JPH0241206B2 - - Google Patents

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, in this conventional type, the position of the piezoelectric vibrating element 3 is easily shifted due to mechanical vibration or shock, and the characteristics are easily distorted, and assembly accuracy must be extremely strict.
A small device with a high frequency has drawbacks such as the fact that it may not be possible to accurately hold the node 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. In,
The piezoelectric vibrator is supported by a holding frame via a connector formed integrally with the vibrating substrate, and the length of the connector is set to a length that minimizes the capacitance ratio of the piezoelectric element.

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,
This case 11 is a pair of half cases 12, 12
Consisting of Each of the half cases 12, 12 is formed into a shallow box shape with open surfaces facing each other. A piezoelectric element 13 in a vibration mode is housed in an internal space of a case 11 formed by abutting both half cases 12, 12 at their opposing surfaces, as will be described later. As shown in FIG. 4, this piezoelectric element 13 has 1
It is formed into a square with a side length of 2L, and the center portion of each edge thereof is supported by a regular quadrilateral holding frame 15 via connectors 14 with a length Lc. The substrate 13a, the connectors 14, and the holding frame 15 of the piezoelectric element 13 are made of pressed constant elastic metal plates such as Elinvar, Amber, Invar, and Coelinvar.
It is formed as an integral frame 16 by a technique such as etching. Then, on one side of this integral frame 16, ZnO
A piezoelectric thin film 13b made of the following is fixed to a predetermined region, that is, the entire surface of the substrate 13a and a region extending from there through a predetermined connector 14 to a predetermined corner of the holding frame 15 by a method such as sputtering.
Further, the electrode 17 facing the substrate 13a and the holding frame 1
A lead portion 18 reaching the predetermined corner of No. 5 is deposited on the piezoelectric thin film 13b. This integral frame 16 has one of the lead wires 19, 19 attached to the tip of the lead part 18 and the other to the holding frame 15, and then both sides of the integral frame 16 are wrapped and covered with the two half cases 12, 12, and then both The joint between the half cases 12, 12 is sealed by adhesion, fusion, or the like. Case 11
The integral frame 16 inserted into the internal space of the holding frame 1
5 are held at a predetermined position within the case 11 by holding the four corners of the half cases 12, 12 in a point-contact manner with respective protrusions 20 protruding from the inner surfaces of the half cases 12, 12.

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 is not precisely aligned with the node point of the piezoelectric element 13. This means that assembly accuracy is no longer required, and assembly is easy even when downsized. Moreover, the integral frame 16 is difficult to move due to mechanical vibrations or shocks applied from the outside, and even if the integral frame 16 is displaced, the holding frame 1
Even if the piezoelectric element 13 comes into contact with the case 11 at a location other than the support point, the piezoelectric element 13 itself
1 and therefore not mechanically restrained, there is no risk that its vibration characteristics will change.

FIG. 5 is a characteristic diagram of this piezoelectric resonator, where the horizontal axis is the ratio of the length Lc of the coupler 14 to the half length L of one side of the piezoelectric element 13, and the capacitance ratio γ (=C _D / C _O ) is plotted 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 to the half length L of one side of the vibrator. = [1+5/3(n-1)]L (where n is a natural number), the capacitance ratio γ (=C _D /C _O ) becomes minimum in the range of 1, 8/3 and its vicinity, and is inverse to the resonant frequency. Good characteristics with a large deviation ΔF from the resonance frequency can be obtained.

As described above, 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, it is difficult to receive from the outside. The piezoelectric element is not easily displaced by applied mechanical vibrations or shocks, 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 displacement of the support point of the holding frame does not affect the vibration characteristics,
Compared to conventional products, which require the support points to be precisely aligned with the node points, assembly accuracy can be improved, and even a small piezoelectric element can be incorporated into the case without disturbing its vibration characteristics. 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 the drawing]

Fig. 1 is a sectional view of a conventional example, Figs. 2 to 4 show an embodiment of the present invention, and Fig. 2 is a longitudinal sectional view;
FIG. 3 is an exploded perspective view, FIG. 4 is a plan view of the integral frame, and FIG. 5 is a characteristic diagram thereof. 11...Case, 13...Piezoelectric element, 13a...
... Vibration substrate, 13b... Piezoelectric thin film, 14... Connector, 15... Holding frame.

Claims (1)

[Claims] 1. A piezoelectric vibrator comprising a case, in which a piezoelectric element in a spreading vibration mode having a vibrating substrate made of a constant-elastic metal, a piezoelectric thin film, and a vibrating electrode film is housed; A piezoelectric vibrator is supported by a holding frame via a connector, and the length of the connector is set to a length that minimizes the capacitance ratio of the piezoelectric element.