JP2011064652A - Acceleration detector - Google Patents

Abstract

A highly accurate and highly sensitive acceleration detector that is easy to manufacture is provided.
A movable portion 24 that is displaced by acceleration applied perpendicularly to the main surface, a base 20 that includes a fixed portion 22 that supports the movable portion 24 via a constricted portion 26, and a force perpendicular to the direction of acceleration. And a pressure sensitive element 30 connected to a pair of base portions 34 and 35 arranged along the detection axis with the detection direction of force as a detection axis, and the pair of base portions 34 and 35 are connected to the movable portion 24 of the base 20. The constricted portion 26 fixed to the fixed portion 22 is an area sandwiched between the pair of base portions 34 and 35 and is formed between the movable portion 24 and the fixed portion 22 in a direction crossing the direction of the detection axis. A fixed end 72 at one end is connected to the fixed portion 22 on the base 20, and a beam portion 70 extending to the movable portion 24 side in a direction intersecting the direction of the constricted portion 26 at the free end 74 at the other end. The pressure sensitive element 30 is formed on the base 35 on the movable part 24 side in plan view. Contact portion 36 is formed in contact with the beam portion 70 at a position overlapping the part 70.
[Selection] Figure 1

Description

  The present invention relates to an acceleration detector using a high-precision and high-sensitivity piezoelectric vibrator in which the degree of design freedom of the size and area of a weight portion is expanded.

Conventionally, an accelerometer as disclosed in Patent Documents 1 to 3 including a pressure-sensitive element using a piezoelectric vibrator and a weight portion is disclosed.
In the acceleration sensor of Patent Document 1, a weight 104 is connected to one base 102 of a pressure sensitive element 101 via a constriction 103 as shown in FIG. As shown in (2) and (3), the weight 104 is disposed at a position opposite to the pressure sensitive element 101 with the constriction 103 as a base point. The constriction 103 is formed on each of the front and back surfaces of the substrate 105.

  As shown in FIG. 12, the accelerometer disclosed in Patent Literature 2 is connected to a weight 203 connected to a base 202 by a hinge coupling 201 so as to freely rotate in the X-axis direction, and connected to the weight 203 and the base 202 to detect the accelerometer. A pressure-sensitive element 204 having an axis formed in the Y-axis direction orthogonal to the X-axis direction is provided, and the pressure-sensitive element 204 is formed on the front and back of the weight 203 and the base 202.

  Patent Document 3 discloses an accelerometer having a beam resonator force transducer. As shown in FIG. 13, an accelerometer 301 having a beam resonator force transducer includes a base 304 connected to a weight 303 by a hinge 302 and a cantilever having one end connected to the weight 303 and the other end extending from the base 304. A pressure sensitive element 307 connected to the free end 306 of the beam 305 is provided. A stop 309 for stopping the displacement of the weight 303 at the breaking limit is formed on the free end 308 side of the weight 303 with a predetermined distance from the weight 303.

US Pat. No. 5,165,279 JP-A-1-302166 JP 59-126261 A

  However, in Patent Document 1, since the size of the weight 104 that can be secured is restricted by the size of the pressure-sensitive portion of the pressure-sensitive element 101, there is a problem that the sensitivity that satisfies the specification cannot be obtained depending on the required specifications of the accelerometer. It was.

  Further, since the constriction 103 is provided on each of the front and back surfaces of the substrate 105, the constriction 103 must be formed on each of the main surfaces of the substrate 105 by a photolithographic etching method. Therefore, there is a problem that the work is complicated and the cost is increased.

  In addition, an acceleration sensor of a cantilever type as disclosed in Patent Document 2 has an upper limit on sensitivity because the acceleration that is the destructive limit is reduced by increasing the sensitivity. As a result, sufficient crystal performance could not be achieved especially for sensors for low acceleration. This is caused by a structure in which stress is linearly applied to acceleration.

  Further, Patent Document 3 is provided with a stopper 309 that serves as a stopper for the weight 303, but the base 304, the weight 303, and the stopper 309 cannot be integrally formed. In addition, due to the problem of processing accuracy, it is difficult to set the weight 303 at a predetermined interval in the gap between the stoppers.

  Furthermore, when a stop (stopper) as shown in Patent Document 3 is applied to an accelerometer as shown in Patent Document 2, a stopper is provided separately from the pressure sensitive element. This stopper has a configuration in which one end of the stopper is fixed to the base in the same manner as the pressure-sensitive element provided on the base, and a free end contacting the weight is cantilevered so as to provide a predetermined distance from the weight. Therefore, there is a problem that it is difficult to position the free end of the stop at a predetermined distance from the weight.

