JPH0553941B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an idling control method for an internal combustion engine, and particularly to an idling control method in which the lower limit opening of an ISC valve is regulated based on a value obtained by correcting an initial value by learning. Regarding control method.

[Conventional technology]

Generally, the so-called idle state in which the throttle valve is fully closed or close to fully closed means that the idle switch (hereinafter referred to as
It is abbreviated as IDL switch. ) is turned on. When the IDL switch is on, the opening degree of the ISC (idle speed control) valve installed in the bypass flow path of the throttle valve is feedback-controlled to maintain the engine speed at the target idle speed. .

However, even if the IDL switch is on, if the throttle valve is slightly open, that is, if the accelerator pedal is slightly depressed,
Through the above-mentioned feedback control, the opening degree of the ISC valve is reduced by the amount of air sucked through the slightly opened throttle valve. In such a case, if the throttle valve is fully closed, the ISC valve opening control using the feedback control described above will not be able to be done in time, resulting in a lack of intake air and a sudden drop in engine speed, or even stalling of the engine. There is a risk that this may occur.

Therefore, in order to prevent the engine from stalling in the above-mentioned conditions, conventionally, in ISC valve feedback control, the lower limit opening of the ISC valve was set, and the minimum amount of air was sucked in to prevent the engine from stalling. I try to do that.

[Problem that the invention seeks to solve]

As a method for setting the lower limit opening of the ISC valve, a method is conventionally known in which a preset initial value is learned to gradually approach the actual ISC valve opening, and the setting is performed based on this learned value. This kind of learning is usually done using computers, etc., and the initial values are stored in nonvolatile memory (ROM, etc.), and the learned values are stored in volatile memory (RAM, etc.). ing. Therefore, once the learning has been sufficiently performed, the lower limit opening of the ISC valve will be set to an appropriate value that reflects the actual situation.

However, the RAM where the learning values are stored
When the power supply (battery) is removed, the learned value is erased, so the lower limit opening degree is again set to a value based on the initial value. Normally, this initial value is set to a relatively high value (for example, a value that takes into consideration cold idling), and the learned value that is corrected by learning is revised at a predetermined timing, and the lower limit (The lower limit is particularly problematic.) Since the ISC valve is limited to a value within 100 degrees, the lower limit opening of the ISC valve is held at a value higher than necessary until corrections through learning are repeated and repeated. Therefore, there is a problem in that it takes a long time until the engine speed is reduced to the idle target speed.

In particular, the timing of revision of the upper and lower limits of the learning value is
When the ignition key is turned on, or at the end of one idle state, that is, when the vehicle speed exceeds a predetermined value, the lower limit opening must be repeated several times to start and stop. There is a problem that it is not sufficiently reduced.

An object of the present invention is to solve the above-mentioned conventional problem, that is, when the power of the volatile memory that stores the reference value of the lower limit opening of the ISC valve is restored,
An object of the present invention is to provide an idling control method for an internal combustion engine that can quickly correct the lower limit opening of an ISC valve from its initial value to a value corresponding to a target idling rotation speed.

[Means for solving problems]

The present invention performs feedback control of the idle speed control (hereinafter abbreviated as ISC) valve opening in order to match the engine speed to the target idle speed, and controls the ISC valve opening and the volatile memory when the power is restored. In order to zero the deviation from the ISC valve opening learned value, which has a predetermined initial value, the learned value is corrected within the lower limit value that is revised at a predetermined timing and stored in volatile memory. The ISC based on learned values stored in volatile memory
In an idling control method for an internal combustion engine in which the lower limit of the valve opening is regulated, when it is detected that the power is restored after the power to the volatile memory has been removed, the learned value is set to the ISC valve opening. The method is characterized in that the lower limit value for the learned value is sequentially and forcibly reduced until they match.

