JP2008281455A - Acceleration sensor element - Google Patents

Abstract

An acceleration sensor element is provided which is suitable for simplification, miniaturization, and low power consumption and has improved detection sensitivity.
When a torsional vibration that rotates about a length direction is caused in a pair of tuning fork arms that extend from a tuning fork base, and an acceleration that is perpendicular to a main surface of the pair of tuning fork arms is applied, The pair of tuning fork arms are displaced in the horizontal direction with respect to the main surface by the Coriolis force, and in the acceleration sensor element configured to detect charges generated by the horizontal displacement, the tuning fork body is formed of quartz, The pair of tuning fork arms are excited in a direction perpendicular to the main surface of the tuning fork arms by a drive electrode provided on the pair of tuning fork arms, and a twisting phenomenon is generated in the pair of tuning fork arms. The electric charge due to the horizontal displacement with respect to the main surface of the pair of tuning fork arms due to force is detected by a detection electrode provided on the tuning fork arm.
[Selection] Figure 1

Description

  The present invention relates to an acceleration sensor element using Coriolis force, particularly to an acceleration sensor element having a sensor body as a piezoelectric body.

(Background of the Invention)
There are many types of acceleration sensor elements such as a mechanical type and an electronic type, and one of them uses the Coriolis force by the present inventors (Non-Patent Document 1). As a sensor element using Coriolis force, an angular velocity sensor element is generally prevalent, and in the present invention, an acceleration sensor is configured based on the opposite idea.

(Example of conventional technology)
FIG. 16 is a diagram of an acceleration sensor element for explaining a conventional example (Non-Patent Document 1). FIG. 16 (a) is a front view, FIG. 16 (b) is an AA sectional view, and FIG. It is BB sectional drawing.

  The acceleration sensor element includes a tuning fork main body 1, a driving piezoelectric body 2, and a detection piezoelectric body 3. The tuning fork main body 1 is made of stainless steel, for example, and a pair of tuning fork arms 5 (ab) extend from the tuning fork base 4. Here, for convenience, the length direction is y, the width direction is x, and the thickness direction is z. These coordinate axes (xyz) are geometrical axes, and are not crystal axes (XYZ) of crystal crystals, for example.

  Both the driving piezoelectric member 2 and the detecting piezoelectric member 3 are made of, for example, piezoelectric ceramics. The driving piezoelectric body 2 includes first to fourth piezoelectric bodies 2 (abcd) provided on both main surfaces of the tuning fork base 4 below the tuning fork arms 5 (ab). The first and second piezoelectric bodies 2 (ab) and the third and fourth piezoelectric bodies 2 (cd) facing each other between the main surfaces of the first to fourth piezoelectric bodies 2 (abcd), and between the same main surfaces The first and third piezoelectric bodies 2 (ac) and the second and fourth piezoelectric bodies 2 (bd) that are parallel to each other have reverse characteristics.

  Specifically, each of the first to fourth piezoelectric bodies 2 (abcd) is indicated by an arrow by an alternating voltage (not shown) as shown in the plan views seen from the heads of FIGS. It expands and contracts in the width direction x. When the first and third piezoelectric bodies 2 (ac) are expanded, the second and fourth piezoelectric bodies 2 (bd) are contracted (FIG. 17 (a)). Accordingly, each tuning fork arm 5 (ab) is bent in an arc shape from one main surface to the other main surface side (FIG. 17 (b)).

  On the contrary, when the first and third piezoelectric bodies 2 (ac) are contracted, the second and fourth piezoelectric bodies 2 (bd) expand (FIG. 18 (a)). Therefore, each tuning fork arm 5 (ab) bends in an arc shape from the other principal surface to the one principal surface side (see FIG. 18 (b). In short, the pair of tuning fork arms 5 (ab) are each piezoelectric fork of the tuning fork base 4. Arcs in the same direction from one main surface side to the other main surface side and from the other main surface side to the one main surface side by an alternating voltage that is in reverse phase between the bodies 2 (ac) and 2 (bd) Bend.

  In this case, since the root portion of the pair of tuning fork arms 5 (ab) is constrained by the tuning fork base portion 4, the outer surface of each tuning fork arm 5 (ab) becomes a free end, and the arcuate shape of each outer surface. Deflection (displacement) increases. Accordingly, the pair of tuning fork arms 5 (ab) generate rotational moments (± M) in opposite directions from the outer surface toward the inner surface on the same plate surface side.

  As a result, the pair of tuning fork arms 5 (ab) are rotated in opposite directions by the alternating voltage, and torsional vibrations in the opposite direction of rotation occur between the pair of tuning fork arms 5 (ab). Each piezoelectric body 2 (abcd) as the driving electrode 2 is formed by continuously forming the piezoelectric body 2 (ac) on one main surface side and the piezoelectric body 2 (bd) on the other main surface side. Even when the piezoelectric bodies are formed one by one, the torsional vibration in which both ends are bent in the same direction is generated.

  As shown in FIG. 19, the acceleration a (m / sec 2) from one main surface side of the tuning fork main body 1 during the torsional vibration caused by the rotational moments ± M in the opposite directions of the pair of tuning fork arms 5 (ab). Is added, the operation (operation) of each tuning fork arm 5 (ab) is as follows.

  That is, when the pair of tuning fork arms 5 (ab) first generate torsional vibrations that rotate from one principal surface to the other principal surface direction, each tuning fork arm 5 (ab) has a direction opposite to each other. “FIG. 19A” in which Coriolis force Fc is generated from the inside to the outside. Next, when the torsional vibration is reversed and a rotational moment ± M is generated in the opposite direction from the other principal surface to one principal surface direction, each tuning fork arm 5 (ab) has a Coriolis force from the outside to the inside. “FIG. 19B” in which Fc occurs.

  In this case, by the Coriolis force Fc acting from the inside to the outside of the pair of tuning fork arms 5 (ab), the inner side surface is extended and the outer side surface is reduced with the tuning fork base 4 of each tuning fork arm 5 (ab) as a substantially fixed end. As a result, the leg is bent from the inside to the outside and opened (FIG. 20 (ab)). On the contrary, when the Coriolis force Fc acts from the outside to the inside, the inner side surface of each tuning fork arm 5 (ab) shrinks and the outer side surface expands, and the outer side surface is bent from the outer side surface to the inner side surface to close the leg. FIG. 21 (ab).

