JP2000329046A - Ignition timing control device for spark ignition engine - Google Patents

Abstract

(57) [Summary] [Problem] In an engine having a relatively low rotation speed such as a large engine such as a bus or a truck, at the time of idling operation,
Provided is an ignition timing control device for a spark ignition type engine capable of performing stable operation while maintaining an engine speed substantially constant and hardly stalling even if the engine speed becomes extremely low for some reason. When the rotational speed Ne is lower than a control lower limit rotational speed Na, a setting of an advance amount of an engine ignition timing It is constant, and a control lower limit rotational speed Na and a control upper limit rotational speed Nb are set.
Is decreased with an increase in the rotation speed Ne, and between the control upper limit rotation speed Nb and the basic characteristic return rotation speed Nc, the advance is made so as to return to the basic ignition timing advance characteristic with the increase in the rotation speed. When the rotation speed is larger than the basic characteristic return rotation speed Nc, the engine is advanced according to the basic ignition timing advance characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition timing of a spark ignition type engine which can operate an engine at a stable rotation speed during idling operation in a gasoline engine, CNG (compressed natural gas), LPG (liquefied petroleum gas) engine or the like. The present invention relates to a control device.

[0002]

2. Description of the Related Art Normally, CNG has been developed from the viewpoint of gasoline engines mounted on vehicles and pollution prevention.
In a spark ignition type engine such as a (compressed natural gas) engine, if the ignition timing changes, the compression work and the magnitude of exhaust loss change even with the same amount of fuel. Minimum advance for the Be
There is an optimal ignition timing called stTorque).

As will be described below, the optimum ignition timing (MBT) becomes slower as the rotation speed and load become lower, and conversely it becomes faster as the rotation speed becomes lower and the load becomes higher.

That is, in the case of a low load, the amount of air is small, and the turbulence of the working gas generated in the intake stroke is rapidly attenuated, so that the combustion speed is reduced. Further, the negative pressure in the intake pipe is high, and the ratio of residual gas And the combustion speed decreases, it is necessary to relatively advance the ignition timing and increase the advance amount.
T becomes faster.

Further, since the turbulence level of the working gas increases with an increase in the number of revolutions, the heat generation period in terms of the crank angle does not change much with respect to the number of revolutions, and the absolute time from ignition to heat generation is substantially equal. It will be constant. However, even if the absolute time is the same, when converted to crank angle,
The higher the rotation speed, the larger the crank angle. As a result, the higher the rotation speed, the faster the ignition timing.

[0006] Normally, the operation at a constant air-fuel ratio is performed near the stoichiometric air-fuel ratio, so that the MBT advances in proportion to the rotation speed. Therefore, the ignition timing of the engine is set so as to advance as the engine speed increases, and the basic ignition timing advancement characteristic Cb is a straight line that rises to the right as shown in FIG.

[0007]

However, in consideration of idling operation, idling operation at a relatively high rotation speed in the engine of a passenger car can stably operate idling, but in a large engine used for a bus or a truck, etc. For some engines, the number of revolutions during idling operation is low, and the number of revolutions during idling operation is low for special applications.

In these low-speed engines,
Although the number of revolutions for idling operation is originally set to be low, idling operation at a lower number of revolutions has been required in order to reduce fuel consumption and noise.
This low-speed idling operation has a problem that the rotation speed fluctuates, the operation becomes unstable, and in some cases, the engine stalls.

That is, in these engines, it is difficult to control the operation in accordance with the stoichiometric air-fuel ratio in an operation region with a remarkably low rotational speed due to the characteristics of the fuel supply system.
It shifts to either lean or rich, and the lower the rotation speed, the more it deviates from the stoichiometric air-fuel ratio,
The advance amount actually required is different from the basic ignition timing advance characteristic Cb in the case of the constant air-fuel ratio in FIG. 5 and, as shown by the solid line in FIG. Go away in the corner direction.

