JPH0681948B2 - Knock control device for internal combustion engine with supercharger - Google Patents

Description

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

[Conventional technology]

Although supercharging of the internal combustion engine increases the output of the engine, a knocking phenomenon also easily occurs. Therefore, a knock control device is used in which a knock sensor including a vibration detector is attached to a cylinder block or the like to detect knock and control the engine so as to suppress knocking. Known methods of suppressing knocking include a method of lowering the supercharging pressure and a method of retarding the ignition timing. The method of operating the boost pressure has an advantage that the exhaust gas temperature does not rise, but has a problem that the response is poor and the knocking cannot be suppressed immediately after the knock is detected. There is a problem that the torque loss is large. On the other hand, the method of operating the ignition timing has a problem that the exhaust temperature rises due to an excessive delay of the ignition timing. To improve this, a device for knock control by linking ignition timing operation and supercharging pressure operation (Japanese Patent Laid-Open No. 57-53968) has been proposed, but it still has a torque loss, an increase in exhaust temperature and a response. A knock control device that solves all three problems of sex has not been proposed.

[Problems to be solved by the invention]

The present invention has been made to solve the above problems, and provides a knock control device that minimizes torque loss, prevents an increase in exhaust temperature, and has sufficient responsiveness. To aim.

[Background of the Invention]

The inventors discovered the following by comprehensively examining the torque characteristic and the knock characteristic with respect to the boost pressure and the ignition timing. That is, in order to eliminate the knock, it is less torque loss to operate only the ignition timing, and conversely, when the knock does not occur and the exhaust temperature is not a problem, increase the boost pressure. It is the fact that the increase in torque is larger. This point will be described with reference to the drawings.

FIG. 6 is a characteristic diagram showing the torque characteristic and the knock characteristic of the boost pressure with respect to the ignition timing. The curve shown by the solid line in the figure is a torque curve for the supercharging pressure with the ignition timing as a parameter. When the ignition timing (θ1 to θ4) is constant, the higher the supercharging pressure is, the higher the torque is. When the pressure is constant, the torque increases as the ignition timing is advanced (θ1 to θ4). The curve displayed with a broken line is
Kn1 is a knock line that connects the points of supercharging pressure and ignition timing where the same knock state occurs, KN1 is a knock line showing no knock or a very small knock state, KN2 is a trace knock state, that is, a moderate knock state. Show the equal knock lines,
KN3 shows iso-knock lines showing a heavy knock condition, ie, a strong knock condition that must be suppressed.

It is now assumed that the vehicle is operating at the supercharging pressure and the ignition timing (θ3) indicated by point A in the figure. At this time, point A is the heavy knock line KN3
It is on the top and a strong knock occurs. Therefore, in order to erase the knock and shift to the trace knock state, only the ignition timing is delayed from θ3 to around θ2, and the ignition timing is set to θ3 from the point A to the point B on the trace knock line KN2. There is a method in which only the supercharging pressure is lowered while maintaining it and the point A is shifted to the point C on the trace knock line KN2. In this case, the torque is obviously higher at point B than at point C. That is, it is understood that the torque loss is smaller when only the ignition timing is operated in order to eliminate the knock.

On the other hand, when the vehicle is operating under the condition of point D where almost no knock occurs, the operating condition can be changed and the torque can be increased until a proper knock occurs, that is, until the trace knock state occurs. In order to shift to the trace knock state, there are a method of advancing only the ignition timing from θ2 to around θ3 and shifting from D point to E point, and a method of increasing only the boost pressure and shifting from D point to F point. is there. In this case, the torque at point F is higher than at point E. That is,
It is understood that when the knock does not occur and the exhaust gas temperature does not become a problem, the increase in the boost pressure increases the torque.

The characteristics shown in FIG. 6 described above are not static,
It is a characteristic that changes and changes every moment according to changes in engine operating conditions such as the number of revolutions and environmental conditions such as outside temperature and humidity.
Therefore, the knock control system not only avoids the knocking phenomenon, but also performs feedback control while detecting the knock, follows the transition of the above characteristics, and constantly keeps the exhaust temperature on the trace knock line at the limit where it does not become a problem. It is desirable to control the operating conditions so as to follow the highest torque point where the torque is high.

[Means for solving problems]

According to the present invention, (1) the characteristics of the torque characteristic and the knock characteristic with respect to the supercharging pressure and the ignition timing described above, and (2) the operation of the supercharging pressure requires time until the supercharging pressure actually changes, and the responsiveness is poor. The following three points are taken into consideration: (3) the property that (3) the exhaust gas temperature rise does not matter when the ignition timing retard correction amount is small.

