JP4905921B2 - Acceleration sensor - Google Patents

Description

  The present invention relates to an acceleration sensor.

  2. Description of the Related Art Conventionally, an acceleration sensor that detects acceleration by using displacement of a piezoelectric material has been proposed (see, for example, Patent Document 1). 22A is a perspective view showing the configuration of the acceleration sensor disclosed in Patent Document 1, and FIG. 22B is a cross-sectional view taken along the line II of the acceleration sensor of FIG. The acceleration sensor 1000 includes a quadrangular columnar detection body 1001 formed of a piezoelectric material such as quartz, and one end (the lower end in FIG. 22A) of the detection body 1001 is fixed. As shown in FIG. 22B, detection electrodes 1002 to 1005 are formed on the outer surfaces of the detection body 1001, respectively. The detection electrodes 1002 and 1004 are connected, and the detection electrodes 1003 and 1005 are connected. Thus, the potential difference between the detection terminals 1006 and 1007 is taken out.

  When acceleration is applied to the acceleration sensor 1000 shown in FIGS. 22A and 22B, for example, in the G direction as shown in FIG. 23A, F = ma ( m is the mass of the detection body 1001, and a is the acceleration), and the detection body 1001 is deformed as shown in FIG. Due to the deformation of the detection body 1001, an arrow is provided between the electrodes 1002 to 1005 on the outer surface of the detection body 1001, as shown in FIG. Such an electric field is generated by the piezoelectric effect. This electric field can be taken out as a potential difference between the detection terminals 1006 and 1007, whereby acceleration can be detected.

JP 2004-085237 A

In the conventional acceleration sensor disclosed in Patent Document 1, the force F applied to the detection body 1001 is expressed by F = ma as described above. However, in the case of a piezoelectric material such as quartz, the mass m is small and the electromechanical coupling is performed. Since the coefficient is small, there is a problem that sufficient detection sensitivity cannot be obtained.
Further, in the conventional acceleration sensor, in a situation where a constant acceleration a is continuously applied, the same force F is continuously applied to the detection body 1001 and generation of electric charge is eliminated. There is a problem that an integration circuit or the like is required to detect.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly sensitive acceleration sensor capable of detecting continuously applied acceleration.

The acceleration sensor of the present invention includes a plate-like base, first and second excitation legs formed so as to extend from the base in the first direction, and the base in a direction opposite to the first direction. A third and a fourth excitation leg formed to extend; and a first that is arranged in the middle of the first and second excitation legs and extends from the base in the first direction. Detection legs, a second detection leg disposed in the middle of the third and fourth excitation legs and extending from the base in a direction opposite to the first direction, and the second First and second fixing portions for fixing both ends of the base portion in a second direction orthogonal to the first direction, and the first direction through the center line of the first and second detection leg portions. The first and second excitation legs are flexibly oscillated symmetrically with respect to a plane parallel and perpendicular to the second direction. Excitation means for bending and vibrating the third and fourth excitation legs symmetrically, and bending vibration of the first and second detection legs along a third direction orthogonal to the first and second directions Remove the voltage signal by the third acceleration applied from the direction of have a detecting means for detecting, based on said voltage signal, prior Symbol excitation means, the first, second, third, fourth A voltage is applied to the first, second, third, and fourth excitation electrodes formed on the excitation legs, and the first, second, third, and fourth excitation electrodes. The first and second excitation legs are bent and oscillated symmetrically, and at the same time the third and fourth excitation legs are bent and oscillated symmetrically, and the detection means is the first detection A first detection for extracting a voltage signal formed by bending vibration of the first detection leg along the third direction, formed on the leg; A second detection electrode formed on the second detection leg and configured to extract a voltage signal generated by bending vibration of the second detection leg along the third direction; and the first and second The first and second detections of the voltage signal generated by the bending vibrations of the first and second detection legs generated according to the bending vibration of the third and fourth excitation legs and the force caused by the acceleration are performed. It comprises a detection circuit that receives from the electrodes and detects the acceleration based on this voltage signal.

Also , one configuration example of the acceleration sensor according to the present invention is characterized in that a weight is provided at each end of the first, second, third, and fourth excitation legs on the side opposite to the base. It is.

