JPH0733802B2 - Idle rotation speed control method for internal combustion engine - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method for controlling an idle speed of an internal combustion engine, and more particularly to an internal combustion engine for controlling an idle speed according to an engine operating state, which is suitable for use in an automobile engine equipped with an electronically controlled fuel injection device. The present invention relates to improvement of an idle speed control method for an engine.

[Prior art]

In recent years, with the development of electronic control technology, in particular, digital control technology, a so-called electronic control engine has been put into practical use in which the air-fuel ratio of the engine is controlled using an electronically controlled fuel injection device or the like. In this electronically controlled engine, for example, the fuel injection time is determined according to the engine load and the engine speed detected from the intake air amount of the engine or the intake pipe pressure, and only the fuel injection time, for example, the intake manifold. It is designed to control the air-fuel ratio of the engine by opening the injector, which is installed in the engine and injects fuel toward the intake port of the engine, and it is necessary to precisely control the air-fuel ratio. However, it has come to be widely used in automobile engines provided with exhaust gas purification measures. In this electronically controlled engine, for example, a linear solenoid type idle speed control valve (hereinafter referred to as ISCV) is generally used to control the throttle valve according to the difference between the engine speed and the target idle speed during idle operation. By controlling the flow rate of the intake air introduced by bypass, the idle speed of the engine is feedback-controlled. According to such idle speed control, it becomes possible to accurately control the idle speed of the engine.

[Problems to be Solved by the Invention]

However, in the past, since the actual drive current applied to the ISCV was not detected, for example, the power supply voltage and coil temperature changed, and the actual drive current corresponded to the calculated duty ratio for obtaining the idle target rotation speed. However, if the target drive current is different from the target drive current, it is impossible to obtain good controllability. In order to solve such a problem, for example, a central processing unit (hereinafter C) in an electronic control unit (hereinafter ECU) is
The idle speed control valve control signal (hereinafter referred to as ISCV control signal) output from (PU) is temporarily smoothed using, for example, a smoothing circuit, and this is corrected by the detection value of the actual drive current sent to ISCV. After that, it is conceivable to convert the signal into an on / off signal for controlling ISCV again and drive ISCV, but if such a configuration is configured entirely by hardware, not only the cost will increase, but also There was a problem that the volume of the ECU also increased. On the other hand, as a hardware similar to the present invention, an air-fuel ratio control device for controlling the air-fuel ratio by changing the duty ratio by the output of an oxygen concentration sensor, as shown in JP-A-56-23536. Although proposed, it does not control the idle rotation speed like the present invention. The present invention has been made to solve the above-mentioned conventional problems, and it is possible to appropriately correct the drive signal of the idle rotation speed control valve whose center duty ratio is constantly changing. It is an object of the present invention to provide a method for controlling the idle speed of an internal combustion engine, which is capable of realizing a highly accurate idle speed control regardless of the change of the above, and at the same time, can reduce the cost and downsize the ECU.

[Means for solving problems]

The present invention relates to an idle speed control method for an internal combustion engine for controlling the idle speed according to an engine operating state, and as shown in the outline of FIG. 1, a calculation duty ratio for obtaining an idle target speed is calculated. Then, the actual drive current supplied to the idle speed control valve is detected based on the calculated duty ratio, the target drive current corresponding to the calculated duty ratio is obtained, and the difference between the target drive current and the actual drive current is determined. Based on the above, the above-mentioned object is achieved by correcting the calculated duty ratio.

[Action]

According to the present invention, the calculated duty ratio is corrected based on the difference between the target drive current and the actual drive current corresponding to the calculated duty ratio for obtaining the idle target rotation speed. Appropriate correction can be made for the drive current of the idle speed control valve that is constantly changing, and highly accurate idle speed control can be realized regardless of changes in the power supply voltage and the coil temperature.
Further, since only the actual drive current detection circuit is left in hardware and most of it is processed in software, cost reduction and ECU miniaturization can be achieved.

