Reducer

Abstract

A speed reducer thinner than a conventional speed reducer is realized without impairing performance and characteristics. 【Solution means】 In a speed reducer 1 including an eccentric shaft 4 in which eccentric portions 41 and 42 perform eccentric motion by rotation of the shaft, planet gears 51 and 52 rotatably supported by the eccentric portions 41 and 42 and performing eccentric motion in synchronization with the eccentric motion of the eccentric shaft 4, a case 9 to which a plurality of outer peripheral pins 6 functioning as internal teeth for the planet gears 51 and 52 are rotatably attached, and lid bodies 71 and 72 rotatably supported by the eccentric shaft 4 and sandwiching the planet gears 51 and 52, and a carrier 7 for outputting the rotation of the planet gears 51 and 52, the planet gears 51 and 52 and the lid bodies 71 and 72 are manufactured with their sizes reduced by an amount corresponding to an increase in torsional rigidity of each component by shot peening when processing the material, and shot peening is applied to the surfaces of the components.

Description

Technical Field

[0001] The present invention relates to a precision control reducer used for joints of industrial robots and the like.

Background Art

[0002] An electric motor, which is a drive source of a link, and a speed reducer integrally connected to an output shaft of the electric motor are attached to a joint portion of an industrial robot. The speed reducer is a device that converts the low-torque and high-speed rotation of the electric motor into high-torque and low-speed rotation and transmits it to the link. There are various problems with the speed reducers provided in the joint portions of industrial robots. Among them, the problems of (1) the teeth of both gears colliding when the two gears mesh, and the gear mechanism being easily damaged, (2) large vibrations, and (3) low control accuracy of the rotational position of the link are major problems.

[0003] Conventionally, as speed reducers for solving these problems, a cycloid reducer and an RV reducer (Rotate Vector Reducer) are known and have been put into practical use. For example, Patent Document 1 describes a multi-joint robot provided with an RV reducer at a joint portion.

[0004] FIG. 18 is a skeleton diagram showing a gear mechanism of an RV reducer. The RV reducer 100 is a two-stage reduction type speed reducer including a first reduction unit 110 and a second reduction unit 120.

[0005] The first reduction unit 110 is composed of a spur gear reduction mechanism combining one input gear 111 and three spur gears 113. Only the meshing portion of the input gear 111 and one spur gear 113 is shown in FIG. 18. The diameter of the input gear 111 is smaller than the diameter of the spur gear 113, and the number of teeth of the input gear 111 is less than the number of teeth of the spur gear 113. An input shaft 112 is attached to the center of the input gear 111, and an output shaft 114 is attached to the center of the spur gear 113.

[0006] The rotation of the electric motor is input to the input shaft 112 of the input gear 111, and the rotation with the input rotation speed reduced is output from the output shafts 114 of the three spur gears 113. The output rotation speed is the speed obtained by reducing the input rotation speed by the gear ratio of the number of teeth of the input gear 111 to the number of teeth of the spur gear 113.

[0007] Two eccentric portions 114A and 114B are provided side by side in the axial direction on the output shafts 114 of the three spur gears 113. The eccentric portions 114A and 114B are eccentric cams that perform eccentric motion due to the rotation output from the first reduction unit 110. The eccentric portions 114A and 114B are members for transmitting the eccentric motion to the two RV gears 122A and 122B of the second reduction unit 120, respectively. The centers of the eccentric portions 114A and 114B are eccentric from the center of the output shaft 114 by a predetermined amount. The eccentric directions of the eccentric portion 114A and the eccentric portion 114B are opposite to each other.

[0008] The second reduction unit 120 is composed of a fixed annular case 121, two disk-shaped RV gears 122A and 122B arranged inside the case 121 so as to be capable of eccentric motion, and a holding member 123 that sandwiches and holds the two RV gears 122A and 122B and outputs the rotation of both RV gears 122A and 122B to the outside, and is composed of an internal planetary gear mechanism.

[0009] A large number of pin gears 121A are rotatably attached at equal intervals as internal peripheral teeth inside the case 121. The RV gears 122A and 122B are composed of trochoid gears having a tooth profile using a trochoid curve formed on the outer periphery. The number of teeth of the outer peripheral teeth of the RV gears 122A and 122B is one less than the number of the pin gears 121A. The holding member 123 is rotatably supported on both sides of the eccentric portions 114A and 114B of the output shaft 114, and the rotation of the two RV gears 122A and 122B is transmitted by a rotation transmission member (not shown).

