Torque Sensor

Abstract

To provide a torque sensor capable of protecting a circuit board from moisture and dust.SOLUTION: Recesses 30 are provided in a first structure 11 and a second structure 12. Strain sensors 20 are provided within the recesses between the first structure and the second structure. A flexible substrate 23 is connected to the strain sensor. A case 41 is disposed on the surface of the second structure and has notches 14a into which flexible substrates are inserted. A first sealing member 31 is arranged between the notch and the flexible substrate within the notch, continuously contacts the side surface of the notch, includes a first protrusion 31a having a first end 31b and a second end 31c, and is tightly fitted into the recess. A second seal member 32 has second protrusions 32b disposed within the notches and contacting the first and second ends of the first protrusions and the recesses.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a torque sensor provided in a joint of, for example, a robot arm. [Background technology]

[0002] The torque sensor has a first structure to which torque is applied, a second structure to which torque is output, a plurality of third structures connecting the first structure and the second structure, and a plurality of strain generating bodies provided between the first structure and the second structure, with a plurality of strain gauges arranged on the surfaces of these strain generating bodies (see, for example, Patent Document 1 and Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-091813 [Patent Document 2] Japanese Patent Application Publication No. 2017-172983 Summary of the Invention [Problem to be solved by the invention]

[0004] The multiple strain gauges arranged on the strain generating element are connected to a circuit board using a flexible substrate. The circuit board is placed inside a case provided in the second structure. For this reason, the case has a notch through which the flexible substrate passes. Because a gap is created between the notch and the flexible substrate, the circuit board needs to be protected from moisture and dust.

[0005] The embodiments of the present invention provide a torque sensor capable of protecting a circuit board from moisture and dust. [Means for solving the problem]

[0006] The torque sensor of this embodiment includes a first structure, a second structure, a plurality of third structures connected between the first structure and the second structure, recesses provided in the first structure and the second structure between adjacent third structures, a strain sensor provided within the recesses between the first structure and the second structure, a flexible substrate having a first end connected to the strain sensor, a case disposed on the surface of the second structure and having a notch into which the flexible substrate is inserted, a first sealing member disposed between the notch and the flexible substrate within the notch, the first sealing member having a first protrusion that is in continuous contact with a side surface of the notch and has a first end and a second end, and is tightly fitted within the recess, and a second sealing member disposed between the first end and the second end of the first protrusion and having a second protrusion that is in contact with a side surface of the recess. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing a torque sensor according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing a state in which a part of FIG. 1 has been removed. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 2 is a perspective view showing the case shown in FIG. 1 . [Figure 5] FIG. 3 is a perspective view showing a first seal member applied to the embodiment. [Figure 6] FIG. 4 is a perspective view showing the relationship between a notch provided in the case and a first seal member. [Figure 7] FIG. 4 is a perspective view showing a second seal member applied to the embodiment. [Figure 8] 7 is a perspective view showing a state in which a second seal member is attached to the configuration shown in FIG. 6. FIG. [Figure 9] FIG. 4 is a perspective view showing the relationship between a first seal member and a second seal member. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same parts or parts having the same functions are designated by the same reference numerals.

[0009] 1, 2, and 3 show a torque sensor 10 according to this embodiment. The configuration of the torque sensor 10 is not limited to this, and the torque sensor 10 can be applied to torque sensors of various configurations. Furthermore, the present embodiment can be applied not only to torque sensors, but also to force sensors using strain gauges, etc.

[0010] 1, 2, and 3, the torque sensor 10 includes a first structure 11, a second structure 12, a plurality of third structures 13, a case 14, a cover 15, a bushing 16, a plurality of strain sensors 20, a plurality of flexible substrates 23, a circuit board 24, a plurality of first sealing members 31 for waterproofing and dustproofing, a plurality of second sealing members 32 for waterproofing and dustproofing, and the like.

[0011] The first structure 11 and the second structure 12 are annular, and the diameter of the second structure 12 is smaller than the diameter of the first structure 11. The second structure 12 is arranged concentrically with the first structure 11, and the first structure 11 and the second structure 12 are connected by a third structure 13 as a plurality of beams arranged radially.

[0012] The first structure 11 is connected to, for example, a measurement object, and the second structure 12 is connected to another structure (not shown). The plurality of third structures 13 transmit torque (moment (Mz) shown in FIG. 2) between the first structure 11 and the second structure 12.

[0013] When this embodiment is applied to a force sensor, the first structure 11, the second structure 12, and the third structure 13 deform three-dimensionally, and detect forces (Fx, Fy, Fz) and moments (Mx, My, Mz) with respect to three orthogonal axes (x, y, z).