On the other hand, in recent years, an acceleration detector capable of detecting a low acceleration while being able to detect an acceleration up to, for example, 100 G is desired. However, the pressure-sensitive element whose sensitivity is increased to detect low acceleration has a problem that it breaks when high acceleration is applied.
In order to solve the above-mentioned problems of the prior art, an object of the present invention is to realize an acceleration detector that is easy to manufacture and has high accuracy and high sensitivity.

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 force that is perpendicular to the main surface and is displaced by an acceleration, a base that includes a fixed portion that supports the movable portion via a constriction, and a force that is perpendicular to the direction of the acceleration. A pressure sensing element having a pressure sensing direction as a detection axis and connected to a pair of bases arranged along the detection axis, wherein the pair of bases and the movable part of the base Fixed to the fixed portion, the constricted portion is a region sandwiched between the pair of base portions, and is formed in a direction intersecting the direction of the detection axis between the movable portion and the fixed portion, In the base, a fixed end at one end is connected to the fixed portion, and a free end at the other end is formed in a direction intersecting the direction of the constricted portion and extending to the movable portion side, The pressure sensitive element is placed in front of the base on the movable part side so as to overlap the beam part in plan view. Acceleration detector, wherein a contact portion for contacting a beam portion is formed.

  Thereby, even when a large negative acceleration G is applied, the beam portion 70 comes into contact with the contact portion 36 to become a stopper of the movable portion 24, and is set in advance without being destroyed by excessive acceleration G. Acceleration can be detected in the measured range.

In addition, the pressure-sensitive portion, the base portion, and the contact portion constituting the pressure-sensitive element are integrally formed by etching and photolithography, so that the contact portion can be easily positioned with respect to the beam portion.
In addition, even when a large acceleration is applied to a highly sensitive acceleration detector that detects low acceleration, the beam portion can stop the displacement of the movable portion at the breaking limit, and the detector can be prevented from being broken.

  Application Example 2 The contact portion is a first contact that contacts the beam portion at a position overlapping the beam portion in plan view on a base portion on the movable portion side of the pressure-sensitive element on one main surface of the base. And a second contact portion facing the first contact portion on the other main surface of the base and contacting the beam portion at a position overlapping the beam portion in plan view. The acceleration detector according to Application Example 1.

  As a result, even when a large positive acceleration G is applied, the beam portion comes into contact with the second contact portion at the fracture limit and becomes a stopper of the movable portion, so that the displacement can be stopped. Therefore, the acceleration can be detected within a predetermined measurement range without being destroyed by excessive acceleration G.

  Application Example 3 The pressure-sensitive element is formed so as to extend from the base portion on the fixed portion side to the base portion on the movable portion side and straddle the constricted portion, and a stopper whose end portion is a free end. The acceleration detector according to Application Example 1, including the acceleration detector.

  As a result, when a negative acceleration G exceeding the destruction limit is applied to the acceleration detector, the beam portion comes into contact with the contact portion and becomes a stopper of the movable portion. On the other hand, when a large positive acceleration G is applied, the stopper can come into contact with the movable part at the breaking limit to stop the displacement of the movable part. Therefore, the acceleration can be detected within a predetermined measurement range without being destroyed by excessive acceleration G.

  Further, the pressure-sensitive part, base part, contact part, and stopper constituting the pressure-sensitive element are integrally formed by etching and photolithography, and the stopper can be easily positioned with respect to the beam part and the movable part.

Application Example 4 The pressure-sensitive element is formed such that the first pressure-sensitive element formed on one main surface of the base and the first pressure-sensitive element facing the other main surface of the base. The acceleration detector according to Application Example 1 or Application Example 3, wherein the acceleration detector includes a formed second pressure-sensitive element.
As a result, the acceleration can be detected in a differential manner, so that the acceleration can be detected with higher sensitivity.

Application Example 5 The acceleration detector according to Application Example 3, wherein the stopper has a variable length between the fixed end and the free end according to a breakage limit.
Thus, the design of the breakage limit point of the acceleration detector can be arbitrarily changed.

It is the schematic of the acceleration detector of Example 1. FIG. It is explanatory drawing of an effect | action of the acceleration detector of Example 1. FIG. It is the schematic of the acceleration detector of Example 2. FIG. It is explanatory drawing of an effect | action of the acceleration detector of Example 2. FIG. It is the schematic of the acceleration detector of Example 3. FIG. It is explanatory drawing of an effect | action of the acceleration detector of Example 3. FIG. It is the schematic of the acceleration detector of Example 4. FIG. It is the schematic of the acceleration detector of Example 5. FIG. It is the schematic of the acceleration detector of Example 6. FIG. It is the schematic of the modification of a pressure sensitive element. It is explanatory drawing of the conventional acceleration sensor. It is explanatory drawing of the conventional pendulum type accelerometer. It is explanatory drawing of the accelerometer which has the conventional beam resonator force converter.

