JP2006226799A - Mechanical quantity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of a sensor element in a mechanical quantity sensor vibrating a cone by using an outside excitation method. <P>SOLUTION: The sensor detecting an angular speed from generating Coriolis force by vibrating the cone at a constant cycle uses a constitution applying vibration from the outside of a detection part 1, and fixes a drive part 3 comprising a piezoelectric element and the detection part 1 through a transmission part 2. The transmission part 2 is composed of a body part 21 fixing a bottom face on the drive part 3 and a projection 22 fixing a projection end face 22a on the detection part 1. The projection end face 22a is formed smaller than an exciting face of the detection part 1. In addition, the projection 22 is formed so as to be projected from a part acted by the maximum amplitude of the drive part 3 in the body part 21. A contact region with a strain deforming region in the drive part 3 can be reduced through the transmission part 2. Therefore, a value of stress acted on the detection part 1 can be reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mechanical quantity sensor that detects a mechanical quantity acting on an object, and more particularly to a mechanical quantity sensor that detects an angular velocity of an object based on a generated Coriolis force.

A sensor called a gyro for detecting the rotational motion of an object is used in a wide range of fields such as a camera shake correction device for a video camera, an in-vehicle airbag device, and a posture control device for a robot.
The gyroscope is a sensor that detects a rotational motion of an object, that is, an angular velocity, and can detect an acting angular velocity regardless of an attachment site or a rotation center position.
The gyro is classified into several types depending on the difference in operating principle, and a gyro using a vibrating body is called a vibrating angular velocity sensor.

A vibration type angular velocity sensor (hereinafter referred to as an angular velocity sensor) detects an angular velocity acting by vibrating a weight body supported by a flexible member at a constant period and detecting a generated Coriolis force.
Specifically, when an angular velocity Ω acts around the x-axis or y-axis in a state where a mass m is vibrated at a velocity v in the z-axis direction, “F = 2 mvΩ” Coriolis is formed at the center of the mass. A force F is generated.
And since a twist arises by the effect | action of the Coriolis force F which generate | occur | produces, a weight body inclines with respect to the surface orthogonal to a vibration direction.
The angular velocity sensor detects the direction and amount of inclination of the weight body, and calculates the angular velocity acting on the weight body based on these detected values.

The angular velocity Ω acting on the weight body appears as a Coriolis force F proportional to the mass m and the speed v of the weight body. Therefore, the detection accuracy (sensitivity) of the angular velocity Ω is improved by increasing the mass m and the velocity v of the weight body.
In order to increase the speed v of the weight body, it is necessary to improve the driving force of the weight body by increasing the vibration frequency or increasing the vibration amplitude.
For example, in a drive system that vibrates a weight body using electrostatic force, the electrostatic force to be applied is increased by increasing the area of the electrode on which the electrostatic force is applied or by narrowing the gap between the electrodes. Can be made.
However, when the area of the electrode is increased, the weight, which is a movable part, must be increased, resulting in an increase in the size of the sensor. In addition, the capacitance between the electrodes increases by narrowing the gap (gap) between the electrodes, but the movable region of the weight body is limited, so that the vibration amplitude cannot be increased.

Furthermore, there is a capacitance detection type angular velocity sensor that detects the tilt of the weight based on the amount of change in capacitance between the movable electrode formed on the weight and the fixed electrode facing the movable electrode.
In such a capacitance detection type angular velocity sensor, when the drive electrode and the detection electrode are formed in the same element, the drive signal and the detection signal interfere with each other, and the detection accuracy of the sensor (Sensitivity) may be reduced.
Therefore, conventionally, a technique for vibrating the entire sensor element with a piezoelectric element provided outside the sensor element as disclosed in Patent Document 1 below has been proposed.
JP 7-159174 A

By the way, in a sensor using the driving method for vibrating the entire sensor element as shown in Patent Document 1, that is, a sensor using an external excitation method, a piezoelectric element is attached to an exterior portion of the sensor element, that is, a portion having no flexibility. It has a configuration.
Therefore, stress acts on the attachment site of the piezoelectric element due to the piezoelectric effect. When the driving force of the piezoelectric element is increased, this stress also increases.
When the stress acting on the attachment portion of the piezoelectric element increases, that is, when the load force applied to the sensor element increases, the durability of the sensor element may decrease.
Accordingly, an object of the present invention is to improve the durability of a sensor element in a mechanical quantity sensor that vibrates a weight body using an external excitation method.

  According to the first aspect of the present invention, the piezoelectric element, the vibration means that vibrates the piezoelectric element by applying an alternating voltage of a predetermined frequency, the flexible portion having flexibility with an end fixed, and the allowable portion. A housing that includes a weight portion that is supported by the flexure portion and vibrates in a predetermined direction, and is disposed between the piezoelectric element and the housing. The first surface and the first surface are disposed to face each other. A second surface having an area equal to or smaller than the area of the first surface and having an area smaller than the smaller one of the vibration surface of the housing or the vibration surface of the piezoelectric element; A transmission portion in which one of the first surface and the second surface is fixed to the housing and the other is fixed to the piezoelectric element, and the weight with respect to a surface orthogonal to the vibration direction of the weight portion Detecting means for detecting the inclination of the part, and the detection means detected by the detecting means Conversion means for converting the inclination of the parts to the angular velocity, to achieve the above object by providing a.

