JP2007239564A - Control device for internal combustion engine - Google Patents

Abstract

An increase in in-cylinder pressure at an ignition timing ADV can be suppressed even when an ignition timing ADV is retarded so that a required secondary voltage does not exceed a limit voltage.
An accelerator opening APO is detected as an engine operating state (S1), and when the amount of change ΔAPO is equal to or greater than a predetermined value (ΔAPO ≧ predetermined value) (S2), retard control of ignition timing ADV is performed. (S3). When the retarded ignition timing ADV is later than the predetermined timing C (S4), the throttle valve opening TVO is limited to limit the intake air amount (S5).
[Selection] Figure 4

Description

  The present invention relates to a control device for an internal combustion engine.

  Conventionally, when accelerating from low-speed driving (transition), if the accelerator pedal depression speed exceeds a predetermined value, the amount of intake air also increases due to a sudden increase in the opening of the throttle valve until the target torque is reached. The time was shortened and the driver sometimes felt as a shock during acceleration. In addition, knocking may occur due to a transient increase in the amount of intake air beyond the target.

For this reason, there is known a technique for coping with such a problem by correcting the ignition timing to the retard side according to the opening speed of the accelerator pedal (Patent Document 1).
Japanese Patent Laid-Open No. 7-19150

  By the way, recent internal combustion engines tend to have higher in-cylinder pressure due to higher compression ratios, turbochargers and the like. Therefore, when the ignition timing is largely retarded in the ignition device control device described in Patent Document 1, the ignition timing approaches the compression top dead center, the cylinder pressure at the ignition timing increases, and the required secondary voltage of the ignition coil Becomes higher. This is because the required secondary voltage is determined by the in-cylinder pressure at the time of ignition, so that the required secondary voltage increases as the ignition timing approaches the compression top dead center.

However, the required secondary voltage of the ignition coil has a limit (limit voltage from the component request), and if this is exceeded, misfire or durability deterioration of the ignition system component occurs, and this needs to be avoided.
The present invention has been made in view of the above problems, and suppresses an increase in in-cylinder pressure at the ignition timing even when the ignition timing is retarded so that the required secondary voltage does not exceed the limit voltage. The purpose is to be able to.

  Therefore, according to the present invention, the amount of intake air is limited when the required secondary voltage of the ignition coil corresponding to the in-cylinder pressure at the ignition timing exceeds a predetermined voltage due to the retard of the ignition timing.

  According to the present invention, the required secondary voltage of the ignition coil can be made less than the limit voltage by limiting the intake air amount and reducing the in-cylinder pressure at the ignition timing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a spark ignition type internal combustion engine 1.
In the internal combustion engine 1, a combustion chamber 4 is defined by a piston 2 and a cylinder head 3. An ignition device 5 that performs spark ignition in the combustion chamber 4 is disposed in the cylinder head 3. The ignition device 5 includes an ignition coil 6 and a spark plug 7. An intake valve 8 and an exhaust valve 9 are disposed in the cylinder head 3 so as to surround the spark plug 7. A fuel injection valve 10 capable of directly injecting fuel into the combustion chamber 4 is provided.

In the intake passage 11 for introducing intake air into the combustion chamber 4, an air cleaner 12 is provided on the upstream side, and an electric throttle valve 13, a collector 14, and an intake manifold 15 are disposed in order downstream of the air cleaner 12. ing.
The electric throttle valve 13 opens and closes the intake passage 11 according to the opening degree. The air that has passed through the electric throttle valve 13 is distributed from the collector 14 by the intake manifold 15 and taken into the combustion chambers 4 (each cylinder) via the intake valve 8.

Here, the fuel injected from the fuel injection valve 10 and the air sucked into the combustion chamber 4 are mixed to form an air-fuel mixture suitable for combustion, and spark ignition is performed by the spark plug 7 of the ignition device 5. In this way, the air-fuel mixture is burned. After combustion of the air-fuel mixture, the gas in the combustion chamber 4 is discharged to the exhaust passage 16 through the exhaust valve 9.
The exhaust passage 16 is provided with an exhaust purification device 17 having a catalyst capable of purifying exhaust. An exhaust passage 16 upstream of the exhaust purification device 17 is provided with an EGR passage 18 for returning a part of the exhaust discharged from the combustion chamber 4 to the intake-side collector 14. The passage 18 is provided with an EGR valve 19 capable of controlling the EGR amount.

