JPH06180246A - Vibration sensor - Google Patents

Abstract

PURPOSE:To enhance the durability of a vibration sensor. CONSTITUTION:In a flexible printed wiring board 21, a lead part 26c is bent, electrode parts 24a, 24b are brought into contact with the surface and the rear surface of a piezoelectric element 8, and electrodes for the piezoelectric element 8 are formed. Also lead parts 26a, 26b are bent to form erected postures, they are bent to the outside at their upper end parts, and terminal contact parts 25a, 25b are formed as horizontal postures. A weight is piled up on the flexible printed wiring board 21 in this state. An attachment bolt is inserted and passed, it is screwed into a sensor housing, and it is mounted inside a piezoelectric- element mounting hole. Coupling holes 27a, 27b in the terminal contact parts 25a, 25b are fitted and coupled to coupling protrusions at an insulating resin ring. When a cap is mounted, coupling holes in terminals are fitted and coupled to the coupling protrusions in the resin ring, the terminal contact parts 25a, 25b at the flexible printed wiring board 21 are brought into pressure contact, sandwiched and held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration sensor for converting mechanical vibration into an electric signal by a piezoelectric element sandwiched in a sensor housing and taking it out from a terminal.

[0002]

2. Description of the Related Art Japanese Utility Model Laid-Open No. 58-180427 discloses a knocking sensor in which a piezoelectric element and a terminal are connected by a flexible printed wiring board having a conical spiral shape. This flexible printed wiring board is formed in a spiral shape centering on the connection portion with the terminal, and a circular plate portion is provided at the outermost end portion. The circular plate portion is sandwiched between the pair of piezoelectric elements, and the central connecting portion is caulked to the terminal.

[0003]

However, to the knocking sensor, vibrations of various frequencies such as vibrations when the engine is driven and vibrations when the vehicle is traveling are transmitted through the engine block, and the piezoelectric element and the terminal are connected to each other. It is also transmitted to a flexible printed wiring board that has a conical spiral shape. Therefore, the conical spiral portion of the flexible printed wiring board vibrates. Since this vibration is generated each time the vehicle travels, the vibrating conical spiral portion causes a state in which bending stress is repeatedly applied to the terminal connection portion, and the vicinity of the terminal connection portion may be fatigued and fractured. However, there is a problem in that durability is poor and reliability is poor. The present invention has been made to solve the above problems, and an object of the present invention is to provide a vibration sensor having excellent durability.

[0004]

In order to achieve the above object, a vibration sensor of the present invention is a vibration sensor for converting mechanical vibration into an electric signal by a piezoelectric element sandwiched in a sensor housing and taking it out from a terminal to the outside. A flexible printed wiring board for forming an electrode portion that contacts both surfaces of the piezoelectric element to form an electrode of the piezoelectric element, a terminal connecting portion, and a linear lead portion that connects the terminal connecting portion and the electrode portion. ,
The electrode portion is sandwiched between the weight and the piezoelectric element in the sensor housing, and the terminal connecting portion is sandwiched in the sensor housing by the terminal mounted on the sensor housing.

[0005]

In the vibration sensor having the above structure, the flexible printed wiring board having the electrode portion, the terminal connecting portion, and the linear lead portion connecting the terminal connecting portion and the electrode portion is formed by the sensor housing with the weight and the piezoelectric element. Sandwiched inside to convert the mechanical vibration transmitted to the piezoelectric element into an electrical signal,
The flexible printed wiring board guides the terminal to the outside.

[0006]

Embodiments of the present invention will be described with reference to the drawings.
1 is a sectional view of the vibration sensor 1, FIG. 2 is a plan view of the same, and FIG. 3 is a sectional view taken along the line AA in FIG. In the sensor housing 2 shown in FIGS. 1 to 3, a cap fitting hole 4 having a caulking portion 3 formed at an upper end portion and a piezoelectric element mounting hole 5 are connected to each other via a step portion 6 and project on a bottom surface. The male screw 7 for mounting is integrally formed. The piezoelectric element 8 is a disk-shaped PZT element having a bolt insertion hole 9 in the center, and is uniformly polarized in the thickness direction.

In the flexible printed wiring board 21, as shown in FIG. 4, conductor layers 23a and 23b having a predetermined pattern are formed on the same surface of a substrate 22 made of a flexible synthetic resin film such as polyester or polyimide. Board 22
Are trimmed along the contours of the conductor layers 23a and 23b. The conductor layer 23a has a ring-shaped pattern electrode portion 24 having an inner diameter larger than that of the bolt insertion hole 9 of the piezoelectric element 8.
a, a terminal contact portion 25a having a rectangular pattern, and a linear lead portion 26a forming a connecting portion between the two. The conductor layer 23b includes a ring-shaped electrode portion 24b having an inner diameter equal to the inner diameter of the ring-shaped electrode portion 24a, a rectangular pattern terminal contact portion 25b, and linear lead portions 26b and 26c forming a connecting portion between the two. And a curved lead portion 26d. The lead portion 26d is the electrode portion 24.
The lead portions 26b and 26c, which are curved outside the line a, are connected to each other.

