JPH0758064B2 - Knock control device for internal combustion engine - Google Patents

Description

The present invention relates to a knock for an internal combustion engine that controls control factors such as ignition timing, air-fuel ratio, boost pressure, etc., according to the knocking state of the internal combustion engine (engine). Regarding the control device.

[Conventional technology]

Conventionally, the knock generation state can be detected from the distribution shape of the value LOG (V) obtained by logarithmically converting the maximum value V of the knock sensor output signal at the time of engine combustion, and the knock determination level can be corrected based on this. However, a method of setting an appropriate knock determination level has been considered (for example, Japanese Patent Laid-Open No.
60-243369).

First, this basic idea will be described. When the maximum value V _MAX of the knock sensor signal in a predetermined section is multicycle sampled and plotted on a log-normal probability paper, it is shown in FIG. 2 (a) in the state without knock and the state in which knock occurs at a certain frequency, respectively. (B) (These are the rotational speeds of a 2000cc 6-cylinder internal combustion engine with a supercharger.
It shows the characteristics of 4000 _rpm , throttle fully open, and fifth cylinder). As described above, the internal combustion engine generally has the characteristic that the distribution when there is no knock becomes a straight line and the distribution when there is a knock bends in accordance with the frequency of the knock. An example of a knocking state detection method utilizing this property will be described with reference to FIG. First, for the median of the distribution, that is, the point V _{50 with} a cumulative probability of 50%, the upper and lower 2
Two thresholds V _H and V _L are set.

V _H = A × D × V _{50 VL} = V ₅₀ / A where A is a variable that is adjusted so that V ≦ V _L has a predetermined frequency, and D is a constant slightly larger than 1. . Assuming that the probabilities of V ≧ V _H , V ≦, and _L with respect to these two thresholds are P _h and P _L , respectively, as is clear from FIG. 2, when there is no knock, P _h <P _L , P _h ≈ P _L at trace knock. Moreover, when the knock becomes larger than the trace knock, the bending of the distribution also becomes larger, and P _h > P _L. In other words, (i) If P _h <P _L , the knocked state is too small.

(Ii) If P _h ≈ P _L , the knock state is appropriate.

(Iii) If P _h > P _L , the knocked state is too large.

It will be. Therefore, a knock state detection counter called PHL is prepared, and this counter is incremented if V ≧ V _h and decremented if V ≦ V _L. If this is performed within a predetermined period, the knocked state can be detected from the magnitude of PHL.

Next, an example of a method for appropriately correcting the knock determination level will be shown. The suitability of the knock determination level cannot be determined only from the knocked state. That is, the fact that knock has not occurred does not necessarily mean that the knock determination level is too low. For example, even if an appropriate knock determination level is set, when a fuel having a high octane number is used, for example, knock does not normally occur. Therefore, because the judgment level is too small, it is necessary to identify whether noise is erroneously detected as knock and the ignition timing is retarded more than necessary to cause knock, or whether knock is caused by factors such as fuel. is there. Both of them can be identified by the frequency of knock determination or the movement of the retard amount. For example, when the knock state is too small, the former can be determined if the frequency of knock determination is high, and the latter can be determined if the frequency is low. The same idea can be applied when the knocked state is too large.

Therefore, (i) if the knock state is too large and the knock determination frequency is low, it is determined that the knock determination level is too high,
Reduce the knock determination level.

(Ii) If the knock state is too small and the frequency of knock determination is high, it is determined that the knock determination level is too small, and the knock determination level is increased. The knock determination level may be corrected in this way.

[Problems to be solved by the invention]

By doing so, it is possible to set the appropriate knock determination level by inhaling the manufacturing error of the engine, the knock sensor, etc., the change over time, etc. However, the inappropriate knock determination level is corrected to an appropriate value. Until then, the knocking determination will be incorrect. Therefore, during this period, there is a problem that the ignition timing may be excessively advanced and knock may occur frequently, or conversely, the ignition timing may be excessively retarded and torque cross and exhaust temperature may be increased.

Therefore, the present invention quickly realizes an appropriate knocking state to reduce frequent knocking and torque cross.

[Means for Solving Problems] Therefore, as shown in FIG. 1, the present invention provides a knock sensor for detecting knock of an internal combustion engine and a determination for creating a determination level for determining knock of the internal combustion engine. Level creating means, knock determining means for determining knock by the determination level and the output signal of the knock sensor, and ignition timing of the internal combustion engine according to the determination result of the knock determining means,
In a knock control device provided with a control means for controlling a knock control factor such as an air-fuel ratio, a knock intensity value V of this signal is obtained from the signal of the knock sensor.
A knock intensity value detecting means for taking out, a distribution shape determining means for determining whether or not the distribution shape obtained when the knock intensity value V is subjected to multi-cycle sampling is a predetermined distribution shape, and a determination result of the distribution shape determining means. According to the knock state detection means for detecting an average knock state over a plurality of cycles, and according to the detection result of the average knock state by the knock state detection means, knock determination is performed so that the distribution shape becomes a predetermined distribution shape. An internal combustion engine comprising: a determination level correction means for correcting the level; and a feedback gain variable means for changing the feedback gain of the knock control factor according to the average detection result of the knock state by the knock state detection means. A knock control device for a vehicle is provided.