  According to the present invention, the first and second excitation legs formed to extend in the first direction from the base, and the third and second formed to extend in the direction opposite to the first direction from the base. Four excitation legs, a first detection leg arranged in the middle of the first and second excitation legs and extending in the first direction from the base, and third and fourth excitations A second detection leg disposed in the middle of the leg and extending from the base in a direction opposite to the first direction, and the excitation means defines the center lines of the first and second detection legs. The first and second excitation legs are flexibly oscillated symmetrically with respect to a plane parallel to the first direction and perpendicular to the second direction. At the same time, the third and fourth excitation legs are symmetrical. Voltage signal due to the bending vibration of the first and second detection legs along the third direction orthogonal to the first and second directions. By taking out, it is possible to detect the acceleration applied from the third direction. In the present invention, the conventional acceleration is obtained by combining the excitation vibration of the first, second, third, and fourth excitation legs along the second direction and the vibration in the third direction according to the acceleration. High detection sensitivity can be realized compared to the sensor. In the present invention, when acceleration is continuously applied along the third direction, vibrations in the third direction of the first, second, third, and fourth excitation legs and the first and second Since the vibration in the third direction of the detection leg is continuously generated, a voltage signal corresponding to the acceleration can be taken out, and the continuously applied acceleration can be detected.

  In the present invention, the first, second, third, and fourth excitations are provided by providing weights at the ends of the first, second, third, and fourth excitation legs on the side opposite to the base. The amplitude of the excitation vibration of the leg can be increased, and the mass of the first, second, third, and fourth excitation legs is increased, so that the acceleration detection sensitivity can be further improved.

  In the present invention, the first and second excitation legs formed so as to extend in the first direction from the base, and the first and second excitation legs are arranged in the middle, and the first to second A first detection leg portion extending in a direction, and passing through the center line of the first detection leg portion by the excitation means in a plane parallel to the first direction and perpendicular to the second direction. On the other hand, the first and second excitation legs are bent and oscillated symmetrically, and the detection means is caused by the bending vibration of the first detection legs along the third direction orthogonal to the first and second directions. By taking out the voltage signal, the acceleration applied from the third direction can be detected. In the present invention, by combining the excitation vibration of the first and second excitation legs along the second direction and the vibration in the third direction according to the acceleration, the detection is higher than that of the conventional acceleration sensor. Sensitivity can be realized. In the present invention, when the acceleration is continuously applied along the third direction, the vibration in the third direction of the first and second excitation legs and the third direction of the first detection leg are detected. Since vibration continuously occurs, a voltage signal corresponding to the acceleration can be taken out, and the continuously applied acceleration can be detected.

  In the present invention, the amplitudes of the excitation vibrations of the first and second excitation legs can be increased by providing weights at the ends of the first and second excitation legs opposite to the base. In addition, since the mass of the first and second excitation legs increases, the acceleration detection sensitivity can be further improved.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is a plan view showing the configuration of the acceleration sensor according to the first embodiment of the present invention, FIG. 2 is a perspective view of the acceleration sensor of FIG. 1, and FIG. 3A is AA of the acceleration sensor of FIG. FIG. 3B is a sectional view taken along line B-B of the acceleration sensor of FIG.

  The acceleration sensor 1 includes a base 2, first and second excitation legs 3 and 4 formed so as to extend from the base 2 in parallel to each other in a first direction (upward in FIG. 1), and the base 2. Arranged in the middle of the third and fourth excitation legs 5 and 6 and the excitation legs 3 and 4 formed so as to extend in parallel to each other in the direction opposite to the first direction (downward in FIG. 1). The first detection leg 7 formed to extend from the base 2 in the first direction and the excitation legs 5 and 6 are disposed in the middle, and the direction opposite to the first direction from the base 2 The first and second detection legs 8 are formed so as to extend in the first direction, and both ends of the base 2 in the second direction (left-right direction in FIG. 1) orthogonal to the first direction are fixed. Fixed portions 9 and 10 and weights 11, 12, 13 and 14 provided at the tips of the excitation leg portions 3, 4, 5 and 6 are provided. 1 to 3, the direction parallel to the second direction is the X-axis direction, the direction parallel to the first direction is the Y-axis direction, and the direction orthogonal to the XY plane is the Z-axis direction.

  The base 2, the excitation legs 3 to 6, the detection legs 7 and 8, the fixing parts 9 and 10, and the weights 11 to 14 are integrally formed by a piezoelectric material such as quartz having a thickness of about 0.1 to 0.3 mm, for example. Has been. In order to manufacture such an acceleration sensor 1, the quartz plate may be processed by, for example, etching. The leg portions 3 to 8 should have a width (dimension in the X-axis direction) of about 0.05 to 0.3 mm and a length (dimension in the Y-axis direction) of about 1.0 to 5.0 mm. . The mass of the excitation leg 3 and the weight 11 is preferably equal to the mass of the excitation leg 4 and the weight 12. Similarly, the mass of the excitation leg 5 and the weight 13 and the mass of the excitation leg 6 and the weight 14 are equal. It is preferable.

