Torque sensor device

Abstract

The present disclosure provides a torque sensor device (100, 100') comprising a circular body including an annular inner flange (10) and an annular outer flange (20) and a circular middle portion (30) located between the annular inner flange (10) and the annular outer flange (20), wherein the annular inner flange (10) is located closer to the center of the circular body than the annular outer flange (20), and wherein the circular middle portion (30) is a continuous solid portion.

Description

Technical Field

[0001] The invention relates to a torque sensor device which is designed to determine the torque of an object, for example a driven shaft or a robot joint. Background Art

[0002] Accurately detecting the torque of an object (such as a driven shaft or joint) is a problem relevant to a variety of applications. One specific application involves measuring torque during the motion of a robot joint. In a robot joint, loads in various directions act on the joint. To accurately detect torque acting in the direction of rotation on the joint, some compensation mechanism must be provided to exclude loads in directions other than the rotational direction from the measurement process. However, reliably eliminating such loads is very difficult.

[0003] In the prior art, it is known to compensate for loads in directions other than the direction of rotation by means of a Wheatstone circuit and a torque sensor comprising a radially elastic torque transmission portion (see, for example, WO 2018 / 041948 A1).

[0004] However, the known torque sensor device still suffers from a lack of accuracy in torque measurement and a relatively bulky construction, and, when it comes to the purpose of sealing the gearbox with the sensor device, requires an additional component connected to the sensor body.

[0005] Therefore, there is a need for a torque sensor device that allows for accurate torque measurement and can be formed in a compact, lightweight structure. Summary of the Invention

[0006] To address the aforementioned needs, the present invention provides a torque sensor device comprising a circular body including an inner annular flange, an outer annular flange, and a circular intermediate portion located between the inner and outer flanges, wherein the inner annular flange is located closer to the center of the circular body than the outer annular flange. The circular intermediate portion is a continuous solid portion (excluding openings / cutouts) that may, at least in part, have a smaller thickness in the axial direction than the inner and / or outer flanges. In principle, the circular body may be a unitary body or may comprise components that are attached to one another.

[0007] This compact construction with a middle portion extending continuously in radial direction from the inner flange to the outer flange allows the use of the torque sensor device to seal, for example, a gearbox without the need for additional sealing devices such as sealing membranes as required in the prior art. For example, the torque sensor device is suitable for sealing a gearbox of a robot joint.

[0008] According to one embodiment, an inner force application opening is formed in the inner flange, and an outer force application opening is formed in the outer flange. The torque to be measured is transmitted, for example, via a connecting member connected to the inner and outer force application openings, via the rotating shaft and a static component involved. Thus, the torque applied between the inner and outer flanges can be measured.

[0009] A plurality of measuring transducers can be formed in pairs in and / or on the circular middle part. The measuring transducers can include or consist of at least one of a silicon strain gauge, a foil strain gauge and a thin-layer strain gauge. In particular, the pair of measuring transducers can be arranged symmetrically with respect to the axial direction of the torque sensor device (an axis extending through the center of the circular body in a direction perpendicular to the main surface of the circular body). The strain gauges can sense shear strains, in particular, being oriented at an angle of 45° relative to a radial axis extending through the center of the circular body in a direction parallel to the main surface of the circular body, the strain gauges of a pair of strain gauges being arranged symmetrically with respect to the radial axis. The pair of measuring transducers positioned relative to each other defines a measuring channel. This arrangement allows the effects of tilting and radial and axial loads on the torque measurement to be eliminated or significantly reduced, and thus allows the accuracy of the measurement results obtained by the torque sensor device of the present invention to be increased (see also the detailed description below).

[0010] According to a specific embodiment, the plurality of measuring transducers includes at least four pairs of measuring transducers, wherein the two measuring transducers in each pair are positioned symmetrically with respect to an axis (radial axis) extending through the center of the circular body in a direction parallel to the main surface of the circular body. This arrangement can be advantageous in terms of measurement accuracy by reliably suppressing the effects of radial and axial loads and tilt.

[0011] Four pairs of measuring transducers (e.g., exactly four pairs of measuring transducers) can be arranged such that, for each of the four pairs of measuring transducers, the two measuring transducers in the pair are positioned symmetrically with respect to a first axis extending through the center of the circular body in a direction parallel to the main surface of the circular body and spaced 90° apart from a second axis in the circumferential direction, and the two measuring transducers in an adjacent pair of measuring transducers are positioned symmetrically with respect to the second axis extending through the center of the circular body in a direction parallel to the main surface of the circular body. This arrangement can improve measurement accuracy because the effects of radial and axial loads and tilt are reliably suppressed.

[0012] With a view to reducing the influence of radial loads on the torque measurement of the object under consideration, it may be advantageous to form a tapered / thinned portion in the circular middle portion, said tapered / thinned portion not extending completely through the thickness direction of the middle portion, i.e., along an axis extending through the center of the circular body in a direction perpendicular to the main surfaces of the circular body. The tapered / thinned portion is, for example, closer to the outer flange than to the inner flange and has a longer extension in the circular direction than in the radial direction.

[0013] In particular, the center of each narrowed portion in the circumferential direction can be spaced 22.5° in the circumferential direction from an axis extending through the center of the circular body in a direction parallel to the main surface of the circular body, and two measuring transducers in a pair of measuring transducers are symmetrically positioned relative to the axis (the axis defines the measuring channel).

[0014] As an alternative to or in addition to the narrowed portion, a radially elastic region may be provided in the middle portion, for example closer to the inner flange than to the outer flange or substantially midway (in the radial direction) between the inner and outer flanges. The radially elastic region may comprise or consist of a groove formed in the middle portion of the circular body.

[0015] Torque measurement using the torque sensor device of the present invention can be based on strain gauges representing the measuring transducers. The strain gauges can be connected to a Wheatstone bridge circuit, which becomes unbalanced when torque is applied and outputs a voltage proportional to the applied torque (caused by the change in resistance of the strain gauges). Thus, according to one embodiment, the torque sensor device of the present invention includes a first printed circuit board arranged on a central portion and including the Wheatstone bridge circuit electrically connected to the measuring transducers. The first printed circuit board may also include a DC or AC excitation source for the Wheatstone bridge circuit.

[0016] Furthermore, the torque sensor arrangement may include a second printed circuit board arranged above the first printed circuit board, and the second printed circuit board may include circuitry for signal conditioning, in particular, components for analog-to-digital conversion and / or amplification of the signal provided by the Wheatstone bridge circuit of the first printed circuit board. The second printed circuit board may cover the first printed circuit board in order to protect it and sensitive circuitry formed on the first printed circuit board and located on a bottom side of the second printed circuit board facing the first printed circuit board.

[0017] Furthermore, a robot, in particular a collaborative robot, is provided, comprising a joint, wherein the joint comprises a gearbox, and wherein the robot further comprises a torque sensor device according to one of the above embodiments. In particular, the torque sensor device can be positioned to seal the gearbox of the robot joint.

[0018] In addition, a method for measuring the torque of a shaft positioned in a gearbox, in particular a gearbox of a joint of a robot, is provided, the method comprising attaching a torque sensor device according to one of the above-described embodiments to the gearbox so that the gearbox is sealed, and measuring the torque by means of the torque sensor device of the sealed gearbox. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Further features and exemplary embodiments and advantages of the present disclosure will be explained in detail with reference to the accompanying drawings. It should be understood that the present disclosure should not be interpreted as being limited by the description of the following embodiments. It should also be understood that some or all of the features described below may also be combined in alternative ways. In the accompanying drawings:

[0020] Figure 1A and Figure 1B Torque sensor devices according to embodiments of the present invention are shown, each comprising an inner flange, an outer flange, and a solid middle portion extending continuously from the inner flange to the outer flange in a radial direction.

[0021] Figure 2 Shown Figure 1A or 1B, and includes a first printed circuit board.

[0022] Figure 3 Shown Figure 2 The torque sensor device includes a second printed circuit board.

[0023] Figures 4A to 4D Shown is the torque measurement with compensation for tilt, axial load and radial load.

[0024] Figure 5 Another embodiment of a torque sensor device is shown, which includes a narrowed region in a mid-portion. DETAILED DESCRIPTION

[0025] The present invention provides a torque sensor device that allows for precise measurement of the torque of an object, such as a rotating shaft or a robot joint, wherein the measurement is not significantly affected by axial or radial loads or tilting moments. In particular, the torque sensor device can be used for sealing purposes, such as for sealing gearboxes. For example, the torque sensor device is suitable for measuring the torque of a joint of a (collaborative) robot. For example, torque control based on the measurements performed by the torque sensor device can be advantageously implemented in the robot to facilitate robot-human interaction.

