JPH0219702Y2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The invention is based on the lead wires of a sensor that picks up mechanical vibrations by applying a so-called unimorph vibrator, which is made by pasting together electrical parts, particularly a metal plate and a piezoelectric element. Regarding structural improvements.

(Background of the Idea) In recent years, sensors to which the above-mentioned unimorph vibrator is applied have been put into practical use as elements for detecting abnormal vibrations of automobile engines or various machines. In this specification, this will be referred to as a vibration sensor.

The general structure of such a vibration sensor is that the first
As shown in the figure. In this figure, a unimorph vibrator 5 consisting of a piezoelectric element 4 attached to a metal plate 3 is attached to a metal case 2 having a threaded portion 1 for attachment to an automobile engine or various machines.
A resin case 8 having terminals is attached for the purpose of sealing and electrical connection with the outside. At this time, an O-ring 9 is provided between the end of the resin case 8 and the bottom of the metal case 2 for airtight sealing, and then the upper end of the metal case 2 is caulked to fix the resin case 8 and seal the inside. Seal.

As the connection terminal, the unimorph resonator 5
Basically, two terminals 7A and 7B are required in order to take out the voltage induced in the terminal. One terminal 7A is connected to one of the piezoelectric element electrodes by a lead wire 10A. The other terminal 7B is similarly connected to lead wire 1.
It is connected by 0B to the electrode on the opposite side of the piezoelectric element, that is, to the metal plate 3. The shape of the unimorph resonator 5 is often a disk or a rectangular plate.

However, since this type of vibration sensor uses the resonance of the unimorph vibrator 5 to pick up mechanical vibrations, connecting the lead wire in a straight line to the metal plate 3 as described above is not suitable for vibration of the unimorph vibrator. This is not preferable in principle because it affects the mode. In fact, in the inventor's experiments, when a lead wire is connected to the metal plate part of a unimorph resonator with solder, conductive adhesive, etc., the resonant frequency of the resonator shifts or the Q at resonance decreases. The probability that such phenomena will occur increases, and due to the design,
Unfavorable for manufacturing.

Structurally, the metal plate of the unimorph resonator is connected to the metal case 2 via the support 6, as shown in FIG. 1, so in many cases, the metal plate 3 and the metal case 2 are electrically It is in a conductive state. Taking advantage of this point, the engine body or machine body 15 to which the vibration sensor is attached, which is usually made of metal, may be used as a return line, and the terminal 7B on the side connected to the metal plate 3 may be omitted. In this case, since the lead wire is not connected to the metal plate, the above characteristic deterioration will not occur. However, with this structure, if the engine body, the machine body, or the metal case of the sensor rusts, there is a risk that the electrical connection between the two will become incomplete and operation will no longer be guaranteed. Therefore, it can be said that it is still desirable to make the connection within the case.

Considering the above points, 1 of the inner wall of the metal case
It is conceivable to connect a lead wire to the point and connect it with the terminal. However, in practice, it is often difficult to employ such a structure due to constraints such as space issues.

Next, when connecting the lead wire to a tongue-shaped metal piece (such as what is usually called a lug) and caulking the resin case, the tongue-shaped metal piece is passed through the resin case to the metal. Crimp it to the inner wall of the case,
A conceivable structure is to connect the lead wire to the terminal. However, in practice, when fixing a resin case by caulking, an O-ring made of rubber or the like is often placed at the bottom end of the resin case to improve the sealing performance. This may lead to partial deformation of the product, and the long-term life of the product may not be guaranteed.

(Purpose of the invention) The present invention aims to improve the above-mentioned points and provide a vibration sensor equipped with a terminal pull-out structure that can improve the characteristics and stability of vibration detection without causing deterioration of the characteristics of the unimorph vibrator. It is something.

(Embodiments of the invention) Hereinafter, embodiments of the vibration sensor according to the invention will be described with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, and FIG. 3 shows metal parts used in the embodiment. In these figures, the metal part 20 consists of a cylindrical part 21 and a collar part 22 integrally formed at the lower end of the cylindrical part 21. Here, the outer diameter of the cylindrical portion 21 is approximately equal to the inner diameter of the resin case 8, and the outer diameter of the collar portion 22 is approximately equal to the inner diameter of the resin case 8.
Set approximately equal to or slightly smaller than the outer diameter of Then, the lead wire 10B is connected to the upper end of the cylindrical portion 21 of the metal component 20 by soldering or the like, and after fitting the O-ring 9 to the cylindrical portion 21, the lead wire 10B is inserted into the resin case 8, and the lead wire 10B is connected to the terminal 7B. , the resin case 8 and the metal part 20 are integrated into the metal case 2. The collar 22 of the metal component 20 is interposed together with the O-ring 9 between the end of the resin case and the inner bottom of the metal case, and when the resin case 8 is caulked and fixed to the metal case 2, it makes surface contact with the bottom of the metal case. do. Note that the other configurations may be the same as the conventional case shown in FIG.

According to the configuration of the above embodiment, the flange portion 22 of the metal component 20 reliably comes into surface contact with the bottom of the metal case 2, so that a highly reliable electrical connection is obtained, and the O-ring 9 is removed during the process. Since it serves as a support, it becomes easier to automate assembly.

The cylindrical portion 21 of the metal part 20 in FIG. 3 is a perfect cylinder, but considering the above effects, it does not need to be a perfect cylinder, and as shown in FIG. Create the shaped part 21A and the brim part 22A.
A metal component 20A integrally formed may also be used.

Further, the cylindrical part of the metal part does not have to be a right cylinder, and a metal part 20B having a cylindrical part 21B whose upper end is slightly constricted as shown in FIG. 5 can also be used. Depending on the internal shape of the resin case 8, the metal part 20B shown in FIG. 5 may be preferable, and when considering insertion of the cylindrical part into the resin case, the metal part 20B shown in FIG. 5 is easier to insert.

