JPH022529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sensor for detecting vibrations of an internal combustion engine such as an automobile, and more particularly to a knocking detection device for an internal combustion engine that detects knocking from this detection signal.

In a certain operating state of an internal combustion engine (hereinafter referred to as the engine), the flame generated at the ignition part in the cylinder spontaneously ignites before it propagates to the unburned part at the end, causing the mixed gas in the cylinder to ignite. If knocking occurs due to temporary sudden combustion, it is undesirable because it causes engine overheating and a decrease in output, making it impossible to operate smoothly and wasting fuel consumption.

Generally, the ignition timing of an engine is advanced to be optimal for the operating condition, but advancing the ignition timing tends to cause knocking, so if knocking occurs, it is necessary to delay the ignition timing. This requires a sensor to detect the knocking phenomenon.

FIGS. 1 and 2 are examples of frequency spectra of engine vibration when knocking occurs. FIG. 1 is for an engine rotation speed of 3500 rpm, and FIG. 2 is for an engine rotation speed of 5500 rpm.

As can be seen from these figures, the frequency at which engine vibration reaches its maximum differs depending on the engine rotation speed.

Conventionally, knocking detection devices use a single resonant acceleration sensor whose resonant frequency is almost the same as the knocking frequency (for example, the
No. 183245) is known. However, with this method, it is difficult to detect a knocking signal that changes depending on the engine speed because the bandwidth is narrow. On the other hand, it is possible to signal-process the vibration signal detected by a wideband acceleration sensor (no literature available), but this method also detects frequency components other than the knocking signal, so the detection accuracy may deteriorate. It is inferred.

In view of these points, it is an object of the present invention to provide a knocking detection device that accurately detects a knocking signal by correcting the frequency change of the knocking signal due to a change in engine speed.

The knocking detection device according to the present invention includes a vibration sensor that detects vibrations of an internal combustion engine, a rotation sensor that detects the rotation speed of the internal combustion engine, and means for outputting an oscillation frequency according to the rotation speed based on the output of the rotation sensor. and a means for modulating a signal from the vibration sensor with the frequency signal, and a knocking signal that changes in accordance with the rotational speed of the internal combustion engine by passing the modulated signal through a predetermined bandpass transducer. The vibration sensor is set to have a practical sensitivity to a vibration frequency of substantially 5 to 10 kHz.

With such a configuration, _o is the frequency of the detection signal from the vibration sensor, c is the frequency from the oscillation frequency output means that changes depending on the output voltage from the rotation sensor, and _c is the center frequency of the bandpass waver. Assuming that _p , the frequency _o of the detection signal from the vibration sensor when knocking occurs changes depending on the engine rotational speed at that time. Therefore, the center frequency _p of the bandpass waver is set to the frequency _c of the modulated signal which is the output of the modulator when knocking occurs.
+ _o band, when a knocking phenomenon occurs, a substantially constant frequency signal is output from the bandpass waveform according to the engine rotation speed. On the other hand, if there is no knotking phenomenon,
Since the output of the modulator is blocked by the bandpass waver, no signal is output from the bandpass waver.

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

FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention. 1 is a vibration sensor attached to the outer wall of the cylinder block, 2 is a preamplifier, 3 is a modulator, 4 is a rotation sensor that detects the engine speed, and 5 is a vibration sensor from the rotation sensor 4. is a voltage controlled oscillator that outputs a frequency _c corresponding to the voltage signal of , and 7 is a band pass wave generator with a center frequency of _p and a frequency _o of the detection signal of the vibration sensor 1.
The modulated signal _c ± _o obtained by modulating the output signal of the oscillator 5 with the frequency _c of the output signal of the oscillator 5 is configured to match the frequency _p .

