JP6366438B2 - Torque detection device - Google Patents

Description

  The present invention relates to a technique for detecting torque in a power transmission device including a planetary gear mechanism.

  A power transmission device using a planetary gear mechanism is provided with a torque detection device that detects torque applied to a load (Patent Document 1).

  In the torque detection device disclosed in Patent Document 1, a strain gauge is attached to a protruding member that protrudes radially outward from the outer peripheral portion of the ring gear of the planetary gear mechanism. On the other hand, the tip of the projecting member engages with a casing surrounding the ring gear to prevent the ring gear from rotating. The planetary gear mechanism includes a sun gear formed on an input shaft, a plurality of planetary gears that mesh with the sun gear, and a ring gear that has an inner peripheral gear that meshes with the plurality of planetary gears on the inner periphery. The plurality of planetary gears are rotatably attached to a cage having a rotation center on the same axis as the input gear.

  When the ring gear is fixed to the casing, when the input shaft rotates, a plurality of planetary gears meshing with the sun gear revolve while rotating, and the cage rotates. At that time, a reaction force acts on the casing. Since distortion occurs in the projecting member due to the bending stress due to the reaction force, the strain applied to the load is detected by detecting the strain by the strain gauge.

  If the protruding length of the protruding member is increased, the amount of deflection of the protruding member increases, and a torque value in a wide range can be detected with high accuracy. However, if the protruding member is lengthened in the radially outward direction, the outer diameter of the casing is lengthened.

  Further, since the strain gauge is attached to the protruding member, for example, replacement of the strain gauge requires a large disassembly of taking out the planetary gear mechanism from the casing, and maintenance is poor.

JP 09-145498 A

  An object of the present invention is to solve the above-described conventional problems, and to provide a torque detection device that can detect torque with high accuracy from a ring gear of a planetary gear mechanism and can easily replace components such as strain gauges. Is.

  A first configuration of a torque detection device that realizes an object of the present invention includes a casing, a ring gear that is disposed in the casing and is relatively rotatable around a rotation center axis with respect to the casing, and an input shaft. A planetary gear mechanism for transmitting the rotation of the ring gear to the output shaft, an engagement protrusion protruding radially outward from the outer periphery of the ring gear, and the engagement protrusion entering the engagement protrusion together with the ring gear An opening formed in the casing that allows movement around the rotation center axis within a predetermined range, and extends along the direction of the rotation center axis, one end of which is fixed to the casing, and a free end A torque detecting lever in which an engaging portion on the distal end side engages with the engaging protrusion, and a strain measuring means for measuring strain of the torque detecting lever which is bent and deformed by a load applied by the engaging protrusion. Having.

  According to a second configuration of the torque detection device that realizes the object of the present invention, in the first configuration described above, the opening of the casing is formed to a size that accommodates the torque detection lever. .

  According to a third configuration of the torque detection device that achieves the object of the present invention, in any one of the configurations described above, the torque detection lever is a fastening member that is attached to the casing at one end side from the outside of the casing. It is fixed.

  According to a fourth configuration of the torque detector for realizing the object of the present invention, in any one of the configurations described above, the ring gear is urged in one direction along the rotation center axis with respect to the casing. It is characterized by being.

  According to a fifth configuration of the torque detection device that realizes the object of the present invention, in any one of the configurations described above, the engagement shaft portion in which the engagement protrusion engages with the engagement portion of the torque detection lever is formed in a barrel shape. It is characterized by being formed.

  According to a sixth configuration of the torque detection apparatus that realizes the object of the present invention, in any one of the configurations described above, the tip of the engagement protrusion extends to a length that engages with the engagement portion of the torque detection lever. It is characterized by being.

  According to the invention which concerns on Claim 1, a torque detection lever can be lengthened and a torque can be measured with high precision. In addition, the engagement protrusion can be made delicate, and the poor appearance that the outer shape of the casing partially protrudes can be eliminated.

  In addition, in the case where replacement is necessary due to a failure of a strain measurement means such as a strain gauge, the torque detection lever equipped with a new strain measurement means such as a strain gauge can be replaced by replacing the torque detection lever from the outside of the casing. Can be attached. At that time, it is not necessary to disassemble the planetary gear mechanism or the like.

  According to the invention which concerns on Claim 2, 6, since a torque detection lever does not protrude from the outer peripheral surface of a casing, it can be set as the shape where the external shape of a casing does not protrude partially. Further, the torque detection lever can be protected, and the torque detection lever can be easily taken out from the outside of the casing.

  According to the invention which concerns on Claim 3, the removal operation | work and attachment operation | work of a torque detection lever can be performed easily.

