Accelerometer

Abstract

To provide an acceleration sensor which can be made more sensitive than an existing sensor.SOLUTION: Acceleration sensors 100, 200, 300, and 400 include: moving units 133 and 433, which move in a moving direction Z by generation of an acceleration; and opposed units 113, 213, 313, 122, 222, 322 facing the moving units across a space in the moving direction. The moving unit has hole parts D1, D2, and D3 having an opening facing the opposed units.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to an acceleration sensor.

Background Art

[0002] Conventionally, a semiconductor capacitance type acceleration sensor that detects the displacement of a movable electrode portion toward a fixed electrode plate as acceleration by detecting a change in capacitance between the movable electrode portion and the fixed electrode plate has been disclosed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, in a semiconductor capacitance type (capacitive) acceleration sensor as described in Patent Document 1, the fluid existing between the fixed electrode and the moving portion (movable electrode) that moves with respect to the electrode becomes a resistance when the moving portion moves with respect to the electrode, so it is difficult to improve the sensitivity when detecting acceleration.

[0005] The present disclosure solves the above problems, and an object thereof is to provide an acceleration sensor that can improve sensitivity more than before.

Means for Solving the Problems

[0006] The acceleration sensor according to this disclosure comprises a flat, movable electrode that moves or tilts in accordance with the direction of the force acting due to acceleration, and a flat, first fixed substrate and a flat, second fixed substrate, which are positioned opposite the movable electrode with a gap between them, respectively, and the movable electrode has a through hole in its center, and further comprises a holding portion disposed inside the through hole, and four connecting portions that electrically connect the movable electrode and the holding portion and elastically deform when the movable electrode moves or tilts, and the first fixed substrate, the movable electrode, and the second fixed substrate are arranged in order with a gap between them to form a three-layer structure, the first fixed substrate is provided with a first terminal, and a first electrode consisting of four electrodes disposed on the surface of a first opposing surface opposite one side of the movable electrode, separate from the first terminal, and the second fixed substrate is The movable electrode is provided with a second terminal and a second electrode consisting of four electrodes arranged on the surface of a second opposing surface facing the other side of the movable electrode, separate from the second terminal, and the through hole penetrates from one side of the movable electrode to the other side, the holding portion is fixed to the first opposing surface of the first fixed substrate and the second opposing surface of the second fixed substrate, and is electrically connected to the first terminal provided on the first fixed substrate and the second terminal provided on the second fixed substrate, the four connection portions are elastically deformed when the distance between the movable electrode and the first and second electrodes changes due to movement or tilting, and the four electrodes of the first electrode are arranged symmetrically four times with respect to the center of the first fixed substrate, the four electrodes of the second electrode are arranged symmetrically four times with respect to the center of the second fixed substrate, and the four connection portions are arranged symmetrically four times with respect to the center of the movable electrode. [Effects of the Invention]

[0007] According to this disclosure, since the moving part that moves when acceleration occurs has a hole that opens on the side facing the opposing part, even if fluid is present between the opposing part and the moving part, the fluid can move more easily, and the influence of the fluid can be suppressed and sensitivity can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] A plan view showing the schematic configuration of the acceleration sensor according to Embodiment 1. [Figure 2] A perspective view showing the schematic configuration of an acceleration sensor according to Embodiment 1. [Figure 3] An exploded view showing an acceleration sensor according to Embodiment 1. [Figure 4] A cross-sectional view showing an acceleration sensor according to Embodiment 1. [Figure 5] Figure 5A is an operation diagram showing the movable electrode substrate in the state where acceleration in the Z direction is occurring in Embodiment 1, Figure 5B is an operation diagram showing the movable electrode substrate in the state where acceleration in the X direction is occurring in Embodiment 1, and Figure 5C is an operation diagram showing the movable electrode substrate in the state where acceleration in the Y direction is occurring in Embodiment 1. [Figure 6] A block diagram showing a processing circuit connected to an acceleration sensor according to Embodiment 1. [Figure 7] A perspective view showing the schematic configuration of an acceleration sensor according to Embodiment 2. [Figure 8] An exploded view showing the configuration of the acceleration sensor according to Embodiment 2. [Figure 9] A perspective view showing the schematic configuration of an acceleration sensor according to Embodiment 3. [Figure 10] An exploded view showing the configuration of the acceleration sensor according to Embodiment 3. [Figure 11] An exploded view showing the configuration of the acceleration sensor according to Embodiment 4. [Figure 12] A plan view showing a movable electrode substrate according to Embodiment 5. [Figure 13] A block diagram showing a processing circuit connected to an acceleration sensor according to Embodiment 6. [Figure 14] A block diagram showing a processing circuit connected to an acceleration sensor according to Embodiment 7. [Modes for carrying out the invention]

[0009] The embodiments relating to this disclosure will be described in detail below with reference to the drawings. Embodiment 1. First, the schematic configuration of the acceleration sensor 100 according to Embodiment 1 will be described with reference to Figures 1 and 2. Figure 1 is a plan view showing the schematic configuration of the acceleration sensor 100 according to Embodiment 1, and Figure 2 is a perspective view showing the schematic configuration of the acceleration sensor 100 according to Embodiment 1. The acceleration sensor 100 according to Embodiment 1 is a capacitive multi-axis acceleration sensor that detects multi-directional acceleration based on the change in capacitance between electrodes in response to the applied acceleration.

[0010] For example, the acceleration sensor 100 is used in seismometers that measure earthquake vibrations, as well as in detecting acceleration in automobiles, robots, unmanned aerial vehicles, and portable devices. As shown in Figures 1 and 2, the acceleration sensor 100 comprises a first fixed electrode substrate 110, a second fixed electrode substrate 120, and a movable electrode substrate 130 which includes a movable electrode 133 that is a weight that vibrates due to an applied external force, a spring portion connected to the movable electrode 133, and a fixed electrode 132 that is mechanically and electrically connected to the movable electrode 133 through the spring portion. For example, the first fixed electrode substrate 110, the second fixed electrode substrate 120, and the movable electrode substrate 130 are each formed in the shape of a balanced plate and are arranged so as to be substantially balanced plates relative to each other. In Embodiment 1, the first fixed electrode substrate 110 constitutes the first substrate.

