JPH10259778A - Knock deciding device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effect setting to an annealing factor to satisfy an under-mentioned demand when responsiveness of a back ground value is actually demanded., make responsiveness of the back ground value compatible with stability, and improve knock deciding precision. SOLUTION: By multiplying a back ground value Vmean(i-1), determined through preceding processing, by a given constant K, a knock decision level Vref is calculated (step 102). (1) In a case of the knock decision level Vref <=a lower limit guard A, setting to Vref = A and an annealing factor (n)=4 is effected, (2) in a case of A < the knock decision level Vref <= B, setting to an annealing factor (n)=8 is effected, (3) in a case of the knock decision level Vref > B, setting to an annealing factor (n)=16 is effected (steps 103-108). Thereafter, a knock sensor signal V is compared with the knock decision level Vref, and when the knock sensor signal V is below the knock decision level Vref, it is decided that knock does not occur (step 110). When the knock sensor signal V exceeds the knock decision level Vref, it is decided that knock occurs (step 111). Further, by using the annealing factor (n), determination is effected by effecting annealing processing of a back ground value Vmean(i) (step 112).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock determination device for an internal combustion engine which detects knock vibration of the internal combustion engine by a knock sensor to determine whether or not knock has occurred.

[0002]

2. Description of the Related Art In a conventional knock determination apparatus, for example, as shown in Japanese Utility Model Publication No. 6-41151, a background value is obtained by smoothing an output signal of a knock sensor for each ignition, and this background value is used as a reference. After calculating the knock determination level, the output signal of the knock sensor is compared with the knock determination level to determine the presence or absence of knock. Further, in this device, when the output signal of the knock sensor is smoothed for each ignition to obtain a background value, the smoothing coefficient for determining the degree of weighting of the smoothing process is corrected to be small during transient operation. by doing,
By increasing the ratio of the latest output signal of the knock sensor that is reflected on the background value during the transient operation, the knock determination accuracy during the transient operation is improved.

[0003]

In the knock determination technique disclosed in the above publication, the reason for reducing the smoothing coefficient during the transient operation is that the output of the knock sensor changes suddenly during the transient operation. Although the response of the background value is improved by increasing the ratio of the latest output signal, if the background value can respond sufficiently without changing the smoothing coefficient even during transient operation (that is, the output change of the knock sensor In some cases, the output of the knock sensor changes abruptly, but the response of the background value needs to be increased.

[0004] For example, even at the same load change rate that is determined to be in the transient operation state, the required responsiveness is different between a low speed and a high speed, and the required responsiveness is also different due to engine variation. There is no direct correlation between the state and the responsiveness of the background value. Therefore, if the transient operation state is detected and corrected to reduce the averaging coefficient as described in the above publication, the response of the background value is not actually required, that is, the output of the knock sensor When the change is small and the stability of the background value is required, the smoothing coefficient is reduced and the background value varies to reduce the knock determination accuracy.On the contrary, the responsiveness of the background value is required. In this case, the averaging coefficient cannot be switched to a small value, and knock may be erroneously determined due to a response delay.

[0005] As a countermeasure, when the background signal is obtained by smoothing the output signal of the knock sensor, the difference between the output signal of the knock sensor and the background value is calculated for each ignition. It is considered to increase the annealing coefficient. In this knock determination method, as shown in FIG. 4, when the accelerator is depressed from the idling operation state to accelerate, the engine operation state is substantially constant during the idling operation.
And the background value Vmean is substantially zero, thereby setting the smoothing coefficient to a large value. When the accelerator is depressed and the vehicle suddenly accelerates from the idling operation state, the knock sensor signal V sharply increases. However, the background value Vmean at the start of acceleration is calculated by smoothing the knock sensor signal V with a large smoothing coefficient. Therefore, the rise of the background value Vmean is delayed, and the rise of the knock determination value Vref set based on the background value Vmean is also delayed. For this reason, during acceleration, knock sensor signal V may temporarily exceed knock determination value Vref even if knock has not occurred, and knock may be erroneously determined.

[0006] The present invention has been made in view of such circumstances, and the object thereof is to set a smoothing coefficient that satisfies the background value when the response is actually required. It is an object of the present invention to provide a knock determination device for an internal combustion engine that can achieve both the responsiveness and stability of the background value and improve the knock determination accuracy.

