JP2017150409A - Electronic control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic control device that can properly detect a failure of a knocking sensor even when a noise level in a disconnection state exceeds a noise level in a normal state.SOLUTION: A microcomputer 23 sets a certain time after a top dead point of an engine 1 is elapsed, as a knocking occurrence interval where a knocking can occur, and detects a signal input failure when a level of a sensor signal output from a knock sensor 16 after lapse of the knocking occurrence interval, exceeds a prescribed threshold.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic control device that detects an abnormality of a knocking sensor disposed in an engine.

  Conventionally, engine ignition timing control is performed using a knocking sensor that detects engine vibration. However, if an abnormality such as a disconnection occurs in the knocking sensor, the occurrence of knocking cannot be detected. Hereinafter, the knocking sensor is referred to as “knock sensor”. As a technique for detecting an abnormality of the knock sensor, for example, there is one disclosed in Patent Document 1. In this technique, a noise gate period is set in the engine cycle, and a knock signal output from the knock sensor within the period is detected as a noise level. Then, the maximum value among the noise levels of each cylinder in one cycle is obtained, and when the maximum value is smaller than the abnormality determination value, the knock sensor abnormality is determined.

JP 2009-144681 A

  By the way, wiring to the ECU (Electronic Control Unit) for engine control is not only a signal line for the knock sensor but also a signal line for connecting to other sensors, actuators and the like in a bundle. Is connected. In this case, for the purpose of reducing the cost, a twisted wire having a noise resistance lower than that of the shielded wire is often used. Then, when the signal line of the knock sensor is disconnected, the disconnected part becomes an antenna, and electrical noise having a higher noise level than normal may be superimposed from other adjacent signal lines.

  In the technique of Patent Document 1, the abnormality determination is performed on the assumption that the noise level at the time of disconnection is smaller than the noise level at the time of normal operation. Therefore, in the above case, the knock sensor is in a normal state. Even if it exists, the problem of misjudging as an abnormality arises.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an electronic control device that can appropriately detect an abnormality of a knocking sensor even when the noise level at the time of disconnection exceeds the noise level at the normal time. It is in.

  According to the electronic control device of the first aspect, the arithmetic unit sets a predetermined time after the top dead center of the internal combustion engine has passed as a knocking occurrence section where knocking may occur. When the level of the sensor signal output from the knocking sensor exceeds a predetermined threshold after the knocking occurrence period has elapsed, a signal input abnormality is detected. With this configuration, it is possible to detect a signal input abnormality of the knocking sensor because the level of the sensor signal has increased during a period in which knocking cannot occur.

  According to the electronic control device of the second aspect, when the signal input abnormality is detected within the period during which the actuator to be controlled is driven and controlled, the arithmetic device disconnects the signal line to which the sensor signal is input. It is determined that In this case, it is assumed that the signal input abnormality has occurred because the signal line that has been disconnected becomes an antenna and the drive signal of the actuator is picked up as noise. Therefore, the disconnection of the signal line can be detected.

  According to another aspect of the electronic control device of the present invention, when the signal input abnormality is detected outside the period during which the actuator to be controlled is driven and controlled, the arithmetic device is disconnected from the signal line to which the sensor signal is input. It is determined that noise superimposition based on a different factor occurs. In this case, since it is clear that the cause is different from the case of claim 2, it can be determined that noise superposition based on the different factor has occurred.

The figure which is 1st Embodiment and shows schematic structure of an engine control system Functional block diagram schematically showing the internal structure of the ECU The flowchart which shows the process which calculates the vibration level A of the area P The figure which shows the sensor signal waveform in the knock occurrence section Flow chart showing abnormality determination processing Diagram showing vibration levels α and β The flowchart which is 2nd Embodiment and shows abnormality determination processing The figure which shows the sensor signal waveform in a knock generation area and the said outside area The flowchart which is 3rd Embodiment and shows abnormality determination processing The flowchart which is 4th Embodiment and shows abnormality determination processing

(First embodiment)
As shown in FIG. 1, an air cleaner 3 is provided at the most upstream portion of the intake pipe 2 of the engine 1. On the downstream side of the air cleaner 3, a throttle valve 5 whose opening is adjusted by a motor 4 and a throttle opening sensor 6 that detects the opening (throttle opening) of the throttle valve 5 are provided. The engine 1 corresponds to an internal combustion engine.

  Further, a surge tank 7 is provided on the downstream side of the throttle valve 5, and an intake pipe pressure sensor 8 for detecting the intake pipe pressure is provided in the surge tank 7. Further, the surge tank 7 is provided with an intake manifold 9 that introduces air into each cylinder of the engine 1. Each cylinder of the engine 1 is provided with a fuel injection valve 10 that injects fuel into the cylinder. Further, a spark plug 11 is attached to each cylinder of the cylinder head of the engine 1, and the air-fuel mixture in each cylinder is ignited by spark discharge of the spark plug 11 of each cylinder.

