Inertial Sensor and Inertial Measurement Device

Abstract

To provide an inertial sensor and an inertial measurement unit that can prevent an in-plane rotation operation.SOLUTION: An inertial sensor 1 is an inertial sensor 1 that, when three axes orthogonal to each other are an X-axis, a Y-axis, and a Z-axis, detects a physical quantity based on the displacement of the Z-axis, and comprises: a substrate 11; and a movable body 31 that is fixed to the substrate 11, swings around a swing axis P along the X-axis, and has two planes 31a, 31b facing each other and side faces 31c connecting the planes with each other. The movable body 31 has a first extension part 41 that is arranged with respect to the swing axis P at a predetermined angle, and a second extension part 42 that is arranged to face the side faces 31c of the first extension part 41.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, inertial sensors manufactured using MEMS (Micro Electro Mechanical Systems) technology have been developed. As such an inertial sensor, for example, Patent Document 1 discloses a substrate, a movable body disposed on the substrate having first and second detection electrodes and rocking like a seesaw around a rotation axis, and first and second fixed electrodes provided on the substrate and facing the first and second detection electrodes, and first and second detection electrodes of the movable body having different rotational moments around the rotation axis, and first and second fixed electrodes disposed at positions facing the first and second detection electrodes respectively, and an inertial sensor capable of detecting an acceleration in the vertical direction based on a change in capacitance between the electrodes is described. Further, in order to suppress the operation in the in-plane direction different from the direction in which the acceleration is detected, this inertial sensor is provided with a damper having a comb structure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the inertial sensor described in Patent Document 1 has a problem that although the operation in the in-plane direction can be suppressed, it is difficult to suppress the operation of in-plane rotation.

Means for Solving the Problems

[0005] The inertial sensor is an inertial sensor that detects a physical quantity based on the displacement of the Z-axis when three mutually orthogonal axes are defined as the X-axis, Y-axis, and Z-axis, and includes a substrate, and a movable body fixed to the substrate and oscillating about a rocking axis along the X-axis, the movable body having two opposing planes and side surfaces connecting therebetween. The movable body has a first extending portion disposed at a predetermined angle with respect to the rocking axis, and a second extending portion disposed opposite to the side surface of the first extending portion.

[0006] The inertial measurement device includes the inertial sensor described above, and a control unit that performs control based on a detection signal output from the inertial sensor.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0008] 1. First Embodiment First, the inertial sensor 1 according to the first embodiment will be described by taking an acceleration sensor that detects acceleration in the vertical direction as an example, with reference to FIGS. 1 and 2. In addition, in FIG. 1, for the sake of convenience in explaining the internal configuration of the inertial sensor 1, a state in which the lid body 21 is removed is illustrated. Also, in FIGS. 1 and 2, illustration of the wiring provided on the substrate 11 is omitted.

[0009] For convenience of explanation, in the following plan view, cross-sectional view, and perspective view, the X-axis, Y-axis, and Z-axis are illustrated as three mutually orthogonal axes. Also, 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". Also, the tip side of the arrow in each axis direction is referred to as the "plus side", the base end side is referred to as the "minus side", the plus side in the Z direction is referred to as "up", and the minus side in the Z direction is also referred to as "down". Also, the Z direction is along the vertical direction, and the XY plane is along the horizontal plane. In this specification, the plus Z direction and the minus Z direction are collectively referred to as the Z direction.

[0010] The inertial sensor 1 shown in FIGS. 1 and 2 can detect the acceleration in the Z direction, which is the vertical direction of the sensor element 30. Such an inertial sensor 1 includes a substrate 11, a sensor element 30 disposed on the substrate 11, and a lid body 21 joined to the substrate 11 and covering the sensor element 30.

[0011] As shown in FIG. 1, the substrate 11 has an extent in the X direction and the Y direction and has the Z direction as its thickness. Also, as shown in FIG. 2, a recess 14 that is recessed downward from the upper surface 12 of the substrate 11 is formed in the substrate 11. This recess 14 encloses the sensor element 30 inside in a plan view from the Z direction and is formed larger than the sensor element 30. The recess 14 functions as a relief portion for the sensor element 30 to swing. Also, the substrate 11 has a fixing portion 13 that protrudes from the inner bottom surface 15 of the recess 14 toward the sensor element 30 side, and the sensor element 30 is joined and fixed on the fixing portion 13. Thereby, the sensor element 30 can be fixed to the substrate 11 in a state of being separated from the inner bottom surface 15 of the recess 14.

[0012] In addition, on the inner bottom surface 15 of the concave portion 14, a first fixed electrode 17, a second fixed electrode 18, and a third fixed electrode 19 serving as a dummy electrode are arranged. The first fixed electrode 17 and the second fixed electrode 18 have substantially equal areas. Also, the first fixed electrode 17 and the second fixed electrode 18 are respectively connected to a QV amplifier of an external device (not shown), and the capacitance difference therebetween is detected as an electrical signal by a differential detection method. Therefore, it is desirable that the first fixed electrode 17 and the second fixed electrode 18 have equal areas.

[0013] Further, the substrate 11 is provided with connection terminals 16 that electrically connect an external device (not shown) to the first to third fixed electrodes 17, 18, 19 on the upper surface 12 of the region where the concave portion 14 is not provided.

[0014] As the substrate 11, for example, a glass substrate made of a glass material containing alkali metal ions such as Na + and other mobile ions, such as borosilicate glass such as Pyrex (registered trademark) glass and Tempax (registered trademark) glass, can be used. However, the substrate 11 is not particularly limited, and for example, a silicon substrate or a quartz substrate may be used.

[0015] Also, for the first to third fixed electrodes 17, 18, 19 and the connection terminals 16, metals such as Au, Pt, Ag, Cu, Al, alloys containing these metals, etc. can be used.

[0016] As shown in FIG. 2, the lid body 21 has a concave portion 22 that is recessed upward formed at a position overlapping the concave portion 14 of the substrate 11. The lid body 21 houses the sensor element 30 in the concave portion 22 and is joined to the upper surface 12 of the substrate 11 with glass frit 6 or the like. Then, an internal space S for housing the sensor element 30 is formed inside by the lid body 21 and the substrate 11.

[0017] The internal space S is an airtight space, preferably filled with an inert gas such as nitrogen, helium, or argon, having an operating temperature of about -40°C to 125°C and being at approximately atmospheric pressure. However, the atmosphere in the internal space S is not particularly limited and may be, for example, in a reduced-pressure state or a pressurized state.

[0018] As the lid 21, for example, a silicon substrate can be used. However, it is not particularly limited thereto, and for example, a glass substrate or a quartz substrate may be used. Also, the bonding method between the substrate 11 and the lid 21 is not particularly limited and may be appropriately selected according to the materials of the substrate 11 and the lid 21. In addition to bonding with a bonding material such as glass frit 6, for example, anodic bonding, activation bonding in which the bonded surfaces activated by plasma irradiation are bonded together, metal eutectic bonding in which the metal films formed on the upper surface of the substrate 11 and the lower surface of the lid 21 are bonded, etc. can be used.

[0019] The sensor element 30 is composed of a movable body 31. The movable body 31 has an upper surface 31a and a lower surface 31b which are two planes facing each other, and a side surface 31c connecting them. As shown in FIG. 1, in a plan view from the Z direction, it has a rectangular shape with the Y direction as the long side. The movable body 31 is joined to a support portion 32 on the fixed portion 13, two support beams 33 connected to the support portion 32 and extending from the support portion 32 in the +X direction and -X direction, a first movable electrode 38 located on the -Y side with respect to the support beam 33, a second movable electrode 39 located on the +Y side with respect to the support beam 33, and a third movable electrode 40 connected to the second movable electrode 39. The first movable electrode 38, the second movable electrode 39, and the third movable electrode 40 are arranged to overlap with a first fixed electrode 17, a second fixed electrode 18, and a third fixed electrode 19 provided on the inner bottom surface 15 of the substrate 11 in a plan view from the Z direction, respectively. Further, a plurality of through holes 43 penetrating 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 the air resistance generated when the movable body 31 is displaced in the Z direction can be reduced.

[0020] Between the first fixed electrode 17 and the second fixed electrode 18, a first opening 36 is provided, and the first movable electrode 38 and the second movable electrode 39 are connected by a first connecting portion 34 at both ends in the X direction. Further, the first connecting portion 34 is connected to the support beam 33 at the center of the first connecting portion 34. Therefore, when an acceleration along the Z direction acts, the movable body 31 swings around the swing axis P along the X axis while twisting and deforming the support beam 33 with the support beam 33 as the swing axis P. Also, between the second movable electrode 39 and the third movable electrode 40, a second opening 37 is provided, and the second movable electrode 39 and the third movable electrode 40 are connected by a second connecting portion 35 at both ends in the X direction.

[0021] Also, the movable body 31 located on the plus side in the Y direction with respect to the swing axis P is configured to be longer in the Y direction than the first movable electrode 38, which is the movable body 31 located on the minus side in the Y direction with respect to the swing axis P, because the second movable electrode 39 and the third movable electrode 40 are connected. Therefore, the movable body 31 located on the plus 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 minus side in the Y direction with respect to the swing axis P when viewed in plan from the Z direction. Thus, when an acceleration in the Z direction is applied, the rotational moment is larger than that of the movable body 31 located on the minus side in the Y direction. Due to this difference in rotational moment, when an acceleration in the Z direction is applied, the movable body 31 swings like a seesaw around the swing axis P. Note that seesaw swinging means that when the first movable electrode 38 is displaced to the plus side in the Z direction, the second movable electrode 39 is displaced to the minus side in the Z direction, and conversely, when the first movable electrode 38 is displaced to the minus side in the Z direction, the second movable electrode 39 is displaced to the plus side in the Z direction.

[0022] When the inertial sensor 1 is driven, a driving signal is applied to the sensor element 30, whereby an electrostatic capacitance C1 is formed between the first movable electrode 38 and the first fixed electrode 17. Similarly, an electrostatic capacitance C2 is formed between the second movable electrode 39 and the second fixed electrode 18. In the natural state where no acceleration is applied, the electrostatic capacitances C1 and C2 are substantially equal to each other.

[0023] When an acceleration in the Z direction is applied to the inertial sensor 1, the movable body 31 swings like a seesaw about the swing axis P. Due to this 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 accordingly, the capacitances C1 and C2 change in opposite phases to each other. Therefore, the inertial sensor 1 can detect the acceleration in the Z direction based on the difference in the capacitance values of the capacitances C1 and C2.

[0024] The movable body 31 has a first opening 36 between the first movable electrode 38 and the second movable electrode 39, and a support portion 32 and a support beam 33 are disposed in the first opening 36. By adopting such a shape, miniaturization of the sensor element 30 can be achieved.

[0025] Also, in the first opening 36, a plurality of first extending portions 41 extending radially from the support portion 32 toward the outer edge of the movable body 31 around the support portion 32 are provided, and the first extending portions 41 are arranged at respective predetermined angles with respect to the swing axis P. In the present embodiment, 10 first extending portions 41 extending at angles of ±30°, ±60°, and ±90° with respect to the swing axis P are arranged, but the present invention is not limited to this, and four or more may be sufficient. Also, the intervals between the first extending portions 41 do not have to be constant.

[0026] Also, around the first opening 36, a plurality of second extending 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, and the second extending portions 42 face the side surface 31c of the first extending portion 41 and are arranged at a predetermined interval. In the present embodiment, 12 second extending portions 42 are arranged between the first extending portions 41 and between the first extending portions 41 and the support beam 33, but the present invention is not limited to this, and they may be arranged according to the number of the first extending portions 41. For example, when the number of the first extending portions 41 is four, the number is six, and when the number of the first extending portions 41 is six, the number is eight.

[0027] The first extending portion 41 radially arranged around the support portion 32 fixed to the substrate 11 has its side surface 31c facing the side surface 31c of the second extending portion 42 with a predetermined gap therebetween. Therefore, when an in-plane rotation operation centered on the support portion 32 is applied, air resistance occurs between the rotatable second extending portion 42 and the fixed first extending portion 41, that is, it functions as a damper and can suppress the in-plane rotation operation of the movable body 31. Further, when an excessive in-plane rotation operation is applied, the second extending portion 42 comes into contact with the first extending portion 41 to which it is fixed, thereby restricting further displacement of the movable body 31.

[0028] The sensor element 30 is formed, for example, by etching a conductive silicon substrate doped with impurities such as phosphorus (P), boron (B), and arsenic (As), and particularly by vertically processing it by a Bosch process, which is a deep etching technique.

[0029] The inertial sensor 1 of the present embodiment has a first extending portion 41 that radially extends from the support portion 32 fixed to the substrate 11 at a predetermined angle with respect to the swing axis P, and a second extending portion 42 that faces the side surface 31c of the first extending portion 41 and is arranged with a predetermined gap therebetween. Therefore, when an in-plane rotation operation centered on the support portion 32 is applied, air resistance occurs between the side surface 31c of the rotatable second extending portion 42 and the side surface 31c of the fixed first extending portion 41, that is, it functions as a damper and can suppress the in-plane rotation operation of the movable body 31.

[0030] 2. Second Embodiment Next, the sensor element 30a included in the inertial sensor 1a according to the second embodiment will be described with reference to FIG. 3.

[0031] The inertial sensor 1a of the present embodiment is the same as the inertial sensor 1 of the first embodiment except that the structure of the movable body 311 of the sensor element 30a is different. Note that the description will focus on the differences from the above-described first embodiment, and descriptions of the same matters will be omitted.

[0032] As shown in Fig. 3, the sensor element 30a is arranged at a predetermined angle with respect to the swing axis P (support beam 33) by the first extension portion 41a connected to the support portion 32 at the first opening 36 of the movable body 311. A third extension portion 44 parallel to the swing axis P (support beam 33) is provided at the tip on the side opposite to the support portion 32. In addition, between the first extension portion 41a and the third extension portion 44 and the support beam 33, a plurality of second extension portions 42a extending from the first movable electrode 38 and the second movable electrode 39 of the movable body 311 toward the support portion 32 are provided.

[0033] With such a configuration, since the side surfaces 31c of the first extension portion 41a and the third extension portion 44 face the side surfaces 31c of the second extension portion 42a, it functions as a damper for the in-plane rotation operation, and the same effect as that of the inertial sensor 1 of the first embodiment can be obtained.

[0034] 3. Third Embodiment Next, the sensor element 30b provided in the inertial sensor 1b according to the third embodiment will be described with reference to Fig. 4.

[0035] The inertial sensor 1b of the present embodiment is the same as the inertial sensor 1 of the first embodiment except that the structure of the movable body 312 of the sensor element 30b is different. The description will focus on the differences from the first embodiment described above, and the description of the same matters will be omitted.

[0036] As shown in Fig. 4, the sensor element 30b has a first extension portion 41b connected to a rectangular support portion 32b extending orthogonally from the support portion 32b with respect to the swing axis P at the first opening 36 of the movable body 312, and a third extension portion 44b parallel to the swing axis P at the tip on the side opposite to the support portion 32b. In addition, between the first extension portion 41b and the third extension portion 44b and the support beam 33, a plurality of second extension portions 42b extending from the first movable electrode 38 and the second movable electrode 39 of the movable body 312 toward the support portion 32b are provided.

[0037] With such a configuration, since the side surfaces 31c of the first extending portion 41b and the third extending portion 44b face the side surface 31c of the second extending portion 42b, it functions as a damper for in-plane rotation motion, and the same effect as that of the inertial sensor 1 of the first embodiment can be obtained.

[0038] 4. Fourth Embodiment Next, an inertial measurement device 2000 including the inertial sensors 1 to 1b according to the fourth embodiment will be described with reference to FIGS. 5 and 6. In the following description, a configuration applying the inertial sensor 1 will be exemplified and described.

[0039] The inertial measurement device 2000 (IMU: Inertial Measurement Unit) shown in FIG. 5 is a device that detects the inertial momentum such as the posture and behavior of a moving object such as an automobile or a robot. The inertial measurement device 2000 functions as a so-called six-axis motion sensor including an acceleration sensor that detects accelerations Ax, Ay, and Az in directions along three axes and an angular velocity sensor that detects angular velocities ωx, ωy, and ωz around the three axes.

[0040] The inertial measurement device 2000 is a rectangular parallelepiped having a substantially square planar shape. Further, screw holes 2110 as fixing portions are formed near two vertices located in the diagonal direction of the square. The inertial measurement device 2000 can be fixed to the mounting surface of a mounted object such as an automobile by passing two screws through the two screw holes 2110. Note that, depending on the selection of components and design changes, it is also possible to miniaturize the size to a size that can be mounted on, for example, a smartphone or a digital camera.

[0041] The inertial measurement device 2000 includes an outer case 2100, a joining member 2200, and a sensor module 2300, and has a configuration in which the sensor module 2300 is inserted into the outer case 2100 with the joining member 2200 interposed therebetween. Further, the sensor module 2300 includes an inner case 2310 and a substrate 2320.

[0042] The outer case 2100 has a rectangular parallelepiped shape with a substantially square planar shape, similar to the overall shape of the inertial measurement device 2000, and screw holes 2110 are formed near two vertices located in the diagonal direction of the square, respectively. Further, the outer case 2100 is box-shaped, and a sensor module 2300 is housed inside thereof.

[0043] The inner case 2310 is a member that supports the substrate 2320 and has a shape that fits inside the outer case 2100. Further, the inner case 2310 is formed with a recess 2311 for preventing contact with the substrate 2320 and an opening 2312 for exposing a connector 2330 described later. Such an inner case 2310 is joined to the outer case 2100 via a joining member 2200. Further, the substrate 2320 is joined to the lower surface of the inner case 2310 via an adhesive.

[0044] As shown in FIG. 6, a connector 2330, an angular velocity sensor 2340z for detecting the angular velocity around the Z axis, an acceleration sensor unit 2350 for detecting the acceleration in each of the X-axis, Y-axis, and Z-axis directions, etc. are mounted on the substrate 2320. Further, an angular velocity sensor 2340x for detecting the angular velocity around the X axis and an angular velocity sensor 2340y for detecting the angular velocity around the Y axis are mounted on the side surface of the substrate 2320.

[0045] The acceleration sensor unit 2350 includes at least the inertial sensor 1 for measuring the acceleration in the Z direction described above, and can detect the acceleration in one-axis direction, the acceleration in two-axis direction, or the acceleration in three-axis direction as necessary. Note that the angular velocity sensors 2340x, 2340y, and 2340z are not particularly limited, and for example, a vibrating gyro sensor using the Coriolis force can be used.

[0046] Also, a control IC 2360 is mounted on the lower surface of the substrate 2320. The control IC 2360, which serves as a control unit for performing control based on the detection signal output from the inertial sensor 1, is an MCU (Micro Controller Unit), and incorporates a storage unit including a non-volatile memory, an A / D converter, etc., and controls each part of the inertial measurement device 2000. The storage unit stores a program that defines the order and content for detecting acceleration and angular velocity, a program for digitizing detection data and incorporating it into packet data, and accompanying data. In addition, a plurality of other electronic components are mounted on the substrate 2320.

[0047] Since such an inertial measurement device 2000 uses an acceleration sensor unit 2350 including the inertial sensor 1, an inertial measurement device 2000 with excellent shock resistance and high reliability can be obtained.

Explanation of Reference Numerals

[0048] 1, 1a, 1b... inertial sensors, 6... glass frit, 11... substrate, 12... upper surface, 13... fixing part, 14... recess, 15... inner bottom surface, 16... connection terminal, 17... first fixed electrode, 18... second fixed electrode, 19... third fixed electrode, 21... lid, 22... recess, 30... sensor element, 31... movable body, 31a... upper surface, 31b... lower surface, 31c... side surface, 32... support part, 33... support beam, 34... first connecting part, 35... second connecting part, 36... first opening, 37... second opening, 38... first movable electrode, 39... second movable electrode, 40... third movable electrode, 41... first extending part, 42... second extending part, 43... through hole, 44... third extending part, 2000... inertial measurement device, C1... capacitance, C2... capacitance, P... swing axis, S... internal space.

Claims

1. When three mutually orthogonal axes are defined as the X-axis, Y-axis, and Z-axis, a substrate orthogonal to the Z-axis and provided with a fixed electrode, including a support portion fixed to the substrate, and in the Z-axis direction along the Z-axis, facing the fixed electrode, two planes orthogonal to the Z-axis and having a front-back relationship with each other, and including side surfaces connecting the two planes, and a movable body provided so as to be swingable with respect to the substrate about a swing axis along the X-axis, and including, the movable body is provided with an opening, the support portion is disposed in the opening in a plan view from the Z-axis direction, the movable body, in the plan view, is disposed at a predetermined angle with respect to the swing axis, and a plurality of first extending portions radially extending from the support portion toward the outer edge of the movable body with the support portion as the center, and a plurality of second extending portions extending from the side of the outer edge toward the center of the support portion, and including, each of the plurality of first extending portions and each of the plurality of second extending portions are opposed to each other with side surfaces facing each other with a predetermined interval therebetween, an inertial sensor.

2. In claim 1, the movable body, includes a third extending portion connected to the tip side opposite to the support portion of the first extending portion, an inertial sensor.

3. In claim 2, the third extending portion is parallel to the X-axis, an inertial sensor.

4. In claim 3, the first extending portion is orthogonal to the X-axis, The third extending portion is an inertial sensor parallel to the X axis.

5. In any one of claims 1 to 4, The fixed electrode includes a first fixed electrode and a second fixed electrode, In a plan view from the Z-axis direction, the movable body is A first movable electrode disposed on one side in the Y-axis direction and facing the first fixed electrode, A second movable electrode disposed on the other side in the Y-axis direction and facing the second fixed electrode, A connecting portion connecting the first movable electrode and the second movable electrode, A support beam connecting the support portion and the connecting portion, including The support beam is the swing axis, an inertial sensor.

6. The inertial sensor according to any one of claims 1 to 5, A control unit that performs control based on a detection signal output from the inertial sensor, including An inertial measurement device.

Images