  The fixing portions 9 and 10 are mounted on a base (not shown), for example. Thereby, the acceleration sensor 1 is fixed to the base so that the base 2, the excitation legs 3 to 6, the detection legs 7 and 8, and the weights 11 to 14 float from the base.

  As shown in FIG. 3A, excitation electrodes 101 to 104 are formed on the four surfaces of the excitation leg 3, respectively, and excitation electrodes 109 to 112 are formed on the four surfaces of the excitation leg 4, respectively. Detection electrodes 105 to 108 are respectively formed on the four surfaces of the portion 7. Further, as shown in FIG. 3B, excitation electrodes 113 to 116 are formed on the four surfaces of the excitation leg portion 5, respectively, and excitation electrodes 121 to 124 are formed on the four surfaces of the excitation leg portion 6, respectively. Detection electrodes 117 to 120 are formed on the four surfaces of the detection leg 8 respectively.

  FIG. 4 is a circuit diagram showing the connection relationship between the electrodes of the acceleration sensor 1. The excitation electrodes 101 and 103 of the excitation leg 3 are connected, the excitation electrodes 110 and 112 of the excitation leg 4 are connected, the excitation electrodes 113 and 115 of the excitation leg 5 are connected, and the excitation leg 6 Excitation electrodes 122 and 124 are connected, and further, these excitation electrodes 101, 103, 110, 112, 113, 115, 122, 124 are connected to a first output terminal D 1 of the excitation circuit 200. Further, the excitation electrodes 102 and 104 of the excitation leg 3 are connected, the excitation electrodes 109 and 111 of the excitation leg 4 are connected, and the excitation electrodes 114 and 116 of the excitation leg 5 are connected to each other. 6 excitation electrodes 121 and 123 are connected, and these excitation electrodes 102, 104, 109, 111, 114, 116, 121, 123 are connected to the second output terminal D 2 of the excitation circuit 200.

  The detection electrodes 106 and 108 of the detection leg 7 are connected, the detection electrodes 118 and 120 of the detection leg 8 are connected, and these detection electrodes 106, 108, 118, 120 are connected to the first detection circuit 201. It is connected to the input terminal P1. The detection electrodes 105 and 107 of the detection leg 7 are connected, the detection electrodes 117 and 119 of the detection leg 8 are connected, and the detection electrodes 105, 107, 117, and 119 are connected to the detection circuit 201. 2 input terminals P2.

  Next, the operation of the acceleration sensor 1 of the present embodiment will be described. The excitation circuit 200 applies, for example, a sinusoidal AC voltage (excitation signal) between the output terminals D1 and D2. For this reason, in some cases, an electric field as indicated by an arrow in FIG. 5 is generated in each of the excitation legs 3 to 6, and then an electric field in the direction opposite to the arrow in FIG. 5 is generated. Thereby, the excitation leg parts 3-6 and the weights 11-14 provided at the front-end | tip perform bending vibration which repeats bending displacement along an X-axis direction.

  FIG. 6 is a plan view schematically showing bending vibration of the excitation legs 3 to 6 and the weights 11 to 14. The excitation legs 3 to 6 and the weights 11 to 14 bend and vibrate as indicated by broken lines in FIG. At this time, the excitation leg 3 and the weight 11, and the excitation leg 4 and the weight 12 pass through the center line L of the excitation legs 7 and 8 and are parallel to the first direction and with respect to the second direction. Bends and vibrates symmetrically with respect to the vertical YZ plane. That is, the excitation leg 3 and the weight 11 spread in the left direction and simultaneously the excitation leg 4 and the weight 12 spread in the right direction. Subsequently, the excitation leg 3 and the weight 11 return in the right direction and the excitation leg 4 and The operation of the weight 12 returning to the left is repeated. Similarly, the excitation leg portion 5 and the weight 13 and the excitation leg portion 6 and the weight 14 flexurally vibrate with respect to the YZ plane passing through the center line L. That is, the excitation leg 5 and the weight 13 spread in the left direction and simultaneously the excitation leg 6 and the weight 14 spread in the right direction. Subsequently, the excitation leg 5 and the weight 13 return in the right direction and the excitation leg 6 and The operation of the weight 14 returning to the left is repeated.

