JP2542116B2 - Knock control device and method for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus and method for detecting and suppressing knock of an internal combustion engine such as a gasoline engine for automobiles, and in particular, improved controllability and cost reduction. The present invention relates to a knock control device and method for an internal combustion engine.

[Prior 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 the air-fuel mixture compressed in each cylinder at an optimum ignition position.
Therefore, an ECU composed of a microcomputer is used for controlling the internal combustion engine to optimally control the ignition timing by the igniter and the fuel injection sequence by the injector for each cylinder.

However, if the ignition position is excessively controlled to the advance side, abnormal combustion causes vibration called knocking, which may damage the cylinder.Therefore, when abnormal vibration is detected, the ignition position of the cylinder is retarded. Need to control.

FIG. 4 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 heat engine, and includes a piezoelectric element or the like for vibration detection.

Reference numeral (2) is a knock detection circuit that receives the output signal A of the knock sensor (1), and a filter (21) that allows a frequency (eg, 7 kHz) peculiar to knocking to pass through and a predetermined output signal of the filter (21). A gate (22) that periodically passes at a timing, a BGL generator (23) that generates a background level BGL based on the output signal A ′ of the gate (22), and an output signal A ′ of the gate (22). A comparator (24) that compares the output signal A ′ with the background level BGL and turns the output signal on when the output signal A ′ exceeds the background level BGL, and an integrator (24) that integrates the output signal of the comparator (24). 25) and are provided. (3) is an AD converter that converts the 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) The output signal V of the AD converter (3)
A retard reflection processing section (45) is provided for generating a retard control angle θ _R for retarding the cylinder ignition position based on _R.

Next, a conventional knock control method for an internal combustion engine using the knock control device for an internal combustion engine of FIG. 4 will be described with reference to the waveform chart of FIG.

Normally, each cylinder is ignited on the advance side from the position (B5 °) about 5 ° before TDC (top dead center = 0 °), and the explosion of the air-fuel mixture is about 10 ° to 60 ° from TDC. Angular position (A
Since it occurs around 10 ° to A60 °), knock due to abnormal combustion also occurs at this explosion timing.

Therefore, when vibration noise of the cylinder, particularly knock, 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 every predetermined period to the gate (22) so that the knock detection circuit (2) efficiently receives the output signal A. The mask signal M is set to have a rising edge of about B75 ° and a falling edge of about B5 ° for a cylinder to be detected, and inhibits the gate (22) when the level is “H”. Further, the reset signal R is output to the integrator (25) every predetermined period, and 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) passes the frequency component when the knock occurs, and the gate (22) passes the output signal A only to the engine whose mask signal M is at "L" level. The BGL generator (23) discriminates the background contained in the output signal A'on the basis of the output signal A'of the gate (22), and generates a background level BGL which serves as a reference for knock detection.

When the output signal A'exceeds the background level BGL, the comparator (24) determines that it is at the knock generation level and sets the output signal to the "H" level. Integrator (2
5) is a comparator (2
The output signal of 4) is integrated, and the AD converter (3)
An output signal of 5) is converted to a digital integral value V _R ECU
Input in (4).

The ECU (4) takes in the AD-converted integral value V _R for each ignition of the cylinder, and generates the retard control angle θ _R based on this.
The ignition position is retarded so as to suppress knocking. At this time, the delay angle reflection processing section (45) causes the current delay angle control angle θ
The present retard angle control angle θ _R is generated by cumulatively adding the present retard angle amount Δθ _R to _R ^* . Therefore, the retard angle control angle θ _R
Is represented by θ _R = θ _R ^* + Δθ _R. Further, the retard amount [Delta] [theta] _R of this time, where _{Δθ R = V R × L,} L: is represented by reflection ratio.

[Problems to be Solved by the Invention] In a conventional knock control device and method for an internal combustion engine, a BGL generator (23) and a comparator (24) are used by using a knock detection circuit (2) having a hardware configuration as described above. And integrators (25)
Since knock control is performed by the knock determination means including the above, there is a problem that the load on the hardware for control becomes large, the overall configuration becomes complicated, and the cost cannot be reduced.

