ROM 42, RAM 43, backup R
The AM 44, the counter / timer group 45, and the I / O interface 46 are configured around a microcomputer connected to each other via a bus line.
A constant voltage circuit 47 for supplying a stabilized power to each section,
A peripheral circuit such as a drive circuit 48 connected to the O interface 46 and an A / D converter 49 is built in.

The counter / timer group 45 is input from various counters such as a free-run counter, a fuel injection timer, an ignition timer, a periodic interrupt timer for generating a periodic interrupt, and a crank angle sensor 29. Various timers such as a pulse signal input interval timer and a system error monitoring watchdog timer are collectively referred to for convenience. In addition, various software counters and timers are used.

The constant voltage circuit 47 is connected to a battery 50 via a first relay contact of the power supply relay 21 having two relay contacts, and is connected to the battery 50 via an ignition switch 51. 21
Of the relay coil is connected, and the other end of the relay coil is connected to the input port of the I / O interface 46.

The constant voltage circuit 47 is connected to the battery 50 via a first relay contact of the power supply relay 21.
Not only connected to the battery 50 but also directly
When the ignition switch 51 is turned on and the relay contact of the power supply relay 21 is closed, power is supplied to each unit in the ECU 40. On the other hand, regardless of whether the ignition switch 51 is on or off, A power supply for backup is supplied to the backup RAM 44. A power supply line to each actuator extends from a second relay contact of the power supply relay 21.

The input port of the I / O interface is connected to the idle switch 22b and the knock sensor 2
5. A crank angle sensor 29, a vehicle speed sensor 30, and a starter switch 31 and an air conditioner switch 32 for detecting an engine start state and an air conditioner operating state are connected to each other. , Throttle opening sensor 22a, intake air temperature sensor 23, intake pipe pressure sensor 24, cooling water temperature sensor 26, and O2 sensor 27
Is connected, and the ignition switch 5
1. The battery voltage VB via the power supply relay 21 is input and monitored.

On the other hand, the ISC valve 10, the FICD valve 11,
The injector 16 is connected via the drive circuit 48, and the igniter 20 is connected.

In accordance with the control program stored in the ROM 42, the CPU 41 processes the detection signals from the sensors and switches, which are input via the I / O interface 46, the battery voltage, and the like, and stores them in the RAM 43. Based on various data, various learning value data stored in the backup RAM 44, and fixed data stored in the ROM 42, a duty ratio of a drive signal for the ISC valve 10, a fuel injection amount, an ignition timing, and the like are calculated. It performs engine control such as idle speed control, fuel injection control, and ignition timing control.

In this case, in the idling speed control, the maximum value of the engine cooling water temperature after the engine is started to solve the shortage of the engine warming performance due to the decrease of the engine cooling water temperature and secure the engine warming performance. To detect
A cooling water temperature drop is calculated from the maximum value of the cooling water temperature and the current engine cooling water temperature, and when the cooling water temperature drop is equal to or more than a predetermined amount, it is determined that the cooling water temperature has dropped. The target rotation speed is set according to the target rotation speed for idle warm-up, which has a high value in the process of warming up for the purpose of promoting warm-up. The control amount for the idle speed control valve is set in accordance with the comparison result of.

As a result, the engine cooling water temperature drops and the engine warm-up performance becomes insufficient even when the vehicle is running at idle and the idle speed is controlled to be lower than the target speed for running warm-up. If this is the case, the process proceeds to the setting of the target rotation speed based on the target rotation speed for idle warm-up, which has a high value during warm-up, and the idle rotation speed is immediately increased. And
Eliminate the lack of engine warm-up performance.

When it is not determined that the cooling water temperature is low, if the vehicle running state is not detected at all once after the engine is started, the target rotation speed is set based on the target rotation speed for the idle warm-up, which has a high value in the warm-up process. The control amount for the idle speed control valve is set in accordance with the result of comparison between the target speed and the engine speed during idling, and the idle speed during the engine warm-up is controlled to be high to promote the warm-up of the engine. To improve. Further, when the vehicle running state is detected, thereafter, the target rotation speed is set based on the target rotation speed for traveling warm-up, which has a low value in the warm-up process with emphasis on quietness and fuel efficiency, and the idle speed is set in accordance with the target rotation speed. By controlling the number of revolutions low, silence and fuel economy are improved, thereby achieving both engine warm-up characteristics, silence, and fuel economy.

That is, the ECU 40 controls the target rotation speed setting means for leaving warm-up, the target rotation speed setting means for running warm-up, the cooling water temperature maximum value detection means, the water temperature decrease judging means, the target rotation speed setting means according to the present invention, Each function of the control amount setting means is realized.

Hereinafter, a specific control process according to the present invention executed by the ECU 40 will be described with reference to flowcharts shown in FIGS.

When the ignition switch 51 is turned on,
When the power is supplied to the ECU 40, the system is initialized, and each flag and each counter are initialized except for data such as various learning values stored in the backup RAM 44. Then, the starter switch 31 is turned on.
When the engine 1 is started, the signal rotor 28 rotates with the rotation of the camshaft, and the projections 28a and 28b of the signal rotor 28
The ECU 40 detects the crank pulse (θ1 pulse, θ2 pulse) from the crank angle sensor 29.
The engine speed calculation routine shown in FIG. 2 is executed for each input, and the engine speed NE is calculated based on the pulse input interval time.
Is calculated, and cylinder discrimination is performed.

In this engine speed calculation routine, first, in step S1, the crank pulse inputted this time is the pulse θ1 for detecting the crank angle or the pulse θ2 for discriminating the cylinder.
Identify whether it is a pulse. That is, the cylinder discriminating projection 2
8b, the time from the previous input of the crank pulse (θ1 pulse), that is, the pulse input interval time is θ, as shown in the time chart of FIG.
This is extremely shorter than the input interval time between one pulse. Therefore, the execution cycle of this routine executed every time a crank pulse is input is measured by a timer, and by comparing the previous and current execution cycles of the routine, the θ1 pulse input or θ2
Identify pulse input. When it is determined that the pulse is the θ2 pulse, the crank pulse input next time is the BTDC θ1 pulse of the # 3 cylinder. From this, the cylinder reaching the compression top dead center can be determined to be the # 3 cylinder. In this case, # 1 cylinder → # 3 cylinder → # 4 cylinder → # 2 cylinder), it is possible to identify the next cylinder and thereafter. Although not described in detail here, this cylinder determination result is reflected in fuel injection control and the like.

