JP2014081001A - Speed reducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed reducer which can perform both large speed reduction and low backlash.SOLUTION: A speed reducer is provided with: a tapered first internal gear 5; a tapered first external gear 6 which revolves while rotating inside the first internal gear 5 in the state that it is engaged with the first internal gear 5; a tapered second internal gear 7; and a tapered second external gear 8 which is joined to the first external gear 8 in an axial direction and revolves while rotating inside the second internal gear 7 in the state that it is engaged with the second internal gear 7. The first external gear 6 is relatively movable in the axial direction with respect to the first internal gear 5, and the second external gear 8 joined to the first external gear 6 is relatively movable in the axial direction with respect to the second internal gear 7. A first disc spring 21 energizes either the first external gear 6 or the first internal gear 5 to the other in the axial direction. A second disc spring 24 energizes either the second external gear 8 or the second internal gear 7 to the other in the axial direction.

Description

  The present invention relates to a speed reducer that reduces the rotational speed of an input shaft with a gear and outputs the reduced speed.

  2. Description of the Related Art As a conventional speed reducer, a speed reducer that obtains a large speed reduction by making a spur gear multistage is known. However, when the spur gear is multi-staged, rattling due to backlash accumulation increases. Backlash is play that occurs between tooth surfaces when a set of gears is engaged. Without the backlash, the spur gear does not rotate, so backlash cannot be avoided. When position control is performed by connecting a reduction gear to the output shaft of a servo motor, rattling due to accumulated backlash causes a problem in position control. For example, there is a problem that the position is shifted between when the servomotor is rotated clockwise and when it is rotated counterclockwise.

  As a method for reducing backlash, a combination of a scissor mechanism and a spring is known. In this case, two spur gears are overlapped and one side is shifted in the rotational direction, and the teeth of the mating spur gear are sandwiched between the springs like scissors. As another method for reducing backlash, a method is known in which a spur gear is thinned and a preload is applied to the meshing portion in the rotational direction using the elastic force of the spur gear itself.

  On the other hand, a planetary gear type reduction device in which a sun gear, a planetary gear, and an internal gear are stacked in the radial direction is known as a reduction device that achieves a large reduction. As a method for reducing the backlash of this planetary gear speed reducer, Patent Document 1 discloses that the planetary gear is a tapered gear, the sun gear and the internal gear are tapered gears corresponding to the planetary gears, and the planetary gears are movable in the axial direction. A method of urging the planetary gear from the large diameter side toward the small diameter side by the urging means is disclosed. Since the planetary gear only moves in the axial direction, it is impossible for the planetary gear to simultaneously contact the sun gear and the internal gear. That is, if the planetary gear contacts the sun gear, backlash remains between the planetary gear and the internal gear, and if the planetary gear contacts the internal gear, backlash remains between the planetary gear and the sun gear. End up. In order to bring the planetary gear into contact with the sun gear and the internal gear at the same time, in the planetary gear type reduction gear of Patent Document 1, the planetary gear is configured to be elastically deformable in the radial direction so that the outer diameter of the planetary gear changes. ing.

JP-A-6-272740

  However, in the method of reducing backlash by combining a scissor mechanism and a spring, there is a limit to the force of the spring, so backlash cannot be reduced for large inputs, and the mechanism has no meaning. There is. Even if the planetary gear type reduction gear is used as the reduction gear and the planetary gear itself is configured to be elastically deformable in the radial direction, the planetary gear itself has low rigidity, so that it can be used for large inputs. There is a problem that backlash cannot be reduced.

  Then, an object of this invention is to provide the reduction gear which can make large deceleration and low backlash compatible.

