JPS6138277Y2 - - Google Patents

Description

[Detailed description of the invention] This invention uses a mechanical filter, especially a torsional vibration transducer, to convert electrical vibration into mechanical vibration, and then transmits this mechanical vibration to a torsional vibration resonator via a coupler. , a mechanical filter that transmits the mechanical vibration in the resonator again via a coupler to a torsional vibration transducer that converts the mechanical vibration into electrical vibration, converts it into electrical vibration, and extracts it, the torsional vibration transducer. The present invention relates to a mechanical filter in which a torsional vibration resonator and a torsional vibration resonator are caused to vibrate in a second-order torsional vibration mode or a higher vibration mode.

As shown in the block diagram of Figure 1A, the mechanical filter converts electrical and mechanical vibrations, and consists of an electro-mechanical transducer 1, a mechanical vibration system 2 consisting of a coupler and a resonator, and a mechanical - Consists of an electrical transducer 3, an electrical vibration input terminal 4, and an electrical vibration output terminal 5.

When electrical vibrations are input to the electrical vibration input terminal 4, the electrical vibrations are converted into mechanical vibrations by the electro-mechanical converter 1. This mechanical vibration is transmitted to the machine via the coupler and resonator of the mechanical vibration system 2.
The vibration is transmitted to the electric transducer 3, where it is converted into electric vibration again, and outputted as electric vibration from the electric vibration output terminal 5.

FIG. 1B shows the transmission characteristic, which is the frequency-transmission loss characteristic, of the mechanical filter. When the vibration frequency is such that the conversion displacement of Become. Therefore, the electrical vibration output terminal 5 shown in FIG. 1A is activated only when a frequency that minimizes the transmission loss is input.
Electrical vibrations are output from.

An example of the above transducer structure is shown in FIG. 1C. In the figure, the electro-mechanical transducer section is made by combining semicircular piezoelectric ceramics 21, 21 that vibrate through thickness shear so that their residual polarization directions (indicated by missing marks) 22 are opposite to each other to form a circular shape. Elastic metal rod 2
Electrode surfaces are formed by vapor depositing or sputtering gold or the like on the surface facing the end surface of 3 and the surface opposite thereto, that is, both circular surfaces, respectively. Then, a constant elastic metal rod 23 is bonded to one electrode surface of this circular piezoelectric ceramic transducer element using a conductive adhesive such as solder to form a torsional vibration transducer. Further, in this torsional vibration transducer, lead wires 24, 24 for applying or extracting electric vibration are attached to the constant elastic metal rod 23 and the other electrode surface of the piezoelectric ceramic.

In order to cause torsional vibration in the torsional vibration transducer, applying electrical vibration between the lead wires 24 and 24 causes sliding displacement in the piezoelectric ceramic as shown by arrows 25 and 26. The displacement shown generates rotational force 27, causing torsional vibration. When the total length l of the torsional vibration transducer including the conversion element part and the constant elastic metal rod is equal to λ/2 of the applied electrical vibration frequency, in the first torsional vibration,
When equal to λ, torsional vibration occurs in the second order torsional vibration. As shown in Figure 3A (described later), the vibration during the second torsional vibration has a maximum point of vibration displacement at a position of 1/2 of the total length, and a node where the vibration displacement becomes zero at a position of 1/4 from both ends. occurs.

Mechanical filters are used in a wide frequency range from several hundred Hz to several hundred KHz, and mechanical filters using torsional vibration are being put into practical use at frequencies of 100 KHz or higher from the viewpoint of reducing the size of the filter.

Conventionally, mechanical filters using torsional vibration have used primary torsional vibration in the torsional vibration converter and torsional vibration resonator that constitute the filter in order to make the entire filter compact. Since the length of the torsional vibration transducer and the torsional vibration resonator is inversely proportional to the resonant frequency, the length of the torsional vibration transducer and the torsional vibration resonator inevitably becomes shorter as the frequency used becomes higher. For example, the resonant frequency is 200K
The length of the combined torsional vibration transducer and torsional vibration resonator of Hz is about 6 mm, so if the frequency is high, it will be too small and it will be difficult to process, adjust, and manufacture the torsional vibration converter and torsional vibration resonator. It is even becoming inconvenient to handle it. Furthermore, in the mechanical filter of the conventional structure, the longitudinal center of the torsional vibration transducer and torsional vibration resonator arranged in parallel becomes the node of the primary torsional vibration. It is joined and held on the filter mounting board etc. by this support wire.

