JPS63113149A - Idling speed control device for engine - Google Patents

Abstract

PURPOSE:To secure such an idling speed control device that makes engine speed so as not to be sharply slippage from the target speed, by compensating a controlled variable of idling speed when an air-fuel ratio of mixture is shifted to the more lean side than a theoretical air-fuel ratio. CONSTITUTION:During till engine drive is shifted to an idling state and the specified time elapses, a control unit 100 outputs a injection pulse signal to a fuel injection valve 25 so as to maintain it to a theoretical air-fuel ratio by feedback control over a fuel injection quantity. After the elapse of the speci fied time, it is shifted to a lean air-fuel ratio while it performs feedback control over a suction air quantity to a flow regulating valve 19. That is to say, the increment correction value added with a lowering degree of engine speed and engine power at a point of time when shifting to the lean air-fuel ratio is added to the last time controlled value. With this controlled value, a suction air quan tity is quickly increased at that point that air-fuel ratio control is shifted to the lean air-fuel ratio. Therefore, it is converged on the target idling speed and never subjected to sharp slippage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention has an object to reduce the air-fuel ratio of the air-fuel mixture to be used for combustion to near the stoichiometric air-fuel ratio when the engine is in an idling state that satisfies predetermined conditions. The present invention relates to an engine idle speed control device that performs control to shift the engine speed to a leaner side and also performs control to converge the engine speed to a target idle speed.

(Prior Art) Conventionally, as one of the technologies related to intake control in an engine installed in a vehicle, for example, in order to maintain the actual engine speed when the engine is idling at a predetermined engine speed (target idle speed), A bypass passage is provided that communicates the upstream and downstream parts of the throttle valve in the intake passage, and a flow rate adjustment valve is installed in this bypass passage when the throttle valve is in the fully closed position B (idling opening position B). It is possible to control the amount of intake air by changing the opening operation amount of the flow rate adjustment valve (the opening degree of the flow rate adjustment valve, the valve opening period per unit period, etc.), so-called idle rotation speed control. Are known.

In an engine to which such idle speed control is performed, normally, when the operating state is in an idling state, for example, when the throttle valve is in a fully closed state and the engine speed is below a predetermined speed, In order to converge the actual engine speed to the target idle speed, feedback control is performed on the opening operation amount of the flow rate regulating valve, and therefore the amount of intake air, based on the difference between the actual engine speed and the target idle speed. be made into

On the other hand, when the engine is in an idling state, in order to improve fuel efficiency, the air-fuel ratio of the mixture used for combustion is set to be leaner than near the stoichiometric air-fuel ratio, and when the engine is in other operating states, i. In order to obtain a required engine output, there are cases where it is desired that the air-fuel ratio be near the stoichiometric air-fuel ratio or richer than near the stoichiometric air-fuel ratio.

However, the output characteristics of conventional general-purpose air-fuel ratio sensors change around the stoichiometric air-fuel ratio, so feedback control based on the detection output obtained from the air-fuel ratio sensor can change the air-fuel ratio to stoichiometric. It is not possible to shift the fuel ratio to the lean side or rich side and maintain it.

For this reason, in conventional engines, in order to maintain the air-fuel ratio leaner or richer than near the stoichiometric air-fuel ratio, it is necessary to maintain the air-fuel ratio based on the engine load and engine speed applied by the intake air amount and intake negative pressure. The air-fuel ratio is controlled in an open-loop manner by calculating the basic fuel supply amount and using the final fuel injection amount obtained by correcting the calculated basic fuel supply amount.