The terminal contact portions 25a and 25b are symmetrically arranged with the ring-shaped electrode portion 24a interposed therebetween, and the ring-shaped electrode portion 24b is arranged in the terminal contact portion 25.
It is arranged at a position equidistant from a and 25b. Locking holes 27a and 27b are formed in the terminal contact portions 25a and 25b. The linear lead portions 26a, 26b, 2
6c and the curved lead portion 26d are made of insulating film 28.
It is covered with.

As shown in FIG. 5, in the flexible printed wiring board 21, the lead portion 26c is bent so that the electrode portion 24a,
24b is brought into contact with the upper surface and the lower surface of the piezoelectric element 8 to form electrodes of the piezoelectric element 8. The lead portions 26a, 26b are also bent to be in a standing posture, and further bent outward at their upper end portions, so that the terminal contact portions 25a, 25b are in a horizontal posture. Then, the weight 10 is placed on the flexible printed wiring board 21 with the piezoelectric element 8 sandwiched therebetween, the mounting bolt 11 is inserted therethrough, and then the sensor housing 2 is screwed into the piezoelectric element mounting hole 5.
Install inside. The locking holes 27a, 27b of the terminal contact portions 25a, 25b in the horizontal position are insulative resin rings fitted in the cap fitting holes 4 of the sensor housing 2 and abutted on the step 6 via the wave washer 12. 13 locking projections 14
It is fitted and locked to a and 14b.

The cap 15 fitted in the cap fitting hole 4 has a connector connecting portion 16 integrally formed therein, and a pair of terminals 1 projecting into a connecting recess 17 of the connector connecting portion 16.
8a and 18b are buried. The other ends of the terminals 18a, 18b project from the cap 15, and locking holes 19a, 19b are formed at the tip ends bent to the left and right sides along the bottom surface thereof. On the outer circumference of the cap 15, a 0 ring 20
Is fitted and fitted into the cap fitting hole 4 of the sensor housing 2. At this time, the locking holes 19a, 1 of the terminals 18a, 18b
9b is fitted and locked to the locking projections 14a and 14b of the resin ring 13, and the terminal contact parts 25a and 25b of the flexible printed wiring board 21 are pressed and sandwiched. Then, the caulking portion 3 of the sensor housing 2 is caulked to fix the cap 15. Substrate 22 of the flexible printed wiring board 21
Is a flexible synthetic resin film such as polyester or polyimide, and functions as an insulator between the electrode portion 24a and the weight 10 and between the electrode portion 24b and the sensor housing 2.

As shown in FIG. 6, the flexible printed wiring board has an electrode portion 124a, a terminal contact portion 125a and a linear lead portion 126a, an electrode portion 124b and a terminal contact portion 12.
5b and the linear lead portion 126b are formed separately from each other to form two flexible printed wiring boards 121a, 121a.
It can also be 21b. Flexible printed wiring board 1
The electrode portion 124 a and the lead portion 126 a of the substrate 21 a are the substrate 1
22a, and the terminal contact portion 125a is formed on the back surface of the substrate 12a.
It is formed on the surface of 2a. The electrode portion 124b, the lead portion 126b, and the terminal contact portion 125b of the flexible printed wiring board 121b are formed on the same surface of the substrate 122b. The length of the lead portion 126a is shorter than that of the lead portion 126b by the thickness of the piezoelectric element 8 and is covered with an insulating film 128.

The electrode portion 124a of the flexible printed wiring board 121a is brought into contact with the upper surface of the piezoelectric element 8 and the lead portion 12
6a is bent twice to bring the terminal contact portion 125a into a horizontal posture. Electrode portion 124 of flexible printed wiring board 121b
b is in contact with the lower surface of the piezoelectric element 8 so that the lead portion 126b
Is bent twice to bring the terminal contact portion 125b into a horizontal posture. In this state, the weights 10 are piled up, the mounting bolts 11 are inserted, and the sensor housings 2 are screwed into the piezoelectric element mounting holes 5. The terminal contact parts 125a and 125b have
Locking holes 127 a and 127 b are formed, and the locking holes 127 a and 127 b are fitted and locked to the locking protrusions 14 a and 14 b of the insulating resin ring 13 fitted in the cap fitting hole 4 of the sensor housing 2. Locking holes 19 of terminals 18a and 18b when cap 15 is fitted
a and 19b to the locking protrusions 14a of the resin ring 13,
Flexible printed wiring board 121
The terminal contact portions 125a and 125b of a and 121b are pressed and sandwiched.

