JPS5999323A - Knocking detector for internal combustion engine - Google Patents

Abstract

PURPOSE:To siplify a circuit constitution and to improve performance, by providing a bypass filter resistor element in parallel with piezoelectric elements between the piezoelectric elements and a output signal taking out terminal, and providing a low pass filter resistor element in series with the piezoelectric elements. CONSTITUTION:A knocking detector has a constitution, wherein a carbon resistor is sealed in a through hole, which is a signal taking out path that is provided in a metallic disk member. The pressure pulsation generated in an engine block is transmitted to a housing 1. Piezoelectric elements 2a and 2b, which are provided between a weight 5 and the housing 1, are deformed in response to the pulsation. A voltage is generated in an electrode plate 3. The voltage signal is sent to an ignition timing control device through a lead wire 16, a connector pin 11b, a carbon resistor 12, and connector 11a. During this period, frequency components less than 6kHz and more than 20kHz are attenuated by a bandpass filter circuit, which is formed by the electrostatic capacity of the piezoelectric elements and the shielded wire and the resistor 12, and only the knocking frequency component is taken into a control device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking detector for an internal combustion engine that is attached to an internal combustion engine body and detects knocking based on vibrations of the internal combustion engine.

Normally, block vibrations that occur in an engine have a frequency spectrum as shown in Figure 1, and when knocking occurs, the frequency spectrum of these vibrations is gKHz.

The vibration amplitude around 12 KHz and 18 KHz increases (indicated by the chain line in the figure). Incidentally, although the frequency range of block vibration is wide as shown in the figure, in order to accurately detect knocking, it is necessary to extract only the frequency component of knocking.

Conventionally, there is a knock detector for this purpose that resonates only at the above-mentioned knocking frequency, but because its resonance band is very narrow, knocking occurs in different types of engines or even in the same type of engine. There was a problem in that if the cylinders were different and the knocking frequency was slightly different, knocking could not be detected.

Therefore, it is recommended to use a combination of a non-resonant knocking detector that can detect vibrations in a wide frequency range and a bandpass filter circuit that cuts frequency components of 5 KHz or less and 2 Q, KHz or more that are unrelated to knocking. However, the above filter circuit uses transistors,
A knocking detector that incorporates an operational amplifier, a capacitor, etc. has a complicated structure and is expensive.

The present invention solves the above problems and has an extremely simple circuit configuration.
The purpose is to provide a band-pass filter circuit for a detector with good performance.The piezoelectric element and the parallel double-pass filter circuit are connected between the piezoelectric element provided in the detector housing and the output signal output terminal of the piezoelectric element. A resistance element is provided, and a resistance element for a low-pass filter is provided in series with the piezoelectric element.

The present invention will be explained below with reference to illustrated embodiments.

2 to 4 show a first embodiment of the present invention. In FIG. 2, the metal housing 1 of the detector
A protruding portion 1a having a threaded portion on the outer periphery is formed at the center of the lower surface of the detector body, whereby the detector body is screwed onto the engine block.

Inside the housing 1, insert a bolt 8 into the screw hole provided at the center of the bottom.
are screwed upright, and on the shaft portion of the bolt 8 are annular piezoelectric elements 2a, which are movable relative to each other, sequentially from below.
The electrode plate 8, piezoelectric element 2b, and metal weight 5 are stacked and fitted. A disc spring 6 is provided between the flat washer 7 provided in contact with the head of the bolt 8 and the weight 5,
Due to this spring force, the piezoelectric element 2a12b1, electrode plate 8, and weight 5 are pressed against the bottom surface of the housing while being in contact with each other. A round resin insulating spacer 4 is interposed between the piezoelectric elements 2a, 2b, the electrode plate 3, and the shaft of the bolt 8. Membrane electrodes (not shown) are printed on both sides of the piezoelectric elements 2a and 2b, and the sides in contact with the electrode plate 3 have the same polarity.

A metal disc member 9 is fitted into the opening of the housing 1 by driving. A through hole 91 is formed in the disc member 9, and a cylindrical carbon resistor having a diameter smaller than the through hole 91 is formed in the through hole 91, and one end of the connector pins 11a and llb are embedded in the upper and lower surfaces of the through hole 91, respectively. It is fixed. The other end of connector pin llb is connected to electrode plate 8 by lead wire 16.
It is connected to.