  According to a second aspect of the present invention, in the first aspect of the present invention, the center of the second surface coincides with the position of the center of gravity of the housing.

  According to a third aspect of the invention, in the first or second aspect of the invention, the transmission portion has a protruding portion protruding in the direction of the housing or the piezoelectric element, and the second surface is The end surface of the protruding portion is configured.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the length in the protruding direction of the protruding portion is longer than the maximum amplitude length of the vibration surface of the piezoelectric element.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the vibration frequency of the piezoelectric element and the resonance frequency of the weight portion are the same or in the vicinity. Is the frequency.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the resonance frequency of the piezoelectric element and the resonance frequency of the weight portion are the same or close to each other. Is the frequency.

  According to a seventh aspect of the invention, there is provided the urging means for urging the housing in a direction in which the piezoelectric element is disposed in the invention according to any one of the first to sixth aspects. .

  According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the piezoelectric elements are provided to face each other with the housing interposed therebetween.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the housing has a vacuum inside, and a through hole and a conductor formed in the through hole. And a fixed electrode that is provided on an inner wall surface and is electrically joined to the lead portion, wherein the detection means is a capacitance element formed by the fixed electrode and the weight portion. The inclination of the weight portion is detected based on a change in capacitance.

  According to the present invention, by fixing the piezoelectric element to the housing via the transmission portion, the stress acting on the housing due to the deformation of the piezoelectric element is reduced as compared with the case where the piezoelectric element and the housing are directly fixed. be able to. Thereby, the durability of the housing can be improved.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. In the present embodiment, a capacitance detection type angular velocity sensor (hereinafter referred to as an angular velocity sensor) will be described as an example of a mechanical quantity sensor that detects angular velocity.
FIG. 1 is a diagram showing a schematic configuration of an angular velocity sensor according to the present embodiment.
As shown in FIG. 1, the angular velocity sensor includes a detection unit 1, a transmission unit 2, and a drive unit 3.
Further, the detection unit 1 is provided with a signal line 4 for inputting / outputting a signal to / from a control unit (not shown). The drive unit 3 is also provided with a signal line 5 for inputting / outputting a signal to / from a control unit (not shown).

FIG. 2 is a cross-sectional view illustrating a schematic configuration of the detection unit 1.
The detection unit 1 is a sensor element that detects an angular velocity that actually acts. The detection unit 1 is a semiconductor sensor element formed by processing a semiconductor substrate. The processing of the semiconductor substrate can be performed using a MEMS (micro electro mechanical system) technique.
In the angular velocity sensor according to the present embodiment, the same direction as the stacking direction of the substrates constituting the detection unit 1 is defined as the vertical direction, that is, the z axis (direction). The axes orthogonal to the z-axis and orthogonal to each other are defined as an x-axis (direction) and a y-axis (direction). That is, the x axis, the y axis, and the z axis are three axes that are orthogonal to each other.

The detection unit 1 includes a movable part structure 11, an upper glass substrate 12, and a lower glass substrate 13. Specifically, the movable part structure 11 has a three-layer structure in which the upper glass substrate 12 and the lower glass substrate 13 are sandwiched from above and below.
FIG. 3 is a plan view showing the configuration of the movable part structure 11. 2 is a view showing a position of the line segment AA ′ shown in FIG. 3, that is, a cross section of the detection unit 1 in the x-axis direction.
The movable part structure 11 is formed from a silicon substrate. The silicon substrate is etched to form the frame 111, the beam 112, and the weight body 113. The weight body 113 functions as a movable part.

The frame 111 is a fixed part provided on the peripheral edge of the movable part structure 11 so as to surround the weight body 113, and constitutes the framework of the movable part structure 11. The frame 111, the upper glass substrate 12, and the lower glass substrate 13 constitute a housing (exterior body) of the detection unit 1.
The beam 112 is four strip-shaped thin members extending in the cross direction in the radial direction (in the direction of the frame 111) from the center of the weight body 113, and has flexibility.
The weight body 113 is a mass body fixed to the frame 111 by four beams 112. The weight 113 can be vibrated or twisted by the external force applied by the beam 112.

