JP2014122651A - Speed reducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an inner diameter of a hollow hole of a hollow crank shaft and also assure rigidity, accuracy and pre-compression without increasing an outer diameter size of a speed reducer.SOLUTION: There are provided a first bearing 3b and a second bearing 3a to hold eccentric cylindrical parts 2b and 2a of a hollow cylindrical crank shaft 2 at an inner ring. An outer ring is installed at a first carrier 15 and a second carrier 16. Inner rings of a third bearing 17b and a fourth bearing 17a are fitted to the outer peripheries of the first and second carriers and then a frame 1 is held by the outer ring. Thin plate legs 22 with arcuate section and output pins 11 are fixed between the first and second carriers. The legs are integrally formed with the first carrier, outer screws 23 with outer peripheries of extremity ends of a plurality of legs as screw outer diameter are arranged at the extremity ends, the outer screws are protruded out through the second carrier, the second carrier is held to and fixed to the first carrier by inner screw members 18 threadably fitted to a plurality of outer screws and further the first to the fourth bearings are held.

Description

  The present invention relates to a speed reducer that takes an input from a hollow crankshaft as an output from a relative rotational difference between internal and external gears, and preferably relates to a speed reducer used for a joint portion of a robot.

  2. Description of the Related Art Conventionally, in a reduction gear for a robot, the space is effectively utilized by making the inside of the reduction gear hollow in a limited outer diameter size and passing wiring for robot control or the like through the hollow portion. Furthermore, as the robot becomes smaller and lighter and the number of wires for robot control increases, it is desirable to increase the hole diameter of the hollow portion while keeping the size of the reduction gear.

  Therefore, in Patent Document 1, the axial direction of the eccentric cylindrical portion (cam) of the hollow cylindrical crankshaft (hollow shaft) provided so that the toothed disk (external gear) meshing with the internal gear is driven eccentrically. Clamp with a tapered roller bearing. Further, the outer ring of the tapered roller bearing is held between the first and second carriers. Further, the outer circumferences of the first and second carriers and the frame (housing) provided with the internal gear are also sandwiched in the axial direction by the tapered roller bearings. Thus, the shaft hole diameter is increased by reducing the diameter of the output pin that maintains rigidity and supports the toothed disk so that it can revolve. The output pin is fixed with a bolt between the first and second carriers.

  On the other hand, although the external gear is a planetary gear and not a hollow cylindrical crankshaft, in Patent Document 2, the carrier is coupled by the legs of the thin plate arc-shaped cross section. Further, in the fifth embodiment of FIG. 12 of Patent Document 3, the output pin side is eccentric rather than the hollow cylindrical crankshaft, but a bowl-shaped hole between a plurality of output pins, The bowl-shaped leg part which penetrates the hole is provided.

JP 2000-65162 A JP 2002-21946 A Japanese Utility Model Publication 4-29986

  Therefore, it is considered that the radial direction of the hollow hole can be increased by adding the leg portion of the arc-shaped cross section to that of Patent Document 1. However, when used for robot joints, frequent forward / reverse rotation, acceleration / deceleration, stop, and the like are performed. For this reason, extremely high rotational accuracy is required, and it is desired to reduce the backlash and backlash and increase the rigidity. However, in the thing of patent document 2, an external gear is a planetary gear and the dimension control of an axial direction is not so required. For this reason, fixing of the leg portion and the carrier is performed by welding, caulking, etc., and there is a problem in that the assembly accuracy, in particular, the preload control of the axial bearing cannot be performed, and the rigidity is low. Moreover, in the thing of patent document 3, since the precision of an axial direction can be made high, but fixing with the volt | bolt part and carrier of an arc-shaped or bowl-shaped cross section with a volt | bolt, the dimension of radial direction cannot be made small, There was a problem that the hollow hole of the crankshaft could not be enlarged.

  In view of such a problem, the object of the present invention is to make the leg portion of the carrier of the speed reducer that takes out the input from the hollow crankshaft as an output the relative rotational difference of the internal and external gears has an arc-shaped cross section, and the hollow hole diameter of the hollow crankshaft Furthermore, it is to provide a reduction gear with high rigidity that ensures axial accuracy and enables axial preload management.

