JPH09211018A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain highly reliable three-dimensional-system acceleration sensor comprising a single element by performing the polarization processing, which can detect the acceleration components of X, Y and Z axes, in a ring-shaped piezoelectric element, and forming a corresponding divided acceleration- component detecting electrode. SOLUTION: When accleration is applied, inertial forces reverse to the acceleration act on component-detecting spindles 12a and 13a of respective axes for the two-dimensiona accelerations of the X and Y axes. Thus, shearing forces are applied to the X-axis and Y-axis component detecting parts constituted in a piezoelectric element 11. As a result, the potentials are generated at electrodes 12 and 13 of the X and Y axes. the magnitudes and the azimuths of the acceleration can be obtained by the vector synthesis of the potentials generated in the X axis and the Y axis. For the acceleration in the direction of the Z axis, the reverse inertial force acts on a metal base 10, which is supported by the central part, and the piezoelectric element 11 attached on the base 10 as the same way as in the two-dimensional component, and deflection stress is applied. As a result, the potential is generated at an electrode 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting speeds in three axial directions.

[0002]

2. Description of the Related Art In a conventional acceleration sensor using a piezoelectric element, a plurality of piezoelectric elements are arranged so as to correspond to each axial component individually. A conventional acceleration sensor will be described below with reference to FIGS. 4 and 5.

FIG. 4 is a perspective view showing the basic structure of an acceleration sensor arranged to detect the XYZ axis components. In this figure, 41a is an X-axis direction detecting piezoelectric element, 41b is an X-axis direction detecting electrode, and 41c is an electrode. Is a weight for detecting the X-axis direction, 42a is Y
Axial direction detecting piezoelectric element, 42b is a Y axis direction detecting electrode,
42c is a Y-axis direction detecting weight, 43a is a Z-axis direction detecting piezoelectric element, 43b is a Z-axis detecting direction electrode, and 44 is a metal base for fixing the piezoelectric elements 41a, 42a, 43a.
FIG. 5 is a diagram showing the behavior of the weight when acceleration in the X-axis or Y-axis direction is applied. The X-axis and Y-axis direction detecting piezoelectric elements 41a and 42a are polarized in the sideways direction, and the Z-axis direction detecting piezoelectric element 43a is polarized in the thickness direction. The voltage generated when acceleration is applied to the piezoelectric element is given by the following equation.

[0004] The individual piezoelectric elements 41a, 42a, 43a are arranged in the XYZ axial directions to detect acceleration in a three-dimensional coordinate system.

[0005]

However, in the above-mentioned conventional structure, in order to accurately detect the acceleration components in the XYZ axial directions, the piezoelectric elements 41a, 42 for detecting the respective components are used.
a and 43a must be arranged at right angles to each other, and if this accuracy cannot be ensured, there is a problem that not only the acceleration direction but also the acceleration itself cannot be detected. In order to improve the system reliability, a plurality of piezoelectric elements 41a, 42a, 43a are provided for each axis.
Had to be arranged, which made the structure of the acceleration sensor even more troublesome.

The present invention solves the above-mentioned problems of the prior art, and has a simple structure to calculate the acceleration component in each of the XYZ axis directions.
The purpose is to detect accurately.

[0007]

In order to achieve this object, an acceleration sensor of the present invention is a ring-shaped piezoelectric element having a ring-shaped metal base portion and a plurality of electrodes for detecting acceleration components in the XYZ axis directions. In addition to the above, the acceleration detecting weights are attached on the X- and Y-axis direction acceleration component detecting electrodes, respectively, to achieve the intended purpose.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a ring-shaped metal base part, and a plurality of parts for bonding the metal base part with an adhesive and for detecting acceleration components in each of the XYZ axis directions. A ring-shaped piezoelectric element having a number of electrodes, and an acceleration detection weight is attached to each of the X-axis and Y-axis direction acceleration component detection electrodes of the piezoelectric element. It becomes possible to detect components in the three axial directions.

The invention according to claim 2 of the present invention is the X-axis,
The shearing stress is used for detecting the acceleration component in the Y-axis direction, and the bending stress is used for detecting the component in the Z-axis direction. Therefore, the single piezoelectric element can detect the three-axis direction components. It will be possible.

According to a third aspect of the present invention, at least two XYZ axial direction component detection electrodes are radially formed in the same plane of the piezoelectric element, whereby the reliability of the acceleration sensor is improved. Is improved.

According to a fourth aspect of the present invention, the X-axis and Y-axis detection electrodes provided on the piezoelectric element are distributed at 90 degrees, which improves the XY two-dimensional component detection accuracy. .

According to a fifth aspect of the present invention, the Z-axis component detecting electrode provided on the piezoelectric element is formed on the outer peripheral portion of the piezoelectric element, and a larger flexural stress can be utilized at the outer peripheral end, and therefore, the Z-axis component can be utilized. The detection accuracy of the directional component is improved.

According to a sixth aspect of the present invention, the metal base is supported inside the X-axis and Y-axis detection electrodes provided on the piezoelectric element. It is possible to constrain the response on the XY axes.

As described above, with the configuration of the present invention, it is possible to provide an acceleration sensor having high accuracy and high reliability.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3, 10 is a metal base, 11 is a piezoelectric element, 12 is an X-axis direction acceleration component detection electrode, 13 is a Y-axis direction acceleration component detection electrode, and 14 is Z.
Axial acceleration component detection electrode, 12a is an X-axis acceleration component detection weight, 13a is a Y-axis acceleration component detection weight, 1
Reference numeral 6 is a lead for extracting a potential from each electrode portion, and 17 is an insulating cylinder. In FIG. 2, reference numeral 15 is a common electrode on the back surface of the piezoelectric element 11, and reference numeral 18 is a flange supporting the metal base 10, which is supported inside the outer peripheral ends of the electrodes 12 and 13. Also one
9 is solder.