  In this way, when acceleration is applied along the thickness direction of the acceleration sensor 1 in the state where the excitation legs 3 to 6 are flexibly oscillating, the force F = ma (force due to inertia in the direction opposite to the acceleration is applied to the acceleration sensor 1. m is the mass of the acceleration sensor 1, and a is acceleration). FIG. 7A is a perspective view schematically showing the movement of the excitation legs 3 to 6, the detection legs 7 and 8, and the weights 11 to 14 when the acceleration G is applied to the acceleration sensor 1. FIG. FIG. 7A is a side view of the acceleration sensor 1 of FIG. 7A viewed from the P side, and FIG. 7C is a side view of the acceleration sensor 1 of FIG. 7A viewed from the Q side.

  In the example of FIGS. 7A to 7C, a case is shown in which acceleration G is applied downward along the Z-axis direction. In this case, as described above, the upward force F is applied to the acceleration sensor 1 along the direction opposite to the acceleration G, that is, along the Z-axis direction. The excitation legs 3 to 6 and the weights 11 to 14 are bent and vibrated along the X-axis direction, and the centers of gravity of the excitation legs 3 to 6 and the weights 11 to 14 are displaced along the X-axis direction. For this reason, the excitation legs 3 to 6 and the weights 11 to 14 are twisted as shown in FIG. 7B and FIG. In addition to the axial component, bending vibration having a Z-axis direction component due to torsion occurs.

  On the other hand, as shown in FIGS. 7B and 7C, the detection legs 7 and 8 are bent by the bending vibrations having the Z-axis direction components of the excitation legs 3 to 6 and the weights 11 to 14 as shown in FIGS. Bending vibration occurs along the axial direction. Due to the deformation of the detection legs 7 and 8, the gap between the detection electrodes 105 to 108 on the outer surface of the detection leg 7 and the detection electrodes 117 to 120 on the outer surface of the detection leg 8 are indicated by arrows in FIG. 8. An electric field is generated by the piezoelectric effect. This electric field can be extracted as a voltage signal between the input terminals P1 and P2 of the detection circuit 201. This voltage signal has a magnitude corresponding to the acceleration G. Therefore, the detection circuit 201 can detect the magnitude of the acceleration G acting in the Z-axis direction based on the magnitude of the voltage signal. Further, the detection circuit 201 can detect the direction of the acceleration G by comparing the phase of the voltage signal with the phase of the excitation signal output from the excitation circuit 200.

  As described above, in the present embodiment, by combining the excitation vibration in the X-axis direction of the excitation legs 3 to 6 and the weights 11 to 14 with the vibration in the Z-axis direction according to the acceleration, Patent Document 1 High detection sensitivity can be realized as compared with the disclosed conventional acceleration sensor. When designing the acceleration sensor 1 of the present embodiment, the degree of detuning, which is the ratio between the frequency Fsd of the excitation vibration in the X-axis direction and the frequency Fsp of the detected vibration in the Z-axis direction according to the acceleration, is set to 1 to 3%, for example. If designed to the extent, excitation vibration and detection vibration corresponding to acceleration can be easily combined, and high detection sensitivity can be obtained. Since the frequency Fsd of the excitation vibration depends on the width and length of the excitation legs 3 to 6, and the frequency Fsp of the detection vibration depends on the thickness and length of the excitation legs 3 to 6 and the detection legs 7 and 8, Each dimension may be appropriately determined so that the frequencies Fsd and Fsp are substantially the same.

  In the present embodiment, when acceleration is continuously applied along the Z-axis direction, vibrations in the Z-axis direction of the excitation legs 3 to 6 and the weights 11 to 14 and the Z-axis direction of the detection legs 7 and 8 are detected. Therefore, a voltage signal corresponding to the acceleration can be taken out from the detection electrodes 105 to 108 and 117 to 120, and the continuously applied acceleration can be detected.

  In the present embodiment, weights 11 to 14 are provided at the tips of the excitation leg portions 3 to 6. By providing the weights 11 to 14, the amplitude of the excitation vibration of the excitation legs 3 to 6 can be increased, and the mass of the excitation legs 3 to 6 is increased, so that the acceleration detection sensitivity can be improved. However, the weights 11-14 are not essential requirements of the present invention.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. 9 is a plan view showing the configuration of the acceleration sensor according to the second embodiment of the present invention, FIG. 10 is a perspective view of the acceleration sensor of FIG. 9, and the same configuration as in FIGS. The code | symbol is attached | subjected.
The acceleration sensor 1a according to the present embodiment includes a base 2, first and second excitation legs 3 and 4, third and fourth excitation legs 5 and 6, and first and second detection legs. Parts 7 and 8, weights 11 to 14, and third and fourth fixing parts 15 and 16 for fixing the ends of the detection leg parts 7 and 8 on the side opposite to the base 2.

