JP4445625B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine control device, and more particularly to a device that prevents the occurrence of pre-ignition.
[0002]
[Prior art]
There is one that prevents the occurrence of pre-ignition (a phenomenon in which self-ignition occurs due to a high temperature inside the cylinder regardless of ignition by the spark plug and is accompanied by a sudden pressure increase) (see JP-A-11-182300). ).
[0003]
Here, it is determined whether the fuel used in the engine is regular or high-octane, and when regular is judged, the idle rotation speed is set higher than when high-octane, or idle in the electric throttle system The occurrence of pre-ignition is avoided by setting a lower upper limiter value that limits the throttle opening at that time, or by setting a higher idle rotation speed and lowering the upper limiter value.
[0004]
[Problems to be solved by the invention]
By the way, in order to prevent the deterioration of the practical fuel consumption, it is not desired to increase the idle rotation speed until the last minute, and in order to prevent the deterioration of the acceleration driving performance, it is not desired to limit the throttle opening to the last minute. On the other hand, the occurrence of pre-ignition is governed by the intake air temperature as shown in FIG. 2, and the pre-ignition is more likely to occur as the intake air temperature is higher.
[0005]
Therefore, by accurately grasping the pre-ignition generation area based on the intake air temperature, if the actual fuel economy is to be improved, the area that does not need to increase the idle rotation speed is expanded, and the acceleration drivability is ensured. Although it is necessary to expand the area where it is not necessary to limit the throttle opening, in the conventional device that avoids the occurrence of pre-ignition based on the fuel properties as described above, the intake air temperature is high because it is not based on the intake air temperature. In order to prevent pre-ignition even under conditions, it is necessary to set a high idle speed with a sufficient safety allowance, or to set an excessive upper limit value. It is difficult to ensure.
[0006]
As can be understood from FIG. 2, preignition is more likely to occur as the intake air temperature is higher. Therefore, in the region where preignition occurs, the upper limit value of the throttle valve opening is reduced to limit the intake air amount ( (The throttle valve opens only to the upper limit value even when the accelerator pedal is largely depressed in the idle state.) By increasing the idle speed, pre-ignition can be avoided, so the upper limit value of the throttle valve opening can be reduced. Pre-ignition can be avoided by either increasing the idling speed, but if both operations are performed simultaneously as in the conventional device, the upper limit value of the throttle valve opening is reduced and the intake air is reduced. Deterioration of acceleration from idle state by limiting the amount and idle rotation speed And the deterioration of fuel economy due to the high will both occur.
[0007]
Therefore, when the present invention determines that the pre-ignition generation region has been reached during idling based on the intake air temperature, only the operation of either decreasing the upper limit value of the throttle valve opening or increasing the idling speed is performed. First to avoid pre-ignition, and when it is determined that the temperature has reached a temperature range where it is not possible to avoid pre-ignition by only one of the performed operations, the other operation that was not performed first is performed and the pre-ignition is performed. By avoiding the object, an object is to avoid pre-ignition while balancing the practical fuel consumption in the idle state and the acceleration performance from the idle state.
[0008]
In addition, there is a disclosure that the pre-ignition avoidance control is performed only when the intake air temperature is detected and the intake air temperature is, for example, 80 ° C. or more (pre-ignition generation region) (see Japanese Patent Laid-Open No. 11-210536). . This only discloses that the intake air temperature is used to determine whether or not it is a pre-ignition occurrence region, and the two operations described above are performed stepwise in the pre-ignition occurrence region as in the present invention. Is not disclosed.
