JP5552359B2 - Reduction gear - Google Patents

Description

  The present invention relates to a reduction gear. In particular, the present invention relates to a speed reduction device in which an external gear rotates relatively eccentrically while meshing with an internal gear.

  2. Description of the Related Art A speed reducer is known in which an external gear rotates relatively eccentrically while meshing with an internal gear. When the external gear rotates eccentrically while meshing with the internal gear, the carrier supporting the external gear rotates relative to the internal gear according to the difference in the number of teeth of both. That is, when the external gear rotates eccentrically once, the carrier shifts with respect to the internal gear by an angle corresponding to the above-described difference in the number of teeth. By such a phenomenon, a large reduction ratio can be obtained between the external gear (carrier) and the internal gear. An example of such a reduction gear is disclosed in Patent Document 1. In the reduction gear of Patent Document 1, an internal gear is formed by a plurality of grooves arranged along the circumferential direction on the inner side surface of the case and pins inserted into the grooves. When the pin and the external gear come into contact with each other, the internal gear and the external gear mesh with each other. In the case of a reduction gear of a type in which the external gear rotates eccentrically, the external gear rotates eccentrically around the axis of the internal gear. Further, in the case of a speed reduction device in which the internal gear rotates eccentrically, the internal gear rotates eccentrically around the axis of the external gear.

JP 2009-204156 A

  In the reduction gear of Patent Document 1, a large force is applied from the external gear to the internal gear (case). Since the pin is inserted into the groove formed on the inner side surface of the case to form the internal gear, the force from the external gear is locally applied to the case via the pin. In order to suppress the deformation of the case, that is, to increase the strength of the case, it is necessary to sufficiently increase the thickness of the case in the radial direction. Therefore, the radial thickness of the case increases and the speed reducer becomes large. The present specification provides a technique for reducing the size of a reduction gear.

  The speed reduction device disclosed in this specification is an eccentric oscillating type in which an external gear relatively rotates eccentrically while meshing with an internal gear. The speed reduction device includes a first member having an internal gear formed on the inner surface and a second member fixed to the outer surface of the first member. The internal gear is formed by a plurality of grooves formed along the circumferential direction on the inner surface of the first member and a plurality of pins inserted into the grooves. The second member is fixed to the outer surface of the first member by shrink fitting so as to surround the plurality of pins.

  In the above reduction gear, the first member and the second member constitute a case of the reduction gear. By compressing the second member to the first member, a compressive force is applied from the second member to the first member. As a result, a force directed toward the radial center of the first member (the radial center of the case) also acts on the first member. In other words, an internal stress is generated in the first member toward the radial center of the first member. An internal force (internal stress of the first member) toward the center in the radial direction of the case counters a part of the force applied to the case from the external gear. The strength of the case can be increased while suppressing an increase in the radial thickness of the case. That is, a small reduction gear can be realized.

  Projections or particles may be embedded in at least one of the outer surface of the first member and the inner surface of the second member. As described above, the first member of the second member is shrink-fitted. For this reason, when a force is applied from the external gear to the internal gear, the first member and the second member may slip relative to each other. For example, since the external gear and the internal gear rotate relatively, torque is applied to the internal gear (case) in the direction in which the external gear rotates. The torque may cause the first member to rotate relative to the second member. If protrusions or particles are embedded in at least one of the outer surface of the first member and the inner surface of the second member, the relative rotation of the first member and the second member can be suppressed. That is, it is possible to suppress slippage between the outer surface of the first member and the inner surface of the second member.

  Particles made of a material harder than both the first member and the second member may be disposed between the first member and the second member. If such particles are arranged between the first member and the second member, the particles are embedded in both the outer surface of the first member and the inner surface of the second member. Slip between the first member and the second member is less likely to occur.

  The technology disclosed in the present specification can increase the strength of the case while suppressing an increase in the radial thickness of the case.

