JPS6242334Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a resonant vibration detector for detecting abnormal vibrations of objects, mechanical devices, etc., and its purpose is to reduce variations in Q value and output voltage.
The object of the present invention is to provide a highly reliable vibration detector with little change in resonance frequency or output voltage due to temperature.

As shown in FIG. 1, a conventional vibration detector has a piezoelectric ceramic plate bonded to a rectangular metal vibrating piece, and the proximal end of the vibrating piece is fixed to a protrusion of a base. The surface electrode of the piezoelectric ceramic plate 2 is connected to a terminal by a lead wire, and the metal vibrating piece 1 is electrically connected to a ground terminal via a metal base. This is an insulator that insulates the base and terminals.

Such a vibration detector detects abnormal vibrations of a mechanical device, etc. by fixing a case (not shown) attached to a base and housing a vibrating piece and a piezoelectric ceramic plate to a mechanical device, etc. When a mechanical device, etc. causes abnormal vibration, the vibration usually has a unique vibration frequency for each device. When the device generates abnormal vibrations, the vibrating element of the vibration detector is excited and resonates, and a large output voltage is obtained from the piezoelectric ceramic plate. By extracting this output voltage from between the terminals, abnormal vibrations of mechanical devices, etc. can be detected as electrical signals. However, this vibration detector has disadvantages in that the mechanical Q value during resonance varies greatly and the resonance output varies greatly depending on how the vibrating piece is attached to the protrusion of the base. Another disadvantage is that the Q value, output voltage, and even the resonant frequency itself vary greatly due to changes in ambient temperature.

In order to improve this drawback, as shown in Figure 2, the vibrating element 1
A structure has been devised in which the width is narrowed by a notch 10 between the proximal end and the distal end of the resonator, but in this case, parasitic vibrations other than the resonant frequency of the vibrating element are occurs, and a new drawback has arisen in that the vibration detector malfunctions at the resonance frequency of this parasitic vibration.

The present invention aims to prevent such inconveniences and provide a highly reliable vibration detector.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. Reference numeral 14 denotes a vibrating piece made of metal, which consists of a vibrating part 14a and a supporting part 14b, the width of the supporting part 14b being wider than the width of the vibrating part 14a. That is, the shape of the vibrating piece 14 as a whole is convex. This vibrating piece 14 is a rear part 20 of the support part 14b.
It is fixed to a protruding part 4 provided on the base 3 with a fixing plate 12 and screws 13, and the front half of the supporting part 14b protrudes forward from the protruding part 4. A piezoelectric ceramic plate 2 is bonded on the vibrating part 14 from the boundary 21 between the vibrating part 14a and the support part 14b of the vibrating plate 14 to above the vibrating part 14a, that is, at the base of the vibrating part 14a. In FIGS. 3 and 4, the end surface 11 of the piezoelectric ceramic plate 2 is shown.
is pasted slightly closer to the support part 14b than the boundary 21 described above, but the end surface 11 is pasted to the boundary 21.
You can also align it on the line. Further, the support portion 14b of the diaphragm 14 may be fixed by welding to the protruding portion 4 of the base 3 instead of being fixed with the screws 13 as shown in FIG.

FIG. 5 shows a diaphragm 14 and a piezoelectric ceramic plate 2 according to another embodiment of the present invention. The diaphragm 14 has a narrow vibrating part 14a and a wide supporting part 14b, as shown in FIG.
The supporting portion 14b further has a wide portion 22 formed by bending it in the thickness direction of the diaphragm. As in FIG. 3, the piezoelectric ceramic 2 is bonded to the base of the vibrating portion 14a so that the end portion 11 of the piezoelectric ceramic 2 is located on the same line as the boundary portion 21 of the diaphragm or slightly toward the support portion 14b.

According to the above two embodiments, as shown by A in FIG. 6, parasitic vibrations with a frequency lower than the resonant frequency of the vibrating element 14 do not occur.

The present invention is constructed as described above, and has excellent effects as described below.

The width of the vibrating piece is wide at the supporting part and narrow at the vibrating part, and is fixed to the base at the rear half of the supporting part. Therefore, the rigidity of the support part increases, and the nodes of vibration of the vibrating element are located near the boundary between the support part and the vibrating part, so that the support part hardly vibrates. In particular, the rear half of the support part has little effect on the resonant frequency and Q value of the vibrating element, and compared to conventional vibration detectors, the resonant frequency, Q value, and output voltage depend on the fixing state when the vibrating element is fixed to the base. etc. do not vary greatly. Similarly, even if the ambient temperature changes, the resonant frequency and output voltage will not change significantly.

Since there is no need to narrow the width of the boundary between the vibrating part and the fixed part as in the conventional example, parasitic vibrations with a frequency lower than the resonant frequency of the vibrating element do not occur. Therefore, the vibration detector does not malfunction due to such parasitic vibration frequencies.

Since a piezoelectric ceramic plate can be pasted on the boundary between the vibrating part and the supporting part, which becomes a node of vibration, the Q value can be lowered, and therefore the rise time of the vibrating piece in response to applied vibration can be shortened, making it possible to improve mechanical equipment. Can quickly detect abnormal vibrations when they occur. In conventional vibration detectors, the piezoelectric ceramic plate is attached slightly to the tip of the vibrating part due to the protrusion of the adhesive that bonds the piezoelectric ceramic to the vibrating piece, and the narrow part provided at the boundary between the vibrating part and the fixed part. This had the disadvantage of increasing the Q value.

Since the piezoelectric ceramic plate was fixed so that it slightly protruded from the boundary between the vibrating part and the support part, the Q
The value can be lowered, and therefore the rise response speed can be further shortened.

When the wide part of the support part is bent in the thickness direction as in the embodiment shown in Fig. 5, the rigidity of the support part increases further, so variations in resonance frequency, Q value, output voltage, and temperature change due to the fixed state of the vibrating element. becomes even smaller.

Due to its simple structure, it is inexpensive and suitable for mass production.

[Brief explanation of drawings]

FIGS. 1 and 2 are perspective views showing conventional examples, respectively. 3 and 4 show an embodiment of the present invention, with FIG. 3 being a perspective view and FIG. 4 being a front view. FIG. 5 is a perspective view of main parts showing another embodiment of the present invention. FIG. 6 is a frequency characteristic diagram of the conventional example and the embodiment of the present invention. 2...Piezoelectric ceramic plate, 3...Base, 4...Protrusion part, 11...End face, 12...Fixing part, 14...Vibration plate, 14b...Vibration part, 14b...Support part, 2
0...Late part, 21...Boundary, 22...Wide part.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In a vibration detector in which one end of a metal vibrating piece to which a piezoelectric ceramic plate is bonded is fixed to a base, the metal vibrating piece is divided into a narrow vibrating part and a wide supporting part. The second half of the supporting part is fixed to the base, and the piezoelectric ceramic plate is attached to the base of the vibrating part so that a part of the piezoelectric ceramic plate straddles a part of the supporting part. vibration detector. 2. The vibration detector according to claim 1 of the utility model registration, characterized in that both ends of the support portion are bent in the thickness direction of the diaphragm to form a wide portion.