Tuning fork type vibrator

Abstract

The objective is to provide a tuning fork-type oscillator that can reduce the equivalent series resistance. [Solution] The tuning fork vibrator 10 has a base 1 and two tuning fork arms 2 and 3 extending from the base 1, with grooves 21, 22, 31, and 32 formed on the first surface and the second surface opposite the first surface of the tuning fork arms 2 and 3, respectively. The widthwise centers of the grooves 21 and 31 formed on the first surface of the tuning fork arms 2 and 3 are offset in a first direction toward the space between the two tuning fork arms 2 and 3 from the widthwise center of the tuning fork arms 2 and 3, and the widthwise centers of the grooves 22 and 32 formed on the second surface of the tuning fork arms 2 and 3 are offset in a second direction opposite to the first direction from the widthwise center of the tuning fork arms 2 and 3.

Description

Technical Field

[0004] , , , , , ,

[0001] The present invention relates to a vibrator, and particularly to a tuning fork type vibrator.

Background Art

[0002] As a small tuning fork type vibrator, one with grooves provided on the tuning fork arms is used (for example, see Patent Document 1). Such a tuning fork type vibrator has a base and two tuning fork arms extending from the base, and grooves are provided on the front and back surfaces of the tuning fork arms, respectively. The grooves provided on the front and back surfaces of the two tuning fork arms are such that the center of the width direction of the groove coincides with the center in the width direction of the tuning fork arm. That is, the grooves on the front and back surfaces of the tuning fork arm are arranged at the center in the width direction of the tuning fork arm, and the grooves on the front and back surfaces are provided symmetrically with respect to the thickness direction of the tuning fork arm. And excitation electrodes for vibrating the tuning fork arms are provided on the side surfaces of each tuning fork arm and the inner surfaces of the grooves, and the excitation electrode provided on the side surface of one (the other) tuning fork arm is connected to the excitation electrode provided on the other (one) tuning fork arm, and by alternately applying voltages with different polarities to the excitation electrodes provided on each tuning fork arm, the two tuning fork arms bend and vibrate in a direction of approaching or separating from each other.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the important characteristics of a tuning fork type vibrator is the equivalent series resistance. The smaller the equivalent series resistance, the more efficiently energy can be converted into mechanical vibration, and the higher the Q value (quality factor) of the oscillation circuit of the tuning fork type vibrator, the higher the selectivity of the oscillation circuit, and stable frequency oscillation becomes possible. Therefore, a tuning fork type vibrator with a small equivalent series resistance is required. The purpose of the present invention is to provide a tuning fork type vibrator capable of reducing the equivalent series resistance. [Means for solving the problem]

[0005] A tuning fork-type vibrator having a base and two tuning fork arms extending from the base, wherein grooves are formed on the first surface and the second surface opposite the first surface of the tuning fork arms, wherein the center in the width direction of the groove formed on the first surface of the tuning fork arm is offset in a first direction toward the space between the two tuning fork arms from the center in the width direction of the tuning fork arm, and the center in the width direction of the groove formed on the second surface of the tuning fork arm is offset in a second direction opposite to the first direction from the center in the width direction of the tuning fork arm. The width of the groove may be approximately 80% of the width of the tuning fork arm. Furthermore, the offset amount of the center of the groove in the width direction may be up to 7% of the width of the tuning fork arm. [Effects of the Invention]

[0006] According to the present invention, a tuning fork type vibrator with effectively reduced equivalent series resistance can be provided. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows one embodiment of the tuning fork type vibrator of the present invention, and is a plan view of the tuning fork type vibrator. [Figure 2] Figure 1 is a cross-sectional view (AA) of the tuning fork type oscillator shown. [Figure 3] This is a schematic cross-sectional diagram of a tuning fork arm, showing the configuration of multiple grooves. [Figure 4] This figure shows the relationship between the equivalent series resistance of a tuning fork-type oscillator with the tuning fork arm configuration shown in Figure 3 and the amount of offset between the widthwise center of the groove and the widthwise center of the tuning fork arm in the groove. [Modes for carrying out the invention]