[0010] The RV gear 122A performs an eccentric motion around the center of the input gear 111 by the eccentric part 114A performing an eccentric motion around the center of the rotation axis 114. The RV gear 122B performs an eccentric motion around the center of the input gear 111 by the eccentric part 114B performing an eccentric motion around the center of the rotation axis 114. The RV gears 122A and 122B rotate relative to the case 121 while a part of the outer peripheral teeth come into contact with the inner peripheral teeth (pin gears 121A) of the case 121 due to the eccentric motion.

[0011] The RV gears 122A and 122B rotate on their own at a speed at which the outer peripheral teeth of the RV gears 122A and 122B move by the amount of one inner peripheral tooth of the case 121 while the spur gear 113 makes one rotation. Synchronized with the rotation of the RV gears 122A and 122B, the holding member 123 also rotates. The rotation of the holding member 123 is output from the output shaft 130 of the RV speed reducer 100 to a load (a link of a robot).

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0013] Since the RV speed reducer is a two-stage reduction type speed reducer composed of a first reduction part and a second reduction part, there is an advantage that a wide range of overall reduction ratios can be easily adjusted by adjusting the reduction ratio of the first reduction part. Since the RV speed reducer uses an internal planetary gear mechanism composed of a pin gear and a trochoid gear for the second reduction part which is the main reduction part, there are advantages such as (1) backlash can be reduced, (2) torsional rigidity is large, (3) a large reduction ratio can be obtained, (4) it is resistant to vibration, and (5) control accuracy is high.

[0014] Since the RV reducer has many advantages that can solve the problems of the reducers of industrial robots described above, it is widely used as a reducer for various industrial robots. As the scope of utilization of industrial robots increases, further thinning, downsizing, and weight reduction of the RV reducer are desired. However, since the RV reducer arranges the first reduction unit and the second reduction unit coaxially and combines a large number of components constituting both reduction units with high density and high precision, simply thinning and downsizing each component will reduce the performance (transmission efficiency, backlash, lost motion, etc.) of the RV reducer. It is difficult to achieve thinning, downsizing, and weight reduction of the RV reducer without impairing it.

[0015] The present invention has been made in view of the above problems, and an object thereof is to provide a reducer for precision control that realizes further thinning, downsizing, and weight reduction of the current reducer without impairing performance and characteristics.

Means for Solving the Problems

[0016] The reducer according to the present invention includes an eccentric shaft having an eccentric portion on a shaft, the shaft rotates by rotation of a motor and the eccentric portion performs an eccentric motion, a planetary gear rotatably supported by the eccentric portion of the eccentric shaft and performing an eccentric motion around the axis center of the eccentric shaft by the eccentric motion of the eccentric portion, a case in which a plurality of outer peripheral pins that function as internal teeth for the external teeth of the planetary gear are rotatably attached to the inner peripheral surface, and two lid bodies that sandwich the planetary gear and are rotatably supported on both end sides of the eccentric portion of the shaft. In a reducer including a carrier that outputs the rotation of the planetary gear based on the eccentric motion of the eccentric portion to the outside, at least the components of the planetary gear and the carrier are manufactured by reducing the size of each component by the ratio at which the torsional rigidity of each component increases by performing shot peening when processing the material to manufacture each component, and the shot peening is performed on the manufactured components to increase the torsional rigidity (Claim 1).

[0017] According to a preferred embodiment of the above-described speed reducer, after the shot peening, the case may be subjected to surface treatments of super-finishing polishing and oil reservoir machining on the concave grooves to which the outer peripheral pins are attached (Claim 2).

[0018] Furthermore, according to a preferred embodiment of the above-described speed reducer, the materials of the carrier and the case are preferably ductile cast iron (Claim 3).

[0019] Furthermore, according to a preferred embodiment of the above-described speed reducer, after each component of the eccentric shaft, the planetary gear, and the plurality of outer peripheral pins is processed to manufacture the component, heat treatments of quenching, cryogenic treatment, and tempering are performed in this order, and then surface treatments of shot peening, super-finishing polishing, and oil reservoir machining are performed in this order (Claim 4).

