JPS60137113A - Piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric vibrator which has no deviation in vibration characteristics due to vibration and impact, permits lower assembly precision, and has sufficiently excellent characteristics even with small-sized constitution by supporting the vibration substrate of the piezoelectric element on a holding frame through a coupler. CONSTITUTION:The piezoelectric element 13 is formed in a square shape whose side length is 2L, and center parts of respective edges are supported on the regularly quadrilateral holding frame 15 through couplers 14... whose length is LC. Further, the substrate 13a of the piezoelectric element 13, couplers 14..., and holding frame 15 are united into a frame 16. Then, a piezoelectric thin plate 13b is fixed to one surface of this united frame 16 within a specific area, i.e. the entire surface of the substrate 13a and an area extending from it to a specific corner part of the holding frame 15 through a specific coupler 14. Thus, the vibration substrate 13a of the piezoelectric element 1 is supported on the holding frame 15 through the couplers 14....

Description

[Detailed description of the invention] The present invention relates to a piezoelectric vibrator.

An example of an electronic component using a conventional expansion oscillator is shown in FIG. What is shown in FIG. 1 is a ceramic piezoelectric resonator. In this figure, 1 is a case, and a piezoelectric element 3 in a spreading vibration mode is housed in the case 1 through an opening 2'. This piezoelectric element 3 is held between a pair of terminal plates 4 at its vibration node points.

The opening 2' of the case 1 is sealed by a sealing base plate 5 and a sealing resin 6. However, with this conventional type, the position of the piezoelectric vibrating element 3 is easily shifted due to mechanical vibrations or shocks, and the characteristics are easily distorted, and assembly precision must be extremely strict, and it is difficult to achieve practical results in a small type with a high frequency. There are drawbacks such as the fact that the node points may not be accurately held between the terminal plates.

In view of the foregoing, it is an object of the present invention to provide a device that does not cause disturbances in vibration characteristics due to vibrations and impacts, allows for rough assembly accuracy, and provides sufficiently good vibration characteristics even with a small device.

For the above-mentioned purpose, the present invention provides a piezoelectric vibrator which is provided with a case and houses a piezoelectric element in a spreading vibration mode, which has a vibrating substrate made of a constant elastic metal, a piezoelectric thin film, and a vibrating electrode film. The piezoelectric vibrator is supported by a holding frame via a connector integrally molded with the vibrating substrate, and the length of the connector is set to a length such that a capacitance ratio of the piezoelectric element is minimized. be.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 2 is a sectional view showing a piezoelectric resonator according to an embodiment of the present invention, and FIG. 3 is an exploded perspective view thereof. In these figures, 11 is a case, and this case 11 consists of a pair of half cases 12. 1 half case each
2 and 12 are formed in the shape of a shallow box with open faces facing each other. A piezoelectric element 13 in a vibration mode is housed in an internal space of a case 11 formed by abutting the two half cases 12 with their opposing surfaces, as will be described later. $
As shown in Figure 4, this piezoelectric element 13 has a side length of 2L.
It is formed into a square shape, and the center portion of each edge thereof is supported by a regular quadrilateral holding frame 15 via connectors 14 having a length Lc. Further, the substrate 13a, the connectors 14... and the holding frame 15 of the piezoelectric element 13 are
The integral frame 16 is formed from a constant elastic metal plate such as invar, invar, or conilivar by pressing, etching, or other methods. Then, on one side of this integral frame 16, ZnO
A piezoelectric thin film 131 consisting of
The electrode 17 facing the substrate 13a and the electrode 17 are fixed to a predetermined corner of the holding frame 15 by a method such as sputtering. ! -c, the lead portion 18 reaching the predetermined corner of the holding frame 15 is deposited on the piezoelectric thin film 131). One of the lead wires 19, 19 is attached to the tip of the lead part 18, and the other is attached to the holding frame 15, and then both sides of the integral frame 16 are wrapped and covered with the two half cases 12, and then both the lead wires 19 are attached to the holding frame 15. The joint of half cases 12 and 12 is glued,
Sealed by fusion etc. The integral frame 16 inserted into the internal space of the case 11 is held by the four corners of the holding frame 15 in point contact with the projections 20 protruding from the inner surface of each half case 12. It is held in a predetermined position within the case 11.

In this way, the piezoelectric element 13 is held by the holding frame 15 via the connectors 14, and this holding frame 15 is supported by the case 11, so that the supporting point can be accurately aligned with the node point of the piezoelectric element 13. This means that there is no need for assembly precision, and it is easy to assemble even if it is miniaturized. Furthermore, the integral frame 16 is difficult to move due to mechanical vibrations and shocks applied from the outside, and even if the integral frame 16 is displaced and the holding frame 15 comes into contact with the case 11 at a location other than the support point, Since the piezoelectric element 13 itself does not come into contact with the case 11 and is therefore not mechanically restrained, there is no possibility that its vibration characteristics will change.

FIG. 5 is a characteristic diagram of this piezoelectric resonator, in which the coupler 14...
The horizontal axis is the ratio of the length Lc of the capacitance ratio γ(-C8/C
o) is taken on the vertical axis. As is clear from this figure,
The ratio of the length Lc of the connector to the half length L of one side of the piezoelectric element 13 is Lc=[1+''(n-1) )] L (However,
The capacitance ratio γ (=cD, /Co) becomes minimum in the range of 1, 8/3 and its vicinity, where n is a natural number), and good characteristics with a large deviation ΔF between the resonant frequency and the anti-resonant frequency are obtained, as described above. As such, in the piezoelectric vibrator according to the present invention, the vibration substrate of the piezoelectric element is supported by the holding frame via the coupler, so compared to the conventional product in which the piezoelectric element is supported at one node point, the piezoelectric vibrator is less susceptible to external forces. The piezoelectric element is not easily displaced by mechanical vibration or impact, and even if it is displaced, the piezoelectric element is not brought into contact with the case, so there is no fear that the vibration characteristics of the piezoelectric element will change. In addition, since the shift in the support point of the holding frame does not affect the vibration characteristics, assembly accuracy can be lowered compared to conventional products that required the support point to be precisely aligned with the 7-dot point. Even a piezoelectric element can be incorporated into the case without disturbing its vibration characteristics, making it quieter. Furthermore, since the length of the connector is set to such a length that the capacitance ratio of the piezoelectric element is minimized, it is possible to obtain extremely good characteristics.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional example, Fig. 2 to Fig. 4 show an embodiment of the present invention, Fig. 2 is a longitudinal sectional view, Fig. 3 is an exploded perspective view, and Fig. 4 is an integral frame thereof. The top view of FIG. 5 is its characteristic diagram. 11... Case, 13... Piezoelectric element, 13a...
Vibration substrate, 13b... piezoelectric thin film, 14... connector,
15... Holding frame. Patent applicant Murata Manufacturing Co., Ltd. Representative Patent Attorney Oka 1) Kazuhide Figure 3 ZU Figure 5 Lc/L

Claims (1)

[Claims] (1) A piezoelectric vibrator including a case and housing a spread vibration mode piezoelectric element having a vibrating substrate made of a constant elastic metal, a piezoelectric thin film, and a vibrating electrode film,
A piezoelectric vibrator is supported by a holding frame via a connector integrally molded with the vibrating substrate, and the length of the connector is set to a length such that a capacitance ratio of the piezoelectric element is minimized.