For example, the frequency at which the vibration frequency _o of the knocking signal that changes depending on the engine rotation speed N passes the lower sideband _c − _o of the modulated signal modulated by the output frequency _c of the oscillator 5 corresponding to the engine rotation speed N If the _knocking phenomenon occurs, the bandpass wave generator 7 outputs a nearly constant frequency signal depending on the engine rotation speed, and if there is no knocking phenomenon, the frequency signal of the output signal of the modulator 3 _c − Since _o is significantly different from the frequency ₀ , the bandpass waveform 7
As a result, the presence or absence of the output voltage from the band-pass wave generator 7 is determined depending on whether or not knocking vibration occurs.
Depending on the presence or absence of this, knocking can be determined. Note that the practical sensitivity of the vibration sensor 1 is usually set in the range of 5 to 10 kHz in consideration of the rotational speeds shown in FIGS. 1 and 2, but this is not the case for high-speed vehicles.

FIG. 4 shows a block diagram of a configuration in which the present invention is actually applied.

That is, this example also includes an ignition delay section and an ignition section that delay the ignition timing of the engine when knocking is detected by the knocking detection device. In the figure, 1 is a vibration sensor, 8 is a high-pass wave device that blocks mechanical vibration frequencies below several thousand Hz, 9 is an automatic gain control circuit (AGC),
3 and 7 respectively indicate a modulator and a bandpass waver as in FIG. 2, and 4 is a rotation sensor, which includes a magnet 4a that is fixed to a crankshaft (not shown) and rotates with the rotation of the crankshaft, and this magnet. The pickup coil 4b detects the rotation of the magnet 4a as an induced voltage output. 5 is a voltage controlled oscillator, 10
is a circuit that determines the occurrence of knocking based on the presence or absence of an output from the wave generator 7. 12 is a battery, 14 is an ignition coil in which a primary coil 14a is connected to the battery 12 via a key switch 13, and a spark plug 15 is connected to a secondary coil 14b. Reference numeral 11 denotes a common collector transistor whose emitter terminal is connected between the connection point between the primary coil 14a and the secondary coil 14b of the ignition coil and the ground. 16 is a changeover switch (including an electronic switch), and a knocking discrimination circuit 1
With the output of 0, the switch is moved to the contact 16a side when there is no knocking, and the switch is moved to the contact 16b side when there is knocking.
connected to the side. When connected to the contact 16b side, an output that delays the ignition timing to the optimum is inputted to the base terminal of the ignition coil transistor 11 by the ignition timing delay circuit 17, thereby driving the transistor 11. Therefore, a voltage is induced in the secondary coil 14b at an optimal timing. As a result, a knocking signal corresponding to the engine speed can be detected, and the spark plug 15 can be optimally discharged.

As described above, according to the present invention, since the occurrence of knocking can be accurately detected, an engine ignition system that can always obtain optimal ignition timing can be provided.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing the frequency spectrum of the engine when knocking occurs, according to the number of rotations, FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. A block diagram shows the configuration when actually applied to an ignition system for an automobile engine. In the figure, 1 is a vibration sensor, 2 is a preamplifier, 3 is a modulator, 4 is a rotation sensor, 4a is a magnet, 4b is a pickup coil, 5 is a voltage controlled oscillator, 7 is a broadband pass wave generator, and 8 is a high frequency band 9 is an automatic gain control circuit, 10 is a knocking generation determination circuit,
14 is the ignition coil, 15 is the spark plug.

Claims (1)

[Claims] 1. A vibration sensor that detects vibrations of an internal combustion engine, a rotation sensor that detects the rotation speed of the internal combustion engine, and means for outputting an oscillation frequency according to the rotation speed based on the output of the rotation sensor. , comprising means for modulating the signal from the vibration sensor with the frequency signal, and by passing the modulated signal through a predetermined bandpass transducer, a knocking signal that changes in accordance with the rotational speed of the internal combustion engine is generated. A knocking detection device for an internal combustion engine, characterized in that it is capable of detecting knocking. 2. The knocking detection device for an internal combustion engine according to claim 1, wherein the vibration sensor has practical sensitivity at vibration frequencies of 5 to 10 kHz.