[0020] Furthermore, according to a preferred embodiment of the above-described speed reducer, the two lid bodies are in the shape of a disc with a first through hole drilled at the center. The two lid bodies are rotatably attached to the eccentric shaft with tapered roller bearings interposed between the first through hole and the eccentric shaft, and are rotatably attached to the case with angular contact bearings interposed between the outer periphery and the inner periphery of the case. The planetary gear is in the shape of a disc with a second through hole drilled at the center. The planetary gear is rotatably attached to the eccentric shaft with needle roller bearings with cages interposed between the second through hole and the eccentric portion. The tapered roller bearings and the angular contact bearings are subjected to shot peening on the entire raceway ring, and surface treatments of super-finishing polishing and oil reservoir machining are performed in this order on the portions where the rollers of the raceway ring contact. The needle roller bearings with cages are subjected to shot peening on the entire needle roller, and surface treatments of super-finishing polishing and oil reservoir machining are performed in this order on the peripheral surface of the needle roller (Claim 5).

[0021] Furthermore, according to a preferred embodiment of the above-described speed reducer, the materials of the eccentric shaft, the planetary gear, and the plurality of outer peripheral pins are preferably structural steel materials that ensure hardenability (Claim 6).

[0022] Furthermore, according to a preferred embodiment of the above-described speed reducer, a second spur gear that meshes with a first spur gear connected to the rotor of the motor at one end of the eccentric shaft and reduces the rotational speed of the first spur gear and transmits it to the eccentric shaft is fixed. It is preferable that the first spur gear and the second spur gear are subjected to surface treatments such as shot peening, super-smoothing polishing, and oil reservoir processing in this order after heat treatments such as quenching, cryogenic treatment, and tempering are performed in this order (Claim 7).

[0023] According to a preferred embodiment of the speed reducer described in Claim 7, it is preferable that a first reduction is performed by the gear mechanism of the first spur gear and the second spur gear, and a second reduction is performed by the gear mechanism of the planetary gear and the case (Claim 8).

Advantages of the Invention

[0024] The speed reducer according to Claim 1 has a disk-shaped planetary gear sandwiched between two disk-shaped lid bodies, and the two lid bodies and the planetary gear are laminated so as to sandwich the disk-shaped planetary gear. The laminate is rotatably attached to an eccentric shaft and housed in a case to form a disk shape. When processing the material to manufacture each part, the planetary gear and the two lid bodies are manufactured with their sizes (especially thickness) reduced by the ratio at which the torsional rigidity of the planetary gear and the two lid bodies is increased by shot peening. Thereby, the thickness of the laminate of the two lid bodies and the planetary gear can be made thinner than that of the conventional speed reducer. That is, the speed reducer can be made thinner and lighter.

[0025] Since each part of the planetary gear and the two lid bodies, which are manufactured with their sizes (especially thickness) smaller than those of conventional parts, is subjected to shot peening on the surface to increase the torsional rigidity, it is possible to provide a speed reducer that realizes thinning and weight reduction without reducing the torsional rigidity compared to conventional speed reducers.

[0026] The speed reducer according to claim 2 has undergone super-smooth polishing on a plurality of concave grooves on the inner circumference of the case to which a plurality of outer peripheral pins are rotatably attached. Therefore, the frictional resistance can be reduced compared to the conventional case, and the surface roughness and fatigue strength can be improved. Furthermore, since oil reservoir machining is performed after the super-smooth polishing, the concave grooves of the case are finished to a plateau-structured surface, and the lubricating oil retention function can be improved compared to the conventional case. As a result, the operating efficiency of the case as an internal gear is improved. In addition, the temperature rise and noise generation of the speed reducer are suppressed, and the speed reducer can have a longer service life.

[0027] The speed reducer according to claim 3 uses tough cast iron, such as ductile cast iron, for the materials of the carrier and the case. Therefore, the torsional rigidity can be enhanced compared to the conventional parts while retaining the properties of tough cast iron inside the parts.