【Example】

An embodiment of an electronic control engine for an automobile, in which an idle speed control method for an internal combustion engine according to the present invention is adopted, will be described below in detail with reference to the drawings. In this embodiment, as shown in FIG. 2, an air cleaner 12 for taking in outside air, an air flow meter 14 for detecting the flow rate of intake air taken in by the air cleaner 12, and an air flow meter 14 are built in the air flow meter 14. , The intake air temperature sensor 16 for detecting the temperature of the intake air, and the intake air flow rate, which is installed in the slot body 18 and is opened and closed in conjunction with an accelerator pedal (not shown) installed in the driver's seat. Throttle valve for controlling 20
And a throttle sensor 22 including an idle switch for detecting whether or not the throttle valve 20 is at the idle opening degree.
A surge tank 24 for preventing intake interference; a bypass passage 26 for bypassing the throttle valve 20; and a linear passage for controlling the idle rotation speed by controlling the opening area of the bypass passage 26. A solenoid type ISC V28, an intake manifold 30 for injecting pressurized fuel toward the intake port of each cylinder of the engine 10, and an air-fuel mixture introduced into the engine combustion chamber 10A. A spark plug 34 for ignition, an exhaust manifold 36 for collecting exhaust gas formed by combustion in the engine combustion chamber 10A, and a high-pressure ignition secondary signal generated by an ignition coil 38 are supplied to each cylinder. Distributor 40 having a distributor shaft that rotates in conjunction with rotation of the crankshaft of engine 10 for distributing power to spark plug 34, and built in said distributor 40 A crank angle sensor 42 that outputs a crank angle signal according to the rotation of the distributor shaft, a water temperature sensor 44 that is arranged in the cylinder block 10B of the engine 10 for detecting the engine cooling water temperature, and a battery 50. The fuel injection amount is determined according to the engine rotation speed or the like obtained from the intake air amount output from the air flow meter 14 and the crank angle signal output from the crank angle sensor 42, and a valve opening time signal is output to the injector 32. At the same time, during the idling operation, when the feed back condition is satisfied, the ECU 52 controls the ISC V28 with the feed back according to the difference between the engine rotation speed and the idle target rotation speed. As shown in detail in FIG. 2 above, the ISCV 28 includes a valve body 28A for changing the opening area of the bypass passage 26, a shaft 28B having the valve body 28A fixed to its tip, and a shaft 28B.
The core 28C is fixed to the rear end of 28B, and the coil 28D is provided around the core 28C. As shown in detail in FIG. 3, the ECU 52 has a CPU 52A such as a microprocessor for performing various arithmetic processes, a clock circuit 52B for generating various clock signals, and a control program, various data, etc. stored in advance. A read-only memory (hereinafter referred to as ROM) 52C for keeping the data, a random maximum memory (hereinafter referred to as RAM) 52D for temporarily storing calculation data in the CPU 52A, and a coil 28D of the ISCV28. Current detection circuit 52E for detecting the actual drive current, the air flow meter 14 output, intake air temperature sensor 16 output, water temperature sensor 44 output, battery 50 output, the current detection circuit 52E output input through the amplifier 52F Multiplexer 52G for sequentially capturing analog signals such as, and analog-digital for converting the multiplexer 52G output into a digital signal Exchanger (hereinafter referred to as A / D converter) 52H and input and output ports 52I for taking the A / D converter 52H Output
An idle switch output of the throttle sensor 22, an input / output port 52K for capturing a digital signal such as an output of the crank angle sensor 42 input via a shaping circuit 52J, and a calculation result of the CPU 52A, Output port for outputting ISCV control signal to the ISCV28 via the drive circuit 52L
52M, output port 52O for outputting a valve opening time signal to the injector 32 via a drive circuit 52N, and a common bus 52P connecting between the respective constituent devices, also according to the calculation result of the CPU 52A. Has been done. The operation of the embodiment will be described below. The idle rotation control in this embodiment is shown in FIGS.
It is executed according to the flow chart as shown in the figure. That is, the above
Analog-to-digital conversion in the A / D converter 52H (hereinafter referred to as A / D
When the processing (referred to as D conversion) is completed, the A / D conversion end check routine shown in FIG. 4 is entered, and in step 102, the current A / D conversion is performed by the current detection circuit 52.
It is determined whether or not this is due to the end of A / D conversion of the ISCV actual drive current Iisc of the E output. If the judgment result is positive,
In step 104, the current A / D converted value is stored in the RAM 52D as the ISCV actual drive current value Iisc. Next, in step 106, according to the difference between the engine rotation speed and the idle target rotation speed, from the calculated duty ratio DUTY for obtaining the idle target rotation speed, which is previously obtained,
For example, the ISCV target drive current If corresponding to the calculated duty ratio DUTY is obtained by using the relationship shown in FIG.
Next, in step 108, it is determined whether or not the ISCV actual drive current Iisc is larger than a value If + β obtained by adding a predetermined value β corresponding to the dead zone to the ISCV target drive current If obtained in step 106. If the determination result is positive, step 11
0, ISCV target drive current If and ISCV
A value obtained by subtracting a predetermined value α from the correction coefficient K for correcting the calculated duty ratio DUTY based on the difference in the actual drive current Iisc is set as a new correction coefficient K. K ← K-α (1) Then, the process proceeds to step 112, where the calculated correction coefficient K is
It is determined whether it is smaller than the lower limit value Kmin. If the determination result is positive, the process proceeds to step 114 and the lower limit value K
Let min be the correction coefficient K. On the other hand, when the result of the determination in the above step 108 is negative, the routine proceeds to step 116, where the ISCV actual drive current Iisc is I
It is determined whether it is smaller than a value If-β obtained by subtracting a predetermined value β corresponding to the dead zone from the SCV target drive current If. If the determination result is positive, the process proceeds to step 118, and a value obtained by adding a predetermined value α to the correction coefficient K is set as a new correction coefficient K as shown in the following equation. K ← K + α (2) Next, in step 120, the calculated correction coefficient K is
It is determined whether it is larger than the upper limit value Kmax. If the determination result is positive, the process proceeds to step 122 and the upper limit value K
Let max be the correction coefficient K. After completion of steps 114 and 122, or the steps 102 and 11
When the determination result of 2, 116, 120 is negative, this routine is exited. Further, the correction of the calculated duty ratio DUTY based on the value of the correction coefficient K calculated in the A / D conversion end check routine as shown in FIG. 4 is performed by the duty ratio calculation routine as shown in FIG. Done in. That is, in step 202 of the duty ratio calculation routine, for example, the calculated duty ratio DUTY for obtaining the idle target rotation speed according to the difference between the engine rotation speed at that time and the idle target rotation speed.
Ask for. Next, at step 204, the output duty ratio DUTYout is obtained by multiplying the calculated duty ratio DUTY by the correction coefficient K as shown in the following equation. DUTYout = K × DUTY (3) According to the output duty ratio signal thus calculated, the ISCV drive current is passed through the ISCV 28. Therefore, IS
When the CV actual drive current Iisc is larger than the ISCV target drive current If, the correction coefficient K is gradually decreased, while when the ISCV actual drive current Iisc is smaller than the ISCV target drive current If, the correction is performed. The coefficient K is gradually increased and the ISCV actual drive current Iisc becomes IS.
It is made to approach the CV target drive current If. In this embodiment, when the correction coefficient K is increased / decreased according to the difference between the ISCV actual drive current Iisc and the ISCV target drive current If, the dead zone β is provided, so that the correction coefficient K is not transiently increased / decreased. , Control stability is particularly high. The dead zone β may be set to zero and may be omitted. Further, in this embodiment, since the correction coefficient K is provided with the upper limit value Kmax and the lower limit value Kmin, the correction coefficient K is not likely to take an abnormal value, and the control stability is high. Note that this guard can be omitted. In the above-mentioned embodiment, the present invention is applied to the electronic control engine for automobile equipped with the intake air amount sensing type electronic control device, but the scope of application of the present invention is not limited to this, and the intake pipe pressure sensing type is applied. It is obvious that the present invention can be similarly applied to an electronic control engine for an automobile equipped with the electronic control device described above, and a general internal combustion engine provided with another air-fuel ratio control device such as a carburetor.

