JPH0352249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a longitudinal vibration type piezoelectric vibrator formed by photoetching.

An object of the present invention is to provide a small, longitudinally vibrating piezoelectric vibrator with stable performance and low leakage of vibration energy at a low cost.

Conventionally, a longitudinal vibration type piezoelectric vibrator as shown in FIG. 1 has been used as a piezoelectric vibrator for a frequency band of several 100 KHz to around 1 MHz. FIG. 1 is a perspective view showing a structure in which an oscillating piece 1 is fixedly supported by thin hanging wires 2 and 2' by soldering. The vertical vibration type piezoelectric vibrator has the following characteristics: 1. Due to variations in the positional accuracy of fixing and supporting the oscillating piece to the hanging wire and variations in the amount of solder, there are large variations in CI value, vibration leakage, etc.

2. Impact resistance is low because the connection strength between the hanging wire and the oscillating piece is weak.

3. Fixing and supporting the hanging wire and the oscillating piece requires skill and increases manufacturing costs.

4. It has drawbacks such as the container becoming large due to the shape of the hanging wire.

Another conventional example of a longitudinal vibration type piezoelectric vibrator is shown in a perspective view in FIG. In the same figure, the longitudinally vibrating piezoelectric vibrator of this example has a main vibrating part 3 that vibrates longitudinally and a connecting part 4.
and a support portion 5 are integrally formed by photoetching, and are further supported by a fixing portion 6, which is a separate member in the shape of a tuning fork. In the longitudinal vibration type piezoelectric vibrator, since the main vibrating part 3, the connecting part 4, and the supporting part 5 are integrally formed, there is little variation in the fixed support position and dimensions. However, since the direction of support is in the width direction of the main vibrating section 3, the supporting section 5 and the fixed section 6 are displaced in the width direction of the main vibrating section 3 due to the short-side vibration that occurs accompanying the longitudinal vibration. By supporting this with a tuning fork-shaped fixing part 6, leakage of main vibration energy is suppressed. In this example with the above configuration, 1. Since the fixed part and the main vibrating part are formed of separate members, vibration loss occurs at the joint, resulting in Q
value becomes lower.

2. It has the disadvantage of high manufacturing costs due to the large number of parts.

Furthermore, a conventional example of a vertical vibration type piezoelectric vibrator produced by another photoetching process is shown in a perspective view in FIG. In the figure, the longitudinal vibration type piezoelectric vibrator of this example includes a main vibrating part 7, double frames 8, 9 surrounding the main vibrating part 7, and connecting parts 10, 1 connecting them.
0', 11, and 11' are integrally formed by photo-etching. In the longitudinal vibration type piezoelectric vibrator of this example, the inner frame 8 bends and vibrates in response to the short side vibration accompanying the longitudinal vibration of the main vibrating part 7, so that the main vibration energy does not leak to the outer frame 9. It is aimed at In this example, 1. It is difficult to sufficiently suppress leakage of main vibration energy only within a limited range of the inner frame 8. As a result, vibration energy leaks through the connecting portions 11, 11', and the outer frame 9 also vibrates. Therefore, when fixing the outer frame 9 to a rigid body, it is necessary to use the vibration nodes of the outer frame 9 for fixing, but since the vibration nodes move due to dimensional variations during photo etching, etc. Strict precision control is required, which increases manufacturing costs.

2. In order to sufficiently suppress the leakage of main vibration energy in the inner frame 8, it is necessary to increase the width or length of the inner frame 8, which makes miniaturization difficult.
It has drawbacks such as:

All of the three conventional examples described above employ various measures to suppress the leakage of main vibration energy, but the effects are not sufficient, and they also have drawbacks in terms of manufacturing cost and dimensions. There is.

The configuration described below eliminates the conventional drawbacks mentioned above, suppresses leakage of main vibration energy, and is compact and
The purpose of the present invention is to provide a longitudinal vibration type piezoelectric vibrator with a structure suitable for cost reduction.

The gist of the present invention is a longitudinally vibrating piezoelectric vibrator in which a main vibrating part that vibrates longitudinally and a supporting part of the main vibrating part are integrally formed by photo-etching. A connecting part provided in the width direction of the main vibrating part at a position where vibration displacement is smallest, a supporting part parallel to one of the main vibrating parts from both ends of the connecting part, and the supporting part has a tuning fork shape. and a base portion that connects both ends of the support portion so as to constitute, and the width of the portion is at least twice the width of the support portion corresponding to the tuning fork arm.