Various sensors are provided to detect the operating state of the internal combustion engine 1, and output signals from these sensors are input to an engine control unit (ECU) 30.
As shown in the figure, an air flow meter 21 for detecting an intake air amount is provided in the intake passage 11 between the air cleaner 12 and the electric throttle valve 13. The collector 14 is provided with an intake air temperature sensor 22 for detecting the temperature of the intake air. An accelerator opening sensor 24 for detecting the accelerator opening (depressing amount of the accelerator) and a crank angle sensor 25 for detecting the engine speed are also provided. The cylinder block is provided with a knocking sensor 26 for detecting knocking. Although not shown, an oxygen sensor for detecting the exhaust air-fuel ratio, a water temperature sensor for detecting the engine water temperature, and the like are also provided.

The ECU 30 performs various calculations based on signals from each sensor, and based on the calculation results, for example, ignition timing control of the ignition device 5, opening / closing control of the electric throttle valve 13, fuel injection control of the fuel injection valve 10, Opening / closing control of the EGR valve 19 is performed. For example, the opening degree of the electric throttle valve 13 is controlled based on the output signal of the accelerator opening sensor 24.
Here, the ignition coil 6 of the ignition device 5 has a limit voltage of a required secondary voltage to be generated in the coil 6 in order to make a spark with the spark plug 7 determined in advance from the component requirements, and must be used below this limit voltage. I must.

As shown in FIG. 2, the required secondary voltage is substantially determined by the in-cylinder pressure at the ignition timing. For this reason, when the ignition timing or in-cylinder pressure changes, the required secondary voltage also changes. For example, when the ignition timing is retarded, the in-cylinder pressure at the ignition timing increases, so the required secondary voltage is Get higher.
However, when the amount of change in the accelerator opening (accelerator pedal depression speed) during acceleration is greater than or equal to a predetermined value (during transition), when the ignition timing is retarded to near the top dead center, as shown in FIG. The required secondary voltage of 6 may exceed the limit voltage.

Therefore, in the present invention, when the required secondary voltage of the ignition coil corresponding to the in-cylinder pressure at the ignition timing exceeds a predetermined voltage due to the retard of the ignition timing, the in-cylinder pressure is reduced by limiting the intake air amount. The required secondary voltage does not exceed the limit voltage.
FIG. 4 is a flowchart in one embodiment of the present invention. The processing according to this flowchart is repeatedly performed every predetermined time.

In step 1 (shown as “S1” in the figure, the same applies hereinafter), the operating state of the internal combustion engine 1 is detected. Here, the accelerator opening APO is detected based on the output signal of the accelerator opening sensor 24 as the operating state.
In step 2, it is determined whether or not the change amount ΔAPO of the accelerator opening APO is equal to or greater than a predetermined value (ΔAPO ≧ predetermined value). This change amount ΔAPO is calculated by subtracting the accelerator opening APO detected in step 1 by the previous value APO (−1) (ΔAPO = APO−APO (−1)). If the change amount ΔAPO is equal to or greater than a predetermined value (ΔAPO ≧ predetermined value), it is determined that the vehicle is in an accelerated state, and the process proceeds to step 3. On the other hand, when the change amount ΔAPO is less than the predetermined value (ΔAPO <predetermined value), it is determined that the vehicle is in the non-accelerated (or steady) state, and the process proceeds to Step 6 described later.