A bottomed cylindrical connector member 1 made of resin is provided on the upper surface of the disc member 9.
0 is the junction. The other end of the connector pin lla passes through the bottom of the connector member 10 and projects into the inner cavity. The connector member 10 is coupled to the housing 1 by wrapping the open end of the housing 1 around a ring spacer 14 attached to a flange on the outer periphery of the bottom of the connector member 10. An O-ring 15 for sealing is provided between the outer circumference of the flange portion and the inner circumference of the open end of the housing l.

FIG. 8 shows an electrical equivalent circuit of a knocking detector having the above structure. The piezoelectric element 2 is shown as a voltage source E and a capacitor C1 connected in series. The resistor R1 is connected to one end of the connector pin llb and the disc member 9
The resistance formed between the connector pins 11a and 11a is the resistance R2.
111b, and the resistance R
8 is a resistance formed between one end of the connector pin tia and the disc member 9. Capacitor C2 is the capacitance of a shielded wire connecting the knocking detector and an ignition timing control device (not shown).

Here, a bypass filter circuit is formed by the capacitor C1 and the resistor R1, and the resistor R2 and the capacitor C
2 form a low-pass filter circuit, and by appropriately selecting the values of the capacitors C1 and C2 and the resistors R1, R2, and R3, a band-pass filter circuit having a predetermined pass band can be obtained. That is, the capacitor C1 based on the capacitance of the piezoelectric element is 800 pF, the capacitor C2 based on the capacitance of the shield wire is 100 pF, and the resistor R1
, R2, and R8 are all 150Ω, the signal level of the knocking detector output signal Vout input to the ignition timing control device is 5KHz or less and 20K, as shown in Fig. 4.
It is lowered at H7 or higher.

In the knocking detector configured as described above, pressure pulsations generated in the engine block are transmitted to the housing 1. The weight 5 constitutes a low-frequency resonance system together with the disc spring 6, and remains substantially stationary against high-frequency block vibrations. Therefore, the piezoelectric elements 2a and 2b inserted between the weight 5 and the housing 1 are deformed in response to the pulsation, and a voltage is generated on the electrode plate 8.

The voltage signal generated from the electrode plate 3 is sent to the ignition timing control device via the lead wire 16, the connector pin 11b1, the force-bond resistor 12, the connector lla, and the shield wire (not shown). The bandpass filter circuit formed by the capacitance and the resistor 12 attenuates frequency components below 5 KHz and above 29 KHz, and only the knocking frequency components are taken into the control device.

As described above, the knocking detector of the present invention forms a high-performance bandpass filter circuit with a simple configuration in which a carbon resistor is disposed in opposition to the through hole, which is a signal extraction passage, provided in a metal disc member. This realizes a low-cost, high-performance knocking detector.

5 and 6 show a second embodiment of the present invention,
A printed circuit board 17 made of glass-filled epoxy resin or ceramic is disposed on the lower surface of the disc member 9. The printed circuit board 17 has a circular shape as shown in FIG. 6, and has punch holes 17B and 17b provided at radially opposite positions on the periphery. The board 17 has both punched holes 17a and 17 as shown in the figure.
An electrode 18 is formed so as to connect the peripheral edge part of b and these parts.

The printed circuit board 17 is mounted on the disk member 9 with the electrode forming surface facing downward.
The connector pin l is in contact with the hole 17b.
lb is inserted and soldered. Further, a bolt 8 is inserted through the hole 17&, and is screwed and suspended from the lower surface of the disc member 9. Piezoelectric element 2 fitted to the shaft of bolt 8
is pressed against the lower surface of the printed circuit board 17 via the weight 5 by the spring force of the disc spring 6.
An upper surface electrode (not shown) of the piezoelectric element 2 and an electrode 18 of the substrate 17
conducts through contact.

This embodiment has the same effects as the first embodiment, and since no lead wire is used, there is no risk of wire breakage and the reliability is high.

FIG. 7 shows an eighth embodiment of the present invention, in which a solid resistor 19a
, 19b, respectively, to form fil'L1 and R2 (see FIG. 8). That is, solid resistance 1
9b is installed between the electrode plate 8 and the flat washer 7, and the solid resistor 19a is installed between the electrode plate 8 and the connector pin 11 inserted through the through hole 91 of the disc member 9.

Although the resistor R8 is not formed in this embodiment, the operation and effect are similar to the embodiment shown in FIG.