  According to the invention which concerns on Claim 4, it can maintain, without shifting | engaging an engaging protrusion and the engaging part of a torque detection lever, and an engagement position.

  According to the invention which concerns on Claim 5, since an engaging shaft part contacts the engaging part by point contact, highly accurate torque detection can be performed.

1 is a longitudinal sectional view showing an embodiment of a torque detection device according to the present invention. The A arrow enlarged view of FIG. The ring gear which comprises the torque detection apparatus of FIG. 1 is shown, (a) is a top view, (b) is BB arrow sectional drawing of (a), (c) is a left view of (a). 1 shows a torque detector constituting the torque detection device of FIG. 1, wherein (a) is a top view, (b) is a front view of (a), (c) is a left side view of (b), and (d) is ( The right view of b), (e) is the figure of the connection state of the lead wire of the strain gauge shown in (b).

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  FIG. 1 is a longitudinal sectional view showing an embodiment of a torque detection device according to the present invention, and FIG. 2 is an enlarged view taken along arrow A in FIG.

  FIG. 1 shows an embodiment of a torque detection device. The torque detection device 100 is provided in a speed reducer in which planetary gear mechanisms that constitute a part of the power transmission device are connected in two stages. A first sun gear 2 is formed at the tip of the first input shaft 1 of the first planetary gear mechanism PG1. The first sun gear 2 is disposed so as to be rotatable with respect to the same axis as the rotation center axis L1. A plurality of first planetary gears 3 are arranged around the first sun gear 2, and the plurality of first planetary gears 3 mesh with the first sun gear 2. The plurality of first planetary gears 3 are rotatably attached to a first carrier (cage) 4.

  The first cage 4 is disposed so as to be rotatable with respect to the same axis as the rotation center axis L1. In the first cage 4, a first support shaft 5 is attached in parallel to the rotation center axis L 1 corresponding to each first planetary gear 3, and the first planetary gear 3 is attached to the first support shaft 5 in a freely rotatable manner.

  The ring gear 6 is rotatably disposed on the same axis as the rotation center axis L1. The ring gear 6 has first inner teeth 7a and second inner teeth 7b formed on the inner periphery thereof, and a plurality of first planetary gears 3 arranged on the inner side of the ring gear 6 mesh with the first inner teeth 7a. The ring gear of the second planetary gear mechanism PG2 is shared with the ring gear 6 of the first planetary gear mechanism PG1, and the second planetary gear 103 of the second planetary gear mechanism PG2 meshes with the second internal teeth 7b.

  The casing 8 of the power transmission device is disposed on the outer periphery of the ring gear 6. A first ball bearing 9 and a second ball bearing 10 are disposed between the inner peripheral surface 8 a of the casing 8 and the outer peripheral surface of the ring gear 6. The ring gear 6 is rotatably held with respect to the casing 8 via the first ball bearing 9 and the second ball bearing 10.

  The front end surface of the first ball bearing 9 (on the second planetary gear mechanism PG2 side) is disposed at a position where it is pushed forward to the step portion 11 of the ring gear 6. A pressing spring 12 is arranged between the rear end of the first ball bearing 9 and a fixing member (not shown) arranged behind the first ball bearing 9. The pressing spring 12 presses the ring gear 6 forward through the first ball bearing 9 and holds the ring gear 6 at a predetermined position along the axial direction.

  A sleeve 13 is rotatably mounted on the outer peripheral portion of the first input shaft 1, and a third ball bearing 14 is disposed between the outer peripheral surface of the sleeve 13 and the inner peripheral surface of the ring gear 6. The rear end portion of the first support shaft 5 is inserted into the flange portion 15 formed at the front end portion of the sleeve 13, and the removal of the first support shaft 5 is prevented by the retaining ring 16. The sleeve 13 rotates integrally with the first cage 4.

  A second input shaft 101 of the second planetary gear mechanism PG2 is integrally formed on the first cage 4 on the same axis as the rotation center axis L1. A second sun gear 102 is formed at the tip of the second input shaft 101. A plurality of second planetary gears 103 are arranged around the second sun gear 102, and the plurality of second planetary gears 103 mesh with the second sun gear 102. The plurality of second planetary gears 103 mesh with the second inner teeth 7 b of the ring gear 6. The plurality of second planetary gears 3 are rotatably attached to a second carrier (cage) 104 via a second support shaft 105. The second cage 104 is formed with a shaft hole 104a centered on the rotation center axis L1. The shaft hole 104a is splined at the inner periphery, for example, and an output shaft (not shown) is splined. The forward movement of the second cage 104 is restricted by a front retaining plate 106 that engages with the inner peripheral surface of the ring gear 6. Further, the rear end portion of the second support shaft 105 is engaged with the rear retaining plate 107 and restricts the second support shaft 105 from slipping forward.

