JPS59139716A - Mechanical filter - Google Patents

Abstract

PURPOSE:To attain both miniaturization and low cost of a mechanical filter by providing at least two vertical oscillation mode converters containing the piezoelectric ceramics which is residually polarized in the thickness direction between two constantly elastic metallic plates of the same shape. CONSTITUTION:The vertical oscillation converters 12 and 12' are equal to each other, and constantly elastic metallic plates 13 and 13' of converters 12 and 12' are unified via connectors 16 and 16' respectively. The supporters 14 and 14' for mechanical filter are provided at the nodal points of the center part of the length direction at the opposite side to the connectors 16 and 16'. Then the piezoelectric ceramics polarized residually in the thickness direction with the same width and same length as metallic plates 16 and 16' are put on the plates 13 and 13'. Furthermore constantly elastic metallic plates 17 and 17' having same sizes as the plates 16 and 16' are adhered on the ceramics. At the same time, input/output terminals 15 and 15' are provided to the plates 17 and 17'. A mechanical filter of such a constitution shows the attenuation characteristics which are virtually free from spurious.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a mechanical filter that is compact, low cost, and highly reliable.

, (b) Background of the technology Mechanical filters have been widely used as frequency selection devices in carrier and radio equipment, and have contributed significantly to the miniaturization, economicalization, and performance improvement of equipment. Improving technology and transportation.

As wireless devices and other devices become digitalized, devices become smaller.

The trend of economicization is rapidly progressing, and the demands on the parts used are becoming stronger and stronger.

(C1 Prior Art and Problems A conventional mechanical filter will be explained with reference to FIG. 1.

FIG. 1 is a schematic diagram of a conventional mechanical filter. This example is a mechanical filter with a frequency of about 100 to 200 KHz, and the transducer 2 is twisted.

The first vibration mode is utilized, and each transducer is fixed by welding at a vibration node approximately at the center in the longitudinal direction by a support wire 3 and a support member 6 of a support fitting 5. A connector 1 is welded to an arbitrary position between each converter 2 to obtain desired characteristics, and an input/output lead wire 4 is bonded to each converter 2.

The mechanical filter shown in Fig. 1 uses a torsional vibration mode in the transducer 2, so the resonance sharpness QM of the transducer can be quite large, and narrow band characteristics can be achieved.The mechanical filter also has a mechanical structure. It has the advantage of being quite resistant to vibration.

However, on the other hand, it has the same drawbacks.

Namely.

(2) As can be seen from FIG. 1, the conventional mechanical filter is designed to be mechanically strong and to reduce vibration leakage from the support base 5 of the torsion transducer.

The support stand 5 is bent into a U-shape. Furthermore, it is difficult to reduce the diameter of the converter to less than 2 to 3 mm due to the manufacturability of the converter, and the height of this type of mechanical filter cannot be less than 4 to 5 mm.

■ Spurious signals are likely to occur, that is, the converter with the structure shown in FIG. - Spurious occurs at all nth-order vibration mode frequencies.

Particularly in the secondary, the support line 3 acts as a connector and a large spurious signal is generated.

It also depends on the diameter and length of the transducer and the precision of the support position, etc., but in the case of a transducer of about φ3°xiol, at frequencies of several hundred Kllz or more, it will be converted not only in the higher order mode of torsional vibration but also in various vibration modes. It is difficult to realize a mechanical filter in which the element vibrates and does not generate much spurious up to a frequency of about 6 to 7 times the center frequency.

■ In order to minimize the influence of the lead wire on the converter, the lead wire is made of as thin and soft a wire as possible. However, this also results in the lead wire becoming mechanically weaker, and lead wire breakage may occur. Further, even though wire rods having the optimum length and diameter are used for the lead wires, unnecessary vibrations may occur in the lead wires or cause spurious waves.

In order to minimize the influence of the lead wire on the converter,
Nodal point approximately in the center of the transducer end (vibration node)
It is adhered to. If the lead wire is not bonded to the vibration node, it will have various adverse effects on the transducer, such as a reduction in the QM of the transducer, vibration leakage, and frequency fluctuation. Therefore, the adhesive to the end of the lead wire becomes a true letter, which increases the number of man-hours.

(2) If an attempt is made to reduce the diameter of the torsional transducer to approximately φ2 or less in order to lower the height of the present mechanical filter, workability and manufacturability will deteriorate significantly.

(2) Problems with connectors and support wires; Wires with a diameter of 0.1 to 0.3 are generally used. Even with a diameter of this size, the height of the entire mechanical filter increases if it is mounted on top of the converter. Furthermore, since the transducer is welded after manufacturing, the cost is high.

It had the following drawbacks.

(d) Object of the Invention In view of the drawbacks of such mechanical filters, an object of the present invention is to provide a small, low-cost, and highly reliable mechanical filter.