  In order to solve the above-described problems, the present invention provides a reduction mechanism that reduces the rotation of an input shaft and transmits it to an output shaft, and includes a housing and a first inner taper that is provided in the housing so as not to rotate. A gear, a tapered second internal gear rotatably provided on the housing, an output shaft rotating together with the second internal gear, and rotatably provided on at least one of the housing and the output shaft An input shaft having an eccentric shaft portion rotating while being eccentric, and supported by the eccentric shaft portion of the input shaft so as to be rotatable and movable in the axial direction of the eccentric shaft portion. A taper-shaped first external gear that revolves while rotating in an engaged state with the first internal gear, and an input shaft connected to the first external gear in the axial direction of the eccentric shaft. Rotating to the eccentric shaft And a second external gear having a tapered shape that is supported so as to be movable in the axial direction of the eccentric shaft portion and revolves while rotating inside the second internal gear while meshing with the second internal gear. And the axial direction of the first external gear and the first internal gear toward the other so that the clearance between the first external gear and the first internal gear is closed. One of the second external gear and the second internal gear is directed toward the other so that the clearance between the second external gear and the second internal gear is closed. Biasing means for biasing in the axial direction, wherein the number of teeth of the first internal gear and the number of teeth of the second internal gear are different and / or the first outer gear In this speed reduction mechanism, the number of teeth of the gear and the number of teeth of the second external gear are different.

  According to the present invention, when the input shaft is rotated, the first external gear supported by the eccentric shaft portion of the input shaft rotates inside the first internal gear while meshing with the first internal gear. Revolving and revolving while rotating inside the second internal gear in a state where the second external gear connected to the first external gear in the axial direction meshes with the second internal gear. Assuming that the number of teeth of the first external gear and the number of teeth of the second external gear are equal, and that the number of teeth of the first internal gear and the number of teeth of the second internal gear are equal, The phase of the first external gear in the second gear matches the phase of the second external gear in the second internal gear. However, since the number of teeth of the first internal gear and the number of teeth of the second internal gear and / or the number of teeth of the first external gear and the number of teeth of the second external gear are different, Deviation occurs between the phase of the external gear and the phase of the second external gear. The output shaft having the second internal gear rotates to absorb this deviation. Reducing the difference between the number of teeth of the first external gear and the number of teeth of the second external gear and / or reducing the difference between the number of teeth of the first internal gear and the number of teeth of the second internal gear. Thus, large deceleration is possible.

  Further, the first external gear and the second external gear are connected in the axial direction, and the first external gear and the second external gear rotate inside the first internal gear and the second internal gear, respectively. However, since the first external gear and the second external gear are biased relatively to the first internal gear and the second internal gear, respectively, the conventional sun gear, planetary gear and Like a planetary reduction mechanism in which internal gears are stacked in the radial direction, backlash can be reduced without elastically deforming the planetary gear itself. Therefore, backlash can be reduced even for a large input.

The perspective view of the reduction gear of the first embodiment of the present invention (the perspective view seen from the input shaft side) The perspective view of the reduction gear of this embodiment (the perspective view seen from the output-shaft side) Cross-sectional view of the speed reducer of this embodiment Exploded perspective view on the input shaft side Exploded perspective view on the output shaft side Sectional drawing which shows the principal part of the reduction gear of 2nd embodiment of this invention.

  Hereinafter, a reduction gear according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG.1 and FIG.2 shows the perspective view of the reduction gear of this embodiment. FIG. 1 is a perspective view of the speed reducer viewed from the input shaft side, and FIG. 2 is a perspective view of the speed reducer viewed from the output shaft side. FIG. 3 shows a cross-sectional view of the speed reducer of this embodiment. In FIG. 1 to FIG. 3, in order to make the internal structure easy to understand, an annular housing and an annular output shaft are shown in a cross section along the center line of the output shaft.

  The speed reducer includes an input shaft 1 and an output shaft 2, and decelerates the rotation of the input shaft 1 and transmits it to the output shaft 2. The input shaft 1 is connected to the output shaft of a servo motor, for example. The output shaft 2 is connected to, for example, a drive unit of a machine tool or a joint of a robot.