[0011] The second fixed electrode substrate 120 is positioned in a direction perpendicular to the surface of the first fixed electrode substrate 110 (the Z direction shown in Figure 1), with a gap between it and the first fixed electrode substrate 110. The movable electrode substrate 130 is positioned between the first fixed electrode substrate 110 and the second fixed electrode substrate 120. In other words, the second fixed electrode substrate 120 is positioned on the opposite side of the movable electrode substrate 130 from the first fixed electrode substrate 110. Thus, the acceleration sensor 100 has a three-layer structure consisting of the first fixed electrode substrate 110, the movable electrode substrate 130, and the second fixed electrode substrate 120.

[0012] Next, referring to FIGS. 3 and 4, the details of the configuration of the acceleration sensor 100 according to Embodiment 1 will be described. FIG. 3 is an exploded view showing the acceleration sensor 100 according to Embodiment 1. As shown in FIG. 3, the first fixed electrode substrate 110 has a substrate body 111, a plurality of fixed electrodes 113, and a plurality of terminals 112. For example, the substrate body 111 is formed of a material having a thermal expansion coefficient close to that of the movable electrode substrate 130. Specifically, the substrate body 111 is formed of a borosilicate glass-based substrate material or a ceramic substrate material such as LTCC (Low Temperature Co-fired Ceramics). Further, for example, the substrate body 111 is formed in a flat plate shape that is rectangular when viewed from the Z direction. In Embodiment 1, the direction along any one side of the substrate body 111 that is rectangular when viewed from the Z direction is also referred to as the X direction, and the direction along the other side orthogonal to the X direction is also referred to as the Y direction. Also, in Embodiment 1, the fixed electrode 113 constitutes a first electrode and an opposing portion.

[0013] The multiple fixed electrodes 113 may be, for example, a metal film of a certain thickness that does not have internal stress, a conductive film, or a film material of a certain thickness in which high-concentration impurities have been diffused. The fixed electrodes 113 are electrodes for detecting changes in capacitance and are formed on the side of the substrate body 111 that faces the movable electrode substrate 130. In Embodiment 1, "the side of the substrate body 111 that faces the movable electrode substrate 130" is also referred to as "the bottom surface of the substrate body 111" or "the bottom surface of the first fixed electrode substrate 110", "the side of the substrate body 111 opposite to the movable electrode substrate 130" is also referred to as "the top surface of the substrate body 111" or "the top surface of the first fixed electrode substrate 110", and either "the bottom surface of the substrate body 111" or "the top surface of the substrate body 111" is also referred to as "the surface of the substrate body 111" or "the surface of the first fixed electrode substrate 110". Multiple fixed electrodes 113 are arranged with gaps between them in the direction in which the surface of the substrate body 111 extends (for example, the X and Y directions shown in Figure 1). For example, on the first fixed electrode substrate 110, multiple fixed electrodes 113 are arranged so as to be rotationally symmetric with respect to the center of the substrate body 111 when viewed from the Z direction. Specifically, on the first fixed electrode substrate 110, four fixed electrodes 113 are formed so as to be four times symmetric with respect to the center of the substrate body 111 when viewed from the Z direction.

[0014] Multiple terminals 112 are arranged with gaps between them in the direction in which the surface of the substrate body 111 extends, and electrically connect multiple fixed electrodes 113 to the processing circuit 150 (see Figure 6). For example, multiple terminals 112 are formed on the upper surface of the substrate body 111 and are electrically connected to multiple fixed electrodes 113 by multiple through holes 114. Alternatively, for example, multiple terminals 112 are formed from a noble metal film that has heat resistance and environmental resistance and low resistivity. When multiple terminals 112 are directly connected to the processing circuit 150, they may be formed from a noble metal material or aluminum metal film that allows for wire bonding.

[0015] For example, the plurality of through-holes 114 are formed by hole machining using a machining method such as an electric discharge machining method in an electrolytic solution, an ultrasonic machining in a liquid, a blasting machining method using fine sand, or a laser machining method using specific light absorption characteristics of the substrate body 111. Also, for example, the through-holes 114 are electrically connected to the plurality of fixed electrodes 113 and the plurality of terminals 112 by imparting conductivity by a plating method of filling the through-holes 114 with a noble metal, a method of filling the through-holes 114 with a conductive resin, a metal vapor deposition method, or a sputtering method. For example, on the first fixed electrode substrate 110, the plurality of through-holes 114 are arranged to be rotationally symmetric with respect to the center of the substrate body | 111 when viewed from the Z direction.

[0016] Note that the first fixed electrode substrate 110 may be configured to electrically connect the plurality of fixed electrodes 113 and the plurality of terminals 112 by embedding conductive electric columns in the substrate body 111 in advance instead of forming the through-holes 114. Also, when the first fixed electrode substrate 110 uses a ceramic base material such as LTCC as the substrate body 111, instead of forming the through-holes 114, it may be configured by integrally forming a low-resistance conductor and a ceramic base material in advance when firing the substrate body 111 at a low temperature.

[0017] As shown in FIG. 3, the second fixed electrode substrate 120 has a substrate body 121, a plurality of fixed electrodes 122, and a plurality of terminals 123. For example, the substrate body 121 is formed of the same material as the substrate body 111 of the first fixed electrode substrate 110. Also, for example, the outer shape of the substrate body 121 is formed so as to overlap the outer shape of the substrate body 111 of the first fixed electrode substrate 110 when viewed from the Z direction.

[0018] The multiple fixed electrodes 122 are electrodes made of the same material as the fixed electrodes 113 and are used to detect changes in capacitance. They are formed on the side of the substrate body 121 facing the movable electrode substrate 130 and are electrically insulated from the multiple fixed electrodes 113 and multiple terminals 112 of the first fixed electrode substrate 110. In Embodiment 1, the "side of the substrate body 121 facing the movable electrode substrate 130" is also referred to as the "upper surface of the substrate body 121" or the "upper surface of the second fixed electrode substrate 120," the "side of the substrate body 121 opposite to the movable electrode substrate 130" is also referred to as the "lower surface of the substrate body 121" or the "lower surface of the second fixed electrode substrate 120," and either the "upper surface of the substrate body 121" or the "lower surface of the substrate body 121" is also referred to as the "surface of the substrate body 121" or the "surface of the second fixed electrode substrate 120." The multiple fixed electrodes 122 are arranged with gaps between them in the direction in which the surface of the substrate body 111 extends. For example, the second fixed electrode substrate 120 has multiple fixed electrodes 122 formed on it such that they are rotationally symmetric with respect to the center of the substrate body 121 when viewed from the Z direction. Specifically, the second fixed electrode substrate 120 has multiple fixed electrodes 113 formed on it such that, when viewed from the Z direction, their outer shape overlaps with the outer shape of the multiple fixed electrodes 113 of the first fixed electrode substrate 110. In Embodiment 1, the fixed electrodes 122 constitute the second electrode and the opposing portion.