[0007]

According to a first aspect of the present invention, there is provided a knock determination apparatus for an internal combustion engine, wherein a background value calculating means outputs an output signal of a knock sensor every ignition. When obtaining the background value by performing the averaging process, the averaging coefficient is set based on the knock determination level. The knock determination level is set based on a background value. The knock determination means determines the presence or absence of knock by comparing the output signal of the knock sensor with a knock determination level.

Conventionally, the smoothing coefficient is set on the basis of the difference between the output signal of the knock sensor and the background value. Therefore, as shown in FIG. Will be the same. This is because the difference between the output signal of the knock sensor and the background value becomes substantially zero in both the idling operation state and the constant speed traveling state. If the accelerator is depressed and the vehicle accelerates suddenly from the idle operation state, the output signal of the knock sensor sharply rises, but since the smoothing coefficient at that time is too large, the rise of the knock determination value is delayed, and no knock occurs during acceleration. However, the output signal of the knock sensor may temporarily exceed the knock determination value, and the knock may be erroneously determined.

On the other hand, in the present invention, the smoothing coefficient is set based on the knock determination level. As illustrated in FIG. 4, since the knock determination level is different between the idling operation state and the constant speed driving state, the smoothing coefficient can be set to a different value. For example, the smoothing coefficient during idle operation corresponds to sudden acceleration. It can be set to a value that can be used. With this, when the response of the background value obtained by smoothing the output signal of the knock sensor is actually required, it is possible to set a smoothing coefficient that satisfies the demand, and the background value can be set. It is possible to achieve both responsiveness and stability, and it is possible to improve knock determination accuracy.

In this case, it is preferable to reduce the smoothing coefficient when the knock determination level is equal to or less than a predetermined value. That is, in the idling operation state, the knock determination level is equal to or less than the predetermined value, and the smoothing coefficient is set to a small value. As a result, the responsiveness of the background value when accelerating from the idling operation state can be improved, and the output signal of the knock sensor can be prevented from temporarily exceeding the knock determination value. Can be prevented.

Further, when the knock determination level exceeds a predetermined value, a smoothing coefficient may be set based on a difference between an output signal of the knock sensor and a background value. The difference between the output signal of the knock sensor and the background value indicates the response delay of the background value due to the change in the output signal of the knock sensor, so if the smoothing coefficient is set according to the difference between them, the smoothing will be performed. The coefficient reflects a change in the output signal of the knock sensor. Therefore, the background value calculated using the smoothing coefficient also reflects a change in the output signal of the knock sensor.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIGS. An air flow meter 1 is provided upstream of an intake pipe 13 connected to an intake port 12 of an engine 11 which is an internal combustion engine.
The air flow sensor 14 converts the intake air flow rate measured by the air flow meter 14 into a voltage signal and outputs the voltage signal. An intake air temperature sensor 16 for detecting the intake air temperature and a throttle valve 17 are provided downstream of the air flow meter 14, and the opening of the throttle valve 17 is detected by a throttle sensor 18. Further, a fuel injection valve 19 is provided near the intake port 12 of each cylinder.

On the other hand, an exhaust pipe 21 connected to an exhaust port 20 of the engine 11 is provided with an O ₂ sensor 22 for detecting the oxygen concentration in the exhaust gas and a catalyst 23 for purifying the exhaust gas. The cylinder block 2 of the engine 11
A knock sensor 51 for detecting knock vibration and a water temperature sensor 25 for detecting an engine cooling water temperature are attached to 4. Further, a distributor 27 for supplying a high-voltage current to the ignition plug 26 of each cylinder of the engine 11.
Are provided with a cylinder discrimination sensor 28 for discriminating a crank angle reference position of a specific cylinder, and a rotation angle sensor 29 for outputting a pulse signal having a frequency corresponding to the engine speed. The distributor 27 includes an igniter 30
Are supplied.

[0014] On the other hand, the control circuit 31 for controlling the operation of the engine 11 (ECU), as shown in FIG. 3, the air flow sensor 15, O ₂ sensor 22, throttle sensor 18,
The sensor signals from the water temperature sensor 25 and the intake air temperature sensor 16 are selected by the multiplexer 32 and read through the A / D conversion circuit 33 and the input / output port 35, and the sensor signals from the cylinder discrimination sensor 28 and the rotation angle sensor 29 Is read by the waveform shaping circuit 34 via the input / output port 36. The signal from the knock sensor 51 is transmitted to the filter 5
2, a vibration component of a predetermined frequency band is extracted, and the vibration component is peak-held by a peak hold circuit 53 (P / H) in a knock determination section for each ignition (TDC), and the peak value is converted to an A / D conversion circuit 54. A / D-converted and read through the input / output port 36. The various sensor signals read from the input / output ports 35 and 36 in this way are read into the CPU 37 via the data bus 45 to calculate the fuel injection amount and the ignition timing. To the drive circuits 42 and 43 to control the operation of the igniter 30 and the fuel injection valve 19.

