JPS6321020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an intake air amount control device for controlling the intake air amount of an internal combustion engine mainly during idling, and particularly relates to characteristics of control coefficients in feedback control.

[Prior art]

Recently, in order to improve the exhaust purification performance and fuel efficiency of automobiles, it has become necessary to precisely control the rotation speed during idling. For this reason, a device has been developed that determines a target rotational speed according to engine operating conditions such as engine temperature, and performs feedback control of the amount of intake air so that the actual rotational speed matches the target rotational speed.

Generally, in feedback control, a so-called PI control method is used, which uses a control signal that is the sum of the proportional part (P) and the integral part (I) of the deviation between the target rotation speed and the actual rotation speed. In this intake air amount control device, the values of the control coefficients, that is, the proportional coefficient and the integral coefficient, were always constant values.

[Problem that the invention seeks to solve]

However, in the case of an intake air amount control device for an internal combustion engine, if the control coefficient is constant, the following problem occurs.

That is, in an internal combustion engine, the time until a change in the amount of intake air in the intake system appears as a change in the rotational speed, that is, the delay time of the control system, is approximately inversely proportional to the rotational speed. Therefore, if the number of control systems is kept constant, there is a risk that the control will not be done in time at low rotations, and conversely, the control will be too fast at high rotations, resulting in hunting.

In particular, in feedback control of idling rotation speed, if the target rotation speed is different, even if the deviation between the actual rotation speed and the target rotation speed is the same, the rate of change in the actual rotation speed will vary widely. The smaller the value, the greater the rate of variation. Therefore, if control is always performed using the same control coefficient, when the actual rotation speed is small, the rate of variation will be large for the same deviation, resulting in a delayed response; conversely, when the actual rotation speed is large, the response will be delayed. Since the rate of variation is small for the same deviation, hunting occurs.

On the other hand, if the deviations are different, even if the target rotation speed is the same, the rate of actual rotation speed variation will vary widely, as described above.

Therefore, good control results cannot be expected even if the control coefficient is changed depending on only one of the deviation and the rotation speed.

The present invention was made in order to solve the above-mentioned problems specific to systems that feedback control the idling speed by controlling the amount of intake air. An object of the present invention is to provide an intake air amount control device that can always perform good control over the air flow.

[Means to solve the problem]

In order to achieve the above object, in the present invention, the integral coefficient when calculating the control amount in feedback control, that is, the rate of change of the integral control amount, is
It is configured to increase as the deviation between the actual rotation speed and the target rotation speed increases, and to decrease it as the absolute level of the actual rotation speed increases.

With the above configuration, in the present invention, when the rotation speed is low or the deviation is large, the integral control amount is rapidly increased to improve responsiveness, and when the rotation speed is high or the deviation is small, the integral control amount is changed. Since hunting can be effectively prevented by reducing the ratio, the idling speed can always be well controlled.

[Embodiments of the invention]

FIG. 1 is an embodiment diagram showing the overall configuration of the present invention, and illustrates a case where the present invention is applied to an internal combustion engine equipped with an electronically controlled fuel injection device.

In Fig. 1, reference numeral 1 denotes the internal combustion engine main body, intake air is supplied from an air cleaner 2 to each cylinder via an air flow meter 3, a throttle chamber 4, and each branch of an intake manifold 5, and fuel is supplied to each cylinder from a fuel injector 6. is injected by. Here, the flow of intake air is controlled by a throttle valve 7 in the throttle chamber 4 that is linked to the accelerator pedal, and the throttle valve 7 is almost closed during idling. Air flow during idling passes through a bypass port 8 and is regulated by an idling adjust screw 9 installed therein, as well as a throttle valve 7.
The air passes through a bypass passage 10 that communicates the upstream and downstream sides of the air, and an idling control valve 11 installed therein ensures necessary air as appropriate.

The idling control valve 11 has a bypass passage 10
a negative pressure working chamber 15 equipped with a valve body 12 interposed therein, a diaphragm 13 to which the valve body 12 is connected, and a spring 14 that biases the diaphragm 13;
The valve body 12 is configured by a diaphragm 13 according to an increase or decrease in the negative pressure introduced into the negative pressure working chamber 15.
Change the amount of lift and decrease or increase its opening. This negative pressure working chamber 15 communicates with the intake passage downstream of the throttle valve 7 via a constant pressure valve (pressure regulator valve) 17 through a negative pressure introduction passage 16, and a pulse solenoid valve 19 through an atmosphere introduction passage 18. It communicates with the intake passage upstream of the throttle valve 7 through the throttle valve 7.
Thus, by opening and closing the pulse solenoid valve 19, the degree of opening of the idling control valve 11 is controlled by changing the dilution ratio of the negative pressure introduced into the negative pressure working chamber 15 with the atmosphere.