Therefore, when the idling operation control based on the basic ignition timing advancement characteristic Cb shown in FIG. 5 is performed as in the prior art, the idling operation becomes unstable, and particularly, the optimum ignition timing ( In an extremely low rotation portion where the MBT is separated from the basic ignition timing advancement characteristic Cb in the advance direction as the rotation decreases, there is a problem that the output is reduced, the stall is likely to occur, and engine stall is likely to occur.

In the control of the idling operation,
Operation control is also performed by an idle speed control (ISC) that controls the number of revolutions by changing the amount of intake air regardless of the ignition timing. However, in this case, the response is poor and the rotation speed is low. There is a limit to idling operation that is stable in number.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. An object of the present invention is to reduce the engine speed during idling operation in a relatively low-speed engine such as a large engine such as a bus or a truck. It is an object of the present invention to provide an ignition timing control device for a spark ignition type engine that is capable of performing stable operation while being maintained at a substantially constant speed and that is difficult to stall even if the engine speed becomes extremely low for some reason.

[0013]

SUMMARY OF THE INVENTION An ignition timing control apparatus for a spark ignition type engine for achieving the above object is as follows.
An ignition timing control device that includes a rotation speed detection unit that detects a rotation speed of the engine, and controls an ignition timing of a spark ignition type engine based on the rotation speed detected by the rotation speed detection unit.
At the time of idling, the lower limit and the upper limit of the rotation speed range for performing control so as to stabilize to the target idle rotation speed are set with the control lower limit rotation speed and the control upper limit rotation speed sandwiching the target idle rotation speed, and the basic characteristic return rotation. Speed is set higher than the control upper limit rotation speed, and when the detected rotation speed is in a first range lower than the control lower limit rotation speed, the ignition timing advance amount is fixed, and the detected When the rotation speed is in the second range between the control lower limit rotation speed and the control upper limit rotation speed, the advance amount of the ignition timing is reduced with an increase in the rotation speed, and the detected rotation speed is the rotation speed. When the rotation speed is within the third range between the control upper limit rotation speed and the basic characteristic return rotation speed, the advance amount of the ignition timing is advanced to return to the basic ignition timing advance characteristic as the rotation speed increases. And the detected rotation speed is When in serial basic characteristic restoration speed greater than the fourth range, by advancing the advance amount in accordance with the basic ignition timing advance characteristic, configured to control the ignition timing.

The spark ignition type engine is also effective in a gasoline engine, but can be particularly effective in a CNG (Compressed Natural Gas) or LPG (liquefied petroleum gas) engine. it can.

When the rotational speed is in the first range lower than the control lower limit rotational speed, the fact that the amount of advance of the ignition timing is constant means not only a single value but also a variation range of several%. Means that

In the second range between the control lower limit rotation speed and the control upper limit rotation speed, it is determined that the idle operation is performed in the range of the rotation speed, and the engine rotation speed is set to the target idle rotation speed. The control lower limit rotation speed and the control upper limit rotation speed are set in advance from the target idle rotation speed and the characteristics of the engine.

The third range between the control upper limit rotational speed and the basic characteristic return rotational speed is narrowed, and the advance is made so as to match the basic advance characteristic as soon as possible as the rotational speed increases. It is preferable that the rate of increase of the advance angle be such that the driving characteristics of the actual vehicle do not cause a sense of incongruity.

Therefore, the rate of increase in the advance amount of the ignition timing with the increase in the rotational speed is greater in the third range than in the fourth range.

In the idling operation, the ignition timing control device having the above-described configuration increases the ignition timing by increasing the ignition timing in a region where the rotational speed is slightly lower than the target idle speed, and conversely, the rotational speed is slightly higher than the target idle speed. In the numerical range, since the advance amount is reduced, the rotational speed of the idling operation is stabilized near the target idle rotational speed.

In the rotation speed region equal to or lower than the control lower limit rotation speed, since the advance amount is set to a constant value, the operation can be performed without stall even at extremely low rotation speed.