The control circuit 31 includes an oscillation circuit 46 for supplying a clock to the CPU 37, a RAM 47, a ROM 49, and the like. The ROM 49 stores a program for a knock determination routine shown in FIG. 1 in addition to various engine control programs such as fuel injection control and ignition control. By executing the knock determination routine, the control circuit 31 smoothes the output signal of the knock sensor 51 (hereinafter referred to as “knock sensor signal”) for each ignition to obtain the background value Vmean. The coefficient is set based on knock determination level Vref.

Hereinafter, the specific processing content of the knock determination routine will be described with reference to the flowchart of FIG. This knock determination routine is repeatedly executed for each ignition, and when the process is started, first, at step 101, knock sensor signal V peak-held in the knock determination section for each ignition.
(Peak value) is read, and in a succeeding step 102, a knock determination level Vref is calculated by multiplying the background value Vmean (i-1) obtained in the previous processing by a predetermined constant K. The processing in step 102 functions as a knock determination level setting means referred to in the claims.

Then, in the next step 103, the knock determination level Vref is compared with the lower limit guard A. If the knock determination level Vref is equal to or smaller than the lower limit guard A, step 10 is executed.
Then, the knock determination level Vref is guarded by the lower limit guard A (Vref = A), and in the next step 105, the smoothing coefficient n is set to a small value (“4” in the present embodiment). Go to 109.

On the other hand, if the knock determination level Vref is larger than the lower limit guard A, the process proceeds from step 103 to step 10.
6 to determine the knock determination level Vref as a determination value B (B = A
If the knock determination level Vref is equal to or less than the determination value B, the process proceeds to step 107, where the smoothing coefficient n is set to an intermediate value (“8” in this embodiment), and the process proceeds to step 109. . If the knock determination level Vref is larger than the determination value B, the routine proceeds to step 108, where the smoothing coefficient n is set to a large value (“16” in the present embodiment), and the routine proceeds to step 109.

In short, the above steps 103 to 10
In the process of No. 8, the guard process of the knock determination level Vref is performed. When the knock determination level Vref ≦ A, the smoothing coefficient n = 4, and A <knock determination level Vref
If .ltoreq.B, the smoothing coefficient n = 8, and if knock determination level Vref> B, the smoothing coefficient n = 16, and the routine proceeds to step 109.

In step 109, the knock sensor signal V is compared with the knock determination level Vref calculated in step 102, and if the knock sensor signal V is equal to or lower than the knock determination level Vref, it is determined that there is no knock (step 109). 110), if knock sensor signal V exceeds knock determination level Vref, it is determined that knock is present (step 111). The processing of steps 109 to 111 functions as a knock determination unit referred to in the claims.

Then, in the next step 112, the smoothing coefficient n set in the above step 105, 107 or 108 is set.
, The background value Vmean (i) is obtained by smoothing processing according to the following equation, and the routine ends.

Vmean (i) = (n-1) /n.times.Vmean (i-
1) + 1 / n × (V−Vmean (i−1)) Here, Verm (i−1) is Verm obtained in the previous process. The processing of the above steps 103 to 108 and 112 functions as a background value calculating means referred to in the claims.

A control example using the above-described knock determination routine will be described with reference to FIG. FIG. 4 is a time chart showing changes in knock sensor signal V, knock determination level Vref, background value Vmean, and smoothing coefficient n when the accelerator is depressed and accelerated from the idling operation state. During the idling operation, the knock determination level Vref calculated in step 102 is smaller than the lower limit guard A, so that Vref = A is set by the guard processing, and the smoothing coefficient n is set to 4 (small value). . Thereby, the responsiveness of the background value Vmean when accelerating from the idle operation state is enhanced.