As described above, in this embodiment, the idling control valve 11, the low pressure valve 17, and the pulse solenoid valve 19 serve as means for adjusting the amount of intake air during idling.

The pulse solenoid valve 19 is controlled by a microcomputer 20, for example.

The microcomputer 20 mainly includes a microprocessor (central processing unit) 21, a memory (storage device) 22, and an interface (input/output signal processing circuit) 23. The rotational speed of the internal combustion engine 1 is detected by an electromagnetic pick-up type rotational speed sensor 24 and inputted to the interface 23 of the microcomputer 20 as a digital signal (actually, the unit is obtained from the rotation of the crankshaft using the crank angle sensor). The engine temperature of the internal combustion engine 1, for example, the cooling water temperature, is detected as an analog signal by the thermistor-type water temperature sensor 25, and the A/D output is inputted.
It is input as a digital signal via a converter 26. A signal from a throttle valve switch 27 that detects that the throttle valve 7 is in the fully closed position is input to the interface 23 . In the figure, the throttle valve switch 27 is an analog type sensor using a variable resistor, and its signal is shown to be inputted via the A/D converter 28. An off-type switch may also be used.

The memory 22 stores in advance an optimal target rotation speed N _SET (target rotation speed during idling) corresponding to engine operating conditions such as engine temperature.

The microprocessor 21 determines the current operating state based on the signal from the water temperature sensor 25, etc., reads out the corresponding target rotation speed _NSET , and also determines the actual rotation speed N based on the signal given from the rotation speed sensor 24. Calculate _RPM and calculate the deviation ΔN between N _SET and N _RPM .

The microprocessor 21 sets a control coefficient, that is, a proportional coefficient and an integral coefficient, according to the actual rotational speed N _RPM and the deviation ΔN, calculates a controlled amount from these control coefficients and the deviation ΔN, and applies the controlled variable to the By changing the duty of the pulse signal that drives the pulse solenoid valve 19 accordingly, the amount of intake air is controlled so that the actual rotation speed N _RPM matches the target rotation speed N _SET . In this embodiment, the above calculation function in the microcomputer 20 corresponds to the control amount calculation means.

Of course, what is described below is also applicable to the case where the position of the throttle adjust screw or throttle stopper of the carburetor is controlled using an actuator such as a motor.

Next, the control coefficient will be explained in detail.

FIG. 2 is a characteristic diagram of the integral coefficient (I component).

In Figure 2, TC is a time constant (integral time constant), and a larger value indicates a smaller integral, that is, a slow control with a small rate of change of the integral control amount, and a smaller TC indicates a slower integral. This means that the rate of change of the integral control amount is large and fast. For example, TC = 1 indicates that the integral is increased or decreased by 0.5% for each revolution of the engine, and TC = 15 indicates that the integral is increased or decreased by 0.5% for every 15 revolutions of the engine.
Indicates an increase or decrease in 0.5% increments. Note that in the region where ΔN is positive, the integral is decreased and ΔN
It is increased in the region where is negative (the part marked TC').

As shown in Figure 2, the larger the rotation speed and the smaller the absolute value of ΔN, the larger the TC and the smaller the integral; conversely, the lower the rotation speed and the smaller the absolute value of ΔN.
By decreasing the TC and increasing the integral as the absolute value of is larger, it is possible to improve response when the rotation is low or when the deviation is large, and to prevent hunting when the rotation is high or the deviation is small.

In addition, in Fig. 2, the upper left part of the dashed-dotted line is
This is a region that does not exist when the minimum value of idling speed is 600 rpm. Also, below 1200 rpm, TC=3 even if ΔN is large, because
This is because if the rotational speed is suddenly reduced in this region, there is a risk of stalling. Further, in FIG. 2, the control coefficient is changed non-linearly, which is particularly effective, but depending on the case, it may be changed linearly.

Next, Figures 3 and 4 are flowcharts when the above calculations are performed using a microcomputer. This shows a case where the actual rotation speed is higher than the target rotation speed, and either the flowchart shown in FIG. 3 or 4 is selected depending on the values of the actual rotation speed N _RPM and the target rotation speed N _SET .