[0028] The speed reducer according to claim 4 processes the material to fabricate each part of the eccentric shaft, planetary gear, and a plurality of outer peripheral pins, and then performs heat treatments of quenching, cryogenic treatment, and tempering in this order. Therefore, the strength of the materials of these parts can be enhanced. Furthermore, since surface treatments of shot peening, super-smooth polishing, and oil reservoir machining are performed in this order, the torsional rigidity of these parts can be increased, and the frictional resistance and surface roughness of the rotating and meshing parts in the gear mechanisms of these parts can be reduced, and the lubricating oil retention force can be improved.

[0029] The speed reducer according to claim 5 performs shot peening on the entire raceways of the tapered roller bearings and angular contact bearings, and performs surface treatments of super-smooth polishing and oil reservoir machining in this order on the portions where the rollers of the raceways come into contact. Therefore, the strength of these bearings can be increased, and the frictional resistance and surface roughness of the raceway surfaces where the rollers roll can be reduced, and the lubricating oil retention force can be improved. In addition, shot peening is performed on the entire needle rollers of the needle roller bearings with cages, and surface treatments of super-smooth polishing and oil reservoir machining are performed in this order on the circumferential surfaces of the needle rollers. Therefore, the torsional rigidity of the needle roller bearings with cages can be increased, and the frictional resistance and surface roughness of the portions where the needle rollers come into contact with the eccentric shafts and planetary gears can be reduced, and the lubricating oil retention force can be improved.

[0030] Since the speed reducer according to claim 6 uses a structural steel material that ensures hardenability for the eccentric shaft, planetary gears, and a plurality of outer peripheral pins, after strengthening the strength of the steel material by heat treatment of quenching, cryogenic treatment, and tempering, shot peening is performed, so that the torsional rigidity of these parts can be sufficiently increased.

[0031] Since the speed reducer according to claim 7 performs heat treatment of quenching, cryogenic treatment, and tempering on the first spur gear and the second spur gear in this order, and then performs surface treatment of shot peening, super smooth polishing, and oil reservoir processing in this order, the torsional rigidity of the first spur gear and the second spur gear can be sufficiently increased, and the frictional resistance and surface roughness of the tooth surfaces of the first spur gear and the second spur gear can be reduced, and the holding power of the lubricating oil can be improved.

[0032] Since the speed reducer according to claim 8 performs a first reduction by the gear mechanism of the first spur gear and the second spur gear, and performs a second reduction by the gear mechanism of the planetary gear and the case, a wide reduction ratio can be easily adjusted.

Brief Description of the Drawings

[0033]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Embodiments for Carrying Out the Invention

[0034] With reference to the drawings, the speed reducer according to the present invention will be described. The following embodiments are merely illustrative. The following embodiments can be variously modified without departing from the gist of the present invention.

[0035] FIG. 1 is a view (front view) of the speed reducer 1 according to the present invention as seen from the side. FIG. 2 is a view (plan view of the first reduction unit 2) showing the gear mechanism of the first reduction unit 2 of the speed reducer 1. FIG. 3 is a view (plan view of the speed reducer 1) of the speed reducer 1 as seen from above. The speed reducer 1 is a two-stage reduction type speed reducer in which the first reduction unit 2 and the second reduction unit 3 are connected. The first spur gear 21 of the first reduction unit 2 is attached to the motor M, and the second spur gear 22 of the first reduction unit 2 is attached to the speed reducer 1. Since the first spur gear 21 and the second spur gear 22 are engaged when the speed reducer 1 and the motor M are incorporated into the joint portion of the robot, FIG. 3 shows a plan view of the speed reducer 1 to which only the second spur gear 22 is attached.

[0036] FIG. 4 is a one-sided sectional view taken along the line A-A of FIG. 1. FIG. 5 is a view (bottom view of the speed reducer 1) of the speed reducer 1 as seen from below. FIG. 6 is a longitudinal sectional view of the speed reducer 1. FIGS. 4 to 6 also depict a bottom view and a sectional view of the speed reducer 1 to which only the second spur gear 22 is attached.

[0037] The speed reducer 1 shown in FIGS. 1 to 6 is a two-stage reduction type speed reducer provided with a first reduction unit 2 constituted by a spur gear reduction mechanism in front of a second reduction unit 3 using an internal planetary gear mechanism.