[0008] Figure 1 is a diagram showing one embodiment of the tuning fork type vibrator of the present invention, and is a plan view of the tuning fork type vibrator. Figure 2 is a cross-sectional view AA of the tuning fork type vibrator shown in Figure 1. The tuning fork type vibrator 10 of the present invention has a base 1 and two tuning fork arms 2 and 3 extending from the base 1. A groove 21 is provided on the first surface (front surface) of one tuning fork arm 2, along the direction in which the tuning fork arm 2 extends from the base 1, and a groove 22 is provided on the second surface (back surface) opposite the first surface. A groove 31 is provided on the first surface of the other tuning fork arm 3, along the direction in which the tuning fork arm 3 extends from the base 1, and a groove 32 is provided on the second surface. The tuning fork arms 2 and 3 and the grooves 21, 22, 31, and 32 have a rectangular cross-section. In this specification, "first surface" refers to one surface of the tuning fork arm, and "second surface" refers to the other surface of the tuning fork arm opposite the first surface. Furthermore, these surfaces do not necessarily depend on a specific direction, and any surface can function as the first or second surface. In this specification, the direction in which the tuning fork arms 2 and 3 extend from the base 1 is defined as the "length direction," the direction perpendicular to the length direction of the tuning fork arms 2 and 3 is defined as the "width direction," and the direction perpendicular to both the width and length directions of the tuning fork arms 2 and 3 is defined as the "thickness direction."

[0009] The grooves 21 and 31 on the first surface of the tuning fork arms 2 and 3, and the grooves 22 and 32 on the second surface, are positioned so that their centers do not coincide in the width direction of the tuning fork arms 2 and 3 on which they are provided. Specifically, the groove 21 on the first surface of the tuning fork arm 2 is offset to the outer surface side (second direction) that is farther from the other tuning fork arm 3 than the center of the tuning fork arm 2 in the width direction, and the groove 22 on the second surface is offset to the inner surface side (first direction) that is closer to the other tuning fork arm 3 than the center of the tuning fork arm 2 in the width direction. Similarly, the groove 31 on the first surface of the tuning fork arm 3 is offset to the outer surface side (second direction) that is farther from the other tuning fork arm 2 than the center of the tuning fork arm 3 in the width direction, and the groove 32 on the second surface is offset to the inner surface side (first direction) that is closer to the other tuning fork arm 2 than the center of the tuning fork arm 3 in the width direction. In other words, the groove 21 on the first surface of one tuning fork arm 2 and the groove 22 on the first surface of the other tuning fork arm 3 are offset from the center in the width direction of each tuning fork arm 2,3 on which they are provided, in a direction that increases their distance from each other, while the groove 22 on the second surface of one tuning fork arm 2 and the groove 32 on the second surface of the other tuning fork arm 3 are offset from the center in the width direction of each tuning fork arm 2,3 on which they are provided, in a direction that decreases their distance from each other. In this specification, "first direction" refers to the direction from one tuning fork arm to the other in a pair of tuning fork arms, that is, the direction towards the space between the arms of the pair of tuning fork arms, and "second direction" refers to the direction opposite to the first direction.

[0010] Furthermore, excitation electrodes 5 are provided on the sides of the tuning fork arms 2 and 3 and on the inner surfaces of the grooves 21, 22, 31, and 32. The excitation electrodes 5 consist of a first excitation electrode 5a, which is electrically connected to an electrode provided on the side of one tuning fork arm 2 and an electrode provided on the inner surface of the grooves 31 and 32 of the other tuning fork arm 3, and a second excitation electrode 5b, which is electrically connected to an electrode provided on the side of the other tuning fork arm 3 and an electrode provided on the inner surface of the grooves 21 and 22 of one tuning fork arm 2.

[0011] Furthermore, the base 1 is provided with connecting electrodes 4. The connecting electrodes 4 are two electrodes electrically connected to the excitation electrodes 5a and 5b, respectively. The connecting electrodes 4 allow an external voltage to be supplied to the excitation electrodes 5, thereby causing the tuning fork arms 2 and 3 to vibrate.

[0012] In this embodiment, the grooves 21, 22, 31, and 32 are set to a width of 80 ± 1% of the width of the tuning fork arms 2 and 3 on which they are provided, and the offset amount is preferably a maximum of 7% of the width of the tuning fork arms 2 and 3. This ensures that the width of the wall portion from the side of the tuning fork arms 2 and 3 to the grooves 21, 22, 31, and 32 is appropriately secured, thereby ensuring the shock resistance of the tuning fork vibrator 10 and reducing the equivalent series resistance.

