JPH10299550A - Idle speed control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent erroneous learning of updating a learning term LR when updating is not necessary in ISC, and to increase the engine speed NE to a target engine speed NT when the fluctuation of the engine load is large. The present invention provides an idle speed control device for an internal combustion engine that can converge on the engine speed. A feedback term is larger than a first predetermined value, and an engine speed is shifted from a target engine speed by a second value.
The value of the learning term in the case where the rotation speed is smaller than the predetermined value and the case where the feedback term is smaller than the third predetermined value and the engine speed is larger than the rotation speed obtained by adding the fourth predetermined value to the target engine speed. To update.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an idle speed control device for an internal combustion engine. More specifically, the present invention relates to an idle speed control device that adjusts the amount of intake air flowing bypassing a throttle valve of an engine by a control valve.

[0002]

2. Description of the Related Art An idle speed control apparatus for an internal combustion engine using the conventional technique is disclosed, for example, in Japanese Patent Laid-Open No. 5-195847.
No., published in Japanese Unexamined Patent Publication No. The idle speed control device described in this publication performs feedback control so that the engine speed matches the target speed by controlling the amount of intake air flowing bypassing the throttle valve of the internal combustion engine by the control valve. . When a load is applied to the engine, for example, when an air conditioner (hereinafter referred to as “air conditioner”) or a light is turned on, the idle speed control is performed unless the engine speed NE takes a value close to a desired target speed NT. (Hereinafter referred to as “ISC”) learning values were not updated.

[0003]

In the above conventional technique, when the load of the air conditioner is different from the estimated amount (for example,
If the refrigerant of the air conditioner leaks out (so-called "no refrigerant", or the temperature inside the vehicle rises), or if an auxiliary machine (alternator) or an ISC system that becomes an engine load fails, the engine speed NE is reduced. The learning value of ISC is not updated because it does not take a value close to the target rotation speed NT. For this reason, the state in which the engine speed NE deviates from the target speed NT continues, and as a result, rough idle due to a decrease in the engine idle speed, deterioration in fuel efficiency due to too high speed, and deterioration in components of exhaust gas are caused. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has an object to solve the problem that the feedback control cannot follow the target rotational speed NT corresponding to the load when the load of the engine fluctuates greatly. And an idle speed control device for an internal combustion engine that converges the engine speed NE to the target speed NT more quickly by updating the learning item even when the prospective correction value of the preset learning item is insufficient. To provide.

[0005]

SUMMARY OF THE INVENTION An idle speed control device for an internal combustion engine according to the present invention is a device for performing feedback control of an engine speed during an idle operation of an internal combustion engine based on a feedback term and a learning term. When the term is larger than the first predetermined value and the engine speed is smaller than the target engine speed minus the second predetermined value, the feedback term is smaller than the third predetermined value and the engine speed is lower than the target engine speed. The value of the learning term is updated when the rotation speed is larger than the rotation speed obtained by adding the fourth predetermined value to the rotation speed, thereby achieving the above object.

[0006]

Embodiments of the present invention will be described with reference to the drawings. In this specification, a state where the switch is in an “on” state refers to a state in which the switch flows current, and a state in which the switch is in an “off” state refers to a state where the switch does not flow current. Units that consume power (for example,
“Air conditioner, light, etc.) is“ on ”when the unit consumes power, and“ off ”is when the unit does not consume power.

FIG. 1 is a schematic configuration diagram of an idle speed control device 100 according to the present invention. The intake passage 102 supplies air to the engine 104. The air passing through the intake passage 102 is supplied to the air cleaner 106 and the throttle valve 10.
8. Through the surge tank 110 and the intake pipe 112 in this order, the engine 104 is reached. Throttle valve 108
Is opened and closed in conjunction with operation of an accelerator pedal (not shown).

[0008] The bypass passage 114 bypasses the flow of air through the intake passage 102. Bypass passage 114
Has a control valve 116 as a valve for performing idle speed control (hereinafter referred to as "ISC"). The control valve 116 adjusts the amount of air flowing through the bypass passage 114 by being duty-driven by the ECU 150.

