JPH045815B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for controlling the idle rotation speed of an internal combustion engine, and particularly to an internal combustion engine suitable for use in an automobile engine equipped with an electronically controlled fuel injection device, and for controlling the idle rotation speed according to the engine operating state. This invention relates to improvements in idle rotation speed control methods.

[Conventional technology]

In recent years, with the development of electronic control technology, especially digital control technology, the air-fuel ratio of the engine has been controlled using electronically controlled fuel injection devices, etc.
So-called electronically controlled engines have been put into practical use. In this electronically controlled engine, for example, the fuel injection time is determined according to the engine load and engine rotation speed detected from the intake air amount or intake pipe pressure of the engine, and the fuel injection time is determined, for example, by the intake manifold. The air-fuel ratio of the engine is controlled by opening an injector installed in the engine that injects fuel toward the engine's intake port, and it is necessary to precisely control the air-fuel ratio. It is becoming widely used in automobile engines equipped 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 during idle operation according to the difference between the engine speed and the idle target speed. By controlling the flow rate of intake air that is bypassed and introduced,
The idle speed of the engine is controlled by feedback.

[Problems to be solved by the invention]

According to such idle rotation speed control, it is possible to accurately control the idle rotation speed of the engine, but conventionally, the above-mentioned ISCV
For example, the power supply voltage or coil temperature may change because the actual drive current flowing through the
If the actual drive current is different from the target drive current corresponding to the calculated duty ratio for obtaining the target idle rotation speed, there is a problem in that good controllability cannot be obtained. In order to solve these problems, for example, the idle speed control valve control signal (hereinafter referred to as ISCV control signal) output from the central processing unit (hereinafter referred to as CPU) in the electronic control unit (hereinafter referred to as ECU) is For example, it is possible to smooth the current using a smoothing circuit, correct it with the detected value of the actual drive current flowing through the ISCV, and then convert it into an on/off signal to control the ISCV again to drive the ISCV. However, if such a configuration were constructed entirely from hardware, there were problems in that not only would the cost be high, but the volume of the ECU would also increase. On the other hand, it is possible to process part of the above configuration using software within the ECU, but when correcting the output duty ratio by converting the detected value of the drive current flowing through the ISCV into a digital signal, analog-to-digital conversion is required. Depending on the timing of A/D conversion (hereinafter referred to as A/D conversion), the A/D conversion value of the drive current may vary from conversion to conversion, and stable controllability may not be obtained. This is especially true when the output duty ratio is dithered to reduce hysteresis or to prevent so-called stuck slip, where the ISCV valve body is stuck halfway and suddenly moves. becomes a problem. On the other hand, as a hardware similar to the present invention, there is an air-fuel ratio control device that controls the air-fuel ratio by changing the duty ratio according to the output of an oxygen concentration sensor, as shown in Japanese Patent Application Laid-Open No. 56-23536. Although it has been proposed, it does not control the idle rotation speed like the present invention. The present invention was made to solve the above-mentioned conventional problems, and achieves highly accurate idle rotation speed control regardless of changes in power supply voltage or coil temperature, and also aims to reduce costs and downsize the ECU. An object of the present invention is to provide a method for controlling the idle rotation speed of an internal combustion engine.

[Means to solve the problem]

The present invention provides a method for controlling the idle rotation speed of an internal combustion engine for controlling the idle rotation speed according to the engine operating condition, as summarized in FIG. a procedure for determining a target drive current for the idle rotation speed control valve corresponding to the central duty ratio; a procedure for determining an output duty ratio by applying a dither to the central duty ratio; , a procedure for on/off controlling the actual drive current flowing through the idle rotation speed control valve, and synchronizing the actual drive current with the on/off of the idle rotation speed control valve, and converting the actual drive current into a digital signal at a cycle that is an integral multiple of the dither cycle. a step of converting; a step of correcting the central duty ratio so that the actual drive current matches the target drive current;
By including this, the above objective has been achieved.

[Effect]

