JPH0684744B2 - 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 control device for detecting knock of an internal combustion engine such as a gasoline engine for an automobile and retarding the ignition position of a cylinder. The present invention relates to a knock control device for an internal combustion engine that prevents erroneous knock detection due to variations.

[Prior Art] Generally, an internal combustion engine driven by a plurality of cylinders has a microcomputer (EC) in order to efficiently obtain output torque.
U) is used to control the ignition timing and the fuel injection sequence for each cylinder according to the load condition.

However, if the ignition position is excessively controlled toward the advance side during high-speed operation or the like, abnormal combustion causes vibration called knocking (hereinafter referred to as knocking), which may damage the cylinder. To suppress the occurrence of such knocks,
Conventionally, a control parameter of an internal combustion engine is controlled in a knock suppressing direction. For example, when an abnormal vibration is detected during ignition, the cylinder ignition position is corrected to the retard side according to the vibration.

FIG. 3 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, which is composed of a piezoelectric element for detecting vibration, etc., and is tuned to a knock-specific frequency (for example, about 7 kHz). It has a resonance characteristic that

(2) is a peak hold circuit that generates a peak level P corresponding to the level (sensor level) of the output signal A of the knock sensor (1) at every predetermined ignition timing, and (3) is a crankshaft or camshaft of an internal combustion engine. Attached to the crank angle sensor for detecting a predetermined crank angle position θ, (4)
Is a timing signal generator that generates a timing signal T for resetting the peak hold circuit (2) based on the crank angle position θ, and (5) detects the rotational speed R of the internal combustion engine based on the crank angle position θ. Speed detector,
(6) is a function generator that generates a threshold level (threshold) TH corresponding to the rotation speed R. (7) is a knock discriminator composed of a comparator or the like, which compares the peak level P with the threshold value TH and outputs a comparison output C of "1" level when P> TH. (8) is a retard amount calculator that generates a retard amount θ _R for cylinder ignition position correction based on the comparison output C.
Reference numeral (9) is an ignition timing controller for controlling the ignition timing (ignition position) of the cylinder, which corrects the base advance value determined according to the engine speed and load condition of the internal combustion engine by the retard amount θ _R. It has become.

The timing signal T generated every predetermined period corresponds to the reference position of the cylinder synchronized with the rotation of the internal combustion engine,
For example, standing up at the first reference position B75 ° of each cylinder,
It consists of pulses that fall at the second reference position B5 °. Therefore, the peak hold circuit (2) is reset at the first reference position B75 ° and masked between the first reference position B75 ° and the second reference position B5 °. Then, from the second reference position B5 ° of a certain cylinder to the first reference position of the next cylinder.
It is enabled up to the reference position B of 75 °, and holds the peak level P.

Next, the operation of the conventional knock control device for an internal combustion engine shown in FIG. 3 will be described with reference to the waveform diagram of FIG. 4 and the characteristic diagram of FIG.

Normally, each cylinder is ignited in the vicinity of the second reference position B5 °, which is about 5 ° before TDC (top dead center = 0 °), so the explosion of the air-fuel mixture is about 10 ° to 60 ° from TDC. It occurs near the excessive crank angle position A10 ° to A60 °, and knock due to abnormal combustion also occurs in synchronization with this explosion timing.

The knock sensor (1) is fixed to a cylinder of a cylinder or the like to detect vibration. When knock occurs, the knock sensor (1) generates an output signal A (see FIG. 4) having a large amplitude with respect to other vibration levels. For example, if a knock occurs in a cylinder,
The output signal A of the knock sensor (1) is the crank angle position A1.
The waveform has a periodically large amplitude in the vicinity of 0 ° to A60 °.

The crank angle sensor (3) is the first that corresponds to the operation of the cylinder.
And a second reference position B75 ° and a crank angle position θ indicating B5 °, and based on the crank angle position θ, the timing signal generator (4) outputs a pulsed timing signal T
Is output.

The peak hold circuit (2) detects the peak level P of the output signal A of the knock sensor (1) from the rising edge of the timing signal T (second reference position B5 °), and determines this from the falling edge of the timing signal T ( First reference position B75
Hold until reset at °).

The rotation speed detector (5) detects the rotation speed R of the internal combustion engine from the crank angle position θ and generates a signal level corresponding to this rotation speed R. The function generator (6) is composed of, for example, a ROM table, and as shown in FIG. 5, generates a threshold value TH that increases with an increase in the rotation speed R. This is because as the rotation speed R increases, the amount of vibration due to knocking and noise increases, and the amplitude of the peak level P increases overall. The characteristic of the threshold value TH as shown in FIG. 5 is preset in the ROM or the like in the function generator (6).

The knock discriminator (7) compares the peak level P with a threshold TH, and when the peak level P exceeds the threshold TH, determines that knock has occurred, and generates a comparison output C of "1" level. The delay amount calculator (8) increases the retard amount θ _R by a predetermined value when the comparison output C is generated (when knock occurs), and when the comparison output C is not generated (knock occurs) If not), the retard angle amount θ _R is decreased by a predetermined value every predetermined time.