FIG. 2 shows an example of the conventional structure of a mechanical filter using the above-mentioned primary torsional vibration. Figure 2A
indicates the vibration state of the torsional vibration resonator in the first torsional vibration, and the torsional vibration resonator 2 exhibits torsional vibration in opposite directions (indicated by dotted lines) as shown by arrows 6 and 8. A node 7 where the vibration displacement becomes zero occurs at 1/2, that is, at the center in the longitudinal direction. In addition, in FIG. 2B, the constant elastic metal rod 2a,
2c and electro-mechanical transducers 1 and 3 made of piezoelectric ceramics are bonded together using an adhesive such as solder. It is the same as a resonator, and there is a node at which the vibration displacement becomes zero at a position of 1/2 of the total length of the transducer including the electro-mechanical transducers 1 and 3 and the constant elastic metal rod. In addition, 2b is the above-mentioned torsional vibration resonator, and 9, 9 are support wires fixed to the nodes of the above-mentioned parallel-arranged torsional vibration transducer and torsional vibration resonator, and both ends of these support lines 9, 9 are shown in the figure. It is held on the filter mounting board. 10 is a longitudinal vibration coupler for transmitting the primary torsional vibration generated in the input side torsional vibration transducer 2a to the torsional vibration resonator 2b and the output side torsional vibration converter 2c.

The applied electrical vibration of the electro-mechanical transducer 1 is converted into first-order torsional vibration by the transducer 2a, and this vibration is transmitted to the coupler 10, the resonator 2b, the coupler 10,
is sequentially transmitted to the transformer 2c, and as a result, the transformer 2c
First-order torsional vibration is generated, which is again converted into electrical vibration by the mechanical-electrical conversion element 3 connected to the transducer 2c and output.

FIG. 4A shows the transmission characteristics of the conventional mechanical filter shown in FIG. 2B. In the figure, 12 is a desired transmission characteristic output at the first torsional vibration frequency o of the transducer and resonator. For this o, transmission characteristics 13 and 14 near frequencies 2o and 3o are transmission characteristics caused by the second and third torsional vibrations of the transducer and resonator, and these are called spurious. Often harmful to use.

In particular, in the transmission characteristics due to the second-order torsional vibration shown in 13 in the figure, spurious noise occurs over a wide band.
This is due to the following reasons. In other words, the state of vibration in the second torsional vibration of the torsional vibration transducer and torsional vibration resonator will be explained in detail later, but at the position (center) of 1/2 of the total length of the torsional vibration converter and torsional vibration resonator. Torsional vibration displacement becomes maximum. As can be seen from FIG. 2B, in the mechanical filter of the above-mentioned conventional structure, a support wire 9 is connected at the central position, and when secondary torsional vibration occurs in the torsional vibration transducer 2a, this support wire 9 Vibrations are transmitted to the output-side torsional vibration transducer 2c via the torsional vibration transducer 2c.

The support wire 9 supports the torsional vibration transducer and the torsional vibration resonator, and is attached and held at both ends to the filter mounting board. In order to prevent damage to the filter, a metal wire that is thicker and stronger than the connector 10 is generally used. This tendency is particularly strong in narrowband mechanical filters.

Therefore, when the secondary torsional vibration is transmitted via the support line 9 as described above, the coupling between the torsional vibration transducer and the torsional vibration resonator etc. by the support line 9 becomes large. As a result, in a mechanical filter with a conventional structure, when an electrical vibration that almost matches the secondary torsional vibration of the torsional vibration transducer and the torsional vibration resonator is applied, it is transmitted to the output end of the filter via the support wire. An electrical vibration output corresponding to the secondary torsional vibration is generated. This frequency response output generates a large spurious as 13 in FIG. 4A.