However, with the engine air-fuel ratio control device that calculates the basic fuel supply amount and performs open-loop control of the air-fuel ratio, control is affected by changes in engine characteristics over time, changes in the operating environment, etc. There is a problem that the control becomes unstable or the control accuracy decreases, making it difficult to always obtain a desired air-fuel ratio. For this reason, for example, as shown in Japanese Unexamined Patent Publication No. 57-105530, when the operating state of the engine satisfies a predetermined condition, the air-fuel ratio is set to the stoichiometric air-fuel ratio based on the detection output obtained from the air-fuel ratio sensor. Feedback control of the fuel supply amount is performed in order to maintain the fuel ratio close to that of the air-fuel ratio, and during this feedback control, learning is performed to determine the feedback correction amount that corrects excess or deficiency in the fuel injection amount. is a method in which the fuel injection amount is corrected using the learning value obtained through learning, and the air-fuel ratio is controlled to maintain the air-fuel ratio at a target air-fuel ratio that is different from the vicinity of the stoichiometric air-fuel ratio after absorbing changes in the engine over time. is proposed.

(Problem to be Solved by the Invention) However, in an engine in which air-fuel ratio control is performed as described above, when the operating state is idling, the air-fuel ratio is set to the stoichiometric air-fuel ratio or to a value richer than the stoichiometric air-fuel ratio. When control is performed to shift the air-fuel ratio from the stoichiometric air-fuel ratio to one leaner than the stoichiometric air-fuel ratio, and control is performed to converge the engine speed to the target idle speed as described above, as described below. There is a hole that causes problems.

In other words, when the engine is in an idling state, if the air-fuel ratio is to be shifted from the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio to a leaner one than the stoichiometric air-fuel ratio, the idling As for the air-fuel ratio in this state, an air-fuel ratio of 15 to 17, where nitrogen oxides (NOx) are likely to be generated, is not used, but an air-fuel ratio of 17 or more on the extremely lean side is used, so it is necessary to shift to a lean side. When this occurs, the air-fuel ratio changes rapidly, resulting in a sudden drop in engine output. Immediately after such a transition, the engine speed deviates significantly from the target idle speed, which can easily lead to engine stall, etc. It becomes.

In view of the above, the present invention aims to change the air-fuel ratio to a leaner side than the stoichiometric air-fuel ratio when the engine is brought into an idling state, or when a predetermined period of time has elapsed after the engine is brought into an idling state. In order to achieve this, the fuel supply amount is corrected, and when the engine is in an idling state, control is performed to converge the engine speed to the target idle speed. An object of the present invention is to provide an engine idle speed control device that prevents the engine speed from significantly deviating from the target speed immediately after the fuel ratio is shifted to a leaner side than the stoichiometric air-fuel ratio. do.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the engine idle speed control device according to the present invention has a basic configuration shown in FIG. , when the air-fuel ratio of the air-fuel mixture used for combustion is shifted to the idling state from the stoichiometric air-fuel ratio or a state richer than the stoichiometric air-fuel ratio, or for a predetermined period of time after the air-fuel ratio is shifted to the idling state. an air-fuel ratio changing means for changing the fuel supply amount so that the air-fuel ratio of the air-fuel mixture becomes leaner than the stoichiometric air-fuel ratio when the engine is in an idling state; It includes an idle rotation speed control means that performs control to converge to an idle rotation speed, and a control amount correction means that corrects a control amount of the idle rotation speed control means, and the control amount correction means is configured to adjust the engine operating state to an idling state. When the air-fuel ratio of the air-fuel mixture is shifted to leaner than the stoichiometric air-fuel ratio, the idle speed control means is controlled to increase the engine speed. lll1t correction is performed.

(Function) In the engine idle speed control device according to the present invention configured as described above, the operating state of the engine is set to the idling state, and the air-fuel ratio shifts to a value on the lean side of the stoichiometric air-fuel ratio. When the control amount correction means causes the idle speed control means to correct the control amount in order to increase the engine speed, the air-fuel ratio is set to a value on the lean side of the stoichiometric air-fuel ratio. The sudden drop in the engine speed immediately after the engine speed is shifted to is alleviated, thereby effectively preventing the engine speed from deviating significantly from the target idle speed.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an example of an engine idle speed control device according to the present invention, together with an engine to which the device is applied.