[0026] Figure 1A and 1BAn exemplary embodiment of a torque sensor device 100 of the present invention is shown. The torque sensor device 100 comprises an inner flange 10 and an outer flange 20. An intermediate portion 30 extends radially continuously from the inner flange 10 to the outer flange 20. The inner flange 10, the outer flange 20 and the intermediate portion 30 form a circular body, for example a one-piece circular body. The circular body can consist of or include, for example, steel, aluminum or an aluminum alloy. When a one-piece circular body is not provided, different parts of the circular body can be made of different materials. No opening extending through the entire material is formed in the intermediate portion 30. Therefore, the intermediate portion 30 can be used as a seal, for example, for sealing a gearbox.

[0027] The middle portion 30 may include sub-portions 30a and 30b, which may be separated from each other by a separator 30c. The separator 30c may be an edge portion, or it may be a Figure 1B Circumferential groove 30c is shown. Such circumferential groove 30c can serve as a radial elastic portion, which is arranged to suppress the influence of radial loads during torque measurement (see also description below).

[0028] A plurality of pairs of measuring transducers 40 are formed on the middle portion 30, for example, on the sub-portion 30a, as shown in FIG. Figure 1A The torque sensor device 100 is shown in a top view of the main surface. The measuring transducers 40 are arranged symmetrically about an axis (axial axis) perpendicular to the main surface and passing through the center of the circular body. In principle, the measuring transducers 40 can be strain-sensitive transducers, in particular strain gauges.

[0029] In addition, internal force application openings 11 and 12 having different sizes are formed in the inner flange 10, and external force application openings 21 and 22 having different sizes are formed in the outer flange 20. The internal and external force application openings 11, 12, 21, and 22 may be holes extending in the axial direction. The holes are open on at least one side or the corresponding flange and may have any suitable geometric shape, such as a circular or polygonal cross-section.

[0030] Figure 2 Shown Figure 1A A torque sensor according to claim 1 or 1B is provided, wherein a first printed circuit board 50 including some circuit devices (e.g., resistors and capacitors) and a connector 55 for connection to another printed circuit board 60 (see below) are provided on the middle part 30. The measuring transducers 40 can be connected to the middle part 30 via the included measuring portion, and they can have free connection portions for connection to the first printed circuit board 50 and thus to the circuit devices of the first printed circuit board 50. In particular, the first printed circuit board 50 can include Wheatstone bridge elements (resistors) for converting the applied torque into a voltage output signal, as is known in the art, and depending on the actual application, a half or full Wheatstone bridge can be used.

[0031] like Figure 3 As shown, the first printed circuit board 50 can be covered by a second printed circuit board 60. The second printed circuit board 60 protects the measuring transducer 40 and the circuit arrangement 55 from environmental influences. In particular, the second printed circuit board 60 can have sensitive circuit arrangements on the bottom (facing the first printed circuit board 50) and a connector 65 for connecting to the first printed circuit board. The second printed circuit board 60 is configured for signal conditioning, for example, for analog-to-digital conversion of a voltage output signal provided by the circuit arrangement of the first printed circuit board 50. Signal conditioning can also include amplifying the voltage output signal provided by the circuit arrangement of the first printed circuit board 50.

[0032] As already mentioned, the measuring transducers 40 can be arranged around an axial axis passing through the center of the circular body in a direction perpendicular to the main surface of the circular body. For example, one or two pairs of measuring transducers 40 can be arranged 90° apart from one or two adjacent pairs of measuring transducers 40 in the circumferential direction. Figures 4A to 4D An embodiment is shown in which the strain gauges 40 are arranged symmetrically in pairs about an axial axis extending through the center of the circular body in a direction perpendicular to the main surface of the circular body, and in which two measurement channels C are defined by opposing pairs of strain gauges 40 spaced 90° from one channel to the other in the circumferential direction. Each measurement channel C passes through the center of a particular pair of strain gauges 40 disposed opposite each other.

[0033] Torque (by Figure 4A ) can be measured based on differential strains +ε and −ε, where +ε is experienced by one of the pair of strain gauges 40 and −ε is experienced by the other of the pair of strain gauges 40. The strain gauges 40 are connected to a Wheatstone bridge circuit formed on a printed circuit board 50. Due to the selected geometry of the arrangement of the strain gauges 40 (and the corresponding structure of the Wheatstone bridge circuit), the voltage output signal provided by the Wheatstone bridge circuit due to the applied torque (the strain in the middle portion of the torque sensor device on which the strain gauges 40 are provided for sensing strain) is proportional to Σε=4ε+4ε=8ε, that is, a sufficiently high desired voltage output signal can be provided.

[0034] On the other hand, Figures 4B to 4D As shown, disturbances due to tilt as well as axial and radial loads can be greatly suppressed. Figure 4BThe arrows in represent the tilt that may be applied to the torque sensor device. The tilt applied to the torque sensor device 100 results in different strains +ε1 and +ε2, +ε2 and +ε1, -ε2 and -ε1, and -ε1 and -ε2, respectively, of the four pairs of strain gauges 40 defining the measurement channel C. Therefore, the strain caused by the tilt is compensated by the selected geometry of the arrangement of the strain gauges 40 (and the corresponding structure of the Wheatstone bridge circuit): Σε = ε1 - ε1 + ε2 - ε2 = 0, and therefore does not contribute to the voltage output signal proportional to the applied torque, as shown in FIG. Figure 4A shown.

[0035] In order to achieve accurate torque measurement, it is also necessary to compensate for any axial load. Figure 4C As shown (arrows indicate applied axial loads), this compensation can also be achieved by the selected geometry of the arrangement of the strain gauges 40 (and the corresponding structure of the Wheatstone bridge circuit). The axial load (due to the axially symmetrical arrangement of the strain gauges 40) results in a strain +ε at each strain gauge 40, so the net effect is zero: Σε = 4ε - 4ε. With regard to the compensation of tilt and axial loads, it may be advantageous to position the strain gauges 40 at the same radial distance from the inner flange 10 and the outer flange 20.

[0036] exist Figure 4D FIGURE 5 illustrates the compensation of radial loads by a selected geometry of the arrangement of strain gauges 40 (and the corresponding configuration of the Wheatstone bridge circuit). Arrows indicate applied radial loads. For the four pairs of strain gauges 40 defining two measurement channels C, radial loads result in different strains, respectively: -ε1 and +ε2, +ε2 and -ε1, -ε1 and +ε2, and +ε2 and -ε1. Consequently, the contribution to the voltage output signal of the Wheatstone bridge circuit of the printed circuit board 50 is proportional to ωε = -2ε1 + 2ε2 + 2ε1 - 2ε2 = 0.

[0037] However, it must be noted that if some radial load is applied in a radial direction that is offset by 22.5° in the circumferential direction relative to the measuring channel C, it may not be possible to achieve the desired result. Figure 4D In this case, Σε≠0 may occur, which has a negative impact on the accuracy of torque measurement. In order to alleviate this problem, a radial elastic portion is provided in the middle part 30 of the torque sensor device 100. The radial elastic portion is implemented by the groove 30c, as shown in FIG. Figure 1B The radial elastic portion can be machined at the top or bottom of the middle portion 30 .

[0038] According to another method, the non-compensation problem of the radial load applied in the radial direction offset by 22.5° in the circumferential direction relative to the measuring channel C is addressed, as Figure 5As shown, a narrowed portion 70 may be formed in the middle portion 30 of the torque sensor device 100'. The narrowed portion 70 may be machined at the top or bottom of the middle portion 30. Figure 5 In the embodiment shown, the narrowed outer portion 70 is arranged closer to the outer flange 20 than to the inner flange 10 at a position of 22.5°. The narrowed portion 70 has a larger dimension in the circumferential direction than in the radial direction.

[0039] Experiments have shown that this arrangement of the narrowed portion 70 significantly reduces any contribution of the corresponding radial load to Σε and thus the measurement result. It must be noted that the narrowed portion 70 does not have to pass through the middle portion 30 in order not to reduce the advantageous sealing properties of the torque sensor device 100 ′.

[0040] According to the above-described embodiment, a torque sensor device that operates precisely and has a compact design, reduced height, and low cost compared to the prior art can be provided. This device can seal a gearbox without requiring any additional sealing devices and provides measurement of at least two channels. In particular, all of the measurement transducers involved can be formed on the same surface of the intermediate portion 30 of the above-described torque sensor device 100 or 100 ′.