[0013] Next, the differences between the embodiment of the present invention and the comparative example will be explained with reference to Figures 3 and 4. Figure 3 is a schematic cross-sectional view of the tuning fork arm, showing the configuration of multiple grooves. Figure 3 shows the following configuration. (a) Comparative Example 1: An example of a conventional vibrator, in which the center in the width direction of the tuning fork arm 41 coincides with the center in the width direction of the groove 42, and the grooves 42 provided on the first and second surfaces of the tuning fork arm 41 are positioned symmetrically with respect to the thickness direction of the tuning fork arm 41. (b) Comparative Example 2: This is an example in which a groove 42 provided on one tuning fork arm 41 is offset to the second direction side with respect to the center of the tuning fork arm 41 in the width direction, and a groove 42 provided on the other tuning fork arm 41 is offset to the first direction side with respect to the center of the tuning fork arm 41 in the width direction. The grooves 42 provided on the first and second surfaces of the tuning fork arm 41 are positioned symmetrically with respect to the thickness direction of the tuning fork arm 41. (c) Comparative Example 3: This is an example in which grooves 42 provided on the first and second surfaces of the two tuning fork arms 41 are offset in the first direction of the tuning fork arms 41. The grooves 42 provided on the first and second surfaces of the tuning fork arms 41 are positioned symmetrically with respect to the thickness direction of the tuning fork arms 41. (d) Comparative Example 4: This is an example in which the groove 42 on the first surface of one tuning fork arm 41 is offset in the first direction, the groove 42 on the second surface is offset in the second direction, the groove 42 on the first surface of the other tuning fork arm 41 is offset in the second direction, and the groove 42 on the second surface is offset in the first direction. The grooves 42 on the first and second surfaces of the tuning fork arm 41 are arranged asymmetrically with respect to the thickness direction of the tuning fork arm 41. (e) Example: This is an embodiment of the present invention in which the groove 42 provided on the first surface of the two tuning fork arms 41 is offset in the first direction, and the groove 42 provided on the second surface is offset in the second direction. The grooves 42 provided on the first and second surfaces of the tuning fork arms 41 are arranged asymmetrically with respect to the thickness direction of the tuning fork arms 41.

[0014] Figure 4 shows the relationship between the equivalent series resistance of a tuning fork-type oscillator having the tuning fork arm configuration shown in Figure 3 and the offset amount of the groove's center in the width direction from the center of the tuning fork arm in the width direction. The horizontal axis represents the groove offset amount (μm), and the vertical axis represents the equivalent series resistance (Ω). Five datasets are plotted, including Comparative Examples 1-4 shown in Figure 3(a)-(d) and an embodiment of the present invention shown in Figure 3(e). Furthermore, the dataset in Figure 4 is the result of simulations performed on a tuning fork-type oscillator in which grooves measuring 0.6 mm in length, 0.048 mm in width, and 0.044 mm in depth are placed on the first and second surfaces of a tuning fork arm made of quartz, with a length of 0.58 mm, a width of 0.058 mm, and a thickness of 0.1 mm, and the distance between the two tuning fork arms is 0.13 mm. The second surface side of the base from which the tuning fork arms extend is fixed, and the position of the grooves is changed in the width direction of the tuning fork arms.

[0015] In FIG. 4, the offset amount shown on the horizontal axis indicates the distance between the center in the width direction of the groove and the center in the width direction of the tuning fork arm when the groove is offset in a predetermined direction. For example, in Comparative Example 1, it indicates the distance between the center in the width direction of the groove and the center in the width direction of the tuning fork arm when the groove is offset in the first direction. Also, in the embodiment, it is the distance between the center in the width direction of the groove and the center in the width direction of the tuning fork arm when the groove provided on the first surface of the two tuning fork arms is offset in the first direction, and the distance between the center in the width direction of the groove and the center in the width direction of the tuning fork arm when the groove provided on the second surface is offset in the second direction. Note that in Comparative Examples 2 to 4 and the embodiment, the offset amounts of the respective grooves provided on each tuning fork arm are the same.

[0016] Comparative Example 1 indicates the position where the offset amount on the horizontal axis in FIG. 4 is 0, and Comparative Examples 2 to 4 and the embodiment were evaluated based on the equivalent series resistance in Comparative Example 1. In Comparative Example 2, it can be seen that as the offset amount increases, the equivalent series resistance decreases, and the equivalent series resistance is smaller than in the case where the offset amount is 0 (the case of Comparative Example 1). Also, Comparative Example 3 showed the same tendency as Comparative Example 2, and the equivalent series resistance value was also almost the same as that of Comparative Example 2. From this, it can be understood that when grooves are provided symmetrically with respect to the thickness direction of the tuning fork arm on the front and back of the tuning fork arm, the equivalent series resistance is smaller than that of Comparative Example 1, which is the prior art where the groove is arranged at the center of the tuning fork arm, regardless of the direction in which the groove is offset.