Therefore, in the present invention, a knock sensor, an ignition timing control means, and a supercharging pressure control means are provided, and a retard correction amount and a supercharging pressure for correcting the ignition timing in the retard direction in accordance with a knocking occurrence state are provided. In a knock control device for an internal combustion engine with a supercharger, the means for increasing the retard correction amount when knock occurs, and the retard correction amount when the knock does not occur are equal to or less than a first predetermined value. Is a means for increasing the supercharging pressure, a means for decreasing the retard correction amount when the knock correction amount is equal to or more than a first predetermined value when no knock occurs, and an operating condition in which the exhaust temperature rises. A knock control device for an internal combustion engine with a supercharger is provided, which is provided with means for reducing the supercharging pressure.

[Action]

According to the above configuration, the knock control operation target is different depending on the magnitude of the ignition timing retard correction amount. When knock does not occur, if the retard correction amount at that time is small, the boost pressure is selected as the operation target, and if the retard correction amount at that time is large, the ignition timing, that is, the retard correction amount itself becomes the operation target. When a knock occurs, the retard correction amount becomes the operation target regardless of the magnitude of the retard correction amount at that time. That is, when a knock occurs, the retard correction amount is increased to retard the ignition timing to quickly eliminate the knock, and the torque loss at this time is also minimized. As a result, when the operating condition in which the exhaust gas temperature rises is entered, the supercharging pressure is lowered, escape from the operating condition is achieved, and the exhaust gas temperature rise is avoided. On the other hand, when knock is hardly generated, the boost pressure is increased and a large torque increase is obtained.
If the retard correction amount is large, it is considered that the vehicle is near the trace knock line, and general knock control is performed only by operating the ignition timing.

In this way, the ignition timing and supercharging pressure can be controlled so as to follow the vicinity of the maximum torque point within the limit where the exhaust temperature on the trace knock line does not matter, so knock control with less torque loss is realized. can do.

〔Example〕

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

FIG. 1 is an overall configuration diagram, 1 is an engine body, 2 is a supercharger, and 3 is an electronic control unit. An electromagnetically-operated fuel injection valve 4 is arranged near each cylinder intake port of the intake manifold. Fuel adjusted to a constant pressure is pressure-fed to each fuel injection valve 4 from a fuel pump (not shown), and the injection amount is controlled by the time during which the fuel injection valve 4 is operated and opened. As is well known, the distributor 6 that distributes power to the spark plug 5 provided in each cylinder is rotated once every two rotations of the crankshaft. Inside, there is a reference angle sensor 7 for detecting a specific position of the crankshaft and rotation of the engine. And a rotation angle sensor 8 for generating an output signal for each constant crank angle. The ignition coil 9 connected to the distributor 6 is configured integrally with an igniter 10 that cuts off the power supply to the ignition coil 9.

A knock sensor 11, which is a piezoelectric vibration detector, is attached to the cylinder block to detect the vibration waveform of the engine. It is needless to say that the knock sensor 11 may be of electrokinetic type, piezoresistive type, strain gauge type, or the like, other than the piezoelectric type.

The turbine 12 of the supercharger 2 is provided in the exhaust passage 13, and the compressor 14 is provided in the intake passage 15. A wastegate valve 17 is provided in a bypass passage 46 that bypasses the turbine 12. The waste gate valve 17 is operated by a diaphragm type actuator 18 to adjust the opening degree of the bypass passage 16. The diaphragm chamber of the diaphragm type actuator 18 is communicated with the intake passage 20 downstream of the compressor 14 by the pressure conduit 19, and the intake air pressurized by the compressor 14 is guided. In addition, the pressure conduit 19 is a solenoid valve
It communicates with the intake passage 15 upstream of the compressor via 21. When the ON / OFF control signal is output from the electronic control unit 3, the solenoid valve 21 is driven ON / OFF, the effective opening of the solenoid valve 21 is controlled by the duty ratio of the ON / OFF control signal, and the diaphragm actuator 18 is actuated. The pressure applied is controlled. The higher the ratio of the opening time of the solenoid valve 21, the larger the amount of air that escapes to the upstream intake passage 15, and the wastegate valve 17 does not operate until the pressure in the downstream intake passage 20, that is, the boost pressure becomes higher. . Therefore, the supply pressure to the engine is controlled by the effective opening of the solenoid valve 21, and the larger the opening, that is, the higher the duty ratio of the on / off control signal and the higher the ratio of the opening time of the solenoid valve 21, the higher the supply. Controlled by pressure. Here, an on / off type solenoid valve is used as the solenoid valve 21, but a control valve having an opening adjustment function proportional to the voltage can be used.