As in the first embodiment, the base 2, the excitation legs 3-6, the detection legs 7, 8, the weights 11-14, and the fixing parts 15, 16 are integrally formed of a piezoelectric material such as quartz. Yes.
In the present embodiment, fixing portions 15 and 16 are provided instead of the fixing portions 9 and 10 of the first embodiment, and the end portions of the detection leg portions 7 and 8 are fixed. The fixing parts 15 and 16 are mounted on a base (not shown). Thereby, the acceleration sensor 1a is fixed to the base so that the base 2, the excitation legs 3 to 6, the detection legs 7 and 8, and the weights 11 to 14 float from the base.

  The cross section along line AA of the acceleration sensor 1a in FIG. 9 is as shown in FIG. 3A, and the cross section along line BB of the acceleration sensor 1a is as shown in FIG. 3B. Further, the connection relationship of the electrodes of the acceleration sensor 1a is as shown in FIG.

Next, the operation of the acceleration sensor 1a will be described. Also in the present embodiment, the excitation legs 3 to 6 and the weights 11 to 14 bend and vibrate as in the first embodiment.
FIG. 11A is a perspective view schematically showing the movement of the excitation legs 3 to 6, the detection legs 7 and 8, and the weights 11 to 14 when the acceleration G is applied to the acceleration sensor 1a, and FIG. 11A is a side view of the acceleration sensor 1a of FIG. 11A viewed from the P side, FIG. 11C is a side view of the acceleration sensor 1a of FIG. 11A viewed from the Q side, and FIG. It is the side view which looked at the acceleration sensor 1a of 11 (A) from the R side.

  In the example of FIGS. 11A to 11D, a case is shown in which acceleration G is applied downward along the Z-axis direction. In this case, as in the first embodiment, an upward force F is applied to the acceleration sensor 1 along the Z-axis direction. Due to the displacement F of the center of gravity and the force F caused by the inertia explained in the first embodiment, the excitation legs 3 to 6 and the weights 11 to 14 are excited by excitation as shown in FIGS. 11 (B) and 11 (C). In addition to the X-axis direction component, bending vibration having a Z-axis direction component due to torsion occurs.

On the other hand, the base 2 and the detection legs 7 and 8 are subjected to flexural vibration and force F having the Z-axis direction components of the excitation legs 3 to 6 and the weights 11 to 14, respectively, as shown in FIGS. ), Bending vibration along the Z-axis direction occurs. Due to the deformation of the detection legs 7 and 8, an electric field as indicated by an arrow in FIG. 8 is generated in the detection electrodes 105 to 108 and 117 to 120 of the detection leg 7. The operation of the detection circuit 201 is as described in the first embodiment.
As described above, also in the present embodiment, the same effect as in the first embodiment can be obtained.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. 12 is a plan view showing the configuration of the acceleration sensor according to the third embodiment of the present invention, and FIG. 13 is a perspective view of the acceleration sensor of FIG. 12, similar to FIGS. 1 to 3, 9, and 10. The same reference numerals are given to the configurations of.
The acceleration sensor 1b of the present embodiment includes a base 2, first and second excitation legs 3 and 4, third and fourth excitation legs 5 and 6, and first and second detection legs. Parts 7 and 8, first and second fixing parts 9 and 10, weights 11 to 14, and a third fixing part 15 that fixes the end of the detection leg 7 on the side opposite to the base 2. ing.

The fixing parts 9, 10, and 15 are mounted on a base (not shown). Thereby, the acceleration sensor 1b is fixed to the base so that the base 2, the excitation legs 3 to 6, the detection legs 7 and 8, and the weights 11 to 14 float from the base.
The cross section along line AA of the acceleration sensor 1b in FIG. 12 is as shown in FIG. 3A, and the cross section along line BB of the acceleration sensor 1b is as shown in FIG. 3B. Further, the connection relationship of the electrodes of the acceleration sensor 1b is as shown in FIG.

Next, the operation of the acceleration sensor 1b will be described. Also in the present embodiment, the excitation legs 3 to 6 and the weights 11 to 14 bend and vibrate as in the first embodiment.
14A is a perspective view schematically showing the movement of the excitation legs 3 to 6, the detection legs 7 and 8, and the weights 11 to 14 when the acceleration G is applied to the acceleration sensor 1b. FIG. 14A is a side view of the acceleration sensor 1b of FIG. 14A viewed from the P side, FIG. 14C is a side view of the acceleration sensor 1b of FIG. 14A viewed from the Q side, and FIG. It is the side view which looked at the acceleration sensor 1b of 14 (A) from the R side.