  Two sets of gear mechanisms 3 and 4 are interposed between the input shaft 1 and the output shaft 2. The first gear mechanism 3 includes a tapered first internal gear 5 and a tapered first external gear 6 that revolves around the first internal gear 5. The second gear mechanism 4 includes a tapered second internal gear 7 and a tapered second external gear 8 that revolves around the second internal gear 7. The taper-shaped first internal gear 5 and the taper-shaped second internal gear 7 gradually decrease in inner diameter in a conical shape from one end in the center line direction toward the other end. The first external gear 6 and the second external gear 8 rotate together. The outer diameters of the tapered first external gear 6 and the tapered second external gear 8 gradually decrease in a conical shape from one end portion toward the other end portion in the center line direction. However, the inner diameters of the first internal gear 5 and the second internal gear 7 need not necessarily be linear when viewed in a cross section along the center line of the first internal gear 5 and the second internal gear 7. It is also possible to form a curve. Further, when viewed in a cross section along the center line of the first external gear 6 and the second external gear 8, the outer diameters of the first external gear 6 and the second external gear 8 are not necessarily formed in a straight line. It is not necessary and can be formed into a curve.

  There is a gap between the first external gear 6 and the first internal gear 5, and there is a gap between the second external gear 8 and the second internal gear 7. The first external gear 6 and the second external gear 8 are rotatably supported by the eccentric shaft portion of the input shaft 1 and rotate together while being eccentric with respect to the center line of the input shaft 1. When the input shaft 1 rotates, the first external gear 6 revolves while rotating in the first internal gear 5 in a state where the first external gear 6 is engaged with the first internal gear 5, and the second external gear 8 is rotated in the second internal gear 5. Revolving while rotating in the second internal gear 7 while meshing with the gear 7. The second internal gear 7 is formed integrally with the output shaft 2. The output shaft 2 rotates together with the second internal gear 7. As the first external gear 6 and the second external gear 8 rotate and revolve, the output shaft 2 rotates at a reduced speed.

  The detailed structure of each part of the reduction gear is as follows.

  The input shaft 1 and the output shaft 2 are rotatably supported by the housing 9. The housing 9 is formed in a substantially cylindrical shape. The input shaft 1 and the output shaft 2 rotate around the center line C of the housing 9. A flange 9 a is formed at one end of the housing 9 in the center line direction. A large number of attachment holes 9b for attaching the housing 9 to a counterpart part are formed in the flange 9a.

  A first bearing housing portion 11 having an enlarged inner diameter is formed at the other end portion in the center line direction of the housing 9. A first angular bearing 12 that rotatably supports the input shaft 1 is accommodated in the first bearing accommodating portion 11. An inner gear fixing portion 13 having a reduced inner diameter is formed at the center portion of the housing 9 in the center line direction. The first internal gear 5 is fixed to the internal gear fixing portion 13. The center line of the first internal gear 5 coincides with the center line C of the housing 9. The first internal gear 5 cannot rotate with respect to the housing 9 and cannot move in the direction of the center line. A second bearing housing portion 14 having an enlarged inner diameter is formed at the other end portion in the center line direction of the housing 9. A needle bearing 15 that rotatably supports the hollow output shaft 2 is accommodated in the second bearing accommodating portion 14 (see also FIG. 5). The needle bearing 15 includes an outer ring 15a fitted in the second bearing housing portion 14 and a large number of needles 15b as rolling elements that roll on the inner raceway surface of the outer ring 15a. A raceway surface 15 c on which a large number of needles 15 b roll is formed on the outer periphery of the output shaft 2, and an inner ring of the needle bearing 15 is integrated with the output shaft 2.

  One end of the input shaft 1 in the axial direction is rotatably supported by a first angular bearing 12 provided in the housing 9, and the other end in the axial direction is rotated by a second angular bearing 16 provided inside the output shaft 2. Supported as possible. As shown in the exploded perspective view of FIG. 4, the input shaft 1 includes a shaft end 1 a protruding from the first angular bearing 12 and a disk-shaped first support directly supported by the first angular bearing 12. Portion 1b, an eccentric shaft portion 1c that is eccentric with respect to the center line of rotation of the input shaft 1, a counterweight 18 that is coupled to one axial end of the eccentric shaft portion 1c, and an axial direction of the eccentric shaft portion 1c. A disc-shaped second support portion 19 coupled to the other end portion and directly supported by the second angular bearing 16, and the second support portion 19 and the tip of the eccentric shaft portion 1c are fastened. And a bolt 20 as a fastening member.

