JPH0416185Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a knocking sensor to be attached to an engine, and particularly to a knocking sensor that is easy to assemble and has good durability.

Prior Art When controlling the ignition timing of an engine, it is extremely advantageous in terms of efficiency and fuel consumption to bring the ignition timing as close as possible to the minimum advance value at the engine's maximum torque without causing extreme knocking. Therefore, when knocking occurs, control is performed to detect the vibration and retard the ignition timing to avoid continuation of knocking. In such control, a sensor that detects the knocking state of the engine is essential, and knocking sensors of various structures have been proposed.

In general, the vibrations generated by knocking are high-frequency vibrations of 6 to 10 KHz, and the attenuation in the vibration transmission path, especially at the component joints, cannot be ignored. By attaching a diaphragm with a resonant frequency in the frequency range directly to the housing of the sensor fixed to the engine, the detection efficiency, that is, S/N, can be improved.
I'm trying to increase the ratio.

FIG. 5 shows an example of a knocking sensor devised in this way, and 1 is a housing having a threaded portion 3 for screwing into the engine. A support base 5 is formed on the top of the housing 1, and a diaphragm 9, which is made by bonding a piezoelectric element 7 with electrodes formed on both sides, is fixed to the support base 5 with a bolt 15, together with a lead piece 11 and an insulating pusher 13. has been done. One end of a lead wire 17 is connected to the lead piece 11 by soldering or the like, and the diaphragm 9
An electric signal generated between both electrodes of the piezoelectric element 7 due to the vibration is extracted as a potential difference between the lead wire 17 and the housing 1. 19 is a cover provided on the housing 1 to protect each component;
This cover 19 may be provided with a signal output terminal (not shown) to which the other end of the lead wire 17 is connected, and may also function as a connector unit.

Problems to be Solved by the Invention However, when assembling the knocking sensor configured as described above, it is necessary to connect the lead wire 17 and the lead piece 11 inside the cover 19, or to close the cover 19 after the connection. There was a problem in that it needed to be installed and required complicated work.

Furthermore, in the above-mentioned configuration, the occurrence of harmful vibrations outside the vibration frequency range such as inhibition of resonance of the vibrating part or knocking due to contact of the lead wire 17 or the lead piece 11 with the diaphragm 9 or the piezoelectric element 7, or Disconnection of the connection between the lead wire 17 and the lead piece 11 due to normal engine vibration or heat generation could not be avoided, resulting in a significant deterioration in detectability of knocking vibration and a decrease in reliability. .

Therefore, an object of the present invention is to provide a knocking sensor that can satisfactorily detect knocking vibrations without causing these problems.

Means for Solving the Problems The problem with the prior art described above is that a diaphragm equipped with a plate-shaped piezoelectric element is fixed to a housing, and a signal output terminal inserted and supported by a connector unit attached to the housing and the piezoelectric In a knocking sensor that is electrically connected to one side of the element, a piezoelectric element,
A through hole passing through the diaphragm and the housing is provided, and a thin film lead terminal is provided on one side of the piezoelectric element to be electrically connected to the signal output terminal, so that the signal can be output when the connector unit is attached to the housing. This problem can be solved by allowing the terminal to penetrate through the lead terminal, and further by welding the signal output terminal and the lead terminal through the through hole in the attached state.

Operation When knocking occurs in the combustion chamber of the engine, this vibration is transmitted to the housing of the knocking sensor via the cylinder block. Since the diaphragm including the piezoelectric element is directly fixed to the housing, it resonates well with the knocking vibration, and accordingly, an electromotive force corresponding to the knocking vibration is generated between the two poles of the piezoelectric element. In the present invention, the thin film lead terminal provided on one side of the piezoelectric element and the signal output terminal are not connected by lead wires, but are directly welded to electrically connect them. This prevents interference with resonance, generation of harmful vibrations, and disconnection of connections due to contact between the two. In addition, after the connector unit is attached to the housing, the signal output terminal and the lead terminal are welded through the piezoelectric element, the diaphragm, and the through hole that passes through the housing. sex is improved.

Embodiment A preferred embodiment of the present invention will be described below with reference to the drawings, in which the same reference numerals are given to substantially the same parts as in FIG. 5 showing the conventional example.

1 is a housing made of conductive metal or the like, and by screwing a threaded part 3 formed at the lower part of the housing into the cylinder block of the engine, etc.
Good transmission of knocking vibrations. Housing 1
A hole 21 extending vertically passes through the center of the housing 1 , and a support base 5 for supporting a vibration detection section 25 is formed around the hole 21 in the upper part of the housing 1 .

As shown in detail in FIG. 2, the vibration detection unit 25 includes a diaphragm 9 that is electrically connected to the support base 5 by, for example, ring projection welding, and a diaphragm 9 that is attached to the diaphragm 9 with an adhesive. It consists of a piezoelectric element 7 bonded under pressure and a lead terminal 27, each arranged in a concentric disk shape. Through holes 91 and 71 are formed in the center of the diaphragm 9 and the piezoelectric element 7, respectively, in correspondence with the hole 21 of the housing 1. This corresponds to the through hole referred to in the first term.
Electrodes (not shown) made of silver or the like are provided on both sides of the piezoelectric element 7, and the electromotive force generated between the electrodes due to knocking vibration is transmitted to the housing 1 and the lead terminal 2.
It is taken out as a potential difference between 7 and 7. The lead terminal 27 is connected to the periphery of the through hole 71 of the piezoelectric element 7 by means such as brazing, and a signal output terminal 33 (described later) passes through the connection hole 28 provided approximately at the center thereof.