According to the present invention, since the A/D conversion of the drive current is performed at a predetermined value phase of the pulsation of the drive current,
The A/D conversion value does not vary from conversion to conversion, and stable controllability can be obtained. Furthermore, if the drive current is converted into a digital signal at the center value of the dither, a more accurate A/D conversion value can be obtained.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an electronically controlled automobile engine in which the idle rotation speed control method for an internal combustion engine according to the present invention is adopted will be described in detail with reference to the drawings. As shown in FIG. 2, this embodiment includes an air cleaner 12 for taking in outside air, and an air flow meter 1 for detecting the flow rate of the intake air taken in by the air cleaner 12.
4, an intake temperature sensor 16 built into the air flow meter 14 for detecting the temperature of intake air;
A throttle valve 20 for controlling the flow rate of intake air, which is disposed on the throttle body 18 and is opened and closed in conjunction with an accelerator pedal (not shown) disposed on the driver's seat; A throttle sensor 22 including an idle switch for detecting whether or not the opening is at idle, and a surge tank 24 for preventing intake interference.
a bypass passage 26 that bypasses the throttle valve 20; a linear solenoid ISCV 28 for controlling the idle rotation speed by controlling the opening area of the bypass passage 26; and an ISCV 28 disposed in the intake manifold 30. engine 1
an injector 32 for injecting pressurized fuel toward the intake port of each cylinder of engine 0; a spark plug 34 for igniting the mixture introduced into the engine fuel chamber 10A; and a spark plug 34 for igniting the air-fuel mixture introduced into the engine fuel chamber 10A. an exhaust manifold 36 for collecting the exhaust gas formed by
and, for distributing the high voltage secondary ignition signal generated by the ignition coil 38 to the ignition plug 34 of each cylinder,
A distributor 40 having a distributor shaft that rotates in conjunction with the rotation of the crankshaft of the engine 10; a crank angle sensor 42 built into the distributor 40 that outputs a crank angle signal in accordance with the rotation of the distributor shaft; A water temperature sensor 44 for detecting the engine cooling water temperature, which is disposed on the cylinder block 10B of No. 10, a battery 50, an intake air amount output from the air flow meter 14, and a crank angle signal output from the crank angle sensor 42. The fuel injection amount is determined according to the engine rotational speed, etc., and a valve opening time signal is output to the injector 32, and at the time of idling operation,
When the feedback condition is satisfied, the ISCV 28 is feedback-controlled according to the difference between the engine rotation speed and the idle target rotation speed.
It consists of an ECU52. 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 to which the valve body 28A is fixed at the tip, and a shaft 28B. It is composed of a core 28C fixed to the rear end and a coil 28D disposed around the core 28C. As shown in detail in FIG. 3, the ECU 52 includes a CPU 52A comprising, for example, a microprocessor for performing various arithmetic operations, and a clock circuit 52 for generating various clock signals.
A read-on memory (hereinafter referred to as ROM) 52C for storing control programs and various data in advance, and a random access memory (hereinafter referred to as ROM) for temporarily storing calculation data, etc. in the CPU 52A.
(referred to as RAM) 52D, a current detection circuit 52E for detecting the actual drive current flowing through the coil 28D of the ISCV 28, the air flow meter 14 output, the intake temperature sensor 16 output, the water temperature sensor 44 output, the battery 50 output, A multiplexer 52G for sequentially taking in analog signals such as the output of the current detection circuit 52E inputted via the amplifier 52F, and an analog-to-digital converter (hereinafter referred to as A/D) for converting the output of the multiplexer 52G into a digital signal. (referred to as a converter) 52H, an input/output port 52I for receiving the output of the A/D converter 52H, and a crank angle sensor 42 that receives the idle switch output of the throttle sensor 22 and the shaping circuit 52J. An input/output port 52K for receiving digital signals such as output, an output port 52M for outputting an ISCV control signal to the ISCV 28 via the drive circuit 52L according to the calculation result of the CPU 52A, An output port 520 for outputting a valve opening time signal to the injector 32 via the drive circuit 52N according to the calculation result, and a common bus 52P for connecting each of the component devices.
It consists of and. The effects of the embodiment will be explained below. The idle rotation control in this embodiment is based on the fourth
The process is executed according to the flowcharts shown in FIGS. 5 and 7. That is, first, in step 102 in the main routine as shown in FIG.
A central duty ratio for obtaining the idle target rotation speed according to the engine operating state, for example, the difference between the engine rotation speed and the idle target rotation speed.
Ask for DUTYcenter. Next, the process proceeds to step 104, where, as shown in the following equation, a predetermined value corresponding to 1/2 of the total amplitude of the dither is calculated from the center duty ratio DUTYcenter obtained in the step 102, for example, the number of stages of the dither is 4. , if the swing width of one staircase is α, the calculated duty ratio DUTY is the value obtained by subtracting 2α. DUTY←DUTYcenter−2α ……(1) Here, calculate the value obtained by subtracting the predetermined value 2α from the center duty ratio DUTYcenter.
This is because the duty control by dither is started from the minimum value of the duty ratio, that is, from the bottom of the stage. The dither processing for the calculated duty ratio DUTY obtained in a part of the main routine shown in FIG. 4 is executed by the time interrupt routine shown in FIG. That is, every predetermined period of time, e.g., 5 milliseconds, the process proceeds to step 202 of the time interrupt routine, and the counter C corresponding to the step position is counted.
It is determined whether the count value of is 0 or not. If the determination result is positive, that is, if it is determined that the current duty ratio is the minimum value, the process proceeds to step 204, and sets a C increase flag indicating that the count value of counter C should be increased. do. Next, the process proceeds to step 206, where the calculated duty ratio DUTY is directly set as the output duty ratio DUTYout. On the other hand, if the judgment result in step 202 is negative, that is, if it is judged that the duty ratio is not the minimum value, the process proceeds to step 208, where the counter C
It is determined whether the count value of is 4 or not. If the determination result is negative, that is, if it is determined that the duty ratio is not the maximum value, the process proceeds to step 210;
Determine whether the C increase flag is set. If the judgment result is positive, step 212
Go to and set the current output duty ratio DUTYout to
As shown in the following formula, the new output duty ratio is calculated by adding a predetermined value α corresponding to the dither staircase height.
DUUT Yout. DUTYout←DUTYout＋α ……(2) After the above step 206 or 212, step 214