Claims

1. A torque sensor device (100, 100'), comprising: A circular body comprising an annular inner flange (10), an annular outer flange (20), and a circular middle portion (30) located between the annular inner flange (10) and the annular outer flange (20). wherein the annular inner flange (10) is positioned substantially closer to the center of the circular body than the annular outer flange (20) and includes inner force application openings (11, 12) formed in the annular inner flange, the inner force application openings (11, 12) being substantially closer to the center of the circular body than the circular middle portion (30), the annular outer flange (20) including outer force application openings (21, 22) formed in the annular outer flange, and the circular middle portion (30) including an inner sub-portion (30a), an outer sub-portion (30b) and a circumferential groove (30c), the circumferential groove being used to suppress the influence of radial loads and to separate the inner sub-portion (30a) and the outer sub-portion (30b) from each other; wherein a plurality of measuring transducers (40) are formed in pairs in and / or on the inner sub-portion (30a) of the circular middle portion (30); and The circular middle portion (30) is a continuous solid portion.

2. The torque sensor device (100, 100') according to claim 1, wherein: The measuring transducers (40) are arranged axially symmetrically with respect to an axis extending through the center of the circular body in a direction perpendicular to the main surface of the circular body.

3. The torque sensor device (100, 100') according to claim 2, wherein: The measuring transducers (40) include at least four pairs of measuring transducers (40), wherein the two measuring transducers (40) in each pair of measuring transducers (40) are positioned symmetrically with respect to an axis extending through the center of the circular body in a direction parallel to the main surface of the circular body.

4. The torque sensor device (100, 100') according to claim 3, wherein: Four pairs of measuring transducers (40) are provided, and for each of the four pairs of measuring transducers (40), the two measuring transducers (40) in the pair are symmetrically positioned relative to a first axis, the first axis extending through the center of the circular body in a direction parallel to the main surface of the circular body, and the first axis and the second axis are kept 90° apart in the circumferential direction, and the two measuring transducers (40) in an adjacent pair of measuring transducers (40) are symmetrically positioned relative to the second axis, and the second axis extends through the center of the circular body in a direction parallel to the main surface of the circular body.

5. The torque sensor device (100, 100') according to claim 1, wherein The circular middle portion (30) includes a narrowing portion (70) that does not extend completely through the middle portion (30) in a direction along an axis extending through the center of the circular body in a direction perpendicular to the main surface of the circular body, wherein the narrowing portion (70) is located closer to the outer flange (20) than to the inner flange (10) and has a longer extension in the circular direction than in the radial direction.

6. The torque sensor device (100, 100') according to claim 5, wherein: The center of each narrowed portion (70) in the circumferential direction is spaced 22.5° in the circumferential direction from an axis extending through the center of the circular body in a direction parallel to the main surface of the circular body, and the two measuring transducers (40) of the pair of measuring transducers (40) are symmetrically positioned relative to the axis.

7. The torque sensor device (100, 100') according to claim 1, wherein: The middle portion (30) includes a radial elastic region that is located closer to the inner flange (10) than to the outer flange (20) or is located midway between the inner flange (10) and the outer flange (20) in the radial direction.

8. The torque sensor device (100, 100') according to claim 1, further comprising a first printed circuit board (50) arranged on the middle part (30), and comprising a Wheatstone bridge circuit electrically connected to the measuring transducer (40).

9. The torque sensor device (100, 100') according to claim 8, further comprising a second printed circuit board (60) arranged above the first printed circuit board (50), and the second printed circuit board comprises circuitry for signal conditioning.

10. The torque sensor device (100, 100') according to claim 1, wherein The measuring transducer (40) comprises a silicon strain gauge or a foil strain gauge.

11. The torque sensor device (100, 100') according to claim 1, wherein: The measuring transducer (40) comprises a thin-layer strain gauge.

12. The torque sensor device (100, 100') according to claim 7, wherein: The radially elastic region includes a groove.

13. The torque sensor device (100, 100') according to claim 9, wherein: The second printed circuit board comprises means for analog-to-digital conversion and / or amplification of the signal provided by the Wheatstone bridge circuit of the first printed circuit board.

14. A robot comprising a joint, wherein the joint comprises a gearbox, and the robot further comprises a torque sensor device (100, 100') according to any one of claims 1 to 13.

15. The robot according to claim 14, wherein: The torque sensor arrangement (100, 100') is positioned to seal the gearbox.

16. The robot according to claim 14, wherein: The robot is a collaborative robot.

17. A method for measuring the torque of a shaft positioned in a gearbox, the method comprising attaching a torque sensor device (100, 100') according to any one of claims 1 to 13 to the gearbox such that the gearbox is sealed, and measuring the torque by means of the torque sensor device (100, 100') of the sealed gearbox.

18. The method according to claim 17, wherein: The gearbox is a gearbox for a joint of the robot.

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