  In short, the pair of tuning fork arms 5 (ab) generate bending vibrations that bend (displace) in opposite directions. In other words, the pair of tuning fork arms 5 (ab) generate so-called tuning fork vibration that repeats opening and closing legs. In this case, the vibration frequency of the tuning fork vibration coincides with the vibration frequency of the torsional vibration that rotates in opposite directions based on the arcuate bending of the pair of tuning fork arms 5 (ab).

  The piezoelectric body for detection 3 is formed with an inner fifth piezoelectric body 3a and an outer sixth piezoelectric body 3b along the length direction on both main surfaces of each tuning fork arm 5 (ab). Figure (c) ". The fifth and sixth piezoelectric bodies 3 (ab) expand and contract in the same manner following the expansion and contraction in the length direction (y direction) of the pair of tuning fork arms 5 (ab), and generate positive and negative charges. Here, positive and negative voltages (charges) are generated on the surfaces of the fifth and sixth piezoelectric bodies 3 (ab) with the stainless steel of the tuning fork main body 1 being the ground potential.

From this, when the pair of tuning fork arms 5 (ab) are opened or closed (tuning fork vibration) by the Coriolis force Fc based on the acceleration a, the detecting piezoelectric body 3 expands and contracts, and each of the inner and outer piezoelectric bodies 3. Positive and negative charges with opposite signs are generated in (ab). Therefore, acceleration can be measured by detecting these positive and negative charges.
Proceedings of Symposium on Basics and Applications of Ultrasonic Electronics, Accelerometer Using Coriolis Force Phenomena, November 1998, 201-202. JP 11-89257 A

(Problems of conventional technology)
However, the acceleration sensor element configured as described above has a structure in which a plurality of piezoelectric bodies (piezoelectric ceramics) 2 (abcd) and 3 (ab) are attached to a tuning fork body 1 made of stainless steel. For this reason, for example, the piezoelectric bodies 2 (abcd) and 3 (ab) are externally connected using conductive wires to connect the piezoelectric bodies 2 and 3 having the same potential, and thus become complicated and large.

  Further, by the expansion and contraction of the first to fourth piezoelectric bodies 2 (abcd) as the driving piezoelectric bodies 2, each tuning fork arm 5 (ab) of the tuning fork main body 1 is forcibly bent into an arc shape to obtain torsional vibration. . Therefore, a large drive power is required to cause torsional vibration in each tuning fork arm 5 (ab). In other words, when the driving power is reduced, the detection sensitivity is lowered.

  For these reasons, the acceleration sensor element having the above-described configuration has problems that are unsuitable as a consumer acceleration sensor element including automobiles in terms of simplification, miniaturization, low power consumption, detection sensitivity, and the like.

(Object of invention)
SUMMARY OF THE INVENTION An object of the present invention is to provide an acceleration sensor element that is suitable for simplification, miniaturization, and low power consumption and has improved detection sensitivity.

(Equivalent to the first to fourth embodiments)
According to the present invention, as shown in the claims (Claim 1), the pair of tuning fork arms extending from the tuning fork base of the tuning fork main body generates torsional vibrations that rotate about the length direction, and When acceleration in the vertical direction is applied to the main surface of the tuning fork arm, the Coriolis force causes a horizontal displacement with respect to the main surface of the pair of tuning fork arms, and the charge generated by the horizontal displacement is detected. In this acceleration sensor element, the tuning fork body is formed of a quartz crystal as a piezoelectric body, and the pair of tuning fork arms are perpendicular to the main surface of the tuning fork arm by a drive electrode provided on the pair of tuning fork arms. The tuning fork arms are excited and cause a twisting phenomenon due to centrifugal force, and the tuning fork arms are charged with a displacement in the horizontal direction relative to the principal surfaces of the pair of tuning fork arms due to the Coriolis force caused by the acceleration. A configuration detected by the detection electrode.

  With such a configuration, crystal as a piezoelectric body is directly used as the tuning fork body, so that the drive electrode and detection electrode having the same potential can be internally connected on the tuning fork body, and the acceleration sensor element can be simplified and miniaturized. Can be planned. In addition, the piezoelectric power of the quartz crystal itself excites in the vertical direction, and the torsional vibration is generated by the centrifugal force. Therefore, the driving power is reduced compared to the case where the torsional vibration is forcibly generated by the piezoelectric ceramics. Detection sensitivity can be increased.

(Embodiment section)
According to a second aspect of the present invention (corresponding to the first and third embodiments), the vibrations perpendicular to the main surface of the pair of tuning fork arms are set in the same direction between the pair of tuning fork arms. The rotational direction of the torsional vibration of the tuning fork arm is reversed, and the horizontal displacement due to the acceleration (Coriolis force) is opposite to each other (open leg or closed leg). In this case, the displacement of the pair of tuning fork arms due to acceleration results in the tuning fork vibration of the open leg or the closed leg, so that the amplitude can be increased by the physical resonance phenomenon and the detection sensitivity can be increased.

  In the third aspect (corresponding to the second and fourth embodiments), vibrations perpendicular to the main surface of the pair of tuning fork arms are opposite to each other between the pair of tuning fork arms, The rotational direction of the torsional vibration of the arm is the same direction, and the horizontal displacement due to the acceleration (Coriolis force) is the same direction. In this case, the pair of tuning fork arms are excited in the opposite vertical directions. Therefore, as compared with the case where the pair of tuning fork arms are excited in the same vertical direction (Claim 2), the vibration displacement is canceled by the tuning fork base and vibration leakage is reduced.

  According to claim 4 (corresponding to the first to fourth embodiments), in claim 1, the tuning fork main body is bonded by direct bonding with the opposite directions of ± X axes of two crystal pieces. As a result, even if the electric field generated in the X-axis direction (width direction) of the tuning fork arm is the same direction, the expansion and contraction directions in the Y-axis direction (length direction) on both main surfaces with the joint surface of the tuning fork arm as a boundary are reversed. Can be oriented. Therefore, the electrode formation on the inner surface of the tuning fork arm is facilitated.

  In claim 5 (corresponding to the first and second embodiments), in claim 1, the tuning fork main body is a two-leg tuning fork in which the pair of tuning fork arms extends only in one direction from the tuning fork base. And Thereby, since the tuning fork main body is a simplified two-leg tuning fork (simple two-leg tuning fork), the configuration can be simplified and the miniaturization can be promoted.

  In claim 6 (corresponding to the third and fourth embodiments), in claim 1, the tuning fork main body is a four-legged H-shaped pair of tuning fork arms extending from the tuning fork base in opposite directions. Two tuning forks. As a result, two tuning forks are formed, so that it is basically possible to detect a large amount of charge due to the Coriolis force and increase the sensitivity.