Returning to the description of FIG. 2, a movable gap which is a space for moving the weight body 113 between the upper surface of the beam 112 and the weight body 113 (a surface facing the upper glass substrate 12) and the upper glass substrate 12. 114 is formed. The upper glass substrate 12 is bonded so as to seal the movable gap 114.
On the lower surface of the beam 112 (the surface facing the lower glass substrate 13) and the bottom surface of the weight body 113, that is, between the lower surface (the surface facing the lower glass substrate 13) and the lower glass substrate 13, and at the periphery of the weight body 113 In addition, a movable gap 115 which is a space for making the weight 113 movable is formed. The lower glass substrate 13 is bonded so as to seal the movable gap 115.
The movable gaps 114 and 115 are in a vacuum state. By setting the vacuum state, the air resistance when the weight body 113 operates can be reduced.

When forming the frame 111, the beam 112, and the weight body 113 in the movable part structure 11, a D-RIE (Deep-Reactive Ion Etching) technique for performing a deep trench etching with a plasma on a silicon substrate is used. And do it.
In the angular velocity sensor according to the present embodiment, the main body of the movable part structure 11 is formed using a silicon substrate, but the forming member of the movable part structure 11 is not limited to this. For example, an SOI (silicon on insulator) substrate in which an oxide film is embedded in an intermediate layer of a silicon substrate may be used.
In this case, in the etching process for processing the beam 112 and the weight body 113, the intermediate oxide film layer functions as an etching blocking layer (stop layer), so that the processing accuracy in the thickness direction can be improved.

The upper glass substrate 12 and the lower glass substrate 13 are glass substrates joined to seal the movable part structure 11. The upper glass substrate 12 and the lower glass substrate 13 are joined to each other by anodic bonding at the frame 111 of the movable part structure 11.
The anodic bonding is a bonding method in which a cathode voltage is applied to the glass substrate (upper glass substrate 12, lower glass substrate 13) side and bonding is performed using electrostatic attraction between glass and silicon.
In addition, the joining method of a glass substrate and the movable part structure 11 is not limited to anodic bonding. For example, eutectic bonding in which metals are laminated on the bonding surface and bonded may be used.

FIG. 4 is a plan view showing the configuration of the upper glass substrate 12. FIG. 4 is a view of the upper glass substrate 12 as viewed from the movable part structure 11 side.
The upper glass substrate 12 includes fixed electrodes 121 to 124, lead terminals 125 to 128, common terminals 129, lead pads 130 to 133, common pads 134, and through holes 135 to 139.
The fixed electrodes 121 to 124 are made of a conductor member such as aluminum disposed on the side surface of the upper glass substrate 12.

The fixed electrodes 121 to 124 are formed of electrodes having the same shape and the same area. The shape of the electrode is a right-angled isosceles triangle, and is arranged every 90 ° so as to surround the center so that the vertices of two sides forming a right angle of each electrode are directed to the center direction of the weight body 113.
Opposing electrodes on the same plane, that is, electrodes positioned on the opposite side across the center, are used as a pair, and are used when detecting each axial component of the posture state of the weight body 113.
Here, the fixed electrode 121 and the fixed electrode 122 are paired to detect the posture state of the weight body 113 in the x-axis direction. In addition, the fixed electrode 123 and the fixed electrode 124 are paired to detect the posture state of the weight body 113 in the y-axis direction.

The lead terminals 125 to 128 are terminals electrically connected to the fixed electrodes 121 to 124 through conductive patterns, respectively. The lead terminals 125 to 128 have the potentials of the fixed electrodes 121 to 124 from the lower surface (the surface facing the movable part structure 11) to the upper surface (the surface not facing the movable part structure 11) of the upper glass substrate 12. It is a terminal to pull out.
The common terminal 129 is a terminal for extracting the potential of the weight body 113 from the lower surface (the surface facing the movable part structure 11) of the upper glass substrate 12 to the upper surface (the surface not facing the movable part structure 11). It is.

The lead pads 130 to 133 are conductive pads (patterns) formed to have the same potential as the lead terminals 125 to 128.
The common pad 134 is a conductive pad (pattern) formed to have the same potential as the common terminal 129.
By connecting the signal line 4 (shown in FIG. 1) to the extraction pads 130 to 133 and the common pad 134, the detection unit 1 and the control unit can be electrically connected.

The through holes 135 to 139 are tapered through holes that penetrate the upper glass substrate 12 and are formed to form the lead terminals 125 to 128 and the common terminal 129. The through holes 135 to 139 are formed so that the area of the opening is smaller on the inner wall side than on the outer wall side of the upper glass substrate 12.
The common terminal 129 is electrically conductive from the upper surface (the surface not facing the movable portion structure 11) because the bottom surface (the end surface facing the movable portion structure 11) of the through hole 139 is in contact with the movable portion structure 11. It can be formed by evaporating a material (such as Al). Since the entire periphery of the bottom surface of the through-hole 139 is completely in close contact with the movable part structure 11, it is possible to maintain airtightness.

