JP5387867B2 - Vibrating piece - Google Patents

Description

  The present invention relates to a piezoelectric vibrating piece.

  In a piezoelectric vibrating piece having a pair of vibrating arms extending from a base, it is known that a vibration is not easily transmitted to the base by forming a notch in the base (Patent Document 1). According to this, it is possible to prevent the vibration from being transmitted (vibration leakage) to the fixed portion of the base portion with the package and to stabilize the CI value. However, when the cut is formed, instead of preventing vibration leakage, the bending strength is lowered and the strength against the drop impact is lowered.

JP 2002-261575 A

  It is an object of the present invention to prevent vibration leakage by increasing bending strength and minimizing a decrease in strength against a drop impact.

(1) The piezoelectric vibrating piece according to the present invention is
A pair of cuts are formed in opposite directions along one straight line so that a shape confined on the front and back surfaces appears, and the first and second parts located on both sides of the pair of cuts, and the pair of cuts A connecting portion connecting the first and second portions between the base portion,
A pair of vibrating arms extending parallel to the front and back surfaces from the first portion;
Have
In the cross section orthogonal to the front and back surfaces and including the one straight line, the connecting portion has a shape in which a triangle is connected to both sides of the rectangle, a shape in which semicircles are connected to both sides of the rectangle, a shape of a group consisting of a rhombus and a circle Is one of the shapes. According to the present invention, since the cross section of the connecting portion has the shape described above, the connecting portion is easily deformed in the direction in which the front and back surfaces are directed, and is not easily deformed in the direction orthogonal thereto. The orthogonal direction has a high bending strength. This can be clarified by calculating the section moment of inertia and section modulus in each direction. (Details will be described later). Therefore, vibration leakage can be prevented by the ease of bending in the direction where the front and back faces, and on the other hand, the strength against drop impact can be improved by increasing the bending strength in the direction perpendicular to the front and back directions. Can do.
(2) In this piezoelectric vibrating piece,
A pair of support arms extending from the second portion of the base may be further included.
(3) In this piezoelectric vibrating piece,
The base and the pair of vibrating arms are made of quartz, and the crystal orientation is such that the front and back surfaces face the Z-axis direction, and the pair of vibrating arms extends from the base along the Y-axis. Also good.
(4) In this piezoelectric vibrating piece,
A through hole penetrating the front and back surfaces may be formed in the connection portion.

FIG. 1 is a plan view showing a piezoelectric vibrating piece according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the piezoelectric vibrating piece shown in FIG. 1 taken along the line II-II. FIG. 3 is a diagram showing a rectangular cross section in which the cross sectional secondary moment Iz is the same as the cross section shown in FIG. 4 is an enlarged sectional view taken along line IV-IV of the piezoelectric vibrating piece shown in FIG. FIG. 5 is a diagram for explaining the operation of the piezoelectric vibrating piece according to the present embodiment. 6A is a diagram showing a first modification of the embodiment of the present invention, and FIG. 6B has the same cross-sectional secondary moment Iz as the cross-section shown in FIG. 6A. It is a figure which shows a rectangular cross section. FIG. 7A is a diagram showing a second modification of the embodiment of the present invention, and FIG. 7B has the same cross-sectional secondary moment Iz as the cross-section shown in FIG. It is a figure which shows a rectangular cross section. FIG. 8A is a diagram showing a third modification of the embodiment of the present invention, and FIG. 8B has the same cross-sectional secondary moment Iz as the cross-section shown in FIG. 8A. It is a figure which shows a rectangular cross section. FIG. 9 is a diagram showing a fourth modification of the embodiment of the present invention.

  FIG. 1 is a plan view showing a piezoelectric vibrating piece according to an embodiment of the present invention. The bottom view appears symmetrically with the plan view. The piezoelectric vibrating piece (for example, a tuning fork type piezoelectric vibrating piece) is made of a piezoelectric material such as quartz, lithium tantalate, or lithium niobate. When the piezoelectric vibrating piece is made of quartz, the quartz wafer is cut out by rotating in the range of 0 to 5 degrees clockwise around the Z axis in an orthogonal coordinate system composed of the X, Y, and Z axes. A crystal Z plate obtained by cutting and polishing to a predetermined thickness is used. The piezoelectric vibrating piece includes a base portion 10 and a pair of vibrating arms 12 extending from the base portion 10.