In the present invention, a hollow cylindrical crankshaft that engages and rotates with the input shaft of the motor and is provided with an eccentric cylindrical portion on the outer peripheral portion thereof, and the axial direction of the eccentric cylindrical portion of the crankshaft is the inner ring side. First and second bearings provided to be sandwiched between, first and second carriers fitted with outer rings of the first and second bearings, respectively, and outer peripheral portions of the first and second carriers A third and a fourth bearing each fitted with an inner ring; a frame sandwiched between the third and fourth bearings on the outer ring side; and a relatively rotatable frame; an inner tooth provided inside the frame; One or more toothed disks provided with external teeth engaged with an eccentric cylindrical portion via an eccentric bearing and meshed with the internal teeth that move eccentrically with rotation of the crankshaft; Inserted into multiple output pin opening holes on the attached disk An output pin that supports the toothed disk so as to be capable of revolving, and takes out the rotational movement of the toothed disk; and a leg portion having a thin circular arc cross section that passes through a plurality of bowl-shaped holes provided in the toothed disk; A reduction gear in which the output pin and the leg are fixed between the first and second carriers,
The leg is formed integrally with the first carrier, and an outer screw having an outer periphery made up of the tips of the plurality of legs is provided at the tip of the leg, and the plurality of outer screws are Providing a reduction gear configured to sandwich and fix the second carrier to the first carrier by an inner screw member that protrudes through the second carrier and is screwed into the plurality of external screws. Solved the problem.

  That is, by screwing a male thread portion provided on the outer peripheral surface of the leg of the thin circular arc cross section of the first carrier with an inner thread member (nut), the second carrier is formed with the first carrier and the inner thread member. Hold it with a pin. Accordingly, the first carrier and the second carrier are integrally fixed while urging the first carrier and the second carrier toward each other in the axial direction. At the same time, the first to fourth bearings are sandwiched to apply preload. The tightening position can be regulated by preventing the inner screw from rotating or by providing a step with a step on the leg side.

  In the invention described in claim 2, the output pin opening hole and the bowl-shaped hole are speed reducers arranged alternately in the circumferential direction as viewed from the axial direction. The positions of the output pin opening hole and the bowl-shaped hole can be appropriately arranged, but the radial thickness can be reduced by arranging them alternately in a circumferential shape.

  In the present invention, in the speed reducer that takes out the input from the crankshaft as an output from the relative rotational difference between the internal and external gears, the second carrier is made up of the legs of the thin circular arc cross section of the first carrier and the internal screw member (nut). The first carrier and the second carrier are urged in the direction approaching each other in the axial direction, and the first to fourth bearings are sandwiched to give the preload, ensuring axial accuracy, and Axis preload management is possible, and a highly rigid reduction gear is provided. Further, unlike the conventional speed reducer, bolt holes and female threads are not formed in the carrier and the leg, so that the thickness of the first and second carriers can be reduced, and accordingly the inner diameter of the hollow hole of the hollow crankshaft can be reduced. Can be bigger.

  Further, in the invention according to claim 2, since the positions of the output pin opening holes and the bowl-shaped holes can be alternately arranged in the circumferential direction to reduce the radial thickness, the thickness of the first and second carriers can be reduced. The inner diameter of the hollow hole of the hollow crankshaft can be further increased.

  The fastening means may use, for example, a snap ring, a key, a pin, etc. via an elastic body capable of urging in the axial direction, but the combination of the male screw and nut of the present invention is simple in structure and accurate. Easy to secure and easy to handle.

It is a longitudinal cross-sectional view of the joint part of the robot with which the reduction gear which shows embodiment of this invention was integrated. It is the elements on larger scale of the carrier of FIG. 1, and a bearing part. It is the XX line partial expanded sectional view of FIG. (A) which shows embodiment of this invention is a left view of a 1st carrier, (b) is a front view, (c) is a right view. (A) which shows embodiment of this invention is a left view of a 2nd carrier, (b) is a front view.

  Embodiments of the present invention will be described with reference to the drawings. In the present embodiment, the crankshaft is arranged at the center of the speed reducer, and the center crank type eccentric oscillating speed reducer (hereinafter simply referred to as “ An example of “reduction gear” will be described.

  As shown in FIG. 1, a base 10 to which a robot arm body and a motor (not shown) are connected and fixed, a speed reducer 100 connected to the base 10 via a carrier 13, and a frame (output member) of the speed reducer 1 and a revolving body 20 connected and fixed by a bolt 33. The base 10 and the swivel body 20 are rotated relative to each other via the speed reducer 100 to constitute a joint portion of the robot. A protective cylindrical body 34 for avoiding interference between the robot control wiring (not shown) and the inner peripheral surface of the crankshaft 2 is attached to the axial center portion of the revolving body 20.

