JP2012242114A - Torsion sensor and driving joint mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torsion sensor capable of detecting accurate torsion quantity.SOLUTION: A torsion sensor 1 includes: an elastic member (torsion bar 2) for generating torsion deformation between a first end (right end 21) and a second end (left end 22) by applying rotation moment as external force; a support member (housing 3) fixed on the second end of the elastic member to support the second end; and a displacement sensor including a detected part and a detection part and capable of detecting relative displacement between the detection part and the detected part. The elastic member includes a first coupling part (disc part 25) for coupling a member for inputting external force to the first end and a first sensor support part 23 for supporting either one of the detection part and the detected part. The support member includes a second coupling part (flange 35) to which a member for inputting external force is coupled, a first rotary support part (outer wheel engagement part 34) for rotatably supporting the first end of the elastic member and a second sensor support part 33 for supporting the other one of the detection part and the detected part.

Description

  The present invention relates to a torsion sensor and a drive joint mechanism including the torsion sensor.

  In recent years, as a drive joint mechanism of a robot, a configuration has been proposed in which an output from a rotational drive source such as a motor or a hydraulic actuator is transmitted to a link connected by a joint via an elastic member such as a spring. Such a drive joint mechanism is called SEA (Serial Elastic Actuator), and when the link collides with an obstacle, the elastic member is deformed to protect the obstacle or the driving source, or the elastic member is deformed. By detecting the load applied to the link based on the amount, it is possible to perform appropriate control of the robot or the like.

  For example, in Patent Document 1, a torsion bar 160 as an elastic member is provided in a joint in FIG. 22, and the torsion bar 160 is elastically twisted and deformed by a force applied to one link connected by the joint. A drive joint mechanism configured to be a joint is disclosed. In this drive joint mechanism, bearings that support the rotation of one link and the other link are provided at both ends of the torsion bar 160.

JP 2008-055441 A

  By the way, in order to appropriately control a robot or the like using SEA, it is necessary to accurately detect the rotational moment applied to the joint. This rotational moment can be calculated from the torsional deformation by measuring the torsional deformation of the elastic member.

  However, in the configuration of Patent Document 1, in the detection of the torsional deformation amount, an error has occurred due to the mutual rotation axes of the bearings at both ends of the elastic member (torsion bar) being not completely coincident with each other. More specifically, in the configuration of Patent Document 1, the two bearings support the rotation of the two links at two locations separated in the axial direction, and one link is connected to the torsion bar via the two bearings. It was comprised so that the both ends could be supported. In such a configuration, when the two links rotate, the two bearings also rotate according to the rotation of the link, and a slight shaft misalignment between the bearings (specifically, the bearing of one link is supported). A force that bends or twists the torsion bar acts according to the deviation of the axis of the portion to be operated, and this force results in an inaccurate rotational moment. The error of the detected rotational moment due to the coaxial manufacturing error is not limited to the case where one link supports both ends of the torsion bar with bearings, but supports the torsion bar according to the rotation of the links. This occurs even when one link supports only one end of the torsion bar when the bearing to be rotated is in a relation of rotation.

  The present invention has been made based on the above-described background, and an object thereof is to provide a torsion sensor that enables accurate detection of the amount of torsion, and a drive joint mechanism including the torsion sensor.

  The present invention that solves the above-described problem is a torsion sensor, and an elastic member that undergoes torsional deformation elastically between a first end and a second end when a rotational moment is applied as an external force, and the elastic member A support member fixed to the second end and supporting the second end, and a displacement sensor having a detected portion and a detecting portion and capable of detecting a relative displacement between the detecting portion and the detected portion. The elastic member has a first coupling part to which a member for inputting an external force is coupled to the first end, and a first sensor support part that supports one of the detection part and the detected part, The support member includes a second coupling portion to which a member that inputs an external force is coupled, a first rotation support portion that rotatably supports the first end of the elastic member, and the detection unit and the detection target portion. It has the 2nd sensor support part which supports the other, It is characterized by the above-mentioned.