(First embodiment A, claims 1, 2, 5)
FIG. 1 is a diagram of an acceleration sensor element for explaining a first embodiment of the present invention. FIG. 1 (a) is a front view, FIG. 1 (b) is a plan view seen from the head showing electrode arrangement, and FIG. (C) is a connection diagram seen from the head. The same reference numerals are given to the same parts as those in the previous conventional example, and the description thereof is simplified or omitted, and in FIG. 1 (c), the detailed symbols are omitted for convenience.

  In the acceleration sensor element, the tuning fork main body 1 in the conventional example is a quartz crystal as a piezoelectric body. Hereinafter, this is referred to as a tuning fork crystal piece 6. The tuning-fork crystal piece 6 is composed of a Z-cut plate whose main surface is orthogonal to the Z-axis. The length direction in which the pair of tuning-fork arms 5 (ab) extend from the tuning fork base 4 is the Y-axis, the width direction is the X-axis, and the thickness is The direction is the Z axis. The pair of tuning fork arms 5 (ab) of the tuning fork crystal piece 6 are provided with a drive electrode 7 and a detection electrode 8.

  The drive electrode 7 includes first to fourth electrodes 7 (abcd) formed on both main surfaces of the pair of tuning fork arms 5 (ab). The first and second electrodes 7 (ab) are formed on the inner surfaces of the tuning fork arms 5 (ab), and the third and fourth electrodes 7 (cd) are formed on the outer surfaces of the main surfaces. In each of the pair of tuning fork arms 5 (ab), two pairs of diagonal directions, the first electrode 7a on the inner side of one main surface and the fourth electrode 7d on the outer side of the other main surface, the third electrode 7c on the outer side of the main surface, and others The second electrode 7b on the inner side of the main surface is connected with the same potential.

  Between the pair of tuning fork arms 5 (ab), the first and fourth electrodes 7 (ad) of one tuning fork arm 5a that are in a pair of diagonal directions (inclined left upward direction and right downward direction) and the other The second and third electrodes 7 (bc) of the tuning fork arm 5b are connected at the same potential. In addition, the second and third electrodes 7 (bc) of one tuning fork arm 5a and the first and fourth electrodes of the other tuning fork arm 5b, which are in another pair of diagonal directions (left diagonally downward direction, right upward direction). 7 (ad) is connected at the same potential.

  In each tuning fork arm 5 (ab), the first and fourth electrodes 7 (ad) of one tuning fork arm 5a and the second and third electrodes 7 (bc) of the other tuning fork arm 5b in a pair of diagonal directions. ) And the second and third electrodes 7 (bc) of one tuning fork arm 5a and the first and fourth electrodes 7 (ad) of the other tuning fork arm 5b which are in the diagonal direction of the other set are connected as opposite potentials. Then, an alternating voltage as a drive (drive) terminal D ± is applied.

  In short, the pair of tuning fork arms 5 (ab) is driven by the first to fourth electrodes 7 (abcd) of the drive electrode 7 so that each tuning fork arm 5 (ab) has a driving voltage that has a potential gradient along the polarity ± of the X axis. (Alternating voltage) D ± is applied. However, the connection is such that the potential gradient is reversed between the one main surface side and the other main surface side of the pair of tuning fork arms 5 (ab).

  The detection electrode 8 is formed with third and fourth electrodes 8 (ab) on both side surfaces of the pair of tuning fork arms 5 (ab). The fifth electrode 8a is formed on the inner surface of each tuning fork arm 5 (ab), and the sixth electrode 8b is formed on the outer surface of each tuning fork arm 5 (ab). The inner surface fifth electrode 8a and the outer surface sixth electrode 8b of each tuning fork arm 5 (ab) of the detection electrode 8 are connected to the detection terminal S ± as the same potential.

  These drive electrodes 7 “first to fourth electrodes 7 (a to d)” and detection electrodes 8 “third and fourth electrodes 8 (ab)” are arranged on the surface of the tuning fork crystal piece 6 by a wiring path (not shown). Commonly connected. Then, they are connected to drive terminals D ± and detection terminals S + as external terminals on the surface of the tuning fork base 4. The drive electrode 7 and the detection electrode 8 including these wiring paths are integrally formed by etching using a photo printing technique together with the outer shape processing of the tuning fork crystal piece.

  In such a case, for example, as shown in FIG. 2 (a), the first to fourth electrodes 7 (a to d) of the drive electrode 7 make one main surface side of each tuning fork arm 5a (lower side of the figure). For example, a positive voltage (+) is applied to the + X axis side, a negative voltage (−) is applied to the −X axis side, and a voltage in the opposite direction is applied to the other main surface side (upper side in the figure). Therefore, on one main surface side of one tuning fork arm 5a, an electric field E from the inner side to the outer side indicated by an arrow is generated from the first electrode 7a to the third electrode 7c.

  As a result, the electric field vector component Ex extending from the + X axis to the −X axis direction causes one main surface side of one tuning fork arm 5a to extend in the Y axis direction with the tuning fork base 4 as a fixed end (FIG. 2B). . This is due to the piezoelectric inverse effect that expands and contracts in the Y-axis direction when a voltage is applied in the X-axis direction. FIG. 2 (b) is a side view seen from the arrow direction A of FIG. 2 (a).

  On the other hand, on the other main surface side of one tuning fork arm 5a, the electric field vector from the −X axis to the + X axis direction (from the outside to the inside) among the electric fields generated from the fourth electrode 7d to the second electrode 7b. “FIG. 2 (a)” depending on the component, “FIG. Therefore, one tuning fork arm 5a bends from one main surface to the other main surface side (FIG. 2 (c)).

  In the other tuning fork arm 5b, as in the case of the one tuning fork arm 5a, one main surface side is in the + X axis direction to the -X axis direction (from the outside to the inside direction), and the other main surface side is in the + X axis direction from the -X axis to the + X axis direction (inside "Fig. 2 (a)" in which an electric field vector component is generated in the direction from the outside to the outside. Accordingly, in this case as well, as with one tuning fork arm 5a, the one main surface side expands and the other main surface side contracts, so that it bends from the one main surface side to the other main surface side [FIG. 2 (c).