The control amount ISC _ON when controlling the idling speed using a microcomputer is calculated, for example, by the following equation (1).

ISC _ON = ISC _TW + ISC _AT + ISC _TR + ISC _AS + ISC _CL … (1) In the above equation (1), ISC _TW is the basic control amount determined by the engine temperature, ISC _AT is the correction amount when equipped with an automatic transmission, ISC _TR and ISC _AS are correction amounts during acceleration and deceleration, respectively, and ISC _CL is a control amount by feedback control. The present invention relates to the control coefficient when calculating ISC _CL , and since other terms are irrelevant, only ISC _CL will be explained.

First, in Figure 3, P ₁ has an engine 1, for example.
The order of calculations rotates once each time it rotates.

At _P2 , it is determined whether the counter PN1 is + or -. Counter PN1 is + when N _RPM < N _SET , that is, when the actual rotation speed is lower than the target rotation speed, and vice versa.
When N _RPM > N _SET , it becomes -.

Figure 3 is a flowchart when N _RPM < N _SET , and when the ISC program was executed last time.
If N _RPM > N _SET , since PN1 < 0, PN1 is set to 0 in P ₃ , and then the proportional portion LP is calculated in P ₄ . Next, at P ₅ , I _OUT (I _OUT = ISC _TW +
Add LP to ISC _AT + ISC _TR + ISC _AS ), perform an overflow check (details will be described later), and calculate ΔN with R ₆ .
(In this case, ΔN=N _SET −N _RPM ) is placed in register A, and register PNR PM+1 (actual rotational speed N _RPM
The contents of the register that stores the value of ) are placed in the B register.

Then at P ₇ to _{P 9} , N _RPM is N _RPM ≦450rpm,
450<N _RPM ≦1000rpm, 1000rpm<N _RPM , and ΔN is ′ΔN≦150rpm,
′ΔN＞150rpm.

Then, in the case of (a) and ', that is, in the range of TC'=1 in FIG. 2, the process immediately goes to _P14 .

Next, (b), in the case of ′, that is, in Fig. 2
In the range of TC'=3, add 5 to PN1 and go to _P13 .

In addition, (c), in the case of ′, that is, in Fig. 2
In the range of TC'=5, add 3 to PN1 and go to _P13 .

Also, in the case of (d), that is, TC' = 15 in Figure 2
In the range, add 1 to PN1 and go to _P13 .

Next, in P ₁₃ , if PN1 is PN1≧15, then P ₁₄
If PN1<15, send to _P16 . i.e.
When PN1 reaches 15, go to _P14 .

Next, after setting PN1 to 0 at P ₁₄ , DELTAI at P ₁₅
After adding 1 to the control amount (corresponding to the ISC _CL ) and performing an overflow check (details will be described later), proceed to _P16 .

In other words, in case (a) above, DELTAI increases by 1 every rotation, in case (b), it increases by 1 every 3 rotations, in case (c), it increases by 1 every 5 rotations, and in case (d), it increases by 1 every 3 rotations. DELTAI will increase by 1.

For example, 0.5 of the control amount per 1 of this DELTAI
If you set it so that it is %, every time you pass P ₁₅ ,
The control amount can be increased by 0.5%.

Next, Figure 4 is a flowchart in the case of N _RPM > N _SET.When the ISC program was executed last time, if N _RPM <N _SET , PN1 > 0, so PN1 is set at P ₁₉ . 0, then ΔN at P ₂₀
(In this case, ΔN=N _RPM −N _SET ) in the A register,
Put the contents of PNRPM+1 into the B register.

Then at P ₂₁ ~ _{P 24} , N _RPM ≦1200rpm, 1200
＜N _RPM ≦2400rpm, 2400rpm＜N _RPM , and ΔN is ′300rpm≦ΔN,
Determine whether it corresponds to '150<ΔN<300rpm or 'ΔN≦150rpm.

And (a), in the case of ′, that is, in Fig. 2
In the range of TC=1, it immediately goes to P ₂₃ .

Next, in the case of (b), de′, de′ and de′,
That is, in the range of TC=3 in FIG. 2, 5 is subtracted from PN1 to reach _P28 .

In addition, (c), in the case of ′, that is, in Fig. 2
In the range of TC=5, subtract 3 from PN1 and go to _P28 .

In case (d), that is, in the range of TC=15 in FIG. 2, 1 is subtracted from PN1 to go to _P28 .