  In the example of FIGS. 14A to 14D, a case is shown in which acceleration G is applied downward along the Z-axis direction. In this case, as in the first embodiment, an upward force F is applied to the acceleration sensor 1 along the Z-axis direction. Due to the displacement of the center of gravity and the inertia force F described in the first embodiment, the excitation legs 3 to 6 and the weights 11 to 14 are excited by excitation as shown in FIGS. 14 (B) and 14 (C). In addition to the X-axis direction component, bending vibration having a Z-axis direction component due to torsion occurs.

  On the other hand, the base 2 and the detection legs 7 and 8 are subjected to flexural vibration and force F having the Z-axis direction components of the excitation legs 3 to 6 and the weights 11 to 14, respectively, as shown in FIGS. ), Bending vibration along the Z-axis direction occurs. Due to the deformation of the detection legs 7 and 8, an electric field as indicated by an arrow in FIG. 8 is generated in the detection electrodes 105 to 108 and 117 to 120 of the detection leg 7. The operation of the detection circuit 201 is as described in the first embodiment.

  As described above, also in the present embodiment, the same effect as in the first embodiment can be obtained. In the present embodiment, the third fixing portion 15 for fixing the end portion of the detection leg portion 7 is provided, but the fourth fixing portion for fixing the end portion of the detection leg portion 8 instead of the fixing portion 15 is provided. It goes without saying that 16 may be provided.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 15 is a plan view showing the configuration of the acceleration sensor according to the fourth embodiment of the present invention. The same configurations as those in FIGS. 1 to 3, 9, 10, 12, and 13 are the same. The code | symbol is attached | subjected.
The acceleration sensor 1c according to the present embodiment includes a base 2, first and second excitation legs 3 and 4, third and fourth excitation legs 5 and 6, and first and second detection legs. The first and second fixing parts 9 and 10 for fixing both ends of the parts 7 and 8 and the base 2, the weights 11 to 14, and the ends of the detection leg parts 7 and 8 on the opposite side of the base 2 are fixed. Third and fourth fixing portions 15 and 16 are provided.

  The cross section along line AA of the acceleration sensor 1c in FIG. 15 is as shown in FIG. 3A, and the cross section along line BB of the acceleration sensor 1c is as shown in FIG. 3B. Further, the connection relationship of the electrodes of the acceleration sensor 1c is as shown in FIG.

Next, the operation of the acceleration sensor 1c will be described. Also in the present embodiment, the excitation legs 3 to 6 and the weights 11 to 14 bend and vibrate as in the first embodiment.
FIG. 16A is a perspective view schematically showing the movement of the excitation legs 3-6, the detection legs 7, 8 and the weights 11-14 when the acceleration G is applied to the acceleration sensor 1c, FIG. 16A is a side view of the acceleration sensor 1c of FIG. 16A viewed from the P side, FIG. 16C is a side view of the acceleration sensor 1c of FIG. 16A viewed from the Q side, and FIG. It is the side view which looked at the acceleration sensor 1c of 16 (A) from the R side.

  In the example of FIGS. 16A to 16D, a case is shown in which acceleration G is applied downward along the Z-axis direction. In this case, as in the first embodiment, an upward force F is applied to the acceleration sensor 1 along the Z-axis direction. Due to the displacement of the center of gravity and the force F caused by the inertia explained in the first embodiment, the excitation legs 3 to 6 and the weights 11 to 14 are excited by the excitation as shown in FIGS. 16 (B) and 16 (C). In addition to the X-axis direction component, bending vibration having a Z-axis direction component due to torsion occurs.

On the other hand, the base 2 and the detection legs 7 and 8 are subjected to flexural vibration and force F having the Z-axis direction components of the excitation legs 3 to 6 and the weights 11 to 14, respectively, as shown in FIGS. ), Bending vibration along the Z-axis direction occurs. Due to the deformation of the detection legs 7 and 8, an electric field as indicated by an arrow in FIG. 8 is generated between the detection electrodes 105 to 108 and 117 to 120 on the outer surface of the detection leg 7. The operation of the detection circuit 201 is as described in the first embodiment.
As described above, also in the present embodiment, the same effect as in the first embodiment can be obtained.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. FIG. 17 is a plan view showing the configuration of the acceleration sensor according to the fifth embodiment of the present invention. The configuration is the same as that shown in FIGS. 1 to 3, 9, 10, 12, 13, and 15. Are given the same reference numerals.
The acceleration sensor 1d according to the present embodiment includes a base 2, first and second excitation legs 3 and 4, a first detection leg 7, first and second fixing parts 9 and 10, Weights 11 and 12 and a third fixing part 15 for fixing the end of the detection leg 7 opposite to the base 2 are provided, and the third to fourth acceleration sensors 1b of the third embodiment are provided. This corresponds to a structure in which the excitation legs 5 and 6, the second detection leg 8, and the weights 13 and 14 are removed.