In the subsequent step S2, the execution cycle of this routine measured by the timer, that is, the time from the previous crank pulse input to the present crank pulse input is read, and a pulse input interval time Tθ is detected.

Then, the program proceeds to a step S 3, wherein the inter-crank pulse angle corresponding to the crank pulse identified this time is read out, and the current engine speed NE is calculated based on the inter-crank pulse angle and the pulse input interval time Tθ. At a predetermined address, and exits the routine. The angle between the crank pulses is known,
In the present embodiment, the angle between the θ1 pulses is 1
80 ° CA, the angle between the θ1 pulse and the θ2 pulse is 30 ° CA, and the angle between the θ2 pulse and the θ1 pulse is 1
50 ° CA.

When the air conditioner switch 32 indicating the operating state of the air conditioner is turned on, the FICD valve 11 is opened and idle-up is performed. When the air conditioner switch 32 is turned off, the FICD valve 11 is closed and the engine is turned off. The engine speed NE calculated by the engine speed calculation routine is read out in the idle speed control routine shown in FIG. 3, and is used for setting a control amount for the ISC valve 10, that is, for idle speed control.

The idle speed control routine shown in FIG. 3 is executed for a predetermined time (for example, 1) after system initialization.
0 ms). First, in steps S11 to S12, a start determination is performed.

That is, the operation state of the starter switch 31 is determined in step S11, and the current engine speed NE is determined in step S12.
When the engine is started at N or when the engine stalls at NE = 0, the process proceeds to step S13, and the start control corresponding to the engine stall or the engine start is performed.

In step S13, the starting characteristic value table is referred to based on the engine cooling water temperature TWN by the cooling water temperature sensor 26, and the ISC at the time of engine stall or start is determined.
The starting characteristic value DUTYST that determines the control amount for the valve 10
Set.

The starting characteristic value table indicates that the ISC valve 10 for obtaining the proper valve opening of the ISC valve 10 in preparation for engine operation.
The duty ratio of the drive signal with respect to the cooling water temperature TWN is determined in advance by an experiment or the like, and this duty ratio is set as a starting characteristic value DUTYST as a table using the cooling water temperature TWN as a parameter, and stored in a series of addresses in the ROM 42. An example of the starting-time characteristic value table is shown in step S13. As shown in step S13, when the cooling water temperature TWN is low and the engine is cold, I
After increasing the valve opening of the SC valve 10 and shifting to engine operation,
Immediately increase the amount of bypass air to increase idle speed,
A high starting characteristic value DUTYST is stored in order to prevent the deterioration of the combustibility and to promote the warm-up of the engine 1. The opening degree of the ISC valve 10 is reduced as the cooling water temperature TWN increases. A starting characteristic value DUTYST for reducing the idling speed after shifting to the engine operation and obtaining a low idling speed for the purpose of reducing engine noise and improving fuel efficiency in the normal temperature range where engine warm-up is completed is stored.

Then, in step S14, the starting characteristic value DUTYST is set as a duty ratio DUTY that determines a control amount for the ISC valve 10 (DUTY ← DUTY).
ST), this duty ratio DUTY is set in step S15, and the routine exits.

As a result, the drive signal of the duty ratio DUTY is output from the ECU 40 to the ISC valve 10 so that the valve opening of the ISC valve 10 at the time of engine start or engine stall is reduced to the engine coolant temperature TWN in preparation for engine operation. It is maintained at an appropriate value.

On the other hand, in steps S11 and S12, when the starter switch 31 is OFF and the engine has been started with NE ≠ 0, the routine proceeds to step S16, where the target idle speed calculation subroutine shown in FIG. Is calculated as the target value of the engine speed (idling speed) of the engine.

In this target idle speed calculation subroutine, in step S21, the current engine coolant temperature TWN is read by the coolant temperature sensor 26, and a target warm-up speed table for a warm-up period is retrieved based on the coolant temperature TWN. And the target rotation speed RPMS for the warm-up
Set T1. This target warm-up rotation speed RPMST
Reference numeral 1 is for promoting warm-up of the engine 1.

That is, the above-mentioned table of the target number of revolutions for leaving warm-up is used to determine the optimum value of the idling number of revolutions corresponding to the engine coolant temperature TWN indicating the warm-up state of the engine 1 in order to promote the warm-up of the engine. The optimal value is set as a table of the cooling water temperature TWN as a parameter, and stored in a series of addresses of the ROM 42, as the target warm-up rotation speed RPMST1. FIG. 7 and FIG. 8 are graphs showing an example and a graph of the target warm-up speed table for leaving warm-up. As shown in the figure, the target warm-up speed table for the warm-up is stored in the low water temperature range (0 in the figure) when the engine is cold.
(° C. or lower), the target rotation speed RP having a relatively high value to accelerate the rise of the engine cooling water temperature and promote the warm-up of the engine 1.
MST1 is stored, and in a normal temperature range (80 ° C. or higher in the figure) where engine warm-up is completed, a target rotation speed RPMST1 having a relatively low value is set to achieve quietness by reducing engine noise and improve fuel efficiency. When the engine is warmed up from the low water temperature range to the normal temperature range, the value of the target rotation speed RPMST1 is sequentially reduced in accordance with the increase in the engine cooling water temperature TWN.

In the subsequent step S22, a target rotational speed table for traveling warm-up is searched based on the current engine coolant temperature TWN, and a target rotational speed for traveling warm-up RPM is calculated by interpolation.
Set ST2. The target rotation speed RPMS for traveling warm-up
T2 emphasizes quietness and fuel efficiency during idling after traveling with respect to the target rotation speed RPMST1 for the unattended warm-up, and during the warm-up of the engine 1,
It is set to a value lower than the target warm-up rotation speed RPMST1.