In order to detect the operating state of the engine, an air flow meter 22 that detects the amount of intake air in the intake passages 15 and 20, an intake temperature sensor 23 that detects the intake temperature, and a throttle valve opening sensor 24 that detects the opening of the throttle valve. The engine body 1 is provided with a cooling water temperature sensor 24, and the exhaust passage is provided with an O ₂ sensor 26 for detecting the oxygen concentration of exhaust gas and notifying the air-fuel ratio.

FIG. 2 is a block diagram showing the detailed configuration of the electronic control unit 3 and the connection with each device.

The electronic control unit 3 includes a control microcomputer 30.

The reference angle sensor 7 and the rotation angle sensor 8 are electromagnetic pickup type detectors, and their output signals are waveform shaping circuits.
It is shaped into a pulse by 31 and 32, and is input to the microcomputer 30 as a reference angle signal and a rotation angle signal, respectively. Further, the signals from the respective sensors 22 to 26 for detecting the operating state are input to the digital input or analog input terminal of the microcomputer 30.

The output signal of knock sensor 11 is input to knock detection circuit 33. The knock detection circuit 33 includes a bandpass filter for extracting only the frequency band (generally 6 to 9 KHZ) peculiar to the knock, and averaging for extracting the average value of the sensor signal by rectifying and integrating the signal of this filter. Circuit, a decision level creation circuit for creating a knock decision level based on this average value signal, a comparator for knock detection of this decision level and the output after passing the filter, and a single unit for extending this comparator output for a certain period of time. It incorporates a stable multi-by-plater. The knock detection circuit 33 detects a knock having a predetermined intensity or more, and inputs a digital signal indicating the presence or absence of the knock to the microcomputer 30.

The microcomputer 30 uses the rotation angle information from the reference angle sensor 7 and the rotation angle sensor 8 and various operating state sensors 22 to 26.
Based on the driving state information from the engine, the ignition timing at which the performance such as fuel consumption and output torque is the best is calculated, the ignition timing is corrected based on the knocking information from the knock sensor 11, and the ignition signal is output. Then, the igniter 10 is driven to energize the ignition coil 9, and the energization is cut off at the calculated ignition timing to guide the high voltage generated at the time of deenergization to the ignition plug 5 of the predetermined cylinder via the distributor 6, Ignite each cylinder in turn. Further, the microcomputer 30 calculates the optimum boost pressure and changes the duty ratio of the on / off control signal to the solenoid valve 21 to control the boost pressure.
Further, the microcomputer 30 outputs an injection signal at a predetermined crank angle position with a pulse width corresponding to the calculated fuel injection amount, and opens the fuel injection valve 4 for each cylinder to inject fuel.

The internal configuration of the microcomputer 30 will be briefly described. The central processing unit (CPU) 41 of 8-bit configuration has C
Via the PU bus 42, a read-only memory (ROM) 43 for storing control programs and constants necessary for calculation, a temporary storage memory (RAM) 44 for temporarily storing calculation data, and interrupt control for the CPU 41 An interrupt control unit 45 for controlling the CPU, a 16-bit timer 46 configured to increase the count value by one for each clock cycle that is a basic cycle of CPU operation, and an analog signal selected by a multiplexer 47 into a digital signal. A / D converter 48 for conversion, input port 49 for digital signals, and output port for outputting digital signals
50 connected. The multiplexer 47 to which the analog signal is input has an air flow meter 22, an intake air temperature sensor 23,
Also, a signal from the cooling water temperature sensor 25 is input. A 2-bit contact signal from the throttle valve opening sensor 24 and a rich lean signal from the O ₂ sensor 26 are input to the input port 49. From the output port 50, an ignition signal to the igniter 10, an injection signal to the fuel injection valve 4, an on / off control signal to the solenoid valve 21, and a control signal to the multiplexer 47 are output. The reference angle signal and the rotation angle signal from the reference angle sensor 7 and the rotation angle sensor 8 are input to the interrupt control unit 45. The engine speed by the timer 46 and the interrupt control unit 45,
And the crank angle position is detected as follows. That is, the CPU 41 reads the count value of the timer 46 when the reference angle signal from the reference angle sensor 7 causes an interrupt. The count value of the timer 46 is the clock cycle (for example, 1
μs), the time interval of the reference angle signal, that is, the time required for one revolution of the engine, is calculated by calculating the difference between the count value at this interrupt and the count value at the previous interrupt. Can be measured. In this way, the engine speed is obtained. The crank angle position is determined by the rotation angle signal from the rotation angle sensor 8 at a constant crank angle (for example, 30 ° CA).
Since it is output every time, the crank angle at that time can be known in units of 30 ° CA with reference to the reference angle signal (for example, the top dead center position) from the reference angle sensor 7. This rotation angle signal for every 30 ° CA is used as a reference point for generating an ignition signal.

