JPH11118824A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce size and increase detecting sensitiveness in an acceleration sensor for detecting an acceleration in multidimensional directions. SOLUTION: Four vibration bodies of canti-lever structure are supported on one ends of the support parts of beams 1 to 4 by a common fixed pedestal 13, and strain detecting elements 9 to 12 such as piezoelectric element and strain gauge element are installed on the surface of each beam. Additional weights 5 to 8 are installed at the other free end parts of the beams 1 and 2 and 3 and 4 on the front and rear vibrating surfaces of the beams so that they are reversed to each other in vertical direction. In addition, the beams 1 and 2 and 3 and 4 are arranged so that the longitudinal directions of them are in parallel to each other. Then, using the beams 1 and 2 and 3 and 4 as a set, respectively, two sets of vibration bodies are arranged in an X and Y rectangular coordinate system so that, using X and Y orthogonal point as a home position, the center axis of one set of the vibrating bodies in longitudinal direction is located on an X-axis at an equal distance from the home position, and the center axis of the other set of the vibrating bodies in longitudinal direction is located on a Y-axis at an equal distance from the home position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor having a cantilever structure for detecting accelerations in a plurality of directions by deflection of a beam.

[0002]

2. Description of the Related Art Conventionally, a cantilever type acceleration sensor for detecting acceleration by deflection of a beam has been widely known. Hereinafter, an example of a one-dimensional acceleration sensor and a three-dimensional acceleration sensor having a conventional configuration will be shown and described. 3A and 3B are illustrative views showing an example of a conventional one-dimensional acceleration sensor having a cantilever structure. This acceleration sensor includes a vibrating body 1 including a plate-shaped vibrating body.
Has an additional mass 5 attached to its free end. Further, a strain detecting element 9 is formed on the surface of the vibrating body.

When acceleration is applied in a direction perpendicular to the surface of the vibrating body of the acceleration sensor, the vibrating body bends as shown in FIG. The amount of electricity obtained from the strain detecting element changes due to the compressive stress generated thereby. The acceleration is detected from the change in the amount of electricity at this time. 4A and 4B are a plan view and a cross-sectional view illustrating an example of a conventional three-dimensional acceleration sensor having a cantilever structure. In this acceleration sensor, an additional mass attached to the free end of the one-dimensional acceleration sensor described above is attached only below the surface of the vibrating body.
The two vibrators are combined and arranged in a cross shape so as to face each other from the integral fixed portion to the free end.

When the additional mass is displaced in the X direction due to acceleration in the acceleration sensor, the strain detecting element provided on the vibrating body 1 arranged on the upper side of the vibrating bodies arranged on the upper and lower sides in FIG. A stress is generated, and a tensile stress is generated in the strain detecting element provided on the vibrating body 3 arranged on the lower side. The acceleration in the X direction is detected from the change in the amount of electricity at this time. Next, when the additional mass is displaced in the Y direction due to the acceleration, a compressive stress is generated in the strain detecting element provided in the vibrating body 4 arranged on the left side in the figure, and is provided in the vibrating body 2 arranged on the right side. A tensile stress is generated in the strain detecting element. The acceleration in the Y direction is detected from the change in the amount of electricity at this time. Further, when the additional mass is displaced in the Z direction due to acceleration, a compressive stress is generated in any of the strain detecting elements provided in the four vibrators 1 to 4, and the change in the quantity of electricity at this time causes a change in the amount of Z.
Detect the acceleration in the direction.

[0005]

However, the above-mentioned 1
The three-dimensional acceleration sensor can only detect acceleration in a direction perpendicular to the surface of the vibrating body. Therefore, in order to detect accelerations in a plurality of different directions, it is necessary to arrange a plurality of one-dimensional acceleration sensors in a direction in which the surface of the vibrating body is orthogonal to the respective acceleration directions. For this reason, it is troublesome to attach a plurality of one-dimensional acceleration sensors in the axial direction of the acceleration applied with high accuracy, and there is a problem that the shape becomes larger than anything. Further, in the three-dimensional acceleration sensor, although the problem shown in the one-dimensional acceleration sensor is solved, in the case of miniaturization, the length of the beam portion of the cantilever vibrator is shortened and the deflection is inevitable. There is a problem that the amount is reduced and the detection sensitivity is reduced. Therefore, a main object of the present invention is to provide an acceleration sensor which can detect accelerations in a plurality of directions, is easily mounted, is small, and has high detection sensitivity.