[Effect]

With this configuration, when the power to the volatile memory is restored, the lower limit value for the learned value is forcibly reduced in sequence, so the learned value is controlled in accordance with the idle target rotation speed. The ISC valve opening is immediately reduced. Therefore, the lower limit opening of the ISC valve determined based on this is also quickly reduced to an appropriate value.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

First, an example of an internal combustion engine to which the present invention is applicable will be described with reference to FIG. 2.

This engine is equipped with an automatic transmission and is controlled by an electronic control circuit such as a microcomputer, and is equipped with an air flow meter 2 downstream of an air cleaner (not shown) to detect the amount of intake air. . The air flow meter 2 includes a compensation plate rotatably provided in the damping chamber, a measuring plate connected to the compensation plate, and a potentiometer 4 that detects the opening degree of the compensation plate. ing. Therefore, the intake air amount is determined from the intake air amount signal output from the potentiometer as a voltage value. Further, an intake temperature sensor 6 is provided near the air flow meter 2 to detect the intake air temperature and output an intake temperature signal.

A throttle valve 8 is arranged downstream of the air flow meter 2, and an idle switch 10 that is turned on when the throttle valve is fully closed (idle position) is attached to the throttle valve 8. A surge tank 12 is installed downstream of the throttle valve 8. is provided. Further, a bypass passage 14 is provided so as to bypass the throttle valve 8 and communicate between the upstream side of the throttle valve and the surge tank 12 on the downstream side of the throttle valve. An ISC valve 16 whose opening degree is adjusted by a stepping motor is attached to this bypass path 14. The surge tank 12 communicates with the combustion chamber of the engine 20 via an intake manifold 18 and an intake port 22. A fuel injection valve 24 is attached to each cylinder so as to protrude into the intake manifold 18.

The combustion chamber of the engine 20 is connected via an exhaust port 26 and an exhaust manifold 28 to a catalytic converter (not shown) filled with a three-way catalyst. This exhaust manifold 28
An O ₂ sensor 30 is attached to detect the residual oxygen concentration in exhaust gas and output an air-fuel ratio signal. The engine block 32 has this block 3.
An engine coolant temperature sensor 34 is mounted so as to penetrate through the engine cooling water jacket 2 and protrude into the water jacket. This cooling water temperature sensor 34 detects the engine cooling water temperature and outputs a water temperature signal.

A spark plug 38 is attached to each cylinder so as to penetrate the cylinder head 36 of the engine 20 and protrude into the combustion chamber. This spark plug 38
is the distributor 40 and the igniter 4.
2, it is connected to an electronic control circuit 44 composed of a microcomputer or the like. Inside the distributor 40, a cylinder discrimination sensor 46 and a crank angle sensor 48 are installed, each of which is constituted by a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing. In the case of a 6-cylinder engine, the cylinder discrimination sensor 46 is, for example,
A cylinder discrimination signal is outputted every 720°C, and the crank angle sensor 48 outputs an engine rotation speed signal, for example, every 30°C.

The electronic control circuit 44 also includes a key switch 5.
0, a neutral start switch 52, an air conditioner switch 54, a vehicle speed sensor 56, and a battery 58 are connected. The key switch 50 outputs a starter signal when starting the engine, the neutral start switch 52 outputs a neutral signal only when the transmission is in the neutral position,
The air conditioner switch 54 outputs an air conditioner signal when the compressor of the air conditioner is activated. The vehicle speed sensor 56 is composed of a magnet fixed to the speedometer cable, a reed switch, and a magnetically sensitive element, and outputs a vehicle speed signal in accordance with the rotation of the speedometer cable.