The present invention has been made to solve the above problems, and uses a simplified hardware configuration
An object is to obtain an economical knock control device and method for an internal combustion engine by increasing the degree of freedom of controllability of U.

In addition, the present invention generates a threshold level that can follow the vibration level during transient operation, prevents sudden changes in the threshold level, and enables knock detection during transient operation, which is economical and reliable. An object is to obtain a high knock control device for an internal combustion engine.

[Means for Solving the Problems] A knock control device for an internal combustion engine according to the present invention includes a knock sensor that detects knock of the engine, and signal processing means that obtains a vibration level for each predetermined section based on an output signal of the knock sensor. A first averaging means for averaging the vibration level and outputting a first average value; and a second averaging means for averaging the first average value and outputting a second average value. Means, a transient operation state determination means for increasing the reflection rate of the averaging process by the first averaging means when the engine is in a transient operation state, and a threshold level for knock determination based on the second average value. Calculating means, a knock determining means for comparing a vibration level and a threshold level and outputting a knock determining signal, and a control means for controlling a control parameter of the engine in a knock suppressing direction based on the knock determining signal. It is provided with.

Further, the knock control method for an internal combustion engine according to the present invention, a step of acquiring the vibration level for each predetermined section based on the output signal of the knock sensor, a step of determining whether the engine is in a transient operating state, A step of averaging the vibration level at a predetermined reflection rate to generate a first average value when the engine is not in a transient operating state, and a first average value based on a large reflection rate when the engine is in a transient operating state To generate a second average value by averaging the first average value at a predetermined reflection rate, and to generate a threshold level for knock determination based on the second average value. Step, comparing the vibration level with the threshold level to determine knock, and controlling the control parameter in the knock suppression direction when the vibration level exceeds the threshold level. That it is obtained by a step.

[Operation] In the present invention, the vibration level at the cylinder reference position is obtained from the output signal of the knock sensor, and when the internal combustion engine is not in the transient operating state, the vibration level is averaged at a predetermined reflection rate, and in the transient operating state. Averaging the vibration level with a large reflection rate and generating a threshold level based on the obtained average value.When the vibration level exceeds the threshold level, the occurrence of knock is determined and the cylinder ignition position is retarded. Control.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a knock control device for an internal combustion engine according to the present invention, and (3) is the same as the above.
In this case, the knock sensor (1) has resonance characteristics at the knock frequency and includes the function of the filter (21) in FIG.

Reference numeral (20) is an interface circuit inserted between the knock sensor (1) and the AD converter (3), and is composed of, for example, a peak hold circuit (26). The interface circuit (20) and the AD converter (3) have a vibration level for each predetermined section based on the output signal A of the knock sensor (1).
It constitutes a signal processing means for obtaining Vp. The reset signal R'to the peak hold circuit (26) is EC
It is generated from U (40). The reset signal R'is synchronized with the rotation of the internal combustion engine, and rises at a reference position (B75 °) for each cylinder, for example, and rises at another reference position (B5 °).
It consists of a pulse that falls at. 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.

The ECU (40) averages the first average value BGL1 and the first filter (41) that averages the vibration level Vp to generate the first background level (first average value) EGL1. Second filter (42) for generating a second background level (second average value) BGL2 by performing the conversion process, and the second average value
Threshold level V for knock determination based on BGL2
Calculation unit for generating a _TH (43), the comparison unit which outputs a knock determination signal Vk when the vibration level Vp is compared with the vibration level Vp and threshold level V _TH exceeds the threshold level V _TH (44) , A delay angle reflection processing unit (45) for generating a delay angle control angle θ _R based on the knock determination signal Vk and a filter constant of the first filter (41) based on a change in the rotation speed Q of the internal heat engine. A filtering operation state determination unit (46) that outputs a switching signal C is provided.

Next, the operation of the knock control device for the internal combustion engine and the knock control method for the internal combustion engine according to the present invention will be described with reference to FIG. 1 and the waveform diagrams of FIG. 2 and the flowchart of FIG.