Then, the count value of counter C is counted up by 1. On the other hand, if the determination result in step 208 is positive, that is, if it is determined that the output duty ratio is at the maximum value, the process proceeds to step 216 and the C increase flag is reset. After step 216 is completed, or when the judgment result in step 210 is negative,
Proceed to step 218 and set the current output duty ratio.
A new output duty ratio DUTYout is obtained by subtracting a predetermined value α from DUTYout, as shown in the following equation. DUTYout←DUTYout−α (3) After step 218 is completed, the process proceeds to step 220, where the count value of counter C is counted down by 1. After completing step 214 or 220, step 222
, and executes ISCV28 on processing. still,
The ISCV 28 off process is performed in a separate interrupt routine depending on the calculation result. After the above step 222 is completed, that is, after the ISCV 28 ON processing is executed, the process proceeds to Step 224, and the count value of the counter E that counts the number of ON processing is
It is determined whether a predetermined value N corresponding to an integral multiple of the dither period has been reached. If the determination result is negative, that is, if it is determined that it is not the time to A/D convert the drive current, the process proceeds to step 226, where the count value of the counter E is incremented by one. on the other hand,
If the judgment result in step 224 is positive, that is, if the ISCV 28 is turned on and the period is determined to be an integral multiple of the dither period,
Proceeding to step 228, A/D conversion of the drive current is executed. Next, proceed to step 230 and count the counter E.
Clear the count value and prepare for the next A/D conversion. Examples of the relationship among the output duty ratio, the ISCV average drive current after weak smoothing, and the A/D conversion value in this embodiment are shown in FIGS. 6A, B, and C. For comparison, an example of A/D conversion values according to the conventional example is also shown in FIG. 6D. As is clear from the figure, in the conventional example, since the timing of A/D conversion of the drive current was not constant, the pulsation of the drive current caused
The A/D conversion value also varied widely, whereas in the case of the present invention, it is approximately constant. Correction of the output duty ratio based on such A/D conversion results can be performed using, for example, an A/D conversion method as shown in FIG.
This is executed by the D conversion completion check routine. That is, the A/D converter 52H
When the D conversion process is completed, the A/D conversion completion check routine shown in FIG. 7 is entered.
In step 302, the current A/D conversion converts the ISCV actual drive current Iisc of the current detection circuit 52E output.
It is determined whether this is due to the completion of A/D conversion. If the judgment result is positive, the step
Proceed to step 304 and convert the current A/D converted value to ISCV
The drive current value Isic is stored in the RAM 52D. Next, the process proceeds to step 306, and from the current center duty ratio DUTYcenter, for example, the eighth
Using the relationship shown in the figure, calculate the ISCV target drive current If corresponding to the center duty ratio DUTYcenter.
seek. Next, the process proceeds to step 308, and it is determined whether the ISCV drive current Iisc is larger than the value If.+β, which is the sum of the ISCV target drive current If obtained in step 306 and a predetermined value β corresponding to the dead zone. If the determination result is positive, proceed to step 310;
As shown in the following equation, the center duty ratio is determined based on the difference between the ISCV target drive current If and the ISCV drive current Iisc.
From the correction coefficient K for correcting DUTYcenter,
The value obtained by subtracting the predetermined value α is set as a new correction coefficient K. K←K−α (4) Next, the process proceeds to step 312, where it is determined whether the calculated correction coefficient K is smaller than its lower limit value Kmin. If the determination result is positive, the process proceeds to step 314, where the lower limit value Kmin is set as the correction coefficient K. On the other hand, if the judgment result in step 308 is negative, the process proceeds to step 316, where the ISCV drive current Iisc is greater than the value If - β, which is the ISCV target drive current If minus the predetermined value β corresponding to the dead zone. Determine whether it is small. If the judgment result is positive,
Proceeding to step 318, the 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 (5) Next, the process proceeds to step 320, where it is determined whether the calculated correction coefficient K is larger than its upper limit value Kmax. If the determination result is positive, the process proceeds to step 322, where the upper limit value Kmax is set as the correction coefficient K. After steps 314 and 322 or the previous step
If the determination results at 302, 312, 316, and 320 are negative, this routine exits. Using the correction coefficient K obtained by this A/D conversion completion check routine, for example, the fourth
In step 102 of the main routine shown in the figure, when calculating the center duty ratio DUTYcenter, the calculated center duty ratio DUTYcenter is multiplied by the correction coefficient K as shown in the following equation. The final central duty ratio DUTYcenter is calculated by . DUTYcenter←K×DUTYcenter (6) The ISCV drive current is passed through the ISCV 28 according to the center duty ratio calculated in this way. Therefore, when the ISCV drive current Iisc is larger than the ISC target drive current If, the correction coefficient K is gradually decreased, while when the ISCV drive current Iisc is smaller than the ISCV target drive current If, The correction coefficient K is gradually increased so that the ISCV drive current Iisc approaches the ISCV target drive current If. In this embodiment, the ISCV drive current Iisc and
Correction coefficient K according to the difference in ISCV target drive current If
Since the dead zone β is provided when increasing or decreasing the correction coefficient K, the correction coefficient K is not excessively increased or decreased, and the stability of the control is particularly high. Note that it is also possible to omit this dead zone β by setting it to zero. In addition, in this embodiment, the correction coefficient K has an upper limit value.
Since Kmax and lower limit value Kmin are provided, there is no possibility that the correction coefficient K will take an abnormal value, and the stability of the control is high. Note that this guard can also be omitted. In the embodiment described above, the A/D conversion was performed at a point slightly on the positive side of the center value of the average drive current, but the timing at which the A/D conversion should be performed is not limited to this. For example, if the A/D conversion is executed at the center value of the dither, that is, when the count value of the counter C used in FIG. 5 is 2, more accurate A/D conversion can be achieved. A D-converted value can be obtained. Also, in this case, A/D
It is also possible to perform the conversion at a period of 1/2 which is an integral multiple of the dither period. In the above embodiments, the present invention was applied to an electronically controlled automobile engine equipped with an intake air amount sensing type electronic control device, but the scope of application of the present invention is not limited thereto, and It is obvious that the present invention can be similarly applied to an electronically controlled automobile engine equipped with an electronic control device, and a general internal combustion engine equipped with other air-fuel ratio control devices such as a carburetor.