The crank angle sensor 120 detects the rotation angle of the crankshaft and outputs a rotation angle detection signal corresponding to the rotation angle to the ECU 150. Idle switch 121 outputs to ECU 150 a signal indicating that throttle valve 108 is at the idle position. Pressure sensor 122 detects the pressure in intake passage 102 and outputs a signal corresponding to the pressure to ECU 150. Water temperature sensor 1
23 detects the temperature of the cooling water and outputs a signal corresponding to the temperature of the cooling water to the ECU 150.

[0010] The ECU 150 is connected to a power supply circuit including the battery 130. The positive electrode of the battery 130 is connected to the headlight 13 through a headlight switch 132.
4 is connected to a blower fan 138 through a blower fan switch 136, and to a compressor 142 through an air conditioner switch 140. The compressor 142 and the alternator 144 are driven by the engine 104 via the belt 146. Compressor 142 is driven by engine 104 only when air conditioner switch 140 is on. ECU 150 also receives a signal indicating whether switches 132, 136, and 140 are on or off, respectively.

The ECU 150 includes a central processing unit (hereinafter, referred to as “CPU”) for executing a control program described below, a read-only memory (hereinafter, referred to as “ROM”) for storing a control program, initial data, and the like. And a random access memory (hereinafter, referred to as a “RAM”) from which data input to the CPU and data necessary for calculation and control are temporarily read and written. The ECU 150 includes a crank angle sensor 120
The engine speed is calculated based on the signal output from the pressure sensor 122, and the pressure in the intake pipe 112 is calculated based on the signal output from the pressure sensor 122. ECU 150 calculates the valve opening time of the injector from the calculated engine speed and intake pipe pressure, and outputs a signal corresponding to the valve opening time to the injector to control the opening and closing of the injector.

The ECU 150 includes an idle switch 1
By reading the state 21, it is detected that the engine 104 is in an idle state. When it is detected that the engine 104 is idle, the ECU 150
A target rotation speed is set according to the state of the load applied to the engine, and a signal corresponding to the target rotation speed is given to the control valve 116. The ECU 150 performs feedback control based on the actual engine speed NE and the target speed NT so that the engine speed NE becomes the target speed NT. This feedback control is performed mainly based on two terms, a feedback term FB and a learning term LR, which will be described in detail later. The ECU 150 may include an engine control unit such as an electronically controlled fuel injection device (EFI) or an electronic advance angle device (ESA).

Here, feedback control used by the internal combustion engine idle speed control device according to the present invention will be described.
FIG. 2 is a schematic diagram of a control loop of feedback control. The control target is the engine 202. Engine 20
2 receives, as inputs, the sum of the air flow rate C of the ISC valve, the feedback term FB, and the learning term LR (the dimension is, for example, [liter / sec]) and outputs the engine speed NE. The block 204 obtains a rotation speed (hereinafter, referred to as “rotation speed deviation”) obtained by subtracting the target rotation speed NT from the engine rotation speed NE. A negative rotation speed deviation indicates that the engine rotation speed NE is smaller than the target rotation speed NT, and a positive rotation speed deviation indicates that the engine rotation speed NE is lower than the target rotation speed NT.
Greater than

A block 206 typically integrates the rotational speed deviation with respect to time and obtains a negative constant (-K, K: positive number).
, Ie, the feedback term FB is output.
Block 208 includes an air flow rate C, a feedback term FB
And the learning term LR, and outputs the result to the engine 202. Here, the air flow rate C is a constant determined according to ON / OFF of the air conditioner and N (neutral) and D (drive) of the shift position. As will be described later, the learning term LR is a correction term used when a large change occurs in the load of the engine or for correcting a temporal error occurring in the control system of the ISC.

FIG. 3 is a flowchart showing the steps of an ISC program for controlling the idle speed control device for an internal combustion engine according to the present invention. 3 described below is typically stored in the ROM in the ECU 150, and is executed by the CPU in the ECU 150.