(e) Structure of the Invention In order to achieve the above object, the present invention provides a structure in which two constant-modulus metal plates having the same shape have a width and length that is approximately the same as that of the constant-modulus metal plates. I have it.

The present invention is characterized in that it is constructed using at least two longitudinal vibration mode converters each having a piezoelectric ceramic that is remanently polarized in the thickness direction.

(f) Embodiments of the Invention Nine embodiments of the mechanical filter of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a diagram showing an example of the configuration of a converter used in the mechanical filter of the present invention.

The transducer shown in FIG. 2 has a piezoelectric ceramic plate 8 which is remanently polarized in the thickness direction and has almost the same width and length as the constant elastic metal plate 7 placed on top of the constant elastic metal plate 7. It has almost the same shape as the constant elastic metal plate 7.

Constant elastic metal plates 9 of the same dimensions are stacked and bonded together.

When an AC voltage is applied between the lead terminals 10 and 11 drawn out from the longitudinal center of the transducer formed in this manner, the transducer resonates at a desired longitudinal vibration mode frequency with no spurious.

For example, the dimension of constant elastic metal plate 7.9 is 0.25 (m)
X 2. O (m+) x 11.2 (n+), and the dimensions of the piezoelectric ceramic 8 are 0.3 (tuna) x 2. O (pass)
In the case of a vibrator set to 11.2 (U), the first resonance frequency of longitudinal vibration can be obtained as approximately 202 KHz.

In addition, only the frequency of the vertical tertiary excavation mode (f to 600 KHz) appears over a range of about 0 to 1000 KHz, so that a converter with extremely low spurious forces can be obtained.

The canonical filter of the present invention uses two of the above-mentioned converters, and an example is shown in FIG.

In this figure, for the sake of explanation, the top and bottom of the transducer are reversed from those in FIG. 2.

As shown in FIG. 3, the mechanical filter of the present invention is as follows:
The converters 12 and 12' used are the same, and two are used. 12.12' constant elastic metal plate 1 for each transducer
3.13' is integrally formed via a connector 16.16', and the width, length, and position of the connector 16.16' on the constant elastic metal plates 13, 13' can be adjusted as desired. determined by the characteristics of

A support member 14.14', which is used as a support for the present mechanical filter, is provided at a nodal point in the longitudinal center of the constant elastic metal plate 13.13' on the side opposite to the connector side.

A piezoelectric ceramic having the same width and length as the constant elastic metal plate 16.16' and remanently polarized in the thickness direction is layered, and a constant elastic metal plate having the same dimensions as the constant elastic metal plate 16.16' is layered on top of the piezoelectric ceramic having the same width and length as the constant elastic metal plate 16.16'. It is formed by overlapping and bonding plates 17 and 17'.

In addition, the constant elastic metal plate 17.17' has an input/output terminal 15.1 used as an input/output terminal of this mechanical filter.
5' is provided at the nodal point in the longitudinal center of the constant elastic metal plate 11.17'.

For example, terminal 1 of the mechanical filter configured as described above.
4.15 is the input side, terminals 14' and 15' are the output side,
When an input signal is applied between terminals 14 and 15, such a mechanical filter can obtain attenuation characteristics with no spurious components.

Ig) Effects of the Invention As explained in detail above, according to the mechanical filter of the present invention, it is possible to realize a filter having a height of one basket or less, as can be seen from the above (()), so the size and shape are smaller than that of the conventional filter. can be done in a few minutes, and again.

Since the connector, supporter, and input/output terminal portion are integrally formed with the converter, the number of man-hours in various manufacturing processes can be reduced, resulting in a low-cost mechanical filter.

Furthermore, since the terminals formed integrally with the transducer can be used as input/output terminals, a mechanical filter without lead wires can be realized, making it possible to realize a highly reliable, low-cost mechanical filter. Santoy Sochi structure of constant elastic metal plate - piezoelectric ceramic - constant elastic metal plate Fully laminated longitudinal vibration transducer is used, so no spurious noise appears at all and a mechanical filter with good characteristics can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a conventional mechanical filter. FIG. 2 is a diagram showing an example of the configuration of a converter used in the mechanical filter of the invention, and FIG. 3 is a diagram showing an example of the configuration of the mechanical filter of the invention. In the figure, 1 is a connector, 2 is a converter, and 3 is a support line. 4 is an input/output terminal, 5 is a support base, 6 is a support element, 7, 9, 1
3, 13', 17, and 17' are constant elastic metal plates. 8 is a piezoelectric ceramic, 10, 11, 14, 14', 1'5, 15' are input/output terminals, 12, 12' are longitudinal transducers, and 16, 16' are connectors. Figure 1 1 Draft 2 Figure 3

Claims (1)

[Claims] Longitudinal vibration mode conversion having a piezoelectric ceramic having approximately the same width and length as the constant elastic metal plate and remanently polarized in the thickness direction between two constant elastic metal plates having the same shape. A mechanical filter characterized in that it is configured using at least two children.