JPH0765560B2 - Knock control device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a knock control device (knock control system) for controlling knock generated in an internal combustion engine.

[Conventional technology]

In the conventional knock control system, the knock determination level for identifying the presence or absence of knock is improperly set due to the variation of the engine / knock sensor, and as a result,
There was a problem that the knocking noise during control was large and varied from vehicle to vehicle.

In order to solve this problem, the present inventors have already disclosed in
Japanese Patent Laid-Open No. 60-243369 discloses a method and apparatus for automatically correcting the knock determination level in an appropriate direction by using the statistical property of the knock sensor signal.

[Problems to be solved by the invention]

However, in a system that automatically corrects the knock determination level in this way, if abnormalities occur in the knock sensor system, or if combustion of the engine becomes abnormal for some reason, if automatic correction is continued, There was a problem that the performance would be lower than that of the conventional system when the engine was restored to its original normal state due to the replacement and repair of the sensors and devices by correcting in the wrong direction.

For example, consider the case where the knock sensor signal system is open or short-circuited and no sensor signal is input.

Generally, when an abnormality occurs in the knock sensor system, it is called a knock sensor fail, and the ignition timing is retarded by a predetermined amount to take safety measures.

In this case, no matter where the knock determination level is set, the ignition timing is set independently of the knock control, so even if the determination level is erroneously corrected, it seems that there is no particular problem, but the knock sensor works normally. Problems will occur if you return. That is, in a system that automatically corrects the knock determination level, the amount that is erroneously corrected when the knock sensor is abnormal is applied as it is when returning to normal. This becomes a particular problem, for example, when the correction amount of the knock determination level is stored in the backup RAM even after the ignition switch is turned off.

The same applies when a sensor device failure that causes an abnormality in the combustion state of the engine occurs other than the knock sensor abnormality.

For example, when an abnormality occurs in the rotation angle sensor, the vehicle is generally allowed to run in a backup mode with degraded performance, but combustion in such a case is different from normal combustion. At this time, since the knock determination level is corrected so as to match this abnormal state, there is a problem that an inappropriate determination level is applied when the engine returns to normal combustion.

Therefore, the present invention prevents an inappropriate knock determination level from being applied when the sensor / device becomes abnormal and the sensor / device is replaced and repaired to return to the original normal state. The purpose is to prevent.

[Means for solving problems]

Therefore, according to the present invention, as shown in FIG. 1, a knock sensor for detecting knock of the internal combustion engine, a knock intensity value detecting means for detecting the knock intensity value V from the signal of the knock sensor, and a knock determination level V _ref are set. Judgment level creating means for creating, knock strength value V and knock judgment level V _ref
Knock determination means for determining the presence or absence of knock by comparison with, drive means for controlling the knock control factors such as ignition timing according to the determination result, knock determination level correction means for automatically correcting the knock determination level, Backup means for holding the correction amount of the knock determination level even when the ignition switch is turned off, and a sensor that controls the combustion state of the internal combustion engine or a sensor that prohibits the correction of the knock determination level when an abnormal state of the device is detected. The invention provides a knock control device for an internal combustion engine, comprising: a device abnormality detecting means.

[Action]

As a result, when the sensor / device abnormality detecting means detects an abnormality in the sensor or the device that affects the combustion state of the internal combustion engine, the knock determination level correction means prohibits the correction of the knock determination level, and as a result, the backup means in the meantime. The erroneous correction of the correction amount of the held knock determination level is prevented.

〔Example〕

The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 2 is a block diagram showing an embodiment of the present invention.

In FIG. 2, 1 is a 4-cylinder 4-cycle engine, 2 is an air cleaner, 3 is an air flow meter that detects the intake air amount of the engine 1 and outputs a signal corresponding to it, 4 is a throttle valve, 5 is a reference of the engine 1. This is a distributor that incorporates a reference angle sensor 5A for detecting a crank angle position (for example, top dead center) and a crank angle sensor 5B that generates an output signal at every constant crank angle of the engine 1. 6
Is a knock sensor for detecting the vibration of the engine block corresponding to the knock phenomenon of the engine 1 by a piezoelectric element type (piezo element type), an electromagnetic type (magnet, coil), etc., and 7 is a peak of the output of the knock sensor for each cylinder. It is a peak hold circuit section for holding. Reference numeral 9 is a water temperature sensor that generates a signal according to the cooling water temperature of the engine, 12 is a fully closed switch (idle switch) 13 for outputting a signal when the throttle valve 4 is fully closed, and the throttle valve 4 is almost fully open. Is a full-open switch (power switch) to output a signal when, and 14 is the exhaust gas air-fuel ratio (A / F)
Is richer or leaner than the stoichiometric air-fuel ratio
It is an O ₂ sensor that generates an output signal according to

Reference numeral 8 is a control circuit for controlling the ignition timing and air-fuel ratio of the engine according to the input / output signal states from the respective sensors and switches, and 10 is an ignition coil which receives an ignition timing control signal output from the control circuit 8. These are an igniter and an ignition coil that cut off energization to the. The high voltage generated in the ignition coil is applied to the ignition plug of a predetermined cylinder at an appropriate time through the power distribution unit of the distributor 5. Reference numeral 11 is an injector for injecting fuel into the intake manifold based on the fuel injection time (τ) determined by the control circuit 8.