In addition, the resonant frequency of the main vibrating part and the resonant frequency of the second harmonic of the support part corresponding to the tuning fork arm are almost the same, and the resonant frequency of the connecting part provided in the width direction of the main vibrating part is It is characterized in that the resonance frequency of the main vibrating part is almost the same as that of the main vibration part. This configuration is shown in a perspective view in FIG. In the figure, the present invention includes a main vibrating section 12 that vibrates longitudinally, connecting sections 13 and 13' provided in the width direction of the main vibrating section 12 at a position where the vibration displacement of the main vibrating section 12 is the smallest, Support parts 14, 14' are extended from both ends of the connecting parts 13, 13' in parallel with one of the main vibrating parts 12,
14' is provided with a base 15 such that the support portion excluding the main vibrating portion 12 forms a tuning fork shape;
The length L of 5 is the supporting part 14,1 corresponding to the tuning fork arm.
This is a longitudinally vibrating piezoelectric vibrator having the above configuration, in which the width W of 4' is twice or more. In this example, the supporting portion and the connecting portion corresponding to the tuning fork arm perform bending vibration even in response to vibration in the short side direction caused by longitudinal vibration of the main vibrating portion. The vibration mode is shown in FIG. In FIG. 5, 16, 16' shown by broken lines are support parts 14, 1 that change due to the bending vibration.
4' and the connecting parts 13, 13' in a vibrating state.
The influence of the bending vibration at this time on the main vibration can be prevented by substantially matching the resonance frequency of the bending vibration with the resonance frequency of the main vibration section 12. Furthermore, since the vibration displacement of the base 15 shown in FIG. 4 is reduced due to the balance of the bending vibrations of the support parts 14 and 14' corresponding to the left and right tuning fork arms, the base 15 can be fixed to a rigid body. Become. At this time, in order to sufficiently reduce the vibration displacement of the portion fixed to the rigid body and suppress the leakage of vibration energy, the length L of the base 15 must be
needs to be as long as possible. That is, since the supports 14 and 14' corresponding to the tuning fork arms vibrate in opposite phases to each other, their vibration energies cancel each other out, and the degree of attenuation of vibration energy at the base depends on the length L of the base. . It has been experimentally confirmed that the length L of the base portion 15 is required to be at least twice the width W of the support portions 14, 14'. Furthermore, since the frequency of a longitudinally vibrating piezoelectric vibrator is generally 100KHz to 1MHz, in order to match the resonance frequency of the main vibrating part mentioned above with the bending vibration of the support part corresponding to the tuning fork arm, it is necessary to width dimension,
Use the second harmonic from the length dimension. FIG. 6 is an explanatory diagram showing the displacement of the second harmonic, in which 17 indicates the base 15 of FIG. 4, 18,
18' is a support part 14 corresponding to the tuning fork arm in FIG.
14' shows the displacement of the second harmonic. 18 and 18' are out of phase by 180 degrees. Since the frequency of the second harmonic is approximately 15 times the frequency of the fundamental wave, a frequency of several 100 KHz to 1 MHz can be easily obtained.

Furthermore, if the center of gravity of the main vibrating section deviates from the connection position due to manufacturing variations or the like, the center of gravity shifts due to longitudinal vibration, resulting in leakage of vibration energy. FIG. 7 shows the state. In the same figure,
A and A' are the center of gravity points, and the vibration displacement shown by the broken line indicates that the center of gravity is moving from point A to point A'. The vibration states at this time are 12 and 20
The phase is shifted by 180°. This leakage of vibrational energy due to the movement of the center of gravity can be solved by making the resonance frequency of the main vibrating section 12 substantially coincide with the resonance frequency of the connecting sections 13, 13'.

As described above, the longitudinal vibration type piezoelectric vibrator with this configuration has the following characteristics: 1. The performance is stable because leakage of the main vibration energy can be reliably suppressed.

2. Manufacturing costs are low because the number of parts is integrally processed. It has the following advantages.

As described above, the present invention has novel features in the configuration of the external shape, but also has novel features in the cut orientation and electrode structure described below. The cut orientation and electrode structure regarding this configuration will be explained with reference to FIG. In the same figure, the figure shows the P-P' cross section of the main vibrating part 12 in FIG. 21 and 22 are electrode films formed on the front and back surfaces of the main vibrating section 12, respectively.

In the longitudinal vibration type piezoelectric vibrator with this configuration in this example, the Z plate of the crystal (a plate perpendicular to the Z axis) is rotated at an angle α around the Y axis, and further rotated at an angle β (not shown) around the X′ axis. It is formed by photoetching a so-called NT-cut crystal wafer that has been rotated by a quartz wafer. At this time, α is selected in the range of 20 to 45 degrees based on conditions such as temperature characteristics, etching properties, and CI value, and β is selected in the range of -5 degrees to 5 degrees based on conditions of temperature characteristics. Further, the length of the main vibration part 12 of the longitudinal vibration type piezoelectric vibrator of the present invention is determined by the desired frequency,
For example, if the frequency is 1MHz, 2700μm,
In the case of 600KHz, it is 4500μm. In addition, the width of the main vibrating part 12 is in the range of 15 to 30% of the length, and the thickness is in the range of 50 to 30%.
It should be selected within the range of 200 μm. The figure also shows that the component Ex in the X-axis direction of the electric field E due to the electrode films 21 and 22 formed on the front and back surfaces of the main vibrating section, that is, the Z' plane, is an effective component for excitation, and the component Ex in the Y-axis direction ( This excites longitudinal vibration in the length direction of the main vibrating section.

