JP7706979B2 - Sensors - Google Patents

Description

An embodiment of the present invention relates to a sensor that detects force.

Torque sensors are known in which a bridge circuit including multiple strain sensors detects the force transmitted between a first structure and a second structure. For example, a torque sensor has been disclosed that detects an abnormality based on the difference in output voltage between two bridge circuits including multiple strain sensors (see, for example, Patent Document 1).

JP 2018-132313 A

However, when duplicating a detection circuit (such as a bridge circuit) using a strain sensor, it is physically impossible to place the two strain sensors in the same location. Therefore, the difference in the placement of the strain sensors in the duplicated detection circuits causes a difference in the detection accuracy of each detection circuit. In this way, the difference in detection accuracy between the duplicated detection circuits is undesirable for the sensor.
The present embodiment aims to provide a sensor that reduces the difference in detection accuracy between the duplicated detection circuits.

According to the embodiment, it is possible to provide a sensor that reduces the difference in detection accuracy between the duplicated detection circuits.

A sensor according to an embodiment of the present invention includes a first structure formed in an annular shape, a second structure formed in an annular shape on the inner periphery of the first structure, a plate-shaped flexure body provided between the first structure and the second structure, and all of the sensor elements constituting a first system detection circuit of two detection circuits in which detection of forces including at least a moment about an axis of rotation perpendicular to a surface of the flexure body is duplicated, the first sensor elements being a plurality of first sensor elements that detect strain and are arranged in line symmetry on one side of the flexure body and on the first structure side of a center line that halves the flexure body, and all of the sensor elements constituting a second system detection circuit of the two detection circuits are a plurality of second sensor elements that detect strain and are arranged in line symmetry on the one side of the flexure body and on the second structure side of a center line that halves the flexure body .

FIG. 2 is an enlarged perspective view of the vicinity of a sensor unit of the torque sensor according to the first embodiment. FIG. 2 is a top view showing the configuration of the torque sensor according to the first embodiment. FIG. 2 is a top view showing the configuration of a sensor unit provided with one terminal unit according to the first embodiment. FIG. 2 is a top view showing the configuration of a sensor unit provided with two terminal portions according to the first embodiment. FIG. 2 is a front view showing an attached state of the torque sensor according to the first embodiment. 6 is a cross-sectional view of the torque sensor mounting plate shown in FIG. 5 taken along line AA. FIG. 4 is a simplified diagram showing a state of the torque sensor when an external load is applied to the torque sensor mounting plate according to the first embodiment. FIG. 11 is a top view showing the configuration of a sensor unit according to a second embodiment. FIG. 13 is a top view showing the configuration of a sensor unit according to a third embodiment.

First Embodiment
Fig. 1 is an enlarged perspective view of the vicinity of a sensor unit 14 of a torque sensor 10 according to a first embodiment. Fig. 2 is a top view showing the configuration of the torque sensor 10 according to the present embodiment. In the drawings, the same parts are denoted by the same reference numerals.

The torque sensor 10 is not limited to the one described here, and may be modified to various shapes or configurations. Furthermore, the torque sensor 10 may be a sensor with a different name, such as a force sensor, as long as it is a sensor that detects at least torque (z-axis moment Mz). For example, the force sensor detects the translational forces Fx, Fy, Fz and moments Mx, My, Mz of the three orthogonal axes (x-axis, y-axis, z-axis) shown in FIG. 2.

The torque sensor 10 includes a first structure 11, a second structure 12, a plurality of third structures 13, a plurality of sensor units 14, a case 15, and a cable 16.

The first structure 11, the second structure 12, and the third structure 13 are integrally formed as a single elastic body. The first structure 11, the second structure 12, and the third structure 13 are made of a metal such as stainless steel, but materials other than metal (such as resin) may be used as long as they have sufficient mechanical strength against applied forces such as torque.

The first structure 11 and the second structure 12 are formed in an annular shape. The diameter of the second structure 12 is smaller than the diameter of the first structure 11. The second structure 12 is arranged on the inner periphery of the circle concentric with the first structure 11. The multiple third structures 13 are arranged radially and are provided as beams connecting the first structure 11 and the second structure 12. Note that any number of third structures 13 may be provided.

The thickness (length in the z-axis direction) of the third structure 13 is thinner than the thicknesses of the first structure 11 and the second structure 12. Specifically, the thickness of the third structure 13 slopes from both ends connected to the first structure 11 or the second structure 12 toward the center, and the central portion has a uniform thickness (flat surface). The third structure 13 has a thickness (length in the z-axis direction) longer than its width (length in the circumferential direction) to make it easier to detect torque, but is not limited to this and the thickness and width of the third structure 13 may be determined arbitrarily.

The case 15 is provided so as to cover a hollow portion provided in the center of the second structure 12. A data processing circuit for processing data detected by each sensor unit 14 is provided in the hollow portion. The data processing circuit is electrically connected to each sensor unit 14 via a flexible printed circuit board. The data processing circuit is supplied with power via a cable 16, and outputs processed sensor signals to the outside.

The sensor unit 14 detects distortion caused by the relative movement of the first structure 11 and the second structure 12. Data indicating the distortion detected by the sensor unit 14 is transmitted to a data processing circuit as an electrical signal. The data processing circuit detects an applied force such as torque based on the distortion detected by the sensor unit 14. Here, a configuration in which four sensor units 14 are provided at equal intervals (90 degree intervals) in the circumferential direction is shown, but any number of sensor units 14 may be provided.

The sensor unit 14 includes a strain body 20, four A-system sensor elements 21a, 21b, 21c, and 21d, and four B-system sensor elements 22a, 22b, 22c, and 22d.

The sensor unit 14 is provided so as to straddle the first structure 11 and the second structure 12. Both ends of the sensor unit 14 are fixed to the first structure 11 and the second structure 12, respectively. In the first structure 11 and the second structure 12, recesses 11a, 12a that are thinner than other parts are formed in order to fix both ends of the sensor unit 14. For example, a cover for protecting the sensor unit 14 from external factors such as waterproofing and dustproofing is fitted into the recesses 11a, 12a on the upper surface of the sensor unit 14. A cover may also be provided on the lower surface of the sensor unit 14 in a similar manner.

The sensor unit 14 is attached by fixing both ends of the strain body 20 to the first structure 11 and the second structure 12. Specifically, a fixing plate 31 is arranged to hold down both ends of the strain body 20 from the top, and both ends of the strain body 20 are fixed together with the fixing plate 31 to the first structure 11 and the second structure 12 with screws 32. The sensor unit 14 may be attached in any manner.

The A-system sensor elements 21a-21d and the B-system sensor elements 22a-22d are disposed between the first structure 11 and the second structure 12 on the upper surface of the strain body 20. The A-system sensor elements 21a-21d and the B-system sensor elements 22a-22d are wired to form an A-system detection circuit and a B-system detection circuit, respectively. The two detection circuits are duplicated detection circuits for detecting torque, etc., and each detects torque, etc. independently. The torque sensor 10 outputs torque, etc. as the detection result based on the detection data from the two detection circuits. Note that the torque sensor 10 may determine the torque, etc. as the detection result based on the detection data from one of the two detection circuits.

Here, the A-system sensor elements 21a-21d and the B-system sensor elements 22a-22d are strain gauges, and the detection circuits are full bridge circuits, but this is not limited to this. For example, the detection circuits of each system may be bridge circuits composed of two strain gauges provided on the strain body 20 and a reference resistor provided in a location that is not substantially deformed by the application of torque or the like (for example, a data processing circuit provided on the second structure 12). Specifically, a bridge circuit may be formed by two sensor elements arbitrarily selected from the four sensor elements 21a-21d and sensor elements 22a-22d of each system and two reference resistors provided in the data processing circuit. In the following embodiments, the bridge circuit is not limited to a full bridge circuit, and a similar bridge circuit may be formed.

Two examples of the configuration of the sensor unit 14 will be described with reference to Figures 3 and 4. Figure 3 is a top view showing the configuration of sensor unit 14a, which is provided with terminal unit T1 that aggregates the terminals of sensor elements 21a to 21d, 22a to 22d in one location. Figure 4 is a top view showing the configuration of sensor unit 14b, which is provided with terminal units Ta and Tb that aggregate the terminals of sensor elements 21a to 21d, 22a to 22d in two locations by system. Note that the wiring of each sensor element 21a to 21d, 22a to 22d is not limited to the configuration described here. For example, three or more terminal units may be provided for sensor elements 21a to 21d, 22a to 22d.

The strain body 20 has a plate shape with rectangular upper and lower surfaces. The sensor elements 21a-21d, 22a-22d have a plate shape with rectangular upper and lower surfaces. The arrangement of the sensor elements 21a-21d, 22a-22d in the strain body 20 of each sensor unit 14a, 14b is almost the same. The A-system sensor elements 21a-21d are arranged on the first structure 11 side of the strain body 20 (left side of the figure). The B-system sensor elements 22a-22d are arranged on the second structure 12 side of the strain body 20 (right side of the figure).

Of the four A-system sensor elements 21a to 21d, the first set of the first A-system sensor element 21a and the second A-system sensor element 21b are provided close to each other but not in contact so as to maintain an electrical insulating distance. The first set of A-system sensor elements 21a and 21b are arranged inclined with respect to the longitudinal direction of the strain body 20 so that the end on the first structure 11 side faces outward, with the same orientation.

Of the four A-system sensor elements 21a to 21d, the third A-system sensor element 21c and the fourth A-system sensor element 21d of the second set are arranged in approximately the same direction and close to each other without contacting each other so as to maintain an electrical insulating distance. The A-system sensor elements 21c and 21d of the second set are arranged symmetrically with the A-system sensor elements 21a and 21b of the first set with respect to the center line that halves the strain body 20 in the longitudinal direction.

The four B-system sensor elements 22a to 22d are arranged so as to be symmetrical with the four A-system sensor elements 21a to 21d with respect to the center line that halves the strain body 20 in the short direction (direction perpendicular to the long direction).

The terminal section T1 shown in FIG. 3 is arranged in the center of the longitudinal direction of the strain body 20, with the terminals arranged adjacent to each other in the lateral direction. Each terminal of the A-system sensor elements 21a to 21d is electrically connected to the terminal located in the center of the terminal section T1 by two wires W1. Each terminal of the B-system sensor elements 22a to 22d is electrically connected to the terminals located at both ends of the terminal section T1 by two wires W1. Note that each terminal of the sensor elements 21a to 21d and 22a to 22d may be connected to any terminal of the terminal section T1.

The terminal parts Ta and Tb shown in FIG. 4 are formed by dividing the terminal part T1 shown in FIG. 3 into two parts. The A-system terminal part Ta is electrically connected to each terminal of the A-system sensor elements 21a to 21d by two wires Wa. The B-system terminal part Tb is electrically connected to each terminal of the B-system sensor elements 22a to 22d by two wires Wb.

The state in which the torque sensor 10 is attached will be described with reference to Figures 5 and 6. Figure 5 is a front view showing the attached state of the torque sensor 10. Figure 6 is a cross-sectional view of the torque sensor mounting plate 41 shown in Figure 5 taken along line A-A. Note that Figure 6 shows a simplified view of the adapter 42, the reducer 43, and the motor 44.

The torque sensor 10 is attached to the torque sensor mounting plate 41. As a result, the first structure 11 of the torque sensor 10 is fixed to the torque sensor mounting plate 41. The torque sensor mounting plate 41 is a member that is attached to a structure to which torque or the like is applied.

The second structure 12 of the torque sensor 10 is fixed to a reducer 43 connected to a motor 44 via an adapter 42. When the motor 44 is driven, the torque output from the motor 44 is applied to the torque sensor mounting plate 41 via the reducer 43, the adapter 42, and the torque sensor 10. As a result, the torque sensor mounting plate 41 and the structure to which it is attached are operated by the torque output from the motor 44.

The second structure 12 of the torque sensor 10 may be attached to the side to which torque or the like is applied (such as the torque sensor mounting plate 41), and the first structure 11 of the torque sensor 10 may be attached to the side to which torque or the like is applied (such as the motor 44).

With reference to Figures 5 and 7, a case where an external load (weight, etc.) Fw is applied to the torque sensor mounting plate 41 will be described. Figure 7 is a simplified diagram showing the state of the torque sensor 10 when an external load is applied to the torque sensor mounting plate 41. Figures 5 and 7 show two arrangement patterns P1 and P2 of the four sensor units 14, and the sensor units 14 are attached in one of the two arrangement patterns P1 and P2. Note that the sensor units 14 are not limited to these two arrangement patterns P1 and P2, and other arrangement patterns may be adopted.

As shown in FIG. 7, when a downward external load Fw, as shown by the arrow, is applied to the torque sensor mounting plate 41, tensile stress is generated on the upper side of the torque sensor mounting plate 41, and compressive stress is generated on the lower side of the torque sensor mounting plate 41.

Due to the deformation of the torque sensor mounting plate 41, the elastic body of the torque sensor 10 (the first structure 11, the second structure 12, and the third structure 13) deforms from a circular shape shown by a dotted line to an elliptical shape shown by a solid line. If the elastic body after deformation is an ellipse, the elastic body is stretched in the long axis direction and compressed in the short axis direction.

Due to the deformation of the elastic body, each sensor unit 14 in both arrangement patterns P1 and P2 deforms from a rectangle indicated by a dotted line to a square indicated by a solid line. In this way, when an external load Fw is applied, the stress that the sensor unit 14 receives from the external load Fw differs depending on the arrangement position in both arrangement patterns P1 and P2.

In the torque sensor 10, each sensor section 14 is provided with A-system sensor elements 21a-21d and B-system sensor elements 22a-22d that respectively constitute a duplicated A-system detection circuit and B-system detection circuit. Therefore, even if the stresses received by each sensor section 14 are different, the detection accuracy of each detection circuit of each system is approximately the same.

In contrast, unlike the torque sensor 10 of this embodiment, consider a case in which a sensor unit 14 having only an A system detection circuit is arranged in arrangement pattern P1, and a sensor unit 14 having only a B system detection circuit is arranged in arrangement pattern P2, thereby providing a duplicated detection circuit.

If no external load Fw is generated and an ideal torque is applied to the torque sensor 10, the stress received by each sensor section 14 of each arrangement pattern P1, P2 will be approximately the same. That is, the strain body 20 of each sensor section 14 will deform in approximately the same way. Therefore, the strain detected by each system will be approximately the same, and there will be little difference in the detection accuracy of the two duplicated detection circuits.

On the other hand, when an external load Fw occurs, even if an ideal torque is applied to the torque sensor 10, as described above, the stress received by the sensor unit 14 differs depending on the position of the sensor unit 14. That is, the strain generating body 20 of each sensor unit 14 deforms differently. Therefore, the strains detected by the two systems are different, and there is a possibility that a large difference will occur in the detection accuracy of the two duplicated detection circuits. For example, if a function is provided to detect an abnormality based on the difference between the two duplicated detection circuits, there is a possibility that an unintended abnormality will be detected even if a normal torque or other force is applied.

According to this embodiment, by providing the sensor elements 21a-21d, 22a-22d of each system of the two duplicated detection circuits in the same sensor unit 14, the difference in detection accuracy between the two duplicated detection circuits can be suppressed even when an external load Fw occurs.

Also, by arranging the A-system sensor elements 21a-21d and the B-system sensor elements 22a-22d in line symmetry on one side (front or back) of one strain body 20, the data indicating the strain detected by the A-system detection circuit and the B-system detection circuit can be made closer to being the same. Note that the A-system sensor elements 21a-21d and the B-system sensor elements 22a-22d may be arranged in line symmetry with respect to a center line that halves the strain body 20 in the longitudinal direction.

Here, all of the sensor elements 21a to 21d and 22a to 22d are provided on the front surface of the strain body 20, but they may also be provided on the rear surface of the strain body 20.

Second Embodiment
FIG. 8 is a top view showing the configuration of a sensor unit 14A according to the second embodiment.
The sensor unit 14A is obtained by changing the arrangement of the sensor elements 21a to 21d and 22a to 22d and the wiring thereof in the sensor unit 14a according to the first embodiment shown in Fig. 3. The other points are the same as those of the torque sensor 10 according to the first embodiment.

Sensor unit 14A has one terminal unit T1, similar to sensor unit 14a shown in FIG. 3. Terminal unit T1 is arranged in the center of the longitudinal direction of strain body 20, with each terminal arranged adjacent to the other in the lateral direction. Each terminal of A-system sensor elements 21a to 21d is electrically connected to terminals located at both ends of terminal unit T1 by two wires W1A. Each terminal of B-system sensor elements 22a to 22d is electrically connected to a terminal located in the center of terminal unit T1 by two wires W1A. Each terminal of sensor elements 21a to 21d, 22a to 22d may be connected to any terminal of terminal unit T1.

The first A-system sensor element 21a is arranged on the first structure 11 side of the strain body 20, tilted with respect to the longitudinal direction of the strain body 20 so that the end on the first structure 11 side faces outward. The fourth A-system sensor element 21d is arranged on the first structure 11 side of the strain body 20 so as to be symmetrical with the first A-system sensor element 21a with respect to the center line that halves the strain body 20 in the longitudinal direction.

The second A-system sensor element 21b and the third A-system sensor element 21c are arranged so as to be symmetrical with the first A-system sensor element 21a and the fourth A-system sensor element 21d, respectively, with respect to the center line that halves the strain body 20 in the short direction.

The B-system sensor elements 22a to 22d are provided in approximately the same direction as the corresponding A-system sensor elements 21a to 21d, close to each other but not in contact so as to maintain an electrical insulating distance. For example, the correspondence between the A-system sensor elements 21a to 21d and the B-system sensor elements 22a to 22d is determined by the electrical circuit positional relationship in the A-system detection circuit and the B-system detection circuit.

Therefore, the arrangement of the sensor elements 21a to 21d, 22a to 22d in the sensor section 14A is the same as that in the sensor section 14a shown in FIG. 3, with the second A-system sensor element 21b and the third A-system sensor element 21c swapped with the first B-system sensor element 22a and the fourth B-system sensor element 22d, respectively.

According to this embodiment, the sensor elements 21a to 21d and 22a to 22d corresponding to each other are arranged close to each other on the strain body 20 between the two duplicated detection circuits, thereby achieving the same effect as the first embodiment.

Third Embodiment
FIG. 9 is a top view showing the configuration of a sensor unit 14B according to the third embodiment.
The sensor unit 14B is obtained by changing the arrangement of the A-system sensor elements 21a to 21d and the wiring thereof in the sensor unit 14a according to the first embodiment shown in Fig. 3. The other points are the same as those of the torque sensor 10 according to the first embodiment.

The arrangement and wiring of the B-system sensor elements 22a to 22d in the sensor unit 14B are the same as those in the sensor unit 14a shown in FIG. 3. The A-system sensor elements 21a to 21d and the B-system sensor elements 22a to 22d are arranged on the second structure 12 side of the strain body 20.

Sensor unit 14B has one terminal unit T1, similar to sensor unit 14a shown in FIG. 3. Terminal unit T1 is located at the center of the longitudinal direction of strain body 20, with each terminal arranged adjacent to the other in the lateral direction. Each terminal of A-system sensor elements 21a to 21d is electrically connected to the terminal located at the center of terminal unit T1 by two wires W1B. Each terminal of B-system sensor elements 22a to 22d is electrically connected to terminals located at both ends of terminal unit T1 by two wires W1B. Each terminal of sensor elements 21a to 21d and 22a to 22d may be connected to any terminal of terminal unit T1.

