JPH0681950B2 - 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. Generally, the ignition timing is controlled by the basic ignition timing θ from the engine speed N and the load Q / N (= intake air amount Q / rotation speed N) or the intake pressure.
This is performed by obtaining β and correcting the ignition timing from the basic ignition timing θβ in the retard direction in accordance with the knocking occurrence state.

In recent years, in addition to a device for avoiding knock by operating only the ignition timing, a device for controlling ignition timing and boost pressure in cooperation with each other has been proposed in order to bring out the advantage of knock control and to obtain high torque. . In this type of device, it is general that the ignition timing is retarded and the supercharging pressure is reduced.However, if the supercharging pressure is reduced, the basic ignition timing θβ shifts to the advance side, so that the supercharging pressure decreases. There is a problem that the ignition timing may be temporarily advanced and conversely knock may easily occur. For example, as shown in FIG. 7, boost pressure Pa
As a result, the knock limit ignition timing θKN, which is the limit of knock generation, is advanced due to the decrease of the ignition timing, but the basic ignition timing θβ is advanced more than that, and the required retardation correction amount R is The problem is that the number of knocks may increase rapidly, causing frequent knocking. Of course, this problem is a transient problem, and the ignition timing will be retarded and controlled to the knock limit ignition timing θKN line due to the occurrence of knock, but a large number of knocks is not desirable temporarily. Therefore, a method has been proposed in which, while the supercharging pressure is being reduced, the basic ignition timing is calculated by the supercharging pressure immediately before the reduction of the supercharging pressure and the ignition timing is controlled (Japanese Patent Laid-Open No. 57-179372).
However, in this method, while the boost pressure is being reduced, the ignition timing will not advance even if knock does not occur, and the torque loss will be controlled on the retard side from the knock limit ignition timing θKN. There was a problem that was large.

[Problems to be solved by the invention]

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a knock control device that prevents a large number of knocks when the boost pressure is reduced and that minimizes torque loss. .

[Means for solving problems]

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. In a knock control device for an internal combustion engine with a supercharger for controlling the engine, when the supercharging pressure is reduced, the knock control device is provided with a means for limiting the moving speed of the target ignition timing in the advance direction. A knock control device for an internal combustion engine with a feeder is provided.

[Action]

According to the above configuration, when the supercharging pressure is reduced, the target ignition timing is gradually moved in the advance direction.
The ignition timing does not rapidly advance when the supercharging pressure decreases, and it is possible to prevent a large number of transient knocks.

〔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 any type such as an electrodynamic type, a piezoresistive type, a strain gauge type, etc., in addition to 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 16 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. Although an on-off type solenoid valve is used as the solenoid valve 21 here, it is also possible to use a control valve having an opening adjustment function proportional to the voltage.

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 25, 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 multivibrator. 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 CPU 41 for interrupt control. Interrupt control unit 45, a 16-bit timer 46 configured so that the count value increases by 1 for each clock cycle that is the basic cycle of CPU operation, and the analog signal selected by the multiplexer 47 is converted into a digital signal A / D converter 48, input port for digital signals
49, and output port 50 for outputting digital signals
Are connected. Signals from the air flow meter 22, the intake air temperature sensor 23, and the cooling water temperature sensor 25 are input to the multiplexer 47 to which the analog signal 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 and the crank angle position are detected by the timer 46 and the interrupt control unit 45 as follows. That is, the CPU 41 reads the count value of the timer 46 each time an interrupt is generated by the reference angle signal from the reference angle sensor 7. The count value of the timer 46 is the clock cycle (eg 1 μs)
Since it goes up every time, the time interval of the reference angle signal, that is, the time required for one engine revolution is measured by calculating the difference between the count value at this interrupt and the count value at the previous interrupt. it can. In this way, the engine speed is obtained. The crank angle position is based on the reference angle signal from the reference angle sensor 7 (for example, the top dead center position) because the rotation angle signal from the rotation angle sensor 8 is output at every constant crank angle (for example, 30 ° CA). Then, the crank angle at that time can be known in units of 30 ° CA. 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 to 5 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 correction of the advance / retard of the ignition timing and the correction of the injection time are performed at the same time 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. In addition, it is possible to set a limit depending on the engine speed.

If it is determined that the knock control is being executed, the routine proceeds to step 105, where the target ignition timing is calculated, and then at step 106, the ignition timing retard correction amount is calculated by knock control and the boost pressure is corrected. . If it is not under the knock control execution condition, steps 105 and 106 are skipped and the routine proceeds to step 107. Then, in the next step 107, the final ignition timing and the final duty ratio are calculated. The final ignition timing is calculated as (target 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 150, it is checked whether the boost pressure is currently decreasing. If the boost pressure is not decreasing, step 151
Then, the basic ignition timing θβ calculated in step 102 is directly used as the target ignition timing θT. On the other hand, if the supercharging pressure is decreasing, the routine proceeds to step 152. In step 152, it is checked whether or not the difference between the basic ignition timing θβ and the target ignition timing θT is less than or equal to a predetermined value ΔA. If it is less than or equal to the predetermined value ΔA, the process proceeds to step 151, and if it is greater than or equal to the predetermined value ΔA, step 153. Proceed to. In step 153, a value obtained by adding the predetermined value ΔA to the current target ignition timing θT is set as a new target ignition timing θT. (Θ
T ← θT + ΔA). In this way, the moving speed of the target ignition timing θT in the advance direction is limited while the boost pressure is decreasing,
The target ignition timing θT can gradually approach the basic ignition timing θβ.