First, the knock sensor (1) detects the vibration of the cylinder for driving the internal combustion engine, and generates the output signal A for detecting the knock state, as described above. Further, the ECU (40) AD-converts and takes in the peak level of the output signal A of the knock sensor (1) each time the cylinder is ignited.

That is, the peak hold circuit (26) holds the peak level of the output signal A of the knock sensor (1), and this peak level is converted into a digital vibration level Vp by the AD converter (3) and then the ECU. (40) is input (step S1).

When the vibration level Vp at the reference position B75 ° is sampled, the ECU (40) raises the reset signal R ′ as shown in FIG. 2 to activate the peak hold circuit (26) at the reference position B75 ° (actually Reset just after B75 °) (step S2).

The peak hold circuit (26) continues to be reset while the reset signal R'is on, and starts its operation at the falling edge of the reset signal R '(for example, B5 °). Therefore, the ECU (40) repeats the B75 ° interrupt processing routine of FIG. 3 every time the vibration level Vp of the reference position 75 ° is obtained.

As shown in FIG. 2, the vibration level Vp obtained for each reference position B75 ° of each cylinder fluctuates in every sampling cycle according to the fluctuation of the output signal A of the knock sensor (1). Since this variation includes knock component and noise component, it is desirable not to contribute to the average value, but vibration level Vp
In consideration of the change with time and the like, it is necessary to obtain an average value that follows the vibration level Vp to some extent in order to reliably detect the knock.

On the other hand, in a transient operation state such as sudden acceleration or sudden deceleration,
Since the vibration level Vp also changes abruptly according to the number of revolutions of the internal combustion engine, it is necessary to quickly follow the average value that is the knock determination reference.

Therefore, the transient operating state determination unit (46) in the ECU (40)
Determines whether or not the engine is in a transient operating state based on the change in the rotational speed Q of the internal combustion engine (step S21).

If it is not in the transient operation state, the transient operation state determination unit (46) does not output the switching signal C and the first filter (41)
Is the vibration level based on the constant N ₁ corresponding to the given reflection rate.
Vp processed _{^{averaging, BGL1 = BGL1 * (N 1}} -1) / N 1 + Vp / N 1 ... ( However, BGL1 ^*: previous average) to produce a first average value BGL1 from (step S3).

If it is determined in step S21 that the engine is in the transient operating state, the transient operating state determination section (46) outputs the switching signal C and sets the filter constant in the equation to a constant smaller than N _1.
Switch to N ₁ ′.

Therefore, the first filter (41) averages the vibration level Vp based on the constant N ₁ ′, and calculates the average value from BGL1 = BGL1 ^* (N ₁ ′ −1) / N ₁ ′ + Vp / N ₁ ′. BGL1 is generated (step S31). This increases the reflection rate of the vibration level Vp with respect to the average value BGL1.

From the formula and the formula, the first average value BGL1 is shifted to a value that reflects the vibration level Vp of this time with respect to the first average value BGL1 ^* up to the previous time, and is rewritten each time. The filter constant N ₁ in the equation that determines the reflection rate of the normal vibration level Vp is
For example, it is set to about 8, and the contribution rate of the vibration level Vp this time is 1/8. On the other hand, the filter constant N ₁ ′ in the equation
Is set to about 1/2 of the constant N ₁ , for example, and the vibration level Vp
The contribution rate of is 1/4, which is twice the normal rate.

On the other hand, in the second filter (42), the timer interrupt process is performed every predetermined time. That is, the first average value BGL1 obtained by the first filter (41) is further averaged, and the second average value BGL2 is calculated as BGL2 = BGL2 ^* (N ₂ −1) / N ₂ + BGL1 / N ₂ ... However, BGL2 ^*: second average value of the previous N _2: obtained from the averaging process constant (step S3 '). From the formula, the second average value BG
L2 is the current 1st against the 2nd average value BGL2 ^* up to the previous time
The average value BGL1 is shifted to a value that reflects and is rewritten each time. This filter constant N ₂ can be set to any value as needed. By this averaging step S3 ', the second average value BGL2 is smoothed and becomes a stable value.