In other words, the target rotational speed table for traveling warm-up includes an appropriate value of the idling rotational speed with an emphasis on quietness and fuel efficiency of the engine during idling after traveling, and an engine cooling value indicating the warm-up state of the engine 1. The value is obtained in advance by an experiment or the like corresponding to the water temperature TWN, and this value is set as a target rotation speed RPMST2 for traveling warm-up as a table using the cooling water temperature TWN as a parameter and stored in a series of addresses of the ROM 42. As shown in FIGS. 7 and 8, the target rotation speed table for traveling warm-up stores a lower target rotation speed value in the course of warm-up than the target rotation speed table for leaving warm-up.

Next, the routine proceeds to step S23, in which a coolant temperature drop determination routine shown in FIG. 5 is executed to detect the maximum value of the engine coolant temperature TWN after the engine is started, that is, the coolant temperature maximum value TWNMAX. Value TWNMAX
And the current engine coolant temperature TWN, the coolant temperature decrease amount (TWNMAX-TWN) is calculated. Even after the engine coolant temperature TWN rises to a temperature at which the engine can be considered to be in a warm-up completed state after the engine is started, the outside air temperature is increased. It is determined whether the cooling water temperature TWN has dropped again due to the use of a low-temperature cold district or the like.

The water temperature drop determination routine will be described. First, in step S31, it is determined whether or not the elapsed time after starting the engine has exceeded a predetermined time KTAFSTA (for example, 80 seconds).

If the elapsed time after starting the engine is shorter than the predetermined time KTAFSTA, the routine proceeds to step S32, where R represents the maximum value of the cooling water temperature TWN after starting the engine.
The cooling water temperature maximum value TWNMAX stored at a predetermined address of the AM 43 is fixed to a preset low water temperature value TWNMAXST (for example, −50 ° C.) that cannot be actually set (TWNM).
AX ← TWNMAXST), and proceeds to step S37.

Here, in the vehicle, if the engine 1 is stopped in a state where the engine warm-up is completed, the engine cooling water temperature TWN in the engine chamber drops after the engine stops, but the radiator portion, the cooling between the radiator and the engine 1 is stopped. Since the radiator hose portion for sending water directly hits the outside air, the temperature of the cooling water in the radiator and the radiator hose drops earlier than the engine cooling water temperature TWN in the engine chamber. When the vehicle is stopped by stopping the engine for a long time, the cooling water temperature in the engine chamber, the radiator, and the radiator hose drops to near the outside air temperature, so there is no problem. When the engine is restarted after the vehicle has stopped for a few tens of minutes when the temperature TWN has not decreased so much, the engine warm-up is almost completed, and as shown in the time chart of FIG. The engine cooling water temperature TWN in the engine warm-up completion state is detected, and thereafter, the cooling water circulates with the operation of the engine 1, and the inside of the radiator
Cooled cooling water in the radiator hose flows into the engine 1, and the engine cooling water temperature TWN detected by the cooling water temperature sensor 26 temporarily drops rapidly. Water temperature drop (TWN
MAX-TWN) becomes greater than or equal to a set value KDTWFB for determining a cooling water temperature drop described later, and a false determination is made that the cooling water temperature has dropped, that is, the engine warm-up has deteriorated.

Therefore, after the engine is started, the predetermined time K
Until TAFSTA has elapsed, the cooling water temperature maximum value T
By fixing WNMAX to a preset low water temperature value TWNMAXST that is not practically possible, (TW
NMAX-TWN) ≧ KDTWFB so that the condition is not satisfied,
Prevent erroneous determination.

On the other hand, if the predetermined time KTAFSTA has elapsed since the engine was started in step S31,
Proceeding to step S33, the current engine cooling water temperature TWN is compared with the cooling water temperature maximum value TWNMAX stored at a predetermined address in the RAM 43. When TWN <TWNMAX, the flow directly proceeds to step S37, and when TWN ≧ TWNMAX,
Proceed to step S34.

In step S34, the current engine coolant temperature TWN is set to a preset warm-up completion water temperature KTWMAXGD (for example, 76) which can be regarded as the completion of the warm-up of the engine 1.
° C). Then, TWN <KTWMAXGD, that is, a predetermined time KTAFSTA has elapsed after the engine is started,
If the engine coolant temperature TWN at this time is equal to or greater than the coolant temperature maximum value TWNMAX stored in the RAM 43 and equal to or less than the warm-up completion coolant temperature KTWMAXGD, the process proceeds to step S35, and the RAM43 is determined by the current engine coolant temperature TWN.
Is updated (TWNMAX ← TWN), and the process proceeds to step S37. Therefore, at this time, the cooling water temperature maximum value TWNMAX is sequentially updated in accordance with the rise of the engine cooling water temperature TWN. In step S34, when TWN ≧ KTWMAXGD and the engine cooling water temperature TWN has reached the warm-up completion water temperature KTWMAXGD, the routine proceeds to step S36, where the warm-up completion water temperature KTWMAXGD
To update the cooling water temperature maximum value TWNMAX (TWNMAX ← K
TWMAXGD), and proceeds to step S37.

That is, when the engine cooling water temperature TWN is equal to or higher than the warming-up completion water temperature KTWMAXGD, which can be regarded as the completion of the warming-up of the engine 1, the engine cooling water temperature TWN is changed in accordance with a change in the situation such as when the vehicle is stopped or running. At this time, the maximum value of the cooling water temperature TWNMAX depends on the engine cooling water temperature TWN.
Is updated, the water temperature fluctuation due to running or stopping of the vehicle is captured as the cooling water temperature decrease amount (TWNMAX-TWN) even though the engine warm-up is completed, and the cooling water temperature in step S38 described later By comparing the amount of decrease with the set value KDTWFB for judging the decrease in cooling water temperature, it is erroneously judged that the cooling water temperature has decreased, that is, the engine warm-up has deteriorated.