  Therefore, the polarity between the main surfaces of the first and third electrodes 7 (ac) and the second and fourth electrodes 7 (bd) of the drive electrode 7 by the above-described connection of the pair of tuning fork arms 5 (ab) is great. When an inverted drive voltage (alternating voltage) D ± is applied, each tuning fork arm 5 (ab) repeatedly bends from one main surface side to the other main surface side and from the other main surface side to the one main surface side (so-called bending). vibration). In short, the pair of tuning fork arms 5 (ab) vibrate in the vertical direction and in the same direction with respect to the plate surface (main surface) (hereinafter referred to as vertical in-phase vibration).

  In this case, since the root portion of the pair of tuning fork arms 5 (ab) is restrained by the tuning fork base portion 4, each inner side surface of each tuning fork arm 5 (ab) becomes a fixed end, so that the outer side surface is a free end. Become. Therefore, as shown in the locus diagram of FIG. 3 (schematic plan view seen from the head), the pair of tuning fork arms 5 (ab) is subjected to centrifugal force on the outer surface from the inner surface by vertical in-phase vibration. As a result, a rotational moment ± M is generated.

  As a result, the pair of tuning fork arms 5 (ab) are accompanied by torsional vibrations rotating in opposite directions together with vertical in-phase vibrations. In the figure, the P0 line represents the initial state (stationary state) of the pair of tuning fork arms 5 (ab), and the P1 and P2 lines represent the pair of tuning fork arms 5 (ab) caused by vertical in-phase vibration centered on the Q point. A schematic moving state is shown.

  When acceleration a is applied from one main surface side while the pair of tuning fork arms 5 (ab) are in vertical in-phase vibrations with torsional vibrations in opposite directions, Coriolis force Fc is applied to each tuning fork arm 5 ( ab) occurs in the X-axis direction (width direction). Then, for torsional vibrations (rotational moments ± M) rotating in opposite directions, tuning fork vibrations (open legs and closed legs) at the same vibration frequency as vertical in-phase vibrations are generated as in the prior art (see FIGS. 20 and 21). (See figure).

  In this case, for example, each outer side surface (right half region) of the pair of tuning fork arms 5 (ab) is reduced and each inner side surface (left half region) is expanded, so that the pair of tuning fork arms 5 (ab) are opened. Then it becomes the following. That is, as shown in FIG. 4, electric fields P1 and P2 from the center to the inner surface and the outer surface are generated in one tuning fork arm 5a. On the other hand, on the other tuning fork arm 5b, electric fields P1 and P2 from the inner side surface and the outer side surface to the center are generated.

  Since the expansion and contraction directions are opposite between the outer side surface and the inner side surface of each tuning fork arm 5 (ab), the electric fields P1 and P2 are also opposite. Since the pair of tuning fork arms 5 (ab) bend in opposite directions, that is, are displaced in the opposite horizontal directions, the directions of the electric fields P1 and P2 are also reversed. These are derived from a piezoelectric phenomenon in which an electric field (positive and negative charges) is generated in the X-axis direction when the crystal axis expands and contracts in the Y-axis direction.

  For example, the electric field P1 from the center of one tuning fork arm 5a toward the inner side faces the first and second electrodes 7 (ab) inside the drive electrodes 7 on both main faces and the detection electrode 8 (first side) on the inner side. A decomposition vector component indicated by an arrow is generated between the five electrodes 8a). The electric field P2 from the center toward the outer surface is a decomposition vector component between the third and seventh electrodes 7 (cd) outside the drive electrodes 7 on both main surfaces and the detection electrode 8 (sixth electrode 8b) on the outer surface. Give rise to The other tuning fork arm 5b is decomposed in the same manner between the drive electrode 7 and the detection electrode 8 in the opposite direction to the one tuning fork arm 5a by the electric fields P1 and P2 opposite to the one tuning fork arm 5a. Produces a vector component.

  For these reasons, the tuning fork vibration generated by the Coriolis force Fc accompanying the acceleration a orthogonal to the plate surface of the tuning fork crystal piece 6 is caused by the first to fourth electrodes 7 (a) of the drive electrode 7 in one tuning fork arm 5a. To d), for example, a positive charge (+), and the third and fourth electrodes 8 (ab) of the detection electrode 8 generate a negative charge (−). On the other hand, in the other tuning fork arm 5 b, conversely, negative charge (−) is applied to the first to fourth electrodes 7 (ad) of the drive electrode 7, and the third and fourth electrodes 8 of the detection electrode 8. (Ab) generates a positive charge (+).

  Therefore, if these positive and negative charges (±) are detected by a detection circuit (not shown) connected to the detection terminal S ± by the connection shown in FIG. 1 (c), the acceleration a can be measured. Note that the generation of an electric field (positive and negative charges) due to tuning fork vibration has an inverse relationship to the case where the tuning fork arm 5 (ab) is caused to vibrate. It is also possible to detect charges generated in the drive electrodes 7 (a to d).

  With such a configuration, as described in the column of the effect of the invention, the crystal (tuning fork-shaped crystal piece 6) as the piezoelectric body is directly used as the tuning fork main body. Therefore, the first, second electrode 7 (ab), third, fourth electrode 7 (cd), fifth electrode 8a, and sixth electrode 8b having the same potential as the drive electrode 7 and the detection electrode 8 are the tuning fork main body. The internal connection can be made above, and the acceleration sensor element can be simplified and miniaturized.

  Further, it is excited in the vertical direction by the piezoelectricity of the quartz crystal itself, and torsional vibration is generated by centrifugal force. Therefore, the driving power is reduced as compared with the case where the torsional vibration is forcibly caused by the piezoelectric ceramics, and conversely, the detection sensitivity is increased. In this example, since the displacement of the pair of tuning fork arms 5 (ab) due to acceleration is the tuning fork vibration of the open leg or the closed leg, the amplitude can be increased by the physical resonance phenomenon, and the detection sensitivity can be increased.

(First embodiment B, claims 1, 2, 5)
FIG. 5 is a diagram of an acceleration sensor element for explaining the first embodiment B of the present invention. FIG. 5 (a) is a plan view seen from the head showing electrode arrangement, and FIG. 5 (bc) shows electric field distribution. It is the same top view. In the following embodiments, the description of the same parts as in the previous embodiments is omitted or simplified.

  In the first embodiment B, the first to fourth electrodes 7 (a to d) of the drive electrode 7 are arranged on both sides of each side surface of each tuning fork arm 5 (ab), and the detection electrodes 8 (ab) are both main electrodes. Place on the surface. The first and second electrodes 7 (ab) of the drive electrode 7 are on the inner surface on the one main surface side and the other main surface side, and the third and fourth electrodes 7 (cd) are on the one main surface side and the other main surface side. "FIG. 5 (a)" formed on the outer surface.