  As shown in FIGS. 1 and 2, the crankshaft 2 is disposed on the axis of the frame 1 (output member) constituting the reduction gear 100. The crankshaft 2 has a hollow cylindrical shape, and a pair of eccentric cylindrical portions 2a and 2b are provided side by side in the axial direction at a substantially central portion in the axial direction on the outer peripheral portion thereof. The eccentric phases of the pair of eccentric cylindrical portions 2a and 2b are shifted from each other (for example, 180 °). A portion on the right side of the eccentric cylindrical portion 2a on one side (right side in the drawing view of FIG. 2) of the crankshaft 2 and a portion on the left side of the eccentric cylindrical portion 2b on the other side (left side in the drawing view of FIG. 2) are each eccentric. The outer diameter is smaller than that of the cylindrical portions 2a and 2b, and the inner rings of the pair of tapered roller bearings (first and second bearings) 3b and 3a are attached to these portions with the large diameter portion side inward. Yes.

  A male spline portion 4 is formed over the entire periphery of the left-side portion (the tip portion of the crankshaft 2) of the eccentric cylindrical portion 2b on the left side of the crankshaft 2. The male spline portion 4 is engaged with a female spline formed on the inner periphery of the gear 5. An external gear is formed on the outer periphery of the gear 5. On the other hand, a motor shaft 6 of a motor (not shown) is attached to the base 10 at a position where its axial direction is along the axis of the frame 1 of the speed reducer 100 and is offset by a predetermined length from the axis. Yes. A tooth portion that engages with the external gear of the gear 5 is formed at the tip of the motor shaft 6, and is connected to the spline portion 4 of the crankshaft 2 via the gear 5. Thus, when the motor shaft 6 is rotated by driving a motor (not shown), the crankshaft 2 rotates in a predetermined direction. In the present embodiment, the crankshaft 2 and the gear 5 are connected by spline coupling, but the crankshaft 2 and the gear 5 may be integrally formed.

  Needle bearings 7 b and 7 a are mounted on the outer peripheral surfaces of the eccentric cylindrical portions 2 b and 2 a of the crankshaft 2. The toothed disks 9 and 8 having outer teeth 9a and 8a formed on the outer peripheral surfaces are rotatably attached to the outer peripheral portions of the pair of needle bearings 7b and 7a, respectively. Since the configuration of the pair of toothed disks 9, 8 is the same except that the phases are shifted, only the toothed disk 9 will be described. As shown in FIG. 3, a large number (for example, 39) of external teeth 9 a made of a pericycloid curve are formed in a wave shape at a certain angle on the peripheral edge of the toothed disk 9. Further, a plurality of output pin opening holes 12 through which each output pin 11 passes and a leg portion 22 having a thin plate arc-shaped cross section provided in the carrier 13 at a peripheral portion of the toothed disk 9 and inside the external teeth 9a. A plurality of bowl-shaped holes 14 that penetrate (described later) are provided. Each output pin opening hole 12 is a circular hole larger than the outer diameter of the output pin 11, and each bowl-shaped hole 14 is larger than the leg portion 22. Each output pin opening hole 12 and each bowl-shaped hole 14 are arranged on substantially the same circumference as viewed in the axial direction so that they alternate.

  Inside the frame 1, internal teeth 31 composed of a large number (for example, 40) of external pins are rotatably provided. The number of teeth (for example, 39 teeth) of the external teeth 9a and 8a of the toothed disk is reduced with respect to the number of teeth of the internal teeth 31, and the internal teeth 31 and the external teeth 9a and 8a of the toothed disks 9 and 8 are reduced. The toothed disks 9 and 8 are arranged inside the inner teeth 31 so as to mesh with each other.

  A substantially cylindrical carrier 13 is disposed outside the crankshaft 2. The carrier 13 includes a first carrier 15 disposed on the left side in the drawing view of FIG. 1, a second carrier 16 disposed on the right side, and a thin plate arc-shaped cross section extending from the first carrier toward the second carrier. The leg portion 22 and the nut 18 are integrally formed.

