JPH05264405A - Knocking detector - Google Patents

Abstract

PURPOSE:To sense knocking accurately from the low-speed region to the high- speed region of the rotating speed of an internal combustion engine. CONSTITUTION:The output signals of a knocking sensor 1 are inputted through input ports A and B of a microcomputer 90 through a filter 3 and two amplifiers 4 and 5 having the different amplification factors A and B, and A/D conversion is performed. Thus, it is sensed whether or not knocking occurs. At this time, when the rotating speed of an engine is low and the output signal of the knocking sensor 1 is small, the output of the amplifier 4 having the large amplification factor is inputted through the input port B. When the rotating speed of the engine is large and the output signal of the knocking sensor 1 is large, the output of the amplifier (attenuator) 5 having the small amplification factor is inputted through the input port A.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking detection device for detecting knocking of an internal combustion engine. 2. Description of the Related Art Conventionally, a device for detecting knock using a knock sensor, an AD converter, and a microcomputer is known. However, when the knock sensor output signal is input to the A / D converter, the knock sensor output signal is extremely small in the low speed range of the internal combustion engine. It was difficult to detect knocking. Further, in the high speed range of the internal combustion engine, the knock sensor output signal becomes extremely large, so
There is a problem that the maximum input voltage of the converter is exceeded and saturation occurs, resulting in incorrect detection. Further, for example, Japanese Unexamined Patent Publication No. 56-77558 discloses a technique of homogenizing the knock sensor output signal regardless of the engine speed by changing the amplification degree of the knock sensor output signal according to the engine speed. However, there was a problem that the dynamic range had to be wide. The present invention has been made to solve the above problems, and an object of the present invention is to provide a knocking detection device capable of accurately detecting knocking from a low speed region to a high speed region of the internal combustion engine. And The above objects of the present invention are as follows:
Preferably, knocking detection means for detecting a signal generated by knocking of the internal combustion engine, filter means for removing noise from the detection signal of the knock detection means, and A for converting an analog signal output by the filter means into a digital signal In the knocking detection device for an internal combustion engine by using the -D conversion means, a plurality of amplification means having different amplification factors for amplifying or attenuating the signal obtained by the filter means and a signal from each of the amplification means are provided. Arithmetic processing means for performing arithmetic processing by performing conversion by the A-D conversion means via an input port; knock determination means for determining presence or absence of knocking based on a result of arithmetic processing of the arithmetic processing processing;
Amplification factor deciding means for taking in the signal of the amplifying device on the side of high amplification factor when the detection signal of the knocking detecting device is small, and for taking in the signal of the amplification device on the side of small amplification factor when the knocking detection signal is large. Can be achieved by a knocking detection device. Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a functional block diagram of a knocking detection device according to the invention. Reference numeral 10 is a knocking detection means such as a voltage element for detecting a signal generated by knocking of the internal combustion engine, 20 is a filter means for removing noise of the signal detected by the knocking detection means 10, and 30A and 30B are amplifications. Multiple amplification means with different rates. Reference numeral 40 denotes A-D conversion means, and each amplification means 30.
The analog signals from A and 30B are taken in through the respective input ports and converted into digital signals. A-D conversion means 4
0, amplification factor determination 60, arithmetic processing 70, and knocking determination means 80 represent means for implementing the arithmetic processing function of the microcomputer 90. When the knock sensor output signal is small, the amplification factor determining means 60 takes in the signal of the amplification means on the high amplification side into the A-D conversion means through the input port, and when the knock sensor output signal is large, the amplification factor is high. The input of the signal of the amplification means on the lower side is taken into the AD conversion means via the input port. The knocking determination means 80 is the arithmetic processing means 70.
The presence or absence of knocking is determined from the processed signal obtained by the above, and a signal indicating the determination result is output. FIG. 2 is a block diagram showing an embodiment of the present invention using a microcomputer, and 90 is an AD.
Includes converter in chip, CPU, IO port, RO
It is a microcomputer including M and RAM. 1
Is a knock sensor that serves as knocking detection means, and 2 is a buffer that impedance-converts the knock sensor output signal obtained by the knock sensor 1 into an input signal to the filter 3 that serves as filter means. Reference numeral 4 is an amplifier which constitutes an amplifying means, and 5 is an attenuator which constitutes an amplifying means and corresponds to the engine rotation speed.
