Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-08-02
2001-03-20
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S340000, C310S348000, C310S349000
Reexamination Certificate
active
06204593
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resonator, and a piezoelectric resonance device, and.
2. Description of the Related Art
A resonator, an example of a piezoelectric resonance device, is used in various types of electronic equipment as a circuit for generating clock signals etc. In general, a resonator is provided with a piezoelectric element and a capacitor. These are made to constitute a signal, generating circuit by connection of the input-output lead terminals and the ground lead terminals. The piezoelectric element and capacitor are integrally covered by a sealing resin comprised of an epoxy resin etc.
It is generally known to use an input-output lead terminal for such a resonator. For example, such a lead terminal is disclosed in Japanese unexamined utility Model Publication (Kokai) No. 63-131414. The lead terminal shown in this publication is produced by punching a metal sheet to form a strip which is then cut and bent.
In the lead terminal shown in this publication, there is the problem of a large number of steps required for production. Furthermore, since this lead terminal is structured to hold an end of the piezoelectric element from the two different sides, the area of the vibrating section of the piezoelectric element is reduced and the longitudinal width of the piezoelectric element has to be increased by the amount of the area required for holding the ends. This runs counter to the demands for reducing the size of piezoelectric resonators.
As another lead terminal according to the related art, there is known the lead terminal shown in Japanese Unexamined Patent Publication (Kokai) No. 3-421. The lead terminal shown in this publication is produced by punching a metal sheet to form a T-shape and then bending the ends to form a U-shape.
However, the lead terminal shown in the 3-421 publication requires a large number of steps for production. Additionally, the lead terminal disclosed in the 3-421 publication is structured to hold a piezoelectric element from two sides. Therefore, the area of the vibrating section of the piezoelectric element is reduced. Thus, the longitudinal width of the piezoelectric element must be increased by the amount of the area required for holding the ends of the piezoelectric element. Furthermore, this solution does not allow the size of the piezoelectric resonators to be reduced.
Further, as shown in Japanese Unexamined Patent Publication (Kokai) No. 63-131414, the resonator of the related art had the piezoelectric element and capacitor positioned facing each other substantially in parallel. If such a piezoelectric resonator is used in an environment with severe temperature changes (for example, mounted in an automobile), however, there is the problem of a susceptibility to reduce vibration. To prevent this problem, it has been confirmed that the piezoelectric element and the capacitor can be positioned offset from each other in the vertical direction. The piezoelectric element and the capacitor are then connected and secured by the lead terminals. Once again, this solution does not allow the size of the piezoelectric resonators to be reduced.
Further, in the resonator of the related art, the size of the vibrating space formed in the sealing resin surrounding the area around the piezoelectric element was determined without regard to the frequency band of the piezoelectric element and therefore there was the problem that good resonance characteristics could not be obtained.
SUMMARY OF THE INVENTION
The present invention was made in consideration of this situation. A first object of the present invention is to provide a resonator that is easy to produce and can be made smaller in size and a method for production of the same.
A second object of the present invention is to provide a resonator which is superior in resistance to thermal shock and can be made smaller in size.
A third object of the present invention is to provide a resonator or other piezoelectric resonance device that maintains the resonance characteristics well and is superior in durability and a method for production of the same.
To achieve the first object, according to a first aspect of the present invention, there is provided a resonator comprising a piezoelectric element; a lead terminal comprised of an electroconductive wire material formed by press working with a tapered receiving groove for holding an end of the piezoelectric element at its top end; and a capacitor connected to the outer circumference of the top end of the lead terminal in a state with the end of the piezoelectric element held in the receiving groove of the lead terminal so as to constitute a resonance circuit together with the piezoelectric element.
The method of production of the piezoelectric resonator according to the first aspect of the present invention comprises the steps of forming a tapered receiving groove at an end of the lead terminal comprised of the electroconductive wire material by press working; inserting an end of the piezoelectric element inside the tapered receiving groove and making the piezoelectric element be held by the lead terminal; and connecting an external electrode of a capacitor constituting a resonance circuit together with the piezoelectric element to the lead terminal.
With the resonator according to the first aspect of the present invention since the tapered receiving groove is formed at the end of the electroconductive wire material by press working, the production of the lead terminal becomes extremely easy. Further, since the tapered receiving groove formed in the lead terminal holds an end of the piezoelectric element by the minimum necessary area, reduction of the size of the piezoelectric resonator becomes easy.
Preferably, the tapered receiving groove has an open portion of a width in the cross-section larger than the thickness of the end of the piezoelectric element and a bottom wall of a width in the cross-section smaller than the thickness of the end of the piezoelectric element. By making such a tapered receiving groove, even ends of piezoelectric elements somewhat different in thickness can be held in the tapered receiving groove and therefore it is possible to use the lead terminal parts universally.
Preferably, the cross-sectional shape of the wire material constituting the lead terminal is substantially circular at the portion not formed with the tapered receiving groove. A wire material of a substantially circular cross-section is easy to obtain and contributes to the reduction of the manufacturing costs.
Preferably, the tapered receiving groove is formed at the top end of the lead terminal at a length of at least the width of the piezoelectric element along the longitudinal direction of the lead terminal.
Preferably, a bent portion is formed in the midway of the lead terminal in the longitudinal direction. The bent portion of the lead terminal acts as a stopper when inserting the lead terminal into a mounting hole of the circuit board and enables the height of the piezoelectric element and capacitor from the circuit board to be made constant and thereby contributes to the stabilization of the characteristics of the piezoelectric resonator.
Preferably, an external electrode formed at the surface of the piezoelectric element is electrically connected to the lead terminal through solder in the receiving groove. Solder paste is inserted in the receiving groove, then the end of the piezoelectric element is inserted into the receiving groove and heat treatment is applied, whereby the end of the piezoelectric element and lead terminal are secured and the external terminal of the piezoelectric element and lead terminal are electrically connected simultaneously.
To achieve the second object, according to a second aspect of the present invention, there is provided a resonator comprising a piezoelectric element; a lead terminal comprised of an electroconductive wire material for holding an end of the piezoelectric element; and a capacitor connected to the top end of the lead terminal in a state with the end
Sugawara Yuuichi
Takahashi Touru
Dougherty Thomas M.
Oliff & Berridg,e PLC
TDK Corporation
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