Embodiments of an acceleration detector according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view of an acceleration detector according to a first embodiment, (1) is an exploded perspective view seen from one main surface side of the base, (2) is a side view, and (3) is a plan view. FIG.

As shown in the figure, the acceleration detector 10 of the first embodiment has a base 20 and a pressure-sensitive element 30 as the main basic configuration.
The base 20 mainly includes a fixed portion 22, a movable portion (weight portion) 24, a constricted portion 26, and a beam portion 70.

  The fixing portion 22 is a member that is not displaced by application of the acceleration G and fixes the base 20 to a substrate (not shown). The movable portion 24 serving as a weight is supported by the fixed portion 22 and is displaced (movable) in the application direction (Z-axis direction) when the acceleration G is applied. The fixed portion 22 and the movable portion 24 include mounting portions 29 a and 29 b that support a pair of base portions of the pressure-sensitive element 30 when a pressure-sensitive element 30 described later is bonded to the one main surface 27 side of the base 20. Yes.

  The constricted portion 26 is a thin-walled portion formed between the fixed portion 22 and the movable portion 24 and having a concave end surface shape in the X-axis direction of the planar rectangular base 20. The constricted portion 26 displaces the movable portion 24 in the direction opposite to the direction in which the acceleration G is applied (direction of inertial force) when the acceleration G is applied to the movable portion 24 and expansion / contraction / compression stress is applied to the pressure-sensitive element 30. It is configured as follows. The constricted portion 26 shown in FIG. 1 is a groove formed by cutting the other main surface 28 of the base 20 into a concave end surface shape.

  As long as the constricted portion 26 has a shape in which a part of the base 20 is thinned so as to have flexibility, in addition to the concave groove formed on the other main surface 28 of the base 20 as illustrated, It can also be set as the structure which forms a concave groove in the one main surface 27 side. In addition, for example, the front and back surfaces of the base 20 can be formed in a semi-circular shape.

  The beam portion 70 includes a fixed end 72 connected to the fixed portion 22 and a free end 74 extending in the direction intersecting the direction of the constricted portion 26 and extending from the fixed portion 22 side to the movable portion 24 side. Since the beam portion 70 does not form the constricted portion 26 provided between the fixed portion 22 and the movable portion 24, the beam portion 70 is not displaced like the movable portion 24 even when the acceleration G is applied to the base 20. The beam portion 70 shown in FIG. 1 is formed at a predetermined interval so that the tip of the free end 74 sandwiches the side surface of the placement portion 29b on the movable portion 24 side.

  It should be noted that the beam portion 70 only needs to be configured to come into contact with a contact portion 36 to be described later at the failure limit and stop the displacement of the movable portion 24. Therefore, the beam portion 70 sandwiches the placement portion 29b as shown in FIG. In addition to the configuration in which two (plural) are formed as described above, any one may be used.

  Further, the fixed portion 22, the movable portion 24, the constricted portion 26, and the beam portion 70 constituting the base 20 are formed by cutting the thinned constricted portion 26 and the beam portion 70 using a rectangular metal material in plan view. It can be formed integrally.

The pressure sensitive element 30 mainly includes a pressure sensitive part 32, a pair of base parts 34 and 35, and a contact part 36.
The pressure-sensitive element 30 has a pair of base portions 34 and 35 arranged at both ends, and a pressure-sensitive portion 32 having a vibration region provided between the pair of base portions 34 and 35, and an excitation electrode (not shown) on the vibration region. Is forming.

  The pressure-sensitive part 32 of the present embodiment has a configuration in which one vibrating arm is provided between the pair of base parts 34 and 35 so as to be connected to the base parts 34 and 35. The pressure sensing unit 32 may be a double tuning fork vibrating piece that has a large frequency change with respect to the applied force and can detect the pressure with high sensitivity. That is, the double tuning fork vibrating piece is a vibrating piece having a flexural vibration mode, and has a structure in which the end faces on the free end sides of two tuning fork type vibrating pieces are opposed to each other, and are parallel to each other in the Y axis. It is good also as a structure which has two bases which are connected to the both ends of the longitudinal direction of this vibration arm, and the vibration arm extends in the direction, and two bases arranged in a line with the vibration arm.

  The resonating arm is elongated in the Y-axis direction and is a portion that is flexed and vibrated by applying a driving voltage by an excitation electrode (not shown) provided on the surface thereof. This is the part where the frequency changes when tension is applied. Therefore, the acceleration can be detected by detecting the frequency change.

  The pressure-sensitive element 30 is a force perpendicular to the direction of acceleration, and the pair of base portions 34 and 35 are fixed to the mounting surfaces 29a and 29b on the base 20 so that the detection direction of the force is a detection axis. Yes. That is, the detection axis of the pressure-sensitive element 30 of the first embodiment is the Y-axis direction.