Therefore, when the engine warm-up is completed with TWN ≧ KTWMAXGD, the cooling water temperature maximum value TWNMAX is set by the warm-up completed water temperature KTWMAXGD, thereby causing the vehicle to run or stop in the engine warm-up completed state. This prevents erroneous determination due to fluctuations in water temperature.

When the flow proceeds to step S37, the lack of the engine warm-up performance due to the decrease in the cooling water temperature is indicated by a flag set state, and a water temperature decrease determination flag FDTWFB instructing the setting of the target rotational speed by the target warm-up rotational speed RPMST1.
When the cooling water temperature is not determined to be low at the time of the first execution of the water temperature reduction determination routine of FDTWFB = 0 or at the time of the previous execution of the routine, the process proceeds to step S38, and the determination of the reduction of the engine cooling water temperature TWN is performed. I do.

In step S38, the cooling water temperature maximum value TW
The current engine coolant temperature TWN is subtracted from NMAX to calculate a coolant temperature decrease amount (TWNMAX-TWN), and the coolant temperature decrease amount is used as a coolant temperature decrease determination value KDTWFB ( For example, 5 ° C.), and based on the amount of cooling water temperature decrease, it is determined whether the engine warm-up performance is insufficient.

That is, in a running warm-up state, the engine speed NE increases and the engine load increases while the vehicle is running, so that the warm-up of the engine 1 is promoted and the engine coolant temperature TWN also increases. However, after that, when the vehicle is stopped, the idle speed is controlled to be low by the idle speed control based on the target speed RPMST2 for traveling warm-up. At this time, if the outside air temperature is low or the wind is blowing, the engine 1 The amount of heat released by the radiator or the like is larger than the amount of heat generated, and the engine cooling water temperature TWN is reduced, which may result in insufficient engine warm-up performance. Therefore,
The balance between the heat generation amount and the heat release amount is determined based on the cooling water temperature decrease amount.

If the cooling water temperature decrease is less than the water temperature decrease determination value ((TWNMAX-TWN) <KDTWFB) and there is no decrease in the engine cooling water temperature by a predetermined amount or more based on the water temperature decrease determination value KDTWFB, the water temperature decrease determination routine is executed. Through step S24 of the target idle speed calculation subroutine.
If the cooling water temperature decrease amount is equal to or greater than the water temperature decrease judgment value ((TWNMAX-TWN) ≧ KDTWFB), the water temperature decrease judgment value K
When the engine cooling water temperature has decreased by a predetermined amount or more by DTWFB, the process proceeds to step S39, and the current engine cooling water temperature TWN is further reduced to a set value KTWLFB (for example, 60 °).
C).

Here, under the idling speed control by the running warm-up target speed RPMST2 at the time of idling after running the vehicle, the running warm-up is not performed until the engine coolant temperature TWN rises to a certain degree. Target RPM RPM
Since ST2 is set to a high value (see FIGS. 7 and 8) and the idle speed is controlled to a relatively high value, the engine coolant temperature TWN tends to increase.

In a vehicle such as an automobile, the engine cooling water is guided to a heater, and warm air exchanged by the heater is blown into the vehicle interior by a heater blower, and the engine cooling water is used for heating the vehicle interior. When the engine coolant temperature TWN decreases, the heating effect deteriorates. For this reason, one of the objects of preventing the cooling water temperature from decreasing is to ensure the heating performance of the vehicle interior by the heater. However, when the cooling water has a low water temperature, the cooling water does not originally have the heating capacity, and at this time, even if the idling speed is increased to a darkness, there is a disadvantage in engine noise.

Therefore, the above state is determined by comparing the engine coolant temperature TWN with the set value KTWLFB.

When TWN ≧ KTWLFB, that is, when the cooling water temperature decrease (TWNMAX−TWN) is equal to or more than a predetermined amount based on the water temperature decrease determination value KDTWFB, and the engine cooling water temperature TwN is equal to or greater than the set value KTWLFB. At this time, it is determined that the engine warm-up performance is insufficient due to the decrease in the coolant temperature, and the process proceeds to step S40, where the engine coolant temperature TWN is set to the set value KW.
A water temperature condition flag FTWLFB indicating that a state above NLFB (60 ° C) has been detected at least once after system initialization.
Is set (FTWLFB ← 1), and in step S41, the target rotation speed RPMST1 for the above-mentioned idle warm-up indicating that the engine warm-up performance is insufficient due to the cooling water temperature drop and the engine warm-up value is high.
A water temperature drop determination flag FDTWFB instructing the setting of the target rotation speed is set (FDWTFB ← 1), and the process exits the water temperature drop determination routine and proceeds to step S24 of the target idle speed calculation subroutine.

In step S39, TWN <KT
In the case of WLFB, the process proceeds to step S42 to refer to the water temperature condition flag FTWLFB, and to detect a state in which the engine cooling water temperature TWN is equal to or higher than the set value KWNLFB (60 ° C.) when FTWLFB = 0, once after system initialization. If not, the process directly exits the water temperature drop determination routine and proceeds to step S24 of the target idle speed calculation subroutine, where FTWLFB = 1 and the engine coolant temperature TWN decreases to the set value KW.
If the state equal to or higher than NLFB (60 ° C.) has been detected even once after system initialization, the above-described step S41 is performed.
After setting the water temperature drop determination flag FDTWFB indicating the insufficient engine warm-up performance due to the cooling water temperature drop, the process exits the water temperature drop determination routine and proceeds to step S24 of the target idle speed calculation subroutine.

On the other hand, in the above step S37, FDTWFB =
If it is determined in step 1 that the engine warm-up performance is insufficient due to the cooling water temperature drop at the time of execution of the previous routine, the process proceeds to step S43, and it is determined whether to cancel the cooling water temperature drop determination.

In step S43, the current engine coolant temperature TWN is changed to the warm-up completion coolant temperature KTWMAXGD (for example, 76
° C).