In step 3, control is performed to retard the ignition timing ADV in accordance with the acceleration state, here, the change amount ΔAPO of the accelerator opening APO. In this retard control, the ignition timing ADV is retarded up to the top dead center of the compression stroke. This corresponds to the ignition timing control means.
In step 4, it is determined whether or not the retarded ignition timing ADV is later than the predetermined timing C (advanced value is less than the predetermined value). As shown in FIG. 2, the predetermined timing C is a predetermined ignition timing at which the required secondary voltage of the ignition coil 6 corresponding to the in-cylinder pressure at the ignition timing is less than the limit voltage from the parts requirements of the ignition coil 6. is there. When the ignition timing ADV is later than the predetermined timing C, the process proceeds to step 5 in order to suppress an increase in the cylinder pressure at the ignition timing ADV. On the other hand, when the ignition timing ADV is earlier than the predetermined timing C, it is not necessary to suppress the in-cylinder pressure at the ignition timing ADV, and thus the process ends.

The actual in-cylinder pressure Pcyd at the retarded ignition timing ADV is calculated, and it is determined whether this in-cylinder pressure Pcyd exceeds a predetermined pressure (for example, the in-cylinder pressure at the ignition timing C shown in FIG. 2). May be.
Further, the required secondary voltage of the ignition coil 6 corresponding to the in-cylinder pressure Pcyd is calculated, and the required 2 in accordance with the in-cylinder pressure Pcyd at the ignition timing ADV, for example, according to the required secondary voltage calculation table shown in FIG. After calculating the secondary voltage, it may be determined whether the required secondary voltage exceeds a predetermined voltage (for example, the required secondary voltage of the ignition coil 6 corresponding to the in-cylinder pressure at the ignition timing C). .

  In step 5, as shown in FIG. 2, in order to keep the required secondary voltage within the normal use range (less than the limit voltage), the air sucked into the cylinder is regulated by restricting the opening degree TVO of the electric throttle valve 13. Limit the amount. This corresponds to intake air amount limiting means. As a result, the amount of air sucked into the cylinder is reduced. As a result, torque shock in the acceleration state is prevented and the in-cylinder pressure Pcyd at the ignition timing ADV is reduced. Therefore, the required secondary voltage of the ignition coil 6 is reduced. Is less than the limit voltage.

  For example, when the throttle opening TVO is controlled based on at least the accelerator opening APO, the throttle opening TVO is controlled against the change in the increasing direction of the accelerator opening APO. The control in the increasing direction is delayed (stopped) for a predetermined time. After a predetermined time has elapsed, control is performed so that the throttle opening TVO becomes the target opening calculated based on the operating conditions (for example, the accelerator opening APO and the engine speed Ne).

  If the process proceeds from step 2 to step 6, it is determined whether knocking is present. For the determination of knocking, for example, knocking is directly detected using the knocking sensor 26. The in-cylinder pressure Pcyd may be estimated to indirectly predict knocking. For example, a part of the exhaust gas in the exhaust passage 16 is introduced into the collector 14 via the EGR passage 18 to thereby take in the intake air. When the temperature becomes high, that is, when knocking is likely to occur, knocking may be indirectly estimated from the intake air temperature by the intake air temperature sensor 22. If it is determined that there is knocking, the routine proceeds to step 3 where knocking is avoided by control to retard the ignition timing ADV. On the other hand, if it is determined that there is no knocking, it is not necessary to avoid knocking, and the process is terminated.

FIG. 5 is a time chart when the control according to this flowchart is performed.
At time t1 when the change amount ΔAPO of the throttle opening APO becomes equal to or greater than a predetermined value (ΔAPO ≧ predetermined value), the ignition timing control means starts retarding the ignition timing ADV in order to reduce the torque step. At this time, the ignition timing control means performs control to retard the ignition timing ADV according to the acceleration state. In the figure, the ignition timing ADV at the time t1 is retarded to the compression top dead center (TDC) from the start time t1 of the ignition timing retard control to the time t3 when the throttle opening APO reaches the target value.

