JP7795950B2 - Torque Sensor - Google Patents

Description

Embodiments of the present invention relate to torque sensors that are installed in joints of, for example, robot arms.

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

Japanese Patent Application Laid-Open No. 2018-091813 JP 2017-172983 A

The multiple strain gauges arranged on the strain-generating body are connected to the 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 cutout portion through which the flexible substrate passes. Because a gap is created between the cutout portion and the flexible substrate, the circuit board must be protected from moisture and dust.

Embodiments of the present invention provide a torque sensor that can protect the circuit board from moisture and dust.

The torque sensor of this embodiment comprises 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 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 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, having a first protrusion continuously contacting the side of the notch and having first and second ends, and being tightly fitted within the recess, and a second sealing member disposed between the first and second ends of the first protrusion and having a second protrusion contacting the side of the recess.

FIG. 1 is a perspective view showing a torque sensor according to an embodiment of the present invention. FIG. 2 is a plan view showing a state in which a part of FIG. 1 has been removed. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 2 is a perspective view showing the case shown in FIG. 1 . FIG. 4 is a perspective view showing a first seal member applied to the embodiment. FIG. 10 is a perspective view showing the relationship between a notch provided in the case and a first seal member. FIG. 4 is a perspective view showing a second seal member applied to the embodiment. FIG. 7 is a perspective view showing a state in which a second seal member is attached to the configuration shown in FIG. 6 . FIG. 4 is a perspective view showing the relationship between a first seal member and a second seal member.

Embodiments will be described below with reference to the drawings. In the drawings, identical parts or parts with identical functions are designated by the same reference numerals.

Figures 1, 2, and 3 show the torque sensor 10 according to this embodiment. The configuration of the torque sensor 10 is not limited to this, and it can be applied to torque sensors of various configurations. Furthermore, this embodiment can also be applied to other sensors, such as force sensors that use strain gauges, in addition to torque sensors.

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

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, which serves as multiple beams arranged radially.

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 multiple third structures 13 transmit torque (moment (Mz) shown in Figure 2) between the first structure 11 and the second structure 12.

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

The first structure 11, the second structure 12, and the multiple 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.

The second structure 12 has a hollow portion 12a. The case 14 is attached to the second structure 12 around the hollow portion 12a, and the cover 15 is attached to the case 14. A circuit board 24 shown in Figure 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 and generates a torque detection signal as a sensor signal.

The bushing 16 shown in Figure 1 is provided in part of the cover 15 and holds a cable (not shown). The cable is connected to the processing circuit inside the case 14. The cable supplies power to the processing circuit from an external source and outputs sensor signals processed by the processing circuit to the outside.

Figure 2 shows the strain sensor 20, flexible substrate 23, first sealing member 31, and second sealing member 32. The three first sealing members 31 and components not necessary for explanation have been removed, exposing the components necessary for explanation.

The strain sensor 20 is provided between the first structure 11 and the second structure 12. That is, as described below, 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.

Specifically, an oval recess 30 is integrally formed in the first structure 11 and the second structure 12. However, in the recess 30, the space between the first structure 11 and the second structure 12 is hollow. 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 provided in approximately the center of the portion that corresponds to the second structure 12.

The strain sensor 20 is provided within 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.

The flexure element 21 is, for example, rectangular, and its length is longer than that of the third structure 13 and shorter than the distance between holes 30a and 30b. One longitudinal end of the flexure element 21 is placed on the surface of the first structure 11 within the recess 30, and the other longitudinal end of the flexure element 21 is placed on the surface of the second structure 12 within the recess 30. One end of the flexure element 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 element 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.

The strain gauges 22 are, for example, thin-film resistor elements, and their resistance changes as the strain body 21 deforms. Multiple strain gauges 22 form a bridge circuit (not shown), which detects changes in resistance 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.

Figure 4 shows the case 14 attached to the second structure 12. The case 14 is annular and has multiple 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 the portion of the recess 30 that corresponds to the second structure 12. In Figure 4, the shape of the cutout 14a has three sides, but this is not limited to this and it may be arc-shaped as long as it is possible to pass the flexible substrate 23 through it.

As shown in Figure 3, the flexible substrate 23 is connected to the strain element 21 and circuit board 24 through a notch 14a provided in the case 14. A gap is created 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.

Figure 5 shows an example of the first sealing member 31. The first sealing member 31 is made of an elastic material, such as silicone rubber. However, it is not limited to silicone rubber, and any elastic material will do. The first sealing member 31 functions as a cap that closes the recess 30, and its planar shape is similar to that of the recess 30.