On the other hand, a signal output terminal 33 made of a conductive material is embedded in the connector unit 31 made of an insulating material such as resin when the connector unit 31 is molded, and is adapted to fit into a socket (not shown) connected to a vibration detection circuit. . A sealant 35 is provided to prevent moisture, dirt, etc. from entering through the gap between the connector unit 31 and the signal output terminal 33.
The connector unit 31 is attached to the housing 1 via a metal plate 37 and an O-ring 39, and then fixed by caulking the thin wall portion 1a of the housing 1.

41 is a resistor whose one end is soldered to the signal output terminal 33 and whose other end is sandwiched between the connector unit 31 and the metal plate 37;
As shown in FIG. 3, it is inserted between the signal output terminal 33 and the ground (housing 1) in parallel with the piezoelectric element 7. By providing the resistor 41, for example, in the signal detection circuit 43, a resistor 45 and a battery 47 having approximately the same resistance value as the resistor 41 are provided in series between point a connected to the signal output terminal 33 and the ground. By measuring the voltage drop value between points a and b at both ends of the resistor 45, it becomes possible to detect a disconnection or short circuit within the knocking sensor.

Next, after the connector unit 31 is caulked and fixed to the housing 1, the signal output terminal 33 penetrates the connection hole 28 of the lead terminal 27. Since it is possible to see through the through hole 91, by welding this penetrating portion using, for example, known laser welding means, the electrical connection between the two members can be ensured. After the welding work is completed, if the hole 21 is sealed with a steel ball 49, the interior of the notching sensor is sealed with a sealant 35,
It is completely sealed by the O-ring 39 and the steel ball 49, and since the quality of the internal electrical connection can be determined by the electric circuit described above, it is maintenance-free.

FIG. 4 shows the output characteristics (solid line) of the knocking sensor configured as described above, with the horizontal axis representing the vibration frequency and the vertical axis representing the output amplitude. As is clear from this figure, no harmful vibrations (a) or interference with resonance (b) due to contact with lead wires, etc., which often occur in conventional products, are observed, and good output characteristics are exhibited.

In this embodiment, a connection hole 28 is formed in advance in the lead terminal 27, so that the signal output terminal 33 passes through this connection hole 28 when the connector unit 31 is attached to the housing 1. However, a metal thin film made as thin as possible to ensure reliability is used for the lead terminal 27, and the tip of the signal output terminal 33 is tapered into a needle shape, so that the needle-like tip penetrates the lead terminal 27 when attached. By doing so, there is no need to form the connection hole 28 in advance, and therefore the signal output terminal 33
There is no need to perform the positioning so strictly.

Effects of the invention As detailed above, according to the invention, the signal can be output from one side of the piezoelectric element without using a lead wire.
The signal output terminal provided on the connector unit,
Since it is welded directly to the lead terminal that is bonded to one side of the piezoelectric element, it prevents interference with resonance and generation of harmful vibrations caused by contact of the lead wire with vibrating parts, and improves the detectability of knocking vibrations. It has the effect of

Furthermore, since a through hole is provided in the housing etc. so that the welding can be performed after the connector unit is attached to the housing, there is also the effect that the ease of assembly is greatly improved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional configuration diagram of a knocking sensor showing a preferred embodiment of the present invention, Fig. 2 is a detailed view of the vibrating part of the knocking sensor, and Fig. 3 is a diagram showing a piezoelectric element, a resistor, etc. 4 is an output characteristic diagram of the knocking sensor shown in FIG. 1, and FIG. 5 is a cross-sectional configuration diagram showing an example of a conventional knocking sensor. DESCRIPTION OF SYMBOLS 1... Housing, 5... Support stand, 7... Piezoelectric element, 9... Vibration plate, 21... Through hole, 25... Vibration part, 27... Lead terminal, 28... Connection hole, 3
1...Connector unit, 33...Signal extraction terminal, 41...Resistor, 43...Vibration detection circuit, 4
9...Steel ball.

Claims (1)

[Claims for Utility Model Registration] (1) A diaphragm equipped with a plate-shaped piezoelectric element is fixed to a housing, and a signal output terminal inserted and supported through a connector unit attached to the housing is connected to one surface of the piezoelectric element. In the electrically connected knocking sensor, a through hole passing through the piezoelectric element, the diaphragm, and the housing is provided, and a thin film lead terminal is provided on one side of the piezoelectric element to be electrically connected to the signal output terminal. , wherein when the connector unit is attached to the housing, the signal output terminal is made to penetrate through the lead terminal, and in the attached state, the signal output terminal and the lead terminal are welded through the through hole. King sensor. (2) The knocking sensor according to claim 1, wherein the welding is laser welding. (3) The knocking sensor according to claim 1 or 2, wherein the through hole of the housing is closed with a steel ball after welding.