JPH08285608A - Angular velocity sensor - Google Patents

Abstract

PURPOSE: To provide a small, highly sensitive, and practical double-axis angular velocity sensor. CONSTITUTION: A metallic oscillating substrate 30 in which concentric slits 31 are formed is held between two piezoelectric elements 20 and 40 and stuck so as to form a three-layer diaphragm. Also four electrodes E1 to E4 are formed on the upper surface of the piezoelectric element 20, and an opposed electrode is formed on the lower surface of it. Electrodes are also formed on both surfaces of piezoelectric elements 40. Then a weight body not shown is connected to the lower surface of the piezoelectric element 40. A pedestal 50 supports the lower surface of the three-layer diaphragm at an annular node position, and is suspended from a circuit board 10 by wire members 52 and 53. In addition, an exciting AC voltage is supplied to electrodes E1 to E4 with charges generated at the electrodes of the piezoelectric element 40 as feed back signals so as to oscillate the weight body in vertical direction. In this case, a Coriolis force acting on the weight body is detected, and an acting angular velocity is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an angular velocity sensor, and more particularly to
The present invention relates to a sensor capable of detecting angular velocity about two independent axes for each axis.

[0002]

2. Description of the Related Art In the automobile industry, machine industry and the like, there is an increasing demand for sensors capable of accurately detecting physical quantities such as acceleration and angular velocity. In general, an acceleration in an arbitrary direction and an angular velocity in an arbitrary rotation direction act on an object that freely moves in a three-dimensional space. Therefore, in order to accurately grasp the motion of this object, it is necessary to independently detect the acceleration in each coordinate axis direction and the angular velocity around each coordinate axis in the XYZ three-dimensional coordinate system. Therefore,
There is an increasing demand for a multi-dimensional acceleration sensor and a multi-axis angular velocity sensor that are small in size, have high accuracy, and can reduce manufacturing costs.

Conventionally, various types of multidimensional acceleration sensors have been proposed. For example, International Publication No. WO88 / 08522 based on the Patent Cooperation Treaty (US Pat. No. 4
No. 9676605 / No. 5182515), International Publication No. WO91 / 10118 (US Patent Application No. 07/761771) based on the Patent Cooperation Treaty, International Publication No. WO92 / 17759 (US Patent Application) based on the Patent Cooperation Treaty. No. 07/952753) discloses an acceleration sensor that detects the applied acceleration for each coordinate axis direction. The characteristics of these acceleration sensors are that a plurality of resistance elements / capacitance elements / piezoelectric elements are arranged at predetermined positions on a flexible substrate, and a change in resistance value of the resistance element / capacitance of the capacitance element. The point is that the applied acceleration is detected based on the change in the value / the change in the voltage generated by the piezoelectric element. A weight body is attached to the flexible substrate, and when acceleration acts, a force is applied to the weight body, and the flexible substrate is bent. If this deflection is detected based on the change in the resistance value / capacitance value / generated charge described above, each axial component of the acceleration can be obtained.

On the other hand, regarding the angular velocity sensor, various types have been conventionally used to detect the angular velocity of a power shaft of a vehicle, but most of them are uniaxial angular velocity sensors, and biaxial or more angular velocity sensors are not. As far as the inventor of the present invention knows, it has not been put to practical use at this stage.

In such a situation, the inventor of the present application
A novel multi-axis angular velocity sensor that is small in size, high in accuracy, and capable of suppressing the manufacturing cost has been proposed and disclosed in International Publication No. WO94 / 23272 based on the Patent Cooperation Treaty. Further, Japanese Patent Application No. 6-191081, Japanese Patent Application No. 6-225894, Japanese Patent Application No. 6-25890.
The specification of No. 9 discloses some improvement plans. These novel sensors can detect the angular velocity about each of the three-dimensional axes. This is based on the principle that when the object is vibrated in the Z-axis direction while the angular velocity ωx around the X-axis is acting, the Coriolis force acts in the Y-axis direction. For example, an AC voltage is applied to a predetermined piezoelectric element arranged on the flexible substrate to vibrate the weight body attached to the flexible substrate in the Z-axis direction. Here, when the angular velocity ωx around the X axis is acting, the Coriolis force acts on the weight body in the Y axis direction, so that the weight body is displaced in the Y axis direction. If this displacement is detected by the charge generated by the piezoelectric element, the applied angular velocity ω
x can be detected indirectly.

[0006]

The basic principle of a multi-axis angular velocity sensor utilizing Coriolis force is disclosed in each of the above-mentioned patent documents. According to this basic principle, it is necessary to detect the Coriolis force acting on the weight body while vibrating the weight body in the predetermined axis direction. However, in order to realize a small and highly sensitive angular velocity sensor that operates on such a principle, various technical problems to be solved remain. First, a mechanism for efficiently vibrating the weight body is required. For example, if the vibration of the weight body propagates to the sensor housing, the supplied vibration energy will be wasted. Therefore, it is necessary to try to prevent the vibration of the weight body from escaping to the outside as much as possible. You will need it. Secondly, a mechanism for detecting the applied Coriolis force as accurately as possible is required. Since the angular velocity is obtained based on the Coriolis force acting in the predetermined axial direction, it is necessary to detect the Coriolis force in the specific axial direction with high accuracy. Since such technical problems remain, it has been difficult to manufacture a practical multi-axis angular velocity sensor that is small in size and has high sensitivity.

Therefore, an object of the present invention is to provide a small-sized and highly sensitive practical biaxial angular velocity sensor.

[0008]

[Means for Solving the Problems]

(1) A first aspect of the present invention is an angular velocity sensor that detects an angular velocity ωx about an X axis and an angular velocity ωy about a Y axis in an XYZ three-dimensional coordinate system, and has a plate shape extending along an XY plane. Then, a flexible vibration substrate capable of vibrating the central portion located at the origin of the coordinate system in the Z-axis direction in a vibration mode having a predetermined circumference as a node,
A plate-shaped piezoelectric element bonded so as to be laminated on the vibrating substrate, a pedestal for directly supporting the lower surface of the vibrating substrate at a node position along the circumference or indirectly through other components, and the vibrating substrate. A weight body that is directly or indirectly bonded to the center of the body, a support substrate that is disposed above the vibration substrate by a predetermined distance, and a predetermined degree of freedom of movement. Then, by applying an AC voltage to the wire member that suspends the pedestal from the support substrate and the piezoelectric element, an excitation that causes the piezoelectric element to undergo periodic bending such that the weight body vibrates in the Z-axis direction. And the excitation means vibrate the weight in the Z-axis direction, the Coriolis force in the X-axis direction and the Coriolis force in the Y-axis acting on the weight are applied to the distribution of the charges generated in the piezoelectric element. Coriolis force detected based on An output means and a calculation means for calculating an angular velocity ωy about the Y axis based on the detected Coriolis force in the X axis direction, and calculating an angular velocity ωx about the X axis based on the detected Coriolis force in the Y axis direction. It is provided.

(2) A second aspect of the present invention is the above-mentioned first aspect.
In the angular velocity sensor according to the aspect (1), a piezoelectric element having a polarization characteristic that a predetermined charge is generated on the upper surface and the lower surface when a stress in a direction along the XY plane is applied is used. X on either side
A plurality of electrodes are formed so as to be arranged in line symmetry with respect to both the axis and the Y-axis, and electrodes are formed on the other surface at positions facing the plurality of electrodes. The voltage applied by the electrodes is applied, and the charges generated in these electrodes are detected by the Coriolis force detection means.

(3) A third aspect of the present invention is the above-mentioned second aspect.
In one aspect of the piezoelectric element, the first electrode is provided in the positive region of the X axis, the second electrode is provided in the positive region of the Y axis, and the negative electrode is provided in the negative region of the X axis. Set the third electrode to Y
The fourth electrode is arranged in the negative region of the axis, and the counter electrode facing the first to fourth electrodes is arranged on the other surface of the piezoelectric element, and the exciting means sets the counter electrode to the ground potential. And to apply the same AC voltage to the first to fourth electrodes to vibrate the weight body in the Z-axis direction,
The Coriolis force detecting means detects the Coriolis force in the X-axis direction based on the difference between the charge generated in the first electrode and the charge generated in the third electrode, and the charge generated in the second electrode and the fourth charge are detected. The Coriolis force in the Y-axis direction is detected on the basis of the difference between the electric charge generated in the electrode and the electric charge generated in the electrode.

(4) The fourth aspect of the present invention is the above-mentioned third aspect.
In the angular velocity sensor according to the above aspect, the first to fourth electrodes are arranged in a region inside a circumference that serves as a node of the vibration substrate.

(5) A fifth aspect of the present invention relates to the above-mentioned first aspect.
In the angular velocity sensor according to the fourth aspect, a plate-shaped auxiliary piezoelectric element bonded so as to be laminated on the vibration substrate is further provided, and the vibration substrate, the piezoelectric element, and the auxiliary piezoelectric element form a three-layer diaphragm. A signal based on the electric charge generated in the auxiliary piezoelectric element is given as a feedback signal to the excitation means so that the vibration substrate can be vibrated by the feedback control by the excitation means.