  On the other hand, the exhaust pipe 12 of the engine 1 is provided with an exhaust gas sensor 13 (such as an air-fuel ratio sensor or an oxygen sensor) that detects the air-fuel ratio or rich / lean of the exhaust gas, and downstream of the exhaust gas sensor 13. A catalyst 14 such as a three-way catalyst for purifying exhaust gas is provided.

  A cooling water temperature sensor 15 that detects the cooling water temperature and a knock sensor 16 that detects knocking are attached to the cylinder block of the engine 1. A crank angle sensor 17 that outputs a pulse signal every time the crankshaft rotates a predetermined crank angle is attached to the outer peripheral side of the crankshaft (not shown), and the crank angle and the engine speed are based on the output signal of the crank angle sensor 17. Is detected. An exhaust gas sensor 18 for detecting the air-fuel ratio or rich / lean of the exhaust gas is also arranged at the rear stage of the catalyst 14.

  Outputs of these various sensors are input to an electronic control unit (hereinafter referred to as “ECU”) 20. The ECU 20 is mainly composed of a microcomputer (hereinafter referred to as “microcomputer”), and executes various engine control programs stored in a built-in ROM (not shown) so as to correspond to the engine operating state. Controls fuel injection amount, ignition timing, throttle opening, etc. The knock sensor 16 and the ECU 20 are connected by a signal line 19.

  As shown in FIG. 2, the low-pass filter 22 provided in the interface circuit 21 of the ECU 20 removes a high-frequency component included in the sensor signal from the knock sensor 16. The A / D converter 24 constituting the microcomputer 23 A / D converts the sensor signal input via the LPF 22 and inputs the converted data to the DFT processor 25 and the A / D peak value calculator 26. .

  The DFT processing unit 25 performs, for example, IIR (Infinite Impulse Response) filter processing on the input data and extracts a frequency component corresponding to a knock signal. The peak hold unit 27 holds the peak level of the filtered frequency component, and inputs the held level to the knock determination unit 28. The knock determination unit 28 compares the input peak level with the knock determination threshold value to perform knock determination, and outputs a determination result.

  The A / D peak value calculation unit 26 calculates a high-side A / D peak value and a low-side A / D peak value for each unit section P such as a TDC cycle, for example. The vibration level calculation unit 29 obtains, for example, the difference between the two peak values and calculates the vibration level of the knock signal. The knock signal abnormality detection unit 30 detects an abnormality of the knock signal from the vibration level. The microcomputer 23 corresponds to an arithmetic unit, and the ECU 20 corresponds to an electronic control unit.

  Steps S1 to S4 in the flowchart shown in FIG. 3 and the waveform diagram shown in FIG. 4 correspond to the processing content of the vibration level calculation unit 29. The unit section P is set to a knock generation section that is a section in which knock can occur, for example, after compression top dead center; between ATDC 10 ° CA and ATDC 90 ° CA.

  Next, the operation of this embodiment will be described. As shown in FIG. 5, when calculating the vibration level α in the knock occurrence section (S11), the knock signal abnormality detecting unit 30 compares the vibration level α with the abnormality determination value 1 (S12). As shown in FIG. 6, the vibration level α is a peak value of amplitude. As shown in the figure, when the knock sensor 16 is normal, a knock signal having a vibration level higher than a predetermined level is input. Therefore, if the vibration level α is below the abnormality determination value 1, (NO) disconnection abnormality occurs. (S17).

  On the other hand, when the vibration level α is larger than the abnormality determination value 1 (S12; YES), the vibration level β outside the knock generation section, that is, outside the knock generation section is calculated (S13). Similarly to the vibration level α, the vibration level β is also the peak value of the amplitude. The outside of the knock generation interval may be limited to an arbitrary interval such as ATDC 100 ° CA to ATDC 180 ° CA.

  In the subsequent step S14, the vibration level β is compared with the abnormality determination value 2. Here, if knock sensor 16 and knock sensor signal line 19 are normal, knock does not occur outside the knock generation interval, and therefore vibration level β becomes smaller than a predetermined value. Therefore, if the vibration level β is smaller than the abnormality determination value 2 (NO), it is determined that the knock signal is normal (S16). On the other hand, when the vibration level β is larger than the abnormality determination value 2 (S14; YES), it is determined that noise is superimposed on the knock sensor signal (S15). The abnormality determination values 1 and 2 are shown in FIG. 8 of the second embodiment. The abnormality determination value 2 corresponds to a threshold value and is set to a value smaller than the abnormality determination value 1.

  As described above, according to the present embodiment, the microcomputer 23 sets a certain time after the top dead center of the engine 1 has elapsed as a knocking occurrence section where knocking may occur. When the level of the sensor signal output from the knock sensor 16 exceeds a predetermined threshold after the knocking occurrence period has elapsed, a signal input abnormality is detected. With this configuration, it is possible to detect a signal input abnormality of the knock sensor 16 due to an increase in the level of the sensor signal during a period in which knocking cannot occur.

