JPH0914042A - Knock detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control any knock by a microcomputer tip for an engine control by using the microcomputer built in plural A/D converters and using one A/D converter for a knock signal processing exclusively. SOLUTION: CPU10 for carrying out various calculation, ROM 16 for storing a program, RAM 15 for storing a calculation result, A/D converters 11, 12, input/output devices 13, 14 are built in a microcomputer 2. A knock signal 3a is inputted in the A/D converter 11 and sampled by a period and the degital signal 11a is analized by a frequency at a frequency analysis part 31 and a specific frequency component included in the knock signal 3a is extracted. The signal 31a after the frequency analysis is smoothening processed in a smoothening precess part 32 (back bround level signal 32a is outputted). The existence of a knock generation in the signal 31a after frequency analysis and the background level signal 32a is judged by the frequency component by which the vibration by the generation of the knock is revealed remarkably in response to the operation state by the knock judgement 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device having a knock detection device.

[0002]

2. Description of the Related Art When a knock occurs in an engine, vibration having a characteristic resonance frequency component is generated. The presence or absence of knocking is detected by detecting the knock signal level and comparing it with the background vibration that occurs other than knocking. In particular, in order to improve the accuracy of knock detection, a method of detecting a specific resonance frequency by using a bandpass filter is widely known, as described in JP-A-58-45520. Further, since the resonance frequency changes depending on the operating state of the engine or the cylinder, as described in JP-A-3-47449, the knock signal is sampled by the A / D converter to analyze a plurality of resonance frequency components, Some further improve the knock detection accuracy.

[0003]

In the prior art, in order to perform frequency analysis of a knock signal, A / D conversion must be performed continuously in a short period. Therefore, other A / D input values cannot be sampled at the same timing. Therefore, an A / D converter is required only for the knock signal input, and when a microcomputer having only one A / D converter is used, the microcomputer is used only for knock detection. Become. When a dedicated microcomputer for knock signal processing is provided in this way, a plurality of microcomputers are required to perform engine control. As a result, the engine control device becomes expensive, and it becomes necessary to send and receive data between both microcomputers, which complicates the control program.

The principle will be described with reference to FIGS.

FIG. 4 is a block diagram when a microcomputer dedicated to knock detection is provided. The engine control unit 1 includes a main microcomputer 43 for calculating fuel injection amount and ignition timing for optimally controlling the engine, and a sub-microcomputer 41 for detecting knock. The microcomputers are connected by a bus 42 and are configured to send and receive data to and from each other. Signals from the airflow sensor 4 and the crank angle sensor 6 are input to the main microcomputer 2, fuel and ignition are calculated based on these signals, and control signals are output to the fuel injection device 7 and the ignition device 8. On the other hand, signals from the crank angle sensor 6 and the knock sensor 3 are input to the sub-microcomputer 41 to determine knock. FIG. 5 is a block diagram of both program processes. Main microcomputer 43
In the inside, the air flow sensor 4 is input as a digital signal from the A / D converter 51, and is input to the fuel calculation unit 53 and the ignition calculation unit 54. At the same time, the signal from the crank angle sensor 6 is input to the rotation detection unit 52, and the result is similarly input to the fuel calculation unit 53 and the ignition calculation unit 54. The respective calculation units output the calculated results as control signals to the fuel injection device 7 and the ignition device 8, respectively. Here, information on the presence / absence of knock is input to the ignition calculation unit from the sub-microcomputer 41 via the bus buffer 55 and used for calculation of ignition timing. On the sub-microcomputer 41 side, the knock signal from the knock sensor 3 is input to the A / D converter 57, the result is analyzed by the frequency analysis unit 58, and the BGL signal 59a smoothed by the BGL unit 59 and the frequency-analyzed value are obtained. The knock determination unit 60 compares the values with and to determine whether or not there is a knock. In the frequency analysis unit, the signal of the crank angle sensor 6 is input via the rotation detection unit 56 in order to set the timing of the frequency analysis start. Further, in order to determine the frequency analysis section, information on the number of revolutions is input from the main microcomputer 43 via the bus buffer 61. The information on the presence or absence of the determined knock is similarly transmitted to the main microcomputer 43 via the bus buffer 61. Thus, both C
Although it is necessary to transmit and receive data between PUs, since the knock is synchronized with the rotation of the engine, the timing of data transmission and reception must be synchronized with the rotation. The timing is the timing of the crank angle sensor 6, but control may be delayed only with that timing, so it is necessary to transmit and receive at other timings.
For this reason, the data transmission / reception program is complicated.

[0006]

In order to solve this problem, a microcomputer incorporating a plurality of A / D converters is used, and at least one of the A / D converters is dedicated to knock signal processing. It is not necessary to provide a microcomputer dedicated to knock signal processing, and knock control can be performed with one chip of the engine control microcomputer.

[0007]

With this configuration, the conventional engine control program and the knock detection program can be realized because the engine control device with knock control using digital signal processing that requires two conventional microcomputers can be realized by the single-chip microcomputer. Since they are integrated into one, there is no need to transmit and receive data between the engine control microcomputer and the knock processing microcomputer, so that the structure of the control program is simplified and an inexpensive engine control device can be supplied. As a result, the area occupied by the microcomputer on the board is reduced, so that the engine controller can be made smaller and lighter, which contributes to the improvement of fuel consumption.