Next, the detailed configuration of the peak hold circuit section 7 will be described with reference to FIG. 701 in FIG. 3 is a filter such as a band pass or a high pass for selecting and extracting only the knock frequency component of the output signal of the knock sensor 6, 702 is an amplifier, 703 is based on the cylinder switching signal from the control circuit 8 It is a peak hold circuit that holds the output signal of the knock sensor by a capacitor or the like.

Next, the detailed configuration and operation of the control circuit 8 will be described with reference to FIG. In FIG. 4, reference numeral 8000 is a central processing unit (CPU) for calculating the ignition timing and the fuel injection amount, which uses an 8-bit microprocessor. 8001 is a read-only storage unit (ROM) for storing control programs and control constants necessary for calculation, 8002 is a CPU 8000
Is a temporary storage unit (RAM) for temporarily storing operation data during operation according to a program. Reference numeral 8003 is a waveform shaping circuit for shaping the output signal of the reference angle sensor 5A, and 8004 is a waveform shaping circuit for shaping the output signal of the crank angle sensor 5B.

8005 is an interrupt control unit that causes the CPU 8000 to perform interrupt processing by an external or internal signal, and 8006 is a 16-bit timer configured to increase the count value by one every clock cycle that is the basic cycle of CPU operation. is there. The engine speed and the crank angle position are detected by the timer 8006 and the interrupt control unit 8005 as follows. That is, the CPU 8000 reads the count value of the timer each time an interrupt is generated by the output signal of the reference angle sensor 5A. The count value of the timer is the clock cycle (for example 1 μ
s), the time interval of the reference angle sensor signal, that is, 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. Time can be measured. In this way, the engine speed is obtained. In addition, the crank angle position is determined based on the top dead center signal of the reference angle sensor 5A because the signal of the crank angle sensor 5B is output at every constant crank angle (for example, 30 ° C). You can know in A units. The crank angle signal for every 30 ° C. is used as a reference point for generating the ignition timing control signal and a cylinder switching signal of the peak hold circuit 703.

The 8007 is an analog that switches multiple analog signals at appropriate times.
It is a multiplexer for guiding to a digital converter (A / D converter) 8008, and the switching timing is controlled by a control signal output from the output port 8010. In this embodiment,
An output signal of the knock sensor signal from the peak hold circuit unit 7, an intake air amount signal from the air flow meter 3, and a water temperature signal from the water temperature sensor 9 are input as analog signals. 8008 is an A / D converter for converting an analog signal into a digital signal. 8009 is an input port for a digital signal, and an idle signal from the idle switch 12 in this embodiment, a power switch
The power signal from 13 and the rich lean signal from the O ₂ sensor 14 are input. 8010 is an output port for outputting a digital signal. Igniter 10 from this output port
Is output, a fuel injection signal for the injector 11, a cylinder switching signal for the peak hold circuit 7, and a control signal for the multiplexer 11.
Reference numeral 8011 denotes a CPU bus, and the CPU 8000 puts a control signal and a data signal on this bus signal line to control peripheral circuits and send and receive data.

The configuration of the device for implementing the present invention has been described above, and the contents of knock control will be described with reference to the flowchart of FIG.

When the knock control routine is started from step 100, the knock intensity value V is fetched in step 200. The intensity value V is, for example, the maximum peak value in a predetermined section of the knock sensor signal.

In step 300, knock determination level V _ref is created as follows.

V _ref = K × KC × V50 Here, K is a constant written in ROM in advance, and is a table of engine speed. KC is a K value for judgment level correction, and is created in step 700.
In addition, this KC also has a table of engine speed, intake air amount Q / N per engine point, cylinder, etc., and
It is desirable to back up. V50 is the median value of the V distribution and is created in step 500 for each cylinder.

In step 400, knock determination and retard amount calculation are performed.

In step 500, the knock state detection parameter is updated.

In step 600, it is judged whether the judgment level correction condition is satisfied.

In step 700, the judgment level is corrected.

In step 800, the knock state detection parameter is initialized.

At step 900, the knock control routine ends.