[0038] The first reduction unit 2 is a spur gear reduction mechanism in which a disk-shaped first spur gear 21 and a disk-shaped second spur gear 22 are engaged (see FIGS. 1 and 2). The first spur gear 21 and the second spur gear 22 are involute gears. A connection portion 211 is provided at the center of one plate surface (the upper plate surface in FIG. 1) of the first spur gear 21. An electric motor M is connected to the connection portion 211 as shown by a virtual line (see FIG. 1). The second spur gear 22 is attached to the upper end of a hollow cylindrical eccentric shaft 4. The second spur gear 22 is non-rotatably fixed to the eccentric shaft 4 by a concentric retaining ring 221 (see FIGS. 2 and 3). The eccentric shaft 4 corresponds to the input shaft of the second reduction unit 3, and when the second spur gear 22 rotates, the eccentric shaft 4 rotates.

[0039] As shown in FIG. 6, the eccentric shaft 4 is disposed so as to extend below the second spur gear 22. In the following description, the posture in which the eccentric shaft 4 extends below the second spur gear 22 will be described as the basic posture of the speed reducer 1. FIG. 1 is a view (front view) of the speed reducer 1 in the basic posture as seen from the side. In FIGS. 1 and 6, the direction along the axis center N of the eccentric shaft 4 is defined as the height direction, the vertical direction, or the perpendicular direction, and the direction perpendicular to the axis center N of the eccentric shaft 4 is defined as the width direction, the left-right direction, or the horizontal direction.

[0040] In the first reduction unit 2, when the first spur gear 21 rotates at a rotational speed ω1 [rpm] by the electric motor M, the second spur gear 22 rotates at a reduced rotational speed ω2 (= n × ω1 [rpm]) with a gear ratio n (= Z1 / Z2) of the number of teeth Z1 of the first spur gear 21 and the number of teeth Z2 (>Z1) of the second spur gear 22. Since the eccentric shaft 4 is fixed to the second spur gear 22, the eccentric shaft 4 also rotates at the rotational speed ω2. The rotation at the rotational speed ω2 reduced in the first reduction unit 2 is input to the second reduction unit 3.

[0041] The second reduction unit 3 includes an eccentric shaft 4, a planetary gear 5 composed of two planetary gears 51 and 52, a plurality of pins 6, a carrier 7 composed of two cover bodies 71 and 72, a rotation transmission member 8, a case 9, tapered roller bearings 11A and 11B, needle rollers 12A and 12B with retainers, and angular contact bearings 13A and 13B (see FIG. 6). The planetary gear 51 and the planetary gear 52 are planetary gears of the same configuration. In the following description, when the planetary gear 51 and the planetary gear 52 are to be distinguished, the planetary gear 51 is referred to as the "first planetary gear 51", and the planetary gear 52 is referred to as the "second planetary gear 52". When the two planetary gears 51 and 52 are described together, they are referred to as the "planetary gear 5".

[0042] The planetary gear 5 is a planetary gear of an internal meshing planetary gear mechanism. The planetary gear 5 is a disk-shaped gear using a trochoid curve as its tooth profile. Fig. 11 shows a top view (plan view) of the first planetary gear 51, and Fig. 12 shows a longitudinal sectional view of the first planetary gear 51. The two cover bodies 71 and 72 that constitute the carrier 7 function to output the rotation of the planetary gear 5 to the outside via the rotation transmission member 8, and also function to sandwich the planetary gear 5 and protect the upper and lower surfaces of the second reduction unit 3. Fig. 7 shows a top view (plan view) of the front cover 71, and Fig. 8 shows a longitudinal sectional view of the front cover 71. Fig. 9 shows a bottom view of the back cover 72, and Fig. 10 shows a longitudinal sectional view of the back cover 72. In the following description, the cover body 71 that sandwiches the first planetary gear 51 from above is referred to as the "front cover 71", and the cover body 72 that sandwiches the second planetary gear 52 from below is referred to as the "back cover 72". The cover bodies 71 and 72 have a circular shape in plan view and have substantially the same size as the planetary gear 5 (see Figs. 7, 9, and 11).