In addition, 14 in the figure is caused by tertiary torsional vibration, and in this case, the transmission of tertiary torsional vibration via the support wire is due to the vibration displacement being zero at the connection position of the support wire. As in the case of primary torsional vibration, it does not exist. Vibration transmission therefore takes place via the coupler 10, resulting in the generation of relatively small spurious waves as shown at 14.

In order to solve the various problems mentioned above, this invention
In a mechanical filter with a conventional structure that utilizes the above-mentioned first-order torsional vibration, it becomes an undesired vibration, and by configuring it to actively utilize the second-order torsional vibration, which is the cause of spurious vibration, the frequency For example, it provides a mechanical filter that is easy to handle even at high frequencies such as 200 KHz or higher, and also suppresses spurious responses and provides more stable support for torsional vibration transducers and torsional vibration resonators. Therefore, the mechanical filter of the present invention includes a torsional vibration transducer and a torsional vibration resonator arranged in parallel, and a longitudinal vibration coupler that couples the torsional vibration converter and torsional vibration resonator at the center in the longitudinal direction. and each of the torsional vibration transducer and torsional vibration resonator is independently supported at at least one nodal point in the second-order vibration or higher vibration between the longitudinal center part and the end part. It is characterized by consisting of a supporting member. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows a perspective view of a main part of an embodiment of the mechanical filter of the present invention using a secondary torsional vibration transducer, a secondary torsional vibration resonator, and a longitudinal vibration coupler. Figure 3A shows the vibration state of the torsional vibration resonator in the second torsional vibration, with both ends of the torsional vibration resonator in the direction of arrows 6 and 8, and the center part in the opposite direction, in the direction of arrow 11. Vibratory displacement (shown in dotted line). As a result, the maximum point of vibration displacement is at 1/2 of the total length in the longitudinal direction, that is, at the center, and at 1/2 from both ends.
Two nodes 7a and 7b where the vibration displacement becomes zero appear at position 4.

In Fig. 3B, electro-mechanical transducers 1 and 3 are made of constant elastic metal rods 2a and 2c and piezoelectric ceramics.
A torsional vibration transducer bonded using an adhesive such as solder and the above-mentioned secondary torsional vibration resonator 2b are arranged in parallel, and the vibration displacement of these 2a, 2b, and 2c is a secondary vibration mode. The support wire 9, the torsional vibration transducer, and the torsional vibration transducer are attached to the above-mentioned node portions (positions 1/4 of the total length from both ends in the length direction) so as to protrude perpendicularly to the length direction. It consists of a coupler 10 that is commonly coupled to the resonator at the center in the longitudinal direction. The support wire 9 holds each of the torsional vibration transducers and the torsional vibration resonators by independently attaching them to a mounting substrate (not shown). Connector 1
0 is for transmitting mechanical vibration from the torsional vibration transducer 2a on the input side to the torsional vibration resonator 2b and the torsional vibration transducer 2c on the output side. 1/2 of the total length in the horizontal direction
points).

When electrical vibration is applied to the input-side conversion element 1 with the above configuration, the electrical vibration is converted into mechanical vibration by the input-side secondary torsional vibration converter 2a, and this mechanical vibration is transmitted via the coupler 10. It is sequentially transmitted to the secondary torsional vibration resonator 2b and the output side secondary torsional vibration converter 2c.
The conversion element 3 converts the vibration into electrical vibration again and outputs it.

The transmission characteristics of the mechanical filter of the present invention are shown in the relationship between the loss and the frequency in FIG. It is a characteristic of The transmission characteristics showing minute changes at 12, 14, and 16 in the figure are due to the first, third, and fifth order torsional vibration modes of the above-mentioned torsional vibration converter and torsional vibration resonator, respectively. This is the transmission output. In this parasitic torsional vibration, as explained in Fig. 2A, the vibration displacement is zero at 1/2 of the total length of the torsional vibration transducer and the torsional vibration resonator. In this respect, the filter is connected by a coupler for transmitting mechanical vibrations as shown in Figure 3B, so mechanical vibrations due to torsional vibrations are generally not transmitted, as described above. Transmission loss is increasing.