Specifically, one longitudinal end of the first seal member 31 is arc-shaped, and a first protrusion 31a is provided at the other longitudinal end in a position corresponding to the notch 14a of the case 14. The first protrusion 31a protrudes perpendicularly from the surface of the first seal member 31, and the height of the first protrusion 31a is equal to the thickness of the case 14, as shown in Figure 3.

The first protrusion 31a is substantially U-shaped so that it continuously contacts the three sides of the cutout 14a and seals them. Therefore, the first protrusion 31a has a first end 31b and a second end 31c.

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 than the length L2 (shown in Figure 2) of the major axis of the oval recess 30 (L1 > L2). The positions of the tips of the first end 31b and the second end 31c are aligned with the inner diameter of the case 14, as shown in Figure 6.

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

The length L3 between one end of the first seal member 31 and the step 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 less than or equal to the width L5 of the protrusion 32b of the second seal member 32 (described below) (L4 ≦ L5).

As shown in Figures 2 and 3, the first seal member 31 is installed within the recess 30, covers most of the recess 30, and is tightly attached to the side of the recess 30.

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, the first protrusion 31 a is disposed between the notch 14 of the case 14 and the flexible substrate 23, and is in continuous contact with the side surface of the notch 14. This prevents moisture and dust from entering the case 14 through the gap between the notch 14 and the recess 30.

Furthermore, the first end 31b and second end 31c of the first protrusion 31a beyond the step 31d are positioned on the surface of the second structure 12, and the step 31d is in close contact with the side of the recess 30 within the second structure 12. This increases the contact area between the second structure 12 and the first end 31b and second end 31c, thereby preventing moisture and dust from entering the case 14 from the back side of the first end 31b and second end 31c.

Furthermore, as shown in Figure 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. This allows the first seal member 31 to be stably fixed.

Figure 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, it is not limited to silicone rubber and any elastic material will do. The second seal member 32 includes an O-ring 32a and multiple second protrusions 32b.

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

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 placed on the case 14, the O-ring 32a can come into contact with the inner edge of the case 14.

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, as shown in FIG. 3, the surface of the O-ring 32a contacts the inner lower end of the cover 15. 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, sealing the interior of the case 14 and cover 15.

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

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.

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 of the recess 30 provided in the second structure 12 and the surface of the second structure 12.

As shown in Figures 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. As a result, 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 thereby sealed.

As shown in FIG. 3, the surface of the second protrusion 32b inside the ring below the step 32c is in close contact with the surface of the second structure 12, and the side surface below the step 32c is in close contact with the side surface of the recess 30. Furthermore, the tip surface of the second protrusion 32b in the direction intersecting the ring (the back surface of the second protrusion 32b) is in close contact with the surface of the fixing member 40b. This increases the contact area between the second structure 12 and the fixing member 40b and the second protrusion 32b, thereby preventing moisture and dust from entering the case 14 from the back side of the second protrusion 32b.

(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.

Furthermore, 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.

Furthermore, the first end 31b and second end 31c of the first protrusion 31a each have a step 31d that allows them to come into contact with the upper surface of the second structure 12 and the side surface of the recess 30, and the second protrusion 32b also has a step 32c that allows them to come into contact with the upper surface of the second structure 12 and the side surface of the recess 30. This further prevents moisture and dust from entering the case 14 compared to when the first protrusion 31a and second protrusion 32b only come into contact with the side surface of the recess 30.

The second seal member 32 also has multiple second protrusions 32b integrally formed on the O-ring 32a. Therefore, by attaching the O-ring 32a to the second structure 12, the multiple second protrusions 32b can be inserted into the corresponding recesses 30 almost simultaneously. This significantly reduces the number of assembly steps compared to when multiple second protrusions 32b are provided individually.

Furthermore, the present invention is not limited to the above-described embodiments as they are, 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 created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all of the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined.

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

Claims (5)

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: The torque sensor described in claim 1, characterized in that the case is annular, and the second seal member includes an O-ring that can contact the inner edge of the case, and a plurality of the second protrusions provided on the O-ring. The torque sensor described in claim 2, characterized in that the height of the first protrusion within the cutout is equal to the thickness of the case at the cutout, and the lower surface of the O-ring contacts the upper surfaces of the first end and the second end of the first protrusion. The torque sensor described in claim 1, characterized in that the first end and the second end of the first protrusion have a step at a position corresponding to the boundary between the side surface of the recess and the surface of the second structure. The torque sensor described in claim 1, characterized in that the second protrusion has a step at a position corresponding to the boundary between the side surface of the recess and the surface of the second structure.