  On the other hand, the lead-out terminal 125 is also a conductive thin film formed along the inner peripheral wall surface of the through hole 135, similarly to the common terminal 129. However, since the lower surface of the through hole 135 is open, it cannot be formed in the same manner as the common terminal 129. Therefore, by connecting a conductive plate-like member (not shown) to the lower surface of the through hole 135 in advance so as to be electrically connected to the fixed electrode 121, the upper portion (movable part structure 11 and the same as the common terminal 129). It can be formed by vapor deposition from the non-opposing surface. Alternatively, after forming a conductive film on the inner peripheral wall surface of the through hole 135 first, the hole on the bottom surface of the through hole 135 may be filled with solder or conductive resin so that the conductive film and the fixed electrode 121 are electrically connected. . The other lead terminals 126 to 128 are formed in the same manner as the lead terminal 125.

Returning to the description of FIG. 1, the transmission unit 2 will be described.
The transmission part 2 is composed of a main body part 21 and a protruding part 22.
The main body 21 is a hexahedral member whose bottom surface is fixed (joined) to the drive unit 3.
The protruding portion 22 is a prismatic portion protruding in a vertical direction from a substantially central portion (central portion) of the upper surface facing the bottom surface of the main body portion 21, and the protruding end surface 22 a is the detecting portion 1 (lower glass substrate). 13) is fixed (joined).
The shape of the protruding portion 22 may be any area as long as the protruding end surface 22a is smaller than the vibration surface 13a. For example, the protruding portion 22 is a rectangle extending in the longitudinal direction or the short-side direction on the upper surface facing the bottom surface of the body portion 21. It may be formed as follows.
Needless to say, the transmission unit 2 needs to be firmly fixed to other members, but the detection unit 1 side has a small fixed area. In practice, since the bonding (or adhesion) with the lower glass substrate 13 is performed, a material having a thermal expansion coefficient close to that of glass such as 42 alloy (iron-nickel alloy) or Kovar (iron-nickel-cobalt alloy) is desirable. Alternatively, the transmission part 2 may be formed of Si and anodic bonded.

Hereinafter, vibration is applied to the surface of the detection unit 1 (lower glass substrate 13) to which the transmission unit 2 is fixed (bonded), that is, the surface of the detection unit 1 (lower glass substrate 13) facing the drive unit 3 (piezoelectric element). It is assumed that the vibration surface 13a is made.
The protruding end surface 22a has a smaller area than the lower end surface (excitation surface 13a) of the lower glass substrate 13 in the detection unit 1.
The fixed surface of the main body 21 of the transmission unit 2 with the drive unit 3 functions as a first fixed surface, and the fixed surface of the protruding portion 22 with the detecting unit 1 (the protruding end surface 22a) is the second fixed surface. Functions as a surface.
Further, the center of the protruding end surface 22a is joined in a balanced state so as to be positioned at the center of the lower glass substrate 13 of the detection unit 1.

Next, the drive unit 3 will be described.
The driving unit 3 is a piezoelectric oscillator that includes a piezoelectric element and can generate a predetermined vibration by the piezoelectric effect of the piezoelectric element.
The piezoelectric effect indicates a property of being charged when compressed or stretched and distorted when a voltage is applied. An element having this piezoelectric effect is a piezoelectric element (electrostrictive element).
Examples of the piezoelectric element (piezo element) include quartz, piezoelectric ceramics, Rochelle salt, barium titanate, EDT, and the like.
The vibration (strain) characteristics of the piezoelectric element vary depending on the arrangement of crystals forming the piezoelectric element and the voltage application method.

In the present embodiment, vibration is generated by applying an alternating voltage (alternating voltage) having a predetermined frequency to the piezoelectric element of the drive unit 3.
When an AC voltage is applied to the piezoelectric element, distortion occurs on all sides of the piezoelectric element. As shown in FIG. 1, when a vibration is actually applied to the detection unit 1, a distortion action on a surface facing the detection unit 1, that is, a surface where the transmission unit 2 is joined is used.
A surface of the driving unit 3 (piezoelectric element) to which the transmission unit 2 is fixed, that is, a working surface that vibrates the detection unit 2 is defined as a vibration surface 3a.
The AC voltage to the drive unit 3 (piezoelectric element) is applied from the control unit via the signal line 5.

Next, the operation of the angular velocity sensor according to this embodiment configured as described above will be described.
In the angular velocity sensor according to the present embodiment, an AC voltage having a high frequency (for example, about 3 kHz) is applied to the drive unit 3 via the signal line 5 to vibrate the drive unit 3 in the z-axis direction. The vibration generated in step 1 is applied to the detection unit 1 through the transmission unit 2.
A control unit (not shown) functions as a vibration unit that applies an AC voltage to the drive unit 3 (piezoelectric element).
When the vibration of the drive unit 3 is applied to the detection unit 1 via the transmission unit 2 joined to the lower glass substrate 13, the entire housing (exterior body) vibrates. This vibration is transmitted from the frame 111 of the movable part structure 11 to the weight body 113 via the beam 112. Thereby, the weight body 113 is forcibly vibrated in the z-axis direction.
Note that the vibration frequency of the weight body 113 matches the vibration frequency of the drive unit 3.