[0009]
[Means for Solving the Problems]
As shown in FIG. 12, the first invention is a means 22 for calculating a target throttle valve opening based on engine operating conditions, and when the target throttle valve opening exceeds an upper limit value of the throttle valve opening. The means 23 for limiting the target throttle valve opening to the upper limit value, the actuator 24 for driving the throttle valve 21 to achieve the limited target throttle valve opening, and the target engine speed at the time of idling. When the intake air temperature becomes high with the idling speed constant, the abscissa indicates the intake air temperature, and the ordinate indicates the idling speed. In the pre-ignition occurrence area diagram, the pre-ignition occurrence area on the higher intake air temperature side and the lower idle rotation speed side The intake air temperature is lower than the boundary temperature A obtained from the boundary line α when the pre-ignition avoidance control is not performed on the boundary line between the low intake air temperature side and the high idle rotation speed pre-ignition region. If it becomes higher, first, by reducing the upper limit value of the throttle valve opening, the boundary line α is shifted to the right side of the pre-ignition generation area diagram, and the temperature range in which the idle rotation speed can be maintained is expanded to increase the pre-ignition. If the intake air temperature further rises and exceeds the boundary temperature B obtained from the shifted boundary line β, the pre-ignition is avoided by increasing the idle rotation speed along the shifted boundary line β. Means 27.
[0010]
As shown in FIG. 13, the second invention is a means 22 for calculating a target throttle valve opening based on engine operating conditions, and when the target throttle valve opening exceeds an upper limit value of the throttle valve opening. The means 23 for limiting the target throttle valve opening to the upper limit value, the actuator 24 for driving the throttle valve 21 to achieve the limited target throttle valve opening, and the target engine speed at the time of idling. When the intake air temperature becomes high with the idling speed constant, the abscissa indicates the intake air temperature, and the ordinate indicates the idling speed. In the pre-ignition occurrence area diagram, the pre-ignition occurrence area on the higher intake air temperature side and the lower idle rotation speed side From the boundary temperature A obtained from the boundary line γ when the throttle valve upper limit value is at the fully open position, which is the boundary line between the low intake air temperature side and the high idle rotation speed side pre-ignition region However, if the intake air temperature rises, the target idle rotation speed is first increased along the boundary γ to avoid pre-ignition, the intake air temperature further rises and the idle rotation speed reaches the upper limit value, and the upper limit value is reached. A means 31 is provided for avoiding pre-ignition by reducing the upper limit value of the throttle valve opening when the boundary temperature C obtained from the reached idle rotation speed and the boundary line γ is exceeded .
[0013]
In the third aspect of the invention comprises means for detecting an engine coolant temperature in the first or second invention, the water temperature is carried out a control to avoid the preignition when on a given value or more.
[0014]
【The invention's effect】
In the first invention, when the intake air temperature becomes high while the idling speed is constant, the horizontal axis indicates the intake air temperature, and the vertical axis indicates the idling speed. Boundary line α when the pre-ignition avoidance control is not performed between the low-speed preignition occurrence area, the low intake air temperature side, and the high idle rotation speed-side preignition non-occurrence area If the intake air temperature becomes higher than the boundary temperature A obtained from the above, first, by reducing the upper limit value of the throttle valve opening, the boundary line α is shifted to the right in the pre-ignition generation region diagram, and the idle rotation speed is maintained as it is. Boundary temperature obtained from boundary β after shifting by increasing the temperature range to avoid pre-ignition and further increasing the intake air temperature If more than B, and avoids pre-ignition by slide into high idle speed along the boundary line after the shift beta. In the second invention, when the intake air temperature becomes high while the idling speed is constant, the horizontal axis indicates the intake air temperature, and the vertical axis indicates the idling speed. When the throttle valve upper limit value is at the fully open position, the boundary between the low-speed preignition occurrence area, the low intake air temperature side, and the idle speed high-side preignition non-occurrence area If the intake air temperature becomes higher than the boundary temperature A obtained from the boundary line γ, the pre-ignition is avoided by first increasing the target idle rotation speed along the boundary line γ, and the intake air temperature further increases to increase the idle rotation speed. Reaches the upper limit value and exceeds the boundary temperature C obtained from the idle speed and the boundary line γ that has reached the upper limit value, the throttle valve opening is increased. To avoid pre-ignition by reducing the limiter value.