Using the flowchart of FIG. 6, step 40 of FIG.
0 will be described in detail.

When the routine for knock determination and retard amount calculation starts from step 4001, it is determined in step 4002 whether the engine is in the knock control region, and if YES, the process proceeds to step 4003.

In step 4003, the knock sensor fail flag is used to check whether the knock sensor is normal.

The knock sensor failure is detected in the main routine,
In this step 4003, only the fail flag which is the detection result is referred to. That is, in the main routine, the representative value of the sensor output (for example, the median value V50 of the maximum _peak value Vpeak)
Is being monitored, and when the sensor output value becomes equal to or less than a predetermined value, it means that the knock sensor system (sensor and signal line) has failed, and the sensor fail flag is set.

Although there are various methods for detecting knock sensor failure, conventional methods are also common and will not be described in further detail.

When it is determined in step 4003 that the knock sensor is in the fail state, the retard amount R is set to the maximum value R _max in step 4010, and the ignition timing is set to the maximum retard side regardless of the knock detection result. Force retard. By such control, even if the knock sensor fails, the engine can be operated safely. If it is determined in step 4003 that the knock sensor is normal, the process proceeds to step 4004.

In step 4004, it is determined whether there is a knock based on the magnitude relationship between V and V _ref . If YES (V ≧ V _ref ), step 400
Go to 5. At step 4005, the retard amount R is increased by a predetermined amount ΔR.

If NO is determined in step 4004, the process proceeds to step 4006, and it is determined whether there is no knocking for a predetermined period. If YES, the process proceeds to step 4007, and if NO, the process proceeds to step 4008. In step 4007, the retard amount R is reduced by a predetermined amount ΔR. In step 4008, the retard amount R is guarded within a predetermined range.

If NO in step 4002, the process advances to step 4009 to set the retard amount to the initial value RO.

This routine ends at step 4011.

The step 500 of FIG. 5 will be described in detail with reference to FIG.

When the update of the knock state detection parameter is started from step 5001, V fetched this time is V50 in step 5002.
It is determined whether it is larger, and if YES, the process proceeds to step 5003. In step 5003, level V _h is created as follows.

V _h = (A + D) × V 50 Here, A is a cylinder-specific variable created in step 700. D is a predetermined constant, and may have various values as a table of engine speed, Q / N, cylinder, and the like.

In the next step 5004, V _h is guarded below a predetermined value.
Next, the routine proceeds to step 5005, where V ≧ V _h is judged, and if YES, it proceeds to step 5006, and if NO, it proceeds to step 5007. In step 5006, the knock state detection counter CPHL (for each cylinder) is incremented. Then proceed to step 5007,
Increase V50 by DV50.

If NO in step 5002, the flow advances to step 5008 to make a determination of V <V50. Here, if YES is determined, the process proceeds to step 5009 to determine A × V ≦ V50.
If YES is determined here, the process proceeds to step 5010,
Decrement the knock state detection counter CPHL. Next, the process proceeds to step 5011, and V50 is reduced by DV50. Next, the processing proceeds to step 5012, and A of the cylinder currently being processed
Set the flag.

If NO in steps 5008 and 5009, the process advances to step 5013.

In step 5013, DV50 is set as follows.

DV50 = (| V−V50 |) / 16 Next, the routine proceeds to step 5014, where DV50 is guarded within a predetermined range.

In step 5015, this routine ends.

Next, using the flowchart of FIG. 8, the steps of FIG.
The 600 will be described in detail. This part is a characteristic part of the present invention. When the determination routine for determining the determination level correction condition is started from step 6001, it is checked in step 6002 whether the knock determination level correction interval has elapsed.
That is, the correction of the knock determination level is executed at predetermined time intervals.

If NO, the process branches to step 900 in FIG. 5, but if YES, the process proceeds to the next step 6003.

In step 6003, the knock sensor fail flag is checked to determine whether or not the knock sensor is normal.

Since the knock determination level is not corrected when the knock sensor is in the fail state, step 7007 in FIG. 9 is executed.
Branch to.

Step 6004 if the knock sensor is considered normal
Then, the process proceeds to and checks whether or not various sensors for controlling the engine (eg, rotation angle sensor, pressure sensor, etc.) and devices (igniter, injector, etc.) are normal.
That is, it is checked whether the engine is currently operating under normal combustion conditions.

The abnormality detection of the sensor device is executed in the main routine, and the result is referred to as a flag.
The abnormality detection method is already common as engine control diagnosis, so it will not be described in detail.
In such an abnormal state, the vehicle enters a retreat traveling state generally called a backup mode.

If various sensors / devices are normal in step 6004, the process proceeds to step 6005 and continues to the knock determination level correction step, but if abnormal is determined, the process branches to step 7007 in FIG. 9 to determine the knock determination level. Skip the correction step of.