As shown in FIG. 3, the electronic control circuit 44 includes a central processing unit (CPU) 60, a read-only memory (ROM) 62, a random access memory (RAM) 64, and a backup RAM (BU-RAM).
66, an input/output port 68, an analog/digital converter (ADC) 70, and buses such as a data bus and a control bus that connect these. The input/output port 68 includes a vehicle speed signal,
A cylinder discrimination signal, an engine speed signal, a fully closed throttle signal from the idle switch 10, an air-fuel ratio signal, a starter signal, a neutral signal, and an air conditioner signal are input. In addition, input/output port 68
outputs the ISC valve control signal to control the opening degree of the ISC valve, the fuel injection signal to open and close the fuel injection valve, and the ignition signal to turn on and off the igniter to the drive circuit, and the drive circuit receives these signals. The ISC valve, fuel injection valve, and igniter are controlled accordingly. Further, an intake air amount signal, an intake air temperature signal, a battery voltage, and a water temperature signal are input to the ADC 70, and the ADC sequentially converts these signals into digital signals according to instructions from the CPU.
The ROM 62 stores the target rotation speed determined according to the engine cooling water temperature, intake temperature, load condition, shift lever range position, etc., the initial value of the ISC valve opening P, and the initial value of the learned value PG of the ISC valve opening. , an estimated amount for performing feedforward control when a load is applied, an increase amount of air amount in the event of an emergency, and other control programs, etc. are stored in advance.

Next, an embodiment in which the present invention is applied to the engine as described above will be described in detail.

FIG. 1 shows the main part of the main loop of the embodiment control procedure according to the present invention. When it is detected at step 100 in the figure that the ignition switch (IG) has been turned on, the following steps are executed. In step 102, it is determined whether or not the battery, which is the power source for the BU-RAM 66, has been removed and then restored. This judgment can be made, for example, by BU-RAM6
This is done based on the contents of the flag stored in the predetermined area of No.6. If the judgment is positive, step 104
, move to ISC valve opening P and its learned value
After setting PG to the initial values stored in the ROM 62, storing the opening degree P in a predetermined area of the RAM 64 and the learned value PG in a predetermined area of the BU-RAM 66, the process proceeds to step 106, and the battery is removed. Flag XVSTB indicating that it has been restored after being
Set to "1" and proceed to step 200. On the other hand, if a negative determination is made in step 102, steps 104 and 106 are skipped and the process proceeds to step 200.

Steps 200 to 212 are the well-known feedback control part of the ISC valve opening.
In step 200, it is determined whether the ISC feedback condition and its timing are met, and if the judgment is negative, the process proceeds to step 318 (described later), and if the judgment is positive, the process proceeds to step 318.
Move to 202. In step 202, the engine speed
The difference DNE between the average value of NE per predetermined time and the idle target rotation speed NE is determined, and in step 204, DNE is compared with a predetermined value ±ε (for example, 20% of NF), and −ε≦DNE If ≦ε, step
Proceed to step 210, and if DNE<-ε, in step 206, rewrite the ISC valve opening degree P in the RAM 64 to a value obtained by adding a predetermined value α (for example, 1 step), and proceed to step 210, and if DNE>ε, proceed to step 210. Rewrite the ISC valve opening degree P to a value obtained by subtracting the predetermined value α and proceed to step 210.
Proceed to. In step 210, the opening degree P is the lower limit opening degree.
It is determined whether or not the opening degree exceeds PG-β (β is, for example, 1 to 20 steps), and if the determination is negative, the opening degree P is rewritten to the lower limit opening degree PG-β and the process proceeds to step 300.

Steps 300 to 306 are the well-known learning control section.
The learned value PG stored in the BU-RAM 66 is determined according to the deviation between the DNE and the opening P and the learned value PG.
Increase or decrease the predetermined value γ (for example, 1/4 to 1 step), and if the learned value PG and the opening degree P are equal, step 308
Set the flag XVSTB to "0".

Next, in step 310, it is determined whether the contents of the flag Each is corrected or modified by feedback control or learning control, and it is determined whether or not they have become equal. When the flag XVSTB is "1", in step 312 the learned value PG minus a predetermined value δ (for example, 1 to 10 steps) is stored in the RAM 64 or the like as the learning correction lower limit value PGMIN, and the process proceeds to step 314. That is, in this step 312, a process is performed in which the learning value PG is forcibly reduced sequentially from its initial value. At step 314, it is determined whether the learned value PG is greater than or equal to its lower limit value PGMIN. At least when executing through step 312, PG≧
Since it is PGMIN, it is judged affirmative and the step is taken.
Move to 318. If a negative judgment is made here,
The process proceeds to step 316, where the predetermined value γ is added to the learning value PG reduced in step 306 to return it to the value before correction, and the process proceeds to step 318. step 318
It is determined whether the vehicle speed SPD is zero, that is, whether the vehicle is not in a running state. If the determination is negative, the step
320, rewrites the learning correction lower limit value PGMIN to the value obtained by subtracting a predetermined value μ (for example, 1 to 10 steps) from the learning value PG, returns to the predetermined step of the loop, and follows the control procedure described above. and repeat.

