JP6077371B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with a variable compression ratio mechanism for changing the compression ratio of the internal combustion engine.

  In a general internal combustion engine, a knock sensor that detects the occurrence of knock is provided, and the knock is eliminated by changing the ignition timing when the knock is detected. For example, as described in Patent Document 1, a request (engine) torque intended by a driver (driver) is calculated based on an accelerator operation amount, and a throttle valve opening and a fuel injection amount are calculated based on the required torque. The required torque intended by the driver is realized by the intake air amount and the fuel injection amount corresponding to the set throttle valve opening.

  Further, for example, Patent Document 2 includes a variable valve mechanism that variably controls the intake valve closing timing, and a compression ratio variable mechanism that variably controls the compression ratio by changing the piston top dead center, and an actual compression ratio during cranking. Describes a control device that optimally controls the intake valve closing timing variable control and the compression ratio variable control in combination.

Japanese Patent No. 3627532 JP 2002-276446 A

  However, in an engine equipped with a variable compression ratio mechanism, the actual compression ratio shifts when carbon adheres to the combustion chamber due to deterioration over time and the volume of the combustion chamber changes. For such changes, the effect of varying the compression ratio cannot be fully used by simply setting the target compression ratio according to the load and the engine speed. Further, under the same load (intake air filling rate) and rotation conditions, the torque generated by the engine differs depending on the compression ratio, so that torque control according to the required torque becomes difficult. In addition, if only the ignition timing is controlled by knock control, the output torque may be reduced or the torque may not be improved.

That is, under conditions where knocking is likely to occur during high compression ratio operation, the torque drop due to the retard of the ignition timing becomes large. This is because at a high compression ratio, the required ignition timing is originally on the retard side, and the torque sensitivity to the ignition timing is high. On the other hand, under conditions where knocking is unlikely to occur during low compression ratio operation, the ignition timing can be advanced if knocking does not occur during operation with MBT (Minimum spark advance for Best Torque). Even if the angle is advanced, an increase in torque cannot be expected, and it may even decrease.

  Thus, in an internal combustion engine equipped with a variable compression ratio mechanism, when the target compression ratio is set according to the load and the engine speed, the merit of the variable compression ratio mechanism is maximized only by correcting the ignition timing when knocking occurs. However, the output (fuel consumption) is lost. Further, even if knock control is performed using a variable compression ratio mechanism, effective compression control cannot always be performed because the variable compression ratio mechanism has a large response delay.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to appropriately set an ignition timing and a compression ratio in an internal combustion engine equipped with a variable compression ratio mechanism in accordance with an operation state of the internal combustion engine. An object of the present invention is to provide a control device for an internal combustion engine that can be controlled.

An internal combustion engine control device according to the present invention is a control device for an internal combustion engine comprising detection means for detecting the occurrence of knock, control means for controlling ignition timing, and a compression ratio variable mechanism for changing the compression ratio of the internal combustion engine. If the ignition timing correction amount by knock control is on the advance side, the ignition timing is advanced until knock occurs, and the compression ratio up allowance is calculated from the ignition timing correction amount. Increase the partial compression ratio, retard the ignition timing in accordance with the increase in the actual compression ratio, return to the ignition timing before the advance, and if the ignition timing correction amount by knock control is on the retard side, Is retarded until knocking stops, the compression ratio down allowance is calculated from the ignition timing correction amount, the compression ratio down allowance is reduced, and the ignition timing is advanced in accordance with the decrease in the actual compression ratio. to, back to the ignition timing before the retarded, this The features.

According to the present invention, in an internal combustion engine equipped with a variable compression ratio mechanism, by changing the compression ratio by controlling the variable compression ratio mechanism in accordance with the occurrence of knocking, the ignition timing according to the condition at that time It is possible to operate at a compression ratio, and the output can be maximized.
Therefore, in the internal combustion engine provided with the variable compression ratio mechanism, it is possible to provide a control device for the internal combustion engine that can appropriately control the ignition timing and the compression ratio in accordance with the operation state of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a system configuration of a vehicle engine (internal combustion engine), showing an internal combustion engine control apparatus according to an embodiment of the present invention. 2 is a flowchart for calculating a compression amount correction amount when the ignition timing correction amount by knock control is on the advance side in the system configuration of the vehicle engine shown in FIG. 1. FIG. 6 is a characteristic diagram showing a relationship between an ignition timing (ADV) and a correction torque when the ignition timing correction amount is on the advance side. 2 is a flowchart for calculating a compression amount correction amount when the ignition timing correction amount by knock control is on the retard side in the system configuration of the vehicle engine shown in FIG. 1. FIG. 6 is a characteristic diagram showing the relationship between ignition timing (ADV) and correction torque when the ignition timing correction amount is on the retard side.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a control apparatus for an internal combustion engine according to an embodiment of the present invention, and is a schematic diagram showing a system configuration of a vehicle engine (internal combustion engine).