It is once determined that the engine warm-up performance is insufficient due to a decrease in cooling water temperature, and idle speed control is performed based on the idle warm-up target speed RPMST1, which has a high value during warm-up, and before the engine warm-up is completed. Since the engine coolant temperature TWN has risen to some extent, the cooling water temperature drop determination is canceled and the target warm-up target rotation speed RPMST is released.
When the idle speed control is returned to the low idle speed by the target speed RPMST2 for traveling warm-up from the idle speed control by 1 as described above,
The engine cooling water temperature TWN cannot be maintained, and the engine cooling water temperature TWN drops again. In such a situation, the idle speed increases, the cooling water temperature increases, the idle speed decreases, the cooling water temperature decreases, and the idle speed decreases. There is a risk that hunting with a long cycle of rising →. Therefore,
The condition for canceling the determination of the decrease in the cooling water temperature is performed when the engine cooling water temperature TWN reaches the warm-up completion water temperature KTWMAXGD, which can be regarded as the completion of the engine warm-up, thereby preventing the hunting.

Then, when TWN <KTWMAXGD, the idle speed control by the idle warm-up target rotational speed RPMST1, which has a high value in the process of warming-up, is performed based on the target warm-up rotational speed RP for traveling.
If it is determined that the hunting is likely to occur when the idle speed is reduced to the low idle speed by the MST2, the water temperature decrease determination routine is exited while the water temperature decrease determination flag FDTWFB is set (FDTFB = 1) and the target is exited. The process returns to step S24 of the idle speed calculation subroutine.

When the engine warm-up is completed when TWN ≧ KTWMAXGD and the condition for canceling the cooling water temperature drop determination is satisfied, in step S44, the water temperature drop determination flag FDTW is set.
After clearing FB (FDWTFB ← 0) and canceling the cooling water temperature drop determination, the process exits the water temperature drop determination routine and returns to step S24 of the target idle speed calculation subroutine. As a result, during idling after the vehicle travels, the idling speed control by forcibly selecting the target warm-up rotation speed RPMST1 is removed from the target warm-up rotation speed RPMST.
Then, the process returns to the normal idle speed control by the control unit 2.

When the process returns to the target idle speed calculation subroutine (see FIG. 4) upon completion of the water temperature drop determination routine,
In step S24, referring to the water temperature decrease determination flag FDTWFB, if FDTWFB = 1 and it is determined that the engine warm-up performance is insufficient due to the decrease in cooling water temperature, the process jumps to step S29, and the warm-up process set in step S21 is performed. The target rotational speed RPMST is set by the above-mentioned target warm-up rotational speed RPMST1 having a high value of (RPMSET ←
RPMST1), terminates the target idle speed calculation subroutine, and proceeds to step S1 of the idle speed control routine.
Proceed to 7.

Accordingly, when it is determined that the engine warm-up performance is insufficient due to a decrease in the cooling water temperature at FDTWFB = 1,
The high target rotation speed RPMST1 is set by the idle warm-up target rotation speed RPMST1 not only when the vehicle running state has not been detected even after the engine is started, but also during idling after the vehicle running, and the idle rotation speed which will be described later. The duty ratio DUTY of the drive signal for the ISC valve 10 is set by the number control feedback correction subroutine so that the engine speed during idling (idling speed) converges to this target speed RPMMSET.
The valve opening of 0 is controlled, and the warm-up of the engine is promoted by the increase of the idle speed.

On the other hand, in step S24, FDTWFB
When = 0, the process proceeds to step S25. If the vehicle running state has not been detected even after the engine has been started by the processing after step S25, the target warm-up target rotation speed RPMST1 having a high value during warm-up is determined by the above-mentioned target warm-up target rotation speed RPMST1. Target RPM RPMS
By setting the ET, the idle speed during the engine warm-up is controlled to be high to improve the engine warm-up promotion.
When the driving state is detected, the target rotation speed RPMST2 is set to the target rotation speed RPMST2 having a low value during the warm-up process, thereby controlling the idle rotation speed to be low and improving quietness. And achieves both engine warm-up characteristics and quietness.

That is, in step S25, the vehicle speed sensor 3
0, the current vehicle speed VSPM is read.
The PM is compared with a predetermined traveling determination vehicle speed KSPDFB (for example, 10 km / h) to determine the vehicle traveling state, and V
When it is determined that the vehicle is in the running state with SPM ≧ KSPDFB, the process proceeds to step S26, in which a vehicle speed condition flag FSPDFB indicating that the vehicle running state has been detected at least once after system initialization is set (FSPDFB ← 1), and step S27 is performed.
Then, the target rotational speed RPMSET is set by the traveling warm-up target rotational speed RPMST2 having a low value on the way of warming-up set in the step S22 (RPMSET ← RPM).
ST2) Also, in the above step S25, VSPM <KSPDFB
In step S28, the routine proceeds to step S28, where the vehicle speed condition flag FS
Referring to PDFB, if FSPDFB = 1 and the vehicle running state has been detected at least once after system initialization, the target rotation speed RPMST2 is set by the target rotation speed for running warm-up RPMST2 in step S27.

Also, if FSPDFB = 0 in step S28,
If the vehicle running state has not been detected after system initialization, the process proceeds to step S29, where the target rotation speed RPMST1 is determined by the target warm-up rotation speed RPMST1.
ET is set, and the target idle speed calculation subroutine ends.

When the target idle speed calculation subroutine is completed by setting the target speed RPMMSET as described above,
The process proceeds to step S17 of the idle speed control routine (see FIG. 3).

In step S17, an idle speed control feedback correction subroutine shown in FIG. 6 is executed, and during idling, the control amount for the ISC valve 10 is controlled according to the result of comparison between the target speed RPMMSET and the engine speed NE. The duty ratio DUTY of the drive signal is set.

Next, the idle speed control feedback correction subroutine will be described. First, an idle determination is made in step S51.