In P ₂₈ , if PN1 is PN1≦−15, go to P ₂₉ ;
If PN1>-15, send to _P31 . That is, when PN1 becomes -15, the process goes to _P29 .

Next, after setting PN1 to 0 at P ₂₉ , DELTAI at P ₃₀
After subtracting 1 from and checking for overflow,
Go to P ₃₁ .

In other words, in case (a) above, DELTAI decreases by 1 every rotation, in case (b), it decreases by 1 every 3 rotations, in case (c), it decreases by 1 every 5 rotations, and in case (d), it decreases by 1 every 5 rotations. DELTA1 will decrease by 1.

Next, the overflow check will be explained.

When calculating with 8 bits = 1 byte,
DELTAI uses the most significant bit to determine + and - (for example, if it is "0", it is + if it is "1", -), and the actual control amount is in the range of +127 to -128, that is, DELTAI
If 1 is 0.5%, it is used within a range of approximately ±64%.

In overflow check, DELTAI
exceeds the above range (+128 or more or -129
In other words, in the case of overflow, the above upper limit (+127) or lower limit (-128)
I try to stop at.

Also, for N _RPM , each bit is set at 12.5rpm,
25rpm, 50rpm, 100rpm, 200rpm, 400rpm,
By supporting 800rpm, 1600rpm, and 3200rpm, 3187.5rpm with 8 bits (1 byte)
It is possible to calculate up to (3200−12.5=3187.5). If the actual N _RPM is above 3200rpm
It is calculated as 3187.5 rpm, but since the present invention controls the idling rotation speed, a very high rotation speed is irrelevant, and the above range is sufficient.

In this embodiment, the integral control amount calculation function in the microcomputer 20 shown in FIGS. 3 and 4 calculates the integral coefficient, that is, the rate of change of the integral control amount when calculating the control amount in feedback control. This corresponds to a means for increasing the deviation between the actual rotational speed and the target rotational speed as it increases, and decreasing it as the absolute level of the actual rotational speed increases.

〔Effect of the invention〕

As explained above, according to the present invention, the integral coefficient when calculating the control amount in feedback control, that is, the rate of change of the integral control amount, is changed to increase as the deviation between the actual rotation speed and the target rotation speed increases. By increasing the absolute level of the actual rotational speed and decreasing it as the absolute level of the actual rotational speed increases, the integral control amount is rapidly increased at low rotational speeds or when the deviation is large, improving responsiveness.
When the rotation speed is high or the deviation is small, the rate of change of the integral control amount can be reduced to effectively prevent hunting, so an excellent effect can be obtained in that the idling rotation speed can always be well controlled.

[Brief explanation of the drawing]

FIG. 1 is an example diagram showing the overall configuration of the present invention, FIG. 2 is an example diagram of characteristics of control coefficients of the present invention, and FIG.
FIG. 4 is a flowchart of the operation of the present invention. Explanation of symbols, 1... Internal combustion engine body, 2... Air cleaner, 3... Air flow meter, 4... Throttle chamber, 5... Intake manifold, 6... Fuel injector, 7... Throttle valve, 8... Bypass port, 9... Idling adjustment screw, 10... Bypass passage, 11... Idling control valve, 12... Valve body, 13... Diaphragm, 14... Spring, 15... Negative pressure operation Chamber, 16...Negative pressure introduction passage, 17...Constant pressure valve, 18...Atmospheric introduction passage, 1
9... Pulse solenoid valve, 20... Microcomputer, 21... Microprocessor, 22... Memory, 23... Interface, 24... Rotation speed sensor, 25... Water temperature sensor, 26... A/D
Converter, 27... Throttle valve switch, 28...
...A/D converter.

Claims (1)

[Claims] 1. A control variable that detects the deviation between the actual rotational speed of the internal combustion engine and the target rotational speed during idling, and provides a signal corresponding to the deviation to a control variable calculating means including at least an integrating means to control the intake air amount adjusting means. is calculated, and the intake air amount adjusting means is controlled based on a signal corresponding to the control amount to control the intake air amount, thereby performing feedback control so that the actual rotation speed during idling matches the target rotation speed. In the intake air amount control device, the integral coefficient when calculating the control amount in the feedback control, that is, the rate of change of the integral control amount, is changed so as to increase as the deviation between the actual rotation speed and the target rotation speed increases. , and means for changing the absolute level of the actual rotational speed to decrease as the absolute level increases.