[0043] The case 9 functions as an internal gear of the internal meshing planetary gear mechanism, and also functions to house the planetary gears 5 (two planetary gears 51 and 52) sandwiched between the front cover 71 and the back cover 72 and protect the peripheral surface of the second reduction unit 3. The case 9 has a hollow cylindrical shape, and its height H1 [mm] (see Fig. 1) is slightly smaller than the height H1' [mm] (see Fig. 1) of the portion where the planetary gears 5 are sandwiched between the front cover 71 and the back cover 72. A protruding portion 901 that protrudes inward is formed at the central portion in the height direction on the inner peripheral wall of the case 9 (see Fig. 4). In Fig. 6, the opening above the protruding portion 901 of the case 9 is the portion where the front cover 71 is housed, and the opening below the protruding portion 901 is the portion where the back cover 72 is housed. The space surrounded by the protruding portion 901 in the case 9 is the portion where the planetary gears 5 are housed.

[0044] On the outer periphery of the case 9, a flange 903 (see FIGS. 3 to 6) is provided approximately at the center in the height direction. The flange 903 is, for example, for installing the speed reducer 1 inside the joint part of the robot. A plurality of mounting holes 903A are provided in the flange 903 in the circumferential direction. The diameters of both openings of the case 9 are set slightly larger than the diameters of the front cover 71 and the back cover 72. The diameter inside the protruding portion 901 of the case 9 is slightly larger than the diameter of the planetary gear 5. The width of the protruding portion 901 is substantially the same as or slightly larger than the thickness obtained by overlapping the two planetary gears 51 and 52 (see FIG. 6). A plurality (for example, 40) of concave grooves 902 (see FIG. 4) are formed at equal intervals in the circumferential direction in the protruding portion 901. The cross-sectional shape of the concave groove 902 is semi-circular.

[0045] The plurality of pins 6 are parts that function as internal teeth of the case 9 (internal gear). The length of the pin 6 is substantially the same as the length of the concave groove 902. The number of pins 6 is, for example, 40, and the pins 6 are rotatably attached to the concave grooves 902 of the protruding portion 901 (see FIG. 4). The number of teeth of the first planetary gear 51 and the second planetary gear 52 is set to a number (39) that is one less than the number of pins 6. A part of the outer teeth 511 (see FIG. 11) of the first planetary gear 51 and the outer teeth 521 of the second planetary gear 52 are each in contact with a plurality of pins 6. In the longitudinal sectional view shown in FIG. 6, the outer teeth 511 on the right side of the first planetary gear 51 are in contact with the outer peripheral pins 6, and the outer teeth 521 on the left side of the second planetary gear 52 are in contact with the outer peripheral pins 6. Since the plurality of pins 6 are arranged around the outside of the outer teeth 511 and 521, they are referred to as "outer peripheral pins 6" in the following description.

[0046] The eccentric shaft 4 is a component that transmits the rotation output from the first reduction unit 2 to the first planetary gear 51 and the second planetary gear 52. At approximately the center in the vertical direction of the eccentric shaft 4, an eccentric portion 41 and an eccentric portion 42 project with a minute interval therebetween (see Fig. 6). The eccentric portion 41 and the eccentric portion 42 are eccentric cams that are eccentric by a predetermined amount in the horizontal plane with respect to the axial center N of the eccentric shaft 4. The eccentric portion 41 and the eccentric portion 42 are eccentric in opposite directions to each other. The eccentric portion 41 is substantially the same as the thickness of the first planetary gear 51, and the eccentric portion 42 is substantially the same as the thickness of the second planetary gear 52 (see Fig. 6). In the following description, when distinguishing between the eccentric portion 41 and the eccentric portion 42, the eccentric portion 41 is referred to as the "first eccentric portion 41", and the eccentric portion 42 is referred to as the "second eccentric portion 42".

[0047] A needled roller 12A with a cage and a needled roller 12B with a cage are respectively attached to the first eccentric portion 41 and the second eccentric portion 42 of the eccentric shaft 4 (see Fig. 6). The needled roller 12A with a cage and the needled roller 12B with a cage are the same component. The needled rollers 12A, 12B with cages are components for smoothly transmitting the respective eccentric motions of the first eccentric portion 41 and the second eccentric portion 4B due to the rotation of the eccentric shaft 4 to the first planetary gear 51 and the second planetary gear 52. The needled rollers 12A, 12B with cages have a structure in which a plurality of needled rollers are rotatably attached at equal intervals to the side surface of a cage made of an annular frame body. The heights of the two needled rollers 12A, 12B with cages are substantially the same as the thicknesses of the first eccentric portion 41 and the second eccentric portion 4B. In the following description, when collectively describing the two needled rollers 12A, 12B with cages, they are referred to as the "needled roller 12 with a cage".