Sectional drawing of the reduction gear device of 1st Example is shown. FIG. 2 shows a cross-sectional view along the line II-II in FIG. 1. The expanded sectional view of the part enclosed with the broken line III of FIG. 2 is shown. The expanded sectional view of the modification of the speed reducer of 1st Example is shown. Sectional drawing of the speed reducer of 2nd Example is shown. Sectional drawing of the deceleration device of 3rd Example is shown.

Before describing the embodiments, the technical features of the embodiments are briefly described below.
(Feature 1) Particles are distributed between the first member and the second member. The particles are made of a material harder than the first member and the second member. More specifically, the first member and the second member are formed of a material having a Brinell hardness (HB) of 140 to 170, and the particles distributed between the first member and the second member are from the Brinell hardness 350. Is also made of a hard material (first embodiment and second embodiment).
(Feature 2) A plurality of grooves are formed along the circumferential direction on the inner surface of the first member. In the plurality of grooves, every other internal tooth pin is inserted (second embodiment).
(Feature 3) The second member is fixed to the base or the rotated member (first and second embodiments).
(Feature 4) The first member is fixed to the base or the rotated member (third embodiment).

  (First Embodiment) A reduction gear 100 will be described with reference to FIGS. FIG. 1 shows a cross section of the reduction gear device 100 along the axial direction. FIG. 2 shows a cross section along the radial direction (direction orthogonal to the axial direction) of the reduction gear 100. In order to clarify the drawing, hatching for representing a cross section is omitted for some parts. The reduction gear 100 is an eccentric oscillating type in which the external gear 26 rotates eccentrically while meshing with the internal gear 32. The internal gear 32 is formed by inserting the internal gear pin 28 into a plurality of grooves 60 formed in the inner surface of the first member 30 along the circumferential direction. In the speed reducer 100, the internal tooth pins 28 are inserted into all the grooves 60. The internal gear 32 will be described in detail. The first member 30 has a ring shape. A plurality of grooves 60 extending in the direction of the axis 44 of the internal gear 32 are formed at equal intervals in the circumferential direction on the inner surface of the first member 30. The internal gear 32 is formed by inserting a cylindrical internal tooth pin 28 into each of the plurality of grooves 60. The external gear 26 rotates eccentrically around the axis 44 while contacting the internal tooth pin 28. The axis 44 can also be referred to as the axis of the reduction gear 100.

  The second member 34 is fixed to the outer surface of the first member 30 by shrink fitting. The second member 34 has a ring shape. The second member 34 is disposed on the radially outer side of the first member 30 so as to surround the internal tooth pin 28. That is, the inner peripheral surface of the ring-shaped second member 34 is fixed to the outer peripheral surface of the ring-shaped first member 30. The second member 34 is shrink-fitted to the first member 30 in a state where metal particles are dispersed between the inner surface of the second member 34 and the outer surface of the first member 30. Although details will be described later, the metal particles are embedded in both the inner surface of the second member 34 and the outer surface of the first member 30. The metal particles make it difficult for the first member 30 to slip relative to the second member 34. The first member 30 (or the internal gear 32) and the second member 34 constitute a case 36 of the reduction gear 100. Although details will be described later, the first member 30 is subjected to internal stress toward the center. The internal stress opposes a part of the force applied from the external gear 26 to the case 36.

  Here, the basic structure of the reduction gear 100 will be briefly described. Inside the case 36, the carrier 8, the external gear 26, the crankshaft 16, and the like are arranged. The carrier 8 is supported on the case 36 by a pair of angular ball bearings 2. The carrier 8 includes a first carrier part 8a and a second carrier part 8c. A columnar portion 8b extends from the first carrier portion 8a toward the second carrier portion 8c, and the columnar portion 8b is fixed to the second carrier portion 8c. The positioning pin 54 prevents the first carrier portion 8a from being displaced in the circumferential direction with respect to the second carrier portion 8c. In other words, the positioning pin 54 prevents relative rotation between the first carrier portion 8a and the second carrier portion 8c. The shape of the positioning pin 54 is a taper shape in which the outer diameter becomes narrower toward the distal end side (first carrier part 8a side). The carrier 8 supports the external gear 26 and the crankshaft 16. Precisely, the carrier 8 supports the crankshaft 16, and the crankshaft 16 supports the external gear 26.

