JPS61258948A - Idle rotation control method for internal-combustion engine - Google Patents

Abstract

PURPOSE:To eliminate unstable condition of idle rotation by determining the solenoid current command level on the basis of the sum of learnt level and air-conditioner load feedback control item under operation of air-conditioner. CONSTITUTION:In step S1, it is decided whether an air-conditioner is operating. In step S12, a learnt level Ixref under turning-off of air-conditioner immediately before turning-on is stored into a memory. In step S22, an air-conditioner load feedback control item Iacfb(n) formed with correspondence to the difference between a target idle rotation and actual engine rotation is defined. In step S26, the learnt level Ixref is added with the control item Iacfb(n) to provide a solenoid current command Icmd to control valve drive circuit. Consequently, unstable condition of idle rotation can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for controlling the idle speed of an internal combustion engine. In particular, when the internal combustion engine is idling, each time an air conditioner load is applied to the engine, The present invention relates to a method for controlling the idle speed of an internal combustion engine, which can avoid a state where the idle speed increases or decreases and obtain a stable idle speed.

(Prior art) Traditionally, automobiles have been equipped with devices for controlling the temperature of the air inside the vehicle.
Equipped with air conditioning. When the air conditioner's compressor is connected to the output system of the engine and the air conditioner is operating (hereinafter referred to as "the air conditioner is on"), the load of the air conditioner is applied to the engine.

For this reason, conventionally, when the air conditioner is turned on, the amount of intake air in the intake system is increased to supply more air-fuel mixture into the engine, thereby preventing the idle speed from decreasing.

It is generally well known that even in electronically controlled fuel injection type internal combustion engines, when the amount of intake air increases, the amount of fuel injected also increases, and as a result, the air-fuel mixture increases fj11. There is.

On the other hand, during idling or low-load operation, the throttle valve is almost fully closed.

For this reason, the intake air amount of the internal combustion engine described above is determined according to the opening degree of a control valve provided in a bypass passage that communicates the upstream and downstream sides of the throttle valve.

Incidentally, the opening degree of this I1+1Il valve is controlled in a closed loop during idling. That is,
The excitation current supplied to the solenoid that proportionally controls the opening degree of the control valve is determined based on the solenoid current command value c+ed obtained by the following equation (1).

I c+ed − 1 fb (n) + I ac
...(11 However, Ifb(n)... Based on the deviation between the target idle speed and the actual engine speed, proportional (P term), integral (
1》, PID feedback control term (one control term) for performing differential (D term) control.

Iac: Addition correction term that adds a certain value when the air conditioner is turned on.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

The load of the air conditioner is (b) Varies depending on the model of air conditioner compressor.

(Example) Even if the compressor is the same model, each compressor is slightly different due to manufacturing inconsistencies.

(C) The load of the air conditioner on the engine also differs depending on the outside temperature and the temperature of the air conditioner refrigerant. Specifically, in the winter when the outside temperature and the air conditioner refrigerant temperature are low, the load of the air conditioner on the engine is light, but in the summer, The load on the air conditioner increases.

Further, since the refrigerant for the air conditioner is gradually cooled from the time the air conditioner, and therefore the compressor, is started, the load on the air conditioner is heavy when the compressor is started, but the load tends to gradually become lighter as time passes.

As described above, the load on the air conditioner changes depending on various conditions.

However, as is clear from equation (1) above, conventionally, when the air conditioner is turned on, a constant value is added to obtain the solenoid current command value I C1d. For this reason, especially immediately after starting the compressor, an appropriate l cg+d could not be obtained, resulting in a state in which the amount of intake air was either too small or too large.

As a result, each time the compressor is switched from an off state to an on state, the idle speed decreases or increases, resulting in a disadvantage that the engine speed becomes unstable.

Note that when the scheduled time elapses from the start of the air conditioner, the feedback control term Ifb(n) in equation (1) above,
The engine speed will now match the target idle speed.

The present invention has been made to solve the above-mentioned problems.