In FIG. 2, the intake passage 12 that guides intake air from the air cleaner 11 into the combustion chamber 14 of the engine main body 10 includes:
A throttle valve 16 is provided which is linked to the accelerator pedal. The opening degree of the throttle valve 16 is detected by the throttle opening sensor 18, and a detection signal St corresponding to the opening degree of the throttle valve 16 is obtained from the throttle opening degree sensor 18, which is transmitted to the control unit 10, which will be described in detail later.
0.

An air flow meter 20 for detecting intake air is disposed upstream of the portion of the intake passage 12 located at the throttle valve 16. From this air flow meter 20,
A detection signal Sa corresponding to the detected intake air amount is supplied to the control unit 100. In addition, the intake passage 12
A surge tank 22 having a relatively large capacity is provided downstream of the part where the throttle valve 16 is arranged, and a fuel injection valve 25 is temporarily provided further downstream from the surge tank 22. There is. Fuel injection valve 25
The valve is electronically controlled, and the valve is opened according to the pulse width (duty) of the injection pulse signal Pc supplied from the control unit 100, and the fuel is pressure-regulated and pumped from the fuel supply system. , is injected intermittently toward the intake boat portion of the combustion chamber 14 at a predetermined timing, for example, in synchronization with the rotation of the engine, to create an air-fuel mixture for combustion within the combustion chamber 14. The air-fuel mixture is supplied to the combustion chamber 14 via the intake valve 27, ignited by the spark plug 28, and combusted. Exhaust gas generated by combustion of the air-fuel mixture in the combustion chamber 14 is discharged into the exhaust passage 26 via the exhaust valve 29.

A starting end of a bypass passage 15 that bypasses the throttle valve 16 is connected to a portion of the intake passage 12 between the throttle valve 16 and the air flow meter 20, and a terminal end of the bypass passage 15 is connected to a portion of the intake passage 12 between the throttle valve 16 and the air flow meter 20. 1
The surge tank 22 is connected to a surge tank 22 provided downstream from the surge tank 6.

A flow rate adjustment valve 19 is interposed in the bypass passage 15, and the flow rate adjustment valve 19 controls the bypass passage 15 according to the pulse width (duty) of the valve opening operation pulse signal Cq supplied from the control unit 100. It opens and closes, thereby adjusting the amount of intake air taken into the combustion chamber 14.

Furthermore, in relation to the crank mechanism 33 that changes the reciprocating motion of the piston 31 in the engine body 10 into rotational motion,
A rotation speed sensor 30 that detects the engine rotation speed is arranged, and a detection signal Sn corresponding to the engine rotation speed is supplied from the rotation speed sensor 30 to the control unit 100.

The control unit 100 has the above-mentioned detection signal Sa.
, Sn, and St, a detection signal So obtained from an Ot sensor 35 arranged in the exhaust passage 26 and whose output characteristics change near the stoichiometric air-fuel ratio is supplied, and a water temperature A group of other detection signals necessary for engine control, including detection signals corresponding to the engine cooling water temperature obtained from sensors (not shown) and detection signals indicating the operating status of external loads such as air conditioners that are applied to the engine. Sx is also supplied. The control unit 100 controls the fuel injection amount in the fuel injection valve 25 based on the various detection signals and detection signal groups described above.
4, the air-fuel ratio of the air-fuel mixture to be subjected to combustion is controlled.

Here, in this example, target air-fuel ratios are set in advance for each of a plurality of regions divided according to the operating state of the engine.

That is, when the operating state of the engine is, for example, in a high load or high rotation range (hereinafter referred to as the R range), the target air fuel ratio is set to a value richer than the stoichiometric air fuel ratio (approximately 13 ) (hereinafter referred to as the rich air-fuel ratio), and when the air-fuel ratio is in the region considered to be a low load and low rotation state (hereinafter referred to as the L region), excluding the idling state, the target In addition to the air-fuel ratio where the air-fuel ratio is on the lean side (approximately 18) than the stoichiometric air-fuel ratio (hereinafter referred to as the lean air-fuel ratio), there is also a region where the acceleration state occurs even under low load and low rotational conditions ( Below, this area is 381
range), the air-fuel ratio is set to the stoichiometric air-fuel ratio. In addition, when the operating state of the engine is in the idling state, the target air-fuel ratio is the stoichiometric air-fuel ratio for a predetermined time H immediately after the engine is shifted to the idling state, and after the elapse of the predetermined time H, the target air-fuel ratio is is set to a lean air-fuel ratio.