[0048] At the center of the first planetary gear 51, a first through-hole 51A for fitting and mounting the first planetary gear 51 onto the eccentric shaft 4 is formed (see FIG. 11). At the center of the second planetary gear 52, a first through-hole 52A (not shown) for fitting and mounting the second planetary gear 52 onto the eccentric shaft 4 is formed. The first planetary gear 51 has the eccentric shaft 4 with the needle roller 12A with a cage fitted into the first through-hole 51A, and the first through-hole 51A and the needle roller 12A with a cage are fitted together and rotatably mounted on the eccentric shaft 4. The second planetary gear 52 has the eccentric shaft 4 with the needle roller 12B with a cage fitted into the first through-hole 52A, and the first through-hole 52A and the needle roller 12B with a cage are fitted together and rotatably mounted on the eccentric shaft 4.

[0049] The first planetary gear 51 attached to the first eccentric portion 41 of the eccentric shaft 4 with the needle roller 12A with a cage interposed therebetween has a part of the external teeth 511 in contact with a plurality of outer peripheral pins 6 provided on the inner periphery of the case 9 (see FIG. 6). The second planetary gear 52 attached to the second eccentric portion 42 of the eccentric shaft 4 with the needle roller 12B with a cage interposed therebetween also has a part of the external teeth 521 in contact with a plurality of outer peripheral pins 6 provided on the inner periphery of the case 9 (see FIG. 6).

[0050] The case 9 is fixed. When the eccentric shaft 4 rotates, the two eccentric portions 41, 42 of the eccentric shaft 4 perform an eccentric motion about the axis center N of the eccentric shaft 4. The eccentric motion of the first eccentric portion 41 is transmitted to the first planetary gear 51 via the needle roller 12A with a cage, and the first planetary gear 51 also performs an eccentric motion about the axis center N of the eccentric shaft 4. The eccentric motion of the second eccentric portion 42 is transmitted to the second planetary gear 52 via the needle roller 12B with a cage, and the second planetary gear 52 also performs an eccentric motion about the axis center N of the eccentric shaft 4.

[0051] Due to the eccentric motion of the first planetary gear 51, the first planetary gear 51 revolves around the axis center N. Since a part of the external teeth 511 of the first planetary gear 51 is in contact with the outer peripheral pins 6 of the case 9, the first planetary gear 51 revolves so as to move the position of the external teeth 511 that rollingly contact the outer peripheral pins 6 of the case 9. Due to the eccentric motion of the second planetary gear 52, the second planetary gear 52 also revolves around the axis center N. Since a part of the external teeth 521 of the second planetary gear 52 is in contact with the outer peripheral pins 6 of the case 9, the second planetary gear 52 also revolves so as to move the position of the external teeth 521 that rollingly contact the outer peripheral pins 6 of the case 9. Since the eccentric directions of the first eccentric part 41 and the second eccentric part 42 are opposite to each other, the positions of the outer peripheral pins 6 where the external teeth 511 of the first planetary gear 51 rollingly contact on the inner peripheral surface of the case 9 and the positions of the outer peripheral pins 6 where the external teeth 521 of the second planetary gear 52 rollingly contact move with a phase difference of 180 degrees.

[0052] In the revolving operation of the first planetary gear 51, since the external teeth 511 in contact with the outer peripheral pins 6 receive a reaction force from the outer peripheral pins 6, the first planetary gear 51 rotates in a direction opposite to the revolving direction around the first eccentric part 41 by the needle roller 12A with a cage. This rotating operation is the rotating operation of the first planetary gear 51 around the first eccentric part 41. The second planetary gear 52 also receives a reaction force from the outer peripheral pins 6 in the revolving operation in the same manner as the first planetary gear 51, and rotates (self-rotates) in a direction opposite to the revolving direction around the second eccentric part 42 by the needle roller 12B with a cage.