  The eccentric shaft portion 1c has a constant outer diameter and extends elongated in the axial direction. The center line of the eccentric shaft portion 1 c is separated from the rotation center line of the input shaft 1 by a predetermined length so as to rotate while being eccentric about the center line of the input shaft 1. A first disc spring 21, a thrust bearing 22, and first and second external gears 6 and 8 as a first elastic body are supported on the eccentric shaft portion 1c. The first disc spring 21 is interposed between the counterweight 18 and the thrust bearing 22 and urges the first external gear 6 axially toward the first internal gear 5 (by the first disc spring 21). The force is shown as F1 in FIG. 3). The thrust bearing 22 allows the first and second external gears 6 and 8 to which axial force is applied from the first disc spring 21 to rotate.

  The counterweight 18 is a weight for balancing the first disc spring 21, the thrust bearing 22, and the first and second external gears 6 and 8 supported by the eccentric shaft portion 1c, and supports these members. The eccentric shaft portion 1c has a mass such that the center of gravity approaches the center line. The counterweight 18 includes an elliptical plate-like main body portion 18a projecting from the eccentric shaft portion 1c and a weight portion 18b coupled to the edge of the plate-like main body portion 18a. The first disc spring 21 comes into contact with the plate-like main body portion 18 a of the counterweight 18.

  A hole 19c is formed at a position eccentric from the center in the second support portion 19 coupled to the tip of the eccentric shaft portion 1c. The bolt 20 that fastens the eccentric shaft portion 1c and the second support portion 19 passes through the hole 19c. The 2nd support part 19 is provided with the main-body part 19a fitted in the 2nd angular bearing 16, and the bearing engaging part 19b to which an outer diameter expands rather than the main-body part 19a. The bearing engaging portion 19 b abuts against the inner ring of the second angular bearing 16 and restricts the second angular bearing 16 from moving in the axial direction with respect to the input shaft 1. As shown in the sectional view of FIG. 3, a second elastic body that urges the second internal gear 7 against the second external gear 8 between the outer ring of the second angular bearing 16 and the output shaft 2. A second disc spring 24 is interposed.

  As shown in the exploded perspective view of FIG. 5, a second internal gear 7 is integrally formed at one end of the inner peripheral surface of the hollow output shaft 2. A bearing housing portion 25 having an inner diameter larger than that of the second internal gear 7 is formed at the other end portion of the inner peripheral surface of the output shaft 2. A second disc spring 24 and a pressure applying disk 26 are accommodated in the bearing accommodating portion 25. As shown in the cross-sectional view of FIG. 3, the pressure applying disk 26 abuts against one end of the second internal gear 7 in the axial direction. A second angular bearing 16 that rotatably supports the output shaft 2 is housed in the bearing housing portion 25 of the output shaft 2. Between the second angular bearing 16 and the second internal gear 7, there are a second disc spring 24 and a pressure applying disk 26 for urging the second internal gear 7 against the second external gear 8. Intervene. The second disc spring 24 urges the second internal gear 7 to the second external gear 8 via the pressure applying disk 26 (the force by the second disc spring is indicated by F2 in FIG. 3). Here, there is a relationship of F1 ≧ F2. A flange 2a is formed at the other end of the output shaft 2 to be attached to a counterpart component. A number of mounting holes 27 are formed in the flange 2a in the circumferential direction.

  The structures of the first gear mechanism 3 and the second gear mechanism 4 are as follows. As described above, the first gear mechanism 3 includes the tapered first internal gear 5 and the tapered first external gear 6. The second gear mechanism 4 includes a tapered second internal gear 7 and a tapered second external gear 8. The taper of the first internal gear 5 and the taper of the first external gear 6 match, and the taper of the second internal gear 7 matches the taper of the second external gear 8. That is, as shown in the cross-sectional view of FIG. 3, the small diameter portions of the first internal gear 5 and the first external gear 6 are located on the right end side, and the inclination angles of these tapers coincide. Further, the small diameter portions of the second internal gear 7 and the second external gear 8 are located on the right end side, and the inclination angles of these tapers coincide.