The operation of the knock control device according to the present invention will be described based on the above configuration.

3 and 4 are flowcharts showing the actual processing in the microcomputer 30.

When the internal combustion engine is started and the ignition timing calculation is interrupted,
Interrupt processing starts from step 100. In step 101, the rotation speed N and the load Q / N (= intake air amount Q / rotation speed N) are calculated. In step 102, the map of the basic ignition timing and the basic injection time stored in advance based on the rotation speed N and the load Q / N calculated in step 101 is searched and interpolated to obtain the basic ignition timing θ _B and the basic ignition timing. The injection time is calculated. In addition, various operating state sensors 22 other than knock sensor 11
The corrections of the ignition timing advance / retardation amount and the injection time are simultaneously performed based on the information from ~ 26. Next, at step 103, the basic duty ratio for setting the basic supercharging pressure is calculated. The basic duty ratio is calculated by searching and interpolating a stored table value based on the rotation speed N.

Next, at step 104, it is judged if the current operating condition is the knock control execution condition. For example, it is generally known that when the load of the engine is light, knocking hardly occurs, and if the light load is forcibly controlled to knock, the output, fuel consumption, etc. are rather lowered. In this embodiment, knock control is executed only when the engine load Q / N is equal to or greater than a predetermined value. It is also conceivable to set a limit by other engine speed.

If it is determined that the knock control execution condition is satisfied, in step 105, the ignition timing retard correction amount is calculated and the boost pressure is corrected by the knock control. Then, in the next step 106, the final duty ratio for setting the final ignition timing and the boost pressure is calculated. The final ignition timing is calculated as (corrected basic ignition timing)-(retard correction amount).

Details of step 105, which is a feature of the present invention, will be described with reference to FIG.

First, in step 201, the presence or absence of knock is determined by the output of the knock detection circuit 33. If it is determined that there is knocking, the routine proceeds to step 202, where the ignition timing retard correction amount R
Is increased by a predetermined angle ΔR. Then, in step 203, it is checked whether or not the supercharging pressure is currently being increased. If the supercharging pressure is currently increasing, then in step 204, the supercharging pressure is stopped from increasing. On the other hand, step 201
When it is determined that there is no knock in step 205, the process proceeds to step 205, and it is determined whether or not there is no knock for a predetermined time T (generally, 0.5 second to 1 second is suitable). If the state without knocking has not continued for the predetermined time T or more, the routine proceeds to step 206, where the current retard correction amount R is held.
If the state without knocking continues for a predetermined time T or more, the process proceeds to step 207. In step 207, it is checked whether or not it is in the boost pressure increase permission range by checking the flag set in step 211 described later. If it is in the boost pressure increase permission range, the routine proceeds to step 208, where the boost pressure is started to increase.
When the boost pressure is increased, the next knock occurs.
At 204, the boost pressure is gradually increased until it stops. If it is not in the boost pressure increase permission range, proceed to step 209,
The retard correction amount R is decreased by a predetermined angle Δr. When the retard correction amount R becomes 0, the value is set to 0 as it is and is not set to a negative value. The predetermined angles ΔR and Δr for increasing / decreasing the retard correction amount R are generally preferably about 1 ° CA (crank angle).

Next, at step 210, the magnitude of the retard correction amount R set as described above is discriminated.

When the retard correction amount R is small and is less than or equal to the first set value R1 close to 0 (R <R1), the process proceeds to step 211, and the increase of the supercharging pressure is permitted. The retard correction amount R is within the predetermined range (R1 ≦ R ≦ R2)
In this case, it is determined that the boost pressure is appropriate, and the routine proceeds to step 212, where the current boost pressure is maintained. The retard correction amount R is large,
If the second predetermined value R2 or more (R2 <R), it is determined that the exhaust temperature is a problematic operating condition, and the process proceeds to step 213, where the duty of the on / off control signal is gradually reduced to gradually reduce the supercharging pressure. Correct the ratio. It is preferable that the first predetermined value R1 for discriminating the magnitude of the positive retardation amount R is set to 2 ° CA and the second predetermined value R2 is set to about 7 ° CA.