Note that when the throttle valve 13 is fully closed and the engine speed is in a deceleration region exceeding a predetermined rotation speed (hereinafter, this region is referred to as region C), a so-called deceleration fuel cut occurs. The air-fuel ratio is not controlled.

And the control unit 100 &;! : Based on the detection signals Sa, Sn, St, and Sx, injection is supplied to the fuel injection valve 25 in order to match the air-fuel ratio of the air-fuel mixture provided for combustion with the target air-fuel ratio set as described above. The fuel injection amount is controlled by changing the pulse width of the pulse signal Pc.

At that time, the control unit 100 controls the detection signal Sa
and Sn calculate the basic fuel injection amount based on the intake air amount and engine rotation speed, respectively. When the operating state of the engine is in eMMs and for a predetermined time H immediately after the engine is shifted to the idling state, the target air-fuel ratio is set to 0.0. The basic fuel injection amount is corrected based on the detection signal So supplied from the sensor 35, an injection pulse signal Pc having a pulse width corresponding to the obtained fuel injection amount is formed, and this is supplied to the fuel injection valve 25. do. As a result, feedback control of the air-fuel ratio is performed, and the actual air-fuel ratio converges to the stoichiometric air-fuel ratio.

When such feedback control is performed, the control unit 100 calculates a feedback correction iGb in order to correct excess or deficiency in the basic fuel injection amount, totals this feedback correction iGb a predetermined number of times (for example, twice), and calculates the feedback correction iGb. An average value MGb is determined, and this average value MGb is stored as a learning value in a built-in memory in place of the previously determined average value, and the average value MGb is updated.

Further, when the engine operating state is NMR, the control unit 100 adds the above-mentioned basic fuel injection amount calculated as described above to the above-mentioned amount stored in the built-in memory in order to make the air-fuel ratio a rich air-fuel ratio. The average value MGb is added, the added value is multiplied by a predetermined coefficient to calculate the fuel injection amount, the calculated fuel injection amount is corrected according to the operating state of the engine when the detection signal group Sx occurs, and a new value is calculated. A fuel injection amount is calculated, an injection pulse signal Pc having a pulse width corresponding to the calculated fuel injection amount is formed, and this is supplied to the fuel injection valve 25. As a result, the ratio of the fuel injection amount to the intake air amount is increased compared to the time of the feedback control described above, and a rich air-fuel ratio is achieved in which the actual air-fuel ratio is set as the target air-fuel ratio.

Furthermore, when the operating state of the engine is in the range and when a predetermined period of time H has elapsed after the engine has been shifted to the idling state, the control unit 100 controls the base fuel to make the air-fuel ratio a lean air-fuel ratio. The average value MGb stored in the built-in memory is added to the injection amount to correct it, the corrected fuel injection amount is multiplied by a predetermined coefficient to calculate the fuel injection amount, and the calculated fuel injection amount is applied to the engine. A new fuel injection amount is calculated by correcting it according to the operating state of the engine.

As a result, the ratio of the fuel injection amount to the intake air amount is reduced compared to during the feedback control described above, and the actual air-fuel ratio becomes a lean air-fuel ratio.

In addition to controlling the fuel injection amount, the control unit 100 also controls the detection signals Sn, S ts and the detection signal group S
Setting a control value that determines the pulse width of the valve-opening pulse signal Cq based on x, forming a valve-opening pulse signal Cq having a pulse width corresponding to the set control value,
By supplying it to the flow rate adjustment valve 19, the throttle valve 1 in the intake passage 12 passes through the bypass passage 15.
6. Controls the amount of intake air guided to the downstream side of the valve.

