JPH02259279A - Idle speed control device for engine - Google Patents

Abstract

PURPOSE:To ensure engine speed stability and engine stop resistance by correcting the basic ignition timing to an advance side, when an engine speed is lower than a target value, while changing a control center value to a delay side at the time of low engine temperature, when an engine is in idle operation. CONSTITUTION:A means A detects a temperature of an engine, while a means B sets the basic ignition timing the more to a delay side the lower is the temperature of the engine. A means C detects an engine speed, while a means D performs speed feedback correction of the basic ignition timing respectively to an advance side, when the engine speed is lower than a target value, further to a delay side when the engine speed is higher than the target value. Further a means E drives an ignition device F of the engine in accordance with the corrected basic ignition timing. A means G changes a control center value of speed feedback to a delay side at the time of low engine temperature. In this way, stability of an idle speed and engine stop resistance against an external load are ensured.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an engine idle speed control device.

(Prior Art) Conventionally, as described in Japanese Patent Publication No. 61-53544, the engine speed is detected during idling operation of the engine, and this engine speed is set as a target according to the engine operating state. It is known that the amount of intake air or the ignition timing is adjusted to match the rotational speed. For example, in idle speed control by adjusting the ignition timing, as stated in the above publication, if the speed at idle is lower than the target value, the ignition timing is advanced, and if the speed is higher than the target value, the ignition timing is retarded. . In this case, advancing the ignition timing increases the engine output, and conversely, retarding the ignition timing decreases the engine output, thereby controlling the engine speed to the target value.

By the way, in the case of idle rotation speed control by adjusting the ignition timing, a correction is usually made to retard the ignition timing compared to normal times when the engine is cold or the like. In addition to promoting warm-up of the catalyst, this is generally for the purpose of stabilizing combustion and improving the stability of idle rotation. However, if control is performed to retard the ignition timing as described above in order to improve the stability of idle rotation when the engine is cold, stability may improve, but the retardation of the ignition timing will cause the engine to Since the output itself decreases, there is a problem that there is insufficient torque margin for external loads such as air conditioners, and the engine is likely to stall when external loads are applied. In other words, in the rotation speed feedback correction of ignition timing, an upper limit value (advanced angle side) and a lower limit value (retarded side) are usually set above and below the control center value (correction amount zero) depending on the knob king limit or misfire limit. If the basic ignition timing is retarded when the engine is cold and the engine output itself is decreasing, it will not be possible to sufficiently increase the amount of advance correction when applying an external load, and therefore the engine output will not match the external load. The engine stall resistance deteriorates because the engine output cannot be secured.

(Purpose of the invention) The present invention has been made in view of the above problems.

It is an object of the present invention to provide an engine idle speed control device by adjusting ignition timing to ensure stability of idle speed during cold operation and at the same time improve engine stall resistance against external loads.

(Structure of the Invention) In the present invention, as shown in FIG. 1, the engine idle speed control device includes an engine temperature detecting means, an engine speed detecting means, and a basic ignition that is retarded as the engine temperature is lower. The basic ignition timing setting means sets the timing, and when the engine speed at idle is lower than the target value, the ignition timing is advanced.
Further, when the engine temperature is high, the rotation speed feedback correction means corrects the basic ignition timing to the retarded side, the ignition drive means receives the output of the rotation speed feedback correction means and drives the engine ignition device, and the engine temperature is low. The above object has been achieved by including a control center value changing means for changing the control center value of the rotation speed feedback by the rotation speed feedback correction means to the retard side.

(Function) When the engine speed at idle is lower than the target value,
The basic ignition timing is corrected to the advanced side, and the engine is ignited at the corrected setting, thereby increasing the output of the engine and increasing the rotational speed. Furthermore, when the rotational speed is higher than the target value, correction is performed to the retard side, and the rotational speed is lowered.

Then, by repeating this rotation speed feedback, the engine speed converges to the target value.

Here, the basic ignition timing at idle is set to be more retarded as the engine temperature is lower, thereby providing stable idle rotation even when the engine is cold.

Further, in a state where the basic ignition timing is retarded in the cold state, the control center of the rotation speed feedback is changed to the retard side. That is, this expands the control range on the advance side. Therefore, when applying an external load, a sufficient amount of feedback correction to the advance angle side is ensured, and engine stall resistance is improved.

(Example) Examples will be described below based on the drawings.