  Further, the constricted portion 26 of the base 20 with respect to the pressure-sensitive element 30 is an area sandwiched between the pair of base portions 34 and 35 and intersects the direction of the detection axis between the movable portion 24 and the fixed portion 22. It becomes the relationship arranged in.

  The contact portion 36 is formed on the base portion 35 on the movable portion 24 side. A pair of contact portions 36 shown in FIG. 1 is formed on the side surface of the base portion 35. The contact portion 36 is formed at a position overlapping the free end 74 of the beam 70 in plan view of the base 20 as shown in (3).

  The contact portion 36 only needs to be configured to come into contact with the beam portion 70 at the fracture limit and stop the displacement of the movable portion 24. Accordingly, as shown in FIG. In addition to the formed structure, any one may be used.

  The pressure-sensitive element 30 can integrally form the base portions 34 and 35, the pressure-sensitive portion 32, and the contact portion 36 by a photolithography technique and an etching technique, for example, as a piezoelectric material. Lithium acid or the like can be used.

  In the pressure-sensitive element 30 formed in this way, the pair of base portions 34 and 35 are bonded to the mounting portions 29a and 29b of the one main surface 27 of the base 20 with a predetermined distance from the base 20 by the bonding means 40. And fixed. At this time, the contact portion 36 is not bonded to the base 20 and is disposed at a position overlapping the free end 74 of the beam portion 70 in plan view.

The predetermined interval that is the gap between the pressure sensitive element 30 and the base 20 is set to a distance at which the pressure sensitive portion 32 and the base 20 do not interfere with each other.
The acceleration detector according to the first embodiment having the above-described configuration operates as follows. FIG. 2 is an explanatory diagram of the operation of the acceleration detector according to the first embodiment.

  As shown in the figure, when a negative acceleration G acts on the base 20 of the acceleration detector 10, the pressure is a force perpendicular to the direction of the acceleration G, and the pressure-sensitive portion 32 of the pressure-sensitive element 30 has the detection direction of the force as a detection axis. Elongation stress is applied. The pressure sensitive element 30 can detect the acceleration G by changing the frequency due to the extension stress.

  When an excessive acceleration G exceeding the breaking stress is applied to the acceleration detector 10 according to the first embodiment, an extensional stress is applied to the pressure-sensitive portion 32 of the pressure-sensitive element 30 according to the displacement of the movable portion 24. On the other hand, the beam portion 70 has a fixed end 72 fixed to the fixed portion 22 of the base 20, and the free end 74 is not fixed, so that it is not affected by the extension stress of the movable portion 24. Accordingly, the contact portion 36 of the pressure-sensitive element 30 that is displaced together with the displaced movable portion 24 comes into contact with the free end 74 of the beam portion 70 and functions to stop the displacement of the movable portion 24.

  When a positive acceleration G acts on the base 20 of the acceleration detector 10, the force is perpendicular to the direction of the acceleration G, and compressive stress is applied to the pressure-sensitive portion 32 of the pressure-sensitive element 30 having the detection direction of the force as a detection axis. Will be added. The pressure sensitive element 30 can detect the acceleration G by changing the frequency due to the compressive stress.

  According to the acceleration detector 10 of the first embodiment as described above, even when a negative acceleration G exceeding the destruction limit acts on the acceleration detector 10, the beam portion 70 comes into contact with the contact portion 36 and the stopper of the movable portion 24. Thus, the acceleration can be detected within a preset measurement range without being destroyed by excessive acceleration G.

  In addition, the present invention is characterized in that the pressure-sensitive portion 32, the base portions 34 and 35, and the contact portion 36 constituting the pressure-sensitive element 30 are integrally formed by etching and photolithography, and the positioning of the contact portion 36 with respect to the beam portion 70 is performed. It can be done easily.

Next, an acceleration detector according to the second embodiment will be described below.
FIG. 3 is a schematic view of the acceleration detector according to the second embodiment. (1) is an exploded perspective view seen from the other main surface side of the base, and (2) is a side view.

As shown in the figure, the acceleration detector 100 of the second embodiment has a configuration in which the second contact portion 50 is provided in the configuration of the first embodiment which is a basic configuration.
The second contact portion 50 is configured by only the base portion 35 and the contact portion 36 on the movable portion 24 side shown in the pressure-sensitive element 30 of the first embodiment, that is, a configuration in which the contact portion 52 is provided on the side surface of the main body 51. 20 is formed so as to face the other main surface 28 of the pressure sensitive element 30 with the base portion 35 and the base 20 interposed therebetween.

  The second contact portion 50 only needs to be configured to come into contact with the beam portion 70 at the fracture limit to stop the displacement of the movable portion 24. Therefore, as shown in FIG. In addition to the configuration in which two (plural) contact portions 52 are formed on the side surface, any one of them may be used.