[Action]

Thereby, the knock intensity value V is extracted from the signal of the knock sensor by the knock intensity value detecting means, and the distribution shape determining means determines whether or not the distribution shape obtained when the knock intensity value V is sampled by multiple samples is a predetermined distribution shape. The average knocking state over a plurality of cycles is detected by the knocking state detecting means according to the determination result, and the distribution shape becomes a predetermined distribution shape according to the detection result of this average knocking state. The knock level is corrected by the judgment level correction means, and the feedback gain of the knock control factor is changed by the feedback gain changing means according to the average detection result of the knock state.

〔Example〕

The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 3 is a block diagram showing an embodiment of the present invention. In FIG. 3, 1 is a 4-cylinder 4-cycle engine, 3 is an air flow meter for detecting an intake air amount of the engine, 5 is a reference angle sensor 5A for detecting a reference crank angle position (for example, top dead center) of the engine. Is a distributor that incorporates a crank angle sensor 5B that generates an output signal at every constant crank angle of the engine. 6 is a knock sensor for detecting the vibration of the engine block corresponding to the knock phenomenon of the engine by a piezoelectric element type (piezo element type), an electromagnetic type (magnet, coil), etc., 7 is a peak for holding the output of the knock sensor. The hold circuit section.

Reference numeral 8 denotes an ignition timing control circuit for controlling the ignition timing of the engine according to the input / output signal states from the respective sensors, and 10 receives the ignition timing control signal output from the control circuit 8 to cut off the energization to the ignition coil. Is an igniter and an ignition coil. 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.

Next, the detailed configuration of the peak hold circuit section 7 will be described with reference to FIG. 701 in FIG. 4 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 from the amplifier 702 according to the 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. 5, reference numeral 8000 denotes a central processing unit (CPU) for calculating the ignition timing, which uses an 8-bit microprocessor. 8001 is a read-only storage unit (ROM) for storing a control program and control constants necessary for computation, and 8002 is a temporary storage unit (RAM) for the CPU 8000 to temporarily store computation data during operation according to the program. Is. 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 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 reads the count value of the timer each time an interrupt is generated by the output signal of the reference angle sensor 5A. Since the count value of the timer rises every clock cycle (for example, 1 μs), the difference between the count value at the time of this interrupt and the count time at the time of the previous interrupt can be calculated to calculate the reference angle sensor signal. The time interval, that is, the time required for one revolution of the engine can be measured. In this way, the engine speed is obtained.
Further, since the signal of the crank angle sensor 5B is output at every constant crank angle (for example, 30 ° C A), the crank angle position is set at 30 ° C based on the top dead center signal of the reference angle sensor 5A. You can know in A units. this
The crank angle signal for every 30 ° C is used as a reference point for generating the ignition timing control signal.

Reference numeral 8007 is a multiplexer for switching a plurality of analog signals at appropriate times to lead them to an analog-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, the output signal of the knock sensor signal from the peak hold circuit 7 and the intake air amount signal from the air flow meter 3 are input as analog signals. 8008 is an A / D converter for converting an analog signal into a digital signal. 8010 is an output port for outputting a digital signal. From this output port, an ignition timing control signal for the igniter 10, a control signal for the peak hold circuit section 7, and a control signal for the multiplexer 8007 are output. 8011 is CP
It is a U bus, and the CPU puts control signals and data signals on this bus signal line to control peripheral circuits and send and receive data.

The configuration of the apparatus for realizing the present invention has been described above, and an embodiment of the present invention will be described below with reference to the flowchart of FIG. When the knock control routine is started from step 100, the maximum value of the knock sensor signal in a predetermined section is taken as the knock intensity value V in step 101 by the output of the peak hold circuit section 7, for example. In step 102, the knock determination level V _ref is set to V _ref = K × Kc × V ₅₀ by, for example, the constant K, the corrected K value Kc created in step 104 described later, and the median value V ₅₀ of the distribution of the knock intensity values V. And create. Next, the routine proceeds to step 103, where knock determination and knock control factor control are performed. This step will be described in detail later. Next, the routine proceeds to step 104, where the knock state is detected and the knock determination level is corrected. This step will also be described later in detail. Next, the routine proceeds to step 105, where the knock control routine ends.