FIG. 2 is an overall system diagram of an embodiment of the present invention. As shown in the figure, in this embodiment, the engine 1 is
A combustion chamber 5 defined by a cylinder 2, a piston 3 that reciprocates within the cylinder 2, and a cylinder head 4 that covers the upper part of the cylinder 2 is provided. Boat 6 and exhaust boat 7
is formed. An intake valve 8 and an exhaust valve 9 are provided to open and close the intake boat 6 and the exhaust boat 7, and a spark plug 10 is provided at the top of the combustion chamber 5. Then, an intake passage t communicating with the intake boat 6
i is provided with a throttle valve 12, and a hot wire type air flow sensor 13 is provided upstream of the throttle valve 12. Further, a fuel injection valve 15 is disposed near the intake boat 6, further downstream of the surge tank 14 formed downstream of the throttle valve 12. Further, a catalyst device 17 is connected to the exhaust passage 16.

The spark plug 10 is connected to an ignition coil 19 via a power distributor 18. Ignition coil 1
9 is actuated by an ignition signal from the control unit 20 and drives the ignition plug 17 via the power distributor 18. Furthermore, the control unit 20 also controls the fuel injection valve 15.
Outputs an injection signal to. The control unit 20 receives the intake air amount (filling amount) from the air flow sensor 13 as information for calculating the ignition signal and injection signal.
A signal, a water temperature signal from the water temperature sensor 21, an idle switch signal, a starter switch signal, etc. are input.

In this embodiment, idle rotation speed control is performed as follows.

First, the intake air 1i which is the output of the air flow sensor 13
Q is read, and the engine speed N is calculated from the output of the crank angle sensor attached to the power distributor 18.
As shown in Figure 3 (functional block diagram), first, Q/N
The apparent upper intake air filling amount C0° is calculated by multiplying by a constant K. Then, in a transient state, the apparent filling amount C is the amount that fills up the volume of the intake system's surge tank, etc.
In order to correct the large detection of 0°, a smoothing process is performed and the actual filling amount C0 is determined. This annealing process uses the previous filling amount C1 and the annealing coefficient α (0≦α<l
), the current filling amount C0 is determined in the form α·C,+(1−α)C0°.

Then, based on the filling amount C6 and engine speed N,
The basic ignition timing thtbse is set using the map.

In addition, the output of the water temperature sensor 21 is taken out, and the output of the water temperature sensor 21 is taken out, and
) Maximum value of idle retardation amount thtr@x according to the table
The idle retard amount calculation thtret is set based on.

Further, based on the water temperature, the target engine speed N0 during idling is set using the table shown in FIG. 4(a). Then, a deviation Nd of the engine rotational speed with respect to the target rotational speed N0 is calculated, and an advance angle feedback amount thtfb corresponding to this deviation Nd is set from the table shown in FIG. 4(b).

Further, acceleration is determined based on the difference dC between the apparent filling amount C0° and the actual filling amount C0, and based on this dCo, the acceleration retardation amount thtac is determined from the table of FIG. 4(d).
is set.

Then, based on the idle switch signal and the rotational deviation Nd, it is determined whether conditions are met to execute idle retardation and whether conditions are met to execute idle feedback correction.

The ignition coil (ignition drive circuit) 19 includes a basic ignition timing thtbse, an acceleration retard amount thtacc, an advance feedback amount thtrb, and an idle retard amount th.
An ignition signal with a final ignition timing thtig set by the combination of tret and tret is output.

In addition, the starter switch signal is taken out, and from this starter switch signal and engine rotation speed signal, the
It is determined whether the conditions for executing the second ignition are met, and if the conditions are met, the ignition timing for the second ignition is set to a predetermined amount retarded than the first ignition. is set and output to the ignition drive circuit.

5 to 8 are flowcharts for executing the above control.

First, in the main routine of FIG. 5, when started, the output Q of the air 70 sensor is read, the engine speed N is read, and the output thw of the water temperature sensor is read.

Next, multiply Q/H by a constant K to obtain the apparent filling amount C0
.degree., then smoothing is performed to calculate the actual filling amount C0, and then the difference dC between C0.degree. and C0 is determined.

Next, the target rotational speed N0 is set according to the water temperature using the table (characteristic diagram ■) in FIG. 4(a), and then the difference Nd between the actual rotational speed N and the target rotational speed N0 is determined.

Next, the basic ignition timing thtbse is set using a map from the actual rotational speed N and the charging amount C0.

Next, go to the acceleration retardation subroutine, then the idle retardation subroutine, then the advance angle feedback subroutine, and then proceed to the acceleration retardation amount thtacc, the advance angle feedback amount thtfb, and the idle angle retardation amount set in these subroutines. The final ignition timing tht i is determined by combining the quantity thtret with the basic ignition timing thtbse.
g and set the ignition timer to ignite at this thtig.