The ignition timing controller (9) corrects the base advance value by the retard amount θ _{R and} controls the calculation of the cylinder ignition position. As a result, the ignition position of the cylinder to be controlled is retarded to the knock suppression side, and knock does not occur.

However, while the threshold value TH is uniquely set for the operating state, the noise level included in the peak level P does not affect the internal combustion engine (engine) or the knock sensor (1) even if the operating state is the same. Fluctuates due to variations in the characteristics of.
Therefore, even if the peak level P is a noise level, it may exceed the threshold value TH.

If the noise is determined to be knock and the retard control is performed, the cylinder ignition position is integrated and retarded each time the knock is detected, and the control efficiency of the cylinder is significantly impaired.

[Problems to be Solved by the Invention] As described above, the conventional knock control device for an internal combustion engine determines the peak level P by using the threshold value TH that is preset corresponding to the operating state. When the noise level of P fluctuates, the noise is apt to be erroneously detected as a knock, and the cylinder ignition position is continuously retarded, resulting in a large loss of control efficiency.

The present invention has been made to solve the above problems, and provides a knock control device for an internal combustion engine that can prevent erroneous detection of noise even if the peak level changes due to variations in the engine and knock sensor. With the goal.

[Means for Solving the Problems] A knock control device for an internal combustion engine according to the present invention stores a threshold value corresponding to each region of an operating state, and a storage means for reading the threshold value based on an output of the sensor means, A threshold correction calculation processing unit that corrects the threshold value according to the level of the output signal of the knock sensor is provided, and the presence or absence of knock is determined by comparing the sensor level and the correction threshold value from the threshold correction calculation processing unit. Is.

[Operation] According to the present invention, when the average value of the sensor level corresponding to the output signal of the knock sensor becomes larger than the preset noise level, the threshold value is corrected to be large and unnecessary noise is eliminated. Suppresses retard control.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a block diagram showing an embodiment of the present invention,
(1) to (4) are the same as described above. Also (17)
~ (19) correspond to (7) to (9), respectively.

Reference numeral (10) is an AD converter for converting the peak level P into a digital value, which is inserted between the peak hold circuit (2) and the knock discrimination processing section (17).

(11) is a load state L as an operating state different from the rotational speed R
Is a load sensor that detects, for example, a semiconductor that detects the intake state of the accelerator.

(12) is an operating state processing unit that determines an operating region D that is two-dimensionally divided based on the crank angle position θ and the load state L, and a rotation speed detector (which detects a rotation speed R from the crank angle position θ ( 5) (see FIG. 3) and a load detector for detecting the load level from the load state L. (13) is a first ROM that stores a threshold TH corresponding to each operation area D as a three-dimensional map table.
TH is to be read. (14) is a second ROM that stores an average noise level N corresponding to each operation area D
The noise level N for the operating area D is read.

Reference numeral (20) is a threshold value correction calculation processing unit for correcting the threshold value TH based on the peak level P and the noise level N, and an averaging processing unit (21) for averaging the peak level P every predetermined period.
And the average value P ^* from the averaging processor (21) and the second ROM (14)
A division unit (22) for generating a correction coefficient K from the ratio with the noise level N read from the memory, and a threshold TH read from the first ROM (13) are multiplied by the correction coefficient K to generate a correction threshold TH ^* . And a multiplication unit (23).

The knock determination processing unit (17) compares the peak level P via the AD converter (10) with the correction threshold TH ^* output from the threshold correction calculation processing unit (20) to generate a comparison output C, The retard amount calculation processing section (18) determines the retard amount θ based on the comparison output C.
_The ignition timing control section (19) retards the cylinder ignition position based on the retard amount θ _R. These are the operating state processor (12), the first ROM (13), the second ROM
It is configured in a microcomputer together with (14) and a threshold value correction calculation processing section (20).

Next, referring to the flowchart of FIG.
The operation of the embodiment of the present invention shown in the figure will be described.

The peak hold circuit (2) generates the peak level P of the output signal A of the knock sensor (1) according to the timing signal T as described above, and the AD converter (10) converts the peak level P into a digital value. It is converted and input to the knock discrimination processing section (17).

The operating condition processing section (12) classifies the rotational speed R and the load level at the time of detection based on the crank angle position θ from the crank angle sensor (3) and the load condition L from the load sensor (11), and Threshold TH corresponding to the three-dimensional driving area D is stored in the first ROM
Read from (13).

At this time, the threshold value TH corresponding to each operating region D of the rotational speed R and the load level is previously stored in the first ROM (13), and the threshold value of the high level is set at the time of the light load when the noise level becomes relatively large. TH is read, making it difficult to mistakenly determine knock.

According to the threshold value correction processing routine of FIG. 2, the threshold value correction calculation processing section (20) first initializes the rotational speed, the load level and the like corresponding to knock detection (step S1).