In the angular velocity sensor according to the present embodiment, in order to increase the vibration amplitude of the weight body 113 in the detection unit 1, the vibration is performed at the resonance frequency of the weight body 113. The resonance frequency is a frequency that is determined based on the natural frequency of the beam 112 and the weight body 113 related to the vibration of the weight body 113. The natural frequency is a vibration frequency of all objects, and is determined by factors such as the rigidity and mass of the object, and is a frequency at which the object is most likely to resonate (sway).
By resonating the weight body 113 in this way, that is, by setting the vibration frequency of the drive unit 3 to the resonance frequency of the weight body 113, the vibration amplitude of the weight body 113 can be increased with less energy. Furthermore, the vibration amplitude can be increased with less energy by setting the resonance frequency unique to the drive unit 3 (piezoelectric element) and the resonance frequency of the weight body 113 to the same or in the vicinity.

When an angular velocity Ω is applied around the mass 113 oscillating in the z-axis direction at the velocity v, a Coriolis force F of “F = 2 mvΩ” is applied to the center of the mass 113 in the direction of movement of the mass 113. Occurs in a direction orthogonal to
When this Coriolis force F is generated, the weight 113 is twisted and the posture of the weight 113 changes. Specifically, the weight body 113 is inclined with respect to a plane orthogonal to the vibration direction of the weight body 113, that is, an xy plane.
In the angular velocity sensor according to the present embodiment, the posture change (inclination amount and inclination direction) of the weight body 113 when the angular velocity acts is detected, and the detected posture change amount of the weight body 113 is converted into an angular velocity.

Here, a method for detecting the posture change of the weight body 113 will be described.
As described above, the beam 112 and the weight body 113 are made of conductive silicon. Therefore, the region facing the upper glass substrate 12 in the beam 112 and the weight body 113 functions as a movable electrode.
In the present embodiment, the posture change of the weight body 113 is detected based on the amount of change in the capacitance of the capacitance element formed by the movable electrode of the weight body 113 and the fixed electrodes 121 to 124. When the weight 113 is inclined with respect to the xy plane, the distance (gap length) between the movable electrode and the fixed electrodes 121 to 124 changes. When the gap length between the electrodes changes, the capacitance of the capacitance element changes.

In the present embodiment, the inclination of the weight 113 in the x-axis direction is detected by measuring the change in capacitance of the capacitive element formed by the fixed electrode 121 and the movable electrode and the fixed electrode 122 and the movable electrode. is doing.
Similarly, the inclination of the weight 113 in the y-axis direction is detected by measuring the change in capacitance of the capacitive element formed by the fixed electrode 123 and the movable electrode and the fixed electrode 124 and the movable electrode. .
The capacitance between the electrodes can be electrically detected using a capacitance / voltage conversion (C / V conversion) circuit.

As the C / V conversion circuit, for example, there is a method in which a carrier signal (reference signal) having a sufficiently high frequency is applied to a capacitance element, and the amount of change in the amplitude of the output signal is detected as capacitance.
The amplitude of the output of the carrier signal applied to the capacitance element is proportional to the capacitance. Therefore, the capacitance can be detected by comparing the amplitudes of the input carrier signal and the output carrier signal.
In the angular velocity sensor according to the present embodiment, an AC signal having a frequency band of several hundred kHz to several MHz is applied to the electrode as a carrier signal.
The angular velocity sensor detects the Coriolis force F generated based on the detected change in the posture of the weight body 113 (inclination direction, degree of inclination, etc.). Then, the angular velocity Ω is calculated (derived) based on the detected Coriolis force F. That is, the amount of change in the posture of the weight body 113 is converted into an angular velocity.
The amount of change in the posture of the weight body 113 is converted into an angular velocity by starting an angular velocity calculation program stored in advance in the control device and performing a predetermined calculation process.

As shown in FIG. 1, in the angular velocity sensor according to the present embodiment, the detection unit 1 and the drive unit 3 are joined via the transmission unit 2.
Here, the function of the transmission unit 2 will be described.
The piezoelectric element constituting the drive unit 3 repeats expansion and contraction due to the action of the piezoelectric effect when an AC voltage is applied. The piezoelectric element may be deformed as shown in FIG. 7 due to variations in the characteristics of the material forming the element.
Note that FIG. 7 shows the distortion state simply and exaggerated for easy understanding of the deformation state, and the deformation is not necessarily limited to the state shown in the figure.

Thus, if a piezoelectric element (driving unit 3) having a large degree of distortion on the side surface of the voltage element due to the piezoelectric effect is directly fixed to the detecting unit 1, the bonding between the detecting unit 1 and the piezoelectric element (driving unit 3) is performed. In the portion, stress acts in the direction in which the piezoelectric element bends.
In addition, when the driving unit 3 (piezoelectric element) is directly fixed to the detection unit 1, a fixed end vibration in a state where the end portion is fixed is generated in a contact area of the detection unit 1 with the driving unit 3. It will be affected by the entire contact area. That is, the stress against the distortion of the voltage element acts on the entire area of the joint surface of the detection unit 1.
When such stress acts on the detection unit 1, there is a possibility that an angular velocity detection error may occur. Moreover, there exists a possibility that durability of the detection part 1 may fall by the effect | action of this stress.