[0019] The multiple terminals 123 are arranged with gaps between them in the direction in which the surface of the substrate body 121 extends, electrically connecting the multiple fixed electrodes 122 to the processing circuit 150, and electrically insulating them from the multiple fixed electrodes 113 and multiple terminals 112 of the first fixed electrode substrate 110. For example, the multiple terminals 123 are formed of a precious metal film, similar to the multiple terminals 112. Also, for example, the multiple terminals 123 are formed on the lower surface of the substrate body 121 and are electrically connected to the multiple fixed electrodes 122 by multiple through holes 124. Also, for example, part of the multiple terminals 123 are arranged along the lower surface of the second fixed electrode substrate 120, and part of them are arranged along the side surface of the second fixed electrode substrate 120 that extends in the Z direction. In this way, because part of the multiple terminals 123 are arranged along the Z direction, it is possible to maintain a stable connection with the processing circuit even if the position of the acceleration sensor 100 in the Z direction changes while connected to the processing circuit 150.

[0020] The characteristics of the multiple through-holes 124 are the same as those of the multiple through-holes 114, so their explanation will be omitted. The acceleration sensor 100 suppresses internal stress generated in the acceleration sensor 100 by arranging the multiple fixed electrodes 113, multiple fixed electrodes 122, multiple through-holes 114, and multiple through-holes 124 so as to be rotationally symmetric with respect to the center of the substrate body 111 when viewed from the Z direction.

[0021] As shown in Figure 3, the movable electrode substrate 130 has a first fixed part 131, a second fixed part 132, a movable electrode 133, and a plurality of connecting parts 134 as spring parts. For example, the movable electrode substrate 130 is formed from a substrate material in which high-concentration impurities are diffused into a substrate material such as silicon, or from a low-resistance semiconductor such as silicon. Alternatively, for example, the movable electrode substrate 130 may be formed using an SOI (Silicon on Insulator) substrate having an insulating layer. Furthermore, for example, the movable electrode substrate 130 may be formed by an anisotropic etching method using a chemical solution, an anodic oxidation method in a chemical solution, a method for selectively etching at a specific impurity concentration, or a composite etching method such as reactive ion etching (RIE) using chemical reactions in the gas phase and accelerated ions, or an etching method combining the etching method using a chemical solution and the reactive etching method in the gas phase.

[0022] The first fixing part 131 and the second fixing part 132 are joined to the lower surface of the first fixed electrode substrate 110 and fixed to the first fixed electrode substrate 110, and are joined to the upper surface of the second fixed electrode substrate 120 and fixed to the second fixed electrode substrate 120. In other words, the first fixing part 131 and the second fixing part 132 hold the second fixed electrode substrate 120 to the first fixed electrode substrate 110. In other words, the second fixed electrode substrate 120 is held to the first fixed electrode substrate 110 via the first fixing part 131 and the second fixing part 132. For example, the first fixed electrode substrate 110, the second fixed electrode substrate 120 and the movable electrode substrate 130 are joined using an anodic bonding method or a surface activation technique. If the first fixed electrode substrate 110, the second fixed electrode substrate 120 and the movable electrode substrate 130 are all made of silicon, they may be joined by a silicon-to-silicon direct bonding method.

[0023] The first fixed portion 131 is positioned on the outer edge of the movable electrode substrate 130 when viewed from the Z direction. For example, the first fixed portion 131 is formed to conform to the outer shapes of the first fixed electrode substrate 110 and the second fixed electrode substrate 120 when viewed from the Z direction, and is positioned to surround the second fixed portion 132 and the movable electrode 133. Specifically, the first fixed portion 131 is formed in a rectangular shape when viewed from the Z direction, with its outer shape overlapping the outer shapes of the first fixed electrode substrate 110 and the second fixed electrode substrate 120, and has a rectangular through-hole D1 in the center that penetrates in the Z direction, housing the second fixed portion 132 and the movable electrode 133 inside the through-hole D1. With this configuration, the acceleration sensor 100 is partitioned so that the space S (see Figure 4) formed by the first fixed electrode substrate 110, the second fixed electrode substrate 120 and the first fixed portion 131 does not communicate with the space outside the acceleration sensor 100. This prevents foreign matter such as dust and dirt from entering the space S that houses the movable electrode 133 of the acceleration sensor 100. Second fixed part 132 In Embodiment 1, this constitutes the holding portion. Also, in Embodiment 1, the through hole D1 constitutes the first hole portion (hole portion).

[0024] Ideally, the space S surrounding the acceleration sensor 100 should be a vacuum. However, in reality, it is difficult to manufacture the acceleration sensor 100 so that the space S is a perfect vacuum. Therefore, the pressure of the fluid (e.g., dry air or inert gas) in space S is set so that it is negatively pressured compared to the external space and the vacuum level is based on the frequency characteristics required for the acceleration sensor 100. By setting the vacuum level of space S in this way, it becomes possible to improve the sensitivity of the acceleration sensor 100 to vibrations in a specific frequency band depending on its application.

[0025] The second fixing portion 132, the movable electrode 133, and the plurality of connecting portions 134 are integrally formed. The second fixing portion 132 is positioned in the center of the movable electrode substrate 130 when viewed from the Z direction. For example, the second fixing portion 132 is formed in a rectangular shape, with each side positioned in a direction that follows the outer shape of the first fixed electrode substrate 110 and the second fixed electrode substrate 120 when viewed from the Z direction. Also, for example, the second fixing portion 132 is electrically connected to one of the plurality of terminals 112 of the first fixed electrode substrate 110 and one of the plurality of terminals 123 of the second fixed electrode substrate 120. In Embodiment 1, the second fixing portion 132 constitutes the fixing portion.

[0026] The movable electrode 133 is positioned between the first fixed portion 131 and the second fixed portion 132 when viewed from the Z direction, and is connected to the second fixed portion 132 by a plurality of connecting portions 134. In other words, the movable electrode 133 is connected to the first fixed electrode substrate 110 and the second fixed electrode substrate 120 via the second fixed portion 132 by a plurality of connecting portions 134. In other words, the movable electrode 133 has a through hole D1 in its central part that opens to face the first fixed electrode substrate 110 and the second fixed electrode substrate 120, and the second fixed portion 132 and the plurality of connecting portions 134 are positioned inside the through hole D1. In other words, the movable electrode 133 has a through hole D1 in its central part that opens to face the fixed electrodes 113 and 122. For example, the movable electrode 133 is formed such that, when viewed from the Z direction, the distance to the first fixed portion 131 is approximately constant, and the distance to the second fixed portion 132 is approximately constant. Specifically, the movable electrode 133 has through holes D1 that, when viewed from the Z direction, have each side of its outer shape aligned with the direction of each side of the rectangular through hole of the first fixed part 131, and each side aligned with the direction of each side of the outer shape of the second fixed part 132.

[0027] The movable electrode 133 is positioned such that one side of it in the Z direction is in close proximity to the fixed electrode 113, and the other side of it in the Z direction is in close proximity to the fixed electrode 122. For example, the movable electrode 133 is positioned so that it overlaps with the fixed electrodes 113 and 122 when viewed from the Z direction. Alternatively, for example, the movable electrode 133 is positioned so that its through hole D1 does not overlap with the fixed electrodes 113 and 122 when viewed from the Z direction.

[0028] Each of the multiple connection parts 134 is formed in a beam shape and connects the first fixed part 131 and the movable electrode 133 at multiple points. For example, the multiple connection parts 134 are formed so as to be rotationally symmetric with respect to the center of the substrate body 111 when viewed from the Z direction. Specifically, the multiple connection parts 134 are composed of four connection parts 134 so as to be four times symmetric with respect to the center of the substrate body 111 when viewed from the Z direction. More specifically, the multiple connection parts 134 are composed of four connection parts 134 formed in a hook-shaped configuration along the outer shape of the rectangular second fixed part 132 and the direction of each side of the rectangular through hole D1 when viewed from the Z direction.

[0029] For example, one of the multiple connection parts 134a has one end connected to the second fixed part 132 and the other end connected to the movable electrode 133, and the length dimension of the path from one end of the connection part 134a to the other end of the connection part 134a is formed to be larger than the width dimension in the direction perpendicular to the direction from one end of the connection part 134a to the other end of the connection part 134a. Furthermore, the connection part 134a has, when viewed from the Z direction, a first connection part 134a1 extending in a first direction from one end of the connection part 134a to the other end of the connection part 134a, a second connection part 134a2 connected to the other end of the first connection part 134a1 and extending in a second direction different from the first direction, and a third connection part 134a3 connected to the other end of the second connection part 134a2 and extending in a third direction different from the second direction.

[0030] Specifically, the connecting portion 134a has, when viewed from the Z direction, a first connecting portion 134a1 extending in the X direction from one end of the connecting portion 134a to the other end of the connecting portion 134a, a second connecting portion 134a2 connected to the other end of the first connecting portion 134a1 and extending in the Y direction, and a third connecting portion 134a3 connected to the other end of the second connecting portion 134a2 and extending in the X direction. In other words, when viewed from the Z direction, the connecting portion 134a is formed to bend multiple times along the outer shape of the second fixing portion 132. This formation makes it possible to increase the length from one end to the other end of the connecting portion 134a while suppressing its size when viewed from the Z direction. It is desirable that the other connecting portions 134 of the multiple connecting portions 134 are formed in the same shape as the above connecting portion 134a so as to be rotationally symmetric with respect to the center of the substrate body 111 when viewed from the Z direction.

[0031] Figure 4 is a cross-sectional view AA of Figure 1, showing the acceleration sensor 100 according to Embodiment 1. As shown in Figure 4, the multiple connection parts 134 are connected to the movable electrode 133 at positions offset in the Z direction from the center of gravity of the movable electrode 133. Furthermore, the multiple connection parts 134 are formed such that their dimensions in the Z direction are smaller than those of the movable electrode 133. The movable electrode 133 is positioned between the fixed electrode 113 and the fixed electrode 122 in the Z direction, and is positioned with a gap between itself and each of the fixed electrode 113. With this configuration, when acceleration occurs, the movable electrode 133 moves between the fixed electrode 113 and the fixed electrode 122, and as it moves in a direction that changes the distance between itself and the fixed electrode 113 and the fixed electrode 122, it elastically deforms the multiple connection parts 134.

[0032] Next, with reference to Figure 5, the operation of the acceleration sensor 100 when acceleration occurs due to an applied external force will be described. Figure 5A is an operation diagram showing the movable electrode substrate 130 when acceleration in the Z direction occurs in Embodiment 1, Figure 5B is an operation diagram showing the movable electrode substrate 130 when acceleration in the X direction occurs in Embodiment 1, and Figure 5C is an operation diagram showing the movable electrode substrate 130 when acceleration in the Y direction occurs in Embodiment 1. Note that in Figures 5A to 5C, the amount of movement of the movable electrode 133 is exaggerated and shown as larger than the actual amount of movement for ease of viewing, but in reality, the movable electrode 133 is movable between a plurality of fixed electrodes 113 (see Figure 3) and a plurality of fixed electrodes 122. As a result of acceleration occurring in the acceleration sensor 100, when a force is applied to the movable electrode 133 against the second fixed part 132, the distance between the movable electrode 133 and each fixed electrode 113 and fixed electrode 122 changes according to the direction and magnitude of the applied force. In this case, when the distance between the movable electrode 133 and the fixed electrode decreases, the capacitance between the movable electrode 133 and the fixed electrode increases, and when the distance between the movable electrode 133 and the fixed electrode increases, the capacitance between the movable electrode 133 and the fixed electrode decreases.

[0033] For example, as shown in Figure 5A, when acceleration is generated in the acceleration sensor 100, and a force in the Z direction acts on the movable electrode 133 against the second fixed part 132, the movable electrode 133 moves in the Z direction relative to the second fixed part 132 while elastically deforming the multiple connection parts 134. At this time, the distance of the movable electrode 133 to each fixed electrode 113 decreases uniformly, and the distance to each fixed electrode 122 increases uniformly.

[0034] Furthermore, as described above, the multiple connection points 134 are connected to the movable electrode 133 at positions offset in the Z direction relative to the center of gravity of the movable electrode 133. For this reason, for example, as shown in Figure 5B, when acceleration is generated in the acceleration sensor 100, and a force in the X direction acts on the movable electrode 133 against the second fixed part 132, the movable electrode 133 tilts in the Z and X directions while elastically deforming the multiple connection points 134. In other words, the movable electrode 133 rotates around a virtual axis along the Y direction relative to the second fixed part 132 while elastically deforming the multiple connection points 134. At this time, the distance between the movable electrode 133 and the fixed electrode 113 located on the X direction side of the multiple fixed electrodes 113 becomes smaller, and the distance between the movable electrode 133 and the fixed electrode 122 located on the X direction side of the multiple fixed electrodes 122 becomes larger. Furthermore, at this time, the distance between the movable electrode 133 and the fixed electrode 113 located on the opposite side of the X direction among the multiple fixed electrodes 113 increases, and the distance between the movable electrode 133 and the fixed electrode 122 located on the opposite side of the X direction among the multiple fixed electrodes 122 decreases.

[0035] Furthermore, as shown in Figure 5C, for example, when acceleration is generated in the acceleration sensor 100, and a force in the Y direction acts on the movable electrode 133 against the second fixed part 132, the movable electrode 133 tilts about a virtual axis along the X direction relative to the second fixed part 132 while elastically deforming the multiple connection parts 134. In other words, the movable electrode 133 rotates about a virtual axis along the X direction relative to the second fixed part 132 while elastically deforming the multiple connection parts 134. At this time, the distance between the movable electrode 133 and the fixed electrode 113 located on the Y direction side of the multiple fixed electrodes 113 decreases, and the distance between the movable electrode 133 and the fixed electrode 122 located on the Y direction side of the multiple fixed electrodes 122 increases. Also, at this time, the distance between the movable electrode 133 and the fixed electrode 113 located on the opposite side of the Y direction of the multiple fixed electrodes 113 increases, and the distance between the movable electrode 133 and the fixed electrode 122 located on the opposite side of the Y direction of the multiple fixed electrodes 122 decreases. Thus, the acceleration sensor 100 is configured such that, among the multiple fixed electrodes 113 and multiple fixed electrodes 122, when viewed from the Z direction, a pair of fixed electrodes that overlap each other are arranged such that as the distance between one fixed electrode and the movable electrode 133 increases, the distance between the other fixed electrode and the movable electrode 133 decreases.

[0036] Next, with reference to Figure 6, a specific example of a processing circuit 150 that detects acceleration using the acceleration sensor 100 according to Embodiment 1 will be described. Figure 6 is a block diagram showing a processing circuit 150 connected to the acceleration sensor according to Embodiment 1. For example, the processing circuit 150 is configured to include a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), I / O (Input / Output) ports, etc., and independently detects acceleration in each of the Z, X, and Y axes. For example, the processing circuit 150 includes a CV converter 11Z, a CV converter 11X, a CV converter 11Y, a Z-axis signal processing unit 12Z, an X-axis signal processing unit 12X, a Y-axis signal processing unit 12Y, a Z-axis voltage signal conversion unit 13Z, an X-axis voltage signal conversion unit 13X, a Y-axis voltage signal conversion unit 13Y, a noise reduction signal processing filter 14Z, a noise reduction signal processing filter 14X, and a noise reduction signal processing filter 14Y. Note that the processing circuit 150 may be configured with dedicated circuits instead of the CPU, ROM, RAM, etc.

[0037] The processing circuit 150, using a CV converter 11Z, a Z-axis signal processing unit 12Z, a Z-axis voltage signal conversion unit 13Z, and a noise reduction signal processing filter 14Z, converts the changes in capacitance C1 to C4 between the movable electrode 133 and the multiple fixed electrodes into voltage signals corresponding to acceleration in the Z-axis direction, and outputs them as analog signals. Similarly, the processing circuit 150, using a CV converter 11X, an X-axis signal processing unit 12X, an X-axis voltage signal conversion unit 13X, and a noise reduction signal processing filter 14X, converts the changes in capacitance C5 to C8 between the movable electrode 133 and the multiple fixed electrodes into voltage signals corresponding to acceleration in the X-axis direction, and outputs them as analog signals. Similarly, the processing circuit 150, using a CV converter 11Y, a Y-axis signal processing unit 12Y, a Y-axis voltage signal conversion unit 13Y, and a noise reduction signal processing filter 14Y, converts the changes in capacitance C9~C12 between the movable electrode 133 and the multiple fixed electrodes into voltage signals corresponding to the acceleration in the Y-axis direction, and outputs them as analog signals.

[0038] As described above, the acceleration sensor 100 according to Embodiment 1 comprises a first fixed electrode substrate 110 on which a fixed electrode 113 is formed, and a movable electrode 133 positioned opposite the fixed electrode 113 with a gap between them, and moving in a direction that changes the distance to the fixed electrode 113 when acceleration occurs. The movable electrode 133 has a through hole D1 that opens on the side facing the fixed electrode 113 and the fixed electrode 122. As described above, it is desirable that the space S, which is the internal space of the through hole D1, be a vacuum, but a perfect vacuum, i.e., an ideal vacuum, is difficult in reality and mechanical resonance characteristics tend to appear. Therefore, a small amount of fluid such as dry air or an inert gas is present in the space S, and the space S is adjusted so that a wide bandwidth and flat characteristics can be obtained while suppressing mechanical resonance. In this way, when the movable electrode 133 moves due to acceleration or the like with fluid present in the space S, the movable electrode 133 is subjected to resistance by the fluid in the space S. For example, when the movable electrode 133 vibrates over a relatively wide frequency bandwidth, its movement is suppressed by fluid resistance due to the viscosity of the fluid, or by an air (or fluid) damping phenomenon where the fluid acts like a spring and repels the fluid. Furthermore, even when the movable electrode 133 vibrates in a low frequency band where the air (or fluid) damping phenomenon does not occur, its movement (vibration) is suppressed by the viscosity of the fluid.

[0039] Such fluid-related effects, such as fluid viscosity which is more likely to appear in the low-frequency band, or air (or fluid) damping which is more likely to affect the high-frequency band, are also called the squeeze film phenomenon and are more likely to occur when wide surfaces are facing each other at a small distance. When the squeeze film phenomenon occurs, the movement of the movable electrode 133 relative to the fixed electrodes 113 and 122 is suppressed, making it difficult to improve the sensitivity of the acceleration sensor and to obtain flat characteristics over a wide bandwidth.

[0040] In the acceleration sensor 100 according to Embodiment 1, the movable electrode 133 has a through hole D1 that opens on the side facing the fixed electrodes 113 and 122. Therefore, when the movable electrode 133 moves relative to the fixed electrodes 113 and 122, the fluid between the movable electrode 133 and the fixed electrodes 113 and 122 moves more easily, suppressing the squeeze film phenomenon and improving the sensitivity of acceleration detection compared to conventional sensors. Furthermore, in capacitive acceleration sensors, increasing the size of the movable electrode is required to improve the sensitivity of acceleration detection. However, in the acceleration sensor 100 according to Embodiment 1, even if the movable electrode 133 is made larger, the width of the portion close to the fixed electrode can be kept relatively small, thus suppressing the squeeze film phenomenon and improving the sensitivity of acceleration detection compared to conventional sensors. Note that the acceleration sensor is not limited to a space S that is a vacuum or near-vacuum, but may also be a space S filled with a predetermined inert gas such as nitrogen gas.

[0041] Furthermore, the acceleration sensor 100 according to Embodiment 1 can improve the sensitivity when detecting acceleration, thereby reducing power consumption. In addition, because the acceleration sensor 100 according to Embodiment 1 can improve the sensitivity when detecting acceleration, it is possible to miniaturize the acceleration sensor 100 by making the size of the movable electrode 133 smaller than in the conventional model, thereby reducing parasitic capacitance caused by each electrode and terminal of the acceleration sensor 100 and further improving sensitivity.

[0042] Furthermore, the acceleration sensor 100 according to Embodiment 1 can improve the sensitivity when detecting acceleration, which increases the degree of freedom in the dimensions of the movable electrode 133, connection part 134, etc., and by adjusting the dimensions of each part to change the characteristics, it becomes possible to use it for a variety of purposes. In particular, the acceleration sensor 100 according to Embodiment 1 can enlarge the movable electrode 133 while suppressing the squeeze film phenomenon, making it easier to improve the sensitivity when detecting low-frequency vibrations such as seismic motion.

[0043] Furthermore, the acceleration sensor 100 according to Embodiment 1 makes it possible to enlarge the movable electrode 133 while suppressing the squeeze film phenomenon. For example, it is not necessary to increase the mass of the movable electrode by joining another part in the thickness direction of the movable electrode. This makes it possible to suppress the increase in manufacturing costs caused by joining another part to the movable electrode, as well as the decrease in accuracy due to the occurrence of strain and warping caused by internal stress.

[0044] Furthermore, in the acceleration sensor 100 according to Embodiment 1, when viewed from the Z direction, the multiple connection portions 134 are formed to bend multiple times along the outer shape of the second fixed portion 132. This suppresses an increase in the size of the acceleration sensor 100, and allows the connection portions 134 to be formed to be elongated so that the movable electrode 133 can move with small acceleration. As a result, the sensitivity when detecting acceleration can be improved compared to conventional designs.

[0045] Furthermore, in the acceleration sensor 100 according to Embodiment 1, the movable electrode 133 is positioned opposite a first fixed electrode substrate 110 on which a fixed electrode 113 is formed, and a second fixed electrode substrate 120 on which a fixed electrode 122 is formed, with a gap between them. For example, when a voltage signal such as an AC voltage signal or a DC voltage signal is applied to either fixed electrode 113, an electrostatic attraction force is generated between the movable electrode 133 and the fixed electrode 113, causing the movable electrode 133 to move. The acceleration sensor 100 according to Embodiment 1 can be equipped with a self-diagnostic function that diagnoses whether the acceleration sensor 100 is operating normally by detecting the change in capacitance between the fixed electrode and the movable electrode 133 when the movable electrode 133 is moved by applying a voltage signal to the fixed electrode in this way. In addition, the acceleration sensor 100 according to Embodiment 1 can perform software calibration based on the results of such a diagnosis, which makes it possible to improve the sensitivity when detecting acceleration and to reduce manufacturing costs by improving the yield.

[0046] Furthermore, the acceleration sensor 100 according to Embodiment 1 can apply a voltage signal to a fixed electrode to move the movable electrode 133, and can also detect changes in capacitance between the fixed electrode and the movable electrode 133 that are paired with the fixed electrode. This makes it possible to suppress interference from acceleration in other directions when detecting acceleration in a specific direction. For example, when detecting acceleration in a specific direction while acceleration in multiple directions is applied to the acceleration sensor 100, applying a voltage signal to the fixed electrode suppresses the movement of the movable electrode 133 due to acceleration in directions other than the direction to be detected. This suppresses interference from acceleration in other directions and improves the sensitivity when detecting acceleration. In addition, the acceleration sensor 100 according to Embodiment 1 can be used as a servo-type acceleration sensor that applies a voltage signal to a fixed electrode to prevent the movable electrode 133 from moving when acceleration occurs, and detects acceleration based on the voltage signal.

[0047] In Embodiment 1, the acceleration sensor 100 has a three-layer structure consisting of a first fixed electrode substrate 110, a movable electrode substrate 130, and a second fixed electrode substrate 120, but is not limited thereto. The acceleration sensor only needs to be able to detect the acceleration occurring on the movable electrode in response to a change in the distance between the movable electrode and the fixed electrode. For example, the acceleration sensor may have a two-layer structure consisting of a first fixed electrode substrate and a movable electrode substrate, or the first fixed electrode substrate may have only one fixed electrode formed on it, or the number of fixed electrodes on the first fixed electrode substrate may be different from the number of fixed electrodes on the second fixed electrode substrate.

[0048] Furthermore, in Embodiment 1, the movable electrode 133 has a through hole D1 to facilitate the movement of surrounding fluid when the movable electrode 133 moves, but it is not limited to this. The movable electrode can have any hole that opens on the side facing the fixed electrode. For example, the movable electrode can have a non-through hole instead of a through hole, a recess formed to be recessed from the surrounding surface, a groove formed to be recessed from the surrounding surface, etc., as long as there is a part that is at a different distance from the surroundings from the surface of the substrate on which the movable electrode is formed when no acceleration is occurring, and various shapes other than through holes can be considered.

[0049] Furthermore, in Embodiment 1, the acceleration sensor 100 is provided with four beam-shaped connecting portions 134 that are bent multiple times along the outer shape of the second fixed portion 132 when viewed from the Z direction, but is not limited to this. The acceleration sensor only needs to have connecting portions that connect the substrate on which the fixed electrode is formed and the movable electrode. For example, the acceleration sensor may have connecting portions that are formed in a straight line without bending, or connecting portions that are formed in a film shape between the fixed portion and the movable electrode, or connecting portions that are formed in a rectangular flat plate shape, or it may have any number of connecting portions other than four, and a variety of configurations for the connecting portions are possible.

[0050] Furthermore, in Embodiment 1, the acceleration sensor 100 has a second fixed portion 132 and a plurality of connection portions 134 arranged inside the through hole D1, but is not limited to this. When viewed from the Z direction, the acceleration sensor only needs to have at least a portion of the plurality of connection portions arranged inside the hole of the movable electrode, a portion or all of the second fixed portion may be arranged outside the through hole, any of the plurality of connection portions may be arranged outside the through hole, or a portion of any of the connection portions may be arranged outside the through hole.

[0051] Furthermore, in Embodiment 1, the acceleration sensor 100 is formed of the same material for the first fixed part 131, the second fixed part 132, and the movable electrode 133, but is not limited to this. The first fixed part, the second fixed part, and the movable electrode may be formed of different materials. However, it is desirable that the substrate body, the substrate body, the first fixed part, and the second fixed part be formed of materials with similar coefficients of thermal expansion.

[0052] Embodiment 2. Next, the acceleration sensor 200 according to Embodiment 2 will be described with reference to Figures 7 and 8. Compared to the acceleration sensor 100 according to Embodiment 1, the acceleration sensor 200 according to Embodiment 2 differs in the shape and arrangement of the fixed electrodes, but the other configurations are the same, and the same reference numerals are used for the same configurations as in Embodiment 1, and their description is omitted.

[0053] Figure 7 is a perspective view showing the schematic configuration of the acceleration sensor 200 according to Embodiment 2, and Figure 8 is an exploded view showing the configuration of the acceleration sensor 200 according to Embodiment 2. The acceleration sensor 200 according to Embodiment 2 has a plurality of fixed electrodes 213 formed on a first fixed electrode substrate 210 and a plurality of fixed electrodes 222 formed on a second fixed electrode substrate 220. When viewed from the Z direction, the gaps between adjacent fixed electrodes 213 and 222 are formed along the diagonals of the rectangular movable electrode 133. Thus, various configurations are possible for the shape and position of the plurality of fixed electrodes. In Embodiment 2, the first fixed electrode substrate 210 and the second fixed electrode substrate 220 constitute the first substrate and the second substrate, respectively. In Embodiment 2, the fixed electrode 213 constitutes the first electrode and the opposing portion. Also in Embodiment 2, the fixed electrode 222 constitutes the second electrode and the opposing portion.

[0054] Embodiment 3. Next, the acceleration sensor 300 according to Embodiment 3 will be described with reference to Figures 9 and 10. Compared to the acceleration sensor 100 according to Embodiment 1, the acceleration sensor 300 according to Embodiment 3 differs in the shape and arrangement of the fixed electrodes, but the other configurations are the same, and the same reference numerals are used for the same configurations as in Embodiment 1, and their description is omitted.

[0055] Figure 9 is a perspective view showing the schematic configuration of the acceleration sensor 300 according to Embodiment 3, and Figure 10 is an exploded view showing the configuration of the acceleration sensor 300 according to Embodiment 3. The acceleration sensor 300 according to Embodiment 3 has eight fixed electrodes 313 formed on a first fixed electrode substrate 310 and eight fixed electrodes 322 formed on a second fixed electrode substrate 320. Because the acceleration sensor 300 according to Embodiment 3 has a larger number of fixed electrodes than the acceleration sensor 100 according to Embodiment 1, it is possible to detect the direction of acceleration in more detail than the acceleration sensor 100 according to Embodiment 1. In Embodiment 3, the fixed electrodes 313 constitute the first electrode and the opposing part. Also, in Embodiment 3, the fixed electrodes 322 constitute the second electrode and the opposing part.

[0056] Embodiment 4. Next, with reference to Figure 11, the acceleration sensor 400 according to Embodiment 4 will be described. Compared to the acceleration sensor 100 according to Embodiment 1, the shape of the movable electrode of the acceleration sensor 400 according to Embodiment 4 is different, but the other configurations are the same, and the same reference numerals are used for the same configurations as in Embodiment 1, and their description is omitted.

[0057] Figure 11 is an exploded view showing the configuration of an acceleration sensor 400 according to Embodiment 4. The acceleration sensor 400 according to Embodiment 4 includes a movable electrode substrate 430 having a movable electrode 433. The movable electrode 433 has a through hole D1 and a groove-shaped recess D2 that connects the space around the movable electrode 433 to the through hole D1 when viewed from the Z direction. The recess D2 is formed at a position that overlaps with the gap between adjacent fixed electrodes among a plurality of fixed electrodes 113 when viewed from the Z direction. As a result, when the movable electrode 433 moves, the fluid inside the space S (see Figure 4) moves more easily through the recess D2, making it possible to suppress the squeeze film phenomenon. The movable electrode may also have a similar recess formed on the side facing the second fixed electrode substrate 120, or it may have a number of groove-shaped recesses other than 4 and a plurality of through holes. The recess D2 constitutes the second hole portion according to Embodiment 4.

[0058] In all of the embodiments described above, the acceleration sensor is arranged with the second fixed portion 132 and the connecting portion 134 inside the through hole D1 when viewed from the Z direction, but is not limited to this. The connecting portion may be arranged around the movable electrode so as to connect the fixed portion, which is arranged to surround the movable electrode, when viewed from the Z direction, with the movable electrode.

[0059] Embodiment 5. Next, with reference to Figure 12, the acceleration sensor according to Embodiment 5 will be described. Compared to the acceleration sensor 100 according to Embodiment 1, the acceleration sensor according to Embodiment 5 has a different shape for the movable electrode substrate, but the other components are the same, and components that are the same as in Embodiment 1 are denoted by the same reference numerals and their description is omitted.

[0060] Figure 12 is a plan view showing the movable electrode substrate 530 of the acceleration sensor according to Embodiment 5. The movable electrode substrate 530 has a through hole D3 formed in the center of the movable electrode 533 when viewed from the Z direction. The movable electrode substrate 530 also has a plurality of connecting parts 534 that connect the movable electrode 533 to a fixed part 532 arranged to surround the movable electrode 533. The plurality of connecting parts 534 are arranged around the movable electrode 533 when viewed from the Z direction. In the acceleration sensor according to Embodiment 5, since the movable electrode 533 has a through hole D3, the surrounding fluid moves more easily when the movable electrode 533 moves, making it possible to suppress the squeeze film phenomenon. In Embodiment 5, the through hole D3 constitutes the first hole (hole).

[0061] Furthermore, in any of the embodiments described above, the acceleration sensor is not limited to one in which the outer shape of the fixed electrode overlaps with the outer shape of the movable electrode when viewed from the Z direction. The fixed electrode only needs to be formed in a position in which at least a part of it does not overlap with the through hole (hole portion) when viewed from the Z direction. Figure 12 shows an example in which the outer shape of the fixed electrode 513 does not overlap with the outer shape of the movable electrode 533 when viewed from the Z direction. In Embodiment 5, the fixed electrode 513 constitutes the first electrode and the opposing portion.

[0062] Embodiment 6. Next, with reference to Figure 13, the acceleration sensor according to Embodiment 6 will be described. The acceleration sensor according to Embodiment 6 has a different processing circuit configuration compared to the acceleration sensor 100 according to Embodiment 1, but other configurations are the same, and the same reference numerals are used for the same configurations as in Embodiment 1, and their description is omitted.

[0063] Figure 13 is a block diagram showing a processing circuit 650 connected to an acceleration sensor according to Embodiment 6. The processing circuit 650 includes a signal strength calculation unit for estimating the detailed direction of acceleration based on the independent directions of each X, Y, and Z axis, for example, for acceleration received from the vector direction of the X and Y axes.

[0064] Embodiment 7. Next, with reference to Figure 14, the acceleration sensor according to Embodiment 7 will be described. The acceleration sensor according to Embodiment 7 has a different processing circuit configuration compared to the acceleration sensor 100 according to Embodiment 1, but other configurations are the same, and the same reference numerals are used for the same configurations as in Embodiment 1, and their description is omitted.

[0065] Figure 14 is a block diagram showing a processing circuit 750 connected to an acceleration sensor according to Embodiment 7. The processing circuit 750 is composed of a highly integrated digital processing circuit. In recent years, based on the development of high-speed signal processing technology and the high integration technology of semiconductor circuits, it has become possible to extract the output signal of an acceleration sensor using a highly integrated digital processing circuit. The processing circuit 750 according to Embodiment 7 is a digital signal processing circuit that uses a highly integrated microprocessor or microcontroller specialized for detecting acceleration by the acceleration sensor described above, and includes a circuit configuration and functions that suppress power consumption.

[0066] In any of the embodiments described above, the acceleration sensor is not limited to a capacitive acceleration sensor that detects acceleration based on a change in capacitance between the movable electrode 133 and the fixed electrode. The acceleration sensor comprises a movable part (weight) that moves in the direction of motion when acceleration occurs, and a facing part that is positioned opposite the movable part with a gap in the direction of motion, and the movable part only needs to have a hole that opens on the side facing the facing part. For example, the acceleration sensor may be a piezoelectric acceleration sensor using a material having a piezoelectric effect or a film material having the same properties, or a piezo-type acceleration sensor using a semiconductor strain resistor.

[0067] Furthermore, this disclosure allows for free combination of each embodiment, modification of any component of each embodiment, or omission of any component in each embodiment. [Explanation of Symbols]

[0068] 100, 200, 300, 400: Accelerometer 110,210,310: First fixed electrode substrate (first substrate, substrate) 111: Main board 112: Terminal 113,213,313,513: Fixed electrode (first electrode, opposing part) 114,124: Through-hole 120, 220, 320: Second fixed electrode substrate (second substrate, substrate) 121: Main board 122,222,322: Fixed electrode (second electrode, opposing part) 123: Terminal 130,430,530: Movable electrode substrate 131: 1st fixed part (fixed part) 132:Second fixing part (holding part) 133,433,533: Movable electrode (moving part) 134,134a,534: Connection part 134a1: First connection section 134a2: Second connection section 134a3: Third connection section 150,650,750: Processing circuit 532:Fixed part D1, D3: Through hole (first hole, hole) D2: Recess (second hole, hole) S: Space

Claims

1. A movable electrode that moves or tilts in accordance with the direction of the force acting due to acceleration, It comprises a flat plate-shaped first fixed substrate and a flat plate-shaped second fixed substrate, which are positioned opposite each other with a gap between them to the movable electrode, The movable electrode has a through hole in its center, Furthermore, a retaining portion is arranged inside the through hole, The movable electrode and the holding portion are electrically connected, and the movable electrode is provided with four connecting portions that elastically deform when the movable electrode moves or tilts. It is an acceleration sensor, The first fixed substrate, the movable electrode, and the second fixed substrate are arranged in order with gaps between them to form a three-layer structure. The first fixed substrate is provided with a first terminal and a first electrode consisting of four electrodes arranged on the surface of a first opposing surface facing one side of the movable electrode, separate from the first terminal. The second fixed substrate is provided with a second terminal and a second electrode consisting of four electrodes arranged on the surface of a second opposing surface that faces the other side of the movable electrode, separate from the second terminal. The through hole penetrates from one side of the movable electrode to the other side. The holding portion is fixed to the first opposing surface of the first fixing substrate and the second opposing surface of the second fixing substrate, and is electrically connected to the first terminal provided on the first fixing substrate and the second terminal provided on the second fixing substrate. The four connecting parts described above are elastically deformed when the distance between the movable electrode and the first and second electrodes changes due to the movement or tilting. The four electrodes of the first electrode are arranged so as to the center of the first fixed substrate, the four electrodes of the second electrode are arranged so as to the center of the second fixed substrate, and the four connecting portions are arranged so as to the center of the movable electrode, each being arranged symmetrically four times. An acceleration sensor characterized by the following features.

2. The first electrode and the second electrode are formed in a position where, when viewed from a direction perpendicular to the surface of the first fixed substrate, at least a portion of them does not overlap with the through hole. The acceleration sensor according to claim 1, characterized in that it is a feature of the present invention.

3. Each of the four connection points is positioned so that, when viewed from a direction perpendicular to the surface of the first fixed substrate, at least a portion of it is located inside the through-hole. The acceleration sensor according to claim 1, characterized in that it is a feature of the present invention.

4. The four connection points are connected to the movable electrode at a position offset from the center of gravity of the movable electrode in a direction perpendicular to the surface of the first fixed substrate. The acceleration sensor according to claim 1, characterized in that it is a feature of the present invention.

5. Each of the four connection points is formed such that the length of the path from one end connected to the holding part to the other end connected to the movable electrode is greater than the width of the path in the direction perpendicular to the direction from one end to the other. The acceleration sensor according to claim 1, characterized in that it is a feature of the present invention.

6. Each of the four connection points is viewed from a direction perpendicular to the surface of the first fixed substrate, A first connecting portion extending in a first direction from one end toward the other end, A second connecting portion is connected to the other end of the first connecting portion and extends in a second direction different from the first direction, The second connecting portion is connected to the other end of the second connecting portion and has a third connecting portion that extends in a third direction different from the second direction. The acceleration sensor according to claim 5, characterized in that it is a feature of the present invention.

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