FIG. 5 is a timing chart showing an example of changes in the supercharging pressure Pa and the retard correction amount R controlled as described above.

When a knock occurs, the retard correction amount R is increased by a predetermined angle ΔR and the ignition timing is retarded (301 in FIG. 5). Then, the boost pressure Pa starts to increase for a predetermined time T without knocking (302 in FIG. 5). When knock occurs due to the increase of the supercharging pressure Pa, the rise of the supercharging pressure Pa is stopped and the retard correction amount R is also increased (303 in FIG. 5). In this way, the retard correction amount R is increased each time a knock occurs, and when the retard correction amount R exceeds the first predetermined value R1, the supercharging pressure Pa is prohibited from increasing and only the delay correction amount R is operated to be increased or decreased. (Fifth
304). However, when knocking occurs frequently and the retard correction amount R increases and the second predetermined value R2 is exceeded, the supercharging pressure Pa is gradually reduced (305 in FIG. 5). When the knock is suppressed due to the decrease of the supercharging pressure Pa, the retard correction amount is decreased every predetermined time T and the ignition timing is advanced (306 in FIG. 5).

In this way, the retard correction amount R is always within the predetermined range (R1
≦ R ≦ R2), and within the limit where the exhaust temperature on the trace knock line (KN3 line in Fig. 6) that generates appropriate knock for ignition timing and boost pressure is not a problem. Since the control can be performed so as to always follow the vicinity of the maximum torque point (for example, point F in FIG. 6), knock control with a large torque merit can be realized.

In the above-described embodiment, the operating condition in which the exhaust gas temperature rises is determined by the magnitude of the retard correction amount R, but the exhaust gas temperature is directly detected by using the exhaust gas temperature sensor, and the exhaust gas temperature rises above the predetermined temperature. In some cases it may be possible, but rather desirable, to reduce the boost pressure. However, at present, it is not possible to find an exhaust gas temperature sensor that satisfies the accuracy, durability and price, and it is more practical to make a determination from the retard correction amount as in the above embodiment.
Of course, such an exhaust temperature sensor will be developed in the near future, and in that case, an embodiment using the exhaust temperature sensor is a more preferable embodiment of the present invention.

〔The invention's effect〕

As described above, according to the present invention, the ignition timing and the supercharging pressure are traced in response to the occurrence of knocking while suppressing the knocking, and the maximum torque point within the limit in which the exhaust temperature on the knock line does not matter. Since the control can be made to follow the vicinity, torque loss is minimized, exhaust gas temperature rise is prevented, and knock control with good responsiveness can be performed.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention, FIG. 1 is an overall configuration diagram, and FIG. 2 is a block diagram showing an electronic control unit.
3 and 4 are flowcharts showing the processing by the microcomputer, FIG. 5 is a timing chart showing the transition of the retard correction amount and the boost pressure, and FIG. 6 is a graph showing the boost pressure and the ignition timing. It is a characteristic view showing a torque characteristic and a knock characteristic. 1 ... Engine body, 2 ... Supercharger, 3 ... Electronic control device, 5 ... Spark plug, 6 ... Distributor, 7
…… Reference angle sensor, 8 …… Rotation angle sensor, 11… Knock sensor, 12 …… Turbine, 14 …… Compressor, 16 …… Bypass passage, 17 …… Waste gate valve, 18 …… Diaphragm actuator, 21… … Solenoid valve, 30 …… Microcomputer, 33 …… Knock detection circuit.

Claims (3)

[Claims] 1. A knock sensor, an ignition timing control means, and a supercharging pressure control means are provided, and a retard correction amount and a supercharging pressure for correcting the ignition timing in a retard direction in accordance with a knocking occurrence state are provided. In a knock control device for an internal combustion engine with a supercharger, a means for increasing the retard correction amount when a knock occurs, and a means for increasing the retard correction amount when a knock does not occur are below a first predetermined value. Is a means for increasing the supercharging pressure, a means for decreasing the retard correction amount when the knock amount is greater than or equal to the first predetermined value when no knock occurs, and an operating condition in which the exhaust temperature rises. A knock control device for an internal combustion engine with a supercharger, comprising: means for reducing supercharging pressure. 2. The knock control device for an internal combustion engine with a supercharger according to claim 1, wherein the first predetermined amount is a small value close to zero. 3. An internal combustion engine with a supercharger according to claim 1 or 2, wherein the operating condition for increasing the exhaust gas temperature is that the retard correction amount is equal to or greater than a second predetermined value. Knock control device.