  When the retard control of the ignition timing ADV is performed, the opening degree TVO of the electric throttle valve 13 is limited at the time t2 when the retarded ignition timing ADV exceeds the predetermined timing D. Specifically, after the ignition timing retard is started, when the ignition timing ADV exceeds the predetermined timing D (or after a predetermined time has elapsed from the time t1), the opening TVO of the electric throttle valve 13 is set by the intake air amount limiting means. Control is performed to delay (stop) the control in the increasing direction of the opening degree TVO of the electric throttle valve 13 for a predetermined time with respect to the change in the increasing direction of the accelerator opening APO.

The predetermined timing D of the ignition timing ADV may be set to the above-described predetermined timing C, but may be an ignition timing advanced from the predetermined timing C for early control.
Then, at the time t2 when the calculated ignition timing ADV becomes an ignition timing ADV that exceeds the required secondary voltage of the ignition coil 6 corresponding to the cylinder pressure at the predetermined timing D of the ignition timing ADV shown in FIG. In order to suppress the inflow of air to 4, the opening degree TVO of the electric throttle valve 13 is temporarily restricted to the restriction value TVO ′ from the time point t2 to the time point t3.

  Thus, even when the ignition timing ADV is retarded from the time t2 to the time t3, that is, when the ignition timing ADV is retarded to the vicinity of the piston top dead center TDC, the opening degree TVO of the electric throttle valve 13 is regulated, and the combustion chamber The required secondary voltage can be made less than the limit voltage by reducing the amount of air sucked into the cylinder 4 and reducing the in-cylinder pressure Pcyd at the ignition timing ADV. And it becomes unnecessary to change the specification of the components (ignition coil 6, spark plug 7, etc.) of ignition device 5, and manufacturing cost, fuel consumption, and output performance can be maintained.

  Further, as a countermeasure for reducing the required secondary voltage of the ignition coil 6, it is conceivable to reduce the compression ratio of the internal combustion engine 1 to reduce the in-cylinder pressure Pcyd at the time of ignition. However, if the compression ratio is lowered, the effect of directly injecting fuel into the combustion chamber 4 to improve fuel efficiency is reduced. For this reason, in the present invention, in the direct injection internal combustion engine 1, by restricting the opening TVO of the electric throttle valve 13 during the transition, the intake air amount is limited, and the ignition coil 6 is not reduced without reducing the compression ratio. The required secondary voltage is reduced.

When the restriction of the opening degree TVO of the electric throttle valve 13 is finished, the opening degree TVO of the electric throttle valve 13 is calculated based on the accelerator opening degree APO from the restriction value TVO ′. On the other hand, the ignition timing ADV is controlled so as to reach the target value from the compression top dead center TDC (period from t3 to t4).
Further, the restriction on the opening degree TVO of the electric throttle valve 13 in step 5 of the above-described flowchart is that the changing speed in the increasing direction of the opening degree TVO of the electric throttle valve 13 with respect to the changing speed in the increasing direction of the accelerator opening degree APO. It may be something that delays.

Specifically, as shown in FIG. 6, the opening degree TVO of the electric throttle valve 13 is set to a final target after the ignition timing ADV reaches the compression top dead center TDC from the retard start time t1 of the ignition timing ADV. Control is performed so that the opening is delayed until time t4 when the value is reached.
The opening method of the electric throttle valve 13 is not limited to the case where the opening degree TVO of the electric throttle valve 13 increases linearly as shown in FIG. 6, and the required secondary voltage of the ignition coil 6 is less than the limit voltage. If it can be made to become, it may be made to increase in the shape of a curve.

  According to the present embodiment, in the control device for the internal combustion engine that includes the ignition timing control means for controlling the ignition timing ADV according to the engine operating conditions, the retard of the ignition timing ADV corresponds to the in-cylinder pressure Pcyd at the ignition timing ADV. When the required secondary voltage of the ignition coil 6 to be exceeded exceeds a predetermined voltage (step 4), intake air amount limiting means (step 5) is provided for limiting the intake air amount. For this reason, the required secondary voltage of the ignition coil 6 can be made less than the limit voltage by limiting the intake air amount and reducing the in-cylinder pressure Pcyd at the ignition timing ADV.