In that case, the control unit 100 sets the control value that determines the pulse width of the valve opening operation pulse signal cq as follows. That is, when the operating state of the engine is in the idling state, when a predetermined time H has elapsed after the engine has been brought into the idling state, the air-fuel ratio of the air-fuel mixture used for combustion changes from near the stoichiometric air-fuel ratio to lean air. Except for the time when the fuel ratio is shifted, the control value is set to the previous control value D°, the target idle speed set according to the engine operating state, and the engine speed at which the detection signal Sn is detected. The feedback correction value set based on the rotation speed difference between
In addition, when the operating state of the engine is not in the idling state, the control value is corrected based on the preset fixed control value and the detection signal group SX, which is set according to the engine operating state such as the engine cooling water temperature. The basic control value DT is set by adding the basic control value DT.

After the operating state of the engine is shifted to the idling state, the control unit 100 changes the control value to the previous control value at the time when the air-fuel ratio of the air-fuel mixture is caused to shift from near the stoichiometric air-fuel ratio to the lean air-fuel ratio. It is set to a value obtained by adding the increase correction value D2 to the value D'. In addition,
In this case, the increase correction value D2 is set in consideration of the degree of fluctuation in engine speed and the degree of decrease in engine output at the time when the air-fuel ratio of the air-fuel mixture is shifted from the stoichiometric air-fuel ratio to the lean air-fuel ratio. By doing this,
When the air-fuel ratio is shifted from near the stoichiometric air-fuel ratio to the normal air-fuel ratio, the amount of intake air is quickly increased.

With the configuration as described above, for example, 1. At the time point indicated by
, if the state is shifted to the following state, from time t to time t2 at which a predetermined time H has elapsed, the state is based on the detection signal SO obtained from the 02 sensor, as shown in FIG. Feedback control of the fuel injection amount is subsequently performed to maintain the air-fuel ratio at a value near the stoichiometric air-fuel ratio (14,7). Moreover, such a time point t.

From then on, feedback control of the intake air amount is performed, and the control value is changed as shown in FIG. 3B. As a result, the engine speed reaches the target idle speed as shown in FIG. 3C. It is made to converge to Na.

Then, a time point t when a predetermined time H has elapsed from the time point t! Then, as shown in FIG. 3A, the air-fuel ratio is shifted from near the stoichiometric air-fuel ratio to near the stoichiometric air-fuel ratio (18), and at the same time, as shown in FIG. 3B, Then, the control value is changed to a value obtained by adding the increase correction value Dz to the previous control value D', and the intake air amount is increased by a predetermined amount. If the increase correction value Dz is not added at time t2, the engine speed will drop significantly immediately after time t2, as shown by the dashed line in FIG. 3C, and the engine speed will reach the target idle speed. Although the intake air amount deviates significantly from Na, as described above, as a result of the rapid increase in the amount of intake air at time t2, the amount of intake air at time 1. The sudden drop in engine output immediately after is alleviated and the engine speed reaches the third level.
As shown by the solid line in Figure C, the idle rotation speed does not vary significantly from the target idle rotation speed Na.

The control unit 100 that performs the above-described control is configured using, for example, a microcomputer, and an example of a program executed by the microcomputer in such a case for fuel injection amount control and idle rotation speed control will be described below. This will be explained with reference to the flowcharts in FIGS. 4 and 5.

FIG. 4 shows a program in the fuel injection amount control routine, and after the program starts, the process 101
Detection signals Sa, Sn, So, St and detection signal group Sx
In the subsequent process 102, the basic fuel injection 1iTp is set according to the intake air IQ at which the detection signal Sa is generated and the engine rotational speed N at which the detection signal Sn is generated.

That is, the calculation 'rp=KxQ/N (where K is a constant) is performed.

In the next proceeding decision 103, the detection signal St
It is determined whether the engine operating state is in the S fJ region where the target air-fuel ratio is the stoichiometric air-fuel ratio based on the throttle opening at which the problem occurs and the engine rotational speed at which the detection signal Sn occurs. If it is determined that there is, the process advances to decision 105.