Therefore, in the angular velocity sensor according to the present embodiment, the detection unit 1 is connected via the transmission unit 2 in order to suppress the influence of the stress acting on the detection unit 1 due to the expansion / contraction deformation of the piezoelectric element (drive unit 3). The driving unit 3 is fixed.
By fixing (joining) via the transmission unit 2, the contact area with the area that is deformed (flexed) is reduced as compared with the case where the driving unit 3 (piezoelectric element) is directly fixed to the detection unit 1. Can do. Thereby, the value of the stress acting on the detection unit 1 can be reduced.

Further, as shown in FIG. 7, the area of the joint surface of the transmission unit 2 with the detection unit 1, that is, the protruding end surface 22 a is set to the vibration surface 13 a of the detection unit 1 and the vibration surface 3 a of the drive unit 3 (piezoelectric element). It is configured so as not to be sufficiently smaller than that. The protruding end surface 22a is desirably formed so as to be as small as possible (at one point).
In this case, since the weight of the detection unit 1 is supported at a single point, the vibration direction may be deviated from the z-axis unless the weight is balanced at the balanced position of the support unit 1, that is, the center of gravity. is there. Therefore, in this Embodiment, it becomes the structure fixed at the center position in the xy direction of the support part 1 as mentioned above.

Specifically, it is possible to reduce the influence of the distortion of the piezoelectric element, that is, the region where the stress of the detection unit 1 acts only on the region of the protruding end surface 22a that is a joint portion with the detection unit 1.
Since the vibration at the joint between the vibration surface 3a and the protruding end surface 22a of the detection unit 1 is not a fixed end vibration but a free end vibration state, the degree of distortion (deformation) can also be suppressed.
Then, the influence of the deformation caused by the vibration in the vibration direction when the detection unit 1 and the piezoelectric element are directly joined, that is, the influence of the deformation (deflection) in the vibration direction of the drive unit 3 (piezoelectric element) is caused to vibrate the entire detection unit 1. This can be solved.
Therefore, it is possible to suppress stress generated on the vibration surface 3a due to deformation (deflection) in the vibration direction in the drive unit 3 (piezoelectric element).

Further, due to deformation of the drive unit 3 (piezoelectric element), the region of the excitation surface 13a of the detection unit 1 that is not joined to the protruding end surface 22a (for example, the peripheral portion of the excitation surface 13a) and the transmission unit 2 There is a possibility that a part of the main body 21 comes into contact.
When such contact occurs, an external force is applied to the contact portion of the vibration surface 13a, and stress may be applied to the detection unit 1.
Therefore, the length β of the projecting direction of the projecting portion 22 in the transmission unit 2 according to the present embodiment, that is, the vibration direction length of the driving unit 3 (piezoelectric element) is at least greater than the maximum amplitude α of the driving unit 3 (piezoelectric element). Is configured to be larger.
By setting the height of the protruding portion 22 in this way, it is possible to avoid undesired contact between the detection unit 1 and the transmission unit 2 during vibration.

In the present embodiment, the angular velocity sensor in which the excitation surface 13a in the detection unit 1 is configured to be smaller than the vibration surface 3a of the drive unit 3 (piezoelectric element) has been described.
In the angular velocity sensor in which the excitation surface 13a in the detection unit 1 is configured to be larger than the vibration surface 3a of the drive unit 3 (piezoelectric element), the area of the protruding end surface 22a of the protruding unit 22 is the transmission unit 2. It is preferable that the driving unit 3 (piezoelectric element) be configured to be smaller than the vibration surface 3a.
In this way, in the angular velocity sensor in which the excitation surface 13a is configured to be larger than the vibration surface 3a, the direct drive unit 3 (piezoelectric element) is detected by configuring the area of the protruding end surface 22a to be smaller than the vibration surface 3a. Compared with the case where it is fixed to the part 1, it is possible to reduce the contact area with the area where distortion (deflection) is deformed. Thereby, the value of the stress acting on the detection unit 1 can be reduced.

Although the transmission part 2 comprised from the main-body part 21 and the protrusion part 22 was demonstrated in this Embodiment, the shape and arrangement | positioning method of the transmission part 2 are not limited to this.
The transmission unit 2 includes a driving side fixing surface fixed to the driving unit 3 (piezoelectric element) and a detection side fixing surface fixed to the lower glass substrate 13 of the detecting unit 1. The driving side fixing surface and the detection side It is sufficient that at least one area of the fixed surface is configured to be smaller than the smaller one of the area of the vibration surface 13a of the detection unit 1 or the vibration surface 3a of the drive unit (piezoelectric element).
For example, the transmission unit 2 may be provided in an upside down state. Specifically, the bottom surface of the main body 21 of the transmission unit 2 is fixed to the vibration surface 13a of the detection unit 1, and the protruding end surface 22a of the protruding unit 22 is fixed to the vibration surface 3a of the driving unit 3 (piezoelectric element). You may make it arrange | position to.