ISC valve opening degree P when controlled along the loop shown in FIG. 1 described above, its lower limit opening degree PG-β,
Fig. 4 shows the temporal changes in the learned value PG and its lower limit value PGMIN. As shown in the figure, when the battery is removed at time _t1 , the learned value PG stored in the BU-RAM is erased. When the battery is restored at _t2 and the ignition switch is turned on at _t3 , the opening degree P and the learning value PG are given initial values. Then, the opening degree P is corrected to be reduced by α steps by feedback control, and the learned value PG is corrected to be reduced by γ steps (where α>γ). However, since the opening degree P is limited to the lower limit opening degree PG-β at t ₄ , the lower limit opening degree PG-β
reaches the opening corresponding to the idle target rotation speed t ₅
Until then, the opening degree P is maintained at its lower limit opening degree PG-β. During that time, the learning value PG is gradually reduced without being limited to the lower limit value PGMIN, and at t ₆ o'clock
PG=P, learning is completed for the time being, and the lower limit value
PGMIN was then transferred to running state at t ₇ ,
It is rewritten to a predetermined value PG-μ.

As described above, according to this embodiment, the learned value having the initial value set to a relatively high value is gradually corrected and the lower limit value for the learned value is sequentially changed until it matches the actual ISC valve opening. Since the learning value is forcibly reduced and the lower limit value of the learning correction is not effectively restricted, the learning value can be changed quickly.
Reduced to ISC valve opening. At the same time, the lower limit opening of the ISC valve, which is determined based on the learned value, is also quickly reduced to an appropriate value. Therefore, the volatile memory that stores the reference value of the lower limit opening of the ISC valve, that is, the learned value.
Even if the power to BU-RAM is removed, its reference value is erased, and a relatively high initial value is set,
Since the lower limit opening of the ISC valve is quickly reduced to an appropriate value, the idling rotation speed is quickly controlled to a predetermined target rotation speed, and fuel efficiency is improved.

〔Effect of the invention〕

As explained above, according to the present invention, when the power of the volatile memory that stores the reference value of the lower limit opening of the ISC valve is restored, the lower limit value with respect to the learned value is forcibly reduced in sequence. Therefore, the reference value of the lower limit opening degree can be quickly corrected from its initial value to a value corresponding to the target idle rotation speed, which has the effect of improving fuel efficiency.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing a control procedure of an embodiment of the present invention, Fig. 2 is a schematic configuration diagram of an example of an engine to which the present invention can be applied, and Fig. 3 is a block diagram of the electronic control circuit shown in Fig. 2. , FIG. 4 is a time chart for explaining the operation of the embodiment of the present invention.

Claims (1)

[Claims] 1 Idle speed control (hereinafter referred to as
Abbreviated as ISC. ) Feedback controls the valve opening and has a predetermined initial value as the ISC valve opening and the value when the volatile memory power is restored.
In order to make the deviation from the ISC valve opening learned value zero, the learned value is corrected within the lower limit value that is revised at a predetermined timing and stored in volatile memory, and the learned value stored in the volatile memory is In the idling control method for an internal combustion engine in which the lower limit of the ISC valve opening is regulated based on the ISC valve opening, when it is detected that the power is restored after the power to the volatile memory has been removed, the learned value is set to the ISC. An idling control method for an internal combustion engine, comprising sequentially forcibly reducing the lower limit value for the learned value until the lower limit value matches the valve opening degree.