  The base 10 is formed with a pair of cuts 14 in the opposing direction along one straight line so that a shape confined to the front and back surfaces appears. The base portion 10 includes first and second portions 16 and 18 positioned on both sides of the pair of cuts 14 and a connection portion 20 that connects the first and second portions 16 and 18 between the pair of cuts 14. And including. Since the transmission of the vibration of the vibrating arm 12 is blocked by the notch 14, it is possible to suppress the vibration from being transmitted to the outside (vibration leakage) through the base 10 and the support arm 30 and to prevent the CI value from increasing. . As the length (depth) of the cut 14 is longer (deeper) within a range in which the strength of the base 10 can be secured, the vibration leakage suppressing effect is larger. The width between the pair of cuts 14 (the width of the connecting portion 20) may be smaller or larger than the distance between the opposing side surfaces of the pair of vibrating arms 12, or the mutual distance between the pair of vibrating arms 12. The distance may be smaller or larger than the distance of the side surface facing the opposite direction.

  FIG. 2 is an enlarged cross-sectional view of the piezoelectric vibrating piece shown in FIG. 1 taken along the line II-II. That is, FIG. 2 shows a cross section of the connecting portion 20 that is orthogonal to the front and back surfaces and includes one straight line (II-II line). In this cross section, the connecting portion 20 has a shape in which a triangle (its side) is connected to both sides of the rectangle (the opposite side).

  According to the present embodiment, since the cross section of the connecting portion 20 has the shape described above, the connecting portion 20 is easily deformed in the direction in which the front and back surfaces are directed, and is not easily deformed in a direction perpendicular to the front and back surfaces. This is apparent when calculating the sectional moment of inertia and section modulus in each direction. The calculation results for one example of the connection unit 20 are shown in the following table.

  In Table 1, W1 is the width of the rectangular portion of the connecting portion 20, W2 is the width of the triangular portion of the connecting portion 20 (projecting length from the rectangular portion), and D1 is the thickness of the connecting portion 20. In the calculation of the secondary moment of section and the section modulus, the width direction of the connecting portion 20 is the X-axis direction and the thickness direction is the Z-axis direction so as to correspond to the crystal orientation.

In the connection portion 20, the cross-sectional secondary moment Iz in the Z-axis direction is 1.54 × 10 ⁷ μm ⁴ . The cross-sectional secondary moment Iz represents the ease of deformation in the Z-axis direction. On the other hand, the cross-sectional secondary moment Ix representing the ease of deformation in the X-axis direction is 8.155 × 10 ⁷ μm ⁴ .

FIG. 3 is a diagram showing a rectangular cross section in which the cross sectional secondary moment Iz is the same as the cross section shown in FIG. In the example shown in FIG. 3, the cross-sectional secondary moment Ix in the X-axis direction is 5.28 × 10 ⁷ μm ⁴ as shown in Table 1.

  That is, when the cross-sectional shapes shown in FIGS. 2 and 3 are compared, the cross-sectional secondary moment in the X-axis direction is larger in the shape shown in FIG. That is, when the ease of deformation (Iz) in the direction in which the front and back surfaces are directed is the same, the cross-sectional shape of the connecting portion 20 according to the present embodiment is orthogonal to the direction in which the front and back surfaces are directed, compared to the rectangular cross-sectional shape. Hard to deform in the direction.

  The section modulus Zx is a value indicating the bending strength in the Z-axis direction. As a result, even if the cross-sectional shapes shown in FIGS. 2 and 3 are compared, Zx in FIG. That is, when Iz is the same, the connecting portion 20 according to the present embodiment has a higher bending strength in a direction orthogonal to the direction in which the front and rear surfaces face, that is, the strength against a drop impact is higher than the rectangular cross-sectional shape. .