The first A-system sensor element 21a is provided inside the strain body 20 relative to the second B-system sensor element 22b, and is provided close to the second B-system sensor element 22b without contacting it so as to maintain an electrical insulating distance. The first A-system sensor element 21a is arranged in approximately the same direction as the second B-system sensor element 22b, tilted relative to the longitudinal direction of the strain body 20 so that the end on the second structure 12 side faces outward.

The second A-system sensor element 21b is provided inside the strain body 20 relative to the first A-system sensor element 21a, close to the first A-system sensor element 21a but without contact so as to maintain an electrical insulating distance. The second A-system sensor element 21b is oriented in approximately the same direction as the first A-system sensor element 21a, and is tilted with respect to the longitudinal direction of the strain body 20 so that the end on the second structure 12 side faces outward.

The third A-system sensor element 21c and the fourth A-system sensor element 21d are arranged so as to be symmetrical with the second A-system sensor element 21b and the first A-system sensor element 21a, respectively, with respect to the center line that halves the strain body 20 in the longitudinal direction.

That is, the fourth A-system sensor element 21d is provided inside the strain body 20 more than the third B-system sensor element 22c, and is provided close to the third B-system sensor element 22c but does not contact the third B-system sensor element 22c so as to maintain an electrical insulation distance. The third A-system sensor element 21c is provided inside the strain body 20 more than the fourth A-system sensor element 21d, and is provided close to the fourth A-system sensor element 21d but does not contact the fourth A-system sensor element 21d so as to maintain an electrical insulation distance.

According to this embodiment, all sensor elements 21a to 21d, 22a to 22d of the two duplicated detection circuits are arranged on the second structure 12 side of the strain body 20, thereby achieving the same effect as the first embodiment.

The sensor elements 21a to 21d and 22a to 22d may be arranged on the first structure 11 side of the strain body 20 so as to be linearly symmetrical to the arrangement shown in FIG. 9. Even in this case, the same effect as in the first embodiment can be obtained.

In addition, the present invention is not limited to the above-mentioned embodiments as they are, and in the implementation stage, the components can be modified and embodied without departing from the gist of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above-mentioned embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components from different embodiments may be appropriately combined.

10...torque sensor, 11...first structure, 12...second structure, 13...third structure, 14...sensor section, 15...case, 16...cable, 20...strain element, 21a, 21b, 21c, 21d...A-system sensor element, 22a, 22b, 22c, 22d...B-system sensor element.

Claims (5)

A first structure formed in an annular shape;
a second structure formed annularly on the inner circumferential side of the first structure;
a plate-shaped strain body provided between the first structure and the second structure;
all sensor elements constituting a first system detection circuit of two detection circuits in which detection of a force including at least a moment with a rotation axis perpendicular to the surface of the strain body is duplicated, the first sensor elements being arranged symmetrically on one surface of the strain body and on the first structure side of a center line dividing the strain body in half;
and a plurality of second sensor elements which detect strain and are all sensor elements constituting a second system detection circuit of the two detection circuits, and which are arranged line-symmetrically on the one surface of the strain body and on the second structure side of a center line which halves the strain body. 2. The sensor according to claim 1, wherein the force detection is detection of translational forces and moments in three orthogonal axes. The plurality of first sensor elements are disposed adjacent to each other of the first sensor elements,
2. The sensor according to claim 1 , wherein each of the second sensor elements is disposed adjacent to each of the other second sensor elements. 2. The sensor according to claim 1 , wherein the plurality of first sensor elements of the first system detection circuit and the plurality of second sensor elements of the second system detection circuit are arranged in line symmetry. 5. The sensor according to claim 4 , wherein the first sensor elements and the second sensor elements are arranged adjacent to each other so as to correspond to each other.

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