(Means and effects for solving the problem) In order to solve the above-mentioned problem, when the air conditioner is turned on, the Ifb(n) term of the equation (1) is changed to the previous air conditioner.
Air conditioner load feedback control that uses the learned value (bi-constant value) Ixref of Ifb(n) when the air conditioner is off, and performs feedback control of term 180 according to the deviation between the target idle speed and the actual engine speed when the air conditioner is turned on. Item I
As acfb(n), a solenoid current command value 1c+++d is obtained based on the sum of both vertices, and a learning value Iacrer is calculated by learning the Iacfb(n). There is.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic diagram of an idle speed control device for an internal combustion engine to which the method of the present invention is applied.

In the figure, the intake air amount in the intake manifold 33 during idling when the throttle valve 32 is almost fully closed is controlled by the control valve 30 provided in the bypass passage 31 that communicates the upstream and downstream of the throttle valve 32. controlled.

The opening degree of this control valve 30 is determined according to the current flowing through the solenoid 16.

The amount of fuel injected from the injection nozzle 34 is determined according to the amount of intake air in the intake manifold 33 by known means. Note that the piston 38 within the cylinder 35 repeatedly reciprocates to apply rotational force to the crankshaft 36.

Further, the TDC sensor 5 generates a pulse when the piston of each cylinder reaches 90 degrees before the top dead center. In other words, the TDC sensor 5 outputs the same number of pulses as the number of cylinders (hereinafter referred to as TDC pulses) every two rotations of the crankshaft 36, and supplies them to the electronic control unit 140.

The engine speed counter 2 detects the engine speed by timing the interval between TDC pulses output from the TDC sensor 5, and supplies a digital engine speed signal corresponding to this to the electronic control device 40. .

The air conditioner sensor (AC sensor) 4 supplies an air conditioner operation signal to the electronic control device 40 when the air conditioner is turned on.

The electronic control unit @40 controls the current flowing through the solenoid 16, as will be described later.

FIG. 3 is a circuit diagram showing an example of the internal configuration of the electronic control device 40 of FIG. 2. As shown in FIG. In the figure, the same reference numerals as in FIG. 2 represent the same or equivalent parts.

Electronic control system! ! 40 is a central processing unit (CPU) 5o;
A microcomputer 53 consisting of a storage device (memory) 51 and an input/output processing circuit (interface) 52, and a control valve drive circuit that controls the current flowing through the solenoid 16 according to a command from the microcomputer 53 (solenoid current command value (ced)). It consists of 54.

The control valve drive circuit 54 outputs a control signal for controlling the current flowing through the solenoid 16 in accordance with the IOd. As a result, the opening degree of the control valve 30 (FIG. 2) is
The idle speed is controlled according to cld, and the idle speed is also controlled according to
It will be controlled according to l c+ed.

The operation of the first embodiment of the method of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart illustrating the operation of the first embodiment of the present invention. Further, FIG. 4 is a graph showing the relationship between the solenoid current command value IC1d and the elapsed time. Note that the operation of the flowchart in FIG. 1 is started by an interrupt caused by a TDC pulse.

In FIG. 1, in step S1, the air conditioner compressor is turned on and it is determined from the output of the AC sensor 4 whether or not the air conditioner is operating.

For example, when the air conditioner is operating (when the air conditioner is on), as in the period from time t3 to t4 in FIG.
When the air conditioner is not operating (air conditioner off), proceed to step S2.

Step S2: The engine rotation speed N refo when the air conditioner is turned off, which is stored in the memory 51 in advance, is read out, and this is set as the target idle rotation speed N rer.

Step S3: Read the reciprocal number (period) of the engine speed detected by the engine speed counter 2 or the amount Me(n) corresponding thereto.

Step S4...The read Me(n) and the target idle rotation speed Nrafo set in Step S2
The reciprocal of or the corresponding deviation Δ from I M rel
Calculate Mef.

Step S5...The Me(n), and the Me(n)
) and the previous measurement value Me for the same cylinder (if the engine is a 6-cylinder engine, Me(n-6))
In other words, the period change rate ΔMe is calculated.