(6) A sixth aspect of the present invention is the above-mentioned fifth aspect.
In the angular velocity sensor according to the aspect of (3), the piezoelectric element is laminated on the upper surface of the vibration substrate, the three-layer diaphragm is configured so that the auxiliary piezoelectric element is laminated on the lower surface, and the lower surface of the three-layer diaphragm is supported by the pedestal. The weight body is joined to the center of the lower surface.

(7) A seventh aspect of the present invention is the above-mentioned second aspect.
~ In the angular velocity sensor according to the fourth aspect, an auxiliary electrode is further provided on one surface of the piezoelectric element, a signal based on the charges generated in the auxiliary electrode is given to the excitation means as a feedback signal, and feedback control by the excitation means is performed. The vibrating substrate can be vibrated.

(8) An eighth aspect of the present invention relates to the above-mentioned first aspect.
~ In the angular velocity sensor according to the seventh aspect, a flexible substrate having a plurality of concentric slits is used as the vibrating substrate.

(9) A ninth aspect of the present invention relates to the above-mentioned first aspect.
-In the angular velocity sensor according to the eighth aspect, the pedestal is configured by a cylindrical structure, a knife edge is formed at the upper end portion thereof, and the lower end portion of the knife edge directly or indirectly supports the lower surface of the vibration substrate. It is something that is done.

(10) According to a tenth aspect of the present invention, in the angular velocity sensor according to the above first to ninth aspects, the supporting substrate is used as a circuit substrate, and the exciting means, the Coriolis force detecting means, and the calculating means are provided. The circuit element as a component is mounted on this circuit board.

(11) An eleventh aspect of the present invention is the angular velocity sensor according to the above-mentioned first to fifth and seventh to tenth aspects, in which the weight body is arranged above the vibrating substrate, and A through hole is provided in the central portion of the support substrate so as not to hinder the vibration of the weight body.

[0019]

[Operation] The basic principle of the angular velocity sensor according to the present invention is that the Coriolis force Fx acting on the weight body in the X-axis direction is applied to the weight body while vibrating the weight body in the Z axis direction in the XYZ three-dimensional coordinate system. By detecting the angular velocity ω around the Y-axis
The y is obtained and the Coriolis force Fy acting on the Y-axis in the Y-axis direction is detected to obtain the angular velocity ωx about the X-axis.

In order to vibrate the weight body in the Z-axis direction, in the present invention, a plate-shaped flexible vibrating substrate (so-called diaphragm) extending along the XY plane is prepared, and the central portion of this vibrating substrate is provided. The weights are joined together. It is generally known that when a central part of such a diaphragm is vertically vibrated, nodes are formed along the circumference. In the present invention, the pedestal supports the circumferential node position of the diaphragm. At this node position, the displacement becomes very small even in a vibrating state, and it is possible to minimize the leakage of vibration to the outside through the pedestal. Moreover, since the pedestal is suspended from the supporting substrate by the wire member while ensuring a predetermined degree of freedom of movement, it is possible to further reduce the vibration component leaking to the outside. With such a structure, the angular velocity sensor according to the present invention can efficiently vibrate the weight body.

A plate-shaped piezoelectric element is bonded to the vibrating substrate to form a laminated structure. When a predetermined voltage is applied to the piezoelectric element from the excitation means, the piezoelectric element bends,
This bending is transmitted to the vibration substrate. Therefore, if the voltage applied by the excitation means is an AC voltage, the flexure transmitted to the vibrating substrate will periodically fluctuate, and the weight body joined to the center of the vibrating substrate will vibrate in the Z-axis direction. It is possible to let When a Coriolis force in the X-axis or Y-axis direction acts on the weight body, the Coriolis force causes another flexure different from the vibration component in the vibrating substrate, and the flexure is transmitted to the piezoelectric element. . Therefore, the piezoelectric element generates an electric charge according to the bending. Since the distribution of the generated charges depends on the directionality of the Coriolis force acting, it becomes possible to detect the Coriolis force based on the distribution of the generated charges. With such a method, the Coriolis force can be detected with high accuracy for each axial component.

As the plate-shaped piezoelectric element, a piezoelectric element having a polarization characteristic that a predetermined charge is generated on the upper and lower surfaces when a stress in a direction along the XY plane is applied is used. Electrodes are formed at both positive and negative positions of the X and Y axes at positions symmetrical with respect to the Y axis, and an alternating current for excitation is supplied through the electrodes, and at the same time, generated charges based on Coriolis force are detected. In this case, the weight body can be vibrated more stably, and the Coriolis force can be efficiently detected. It should be noted that by arranging each electrode in a region inside a circumference that serves as a node of the vibrating substrate, vibration of the weight body and Coriolis force detection can be performed more efficiently. Further, in order to stabilize the vibration of the weight body against various disturbances, an auxiliary piezoelectric element for detecting the vibration or an electrode for detecting the vibration is added to detect the vibration detection signal. Is preferably used as feedback signal.

If a flexible substrate having a plurality of concentric slits is used as the vibrating substrate, the center portion can be easily moved in each direction, and efficient vibration and detection can be expected. Further, if the node position of the vibrating substrate is supported by the knife edge formed on the upper end portion of the cylindrical pedestal, it is effective in suppressing the vibration of the vibrating substrate from leaking to the outside. Further, by using the supporting substrate as a circuit substrate, circuit elements such as a circuit for supplying an AC signal to the vibration substrate, a circuit for detecting Coriolis force, a circuit for calculating angular velocity, etc. may be mounted on this circuit substrate. if,
It is possible to make the entire sensor smaller, and
If a through hole is provided in the center of the support substrate and the weight body is arranged at the position of the through hole, the size of the entire sensor can be further reduced.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to illustrated embodiments.

§1. Basic Structure of Embodiment FIG. 1 shows a perspective view of an angular velocity sensor according to an embodiment of the present invention which is disassembled and is viewed obliquely from above, and FIG. 2 is a perspective view which is viewed from obliquely below. The upper surface of the member is shown in Figure 1.
And the bottom surface will be as shown in FIG. 2). The basic components of this angular velocity sensor are a circuit board 10, a piezoelectric element 20, a vibration substrate 30, an auxiliary piezoelectric element 40, and a pedestal 50, as shown in the figure. The circuit board 10 fulfills a function as a support board for supporting the other constituent elements shown in the figure and a function as a circuit element mounting board for mounting a circuit element (not shown) described later. In the embodiment, the circuit board 10 is composed of a general printed circuit board.

Each of the piezoelectric element 20, the vibration substrate 30, and the auxiliary piezoelectric element 40 is a thin disk-shaped member having the same diameter, and the exploded state is shown in the figure. The disks are in a state of being bonded to each other by an epoxy adhesive. The vibration substrate 30 is formed by forming concentric circular slits 31 on a metal disk,
The substrate is flexible as a whole. In particular, since the concentric circular slit 31 is formed, the central portion can be easily displaced. The piezoelectric element 20 and the auxiliary piezoelectric element 40 have the first property that a predetermined charge is generated on the upper and lower surfaces when a stress in a direction that expands or contracts in the horizontal direction acts, and conversely, when a predetermined voltage is applied to the upper and lower surfaces. , A thin disk-shaped piezoelectric element having a second property of generating stress in a direction that expands or contracts in the horizontal direction.

As shown in FIG. 1, on the upper surface of the piezoelectric element 20, four fan-shaped electrodes of a first electrode E1 to a fourth electrode E4 are formed, and each of these electrodes E1 to E4 is Each is connected to the wiring pads P1 to P4. On the lower surface of the piezoelectric element 20, as shown in FIG.
0 is formed. The counter electrode E0 is a circular electrode that functions as a common electrode that faces all of the four fan-shaped electrodes E1 to E4, and the wiring portion provided at one end of the circumference of the counter electrode E0 of the piezoelectric element 20. The wiring pad P0 is formed extending to the upper surface (see FIG. 1). After all, the wirings for the five electrodes E0 to E4 formed on the piezoelectric element 20 are the five wiring pads P formed on the upper surface of the piezoelectric element 20.
It may be performed for 0 to P4.

A circular fifth electrode E5 is formed on the upper surface of the auxiliary piezoelectric element 40 as shown in FIG. 1, and a lower surface of the auxiliary piezoelectric element 40 is opposed to the fifth electrode E5 as shown in FIG. A circular sixth electrode E6 is formed on the. The wiring portion provided at one end of the circumference of the fifth electrode E5 extends to the lower surface of the auxiliary piezoelectric element 40 to form the wiring pad P5 (see FIG. 2), and at one end of the circumference of the sixth electrode E6. The provided wiring portion forms a wiring pad P6. After all, the auxiliary piezoelectric element 4
The wiring for the two electrodes E5 and E6 formed in 0 is
Two wiring pads P formed on the lower surface of the auxiliary piezoelectric element 40
5 and P6.