Further, according to the present embodiment, the ignition timing control means detects the acceleration state (step 2), and implements control for retarding the ignition timing ADV according to this (step 3). For this reason, the ignition timing ADV can be delayed so that a sudden torque is not generated during the transition.
Further, according to the present embodiment, the ignition timing control means detects or predicts knocking (step 6), and performs control to retard the ignition timing ADV when knocking is present (step 3). Therefore, for example, when a part of the exhaust gas in the exhaust passage 16 is introduced into the collector 14 via the EGR passage 18 and the intake air temperature becomes high (when knocking is likely to occur), ignition is performed. Knocking can be avoided by controlling to retard the timing ADV.

Further, according to the present embodiment, the intake air amount limiting means regulates the throttle opening TVO (step 5). For this reason, the amount of air sucked into the combustion chamber 4 can be reduced, the in-cylinder pressure Pcyd can be reduced, and the required secondary voltage of the ignition coil 6 corresponding to the in-cylinder pressure Pcyd at the ignition timing ADV can be reduced. be able to.
Further, according to the present embodiment, the throttle opening TVO is regulated such that when the throttle opening TVO is controlled based on at least the accelerator opening APO, the throttle opening TVO is controlled against the change in the increasing direction of the accelerator opening APO. The control in the increasing direction is delayed for a predetermined time (step 5). For this reason, the throttle opening TVO at the time of delay is regulated, and the required secondary voltage of the ignition coil 6 can be made less than the limit voltage.

  Further, according to the present embodiment, the restriction of the throttle opening degree is such that when the throttle opening degree TVO is controlled based on at least the accelerator opening degree APO, the throttle opening degree TVO is controlled against the change in the increasing direction of the accelerator opening degree APO. The rate of change in the increasing direction is delayed (step 5). For this reason, increase in the throttle opening TVO is suppressed, the amount of air sucked into the combustion chamber 4 is also suppressed, and the in-cylinder pressure Pcyd is reduced, so that the required secondary voltage of the ignition coil 6 is made less than the limit voltage. can do.

Configuration diagram of control device for internal combustion engine Diagram showing in-cylinder pressure and required secondary voltage at ignition timing Diagram showing in-cylinder pressure and required secondary voltage at ignition timing Flowchart in the embodiment of the present invention Time chart for control by flowchart Time chart for control by flowchart

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4 Combustion chamber 5 Ignition device 6 Ignition coil 7 Ignition plug 8 Intake valve 9 Exhaust valve 10 Fuel injection valve 11 Intake passage 13 Electric throttle valve 14 Collector 15 Intake manifold 16 Exhaust passage 18 EGR passage 19 EGR valve 21 Air flow meter 22 Intake air temperature sensor 24 Accelerator opening sensor 25 Crank angle sensor 26 Knock sensor 30 ECU

Claims (6)

In an internal combustion engine control device comprising an ignition timing control means for controlling the ignition timing according to engine operating conditions,
Intake air amount limiting means is provided for limiting the intake air amount when the required secondary voltage of the ignition coil corresponding to the in-cylinder pressure at the ignition timing exceeds a predetermined voltage by retarding the ignition timing. Control device for internal combustion engine.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the ignition timing control means detects an acceleration state and performs control for retarding the ignition timing in accordance with the detected acceleration state.   3. The control apparatus for an internal combustion engine according to claim 1, wherein the ignition timing control means detects or predicts knocking and performs control for retarding the ignition timing when knocking is present.   The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the intake air amount restriction means regulates a throttle opening.   The restriction of the throttle opening delays the control in the increasing direction of the throttle opening for a predetermined time with respect to the change in the increasing direction of the accelerator opening when the throttle opening is controlled based on at least the accelerator opening. 5. The control apparatus for an internal combustion engine according to claim 4, wherein the control apparatus is provided.   The restriction of the throttle opening delays the changing speed in the increasing direction of the throttle opening relative to the changing speed in the increasing direction of the accelerator opening when the throttle opening is controlled based on at least the accelerator opening. The control apparatus for an internal combustion engine according to claim 4, wherein the control apparatus is provided.

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