  In each tuning fork arm 5 (ab), two pairs of diagonal first and third electrodes 7 (ad) and second and fourth electrodes (bc) are set to the same potential, and the two pairs of diagonal directions Then, the reverse potential is used. Then, between the pair of tuning fork arms 5 (ab), the diagonal direction which is the same direction is set to the same potential, and the diagonal direction which is the reverse direction is set to the reverse potential, as shown in FIG. 5 (b). Is done. This is basically the same as the connection in the first embodiment. A drive voltage (alternating voltage) is applied from the drive terminal D ±.

  Even in this case, electric fields opposite to each other are generated on both main surface sides (upper and lower half regions) of each tuning fork arm 5 (ab). For example, when one main surface side expands, the other main surface side contracts and one main surface side contracts. When the side shrinks, the other main surface side expands. And between each tuning fork arm 5 (ab), since both main surface sides expand and contract in the same direction, it becomes vertical in-phase vibration like the first embodiment A.

  When the acceleration a from the vertical direction is applied to the main surface of the tuning fork crystal piece 6 “the pair of tuning fork arms 5 (ab)”, the pair of tuning fork arms 5 (by the Coriolis force Fc as in the first embodiment A). ab) produces tuning fork vibrations of the open and closed legs. Therefore, each tuning fork arm 5 (ab) expands and contracts with the tuning fork arm vibration, so that the piezoelectric phenomenon causes the tuning fork arm 5 (ab) to move from the center to the inner / outer surface and from the inner / outer surface to the center. Electric fields P1 and P2 that are opposite to each other are generated.

  Thus, as in the first embodiment, the third and fourth electrodes 8 (ab) and the fourth electrodes 8 (ab) and the detection electrodes 8 of the tuning fork arms 5 (ab) are separated by the decomposition vector components of the electric fields P1 and P2 that are opposite to each other. Positive and negative charges having opposite signs are generated between the pair of tuning fork arms 5 (ab) on the first to fourth electrodes 7 (a to d) of the drive electrode 7. From these facts, acceleration can be measured by detecting positive and negative charges based on tuning fork vibration in response to acceleration.

  In the first embodiment B, the divided drive electrodes 7 “first and second electrodes 7 (ab)” are provided on the inner surface of each tuning fork arm 5 (ab). In the case of manufacturing by etching using technology, the manufacturing is difficult. Therefore, for example, it may be as shown in FIG.

  That is, the seventh electrode 7e having the first and second electrodes 7 (ab) of the drive electrode 7 in common is provided on the inner surface, and the third and fourth electrodes 7 (cd) are provided on the outer surface. Then, the seventh electrode 7e may be set to the reference potential E0, and an alternating voltage (drive voltage) having a reverse polarity may be applied to the second and third electrodes 7 (cd). Even in this case, since opposite electric fields are similarly generated on both main surfaces, vertical in-phase vibration can be obtained.

(First embodiment C, claims 1, 2, 4, 5)
FIG. 7 (ab) is a plan view seen from the head of the acceleration sensor element for explaining the first embodiment C of the present invention. In the second embodiment, the tuning fork crystal piece is not a single plate, but two crystal pieces are bonded together by direct bonding.

  The tuning fork crystal piece 6 is directly joined by, for example, a siloxane bond (Si-O-Si) to two crystal pieces 6 (ab) whose surfaces (main surfaces) are mirror-polished to be hydrophilic. The two crystal pieces 6 (ab) are joined with the ± X axes (electrical axes) of the crystal axes being opposite to each other. Then, the drive electrode 7 and the detection electrode 8 are formed on the pair of tuning fork arms 5 (ab). The crystal axis YZ (mechanical axis, optical axis) basically has no ± polarity.

  The drive electrode 7 is provided with an eighth electrode 7f on each inner surface of the pair of tuning fork arms 5 (ab) and a ninth electrode 7g on each outer surface. Then, the eighth electrode 7f on the inner surface of one tuning fork arm 5a and the ninth electrode 7g on the outer surface of the other tuning fork arm 5b, and the ninth electrode 7g on the outer surface of one tuning fork arm 5a and the other tuning fork arm 5b. The eighth electrode 7f on the inner surface is connected at the same potential, and a drive voltage (alternating voltage) is applied between them as a reverse potential. The detection electrodes 8 are provided on both main surfaces of each tuning fork arm 5 (ab), and a fifth electrode 8a is provided on one main surface and a fourth electrode 8b is provided on the other main surface (FIG. 7 (a)).

  In such a case, when the electric field is generated from the inner surface to the outer surface in one tuning fork arm 5a and from the outer surface to the inner surface in the other tuning fork arm 5b by the above-described connection and driving voltage, each tuning fork arm 5 (ab). The next operation is “FIG. 7B”. That is, in the two crystal pieces 6 (ab) of each tuning fork arm 5 (ab), since the polarity ± of the X axis is in the reverse direction, the electric field is directed from the + X axis to the −X axis on one main surface side, and the other main surface side Then, the electric field is directed from the −X axis to the + X axis. Therefore, the expansion / contraction direction in the Y-axis direction is reversed between the one main surface side and the other main surface side by the two crystal pieces 6 (ab).

  For example, if one main surface side of each tuning fork arm 5 (ab) is expanded by an electric field from the + X axis to the −X axis, the other main surface side is reduced by an electric field from the −X axis to the + X axis. Then, if one main surface side contracts due to an electric field in the opposite direction, the other main surface side expands. Accordingly, the pair of tuning fork arms 5 (ab) generate vertical in-phase vibrations that bend in the same direction with respect to the main surface, as in the first and second embodiments AB described above.

  The pair of tuning fork arms 5 (ab) generate torsional vibrations due to the rotational moments ± M in the opposite directions as in the previous embodiment A (see FIG. 3) due to vertical in-phase vibrations. As a result, when acceleration a in the vertical direction is applied to the main surface of the tuning-fork crystal piece 6, each tuning-fork arm 5 (ab) is subjected to Coriolis force Fc to generate tuning-fork vibration that repeats opening and closing legs. .

  In this case, if the pair of tuning fork arms 5 (ab) are opened, for example, the inner surface of each tuning fork arm 5 (ab) extends in the Y-axis direction and the outer surface contracts, an electric field (charge) is generated. Is next. That is, the tuning fork-shaped crystal piece 6 here is composed of two crystal pieces 6 (ab) whose X-axis polarity (±) is reversed. Therefore, if electric fields P1 and P2 directed from the center to the inner and outer side surfaces (both side surfaces) are generated on one main surface side of one tuning fork arm 5a, electric fields P1 and P2 directed to the center from both side surfaces are formed on the other main surface side. .

  Then, due to the decomposition vector component based on these electric fields P1 and P2, a positive charge is applied to the detection electrode 8a on one main surface side of one tuning fork arm 5a, and the drive electrode 7 (fg) on the outer and inner side surfaces (both side surfaces). Generate negative charge. On the other main surface side of one tuning fork arm 5a, on the contrary, a positive charge is generated on the drive electrode 7 (fg) on both side surfaces and a negative charge is generated on the detection electrode 8b on the other main surface side.

  In this case, on both main surfaces, the driving electrodes 7 (fg) on both sides have different signs of charges, so they are canceled out and basically become zero potential. Since the other tuning fork arm 5b is a tuning fork vibration, the horizontal displacement direction is opposite to that of the one tuning fork arm 5a.

  Therefore, also in the first embodiment C, the acceleration a can be measured by detecting positive and negative charges from the detection electrode 8 (ab). Then, the tuning fork crystal piece 2 is formed from two crystal pieces 6 (ab) whose X-axis polarities are opposite to each other. Therefore, since the drive electrodes 7 (ab) formed on both side surfaces of each tuning fork arm 5 (ab) are formed as a single electrode without being divided, it is advantageous in terms of manufacturing, particularly in downsizing.

(Second embodiment, claims 1, 3, 4, 5)
FIG. 8 is a diagram of an acceleration sensor element for explaining a second embodiment of the present invention. FIG. 8 (a) is a plan view seen from the head explaining the operation, and FIG. 8 (bc) is a side view thereof. .

  In the first embodiment (A to C), in any case, the drive electrode 7 causes the pair of tuning fork arms 5 (ab) to be perpendicular to the plate surface (main surface) and bend in the same direction and vibrate. In the second embodiment, the vertical in-phase vibration is a vertical anti-phase vibration that vibrates in a direction perpendicular to the main surface and in a direction opposite to each other.

  That is, in the second embodiment, the electric field direction by the drive electrode 7 is reversed in one tuning fork arm 5a and the other tuning fork arm 5b. For example, when the electrode arrangement corresponding to the first embodiment A is adopted, the following operation is performed. That is, on one main surface side of one tuning fork arm 5a, the first electrode 7a on the inner side of the one main surface leads to the third electrode 7c on the outer side of the one main surface, and on the other main surface side, the fourth electrode on the outer side of the other main surface changes from the fourth electrode. When the electric field direction is directed to the second electrode 7b on the inner side of the main surface, the electric field direction is opposite to those on both main surface sides of the other tuning fork arm 5b (FIG. 8 (a)).

  In short, in the second embodiment, in the pair of tuning fork arms 5a, one principal surface side is, for example, the same electric field direction as the X-axis polarity, the other principal surface side is the opposite electric field direction, and the other principal surface side of the other tuning fork arm 5b. Then, the pair of tuning fork arms 5a is reversed. On the other hand, in the first embodiment, each tuning fork arm 5 (ab) has the same electric field direction.

  In such a case, when one main surface side of one tuning fork arm 5a expands and the other main surface side contracts, “solid line in FIG. 8 (b)”, one main surface side of the other tuning fork arm 5b contracts. The other main surface side extends (dotted line). Therefore, one tuning fork arm 5a bends from one main surface side to the other main surface side, and the other tuning fork arm 5b bends from the other main surface side to the one main surface side (FIG. 8 (c)). As a result, during application of the drive voltage (alternating voltage) D ±, the pair of tuning fork arms 5 (ab) bend to the main surface sides in the opposite directions, resulting in vertical antiphase vibration.

  Even in this case, as shown in FIG. 9 (trajectory diagram), the rotating moment M having the same rotational direction acts on the tuning fork arms 5 (ab) bent in opposite directions by centrifugal force, Torsional vibration in the same direction occurs with vertical antiphase vibration. Therefore, when acceleration a is applied to the tuning fork crystal piece 6 “a pair of tuning fork arms 5 (ab)” from one main surface side, each tuning fork arm 5 (ab) rotates in the same direction. For example, a Coriolis force Fc (solid line in the figure) facing rightward in the figure is generated. When the pair of tuning fork arms 5 (ab) bend in the opposite direction, a leftward Coriolis force Fc (dotted line in the figure) is generated.

  As a result, the pair of tuning fork arms 5 (ab) cause the tuning fork vibration in the first embodiment, that is, the horizontal anti-phase vibration in which each tuning fork arm 5 (ab) bends in the opposite horizontal direction by the Coriolis force Fc. Instead, as shown in FIGS. 10 and 11, the tuning fork arms 5 (ab) are horizontally in-phase oscillating in the same horizontal direction. In this case, for example, each inner surface side of the pair of tuning fork arms 5 (ab) expands (contracts) and each outer surface side contracts (extends).

  Then, for example, electric fields P1 and P2 in the same direction from the center to both side surfaces of each tuning fork arm 5 (ab) accompanying horizontal in-phase vibrations cause drive electrodes 7 (ab) and 7 (cd) on both main surfaces to A decomposition vector component is generated in the detection electrode 8 (ab) (FIG. 12). As a result, for example, a positive charge is applied to the drive electrode 7 (abcd) of each tuning fork arm 5 (ab), and a negative charge is generated to the detection electrode (ab). Then, when the electric field is directed from both side surfaces toward the center, charges having opposite signs are generated.

  Therefore, also in the second embodiment A, the acceleration a can be measured by detecting these positive and negative charges. In this case, since the pair of tuning fork arms 5 (ab) is caused to have vertical anti-phase vibration by the drive electrode 7 (abcd), the tuning fork base 4 is made to be compared with the case of vertical in-phase vibration in the first embodiment. Reduce vibration leakage when held. Therefore, driving efficiency can be increased.

  In the second embodiment, the direction of the electric field applied to the pair of tuning fork arms 5 (ab) is changed as the same electrode arrangement as in the first embodiment A, but the same applies to the electrode arrangement in the first embodiment B. Applicable to. In the second embodiment, the tuning fork-like crystal piece 6 is formed of a single plate, but it can also be applied to the bonding by direct bonding in the first embodiment C.

(Third embodiment, claims 1, 2, 4, 5)
FIG. 13 is a view of an acceleration sensor element for explaining a third embodiment of the present invention. FIG. 13 (ac) is a front view for explaining the operation, and FIG. 13 (b) is a side view thereof. In addition, 3rd Embodiment is an example at the time of providing the tuning fork-shaped crystal piece of 1st and 2nd embodiment up and down, and making it H shape.

  That is, in the third embodiment, a pair of tuning fork arms 5 (ab) and 5 (cd) are formed in an H shape extending in the vertical direction opposite to each other from the tuning fork base 4, and the upper and lower parts composed of the upper tuning fork 6x and the lower tuning fork 6y. A 4-legged 2-tuning fork. And the center part of the other main surface shown by the dotted line (circle) of the tuning fork base part 4 which is an extension start end of the upper and lower tuning fork 6 (xy) is made into a support point (holding position).

  The tuning fork arms 5 (ab) and 5 (cd) of the upper and lower tuning forks 6 (xy) have the same electrode arrangement as that of the first embodiment A, and have vertical in-phase vibration. In this example, when the tuning fork arm 5 (ab) of the upper tuning fork 6x bends from one main surface side to the other main surface side as indicated by ○ in the figure, the tuning fork arm 5 (cd) of the lower tuning fork 6y is As indicated by the black dots, it bends from one main surface side to the other main surface side and bends in opposite directions (reverse phase) to the main surface. In FIG. 13 (b), the direction of bending is indicated by a double arrow.

  In such a case, as described in the first embodiment (for example, FIG. 3), each tuning fork arm 5 (ab) of the upper tuning fork 6x is moved from one main surface side to the other main surface by centrifugal force accompanying vertical in-phase vibration. Torsional vibration is generated due to rotational moments ± M in opposite directions to the sides. Further, each tuning fork arm 5 (cd) of the lower tuning fork 6y generates torsional vibration due to rotational moments in opposite directions from the other principal surface side to the one principal surface side.

  In this state, for example, when acceleration a is applied from one main surface side, in the upper tuning fork 6x, each tuning fork arm 5 (ab) is bent outward by receiving, for example, Coriolis force Fc from the inside to the outside. In the lower tuning fork 6y, each tuning fork arm 5 (cd) bends inward by receiving Coriolis force Fc from the outside to the inside (FIG. 13 (c)).

  When the bending directions of the tuning fork arms 5 (ab) and 5 (cd) of the upper and lower tuning forks 6 (xy) by the driving voltages are opposite, the tuning fork arms 5 (ab) and 5 (cd) act. The Coriolis force Fc is also reversed. Therefore, the tuning fork arms 5 (ab) and 5 (cd) of the upper and lower tuning forks 6 (xy) are in the opposite directions of tuning fork vibrations (horizontal antiphase vibrations). From these facts, the acceleration a can be measured by detecting the electric charge caused by the tuning fork vibration of the upper and lower tuning forks 6 (xy).

  In such a case, as an H-shaped four-legged two tuning fork having an upper and lower tuning fork 6 (xy), for example, the charge due to acceleration a is detected by each tuning fork arm 5 (ab) and 5 (cd) of the upper and lower tuning fork 6 (xy). To do. Accordingly, the detection charge amount is increased as compared with the conventional simple biped tuning fork, so that the detection sensitivity can be increased.

  Also, here, the tuning fork arms 5 (ab) and 5 (cd) of the upper and lower tuning forks 6 (xy) are set as vertical in-phase vibrations, and are opposite to each other between the upper and lower tuning forks 6 (xy). Therefore, the tuning fork arm 5 (ab) of the upper tuning fork 6x and the tuning fork arm 5 (cd) of the lower tuning fork 6 are referred to as a seesaw motion with the holding position of the tuning fork base 4 as a fulcrum, as shown in FIG. 13 (b). Therefore, the vertical in-phase vibrations in the opposite directions in the upper and lower tuning forks 6 (xy) are increased, and the amount of deflection with respect to the driving voltage is increased, thereby increasing the driving efficiency.

  Further, the tuning fork arms 5 (ab) and 5 (cd) of the upper and lower tuning forks 6 (xy) vibrate in a direction opposite to each other by the Coriolis force Fc caused by the acceleration a (FIG. 13 (c)). Therefore, also in this case, the upper and lower tuning fork 6 (xy) each tuning fork arm in the diagonal direction performs seesaw motion (here, for example, scissors motion) with the holding position as a fulcrum. Therefore, the tuning fork vibration between the upper and lower tuning fork arms 6 (xy) is increased, and the detection sensitivity can be further increased.

  In the third embodiment, the electrode arrangement of the first embodiment A has been described as an example, but the same applies to the case of the first embodiment B or the first embodiment C of direct bonding.

(Fourth embodiment, claims 1, 3, 4, 5)
FIG. 14 is a diagram of an acceleration sensor element for explaining a fourth embodiment of the present invention, and FIG.

  In the fourth embodiment, as in the third embodiment, a four-legged two tuning fork is formed in an H shape, and the tuning fork arms 5 (ab) and 5 (cd) of the upper and lower tuning forks 6 (xy) are the same as in the second embodiment. The vertical antiphase vibration of Then, one diagonal tuning fork arm 5 (ac) of the upper and lower tuning forks 6 (xy) is in phase, and the other diagonal tuning fork arm 5 (bd) is in phase, and one diagonal tuning fork arm 5 (ac) ) And opposite phase. The electrode arrangement and the electric field direction for obtaining these vibrations are obtained in the same manner as in the second embodiment ABC.

  In such a case, for example, when the tuning fork arm 6 (ac) of the upper and lower tuning forks 6 (xy) in one diagonal direction bends from one main surface side to the other main surface side, the other tuning fork arm 6 ( bd) bends from the other main surface side to the one main surface side. Accordingly, each tuning fork arm 6 (ab) of the upper tuning fork 6x exhibits torsional vibration due to the rotational moment M having the same rotation direction in the counterclockwise direction, and the lower tuning fork arm 6 (cd) has a clockwise rotation which is opposite to this. Torsional vibration due to the same rotational moment -M occurs.

  When an acceleration a (not shown) is applied to one principal surface side, as described in the second embodiment (FIGS. 10 and 11), each tuning fork arm 5 (ab) of the upper tuning fork 6x is applied from the left. The Coriolis force Fc in the right direction acts on the tuning fork arms 5 (cd) of the lower tuning fork 6y.