Piezoelectric element 11 used in the acceleration sensor
After forming the electrodes for polarization on the inner and outer peripheral surfaces of the piezoelectric element 11, a high direct current voltage is applied in insulating oil to polarize the piezoelectric element 11 in the horizontal direction. Next, a common electrode 15 is formed on the entire back surface of the piezoelectric element 11, and split electrodes 12, 13, 14 for detecting the XYZ axis components are formed on the surface by plating or the like. At this time, the pair of the X-axis electrode 12 and the Y-axis electrode 13 were alternately arranged by shifting by 90 degrees. Next, the piezoelectric element 11
A high DC voltage was applied between the Z-axis electrode 14 of the device and the common electrode 15 in insulating oil to polarize the piezoelectric device 11 in the direction perpendicular to the main plane. As a result, a polarization process capable of detecting shear stress on the X-axis and Y-axis and flexural stress on the Z-axis is performed. The piezoelectric element 11 for the sensor, which has been polarized, is attached to the metal base 10 with an adhesive (not shown), and shear stress is detected on the X-axis and Y-axis electrodes 12 and 13 of the piezoelectric element 11, respectively. The weights 12a and 13a for bonding are attached with an adhesive.

When acceleration is applied in the above-mentioned configuration, the two-dimensional acceleration on the XY axes is the inertia of the component detecting weights 12a, 13a of each axis opposite to the acceleration, as in the principle shown in FIG. 5 of the conventional example. A force is exerted, which causes shear stress to be applied to the X-axis and Y-axis component detection portions formed in the piezoelectric element 11,
As a result, a potential is generated at the XY axis electrodes 12 and 13. The magnitude and direction of the acceleration can be obtained by synthesizing the vectors of the electric potentials generated on the X axis and the Y axis. Therefore, by forming a large number of pairs of the electrodes 12 and 13 for detecting the two-dimensional component of the XY axes which are distributed at 90 degrees in the plane of the piezoelectric element 11, the accuracy of detecting the two-dimensional component is further improved.

With respect to the acceleration in the Z-axis direction, the metal base 10 supported at the central portion and the piezoelectric element 11 attached to the same act on the opposite inertial force as in the two-dimensional component, and as a result, a bending stress is applied, resulting in a result. An electric potential is generated at the electrode 14. In this case, since the Z-axis component detecting electrode 14 is formed on the outer peripheral portion of the piezoelectric element 11, it receives a large flexural stress even with a small acceleration, and the detection accuracy is improved. The size and direction in the Z-axis direction can be obtained by synthesizing the two-dimensional components of the XY axes and the Z-axis component vectors.

The end portion of the flange 18 for supporting the central portion of the metal base 10 is made to coincide with the outer end portions of the electrodes 12 and 13 for detecting the XY axis components formed on the piezoelectric element 11, so that the direction of the vertical Z axis is increased. It is possible to suppress the flexural stress of the XY-axis detection unit with respect to the acceleration of 1, and to improve the accuracy of the three-dimensional coordinate system acceleration sensor using a single element. Furthermore, in the present invention, since one piezoelectric element 11 is used, there is no variation in the piezoelectric constant d, and it is not necessary to correct the detected potential amount for each detection element, and the reliability of the entire system is improved. It will be expensive.

[0020]

As described above, according to the present invention, the electrodes for detecting the XYZ axis acceleration components are provided in one piezoelectric element, so that the structure can be simplified and the accuracy is high.

[Brief description of drawings]

FIG. 1 is a perspective view of an acceleration sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view of a piezoelectric element of the acceleration sensor.

FIG. 3 is a partial sectional view of FIG.

FIG. 4 is a perspective view of a conventional acceleration sensor.

[Figure 5] Diagram of the same detection principle

[Explanation of symbols]

 10 Metal Base 11 Piezoelectric Element 12 X-Axis Direction Acceleration Component Detection Electrode 12a X-Axis Direction Acceleration Component Detection Weight 13 Y-Axis Direction Acceleration Component Detection Electrode 13a Y-Axis Direction Acceleration Component Detection Weight 14 Z-Axis Direction Acceleration Component Detection Electrode 15 Common electrode 16 Lead part 17 Insulation cylinder 18 Flange 19 Solder

Claims (6)

[Claims] 1. A piezoelectric element, comprising: a ring-shaped metal base portion; and a ring-shaped piezoelectric element that is attached to the metal base with an adhesive and has a plurality of electrodes for detecting acceleration components in the XYZ axis directions. An acceleration sensor in which acceleration detecting weights are bonded on the X-axis and Y-axis direction acceleration component detecting electrodes of the element. 2. The piezoelectric element is polarized so as to utilize shear stress for detecting acceleration components in the X-axis and Y-axis directions and flexural stress for detecting Z-axis directions. The acceleration sensor described. 3. The piezoelectric element according to claim 1, wherein a common electrode is provided on a surface side to be bonded to a metal base, and at least two XYZ axial acceleration component detection electrodes are radially formed on the opposite surface. Acceleration sensor. 4. The acceleration sensor according to claim 1, wherein the X-axis and Y-axis detection electrodes provided on the piezoelectric element are formed so as to be distributed at 90 degrees. 5. The acceleration sensor according to claim 1, wherein the Z-axis detecting electrode provided on the piezoelectric element is formed on an outer peripheral portion of the piezoelectric element. 6. The acceleration sensor according to claim 1, wherein the metal base is supported inside the Z-axis detection electrode provided on the piezoelectric element.