  According to such a configuration, a member for inputting an external force such as one link constituting the joint is coupled to the first coupling portion, and the other link constituting the joint is coupled to the second coupling portion. When a rotational moment is generated between the two links, the rotational moment is applied between the first coupling portion and the second coupling portion. Then, a force is applied from one link to the first end of the elastic member via the first coupling portion, and a force is applied to the support member from the other link via the second coupling portion. It is transmitted to the second end of the member. As a result, the elastic member is elastically twisted and deformed, and the amount of deformation is detected by the displacement sensor. In this torsion sensor, the support member rotatably supports the first end of the elastic member. However, since the same support member is fixed to the second end of the elastic member, the first rotation support portion and the first end are supported. Is relatively rotated by the amount of twist of the elastic member, and does not rotate according to the rotation of the two links coupled to the first coupling portion and the second coupling portion. Therefore, a force that twists the elastic member according to the rotation of the two links does not occur, so that the twist amount can be accurately detected. Then, the rotational moment as the external force can be accurately calculated from the twist amount thus detected.

  In the torsion sensor described above, it is preferable that the first rotation support portion supports the first end via a rolling bearing.

  When the first rotation support portion supports the first end via the rolling bearing, the friction between the first rotation support portion and the first end is reduced, and a more accurate amount of twist is detected and more accurate. A simple rotational moment can be calculated.

  The present invention for solving the above-described problems is a drive joint mechanism including the above-described torsion sensor, and supports the first link coupled to the first coupling portion of the torsion sensor and the first link rotatably. A second link having a second rotation support portion and coupled to the second coupling portion of the torsion sensor; and provided between the first coupling portion and the first link; And a drive source that generates a relative rotational driving force between the first links. In the drive joint mechanism, a drive source is provided between the first coupling portion and the first link, and generates a relative rotational driving force between the first coupling portion and the first link. It may be.

  In such a drive joint mechanism, as described above, when a rotational moment is applied between the first link and the second link, the torsion sensor accurately detects the torsion amount of the elastic member, and the first link and the second link. It is possible to accurately calculate the rotational moment applied between the two.

  In this drive joint mechanism, the second link has a third rotation support portion that supports the mutual rotation of the first link and the second link in the axial direction of the rotation from the second rotation support portion. It can be set as the structure provided in the distant position.

  According to the torsion sensor or the drive joint mechanism of the present invention, the torsion amount of the elastic member can be accurately detected, and the rotational moment applied to the two members coupled to the torsion sensor can be accurately calculated.

It is sectional drawing of the twist sensor which concerns on one Embodiment of this invention. It is sectional drawing of the torsion sensor which concerns on a modification. It is sectional drawing of the drive joint mechanism which concerns on one Embodiment of this invention.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description of one embodiment, for convenience, description will be made using the top, bottom, left and right with reference to the drawings. However, the torsion sensor and the drive joint mechanism of the present invention can be used in any posture regardless of the direction of gravity. Needless to say.

  As shown in FIG. 1, a torsion sensor 1 according to an embodiment of the present invention includes a torsion bar 2 as an example of an elastic member, a housing 3 as an example of a support member, and an optical encoder as an example of a displacement sensor. 4.

  The torsion bar 2 is a member that elastically twists and deforms between the right end (first end) 21 and the left end (second end) 22 when a rotational moment is applied as an external force. Therefore, the torsion bar 2 has a shaft 20 formed from a moderately thin metal tube. The right end 21 of the torsion bar 2 is provided with a disk portion 25 that extends in the radial direction about the axis of the shaft 20 as an example of the first coupling portion. The disk portion 25 is provided with a plurality of screw holes 25A for fastening a member for inputting an external force with a bolt. The disc portion 25 is formed with a cylindrical portion 25B extending from the outer peripheral edge toward the left, and the inner periphery of the cylindrical portion 25B supports an encoder plate 41 as a detected portion of the optical encoder 4. It becomes the 1st sensor support part 23, and the outer periphery becomes the inner ring fitting part 24 fitted with the inner ring of the rolling bearing 5. The left end 22 of the torsion bar 2 also extends slightly in a disc shape around the axis of the shaft 20, and an outer peripheral surface 22 </ b> A that can be fitted to a support portion 31 of the housing 3 described later is provided on the outer periphery thereof. .