The ISC program starts from step 302 once every 180 ° crank angle (° CA).
Proceed to step 304.

In step 304, it is determined whether a precondition for executing the ISC program is satisfied. The prerequisites are typically that the idle switch 121 is on, the vehicle speed is less than 3 km / hour, the temperature of the cooling water is 80 ° C. or lower, and that the vehicle is not started. Condition. If all four of these conditions are met, go to step 306; if none of these are met, go to step 350. When the control shifts to step 350, step 30 is executed again.
Return to 2.

Step 306 determines whether or not the learning timing is established. The learning timing is once for every 128 revolutions of the engine. ECU 150 calculates the rotation of the engine crank based on the signal output from crank angle sensor 120, and proceeds to step 308 once every 128 rotations of the engine, otherwise proceeds to step 350.

In step 308, it is determined whether or not the above precondition is satisfied for three seconds or more. If yes, go to step 310; if not, go to step 350. In the present embodiment, the time is set to 3 seconds. However, the time is not limited to 3 seconds, and can be appropriately changed according to the characteristics of the internal combustion engine. In order to determine whether or not the precondition is continuously satisfied for a predetermined time, a timer built in the CPU is typically used.

Step 310 determines whether the air conditioner is on. If the air conditioner is on, the process proceeds to step 312. If the air conditioner is off, the process proceeds to step 330.

Step 312 includes a feedback term FB
Is greater than a predetermined value FBU. The value FBU is changed from an upper limit value FBU0 (for example, 0.98 (liter / second)) which is a maximum value that the feedback term can take in the ISC to a predetermined value FBUΔ (for example, 0.06
(Liter / second)). If the feedback term FB is larger than the value FBU, go to step 314; if the feedback term FB is not larger than the value FBU, go to step 318.

Step 314 is an engine speed NE.
Is smaller than the value obtained by subtracting 80 (rpm) from the target rotation speed NT (rpm). If smaller, go to step 316; if not, step 3
Go to 50.

Step 316 replaces the learning term with a value obtained by adding 0.043 (liter / second) to the current learning term, and then proceeds to step 350.

Step 318 includes a feedback term FB
Is smaller than a predetermined value FBL. The value FBL is set to a lower limit value FBL0 (for example, -0.14 (liter / second)) which is a minimum value that the feedback term can take in the ISC, and a predetermined value FBLΔ (for example, 0.06
(Liter / second)). If the feedback term FB is smaller than the value FBL, the process proceeds to step 320. If the feedback term FB is not smaller than the value FBL, the process proceeds to step 350.

In step 320, the engine speed NE is set.
Is greater than the value obtained by adding 200 (rpm) to the target rotation speed NT (rpm). If yes, go to step 322; if not, go to step 3
Go to 50.

Step 322 replaces the learning term with a value obtained by subtracting 0.043 (liter / second) from the current learning term, and then proceeds to step 350.

Step 330 includes a feedback term FB
Is greater than zero. If yes, go to step 332; if not, go to step 3
Proceed to 34.

In step 332, the engine speed NE is set.
Is smaller than a value obtained by adding 20 (rpm) to the target rotation speed NT (rpm). If smaller, go to step 316; if not, step 35
Go to 0.

Step 334 includes a feedback term FB
Is less than zero. If smaller, go to step 336; if not, step 3
Go to 50.

In step 336, the engine speed NE is set.
Is larger than a value obtained by subtracting 20 (rpm) from the target rotation speed NT (rpm). If yes, go to step 322; if not, go to step 3
Go to 50.

The maximum value and the minimum value of the learning term LR are 2.75 (liter / second) and 0.50 (liter / second), respectively. Therefore, steps 316 and 32
The learning value in 2 is not updated beyond these maximum and minimum values.

FIGS. 4 to 6 show the state of the air conditioner, the engine speed NE, the target speed NT, and the feedback term F in the idle speed control apparatus for the internal combustion engine according to the present invention.
6 is a graph showing changes in B and a learning term LR. In the graph, “AC” indicates on / off of the air conditioner and “N”
"E" (solid line graph) indicates the actual engine speed, and "N
"T" (dotted line graph) indicates the target engine speed and "F
“B” indicates a feedback term, and “LR” indicates a learning term. 4 to 6 schematically show the cases shown in Table 1. Hereinafter, each case will be described.

