JPH0361133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a failure detection device for a knocking sensor, and in particular to a device for retarding the ignition timing in response to a knocking signal from a knocking state detection means including a knocking sensor. The present invention relates to a failure detection device for a knocking sensor used in an ignition timing control device that controls the ignition timing to the maximum advance state that does not cause knocking.

[Conventional technology]

Engine knocking is a dangerous phenomenon that can lead to engine destruction in the worst case.
In conventional ignition timing control devices, the ignition timing is set on the retarded side to allow some margin from the ignition timing at which knocking occurs. However, since it is unfavorable in terms of fuel efficiency to take a margin for the ignition timing from the knocking limit, ignition timing control devices have been developed that feedback control the ignition timing to the knocking limit (the highest advance state that does not cause knocking) (for example, in Japanese Patent Application Laid-Open No. (Sho 52-87537).

[Problem that the invention seeks to solve]

By the way, the ignition timing control device as described above is
This system detects engine knocking and performs feedback control of the ignition timing. If knocking occurs, the ignition period is retarded, and if knocking does not occur, the ignition timing is advanced, thereby adjusting the ignition timing. Although the ignition timing is feedback-controlled to the engine body so that it reaches the knocking limit, if an abnormality such as a disconnection occurs in the knocking sensor, the knocking condition cannot be detected.
Even though the engine is knocking, the knocking sensor outputs a signal indicating no knocking, which causes the ignition timing to advance abnormally, causing severe knocking in the engine and, in severe cases, causing damage to the piston. The drawback was that the exhaust valves could be melted and the engine could be damaged.

SUMMARY OF THE INVENTION An object of the present invention is to provide a knocking sensor failure detection device that can automatically detect with a simple configuration whether or not any abnormality such as a failure has occurred in the knocking sensor.

[Means for solving problems]

In order to achieve the above object, the present invention provides a first means for converting a knocking sensor signal outputted from a knocking sensor that detects knocking in an internal combustion engine into a DC voltage signal, and a first means for converting a knocking sensor signal outputted from a knocking sensor that detects knocking in an internal combustion engine, and a second means for setting a reference signal indicating that the knocking sensor is abnormal when the DC voltage signal and the reference signal are compared, and the level of the DC voltage signal is smaller than the level of the reference signal; and a third means.

[Effect]

The failure detection device of the present invention is comprised of a first means, a second means, and a third means. 1st
The means converts the knocking sensor signal output from the knocking sensor into a DC voltage signal. Second
The means establish a reference signal indicating a normal level of the knocking sensor. The third means compares the DC voltage signal with the reference signal, and determines that the knocking sensor is abnormal when the level of the DC voltage signal is lower than the level of the reference signal. Thereby, an abnormality such as a disconnection of the signal line connected to the knocking sensor can be automatically detected. Further, by using the knocking sensor failure detection device of the present invention to notify the driver of a knocking sensor abnormality and by retarding the ignition timing, damage to the engine can be prevented.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an ignition timing control device for an engine equipped with a failure detection device according to the present embodiment.

In the figure, a pulse rotor 1, which has a required number of protrusions 1a formed on its peripheral edge, is rotated by the crankshaft of the engine as is well known, and is mounted to be advanced by a centrifugal advance mechanism, a vacuum advance mechanism, etc. It is being
There is a pulse rotor 1 near this pulse rotor 1.
A pick-up 2 is provided for taking out the ignition pulse, and a waveform shaping circuit 3 for shaping the waveform of the ignition pulse taken out by the pick-up 2 is connected to the pick-up 2. The pulses waveform-shaped and outputted by the waveform shaping circuit 3 are configured to be input to an ignition timing calculation circuit 5 and an up-down counter 6 in a delay control circuit 4 connected to the waveform shaping circuit 3. The ignition timing calculation circuit 5 generates a pulse by delaying the ignition pulse input from the waveform shaping circuit 3 by an amount proportional to the output of the up-down counter 6.
This circuit configuration is well known and will not be described in detail. The ignition timing calculation circuit 5 is connected to an output circuit 7 for outputting a delayed pulse output from the ignition timing calculation circuit 5 to the outside as an ignition pulse. Knocking is a phenomenon in which the wall of a combustion chamber of a gasoline engine is rapidly struck with a small hammer, or a phenomenon in which such a sound is emitted. Knocking sensor 8 is used to detect this knocking. The knocking sensor 8 detects vibrations of the engine body or sound waves generated by the vibrations and converts them into electrical signals, and detects all vibrations occurring in the engine. This vibration includes vibrations of moving parts due to the meshing of engine shaft gears and camshaft gears, vibrations due to valve seating, vibrations due to cam striking, etc., and the knocking sensor 8 detects vibrations that occur in these engines. All kinds of vibrations are detected, and knocking is determined from among the vibrations by a circuit connected to the knocking sensor 8. A bandpass filter 9 and a half-wave rectifier circuit 11 in a fault detection device 10 are connected to the knocking sensor 8 for passing only signals in the knocking natural frequency band among the output signals of the knocking sensor 8. There is. The band pass filter 9 detects as a knocking signal the signal outputted from the band pass filter 9 whose magnitude exceeds a certain value, and sends the detected pulse to the up/down counter 6 via the switch circuit 12.
A knocking determination circuit 13 is connected to the knocking determination circuit 13, which is configured to output an output to the knocking determination circuit 13. The switch circuit 12 includes
A simulated signal generation circuit 17 is connected which always outputs the same signal as the one in which knocking occurs.