  The housing 3 is a member that is fixed to the left end 22 of the torsion bar 2 and supports the left end 22. The housing 3 has a conical shape coaxial with the axis of the shaft 20 and has a flange 35 at the opening edge at the right end. The flange 35 is an example of a second coupling portion to which a member for inputting an external force is coupled, and in the present embodiment, a hole 35A for passing a bolt is formed. The left end of the housing 3 is a support portion 31 that supports the left end 22 of the shaft 20, and a through hole 31 </ b> A is formed at the center. The left end through hole 31A is machined so that it can be fitted to the outer peripheral surface 22A of the left end 22 of the torsion bar 2. In this embodiment, the outer peripheral surface 22A of the left end 22 of the shaft 20 is welded to the through hole 31A. As a result, the support portion 31 is fixed to the left end 22. However, the fixing method of the left end 22 of the shaft 20 and the housing (support member) 3 is not limited to press-fitting, and any fixing method can be used. In addition, the shaft 20 of the torsion bar 2 is elastic enough to be torsionally deformed, whereas the housing 3 has sufficient rigidity so as not to be deformed by an equivalent external force.

  An outer ring fitting portion 34 as an example of a first rotation support portion formed in a cylindrical surface on the inner periphery is provided in the middle in the left-right direction of the housing 3. The outer ring fitting portion 34 is a portion that rotatably supports the right end 21 of the torsion bar 2. In the present embodiment, the outer ring fitting portion 34 is fitted to the outer ring of the rolling bearing 5 and is connected to the right end of the torsion bar 2 via the rolling bearing 5. 21 is supported.

  The optical encoder 4 includes the encoder plate 41 and an optical sensor 42 as an example of a detection unit that reads a code provided on the encoder plate 41. The encoder plate 41 is fixed to a cylindrical bracket 41 </ b> A, and the bracket 41 </ b> A is fixed to the right end 21 of the torsion bar 2 by fitting with the first sensor support portion 23 described above.

A sensor hole 36 penetrating the inside and outside of the housing 3 is formed on the left side of the outer ring fitting portion 34 of the housing 3, and the encoder plate 41 protrudes outside through the sensor hole 36.
A second sensor support portion 33 is provided on the left side of the sensor hole 36, and the optical sensor 42 is fixed to the second sensor support portion 33 using a bolt 49. Thereby, the optical sensor 42 faces the encoder plate 41, and when the torsion bar 2 is twisted, the relative displacement of the optical sensor 42 with respect to the encoder plate 41 can be detected.

The torsion sensor 1 configured as described above can be used as a sensor for measuring the amount of twist by fixing different members to the disk portion 25 and the flange 35, respectively.
More specifically, when a rotational moment about the shaft 20 is applied to the disk portion 25 and the flange 35, a force is transmitted from the flange 35 to the left end 22 of the shaft 20, while a force is applied from the disk portion 25 to the right end 21 of the shaft 20. Is transmitted. As a result, the right end 21 is twisted and deformed with respect to the left end 22. At this time, since the disk portion 25 is supported by the rolling bearing 5 for rotation with respect to the housing 3, the disk portion 25 can rotate with respect to the housing 3 with little resistance. When the right end 21 rotates with respect to the housing 3, the encoder plate 41 also rotates together with the right end 21, and the position of the encoder plate 41 with respect to the optical sensor 42 changes. Since the optical sensor 42 detects and outputs the relative displacement of the encoder plate 41, the torsion amount of the torsion bar 2 can be obtained from this output. Then, using the elastic coefficient for the twist of the shaft 20, the magnitude of the rotational moment applied as an external force can be calculated from the twist amount of the torsion bar 2.

  When the torsional deformation is performed, the relative rotation amount of the housing 3 and the right end 21 of the rolling bearing 5 is only the amount of twisting of the shaft 20, and relative rotation of the link attached to the disk portion 25 and the flange 35 or the like. Does not depend on the amount of rotation. For this reason, even when the two shaft support portions that support relative rotation, such as the two links, have a shaft shift due to a manufacturing error, an accurate twist amount can be detected without being affected by the shaft shift. Of course, the shaft 20 is displaced even when the shafts of the left end 22 and the right end 21 of the shaft 20 are supported. However, since the rotation amount of the right end 21 is small only by the amount of twist of the shaft 20, the left end 22 and the right end 21. It can be said that there is no deterioration in the detection accuracy of the torsional amount due to the shaft misalignment.

  As described above, according to the torsion sensor 1 of the present embodiment, a force that twists the elastic member in accordance with the rotation of the two links does not occur, so that the amount of twist can be accurately detected. Further, since the outer ring fitting portion 34 rotatably supports the right end 21 of the torsion bar 2 via the rolling bearing 5, the rotation resistance is small, and the amount of twist can be detected more accurately.