As described above, an epoxy adhesive is filled between the lower surface of the piezoelectric element 20 and the upper surface of the vibration substrate 30, and between the lower surface of the vibration substrate 30 and the upper surface of the auxiliary piezoelectric element 40. The three disks are bonded and fixed in a laminated state. The vibrating substrate 30 is sandwiched between the piezoelectric elements 20 and 40 and is in a so-called sandwich state. A weight body 41 is joined to the center of the lower surface of the auxiliary piezoelectric element 40. The weight body 41 is a weight made of metal, and in order to improve the detection sensitivity, it is preferable to use the weight body 41 having the largest possible mass. As described above, the vibration substrate 30 has a certain degree of flexibility, and in particular, the central portion thereof has a structure that can be displaced relatively easily. Therefore, the piezoelectric element 20, the vibration substrate 30, the auxiliary piezoelectric element 4
The laminated structure of 0 also has flexibility as a whole, and functions as a three-layer diaphragm in which the center portion is easily displaced up and down. Therefore, the weight body 41 functions as a vibrator attached to the central portion of the lower surface of the three-layer diaphragm, and vertically vibrates as described later. In this embodiment, the piezoelectric elements 20,
Although the three-layer diaphragm is configured by laminating the vibrating substrate 30 and the auxiliary piezoelectric element 40, the order of laminating the three layers is not necessarily the same. However, in order to perform efficient detection, it is preferable to use the vibration substrate 30 as an intermediate layer.

The pedestal 50 is the three-layer diaphragm (a laminated body of the piezoelectric element 20, the vibration substrate 30, and the auxiliary piezoelectric element 40).
Fulfills the function of supporting from below. In this embodiment, the pedestal 50 is composed of the cylindrical structure 51, and the upper end portion of the pedestal 50 is at the lower surface (sixth electrode E6) of the auxiliary piezoelectric element 40.
The outer side of the outer periphery of) is fixed by adhesion with an epoxy adhesive. The weight body 41 is housed inside the cylinder of the cylindrical structure 51. Further, one end of each of the L-shaped wire members 52 and 53 is bonded to the side surface of the cylindrical structure 51. The upper ends of the wire members 52 and 53 are soldered to the lower surface of the circuit board 10.

FIG. 3 is a side sectional view showing an assembled state of the angular velocity sensor having the above-mentioned disassembled structure (here, for convenience of explanation, the dimensional ratio of each part is neglected.
In particular, the piezoelectric element 20, the vibration substrate 30, the auxiliary piezoelectric element 40
Are actually much thinner than shown in the dimensional ratios shown). The circuit board 10 is attached to a sensor housing (not shown). As shown in the drawing, the upper ends of the wire members 52 and 53 are bonded to the lower surface of the circuit board 10 at the solder bonding portion 11, and the cylindrical structure 51 and the three-layer diaphragm supported thereon are Circuit board 10
On the other hand, it is in a state of being suspended by the wire members 52 and 53. The weight body 41 is a cylindrical structure body 51.
It will vibrate in the up and down direction in the figure while being stored inside. Therefore, the piezoelectric element 20 and the circuit board 1
It is necessary to secure a certain distance between 0 and 0 so that they do not come into contact with each other due to this vibration.

FIG. 4 is a top view of the vibrating substrate 30, showing the structure of the concentric circular slits 31 in more detail.
In this embodiment, as shown in the figure, four slits are arranged on the same circumference, and the slits are arranged as four concentric circles to provide a total of 16 slits. The even-numbered concentric circles and the odd-numbered concentric circles are arranged such that the phases of the slits in the circumferential direction are shifted by 45 °. By forming such concentric slits 31, it becomes possible to efficiently displace the central portion thereof in an arbitrary three-dimensional direction.

§2. Support Position by Pedestal In the basic structure shown in FIG. 3, the support position of the three-layer diaphragm (the laminated body of the piezoelectric element 20, the vibration substrate 30, and the auxiliary piezoelectric element 40) by the pedestal 50 (cylindrical structure 51) is important. The basic concept for determining the ideal support position,
This will be described with reference to FIGS. 5 and 6. Now, a diaphragm 70 (shown by a broken line) as shown in a side sectional view in FIG.
think of. Here, it is assumed that the weight body 75 is joined to the central portion of the lower surface of the diaphragm 70. The broken line in FIG. 5 shows a reference state in which no force acts on the diaphragm 70. Here, in the state where the outer peripheral portion of the diaphragm 70 is supported, with respect to the weight body 75,
If an upward force Fu acts in the figure, the diaphragm 70 is deformed like the diaphragm 70a. Conversely, if a downward force Fd is applied, the diaphragm 7
0 deforms like a diaphragm 70b. Therefore, if the forces Fu and Fd are alternately applied to the weight body 75, the weight body 75 vibrates in the vertical direction of the figure, and the diaphragm moves 70 → 70a → 70 → 70.
It will be deformed periodically such as b → 70 →. It is known that when the diaphragm 70 is vibrated in this manner, there are nodes N1 and N2 that maintain a stationary state even during vibration.

FIG. 6 is a side sectional view showing a deformed state of the diaphragm when a force in the lateral direction of the drawing is applied to the weight body 75. The diaphragm 70 and the weight body 75 indicated by broken lines are shown in FIG. , A reference state when no force is applied, and the diaphragm 70c and the weight body 75c indicated by solid lines are in a deformed state when a force Fr in the right direction in the drawing is applied. On the contrary, when a leftward force Fl is applied,
A deformed state is obtained, which looks like a mirror of. Therefore, if the forces Fr and Fl are alternately applied to the weight body 75, the weight body 75 can be vibrated in the left-right direction in the drawing. It is known that there are nodes N1 and N2 that maintain a stationary state even in such a horizontal vibration mode, and normally, in both the vertical vibration mode and the horizontal vibration mode, the node N1 , N2 appear at almost the same position.

Such nodes N1 and N2 correspond to points where the internal stress generated by the deformation of the diaphragm 70 becomes zero. For example, in the deformed state shown in FIG. 6, the stress distribution on the upper surface and the stress distribution on the lower surface of the diaphragm 70 are as shown in the graph of the figure. In both cases, the stress in the laterally extending direction is shown as positive, and the stress in the laterally contracting direction is shown as negative. At the positions of the nodes N1 and N2, the internal stress becomes 0 on both the upper surface and the lower surface. In the region on the right side of the node N2 in the graph shown in FIG. 6, it is shown that the stress acting in the lateral contracting direction acts on the upper surface, and the stress acting in the lateral extending direction acts on the lower surface. On the other hand, in the area on the left side of the node N2, it is shown that the stress acting in the laterally extending direction acts on the upper surface and the stress acting in the laterally contracting direction acts on the lower surface. In any case, the node N
In 1 and N2, the stress becomes 0, neither expands nor contracts, and as a result, the stationary state is maintained even during vibration.

In the above description of FIGS. 5 and 6, only the nodes N1 and N2 in the side cross section are taken into consideration. However, in the disk-shaped diaphragm 70 as in this embodiment, when the center portion is vibrated in a predetermined direction. , The nodes are distributed along the circumference. The radius of the circumference in which such nodes are distributed is slightly different depending on conditions such as the material of the diaphragm 70, the size of each part, the mass of the weight body 75 joined to its center, and the like. As shown in FIG. 3, normally, when the radius of the diaphragm 70 is r, 0.
It was confirmed that the distribution was in the range of 54r to 0.70r (hatched area in FIG. 7). The exact node position (circumferential position) can be obtained by computer simulation in which a method such as the finite element method is applied to each diaphragm 70.

Therefore, in the present embodiment, the node position (circumferential position) is calculated by such a simulation, and the pedestal 50 supports the lower surface of the diaphragm 70 at this node position. In other words,
The circumference that forms the upper end of the cylindrical structure 51 that forms the pedestal 50 matches the node position of the diaphragm 70 that is calculated. FIG. 8 is a side sectional view for explaining a support mode of the diaphragm 70 by the cylindrical structure 51 in this embodiment. Nodes N1 and N2 in the figure indicate node positions (circumferential positions) calculated by simulation. In this embodiment,
In order to support the nodes N1 and N2 as accurately as possible, a knife edge 54 is formed on the upper end portion of the cylindrical structure 51, and the lower end of the diaphragm 70 is formed by the tip end portion of the circular knife edge 54. To support. FIG. 9 is an enlarged side sectional view showing in detail the supporting state by the tip portion of the knife edge 54.
Actually, the tip portion of the knife edge 54 constitutes a surface having a very small area. Therefore, an epoxy adhesive is applied to this surface to adhere it to the lower surface of the auxiliary piezoelectric element 40 so as to support the diaphragm 70. ing.

In this way, by supporting the circumferential node position of the diaphragm 70 by the pedestal 50, the weight body 41 can be vibrated very efficiently. This is because, as described above, this node position remains stationary even if the weight body 41 vibrates, so that vibration does not leak to the outside as long as the node position is supported.
However, as can be seen from the positions of the nodes N1 and N2 in FIG. 8, the node position is located at the center in the thickness direction of the diaphragm 70, while the knife edge 54 directly supports the lower surface of the diaphragm 70 (auxiliary). Strictly speaking, since it is the lower surface of the piezoelectric element 40, the knife edge 5
It does not directly support the node by 4. Further, as shown in FIG. 9, since the tip portion of the knife edge 54 is also a region having an area, supporting the node position does not mean that the vibration of the weight body 41 leaks to the outside at all. is not. Therefore, in this embodiment, as shown in the side sectional view of FIG.
The pedestal 50 is entirely suspended by the structure.
That is, the pedestal 50 is provided with the wire members 52 and 53 in a state where a predetermined degree of freedom of movement is secured, and
Therefore, even if a part of the vibration of the weight body 41 leaks to the pedestal 50, it is possible to prevent the vibration from further leaking to the sensor housing via the circuit board 10. it can.