  Therefore, according to the present embodiment, vibration leakage is prevented by the ease of bending (stress concentration) in the direction in which the front and rear surfaces face, and the bending strength in the direction orthogonal to this can be increased. Strength against drop impact can be improved.

  4 is an enlarged sectional view taken along line IV-IV of the piezoelectric vibrating piece shown in FIG. The pair of vibrating arms 12 extends in parallel to the front and back surfaces from the first portion 16 of the base 10. The resonating arm 12 has front and back surfaces that are opposite to each other, and first and second side surfaces 22 and 24 that connect the front and back surfaces on both sides. When the piezoelectric vibrating piece is made of crystal, with respect to crystal orientation, the first side surface 22 faces the + direction of the X axis, the second side surface 24 faces the − direction of the X axis, and extends from the base 10 along the + Y axis. Configure to extend.

  The first side surface 22 of one (left side in FIG. 4) and the second side surface 24 of the other (right side in FIG. 4) vibration arm 12 are arranged in parallel. The first side surface 22 is formed to have a mountain shape that increases in the center direction of the thickness of the vibrating arm 12 defined by the distance between the front and back surfaces. The height of the mountain shape drawn by the first side surface 22 is more than 0% and not more than 12.5% of the width of the vibrating arm 12 defined by the distance between the first and second side surfaces 22 and 24.

  The resonating arm 12 is wide at the base portion connected to the base portion 10 toward the base portion 10 and is connected to the base portion 10 with a wide width, so that the rigidity is high. The width defined by the distance between the first and second side surfaces 22 and 24 of the vibrating arm 12 is narrowed from the base 10 toward the tip. By forming such a taper, the vibrating arm 12 is easily vibrated. However, the resonating arm 12 is reverse-tapered at a position close to the tip so that the width increases toward the tip. By applying the reverse taper, the tip portion functions as a weight, so that the vibration frequency can be lowered. The vibrating arm 12 is formed so that the position where the taper is reversed to the reverse taper is located closer to the tip than the long groove 26.

  In the vibrating arm 12, long grooves 26 extending in the longitudinal direction are formed on the front and back surfaces, respectively. Since the long arm 26 makes the vibrating arm 12 easy to move and vibrates efficiently, the CI value can be lowered. The long groove 26 has a length of 50 to 70% of the length of the vibrating arm 12. The long groove 26 has a width of 60 to 90% of the width of the vibrating arm 12.

  The long groove 26 includes a first inner surface that extends back to back with the first side surface 22, and a second inner surface that extends back to back with the second side surface 24. The angle with respect to the front and back surfaces of the first inner surface is closer to that of the second inner surface. The first inner surface may be a flat surface. The second inner surface may also be a flat surface, but in the example shown in FIG. 4, surfaces with different angles are connected. The first and second side surfaces 22 and 24 have an angle with respect to the front and back surfaces (an angle of a portion connected to the front and back surfaces) closer to vertical than the second inner surface.

  The piezoelectric vibrating piece has a pair of support arms 30 extending from the second portion 18 of the base 10. The pair of support arms 30 extend in directions opposite to the direction in which the pair of vibrating arms 12 extend from the base portion 10 and extend in directions opposite to each other, and further bend and extend in the direction in which the pair of vibrating arms 12 extend. By bending, the support arm 30 is reduced in size. The support arm 30 is a part that is attached to a package (not shown) or the like, and the vibration arm 12 and the base 10 are in a floating state by being attached by the support arm 30.

  An excitation electrode film 40 is formed on the vibrating arm 12. The excitation electrode film 40 may have a multilayer structure including a base Cr film having a thickness of 100 to 300 mm and an Au film having a thickness of 200 to 500 mm formed on the Cr film. It is known that the Cr film has high adhesion to quartz, and the Au film has low electrical resistance and is difficult to oxidize.