When the accelerator is depressed and the vehicle is rapidly accelerated from the idling operation state, the knock sensor signal V sharply increases. In this case, the smoothing coefficient n is set to 4 (small value) during the idling operation, and the responsiveness of the background value Vmean is enhanced. Therefore, if the knock sensor signal V rises sharply, the knock follows. The judgment level Vref increases. For this reason, it is possible to prevent the knock sensor signal V from temporarily exceeding the knock determination value Vref during acceleration, and to prevent erroneous determination of knock.

After the start of acceleration, when the knock determination level Vref calculated in step 102 exceeds the lower limit guard A, the smoothing coefficient n is switched to 8 (intermediate value). Thereafter, when the knock determination level Vref exceeds the determination value B, the smoothing coefficient n is switched to 16 (large value),
The stability of the background value Vmean is improved.

In the above embodiment (1), the smoothing coefficient n is set to 4, 8, and 16 based on the knock determination level Vref, but it may be set to any other value. Needless to say. Also, knock determination level Vre
The smoothing coefficient n may be switched to four or more stages based on f.

[Embodiment (2)] In the above-described embodiment (1), the smoothing coefficient n is switched in three stages based on the knock determination level Vref. However, the embodiment (2) of the present invention shown in FIG. In), the smoothing coefficient n is switched between two levels based on the knock determination level Vref. Hereinafter, the processing content of the knock determination routine of FIG. 5 executed in the embodiment (2) will be described. The knock determination routine of FIG. 5 performs the processing of steps 106 to 108 of FIG.
6a, and the other steps are the same as the steps in FIG.

In the knock determination routine of FIG. 5, the knock determination level Vref calculated in step 102 is compared with the lower limit guard A. If the knock determination level Vref is equal to or smaller than the lower limit guard A, the routine proceeds to step 104, where the knock determination level Vref is obtained. With a lower limit guard A (Vref = A),
In the next step 105, the smoothing coefficient n is set to a small value (“4” in the present embodiment), and the process proceeds to step 109.

On the other hand, if the knock determination level Vref is larger than the lower limit guard A, the process proceeds from step 103 to step 106a, where the smoothing coefficient n is set to a large value ("16" in this embodiment), and step 109 is performed. Proceed to.

Thereafter, the knock determination process (steps 109 to 111) and the background value Vmean are performed in the same manner as in FIG.
(i) is calculated (step 112), and this routine is terminated. In the embodiment (2) described above, substantially the same effects as in the embodiment (1) can be obtained.

[Embodiment (3)] In the embodiments (1) and (2) described above, the setting of the smoothing coefficient n is all performed based on the knock determination level Vref, but the present invention shown in FIG. In the embodiment (3), when the knock determination level Vref exceeds a predetermined value, the smoothing coefficient n is set based on the difference between the knock sensor signal V and the background value Vmean.
Hereinafter, the processing content of the knock determination routine of FIG. 6 executed in the embodiment (3) will be described.

This knock determination routine is also repeatedly executed for each ignition, and when the process is started, first, at step 201
Then, the knock sensor signal V (peak value) peak-held in the knock determination section for each ignition is read, and in the following step 202, the background value Vmean obtained in the previous processing is read.
By multiplying (i-1) by a predetermined constant K, a knock determination level Vref is calculated.

Then, in the next step 203, the knock determination level Vref is compared with a lower limit guard A which is a predetermined value.
If the knock determination level Vref is equal to or lower than the lower limit guard A, the process proceeds to step 204, where the knock determination level Vref
Is guarded by the lower limit guard A (Vref = A), and in the next step 205, the smoothing coefficient n is set to a small value (“4” in this embodiment), and the routine proceeds to step 211. The above processing is the same as in the above-described embodiments (1) and (2).

On the other hand, if the knock determination level Vref is larger than the lower limit guard A, steps 103 to 20
In step 6, the difference Verm (i) between the knock sensor signal V and the background value Vmean (i-1) obtained in the previous process is obtained by a smoothing process using the following equation. Verm (i) = 15/16 × Verm (i−1) + 1/16 × ｛(V
−Vmean (i−1)) − Verm (i−1)｝ Here, Verm (i−1) is Verm obtained in the previous process. The smoothing process in the above formula is 1/16 smoothing, but may be, for example, 1/12 smoothing, 1/8 smoothing, 1/4 smoothing or the like.