Next, the step 103, which is a feature of the present invention, will be described in detail with reference to the flowchart of FIG. Step 10
In 3-1 it is determined whether or not the engine is in a condition for knock control, and if YES, the process proceeds to step 103-2, and if NO, the process proceeds to step 104. In step 103-2, the knock intensity value V is compared with the knock determination level V _ref to determine whether knock has occurred. If YES, step 103-
If NO, go to step 103-4. Step 103
At -3, the ignition timing retard amount R is increased by R _r and the knock flag is set. In step 103-4, it is determined whether or not a predetermined period Ta has elapsed, and if YES, step 103-5.
If NO, go to step 103-6. Step 103-
5 In the retard amount R reduce only R _a. In step 103-6, it is determined whether the retard amount is larger than the maximum guard value RMAX. If YES, the process proceeds to step 103-7 to guard the retard amount, and if NO, the process proceeds to step 103-8. Step 103-
At 8, it is determined whether the retard amount is smaller than the minimum guard delay RMIN. If YES, the process proceeds to step 103-9 to guard the retard amount.

Next, step 104 will be described in detail with reference to the flowchart of FIG. In step 104-1, it is judged whether or not the knock intensity value V this time is larger than the median value V _{50 of the} distribution, and YES
If NO, go to step 104-2, and if NO, go to step 104-
Go to 6. In step 104-2, the upper threshold V _h is set to
V _H = A × D × V ₅₀ is created by the variable A and the number D which is slightly larger than 1. Next, the routine proceeds to step 104-3, where V ≧ V _H is determined, and if YES, the routine proceeds to step 104-4, and if NO, the routine proceeds to step 104-12. In step 104-4, the knock state detection counter PHL is incremented. Next, in step 104-5, the median value V _{50 of the} distribution is set to a predetermined amount ΔV.
Just make it bigger. In step 104-6, it is determined that V <V _50. If YES, the process proceeds to step 104-7, and if NO, the process proceeds to step 104-12. The lower step 104-7 the threshold V _L, to create a V _L = V ₅₀ / A. Then, the routine proceeds to step 104-8, where V ≦ _VL is judged, and if YES, the routine proceeds to step 104-9, and if NO, the routine proceeds to step 104-11. In step 104-9, the knock state detection counter PHL is decremented. Step 104-
At 10, the variable A is increased by a predetermined amount ΔA. Step 10
In 4-11, the median value V _{50 of the} distribution is reduced by a predetermined amount ΔV. This step 104-11 causes V ₅₀ to converge to the median value of the distribution. In step 104-12, it is judged whether or not a predetermined period _Tc has passed, and if YES, step 104-13
If NO, go to step 105. In step 104-13, the variable A is reduced by a predetermined amount ΔA. The variable A is adjusted by this step and step 104-10, and the frequency of V ≦ _VL becomes once within the predetermined period T _c . In step 104-14, it is judged whether the engine condition is to execute knock control,
If YES, go to step 104-15. If NO, go to step 104-2.
Go to 4. In step 104-15, it is determined whether the engine is in a steady state. If YES, the process proceeds to step 104-16, and if NO, the process proceeds to step 104-24. In step 104-16, the knock state detection counter PHL is checked to see if the knock state is too large.
If YES, that is, if PHL> 0, it is determined that the knocking state is too large, the process proceeds to step 104-17, and if NO, step 104-20.
Go to. In step 104-17 in the predetermined time period T _c, it is determined by whether the knock flag was no knock determination has been reset, if YES, it can be determined that the knock determination level is too high, the flow advances to step 104-18, The corrected K value K _c is reduced by a predetermined amount ΔK. Step
In 104-19, the retard amount R _r per step is set to a value obtained by adding the correction amount r _c to the basic amount r _r so that the retard can be quickly performed.

In step 104-20, it is determined whether the knocked state is too small. If YES (PHL <0), the process proceeds to step 104-21, NO.
If so, proceed to step 104-24. In step 104-21 knock flag is determined whether it is set, it can be determined that if YES knock determination level is too low the process proceeds to step 104-22, to increase the correction value K K _c by a predetermined amount [Delta] K.

It is set to a value obtained by adding the correction amount r _c the advance amount R _a per step to the basic amount r _a for quick advance in step 104-23. In step 104-24, the advance / retard amount per step is set to the basic amount. In step 104-25, the knock state detection counter PHL and the knock flag are reset.