Next, it is determined whether or not the set number of revolutions at the time of knock detection (step S2), and if the set number of revolutions is reached, it is further determined whether or not the set load level is reached (step S3).

If the set number of revolutions and the set load level at the time of knock detection are reached, the average value P ^* of the current peak level P is calculated by the averaging processing section (21) (step S4).

Then, the noise level N that corresponds to the current rotation speed and load level and that corresponds to the average value P ^* is set to the second R
The OM (14) is read (step S5), the dividing unit (22) calculates the ratio of the average value P ^* and the noise level N, and the correction coefficient K is calculated from K = P ^* / N (step S6).

Finally, the multiplication unit (23) multiplies the threshold TH read from the first ROM (13) by the correction coefficient K, and calculates the correction threshold TH ^* from TH ^* = TH × K (step S7). The correction threshold TH ^* is input to the reference terminal of the knock discrimination processing section (17).

On the other hand, if it is determined in step S2 or S3 that the set rotation speed or the set load level is not reached, knock detection is not performed, so the threshold value correction processing routine is not executed, and immediately returns and ends.

By the above threshold correction processing, the threshold value TH preset in correspondence with the driving state is not used as it is as the reference level of the knock determination processing section (17), but the average value P ^* of the peak level P at that time point ^. Is corrected according to the fluctuation of.

If the average value P ^* is larger than the preset noise level N, the correction coefficient K becomes K> 1, so the correction threshold TH ^* becomes TH ^* > TH, and the noise level is erroneously regarded as a knock level. Detection is suppressed. As described above, even if the peak level P fluctuates due to variations in individual characteristics of the knock sensor (1), the fluctuation amount is absorbed by the threshold correction calculation processing section (20), and the correction threshold value corresponding to the peak level P is always maintained. Accurate knock discrimination can be performed based on TH ^* .

In the above embodiment, the crank angle sensor (3) for detecting the crank angle position θ corresponding to the rotational speed and the load sensor for detecting the load state L corresponding to the load level are used as the sensor means for detecting the operating state. (11) and were used,
Other sensor means may be used, and as shown in FIG.
One sensor means may be used.

Further, although the peak level P is used as the sensor level corresponding to the output signal A of the knock sensor (1), the integration level via the integration circuit may be used.

Further, although the knock determination processing section (17) is composed of a comparison circuit, it may be composed of a comparison operation circuit so as to obtain an output signal according to an input signal difference.

[Effects of the Invention] As described above, according to the present invention, the threshold value corresponding to each region of the operating state is stored, and the threshold value is read out based on the output of the sensor means and the output signal of the knock sensor. A threshold correction calculation processing unit that corrects the threshold according to the level is provided, and the presence or absence of knock is determined by comparing the sensor level corresponding to the output signal of the knock sensor and the correction threshold from the threshold correction calculation processing unit. Therefore, there is an effect that an unnecessary retard control due to erroneous knock detection can be suppressed, and a knock control device for an internal combustion engine with improved reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flow chart for explaining the operation of the threshold value correction calculation processing section in FIG. 1, and FIG. 3 is a conventional knock control for an internal combustion engine. FIG. 4 is a block diagram showing the device, FIG. 4 is a waveform diagram for explaining the operation of the device of FIG. 3, and FIG. 5 is a characteristic diagram showing the contents of the function generator in FIG. (1) …… Knock sensor (3) …… Crank angle sensor (11) …… Load sensor, (13) …… First ROM (14) …… Second ROM (17) …… Knock discrimination processing unit (20)… ... Threshold correction calculation processing unit A ... knock sensor output signal θ ... crank angle position, L ... load state TH ... threshold, TH ^* ... correction threshold N ... noise level, P ... peak level C ... … Comparison output, θ _R …… Amount of delay angle In the drawings, the same reference numerals indicate the same or corresponding portions.

Claims (2)

[Claims] 1. A knock sensor for detecting vibration of an internal combustion engine, at least one sensor means for detecting an operating state of the internal combustion engine, a threshold value corresponding to each region of the operating state, and the sensor means. A storage unit for reading out the threshold value based on the output of, a threshold value correction calculation processing unit for correcting the threshold value read out from the storage unit according to the level of the output signal of the knock sensor, and the threshold value correction calculation processing unit. And a knock determination means for comparing the output of the knock sensor with the correction threshold of the knock sensor, and a control means for controlling the control parameter of the internal combustion engine in the knock suppression direction according to the output of the knock determination means. A knock control device for an internal combustion engine, comprising: 2. A peak hold circuit for detecting a peak level of an output signal of the knock sensor every predetermined period, a noise level corresponding to each region of the operating state is stored, and based on an output of the sensor means. Another storage unit from which the noise level is read out, the threshold value correction calculation processing unit averages the peak level for each predetermined period, and an average obtained by the averaging processing unit. 3. A division unit for generating a correction coefficient from a ratio between a value and the noise level, and a multiplication unit for multiplying the threshold value by the correction coefficient to generate a correction threshold value. A knock control device for an internal combustion engine as described.