In addition, the transmission characteristic portions indicated by 15 and 17 in the figure are transmission outputs due to even-numbered torsional vibrations such as the fourth and sixth orders by the torsional vibration converter and torsional vibration resonator, and these are coupled. As explained in Fig. 3B, the element is only the connector 10, and there is no vibration coupling by the support wire 9 as explained in the conventional Fig. 2B, so the large No spurious output occurs.

As described above, according to the mechanical filter of the present invention, the secondary torsional vibration transducer and the secondary torsional vibration resonator are longitudinally vibration-coupled at the position of 1/2 (center) of the total length in the longitudinal direction. The transducer and the resonator are connected to each other using a transducer and a resonator, and support parts are provided at the nodal points of the second torsional vibrations that occur at 1/4 of the total length in the longitudinal direction from both ends of the transducer and the resonator. Therefore, it is possible to reduce the occurrence of spurious caused by higher-order vibration modes in the frequency-transmission loss characteristics of the mechanical filter.
Since the coupler is connected at the position of 1/2 (center) of the total length where the vibration displacement is maximum, even if the connection position is slightly shifted, the effect on the transmission characteristics is extremely small, resulting in stable transmission characteristics. is obtained.

In addition, by using the second torsional vibration mode, the total length l of the torsional vibration transducer and torsional vibration resonator can be made twice as large as that of the first torsional vibration mode, which is particularly useful for high frequencies. It is relatively easy to handle when manufacturing filters, and since each of these torsional vibration transducers and torsional vibration resonators is provided with two support parts, it is convenient when adjusting the frequency of them. has many advantages. As mentioned above, the higher the frequency, the more effectively the mechanical filter of the present invention can exhibit its characteristics.

Below, the general specifications, dimensions, etc. of the frequency range that can be realized by the filter according to the present invention will be described for reference. The range of the realized frequency o is approximately 100kHz to 400kHz due to the miniaturization and ease of handling of the torsional vibration transducer and torsional vibration resonator, and the transmission bandwidth varies depending on the realized frequency o, but is 300Hz to 3,000Hz.
The mechanical filter of the present invention can fully demonstrate its characteristics when the specifications are as follows. According to the above specifications, the dimensions of each component part can be realized approximately as follows. Torsional vibration transducer, resonator has a diameter of 2 to 5 mmφ, total length is 28 to 7 mm, longitudinal vibration coupler has a diameter of 0.13 to 0.20 mm, and the coupling interval is 4
~6mm, and the support line of the support part is 0.2~0.4mm in diameter.
If the diameter is 3 to 5 mm, a durable filter support structure that can withstand vibrations, shocks, etc. applied from the outside can be obtained.

[Brief description of the drawings]

Figure 1A is a general block diagram of a mechanical filter that uses electrical and mechanical vibrations, Figure 1B is its frequency vs. transmission loss characteristic diagram, and Figure 1C is a mechanical filter that uses shear vibration of piezoelectric ceramics. A perspective view for explaining a configuration example of a torsional vibration transducer and its function, FIG. 2A is a perspective view showing the vibration state of the primary torsional vibration resonator, and FIG. 2B shows the primary vibration mode. FIG. 3A is a perspective view showing the vibration state of the second-order torsional vibration resonator, and FIG. 3B is a perspective view of a conventional mechanical filter configuration example using the second-order torsional vibration mode according to the present invention. FIG. 4A is a diagram of frequency versus transmission loss characteristics of a mechanical filter according to a conventional configuration; FIG. 4B is a diagram of frequency vs. transmission loss characteristics of a mechanical filter according to an embodiment of the present invention. shows. In the figure, 1 represents an electro-mechanical variable element, 2 a torsional vibration transducer and a torsional vibration resonator, 3 a mechanical-electrical transducer, 7 a vibration node, 9 a support line, and 10 a coupler.

Claims (1)

[Scope of utility model registration request] A torsional vibration transducer and a torsional vibration resonator arranged in parallel, a longitudinal vibration coupler that couples the respective torsional vibration converters and the torsional vibration resonator at a central portion in the length direction, and each of the torsional vibration converters. A supporting member is provided between the longitudinal center and end of the torsional vibration resonator and the torsional vibration resonator, and supports each independently at at least one nodal point in secondary vibration or higher vibration. Characteristic mechanical filter.