[0015]
Thus, the first and second inventions avoid pre-ignition by executing two operations step by step. That is, according to the first aspect of the invention, the idle rotational speed can be kept unchanged while avoiding pre-ignition only by first reducing the upper limit value of the throttle valve opening. This makes it possible to avoid pre-ignition while minimizing the deterioration of practical fuel consumption during idling. According to the second aspect of the invention, the upper limit value of the throttle valve opening can be kept as it is while avoiding pre-ignition only by increasing the idling speed first. This makes it possible to avoid pre-ignition while minimizing deterioration in acceleration from the idle state.
[0017]
According to the fifth invention, since neither of the two operations is performed in the water temperature range where it is not necessary to perform the preignition avoidance control, it is possible to prevent the deterioration of the practical fuel consumption during idling and the deterioration of acceleration from the idling state.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 1 denotes an engine body, which is provided with a fuel injection valve 4 facing directly into a combustion chamber, and injects fuel so that a predetermined air-fuel ratio is obtained according to operating conditions by an injection signal from a control unit 11 . 2 is an intake passage, 3 is a throttle valve control device capable of controlling the opening of the throttle valve 3A regardless of the accelerator pedal by a step motor 3B, and 5 is an ignition plug.
[0019]
The control unit 11 receives an engine rotation speed signal from the crank angle sensor 12, an intake air amount signal from the air flow meter 13, an engine water temperature signal from the water temperature sensor 15, and the like based on these values. Drive in.
[0020]
The control unit 11 also controls the opening of the throttle valve 3A as follows. First, the target air amount is calculated based on the accelerator opening detected by the accelerator sensor 14 and the engine speed, the target throttle valve opening area is calculated from the target air amount and the engine speed, and the target throttle is calculated from the opening area. Calculate the valve opening. Then, the amount of drive applied to the step motor 3B as a throttle actuator is feedback-controlled so that the actual throttle valve opening detected by the throttle sensor 16 matches the target throttle valve opening. On the other hand, during idle, the feedback correction air amount is calculated by integral control or the like so that the engine rotation speed approaches the target idle rotation speed, and the target air amount is corrected by the feedback correction air amount.
[0021]
In addition, the control unit 11 has a function of setting an upper limiter for the throttle valve opening for failsafe or the like. The upper limit value is a fully closed position at the minimum and a fully open position at the maximum. Normally, the fully open position is the upper limit value. For this reason, when the calculated value of the target throttle valve opening exceeds the upper limit limiter, the calculated value of the target throttle valve opening is limited to the upper limit limiter.
[0022]
As described in the section of the prior art, pre-ignition is likely to occur when the idle rotation speed is low or the compression ratio is high. The former is because the lower the idle rotation speed, the longer it takes for the air-fuel mixture sucked into the cylinder to be ignited by the spark plug, which increases the amount of heat received from the engine and raises the air-fuel mixture temperature. . The latter is because when the same amount of air is inhaled, the temperature rise increases as the compression ratio increases (the volume after compression decreases). In order to avoid such pre-ignition, the control unit 11 controls the upper limit value of the throttle valve opening and the target idle speed as follows.
[0023]
<1> First Embodiment: When it is determined that a pre-ignition generation region has occurred during idling based on the intake air temperature from an intake air temperature sensor (installed immediately downstream of the air flow meter 13) 17, first, an upper limit limiter for the throttle valve opening The target idle speed is increased when it is determined that the temperature range is such that pre-ignition cannot be avoided only by reducing the value and reducing the upper limit value of the throttle valve opening based on the intake air temperature.
[0024]
<2> Or, Second Embodiment: When it is determined that the pre-ignition generation region has been reached based on the intake air temperature, the target idle rotation speed is first increased, and the target idle rotation speed is also set based on the intake air temperature. When it is determined that the temperature range is such that preignition cannot be avoided only by increasing the value, the upper limiter value is decreased.
[0025]
The above <1> will be specifically described with reference to FIG. For simplicity, the conditions other than the intake air temperature are not changed. Further, the boundary line of the pre-ignition occurrence region when the pre-ignition avoidance control in the present invention is not performed is defined as α. When the intake air temperature increases with the idling rotational speed being constant, the boundary of the pre-ignition generation region is reached at the temperature of A. In a temperature range higher than the boundary temperature A, first, the pre-ignition is avoided only by reducing the upper limit value of the throttle valve opening to a predetermined intermediate opening (that is, the idling speed is not increased). At this time, since the boundary line of the pre-ignition generation region shifts to the right and moves to the position β, the idle rotation speed can be maintained as it is in the temperature range from A to B. When the intake air temperature further rises to a temperature range equal to or higher than B, pre-ignition is avoided by increasing the idle rotation speed along the boundary line β.