[0033]

[Table 1]

(Case 1) In case 1 shown in FIG. 4, since the difference between the engine speed NE and the target speed NT is small, the engine speed NE is increased by 80 (from the target speed NT (rpm)). rpm), and the feedback term FB is also in the range from the value FBL to the value FBU. Therefore, the learning term LR is not updated. Specifically, after step 310, steps 312, 318 and 3
Control is transferred in the order of 50. For a while from time t40 when the air conditioner turns off to on, the engine speed N
Although there is a change in E, the learning term LR is not updated and remains constant.

(Case 2) In Case 2 shown in FIG. 5, the feedback term FB becomes equal to the predetermined value FBU at time t52. However, at time t52, the engine speed NE is not smaller than a value obtained by subtracting 80 (rpm) from the target engine speed NT (rpm). Therefore, the learning term LR is not updated.

The determination flow of Case 2 will be described in more detail. From time t50 to time t51 when the air conditioner is turned on from off, the engine speed NE is smaller than the value obtained by subtracting 80 (rpm) from the target engine speed NT (rpm), but the feedback term FB has the value FBU. Not bigger. Therefore, as in case 1, step 31
After 0, control is transferred in the order of step 312, step 318, and step 350. As a result, between time t50 and time t51, the learning term LR is not updated and remains constant.

During the period from time t51 to time t52, the engine speed NE is changed from the target engine speed NT (rpm) by eight.
It is not smaller than the value obtained by subtracting 0 (rpm), and the feedback term FB is not larger than the value FBU. Therefore, similarly to the case 1, the control shifts to the steps 310, 318, and 350 in the order of step 310 and subsequent steps. As a result, between time t51 and time t52, the learning term LR is not updated and remains constant.

After time t52, since the feedback term FB is larger than the value FBU, the control moves from step 312 to step 314 after step 310.
In step 314, it is determined whether or not the engine speed NE is smaller than a value obtained by subtracting 80 (rpm) from the target engine speed NT (rpm). As shown in FIG.
Since the engine speed NE is not smaller than the value obtained by subtracting 80 (rpm) from the target engine speed NT (rpm), the control moves to step 350. As a result, after time t52, the learning term LR is not updated and remains constant. As a result, as in the case 1, the learning term LR is not updated and remains constant in the case 2.

(Case 3) In Case 3 shown in FIG. 6, the feedback term FB is larger than the predetermined value FBU after time t61. Moreover, from time t60 to time t62
, The engine speed NE is equal to the target engine speed NT.
It is smaller than the value obtained by subtracting 80 (rpm) from (rpm).
Therefore, from time t61 to time t62, the learning term L
R is updated. As a result, from time t61 to time t62, the learning term LR increases in a certain increment per unit time.

The determination flow of Case 3 will be described in more detail. Between time t60 and time t61 when the air conditioner is turned on from off, the engine speed NE is smaller than the value obtained by subtracting 80 (rpm) from the target engine speed NT (rpm), but the feedback term FB has the value FBU. Not bigger. Therefore, as in case 1, step 31
After 0, control is transferred in the order of step 312, step 318, and step 350. As a result, between time t60 and time t61, the learning term LR is not updated and remains constant.

During the period from time t61 to time t62, the feedback term FB is larger than the value FBU, and the engine speed NE is increased by 80 from the target engine speed NT (rpm).
(Rpm). Therefore, after step 310, control shifts in the order of step 312, step 314, step 316, and step 350. As a result, the learning term LR is updated. Time t61 to time t
During the period 62, the step 316 is executed a fixed number of times per unit time, so that the learning term LR increases at a constant slope as shown in the graph of the learning term LR in FIG.