  The second contact portion 50 formed in this way has the main body 51 bonded to the placement portion 29b of the other main surface 28 of the base 20 and the placement portion 29c facing each other with the base 20 therebetween, with a predetermined interval therebetween. It is fixed by gluing. At this time, the contact portion 52 is disposed at a position overlapping the free end 74 of the beam portion 70 in a plan view without bonding the base portion 20 to the base 20.

The acceleration detector according to the second embodiment having the above-described configuration operates as follows. FIG. 4 is an explanatory diagram of the operation of the acceleration detector according to the second embodiment.
As shown in (1), when an excessive negative acceleration G exceeding the breaking stress is applied to the acceleration detector 100 according to the second embodiment, the pressure-sensitive portion 32 of the pressure-sensitive element 30 responds to the displacement of the movable portion 24 so that the extension stress. Will be added. On the other hand, the beam portion 70 fixes the fixed end 72 to the fixed portion 22 of the base 20 and the free end 74 is not fixed, so that it is not affected by the stretching stress of the movable portion 24. Accordingly, the contact portion 36 of the pressure-sensitive element 30 that is displaced together with the displaced movable portion 24 comes into contact with the free end 74 of the beam portion 70 and functions to stop the displacement of the movable portion 24.

  On the other hand, as shown in (2), when an excessive positive acceleration G exceeding the breaking stress is applied to the acceleration detector 100 according to the second embodiment, the pressure-sensitive portion 32 of the pressure-sensitive element 30 corresponds to the displacement of the movable portion 24. Compressive stress is applied. Since the beam portion 70 fixes the fixed end 72 to the fixed portion 22 of the base 20 and the free end 74 is not fixed, the beam portion 70 is not affected by the compressive stress of the movable portion 24. Accordingly, the free end 74 of the beam portion 70 comes into contact with the second contact portion 50 that is displaced together with the displaced movable portion 24 and functions to stop the displacement of the movable portion 24.

  As a result, even when a large positive acceleration G is applied, the beam portion 70 comes into contact with the second contact portion at the breaking limit and becomes a stopper of the movable portion 24, so that the displacement can be stopped. Therefore, the acceleration can be detected within a predetermined measurement range without being destroyed by excessive acceleration G.

Next, the acceleration detector of Example 3 will be described below.
The acceleration detector 200 according to the third embodiment has a configuration in which a stopper 80 is provided in the configuration of the pressure-sensitive element 30 according to the first embodiment, which is a basic configuration. Specifically, the pressure-sensitive element 300 according to the third embodiment mainly includes a pressure-sensitive portion 32, a pair of base portions 34 and 35, a contact portion 36, and a stopper 80.

  In the pressure-sensitive element 300, a pair of base portions 34 and 35 are arranged at both ends, and a pressure-sensitive portion 32 having a vibration region is provided between the pair of base portions 34 and 35, and excitation electrodes (not shown) are provided on the vibration region. Is forming.

  The pressure-sensitive part 32 of the present embodiment has a configuration in which one vibrating arm is provided between the pair of base parts 34 and 35 so as to be connected to the base parts 34 and 35. The pressure sensing unit 32 may be a double tuning fork vibrating piece that has a large frequency change with respect to the applied force and can detect the pressure with high sensitivity. That is, the double tuning fork vibrating piece is a vibrating piece having a flexural vibration mode, and has a structure in which the end faces on the free end sides of two tuning fork type vibrating pieces are opposed to each other, and are parallel to each other in the Y axis. It is good also as a structure which has two bases which are connected to the both ends of the longitudinal direction of this vibration arm, and the vibration arm extends in the direction, and two bases arranged in a line with the vibration arm.

  The resonating arm is elongated in the Y-axis direction and is a portion that is flexed and vibrated by applying a driving voltage by an excitation electrode (not shown) provided on the surface thereof. This is the part where the frequency changes when tension is applied. Therefore, the acceleration can be detected by detecting the frequency change.

  The pressure-sensitive element 300 is a force perpendicular to the direction of acceleration, and the pair of base portions 34 and 35 are fixed to the mounting surfaces 29a and 29b on the base 20 so that the detection direction of the force is a detection axis. Yes. That is, the detection axis of the pressure sensitive element is in the Y-axis direction.

  Further, the constricted portion 26 of the base 20 with respect to the pressure-sensitive element 300 is an area sandwiched between the pair of base portions 34 and 35 and intersects the direction of the detection axis between the movable portion 24 and the fixed portion 22. It becomes the relationship arranged in.

  The contact part 36 is connected to the base part 35 on the movable part 24 side. A pair of contact portions 36 shown in FIG. 5 is formed on the side surface of the base portion 35. The contact portion 36 is formed at a position overlapping the free end 74 of the beam 70 in plan view of the base 20 as shown in (3).