[0026]
When controlled in this way, the characteristic of the target idle speed with respect to the intake air temperature is as indicated by the thick solid line in FIG. For comparison, FIG. 3 shows what happens to the characteristics of the idle rotation speed with respect to the intake air temperature when the upper limit value is not fully reduced and the upper limit value is at the fully open position (when the throttle valve opening degree is not regulated). It is a thick broken line.
[0027]
Next, the above <2> will be specifically described with reference to FIG. For comparison with FIG. 3, the idle rotation speed in the region where the intake air temperature is low and the boundary temperature of the pre-ignition generation region when the idle rotation speed and the throttle valve upper limiter value are in the fully open position are the same as in FIG. Suppose that However, in FIG. 3, as long as the idle rotation speed is increased in the intake air temperature range of B or higher, the occurrence of pre-ignition can be avoided up to the maximum intake air temperature without the idle rotation speed reaching the upper limit value. FIG. 4 shows a case where a temperature range (a temperature range of C or more in the drawing) where pre-ignition occurs remains even when the idle rotation speed is set to the upper limit value. Therefore, the boundary line corresponding to the boundary line α in FIG.
[0028]
In this case, when the intake air temperature is higher than A, the pre-ignition is avoided only by increasing the target idle rotation speed along the boundary line γ of the pre-ignition generation region (that is, the upper limit value is kept at the fully open position). When the intake air temperature rises and the idling speed exceeds the upper limit temperature C, the upper limit value of the throttle valve opening is reduced (preventing pre-ignition by limiting the intake air amount of the engine). To do.
[0029]
The characteristic of the target idle rotation speed when controlled in this way is as indicated by the thick solid line in FIG. As can be seen from the comparison with FIG. 3, the difference between the two is that in the pre-ignition generation region, FIG. 3 only avoids the pre-ignition by only reducing the upper limit value of the throttle valve, whereas in FIG. The first point is to avoid pre-ignition only by increasing the speed.
[0030]
The contents of these controls executed by the control unit 11 will be described in detail with reference to the flowcharts of FIGS.
[0031]
The flowchart of FIG. 5 is for setting the target idle speed and the upper limit value of the throttle valve opening according to the first embodiment, and is executed at regular intervals (for example, every 10 ms).
[0032]
In step 1, the intake air temperature is read, and this intake air temperature is compared with a constant value. This constant value is A in FIG. 3, that is, the boundary of the pre-ignition generation region when the idling speed at that time is maintained and the upper limit value of the throttle valve opening is not reduced (the upper limit value at this time is the fully open position). Temperature. This value is given in advance.
[0033]
If the intake air temperature is equal to or higher than a certain value, the routine proceeds to step 3 where a predetermined intermediate opening is set as the upper limit value of the throttle valve opening. This intermediate opening is determined in consideration of the acceleration performance from the idle state. That is, since the idle air amount is proportional to the engine output, the temperature range where the idle rotation speed can be maintained as it is as the upper limiter value is brought closer to the fully closed position is expanded, while the output is insufficient and the desired acceleration performance is obtained. Absent. On the contrary, if the upper limit value is brought close to the fully open position, the temperature range in which the idle rotation speed can be maintained as it is is limited. Therefore, it is preferable to select the fully closed throttle valve opening as an intermediate opening within a range that does not hinder the acceleration driving performance from the idle state.
[0034]
In step 4, a target idle speed is set by searching a table having the contents shown in FIG. 6 from the intake air temperature. FIG. 6 gives an idling speed that increases as the intake air temperature rises in a temperature range equal to or higher than B (a temperature range in which pre-ignition cannot be avoided only by reducing the upper limit value of the throttle valve opening). That is, the characteristic of FIG. 6 is the same as the characteristic of the thick solid line in FIG.