That is, it is difficult to control the air-fuel ratio to an appropriate value at an extremely low rotation speed. In particular, the lower the rotation speed becomes, the more difficult it becomes, and in many cases, an extremely rich or lean state occurs. Further, in gas engines such as CNG and LPG, the mixture of air and fuel is particularly deteriorated at low revolutions, and a phenomenon in which a lean mixture or a rich mixture exists in the vicinity of an ignition plug is likely to occur. Hard to do,
In the worst case, a stall will result.

For example, as shown in FIG. 6, the MBT also changes depending on the air-fuel ratio, departs from the basic ignition timing advance characteristic Cb based on the stoichiometric air-fuel ratio, and the MBT shifts in the advance direction. Considering this, it is necessary to control the ignition timing to advance from the basic ignition timing advance characteristic Cb as the rotation speed decreases at an extremely low rotation speed.

Accordingly, in the rotation speed region equal to or lower than the control lower limit rotation speed, the amount of advance is set to a substantially constant value, so that the engine torque in this extremely low rotation speed region increases. Therefore, it is improved that the control of the related art takes a long time to stall or return to the target rotation speed.

Further, in the rotational speed region equal to or higher than the control upper limit rotational speed, the basic ignition timing advance characteristic is quickly returned.
Normal ignition timing control is performed, and normal operation becomes possible.

[0025]

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

The ignition timing control device for controlling the ignition timing of the spark ignition type engine controls the operating speed Ne detected by the speed detecting means for detecting the engine speed as various control speeds. And controls the ignition timing according to the ignition timing advance characteristic Ca as shown in FIG.

The ignition timing advancing characteristic Ca is determined by setting the control lower limit rotation speed Na and the control upper limit rotation speed Nb, which are the lower and upper limits of the rotation speed range Z2 for performing control so as to be stabilized at the target idle rotation speed Nt. It is set with the rotation speed Nt in between. Further, a basic characteristic return rotation speed Nc that returns to the basic ignition timing advance characteristic Cb is set.

The basic characteristic return rotation speed Nc is set higher than the control upper limit rotation speed Nb.
a <Nt ≦ Nb <Nc.

As shown in FIG. 1, when the ignition timing advance characteristic Ca is in the first range Z1 lower than the control lower limit rotation speed Na, the ignition timing advance amount It (° BTD
C: crank angle before top dead center) is a constant value It1, and the second range Z between the control lower limit rotation speed Na and the control upper limit rotation speed Nb.
2, the advance amount It of the ignition timing decreases with an increase in the rotation speed Ne, and when the ignition timing advances in the third range Z3 between the control upper limit rotation speed Nb and the basic characteristic return rotation speed Nc,
With the increase in the rotation speed Ne, the advance amount It of the ignition timing is quickly changed to the basic ignition timing advance characteristic Cb and the basic ignition timing is advanced at a relatively large advance amount that does not cause a sense of incongruity in accordance with the actual operation characteristics. When the rotation is returned to the angular characteristic Cb and is in the fourth range Z4 which is larger than the basic characteristic return rotation speed Nc, it matches the basic ignition timing advancement characteristic Cb, and the ignition timing advance amount It increases with the rotation speed Ne. Grows gently.

In each of the first to fourth ranges, the advancing angle It indicates that the inclination angles in FIG.
2, θ3, θ4, and It = θ1 × Ne + It1 = I
t1, It = θ2 × Ne + It2, It = θ3 × Ne +
When It3 and It = θ4 × Ne + It4, the slopes θ1 to θ4 of the characteristic curves in each range are θ1 = 0,
θ2 <0, θ3>θ4> 0.

These various data for control are prepared in advance based on experimental results, measured results, calculated results, etc., taking into account the characteristics of the fuel supply device of the engine, the target rotational speed Nt during idling operation, the response characteristics, and the like. Set the engine controller (C
PU), etc., and stored.

Next, the ignition control based on the ignition timing advance characteristic Ca of FIG. 1 is performed based on the ignition timing control flowchart as shown in FIG.