In this embodiment, the wiring for each of the electrodes E0 to E5 is designed so as not to be affected by the vibration of the weight body 41 as much as possible. FIG. 10 is a top view of the piezoelectric element 20, and a node N on the circumference is shown by a broken line. The point to be noted here is that each of the electrodes E0 to E
The wiring pads P0 to P4 for 4 are all located on this node N. Since the node N is a position that maintains a stationary state even during vibration, wiring at each of the wiring pads P0 to P4 at this position can prevent wiring failure due to vibration from occurring. Further, it is possible to prevent vibration from leaking through the wiring. As shown in FIG. 10, each of the electrodes E1 to E4
Have a shape and arrangement that are line-symmetric with respect to both the X axis and the Y axis. The reason will be described later.

§3. Properties of Piezoelectric Element As described above, the piezoelectric element 20 and the auxiliary piezoelectric element 40 according to the present embodiment have the first property that a predetermined charge is generated on the upper and lower surfaces when a stress in a direction that expands or contracts in the horizontal direction is applied. On the contrary, a thin disk-shaped piezoelectric element having the second property that, when a predetermined voltage is applied to both upper and lower surfaces, stress is generated in a direction that expands or contracts in the horizontal direction. Such a property is generally called the polarization characteristic of the piezoelectric element. FIG. 11 is a diagram for explaining this polarization characteristic. FIG. 11A shows a state in which a force is applied to the piezoelectric element 20 in a direction extending in the left and right directions in FIG.
(b) shows a state in which a force in the direction of contracting to the left and right in the drawing acts on the piezoelectric element 20. In the polarization characteristics shown here, when a force in the extending direction is applied, positive charges are generated on the upper electrode A side and negative charges are generated on the lower electrode B side, as shown in FIG. On the contrary, when a force in the contracting direction acts,
As shown in FIG. 11B, negative charges are generated on the upper electrode A side and positive charges are generated on the lower electrode B side.

Of course, the polarization characteristic shown here is one example of the polarization characteristic that a general piezoelectric element has, and in addition to this, for example, charge is generated based on a force acting in the thickness direction. There is also a piezoelectric element having various polarization characteristics. As described above, the voltage applying method and the charge detecting method are slightly different depending on the polarization characteristics of the piezoelectric element used, but in the present embodiment, the piezoelectric element having the polarization characteristics as shown in FIG. 11 will be described below. The operation as the angular velocity sensor will be described for the case of using.
For convenience of explanation of this operation, an XYZ three-dimensional coordinate system will be defined as follows. That is, FIG.
In the piezoelectric element 20 shown in FIG. 0, the X axis is defined on the right side of the figure, the Y axis is defined on the upper side of the figure, and the Z axis is defined on the upper side of the drawing (the upper side in the side sectional view of FIG. 8 is the Z axis). . After all,
Piezoelectric element 20 constituting diaphragm 70, vibration substrate 3
The 0 and the auxiliary piezoelectric element 40 are all plate-shaped members extending along the XY plane.

The diaphragm 70 used in the angular velocity sensor of this embodiment has a three-layer laminated structure of the piezoelectric element 20, the vibrating substrate 30, and the auxiliary piezoelectric element 40. Here, the phenomenon that occurs in the piezoelectric element 20 in the upper layer. Let's take a look. Now, as shown in FIG. 12, in the state where the diaphragm 70 is supported by the knife edge 54 at its node position, a force + Fx in the positive direction of the X axis is applied to the weight body 41 joined to the center of the lower surface of the diaphragm 70. Consider the case in which is applied (the broken line shows the original reference state). In this case, the diaphragm 70 is deformed as shown.
At this time, in the upper surface of the diaphragm 70 (that is, the piezoelectric element 20) in the horizontal direction (direction parallel to the XY plane).
The distribution of the stress acting on is as shown in each graph of FIG. As described above, the stress becomes 0 at the positions of the nodes N1 and N2, and with this node position as a boundary, positive stress (force extending in the horizontal direction) on one side and negative stress (horizontal direction on the other side). Force to shrink) will be applied. On the contrary, as shown in FIG.
Consider a case where a force −Fx in the negative direction of the X axis is applied (the broken line shows the original reference state). In this case, the diaphragm 7
The distribution of stress acting in the horizontal direction (direction parallel to the XY plane) on the upper surface of 0 (that is, the piezoelectric element 20) is as shown in each graph of FIG.

The direction of the stress distribution is 90 when the force + Fy in the positive direction of the Y-axis or the force -Fy in the negative direction of the Y-axis is applied.
The difference is exactly the same as when the force in the X-axis direction is applied. Next, as shown in FIG. 14, consider a case where a force + Fz in the Z-axis positive direction is applied to the weight body 41. In this case, the diaphragm 70 is deformed as shown. At this time, the distribution of the stress acting in the horizontal direction (the direction parallel to the XY plane) on the upper surface of the diaphragm 70 (that is, the piezoelectric element 20) is as shown in each graph of FIG. On the contrary, as shown in FIG. 15, when a force −Fz in the negative Z-axis direction is applied to the weight body 41, the stress distribution shown in each graph of FIG. 15 is obtained.

By the way, the piezoelectric element 20 is a piezoelectric element having polarization characteristics as shown in FIG. Therefore, in each of the graphs shown in FIGS. 12 to 15, in the portion to which the positive stress (force in the extending direction) acts, the positive charge is applied to the upper electrode and the negative charge is applied to the lower electrode. On the contrary, in the portion where the negative stress (the force in the contracting direction) is applied, negative charges are generated in the upper surface side electrode and positive charges are generated in the lower surface side electrode.

Considering the above points, the charges generated in the four electrodes E1 to E4 on the upper surface side of the piezoelectric element 20 when the forces 41Fx, ± Fy, ± Fz in the predetermined direction act on the weight body 41. It can be seen that the polarities of are as shown in FIG. For example, when a force + Fx in the positive direction of the X axis acts on the weight body 41, the diaphragm 70 is deformed as shown in FIG.
Here, since the four electrodes E1 to E4 are all arranged in the region inside the node N, only the hatched portion in the stress distribution graph of FIG. 12 is related to the generated charge of each electrode. Become. Therefore, as shown in FIG. 16A, positive charges are generated on the electrode E1 and negative charges are generated on the electrode E3. Conversely, the force in the negative direction of the X axis −
When Fx acts on the weight body 41, the diaphragm 70 is deformed as shown in FIG. Here, again, only the hatched portion in the stress distribution graph is related to the charge generated in each electrode, and as shown in FIG. 16 (b), the negative charge is generated in the electrode E1 and the electrode E3 is generated. Will generate a positive charge. Moreover, the electrodes E1 and E3 are Y
Since the shape and the arrangement are line symmetric with respect to the axis, the negative charges generated in the electrode E1 and the positive charges generated in the electrode E3 have the same charge amount. On the other hand, like this, X
When a force is applied in the axial direction, positive charges and negative charges are partially generated in the electrodes E2 and E4 arranged on the Y axis, which is shown in the top view of FIG. As described above, since the electrodes E2 and E4 both have a shape and arrangement that are line-symmetric with respect to the Y-axis, the generated charges are canceled by each electrode, and in total, the generated charges are 0 in both electrodes E2 and E4. Become.

Similarly, the force ± Fy in the Y-axis direction is the weight 41.
16 (c) and 16 (d), Y
Positive or negative charges are generated in the electrodes E2, E4 arranged on the axis. On the other hand, since the electrodes E1 and E3 both have a shape and arrangement that are line-symmetric with respect to the X axis, the generated charges of the electrodes E1 and E3 are 0 in total.

Further, the force + Fz in the Z-axis positive direction is equal to the weight 41.
The diaphragm 70 is deformed as shown in FIG. Here, again, only the hatched portion in the stress distribution graph is related to the generated charge of each electrode. Although FIG. 14 shows a side cross section along the X axis, the side cross section along the Y axis is also exactly the same, and as a result, as shown in FIG. 16 (e), four electrodes E1 to E4 A positive charge is generated in all of. Conversely, the force in the negative direction of the Z-axis -F
When z acts on the weight body 41, the diaphragm 70 is moved to the position shown in FIG.
As shown in FIG. 16F, negative charges are generated in all four electrodes E1 to E4.

As described above, when the forces ± Fx, ± Fy, ± Fz in the predetermined direction act on the weight body 41, the polarities of the charges generated in the four electrodes E1 to E4 on the upper surface side of the piezoelectric element 20. However, it will be understood that as shown in FIG. Here, the amount of generated charge indicates the magnitude of the applied force. Since each of the electrodes E1 to E4 has a shape and arrangement that are line-symmetric with respect to both the X axis and the Y axis, the distribution pattern of generated charges is very simple as shown in FIG.

The counter electrode E on the lower surface side of the piezoelectric element 20
Since 0 is a common electrode facing all of the four electrodes E1 to E4 on the upper surface side, if the counter electrode E0 is connected to the ground potential, the charge generated on the electrodes E1 to E4 on the upper surface side will be reduced. It becomes possible to take out as an electric potential. Therefore, the charge polarities shown in the respective electrodes in FIG. 16 are the polarities of the voltages extracted as they are.