[0035]
On the other hand, since it is not necessary to avoid pre-ignition when the intake air temperature is less than a certain value, the process proceeds from step 2 to steps 5 and 6, and the fully open position is set as the upper limit value, and the target idle rotation is performed as in the conventional case. Calculate the speed.
[0036]
As described above, in the first embodiment, when the pre-ignition occurs in the idling state, the pre-ignition is avoided only by reducing the upper limit value while the idling speed remains unchanged, and then the upper limit limiter of the throttle valve opening. If the temperature is in a range where pre-ignition cannot be avoided simply by reducing the value, this time the pre-ignition is avoided by increasing the idle rotation speed. Can be avoided.
[0037]
The flowchart of FIG. 7 is for setting the target idle rotation speed and the upper limit value of the throttle valve opening according to the second embodiment, and is executed at regular intervals (for example, every 10 ms).
[0038]
In step 11, the intake air temperature is read, and a table having the contents shown in FIG. 8 is retrieved from the intake air temperature to set a target idle speed. The characteristics of FIG. 8 are the same as the characteristics of the thick solid line in FIG.
[0039]
In step 13, the intake air temperature is compared with a constant value. The constant value is C in FIG. 4, that is, the boundary temperature of the pre-ignition generation region when the upper limit value of the throttle valve opening is the fully open position and the idle rotation speed is the upper limit value. This temperature is given in advance.
[0040]
If the intake air temperature is equal to or higher than a certain value, the routine proceeds to step 14 where a predetermined intermediate opening is set as the upper limit value of the throttle valve opening. This intermediate opening is determined in consideration of acceleration from the idle state as in the first embodiment.
[0041]
On the other hand, when the intake air temperature is less than a certain value, the routine proceeds from step 13 to step 15, and the fully open position is set as the upper limit value.
[0042]
As described above, in the second embodiment, when the pre-ignition occurs during idling, the pre-ignition can be avoided only by increasing the idling speed while maintaining the upper limit value of the throttle valve opening, and then the target idling speed. When it reaches a temperature range where it is not possible to avoid pre-ignition only by increasing the speed, this time, by reducing the upper limiter value, the pre-ignition is avoided, so the deterioration of acceleration from the idle state is minimized. Pre-ignition can be avoided while holding down.
[0043]
The flowcharts of FIGS. 9 and 10 are the third and fourth embodiments, respectively, and are replaced with FIGS. 5 and 7, respectively. In FIG. 9, the same step number is assigned to the same part as in FIG. 5, and in FIG. 10, the same step number is assigned to the same part as in FIG.
[0044]
In the third and fourth embodiments, the engine water temperature is limited with respect to the first and second embodiments, and pre-ignition avoidance control is not performed when the engine water temperature is lower than a predetermined value D. (Steps 21 and 22).
[0045]
This will be described with reference to FIG. 11. This figure shows how the pre-ignition occurrence region changes when the intake air temperature and the engine water temperature are changed. Although the pre-ignition generation area expands as the idle speed decreases, the pre-ignition does not occur regardless of the intake air temperature in the temperature range where the engine water temperature is lower than the constant value D. Therefore, the pre-ignition occurs in the low water temperature range. Avoidance control can be avoided.
[0046]
In this way, in the low water temperature range where there is no need to perform pre-ignition avoidance control, the throttle valve opening is not restricted and the target idle speed is not changed. Deterioration can be prevented.
[0047]
In the embodiment, the target idle rotation speed is described as being given by the map values (substantially continuous values) shown in FIGS. 6 and 8. However, the present invention is not limited to this and can be given by stepwise values. Nor.
[0048]
Further, in the embodiment, the engine provided with the fuel injection valve directly facing the combustion chamber has been described. However, the present invention is not limited to this, and the fuel injection valve is installed so as to inject fuel toward the intake passage. It can also be applied to engines.
[Brief description of the drawings]
FIG. 1 is a control system diagram of one embodiment.