The ignition timing control flow of FIG. 3 is repeatedly called from the main operation control flow that governs the operation of the engine. After the ignition timing advance is determined, the main ignition control is performed with the determined advance value. Returning to the operation control flow, ignition is performed based on this advance value. Note that this advance value may be corrected as needed.

According to the timing control flow of FIG. 3, the advance angle value is obtained as follows.

First, when this timing control flow is called and started, various data are input in step S10. These data include the measured rotation speed Ne, the control lower limit rotation speed Na, the control upper limit rotation speed Nb, the basic characteristic return rotation speed Nc, and θ1, θ2, θ3, θ4, It1, and It.
2, It3 and It4.

Then, first, in step S11, the rotational speed Ne
Is in the first range Z1 (Ne ≦ Na), and
If the rotation speed Ne is in the first range Z1, in step S12,
Set It = θ1 × Ne + It1 = It1 and return.

If the rotation speed Ne is not in the first range Z1 in step S11, it is determined in step S13 whether or not the rotation speed Ne is in the second range Z2 (Na <Ne ≦ Nb). If the number Ne is in the second range Z2, step S14
Then, It = θ2 × Ne + It2, and the process returns.

If the rotational speed Ne is not in the second range in step S13, the rotational speed Ne is set in the third range Z3 in step S15.
(Nb <Ne ≦ Nc) is determined, and the rotation speed N
If e is in the third range Z3, in step S16, It = θ
Set 3 × Ne + It3 and return.

If it is determined in step S15 that the rotation speed Ne is not in the third range Z3, the rotation speed Ne is changed to the fourth range Z4 (N
c <Ne), and in step S17, It = θ
4 × Ne + It4, and the process returns.

By performing the above-described ignition timing control by the ignition timing control device for controlling the ignition timing of the spark ignition type engine having the above-described configuration, the idling operation during the second range Z2 in FIG. When the number Ne increases and becomes greater than the target idling rotational speed Nt, the ignition timing is delayed, and the rotational speed Ne is decreased, so that the engine speed returns to the target idling rotational speed Nt. When the rotation speed Ne decreases and becomes smaller than the target idling rotation speed Nt, the advance value It increases, so that the ignition timing advances and the rotation speed Ne increases.

Therefore, in the idling operation during the second range Z2, the ignition control is performed so that the rotation speed Ne becomes the target idling rotation speed Nt.

When this effect is viewed in the time series of FIG. 4, when the engine speed Ne rises above the target idle engine speed Nt at the point A in the idling operation as shown by a dotted line, the ignition timing It immediately changes from the idle ignition timing It0. The delay rotation speed Ne decreases.

When the rotation speed falls below the target idle rotation speed Nt as indicated by the dotted line at point B, the ignition timing It immediately advances from the idle ignition timing It0 and the rotation speed Ne.
Rises. Therefore, as indicated by a straight line, the idling operation can be performed with a very small fluctuation in the vicinity of the target idle speed Nt.

Further, in the rotation speed range Z1 below the control lower limit rotation speed Na, the advance angle It is set to a constant value It.
Since the optimum ignition timing at extremely low rotation can be provided as 1, the minimum output can be maintained to prevent stall due to stall.

That is, in the extremely low rotation speed range Z1, it is difficult to control the air-fuel ratio to an appropriate value in a gasoline engine, and in a gas engine such as CNG or LPG, mixing of air and fuel is difficult. As a result, the vicinity of the spark plug becomes extremely rich or lean, and normal combustion is difficult to be performed. In the worst case, a stall occurs. However, as the rotational speed Ne decreases in the extremely low rotational speed region Z1, the rotational speed Ne decreases. Since the basic ignition timing advance characteristic Cb is advanced to control the advance amount It to be a constant value It1, the rotational force of the engine in this extremely low rotation range Z1 increases.
The engine stall prevention and the time required to return to the target idle speed Nt can be reduced.

Further, in the rotation speed regions Z3 and Z4 which are equal to or higher than the control upper limit rotation speed Nb, since the basic ignition timing advance characteristic Cb is quickly returned, normal ignition timing control is performed, and normal operation becomes possible.