That is, in step S51, the operation state of the idle switch 22b is determined, and
When b is OFF (throttle valve 5a is in the open state), the routine returns to the idle speed control routine and exits from the routine. Therefore, when not idle, I
The valve opening of the SC valve 10 is maintained as it is.

On the other hand, when the idle switch 22b is in the idling state where the throttle switch 22b is ON (throttle valve is fully closed), the process proceeds to step S52, in which the target engine speed RPMSET is calculated by subtracting the target engine speed RPMSET from the current engine engine speed NE by the processing after step S52. A feedback correction amount DFB is set based on the differential rotation DELTAN, and the duty ratio DUTY previously set is corrected by the feedback correction amount DFB to obtain an ISC.
The duty ratio DUTY of the drive signal for the valve 10 is set, and feedback control is performed so that the engine speed NE during idling, that is, the idle speed converges to the target engine speed RPMSET.

In step S52, the current engine speed NE is read, and the target engine speed RPMSET set in the target idle engine speed calculation subroutine is subtracted from the current engine speed NE to obtain a differential rotation DELT.
Calculate AN (DELTAN ← NE-RPMSET),
In step S53, the feedback correction amount DFB is set by referring to a table based on the differential rotation DELTAN and the current engine speed NE.

The feedback correction amount DFB is a correction value [%] of the duty ratio DUTY when the engine speed NE during idling is feedback-controlled to the target engine speed RPMSET. The optimum value of the feedback correction amount DFB is obtained for each area based on NE and the differential rotation DELTA, and the feedback correction amount DFB is set as a table using the engine speed NE and the differential rotation DELTAN as parameters. It is the one that is stored in memory. An example of this table is shown in step S53.

As shown in step S53, when the differential rotation DELTAN is a negative value, that is, when the current engine speed NE is equal to the target engine speed RPMMS, the above table is displayed.
When it is lower than T, as the absolute value of the differential rotation becomes larger and the engine rotational speed NE becomes higher, the duty ratio DUTY is further corrected to increase and the valve opening of the ISC valve 10 is corrected to increase. The feedback correction amount DFB having a large value is stored in order to increase the intake air amount 1 and increase the engine speed NE. When the differential rotation DELTAN is a positive value, that is, when the current engine speed NE is When the target rotation speed RPMSET is higher than the target rotation speed RPSET, the duty ratio DUTY is further reduced and corrected so that the valve opening of the ISC valve 10 is reduced and corrected as the differential rotation DELTAN is larger and the engine rotation speed NE is higher. The feedback correction amount DFB on the more negative side is stored in order to decrease the intake air amount and decrease the engine speed NE by the decrease. To have.

Then, the above steps S53 to S54
To the duty ratio D set during the previous execution of the routine.
The current duty ratio DUTY is set by adding the feedback correction amount DFB set in step S53 to UTY (DUTY ← DUTY + DFB), and the following step S55
Then, the duty ratio DUTY is compared with a lower limit value DUTYMIN (for example, 25%) that determines a control lower limit.
If <DUTYMIN, in step S56, the current duty ratio DUTY is reset by the lower limit value DUTYMIN (DUTY ← DUTYMIN), and DUTY ≧ DU
If it is TYMIN, the process proceeds to step S57, where the current duty ratio DUTY is set to the upper limit value DUTYMA that defines the control upper limit.
X (for example, 100%). And DUTY
If> DUTYMAX, in step S58, the current duty ratio DUTY is reset using the upper limit value DUTYMAX (DUTY ← DUTYMAX), and DUTY ≦
DUTYMAX, ie DUTYMIN ≦ DUTY ≦ DUTY
At MAX, if the current duty ratio DUTY set in step S54 is in the controllable region, the routine exits from the routine.

When the idle speed control feedback correction subroutine is completed by setting the above duty ratio DUTY, an idle speed control routine (see FIG. 3).
To step S15, the current duty ratio DUTY set in the idle speed control feedback correction subroutine is set, and the routine exits. As a result, the drive signal of the duty ratio DUTY is
The signal is output from the control unit 40 to the ISC valve 10 and feedback-controlled so that the engine speed NE during idling converges on the target speed PRMSET.

An example of the behavior of the idle speed by the above idle speed control will be described with reference to FIG.

For example, when the outside air temperature is low such as in a cold region, the engine cooling water temperature TWN is in a low temperature state (-1 in the figure).
When the engine is started at 5 ° C., the respective flags are cleared at the start of the engine. First, the target rotation speed RPMST1 is set to a target rotation speed RPMST1 having a high value during warm-up for the purpose of promoting engine warm-up. When the RPMSET is set, the engine speed NE, that is, the idle speed is controlled to be high by the feedback control at the time of idling, and the engine warm-up promotion is improved.

Note that after the engine is started, a predetermined time KTAF
Until STA (80 seconds in the present embodiment) elapses, the cooling water temperature maximum value TWNMAX is fixed to a low water temperature value TWNMAXST that cannot actually exist in step S32 of the water temperature drop determination routine, and after a predetermined time KTAFSTA has elapsed, Until the cooling water temperature TWN reaches the warm-up completion water temperature KTWMAXGD (76 ° C. in this embodiment), the cooling water temperature maximum value TWNMAX is updated in accordance with the increase in the engine cooling water temperature TWN (steps S34 and S35). .

After that, when the vehicle starts running (TWN = 1 ° C. in the figure), the vehicle running state is detected in step S25 of the target idle speed calculation subroutine, and the vehicle speed condition flag FSPDFB is set ( Step S
26) After the engine is started, that is, after the system is initialized by turning on the ignition switch 51, if the vehicle traveling state is detected even once, the vehicle speed condition flag FSP
By setting the DFB, the target rotation speed RPMSET is set by the target rotation speed RPMST2 for traveling warm-up, which has a low value on the way of warm-up with emphasis on quietness and fuel efficiency (step S27).
Target speed RPM for running warm-up by feedback control
The idle speed is controlled to be low so as to converge to the target speed RPMSET by ST2, thereby achieving quietness,
Fuel efficiency is improved.