  The excitation electrode film 40 includes front and back electrode films (a plurality of front electrode films and a plurality of back electrode films) formed on the front and back surfaces, and first and second surfaces formed on the first and second side surfaces 22 and 24, respectively. Two side surface electrode films, and first and second inner surface electrode films formed on the first and second inner surfaces, respectively. The plurality of front electrode films are electrically separated from each other, and the plurality of back electrode films are electrically separated from each other.

  The excitation electrode film 40 constitutes first and second excitation electrodes 42 and 44. In one vibrating arm 12, the voltage is applied between the first and second excitation electrodes 42 and 44, and the first and second side surfaces 22 and 24 of the vibrating arm 12 are expanded and contracted to vibrate the vibrating arm 12. Let It is known that the CI value of the first and second excitation electrodes 42 and 44 decreases as the length increases to 70% of the vibrating arm 12.

  The first excitation electrode 42 includes first and second inner surface electrode films formed on the first and second inner surfaces of the long groove 26, and front and back electrode films respectively formed on the front and back surfaces. The first and second inner surface electrode films formed in one long groove 26 are continuously formed and electrically connected to each other. Further, the first and second inner surface electrode films formed in one long groove 26 are formed on one of the front and back electrode films (for example, the first and second inner surface electrode films formed in the long groove 26 formed on the surface). Corresponding to the surface electrode film) is formed continuously and electrically connected. Further, the first and second inner surface electrode films formed in the long groove 26 on one of the front and back surfaces (for example, the front surface) and one of the front and back electrode films (for example, the front electrode film) electrically connected to these, The first and second inner surface electrode films formed in the other (for example, the back surface) long groove 26 and the other of the front and back electrode films (for example, the back electrode film) electrically connected thereto are electrically connected. . That is, the pair of first excitation electrodes 42 formed on the front and back surfaces are electrically connected. The pair of first excitation electrodes 42 formed on one vibrating arm 12 is connected to extraction electrodes 48 formed on the front and back surfaces of the base 10, and these extraction electrodes 48 are connected to the other vibrating arm 12. Electrical connection is established by connecting to the first or second side electrode film.

  The second excitation electrode 44 includes first and second side surface electrode films formed on the first and second side surfaces 22 and 24, and front and back electrode films formed on the front and back surfaces. Specifically, front and back electrode films are formed so as to be continuous with the first side electrode film, and similarly, other front and back electrode films are formed so as to be continuous with the second side electrode film. The first and second side electrode films are electrically connected. The electrical connection is made by a connection electrode 46 formed on at least one (or both) of the front and back surfaces of the vibrating arm 12 where the long groove 26 is not formed (for example, the tip).

  The first excitation electrode 42 formed on one vibrating arm 12 and the second excitation electrode 44 formed on the other vibrating arm 12 are electrically connected by a lead electrode 48 on the base 10. . The extraction electrode 48 is formed up to the support arm 30 arranged next to the vibrating arm 12 on which the second excitation electrode 44 is formed. The extraction electrode 48 may be formed on the front and back surfaces (or further side surfaces) of the support arm 30. On the support arm 30, the extraction electrode 48 can be used as an electrical connection portion with the outside.

  FIG. 5 is a diagram for explaining the operation of the piezoelectric vibrating piece according to the present embodiment. As shown in FIG. 5, a voltage is applied to the first and second excitation electrodes 42 and 44 of one vibrating arm 12, and a voltage is applied to the first and second excitation electrodes 42 and 44 of the other vibrating arm 12. Applied. Here, the first excitation electrode 42 of one vibrating arm 12 and the second excitation electrode 44 of the other vibrating arm 12 have the same potential (+ potential in the example of FIG. 5), and the second excitation electrode 12 of one vibrating arm 12 has the second potential. The first excitation electrode 42 and the second excitation electrode 44 are crossed so that the first excitation electrode 42 and the first excitation electrode 42 of the other vibrating arm 12 have the same potential (-potential in the example of FIG. 5). It is connected to an AC power supply by wiring, and an alternating voltage as a drive voltage is applied. An electric field is generated by the applied voltage as shown by an arrow in FIG. 5, whereby the vibrating arms 12 are excited so as to be in opposite-phase vibrations (so that the distal ends of the vibrating arms 12 approach and separate from each other). Bends and vibrates. The alternating voltage is adjusted so as to vibrate in the basic mode.