  Note that the contact portion 36 only needs to be configured to come into contact with the beam portion 70 at the fracture limit and stop the displacement of the movable portion 24. Therefore, two contact portions 36 are provided on the side surface of the base portion 35 as shown in FIG. In addition to the formed structure, any one may be used.

  The stopper 80 includes a fixed end 82 connected to the base portion 34 on the fixed portion 22 side, and a free end 84 extending from the fixed portion 22 side to the base portion 34 on the movable portion 24 side across the constricted portion 26.

  The length of the stopper 80 is configured to arbitrarily change the length between the fixed end 82 and the free end 84 according to a predetermined breaking limit of the acceleration detector 200. The breakage limit of the acceleration detector 200 is, for example, that excessive acceleration is applied to the movable part 24 of the base 20 to increase the amount of displacement, and the expansion and contraction stress acts on the pressure-sensitive element 300 connected to the base 20 to break the element. That means. Specifically, when the length of the stopper 80 is increased, the free end 84 is easily brought into contact with the displaced movable portion 24, and the amount of displacement of the movable portion 24 can be reduced (the displacement range of the movable portion 24 can be reduced). . On the other hand, when the length of the stopper 80 is shortened, the free end 84 does not come into contact unless the movable part 24 is greatly displaced, and therefore the width of the displacement range of the movable part 24 is widened.

  It should be noted that the stopper 80 only needs to be configured to come into contact with the movable portion 24 at the breaking limit to stop the displacement of the movable portion 24. Accordingly, as shown in FIG. 5, two stoppers 80 sandwich the pressure-sensitive portion 32. In addition to the (multiple) formed structure, one may be used.

  The pressure-sensitive element 300 can integrally form the bases 34, 35, the pressure-sensitive part 32, the contact part 36, and the stopper 80 by a photolithography technique and an etching technique, for example, as a piezoelectric material. Lithium, lithium niobate, or the like can be used.

  In the pressure-sensitive element 300 formed as described above, the pair of base portions 34 and 35 are bonded to the mounting portions 29 a and 29 b of the one main surface 27 of the base 20 with a predetermined interval between the base 20 and the bonding means 40. And fixed.

  The predetermined interval that is the gap between the pressure sensitive element 30 and the base 20 is set to a distance at which the pressure sensitive portion 32 and the base 20 do not interfere with each other. At this time, the contact portion 36 is not bonded to the base 20 and is disposed at a position overlapping the free end 74 of the beam portion 70 in plan view.

The acceleration detector according to the third embodiment having the above-described configuration operates as follows. FIG. 6 is an explanatory diagram of the operation of the acceleration detector according to the third embodiment.
As shown in (1), when an excessive negative acceleration G exceeding the destructive stress is applied to the acceleration detector 200 of the third embodiment, the pressure-sensitive portion 32 of the pressure-sensitive element 300 responds to the displacement stress according to the displacement of the movable portion 24. Will be added. On the other hand, the beam portion 70 fixes the fixed end 72 to the fixed portion 22 of the base 20 and the free end 74 is not fixed, so that it is not affected by the stretching stress of the movable portion 24. Accordingly, the contact portion 36 of the pressure-sensitive element 30 that is displaced together with the displaced movable portion 24 comes into contact with the free end 74 of the beam portion 70 and functions to stop the displacement of the movable portion 24.

  On the other hand, as shown in (2), when an excessive positive acceleration G exceeding the breaking stress is applied to the acceleration detector 100 of the third embodiment, the pressure-sensitive portion 32 of the pressure-sensitive element 30 is changed according to the displacement of the movable portion 24. Compressive stress is applied. The stopper 80 fixes the fixed end 82 to the fixed portion 22 of the base 20 through the base 34 of the pressure-sensitive element 300, and the free end 84 is not fixed. Therefore, the stopper 80 may be affected by the compressive stress of the movable portion 24. Absent. Accordingly, the displaced movable portion 24 and the free end 84 of the stopper 80 come into contact with each other and work to stop the displacement of the movable portion 24.

  As a result, when a negative acceleration G exceeding the destruction limit acts on the acceleration detector 200, the beam portion 70 comes into contact with the contact portion 36 and becomes a stopper of the movable portion 24, and is not destroyed by the excessive acceleration G. , Acceleration can be detected within a preset measurement range. When a large positive acceleration G is applied, the stopper 80 comes into contact with the movable part 24 at the destruction limit, and the displacement of the movable part 24 can be stopped. Therefore, the acceleration can be detected within a predetermined measurement range without being destroyed by excessive acceleration G.

