JP2795976B2 - Knock control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting a knock of an internal combustion engine such as a gasoline engine for an automobile and performing a retarding (knock suppression) control, and more particularly, to a knock detection reliability and reliability. The present invention relates to a knock control device for an internal combustion engine with improved controllability.

2. Description of the Related Art Generally, an internal combustion engine such as a gasoline engine for an automobile is driven by a plurality of cylinders, and it is necessary to burn an air-fuel mixture compressed in each cylinder at an optimum ignition position.
Therefore, a microcomputer (EC
U) is used to optimally control the ignition timing of the igniter and the fuel injection sequence of the injector for each cylinder.

However, if the ignition position is controlled to the advanced side too much, vibration called knocking occurs due to abnormal combustion, which may damage the cylinder. Therefore, when abnormal vibration is detected, control parameters of the cylinder (for example, ignition position ) Needs to be controlled to the retard side.

FIG. 7 is a block diagram showing a conventional knock control device for an internal combustion engine.

In the figure, (1) is a knock sensor attached to one or each of the cylinders for driving the internal combustion engine, and is composed of a piezoelectric element or the like for detecting vibration. (2) is a knock detection circuit that receives the output signal A of the knock sensor (1),
A filter (21) for passing a knocking-specific frequency (for example, 7 kHz), a gate (22) for periodically passing an output signal of the filter (21) at a predetermined timing, and an output signal A 'of the gate (22) A BGL generator (23) for generating a background level BGL based on a signal obtained by averaging
The output signal A 'of the gate (22) and the background level BG
And the output signal A 'is compared with the background level BGL.
A comparator (24) that turns on the output signal when
An integrator (25) for integrating an output signal of the comparator (24). (3) is an AD converter for converting an output signal of the integrator (25) into a digital signal V _R.

(4) controls retarding the ignition position of each cylinder based on the output signal V _R of the AD converter (3), outputs a reset signal R to the gate mask signal M and the integrator for (22) (25) microcomputer (hereinafter, referred to as ECU) is, AD converter (3) retard reflection processing section that generates a retard control angle theta _R for retarding the cylinder ignition position based on the output signal V _R of ( 45).

Next, the operation of the conventional knock control device for an internal combustion engine shown in FIG. 7 will be described with reference to the waveform diagram of FIG.

Normally, each cylinder is ignited at an advanced angle from a position (B5 °) about 5 ° before TDC (top dead center = 0 °), and the explosion of the air-fuel mixture is cranked about 10 ° to 60 ° past TDC. Angle position (A
Since it occurs near 10 ゜ to A60 ノ), knock due to abnormal combustion also occurs at this explosion timing.

Therefore, when vibration noise (especially knock) of the cylinder occurs, the output signal A of the knock sensor (1) has a periodic and large amplitude waveform as shown in FIG.

The ECU (4) outputs a mask signal M that is inverted at predetermined intervals to the gate (22) so that the knock detection circuit (2) receives the output signal A efficiently. The mask signal M has, for example, a rise of about B75 ° and a fall of about B5 ° with respect to the cylinder to be detected, and prohibits the gate (22) when the level is “H”. A reset signal R is output to the integrator (25) at predetermined intervals. The output timing of the reset signal R coincides with the rising edge of the mask signal M.

The filter (21) in the knock detection circuit (2) filters the frequency component at the time of knock occurrence, and the gate (22) allows the output signal A to pass only during the period when the mask signal M is at the "L" level. The BGL generator (23) determines the background included in the output signal A 'based on the output signal A' of the gate (22), and generates a background level BGL serving as a reference for knock detection.

When the output signal A 'exceeds the background level BGL, the comparator (24) determines that the knocking occurs, and sets the output signal to the "H" level. Integrator (2
5) is the comparator (2) each time it is reset by the reset signal R.
The output signal of 4) is integrated, and the AD converter (3) is integrated by the integrator (2
An output signal of 5) is converted to a digital integral value V _R ECU
Enter in (4).