The configuration of the present invention is shown in FIGS. 9 and 10. 9th
The figure is a perspective view of this example, which is composed of a main vibrating part 23, connecting parts 24, 24', supporting parts 25, 25', and a base part 26, which are integrally formed by photoetching. . The longitudinally vibrating piezoelectric vibrator of this example is formed from a crystal wafer with a crystal Z plate rotated in the range of -5° to 5° around the X axis, and the thickness direction of the longitudinally vibrating piezoelectric vibrator The cutting direction corresponds to the Z axis, the length direction to the Y axis, and the width direction to the X axis. From this configuration, as shown in the cross-sectional view along Q-Q′ in FIG. 9 and in FIG.
By forming electrode films 27 and 28 on the side surfaces (X-plane) of the substrate, an electric field in the X-axis direction is generated, and longitudinal vibration in the Y-axis direction is excited. According to this example, since the main electrode films 27 and 28 are formed on the side surfaces of the main vibrating section 23, it is possible to sufficiently reduce the dimension of the main vibrating section 23 in the width direction (X direction). For example, when the frequency is 1 MHz, the thickness of the main vibrating section 23 may be selected in the range of 150 to 300 μm, and the width may be selected in the range of 60 to 150 μm. Therefore, the displacement of the short-side vibration that occurs along with the longitudinal vibration becomes relatively small, and the bending vibration of the support part also becomes small, and the vibration energy is further reduced compared to the embodiment shown in FIG. A small, longitudinally vibrating piezoelectric vibrator with stable characteristics and low leakage can be provided at low cost.

As described above, the present invention provides the following effects.

a According to the present invention, the Z plate can be rotated by -5° around the X axis.
A longitudinally vibrating piezoelectric vibrator is formed by photo-etching from a crystal wafer rotated by 5 degrees, and by making the width of the main vibrating part smaller than the thickness, displacement in the width direction during vibration is reduced, and vibration to the supporting part is reduced. The dimensions of the support part are determined so that the influence of leakage is reduced, and the support part vibrates as a second harmonic when the main vibration part vibrates, and the vibration frequencies of the main vibration part and the support part are matched or By placing them close to each other, vibration leakage from the support part is reduced as much as possible, and by making the width of the base of the support part more than twice the width of the support part as a fixed part, displacement at the fixed part can be reduced. Vibration leakage from fixed parts is excluded. Therefore, it is possible to provide a longitudinally vibrating piezoelectric vibrator with extremely high vibration efficiency.

b In the photo etching process, if the width is shorter than the thickness, the shape may collapse and unnecessary parasitic vibrations may occur, but in this application, the wafer is photo etched by rotating the Z plate by -5° to 5° around the X axis. With this configuration, even if the width is made smaller than the thickness, the shape of the vertical vibration type piezoelectric vibrator can be accurately obtained, which contributes to reducing vibration leakage when coupled to the support part.

[Brief explanation of drawings]

1 to 3 are perspective views showing conventional examples of longitudinal vibration type piezoelectric vibrators. FIG. 4 is a perspective view showing the preceding example, and FIG. 5 is an explanatory diagram showing the vibration state of the preceding example. FIG. 6 is an explanatory diagram showing the displacement of the second harmonic in the prior example. FIG. 7 is an explanatory diagram showing the state of leakage of vibration energy due to the movement of the center of gravity in the prior example. FIG. 8 is an explanatory diagram of the cut orientation and electrode structure regarding the prior example. FIG. 9 is a perspective view showing the present invention. FIG. 10 is an explanatory diagram of the cut orientation and electrode structure related to the present invention. 12 is the main vibration part, 13 and 13' are connection parts, 14,
14' is a support part, 15 is a base, 16, 16' are vibration (displacement) states, 17 is a base, 18, 18' are displacements of the support parts 14, 14', 19, 20 are vibration states, 2
1 and 22 are electrode films, 23 is a main vibration part, 24 and 2
4' is a connecting part, 25 and 25' are support parts, 26 is a base part, and 27 and 28 are electrode films.

Claims (1)

[Claims] 1. A longitudinal vibration type piezoelectric vibrator in which a main vibrating part that vibrates longitudinally at a frequency of 100 KHz to 1 MHz and a frame-shaped supporting part of the main vibrating part are integrally formed by photo-etching. It is formed from a crystal wafer rotated within a range of -5° to 5°, the main vibrating part is formed so that the width is smaller than the thickness, and the frame-shaped supporting part is connecting portions provided in the width direction of the main vibrating portion at positions on both sides of the central portion where vibration displacement is smallest; and supporting portions extending from each of the connecting portions toward one end side of the main vibrating portion; a base that connects each end of the support section so as to surround one end of the main vibrating section; The width of the portion is configured such that when the main vibration portion vibrates longitudinally, the support portion performs second harmonic bending vibration, so that the vibration frequency of the main vibration portion and the vibration frequency of the support portion match or are close to each other. A vertical vibration type piezoelectric vibrator characterized by: