JP2013011550A - Physical quantity sensor, and physical quantity detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a physical quantity sensor having good temperature characteristics.SOLUTION: An acceleration sensor 10 comprises: a fixing part 21; a cantilever 20 having a plate-shaped movable part 23 connected to the fixing part 21 via a joint part 24; an acceleration detecting element 30 including a first supporting member 34 and a second supporting member 33, in which the first supporting member 34 is fixed to a principal surface of the fixing part 21, and the second supporting member 33 is fixed to a principal surface of the movable part 23; and a weight body 50 which includes, on the principal surface of the movable part 23, a mass part 51 disposed on a tip side of the movable part 23 of the second supporting member 33, and a first fixed end 52 and a second fixed end 53 branched and extended from the mass part 51 and continuing through strain buffering portions 54 and 55, in which the mass part 51, the first fixed end 52 and the second fixed end 53 are fixed to the principal surface of the movable part 23, and the strain buffering portions 54 and 55 are not fixed to the movable part 23. The movable part 23 is displaceable in a direction crossing a principal surface 20a using the joint part 24 as a fulcrum.

Description

  The present invention relates to a physical quantity sensor and a physical quantity detection device including the physical quantity sensor.

  As a device for detecting physical quantities such as acceleration, inclination, angular velocity, etc., a sensor chip having a fixed end and a movable part formed with a plurality of sensor parts is used as a base material at two point bonding points in the width direction of the fixed end. There is a fixed physical quantity sensor (see, for example, Patent Document 1).

  In addition, the mass part, which is a movable body, is connected to the anchor part with a beam, the anchor part is joined to the bottom substrate, which is a base material, and the change in charge between the movable electrode and the fixed electrode due to the displacement of the position of the mass part There is an inertial sensor that detects (see, for example, Patent Document 2).

JP 2010-175376 A JP 2004-333133 A

  In Patent Document 1 described above, the sensor chip is bonded and fixed to the base member at two locations on the fixed end. However, since the movable portion is located at a position where the area is large and the center of gravity is separated from the fixed end portion, when the fixed end portion is bonded and fixed, it is easy to tilt and the movable portion may come into contact with the base material. When a movable part contacts a base material, there exists a subject that physical quantity cannot be detected correctly by generation | occurrence | production of noise, obstructing the free displacement of a movable part, etc.

  Further, in Patent Document 2, since the movable electrode electrode part fixed to the substrate and the anchor part are electrically connected by a spring structure integrally formed with the device layer, the anchor caused by the temperature change in the peripheral part is provided. The spring structure is intended to absorb the influence of the distortion and displacement on the output zero point fluctuation. However, a decrease in detection accuracy due to a variation in the distance between the movable electrode and the fixed electrode accompanying a change in temperature can be considered.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A physical quantity sensor according to this application example includes a fixed part, a cantilever having a plate-like movable part connected to the fixed part via a joint part, a first support part, and a second support part. A physical quantity detection element fixed to the main surface of the movable part, and the first support part fixed to the main surface of the movable part, and the main part of the movable part. A first fixed portion that is on the surface and is disposed closer to the distal end side of the movable portion than the second support portion, and that extends in a bifurcated manner from the mass portion via a strain buffer portion. An end portion and a second fixed end portion, and the mass portion, the first fixed end portion, and the second fixed end portion are fixed to a main surface of the movable portion, and the strain The buffer portion includes a weight body that is not fixed to the movable portion, and the movable portion is displaced in a direction intersecting the main surface with the joint portion as a fulcrum. It is the ability, characterized by.

The physical quantity sensor according to this application example detects the physical quantity by using the change in the resonance frequency of the physical quantity detection element due to the displacement of the cantilever. For example, the physical quantity sensor such as an acceleration sensor, a tilt sensor, or an angular velocity sensor Can be used as By disposing a weight body on the movable part of the cantilever, the displacement mass of the movable part is increased to increase detection sensitivity. Therefore, a metal material having a large specific gravity is used for the weight body.
According to this application example, since the weight body is fixed to the movable portion of the cantilever at three points of the mass portion, the first fixed end portion, and the second fixed end portion, the inclination of the weight body with respect to the main surface of the cantilever is set. The fixing strength can be ensured while preventing.

  Further, since the weight body is provided with a strain buffering portion between the mass portion and the first fixed end portion and the second fixed end portion, the weight is generated between the mass portion and the fixed end. The strain can be relaxed by the strain buffer, and the influence on the displacement of the cantilever due to the strain can be eliminated.

  Furthermore, when the linear expansion coefficients of the cantilever and the weight body are different, the strain of the weight body affects the cantilever due to the temperature change. Therefore, this strain can be absorbed and alleviated by the strain buffer. Therefore, there is an effect that good temperature characteristics can be obtained.

  Application Example 2 In the physical quantity sensor according to the application example described above, it is preferable that an elastic modulus of the strain buffer portion is smaller than an elastic modulus of the mass portion.

  If it does in this way, distortion between a mass part, the 1st fixed end part, and the 2nd fixed end part can be relieved by a distortion buffer part.

  Application Example 3 In the physical quantity sensor according to the application example described above, in the strain buffer portion, an elastic modulus in a direction along the main surface of the movable portion is smaller than an elastic modulus in a direction intersecting the main surface. preferable.

  If it does in this way, the displacement of the distortion buffer part of the direction along the main surface of a movable part can be made smaller than the direction which cross | intersects the main surface of a movable part.

  Application Example 4 In the physical quantity sensor according to the application example described above, it is preferable that a gap is provided between the main surface of the movable part and the strain buffering part.

  If comprised in this way, the distortion buffer part will not interfere with the distortion relaxation function mentioned above by contacting a movable part, and generation | occurrence | production of the noise which generate | occur | produces when both contact may be excluded.

  Application Example 5 In the physical quantity sensor according to the application example described above, the first fixed end portion and the second fixed end portion are disposed at a position sandwiching the physical quantity detection element on the same main surface of the movable portion. It is preferable that

  In this way, it is possible to increase the distance between the fixed portion of the mass portion with the cantilever and the fixed portion of the fixed end portion with the cantilever, and the weight can be further stabilized in the fixed posture.

  Application Example 6 In the physical quantity sensor according to the application example, it is preferable that the strain buffering portion has a spring structure.

  By making the strain buffering portion a spring structure, it is easy to follow the displacement of the cantilever, and the influence of the weight on the strain of the cantilever can be mitigated.

  Application Example 7 In the physical quantity sensor according to the application example described above, it is preferable that the weight body is disposed on the main surface of the movable portion and the back surface of the main surface.

  As described above, by arranging the weights on the main surfaces of the front and back surfaces of the cantilever, the mass of the movable part of the cantilever is increased and the displacement sensitivity is increased, so that the detection sensitivity of the physical quantity can be increased.

  Application Example 8 A physical quantity detection device according to this application example includes the physical quantity sensor according to any one of the application examples described above and a package that stores the physical quantity sensor.

According to this application example, by using the physical quantity sensor described in each of the application examples described above, it is possible to realize a physical quantity detection device with good temperature characteristics and low noise and high detection sensitivity.
The physical quantity sensor is stored in a package formed of ceramic or the like. If the inside of the package is evacuated, the physical quantity detection element can maintain stable vibration over a long period of time. By storing the physical quantity detection element in the package, it is easy to handle and protects from the external environment such as humidity. be able to.

The physical quantity sensor which concerns on Embodiment 1 is shown, (a) is a top view, (b) is sectional drawing which shows the AA cut surface of (a), (c) is a BB cut surface of (a). FIG. FIG. 3 is a cross-sectional view illustrating an example of the acceleration detection device according to the first embodiment. 3 is a graph showing a relationship between temperature and frequency deviation of the acceleration sensor according to the first embodiment. Sectional drawing which shows the acceleration sensor which concerns on Embodiment 2. FIG. The weight body which concerns on a modification is shown, (a) is the modification 1 and (b) is a partial top view which shows the modification 2. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings referred to in the following description are schematic views in which the vertical and horizontal scales of each member or part are different from actual ones in order to easily understand the configuration of each member.
(Embodiment 1)

  1A and 1B show a physical quantity sensor according to the first embodiment, FIG. 1A is a plan view, FIG. 1B is a cross-sectional view showing a section AA in FIG. 1A, and FIG. It is sectional drawing which shows the BB cut surface of (a). Note that the physical quantity sensor described in the present embodiment can be adapted to a physical quantity detection sensor such as acceleration, tilt, and angular velocity, but the acceleration sensor 10 will be described as a specific example.

  As shown in FIGS. 1A, 1 </ b> B, and 1 </ b> C, the acceleration sensor 10 as a physical quantity sensor includes a plate-shaped cantilever 20 and a physical quantity detection fixed to one first main surface 20 a of the cantilever 20. The acceleration detection element 30 is an element, and a weight body 50 is disposed and fixed on the first main surface 20a of the cantilever 20 so as not to overlap the acceleration detection element 30.

  The cantilever 20 is formed of a rectangular flat plate, and includes a frame-shaped support frame portion 25 including a fixed portion 21 and a movable portion 23 protruding from the fixed portion 21 by a slit 22. The movable part 23 and the fixed part 21 are connected by a joint part 24. The joint portion 24 has both the first main surface 20a, the first main surface 20a, and the second main surface 20b on the back surface of the first main surface 20a in the vicinity of the base close to the fixed portion 21 of the movable portion 23. It is a thin part formed by a groove. Furthermore, the width of both side surfaces of the joint portion 24 is reduced in a notch shape.

  The cantilever 20 is made of ceramic or quartz in the present embodiment, but preferably has a linear expansion coefficient substantially equal to the linear expansion coefficient of the acceleration detecting element 30. In the following description, the width direction is the X axis, the length direction is the Y axis, and the thickness direction is the Z axis. The fixing portion 21 of the cantilever 20 is bonded and fixed to a package base 110 (see FIG. 2) described later. The cantilever 20 is displaceable in a direction (Z-axis direction) in which the movable part 23 on the free end side intersects the first main surface 20a with the joint part 24 as a fulcrum. For example, the cantilever 20 is accelerated in the + Z-axis direction from the outside. Is loaded, the movable portion 23 is displaced in the −Z-axis direction. At this time, since the joint portion 24 is thin, the movable portion 23 and the joint portion 24 are easily displaced in the Z direction.

  Connection terminals 41 and 42 are provided on the first main surface 20a of the fixing portion 21 on the side opposite to the free end of the cantilever 20, and external connection terminals 71 and 72 are provided on the second main surface 20b. Yes. The connection terminal 41 is connected to the external connection terminal 71 via a lead electrode (not shown), and the connection terminal 42 is connected to the external connection terminal 72 via a lead electrode (not shown).

  The acceleration detection element 30 has two arms 31 and 32, and is supported by support portions 33 and 34 at both ends in the longitudinal direction (Y-axis direction) intersecting the vibration direction (X-axis direction) of the arms 31 and 32. It is connected. The acceleration detecting element 30 configured as described above is called a double tuning fork vibrator in its form, and in this embodiment is a Z-plate vibrator formed of quartz.

  In the acceleration detecting element 30, the support portion 33 is fixed to the movable portion 23 of the cantilever 20, and the support portion 34 is fixed to the fixing portion 21 using the adhesive 60 across the joint portion 24. The acceleration detecting element 30 is bonded and fixed to the cantilever 20 and does not contact the first main surface 20a of the cantilever 20 except for the support portion. In the initial state where there is no displacement in the Z-axis direction, the acceleration detection element 30 is formed with an excitation electrode (also used as a detection electrode, not shown) so as to vibrate in the plane in the X-axis direction at a predetermined resonance frequency. Yes.

  On the surface of the support portion 34 of the acceleration detection element 30, an extraction electrode 43 connected to one of excitation electrodes (not shown) and an extraction electrode 44 connected to the other excitation electrode are provided. The extraction electrode 43 is connected to the connection terminal 41 of the cantilever 20 by a metal wire 70. The extraction electrode 44 is connected to the connection terminal 42 of the cantilever 20 by a metal wire 70.

  The weight body 50 is divided into a mass part 51, a bifurcated portion from the mass part 51, and strain buffer parts 54, 55 are extended. The first fixed end part 52 continuous via the strain buffer part 54, and the strain buffer part And a second fixed end portion 53 continuous through 55. As shown in FIG. 1A, the mass portion 51 is disposed in the distal direction on the extension of the main surface 20a of the movable portion 23 of the cantilever 20, and includes a first fixed end portion 52 and a second fixed end portion 53. Each of them is arranged on both sides of the same principal surface as the mass part 51 with the width direction of the acceleration detecting element 30 interposed therebetween. The weight body 50 and the acceleration detection element 30 are disposed at a position where they do not contact each other.

  The strain buffering portions 54 and 55 have a curved shape in plan view between the mass portion 51, the first fixed end portion 52, and the second fixed end portion 53, and in the Y-axis direction and the X-axis direction. It is designed to be flexible and elastic. That is, it has a spring structure. The elastic modulus of the strain buffer parts 54 and 55 is smaller than that of the mass part 51. Further, in the strain buffer portions 54 and 55, the elastic modulus in the direction along the main surface 20a of the movable portion 23 is smaller than the elastic modulus in the direction intersecting with the main surface 20a.

  The weight body 50 includes a first main portion of the movable portion 23 of the cantilever 20 at a fixed portion 61 of the mass portion 51, a fixed portion 62 of the first fixed end portion 52, and a fixed portion 63 of the second fixed end portion 53. It is fixed to the surface 20a using an adhesive 60. The fixed area by the adhesive 60 is preferably as small as the area for fixing the mass portion 51 is smaller than the area not fixed, and as long as it has sufficient strength within the assumed acceleration range. The positions of the fixed portion 61 of the mass portion 51, the fixed portion 62 of the first fixed end portion 52, and the fixed portion 63 of the second fixed end portion 53 are arranged in a balanced manner so that the weight body 50 does not tilt in the thickness direction. Is done. The cantilever 20, the acceleration detection element 30, and the weight body 50 are symmetrical with respect to the central axis G and are arranged symmetrically.

  The cantilever 20 is arranged for the purpose of increasing detection sensitivity because it is easily displaced by providing the weight body 50. Therefore, a material having a high specific gravity is selected as the material of the weight body 50. For example, copper-based metal, iron-based alloy, stainless-based alloy, and the like.

As described above, the acceleration detecting element 30 arranged in the acceleration sensor 10 vibrates at a constant resonance frequency in a state where no acceleration is applied. When acceleration is applied in the Z-axis direction, the movable part 23 of the cantilever 20 is displaced in the direction opposite to the direction of acceleration, and the arms 31 and 32 are expanded and contracted according to the displacement of the movable part 23, The vibration frequency of the arms 31 and 32 changes due to the tensile stress and compressive stress generated at this time. Here, if the excitation electrode is configured to increase the resonance frequency when tensile stress occurs, the resonance frequency decreases when compressive stress occurs. Therefore, if the change in the resonance frequency is acquired according to the magnitude and direction of the acceleration, the acceleration can be detected.
(Acceleration detection device)

The acceleration sensor 10 is used by being stored in a package. Therefore, an acceleration detection device as a physical quantity detection device in a state where the acceleration sensor 10 is stored in a package will be described with reference to the drawings.
FIG. 2 is a cross-sectional view showing an example of the acceleration detection device according to the present embodiment. The acceleration detection device 100 includes the above-described acceleration sensor 10 and a package that stores the acceleration sensor 10.

  The package includes a container-shaped package base 110 having a space 111 for storing the acceleration sensor 10 and a lid 120 for sealing the space 111. The package base 110 is formed by stacking ceramic sheets in layers. The acceleration sensor 10 is packaged in fixed portions 64.65 disposed at both −Y direction corners of the support frame portion 25 shown in FIG. 1 and fixed portions 66 and 67 disposed at both + Y direction corners of the fixed portion 21. The base 110 is fixed to the inner bottom surface 110 a using an adhesive 60.

  In the fixing portion 66, the external connection terminal 71 on the second main surface 20b of the cantilever 20 and the internal terminal 141 provided on the inner bottom surface 110a of the package base 110 are electrically connected using the adhesive 60, and the external connection terminal 72 and the internal terminal 142 are electrically connected and fixed using the adhesive 60. Therefore, the adhesive 60 used here is a conductive adhesive.

  In the fixing portions 64 and 65, the cantilever 20 and the inner bottom surface 110 a of the package base 110 are directly joined using the adhesive 60. However, also in the fixing portions 64 and 65, electrodes corresponding to the external connection terminals 71 and 72 may be provided on the cantilever 20, and electrodes corresponding to the internal terminals 141 and 142 may be provided on the inner bottom surface 110a. In this way, the layer thickness of the adhesive 60 can be made substantially the same, and the adhesive curing conditions can be made constant.

  The lid 120 is a plate-like member formed of ceramic, glass, metal, or the like, and hermetically seals the space 111 using a bonding member 130 at the periphery of the package base 110. The space 111 is preferably in a vacuum or a state close to a vacuum.

In the acceleration sensor 10, the weight body 50 is fixed to the cantilever 20 with the three fixing portions 61, 62, 63 as described above, the mass portion 51, the first fixed end portion 52, and the second fixed portion. Strain buffering portions 54 and 55 are provided between the end portion 53 and the strain of the cantilever 20 due to the provision of the weight body 50 is alleviated.
Next, the influence on the detection accuracy due to the presence or absence of distortion of the cantilever 20 will be described with reference to measurement results.

  FIG. 3 is a graph showing the temperature-frequency deviation relationship of the acceleration sensor. FIG. 3 shows a comparison of resonance frequency fluctuations due to the presence or absence of distortion of the cantilever 20, wherein the horizontal axis represents temperature T [° C.] and the vertical axis represents frequency deviation Δ [ppm]. As shown in FIG. 3, when there is no distortion, a clean quadratic curve having a vertex temperature near 20 ° C. is obtained, and when there is distortion, the vertex temperature is unclear and the temperature characteristics are deteriorated. It is shown that. Therefore, it can be seen that if the distortion of the cantilever 20 due to temperature fluctuations is eliminated, the temperature characteristics do not deteriorate. It should be noted that the generation of strain in the cantilever 20 due to temperature change is dominated by the difference in the linear expansion coefficient accompanying the difference in material between the cantilever 20 and the weight body 50.

  The acceleration sensor 10 as the physical quantity sensor described in the first embodiment described above detects acceleration by changing the resonance frequency of the acceleration detection element 30 due to the displacement of the cantilever 20 in the Z direction. By disposing the weight body 50 on the movable portion 23, the displacement mass of the movable portion 23 is increased to increase the detection sensitivity. Therefore, a metal material having a large specific gravity is used for the weight body 50. According to the present embodiment, the weight body 50 is fixed to the cantilever 20 at the three points of the mass portion 51, the first fixed end portion 52, and the second fixed end portion 53, and thus the first main surface of the cantilever 20. Since the fixing strength can be secured while preventing the inclination of the weight body 50 with respect to 20a, a decrease in detection sensitivity can be prevented.

  Moreover, since the weight body 50 is provided with the strain buffer portions 54 and 55 between the mass portion 51 and the first fixed end portion 52 and the second fixed end portion 53, respectively, the mass portion and the fixed end The distortion occurring between them can be relaxed by the strain buffering section, and the influence on the displacement of the cantilever 20 caused by the distortion can be eliminated. Further, the strain buffering portions 54 and 55 alleviate strain generated between the mass portion 51 and the fixed end portions 52 and 53 due to temperature changes due to the difference in linear expansion coefficient between the cantilever 20 and the weight body 50. Can do. Therefore, there is an effect that good temperature characteristics can be obtained.

  Further, the elastic modulus of the strain buffer parts 54 and 55 is smaller than the elastic modulus of the mass part 51. Accordingly, the strain between the mass portion 51 and the first fixed end portion 52 and the second fixed end portion 53 can be relaxed by the strain buffer portions 54 and 55.

  Furthermore, in the strain buffering portions 54 and 55, the elastic modulus in the direction along the main surface 20a of the movable portion 23 is made smaller than the elastic modulus in the direction intersecting the main surface 20a (Z direction). The displacement of the strain buffer portion in the direction along the main surface can be made smaller than the direction intersecting the main surface of the movable portion 50.

  In addition, since the gap is provided between the main surface 20a of the movable portion 50 and the strain buffer portions 54 and 55, the strain buffer portions 54 and 55 come into contact with the movable portion 50 to prevent the above-described strain relaxation function. In addition, it is possible to eliminate the generation of noise caused by contact between the two.

  Further, the first fixed end 52 and the second fixed end 53 are disposed on the same main surface of the movable unit 50 at a position sandwiching the physical quantity detection element 30, so that the mass unit 51, The distance between the first fixed end 52 and the second fixed end 53 can be increased, and the fixed posture of the weight body 50 can be further stabilized.

The acceleration detection device 100 as a physical quantity detection device in which the acceleration sensor 10 described above is stored in a package is an acceleration sensor having good temperature characteristics, low noise and high detection sensitivity by using the acceleration sensor 10 described above. 10 can be realized.
The acceleration sensor 10 is stored in a package formed of ceramic or the like. If the inside of the package is evacuated, the acceleration detecting element 30 can maintain stable vibration for a long period of time, and it is easy to handle and protects from the external environment such as humidity and dust by being stored in the package. be able to.
(Embodiment 2)

Subsequently, an acceleration sensor 150 as a physical quantity sensor according to the second embodiment will be described with reference to the drawings. The second embodiment is characterized in that the weight body 50 is disposed on both the first main surface 20a of the cantilever 20 and the second main surface 20b that is the back surface of the first main surface 20a. Therefore, it demonstrates centering on a different location from Embodiment 1. FIG.
FIG. 4 is a cross-sectional view illustrating the acceleration sensor according to the second embodiment. FIG. 4 corresponds to the AA cut plane in FIG. The acceleration sensor 150 of the present embodiment is configured so that the cantilever 20, the acceleration detection element 30 fixed to one first main surface 20 a of the cantilever 20, and the acceleration detection element 30 do not overlap the first main surface 20 a of the cantilever 20. And a weight body 80 fixed to the second main surface 20b on the back surface side of the cantilever 20.

  The weight 80 has the same shape and material as the weight 50, and the weight 80 is symmetrical with the weight 50 with respect to the first main surface 20a or the second main surface 20b of the cantilever 20. Is arranged. Specifically, the weight body 80 is fixed using the adhesive 60 at a position overlapping the fixing portions 61, 62, and 63 (see FIG. 1A).

  Next, the acceleration detection device of this embodiment will be described with reference to FIG. The acceleration detection device of this embodiment is configured by storing the above-described acceleration sensor 150 in a package. At this time, a step portion is provided on the inner bottom surface 110a of the package base 110 so that a part of the inner bottom surface 110a does not come into contact with the weight 80, and the fixing portions 64, 65, 66 of the cantilever 20 are formed on the upper surface of the step portion. At 67, the adhesive is fixed.

  Specifically, the fixing portions 64 and 65 disposed at both −Y direction corners of the support frame portion 25 of the cantilever 20 illustrated in FIG. 1 and the fixing portions 66 and 67 disposed at both corners of the fixing portion 21 in the + Y direction. In this case, the adhesive 60 may be used to fix the upper surface of the stepped portion of the inner bottom surface 110 a of the package base 110. Then, the space 111 of the package base 110 is hermetically sealed with the lid 120.

  According to the second embodiment described above, the weight 50 and the weight body 80 are disposed on the first main surface 20a and the second main surface 20b of the cantilever 20, thereby further increasing the mass of the movable portion 23 of the cantilever 20. By increasing the displacement sensitivity of the movable portion 23, the effects of the first embodiment described above can be obtained, and the acceleration detection sensitivity can be further increased.

It should be noted that the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved.
For example, the modifications described below can be adapted to the first and second embodiments.
(Modification)

FIG. 5 shows a weight body according to a modified example, in which (a) is a partial plan view showing a modified example 1 and (b) is a modified example 2.
First, Modification 1 will be described with reference to FIG. In the first modification, the beam lengths of the strain buffer portions 54 and 55 of the weight body 50 are curved so as to be long. In this way, in addition to the effect of the first embodiment described above, the elastic modulus of the strain buffer parts 54 and 55 is increased with respect to the elastic modulus of the mass part 51 by increasing the tension length of the strain buffer parts 54 and 55. Thus, the elastic modulus in the direction along the main surface of the movable portion 50 can be made smaller than the elastic modulus in the direction intersecting the main surface.
The illustrated curved shape is not limited to this, and can be designed based on the technical idea of strain buffering.

  Next, Modification 2 will be described with reference to FIG. In the second modification, the strain buffering portions 54 and 55 of the weight body 50 are each configured to be two, and two buffer arms 54a and 54b are provided on the fixed end 52 side, and buffer arms 55a and 54b are provided on the fixed end portion 53 side. It is comprised by two of 55b. The buffer arms 54a, 54b, 55a, 55b are curved in an arc shape at substantially the center in the length direction.

  According to the second modified example, the strain buffer units 54 and 55 have the same strain buffer function as that of the first embodiment, and the strain buffer unit 54 includes the two buffer arms 54a and 55b, and the strain buffer unit. Since 55 is composed of two buffer arms 55a and 55b, the strain buffer parts 54 and 55 and the fixed end parts 53 and 54 are less likely to twist with respect to the mass part 51, and the strain buffer function can be further enhanced. it can.

  In addition, although the thickness of the mass part 51 and the fixed end parts 52 and 53 is made the same in Embodiment 1 mentioned above, the modification 1, and the modification 2, the mass part 51 is thickened, the distortion buffer part 54, 55 and the fixed end portions 52 and 53 may be thinned. And by making the planar shape of the strain buffer portions 54 and 55 the same as in the first embodiment and the first to third modifications, the strain buffer function is maintained and the mass of the mass portion 51 is increased. The detection sensitivity can be further increased by bringing the center of gravity of the mass portion 51 toward the distal end.

  The present invention has been described by exemplifying the acceleration sensors 10 and 150 as physical quantity sensors. However, the present invention is preferably used as an acceleration sensor such as an inclinometer, a seismometer, a navigation device, a posture control device, a game controller, a mobile phone, and an inclination sensor. In any case, the effects described in the embodiment and the modification can be obtained.

  In each of the above embodiments and modifications, the material of the cantilever 20 is not limited to quartz, and may be a semiconductor material such as glass or silicon.

The base material of the acceleration detecting element 30 is not limited to quartz, but lithium tantalate (LiTaO ₃ ), lithium tetraborate (Li ₂ B ₄ O ₇ ), lithium niobate (LiNbO ₃ ), titanate Piezoelectric materials such as lead zirconate (PZT), zinc oxide (ZnO), and aluminum nitride (AlN), or semiconductor materials such as silicon provided with a piezoelectric material such as zinc oxide (ZnO) and aluminum nitride (AlN) as a coating There may be.

  DESCRIPTION OF SYMBOLS 10 ... Acceleration sensor, 20 ... Cantilever, 20a ... 1st main surface, 20b ... 2nd main surface, 21 ... Fixed part, 23 ... Movable part, 24 ... Joint part, 30 ... Acceleration detection element, 31, 32 ... Arm, 33, 34 ... support part, 50 ... weight body, 51 ... mass part, 52 ... first fixed end part, 53 ... second fixed end part.

Claims (8)

A cantilever having a fixed portion, and a plate-like movable portion connected to the fixed portion via a joint portion;
A first support portion and a second support portion, wherein the first support portion is fixed to a main surface of the fixed portion, and the second support portion is fixed to a main surface of the movable portion. A physical quantity detection element;
On the main surface of the movable part, the mass part disposed on the distal end side of the movable part with respect to the second support part, and extending from the mass part to the fork and continuously through the strain buffering part A first fixed end portion and a second fixed end portion, and the mass portion, the first fixed end portion, and the second fixed end portion are fixed to a main surface of the movable portion. The strain buffering part is a weight body not fixed to the movable part,
With
The movable part is displaceable in a direction intersecting the main surface with the joint part as a fulcrum;
Physical quantity sensor characterized by. The elastic modulus of the strain buffer portion is smaller than the elastic modulus of the mass portion;
The physical quantity sensor according to claim 1. In the strain buffer portion, the elastic modulus in the direction along the main surface of the movable portion is smaller than the elastic modulus in the direction intersecting the main surface.
The physical quantity sensor according to claim 2. A gap is provided between the main surface of the movable part and the strain buffer part,
The physical quantity sensor according to any one of claims 1 to 3, wherein The first fixed end portion and the second fixed end portion are disposed at a position sandwiching the physical quantity detection element on the same main surface of the movable portion;
The physical quantity sensor according to any one of claims 1 to 4, wherein The strain buffer has a spring structure;
The physical quantity sensor according to claim 1. The weights are disposed on the main surface of the movable part and the back surface of the main surface;
The physical quantity sensor according to claim 1. A physical quantity sensor according to any one of claims 1 to 7,
A package for storing the physical quantity sensor;
A physical quantity detection device comprising:

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