  Therefore, the upper and lower tuning forks 6 (xy) are both in the horizontal in-phase vibration described above, and are in opposite directions (reverse phase) between the upper and lower tuning forks 6 (xy) (FIG. 14B). The acceleration a can be measured by detecting positive and negative charges generated by vibrations of the tuning fork arms 5 (ab) and 5 (cd).

  According to this, since the rotational moments opposite to each other act on the upper and lower tuning forks 6 (xy), the torsional vibrations of the tuning fork arms 5 (ab) and 5 (cd) also become strong. Therefore, the driving efficiency is increased, and the Coriolis force Fc due to the acceleration a is increased, so that the detection sensitivity can be increased. Even in this case, as in the third embodiment, the detection sensitivity is increased because the four-legged 2-tuning fork is used as the H shape.

(Other matters)
In each of the above embodiments, a simple two-leg tuning fork (first and second embodiments) and an H-shaped four-leg two tuning fork have been described. For example, as shown in FIG. 15 (ab), each tuning fork arm 5 ( a weight 8 protruding in the width direction may be provided on the tip side of each of the ab) and the tuning fork arms 5 (ab), 5 (cd). In this case, the rotational moment is increased by the weight 8 and the torsional vibration can be made strong.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the acceleration sensor element explaining 1st Embodiment A of this invention, The figure (a) is a front view, The figure (b) is the top view seen from the head which shows electrode arrangement | positioning, The figure (c). Is a connection diagram seen from the head. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the acceleration sensor element explaining 1st Embodiment A of this invention, The figure (a) is a top view seen from the head explaining an effect | action especially, The figure (b) is the arrow of the figure (a). It is the side view seen from A direction. It is the top view seen from the head which shows the typical locus | trajectory of each tuning fork arm of the acceleration sensor element explaining the effect | action of 1st Embodiment A of this invention. It is the top view seen from the head of the acceleration sensor element explaining the operation of the first embodiment of the present invention. The first embodiment B of the present invention is a view of an acceleration sensor element, and FIG. It is the top view seen from the head of the acceleration sensor element explaining the effect | action of the other example of 1st Embodiment B of this invention. It is a figure of the acceleration sensor element explaining 1st Embodiment C of this invention, and the same figure (ab) is the top view seen from the head explaining an effect | action especially. It is a figure of the acceleration sensor element explaining 2nd Embodiment of this invention, The figure (a) is the top view seen from the head explaining an effect | action especially, The figure (bc) is the same side view. It is the top view seen from the head which shows the typical locus | trajectory of each tuning fork arm of the acceleration sensor element explaining the effect | action of 2nd Embodiment of this invention. It is a figure of the acceleration sensor element of 2nd Embodiment of this invention, and the same figure (ab) is a front view explaining an effect | action especially. It is a figure of the acceleration sensor element of 2nd Embodiment of this invention, and the same figure (ab) is a front view explaining an effect | action especially. It is a top view of the acceleration sensor element seen from the head explaining the effect | action of 2nd Embodiment of this invention. It is a figure of the acceleration sensor element explaining 3rd Embodiment A of this invention, The figure (ac) is a front view explaining an effect | action especially, The figure (b) is the side view. It is a figure of an acceleration sensor element explaining a 4th embodiment of the present invention, and the figure (ab) is a front view explaining an operation especially. It is a figure of the acceleration sensor element explaining the other application example of this invention, and the figure (ab) is a front view. It is a figure of the acceleration sensor element explaining a prior art example, the figure (a) is a front view, the figure (b) is an AA sectional view, and the figure (c) is a BB sectional view. FIG. 4A is a diagram of an acceleration sensor element for explaining a conventional example, in which FIG. 1A is a plan view seen from the head, particularly explaining the operation, and FIG. 2B is a diagram of the same pair of tuning fork arms. FIG. 4A is a diagram of an acceleration sensor element for explaining a conventional example, in which FIG. 1A is a plan view seen from the head, particularly explaining the operation, and FIG. 2B is a diagram of the same pair of tuning fork arms. It is a figure of the acceleration sensor explaining the effect | action of a prior art example, and the same figure (ab) is the figure seen from the head explaining an effect | action especially. It is a figure of the acceleration sensor element explaining the effect | action of a prior art example, and the same figure (ab) is a front view explaining an effect | action especially. It is a figure of the acceleration sensor element explaining the effect | action of a prior art example, and the same figure (ab) is a front view explaining an effect | action especially.

Explanation of symbols

1 tuning fork body 2 driving piezoelectric body 3 detecting piezoelectric body 4 tuning fork base 5 tuning fork arm 6
Tuning fork crystal piece, 7 drive electrode, 8 detection electrode, 9 support point (holding position), 10 weight.

Claims (6)

  When a pair of tuning fork arms extending from the tuning fork base of the tuning fork main body are caused torsional vibrations that rotate about the length direction and an acceleration in a direction perpendicular to the main surface of the pair of tuning fork arms is applied, The pair of tuning fork arms cause a horizontal displacement with respect to the main surface thereof, and in the acceleration sensor element that detects charges generated by the horizontal displacement, the tuning fork body is formed of quartz, The pair of tuning fork arms are excited in a direction perpendicular to the main surface of the tuning fork arms by a drive electrode provided on the pair of tuning fork arms, and a twisting phenomenon is generated in the pair of tuning fork arms. An acceleration sensor element, wherein a charge due to a displacement in a horizontal direction with respect to a main surface of the pair of tuning fork arms due to force is detected by a detection electrode provided on the tuning fork arm.   The vibration in the direction perpendicular to the main surface of the pair of tuning fork arms according to claim 1 is the same direction between the pair of tuning fork arms, and the rotational direction of the torsional vibration of the pair of tuning fork arms is reversed. An acceleration sensor element in which horizontal displacement due to acceleration is opposite to each other.   The vibration in the direction perpendicular to the main surface of the pair of tuning fork arms according to claim 1, wherein the rotation directions of the torsional vibrations of the pair of tuning fork arms are the same as the directions opposite to each other between the pair of tuning fork arms, An acceleration sensor element in which the horizontal displacement due to acceleration is the same direction.   2. The acceleration sensor element according to claim 1, wherein the tuning fork main body is bonded by direct bonding so as to be opposite to the ± X axes of two crystal pieces.   2. The acceleration sensor element according to claim 1, wherein the tuning fork body is a two-leg tuning fork in which a pair of tuning fork arms extend in one direction from the tuning fork base.   2. The acceleration sensor element according to claim 1, wherein the tuning fork main body is a four-legged two tuning fork in which the pair of tuning fork arms extend in opposite directions from the tuning fork base.

Images