Next, in the B75 ° interrupt processing routine,
3) is for amplifying the second average value BGL2 and adding the offset V _OF to finally obtain the threshold level V _TH used for knock determination, where V _TH = K · BGL2 + V _OF ... where K: amplification coefficient (Step S4). At this time, the second average value BGL2
Is sufficiently smoothed, the threshold level V _TH obtained by the equation has a highly reliable value because variation in cycle-to-cycle variation is suppressed.

Next, in order to compare the vibration level Vp and the threshold level V _TH , the comparison unit (44) serving as knock detection means obtains a difference Vk between them from Vk = Vp−V _TH (step S5), and then, It is determined whether the difference Vk is positive (step S6).

Then, when the vibration level Vp exceeds the threshold value V _TH, that is, when Vk> 0, this is output as a knock determination signal V _K indicating occurrence of knocking.

When the knock determination signal Vk is obtained, the retard reflection processing section (45) determines the retard amount Δθ _R required for knock suppression as Δθ _R = (Vk / V _TH ) × L ′ ... where L ′: Calculate from the reflection rate (step S7). From the equation, the retard amount Δθ _R is calculated based on the ratio of the knock determination signal Vk and the threshold level V _TH , so that even if the vibration level Vp itself changes with time, an appropriate retard amount Δθ _R is always obtained. To be

Further, the retard angle reflection processing unit (45), based on the retard amount [Delta] [theta] _R, the retard control angle theta _R for retarding the ignition position in the knock suppression direction, by the above equation, theta _{R =} theta _R ^* + Δθ _R However, θ _R ^* : Obtained from the current retard angle control angle (step S8).

On the other hand, if it is determined in step S6 that Vk ≦ 0, the knock determination signal Vk is not output, and the retard angle amount Δθ _R is Δθ _R = 0 from the equation (step S9). Therefore, the retard angle control angle θ _R remains at the current value.

By the retard control angle θ _R thus obtained, the ignition position of the cylinder to be controlled is corrected to the retard side, and knock does not occur.

Thus, during normal operation, the second average value is sufficiently smoothed without being greatly affected by the sudden change in the vibration level Vp.
Reliable threshold level V _TH based on BGL2
Is set, it is possible to accurately determine the occurrence of knock.

Also, during transient operation, the filter constant is reduced to increase the contribution rate to the vibration level Vp, so the threshold level V _TH can be made to quickly follow the vibration level Vp, and the occurrence of knock can be accurately determined. You can

In the embodiment of the present invention, only the peak hold circuit (26) is configured by hardware, and the other knock determination means is configured in the ECU (40), so that the degree of freedom of controllability is high. In addition, the hardware load is reduced and the cost is reduced.

In the above embodiment, the interface circuit (20) for generating the vibration level VP is replaced by the peak hold circuit (26).
However, it goes without saying that the same effect can be obtained even if the integrator (25) similar to the conventional example is used.

Further, the comparison unit (44) outputs the difference Vk between the vibration level Vp and the threshold level V _TH as a knock determination signal. However, the vibration level Vp does not exceed the threshold level V _TH.
Alternatively, the comparator (44) may simply generate an output signal of "H" level when the value exceeds the limit.

Also, the second average value BGL2 is used as the average value for generating the threshold level V _TH , but the first filter (4
The first average value BGL1 may be used as long as it can be sufficiently smoothed by the averaging process according to 1). In this case, the second filter (42)
Can be omitted.

Furthermore, the transient operating state determination unit (46) determines the transient operating state based on the change in the rotational speed Q, but since the vibration level Vp corresponds to the rotational speed Q, the transient based on the change in the vibration level Vp. The driving state may be determined. For example, during normal operation, the vibration level Vp fluctuates up and down around the second average value BGL2, but during sudden acceleration, the vibration level Vp continuously exceeds the average value, and during sudden deceleration, the vibration level Vp.
Vp is continuously below the average value. Therefore, the vibration level Vp
Can be determined to be in the transient operating state when the value becomes equal to or higher than or equal to the average value continuously for a predetermined number of times or more.