The failure detection device 10 includes a half-wave rectification circuit 11, an integration circuit 14, a comparison circuit 15, and an abnormality determination level setting circuit 16. A half-wave rectifier circuit 11 inputs the output signal from the knocking sensor 8, performs half-wave rectification and outputs the signal, and an integrator circuit 14 that integrates the half-wave rectified output signal and converts it into a DC voltage value corresponding to the signal amplitude.
is connected. A comparison circuit 1 to which a signal output from the integration circuit 14 is connected to the integration circuit 14
5 is input. This comparison circuit 15 is connected to a preset voltage output signal (reference signal) inputted from the abnormality determination level setting circuit 16 and to the integration circuit 14.
The comparator circuit 15 outputs a signal when the output signal from the integrating circuit 14 is smaller than the voltage output signal from the abnormality determination level setting circuit 16. ing. The output signal from this comparison circuit 15 is input to a switch circuit 12 connected to the comparison circuit 15. When the switch circuit 12 receives a signal input from the comparison circuit 15, the output signal from the knocking discrimination circuit 13 is connected to the up-down counter 6, and the output signal from the simulated signal generation circuit 17 is connected to the up-down counter. 6, and when the input from the comparator circuit 15 disappears,
It is configured to restore the original state, that is, the state in which the output signal from the knocking discrimination circuit 13 is connected to the up-down counter 6. The up-down counter 6 receives the pulse from the waveform shaping circuit 3 as a reference pulse at its down input, and receives the pulse from the knocking discrimination circuit 13 at its up input, which corresponds to the difference between the two input pulses. It is configured to provide a count output to the ignition timing calculation circuit 5. Note that the reference pulse input to the up-down counter 6 is not limited to a pulse depending on the engine circuit, such as an ignition pulse, but may be an oscillation pulse that oscillates at a constant cycle.

In this ignition timing control device, when the engine rotates, the ignition pulse generated in the pickup 2 is converted into a rectangular wave by the waveform shaping circuit 3. On the other hand, the signal detected by the knocking sensor 8 is transmitted to the knocking discrimination circuit 13 via the bandpass filter 9, and one pulse is output for each ignition cycle in which knocking occurs. When the ignition pulse is input to the up-down counter 6 via the waveform shaping circuit 3, the up-down counter 6 counts down by one for each pulse signal from the waveform shaping circuit 3.
On the other hand, upon receiving one pulse signal from the knocking discrimination circuit 13, the up-down counter 6 counts up to increase the count by one. Then, the ignition timing calculation circuit 5 delays the ignition pulse from the waveform shaping circuit 3 in accordance with the count value of the up-down counter 6. The delayed ignition pulse is output to the output circuit 7, and the ignition timing is determined. The signal from the knocking sensor 8 is also transmitted to a failure detection device 10. The signal from the knocking sensor 8 is input to a half-wave rectifier circuit 11 of a failure detection device 10, and is half-wave rectified. A half-wave rectified pulse outputted by the half-wave rectifier circuit 11 is integrated by an integrating circuit 14 and converted into a DC voltage value corresponding to the signal amplitude. This converted DC voltage value is input to the comparator circuit 15,
It is compared with a preset voltage value in the abnormality determination level setting circuit 16.

When the voltage signal from the abnormality determination level setting circuit 16 is larger than the input voltage signal from the integrating circuit 14, that is, when the knocking sensor 8 is abnormal, a signal is output from the comparison circuit 15, and the switch circuit 12 is activated. When the switch circuit 12 is activated, it cuts off the signal from the knocking discrimination circuit 13 and outputs to the up-down counter 6 a signal from the simulated signal generating circuit 17, which is always outputting a signal equal to the knocking state. In addition, the comparison circuit 15
When there is no output to the switch circuit 12, the switch circuit 12 always outputs the output signal from the knocking discrimination circuit 13 to the up-down counter 6. When the signal from the simulated signal generation circuit 17 is transmitted to the up-down counter 6, the up-down counter 6 is saturated to the maximum countable value set in advance, and the delay control circuit 4 outputs the maximum value of the retard amount. 7, and the ignition timing is determined.

Therefore, the signal of the knocking sensor itself, including the vibration caused by knocking,
The presence or absence of an abnormality in the knocking sensor is determined from the vibrations generated in other parts of the engine body, and when the knocking sensor is abnormal, the ignition timing is set to a preset position retarded than the normally used range, leading to piston erosion. Engine troubles can be avoided.