Next, an acceleration detector of Example 4 will be described below.
FIG. 7 is a schematic diagram of an acceleration detector according to the fourth embodiment. As illustrated, the acceleration detector 400 according to the fourth embodiment has a configuration in which a second pressure-sensitive element 60 is provided instead of the second contact portion 50 according to the second embodiment. The second pressure-sensitive element 60 is composed of the same shape and material as the pressure-sensitive element 30 of the first embodiment, exhibits the same action, and a detailed description thereof is omitted. The second pressure-sensitive element 60 is provided on the other main surface 28 of the base 20 so as to be symmetric with respect to the first pressure-sensitive element 30 on the one main surface 27 of the base 20 and the base 20. Specifically, the base 34 of the second pressure-sensitive element 60 is bonded to the mounting surface 29 d facing the mounting surface 29 a of the base 34 of the first pressure-sensitive element 30. The base 35 of the second pressure-sensitive element 60 is bonded to the mounting surface 29c facing the mounting surface 29b of the base 35.

The acceleration detector according to the fourth embodiment having the above-described configuration operates as follows.
Since the acceleration detector 400 according to the fourth embodiment includes the first and second pressure-sensitive elements 30 and 60 on one and the other main surfaces 27 and 28 of the base, for example, a positive acceleration G is applied. Then, the first pressure-sensitive element 30 is subjected to compressive stress, and the second pressure-sensitive element 60 is subjected to tensile stress. Therefore, a positive / negative detection signal is reversed, and by taking this difference, highly sensitive acceleration detection can be performed.

  When an excessive negative acceleration G exceeding the destructive stress is applied to the acceleration detector 400 of the fourth embodiment, the pressure-sensitive portion of the first pressure-sensitive element 30 according to the displacement of the movable portion 24 as in FIG. No. 32 is subjected to elongation stress. On the other hand, the beam portion 70 fixes the fixed end 72 to the fixed portion 22 of the base 20 and the free end 74 is not fixed, so that it is not affected by the stretching stress of the movable portion 24. Accordingly, the contact portion 36 of the first pressure-sensitive element 30 displaced together with the displaced movable portion 24 contacts the free end 74 of the beam portion 70 and functions to stop the displacement of the movable portion 24.

  When an excessive positive acceleration G exceeding the destructive stress is applied to the acceleration detector 400 of the fourth embodiment, the pressure-sensitive portion of the second pressure-sensitive element 60 according to the displacement of the movable portion 24 as in FIG. No. 32 is subjected to elongation stress. On the other hand, the beam portion 70 fixes the fixed end 72 to the fixed portion 22 of the base 20 and the free end 74 is not fixed, so that it is not affected by the stretching stress of the movable portion 24. Accordingly, the contact portion 36 of the second pressure-sensitive element 60 displaced together with the displaced movable portion 24 comes into contact with the free end 74 of the beam portion 70 and functions to stop the displacement of the movable portion 24.

  As a result, the acceleration can be detected in a differential manner, so that the acceleration can be detected with higher accuracy. Even when a plus or minus excessive acceleration is applied to the acceleration detector, the first and second pressure-sensitive elements 30 formed on the base beam portion and both main surfaces of the base at the destructive limit, The 60 projecting portions 36 can stop the displacement of the movable portion, and the acceleration detector can be prevented from being destroyed.

  Next, an acceleration detector according to Embodiment 5 will be described below. FIG. 8 is a schematic diagram of an acceleration detector according to the fifth embodiment. The acceleration detector 500 according to the fifth embodiment has a configuration in which one of the first and second pressure sensitive elements 30 and 60 according to the fourth embodiment is replaced with the pressure sensitive element 300 according to the third embodiment. The acceleration detector 500 according to the fifth embodiment illustrated in FIG. 8 has a configuration in which the first pressure sensitive element 30 is replaced with the pressure sensitive element 300 according to the third embodiment.

  Even with such a configuration, the acceleration can be detected in a differential manner, so that the acceleration can be detected with higher accuracy. In addition, even when excessive plus or minus acceleration is applied to the acceleration detector, the beam parts formed on both main surfaces of the base at the fracture limit can stop the displacement of the movable part, and the acceleration detector It can be prevented from being destroyed.

  Next, an acceleration detector according to Embodiment 6 will be described below. FIG. 9 is a schematic diagram of an acceleration detector according to the sixth embodiment. The acceleration detector 600 according to the sixth embodiment has a configuration in which the first and second pressure sensitive elements 30 and 60 according to the fourth embodiment are replaced with the pressure sensitive element 300 according to the third embodiment.

  Even with such a configuration, the acceleration can be detected in a differential manner, so that the acceleration can be detected with higher accuracy. In addition, even when excessive plus or minus acceleration is applied to the acceleration detector, the beam parts formed on both main surfaces of the base at the fracture limit can stop the displacement of the movable part, and the acceleration detector It can be prevented from being destroyed.