Step S6... Said ΔMil! and ΔMef, and the integral term control gain K111, the proportional term IIJ control gain Kpm, and the differential term control gain Kdm.
11 The proportional term Ip and the differential term 1d are calculated according to the equations shown in the figure, respectively. Note that each of the control gains is obtained by reading out those stored in the memory 51 in advance.

Step S7... It is determined whether the air conditioner was operating last time. This stores the previous AC sensor 4 in the memory 51.
This is done by temporarily storing the output of and reading it out.

When the determination in step S7 is established, it is assumed that the operating state of the air conditioner has changed from on to off, and the process proceeds to step S8. If the determination is not satisfied, it is assumed that the operating state of the air conditioner continues to be off, and the process proceeds to step S9.

Step S8: The learned value 1xref from the previous time the air conditioner was turned off (before time t1 in this embodiment) is read out as the initial value of the term Iai(n) in step S10, which will be described later. Note that the learned value is stored in the memory 51 in step S12, which will be described later.

Furthermore, if the learning value 1 xref is not yet stored in the memory 51, a numerical value similar to the learning value may be stored in the memory 51 in advance, and this numerical value may be read out as the learning value t xrer. good. After that, the process advances to step S10.

Step $9...1ai (current value; n), 1a
The integral term 1i obtained in step S6 is added to i (previous value: n-1). It should be noted that, as a matter of course, if the judgment in step S7 is not satisfied until the air conditioner is switched from on to off, and the process moves to step S9, Iai(n-1) is set to the value in step S8. value is used.

Step 810...Step S9 or Step S8
Ip and ld calculated in step S6 are added to Iai(n) calculated in step S6, and defined as [b(n).

Step 811: A fixed learning value Ixref(n) is calculated using two equations to be described later.

Ixref(n) = Iai(n)XCcr
r /la+ Ixref(n −1)x (a
+ -Ccrr )/gc...' (2) In addition, - and (:, err in the above formula (2) are arbitrarily set positive numbers, and the relationship between - and Ccrr is m>
Ccrr.

Step 812: The learning value 1 xref calculated as described above is stored in the memory 51.

Step 813: x calculated in step S10
fb(n) is output to the control valve drive circuit 54 as a solenoid current command value ICd. Processing then returns to the main program.

As a result, during the period when the air conditioner is off, such as from time t2 to time t3 in FIG.
Its opening degree is controlled according to C1d.

Next, in step S1, when the determination in step S1 is established, that is, for example, from time t3 to t
Step 8 Assuming that the air conditioner operates as in period 4
Proceeding to step 14, here, similarly to step S2,
The engine rotation speed N refac when the air conditioner is turned on, which is stored in advance in the memory 51, is read out, and this is set as the target idle rotation speed N ref.

fc data L,, N refac and N r in step S2
The relationship of efO is N refac 2 N refot
This is because by setting the target idle rotation speed Nrer when the air conditioner is turned on relatively large, it is possible to avoid, for example, discharging (power consumption) from a battery (not shown).

Step 815: Read the reciprocal number (period) of the engine speed detected by the engine speed counter 2 or the amount Me(n) corresponding thereto.

Step 816: The read Me(n) and the target idle rotation speed N ref set in step 814
A deviation ΔMet from the reciprocal of ac or the amount M refac equivalent thereto is calculated.

Step 817... Said Me (n), and said Me
Previous measurement rMe(n-
6), that is, the rate of change ΔMe of the period is calculated.

Step 818...Similar to step S6 described above,
An integral term 1i, a proportional term to, and a differential term 1d are calculated.

Note that each control gain) (is
, )(pm and Kdm do not need to be the same as each control gain in step S6, and may be different values.

Step S19... It is determined whether the air conditioner was operating last time. If the determination in step 819 is not satisfied, it is assumed that the operating state of the air conditioner has changed from off to on, and the process proceeds to step 820. If the determination is true, it is assumed that the air conditioner continues to be on, and the process proceeds to step S21.