If it is determined in decision 103 that the engine is not in the S/N range, the process proceeds to decision 106, where it is determined whether or not the engine operating state is in an idling state. If it is determined that the engine is in an idling state, The process advances to decision 107, and if it is determined that the vehicle is not in an idling state, the process advances to decision 118.

In decision 107, it is determined whether a learning flag F set in an idle rotation speed control routine to be described later is 1, and if it is determined that the learning flag F is 1, a decision is made to perform feedback control. 1
The process advances to step 05, and if it is determined that the learning flag F is not 1, the process advances to process 122. In decision 105, it is determined whether or not the air-fuel ratio (A/F) was on the rich side compared to the stoichiometric air-fuel ratio last time based on the detection signal SO taken in in the previous process 101. If it is determined that there is a If it is determined that the air-fuel ratio is richer than the stoichiometric air-fuel ratio, that is, if the air-fuel ratio is determined to be richer than the stoichiometric air-fuel ratio twice in a row, the process proceeds to process 111, and the feedback correction amount cb is set to a predetermined value. Value -■
, and proceed to decision 118.

Further, in the decision 110, if it is determined that the air-fuel ratio is not on the richer side than the stoichiometric air-fuel ratio, that is,
If it is determined that the air-fuel ratio has reversed from the rich side to the lean side from the stoichiometric air-fuel ratio, the process proceeds to process 114, where the previous feedback correction iGb'' is set to a set value P (where P<
Set a new feedback correction iGb by adding I) and proceed to process 116. Process 11
In step 6, the average value MGb of the feedback correction amount is calculated by dividing the sum of the current feedback correction iGb and the previous feedback correction amount Gb'' by 2, and in the subsequent process 117, the average value MGb calculated in process 116 is calculated. The value MGb is stored as a learning value in a built-in memory in place of the previously stored average value MGb, and the average value MGb is updated.

On the other hand, if it was previously determined in decision 105 that the air-fuel ratio was not richer than the stoichiometric air-fuel ratio, the process advances to decision 112, where it is determined whether or not the air-fuel ratio is richer than the stoichiometric air-fuel ratio. However, this time as well, if it is determined that the air-fuel ratio is not on the richer side than the stoichiometric air-fuel ratio,
If it is determined that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, the process proceeds to process 113, where the feedback correction amount Gb is set to I, and the process proceeds to decision 118. Further, if it is determined in decision 112 that the air-fuel ratio is richer than the stoichiometric air-fuel ratio, that is,
If it is determined that the air-fuel ratio has reversed from the lean side to the rich side with respect to the stoichiometric air-fuel ratio, the process proceeds to process 115, and a new feedback correction value is calculated by subtracting the predetermined value P from the previous feedback correction value Gb'. Set Gb,
Thereafter, processes 116 and 117 are sequentially executed in the same manner as described above, and the process proceeds to decision 118.

In decision 118, based on the detection signals st and Sn, it is determined whether the operating state of the engine is in the C region where deceleration fuel is cut, and if it is determined that it is in the CjJt region, the process proceeds to process 119, Set fuel injection lTi to zero and proceed to process 127;
If it is determined in step 18 that the target air-fuel ratio is not in the C region, the process proceeds to decision 121, in which it is determined whether the engine operating state is in the L region where the target air-fuel ratio is considered to be a lean air-fuel ratio, and the target air-fuel ratio is determined to be in the L'J region. If it is determined that there is a
After the fuel injection 11Ti is calculated using the following equation (1), the process proceeds to process 127. However, in the following equation, A is a correction coefficient for changing the air-fuel ratio from the stoichiometric air-fuel ratio to a lean air-fuel ratio, and CT is a correction value set based on the operating state of the engine when the detection signal group Sx occurs.