[0006]

The present invention comprises two solutions. A first solution is to provide two plate-shaped vibrators and a piezoelectric element formed on the surface of the vibrator, a strain detecting element such as a strain gauge element, and a table of plates at one free end of the vibrator. The back surface includes additional masses disposed so as to be opposite to each other, and one end supporting portion of the vibrating body is supported by a common fixed pedestal, and the longitudinal center lines of these vibrating bodies are parallel to each other. A second solution is to combine two sets of the acceleration sensors having the above-described configuration, and to dispose them in an X, Y orthogonal coordinate system in an X, Y orthogonal coordinate system. A set of the acceleration sensors on the X axis and another set of the acceleration sensors on the Y axis at an equal position from the origin at right angles. It is.

[0007]

FIG. 2de shows an embodiment of the present invention. In the figure, when acceleration is applied in the Z direction orthogonal to the vibrating body surface, the displacement of the compressive stress due to the bending in the same direction on the two vibrating bodies causes the electric quantity of the strain detecting element provided on the vibrating body surface to change in the same polarity. . The acceleration in the Z direction is detected from the change in the amount of electricity at this time. FIG. 2E shows a case where an acceleration in the X direction parallel to the vibrating body is applied, of which the vibrating body 1 flexes upward with respect to the vibrating body surface and the vibrating body 2 flexes downward with respect to the vibrating body surface. . The strain detecting element provided on each vibrating body surface generates a compressive stress due to the bending of the vibrating body 1 and a tensile stress due to the bending of the vibrating body 2,
A change in the amount of electricity of the opposite polarity corresponding to the stress is caused. At this time, the acceleration in the X direction is detected from the changes in the opposite electric quantities obtained from the two strain detecting elements.
With the above configuration, it is possible to detect accelerations in two directions.

FIGS. 1A to 1D show an embodiment of the second solving means. FIG. 1C shows that when acceleration is applied in a Z direction perpendicular to the plane of the vibrating body, all four vibrating bodies are bent in the same direction. Is generated. The changes in the amount of electricity generated by the strain detecting elements provided on the respective vibrators all have the same polarity. Thereby, the acceleration in the Z direction is detected. FIG. 1D shows a case where an acceleration in the X direction parallel to the vibrators 1 and 2 is applied, and the operation is the same as that shown in FIG. In this case, no displacement occurs in the vibrators 3 and 4. Thereby, the acceleration in the X direction is detected. FIG. 1D shows a case in which acceleration in the Y direction parallel to the vibrators 3 and 4 is applied. The vibrator 3 bends upward with respect to the vibrator surface, and the vibrator 4 bends downward. The stress displacement due to the deflection of the vibrators 3 and 4 causes a change in the amount of electricity in a direction opposite to the strain detecting elements provided on the respective vibrator surfaces. Thus, the acceleration in the Y direction is detected. In this case, no displacement occurs in the vibrators 1 and 2. With the above configuration, it is possible to detect acceleration in two-dimensional or three-dimensional directions.

Table 1 shows the polarities of the quantities of electricity obtained from the strain detecting elements provided on the respective vibrators corresponding to the accelerations in the respective directions shown above.

Table 2 shows that the acceleration applied can be detected for each axis component by performing addition and subtraction processing on the change in the amount of electricity obtained from each strain detection element.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to the drawings. 2a to 2c show an embodiment of an acceleration sensor having a two-dimensional cantilever structure. The vibrators 1 and 2 on the two plates are made of a material having a small thermal expansion coefficient and causing mechanical vibration, such as iron-nickel alloy, brass, ceramic, glass, etc., and may have a rectangular or trapezoidal shape. Absent. 2
The support portions of the two vibrators may be connected to each other to form a U-shape as an integral shape. At the one free end of the vibrating body, additional masses 5 and 6 are provided for causing the vibrating body to generate a large displacement and a displacement corresponding to the direction of the acceleration. It is arranged upside down. The positions of the respective additional masses from the vibrating body support portion are preferably arranged to be slightly different from each other in order to compensate for the influence of gravity and equalize the bending displacement of the two vibrating bodies, or the weights of the additional masses are slightly different. Better. These materials may be of any shape as long as they have an appropriate weight and can perform the above-mentioned functions, and may be cylindrical or prismatic. On the surface of the vibrating body, a strain detecting element such as a piezoelectric element or a strain gauge element for changing a stress generated in each beam into a change in electric quantity is formed. The case where the strain detecting element is formed of a piezoelectric element will be described as an example. Piezoelectric plates 9, 1 made of piezoelectric ceramic
The electrodes are formed on both sides of the “0”. Then, the electrode 16 is bonded to the main surfaces of the vibrators 1 and 2. Each piezoelectric plate polarizes from the electrode 15 toward the vibrator. Of course, in order to obtain excellent temperature characteristics and high precision, a vibrating body generally called a parallel bimorph structure may be formed by bonding piezoelectric plates polarized with opposite polarities to opposing main surfaces of the vibrating body. One end supporting portions of the two vibrators are supported by a common fixed pedestal 13, which also serves as a mounting pedestal when the present acceleration sensor is installed. The operation of the acceleration sensor is characterized in that the longitudinal center lines of the beams of the two vibrating bodies configured as described above are arranged parallel to each other.