Then, as the engine coolant temperature TWN rises, the target rotation speed RPMST2 is gradually reduced by the target rotation speed RPMST2 for traveling warm-up, and the idle speed is correspondingly reduced by feedback control.

In this process, if the vehicle is warming up during traveling, the engine speed NE increases and the engine load increases while the vehicle is traveling. Therefore, the warming-up of the engine 1 is promoted and the engine coolant temperature TWN also decreases. Then, when the vehicle is stopped, the target rotation speed RPMST for traveling warm-up
The idle speed is controlled low by the idle speed control 2, and at this time, if the outside air temperature is low or the wind is blowing due to the use of a cold region or the like, the amount of heat radiation by the radiator or the like is larger than the amount of heat generated by the engine 1. As a result, the engine coolant temperature TWN decreases, and the engine warm-up performance becomes insufficient.

Then, the steps of the routine for judging the decrease in water temperature
In S38, the coolant temperature decrease amount (TWNMAX) calculated by subtracting the current engine coolant temperature TWN from the coolant temperature maximum value TWNMAX.
−TWN) is the water temperature drop judgment value KDTWFB (5 ° in this embodiment).
C) or more, that is, the engine coolant temperature decreases by a predetermined amount or more based on the coolant temperature decrease determination value KDTWFB, and at this time, the current engine coolant temperature TWN is set to a set value KTWLFB (60 ° in this embodiment) in step S39. C) When
Judging that the engine warm-up performance is insufficient due to the cooling water temperature drop,
In step S41, the target rotation speed RPM based on the idle rotation target rotation speed RPMST1 having a high value during engine warm-up
A water temperature drop determination flag FDTWFB for instructing the setting of SET is set (FDWFB ← 1), and the water temperature drop determination flag FD is set.
Due to the setting of TWFB, even when the vehicle is idling after running, the target speed RP for the above-mentioned idle warm-up, which has a high value in the warm-up process,
The target rotation speed RPMSET is set by MST1.
(Step S24 of the target idle speed calculation subroutine,
S29), thereby, the idle speed is controlled to be high, and the engine warm-up is promoted by increasing the idle speed when the engine warm-up performance is insufficient.

Here, since the idling speed is increased by detecting a decrease in the engine cooling water temperature TWN, the cost can be suppressed and increased without providing a new sensor or switch for detecting the outside air temperature. Becomes possible.

Thereafter, the engine cooling water temperature TWN becomes equal to the warm-up completion water temperature K which can be regarded as the completion of the warm-up of the engine 1.
When the temperature reaches TWMAXGD (76 ° C.), the water temperature drop flag FDTWFB is cleared (steps S43 and S44 of the water temperature drop determination routine), and the cooling water temperature drop determination is released.
The process returns to the normal idle speed control in which the target speed RPMST is set by the target speed RPMST2 for traveling warm-up.

[0109]

As described above, according to the first aspect of the present invention, the maximum value of the engine coolant temperature after the engine is started is detected, and the maximum value of the coolant temperature and the current engine coolant temperature are used as the coolant temperature. The amount of decrease is calculated, and when the amount of decrease in the cooling water temperature is equal to or more than a predetermined amount, it is determined that the temperature of the cooling water has decreased. The target rotation speed is set by the target rotation speed for warm-up, and the control amount for the idle rotation speed control valve is set according to the result of comparison between the target rotation speed based on the target rotation speed for idle warm-up and the engine rotation speed during idling. Therefore, when the vehicle is idling after the vehicle is running, the engine speed is controlled to a low idle speed by the target rotation speed for traveling warm-up. If the amount of heat released by the radiator, etc. increases more than the heat generated by the engine and the engine cooling water temperature drops and the engine warm-up performance is insufficient, the warm-up target The engine speed can be raised immediately after shifting to the setting of the target engine speed, and when the engine warm-up performance is insufficient due to the cooling water temperature drop, the engine warm-up is promoted by the increase in the idle speed, and the engine warm-up performance is improved. Shortage can be eliminated.

When it is not determined that the cooling water temperature is low, if the vehicle running state is not detected at all once after the engine is started, the target rotating speed is set by the target warming-up target rotation speed, and the vehicle running state is detected. In this case, the target rotation speed is set based on the target rotation speed for traveling warm-up, which has a low value in the warm-up process with emphasis on quietness and fuel efficiency, and when idling, the target rotation speed is compared with the engine rotation speed. Since the control amount for the idle speed control valve is set accordingly, if the vehicle running state has not been detected even after the engine starts,
The idle speed during the engine warm-up can be controlled to be high, and the engine warm-up can be promoted by the target speed based on the target warm-up speed for the warm-up during which the warm-up process is high. In addition, when the vehicle running state is detected, the idle speed is controlled to be low by the target speed based on the target speed for running warm-up, which has a low value during warm-up, to improve quietness and fuel efficiency. be able to. Therefore, it is possible to achieve both engine warm-up characteristics, quietness, and fuel efficiency.

When the engine warm-up performance is insufficient due to a decrease in the cooling water temperature, the target speed is shifted to the target warm-up rotational speed, so that the target warm-up rotational speed can be set low.
Silence during idling after traveling can be further improved.

Further, since the idling speed is increased by detecting a decrease in the temperature of the engine cooling water, it is possible to suppress the increase in cost without providing a new sensor or switch for detecting the outside air temperature.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, when the maximum value of the cooling water temperature is detected, a predetermined time after the start of the engine elapses.
Since the maximum value of the cooling water temperature is fixed to a predetermined low water temperature value that cannot actually be achieved, the cooling water of the radiator section or the like at the time of restarting the engine after a short stop when the engine is in a substantially warm-up completed state. Can be prevented from being erroneously determined due to a temporary decrease in the temperature of the engine cooling water caused by flowing into the engine, and the controllability can be improved.