Next, details of step 106 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 a knock, the process proceeds to step 202. In step 202, it is checked whether or not the supercharging pressure is being reduced. If it is not decreasing, it is in a steady state, so the routine proceeds to step 203, where the retard correction amount R is increased by the predetermined angle Δθ1. The value of Δθ1 is, for example, 1 ° CA
Set to (crank angle). If the supercharging pressure is decreasing, it means that it is in a transient state, so the routine proceeds to step 204, where the retard correction amount R is increased by Δθ2 larger than Δθ1. The value of Δθ2 is set to 2 ° CA, for example.

On the other hand, if it is determined in step 201 that there is no knock, the process proceeds to step 205. In step 205, it is determined whether or not knocking has continued for a predetermined time (generally 0.5 to 1 second) or more. Step if not continued for more than a predetermined time
The process proceeds to 206 and holds the current retard correction amount R. If the state without knocking continues for a predetermined time or more, the process proceeds to step 207.

In step 207, similarly to step 202, it is checked whether or not the supercharging pressure is being reduced. Step 20 if not decreasing
In step 8, the retard correction amount R is decreased by the predetermined angle Δθ3.
The value of Δθ3 is set to, for example, 1 ° CA, which is the same as Δθ1, but may be set to a value different from Δθ1 as a matter of course. If the boost pressure is decreasing, it means that it is in a transient state.
Then, the retard correction amount R is decreased by the predetermined angle Δθ4.
The value of Δθ4 is, for example, larger than Δθ3 and equal to Δθ2, which is 2
Set to ° CA, but depending on the type of engine Δθ3
In some cases, it may be preferable to set the size as small as.

In this way, the ignition timing retard correction amount R is increased, decreased, or held in accordance with the knocking occurrence state.

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 equal to or less than the first set value R1 close to 0 (R> R1), the routine proceeds to step 211, where the duty ratio of the on / off control signal is increased in order to increase the supercharging pressure Pa by a predetermined pressure ΔP. To correct. The retard correction amount R is within the predetermined range (R1 ≦ R
If ≦ R2), it is determined that the boost pressure is appropriate and step 212
Go to and keep the current boost pressure. If the retard correction amount R is large and is equal to or greater than the second predetermined value R2 (R2 <R), it is determined that the exhaust temperature is an operating condition that causes a problem, and step 213
Then, the duty ratio of the on / off control signal is corrected so as to reduce the supercharging pressure Pa by the predetermined pressure Δp. The predetermined pressures ΔP and Δp for increasing / decreasing the supercharging pressure Pa are preferably about 50 mmHg, and the first predetermined value R1 for discriminating the magnitude of the retard correction amount R is 2 ° CA.
In addition, the second predetermined value R2 is preferably set to about 7 ° CA.

FIG. 6 is a timing chart showing an example of changes in the supercharging pressure and the ignition timing controlled as described above.

Under the knock control execution condition, the retard correction amount R is increased / decreased according to the knock occurrence state, and the final ignition timing θF is controlled to be retarded by the retard correction amount R from the target ignition timing θT. When the supercharging pressure drops, the target ignition timing θT is determined by the supercharging pressure at that time, the number of revolutions, etc.
The ignition timing is controlled so that the ignition timing is gradually approached, and the amount of increase / decrease in the retard correction amount R depending on the presence or absence of knock is also increased, so that the target ignition timing θT is quickly followed, and frequent occurrence of knock is prevented.

In this way, in the steady state as well as in the transient state,
Since the retard correction amount R is controlled so that the ignition timing is near the knock limit ignition timing (θKN line in FIG. 7), knock control with small torque loss is realized.

〔The invention's effect〕

As described above, according to the present invention, it is possible to prevent the knock from occurring frequently when the boost pressure is reduced, minimize the torque loss, and perform high torque knock control in which the ignition timing and the boost pressure are linked. It has an excellent effect that it can be performed.

[Brief description of drawings]

1 to 6 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.
FIGS. 3, 4, and 5 are flowcharts showing the processing by the microcomputer, FIG. 6 is a timing chart showing the transition of the boost pressure and the ignition timing, and FIG. 7 is a chart when the boost pressure drops. It is a characteristic view showing knock limit ignition timing characteristics. 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 …… wastegate valve, 18 …… diaphragm type actuator, 21 …… solenoid valve, 30 …… microcomputer, 33 …… knock detection circuit.

Claims (2)

[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. A knock control device for an internal combustion engine with a supercharger, which is controlled, is provided with means for limiting a moving speed of a target ignition timing in an advance direction when the supercharging pressure is reduced. Knock control device for internal combustion engine with engine. 2. A knock control for an internal combustion engine with a supercharger according to claim 1, further comprising means for increasing an increase amount of the retard correction amount when a knock occurs when the supercharging pressure is reduced. apparatus.