【Effect of the invention】

As explained above, according to the present invention, A/D conversion of the ISCV drive current is performed at a predetermined phase of the pulsation of the drive current, so the A/D conversion value does not vary from conversion to conversion, and is stable. Gain control. Therefore, highly accurate idle rotation speed control can be achieved. Also, since the output duty ratio is dithered, hysteresis is reduced and stake slip is also prevented. Furthermore, since most of the steps can be performed using software, there are excellent effects such as cost reduction and miniaturization of the ECU.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the idle rotation speed control method for an internal combustion engine according to the present invention, and FIG.
FIG. 3 is a cross-sectional view, including a partial block diagram, showing the structure of an embodiment of an electronically controlled engine for an automobile in which the present invention is adopted. FIG. 3 shows the structure of the electronic control unit used in the embodiment. The block diagram, FIG. 4 is a flowchart showing the main part of the main routine for calculating the calculated duty ratio, and FIG. 5 is a flowchart showing the main routine for calculating the calculated duty ratio. A flowchart showing a time interrupt routine for performing analog-to-digital conversion of the drive current flowing through the control valve, FIGS. FIG. 7 is a diagram showing an example of the relationship between the average drive current of a control valve and an analog-to-digital conversion value of the average drive current. FIG. 8 is a flowchart showing an analog-to-digital conversion end check routine for calculating a correction coefficient of .FIG. 8 is a diagram showing the relationship between the center duty ratio and the target drive current used in the routine. 10... Engine, 14... Air flow meter, 20... Throttle valve, 22... Throttle sensor, 26... Bypass circuit, 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...drive circuit.

Claims (1)

[Scope of Claims] 1. A method for controlling idle rotation speed of an internal combustion engine for controlling idle rotation speed according to engine operating conditions, comprising: a procedure for determining a center duty ratio for obtaining a target idle rotation speed; a procedure for determining a target drive current for the idle rotation speed control valve corresponding to the ratio; a procedure for determining an output duty ratio by dithering the central duty ratio; a procedure for controlling on/off the actual drive current flowing; a procedure for synchronizing the actual drive current with the on/off of the idle rotation speed control valve, and converting the actual drive current into a digital signal at a cycle that is an integral multiple of the dither cycle; A method for controlling an idle rotation speed of an internal combustion engine, comprising: correcting the center duty ratio so that the drive current matches the target drive current. 2. Conversion of the actual drive current into a digital signal,
2. The idle rotation speed control method for internal combustion engines according to claim 1, wherein the control is performed at the center value of the dither.