(Second Embodiment)
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and different parts will be described. As shown in FIG. 7, in the abnormality detection process of the second embodiment, when “YES” is determined in step S14 of the flowchart shown in FIG. 5, the process proceeds to step S18 and the abnormality determination factor is separated. In step S18, it is determined whether or not the time is synchronized with the timing at which a drive signal is output to an actuator that is controlled by the ECU 20, such as an electronic throttle, an alternator, or a starter.

  Here, as shown in FIG. 8, when synchronized with the output timing of the drive signal (YES), the knock sensor signal line 19 is disconnected and the disconnected portion is turned into an antenna, so that from the other adjacent signal lines It is determined that there is an abnormality due to a state in which electrical noise is superimposed (S19). On the other hand, when it is not synchronized with the output timing of the drive signal (NO), it is determined that the abnormality is based on noise superposition due to a factor different from the disconnection of the knock sensor signal line 19 (S20).

  As described above, according to the second embodiment, when the signal input abnormality is detected within the period during which the actuator to be controlled is driven and controlled, the microcomputer 23 breaks the signal line to which the sensor signal is input. It is determined that In this case, it is assumed that a signal input abnormality has occurred due to the signal line 19 being disconnected serving as an antenna and the drive signal of the actuator being picked up as noise. Therefore, the disconnection of the signal line can be detected.

  When the signal input abnormality is detected outside the period during which the actuator to be controlled is driven and controlled, the microcomputer 23 superimposes noise based on a factor different from the disconnection of the signal line 19 to which the sensor signal is input. Is determined to have occurred. In this case, since it is clear that the cause is different from the above case, it can be determined that noise superposition based on the different factor has occurred.

(Third embodiment)
In order to detect knocking, the microcomputer 23 needs to perform A / D conversion of the sensor signal voltage of the knock sensor 16 and digital filter processing at high speed. However, it is conceivable that the load on the microcomputer 23 will be excessive if the sensor signal is captured even outside the knock generation interval as in the above embodiment.

  Therefore, in the third embodiment, it is considered to minimize the processing section in step S13. The vibration level determination in step S18 may be performed based on the sensor signal at the output timing of the drive signal for the actuator such as the motor 4, for example. That is, since the sensor signal outside the output timing of the actuator drive signal is not necessary for the process of step S18, in step S21 shown in FIG. The vibration level γ is calculated by capturing only the output timing. Then, the presence or absence of noise is determined based on the vibration level γ.

  As described above, according to the third embodiment, the microcomputer 23 performs the sampling of the sensor signal performed after the knocking occurrence section elapses within the period during which the actuator is driven and controlled. Thereby, the processing load of the microcomputer 23 can be reduced.

(Fourth embodiment)
In the third embodiment, noise superimposition due to disconnection is determined based on the output timing of the drive signal of the actuator that can be a noise source. However, since each actuator is driven at an appropriate timing in the control of the engine 1 by the ECU 20, the actuator is not necessarily driven outside the knock generation interval. Therefore, there is a possibility that the frequency of noise superimposition abnormality determination outside the knock occurrence section cannot be sufficiently ensured.

  Therefore, in the fourth embodiment, in step S23 shown in FIG. 10, the ECU 20 intentionally drives the actuator for the purpose of detecting noise superposition outside the knock generation interval, so that the abnormality determination frequency becomes a certain level or more. To ensure. Here, since the drive timing of the actuator in step S23 should not adversely affect normal engine control, for example, the EGR valve may be driven when the engine is stopped during idling stop.

  As described above, according to the fourth embodiment, the ECU 20 samples the sensor signal in parallel while controlling the driving of the actuator after the knocking generation period has elapsed. Therefore, the abnormality determination frequency can be increased.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
What is necessary is just to change suitably the fixed time after the top dead center progress which sets a knock generation area according to an individual design.

  1 engine, 4 motor, 16 knocking sensor, 19 signal line, 20 ECU, 23 microcomputer.

Claims (5)

An arithmetic unit (23) for determining the presence or absence of knocking based on a sensor signal output from a knocking sensor (16) disposed in the internal combustion engine (1) for detecting knocking;
The arithmetic unit sets a certain time after the top dead center of the internal combustion engine has passed as a knocking occurrence section where knocking can occur,
An electronic control device that detects a signal input abnormality when the level of the sensor signal exceeds a predetermined threshold after the knocking occurrence period.   When the signal input abnormality is detected within a period during which the actuator (4) to be controlled is driven and controlled, the signal line (19) to which the sensor signal is input is disconnected. The electronic control device according to claim 1, which is determined as follows.   When the signal input abnormality is detected outside the period during which the actuator (4) to be controlled is driven and controlled, the arithmetic device is based on a factor different from the disconnection of the signal line to which the sensor signal is input. The electronic control unit according to claim 1, wherein the electronic control unit determines that noise is superimposed.   The electronic control device according to claim 2, wherein the arithmetic device performs the sampling of the sensor signal performed after the knocking occurrence section has elapsed within a period during which the actuator is driven.   5. The electronic control device according to claim 2, wherein the arithmetic device performs sampling of the sensor signal in parallel while driving and controlling the actuator after the knocking occurrence section has elapsed. 6.

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