Next, check whether the starter switch is on, and if yes, then check whether the engine speed N is smaller than the predetermined value KN, and if both are yes,
Go to the second ignition timing setting step. Also, when the starter switch is not on, that is, when cranking is not in progress, the engine returns to its original state. If N<KN, the rotation is high and ignition twice will overlap with the ignition of the next ignition cylinder, so the engine will return to its original state.

In the step of setting the second ignition timing, the ignition timing tht ig2 is set to a position delayed by a predetermined amount from the first ignition. Then, after a certain period of time has elapsed after the first ignition at tht ig ends, the coil is energized and the ignition timer is set to ignite at thtig2.

Next, each subroutine will be explained.

In the acceleration retardation subroutine shown in FIG. 6, first, it is checked whether the previously obtained dC, is larger than the constant value KD,
If YES, it means acceleration, and the acceleration retard amount thtacc is set according to the table (characteristic diagram ■) in FIG. 4(d).

Further, if dC,>KD, the acceleration retard amount thtacc is gradually reduced to avoid shock, and when the retard amount becomes more advanced than the predetermined value KA, it is returned to zero at once.

In the idle retard subroutine shown in FIG. 7, it is first checked whether the idle switch is on, and if so, it is then checked whether the absolute value of the rotational deviation Nd is smaller than a predetermined value KH.

Then, the idle switch is on and Ndl<K
If it is H, it means that the conditions for idle retard have been met, and in the next step, increase the retard amount (retard amount) thtret by a constant value KIP, and then,
From the table (characteristic diagram ■) in Figure 4 (C), the maximum retardation value t
Set htrIix. And the retard amount thtret
is on the retard side from this maximum value thtrn+x, and if it is on the retard side from the maximum value thtrmx, the retard amount thtret is clipped to this maximum value thtrmχ.

Further, when the idle switch is not on, or when I ND I <KH, the already retarded amount is gradually reduced (by a constant value KIM). Then, it is checked whether thtret<O, that is, whether the retard amount has become negative, and if yes, thtret is clipped to 0, which is the minimum retard value.

In the advance angle feedback subroutine of FIG. 8, it is first determined whether the idle switch is on, and if so, it is then determined whether the absolute value of the rotational deviation Nd is smaller than a predetermined value KL.

If both of the above determinations are YES, it means that the conditions for executing idle feedback have been met, and the advance angle feedback amount thtfb is then set from the table (characteristic diagram ■) in FIG. 4(b).

Then, the advance angle amount th due to this feedback
Whether trb is on the retard side by more than a predetermined value KF with respect to the idle retard angle 11thtret, that is, th
Determine whether tfb<-thtret1K F,
If yes, clip thtrb to the above KF.

That is, this KF is set as the lower limit value of the advance angle feedback amount.

Also, if thtfb<-thtret1KF is not true, then check whether thtrb>-thtret, that is, the advance amount due to advance angle feedback is larger than the idle angle retard amount, and according to this, the basic ignition timing is lower than the basic ignition timing. See if it is even more advanced, and if yes, use this -thtret
Clip thtrb to the value of . That is, -tht
Let ret be the upper limit value of the advance angle feedback amount.

Further, when the idle switch is not on, or when 1Ndl<KL, the advance angle feedback is reset.

By the above control, the control center value of the advance angle feedback is shifted to the retard side, and the control range on the advance side is expanded, so that there is a torque margin against the external load.

(Effects of the Invention) Since the present invention is configured as described above, in an engine idle speed control device that controls the idle speed by adjusting the ignition timing, the stability of the idle speed when the engine is cold is ensured. At the same time, it is possible to secure surplus torque against external loads and improve engine stall resistance.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2 is an overall system diagram of an embodiment of the invention, Fig. 3 is a functional block diagram of the embodiment, Fig. 4 is a characteristic diagram of the embodiment, and Fig. 4 is a characteristic diagram of the embodiment. 5 to 8 are flowcharts for executing control in this embodiment. 1: Engine, 10: Spark plug, 19: Ignition coil, 20. Control unit, 21: Water temperature sensor.

Claims (1)

[Claims] (1) An engine temperature detection means, an engine rotation speed detection means, a basic ignition timing setting means that sets the basic ignition timing to the retarded side as the engine temperature is lower, and when the engine rotation speed at idle is lower than the target value. a rotation speed feedback correction means for correcting the basic ignition timing to an advance side or to a retard side when the rotation speed is high; and an ignition drive means for receiving an output of the rotation speed feedback correction means and driving an ignition device of the engine. 1. An engine idle speed control device comprising control center value changing means for changing the control center value of the rotation speed feedback by the rotation speed feedback correction means to a retarded side when the engine temperature is low.