ECU (4) takes the integrated value V _R which has been AD converted into each ignition of the cylinders, based on this generated a retard control angle theta _R, corrected retarding the ignition position in the direction of suppressing the knock. At this time, the retard reflection processing unit (45) sets the retard control angle θ up to the present.
_The current retard amount Δθ _R is cumulatively added to _R ^* to generate a current retard control angle θ _R. Therefore, the current retard control angle θ _R
Is represented by θ _R = θ _R ^* + Δθ _R. Further, in the equation, the current retard amount Δθ _R
Is represented by Δθ _R = V _R × L, where L: reflection ratio.

However, the level of the output signal A of the knock sensor (1) differs depending on the operating state, and for example, the engine speed
When Ne rises, the level of the output signal A also rises, and at the same time, the level of the background level BGL also rises. As a result, the signal level input to the comparator (24) increases with the engine speed Ne, so that the dynamic range of the input signal of the comparator (24) must be set large.
Therefore, the knock detection accuracy obtained as a result of comparison by the comparator (24) is degraded.

In order to prevent this, conventionally, a method has been adopted in which an amplifier is built in the knock detection circuit (2) and the level fluctuation of the output signal A is suppressed by switching the gain of the amplifier according to the engine speed Ne. I have. However, since the engine itself and the knock sensor (1) have variations and the correlation between the engine speed and the output signal level is not absolute, switching the amplification gain of the output signal A only by the engine speed Ne is The reliability of gain switching accuracy is low and not practical.

[Problem to be Solved by the Invention] As described above, the conventional knock control device for an internal combustion engine switches the amplification gain of the output signal A in accordance with the engine speed, so that the level fluctuation of the output signal A can be sufficiently reduced. Therefore, there is a problem that the reliability and controllability of knock detection cannot be improved.

Also, for example, as disclosed in Japanese Patent Application Laid-Open No. 60-138427, a knock detection device that adjusts the gain of the variable amplification degree in accordance with the background noise or the average value circuit output has been proposed. In this case, since the control is performed in a controlled manner, a control delay occurs, and the control cannot follow up during the transient operation, so that an appropriate gain cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. By switching the amplification gain without causing a control delay, the switching of the amplification gain of the output signal is performed with high accuracy, and the reliability of knock detection is improved. It is an object of the present invention to obtain a knock control device for an internal combustion engine having improved controllability and controllability.

Means for Solving the Problems A knock control device for an internal combustion engine according to the present invention includes a knock sensor for detecting vibration of the internal combustion engine, an interface circuit for generating a vibration level based on an output signal of the knock sensor, and a knock sensor An amplifier that amplifies the output signal of the amplifier with a plurality of amplification gains set in advance, and an arithmetic unit that generates a threshold for knock determination based on the vibration level,
A comparison unit that outputs a knock determination signal when the vibration level exceeds a threshold; a retard reflection processing unit that controls a cylinder control parameter to a knock suppression side based on the knock determination signal; A gain switching control unit that switches the amplification gain to suppress a change in the level of the output signal of the knock sensor. The gain switching control unit determines whether the amplification gain is the first gain, Is the first gain, it is determined whether or not the threshold for knock determination is equal to or more than the upper limit value,
Switching the amplification gain to a second gain smaller than the first gain when the threshold is equal to or more than the upper limit, determining whether the threshold is smaller than the lower limit when the amplification gain is the second gain, and setting the threshold to the lower limit. When it is smaller, the amplification gain is switched to the first gain.