  The crankshaft 16 extends along the axis 44. The crankshaft 16 is supported on the carrier 8 by a pair of tapered roller bearings 22. The crankshaft 16 includes a gear 14 and an eccentric body 18. The gear 14 meshes with a gear (not shown) fixed to the output shaft of the motor. The axis of the eccentric body 18 is deviated from the axis of the crankshaft 16. Therefore, when the crankshaft 16 rotates, the eccentric body 18 rotates eccentrically.

  As shown in FIG. 2, the external gear 26 has a first through hole 38, a second through hole 56, and a third through hole 46. The crankshaft 16 passes through the first through hole 38. The eccentric body 18 of the crankshaft 16 is fitted into the first through hole 38 via the cylindrical roller bearing 24. Therefore, when the crankshaft 16 rotates, the external gear 26 rotates eccentrically with the eccentric rotation of the eccentric body 18. The columnar portion 8 b of the carrier 8 passes through the second through hole 56. There is a gap between the wall surface of the second through hole 56 and the columnar portion 8 b, and the columnar portion 8 b does not contact the wall surface of the second through hole 56 even if the external gear 26 rotates eccentrically. The third through hole 46 will be described later.

  When torque of a motor (not shown) is transmitted to the gear 14, the crankshaft 16 rotates. When the crankshaft 16 rotates, the eccentric body 18 rotates eccentrically. As the eccentric body 18 rotates eccentrically, the external gear 26 rotates eccentrically around the axis 44 while meshing with the internal gear 32. The number of teeth of the external gear 26 and the number of teeth of the internal gear 32 (number of internal pins 28) are different. Therefore, when the external gear 26 rotates eccentrically, the carrier 8 that supports the external gear 26 with respect to the internal gear 32 (case 36) according to the number of teeth difference between the external gear 26 and the internal gear 32. Rotate. That is, when the crankshaft 16 rotates, the carrier 8 rotates relative to the internal gear 32 (case 36). In the reduction gear 100 of the present embodiment, the number of external teeth of the external gear 26 is 39, and the number of internal teeth (internal gear pins 28) of the internal gear 32 is 40. Therefore, a reduction ratio of “40” can be obtained between the external gear 26 and the internal gear 32. In other words, the rotation input to the crankshaft 16 is reduced by a factor of 40 between the external gear 26 and the internal gear 32 and output from the reduction gear 100.

  With reference to FIG. 3, features of the speed reduction device 100 will be described in detail. As described above, in the reduction gear 100, a reduction ratio of “40” can be obtained between the external gear 26 and the internal gear 32. In order to generate such a large reduction ratio, a large force is applied from the external gear 26 to the internal gear 32 (internal gear pin 28). The force applied from the external gear 26 to the internal gear 32 is locally concentrated in the groove 60 of the first member 30. Therefore, a large force is applied to the first member 30 in the direction of the arrow 64 (the direction from the center of the internal gear 32 toward the radially outer side). However, in the reduction gear 100, the second member 34 is shrink-fitted onto the first member 30. A force is applied from the second member 34 to the first member 30 in the direction of the arrow 62 (the direction from the radially outer side of the internal gear 32 toward the center). In other words, an internal stress directed toward the center of the internal gear 32 is generated in the first member 30. Therefore, even if a force in the direction of the arrow 64 is applied from the external gear 26 to the first member 30, the first member 30 is suppressed from being deformed. Since the strength of the case 36 is increased, the deformation of the internal gear 32 is suppressed, and the durability of the reduction gear 100 is improved.

  If the thickness of the first member 30 in the radial direction is increased, the second member 34 may not be shrink-fitted onto the first member 30 (even if the speed reduction device case is formed only by the first member 30). Deformation of the first member 30 can be suppressed. However, in this case, the size of the reduction gear increases. The thickness of the first member 30 when the case of the speed reducer is formed only by the first member 30 is thicker than the total thickness in the radial direction when the second member 34 is shrink-fitted on the first member 30. It is necessary to. That is, if the case 36 is formed by shrink fitting the second member 34 on the first member 30, the strength of the reduction gear can be increased without increasing the size of the reduction gear. In other words, the size of the reduction gear can be reduced without impairing the strength of the reduction gear.

  Other features of the reduction gear 100 will be described. In the speed reducer 100, the second member 34 is fixed to the base or the rotated member. A force is applied to the first member 30 to rotate the second member 34 in the same direction as the direction in which the external gear 26 rotates. When a large force is applied to the first member 30, the first member 30 may rotate with respect to the second member. However, the second member 34 is shrink-fitted to the first member 30 with the metal particles 70 disposed on the outer surface of the first member 30. The hardness of the metal particles 70 is harder than the hardness of the first member 30 and the second member 34. Therefore, when the second member 34 is shrink-fitted to the first member 30 in a state where the metal particles 70 are arranged on the outer surface of the first member 30, the metal particles 70 are aligned with the outer surface of the first member 30 and the second member 34. It is embedded in both the inside surfaces of the. In other words, the metal particles 70 bite into both the outer surface of the first member 30 and the inner surface of the second member 34. As a result, the first member 30 is prevented from rotating with respect to the second member. In other words, the first member 30 is prevented from slipping with respect to the second member 34. The “base” indicates a part to which the reduction gear 100 is fixed. “Rotated member” means a component that the reduction device 100 rotates with respect to the “base”.

  As described above, since the case 36 (second member 34) is fixed to the base or the rotated member, a moment acts on the case 36 from the carrier 8 that is the output shaft. In such a case, a force that slides in the direction of the axis 44 with respect to the second member 34 may be applied to the first member 30. If the second member 34 is shrink-fitted to the first member 30 with the metal particles 70 disposed on the outer surface of the first member 30, the first member 30 can also be prevented from sliding in the direction of the axis 44.

  The material of the metal particle 70, the 1st member 30, and the 2nd member 34 is demonstrated. The metal particle 70 is typically a steel material. As a material of the metal particles 70, for example, SUS440C, SKH57, SKD11, S55C quenching material, SUJ2 quenching material, or the like can be used. The Brinell hardness of SUS440C, SKH57, and SKD11 is HB582, HB452, and HB397, respectively. Further, the Brinell hardness of the S55C quenching material and the SUJ2 quenching material are both HB500 or more. On the other hand, FCD450 or the like can be used as a material for the first member 30 and the second member 34. The Brinell hardness of FCD450 is HB140-170. Note that SUS440C, SKH57, SKD11, S55C, SUJ2 and FCD450 are standardized in JIS G 4303, JIS G 4403, JIS G 4304, JIS G 4051, JIS G 4805 and JIS G 5501, respectively.

  The size of the metal particles 70 is preferably 5 to 100 μm. By using the metal particles 70 of such a size, the metal particles 70 can be embedded on both surfaces while the inner surface of the second member 34 is in close contact with the outer surface of the first member 30. Further, the shape of the metal particle 70 may be a “sphere”, an elongated “wedge”, or a “pin shape”. In the case of a “sphere” shape, the size of the metal particle 70 means the diameter of the “sphere”. In the case of “wedge” or “pin shape”, the size of the metal particle 70 means the length of the metal particle 70. In addition, as the metal particles 70, polishing powder generated when a part (for example, a race of the angular ball bearing 2) constituting the reduction gear 100 is polished may be used. Waste generated in the process of manufacturing the reduction gear 100 can also be reduced.