  The first external gear 6 and the first internal gear 5 are formed in an involute tooth profile. The first external gear 6 and the first internal gear 5 are not shifted, and the modules of the first external gear 6 and the first internal gear 5 continuously change in the axial direction. The second external gear 8 and the second internal gear 7 are also formed in involute teeth. The second external gear 8 and the second internal gear 7 are not shifted, and the modules of the second external gear 8 and the second internal gear 7 are continuously changed in the axial direction. Thus, efficiency can be improved by changing a module continuously, without applying a dislocation. Of course, it is also possible to taper the gear by applying only dislocation without changing the module.

  The number of teeth of the second external gear 8 is larger than the number of teeth of the first external gear 6. The difference in the number of teeth between the second external gear 8 and the first external gear 6 is set to 1, for example. The second external gear 8 has a larger outer diameter than the first external gear 6. The number of teeth of the second internal gear 7 is larger than the number of teeth of the first internal gear 5. The difference in the number of teeth between the second internal gear 7 and the first internal gear 5 is set to 1, for example. The second internal gear 7 has an outer diameter larger than that of the first internal gear 5.

  As shown in FIG. 4, the first external gear 6 and the second external gear 8 are arranged such that the small diameter portion of the first external gear 6 and the large diameter portion of the second external gear 8 are adjacent to each other. And the center line of the first external gear 6 and the center line of the second external gear 8 are connected in the axial direction so as to coincide with each other. In this embodiment, the first external gear 6 and the second external gear 8 are integrally coupled, and the first external gear 6 and the second external gear 8 rotate together and face each other. Therefore, it cannot move relatively in the axial direction. Between the first external gear 6 and the second external gear 8 and the eccentric shaft portion 1c of the input shaft 1, the first external gear 6 and the second external gear 8 are rotated with respect to the eccentric shaft portion 1c. There is an intervening needle bearing 28. The first external gear 6 and the second external gear 8 are movable in the axial direction of the eccentric shaft portion 1c.

  The operating principle of the speed reducer configured as described above is as follows. When the input shaft 1 is rotated, the first external gear 6 supported by the eccentric shaft portion 1 c of the input shaft 1 rotates in the first internal gear 5 while being in mesh with the first internal gear 5. Revolve. Then, the second external gear 8 connected in the axial direction to the first external gear 6 revolves while rotating inside the second internal gear 7 while meshing with the second internal gear 7. Assuming that the number of teeth of the first external gear 6 and the number of teeth of the second external gear 8 are equal, and that the number of teeth of the first internal gear 5 and the number of teeth of the second internal gear 7 are equal, The phase of the first external gear 6 in the internal gear 5 coincides with the phase of the second external gear 8 in the second internal gear 7. However, since the number of teeth of the first internal gear 5 and the number of teeth of the second internal gear 7 and the number of teeth of the first external gear 6 and the number of teeth of the second external gear 8 are different, There is a deviation between the phase of the first external gear 6 and the phase of the second external gear 8. The output shaft 2 with which the second internal gear 7 is integrally formed rotates so as to absorb this deviation. The difference between the number of teeth of the first external gear 6 and the number of teeth of the second external gear 8 is reduced, and the difference between the number of teeth of the first internal gear 5 and the number of teeth of the second internal gear 7 is reduced. Thus, it becomes possible to obtain a large deceleration.

  The principle of preloading of the reduction gear is as follows. The first internal gear 5 is fixed to the housing 9. The first external gear 6 and the second external gear 8 are supported by the eccentric shaft portion 1c so as to be movable in the axial direction. The first internal gear 5 is fixed to the housing 9 so as not to move in the axial direction. The second internal gear 7 is supported by the housing 9 so as to be movable in the axial direction. The first disc spring 21 as the urging means turns the first external gear 6 into the first internal gear 5 so that the clearance between the first external gear 6 and the first internal gear 5 is closed. Energize in the axial direction. The second disc spring 24 as the urging means causes the second internal gear 7 to become the second external gear 8 so that the clearance between the second external gear 8 and the second internal gear 7 is closed. Energize towards. For this reason, backlash between the first external gear 6 and the first internal gear 5 is reduced, and backlash between the second external gear 8 and the second internal gear 7 is reduced. Is possible.