  Air is drawn into the combustion chamber 2 of each cylinder of the engine 1 from the air cleaner 3 of the intake system via the intake compressor 5, the intercooler 6, the electric throttle valve 7, and the intake manifold 8 of the supercharger 4. The fuel supply system is configured to include a fuel injection valve 9 that can inject and supply fuel adjusted to a predetermined pressure to a branch portion of the intake manifold 8 (or directly into the combustion chamber 2) for each cylinder. Fuel injection is performed at a predetermined timing, and the fuel is ignited and burned in the combustion chamber 2 by the spark plug 10. The exhaust gas after combustion is discharged through an exhaust manifold 11 of the exhaust system, an exhaust turbine 12 of the supercharger 4, and an exhaust purification catalyst 13.

The operation of the electric throttle valve 7, the fuel injection valve 9 and the spark plug 10 is controlled by an engine control unit (hereinafter referred to as ECU) 20.
For this control, the ECU 20 generates a crank angle signal synchronized with the engine rotation, thereby detecting the crank angle sensor 21 that can detect the engine speed Ne, and the accelerator opening (depressing amount of the accelerator pedal) APO. An accelerator opening sensor 22, a throttle opening sensor 23 for detecting the opening TVO of the fuel injection valve 9, an air flow meter 24 for detecting the intake air amount Qa, a water temperature sensor 25 for detecting the engine water temperature Tw, and an intake air temperature Ta are detected. An intake air temperature sensor 26, a knock sensor 27 that detects the level of knock vibration of a specific frequency component from the vibration of the engine 1 as a knock detection means, and a wide area type that linearly detects the air-fuel ratio of the combustion mixture according to the oxygen concentration in the exhaust gas. The signal of the air-fuel ratio sensor 28 is input.

Here, the ECU 20 normally sets the target throttle opening tTVO based on the accelerator opening APO, and controls the opening of the electric throttle valve 7 so as to obtain the target throttle opening tTVO.
Further, a basic fuel injection amount Tp = K × Qa / Ne (K is a constant) is calculated from the intake air amount Qa and the engine speed Ne, and further corrected by various correction coefficients COEF to obtain a final fuel injection amount Ti. = Tp × COEF is calculated, and a fuel injection pulse signal having a pulse width corresponding to this Ti is output to the fuel injection valve 9 for each cylinder at a predetermined timing to cause fuel injection.

  The basic ignition timing MADV is set mainly based on the engine speed Ne and the load Te (for example, intake air amount Qa, basic fuel injection amount Tp, accelerator opening APO, throttle opening TVO), and a knock sensor. The final ignition timing ADV is set by correcting the ignition timing and the compression ratio in accordance with the occurrence of knock detected by the engine 27, and the ignition operation of the spark plug 10 is performed at the ignition timing ADV. To do.

  The engine 1 further includes a variable compression ratio mechanism 100. The variable compression ratio mechanism 100 is configured to be able to change the compression ratio, for example, by changing the top dead center position of the piston. The compression ratio control using the variable compression ratio mechanism 100 is basically performed by engine speed Ne and load Te (for example, intake air amount Qa, basic fuel injection amount Tp, accelerator opening APO, throttle opening TVO). The compression ratio is set based on the above. And an actuator (motor) etc. are controlled so that it may become the set compression ratio, and the rotation position of a control shaft is changed (in the case of a multi-link type compression ratio variable mechanism).

In addition to the basic compression ratio setting as described above, in the operating range near the fully open position, the engine can be operated at the ignition timing near the MBT within a range where knocking does not occur (or minor knocking occurs). By controlling so as to obtain a proper compression ratio, the engine is operated at an optimal ignition timing and compression ratio according to the condition at that time.
The actual compression ratio can be detected by detecting, for example, the rotational position of the control shaft with the rotary encoder 29 or the like.

Next, the compression ratio changing operation will be described in detail for the case where the ignition timing correction amount (the amount of change in the ignition timing) by the knock control is on the advance side and on the retard side.
FIG. 2 is a flowchart for calculating the correction amount of the compression ratio when the ignition timing correction amount by the knock control is on the advance side in the system configuration of the vehicle engine shown in FIG. FIG. 3 shows the relationship between the ignition timing (ADV) and the correction torque at this time.
This example corresponds to the condition where knocking is difficult to occur. Specifically, conditions such as when the intake air temperature and engine temperature (oil temperature) are low, or when the humidity is high, and when the octane number of gasoline is high. It is.