Step 820: As will be clear from what will be described later, the learning value l acrer learned during the previous time the air conditioner was turned on (in this embodiment, the period from time t1 to t2)
I acai (n) in step 822, which will be described later.
Read as the initial value of the term. Note that the learned value is stored in the memory 51 in step 825, which will be described later.

In addition, if learning@1acref is not yet stored in the memory 51, a numerical value similar to the learned value is stored in the memory 51 in advance, and the numerical value can be read out as the learned value (acref'). Bye.

In this embodiment, the correction value α is added to the 1 acref to obtain (acai <n). This is due to the following reason.

That is, the load on the air conditioner tends to gradually become lighter from the time the air conditioner is started, but as described later, I ac
ref is not learned in a transient state immediately after the air conditioner is started, and does not reflect the heavy load state of the air conditioner.

For this, 1 acrer is the actual required IaCai
This is because Iacai(n) tends to be smaller than the initial value of term (n) by 8°, but it is desirable to obtain Iacai(n) by adding the correction value α to l acref.

Note that the correction value α is a constant value determined empirically. Thereafter, the process proceeds to step 7', step 822.

Step 521 - “I acai(n )”
The integral term 1i obtained in step 518 is added to cai (n-1).

It should be noted that, as a matter of course, if the judgment in step 819 is established only after the air conditioner is switched from off to on, and the process moves to step S21, the above-mentioned Iaca
The value of step 820 is used as i (n −1).

Step 822...Step S21 or Step 8
Step 8
The IQ and ld calculated in step 18 are added,
! Defined as ael(n).

Step S23... It is determined whether a scheduled time (Tacref seconds) has elapsed since the air conditioner started operating (time t3 in this embodiment), and if the determination is not established, steps S24 and Step 825, which will be described later, are performed. Jump to step 826.

In other words, as is clear from what will be described later, before T acrer seconds have elapsed since the air conditioner started, the air conditioner
Learning is not performed when it is on.

This is because the air conditioner is in a transient state for a certain period of time after it is started, and an appropriate learning value cannot be obtained.

On the other hand, Tacrer seconds have passed (in this example, time [3
') Occasionally, proceed to step 824〇Step 824...
・Described later (Learned value 1acre defined by formula 31
f (n) is calculated.

Iacref (n) −1ai (n) xC
crr /ra'+ 1acref (n -1)
X (N'-Ccrr) /e'...(3 In addition, m' and Cerr in the above formula (3) are the above (
2) It is a positive number that has the same relationship as Eq.

Step 825: The learning value 1acref calculated as described above is stored in the memory 51.

Step S26...Learned value I xref of the time when the air conditioner is turned off (in the present embodiment, the period from time t2 to t3), which is stored in step S12 and immediately before the time when the air conditioner is turned on.
Iacfb(n) calculated in step S22 is added to the value, and the result is output to the control valve drive circuit 54 as a solenoid current command value I cod. Processing then returns to the main program.

As a result, during the period when the air conditioner is on, such as from time t3 to time t4 in FIG.
Its opening degree is controlled according to cld.

FIG. 5 is a flowchart illustrating a second embodiment of the present invention. In this figure, the same reference numerals as in FIG. 1 indicate steps that perform the same processing or judgment.

This second embodiment is similar to the first embodiment described with reference to FIG.
The difference from the embodiment is that step S7 and step 319
are provided immediately after step S2 and step 814, respectively, and when the determinations in step S7 and step 819 are established or not established, respectively, the process proceeds to step 813 or step 826 after performing the process of step 830 or step S31. This is the point where I decided to move forward.

In step 830, the learned value I
I try to define it as Therefore, the initial value of i cmd when the operating state of the air conditioner changes from on to off is 1 xref in the second embodiment.

Further, in step 831, the correction value α is added to the learning value 1acrer learned when the air conditioner φ was turned on the previous time, and the value obtained by adding the correction value α is added to IaCfb(n
).

Therefore, in the case of this second embodiment, the initial value of lcmd when the operating state of the air conditioner changes from off to on is the learned value 1xre stored in step 812.
It is the value obtained by adding the above-mentioned (acfb(n) and α to f.