A knock control device for an internal combustion engine according to another aspect of the present invention includes a knock sensor for detecting a vibration of the internal combustion engine, an interface circuit for generating a vibration level based on an output signal of the knock sensor, and an output of the knock sensor. An amplifier for amplifying a signal with a plurality of preset amplification gains, an arithmetic unit for generating a threshold for knock determination based on the vibration level, and a comparison unit for outputting a knock determination signal when the vibration level exceeds the threshold And a delay reflection processing means for controlling the control parameter of the cylinder to the knock suppression side based on the knock discrimination signal, and switching the amplification gain according to the threshold level so as to change the level of the output signal of the knock sensor. A gain switching control unit that suppresses whether the amplification gain is the first gain. When the amplification gain is the first gain, it is determined whether or not the threshold for knock determination is equal to or higher than the upper limit. If the threshold is equal to or higher than the upper limit, the upper limit engine speed corresponding to the upper limit is determined. The gain is stored and the amplification gain is switched to a second gain smaller than the first gain. When the amplification gain is the second gain, it is determined whether or not the engine speed is smaller than a lower limit speed by a predetermined value smaller than the upper limit speed. The amplification gain is switched to the first gain when the rotation speed of the engine is smaller than the lower limit rotation speed.

[Operation] In the knock control device for an internal combustion engine according to the present invention, when the threshold level rises to a predetermined value or more, the amplification gain of the output signal is switched to a small value, and the threshold level becomes smaller than the predetermined value. In this case, the amplification gain is switched to a larger value.

In addition, when the amplification gain is the first gain, it is determined whether or not the threshold for knock determination is equal to or more than the upper limit, and if the threshold is equal to or more than the upper limit, the amplification gain is switched to the second gain smaller than the first gain. . On the other hand, when the amplification gain is the second gain, it is determined whether the threshold is smaller than the lower limit. If the threshold is smaller than the lower limit, the amplification gain is switched to the first gain larger than the second gain.

Further, in the knock control device for an internal combustion engine according to another invention of the present invention, it is determined whether or not a threshold for knock determination is equal to or more than an upper limit value when the amplification gain is the first gain, and the threshold value is equal to or more than the upper limit value. In the case of, the upper limit engine speed corresponding to the upper limit value is stored, and the amplification gain is switched to the second gain smaller than the first gain. On the other hand, when the amplification gain is the second gain, it is determined whether or not the engine speed is smaller than a lower limit speed which is smaller than the upper limit speed by a predetermined value. The gain is switched to the first gain which is larger than the second gain.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a knock control device for an internal combustion engine according to the present invention, wherein (3) and (45) are the same as those described above. In this case, knock sensor (1)
Includes the function of the filter (21) in FIG.

(20) is an interface circuit inserted between the knock sensor (1) and the AD converter (3), for example, a peak hold circuit (26) and an interface circuit inserted on the input side of the peak hold circuit (26). And an amplifier (27).

The reset signal R 'for the peak hold circuit (26) is generated from the ECU (40) in synchronization with the rotation of the internal combustion engine, and, for example, as shown in FIG. At the other reference position (B5 ゜)
The pulse consists of a falling edge. Therefore, the peak hold circuit (26) generates a peak level at the reference position B75 # of each cylinder, and inputs this to the ECU (40) as the vibration level Vp via the AD converter.

Further, the gain of the amplifier (27) is determined by the gain switching signal C from the ECU (40) to the first gain G1 or the second gain G2 (<
G1).

The ECU (40) averages the vibration level Vp obtained for each cylinder ignition to generate a first background level (first average value) BGL1, a first filter (41), and a first average value.
A second filter (42) for averaging BGL1 every predetermined period to generate a second background level (second average value) BGL2, and a threshold V _TH for knock determination based on the second average value BGL2 an arithmetic unit for generating (43), a comparing unit for outputting the knock determination signal Vk (44) when the vibration level V _P exceeds the threshold V _TH, retarded ignition position of the cylinder on the basis of the knock determination signal Vk Retard control angle θ for turning
A delay reflection processing unit (45) for generating _R , and a threshold
It includes gain switching control unit for outputting a gain switching signal C to switch the gain of the amplifier (27) depending on the level of V _TH and (46).

The gain switching control section (46) takes in not only the threshold V _TH but also the operating state Q including the engine speed Ne, and generates a gain switching signal C according to the operating state Q.

Next, the operation of the internal combustion engine knock control device according to the present invention shown in FIG. 1 will be described with reference to the waveform diagram of FIG.