In the next step 207, the above step 20
It is determined whether the absolute value of Verm (i) calculated in step 6 corresponds to any of the following. | Verm (i) | <88 <= | Verm (i) | <12 | Verm (i) | ≧ 12

If | Verm (i) | <8, the routine proceeds to step 208, where the smoothing coefficient n for smoothing the background value Vmean (i) by 1 / n is set to 16. If 8 ≦ | Verm (i) | <12, step 20
Proceeding to 9, the smoothing coefficient n is set to 8, and | Verm (i) |
If ≧ 12, the routine proceeds to step 210, where the smoothing coefficient n is set to 4. By such processing, the knock sensor signal V and the background value Vmean obtained in the previous processing are obtained.
As the difference Verm (i) from (i-1) increases, that is, as the change in the knock sensor signal V increases, the smoothing coefficient n is reduced and the latest knock sensor is reflected on the background value Vmean (i). The response of the background value Vmean (i) is increased by increasing the ratio of the signal V.

In the next step 211, the above step 20
The background value Vmean (i) is obtained by smoothing the background value Vmean (i) according to the following equation using the smoothing coefficient n obtained in 8 to 210. Vmean (i) = (n-1) / nxVmean (i-1) + 1 / nx
(V-Vmean (i-1))

Thereafter, in step 212, the knock sensor signal V is compared with the knock determination level Vref calculated in step 203, and if the knock sensor signal V is equal to or lower than the knock determination level Vref, it is determined that there is no knock. (Step 213) If the knock sensor signal V exceeds the knock determination level Vref, it is determined that knock is present (Step 214).

In the embodiment (3) described above, the difference Verm (i) between the knock sensor signal V and the background value Vmean is calculated in a region where the knock determination level Vref exceeds a predetermined value (lower limit guard A). The greater the difference Verm (i), the smaller the smoothing coefficient n. Therefore, the more rapidly the knock sensor signal V changes, the more the latest knock sensor signal V reflected on the background value Vmean (i). And the responsiveness of the background value Vmean (i) can be increased. Therefore, knock determination level V
In a region where ref exceeds a predetermined value (lower limit guard A), even if the knock sensor signal V sharply changes greatly, the background value Vmean (i) changes following the knock sensor signal V, resulting in a response delay. Thus, it is possible to prevent erroneous determination of knock.

In the embodiment (3), the difference Verm (i) between the knock sensor signal V and the background value Vmean in a region where the knock determination level Vref exceeds the lower limit guard A.
, The smoothing coefficient n is set based on Verm (i) in a region where the knock determination level Vref exceeds a predetermined value C (C = A + β). May be. In this case, in the region where knock determination level Vref is equal to or less than predetermined value C, smoothing coefficient n may be switched to two or more levels based on knock determination level Vref.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the flow of processing of a knock determination routine according to an embodiment (1) of the present invention.

FIG. 2 is a diagram showing a schematic configuration of an entire engine control system;

FIG. 3 is a block diagram illustrating a configuration of a control circuit.

FIG. 4 is a time chart for explaining a difference between the conventional example and the embodiment (1).

FIG. 5 is a flowchart showing a flow of processing of a knock determination routine in the embodiment (2) of the present invention.

FIG. 6 is a flowchart showing the flow of processing of a knock determination routine according to the embodiment (3) of the present invention.

[Explanation of symbols]

11: engine (internal combustion engine), 31: control circuit (background value calculation means, knock determination level setting means, knock determination means), 51: knock sensor, 52: filter,
53 ... Peak hold circuit.

Claims (3)

[Claims] 1. A knock sensor for detecting knock vibration of an internal combustion engine, a background value calculating means for smoothing an output signal of the knock sensor for each ignition to obtain a background value, and a reference value based on the background value. Knock determination level setting means for determining a knock determination level, and a knock determination apparatus for an internal combustion engine, comprising: a knock determination means for determining the presence or absence of knock by comparing the output signal of the knock sensor with the knock determination level. The knock determination device for an internal combustion engine, wherein the background value calculation means sets a smoothing coefficient used for the smoothing process based on the knock determination level. 2. The knock determination device for an internal combustion engine according to claim 1, wherein said background value calculation means reduces said smoothing coefficient when said knock determination level is equal to or less than a predetermined value. 3. The method according to claim 1, wherein the background value calculation means sets a smoothing coefficient based on a difference between an output signal of the knock sensor and the background value when the knock determination level exceeds a predetermined value. The knock determination device for an internal combustion engine according to claim 1 or 2, wherein: