Inertial sensor and inertial measurement device

Abstract

Provided is an inertial sensor and an inertial measurement device that can suppress in-plane rotational movement. An inertial sensor (1) that detects a physical quantity based on displacement in a Z-axis, when three axes orthogonal to each other are set as an X-axis, a Y-axis, and the Z-axis, includes a substrate (11) and a movable body (31) fixed to the substrate (11), which oscillates around an oscillation axis (P) along the X-axis and has two opposing flat surfaces (31a, 31b) and a side surface (31c) connecting the flat surfaces. The movable body (31) has a first extension (41) disposed at a predetermined angle with respect to the oscillation axis (P) and a second extension (42) disposed opposite the side surface (31c) of the first extension (41).

Description

TECHNICAL FIELD

[0001] The present application relates to an inertial sensor and an inertial measurement device. BACKGROUND

[0002] In recent years, an inertial sensor manufactured using MEMS (Micro Electro Mechanical Systems) technology has been developed. As such an inertial sensor, for example, Patent Literature 1 describes an inertial sensor constituted by a substrate, a movable body disposed on the substrate, first and second detection electrodes, and first and second fixed electrodes disposed on the substrate and opposed to the first and second detection electrodes, and capable of detecting an acceleration in a vertical direction based on a change in electrostatic capacitance generated between the first and second detection electrodes of the movable body and the first and second fixed electrodes respectively disposed at the opposed positions, the rotational moment of the first and second detection electrodes around the rotation axis being different from each other.

[0003] In addition, in order to suppress motion in a plane direction different from the direction of the detected acceleration, the inertial sensor is provided with a damper of comb-tooth structure.

[0004] Patent Literature 1: U.S. Patent Application Publication No. 2015 / 0053002 Specification.

[0005] However, the inertial sensor described in Patent Literature 1, while being able to suppress motion in the plane direction, has a technical problem that it is difficult to suppress motion of rotation in the plane direction. SUMMARY

[0006] The inertial sensor is an inertial sensor that detects a physical quantity based on displacement in a Z-axis direction when three axes orthogonal to each other are set as an X-axis, a Y-axis, and the Z-axis, and has a substrate and a movable body fixed to the substrate and oscillating around an oscillation axis along the X-axis and having two planes opposed to each other and a side surface connecting them, the movable body having a first extension portion disposed at a predetermined angle with respect to the oscillation axis and a second extension portion disposed opposite the side surface of the first extension portion.

[0007] The inertial measurement device has the inertial sensor described above and a control portion that controls based on a detection signal output from the inertial sensor. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 A plan view showing a brief structure of the inertial sensor according to the first embodiment.

[0009] Figure 2 A plan view showing a brief structure of the inertial sensor according to the first embodiment.Figure 1 a cross-sectional view taken along line A-A in Fig. 1.

[0010] Figure 3 Fig. 2 is a plan view for showing a brief structure of a sensor element provided in an inertial sensor according to a second embodiment.

[0011] Figure 4 Fig. 3 is a plan view for showing a brief structure of a sensor element provided in an inertial sensor according to a third embodiment.

[0012] Figure 5 Fig. 4 is an exploded perspective view for showing a brief configuration of an inertial measurement device provided with an inertial sensor according to a fourth embodiment.

[0013] Figure 6 Fig. 5 is a perspective view of a substrate. Figure 5

[0014] Explanation of Reference Numerals

[0015] 1, 1a, 1b: inertial sensor; 6: frit; 11: substrate; 12: upper surface; 13: fixed portion; 14: recessed portion; 15: inner bottom surface; 16: connection terminal; 17: first fixed electrode; 18: second fixed electrode; 19: third fixed electrode; 21: cover; 22: recessed portion; 30: sensor element; 31: movable body; 31a: upper surface; 31b: lower surface; 31c: side surface; 32: support portion; 33: support beam; 34: first link portion; 35: second link portion; 36: first opening portion; 37: second opening portion; 38: first movable electrode; 39: second movable electrode; 40: third movable electrode; 41: first extension portion; 42: second extension portion; 43: through-hole; 44: third extension portion; 2000: inertial measurement device; Cl: electrostatic capacitor; C2: electrostatic capacitor; P: swing axis; S: internal space. DETAILED DESCRIPTION

[0016] 1. First Embodiment

[0017] First, with respect to the inertial sensor 1 according to the first embodiment, an acceleration sensor that detects acceleration as a physical quantity in the vertical direction will be exemplified, and a description will be given with reference to Figs. 1 and 2. Figure 1 and Figure 2

[0018] Note that, in Figs. 1 and 2, a state in which the cover 21 is removed is illustrated in order to facilitate explanation of the configuration of the inside of the inertial sensor 1. In addition, in Figs. 1 and 2, the illustration of the wiring provided to the substrate 11 is omitted. Figure 1 Figure 1 and Figure 2

[0019] ​​​​In addition, in the following plan view, sectional view, and perspective view, the X axis, Y axis, and Z axis are illustrated as three axes orthogonal to each other. In addition, the direction along the X axis is referred to as the "X direction", the direction along the Y axis is referred to as the "Y direction", and the direction along the Z axis is referred to as the "Z direction". In addition, the side of the arrowhead of each axis is referred to as the "positive side", and the base end side is referred to as the "negative side". In addition, the Z direction is along the vertical direction, and the XY plane is along the horizontal plane. In addition, in the present specification, the positive Z direction and negative Z direction are collectively referred to as the Z direction.

[0020] Figure 1 and Figure 2 The inertial sensor 1 illustrated in the drawing is capable of detecting acceleration as a physical quantity of the sensor element 30 in the vertical direction, that is, the Z direction. Such an inertial sensor 1 has a substrate 11, a sensor element 30 disposed on the substrate 11, and a cover 21 joined to the substrate 11 and covering the sensor element 30.

[0021] As illustrated in Figure 1 , the substrate 11 has a width in the X direction and Y direction, and a thickness in the Z direction. In addition, as illustrated in Figure 2 , the substrate 11 is formed with a recessed portion 14 recessed downward from the upper surface 12 of the substrate 11. In plan view from the Z axis direction, the recessed portion 14 contains the sensor element 30 inside, and is formed larger than the sensor element 30. The recessed portion 14 functions as an evacuation portion for swinging the sensor element 30. In addition, the substrate 11 has a fixing portion 13 protruding from the inner bottom surface 15 of the recessed portion 14 toward the sensor element 30, and the sensor element 30 is joined to the fixing portion 13. Thereby, the sensor element 30 can be fixed to the substrate 11 in a state separated from the inner bottom surface 15 of the recessed portion 14.

[0022] In addition, the first fixing electrode 17, second fixing electrode 18, and third fixing electrode 19 which is a virtual electrode are disposed on the inner bottom surface 15 of the recessed portion 14. The first fixing electrode 17 and second fixing electrode 18 have substantially equal areas. In addition, the first fixing electrode 17 and second fixing electrode 18 are connected to a QV amplifier of an external device not illustrated, and detect a difference in electrostatic capacity by a differential detection method as an electric signal. Therefore, it is desirable that the first fixing electrode 17 and second fixing electrode 18 are equal in area.

[0023] In addition, the substrate 11 is provided with a connection terminal 16 electrically connecting the external device not illustrated and the first to third fixing electrodes 17, 18, 19 on the upper surface 12 of the region where the recessed portion 14 is not provided.

[0024] As the substrate 11, for example, a substrate made of a material containing Na +A glass substrate made of a glass material such as a borosilicate glass, for example, Pyrex (registered trademark) glass, TEMPAX (registered trademark) glass, which is a mobile ion, i.e., an alkali metal ion. However, there is no particular limitation on the substrate 11, and for example, a silicon substrate, a quartz substrate can also be used.

[0025] In addition, the first to third fixed electrodes 17, 18, 19, and the connection terminal 16 can use a metal such as Au, Pt, Ag, Cu, Al, and an alloy containing these metals, and the like.

[0026] As shown in FIG. 1, the substrate 11 is formed with a recess 14 in a position overlapping the sensor element 30. The substrate 11 is joined to the upper surface 12 of the cover 21 by a glass frit 6 or the like. Figure 2 As shown in FIG. 1, the cover 21 is formed with a recess 22 recessed upward in a position overlapping the recess 14 of the substrate 11. The cover 21 houses the sensor element 30 in the recess 22 and is joined to the upper surface 12 of the substrate 11 by a glass frit 6 or the like. Further, an internal space S housing the sensor element 30 is formed inside the cover 21 and the substrate 11.

[0027] The internal space S is an airtight space, seals a non-reactive gas such as nitrogen, helium, argon, and has a use temperature of -40°C to 125°C, and is preferably approximately atmospheric pressure. However, the atmosphere of the internal space S is not particularly limited, and for example, can be a reduced pressure state or a pressurized state.

[0028] As the cover 21, for example, a silicon substrate can be used. However, it is not limited thereto, and for example, a glass substrate, a quartz substrate can also be used. Further, as the joining method of the substrate 11 and the cover 21, there is no particular limitation, and it is appropriate to select according to the materials of the substrate 11 and the cover 21, and in addition to joining based on a joining material such as a glass frit 6, for example, anodic bonding, active bonding in which joining surfaces activated by plasma irradiation are joined to each other, metal eutectic bonding in which metal films formed on the upper surface of the substrate 11 and the lower surface of the cover 21 are joined to each other, and the like can be used.

[0029] The sensor element 30 is composed of a movable body 31, and the movable body 31 is orthogonal to the Z-axis, and has two planes, i.e., an upper surface 31a and a lower surface 31b, which are in a front and back relationship with each other, and a side surface 31c connecting them, as shown in FIG. 2. Figure 1As shown, in a plan view from the Z direction, it has a rectangular shape with the Y direction as the long side. Further, the movable body 31 has a support portion 32 joined to the fixed portion 13, two support beams 33 connected to the support portion 32 and extending from the support portion 32 to the positive and negative sides in the X direction, a first movable electrode 38 located on the negative side in the Y direction with respect to the support beams 33, a second movable electrode 39 located on the positive side in the Y direction with respect to the support beams 33, and a third movable electrode 40 connected to the second movable electrode 39. In a plan view from the Z direction, the first movable electrode 38, the second movable electrode 39, and the third movable electrode 40 are arranged so as to overlap the first fixed electrode 17, the second fixed electrode 18, and the third fixed electrode 19, respectively, provided on the inner bottom surface 15 of the substrate 11. Further, a plurality of through-holes 43 that penetrate the upper surface 31a and the lower surface 31b are provided in the first to third movable electrodes 38, 39, 40 of the movable body 31, and air resistance generated when the movable body 31 is displaced in the Z direction can be reduced.

[0030] Note that a first opening portion 36 is provided between the first fixed electrode 17 and the second fixed electrode 18 and is connected by a first connecting portion 34 at both ends in the X direction of the first movable electrode 38 and the second movable electrode 39. Further, the first connecting portion 34 is connected to the support beam 33 at the center of the first connecting portion 34. Thus, once an acceleration in the Z direction acts, the movable body 31 swings around the swing axis P in the X axis with the support beam 33 as the swing axis P, while deforming in torsion the support beam 33. Further, a second opening portion 37 is provided between the second movable electrode 39 and the third movable electrode 40 and is connected by a second connecting portion 35 at both ends in the X direction of the second movable electrode 39 and the third movable electrode 40.

[0031] Further, the movable body 31 located on the positive side in the Y direction with respect to the swing axis P is longer in the Y direction than the movable body 31 located on the negative side in the Y direction with respect to the swing axis P, i.e., the first movable electrode 38, because the second movable electrode 39 and the third movable electrode 40 are connected thereto. Therefore, in a plan view from the Z direction, the movable body 31 located on the positive side in the Y direction with respect to the swing axis P has a larger area and a larger mass than the movable body 31 located on the negative side in the Y direction with respect to the swing axis P, so the rotational moment when an acceleration in the Z direction is added is larger than that of the movable body 31 located on the negative side in the Y direction. Due to the difference in the rotational moment, once an acceleration in the Z direction is added, the movable body 31 performs a seesaw swing around the swing axis P. Note that the seesaw swing means that, once the first movable electrode 38 is displaced to the positive side in the Z direction, the second movable electrode 39 is displaced to the negative side in the Z direction, and conversely, once the first movable electrode 38 is displaced to the negative side in the Z direction, the second movable electrode 39 is displaced to the positive side in the Z direction.

[0032] When the inertial sensor 1 is driven, electrostatic capacitances CI and C2 are formed between the first movable electrode 38 and the first fixed electrode 17 and between the second movable electrode 39 and the second fixed electrode 18, respectively, by applying a drive signal to the sensor element 30. The electrostatic capacitances CI and C2 are substantially equal to each other in a natural state where no acceleration is applied.

[0033] If acceleration in the Z direction is applied to the inertial sensor 1, the movable body 31 performs a seesaw swing about the swing axis P. By the seesaw swing of the movable body 31, the gap between the first movable electrode 38 and the first fixed electrode 17 and the gap between the second movable electrode 39 and the second fixed electrode 18 change in opposite phases, and the electrostatic capacitances CI and C2 change in opposite phases with respect to each other in correspondence with this. Thus, the inertial sensor 1 can detect acceleration in the Z direction on the basis of the difference between the capacitance values of the electrostatic capacitances CI and C2.

[0034] The movable body 31 has a first opening portion 36 between the first movable electrode 38 and the second movable electrode 39, and the support portion 32 and the support beam 33 are arranged in the first opening portion 36. By being shaped like this, the sensor element 30 can be made small.

[0035] In addition, when viewed from above in the Z direction, a plurality of first extension portions 41 extending radially from the support portion 32 toward the outer edge of the movable body 31 are provided in the first opening portion 36 so as to be arranged at predetermined angles with respect to the swing axis P. Note that, in the present embodiment, ten first extension portions 41 extending at angles of ±30°, ±60°, and ±90° with respect to the swing axis P are arranged, but the number is not limited to this and can be four or more. In addition, the intervals between the first extension portions 41 can not be constant.

[0036] In addition, a plurality of second extension portions 42 extending from the first movable electrode 38 and the second movable electrode 39 of the movable body 31 toward the support portion 32 are provided around the first opening portion 36, the second extension portions 42 are arranged at predetermined intervals opposite the side surface 31c of the first extension portions 41. Note that, in the present embodiment, twelve second extension portions 42 are arranged between the first extension portions 41 and the first extension portions 41 and between the first extension portions 41 and the support beam 33, but the number is not limited to this and can be arranged in correspondence with the number of the first extension portions 41. For example, in the case where the first extension portions 41 are four, the second extension portions 42 are six, and in the case where the first extension portions 41 are six, the second extension portions 42 are eight.

[0037] The first extension portion 41 arranged radially with the support portion 32 of the substrate 11 as the center is opposed to the side surface 31c of the second extension portion 42 with a predetermined interval, and therefore, in the case where an in-plane rotation motion with the support portion 32 as the center is added, air resistance is generated between the second extension portion 42 which performs a rotational displacement and the first extension portion 41 which is fixed, that is, functions as a damper, and the in-plane rotational motion of the movable body 31 can be suppressed. In addition, in the case where an excessive in-plane rotational motion is added, the movable body 31 can be further limited by the contact between the second extension portion 42 and the first extension portion 41 which is fixed.

[0038] The sensor element 30 is formed by vertically processing a conductive silicon substrate doped with an impurity such as phosphorus (P), boron (B), arsenic (As), or the like, by using etching, particularly Bosch process which is a deep etching technique.

[0039] The inertial sensor 1 of the present embodiment has a first extension portion 41 extending radially at a predetermined angle with respect to the swing axis P from a support portion 32 fixed to the substrate 11, and a second extension portion 42 arranged in opposition to the side surface 31c of the first extension portion 41 with a predetermined interval. Therefore, in the case where an in-plane rotational motion with the support portion 32 as the center is added, air resistance is generated between the side surface 31c of the second extension portion 42 which performs a rotational displacement and the side surface 31c of the first extension portion 41 which is fixed, that is, functions as a damper, and the in-plane rotational motion of the movable body 31 can be suppressed.

[0040] 2. Second Embodiment

[0041] Next, the inertial sensor 1a of the second embodiment will be described with reference to Figure 3 The sensor element 30a provided in the inertial sensor 1a of the second embodiment will be described.

[0042] The inertial sensor 1a of the present embodiment is the same as the inertial sensor 1 of the first embodiment except for the structure of the movable body 311 of the sensor element 30a. Note that the description will be made focusing on the difference from the first embodiment, and the description of the same matters will be omitted.

[0043] As Figure 3As shown, the sensor element 30a is arranged at a predetermined angle with respect to the swing axis P (support beam 33) at the first extension portion 41a of the movable body 311 which is connected to the support portion 32 at the first opening portion 36, and has a third extension portion 44 at the front end portion on the side opposite to the support portion 32 which is parallel to the swing axis P (support beam 33). Further, a plurality of second extension portions 42a which extend from the first movable electrode 38 and the second movable electrode 39 of the movable body 311 toward the support portion 32 are provided between the first extension portion 41a and the third extension portion 44 and the support beam 33.

[0044] Since the side surface 31c of the first extension portion 41a and the third extension portion 44 is opposed to the side surface 31c of the second extension portion 42a by being configured as such, the function as a damper is exerted with respect to the in-plane rotation operation, and the same effect as that of the inertial sensor 1 of the first embodiment can be obtained.

[0045] 3. Third Embodiment

[0046] Next, the inertial sensor 1b according to the third embodiment will be described with reference to the drawings. Figure 4 The sensor element 30b of the inertial sensor 1b according to the third embodiment will be described.

[0047] The inertial sensor 1b according to the present embodiment is the same as the inertial sensor 1 according to the first embodiment except for the structure of the movable body 312 of the sensor element 30b. Note that the description will be made focusing on the difference from the first embodiment, and the description of the same matters will be omitted.

[0048] Figure 4 As shown, the sensor element 30b is arranged at a predetermined angle with respect to the swing axis P (support beam 33) at the first extension portion 41b of the movable body 312 which is connected to the support portion 32b at the first opening portion 36, and has a third extension portion 44b at the front end portion on the side opposite to the support portion 32b which is parallel to the swing axis P. Further, a plurality of second extension portions 42b which extend from the first movable electrode 38 and the second movable electrode 39 of the movable body 312 toward the support portion 32b are provided between the first extension portion 41b and the third extension portion 44b and the support beam 33.

[0049] Since the side surface 31c of the first extension portion 41b and the third extension portion 44b is opposed to the side surface 31c of the second extension portion 42b by being configured as such, the function as a damper is exerted with respect to the in-plane rotation operation, and the same effect as that of the inertial sensor 1 of the first embodiment can be obtained.

[0050] 4. Fourth Embodiment

[0051] Next, the inertial sensor 1b according to the third embodiment will be described with reference to the drawings. Figure 5 andFigure 6 An inertial measurement device 2000 provided with the inertial sensor 1-1b according to the fourth embodiment will be described. Note that, in the following description, the configuration of the inertial sensor 1 is exemplified for the description.

[0052] Figure 5 The inertial measurement device 2000 (IMU: Inertial Measurement Unit) shown is a device that detects the posture, behavior, and the like of a moving body such as a vehicle or a robot. The inertial measurement device 2000 functions as a so-called six-axis motion sensor provided with an acceleration sensor that detects accelerations Ax, Ay, and Az in the directions of three axes, and an angular velocity sensor that detects angular velocities ωx, ωy, and ωz around the three axes.

[0053] The inertial measurement device 2000 is a rectangular parallelepiped having a planar shape that is substantially a square. Further, screw holes 2110 as fixing portions are formed near two points on the diagonal line direction of the square. Two screws are inserted through the two screw holes 2110, whereby the inertial measurement device 2000 can be fixed to a mounting surface of a mounting body such as a vehicle. Note that, by selection of parts and design change, the inertial measurement device 2000 can be miniaturized to a size that can be mounted to, for example, a smartphone or a digital camera.

[0054] The inertial measurement device 2000 has a housing 2100, a joint member 2200, and a sensor module 2300, and is configured such that the sensor module 2300 is inserted into the inside of the housing 2100 via the joint member 2200. Further, the sensor module 2300 has an inner housing 2310 and a substrate 2320.

[0055] The housing 2100 has the same outer shape as the overall shape of the inertial measurement device 2000, and is a rectangular parallelepiped having a planar shape that is substantially a square, with screw holes 2110 formed near two points on the diagonal line direction of the square. Further, the housing 2100 is a box shape, and the sensor module 2300 is housed in the inside thereof.

[0056] The inner housing 2310 is a member that supports the substrate 2320, and has a shape that is housed in the inside of the housing 2100. Further, a recess 2311 for preventing contact with the substrate 2320 and an opening 2312 for exposing a connector 2330 described later are formed in the inner housing 2310. Such an inner housing 2310 is joined to the housing 2100 with the joint member 2200. Further, the substrate 2320 is joined to the lower surface of the inner housing 2310 with an adhesive.

[0057] As shown in FIG. 2, the inertial measurement device 2000 has a planar shape that is substantially a square, and is a rectangular parallelepiped having a planar shape that is substantially a square. Further, screw holes 2110 as fixing portions are formed near two points on the diagonal line direction of the square. Two screws are inserted through the two screw holes 2110, whereby the inertial measurement device 2000 can be fixed to a mounting surface of a mounting body such as a vehicle. Figure 6As shown, a connector 2330, an angular velocity sensor 2340z that detects an angular velocity around the Z axis, an acceleration sensor unit 2350 that detects accelerations in the X, Y, and Z axes, and the like are mounted on the substrate 2320. In addition, an angular velocity sensor 2340x that detects an angular velocity around the X axis and an angular velocity sensor 2340y that detects an angular velocity around the Y axis are mounted on the side surface of the substrate 2320.

[0058] The acceleration sensor unit 2350 includes at least the aforementioned inertial sensor 1 for measuring an acceleration in the Z direction, and can detect an acceleration in one axis or an acceleration in two axes, three axes as needed. Note that, as the angular velocity sensors 2340x, 2340y, 2340z, there is no particular limitation, and, for example, a vibrating gyro sensor that utilizes Coriolis force can be used.

[0059] In addition, a control IC 2360 is mounted on the lower surface of the substrate 2320. The control IC 2360, which is a control unit that controls based on a detection signal output from the inertial sensor 1, is an MCU (Micro Controller Unit), and has a storage unit including a nonvolatile memory, an A / D converter, and the like built in, and controls each unit of the inertial measurement device 2000. In the storage unit, an acceleration, a program that specifies an order and content for detecting an angular velocity, a program that digitizes detection data and incorporates it into packet data, accompanying data, and the like are stored. Note that, a plurality of electronic parts are further mounted on the substrate 2320.

[0060] Such an inertial measurement device 2000, due to the use of the acceleration sensor unit 2350 including the inertial sensor 1, can achieve an inertial measurement device 2000 that is excellent in impact resistance and high in reliability.

Claims

1. An inertial sensor, characterized by comprising: a substrate orthogonal to a Z-axis when three axes orthogonal to each other are set as an X-axis, a Y-axis, and the Z-axis, and provided with a fixed electrode; and a movable body opposed to the fixed electrode in a Z-axis direction along the Z-axis, orthogonal to the Z-axis, including two planes in a surface and back relation to each other and a side surface connecting the two planes, and provided to be able to swing with respect to the substrate with a swing axis along the X-axis as a center, the fixed electrode including: a first fixed electrode and a second fixed electrode, the movable body including: a first movable electrode opposed to the first fixed electrode; a second movable electrode opposed to the second fixed electrode; a connecting portion connecting the first movable electrode and the second movable electrode; a supporting portion fixed to the substrate; and a supporting beam connecting the supporting portion and the connecting portion, and being the swing axis, the movable body provided with an opening portion between the first movable electrode and the second movable electrode, the supporting portion being disposed at the opening portion in a plan view from the Z-axis direction, the movable body including, in the plan view: a plurality of first extension portions disposed at a predetermined angle with respect to the swing axis and extending radially from the supporting portion to an outer edge of the movable body with the supporting portion as a center; and a plurality of second extension portions extending from a side of the outer edge to a center of the supporting portion, each of the plurality of first extension portions and each of the plurality of second extension portions being opposed to each other at a predetermined interval apart from each other's side surface.

2. The inertial sensor according to claim 1, characterized in that the movable body includes a third extension portion connected to a front end side of the first extension portion on a side opposite to the supporting portion.

3. The inertial sensor according to claim 2, characterized in that the third extension portion is parallel to the X-axis.

4. The inertial sensor according to claim 3, characterized in that the first extension portion is orthogonal to the X-axis, the third extension portion is parallel to the X-axis.

5. An inertial measurement device, characterized by comprising: the inertial sensor according to claim 1; and a control portion that controls based on a detection signal output from the inertial sensor. ​ ​ ​ ​ ​

Images