In the above embodiment, if the knock condition is too large, 1
Increase the amount of retard angle R _r per step so that the angle can be retarded quickly (step 104-19). Conversely, if the knocked state is too small, the amount of advance angle R _a per step can be increased to advance the angle quickly. (Step 104-2)
It is also effective to do 3) as shown in FIG. FIG. 9 shows only the changed portion of the steps of FIG.
FIG. 9 (a) shows the advance amount when the knocked state is too large.
By reducing R _a , an unnecessary advance angle is prevented, and when the knocked state is too small, the retard amount R _r is reduced to prevent an unnecessary retard angle. The Fig. 9 (b) is advancing time period when knock state is too large T _a, longer by adding the correction time t _c to the basic time t _a (step 104-19) to slow down the advance speed by, knock state is shorter the advance time T _a when too small (step 104-23) proceeds is obtained by such that faster angular velocity by, not detected or knock state when the knock state is appropriate When advanced, the advance time T _a
(Step 104-24).

Of course, these three embodiments (FIG. 6, FIG. 9 (a),
You may use (b) in combination.

Further, in the present embodiment, the ignition timing retard amount is treated as the knock control factor, but the air-fuel ratio, the boost pressure, etc. may be changed in conjunction with this.

Although the maximum value of the knock sensor signal in the predetermined section is used as the knock strength value in the present embodiment, a value obtained by integrating the knock vibration output, an effective value of the knock vibration output, or the like may be used as the knock strength value.

〔The invention's effect〕

As described above, in the present invention, an inappropriate knock determination level is appropriate when correcting the knock determination level so that the distribution shape obtained when the knock intensity value V is subjected to multi-cycle sampling has a predetermined distribution shape. Even before being corrected to a different value, it is possible to quickly realize an appropriate knocking state by changing the feedback gain of the knocking control factor according to the knocking state, and reduce frequent knocking and torque crossing. It has the excellent effect of being able to.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the scope of claims of the present invention, FIGS. 2 (a) and 2 (b) are cumulative distribution diagrams of logarithmic conversion values of a knock sensor output signal, and FIG. 3 is an embodiment of the device of the present invention. FIG. 4 is a partial cross-sectional configuration diagram showing the same, FIG. 4 is a more detailed block diagram of the peak hold circuit section in FIG. 3, FIG. 5 is a more detailed block diagram of the ignition timing control circuit in FIG. 3, and FIG. FIG. 5 is a flow chart for explaining the operation of the circuit shown in FIG.
A more detailed flowchart of step 103 in the figure, eighth
The figure is a more detailed flowchart of step 104 in FIG. 6, and FIG. 9 (a) is step 104-19, 104- in FIG.
23 is a flowchart showing another embodiment, and FIG. 9 (b) is a flowchart showing still another embodiment of steps 104-19, 104-23, 104-24 in FIG. 1 ... Engine, 6 ... Knock sensor, 7 ... Peak hold circuit, 8 ... Ignition timing control circuit, 8000 ... CPU.

Claims (4)

[Claims] 1. A knock sensor for detecting knocking of an internal combustion engine, a decision level creating means for creating a decision level for judging knocking of the internal combustion engine, and knocking by means of this decision level and an output signal of the knock sensor. In a knock control device having a knock determination means for determining and a control means for controlling a knock control factor such as an ignition timing of an internal combustion engine or an air-fuel ratio according to the determination result of the knock determination means, from the signal of the knock sensor, Knock strength value V of this signal
A knock intensity value detecting means for taking out, a distribution shape determining means for determining whether or not the distribution shape obtained when the knock intensity value V is subjected to multi-cycle sampling is a predetermined distribution shape, and a determination result of the distribution shape determining means. According to the knock state detecting means for detecting an average knock state over a plurality of cycles, the determination is made so that the distribution shape becomes a predetermined distribution shape according to the detection result of the average knock state by the knock state detecting means. An internal combustion engine comprising: a determination level correction means for correcting the level; and a feedback gain variable means for changing the feedback gain of the knock control factor according to the average detection result of the knock state by the knock state detection means. Knock control device. 2. The knock control factor is ignition timing, and the feedback gain changed by the feedback gain varying means is a retard amount per step for retarding the ignition timing when knock is determined, and an ignition amount. The internal combustion engine according to claim 1, wherein the internal combustion engine has at least one of an advance time for advancing the timing and an advance amount per step for advancing the ignition timing. Knock control device for engines. 3. The feedback gain variable means increases the retard amount per step by a predetermined amount when the average knock state detection result by the knock state detection means is a large knock state, or per step. Is decreased by a predetermined amount, and when the average knocking state detection result by the knocking state detection means is a small knocking state, the advancement amount per step is increased by a predetermined amount or delayed per step. The knock control device for an internal combustion engine according to claim 2, wherein the angular amount is reduced by a predetermined amount. 4. The knock determination level correcting means determines that the knock determination means determines that the knock state is not knocked when the average knock state detected by the knock state detecting means is a large knock state. Claim that the knock determination level is increased when the average knock state detection result by the knock state detection means is knocked by the knock determination means when the knock state is small. The knock control device for an internal combustion engine according to claim 1, 2 or 3.