As described above, according to the present invention, the first averaging means for averaging the vibration level and outputting the first average value,
Second averaging means for averaging the first average value and outputting a second average value; and a first averaging means when the engine is in a transient operating state.
Transient operation state determining means for increasing the reflection rate of the averaging processing by the averaging means, and computing means for outputting a threshold level for knock determination based on the second average value.
The vibration level and the threshold level are compared with each other to output a knock determination signal, and a control means for controlling the engine control parameter in the knock suppression direction based on the knock determination signal is provided to change the vibration level during transient operation. It also generates a threshold level that can be tracked, and prevents knocking of the threshold level to enable knock detection during transient operation, so an economical and highly reliable knock control device for an internal combustion engine can be obtained. There is.

Further, according to the present invention, a step of averaging the vibration level at a predetermined reflection rate to generate a first average value when the engine is not in the transient operating state, and a large step when the engine is in the transient operating state Generating a first average value based on the reflection rate, averaging the first average value at a predetermined reflection rate to generate a second average value, and based on the second average value To generate a threshold level for knock determination, to determine knock by comparing the vibration level with the threshold level, and to control the control parameter in the knock suppression direction when the vibration level exceeds the threshold level. Is provided to generate a threshold level that can follow the vibration level during transient operation, and prevent sudden changes in the threshold level to prevent Since also it allows click detection, the effect of economic and reliable internal combustion engine knock control method is obtained.

[Brief description of drawings]

1 is a block diagram showing a knock control device for an internal combustion engine according to an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the device of FIG. 1, and FIG. 3 is an internal combustion engine according to the present invention. Fig. 4 is a flowchart showing a knock control method for a vehicle, Fig. 4 is a block diagram showing a conventional knock control device for an internal combustion engine,
FIG. 5 is a waveform diagram for explaining the operation of the conventional apparatus of FIG. (1) …… Knock sensor, (40) …… ECU (41) …… First filter, (42) …… Second filter (43) …… Computing unit, (44) …… Comparison unit (45)… … Delay angle reflection processing unit (46) …… Transient operation state determination unit A …… Knock sensor output signal B75 ° …… Reference position, Vp …… Vibration level BGL1 …… First average value, BGL2 …… Second average Value N ₁ …… Predetermined constant, N ₁ ′ …… Constant less than N ₁ V _TH …… Threshold level θ _R …… Delay angle control angle S1 …… Step to obtain vibration level S21 …… Determine the transient operation state Step S3: Step of averaging with a predetermined constant N ₁ Step S3 ′: Step of averaging the first average value with a predetermined constant N ₂ Step S31: Average with a constant N ₁ ′ (<N ₁ ) Step S4 …… Generates threshold level Step S6 …… Determines if knock is present S8 …… Delay angle control Step of Generating Corner In the drawings, the same reference numerals indicate the same or corresponding portions.

Claims (2)

(57) [Claims] 1. A knock sensor for detecting a knock of an engine, a signal processing means for obtaining a vibration level for each predetermined section based on an output signal of the knock sensor, and a first average by averaging the vibration level. A first averaging means for outputting a value; a second averaging means for averaging the first average value and outputting a second average value; Transient operating state determination means for increasing the reflection rate of the averaging processing by the first averaging means, computing means for outputting a threshold level for knock determination based on the second average value, the vibration level and the A knock discrimination means for comparing a threshold level with each other and outputting a knock discrimination signal; and a control means for controlling a control parameter of the engine in a knock suppressing direction based on the knock discrimination signal. Combustion engine knock control system for. 2. A step of acquiring a vibration level for each predetermined section based on an output signal of a knock sensor, a step of determining whether or not the engine is in a transient operation state, and a step of determining a predetermined level when the engine is not in a transient operation state. Averaging the vibration level with a reflection rate to generate a first average value, and calculating the first average value based on a reflection rate higher than the reflection rate when the engine is in a transient operation state. And a step of averaging the first average value with a predetermined reflection rate to generate a second value.
A step of generating an average value of, a step of generating a threshold level for knock determination based on the second average value, a step of comparing the vibration level and the threshold level to determine knock, A knock control method for an internal combustion engine, comprising: controlling a control parameter in a knock suppression direction when a vibration level exceeds the threshold level.