  In the torsion sensor 1, the housing 3 supports the outer ring of the rolling bearing 5, and the torsion bar 2 supports the inner ring of the rolling bearing 5. However, this may be reversed. For example, FIG. 2 is a diagram showing a modified example of the embodiment, and only different points are attached to the substantially different points from the example of FIG. The torsion sensor 1 'shown in FIG. 2 is provided with an outer ring fitting portion 24' fitted to the outer ring of the rolling bearing 5 at the right end 21 of the torsion bar 2, and the housing 3 (second housing 3B) has an inner ring of the rolling bearing 5 and An inner ring fitting portion 34 'to be fitted is provided. As illustrated in FIG. 2, the optical encoder 4 does not need to pass through the housing 3 and may be housed in the housing 3. Further, the torsion bar 2 and the housing 3 may be composed of a plurality of parts. As an example, FIG. 2 shows an example in which the housing 3 is composed of two parts, a first housing 3A and a second housing 3B.

  Next, an embodiment in which the torsion sensor 1 is applied to a drive joint mechanism such as a robot will be described. As shown in FIG. 3, the drive joint mechanism 100 includes a first link 110, a second link 120, a motor 130, and a torsion sensor 1.

  The first link 110 is coupled to the flange 35 of the housing 3 by a bolt 152. The second link 120 is coupled to the disk portion 25 at the right end 21 of the torsion bar 2 via a motor 130 and a transmission 140 as an example of a drive source. The second link 120 has an outer ring fitting portion 122 as an example of a second rotation support portion at the left end portion, and the outer ring fitting portion 122 supports the first link 110 rotatably via a rolling bearing 192. Yes. Further, the second link 120 has an outer ring fitting portion 123 as an example of a third rotation support portion at the right end portion, and the first link 110 can be rotated via the rolling bearing 193 in the outer ring fitting portion 123. I support it. As a result, the rotation of the first link 110 is supported by the second link 120 at two locations separated in the axial direction of rotation.

  The motor 130 includes a stator 131 and a rotor 132, and the stator 131 is fixed to the first link 110. The rotor 132 has an output shaft 133, and a wave generator 141 that is a rotating body on the input side of the transmission 140 is fixed to the output shaft 133.

  The transmission 140 is a wave gear device that includes a wave generator 141, a ball bearing 142, a flex spline 143, and a circular spline 144. The circular spline 144 is fixed to the first link 110 together with the stator 131 of the motor 130. The flex spline 143 is fastened to the disc portion 25 at the right end 21 of the torsion bar 2 by a bolt 151. In the above configuration, the axes of the torsion bar 2, the transmission 140, the motor 130, and the rolling bearings 192 and 193 are the same in design.

  According to such a driving joint mechanism 100, when the motor 130 is rotated, the rotation is decelerated by the transmission 140, and the rotation output from the flex spline 143 rotates the disk portion 25 of the torsion bar 2. As a result, the torsion sensor 1 rotates relative to the first link 110. And since the flange 35 of the housing 3 used as the output side is being fixed to the 2nd link 120, the 2nd link 120 will rotate when the torsion sensor 1 rotates. Therefore, if the motor 130 is rotated forward or reverse, the second link 120 can be rotated forward or reverse with respect to the first link 110. That is, the drive joint mechanism 100 can be used as a joint of a robot or the like.

  When an external force is applied to the first link 110 or the second link 120 of the drive joint mechanism 100 due to an object hitting the first link 110 or the second link 120, a force to rotate the first link 110 and the second link 120 is applied. This force is applied to the disk portion 25 of the torsion bar 2 of the torsion sensor 1 and the flange 35 of the housing 3, and acts as a rotational moment that attempts to rotate the disk portion 25 and the flange 35 with respect to each other. Then, as described above, the rotation amount of the right end 21 with respect to the left end 22 of the torsion bar 2 (the amount of twist of the shaft 20) is detected by the optical encoder 4. That is, the amount of twist due to the rotational moment applied to the first link 110 and the second link 120 of the drive joint mechanism 100 is detected, and the rotational moment can be calculated from the amount of twist.