8 and 9 show a fourth embodiment of the present invention, in which a disk member 9
As shown in FIG. 9, a circular printed circuit board 17 is disposed on the bottom surface of the holder. The substrate 17 is provided with punch holes 17&, 17b, and 170 at approximately symmetrical positions in the center and radial direction. The above-mentioned punch holes 17a, 17b, 1 are formed on one surface of the substrate 17.
Electrodes 18a, 18b and 118C are formed on the peripheral edge of electrode 7C, electrode 18B has two extensions in the radial direction, and tiaisb and isc each have one extension. Then, a thick film resistor 20a is formed between the electrodes 18&, 18b to serve as a NiH resistance R2 (see FIG. 8), and a thick film resistor 20b to serve as a resistor R1 is formed between the electrodes 18a and 180.

The printed circuit board 17 is brought into contact with the disk member 9 with the electrode forming surface facing downward, and the connector pins 11 are inserted into the punched holes 17b and soldered. Further, a screw 19 is inserted through the hole 170 and screwed onto the lower surface of the disc member 9. The head of the screw 19 is connected to the electrode 18 when screwed.
0 is brought into pressure contact conduction. Bolt 8 is inserted into the hole 17a.
is inserted and screwed onto the lower surface of the disc member 9. The piezoelectric element 2 fitted onto the shaft of the bolt 8 is pressed against the lower surface of the printed circuit board 17 by the disk spring 6 via the weight 5, and the upper surface electrode (not shown) of the piezoelectric element and the electrode 1 of the substrate 17 are pressed together.
8B conducts through contact.

This embodiment has the same effects as the first embodiment, and is easier to assemble.

In each of the above embodiments, the capacitor C2 is formed by the capacitance of the shielded wire, but if the shielded wire is not used, a capacitor is provided within the ignition timing adjustment device.

As described above, the knocking detector of the present invention has a resistance element for a bypass filter provided in parallel with the piezoelectric element between the piezoelectric element provided in the detector and the signal extraction terminal, and a resistance element for a low-pass filter provided in series with the piezoelectric element. By providing a resistance element and forming an extremely simple and low-cost bandpass filter circuit, knocking can be reliably detected by extracting only the knocking frequency component from the flock vibration having a wide frequency range.

[Brief explanation of drawings]

FIG. 1 is a frequency spectrum diagram of block vibration, and FIGS. 2 to 4 show the first embodiment of the present invention.
The figure is an overall sectional view of the detector, Figure 8 is its electrical equivalent circuit diagram, Figure 4 is a diagram showing the filter characteristics of the bandpass filter, and Figures 5 and 6 show the second embodiment. , FIG. 5 is an overall sectional view of the detector, FIG. 6 is a plan view of the printed circuit board, FIG. 7 is an overall sectional view of the detector showing the third embodiment, and FIGS. 8 and 9 are views of the present invention. FIG. 8 is an overall sectional view of the detector, and FIG. 9 is a plan view of the printed circuit board. 1...Detector housing 2...Piezoelectric element 8...Electrode plate 5...Weight 9...Disc member 91... ...Through holes 11a, llb of the disc member...Connector pin 12...
...Carbon resistor 17...Printed circuit board 19&, 19b...Solid resistor 20a, 20
b... Thick film resistor 251 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7

Claims (1)

[Claims] (1) A piezoelectric element is provided in a metal housing that vibrates integrally with the internal combustion engine body, and the piezoelectric element is provided on the housing surface and inside the housing, and does not substantially vibrate in the 7 knocking frequency range. In a knocking detector for an internal combustion engine, which is clamped between the piezoelectric element and a weight and extracts an output signal proportional to the distortion of the piezoelectric element caused by engine block vibration, a A resistor element for bypass filter is installed in parallel with the piezoelectric element,
A knocking detector for an internal combustion engine, characterized in that a resistance element for a low-pass filter is provided in series with the piezoelectric element. (2) A through hole is provided in the housing, and the through hole is filled with carbon, and inside the carbon is a tip of a terminal that takes out the output signal of the piezoelectric element, and a tip of the terminal that takes out the output signal to the outside of the housing. A patent in which a resistor element for a low-pass filter is formed between the opposing ends of the terminals, and a resistor element for a bypass filter is formed between the embedded parts in the carbon of both terminals and the housing. A knocking detector for an internal combustion engine according to claim 1. (8) Claim 1, wherein an insulating substrate is provided between the piezoelectric element and the signal extraction terminal, and a low-pass filter resistance element and a bypass filter resistance element printed in a film form are provided on the substrate. The knocking detector for the internal combustion engine described. (4) A knocking detector for an internal combustion engine according to claim 1, wherein a solid resistance is connected between the piezoelectric element and the signal extraction terminal to form a low-pass filter resistance element and a bypass filter resistance element.