Using the flowchart of FIG. 9, step 70 of FIG.
0 will be described in detail.

When the judgment level correction routine starts from step 7001, the routine proceeds to step 7002, where it is judged whether the knock state is too large. For example, when CPHL> 0 or A ≧ A _max , it is determined that the knocking state is too large. If YES, the process proceeds to step 7003, and the determination level is reduced. For example, KC is reduced by a predetermined amount DK.

If NO is determined in step 7002, the process proceeds to step 7004, and it is determined whether the knocked state is too small. For example, CP
When HL <0, it is judged that the knocked state is too small. If YES, the process proceeds to step 7005, and the determination level is increased. For example, KC is increased by a predetermined amount DK.

In step 7006, the judgment level is guarded within a predetermined range. For example, guard KC between KC _min and KC _max . this
It is desirable to have KC _min and KC _max in a table of engine speed.

In step 7007, it is determined whether the A flag of the target cylinder is set. If YES, then step 7008
If NO, go to 7009. In step 7008, A is increased by a predetermined amount DA, and in step 7009, A is decreased by a predetermined amount DA. Next, the routine proceeds to step 7010, where A is guarded within a predetermined range. The above steps 7002 to 7010 are executed for all cylinders, and this routine ends in step 7011.

Step 800 of FIG. 5 will be described in detail with reference to FIG. When the knock state detection parameter initialization routine starts from step 8001, the process proceeds to step 8002, where CPHL,
Clear the A flag. Next, the process proceeds to step 8003, and it is determined whether the processing for all cylinders is completed. If NO, the process of step 8002 is performed for the next cylinder. If YES, this routine ends in step 8004.

In the above-described embodiment, the knock determination level is corrected by the distribution shape of the maximum peak value of the knock sensor signal, but the same is applied to all of those that correct the knock determination level according to the combustion state of the engine or the knock detection result. The invention can be applied.

Further, in the above-described embodiment, although the abnormality in the rotation angle sensor and the pressure sensor is detected, the same determination is made when the sensor that influences the combustion state is abnormal, which is related to the engine control such as the air flow meter and the water temperature sensor. Level modification can be prohibited. Further, in the device, the same can be considered for the failure of the supercharger.

〔The invention's effect〕

As described above, in the present invention, the combustion state of the internal combustion engine is influenced even if the correction amount of the knock determination level is held even when the ignition switch is turned off in consideration of the influence of the secular change of the knock determination level. When the abnormal state of the sensor or device is detected, the knock determination level is not corrected in the wrong direction, so the backup means also does not hold the incorrect correction amount. There is an excellent effect that an inappropriate knock determination level can be prevented from being applied when returning to the original normal state, and the knock can be accurately determined.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram for clarifying the configuration of the device according to the present invention, FIG. 2 is a diagram showing an embodiment of the device for implementing the present invention, and FIG. 3 is a peak in FIG. FIG. 4 is a block diagram of the hold circuit section, and FIG. 4 is a detailed block diagram of the control circuit in FIG.
FIG. 5 is a flow chart showing the procedure of knock control in the present invention, and FIGS. 6 to 10 are flow charts showing specific examples of steps 400 to 800 in FIG. 1 ... Engine, 5 ... Distributor, 6 ... Knock sensor, 7 ... Peak hold circuit section, 8 ... Control circuit, 10
...... Ignitioner and ignition coil, 703 ...... Peak hold circuit, 8000 ...... Central processing unit, 8001 ......
ROM, 8002 …… RAM.

Continuation of front page (56) References JP-A-60-243369 (JP, A) JP-A-60-164234 (JP, A) JP-A-61-101675 (JP, A)

Claims (2)

[Claims] 1. A knock sensor for detecting knock of an internal combustion engine, and a knock intensity value V from a signal of the knock sensor.
For detecting knock intensity value and knock determination level
And determining the level generating means for generating V _ref, and the knock determining means determines the presence or absence of knock by comparing said knock intensity value V and the knock determination level V _ref, knock control factor of the ignition timing or the like according to the determination result Drive means for controlling, knock determination level correction means for automatically correcting the knock determination level V _ref , backup means for holding the correction amount of the knock determination level even when the ignition switch is off, and the combustion state of the internal combustion engine. A knock control device for an internal combustion engine, comprising: a sensor / device abnormality detection means that prohibits correction of the knock determination level when an abnormal state of a sensor or a device that influences is detected. 2. The sensor device is a knock sensor,
The knock control device for an internal combustion engine according to claim 1, wherein the knock control device is at least one of a rotation angle sensor, a pressure sensor, an air flow meter, an igniter, and an injector.