First, the knock sensor (1) detects the vibration of the cylinder for driving the internal combustion engine in the same manner as described above, and generates an output signal A for detecting the knock state. The ECU (40) converts the peak level of the output signal A of the knock sensor (1) into an analog signal for each ignition of the cylinder.

That is, the peak hold circuit (26) holds the peak level of the output signal A of the knock sensor (1), which is converted into a digital vibration level Vp by the AD converter (3), Entered in (40).

When the vibration level Vp at the reference position B75 # is sampled, the ECU (40) raises a reset signal R 'as shown in FIG. Just after B75 ゜).

The peak hold circuit (26) continues to be reset while the reset signal R 'is on, and starts operating at the time when the reset signal R' falls (for example, B5 #). Therefore, the ECU (40) repeats the above-described interrupt processing routine of B75 # every time the vibration level Vp of the reference position 75 # is obtained.

As shown in FIG. 2, the vibration level Vp obtained at each reference position B75 ° of each cylinder changes every sampling cycle in accordance with the change of the output signal A of the knock sensor (1). Although this fluctuation includes knock and noise other than knock, considering a temporal change of the vibration level Vp and the like, in order to reliably detect knock, a background level that follows the vibration level Vp to some extent is obtained. There is a need. However, if the background level follows the vibration level Vp when the vibration level Vp suddenly increases, the threshold
Knock detection is not performed accurately due to a sudden increase in V _TH .

Therefore, ECU (40) the first filter (41) in the vibration level Vp by averaging based on a predetermined constant ^{_{N 1, BGL1 = BGL1 * (}} N 1 -1) / N 1 + Vp / N 1 (However, GBL1 ^* : previous average value) generates the first average value BGL1. This first average value BGL1
Is the current vibration level with respect to the previous first average BGL1 ^*
Vp is shifted to the reflected value and rewritten each time.

In the second filter (42), a timer interruption process is performed at predetermined intervals, and further averaging is performed on the first average value BGL1 obtained by the first filter (41). , the second average value ^{BGL2, BGL2 = BGL2 * (N} 2 -1) / N 2 + BGL1 / N 2 where, BGL2 ^*: second average value of the previous N _2: obtained from averaging constant. This second average BGL2 is the previous second average
BGL2 ^* is shifted to a value reflecting the current first average value BGL1, and is rewritten each time. By this averaging process, the second average value BGL2 becomes a stable value that does not significantly contribute to the fluctuation of the vibration level Vp. Note that the constants N ₁ and N ₂ can be optionally set.

Next, in the B75 interrupt processing routine, the operation unit (4
3) adds the and offset V _OF amplifies the second average value BGL2, ultimately threshold V _TH used for judgment of the _{knock, V TH = K · BGL2 +} V OF However, K: obtained from amplification factor . At this time, since the second average value BGL2 is sufficiently smoothed, the variation in the threshold value V _TH for each cycle is suppressed, and the threshold value V _TH becomes a highly reliable value.

Next, the comparison unit as a knock detecting means (44) for comparing the vibration level Vp and threshold level V _TH, obtain the difference of both Vk from Vk = Vp-V _TH, the difference Vk is positive or not Is determined. When the vibration level Vp exceeds the threshold value V _TH, i.e., Vk
If> 0, this is output as knock determination signal Vk indicating occurrence of knocking.

When the knock determination signal Vk is obtained, the retard reflection processing unit (45) calculates the retard amount Δθ _R required for knock suppression as Δθ _R = (Vk / V _TH ) × L ′, where L ′: reflection Calculate from the ratio. At this time, since the retard amount Δθ _R is calculated based on the ratio between the knock determination signal Vk and the threshold level V _TH , even if the vibration level Vp itself varies with time,
An appropriate retard amount Δθ _R is always obtained.

Further, the retard reflection processing unit (45) calculates a retard control angle θ _R for retarding the ignition position in the knock suppression direction based on the retard amount Δθ _R according to the above-mentioned equation, θ _R = θ. _R ^* + Δθ _R where θ _R ^* is obtained from the retard control angle up to the present.