[0007] This is as described in the embodiment.

Next, a second embodiment of the present invention will be described with reference to the drawings. 1a and 1b show an embodiment of an acceleration sensor having a three-dimensional cantilever structure. This embodiment is different from the first embodiment in that the two-dimensional acceleration sensor of the first embodiment is an X, Y orthogonal coordinate system.
They are arranged so as to be orthogonal to each other with the orthogonal point as the origin, and the detailed configuration is the same as that shown in the first embodiment, so description thereof will be omitted. By arranging the two acceleration sensors at right angles, a three-dimensional arrangement in which the four one-dimensional acceleration sensors previously described in the related art are combined in a cross shape such that the free ends face the center from the integral fixed part. When the external dimensions are the same as those of the acceleration sensor configuration, the length of the beam portion of the vibrating body can be significantly increased, and thus the detection sensitivity is greatly improved. As for the operation,

As shown in the embodiment, X, Y, and Z3 are obtained from changes in the amount of electricity generated corresponding to the displacement of each vibrating body.
The acceleration of the direction component is detected.

[0011]

As described above, according to the present invention, an acceleration sensor for detecting accelerations in a plurality of directions can be easily installed. It is also possible to double the length of the beam portion of the four cantilever vibrating members without increasing the length of the vibrating member, thereby increasing the mechanical displacement of the vibrating member and greatly improving the acceleration detection sensitivity. In other words, if the detection sensitivity is set to the same level as that of the acceleration sensor having the conventional configuration, it is possible to make the shape ultra-small.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1a is a perspective view showing an embodiment of claim 2 of the present invention b: top view showing an embodiment of claim 2 of the present invention c, d: description of the operation of the beam of the acceleration sensor shown in FIGS. Figure

2a: a perspective view showing an embodiment of the first aspect of the present invention; b: a side view showing an embodiment of the first aspect of the present invention; c: a top plan view showing an embodiment of the first aspect of the present invention; : Operation explanatory view of beam of acceleration sensor shown in FIGS.

3a is an illustrative view of a one-dimensional acceleration sensor having a conventional configuration. B: operation explanatory view of a beam of the acceleration sensor shown in FIG.

4A is a top view of a three-dimensional acceleration sensor having a conventional configuration. B is a cross-sectional view of a three-dimensional acceleration sensor having a conventional configuration. C and d are operation explanatory diagrams of beams of the acceleration sensor shown in FIGS. 4A and 4B.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1 cantilever vibrating body 2 2nd cantilever vibrating body 3 3rd cantilever vibrating body 4 4th cantilever vibrating body 5 Addition formed in 1st cantilever vibrating body Mass 6 Additional mass formed on second cantilever vibrating body 7 Additional mass formed on third cantilever vibrating body 8 Additional mass formed on fourth cantilever vibrating body 9 First Strain detecting element formed on cantilever vibrating body 10 Strain detecting element formed on second cantilever vibrating body 11 Strain detecting element formed on third cantilever vibrating body 12 Fourth cantilever Strain detecting element formed on beam vibrator 13 Fixed pedestal 14 Mounting hole for installation 15 Electrode 16 Electrode

[Table 1]

[Table 2]

Claims (2)

[Claims] 1. A vibrating body on two plates, a strain detecting element such as a piezoelectric element or a strain gauge element formed on a surface of the vibrating body, and a free end of one end of the vibrating body on a front surface and a back surface of the plate. An end of the vibrator is supported by a common fixed pedestal and includes additional masses arranged upside down with respect to each other, and the longitudinal center lines of these vibrators are arranged parallel to each other. Acceleration sensor with cantilever structure. 2. The two sets of acceleration sensors according to claim 1 are arranged orthogonally at the X and Y orthogonal coordinate systems, with the X and Y orthogonal points as the origin, and one set of the acceleration sensors on the X axis at the same position from the origin. An acceleration sensor having a cantilever structure.