Although all the explanations so far have been made on charges generated in the piezoelectric element 20, when a force acts on the weight body 41, charges are generated in the auxiliary piezoelectric element 40 in the same manner. However, since the auxiliary piezoelectric element 40 is for taking out a feedback signal as described later, only the fifth electrode E5 is formed on the upper surface and the sixth electrode E6 is formed on the lower surface. Here, if the fifth electrode E5 is fixed to the ground potential, a voltage corresponding to the force acting on the weight body 41 in the Z-axis direction is obtained at the sixth electrode E6.
Considering that the stress distribution on the upper surface of the diaphragm 70 and the stress distribution on the lower surface are completely opposite and that the signal is taken out from the electrode E6 on the lower surface of the auxiliary piezoelectric element 40, the weight body 41 is When the force + Fz in the Z-axis positive direction acts, a positive voltage is obtained at the sixth electrode E6, and when the force −Fz in the Z-axis negative direction acts, a negative voltage is obtained at the sixth electrode E6. You can understand that.

By the way, the properties of the piezoelectric element described so far relate to one of the properties of the piezoelectric element that a predetermined charge is generated at a predetermined position when a stress acts in a predetermined direction. In fact, as a property of this property and the front and back together,
It should also be noted that there is another property that stress is generated in a predetermined direction when a predetermined voltage is applied to a predetermined position. For example, when the counter electrode E0 is fixed to the ground potential and a positive voltage is simultaneously applied to the four electrodes E1 to E4 as shown in FIG. 16 (e), the diaphragm 70 is in a state as shown in FIG. As a result, a stress that causes deformation is generated, and as a result, the force + Fz in the Z-axis positive direction can be applied to the weight body 41. On the contrary, as shown in FIG. 16 (f), when a negative voltage is applied to the four electrodes E1 to E4 at the same time, a stress that deforms the diaphragm 70 into the state shown in FIG. Therefore, the force −Fz in the negative Z-axis direction can be applied to the weight body 41. In fact, the angular velocity sensor of this embodiment utilizes such a property to vibrate the weight body 41 in the Z-axis direction.

§4. Detection Principle of ωx, ωy The angular velocity sensor of this embodiment is intended to detect both the angular velocity ωx around the X axis and the angular velocity ωy around the Y axis. Therefore, the basic principle for detecting the angular velocity will be described below.

Now, consider a XYZ three-dimensional coordinate system in which a weight body 80 is prepared as shown in FIG. 17 and X, Y, and Z axes are defined in the directions as shown. In such a system,
The weight 80 is reciprocated in the Z-axis direction to give vibration Uz. At this time, it is known that if an angular velocity ωx that rotates around the X axis acts on the weight body 80, a Coriolis force Fy in the Y axis direction is generated. Similarly, as shown in FIG. 18, when a vibration Uz is applied to the weight body 80, when an angular velocity ωy that rotates around the Y axis acts, a phenomenon that a Coriolis force Fx in the X axis direction is generated is known. Has been. This phenomenon is a mechanical phenomenon that has long been known as the Foucault pendulum, and FIG.
The Coriolis force Fy generated in the case of and the Coriolis force Fx generated in the case of FIG. 18 are represented by Fy = 2m · Vz · ωx Fx = 2m · Vz · ωy. Here, m is the mass of the weight body 80, and Vz is the instantaneous speed of the vibration of the weight body 80.

The angular velocity sensor according to the present invention utilizes such a phenomenon to detect the Coriolis force Fx generated in the X-axis direction when the weight body 80 is vibrated in the Z-axis direction. By detecting the angular velocity ωy about the axis and the Coriolis force Fy generated in the Y-axis direction, X
The angular velocity ωx around the axis is detected.

As described above, when the counter electrode E0 formed on the lower surface of the piezoelectric element 20 is fixed to the ground potential and a positive voltage is applied to all the four electrodes E1 to E4 on the upper surface, the weight body is Force to move 41 in the Z-axis positive direction + F
z can be generated, and conversely, when a negative voltage is applied,
A force −Fz that moves the weight body 41 in the negative Z-axis direction can be generated. Therefore, by applying an AC voltage (excitation voltage) as shown in FIG. 19 to all the four electrodes E1 to E4, the weight body 41 can be oscillated in the Z-axis direction. That is, vibration Uz in the Z-axis direction can be applied to the weight body 41. At this time, if the fifth electrode E5 formed on the upper surface of the auxiliary piezoelectric element 40 is fixed to the ground potential and the potential of the sixth electrode E6 formed on the lower surface is monitored, the weight body 41 is displaced in the Z-axis direction. The corresponding voltage value (Fig. 1
An AC voltage value having the same cycle as the AC voltage shown in FIG. 9 is obtained. Therefore, if this voltage value is used as a feedback signal to control the AC voltage for excitation given to the electrodes E1 to E4, the weight body 4 is subjected to feedback control.
It becomes possible to vibrate 1 stably. The reason for providing the auxiliary piezoelectric element 40 is to take out such a feedback signal.

As described above, when the weight 41 is vibrated in the Z-axis direction, if the angular velocity ωx about the X-axis acts on the weight 41, the weight 41 does not move. Coriolis force Fy is generated in the Y-axis direction. If the angular velocity ωy about the Y axis acts on the weight body 41, the Coriolis force Fx is generated on the weight body 41 in the X axis direction. Therefore, if the force in the Y-axis direction (Coriolis force Fy) and the force in the X-axis direction (Coriolis force Fx) acting on the weight body 41 can be detected, the angular velocities ωx and ωy are calculated based on the above equation. Can be sought by. Because the mass of the weight body 41 is m
Is known, and the instantaneous velocity Vz in the Z-axis direction can also be known (for example, when an excitation voltage as shown in FIG. 19 is applied, the weight body 41 at each instantaneous instant of each phase 0 to 2π). It is sufficient to measure the instantaneous velocity Vz of.

By the way, the force in the Y-axis direction ± F is applied to the weight body 41.
When y acts, as shown in FIG. 16 (c) or (d), charges of a predetermined polarity are generated in the electrodes E2, E4, and this can be extracted as a voltage value. In addition, the weight body 41
When a force ± Fx in the X-axis direction is applied to the electrodes, electric charges of a predetermined polarity are generated in the electrodes E1 and E3 as shown in FIG. 16 (a) or (b), and this can be taken out as a voltage value. That is, if the angular velocity sensor of this embodiment is used, the force Fy in the Y-axis direction and the force F in the X-axis direction that act on the weight body 41 when the weight body 41 is vibrated in the Z-axis direction.
x can be taken out as the voltage value of the electrodes E1 to E4. Force (Coriolis force) F extracted in this way
The angular velocities ωx and ωy can be obtained by performing calculations using the above equations using y and Fx. This is the principle of detecting the angular velocities ωx and ωy in the angular velocity sensor according to the present invention.

However, in this embodiment, the electrodes E1 to E4 are
It is used as an excitation electrode for applying an AC voltage for vibrating the weight body 41 in the Z-axis direction, and also as a detection electrode for detecting a voltage indicating the Coriolis force acting on the weight body 41. . Therefore, in order to detect the voltage indicating the Coriolis force, it is necessary to exclude the component of the voltage applied for excitation from the voltages of the electrodes E1 to E4. Such a technical problem can be solved by adopting the following detection method. That is, as the value of the Coriolis force Fx, the difference between the voltage of the electrode E1 and the voltage of the electrode E3 is taken. Since the excitation voltage is supplied to all the four electrodes E1 to E4, it is offset by taking such a difference. On the other hand, the voltage generated based on the Coriolis force Fx is, as shown in FIGS. 16 (a) and 16 (b),
The polarities of the electrodes E1 and E3 are inverted. Therefore, taking the difference means taking the sum of the absolute values of both. Thus, if the difference between the voltage of the electrode E1 and the voltage of the electrode E3 is taken, the value shows only the component based on the Coriolis force Fx. Exactly the same, the voltage of the electrode E2 and the electrode E
If the difference with the voltage of 4 is taken, the value shows only the component based on the Coriolis force Fy.

§5. Specific Detection Circuit Next, an example of a specific circuit that detects both the angular velocity ωx about the X axis and the angular velocity ωy about the Y axis based on the detection principle described in §4 is shown in the circuit diagram of FIG. Let's explain based on

First, the wiring pad P on the upper surface of the piezoelectric element 20.
0 is grounded, and the wiring pad P5 on the lower surface of the auxiliary piezoelectric element 40
Ground. As a result, the counter electrode E0 and the fifth electrode E5 are fixed to the ground potential. Also, the electrode E
1 to E4 are impedance conversion circuits 121 to 121, respectively.
It is connected to the input terminals of the differential amplifier circuits 131 and 132 via 124, and the output signals of the differential amplifier circuits 131 and 132 are given to the synchronous detection circuits 141 and 142. On the other hand, the potential of the sixth electrode E6 is supplied to the excitation voltage generation circuit 110 after being amplified by the amplification circuit 115. Here, the excitation voltage generation circuit 110 is a circuit that generates an excitation voltage as shown in FIG. 19, and the generated excitation voltage is applied to each of the electrodes E1 to E4 via the resistor R. In addition, the amplifier circuit 1
The output signal of 15 is given to the comparator 143.
The comparator 143 has a function of comparing the input signal with a predetermined threshold value, generating a binary signal (rectangular wave signal), and outputting a signal obtained by shifting the phase of the binary signal by 90 °. The binary signal output from the comparator 143 is given to the synchronous detection circuits 141 and 142. Synchronous detection circuit 1
41 and 142 refer to this binary signal to perform full-wave rectification on the output signals of the differential amplifier circuits 131 and 132. This full-wave rectified signal is smoothed through low-pass filter circuits 151 and 152 that pass low-frequency components and converted into a DC signal. This DC signal is amplified by the DC amplifier circuits 161, 162 and finally output to the output terminals Tx, Ty. As will be described later, the output terminals Tx and Ty are
The DC voltage value obtained at 1 indicates the time average value of the Coriolis forces Fx and Fy acting on the weight body 41. After all, according to the above formula, the voltage Vx obtained at the output terminal Tx shows the time average value of the angular velocity ωy about the Y axis, and the voltage Vy obtained at the output terminal Ty shows the time average value of the angular velocity ωx about the X axis. Will be shown.