On the other hand, if the comparison section (44) determines that Vk <0, since the knock determination signal Vk is not output, the retard amount Δ
theta _R is 0, retarded control angle theta _R remains at the current value.

Thus, the retard control angle theta _R, since the ignition position of the cylinder under control is corrected to the retard side, knocking will not occur.

On the other hand, the gain G of the amplifier (27) is set to a large first gain G1 at the time of initial setting. However, when the level of the threshold V _TH rises to a predetermined value or more, the gain switching control section (46)
To switch the gain G of the amplifier (27) from the first gain G1 to the second gain G2 (<G1). Conversely, the second gain G2
After setting, for example, when the level of the threshold V _TH with decreasing engine speed Ne is reduced to switch the gain G of the amplifier (27) to the first gain G1. At this time, since the amplification gains G1 and G2 are values set in advance in the amplifier 27, there is no control delay at the time of switching, and the gain can be immediately set to an appropriate gain.

Accordingly, the vibration level Vp and threshold V _TH is to take a value within a predetermined range, not the dynamic range of the input signal to the comparator unit (44) is increased, it is possible to perform accurate knock detection.

In the above embodiment, the interface circuit (20) for generating the vibration level Vp is replaced with the peak hold circuit (26).
However, it is needless to say that the same effect can be obtained by using an integrator.

In addition, the comparison unit (44) detects the vibration level Vp and the threshold.
Although the difference Vk between V _TH is outputted as the knock determination signal, when the vibration level Vp exceeds the threshold V _TH, comparator unit (44) is simply to generate an output signal of the "H" level You may.

Next, a specific operation according to an embodiment of the present invention will be described with reference to the flowchart of FIG. 3 and the characteristic diagram of FIG. Note that the upper limit value _VH and the lower limit value _VL for the threshold value _VTH are preset in the gain switching control unit (46), and the gain switching control routine shown in FIG. Be executed.

First, the amplification gain G for the knock sensor output signal A
Is determined to be the first gain G1 (large value) (step S1). If the amplification gain G is the first gain G1, whether the threshold value V _TH for knock determination is equal to or more than the upper limit value V _H or not is determined. It is determined whether or not it is (step S2).

If the threshold V _TH is higher than the upper limit V _H ,
The amplification gain G is switched to the second gain G2 smaller than the first gain G1 (step S3).

On the other hand, in step S1, the amplification gain G is set to the second gain.
If it is determined to be G2, it is determined whether the threshold V _TH is smaller than the lower limit _VL (step S4). If the threshold V _TH is smaller than the lower limit _VL , the amplification gain G is set to the first gain. Switch to G1 (step S5).

The above gain switching steps S1 to S5 are repeatedly executed each time the vibration level Vp is obtained.

Thus, the amplification gain G, as shown in FIG. 4, the first gain when the engine speed Ne is increased reaches the upper limit V _H
Switched to the second gain G2 lower than G1, the engine speed
When Ne decreases and reaches the lower limit value _VL , it is switched to the first gain G1 higher than the second gain G2. Therefore, the threshold
The value of V _TH is switched with a hysteresis in the predetermined range, the increase in dynamic range without causing hunting can be prevented, thereby improving the reliability and controllability of the knock detection.

Next, a specific operation of the knock control device for an internal combustion engine according to another embodiment of the present invention will be described with reference to a flowchart of FIG. 5 and a characteristic diagram of FIG. still,
In FIG. 5, S1 to S3 and S5 are the same steps as in FIG.

As described above, when it is determined in step S1 that the amplification gain G is the first gain G1, the threshold V
_TH is equal to or greater than or equal to the upper limit value V _H is determined (step
S2). If any threshold V _TH is less than the upper limit value V _H, read from the rotational speed detector the maximum rotational speed Ne _H of the engine corresponding to the upper limit value V _H, and stores this (step S
6). At this time, the amplification gain G is switched to the second gain G2 (step S3).