  As shown in FIG. 2, the first carrier 15 includes a thick hollow disk-shaped base 21 supported by the tapered roller bearing 3 b and the ball bearing 17 b, and an axial direction from the base 21 to the second carrier 16. And a leg portion 22 having a thin-arc-shaped cross section projecting along the line. As shown in FIG. 4, a plurality of leg portions 22 of the first carrier 15 are provided in the circumferential direction in order to avoid interference with each output pin 11. An outer screw 23 is provided at the tip of each leg portion 22 with the outer periphery formed by the tip portions of the plurality of leg portions having a screw outer diameter. A male screw portion 23 is formed as the whole leg portion. An output pin support hole 26 for fitting and supporting the end portion of each output pin 11 is provided on the base end surface of the leg portion 22. In order to increase the rigidity of the leg portion 22, it is desirable that the connecting portion 19 between the base portion 21 and the leg portion 22 has a curved shape having a large radius or that the connecting portion 19 is thick. In addition, a large number of female screw portions 21 a for screwing bolts 24 connected to the base 10 are formed on the end surface of the base portion 21 on the side opposite to the leg portion at a certain angle in the circumferential direction. An escape hole 25 for arranging the motor shaft 6 is provided.

  On the other hand, as shown in FIG. 5, the second carrier 16 has a short cylindrical shape (ring shape or annular shape) with a flange 16a. The second carrier 16 is fitted with an output pin support hole 27 for fitting and supporting the end portion of each output pin 11 along the axial direction, and a leg portion 22 extending from the first carrier 15. A leg support opening hole 28 for penetrating is provided. A small-diameter portion 16a is formed on the anti-support pin hole side of the second carrier. The small diameter part 16a is made substantially the same as the inner diameter of the leg part, and the inner diameter side arc of the leg part 22 is fitted. An inner screw member (nut) 18 is screwed onto the outer screw 23 protruding from the flange 16b by fitting and penetrating the leg portion 22 of the first carrier into the leg support opening hole 28 of the second carrier. And the second carrier is assembled together. A washer 29 is provided between the nut 18 and the flange 16a to prevent the nut from being loosened and positioned.

  As shown in FIGS. 1 and 2, the carrier 13 is in a state where the first and second carriers 15 and 16 are integrally fixed by screwing the leg portion 22 and the nut 18 together. At this time, the inner diameter side of the carrier 13 is a pair of tapered roller bearings (first and second bearings) composed of inner rings mounted on both sides of the eccentric cylindrical portions 2b and 2a of the crankshaft 2 with the large diameter portion sides inside. ) 3b and 3a are assembled so as to sandwich the outer ring, and the first and second carriers 15 and 16 sandwich the tapered roller bearings (first and second bearings) 3b and 3a and the eccentric cylindrical portions 2b and 2a. Apply preload.

  Similarly, third and fourth (ball) bearings 17b and 17a, in which inner rings are fitted to the outer peripheral portions of the first and second carriers of the carrier 13, are provided, and the frame is formed on the outer ring side of the third and fourth bearings. 1, the frame 1 and the carrier 13 are supported so as to be relatively rotatable. The inner and outer rings of the third and fourth bearings are mounted so that the outer diameter is larger than the outer diameter, and the outer rings are mounted such that the outer diameter is smaller and the outer diameter is smaller. The four bearings 17b, 17a and the inner teeth of the frame 1 are clamped to give preload.

  As described above, in the present embodiment, the carrier 13 is coupled and integrated by the male screw 23 and the nut 18 of the leg portion 22 having a thin plate arc-shaped cross section, and the crankshaft 2 and the frame 1 are sandwiched and supported for rotation. Preload can be applied to the four bearings.

  Next, the operation of the present embodiment will be described. As shown in FIGS. 1 to 3, when the motor shaft 6 is rotated by operating a motor (not shown), the crankshaft 2 rotates in a predetermined direction. A pair of toothed disks 8 and 9 are rotated by the eccentric cylindrical portions 2 a and 2 b of the crankshaft 2. At this time, the external teeth 8a and 9a of the toothed disks 8 and 9 perform operations such as to get over the respective external pins 31, whereby the frame 1 is pushed. In this embodiment, the external pins 31 are pushed. Rotate by one pitch. Each of the external teeth 8a and 9a gets over the one outer pin 31 when the pair of eccentric cylindrical portions 2a and 2b makes one rotation. Therefore, the reduction ratio between the frame 1 and the carrier 15 is the same as that of the present embodiment. In this case, 1 / the number of outer pins 31 (the number of outer pins 31 is 40, so the reduction ratio is 1/40). The reduction ratio of the speed reducer of the present embodiment is ((the number of external teeth 8a, 9a of the toothed disks 8, 9−the number of external pins 31) / the number of external pins) × (the number of gear teeth of the motor shaft 6). / Number of teeth of the gear 5 of the crankshaft 2), and a high reduction ratio of 100 or more is obtained.