According to the third aspect of the invention, in addition to the effect of the first aspect, when the engine cooling water temperature is equal to or higher than the warm-up completion water temperature at which it is determined that the warm-up of the engine is completed.
Since the maximum value of the cooling water temperature is set by the warming-up completion water temperature, the cooling water temperature decreases due to the water temperature fluctuation caused by running, stopping, etc. of the vehicle in the engine warming-up completion state despite the engine warming-up completion state. It is possible to prevent erroneous determination that the engine warm-up performance is insufficient.

According to the fourth aspect of the present invention, in addition to the effect of the first aspect of the present invention, when determining the decrease in the water temperature, the amount of the decrease in the coolant temperature is equal to or more than a predetermined amount, and the engine coolant temperature at this time is not less than the predetermined amount. When the engine coolant temperature is higher than the set value, it is determined that the coolant temperature is low. Since the target engine speed is set to a high value, the idle speed is controlled to a relatively high value. Therefore, this state is determined based on the temperature of the engine coolant, and the running warm-up at this time is determined. Unnecessary switching from the setting of the target rotation speed based on the target rotation speed for use to the setting of the target rotation speed based on the target rotation speed for neglected warm-up can be prevented.

According to the fifth aspect of the present invention, in addition to the effects of the first or fourth aspect of the present invention, after it is determined that the cooling water temperature has decreased, it is determined that the engine cooling water temperature has been completely warmed up. When the coolant temperature becomes equal to or higher than the warm-up completion water temperature, the cooling water temperature drop determination is canceled, so that the engine coolant temperature rise and fall caused by canceling the coolant temperature drop determination before the engine warm-up is completed, and It is possible to prevent hunting of the rise and fall of the idle speed caused by switching between the setting of the target speed based on the target speed for leaving warm-up and the setting of the target speed based on the target speed for traveling warm-up.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a flowchart of an engine speed calculation routine.

FIG. 3 is a flowchart of an idle speed control routine.

FIG. 4 is a flowchart of a target idle speed calculation subroutine.

FIG. 5 is a flowchart of a water temperature drop determination routine.

FIG. 6 is a flowchart of an idle speed control feedback correction subroutine.

FIG. 7 is an explanatory diagram of a target rotation speed table for leaving warm-up and a target rotation speed table for traveling warm-up.

FIG. 8 is a characteristic diagram of a target rotation speed for leaving warm-up and a target rotation speed for running warm-up.

FIG. 9 is a time chart showing the behavior of the engine coolant temperature when the engine is restarted after the engine has been stopped for a short time.

FIG. 10 is an explanatory diagram showing an example of the behavior of the idle speed according to the idle speed control of the present invention;

FIG. 11 is a time chart of a pulse signal output from a crank angle sensor.

FIG. 12 is an overall schematic diagram of an engine.

FIG. 13 is a front view of a crank angle sensor and a signal rotor.

FIG. 14 is a circuit configuration diagram of an electronic control system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 10 ISC valve (idle rotation speed control valve) 26 Cooling water temperature sensor 40 Electronic control device (target rotation speed setting means for leaving warm-up,
TWN Engine cooling water temperature TWNMAX Cooling water temperature maximum value (TWNMAX-TWN) Cooling water temperature Decrease amount KDTWFB Water temperature drop judgment value (predetermined amount) RPMST1 Target rotation speed for leaving warm-up RPMST2 Target rotation speed for running warm-up RPMSET Target rotation speed NE Engine rotation speed DUTY Duty ratio (control amount) KTAFSTA predetermined time TWNMAXST Low water temperature value KTWMAXGD Warm-up completion water temperature KTWLFB Set value

Claims (5)

[Claims] When the vehicle running state is not detected even once after the engine is started, a target engine speed is set based on an engine warm-up target engine speed for which the value gradually decreases as the engine coolant temperature rises. When the vehicle running state is detected, thereafter, the target rotation speed is set based on the target rotation speed for traveling warm-up, which is lower than the target rotation speed for idle warm-up, and the target rotation speed during idling is set. An idle speed control device for controlling the idle speed by setting a control amount for the idle speed control valve according to the result of comparison between the engine speed and the engine speed. A target rotation speed setting means for setting a rotation speed, and a target rotation speed setting device for traveling warm-up for setting the target rotation speed for traveling warm-up based on an engine coolant temperature. A cooling water temperature maximum value detecting means for detecting a maximum value of the engine cooling water temperature after the engine is started; and calculating a cooling water temperature reduction amount based on the cooling water temperature maximum value and the current engine cooling water temperature. When the cooling water temperature is lower than the predetermined amount, the cooling water temperature determining unit determines a cooling water temperature drop. Sometimes, if the vehicle running state is not detected even once after the engine is started, the target rotation speed is set by the target rotation speed for leaving warm-up, and if the vehicle running state is detected,
Thereafter, a target rotation speed setting means for setting a target rotation speed based on the target rotation speed for traveling warm-up, and a control amount for the idle rotation speed control valve according to a result of comparison between the target rotation speed and the engine rotation speed during idling. And a control amount setting means for setting the engine speed. 2. The cooling water temperature maximum value detection means fixes the cooling water temperature maximum value to a preset low water temperature value that cannot actually exist until a predetermined time elapses after the engine is started. The idle speed control device for an engine according to claim 1. 3. The cooling water temperature maximum value detecting means sets the cooling water temperature maximum value based on the warming-up completed water temperature when the engine cooling water temperature is equal to or higher than the warming-up completed water temperature at which it is determined that the engine has been completely warmed up. The idle speed control device for an engine according to claim 1, wherein: 4. The cooling water temperature drop determining means determines that the cooling water temperature has dropped when the amount of cooling water temperature drop is equal to or greater than a predetermined value and the engine coolant temperature at this time is greater than or equal to a set value. Item 2. An engine idle speed control device according to Item 1. 5. The cooling water temperature drop judging means, when judging that the cooling water temperature is dropping, when the engine cooling water temperature becomes equal to or higher than the warm-up completion water temperature at which it is judged that the engine has been completely warmed up, judges whether the cooling water temperature has dropped. The engine idle speed control device according to claim 1 or 4, wherein the control is canceled.