(First modification)
FIG. 6A is a diagram showing a first modification of the embodiment of the present invention. In this modification, the connecting portion 120 has a rhombus shape in a cross section orthogonal to the front and back surfaces and including one straight line. Even in this case, it is clear from the calculation that the same effect as the above-described embodiment can be obtained. FIG. 6B is a diagram showing a rectangular cross section in which the cross section secondary moment Iz is the same as the cross section shown in FIG. The calculation results are shown in Table 2.

(Second modification)
FIG. 7A is a diagram showing a second modification of the embodiment of the present invention. In this modification, the connecting portion 220 has a shape in which semicircles are connected to both sides of a rectangle in a cross section orthogonal to the front and back surfaces and including one straight line. Even in this case, it is clear from the calculation that the same effect as the above-described embodiment can be obtained. FIG. 7B is a diagram showing a rectangular cross section in which the cross sectional secondary moment Iz is the same as that shown in FIG. Table 3 shows the calculation results.

(Third Modification)
FIG. 8A is a diagram showing a third modification of the embodiment of the present invention. In this modification, the connection part 320 is circular in the cross section orthogonal to the front and back surfaces and including one straight line. Even in this case, it is clear from the calculation that the same effect as the above-described embodiment can be obtained. FIG. 8B is a diagram showing a rectangular cross section in which the cross sectional secondary moment Iz is the same as the cross section shown in FIG. Table 4 shows the calculation results.

(Fourth modification)
FIG. 9 is a diagram showing a fourth modification of the embodiment of the present invention. In this modification, a through hole 422 that penetrates the front and back surfaces is formed in the connection portion 420. The through hole 422 is formed only by an inner wall surface perpendicular to the front and back surfaces. Even if the through hole 422 is formed, the above-described effects can be achieved.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and results). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  DESCRIPTION OF SYMBOLS 10 ... Base part, 12 ... Vibrating arm, 14 ... Cutting, 16 ... 1st part, 18 ... 2nd part, 20 ... Connection part, 22 ... 1st side surface, 24 ... 2nd side surface, 26 ... Long groove, DESCRIPTION OF SYMBOLS 30 ... Support arm, 40 ... Excitation electrode film | membrane, 42 ... 1st excitation electrode, 44 ... 2nd excitation electrode, 46 ... Connection electrode, 48 ... Extraction electrode, 120 ... Connection part, 220 ... Connection part, 320 ... Connection Part, 420 ... connection part, 422 ... through hole

Claims (4)

A base portion having a first portion, a second portion, and a connection portion disposed between the first portion and the second portion in plan view;
A pair of vibrating arms extending in parallel from the first portion in plan view;
With
The connection portion has a width in a direction orthogonal to a direction in which the first portion, the connection portion, and the second portion are arranged in a plan view, and the first portion and the second portion Narrower than the width of the part,
The connection part has an outer shape of a cross section in a thickness direction orthogonal to a direction in which the first part, the connection part, and the second part are arranged.
A first side and a second side that are parallel and define the thickness;
Within the thickness range, connected to one end of the first side and one end of the second side, from the first side and the second side A first outer portion bent so as to protrude toward the direction of separation;
And within the thickness range, and connected to the other end of the first side and the other end of the second side, and the first side and the second side A second outer portion bent so as to protrude in a direction away from the side;
A shape having a vibration Dohen. In Dohen vibration according to claim 1,
It said second Dohen vibration are further Nde contains an extending Biteiru pair of support arms from a portion of the base. In Dohen vibration according to claim 1 or claim 2,
The base and the pair of vibrating arms are made of quartz, and the crystal orientation has the thickness
Direction is the Z-axis direction, Dohen vibration of the pair of vibrating arms from the base portion extends along the Y-axis. In Dohen vibration according to any one of claims 1 to 3,
The connecting portion Dohen vibration has a through hole extending through in the direction of the thickness.