[0014] The first structure 11, the second structure 12, and the plurality of third structures 13 are made of metal, such as stainless steel, but materials other than metal can also be used as long as they have sufficient mechanical strength to withstand the applied torque.

[0015] The second structure 12 has a hollow portion 12a. A case 14 is attached to the second structure 12 around the hollow portion 12a, and a cover 15 is attached to the case 14. A circuit board 24 shown in FIG. 3 is provided inside the case 14. A processing circuit is provided on the circuit board 24, and the processing circuit processes the electrical signal supplied from the strain sensor 20 to generate a torque detection signal as a sensor signal.

[0016] 1 is provided in a part of the cover 15 and holds a cable (not shown). The cable is connected to a processing circuit inside the case 14. The cable supplies power to the processing circuit from an external source and outputs a sensor signal processed by the processing circuit to the outside.

[0017] In order to show the strain sensor 20, the flexible substrate 23, the first sealing member 31, and the second sealing member 32, the three first sealing members 31 and components not necessary for explanation have been removed from Figure 2, exposing the components necessary for explanation.

[0018] The strain sensor 20 is provided between the first structure 11 and the second structure 12. That is, as will be described later, one end of the strain sensor 20 is joined to the first structure 11, and the other end of the strain sensor 20 is joined to the second structure 12.

[0019] Specifically, an oval recess 30 is integrally formed in the first structure 11 and the second structure 12. However, in the recess 30, a hollow is formed between the first structure 11 and the second structure 12. The shape of the recess 30 is not limited to an oval shape. A hole 30a is provided in approximately the center of the portion of the recess 30 that corresponds to the first structure 11, and a hole 30b is also provided in approximately the center of the portion that corresponds to the second structure 12.

[0020] The strain sensor 20 is provided in the recess 30 between the first structure 11 and the second structure 12. The strain sensor 20 includes a strain element 21 made of, for example, metal, and a plurality of strain gauges 22 as sensor elements arranged on the surface of the strain element 21.

[0021] The flexure body 21 is, for example, rectangular, and the length of the flexure body 21 is longer than the length of the third structure 13 and shorter than the distance between the holes 30a and 30b. One longitudinal end of the flexure body 21 is placed on the surface of the first structure 11 within the recess 30, and the other longitudinal end of the flexure body 21 is placed on the surface of the second structure 12 within the recess 30. One end of the flexure body 21 is fixed to the first structure 11 by a fixing member 40a arranged within the recess 30 and a screw 41a inserted into the hole 30a from the back surface of the first structure 11 and threaded into the screw hole 40c. The other end of the flexure body 21 is fixed to the second structure 12 by a fixing member 40b arranged within the recess 30 and a screw 41b inserted into the hole 30b from the back surface of the second structure 12 and threaded into the screw hole 40d.

[0022] The strain gauges 22 are, for example, thin-film resistor elements, and their resistance value changes as the strain body 21 deforms. The multiple strain gauges 22 form a bridge circuit (not shown), which detects the change in resistance value as an electrical signal. The multiple strain gauges 22 are connected to one end of a flexible substrate 23 provided in the center of the strain body 21. The other end of the flexible substrate 23 is connected to a processing circuit within the case 14. The electrical signal output from the bridge circuit is supplied to the processing circuit via the flexible substrate 23, and the processing circuit generates a torque detection signal as a sensor signal.

[0023] FIG. 4 shows the case 14 attached to the second structure 12. The case 14 is annular and has a plurality of cutouts 14a on the inside. Each cutout 14a is provided at a position corresponding to a recess 30 provided in the first structure 11 and the second structure 12. Specifically, the cutout 14a is provided in a portion of the recess 30 corresponding to the second structure 12. In FIG. 4, the shape of the cutout 14a has three sides, but is not limited to this and may be an arc shape as long as it allows the flexible substrate 23 to pass through.

[0024] 3, the flexible substrate 23 is connected to the strain element 21 and the circuit board 24 through a notch 14a provided in the case 14. A gap is generated between the notch 14a and the flexible substrate 23. A first seal member 31 and a second seal member 32 are attached to close this gap.

[0025] 5 shows an example of the first seal member 31. The first seal member 31 is made of an elastic material, such as silicone rubber. However, the material is not limited to silicone rubber, and any elastic material may be used. The first seal member 31 functions as a cap that closes the recess 30, and has a planar shape similar to that of the recess 30.

[0026] Specifically, one longitudinal end of first seal member 31 is arc-shaped, and a first protrusion 31a is provided at the other longitudinal end at a position corresponding to notch 14a of case 14. First protrusion 31a protrudes perpendicularly from the surface of first seal member 31, and the height of first protrusion 31a is equal to the thickness of case 14, as shown in FIG.

[0027] The first protrusion 31a is substantially U-shaped so as to continuously contact the three side surfaces of the cutout 14a and seal the three side surfaces of the cutout 14a, and therefore has a first end 31b and a second end 31c.

[0028] The length L1 between one end of the first seal member 31 and the tip of the first end 31b or the second end 31c is longer (L1>L2) than the length L2 (shown in FIG. 2) of the major axis of the oval recess 30. The positions of the tips of the first end 31b and the second end 31c are aligned with the position of the inner diameter of the case 14, as shown in FIG.

[0029] The first end 31b and the second end 31c each have a step 31d on the back surface thereof. The step 31d is provided at a position corresponding to the boundary between the side surface of the recess 30 provided in the second structure 12 and the surface of the second structure 12.

[0030] The length L3 between one end of the first seal member 31 and the step portion 31d is shorter than L1 and approximately equal to L2 (L1>L3≈L2). The length L4 between the first end 31b and the second end 31c is equal to or shorter than the width L5 of the protrusion 32b of the second seal member 32 (described later) (L4≦L5).

[0031] As shown in FIGS. 2 and 3, the first seal member 31 is mounted in the recess 30, covers most of the recess 30, and is in close contact with the side surface of the recess 30.

[0032] FIG. 6 shows a state in which the first seal member 31 is installed in the recess 30 and the case 14 is attached to the second structure 12. In this state, first protrusion 31a is disposed between notch 14 of case 14 and flexible substrate 23, and is in continuous contact with the side surface of notch 14. This prevents moisture and dust from entering case 14 through the gap between notch 14 and recess 30.

[0033] Furthermore, the portions of first end 31b and second end 31c of first projection 31a beyond step 31d are positioned on the surface of second structure 12, and step 31d is in close contact with the side surface of recess 30 in second structure 12. Therefore, the contact area between second structure 12 and first end 31b and second end 31c can be increased, making it possible to prevent moisture and dust from entering case 14 from the backside of first end 31b and second end 31c.

[0034] 3, when the first seal member 31 is installed in the recess 30, the back surface of the first seal member 31 is in close contact with the upper surfaces of the fixing members 40a and 40b, thereby enabling the first seal member 31 to be stably fixed.

[0035] 7 shows an example of the second seal member 32. The second seal member 32 is made of an elastic material, such as silicone rubber. However, the material is not limited to silicone rubber and may be any elastic material. The second seal member 32 includes an O-ring 32a and a plurality of second protrusions 32b.

[0036] The inner diameter D1 of the O-ring 32a is slightly shorter than the distance between the two recesses 30 that are 180° apart, as shown in Fig. 2. In other words, the inner diameter D1 of the O-ring 32a is equal to the inner diameter of the case 14, as shown in Fig. 4.

[0037] The outer diameter D2 of the O-ring 32a is longer than the distance between two recesses 30 that are 180° apart. In other words, as shown in Fig. 4, the outer diameter D2 of the O-ring 32a is larger than the inner diameter of the case 14. Therefore, when the O-ring 32a is placed on the case 14, it can come into contact with the inner edge of the case 14.

[0038] Specifically, the back surface of the O-ring 32a (the portion other than the second protrusion 32b) contacts the inner edge of the case 14 and the upper surfaces of the first end 31b and second end 31c of the first protrusion 31. Furthermore, the front surface of the O-ring 32a contacts the inner lower end of the cover 15, as shown in FIG. 3. Therefore, by attaching the cover 15 to the case 14, the first end 31b and second end 31c of the first seal 31 and the second protrusion 32b of the second seal member are pressed against the second structure 12 via the O-ring 32a, and the interiors of the case 14 and the cover 15 are sealed.

[0039] The multiple second protrusions 32b are provided at positions corresponding to the cutouts 14a of the case 14. The length L5 of each second protrusion 32b in the direction along the ring is equal to or greater than the length L4 between the first end 31b and the second end 31c of the first protrusion 31a (L5≧L4). In other words, the length L5 of each second protrusion 32b in the direction along the ring is the length at which both ends of the second protrusion 32b in the longitudinal direction come into close contact with the first end 31b and the second end 31c when the second protrusion 32b is inserted between the first end 31b and the second end 31c.

[0040] The length L6 of each second protrusion 32b in the direction intersecting the ring is a length that allows the tip of the second protrusion 32b to contact the upper surface of the fixing member 41b provided on the second structure 12 when the second protrusion 32b is inserted into the recess 30.

[0041] A step 32c is provided on the inside of each second protrusion 32b. The step 32c is provided at a position corresponding to the boundary between the side surface of the recess 30 provided in the second structure 12 and the surface of the second structure 12.

[0042] 8 and 9, when each second protrusion 32b of the second seal member 32 is inserted into each recess 30, both ends of the second protrusion 32b in the longitudinal direction along the ring are tightly attached to the first end 31b and the second end 31c. Therefore, the flexible substrate 23 is surrounded by the first protrusion 31a of the first seal member 31 and the second protrusion 32b of the second seal member 32 and is sealed thereby.

[0043] 3, the surface of second protrusion 32b inside the ring from step 32c is in close contact with the surface of second structure 12, and the side surface below step 32c is in close contact with the side surface of recess 30. Furthermore, the tip surface of second protrusion 32b in the direction intersecting the ring (the back surface of second protrusion 32b) is in close contact with the surface of fixing member 40b. Therefore, the contact area between second structure 12 and fixing member 40b and second protrusion 32b can be increased, making it possible to prevent moisture and dust from entering case 14 from the back side of second protrusion 32b.

[0044] (Effects of the embodiment) According to the torque sensor 10 of this embodiment, most of the recess 30 is covered by the first seal member 31, and the cutout portion 14a of the case 14 through which the flexible substrate 23 passes is sealed by the first protrusion 31a of the first seal member 31 and the second protrusion 32b of the second seal member 32. This makes it possible to prevent moisture and dust from entering the case 14, and allows the torque sensor 10 to operate stably.

[0045] Moreover, when placed in the case 14, the O-ring 32a of the second seal member 32 is tightly fitted to the inner periphery of the case 14. This prevents moisture and dust from entering the case 14 from the inner periphery.

[0046] Furthermore, first end 31b and second end 31c of first protrusion 31a each have step 31d so as to be able to come into contact with the upper surface of second structure 12 and the side surface of recess 30, and second protrusion 32b also has step 32c so as to be able to come into contact with the upper surface of second structure 12 and the side surface of recess 30. Therefore, compared to a case in which first protrusion 31a and second protrusion 32b come into contact only with the side surface of recess 30, it is possible to further prevent moisture and dust from entering case 14.

[0047] Furthermore, the second seal member 32 has a plurality of second protrusions 32b integrally formed on the O-ring 32a. Therefore, by attaching the O-ring 32a to the second structure 12, the plurality of second protrusions 32b can be inserted into the corresponding recesses 30 almost simultaneously. Therefore, it is possible to significantly reduce the number of assembly steps compared to when the plurality of second protrusions 32b are provided individually.

[0048] Furthermore, the present invention is not limited to the above-described embodiments, and in the implementation stage, the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0049] 11...first structure, 12...second structure, 13...third structure, 14...case, 14a...notch portion, 20...strain sensor, 21...flexible body, 22...strain gauge, 23...flexible substrate, 31...first sealing member, 31a...first protrusion, 32...second sealing member, 32a...O-ring, 32b...second protrusion.

Claims

1. a first structure; a second structure; and a plurality of third structures connected between the first structures and the second structures; a recess provided in the first structure and the second structure between adjacent third structures; a strain sensor provided in the recess between the first structure and the second structure; a flexible substrate having a first end connected to the strain sensor; a case disposed on a surface of the second structure and having a notch into which the flexible substrate is inserted; a first sealing member disposed between the notch and the flexible substrate within the notch, continuously contacting a side surface of the notch, and including a first protrusion having a first end and a second end, the first sealing member being tightly fitted within the recess; a second seal member having a second protrusion disposed between the first end and the second end of the first protrusion and contacting a side surface of the recess; A torque sensor comprising:

2. 2. The torque sensor according to claim 1, wherein the case is annular, and the second seal member includes an O-ring that can contact an inner edge portion of the case, and a plurality of the second protrusions provided on the O-ring.

3. 3. The torque sensor according to claim 2, wherein a height of the first protrusion within the notch is equal to a thickness of the case at the notch, and a lower surface of the O-ring contacts upper surfaces of the first end and the second end of the first protrusion.

4. 2. The torque sensor according to claim 1, wherein the first end and the second end of the first protrusion have a step portion at a position corresponding to a boundary between a side surface of the recess and a surface of the second structure.

5. 2. The torque sensor according to claim 1, wherein the second protrusion has a step at a position corresponding to a boundary between a side surface of the recess and a surface of the second structure.

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