FIG. 2 shows an ignition timing control device equipped with a failure detection device according to another embodiment of the present invention.

In the figure, the failure detection device 10 is provided with a peak value holding circuit 23 instead of the half-wave rectifier circuit 11 and the integrating circuit 14 in FIG. 1, and the peak value of the signal from the knocking sensor 8 is held and compared. The signal is configured to be output to the circuit 15. This comparison circuit 15 compares the preset signal inputted from the abnormality determination level setting circuit 16 and the output signal from the peak value holding circuit 23, and determines the peak value of the output signal from the peak value holding circuit 23. is smaller than the peak value of the output signal from the abnormality determination level setting circuit 16, the output signal is output. The output signal from this comparison circuit 15 is input to an AND circuit 21 connected to the comparison circuit 15. Connected to the AND circuit 21 is an engine load detection device 20 that detects the engine load using an appropriate method and outputs a signal when the load exceeds a preset value. This AND circuit 21 is the comparison circuit 15
It is configured to output a signal to the switch circuit 18 when the logical product of the output signal from the engine load detection device 20 and the output signal from the engine load detection device 20 is established.
Further, the output from the AND circuit 21 is input to the display device 22, and an abnormality in the knocking sensor 8 is displayed. This switch circuit 18 is provided between the ignition timing calculation circuit 5 and the up-down counter 6 in the delay control circuit 4, and when there is an output from the AND circuit 21, the signal output from the up-down counter 6 is Instead, the digital signal outputted from the abnormality delay amount setting circuit 19 is configured to be outputted to the ignition timing calculation circuit 5.

The signal output from the knocking sensor 8 is converted into a DC voltage value by the peak value holding circuit 23,
The output voltage from the abnormality determination level setting circuit 16,
A comparison is made in the comparison circuit 15, and the presence or absence of an abnormality in the knocking sensor 8 is determined in the same manner as in the embodiment shown in FIG. That is, the comparison circuit 15 compares a preset voltage output signal inputted from the abnormality determination level setting circuit 16 connected to the comparison circuit 15 with the voltage output signal outputted from the peak value holding circuit 23, and determines the peak value. Holding circuit 2
When the voltage output signal output from the abnormality determination level setting circuit 16 is smaller than the voltage output signal from the abnormality determination level setting circuit 16, it is determined that an abnormality has occurred in the knocking sensor 8, and a signal is output from the comparison circuit 15 to the AND circuit 21. On the other hand, if the engine load detected by an appropriate method is greater than a preset value, the engine load detection device 20 outputs a signal.
It is output to the AND circuit 21. The AND circuit 21 is
When the AND of the output signal from the comparison circuit 15 and the output signal from the engine load detection device 20 is established,
A composite signal is output to the switch circuit 18. AND
When the signal from circuit 21 is input, switch circuit 1
8 outputs a digital signal outputted from the abnormality delay amount setting circuit 19 to the ignition timing calculation circuit 5 in place of the signal from the up-down counter 6.

Therefore, according to this embodiment, with a simple circuit,
In order to detect an abnormality in the knocking sensor, and to eliminate loss of engine performance in the light load range where knocking does not occur even when the knocking sensor is abnormal, the system detects abnormality when the knocking sensor is abnormal depending on the engine load condition. It is possible to control whether or not the process is accepted. In addition, when the knocking sensor is abnormal, the ignition timing control amount should be controlled to be slightly retarded than the normally used range, rather than being controlled to a greater degree than the normally used range, taking safety into consideration. It is possible to separately warn the driver of abnormalities.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to automatically detect with a simple configuration whether or not any abnormality such as a failure has occurred in the knocking sensor.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an engine ignition timing control device equipped with a failure detection device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing another embodiment of a failure detection device for a knocking sensor and an engine load detection circuit. FIG. 2 is a circuit diagram showing an engine ignition timing control device that is used. 5...Ignition timing calculation circuit, 6...Up-down counter, 7...Output circuit, 10...Failure detection device, 12...Switch circuit, 13...Knocking discrimination circuit, 15...Comparison circuit, 16... Abnormality determination level setting circuit, 17... Simulation signal generation circuit, 2
0...Engine load detection device.

Claims (1)

[Scope of Claims] 1. A first means for converting a knocking sensor signal outputted from a knocking sensor that detects knocking in an internal combustion engine into a DC voltage signal, and a reference signal indicating a normal level of the knocking sensor. a third means for comparing the DC voltage signal and the reference signal and determining that the knocking sensor is abnormal when the level of the DC voltage signal is smaller than the level of the reference signal; A failure detection device for a knocking sensor, comprising: means. 2. The method according to claim 1, wherein the first means converts the knocking sensor signal into a DC voltage signal by half-wave rectifying the knocking sensor signal and integrating the signal obtained by the half-wave rectification. King sensor failure detection device. 3. The knocking sensor failure detection device according to claim 1, wherein the first means converts the knocking sensor signal into a DC voltage signal by holding the peak value of the knocking sensor signal. .