  The description of other features of the reduction gear 100 will be continued. As shown in FIG. 1, a through hole 10 is formed at the center of the first carrier portion 8a, and a through hole 48 is formed at the center of the second carrier portion 8c. Further, as described above, the third through hole 46 is formed at the center of the external gear 26. By the through holes 10, 48 and 46, a through hole 42 that penetrates the reduction gear 100 in the axial direction (in the direction of the axis 44) is formed. Wiring, piping, etc. can be passed through the through hole 42. Alternatively, a motor (not shown) can be attached to the second carrier portion 8 c side, and a motor output shaft for transmitting torque to the gear 14 can be passed through the through hole 42. The oil seal 4 is provided between the case 36 (second member 34) and the first carrier portion 8a. The oil seal 4 prevents oil (lubricant) in the reduction gear 100 from leaking to the outside.

  With reference to FIG. 4, a reduction gear 100a, which is a modification of the reduction gear 100, will be described. Note that the appearance and cross-sectional shape of the reduction gear 100a described here are substantially the same as those of the reduction gear 100. Therefore, the shape of FIG.1 and FIG.2 is applied also to the speed reducer 100a. FIG. 4 shows an enlarged sectional view of the reduction gear 100a corresponding to the enlarged sectional view (FIG. 3) of the reduction gear 100. FIG. In the speed reduction device 100, the second member 34 with the metal particles 70 disposed between the first member 30 and the second member 34 in order to prevent the first member 30 from sliding relative to the second member 34. (See FIG. 3). Therefore, it is necessary to prepare the metal particles 70 separately from the first member 30 and the second member 34. On the other hand, as shown in FIG. 4, in the speed reduction device 100 a, the protrusion 72 is formed in advance on the outer surface of the first member 30, and the second member 34 is shrink-fitted onto the first member 30. The protrusion 72 is embedded in the inner surface of the second member 34, and the first member 30 and the second member 34 can be prevented from slipping. Further, in the speed reducer 100a, the first member 30 is manufactured from a material harder than the second member 34. Thereby, the protrusion 72 is reliably embedded in the inner surface of the second member 34. In the reduction gear 100 a, protrusions can be formed in advance on the inner surface of the second member 34 and the second member 34 can be shrink-fitted onto the first member 30. In this case, the second member 34 is made of a material harder than the first member 30.

  The characteristics of the speed reduction device 100a can be summarized as follows. In the speed reduction device 100a, a protrusion is formed on one of the outer surface of the first member 30 and the inner surface of the second member 34, and the protrusion is embedded in the other surface. The protrusion bites into the other surface. In other words, the protrusion embedded in one of the outer surface of the first member 30 and the inner surface of the second member 34 is formed on the other surface.

  In addition, it is preferable that the size of the protrusion formed on the outer surface of the first member 30 or the inner surface of the second member 34 is 5 to 100 μm. The protrusion of such a size can be easily formed by reducing the processing accuracy when processing the outer surface of the first member 30 or the inner surface of the second member 34. The speed reduction device 100a can reduce the material (particles) to be prepared as compared with the speed reduction device 100, and can easily process the first member 30 or the second member 34.

  In the reduction gears 100 and 100a, the second member 34 covers almost the entire outer surface of the first member 30 (shrink-fitted). However, the second member 34 may be shrink-fitted only in the axial range where the external gear 26 and the internal pin 28 mesh. That is, the second member 34 may be shrink-fitted only in a range in which a force is applied to the first member 30 from the external gear 26 via the internal tooth pin 28. If the inner surface of the first member 30 before the groove 60 is formed is circular, the outer surface of the first member 30, the inner surface of the second member 34, and the outer surface of the second member 34 are not circular. May be. However, the outer surface of the first member 30 and the inner surface of the second member 34 need to have the same shape.

  (Second Embodiment) The speed reduction device 200 will be described with reference to FIG. The reduction gear 200 is a modification of the reduction gear 100. Hereinafter, the same parts as those of the reduction gear 100 are denoted by the same reference numerals, and the description thereof is omitted. In the reduction gear 200, a cross section along the axial direction (a cross section corresponding to FIG. 1 of the reduction gear 100) is omitted. The cross section along the axial direction of the reduction gear 200 is substantially equal to that of the reduction gear 100. In the speed reducer 200, every other internal tooth pin 28 is inserted into the groove 60 of the first member 30. Therefore, the speed reducer 200 requires half the number of internal tooth pins 28 than the speed reducer 100. Parts cost and assembly cost can be reduced.