[0017] In Comparative Example 4, the equivalent series resistance value increased as the offset amount increased from 0 to 2 μm, and tended to decrease as the offset amount increased in the range where the offset amount was greater than 2 μm. From this, it can be understood that offsetting the groove on the first surface and the groove on the second surface in the two tuning fork arms in the opposite direction is inferior in terms of the equivalent series resistance compared to Comparative Example 1.

[0018] It can be seen that in the examples, as the offset amount increases, the equivalent series resistance decreases, and the equivalent series resistance is smaller than that in the case of an offset amount of 0 (Comparative Example 1). In particular, when the absolute value of the offset amount is about 1.0 μm or more, a smaller equivalent series resistance value is shown compared to any of the conditions of Comparative Examples 1 to 4. From this, it can be understood that the examples of the present invention can most effectively reduce the equivalent series resistance compared to Comparative Examples 1 to 4.

[0019] Here, in a tuning fork type vibrator, by making the groove provided in the tuning fork arm as wide as possible and making the width of the wall portion from the side surface of the tuning fork arm to the groove small, the distance between the excitation electrode provided on the side surface of the tuning fork arm and the excitation electrode provided on the side surface of the groove becomes small, and as a result, a tuning fork type vibrator with a small equivalent series resistance can be obtained. However, a tuning fork type vibrator with a small wall portion width has low strength, and the shock resistance of the vibrator has been a problem. In particular, as the miniaturization of the tuning fork type vibrator progresses, the dimensions of the tuning fork arms are reduced, so the wall portion becomes thinner, and as a result, the strength is likely to decrease.

[0020] In the examples of the present invention, by adopting a configuration in which the grooves provided on the first surface and the second surface of the tuning fork arm are arranged at positions asymmetric with respect to the thickness direction of the tuning fork arm, compared with the configurations shown in Comparative Examples 2 to 4, in which the grooves provided on the first surface and the second surface of the tuning fork arm are symmetric with respect to the thickness direction of the tuning fork arm, it is expected that when an impact or the like is applied to the vibrator, the stress of the entire tuning fork arm is dispersed, thereby relaxing local stress concentration, and also the rigidity is relatively easily maintained. Also, since the equivalent series resistance is smaller than that of Comparative Example 1, it is possible to reduce the equivalent series resistance while ensuring a predetermined width of the wall portion and maintaining the strength. By appropriately adjusting the offset amount of the groove, it is possible to realize a high-performance vibrator having impact resistance while reducing the equivalent series resistance.

[0021] The tuning fork type oscillator of the present invention has been described above based on examples, but the tuning fork type oscillator of the present invention is not limited to the form shown in the examples. In the examples, the tuning fork arms and the grooves formed on the tuning fork arms have a rectangular cross-section, but they are not limited to a rectangular cross-section. For example, when a tuning fork type quartz oscillator is formed from a quartz substrate by wet etching, etching residue is generated due to the anisotropy of the quartz, but the tuning fork arms and grooves may have a roughly rectangular cross-section or a roughly U-shaped cross-section that includes the etching residue. [Explanation of Symbols]

[0022] 1 base 2,3,41 Tuning Fork Arm 21,22,31,32,42 groove 4 connecting electrodes 5,5a,5b Excitation electrode

Claims

1. A tuning fork vibrator having a base and two tuning fork arms extending from the base, wherein grooves are formed on the first surface of the tuning fork arms and on the second surface facing the first surface, The widthwise center of the groove formed on the first surface of the tuning fork arm is offset from the widthwise center of the tuning fork arm in a first direction toward the space between the two tuning fork arms. A tuning fork vibrator characterized in that the center in the width direction of the groove formed on the second surface of the tuning fork arm is offset from the center in the width direction of the tuning fork arm in a second direction opposite to the first direction.

2. The tuning fork vibrator according to claim 1, characterized in that the width of the groove is approximately 80% of the width of the tuning fork arm.

3. The tuning fork vibrator according to claim 1, characterized in that the offset amount of the center in the width direction of the groove is a maximum of 7% with respect to the width of the tuning fork arm.

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