[0008]

Embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the present invention. Reference numeral 1 represents an engine control device. Reference numeral 3 is a knock sensor for detecting engine knock, 4 is an air flow sensor for detecting the amount of air taken into the engine cylinder, 5 is a water temperature sensor for detecting the temperature of cooling water of the engine, and 6 is rotation of the engine. A crank angle sensor, 7 is a fuel injection device that supplies fuel to the engine, 8 is an ignition device, and 18 is a battery that supplies power to the engine control device.
Then, the engine control device 1 inputs signals from the respective sensors to execute arithmetic operations for controlling the engine in an optimum state, and supplies power to the microcomputer 2 and the microcomputer 2 that output various control signals. Power supply circuit 9 for The microcomputer 2 includes a CPU 10 that executes various calculations, a ROM 16 that stores program data for operating the CPU 10, and a CPU
RAM 15 for storing the result calculated in 10, A / D converter 11 for inputting knock signal 3a, Air flow rate signal 4
a, a water temperature signal 5a, an A / D converter 12 provided separately from the A / D converter 11, an input device 13 for inputting a signal 6a from the crank angle sensor 6, a fuel injection device 7 and an ignition device. 8 has a built-in output device 14 for outputting a control signal, each of which is connected by a bus 17. FIG. 2 is a timing chart showing that the sampling timings of A / D conversion of the knock signal and the air flow rate signal are different. Reference numeral 6a is a crank angle signal, which is generated at every predetermined angle of the engine (for example, ATDC 10 °). Reference numeral 8a is an ignition signal, and the fall of the signal is the ignition timing. 3a is a knock signal, 21 is an air flow rate sampling timing, 22 is a knock signal sampling timing, 11
a shows the waveform after the knock signal is sampled. The crank angle signal 6a is a signal output when the piston reaches a predetermined position, and the fuel injection timing 7a and the ignition signal 8a calculated by the CPU 10 are based on this signal.
The ignition signal 8a is a fall reference. Since the knock signal 3a is a sensor for examining engine vibration, the background level signal (BGL) is constantly input during engine rotation, and when knock occurs, a certain angle after ignition (for example, ATDC 10 ° to 50 °). In the section, the signal level increases, and the difference between the presence and absence of knock increases. In order to perform the digital frequency analysis of the knock signal 3a only in a specific section in order to determine the presence or absence of knock, a short cycle (for example, sampling rate 2
It is necessary to perform sampling at 5 [μS] (the waveform after sampling becomes 11a). At this time, A
If the conversion speed of the / D converter 11 is about 15 [μS], the A / D converter 11 does not have time for A / D conversion of other signals. In FIG. 2, 21 is an airflow sensor 4
The sampling is performed at regular intervals at the sampling timing of the air flow rate signal 4a detected in. At this time, since the knock signal 3a and the air flow rate signal 4a are sampled asynchronously, it is necessary to start A / D conversion of the air flow rate signal 4a while sampling the knock signal 3a. If both signals are in the same section, A / D conversion of the air flow rate signal 4a can be started. As a result, A used for knock detection
The / D converter is not used for processing input from other sensors. Therefore, if the A / D converter 11 is dedicated to knocking and a signal other than the knock signal 3a is input to the separately provided A / D converter 12, the problem can be prevented.

FIG. 3 shows a program process from when the knock signal 3a is input to when the ignition signal is output. The knock signal 3a detected by the knock sensor 3 is input to the A / D converter 11, sampling is performed at a cycle, and the digital signal 1
1a performs frequency analysis by the frequency analysis unit 31 and extracts a specific frequency component contained in the knock signal 3a. The signal 31a after the frequency analysis is smoothed by the smoothing processing unit 32 and a background level signal 32a is output.
Signal 31a after frequency analysis and background signal 32a
In knock determination 33, the presence or absence of knock is determined by using the frequency component in which the vibration due to the occurrence of knock is most prominent according to the operating state. Then, the result 33a is input to the ignition timing control unit 34 to obtain the optimum ignition timing, and the ignition control signal 34a is output to the ignition device 8 via the output device 14 as the ignition signal 8a. This eliminates the need for data transmission / reception between the two microcomputers, as compared with the configuration in which knock determination is conventionally performed by requiring a dedicated microcomputer.

[0011]

Since an engine control device with knock control using digital signal processing can be realized by a single chip microcomputer, an inexpensive engine control device can be supplied. In addition, the engine control program and the knock detection program are integrated in the ROM of one microcomputer, and it becomes unnecessary to transmit and receive data between the microcomputers, so that the program structure is simplified. As a result, by adopting a one-chip microcomputer, the board occupation ratio of the microcomputer in the engine control unit is reduced, the engine control unit can be made smaller and lighter, and the fuel consumption of the vehicle can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart showing the features of the present invention.

FIG. 3 is a block diagram of control in the apparatus of FIG.

FIG. 4 is a block diagram when two microcomputers are used.

FIG. 5 is a block diagram when two microcomputers are used.

[Explanation of Codes] 1 ... Engine control device, 2 ... Microcomputer, 3
... knock sensor, 4 ... air flow sensor, 5 ... water temperature sensor, 6 ... crank angle sensor, 7 ... fuel injection device, 8 ... ignition device, 9 ... power supply circuit, 10 ... CPU, 11 ... knock signal input dedicated A / D conversion Vessel, 12 ... A / D converter, 13 ...
Input device, 14 ... Output device, 15 ... RAM, 16 ... RO
M, 18 ... Battery.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsuru Watanabe 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (1)

[Claims] 1. A knock sensor for detecting engine vibration or cylinder pressure vibration, and an engine controller for inputting a signal from the knock sensor to calculate optimum ignition timing and the like, wherein the engine controller is independent. Of a single-chip microcomputer provided with a plurality of A / D converters capable of operating at the timing
A means for inputting a knock signal from a knock sensor to at least one A / D converter of the D converters and determining the knock of the engine at a cycle at which the signal can be analyzed by digital frequency is provided. Knock detection device.