  In the speed reduction device 200, the force applied from the external gear 26 to one internal tooth pin 28 is greater than that of the speed reduction device 100. Therefore, if an internal gear (case) is formed only by the first member 30, it is necessary to extremely increase the thickness of the case in the radial direction. Since the second member 34 is shrink-fitted on the first member 30, it is not necessary to increase the radial thickness of the case 36 (the sum of the thickness of the first member 30 and the thickness of the second member 34). The technique of shrink-fitting the second member 34 to the first member 30 to form the case 36 is particularly useful when the internal pin 28 is not inserted into some of the grooves 60.

  (Third Embodiment) A reduction gear 300 will be described with reference to FIG. The reduction gear 300 is a modification of the reduction gear 100. In the following description, the same components as the speed reduction device 100 are denoted by the same reference numerals or the last two digits, and the description thereof is omitted. In the reduction gear 300, a cross section along the radial direction (a cross section corresponding to FIGS. 2 and 3 of the reduction gear 100) is omitted. The cross section along the radial direction of the speed reduction device 300 is substantially the same as that of the speed reduction device 100 (the thickness ratio in the radial direction of the first member and the second member is different). In the reduction gear device 300, the internal gear 332 is formed by inserting the internal gear pin 28 into a groove formed in the circumferential direction of the first member 330. A case 336 is formed by the second member 334 and the first member 330 (internal gear 332). The second member 334 is shrink-fitted onto a part of the outer surface of the first member 330.

  In the speed reduction device 300, the first member 330 is fixed to the base or the rotated member. The second member 336 is shrink-fitted on the outer surface of the first member 330. Therefore, the first member 330 does not rotate relative to the second member 336. In the speed reduction device 300, particles are disposed between the first member 330 and the second member 336, or a protrusion is formed on either the outer surface of the first member 330 or the inner surface of the second member 334. There is no need. In the reduction gear 300 as well, the second member 336 is shrink-fitted in the axial range where the external gear 26 and the internal pin 28 mesh.

  In the above embodiment, the first through hole 38 is formed in the external gear 26, and the eccentric body 18 of the crankshaft 16 is fitted into the first through hole 38 via the cylindrical roller bearing 24. As a result, the external gear 26 rotates eccentrically around the axis 44. However, a through hole may be formed in the internal gear, and the eccentric body of the crankshaft may be fitted into the through hole of the internal gear via a cylindrical roller bearing. The internal gear may rotate eccentrically around the axis of the reduction gear. The eccentric body of the crankshaft only needs to be engaged with a through hole formed in one of the internal gear and the external gear.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

26: External gear 28: Pin (internal tooth pin)
30: First member 32: Internal gear 34: Second member 60: Groove 70: Particle 72: Projection 100: Reduction gear

Claims (3)

The external gear is a reduction device that rotates relatively eccentrically while meshing with the internal gear,
Case and
A carrier supported on the case by a pair of bearings,
The case is
A ring-shaped first member;
A second member fixed to the outer surface of the first member;
With
The pair of bearings are attached to the inner surfaces of both end portions in the axial direction of the first member ,
A plurality of grooves are formed along the circumferential direction on the inner surface of the intermediate portion in the axial direction of the first member,
Wherein the internal gear to result in the interior by inserting the plurality of pins into a plurality of grooves are configured,
The speed reducer , wherein the second member is fixed to the outer surface of the first member by shrink fitting so as to surround the pair of bearings and the plurality of pins.   The speed reducer according to claim 1, wherein protrusions or particles are embedded in at least one of the outer surface of the first member and the inner surface of the second member.   The speed reducer according to claim 2, wherein particles made of a material harder than both the first member and the second member are disposed between the first member and the second member.

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