  As shown in FIG. 3, an engagement protrusion 17 extending outward in the radial direction is formed on the outer peripheral portion of the ring gear 6. The engagement protrusion 17 has an engagement shaft portion 17b formed on the tip side from a base portion 17a formed in a columnar shape. The engagement shaft portion 17b is formed in a barrel (barrel type) shape in which the diameter of the central portion in the length direction is maximized, and the diameter gradually decreases toward the distal end side and the base portion side. And the largest diameter part of the engaging shaft part 17b makes point contact with the inner peripheral surface of the engaging recessed part 22 mentioned later.

  As shown in FIG. 2, an elongated opening 18 is formed in the peripheral wall portion of the casing 8 along the axial direction of the central axis L1. The engaging protrusion 17 enters the front side of the opening 18. A width W in the circumferential direction (short direction) of the opening 18 is formed longer than the outer diameter of the engagement protrusion 17.

  A torque detection lever 20 is disposed in the opening 18. The torque detection lever 20 has a rectangular parallelepiped fixing portion 21 on the rear end portion side, and an engagement concave portion 22 in which the engagement shaft portion 17b of the projection portion 17 is engaged is formed on the front end side.

  The torque detection lever 20 disposed in the opening 18 has a rectangular parallelepiped fixed portion 21 fixed to the casing 18 by a bolt 50 and a cantilever support structure having an engagement recess 22 extending forward from the fixed portion 21 as a free end. It is said.

  As shown in FIG. 4, a rectangular parallelepiped lever main body 23 is integrally formed between the fixing portion 21 and the engaging recess 22. Strain gauges that constitute strain detecting means are attached to the opposing one side wall surface 23a and the other side wall surface 23b of the lever main body 23 to constitute a torque detector. The strain detection means is not limited to the strain gauge, and any strain detection means may be used as long as it can detect the strain of the lever main body 23.

  In the present embodiment, two strain gauges 24a and 24b are attached to one side wall surface 23a. A wiring board 26 is attached to the upper wall surface 23c of the fixing portion 21. The wiring board 26 has a wiring pattern to which the lead wires 25a and 25b of the strain gauges 24a and 24b are connected. An output terminal cable (not shown) that outputs a detection signal to a control unit (not shown) of the power transmission device is connected to the wiring board 26.

  When the torque detection lever 20 receives a bending load in the width direction orthogonal to the rotation center axis L1 and the lever main body portion 23 is bent, the strain gauges 24a and 24b detect strain accompanying the generation of bending stress. Based on the strain detected by the torque detection lever 20, the control unit obtains the torque. When the length of the lever main body 23 in the direction of the rotation center axis L1 is long, high detection accuracy is obtained. In the present embodiment, even if the lever main body portion 23 is lengthened, it only becomes longer in the direction of the rotation center axis L1 and does not extend outward in the radial direction of the casing 8. For this reason, the outer shape of the casing 8 can be formed in a cylindrical shape, for example. Here, when the engagement protrusion 17 shown in FIG. 1 has the same length as that of the torque detection lever 20 and the engagement protrusion 17 has the role of the torque detection lever 20, a part of the casing 8 is radially aligned. It will protrude greatly outward, making it unusable.

  Two bolt holes 27a and 27b are formed through the fixing portion 22 in the width direction in the front-rear direction. An insertion hole portion 28 into which the bolt 50 is inserted is formed in the front-rear direction in the wall portion 18 c on one end side in the width direction of the opening portion 18. In addition, a screw hole 29 into which the screw part of the bolt 50 is screwed is formed in the wall part 18 d on the other end side in the width direction of the opening part 18, corresponding to the insertion hole part 28. The width of the fixed portion 21 is formed to a size that can be accommodated in the opening 18 without play.

  In order to fix the torque detection lever 20 to the opening 18, the torque detection lever 20 is disposed in the opening 18 from above the opening 18. Next, the bolt holes 27a and 27b of the fixing portion 21 are aligned with the insertion hole portion 28 of the wall portion 18c. Then, the bolt 50 is inserted into the bolt holes 27 a and 27 b from the insertion hole portion 28 side, and screwed into the screw hole 29 and fixed.

  When the torque detection lever 20 is fixed in the opening 18, alignment in the direction of the rotation center axis L <b> 1 is performed with the protrusion 17 entering the engagement recess 22. Positioning is performed such that the fixed end of the torque detection lever 20 and the protrusion 17 are brought into contact with each other by point contact, and the distance between the acting point on which the bending load acts is a predetermined distance.