  The leg 22 of the first carrier 15 is inserted into the leg support opening 28 of the second carrier 16 through the carrier opening 14 of each toothed disk 8, 9. In this state, the male screw portion 23 at the distal end of the leg portion 22 comes out of the leg portion support opening 28 and is disposed on the small diameter portion 16 a of the second carrier 16. At this time, the inner peripheral surface of the leg portion 22 is disposed on the outer peripheral surface of the small diameter portion 16a with a slight gap. Then, the nut 18 is screwed and tightened to the male screw portion 23 of the leg portion 22 via a washer 29 (star washer), and the first carrier 15 and the second carrier 16 are paired with a pair of tapered roller bearings 3b and 3a and a pair. The ball bearings 7b and 7a and the frame 1 are sandwiched and fixed together so as to be preloaded. For this reason, the axial lengths of the first carrier 15 and the second carrier 16 are regulated by the pair of tapered roller bearings 3b and 3a, the pair of ball bearings 17b and 17a, and the frame 1.

  The external screw 23 at the tip of the leg portion 22 of the first carrier 15 is integrally formed with the second carrier 16 by being screwed and tightened with a nut 18. For this reason, even if the thickness of the leg portion 22 of the first carrier 15 is thin, there is no possibility that the rigidity thereof is lowered. The crankshaft 2 can be brought closer to the inner peripheral surface of the leg portion 22 as much as the thickness of the leg portion 22 can be reduced. As a result, the inner diameter of the hollow hole of the hollow crankshaft 2 can be increased. .

  In this embodiment, the base is connected to the arm body or the like of the robot and the frame side is set as the output side, but conversely, the frame side may be connected to the main body or the like and the base side may be set as the revolving body. . The first to fourth bearings are tapered roller bearings and angular ball bearings, respectively, but may be reversed or the same, and are not limited to these, and are bearings that can provide axial preload and increase rigidity. I just need it. Furthermore, although the present invention is suitable for a hollow crankshaft type speed reducer, it is needless to say that the present invention can be appropriately applied to other speed reducers.

1 frame (output member)
2 (Hollow) crankshaft 2a, 2b Eccentric cylindrical part 3a, 3b Second, first bearing (tapered roller bearing)
6 Motor shaft (input shaft)
7a, 7b Eccentric bearings (needle bearings)
8, 9 Discs with teeth 8a, 9a External teeth 11 Output pin (pin)
12 output pin opening hole 13 carrier 14 bowl-shaped hole 15 first carrier 16 second carrier 17a, 17b fourth and third bearings (ball bearings)
18 Internal thread member (nut)
22 Leg 23 External screw 31 Internal tooth (External pin)
100 reducer

Claims (2)

A hollow cylindrical crankshaft that engages and rotates with the input shaft of the motor and is provided with an eccentric cylindrical portion on its outer peripheral portion;
First and second bearings provided so as to sandwich the axial direction of the eccentric cylindrical portion of the crankshaft on the inner ring side;
First and second carriers fitted with outer rings of the first and second bearings, respectively;
Third and fourth bearings in which inner rings are fitted to the outer peripheral portions of the first and second carriers, respectively.
A frame sandwiched on the outer ring side of the third and fourth bearings and capable of relative rotation;
Internal teeth provided inside the frame;
One or more toothed disks provided with external teeth engaged with the eccentric cylindrical portion via an eccentric bearing and engaged with the internal teeth that move eccentrically with rotation of the crankshaft;
An output pin inserted through a plurality of output pin opening holes provided in the toothed disk to support the toothed disk so as to be capable of revolving, and to take out the rotation of the toothed disk;
A thin plate arc-shaped leg portion penetrating a plurality of bowl-shaped holes provided in the toothed disk, and
The speed reducer in which the output pin and the leg are fixed between the first and second carriers,
The leg is formed integrally with the first carrier, and an outer screw having an outer periphery made up of the tips of the plurality of legs is provided at the tip of the leg, and the plurality of outer screws are A speed reducer characterized in that the second carrier is clamped and fixed to the first carrier by an inner screw member that protrudes through the second carrier and is screwed into the plurality of external screws.   The speed reducer according to claim 1, wherein the output pin opening holes and the bowl-shaped holes are alternately arranged in a circumferential direction when viewed from the axial direction.

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