Note that Na to Nt and Nt to N in FIG.
As shown in FIG. 2, the ignition timing during b
1, may differ from θ22, and even when Nt = Nb, the effect of stable operation can be obtained.

Further, the ignition timing advancing characteristics may be not only characteristics that can be expressed only by a combination of straight lines, but also characteristics that partially express them by a curve. May be calculated from the function display, or may be calculated from data of the ignition timing (advance amount) based on the rotation speed, for example, by comparing the ignition timing data with map data or the like input for each rotation speed. Good.

The fact that the ignition timing advance amount It in the first range Z1 is set to the constant value It1 means that, in the actual case, the only value It1 is the only value It1 due to control. Instead, it may include a fluctuation range of several percent.

[0050]

As described above, according to the ignition timing control apparatus for idling of the present invention, control can be performed so as to converge on the target idling speed in the vicinity of the target idling speed for idling operation. In the engine speed range below the control lower limit engine speed that is lower than the target engine idle speed, the ignition timing is substantially constant and stall is prevented, so that stall resistance is improved. be able to.

That is, in the extremely low rotation speed region, the vicinity of the spark plug becomes extremely rich or lean, and normal combustion is hardly performed. However, in the extremely low rotation speed region, the basic ignition timing advances as the rotation speed decreases. Since the angle is advanced from the angular characteristic and the control is performed with the amount of advance constant, the engine torque in this extremely low speed range increases, preventing engine stall and reducing the time required to return to the target idle speed. Can be shortened.

In the rotation speed region equal to or higher than the control upper limit rotation speed, the basic ignition timing advance characteristics are quickly returned.
Normal ignition timing control is performed, and normal operation becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram of an ignition timing advance characteristic showing a relationship between a rotation speed and an ignition timing used for controlling an ignition timing according to the present invention.

FIG. 2 is another ignition timing advance characteristic showing the relationship between the rotation speed and the ignition timing used for controlling the ignition timing according to the present invention.

FIG. 3 is a flowchart for ignition timing control showing the ignition timing control of the present invention.

FIG. 4 is a time series diagram of the advance amount of ignition timing and the number of revolutions during idling operation showing the control effect of the present invention.

FIG. 5 is a diagram of a basic ignition timing advance characteristic showing a relationship between a rotation speed and an ignition timing used for controlling the ignition timing in the related art.

FIG. 6 is a diagram showing a relationship between an optimal ignition timing and an air-fuel ratio.

[Explanation of symbols]

 It Ignition timing (advance angle) Na Control lower limit speed Nb Control upper limit speed Nc Basic characteristic return speed Ne Speed (detected value) Nt Idle target speed

Claims (2)

[Claims] An ignition timing control device for controlling the ignition timing of a spark ignition type engine based on the number of revolutions detected by the number of revolutions detected by the number of revolutions detected by the number of revolutions detected by the number of revolutions of the engine. The control lower limit rotation speed and the control upper limit rotation speed which are the lower limit and the upper limit of the rotation speed range for performing control to stabilize the target idle rotation speed are set with the target idle rotation speed interposed therebetween, and the basic characteristic return rotation speed is set. When the detected rotation speed is in a first range lower than the control lower limit rotation speed, the advance amount of the ignition timing is fixed, and the detected rotation speed is set higher than the control upper limit rotation speed. Is in a second range between the control lower limit rotation speed and the control upper limit rotation speed, the advance amount of the ignition timing is reduced with an increase in the rotation speed, and the detected rotation speed is the control upper limit. Speed When the rotation speed is within the third range between the basic characteristic return rotation speed and the rotation speed, the advance amount of the ignition timing is advanced so as to return to the basic ignition timing advance characteristic. If the determined rotation speed is in a fourth range greater than the basic characteristic return rotation speed, the ignition timing is advanced according to the basic ignition timing advancement characteristic to control the ignition timing. Control device. 2. The ignition timing control device for a spark ignition engine according to claim 1, wherein said spark ignition engine is a CNG engine.