  The speed reducer according to the present embodiment further provides the following effects. Even if the first external gear 6 and the first internal gear 5 are in contact with each other and the first external gear 6 is in an axially immovable state with respect to the first internal gear 5, Since the external gear 8 can move relative to the second internal gear 7 in the axial direction, the first external gear 6 can be brought into contact with the first internal gear 5 and the second external gear 8 The gear 8 can be brought into contact with the second internal gear 7. Therefore, it is possible to minimize or eliminate the backlash.

  Specifically, the first internal gear 5 is fixed to the housing 9, and the first external gear 6 is integrally coupled so that the small diameter portion of the first external gear 6 is adjacent to the large diameter portion of the second external gear 8. By allowing the second internal gear 7 to move in the axial direction with respect to the housing 9, the first external gear 6 and the first internal gear 5 can be brought into contact with each other, and the second internal gear 7 can be moved in the axial direction. The external gear 8 and the second internal gear 7 can be brought into contact with each other.

  By constituting the biasing means from the first disc spring 21 and the second disc spring 24, the first external gear 6 can be biased to the first internal gear 5, and the second The internal gear 7 can be biased to the second external gear 8.

  FIG. 6 shows a main part of the speed reducer according to the second embodiment of the present invention. Also in the reduction gear of this embodiment, like the reduction gear of the first embodiment, between the input shaft 1 (only the eccentric shaft portion 1c of the input shaft 1 is shown in FIG. 6) and the output shaft 2, Two sets of gear mechanisms 3 and 4 are interposed. The first gear mechanism 3 includes a tapered first internal gear 5 and a tapered first external gear 6 having a taper matched to the first internal gear 5. The second gear mechanism 4 includes a tapered second internal gear 7 and a tapered second external gear 8 having a taper matched to the second internal gear 7. There is a gap between the first external gear 6 and the first internal gear 5, and there is a gap between the second external gear 8 and the second internal gear 7. The first external gear 6 and the second external gear 8 are rotatably supported by the eccentric shaft portion 1 c of the input shaft 1, and rotate while being eccentric with respect to the center line of the input shaft 1. When the input shaft 1 rotates, the first external gear 6 revolves while rotating in the first internal gear 5 in a state where the first external gear 6 is engaged with the first internal gear 5, and the second external gear 8 is rotated in the second internal gear 5. Revolving while rotating in the second internal gear 7 while meshing with the gear 7. The second internal gear 7 is coupled integrally with the output shaft 2. As the first external gear 6 and the second external gear 8 rotate and revolve, the output shaft 2 rotates at a reduced speed.

  In this embodiment, the first external gear 6 and the second external gear 8 are elastic as urging means so that the large diameter portions of both the first external gear 6 and the second external gear 8 are adjacent to each other. It is connected via the body 31. The elastic body 31 is made of, for example, rubber formed in a ring shape, and allows the first external gear 6 and the second external gear 8 to move in the axial direction of the eccentric shaft portion 1c. And it restrict | limits that the 2nd external gear 8 rotates relatively with respect to the 1st external gear 6 so that the 1st external gear 6 and the 2nd external gear 8 may rotate together.

  The first internal gear 5 is fixed to the housing 9. The second internal gear 7 is rotatably supported by the housing 9 via an angular bearing 32. The second internal gear 7 is not movable in the axial direction with respect to the housing 9.

  As described above, the first internal gear 5 and the second internal gear 7 are not movable in the axial direction. On the other hand, the first external gear 6 and the second external gear 8 are movable in the axial direction. The elastic body 31 interposed between the first external gear 6 and the second external gear 8 urges the first external gear 6 in the axial direction toward the first internal gear 5 and The external gear 8 is urged in the axial direction toward the second internal gear 7. Therefore, backlash between the first external gear 6 and the first internal gear 5 can be reduced, and backlash between the second external gear 8 and the second internal gear 7 can be reduced. It becomes possible.