After time t62, since the feedback term FB is larger than the value FBU, the control shifts from step 312 to step 314 after step 310.
In step 314, it is determined whether or not the engine speed NE is smaller than a value obtained by subtracting 80 (rpm) from the target engine speed NT (rpm). As shown in FIG.
Since the engine speed NE is not smaller than the value obtained by subtracting 80 (rpm) from the target engine speed NT (rpm), the control moves to step 350. As a result, after the time t62, the learning term LR is not updated and remains constant.

In steps 312 and 318, the upper limit value FBU0 and the lower limit value FB of the feedback term FB
The value FBUΔ and the value FBLΔ used for calculating the value FBU and the value FBL from L0 are not limited to the values described above. However, by setting parameters so that the condition for updating the learning value LR is easily satisfied,
In order to perform quicker control, it is preferable that the value FBUΔ and the value FBLΔ take positive values.

The value of 80 (rpm) subtracted from the target rotational speed NT in step 314 and 200 (rpm) added to the target rotational speed NT in step 320 are not limited to these values, but may vary depending on the characteristics of the engine to be controlled. May be changed.

According to the present invention, when the feedback term FB deviates from the predetermined range as described above (that is, when the feedback term FB is larger than the predetermined value or smaller than the predetermined value), the engine speed NE and the target speed NT The learning term LR is updated only when the rotation speed deviation is larger than a predetermined value. As a result, it is possible to prevent a so-called “erroneous learning” in which the learning term LR is updated even though there is no need to update. In other words, according to the present invention, the learning term LR is updated only when the update is necessary, such as when the fluctuation of the engine load is large or when the error caused by the aging of the control system is large. As a result, it is possible to prevent engine stall due to ISC failure. Further, even when the engine load fluctuates greatly, the engine speed NE can be made to converge to the target speed NT in a short time.

In the above description, it is assumed that the air conditioner is switched from off to on as a cause of an increase in the engine load and a decrease in the engine speed NE. However, the present invention is not limited to this. For example, the control shown in FIG. 3 may be applied to a case where an auxiliary machine that needs to increase the estimated air amount is turned on from off. The same control may be applied when the load on the alternator is large, such as extracting a large current from a cigarette plug or the like.

[0047]

According to the present invention, in the ISC, erroneous learning of updating the learning term LR when updating is unnecessary is prevented, and the engine speed NE is quickly set when the fluctuation of the engine load is large. An idle speed control device for an internal combustion engine that can converge on the speed NT can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an idle speed control device 100 according to the present invention.

FIG. 2 is a schematic diagram of a control loop of feedback control.

FIG. 3 is a flowchart showing steps of an ISC program for controlling an idle speed control device for an internal combustion engine according to the present invention.

FIG. 4 shows a state of an air conditioner, an engine speed NE, a target speed NT, and a feedback term FB in the idle speed control device for an internal combustion engine according to the present invention in Case 1;
6 is a graph showing changes in a learning term LR.

FIG. 5 shows a state of an air conditioner, an engine speed NE, a target speed NT, and a feedback term FB in the idle speed control device for an internal combustion engine according to the present invention in Case 2;
6 is a graph showing changes in a learning term LR.

FIG. 6 shows a state of an air conditioner, an engine speed NE, a target speed NT, and a feedback term FB in the idle speed control device for an internal combustion engine according to the present invention in Case 3;
6 is a graph showing changes in a learning term LR.

[Explanation of symbols]

302, 304, 306, 308, 310, 312, 3
14, 316, 318, 320, 322, 330, 33
2, 334, 336, 350 Control program steps

Claims (1)

[Claims] 1. An apparatus for performing feedback control of an engine speed during an idling operation of an internal combustion engine based on a feedback term and a learning term, wherein the feedback term is larger than a first predetermined value and the engine speed is set to a target value. When the engine speed is smaller than the engine speed obtained by subtracting the second predetermined value, the feedback term is smaller than the third predetermined value, and the engine speed is smaller than the engine speed obtained by adding the fourth predetermined value to the target engine speed. An idle speed control device for an internal combustion engine that updates the value of the learning term when the value is large.