  The maximum width W <b> 1 of the engagement recess 22 is formed narrower than the width W of the opening 18. Therefore, the torque detection lever 20 is bent and deformed until the engagement recess 22 abuts on the inner peripheral surfaces 18 a and 18 b of the opening 18. The contact wall surfaces 22a and 22b that face each other in the width direction of the engagement recess 22 and contact the engagement shaft portion 17b of the protrusion 17 are formed symmetrically with respect to the rotation center axis L1. In the present embodiment, the torque at the time of both the forward rotation and the reverse rotation can be detected.

  The facing width between the contact wall surfaces 22a and 22b is such that the width D1 at the open end is wider than the width D0 at the back side. That is, both of the contact wall surfaces 22a and 22b are formed as inclined surfaces that are spread outward toward the front with respect to the rotation center axis L1.

  When the ring gear 6 receives a rotational force in a clockwise direction, for example, the engagement shaft portion 17b of the engagement protrusion 17 contacts the contact wall surface 22a and bends the torque detection lever 20. At this time, if the engagement shaft portion 17b is in contact with the specific position of the contact wall surface 22a, the position of the point of application of the load on the torque detection lever 20 does not shift. Assuming that the contact wall surface 22a is parallel to the rotation center axis L1, as the torque detection lever 20 is bent, the position of the contact wall surface 22a with which the engagement shaft portion 17b contacts is shifted. That is, when the ring gear 6 rotates, the engagement shaft portion 17b moves linearly in the width direction. Since the torque detection lever 20 is bent by the load applied by the engagement shaft portion 17b, the position where the engagement shaft portion 17b contacts the contact wall surface 22a moves to the tip side from the position where the engagement shaft portion 17b first contacts. Therefore, the contact wall surface 22a is inclined with respect to the rotation center axis L1, so that when the load is applied to the torque detection lever 20 by the engagement shaft portion 17b, the engagement shaft portion 17b contacts the contact wall surface 22a. The contact position is kept from shifting as much as possible.

  As described above, since the ring gear 6 is pressed to a predetermined position in front by the pressing spring 12, the engagement shaft portion 17b and the engagement concave portion 22 of the torque detection lever 20 are located on the rotation center axis L1. The contact position in the axial direction is positioned with high accuracy.

  The torque detection operation of the torque detection device 100 configured as described above will be described below.

  When a motor (not shown) rotates clockwise (forward rotation), in the first planetary gear mechanism PG1, the first sun gear 2 integrated with the first input shaft 1 rotates in the forward direction. The second sun gear 102 of the second planetary gear mechanism PG2 also rotates in the forward direction via the first cage 4 and is loaded via an output shaft (not shown) connected to the second cage 104 of the second planetary gear mechanism PG2. Rotate. By rotating the load, the ring gear 6 rotates in the forward direction, and the engagement protrusion 17 of the ring gear 6 applies a bending load to the torque detection lever 20. If the load torque is small, there is little bending deformation of the torque detection lever 20, so that the distortion accompanying the bending stress of the lever main body 23 is small. Moreover, since the bending deformation of the torque detection lever 20 is large when the load torque is large, the strain accompanying the bending stress of the lever main body 23 is large. The strain gauges (24a, 24b) constituting the torque detection body together with the torque detection lever 20 detect the strain of the lever main body 23 and output a detection signal to the control unit. When the load torque is very large, the outer end of the engagement recess 21 of the torque detection lever 20 contacts the inner wall surface 18a of the opening 18 to prevent the torque detection lever 20 from being damaged.

  On the other hand, when exchanging the torque detection body, when the bolt 50 fixing the torque detection lever 20 is removed from the outside of the casing 8, the fixing of the fixing portion 21 of the torque detection lever 20 and the casing 8 is released. The opening 18 is covered from the outside of the casing 8 by a cover member (not shown) that is screwed. Therefore, the cover member is removed from the opening 18 before replacing the torque detector.

  When the fixing of the fixing portion 21 of the torque detection lever 20 and the casing 8 is released, the torque detection lever 20 can be pulled out of the casing 8 from the opening 18. At that time, when a connector cable (not shown) connected to the wiring board 26 attached to the torque detection lever 20 is removed from the wiring board 26, the torque detection body can be completely removed from the casing 8. On the other hand, when a new torque detector is attached to the casing 8, the procedure may be the reverse of the above-described removal operation.