  The present invention is not limited to the embodiment described above, and can be embodied in various embodiments without departing from the scope of the present invention.

  In the first embodiment, the first external gear and the second external gear are integrally coupled, and in the second embodiment, the first external gear and the second external gear are made of an elastic body. Are connected through. However, the first external gear and the second external gear rotate together and allow the first external gear to move axially relative to the second external gear. It is also possible to connect the second external gear via a spline shaft. However, it should be noted that the clearance between the first external gear and the second external gear and the spline shaft causes backlash.

  In the first and second embodiments, the first internal gear is not movable in the axial direction and the first external gear is movable in the axial direction. The axial movement of the external gear is relative and can be reversed.

  In the first and second embodiments, the input shaft is rotatably supported at two locations of the housing and the output shaft, but the input shaft can also be rotatably supported at only one location of the housing. It is.

  In the first embodiment, the urging means is composed of the first and second disc springs. However, the urging means can be composed of only the first disc spring. In this case, the first and second internal gears are supported by the housing so as not to move in the axial direction. The first disc spring biases the first and second external gears in the axial direction toward the first and second internal gears.

  In the above embodiment, the number of teeth of the first internal gear and the number of teeth of the second internal gear are different, and the number of teeth of the first external gear and the number of teeth of the second external gear are different. However, either one can be matched if the reduction ratio can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Input shaft, 1c ... Eccentric shaft part, 2 ... Output shaft, 3, 4 ... 1st and 2nd gear mechanism, 5 ... 1st internal gear, 6 ... 1st external gear, 7 ... 2nd Internal gear, 8 ... second external gear, 9 ... housing, 21 ... first disc spring (first elastic body, biasing means), 24 ... second disc spring (second elastic body, biasing) Means), 31 ... elastic body

Claims (4)

A deceleration mechanism that decelerates the rotation of the input shaft and transmits it to the output shaft,
A housing;
A tapered first internal gear provided in the housing in a non-rotatable manner;
A tapered second internal gear rotatably provided in the housing;
An output shaft that rotates together with the second internal gear;
An input shaft having an eccentric shaft portion that is rotatably provided on at least one of the housing and the output shaft and rotates while being eccentric.
While being supported by the eccentric shaft portion of the input shaft so as to be rotatable and movable in the axial direction of the eccentric shaft portion, the inside of the first internal gear is rotated while being engaged with the first internal gear. A taper-shaped first external gear that revolves;
The second external gear is coupled in the axial direction of the eccentric shaft, and is rotatably supported by the eccentric shaft portion of the input shaft and movable in the axial direction of the eccentric shaft portion, A taper-shaped second external gear that revolves while rotating inside the second internal gear while being engaged with the second internal gear;
Attach one of the first external gear and the first internal gear in the axial direction toward the other so that the clearance between the first external gear and the first internal gear is closed. And either one of the second external gear and the second internal gear is directed toward the other so that the clearance between the second external gear and the second internal gear is closed. Biasing means for biasing in the axial direction,
The number of teeth of the first internal gear is different from the number of teeth of the second internal gear, and / or the number of teeth of the first external gear and the number of teeth of the second external gear are Different speed reduction mechanism. The first external gear and the second external gear are integrally coupled so that one of the small diameter portions is adjacent to the other large diameter portion,
The first internal gear is fixed to the housing;
The speed reduction mechanism according to claim 1, wherein the second internal gear is supported by the housing so as to be movable in the axial direction. The biasing means is
A first elastic body for biasing the first external gear in the axial direction toward the first internal gear;
The speed reduction mechanism according to claim 1, further comprising: a second elastic body that urges the second internal gear toward the second external gear in the axial direction. The first external gear and the second external gear are connected via an elastic body as the urging means so that the large diameter portions of both the first external gear and the second external gear are adjacent to each other. Concatenated,
The first internal gear is fixed to the housing;
The second internal gear is supported by the housing so as not to be axially movable;
The elastic body urges the first external gear in the axial direction toward the first internal gear, and causes the second external gear in the axial direction toward the second internal gear. The speed reduction mechanism according to claim 1, wherein the speed reduction mechanism is biased.

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