After switching to the second gain G2, the criterion for the gain switching control is based on the engine speed Ne. Therefore, the gain switching control unit (46) sets the lower limit rotation speed Ne _L smaller than the upper limit rotation speed Ne _H by a predetermined value Neα corresponding to the hysteresis.
Is calculated from Ne _L = Ne _H −Neα.

If it is determined in step S1 that the amplification gain G is the second gain G2, it is determined whether the engine speed Ne is smaller than a lower limit speed Ne _L (step S1).
7) If the engine speed Ne is smaller than the lower limit speed Ne _L , the amplification gain G is switched to the first gain G1 (step
S5).

Thus, after switching to the second gain G2 lower level on the basis of the upper limit value V _H of the threshold V _TH, by the hysteresis amount is set based on the engine speed Ne, the stability of the gain switching control further improves.

This is because the hysteresis component based on the threshold _VTH has many variable elements and is unstable, whereas the engine speed Ne is relatively stable. Therefore, the hysteresis of the upper limit _VH and the lower limit _VL needs to be set large, but the hysteresis of the engine speed Ne, that is, the value of the predetermined value Neα, does not need to be set too large.

In each of the above embodiments, the case is described in which the ignition timing is retarded, but other control parameters may be retarded to the knock suppression side.

[Effects of the Invention] As described above, according to the present invention, a knock sensor that detects vibration of an internal combustion engine, an interface circuit that generates a vibration level based on an output signal of the knock sensor, and an output signal of the knock sensor are preset. An amplifier for amplifying with a plurality of amplified gains, a calculating means for generating a knock determination threshold based on the vibration level, a comparison means for outputting a knock determination signal when the vibration level exceeds the threshold, and a knock determination. A delay reflection processing means for controlling the control parameter of the cylinder to the knock suppression side based on the signal, and a gain for suppressing a change in the level of the output signal of the knock sensor by switching the gain of the amplifier according to the threshold level A switching control unit, wherein the gain switching control unit determines whether the amplification gain is the first gain,
When the amplification gain is the first gain, it is determined whether or not a threshold for knock determination is equal to or more than an upper limit, and when the threshold is equal to or more than the upper limit, the amplification gain is switched to a second gain smaller than the first gain; When the amplification gain is the second gain, it is determined whether the threshold is smaller than the lower limit, and when the threshold is smaller than the lower limit, the amplification gain is switched to the first gain.
There is an effect that a knock control device for an internal combustion engine having high knock detection reliability and controllability can be obtained.

According to another aspect of the present invention, a knock sensor that detects vibration of an internal combustion engine, an interface circuit that generates a vibration level based on an output signal of the knock sensor,
An amplifier for amplifying the output signal of the knock sensor with a plurality of amplification gains set in advance; a calculating means for generating a threshold for knock determination based on the vibration level; and a knock determination signal when the vibration level exceeds the threshold. A comparison means for outputting, a delay angle reflection processing means for controlling a cylinder control parameter to a knock suppression side based on a knock determination signal, and an amplification gain switched according to a threshold level, and an output signal of the knock sensor is output. A gain switching control unit that suppresses a level change, wherein the gain switching control unit determines whether the amplification gain is the first gain, and when the amplification gain is the first gain, the threshold for knock determination is reduced. Determines whether or not the engine speed is equal to or higher than the upper limit, and if the threshold is equal to or higher than the upper limit, the upper limit engine speed corresponding to the upper limit And the amplification gain is switched to a second gain smaller than the first gain. When the amplification gain is the second gain, it is determined whether or not the engine speed is smaller than a lower limit speed smaller by a predetermined value than the upper limit speed. Since the determination is made and the amplification gain is switched to the first gain when the engine speed is smaller than the lower limit speed, there is an effect that a knock control device for an internal combustion engine having high knock detection reliability and controllability is obtained. . The effect is obtained.