Furthermore, the lead wires 10A and 10B for connecting the unimorph vibrator 5 and the terminal 7A, and the metal parts 20, 20A or 20B and the terminal 7B will be considered.
Normally, a thin, soft copper single wire or stranded wire is used as a lead wire and connected to the bases of the terminals 7A and 7B (ends near the vibrator) with solder or the like. In this case, the lead wires 10A and 10B must be connected with the resin case 8 separated from the metal case 2, and then the resin case 8 must be inserted into the metal case 2, so the length of the lead wires is required. It must be kept for longer than that. Therefore, after assembly (inserting the resin case 8 into the metal case 2), if the lead wires 10A and 10B become slack inside the case and come into contact with the vibrator (at a place other than the lead wire connection part), the characteristics of may become unstable.

The present invention proposes the use and combination of the metal parts as described below. That is, through holes are provided inside the terminals 7A and 7B shown in FIG.
As 0A and 10B, springy, so-called strong wires such as phosphor bronze or piano wire are used, and the wires are pulled out through the through holes of the terminals 7A and 7B, and the tips (second Figure P,
At point P'), connect the lead wire 10A with solder, etc.
It also serves to fix the 10B connection and seal the hole. The reason why wires with spring properties are used as the lead wires 10A and 10B is to improve the workability when passing the terminals 7A and 7B through the through holes. If the through hole is widened into a funnel shape at the base of the terminal, the workability when passing the wire through it will be improved. Make the wire thicker than necessary,
Or if you don't make it hard, lead wires 10A, 10
B curves naturally without sagging, and no extra force is applied especially at the connection point with the vibrator 5.

Lead wire 10A, 10 due to external factors such as temperature
If B expands or contracts and there is a possibility that tensile or compressive stress will occur at the connection point with the vibrator 5, for example, as shown in FIG. 6A, B, and C, It is also possible to provide bent portions 30, 31 or a spiral portion 32 in a part of the structure so that stress can be absorbed by this portion. Note that it is also possible to use a lead wire that is coated with insulation except for the connecting portions at both ends.

When using the metal parts 20, 20A, and 20B mentioned above, the lead wire 10B is attached to a part of the cylindrical part in advance.
Connect one end with solder, etc., fit the O-ring 9 into the metal part, and connect the lead wire 1.
0B is pulled out of the resin case 8 through the through hole of the terminal 7B, and the resin case 8 and the metal parts are fitted together. The resin case 8 and the metal parts can now be handled almost as one unit (if necessary, the soldering at point P' in Figure 2 may be completed). After that, by inserting the resin case 8 into the metal case 2 while passing the lead wire 10A through the through hole of the terminal 7A, the vibration sensor can be assembled very easily and can be easily automated.

(Effects of the invention) As described above, according to the vibration sensor of the invention, a unimorph vibrator is installed in a metal case,
In a structure in which a resin case having a terminal for taking out electrical output to the outside and the metal case are sealed, a cylinder having a brim or a metal part formed by rolling a plate into a cylindrical shape is connected to one terminal with a lead wire. The structure is such that when the resin case and the metal case are integrated so that the flange of the metal part is electrically connected to the metal case, deterioration of the characteristics of the sensor is avoided. This can improve reliability and stability, and also facilitate manufacturing. Further, a springy wire material such as phosphor bronze or piano wire is used to connect the unimorph vibrator and the terminal, and the metal component and the terminal, and the wire material is pulled out through a through hole provided in the terminal, and the terminal is connected to the terminal. By connecting with solder or the like at the tip, further stability in quality and improvement in workability can be obtained.
In addition, if compressive or tensile stress is likely to occur at the connection point between the vibrator and the lead wire due to expansion or contraction of the lead wire due to external factors such as temperature, a portion of the lead wire may be This problem can be solved by providing a bent portion.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view showing a conventional vibration sensor, Fig. 2 is a front sectional view showing an embodiment of the vibration sensor according to the present invention, and Fig. 3 is a perspective view showing a specific example of metal parts used in the embodiment. , FIG. 4 is a perspective view showing another specific example of the metal part, and FIG. 5 is a perspective view showing yet another example of the metal part.
A perspective view showing two other specific examples, FIGS. 6A, B, and C.
FIG. 2 is a front view showing a specific example of a lead wire used in each example. 2...Metal case, 5...Unimorph resonator,
6...Strut, 7A, 7B...Terminal, 8...Resin case, 9...O ring, 10A, 10B...Lead wire, 20, 20A, 20B...Metal parts, 2
2, 22A...Brim part, 30, 31...Bending part, 32...Spiral part.

Claims (1)

[Claims for Utility Model Registration] (1) A structure in which a unimorph resonator is provided in a metal case, and the opening of the metal case is sealed with a resin case having first and second terminals for taking out electrical output to the outside. In the vibration sensor, the first
a cylindrical metal part having a flange, the terminal of which is connected to the first electrode of the unimorph vibrator by a first lead wire, the second electrode of the unimorph vibrator is supported by a support on the metal case side; Said second
and a terminal thereof with a second lead wire, and the collar portion of the metal component is interposed between the end portion of the resin case and the inner bottom surface of the metal case and brought into surface contact with the inner bottom surface of the metal case. According to
A vibration sensor comprising a structure in which the metal component is electrically connected to the metal case. (2) The vibration sensor according to claim 1, wherein the first and second lead wires are made of springy wires. (3) The vibration sensor according to claim 2 of the utility model registration, characterized in that a bent portion is provided in a portion of the first and second lead wires.