T i= (Tp+Mcb) ・A+Ct...
(1) Also, if it is determined in decision 121 that it is not in the L area, proceed to decision 123,
The engine operating state is 1N with the target air-fuel ratio being a rich air-fuel ratio! If it is determined that it is within the R81 range, the process proceeds to process 124, where the fuel injection amount Ti is calculated using the following equation (2), and then the process proceeds to process 127. However, in the following equation, B is a correction coefficient for changing the air-fuel ratio from the stoichiometric air-fuel ratio to the rich air-fuel ratio.

Ti= (Tp+MGb) ・B+Ct...(
2) On the other hand, if it is determined in decision 123 that the engine is not in the R9i region, the engine operating state is in the sl region, so the process proceeds to process 125, where the fuel injection amount Ti is set by adding Gb to Tp. process 126
Proceed to. In process 126, the feedback correction fiGb calculated this time is used as the feedback correction lGb calculated this time.
” and proceed to process 127.

Also, in the above-mentioned decision 107, the learning flag F
If it is determined that is not 1, in this case, the above-described process 122 is executed to make the air-fuel ratio a lean air-fuel ratio, and the process proceeds to process 127. Then, in process 127, an injection pulse signal P having a pulse width corresponding to the fuel injection amount Ti
c and supplies it to the fuel injection valve 25, then returns to the previous step.

FIG. 5 shows a program in the idle rotation speed control routine, which starts, for example, when the engine is started, first takes in the detection signals Sn, St and the detection signal group Sx in a process 131, and continues. In process 132, a basic control value is set by adding a correction value calculated according to the operating state of the engine detected by the detection signal group Sx to a preset fixed control value, and the process proceeds to decision 133. .

In decision 133, it is determined whether or not the engine operating state is in an idling state. If it is determined that the engine is not in an idling state, the process proceeds to process 134, sets the learning flag F to O, and then proceeds to process 135. . In process 135, the control value is set to the basic control value Dr set in process 132, and the process proceeds to process 151.
In process 151, a valve opening actuation pulse signal Cq having a pulse width according to the control value set in process 135 is
is formed and supplied to the flow rate adjustment valve 19 for process 1.
Proceed to step 52. In process 152, the control value used in process 151 is stored in the built-in memory as the previous control value D'', and the process returns to the halo.

On the other hand, if it is determined in decision 133 that it is in an idling state, the process proceeds to process 136, where it is determined whether or not it was in an idling state last time.If it is determined that it was not in an idling state last time, in this case Since this is immediately after the engine operating state has been shifted to the idling state, the process proceeds to process 137, sets the learning flag F to 1, and proceeds to process 138. In process 138, a built-in timer is loaded with a predetermined time H8 and started, and the process starts to measure the elapsed time H after transitioning to the idling state, and then proceeds to decision 139. In addition, if it is determined in decision 136 that the process was in an idling state last time, the process 1
37 and 138 (Decision 139)
Proceed to.

In decision 139, it is determined whether the elapsed time H is greater than or equal to a predetermined time H3, and if it is determined that it is greater than or equal to the predetermined time H+, the process proceeds to decision 140, and whether or not the learning flag F is 1 is determined. to judge.

Then, in decision 140, the learning flag F is set to 1.
If it is determined that this is the case, in this case, the predetermined time H has just passed after the engine was shifted to the idling state, and the air-fuel ratio is about to shift from the stoichiometric air-fuel ratio to the lean air-fuel ratio. , the process proceeds to process 141 and the previous control value is determined.

The control value is set by adding the increase correction value Dz to , and in the subsequent process 142, the learning flag F is set to 0, and the process proceeds to process 151. In process 151, process 14
After forming a valve opening operation pulse signal Cq corresponding to the control value set in step 1 and supplying it to the flow rate regulating valve 19, the process proceeds to process 152. In process 152, the control value is changed to the previous control value D'. to store it in memory and return to the original state. As a result, the amount of intake air is increased immediately after the air-fuel ratio is shifted from the stoichiometric air-fuel ratio to the lean air-fuel ratio.