  At this time, since the first link 110 and the second link 120 are supported by the two rolling bearings 192 and 193 that are axially separated from each other, the two outer ring fitting portions 122 and 123 are processed. Due to the shaft misalignment, a force that twists or bends the first link 110 supported by the rolling bearings 192 and 193 slightly works. This force changes little by little depending on the direction (phase) of the second link 120 with respect to the first link 110 according to the tendency of the axis deviation. In the conventional drive joint mechanism, the force causing this error is applied to the torsion bar. Therefore, if the rotational moment as the external force is calculated from the torsion amount of the torsion bar, an accurate value cannot be calculated. In the drive joint mechanism 100, the force due to this axial deviation hardly applies to the torsion bar 2, and therefore the amount of twist can be accurately detected. Then, the rotational moment can be accurately calculated from the detected twist amount.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be appropriately modified and implemented.
For example, in the drive joint mechanism 100, the drive source is provided between the disk portion 25 (first coupling portion) of the torsion bar 2 and the first link 110, but the drive source is the second coupling portion (flange 35). And the second link 120 may be provided. Further, although the transmission 140 is provided between the motor 130 and the torsion sensor 1, the transmission 140 may not be provided.

  Further, although the torsion bar 2 (shaft 20) is illustrated as an example of the elastic member, the elastic member may be any member as long as it is an element that can be elastically twisted and deformed, such as a leaf spring or a coil spring. Absent.

  In the embodiment, the first link 110 and the second link 120 are supported by the two rolling bearings 192 and 193, but the rotation may be supported by only one bearing. Further, the rotation support is not limited to using a rolling bearing, but a sliding bearing or a fluid bearing can also be used. Similarly, the rotation support of the elastic member by the support member is not limited to the case of using a rolling bearing, and a sliding bearing or a fluid bearing can be used.

  In the above embodiment, the detection member of the displacement sensor is provided on the support member, and the detection unit is provided on the first end of the elastic member, but this may be reversed. A detection part can also be provided in the 1st end of an elastic member. The displacement sensor is not limited to an optical encoder, and other displacement sensors such as a resolver, a Hall element, and an MR sensor can be employed.

  In addition, the torsion sensor of the present invention can be used not only for a drive joint mechanism but also for any device that measures a rotational moment. For example, the torsion sensor of the present invention can be used to detect torque (rotational moment) in a torque wrench.

DESCRIPTION OF SYMBOLS 1 Sensor 2 Torsion bar 3 Housing 4 Optical encoder 5 Rolling bearing 20 Shaft 21 Right end 22 Left end 23 1st sensor support part 24 Inner ring fitting part 24 'Outer ring fitting part 25 Disk part 31 Support part 33 2nd sensor support part 34 Outer ring fitting part 35 Flange 41 Encoder plate 42 Optical sensor 100 Drive joint mechanism 110 First link 122 Outer ring fitting part 123 Outer ring fitting part 120 Second link 130 Motor 140 Transmission 192 Rolling bearing 193 Rolling bearing

Claims (5)

An elastic member that undergoes a torsional deformation elastically between the first end and the second end by applying a rotational moment as an external force;
A support member fixed to the second end of the elastic member and supporting the second end;
A displacement sensor having a detected portion and a detecting portion and capable of detecting a relative displacement between the detected portion and the detected portion;
The elastic member includes, at the first end, a first coupling portion to which a member that inputs an external force is coupled, and a first sensor support portion that supports one of the detection unit and the detected portion.
The support member includes a second coupling portion to which a member that inputs an external force is coupled, a first rotation support portion that rotatably supports the first end of the elastic member, and the detection unit and the detection target portion. A torsion sensor comprising: a second sensor support portion supporting the other.   The torsion sensor according to claim 1, wherein the first rotation support portion supports the first end via a rolling bearing. The torsion sensor according to claim 1 or 2,
A first link coupled to the first coupling portion of the torsion sensor;
A second link coupled to the second coupling part of the torsion sensor, the second link having a second rotation support part for rotatably supporting the first link;
A drive joint mechanism comprising: a drive source provided between the first coupling portion and the first link and generating a relative rotational driving force between the first coupling portion and the first link. . The torsion sensor according to claim 1 or 2,
A first link coupled to the first coupling portion of the torsion sensor;
A second link coupled to the second coupling part of the torsion sensor, the second link having a second rotation support part for rotatably supporting the first link;
A drive joint mechanism, comprising: a drive source provided between the second coupling portion and the second link and generating a relative rotational driving force between the second coupling portion and the second link. .   The second link includes a third rotation support portion that supports the mutual rotation of the first link and the second link at a position away from the second rotation support portion in the axial direction of the rotation. The drive joint mechanism according to claim 3 or 4, wherein:

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