Note that, as in the first embodiment, the addition of the correction value α may be omitted.

As is clear from the above explanation, in the present invention, the l c-d when the air conditioner is turned on is compared to the l c-d when the air conditioner was turned off last time.
The learned value 1 xref of fb(n) is the air conditioner load feedback control term I obtained according to the deviation between the target idle speed and the actual engine speed when the air conditioner is turned on.
It is created by adding acfb(n).

Further, in the present invention, the air conditioner load feedback control term Iacrb(n) is learned, and the learned value 1 a
Get the cref and lage the next time you turn on the air conditioner.
The initial value of (xref), at least the lac
It is obtained by adding ref.
1 (Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

When the air conditioner is turned on, an appropriate initial value of l C1ad can be obtained according to the load of the air conditioner, so predictive control of the control valve when starting the air conditioner is performed with high accuracy. As a result, the unstable state in which the idling speed decreases or increases each time the air conditioner is switched from off to on or from on to off, which conventionally occurs, is eliminated.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for explaining the operation of the first embodiment of the present invention. FIG. 2 is a schematic diagram of an idle speed control device for an internal combustion engine to which the method of the present invention is applied. FIG. 3 is a circuit diagram showing an example of an internal configuration of the electronic control device shown in FIG. 2. FIG. 4 is a graph showing the relationship between the solenoid current command value I C11ld and the elapsed time t in the first embodiment. FIG. 5 is a flowchart for explaining the operation of the second embodiment of the present invention. 2... Engine revolution counter, 4... AC sensor, 5... TDC sensor, 16... Solenoid, 30
... Control valve, 31 ... Bypass passage, 32 ... Throttle valve, 34 ... Injection nozzle, 35 ... Cylinder, 36 ... Crankshaft, 38 ... Piston, 40
...Electronic control unit, 50...Central processing unit (CPU
), 51...Storage device f (memory), 52...Input/output signal processing circuit (interface), 53...Microcomputer, 54...Control valve drive circuit Patent attorney Michito Hiraki, etc.1 second name

Claims (5)

[Claims] (1) A control valve is provided in a bypass passage that communicates between the upstream and downstream of a throttle valve of an internal combustion engine, and the opening degree of the control valve is proportionally controlled according to a solenoid current command value Icmd. In an internal combustion engine idle speed control method that controls the intake air amount of an internal combustion engine during idling, when the air conditioner is stopped (hereinafter referred to as "air conditioner off"), the target idle speed and the actual engine speed are Feedback control term Ifb(n
), the Icmd is determined based on the Ifb
A first learned value is calculated by learning (n), and when the air conditioner is operating (hereinafter referred to as "air conditioner on"), the first learned value, the target idle speed, and the actual engine speed are calculated. Icmd is determined based on the sum of the air conditioner load feedback control term Iacfb(n) created according to the deviation of A method for controlling the idle speed of an internal combustion engine, characterized in that: (2) The initial value of Icmd at the time of starting feedback when the air conditioner is turned on is the first learning value and the second learning value.
2. The method for controlling the idle speed of an internal combustion engine according to claim 1, wherein the idle speed control method is determined based on a sum of learned values. (3) Set the target idle speed when the air conditioner is off to N
The mutual relationship is Nref when ref0 is the target idle rotation speed when the air conditioner is turned on and Nrefac is the target idle rotation speed when the air conditioner is turned on.
The idle speed control method for an internal combustion engine according to claim 1 or 2, wherein the idle speed control method is 0 Nrefac. (4) The internal combustion according to claim 1, 2, or 3, wherein the initial value of Icmd at the time of starting feedback when the air conditioner is turned off is the first learned value. Engine idle speed control method. (5) The initial value of Icmd at the time of starting feedback when the air conditioner is turned on is characterized by adding a correction value α to the sum of the first learning value and the second learning value. A method for controlling the idle speed of an internal combustion engine according to claim 1, 2, 3, or 4.