In step S101, it is determined whether it is a knock control area.
If it is determined that it is a knock control region, it is determined in step S102 whether a knock has occurred.
If it is determined in step S101 that the region is not the knock control region, or if it is determined in step S102 that knocking has occurred, the process ends.

If knock has not occurred, the ignition timing is advanced by a predetermined value in step S103, and it is determined whether knock has occurred in step S104.
If it is determined in step S104 that knock has not occurred, the process returns to step S103 to advance the ignition timing by a predetermined value, and advance the ignition timing until knock occurs.
If knocking occurs, the process proceeds to step S105, and the advance amount from the original ignition timing is calculated.

In step S106, it is determined whether or not the calculated advance amount is greater than or equal to a predetermined value.
If it is determined in step S106 that the advance amount is greater than or equal to a predetermined value, a compression ratio up allowance is calculated from the ignition timing advance amount in step S107. As described above, when the ignition timing correction amount by the knock control is on the advance side (knock does not easily occur), the compression ratio up margin is calculated from the ignition timing correction amount. This compression ratio increase allowance can be expressed by the following equation (1).

Compression ratio up allowance = knock ignition timing correction amount x correction coefficient (1)
Here, the correction coefficient (sensitivity obtained experimentally) represents the correlation between the compression ratio and the ignition timing, and is, for example, the ignition timing 5 deg with respect to the compression ratio 1. Therefore, for example, if knocking occurs when the angle is advanced by 5 degrees, the compression ratio ε can be increased by one. That is,
Compression ratio up allowance = 5 deg × 1/5 = 1
It is.

In the next step S108, the compression ratio up margin is reflected in the target compression ratio, and the compression is controlled to the target.
In step S109, the ignition timing is retarded in accordance with the change in the actual compression ratio, and the process ends. Since the ignition timing changing speed is sufficiently faster than the compression ratio changing speed, the ignition timing can be controlled in accordance with the change in the actual compression ratio.

  Specifically, as shown in FIG. 3, for example, when the compression ratio is 11 (ε = 11) and the operation is performed at MBT, the trace knock occurs at the ignition timing S1 advanced by 5 deg from MBT by the knock control. Then, the compression ratio up allowance is calculated from this knock ignition timing correction amount, the compression ratio up allowance is increased, and the ignition timing is restored to the original as the compression ratio increases. In this example, since the compression ratio can be increased by 1, the compression ratio is set to 12 (ε = 12), and the ignition timing is set to the ignition timing S2 obtained by retarding the ignition timing by 5 degrees. By increasing the compression ratio in this way, the torque can be improved as shown in FIG.

  Therefore, in an internal combustion engine equipped with a variable compression ratio mechanism, a compression ratio that can be operated at an ignition timing in the vicinity of the MBT within a range where the knock is not generated or a slight knock is generated in the operating region near the fully open position. Can be controlled.

FIG. 4 is a flowchart for calculating the correction amount of the compression ratio when the ignition timing correction amount by the knock control is on the retard side in the system configuration of the vehicle engine shown in FIG. FIG. 5 shows the relationship between the ignition timing (ADV) and the correction torque at this time.
This example corresponds to the condition where knocking is likely to occur. Specifically, conditions such as when the intake air temperature or engine temperature (oil temperature) is high, or when the humidity is low, or when the gasoline octane number is low. It is.

In step S201, it is determined whether it is a knock control area.
If it is determined that it is a knock control region, it is determined in step S102 whether a knock has occurred.
If it is determined in step S201 that the region is not the knock control region, or if it is determined in step S202 that no knock has occurred, the process ends.

If knocking has occurred, the ignition timing is retarded by a predetermined value in step S203, and it is determined whether knocking has occurred in step S204.
If it is determined in step S204 that knocking has occurred, the process returns to step S203 to retard the ignition timing by a predetermined value, and retard the ignition timing until no knocking occurs. At this time, since the sensitivity with respect to the ignition timing is large, if the retard is made to a point where knocking does not occur, the torque decreases greatly, and control is performed when the torque decreases.
When the knocking stops, the process proceeds to step S205, and the retardation amount from the original ignition timing is calculated.