  FIG. 10 is a schematic view of a modification of the pressure sensitive element. The pressure sensitive element shown in (1) is a modification of the pressure sensitive element 30 of the first embodiment. As shown in the drawing, the pressure sensitive element 30 </ b> A of the first modification is arranged so that the detection axis of the pressure sensitive part 32 is parallel to the direction of the constricted part 26 (X-axis direction). Specifically, the pressure-sensitive element 30A of Modification 1 is a force that is perpendicular to the acceleration direction (Z-axis direction) through the pair of base portions 34 and 35 and intersects the detection direction of the force (X-axis direction). (Y-axis direction). Then, the end plates 33 (both ends) of the pressure sensing unit 32A having the detection direction of the force as a detection axis are supported by the four links 31. Here, in the configuration of the pressure-sensitive part in which both ends are connected to a pair of bases arranged along the detection axis, a bias of force acting on the pressure-sensitive element occurs between the base on the movable part side and the base on the fixed part side. It was. However, in the configuration of the pressure sensitive element 30 </ b> A according to the first modification, since the bias of force acts uniformly on the pressure sensitive part 32 </ b> A via the link 31, the detection sensitivity can be improved.

  The pressure sensitive element shown in (2) is a modification of the pressure sensitive element 300 of the third embodiment. As illustrated, the pressure-sensitive element 300A of the second modification has a configuration in which a stopper 80A is provided in the structure of the pressure-sensitive element 30A of the first modification. Even in such a configuration, since the bias of force acts uniformly on the pressure-sensitive portion 32A via the link 31, the detection sensitivity can be improved. In addition, when a large positive acceleration G is applied, the stopper can come into contact with the movable part 24 at the breaking limit to stop the displacement of the movable part 24. Therefore, the acceleration can be detected within a predetermined measurement range without being destroyed by excessive acceleration G.

10, 100, 200, 400, 500, 600 ... Acceleration detector, 20 ......... Base, 22 ......... Fixed portion, 24 ......... Moving portion, 26 ......... Necked portion, 27 ......... One 28 ......... the other main surface, 29 ......... mounting portion, 30, 300 ......... pressure-sensitive element, 32 ...... pressure-sensitive portion, 34, 35 ......... base, 36 ... ... Contact part 37 ......... Free end 38 ......... Fixed end 40 ......... Adhesion means 50 ......... Second contact part 51 ......... Main body 52 ......... Contact part 60 ... ...... Second pressure-sensitive element 70... Beam section 72... Fixed end 74.. Free end 80. Stopper 82 82 Fixed end 84 Free end 101 ......... Pressure-sensitive element, 102 ......... Base, 103 ......... Constriction, 104 ......... Weight, 105 ...... Substrate, 201 ...... Hinge coupling, 202 ......... , 203 ......... Weight, 204 ......... Pressure-sensitive element, 301 ......... Accelerometer, 302 ......... Hinge, 303 ......... Weight, 304 ...... Base, 305 ......... Cantilever 306 ......... Free end, 307 ......... Pressure-sensitive element, 308 ......... Free end, 309 ......... Stopped.

Claims (5)

A movable part that is displaced by acceleration applied perpendicularly to the main surface, and a base that includes a fixed part that supports the movable part via a constricted part;
A pressure-sensitive element having a pressure-sensitive portion connected to a pair of bases that are forces perpendicular to the direction of acceleration, the detection direction of which is the detection axis, and arranged along the detection axis;
With
The pair of base portions is fixed to the movable portion and the fixed portion of the base;
The constricted portion is a region sandwiched between the pair of base portions, and is formed in a direction intersecting the direction of the detection axis between the movable portion and the fixed portion,
In the base, a fixed end at one end is connected to the fixed portion, and a free end at the other end is formed in a direction intersecting the direction of the constricted portion and extending to the movable portion side,
The acceleration detector according to claim 1, wherein a contact portion that contacts the beam portion is formed at a position overlapping the beam portion in a plan view at a base portion on the movable portion side. The contact portion is
A first contact portion that contacts the beam portion at a position overlapping the beam portion in a plan view on a base portion of the pressure-sensitive element on one main surface of the base;
A second contact portion facing the first contact portion on the other main surface of the base and contacting the beam portion at a position overlapping the beam portion in plan view;
The acceleration detector according to claim 1, comprising:   The pressure-sensitive element is formed to extend from the base portion on the fixed portion side to the base portion on the movable portion side so as to straddle the constricted portion, and has a stopper whose end portion is a free end. The acceleration detector according to claim 1. The pressure sensitive element is:
A first pressure sensitive element formed on one main surface of the base;
A second pressure sensitive element formed on the other main surface of the base so as to face the first pressure sensitive element;
The acceleration detector according to claim 1 or 3, characterized by comprising:   The acceleration detector according to claim 3, wherein the stopper has a variable length between the fixed end and the free end according to a breakage limit.

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