Next, the operation of this circuit will be described. First, the excitation operation, that is, the operation for vibrating the weight body 41 in the Z-axis direction will be described. As described above, the excitation voltage generation circuit 110 generates the excitation voltage as shown in FIG. 19, and the excitation voltage is applied to each of the electrodes E1 to E4 via the resistor R.
Apply to. As a result, the weight body 41 is driven at the cycle of the excitation voltage.
Vibrates in the Z-axis direction as described above.
This vibration is monitored as an output signal of the sixth electrode E6. That is, the output signal of the sixth electrode E6 is transmitted to the amplifier circuit 1
It is amplified by 15 and returned to the excitation voltage generation circuit 110 as a feedback signal. Excitation voltage generation circuit 11
0 determines the frequency and phase of the excitation voltage to be output based on this feedback signal. In this embodiment, an AC voltage obtained by shifting the phase of the feedback signal by 90 ° is output as the excitation voltage. By vibrating the weight body 41 while performing such feedback control, it becomes possible to vibrate the weight body 41 at the resonance frequency peculiar to the diaphragm 70.
It becomes possible to stabilize the vibration.

Next, the detection operation, that is, the operation for detecting the Coriolis force ± Fx in the X-axis direction and the Coriolis force ± Fy in the Y-axis direction acting on the weight body 41 will be described. First, the Coriolis force ± Fx in the X-axis direction is applied to the electrodes E1, E
The operation of detecting based on the voltage of 3 will be described. Electrode E
The voltages 1 and E3 are obtained by superposing the excitation voltage supplied from the excitation voltage generation circuit 110 and the voltage generated based on the Coriolis force ± Fx in the X-axis direction (hereinafter, referred to as Coriolis force voltage). . Now, the excitation voltage V1e supplied to the electrode E1 is an AC voltage as shown in FIG. 21 (a),
Similarly, the excitation voltage V3e supplied to the electrode E3 is shown in FIG.
Suppose that the AC voltage is as shown in 1 (b) (both have the same AC voltage). Further, the Coriolis force voltage V1c generated at the electrode E1 is an AC voltage as shown in FIG. 21 (c), and similarly, the Coriolis force voltage V3c generated at the electrode E3.
Is an alternating voltage as shown in FIG. 21 (d) (both are alternating voltages with reversed polarities). Here, for reference, the Coriolis force voltage is 90 ° out of phase with the excitation voltage. Because, at the moment when the excitation voltage takes a positive and negative peak position (at the time of phase π / 2 and π3 / 2 in each graph of FIG. 21), the weight body 4 is
Since 1 is at the highest or lowest position in the amplitude section,
The instantaneous velocity in the Z-axis direction becomes 0, and the Coriolis force at this point becomes 0. On the contrary, at the moment when the excitation voltage becomes 0 (see FIG.
Of the phase 0, π in each graph of
Is passing through the center position of the amplitude at the maximum speed, and the Coriolis force at this point is maximized.

Now, according to the circuit of FIG. 20, the electrodes E1,
The voltage of E3 is the impedance conversion circuits 121 and 123.
Is given to the input terminal of the differential amplifier circuit 131 via the, and the output of the differential amplifier circuit 131 becomes the difference between the voltage of the electrode E1 and the voltage of the electrode E3. Here, if the weight body 41
If the angular velocity ωy about the Y-axis is not acting on the electrode, naturally, the Coriolis force ± Fx in the X-axis direction is not generated, so that the voltages of the electrodes E1 and E3 are respectively as shown in FIG.
, (B) are only the excitation voltages V1e and V3e. Therefore, the output of the differential amplifier circuit 131 becomes the difference between the two, that is, 0. After all, if the angular velocity ωy about the Y axis is not acting at all, the output voltage at the output terminal Tx becomes zero.
However, when the angular velocity ωy around the Y axis is acting,
Since the Coriolis force ± Fx in the X-axis direction is generated, the electrode E1
21 is the same as the excitation voltage V1e shown in FIG. 21 (a).
It is a superposition of the Coriolis force voltage V1c shown in (c).
Similarly, the voltage of the electrode E3 is the excitation voltage V3e shown in FIG. 21 (b) superimposed with the Coriolis force voltage V3c shown in FIG. 21 (d). Therefore, the output voltage of the differential amplifier circuit 131 becomes the voltage V131 as shown in FIG. The excitation voltages cancel each other out, and this voltage V131 is as if the Coriolis force voltage V1c was inverted and added to the Coriolis force voltage V1c, indicating only the components of the Coriolis force ± Fx in the X-axis direction. .

The output signal of the differential amplifier circuit 131 is applied to the synchronous detection circuit 141 to be full-wave rectified. At this time, based on the phase relationship with the binary signal applied from the comparator 143. , Full-wave rectification on the positive side or full-wave rectification on the negative side is determined. For example, with the signal waveform of the voltage V131 as shown in FIG. 22 (a1),
When the signal waveform of the output voltage V143 of the comparator 143 as shown in FIG. 22 (a2) is obtained, the signal waveform of the voltage V131 is in phase with the signal waveform of the voltage V143, so full-wave rectification to the positive side is performed. 22 (a3), the signal waveform as shown in FIG. 22 (a3) is output as the output voltage V141 of the synchronous detection circuit 141, and the voltage Vx finally output to the output terminal Tx is shown in FIG. 22 (a4). It becomes something like. On the other hand, along with the signal waveform of the voltage V131 as shown in FIG. 22 (b1), the comparator 143 as shown in FIG. 22 (b2).
When the signal waveform of the output voltage V143 of
Since the signal waveform of 131 has a phase opposite to that of the voltage V143, full-wave rectification is performed to the negative side, and the signal waveform as shown in FIG. 22 (b3) is output as the output voltage V141 of the synchronous detection circuit 141. The voltage Vx finally output to the output terminal Tx is as shown in FIG. 22 (b4).

As described above, changing the positive and negative directions of full-wave rectification in the synchronous detection circuit 141 based on the phase difference from the signal waveform of the output voltage V143 of the comparator 143 is as follows.
This is so that the information on the direction of the acting angular velocity can be expressed by the positive or negative of the voltage. For example, when the output voltage V143 as shown in FIG. 22 (a2) or FIG. 22 (b2) is obtained, the weight body 41 moves at the maximum speed in the + Z-axis direction at the moment of phase 0. It can be recognized that the moment of the phase π is the moment when the weight body 41 is moving at the maximum speed in the −Z axis direction. Here, it is important to recognize in which direction the motion of the weight body 41 has obtained the value at each phase position of the output voltage V131 of the differential amplifier circuit 131. Because even if
Even if the Coriolis force Fx of the same polarity and the same magnitude is obtained, if the motion direction of the weight body 41 at that time is opposite, the direction of the angular velocity about the acting Y axis becomes opposite. Is. If the positive and negative directions of full-wave rectification in the synchronous detection circuit 141 are reversed based on the phase difference with the output voltage of the comparator 143 (whether it is advanced or delayed by 90 °), the information on the direction of this angular velocity is obtained. Can be expressed by the positive and negative of the voltage value.

From the above description of the operation, it can be understood that the angular velocity ωy about the Y axis can be obtained as the output voltage Vx of the output terminal Tx by using the circuit shown in FIG. That is, the magnitude of the output voltage Vx depends on the angular velocity ωy.
Of the Y axis, the sign indicates the direction of clockwise or counterclockwise rotation with respect to the Y axis. In exactly the same manner, the angular velocity ωx around the X axis can be obtained as the output voltage Vy of the output terminal Ty. As described above, the components of each circuit shown in FIG. 20 are preferably mounted on the circuit board 10.

§6. Merits of this Embodiment Here, the merits of this embodiment described above will be described collectively. In order to realize a compact and highly sensitive and practical biaxial angular velocity sensor which is the object of the present invention, it is necessary to achieve the following two technical problems. That is, the first problem is to vibrate the weight body as efficiently as possible, and the second problem is to detect the applied Coriolis force as sensitively as possible. In the embodiment described above, these two problems are successfully solved in the following points.