In the low speed region, the signal is input from the amplifier 4 to the micro computer 90 through the input port B, and undergoes conversion processing by the AD converter therein. The CPU corrects the amplification factors of the amplifier 4 and the attenuator 5, arithmetically processes the knock sensor signal, detects knocking, determines the presence or absence of knocking, and outputs a signal indicating the determination result. In this embodiment, the input port is switched between a high speed range where the knock sensor signal is large and a low speed range where the knock sensor signal is small to keep the linearity of the knock sensor output signal in a wide range.
The structure which prevents saturation of the -D conversion value is shown. FIG. 3 shows a first example of a flow chart showing the software of the micro computer. When the internal combustion engine is started, the programs stored in the ROM and the RAM are executed, initial values are set in step 100, and the input port switching rotation speed (for example, 3000 r.p.
m.) is initialized. Next, in step 110, the engine rotation speed Ne is detected, and in step 120 it is compared with the set input port switching rotation speed. When the set input port switching rotation speed is 3000 rpm and the engine rotation speed is in the high speed range, the routine proceeds to step 130, where the input port A
The knock sensor output signal is taken into the AD converter. In step 140, the knock sensor output signal is averaged for each peak,
Calculate the average value VAD of peaks and the maximum value Vmax of peaks,
At the same time, the amplification factor is corrected by multiplying the average value VAD and the maximum value Vmax of the peak of the knock sensor output signal by the ratio α = B / A of the attenuation factor A and the amplification factor B, respectively. On the other hand, if the engine speed Ne is lower than 3000 rpm set as the input port switching speed as a result of the determination in step 120, step 1
50, the knock sensor output signal from the input port B to A
-Incorporate into D converter. Then, in step 160, the averaging process is performed for each peak, and the average VAD of the peaks of the knock sensor and the maximum value Vmax of the peaks are calculated. In step 170, the average value VAD of the peaks calculated in steps 140 and 160 is averaged with the average value Vmean of the output signals of the past knock sensors and the weighted addition,
A new knock sensor output signal average value Vmean is calculated. Next, at step 180, the calculated new knock sensor output signal average value Vmean is multiplied by a constant K, an offset Voff is added, and a judgment level Vref is calculated. In step 190, the determination level Vref and the maximum value Vmex of the knock sensor output signal are compared in magnitude. When the maximum value Vmax of the knock sensor output signal is larger than the judgment level (Vmax> Vref), it is judged that there is a knock, and the routine proceeds to step 200, where knock pulses of the number of times when the knock sensor output signal exceeds the judgment level. The signal is output. After the output of the knock pulse signal, the process returns to step 110 to start knock detection again. In step 190, when the maximum value Vmax of the knock sensor output signal is smaller than the determination level (Vmax <Vref)
It is determined that there is no knock, and the process returns to step 110. Then, steps 120, 130 and 150
Corresponds to the amplification factor determining means of the present invention, and the step 140,
160, 170 and 180 correspond to the arithmetic processing means of the present invention, and steps 190 and 200 correspond to the knocking determination means of the present invention. FIG. 4 shows a second example of a flow chart showing the software of the micro computer. In this second example, the input port switching rotational speed has a hysteresis characteristic, and in the initial setting stage of step 300, the input port switching rotational speed corresponding to the hysteresis characteristic (for example, 3500r.pm, 2900r.pm). Perform the initial setting of. The detection of the engine speed in step 310 is the same as in the first example. In step 320, a process for determining whether the engine speed is increasing or decreasing is performed, and in step 330, it is determined whether the engine speed is increasing or decreasing. FIG. 5 is a characteristic diagram showing the relationship between the knock sensor output voltage having the hysteresis characteristic and the engine rotation speed in the above-mentioned second example, when the engine rotation speed rises. When the rotation speed indicated by 1 is exceeded, the input port is switched from port A to port B. Similarly, when the rotation speed of the engine is decreasing and falls below the rotation speed indicated by 2, the input port is switched from the port B to the port A. The dotted line C in FIG. 5 shows the conventional knock sensor output characteristic. Next, if it is determined in step 330 that the engine speed is increasing, the process proceeds to step 400,
When the engine speed and the input port switching speed (3500 rpm) with hysteresis characteristics are compared, the engine speed Ne is higher than the input port switching speed (Ne> 3500 rpm). In step 410, the knock sensor output signal is input through the input port A, and in step 420, step 1 of FIG.