【The invention's effect】

As described above, according to the present invention, it is possible to perform appropriate correction for the drive current of the ISCV whose center duty ratio is constantly changing, and to control the ISCV well even when the power supply voltage or the coil temperature changes. can do. Moreover,
Since the hardware is only the actual drive current detection circuit, and most of it is implemented as software, it is possible to realize inexpensive and highly accurate idle rotation speed control, and at the same time, it is possible to reduce the size of the ECU. Have.

[Brief description of drawings]

FIG. 1 is a flow chart showing an outline of an idle speed control method for an internal combustion engine according to the present invention, and FIG. 2 is a partial view showing a configuration of an embodiment of an electronic control engine for an automobile to which the present invention is adopted. FIG. 3 is a sectional view including a block diagram, FIG. 3 is a block diagram showing the configuration of the electronic control unit used in the above embodiment, and FIG. 4 is similarly showing the difference between the target drive current and the actual drive current. FIG. 5 is a flowchart showing an analog-digital conversion end check routine for calculating a correction coefficient for correcting the calculated duty ratio based on FIG. 5, and FIG. 5 is an example of the relationship between the calculated duty ratio and the target drive current used in the routine. FIG. 6 is a flow chart showing a main part of a duty ratio calculation routine for correcting the calculation duty ratio according to the correction coefficient, which is used in the above embodiment. 10 …… Engine, 14 …… Air flow meter, 20 …… Slottle valve, 22 …… Slottle sensor, 26 …… Bypass passage, 28 …… Idle speed control valve (ISCV), 32 …… Injector, 42 …… Crank angle sensor, 52 ... Electronic control unit (ECU), 52A ... CPU, 52E ... Current detection circuit, 52F ... Amplifier, 52G ... Multiplexer, 52H ... Analog-digital converter (A / D converter) ), 52I …… input / output port, 52M …… output port, 52L …… driving circuit.

Claims (1)

[Claims] 1. In an idle speed control method for an internal combustion engine for controlling an idle speed according to an engine operating state, a calculated duty ratio for obtaining an idle target speed is obtained, and based on the calculated duty ratio. The actual drive current supplied to the idle speed control valve is detected, the target drive current corresponding to the calculated duty ratio is obtained, and the calculated duty ratio is calculated based on the difference between the target drive current and the actual drive current. A method for controlling an idle speed of an internal combustion engine, which comprises performing correction.