Further, the flexible printed wiring board 221 used for the piezoelectric element 8 (FIG. 7) in which the polarization directions applied in the thickness direction are opposite to each other, as shown in FIG. 8, is made of a flexible material such as polyester or polyimide. On the same surface of the substrate 222 made of synthetic resin film, the conductor layers 2 having a symmetrical pattern are formed.
23a and 223b are formed, respectively, and are composed of arc-shaped pattern electrode portions 224a and 224b, rectangular pattern terminal contact portions 225a and 225b, and linear lead portions 226a and 226b which form a connecting portion between them. The terminal contact portions 225a, 225b have locking holes 227a, 227b.
Are formed. Then, the linear lead portion 22
6a and 226b are covered with an insulating film 228.

In the flexible printed wiring board 221, the electrode portions 224a and 224b are brought into contact with the lower surface of the piezoelectric element 8 so that the lead portions 226a and 226b are bent so as to be in an upright posture, and the upper end portion is bent outward to bend the terminal. The contact portions 225a and 225b are in a horizontal posture. Then, in the flexible printed wiring board 221 and the piezoelectric element 8 in this state,
The weights 10 are overlapped with each other, the mounting bolts 11 are inserted through the weights 10, and the sensor housings 2 are screwed into the piezoelectric element mounting holes 5. The terminal contact portions 225a and 225b are held by the sensor housing 2 when the cap 15 is fitted, as in the case of the flexible printed wiring boards 21 and 121a and 121b.

Each flexible printed wiring board 21 described above,
121a, 121b and 221 are formed by forming an electrode part, a lead part and a terminal contact part on a single insulating synthetic resin film substrate, and it is not necessary to assemble each part individually, and work steps such as soldering are also possible. Since it is not necessary, there is an advantage that the number of parts can be reduced and the number of assembling steps can be reduced.

The vibration sensor 1 constructed by sandwiching each of the above flexible printed wiring boards has a male screw 7 for mounting, respectively.
Is screwed into the engine block 31 as shown in FIG. 9 to be used as a knocking sensor. Vibration of the engine is transmitted to the piezoelectric element 8 via the sensor housing 2. The piezoelectric element 8 generates an electric signal according to the vibration. This electric signal is transmitted to the connector connecting portion 1 of the cap 15.
6, the wire harness 32 is connected to the terminals 18a, 18b and is taken out to the outside and input to the electronic control unit 33. The electronic control unit 33 calculates and analyzes the electric signal by a predetermined program to perform knock determination processing, and outputs an ignition timing control signal.

[0017]

As described above, in the vibration sensor of the present invention, the electrode portion, the terminal connecting portion, and the linear lead portion connecting the terminal connecting portion and the electrode portion are formed by the flexible printed wiring board. The electrode portion contacting both surfaces of the piezoelectric element is sandwiched between the weight and the sensor housing, and the terminal connecting portion is sandwiched between the terminal and the sensor housing when the terminal is mounted on the sensor housing, and the electrode portion and Since the terminal contact portion is connected by the straight lead portion without slack, even if vibration is transmitted, the terminal contact portion does not swing greatly and the lead portion does not fatigue and break. Further, since the lead portion is linear, the electrode portion and the terminal contact portion can be connected to each other at the shortest distance, and the space for arranging the flexible printed wiring board can be reduced and the vibration sensor can be downsized. There is.

[Brief description of drawings]

FIG. 1 is a sectional view of a vibration sensor.

FIG. 2 is a plan view of a vibration sensor.

3 is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is a development view of a flexible printed wiring board.

FIG. 5 is a perspective view showing an assembled state of a flexible printed wiring board and a piezoelectric element.

FIG. 6 is a perspective view showing an assembled state of a flexible printed wiring board and a piezoelectric element of another embodiment.

FIG. 7 is a perspective view showing a polarization direction of a piezoelectric element.

FIG. 8 is a development view of a flexible printed wiring board according to another embodiment.

FIG. 9 is a schematic view showing a usage mode of the vibration sensor.

[Explanation of symbols]

1 ... Vibration sensor 2 ... Sensor housing 8 ... Piezoelectric element 10 ... Weight 18a, 18b ... Terminal 21, 121a, 121b, 221 ... Flexible printed wiring board 24a, 24b, 124a, 124b, 224a, 22
4b ... Electrode parts 25a, 25b, 125a, 125b, 225a, 22
5b ... Terminal contact portion 26a, 26b, 126a, 126b, 226a, 22
6b ... Lead part

Claims (1)

[Claims] 1. A vibration sensor for converting mechanical vibration into an electric signal by a piezoelectric element sandwiched in a sensor housing and taking it out from a terminal to the outside, and forming electrodes of the piezoelectric element by contacting both surfaces of the piezoelectric element. An electrode portion, a terminal connecting portion, and a linear lead portion connecting the terminal connecting portion and the electrode portion are formed by a flexible printed wiring board, and the electrode portion is held together with the weight and the piezoelectric element in the sensor housing. With
A vibration sensor, wherein the terminal connecting portion is sandwiched in the sensor housing by the terminal mounted on the sensor housing.