Moreover, the shape of the transmission part 2 fixed between the detection part 1 and the drive part 3 (piezoelectric element) may be a cylinder, a polygonal column, a truncated cone, or a truncated polygonal cone, for example.
When the transmission unit 2 is formed of a cylindrical or polygonal column-shaped member, the bottom surface thereof is the smaller one of the excitation surface 13a of the detection unit 1 or the vibration surface 3a of the drive unit 3 (piezoelectric element) It is preferable that it is formed to be smaller than the area.
In the case of a truncated cone or truncated polygonal pyramid shaped member, the upper end surface (the end surface on the truncated side) is the vibration surface 13a of the detection unit 1 or the vibration surface of the drive unit 3 (piezoelectric element). It is preferable that it is formed to be smaller than the smaller one of 3a.
Moreover, it is preferable that the height of the cylinder, the polygonal column, the truncated cone, and the truncated polygonal pyramid is at least larger than the maximum amplitude α of the drive unit 3 (piezoelectric element).

In the angular velocity sensor according to the present embodiment, the vibration control circuit in the drive unit 3 and the posture change detection circuit of the weight body 113 in the detection unit 1 are formed as different and independent control systems.
Since the drive unit 3 is provided outside the detection unit 1, the drive signal of the drive unit 3 and the detection signal of the posture change of the weight body 113 can be easily separated.
Therefore, it is possible to suppress the occurrence of crosstalk (mutual interference) in which the drive signal in the control circuit of the drive unit 3 wraps around the posture detection circuit of the weight body 113.
Thereby, since the control system in the angular velocity sensor is stabilized in an appropriate state, detection accuracy with a high angular velocity can be maintained.

Next, a modification of the angular velocity sensor according to the present embodiment will be described.
The piezoelectric element forming the drive unit 3 has a relatively high strength against a stress in a contracting direction (compression stress), but has a low strength against a stress in an extending direction (tensile stress). have.
Therefore, the angular velocity sensor according to the present embodiment is driven in a state in which a compressive stress is always applied to the piezoelectric element (driving unit 3), that is, in a state where a preliminary pressure (biasing force) is applied to the piezoelectric element. It is configured to (vibrate).

(Modification 1)
FIG. 5 is a diagram showing a configuration of Modification 1 of the angular velocity sensor according to the present embodiment. In addition, the same code | symbol is used for the site | part which overlaps with the angular velocity sensor mentioned above, and the description is abbreviate | omitted.
As shown in the figure, the variation 1 of the angular velocity sensor includes a detection unit 1, a first transmission unit 102, a first drive unit 103, a second transmission unit 202, and a second drive unit 203. These devices are the angular velocity sensor. Arranged inside the housing 6.
The 1st transmission part 102 and the 2nd transmission part 202 have the same structure as the transmission part 2 mentioned above, and the 1st drive part 103 and the 2nd drive part 203 have the same structure as the drive part 3 mentioned above.

Variation 1 of the angular velocity sensor is configured to vibrate the detection unit 1 simultaneously from two directions (vertical direction) on the z axis. That is, the detection unit 1 is configured to vibrate from the same direction as the vibration direction of the weight body 113.
Specifically, the first drive unit 103 is fixed to the upper end surface of the detection unit 1 via the first transmission unit 102, and the second drive unit 203 is fixed to the lower end surface of the detection unit 1 via the second transmission unit 202. .
The first drive unit 103 and the second drive unit 203 are each fixed to the casing 6 (fixed part) of the angular velocity sensor. The first drive unit 103 and the second drive unit 203 are fixed to the inner wall surface of the housing 6 on the side opposite to the side facing the detection unit 1.

In this manner, the detection unit 1 is sandwiched between the first drive unit 103 and the second drive unit 203, and the detection unit 1 is vibrated while being in close contact with the housing 6.
When vibration is applied to the detection unit 1, AC voltages having opposite phases are applied to the first drive unit 103 and the second drive unit 203, respectively.
In the angular velocity sensor fixed in such a close contact (clamping) state, a preliminary pressure (biasing force) is always applied (applied) to the first drive unit 103 and the second drive unit 203. .
As a result, even when the piezoelectric elements forming the first driving unit 103 and the second driving unit 203 are greatly deformed in the extending direction, the amount of displacement at the time of deformation is limited, so that the acting tensile stress is suppressed. Can do. Accordingly, since the durability of the piezoelectric element can be improved, the durability of the angular velocity sensor can be improved.