[Brief description of the drawings]

1 is a block diagram showing an embodiment of a knock control device for an internal combustion engine according to the present invention, FIG. 2 is a waveform diagram showing the operation of the device shown in FIG. 1, and FIG. 3 is a diagram shown in FIG. FIG. 4 is a flowchart specifically showing the operation of the device, FIG. 4 is a characteristic diagram showing a hysteresis operation according to FIG. 3, and FIG. 5 is a diagram specifically illustrating the operation of a knock control device for an internal combustion engine according to another invention of the present invention. FIG. 6 is a characteristic diagram showing a hysteresis operation according to FIG. 5, FIG. 7 is a block diagram showing a conventional knock control device for an internal combustion engine, and FIG.
FIG. 4 is a waveform chart showing the operation of the conventional device shown in FIG. (1) Knock sensor (20) Interface circuit (27) Amplifier (43) Calculation unit (44) Comparison unit (45) Delay angle reflection processing unit (46) … Gain switching control unit A… Knock sensor output signal Vp… Vibration level, V _TH … Threshold V _H … Upper limit, _VL … Lower limit Vk… Knock discrimination signal, C… Gain switching signal θ _R … retard control angle, G… amplification gain G1… first gain, G2… second gain Ne… engine speed, Neα… predetermined value Ne _H … upper limit speed, Ne _L … ... Lower limit rotational speed S1... Step of determining whether or not G is G1 S2... Step of determining whether V _TH is not less than V _H S3... Step of switching G from G1 to G2 S4. _TH stores the step S6 ...... Ne _H for switching the step S5 ...... G determines V _L smaller than the G2 to G1 step S7 ...... Ne is Ne _L Ri or step Incidentally determining small, in the figure, the same reference numerals denote the same or corresponding parts.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yasuhiko Hosoya 840 Chiyoda-cho, Himeji-shi, Hyogo Mitsubishi Electric Corporation Himeji Works (56) References JP-A-58-120132 (JP, A)

Claims (2)

(57) [Claims] 1. A knock sensor for detecting vibration of an internal combustion engine, an interface circuit for generating a vibration level based on an output signal of the knock sensor, and an output signal of the knock sensor amplified by a plurality of preset gains An amplifier that generates a threshold for knock determination based on the vibration level; a comparison unit that outputs a knock determination signal when the vibration level exceeds the threshold; and Delay angle reflection processing means for controlling the control parameter of the cylinder to the knock suppression side; and gain switching control for switching the amplification gain in accordance with the threshold level to suppress a change in the level of the output signal of the knock sensor. And a gain switching control section, wherein the gain gain is a first gain or not. Determining whether the threshold for knock determination is equal to or greater than an upper limit when the amplification gain is the first gain; and determining the amplification gain when the threshold is equal to or greater than the first gain when the threshold is equal to or greater than the upper limit. Switching to a smaller second gain, determining whether the threshold is smaller than a lower limit when the amplification gain is the second gain, and changing the amplification gain to the second when the threshold is smaller than the lower limit. A knock control device for an internal combustion engine, wherein the knock control device switches to one gain. 2. A knock sensor for detecting vibration of an internal combustion engine, an interface circuit for generating a vibration level based on an output signal of the knock sensor, and an output signal of the knock sensor being amplified by a plurality of preset gains. An amplifier that generates a threshold for knock determination based on the vibration level; a comparison unit that outputs a knock determination signal when the vibration level exceeds the threshold; and Delay angle reflection processing means for controlling the control parameter of the cylinder to the knock suppression side; and gain switching control for switching the amplification gain in accordance with the threshold level to suppress a change in the level of the output signal of the knock sensor. And a gain switching control section, wherein the gain gain is a first gain or not. When the amplification gain is the first gain, it is determined whether or not a threshold for knock determination is equal to or more than an upper limit value. When the threshold is equal to or more than the upper limit value, an engine corresponding to the upper limit value is determined. Storing an upper limit rotation speed and switching the amplification gain to a second gain smaller than the first gain; and when the amplification gain is the second gain, the rotation speed of the engine is smaller than the upper limit rotation speed by a predetermined value. A knock control device for an internal combustion engine, which determines whether or not the engine speed is lower than a lower limit speed, and switches the amplification gain to the first gain when the engine speed is lower than the lower limit speed.