FIG. 2 is a pre-ignition generation region diagram with respect to intake air temperature and idle rotation speed.
FIG. 3 is a region diagram showing the contents of preignition avoidance control according to the first embodiment.
FIG. 4 is a region diagram showing the contents of preignition avoidance control according to the second embodiment.
FIG. 5 is a flowchart for explaining setting of an upper limit limit value of a target idle speed and a throttle valve opening according to the first embodiment.
FIG. 6 is a characteristic diagram of a target idle rotation speed according to the first embodiment.
FIG. 7 is a flowchart for explaining setting of an upper limit limit value of a target idle speed and a throttle valve opening according to the second embodiment.
FIG. 8 is a characteristic diagram of a target idle rotation speed according to the second embodiment.
FIG. 9 is a flowchart for explaining setting of an upper limit limit value of a target idle speed and a throttle valve opening according to the third embodiment.
FIG. 10 is a flowchart for explaining setting of an upper limit limit value of a target idle speed and a throttle valve opening according to the fourth embodiment.
FIG. 11 is a pre-ignition generation region diagram with respect to engine water temperature and intake air temperature.
FIG. 12 is a view corresponding to claims of the first invention.
FIG. 13 is a diagram corresponding to claims of the second invention.
[Explanation of symbols]
3 throttle valve control device 11 control unit 14 accelerator sensor 17 intake air temperature sensor

Claims (3)

Means for calculating a target throttle valve opening based on engine operating conditions;
Means for limiting the target throttle valve opening to the upper limit value when the target throttle valve opening exceeds the upper limit value of the throttle valve opening;
An actuator that drives the throttle valve to achieve the limited target throttle valve opening;
Means for feedback control to bring the engine speed close to the target idle speed during idling;
Means for detecting the intake air temperature;
In the pre-ignition generation area diagram where the horizontal axis is the intake air temperature and the vertical axis is the idle rotation speed when the intake air temperature increases while the idle rotation speed is constant, the high intake air temperature side and the low idle rotation speed side Boundary temperature A obtained from the boundary line α between the pre-ignition occurrence region and the pre-ignition non-occurrence region where the intake air temperature is low and the idle rotation speed is high, and when the pre-ignition avoidance control is not performed If the intake air temperature rises, the upper limit value of the throttle valve opening is first reduced to shift the boundary line α to the right side of the pre-ignition generation area diagram and expand the temperature range that can maintain the idle speed as it is Therefore, pre-ignition is avoided, the intake air temperature rises further, and it can be higher than the boundary temperature B obtained from the boundary line β after the shift. And means for avoiding pre-ignition by along the boundary line after the shift β slide into high idle speed,
An engine control device comprising: Means for calculating a target throttle valve opening based on engine operating conditions;
Means for limiting the target throttle valve opening to the upper limit value when the target throttle valve opening exceeds the upper limit value of the throttle valve opening;
An actuator that drives the throttle valve to achieve the limited target throttle valve opening;
Means for feedback control to bring the engine speed close to the target idle speed during idling;
Means for detecting the intake air temperature;
In the pre-ignition generation area diagram where the horizontal axis is the intake air temperature and the vertical axis is the idle rotation speed when the intake air temperature increases while the idle rotation speed is constant, the high intake air temperature side and the low idle rotation speed side From the boundary line γ between the pre-ignition occurrence region and the pre-ignition region where the intake air temperature is low and the idle rotation speed is high, and the upper limit value of the throttle valve is at the fully open position If the intake air temperature becomes higher than the obtained boundary temperature A, first, the target idle rotation speed is increased along the boundary line γ to avoid pre-ignition, the intake air temperature further increases, and the idle rotation speed reaches the upper limit value. When the boundary temperature C obtained from the idle speed and the boundary line γ reaching the upper limit value is exceeded, the upper limit value of the throttle valve opening is set. And means for avoiding pre-ignition by fence,
An engine control device comprising: The engine control device according to claim 1 or 2 , further comprising means for detecting an engine water temperature, and performing control for avoiding the pre-ignition when the water temperature is equal to or higher than a predetermined value .

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