(Modification 2)
FIG. 6 is a diagram showing a configuration of Modification 2 of the angular velocity sensor according to the present embodiment. In addition, the same code | symbol is used for the site | part which overlaps with the angular velocity sensor mentioned above, and the description is abbreviate | omitted.
As shown in FIG. 6, the second modified example of the angular velocity sensor includes a detection unit 1, a transmission unit 2, a drive unit 3, and a spring 7, and these devices are arranged inside a housing 6 of the angular velocity sensor.
The drive unit 3 is fixed to the inner wall surface of the casing 6 (fixed part) of the angular velocity sensor. The drive unit 3 is fixed to the detection unit 1 via the transmission unit 2. Further, a spring 7 functioning as an urging means is disposed between the upper end surface of the detection unit 1, that is, the side surface opposite to the side surface facing the driving unit 3 and the housing 6.
The spring 7 is fixed between the detection unit 1 and the housing 6 in a state shorter than the natural length, that is, in a contracted state. Therefore, the detection unit 1 always has a structure in which a preliminary pressure (biasing force) is applied (applied) in the direction of the drive unit 3. The preliminary pressure (biasing force) applied to the detection unit 1 by the spring 7 acts on the drive unit 3 via the transmission unit 2.

Accordingly, even when the piezoelectric element forming the driving unit 3 is greatly deformed in the extending direction, the amount of displacement at the time of deformation is limited, so that the acting tensile stress can be suppressed. Accordingly, since the durability of the piezoelectric element can be improved, the durability of the angular velocity sensor can be improved.
The biasing means for applying the preliminary pressure (biasing force) to the detection unit 1 is not limited to the spring 7. Other elastic members may be used as long as the pre-pressure can be appropriately applied.

It is the figure which showed schematic structure of the angular velocity sensor which concerns on this Embodiment. It is sectional drawing which showed schematic structure of the detection part. It is the top view which showed the structure of the movable part structure. It is the top view which showed the structure of the upper glass board | substrate. It is the figure which showed the structure of the modification 1 of the angular velocity sensor which concerns on this Embodiment. It is the figure which showed the structure of the modification 2 of the angular velocity sensor which concerns on this Embodiment. It is the figure which showed the mode of the deformation | transformation of a piezoelectric element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection part 2 Power transmission part 3 Drive part 4 Signal line 5 Signal line 6 Case 7 Spring 11 Movable part structure 12 Upper glass substrate 13 Lower glass substrate 21 Main body part 22 Projection part 111 Frame 112 Beam 113 Weight body 114 Movable gap 115 Movable gaps 121-124 Fixed electrodes 125-128 Lead terminals 129 Common terminals 130-133 Lead pads 134 Common pads 135-139 Through holes

Claims (9)

A piezoelectric element;
Vibration means for vibrating the piezoelectric element by applying an alternating voltage of a predetermined frequency;
A housing that includes a flexible portion having a fixed end and a weight portion that is supported by the flexible portion and vibrates in a predetermined direction;
The housing is disposed between the piezoelectric element and the housing, has a first surface, and is disposed to face the first surface, and has an area equal to or smaller than an area of the first surface, and the housing And a second surface having an area smaller than the smaller one of the vibration surfaces of the piezoelectric element, and one of the first surface and the second surface is in the housing. A transmission portion fixed and the other fixed to the piezoelectric element;
Detecting means for detecting an inclination of the weight portion with respect to a plane orthogonal to the vibration direction of the weight portion;
Conversion means for converting the inclination of the weight portion detected by the detection means into an angular velocity;
A mechanical quantity sensor characterized by comprising:   The mechanical quantity sensor according to claim 1, wherein the center of the second surface coincides with the position of the center of gravity of the housing. The transmission portion has a protruding portion protruding in the direction of the housing or the piezoelectric element,
The mechanical quantity sensor according to claim 1, wherein the second surface is configured by an end surface of the protruding portion.   The mechanical quantity sensor according to claim 3, wherein a length in a protruding direction of the protruding portion is longer than a maximum amplitude length in a vibration surface of the piezoelectric element.   The mechanical quantity sensor according to any one of claims 1 to 4, wherein the vibration frequency of the piezoelectric element and the resonance frequency of the weight portion are the same or close to each other. .   The mechanical quantity sensor according to any one of claims 1 to 5, wherein the resonance frequency of the piezoelectric element and the resonance frequency of the weight portion are the same or close to each other. .   The mechanical quantity sensor according to any one of claims 1 to 6, further comprising an urging unit that urges the housing in a direction in which the piezoelectric element is disposed.   The mechanical quantity sensor according to any one of claims 1 to 7, wherein the piezoelectric elements are provided to face each other with the housing interposed therebetween. The housing has a vacuum inside, and includes a through hole, a lead portion made of a conductor formed in the through hole, and a fixed electrode provided on an inner wall surface and electrically connected to the lead portion,
The said detection means detects the inclination of the said weight part based on the change of the electrostatic capacitance of the electrostatic capacitance element formed with the said fixed electrode and the said weight part. The mechanical quantity sensor according to claim 1.

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