  The cross section along line AA of the acceleration sensor 1d in FIG. 17 is as shown in FIG. FIG. 18 is a circuit diagram showing the connection relationship between the electrodes of the acceleration sensor 1d. The connection relationship of the electrodes of the acceleration sensor 1d corresponds to that obtained by removing the third and fourth excitation legs 5 and 6, the second detection leg 8 and the weights 13 and 14 from FIG.

Next, the operation of the acceleration sensor 1d will be described. Also in the present embodiment, the excitation legs 3 and 4 and the weights 11 and 12 bend and vibrate as in the first embodiment.
FIG. 19A is a perspective view schematically showing the movements of the excitation legs 3 and 4, the detection legs 7 and the weights 11 and 12 when the acceleration G is applied to the acceleration sensor 1d, and FIG. 19A is a side view of the acceleration sensor 1d viewed from the P side, and FIG. 19C is a side view of the acceleration sensor 1d of FIG. 19A viewed from the R side.

  In the example of FIGS. 19A to 19C, the acceleration G is applied downward along the Z-axis direction. In this case, the movement of the base 2, the excitation legs 3 and 4, the detection legs 7, and the weights 11 and 12 is the same as that in the third embodiment described with reference to FIG. To do.

Due to the deformation of the detection leg 7, an electric field as indicated by an arrow in FIG. 20 is generated between the detection electrodes 105 to 108 of the detection leg 7. This electric field can be extracted as a voltage signal between the input terminals P1 and P2 of the detection circuit 201. The detection circuit 201 can detect the magnitude of the acceleration G acting in the Z-axis direction based on the magnitude of the voltage signal. Further, the detection circuit 201 can detect the direction of the acceleration G by comparing the phase of the voltage signal with the phase of the excitation signal output from the excitation circuit 200.
As described above, also in the present embodiment, the same effect as in the first embodiment can be obtained.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. FIG. 21 is a plan view showing the configuration of the acceleration sensor according to the sixth embodiment of the present invention, which is the same as FIGS. 1 to 3, 9, 10, 12, 13, 15, and 17. The same reference numerals are given to the configurations of.
The acceleration sensor 1e according to the present embodiment includes a base 2, first and second excitation legs 3, 4, first detection legs 7, weights 11, 12, and detection opposite to the base 2. A third fixing portion 15 for fixing the end portion of the leg portion 7, and a supporting leg portion 17 formed so as to extend from the base portion 2 in a direction opposite to the first direction (downward in FIG. 21); And a fifth fixing portion 18 for fixing the end of the supporting leg 17 on the opposite side of the base 2, and the third and fourth excitation legs 5 from the acceleration sensor 1a of the second embodiment. 6, the second detection leg 8, the weights 13 and 14, and the fourth fixing part 16 are removed, and a supporting leg 17 and a fixing part 18 are added.

The cross section along line AA of the acceleration sensor 1e in FIG. 21 is as shown in FIG. 3A, and the connection relationship of each electrode of the acceleration sensor 1e is as shown in FIG.
Also in the present embodiment, the excitation legs 3 and 4 and the weights 11 and 12 bend and vibrate as in the first embodiment. The movement of the base 2, the excitation legs 3, 4, the detection legs 7, the weights 11, 12, and the support legs 17 when the acceleration G is applied to the acceleration sensor 1e is the second embodiment described with reference to FIG. Since it is the same as that of the form, detailed description is abbreviate | omitted. The movement of the support leg 17 is the same as that of the detection leg 8.

Due to the deformation of the detection leg 7, an electric field as indicated by an arrow in FIG. 20 is generated between the detection electrodes 105 to 108 of the detection leg 7. The operation of the detection circuit 201 is as described in the fifth embodiment.
As described above, also in the present embodiment, the same effect as in the first embodiment can be obtained.

  In the first to sixth embodiments, the explanation has been given by taking quartz as an example of the piezoelectric material of the acceleration sensor. However, the present invention is not limited to this, and other piezoelectric materials such as piezoelectric ceramics may be used. Good.

  The present invention can be applied to an acceleration sensor.