<First Problem: Vibrating the Weight Efficiently> Since the position of the node N of the diaphragm 70 is supported by the pedestal 50, it is possible to suppress the vibration of the diaphragm 70 from leaking to the outside. it can. Since the pedestal 50 is supported by the wire members 52 and 53 in a suspended state with respect to the circuit board 10, even if there is vibration that leaks to the pedestal 50, this vibration will not occur.
It becomes difficult to transmit to 0, that is, to the sensor housing. Therefore, even if the housing is touched with the hand during the operation of this sensor, the vibration of the weight body is not adversely affected. Since feedback control is used for the excitation operation,
The diaphragm 70 can be efficiently vibrated at the resonance frequency.

<Second Problem: Sensitive Detection of Coriolis Force> As shown in FIG. 4, since the concentric circular slit 31 is formed in the vibration substrate 30, the diaphragm 70 has sufficient flexibility as a whole. For this reason, even if a relatively small Coriolis force is applied, the diaphragm 70 is sufficiently deformed and electric charges necessary for high-sensitivity detection are generated. As shown in FIG. 10, the electrodes E1 to E1 on the piezoelectric element 20
Since all E4 are arranged in the region inside the node N, only the stress in the hatched portion in the graphs of FIGS. 12 to 15 can be efficiently converted into electric charges and taken out (conversely). For example, if the electrodes are arranged so as to straddle the node N, charges of opposite polarities are generated in the same electrode, and the charges are partially offset, so that efficient detection cannot be performed). Since the same electrode is used not only as a voltage application electrode for excitation but also as an electrode for Coriolis force detection, the area of each electrode can be increased and detection sensitivity is improved.

§7. Some Modifications Although the present invention has been described based on the illustrated embodiments,
The present invention is not limited to this embodiment and can be implemented in various modes other than this. Here, some modified examples will be described.

The modification shown in the side sectional view in FIG. 23 has a structure in which the auxiliary piezoelectric element 40 is not used. In this modification, the diaphragm 70 has a two-layer laminated structure of the piezoelectric element 25 and the vibration substrate 30. The weight body 41 is the vibration substrate 3
0 is directly bonded to the lower surface, and the upper end (knife edge) of the pedestal 50 is directly bonded to the lower surface of the vibration substrate 30. The piezoelectric element 25 in this modified example is slightly different from the piezoelectric element 20 in the above-described embodiment in the electrode configuration on the upper surface side. That is, as shown in the top view of FIG. 24, the four electrodes E1 to E are provided on the upper surface of the piezoelectric element 25.
4, a cross-shaped seventh electrode E7 is arranged,
It is connected to the wiring pad P7. The seventh electrode E7 is
It has the same function as the sixth electrode E6 in the above-described embodiment. That is, the feedback signal for controlling the vibration is taken out from the wiring pad P7. In this way, if the feedback signal is extracted using the piezoelectric element 25, the auxiliary piezoelectric element 40 can be omitted, and the structure is further simplified.

In the modification shown in the side sectional view in FIG. 25, a weight body 42 is used in place of the weight body 41 in the above-described embodiment. The weight body 41 is bonded to the lower surface of the auxiliary piezoelectric element 40, while the weight body 42 is bonded to the upper surface of the piezoelectric element 20. Moreover, the through hole 12 is formed in the center of the circuit board 10, and the weight body 42 is inserted into the through hole 12. Therefore, the vibration of the weight body 42 is not disturbed by the circuit board 10. The merit of this modification is that the weight body 42 is arranged above, so that the cylindrical structure 55 can be made thin and the overall thickness can be made small.

In the embodiment described above, the cylindrical structure 51
The circuit board 1 by the two wire members 52 and 53.
It was hung from 0, but as shown in FIG.
27 may be hung from the circuit board 10 by the two wire members 52, 53, 56, 57, or two wire members 58, 59 parallel to each other may be fixed at the connection point Q as shown in FIG. The circuit board 10 may be hung. Of course, other than this, any number of wire members may be used.

In the above-mentioned embodiment, the piezoelectric element 20 is used.
Although the four electrodes E1 to E4 are arranged on the upper surface and the common counter electrode E0 is arranged on the lower surface, conversely, the four electrodes E1 to E4 are arranged on the lower surface and the common counter electrode is arranged on the upper surface. You may arrange E0. Alternatively, instead of using the common counter electrode E0, four independent counter electrodes facing each of the four electrodes E1 to E4 may be used.

Further, in the above-mentioned embodiment, the electrodes E1 to E are used.
4 is used as the excitation electrode and the detection electrode, and the electrode E6 is used as the feedback electrode.
4 may be used as the detection electrode and the feedback electrode, and the electrode E6 may be used as the excitation electrode.

In the above-described embodiments, it is explained that a single vibration node N occurs at a circumferential position having a predetermined radius peculiar to the diaphragm, but in reality, this single node N When the position is fixedly supported by the cylindrical pedestal, the second node M may occur inside thereof. FIG. 28 is a side sectional view showing a plurality of nodes on such a diaphragm. The node N is the circumferential node described above, and this position is fixedly supported by the pedestal 50. On the other hand, the node M is a circumferential node having a radius smaller than that of the node N, and the stress on the upper surface and the lower surface of the diaphragm is, as shown in the graph of the figure, the nodes N and M. It becomes 0 in any case. Further, if the diaphragm is supported by the pedestal 50 and the outer peripheral portion of the diaphragm is the free end, the stress on the portion outside the node N is also zero. The theory of generation of such a second node M has not been analyzed in detail at this stage, but when a diaphragm having concentric circular slits 31 as shown in FIG. Occurrence of the second node M,
It was confirmed by the analysis by the finite element method.

As described above, when a plurality of nodes occur, it is preferable to form the individual electrodes in a region that does not cross the nodes. For example, in the example of FIG. 28, in this side sectional view, if electrodes are formed so as to extend to the left and right sides of the node M, when the diaphragm is in the deformed state as shown in the figure, a part of the electrode is formed. Causes a positive charge and another part generates a negative charge, so that only the charge corresponding to the difference between the two is detected, which lowers the detection sensitivity.

Therefore, in such a case, as shown in the top view of FIG. 29, the node M is formed on the upper surface of the piezoelectric element 20.
It is preferable that the electrodes E11 to E14 are formed in the region inside and the electrodes E21 to E24 are formed in the region outside the node M so that the generated charges are taken out separately. In this case, as is clear from the stress distribution graph of FIG. 28, the charges generated in the electrodes E11 to E14 and the electrode E2 are
Since the polarities are always opposite to the electric charges generated in 1 to E24, it is necessary to process the electric signals obtained from the respective electrodes in the signal processing circuit in consideration of the fact that the polarities are reversed. . Also, when the excitation voltage is supplied to these electrodes, the electrodes E11 to E14 and the electrodes E21 to E14 are also included.
24 and 24, it is necessary to always apply voltages of opposite polarities. Alternatively, by partially reversing the polarization characteristics of the piezoelectric element 20, it is possible to eliminate the inconvenience caused by such polarity reversal. For example, the polarization characteristics of the piezoelectric element 20 are reversed in the region narrowed by the circumferential node M and the circumferential node N (the region where the electrodes E21 to E24 are formed in FIG. 29). It suffices to perform polarization processing (processing having characteristics such that the positive and negative polarities are reversed from the polarization characteristics shown in FIG. 11).

Of course, in the embodiment shown in FIG.
The electrodes E11 to E14 are formed without forming the electrodes E21 to E24.
The angular velocity sensor can be operated using only
On the contrary, the electrodes E21 to E14 are formed without forming the electrodes E11 to E14.
This angular velocity sensor can operate even if only E24 is used. However, in order to improve the detection sensitivity, it is preferable to use the eight electrodes E11 to E24 as described above.

[0080]

As described above, according to the angular velocity sensor of the present invention, the weight body is supported so that it can efficiently vibrate, and the Coriolis force acting on the weight body can be detected with high sensitivity. A compact, highly sensitive and practical biaxial angular velocity sensor can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view of a state in which an angular velocity sensor according to an embodiment of the present invention is disassembled as seen obliquely from above.

FIG. 2 is a perspective view of a state in which the angular velocity sensor according to the embodiment of the present invention is disassembled, as seen obliquely from below.

FIG. 3 is a side sectional view showing a state where the angular velocity sensor shown in FIGS. 1 and 2 is assembled.

4 is a top view of a vibration substrate 30 of the angular velocity sensor shown in FIG.

FIG. 5 is a side sectional view showing a deformed state of the diaphragm when a force in the vertical direction of the figure is applied to the weight body 75, and the diaphragm 70 and the weight body 75 indicated by broken lines are
The standard condition when no force is applied is shown.

6 is a side cross-sectional view showing a deformed state of the diaphragm when a force in the right direction in the figure is applied to the weight body 75, and the diaphragm 70 and the weight body 75 indicated by broken lines are
The standard condition when no force is applied is shown.

FIG. 7 is a side sectional view showing a distribution position of nodes for a general diaphragm.

FIG. 8: Cylindrical structure 5 in the embodiment shown in FIGS.
3 is a side cross-sectional view for explaining a support mode of the diaphragm 70 according to FIG.

FIG. 9 is an enlarged side sectional view showing in detail a supporting state by the tip portion of the knife edge 54 in FIG.

FIG. 10 is a piezoelectric element 20 in the embodiment shown in FIGS.
Is a top view of a node N on the circumference and is shown by a broken line.

FIG. 11 is a piezoelectric element 20 in the embodiment shown in FIGS.
It is a figure explaining the polarization characteristic of.