In step S206, it is determined whether or not the calculated retardation amount is greater than or equal to a predetermined value.
If it is determined in step S206 that the retard amount is greater than or equal to a predetermined value, a compression ratio down allowance is calculated from the ignition timing retard amount in step S207. In this way, when the ignition timing correction amount by knock control is on the retard side (knock has occurred), the compression ratio down allowance is calculated from the ignition timing correction amount. This compression ratio down allowance can be expressed by the following equation (2).

Compression ratio down allowance = knock ignition timing correction amount × correction coefficient (2)
Here, the correction coefficient (experimentally determined sensitivity) represents the correlation between the compression ratio and the ignition timing, and is, for example, the ignition timing −5 deg with respect to the compression ratio 1. Therefore, for example, if knocking is stopped when the angle is delayed by 5 degrees, the compression ratio ε can be reduced by one. That is,
Compression ratio down allowance = −5 deg × 1/5 = −1
It is.

In the next step S208, the compression ratio down allowance is reflected in the target compression ratio, and the compression is controlled to the target.
In step S209, the ignition timing is advanced to the original ignition timing in accordance with the change in the actual compression ratio, and the process ends. Since the ignition timing changing speed is sufficiently faster than the compression ratio changing speed, the ignition timing can be controlled in accordance with the change in the actual compression ratio.

  Specifically, as shown in FIG. 5, for example, when a trace knock occurs when the compression ratio is 12 (ε = 12), the ignition timing is retarded by knock control and the ignition is delayed by 5 deg from MBT. Assuming that the trace knock is stopped at the timing S3, if the compression ratio is high, the torque decreases steeply with respect to the ignition timing, so the torque decreases sharply. Therefore, the compression ratio down allowance is calculated from this knock ignition timing correction amount, the calculated compression ratio down allowance is reduced, and the ignition timing is restored to the original when the compression ratio decreases. In this example, since the compression ratio ε can be decreased by 1, the compression ratio is set to 11 (ε = 11) and the ignition timing is set to the ignition timing S4 advanced by 5 degrees. By reducing the compression ratio in this way, the torque can be improved as shown in FIG.

Therefore, in an internal combustion engine equipped with a variable compression ratio mechanism, a compression ratio that can be operated at an ignition timing in the vicinity of MBT in a range where knocking does not occur (or minor knocking occurs) in the operating region near full opening. Can be controlled.
In the above embodiment, the variable compression ratio mechanism is controlled by detecting the knock by the knock sensor. However, any one of the effective (actual) compression ratio, the fresh air amount, the remaining gas amount, the compression temperature, and the knock sensitivity is selected. Alternatively, it may be limited by a plurality of combinations or the correction amount may be increased or decreased. Furthermore, since the changing speed of the ignition timing is sufficiently faster than the changing speed of the compression ratio, the ignition timing may be controlled when knocking occurs due to overcorrection.
In addition, although the explanation has been made focusing on the control for improving the torque, it is not always necessary to set the actual compression target to the target compression ratio, and the actual compression target may be made lower than the target compression ratio according to the required characteristics. it can.

  According to the above configuration, by controlling the compression ratio so that it can be operated by MBT according to the state of knocking, the condition at that time, for example, the environment such as temperature and humidity, the octane number of gasoline, etc. It is possible to operate with the optimal ignition timing and compression ratio according to the output, and the output can be maximized. This can be expected to improve acceleration performance and fuel efficiency.

  DESCRIPTION OF SYMBOLS 1 ... Engine (internal combustion engine), 20 ... ECU (control means), 27 ... Knock sensor (detection means), 100 ... Compression ratio variable mechanism (variable mechanism)

Claims (2)

A control device for an internal combustion engine comprising detection means for detecting occurrence of knock, control means for controlling ignition timing, and a compression ratio variable mechanism for changing the compression ratio of the internal combustion engine,
When the ignition timing correction amount by knock control is on the advance side, advance the ignition timing until knock occurs, calculate the compression ratio up allowance from the ignition timing correction amount, and this compression ratio up allowance compression ratio Increase the actual compression ratio, retard the ignition timing, return to the ignition timing before the advance,
If the ignition timing correction amount by knock control is on the retard side, retard the ignition timing until knocking stops, calculate the compression ratio down allowance from the ignition timing correction amount, and calculate the compression ratio down allowance. A control device for an internal combustion engine, wherein the compression ratio is lowered, the ignition timing is advanced in accordance with a decrease in the actual compression ratio, and the ignition timing is returned to the ignition timing before being retarded . 2. The control apparatus for an internal combustion engine according to claim 1 , wherein when the amount of change in the ignition timing is less than a predetermined advance angle or retard angle, the compression ratio is not changed by the variable compression ratio mechanism.