It is a top view which shows the structure of the acceleration sensor which concerns on the 1st Embodiment of this invention. It is a perspective view which shows the structure of the acceleration sensor which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the acceleration sensor which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows the connection relation of each electrode of the acceleration sensor which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the electric field which arises in an excitation leg part by the voltage application from an excitation circuit in the 1st Embodiment of this invention. It is a top view which shows typically the bending vibration of an excitation leg part and a weight in the 1st Embodiment of this invention. It is the perspective view and side view which show typically the motion of an excitation leg part, a detection leg part, and a weight when acceleration is added in the 1st Embodiment of this invention. It is sectional drawing which shows the electric field which arises in a detection leg part when acceleration is added in the 1st Embodiment of this invention. It is a top view which shows the structure of the acceleration sensor which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the structure of the acceleration sensor which concerns on the 2nd Embodiment of this invention. It is the perspective view and side view which show typically the motion of an excitation leg part, a detection leg part, and a weight when acceleration is added in the 2nd Embodiment of this invention. It is a top view which shows the structure of the acceleration sensor which concerns on the 3rd Embodiment of this invention. It is a perspective view which shows the structure of the acceleration sensor which concerns on the 3rd Embodiment of this invention. It is the perspective view and side view which show typically the motion of an excitation leg part, a detection leg part, and a weight when acceleration is added in the 3rd Embodiment of this invention. It is a top view which shows the structure of the acceleration sensor which concerns on the 4th Embodiment of this invention. It is the perspective view and side view which show typically the motion of an excitation leg part and a detection leg part when an acceleration is added in the 4th Embodiment of this invention. It is a top view which shows the structure of the acceleration sensor which concerns on the 5th Embodiment of this invention. It is a circuit diagram which shows the connection relation of each electrode of the acceleration sensor which concerns on the 5th Embodiment of this invention. It is the perspective view and side view which show typically the motion of an excitation leg part, a detection leg part, and a weight when acceleration is added in the 5th Embodiment of this invention. It is sectional drawing which shows the electric field which arises in a detection leg part when acceleration is added in the 5th Embodiment of this invention. It is a top view which shows the structure of the acceleration sensor which concerns on the 6th Embodiment of this invention. It is the perspective view and sectional drawing which show the structure of the conventional acceleration sensor. It is a figure for demonstrating operation | movement when an acceleration is added to the acceleration sensor of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c, 1d, 1e ... Acceleration sensor, 2 ... Base part, 3-6 ... Excitation leg part, 7, 8 ... Detection leg part, 9, 10, 15, 16, 18 ... Fixed part, 11- DESCRIPTION OF SYMBOLS 14 ... Weight, 17 ... Supporting leg part, 101-104, 109-116, 121-124 ... Excitation electrode, 105-108, 117-120 ... Detection electrode, 200 ... Excitation circuit, 201 ... Detection circuit.

Claims (2)

A plate-like base;
First and second excitation legs formed to extend from the base in a first direction;
Third and fourth excitation legs formed to extend from the base in a direction opposite to the first direction;
A first detection leg disposed in the middle of the first and second excitation legs and formed to extend from the base in the first direction;
A second detection leg disposed in the middle of the third and fourth excitation legs and extending from the base in a direction opposite to the first direction;
First and second fixing portions for fixing both ends of the base portion in a second direction orthogonal to the first direction;
The first and second excitation legs are symmetric with respect to a plane that passes through the center line of the first and second detection legs and is parallel to the first direction and perpendicular to the second direction. Excitation means for bending and vibrating the third and fourth excitation legs symmetrically at the same time as
A voltage signal generated by bending vibration of the first and second detection legs along a third direction orthogonal to the first and second directions is extracted, and an acceleration applied from the third direction is calculated as the voltage. have a detection means for detecting on the basis of the signal,
The excitation means includes
First, second, third, and fourth excitation electrodes formed on the first, second, third, and fourth excitation legs; and
A voltage is applied to the first, second, third, and fourth excitation electrodes to cause the first and second excitation legs to flexibly vibrate symmetrically with respect to the plane, and at the same time, the third and fourth And an excitation circuit that flexibly vibrates the excitation legs of
The detection means includes
A first detection electrode formed on the first detection leg and for extracting a voltage signal due to bending vibration of the first detection leg along the third direction;
A second detection electrode formed on the second detection leg and for extracting a voltage signal by bending vibration of the second detection leg along the third direction;
The voltage signal generated by the bending vibration of the first and second detection legs generated in response to the bending vibration of the first, second, third, and fourth excitation legs and the force caused by the acceleration is expressed as the first signal. 1. An acceleration sensor comprising: a detection circuit that receives the first detection electrode and detects the acceleration based on the voltage signal . The acceleration sensor according to claim 1,
An acceleration sensor characterized in that a weight is provided at each end of the first, second, third, and fourth excitation legs on the side opposite to the base .

Images