  In the torque detection device 100 of the present embodiment, a torque detection lever 10 extending in parallel with the rotation center axis is disposed in the casing 8 and is provided in the ring gear 6 using a reaction force generated in the ring gear 6 of the planetary gear mechanism PG1. A bending load is applied to the torque detection lever 20 by the engaging projection 6.

  According to this configuration, the engaging protrusion 6 may protrude from the ring gear 6 outward in the radial direction by a length that can engage with the engaging recess 22 of the torque detection lever 20. For this reason, the casing 8 can be formed in an arbitrary outer shape without being affected by the protruding length of the engaging protrusion 8. In addition, since the torque detection lever 20 is disposed on the peripheral wall portion of the casing 8 along the rotation center axis direction, the lever main body portion 23 can be lengthened to increase the strain detection accuracy.

  On the other hand, the torque detection lever 20 is accommodated in the opening 18 facing the outer peripheral surface of the casing 8, and can be removed and attached from the outside of the casing 8. For this reason, even if a sensor such as a strain gauge attached to the torque detection lever breaks down, only the torque detection body needs to be replaced. At this time, since it is not necessary to disassemble the planetary gear mechanism or the like disposed in the casing 8, the replacement operation of the torque detection lever 20 can be easily performed.

  In the above-described embodiment, a power transmission device in which a planetary gear mechanism is connected in two stages to configure a reduction gear is taken as an example, but a planetary gear mechanism having one or three or more stages may be used. The drive source may be not only an electric motor but also an air motor, an engine, or the like.

  Further, although the torque detection lever 20 is accommodated in the opening 18 provided in the casing 8, a through-hole portion through which the engagement shaft portion 17 b of the engagement projection portion 17 passes is formed in the peripheral wall portion of the casing 8. The through hole is a horizontally long hole through which the engaging protrusion 17 can move to some extent in the width direction. The torque detection lever 20 may fix the fixing portion 21 to the outer peripheral surface of the casing 8 with a bolt or the like.

100 Torque detection device PG1 First planetary gear mechanism PG2 Second planetary gear mechanism L1 Rotation center shaft 1 First input shaft 101 First input shaft 2 First sun gear 102 Second sun gear 3 First planetary gear 103 Second planetary gear 4 First carrier (cage) 104 Second carrier (cage)
5 1st support shaft 105 2nd support shaft 6 Ring gear 7a 1st internal tooth 7b 2nd internal tooth 8 Casing 8a Inner peripheral surface 9 1st ball bearing 10 2nd ball bearing 11 Step part 12 Pressing spring 13 Sleeve 14 3rd Ball bearing 15 Flange 16 Retaining ring 106 Front retaining plate 107 Rear retaining plate 17 Engaging projection 17a Root 17b Engaging shaft 18 Opening 18a, 18b Inner peripheral wall 18c, 18d Wall 20 Torque detection lever 21 Fixing part 22 Engaging recess 23 Lever body part 22a, 22b Abutting wall surface 23a One side wall surface 23b Other side wall surface 23c Upper wall surface 24a, 24b Strain gauge 25a, 25b Lead wire 26 Wiring board 27a, 27b Bolt hole 28 Insertion hole 29 Screw hole 50 bolt

Claims (6)

A casing,
A planetary gear mechanism that is disposed in the casing, has a ring gear that can rotate relative to the casing around a rotation center axis, and transmits the rotation of the input shaft to the output shaft;
An engagement protrusion that protrudes radially outward from the outer periphery of the ring gear;
An opening formed in the casing for allowing the engagement protrusion to enter, and the engagement protrusion together with the ring gear to allow movement around the rotation center axis within a predetermined range;
A torque detection lever that extends along the direction of the rotation center axis, one end side of which is fixed to the casing, and a front end side engaging portion that forms a free end engages with the engaging protrusion;
Strain measuring means for measuring strain of the torque detection lever that is bent and deformed by a load applied by the engaging protrusion;
A torque detection device.   The torque detection device according to claim 1, wherein the opening of the casing is formed in a size that accommodates the torque detection lever.   The torque detection device according to claim 1 or 2, wherein the torque detection lever is fixed at one end to the casing by a fastening member attached from the outside of the casing.   The torque detection device according to claim 1, wherein the ring gear is urged and positioned in one direction along a rotation center axis with respect to the casing.   The torque detecting device according to any one of claims 1 to 4, wherein an engaging shaft portion in which the engaging protrusion engages with an engaging portion of the torque detection lever is formed in a barrel shape. 6. The torque detection device according to claim 1, wherein a distal end of the engagement protrusion extends to a length that engages with an engagement portion of the torque detection lever.