FIG. 12: Force on the diaphragm 70 in the positive direction of the X axis + Fx
It is a figure which shows the deformation state and stress distribution at the time of making it act.

FIG. 13 is a diagram showing a force X-axis negative direction −Fx applied to the diaphragm 70.
It is a figure which shows the deformation state and stress distribution at the time of making it act.

FIG. 14: Force + Fz in the positive Z-axis direction on the diaphragm 70
It is a figure which shows the deformation state and stress distribution at the time of making it act.

FIG. 15 is a diagram showing a force applied to the diaphragm 70 in the negative Z-axis direction −Fz.
It is a figure which shows the deformation state and stress distribution at the time of making it act.

16 is a weight body 41 in the embodiment shown in FIGS.
FIG. 6 is a diagram showing the polarities of charges generated in the four electrodes E1 to E4 on the upper surface side of the piezoelectric element 20 when forces of ± Fx, ± Fy, and ± Fz in a predetermined direction are applied to.

FIG. 17 is a diagram showing the principle of detecting the angular velocity ωx about the X axis in the angular velocity sensor according to the present invention.

FIG. 18 is a diagram showing the principle of detecting the angular velocity ωy about the Y axis in the angular velocity sensor according to the present invention.

FIG. 19 is a waveform diagram showing an example of an excitation voltage used in the examples shown in FIGS.

FIG. 20 shows the angular velocity ωx in the embodiment shown in FIGS.
FIG. 6 is a circuit diagram showing an example of a specific circuit that detects both the angular velocity ωy and the angular velocity ωy.

21 is a waveform diagram illustrating the operation of the circuit shown in FIG.

22 is another waveform chart explaining the operation of the circuit shown in FIG. 20. FIG.

FIG. 23 is a side cross-sectional view of a modified example in which the auxiliary piezoelectric element 40 is not used.

24 is a top view of the piezoelectric element 25 in the modification example shown in FIG.

FIG. 25 is a side sectional view of a modified example in which a weight body is arranged above.

FIG. 26 is a side sectional view of a modified example in which the pedestal 50 is suspended by four wire members.

FIG. 27 is a side sectional view of a modified example in which the pedestal 50 is suspended by two parallel wire members.

FIG. 28 is a side sectional view showing a state in which a plurality of nodes N and M are generated in the diaphragm.

29 is a top view showing an electrode arrangement when a plurality of nodes are generated as shown in FIG. 28. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Circuit board 11 ... Solder joint part 12 ... Through hole 20 ... Piezoelectric element 25 ... Piezoelectric element 30 ... Vibrating substrate 31 ... Concentric circular slit 40 ... Auxiliary piezoelectric elements 41, 42 ... Weight body 50 ... Pedestal 51 ... Cylindrical structure Body 52, 53 ... Wire member 54 ... Knife edge 55 ... Cylindrical structure 56-59 ... Wire member 70, 70a-70c ... Diaphragm 75, 75c ... Weight body 80 ... Weight body 110 ... Excitation voltage generating circuit 115 ... Amplifier circuit 121-124 ... Impedance conversion circuit 131, 132 ... Differential amplifier circuit 141, 142 ... Synchronous detection circuit 143 ... Comparator 151, 152 ... Filter circuit 161, 162 ... DC amplifier circuit A ... Upper electrode B ... Lower electrode E0 ... Counter electrode E1 ... First electrode E2 ... Second electrode E3 ... Third electrode E4 ... Fourth electrode E5 ... Fifth electrode E6 ... Sixth Electrode E7 ... Seventh electrode E11-E24 ... Electrode N, N1, N2, M ... Node P0-P7 ... Wiring pad Q ... Connection point R ... Resistor Tx, Ty ... Output terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Terao 4107 Miyota, Miyota-cho, Kitasaku-gun, Kitano, Nagano 5 Miyota Co., Ltd. Incorporated (72) Inventor Riyasu Shigeta 5107 Miyota, Miyota-cho, Kitasaku-gun, Kitano, Nagano Prefecture 5107 Miyota Co., Ltd. (72) Inventor Kazuhiro Okada 4-73 Sugaya, Ageo City, Saitama Prefecture

Claims (11)

[Claims] 1. An angular velocity sensor for detecting an angular velocity ωx about an X axis and an angular velocity ωy about a Y axis in an XYZ three-dimensional coordinate system, the angular velocity sensor having a plate-like shape extending along an XY plane. A flexible vibration substrate capable of vibrating in the Z-axis direction in a vibration mode having a predetermined circumference as a node, and a central portion located at the origin of is bonded to be laminated on this vibration substrate. A plate-shaped piezoelectric element, a pedestal that supports the lower surface of the vibration substrate directly or indirectly via other components at the node position, and directly or via other components to the center of the vibration substrate. The weight body indirectly joined to the supporting substrate, which is disposed above the vibrating substrate at a predetermined distance, and the pedestal is suspended from the supporting substrate with a predetermined degree of freedom of movement secured. Wire to wear A material, an excitation means for causing the piezoelectric element to undergo periodic flexure such that the weight body vibrates in the Z-axis direction by applying an AC voltage to the piezoelectric element, and the weight means uses the weight means. Coriolis force for detecting the Coriolis force in the X-axis direction and the Coriolis force in the Y-axis direction acting on the weight body in a state where the body is vibrated in the Z-axis direction, based on the distribution of charges generated in the piezoelectric element. A detecting means and a calculating means for calculating the angular velocity ωy about the Y axis based on the detected Coriolis force in the X axis direction, and calculating the angular velocity ωx about the X axis based on the detected Coriolis force in the Y axis direction. An angular velocity sensor, comprising: 2. The angular velocity sensor according to claim 1, wherein a piezoelectric element having a polarization characteristic that a predetermined charge is generated on the upper surface and the lower surface when stress in a direction along the XY plane is applied, A plurality of electrodes are formed on either one of the upper surface and the lower surface of the piezoelectric element so as to be arranged in line symmetry with respect to both the X axis and the Y axis, and the other surface faces the plurality of electrodes. An angular velocity sensor characterized in that electrodes are formed at the positions, a voltage is applied to these electrodes by an excitation means, and a charge generated in these electrodes is detected by a Coriolis force detection means. 3. The angular velocity sensor according to claim 2, wherein one surface of the piezoelectric element has a first electrode in a positive region of the X axis and a second electrode in a positive region of the Y axis. A third electrode is arranged in the negative region of the X axis and a fourth electrode is arranged in the negative region of the Y axis, and the other surface of the piezoelectric element faces the first to fourth electrodes. A counter electrode is arranged, and the excitation means fixes the counter electrode to the ground potential and applies the same AC voltage to the first to fourth electrodes to move the weight body in the Z-axis direction. The Coriolis force detecting means detects the Coriolis force in the X-axis direction based on the difference between the charge generated in the first electrode and the charge generated in the third electrode, It is possible to detect the Coriolis force in the Y-axis direction based on the difference between the generated charge and the charge generated in the fourth electrode. Characteristic angular velocity sensor. 4. The angular velocity sensor according to claim 3, wherein the first to fourth electrodes are arranged in a region inside a circumference which is a node of the vibration substrate. 5. The angular velocity sensor according to claim 1, further comprising a plate-shaped auxiliary piezoelectric element bonded so as to be laminated on the vibration substrate, the vibration substrate, the piezoelectric element, and the auxiliary piezoelectric element. A three-layer diaphragm is configured, and a signal based on the electric charge generated in the auxiliary piezoelectric element is applied as a feedback signal to the excitation means so that the vibration substrate can be vibrated by the feedback control by the excitation means. And angular velocity sensor. 6. The angular velocity sensor according to claim 5, wherein the three-layer diaphragm is configured such that the piezoelectric element is laminated on the upper surface of the vibration substrate and the auxiliary piezoelectric element is laminated on the lower surface, and the lower surface of the three-layer diaphragm. An angular velocity sensor characterized in that the base is supported by a pedestal, and a weight body is joined to the center of the lower surface. 7. The angular velocity sensor according to claim 2, further comprising an auxiliary electrode provided on one surface of the piezoelectric element, and a signal based on the electric charge generated in the auxiliary electrode is used as a feedback signal for exciting means. The angular velocity sensor is characterized in that the vibrating substrate can be vibrated by feedback control by the excitation means. 8. The angular velocity sensor according to claim 1, wherein a flexible substrate having a plurality of concentric circular slits is used as the vibrating substrate. 9. The angular velocity sensor according to claim 1, wherein the pedestal is formed of a cylindrical structure, and a knife edge is formed at an upper end portion of the pedestal, and the vibrating substrate is formed by the tip end portion of the knife edge. An angular velocity sensor characterized in that the lower surface of the is directly or indirectly supported. 10. The angular velocity sensor according to claim 1, wherein the support substrate is used as a circuit board, and the circuit elements serving as constituent elements of the excitation means, the Coriolis force detection means, and the arithmetic means are provided in this circuit. An angular velocity sensor characterized by being mounted on a substrate. 11. The angular velocity sensor according to any one of claims 1 to 5 and 7 to 10, wherein the weight body is arranged above the vibrating substrate, and the vibration of the weight body is not hindered. An angular velocity sensor characterized in that a through hole is provided in a central portion of a supporting substrate.