Similar to 40, the knock sensor output signal is averaged,
The amplification factor correction is performed on the average value VAD of the peaks and the maximum value Vmax of the peaks.
The process proceeds from 0 to step 460. At step 400, when the engine rotation speed Ne is lower than the input port switching rotation speed Ne (Ne <35
00r.pm), the same processing as in FIG. 3 is performed, and the process proceeds from step 470 to step 480. Step 33
0, when the engine speed Ne is decreasing, the routine proceeds to step 500, where the engine speed and the input port switching speed (2900r.
pm) is compared, and in accordance with the magnitude relationship between the two, the process proceeds to step 510 or step 570, and the processing in each step is executed and step 56
Go to 0. According to the arithmetic processing of the second example, the knock sensor has a hysteresis in the relationship between the knock sensor output voltage and the input port switching rotation speed when the engine speed increases and decreases. Even if the output characteristics of the signal may change to some extent, the amplification factor can be corrected with respect to the knock sensor output signal, so that knock determination is ensured. As described above, according to the present invention, the rotation speed of the internal combustion engine changes over a wide range from the low speed region to the high speed region, and the magnitude of the knock sensor signal changes greatly accordingly. However, when the nonk sensor signal is small, it is amplified by the amplifying means having a large amplification factor, and when the knock sensor signal is large, it is amplified by the amplifying means having a small amplification factor, and then A-D converted, whereby A of the A-D converting means is obtained. −
Since knock determination can be performed without the D-converted value being saturated, an excellent effect that the presence or absence of knock can be accurately determined is obtained. Further, since each amplification means always amplifies the knocking signal with a different amplification rate, the amplification rate of the knocking signal is determined by the selection of each input port, and the A-D conversion means performs the A-D conversion. There is an excellent effect that noise at the time of switching the amplification factor is unlikely to occur, and that a knocking signal having a predetermined amplification factor can be AD-converted immediately.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a functional block diagram of a knocking detection device according to the present invention. FIG. 2 is a block diagram showing an embodiment of the present invention using a microcomputer. FIG. 3 is a first arithmetic process of the microcomputer of FIG.
It is a flowchart which shows an example. FIG. 4 is a second arithmetic processing of the microcomputer of FIG.
It is a flowchart which shows an example. FIG. 5 is a characteristic diagram showing a relationship between a knock sensor output voltage and an engine rotation speed of a knocking detection device having a hysteresis characteristic according to the present invention. [Description of Reference Signs] 1 knock sensor 3 filter 4 amplifier 5 attenuator 10 knocking detection means 20 filter means 30A amplification means 30B amplification means 40 AD conversion means 60 amplification factor determination means 70 arithmetic processing means 80 knocking determination means 90 microcomputer

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Claims (1)

Claims: Knocking detection means for detecting a signal generated by knocking of an internal combustion engine; filter means for removing noise by a detection signal of the knocking detection means; and an analog signal output by the filter means converted to a digital signal. In the knocking detection device for detecting knocking of an internal combustion engine by using the A-D converting means, a plurality of amplifying means having different amplification factors for amplifying or attenuating the signal obtained by the filter means, and the width means. Signal from the above-mentioned A through each input port
An arithmetic processing unit that converts by the -D conversion unit and performs arithmetic processing, a knocking determination unit that determines the presence or absence of knocking based on the result of the arithmetic processing of the arithmetic processing unit, and an amplification when the detection signal of the knocking detection unit is small. A knocking detection device, comprising: an amplification factor determining unit that takes in a signal from the amplification unit having a high amplification factor and that receives a signal from the amplification unit having a small amplification factor when the detection signal from the knocking detection unit is large. ..