On the other hand, if it is determined in decision 139 that the elapsed time H is not equal to or greater than the predetermined time H, and if it is determined in decision 140 that the learning flag F is not 1, the process proceeds to process 144, and the detection signal group Sx is The target idle rotation speed Na is set based on the operating condition B of the engine, such as the engine cooling water temperature and the magnitude of the external load borne by the engine. Then, in the subsequent process 145, a rotation speed difference ΔN between the target idle rotation speed Na and the actual engine rotation speed N detected by the detection signal Sn is calculated, and the process proceeds to decision 146.

In decision 146, the magnitude of the rotational speed difference ΔN calculated in process 145 is determined, and if it is determined that the rotational speed difference ΔN is zero or a value near it (-NX<ΔN×Nx), the process The process proceeds to step 147, where the value of the feedback correction value is set to zero, and the process proceeds to process 150.

Further, if it is determined that the rotational speed difference ΔN is greater than or equal to Nx or less than -Nx, processes 148 and 1 are performed, respectively.
Proceed to step 49, and set the values of the feedback correction values D1 to −α.
Alternatively, set it to α and proceed to process 105.

In process 150, the control value is set by adding the feedback correction value Dr set in processes 147, 148, or 149 to the previous control value D° stored in the memory, and the process proceeds to process 151. In process 151, a valve opening actuation pulse signal Cq having a pulse width corresponding to the control value set in process 150 is formed and supplied to the flow rate regulating valve 19, and then the process proceeds to process 152, where the process is performed in the same manner as described above. The control value used in step 119 is stored in the memory as the previous control value D'' and the process returns to the original state.

In the above example, after learning to calculate the feedback correction fiGb is performed for a predetermined time H immediately after the engine operating state becomes idling, the learning value obtained by such learning is used to calculate the empty value. Although it is designed to shift the fuel ratio from near the stoichiometric air-fuel ratio to a lean air-fuel ratio, the engine idle speed control device according to the present invention does not necessarily have to do this. The air-fuel ratio may be shifted to a lean air-fuel ratio, and at the same time, the amount of intake air may be increased using, for example, a learned value obtained when the engine operating state is in the S region.

Furthermore, in the above example, control is performed to converge the idle rotation speed to the target idle rotation speed by changing the amount of intake air.
For example, this may be done by changing the ignition timing of the engine.

(Effects of the Invention) As is clear from the above explanation, in the engine idle speed control device according to the present invention, the engine operating state is set to the idling state, and the air-fuel ratio shifts to a value on the lean side of the stoichiometric air-fuel ratio. When the air-fuel ratio is shifted to a leaner value than the stoichiometric air-fuel ratio, the engine speed is corrected to increase the engine speed. A sudden drop in the engine speed is alleviated, thereby effectively preventing the engine speed from deviating significantly from the target idle speed.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram showing an engine idle speed control device according to the present invention in accordance with the claims, and FIG. 2 is an example of an engine idle speed control device according to the present invention to which it is applied. FIG. 3 is a time chart for explaining the operation of the example shown in FIG. 2, and FIGS. 12 is a flowchart showing an example of a program executed by a microcomputer when a microcombiator is used in the unit. In the figure, IO is the engine body, 12 is an intake passage, 15 is a bypass passage, 18 is a throttle opening sensor, 19 is a flow rate adjustment valve, 25 is a fuel injection valve, 30 is a rotation speed sensor, 35
is 0. The sensor 100 is a control unit. tl t2

Claims (1)

[Claims] When the operating state of the engine is shifted from a state in which the air-fuel ratio of the air-fuel mixture used for combustion is the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio to an idling state, or when the engine is shifted to an idling state. an air-fuel ratio changing means for changing the fuel supply amount so that the air-fuel ratio of the air-fuel mixture becomes leaner than the stoichiometric air-fuel ratio when a predetermined period of time has elapsed after the stoichiometric air-fuel ratio; At some point, an idle speed control means for controlling the engine speed to converge to a target idle speed, the operating state of the engine is set to an idling state, and the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. control amount correction means for causing the idle rotation speed control means to correct the control amount in order to increase the engine rotation speed when the idle rotation speed of the engine is changed to Number control device.