[0053] Therefore, the planetary gear 5 revolves around the axis center N of the eccentric shaft 4 while rotating according to the rotation of the eccentric shaft 4. The rotation of the planetary gear 5 is transmitted to the carrier 7 by the rotation transmission member 8 and output from the carrier 7 to the outside (for example, the link of a multi-joint robot). The configuration of the rotation transmission member 8 that transmits the rotation of the planetary gear 5 to the carrier 7 will be described later.

[0054] As shown in FIG. 7, a through-hole 71A is formed at the center of the front cover 71, and as shown in FIG. 9, a through-hole 72A is formed at the center of the back cover 72. The through-hole 71A is a hole for fitting and mounting the front cover 71 at a position outside the eccentric portion 41 of the eccentric shaft 4 (the upper position in FIGS. 1 and 6). The through-hole 72A is a hole for fitting and mounting the back cover 72 at a position outside the eccentric portion 42 of the eccentric shaft 4 (the lower position in FIGS. 1 and 6).

[0055] A tapered roller bearing 11A is attached between the mounting position of the front cover 71 of the eccentric shaft 4 and the through-hole 71A of the front cover 71 (see FIG. 6). A tapered roller bearing 11B is attached between the mounting position of the back cover 72 of the eccentric shaft 4 and the through-hole 72A of the back cover 72 (see FIG. 6). The tapered roller bearings 11A and 11B are the same parts. By interposing the tapered roller bearing 11A between the eccentric shaft 4 and the through-hole 71A of the front cover 71 and interposing the tapered roller bearing 11B between the eccentric shaft 4 and the through-hole 72A of the back cover 72, the eccentric shaft 4 rotatably supports the front cover 71 and the back cover 72.

[0056] Although not shown, the tapered roller bearings 11A and 11B are composed of two annular raceway rings (inner ring and outer ring), a plurality of rolling elements, and a cage. The rolling elements are frustum-shaped rollers. The cage is an annular frame body with inclined sides and is a member that rotatably holds a plurality of rollers at equal intervals in the circumferential direction. The inner ring and the outer ring are members that sandwich the cage with a plurality of rollers attached thereto inside and outside, and provide raceway surfaces inclined with respect to the plurality of rollers by both rings. The inner ring, the outer ring, and the cage with a plurality of rollers attached thereto are assembled such that the vertices of the cones of the inner ring and the outer ring and the cone of the cage converge at one point on the central axis.

[0057] The front cover 71 rotatably attached to the eccentric shaft 4 by the tapered roller bearings 11A is housed in the upper opening of the case 9, and the back cover 72 rotatably attached to the eccentric shaft 4 by the tapered roller bearings 11B is housed in the lower opening of the case 9. An angular contact bearing 13A is attached between the outer periphery of the front cover 71 and the inner periphery of the case 9, and an angular contact bearing 13B is attached between the outer periphery of the back cover 72 and the inner periphery of the case 9 (see Fig. 6). The angular contact bearings 13A and 13B are members for smoothly rotating the front cover 71 and the back cover 72 within the case 9 when the front cover 71 and the back cover 72 housed in the case 9 rotate around the eccentric shaft 4.

[0058] The angular contact bearings 13A and 13B are also composed of two annular raceway rings (inner ring and outer ring), a plurality of rolling elements, and a cage, similar to the tapered roller bearings 11A and 11B. The rolling elements are needle rollers. The cage is an annular frame body with inclined sides and is a member for rotatably holding a plurality of needle rollers at equal intervals in the circumferential direction. The inner ring and the outer ring are members for sandwiching the cage with a plurality of needle rollers attached thereto from the inside and the outside. The raceway surfaces of the inner ring and the outer ring are inclined with respect to the sides (see Fig. 6).

[0059] As described above, the rotation of the two planet gears 51 is transmitted to the front cover 71 and the back cover 72 by the rotation transmission member 8. The front cover 71 is rotatably housed in the case 9 by the tapered roller bearing 11A and the angular contact bearing 13A, and the back cover 72 is rotatably housed in the case 9 by the tapered roller bearing 11B and the angular contact bearing 13B. Therefore, the carrier 7 (front cover 71 and back cover 72) rotates in synchronization with the rotation of the planet gears 5 (two planet gears 51 and 52).

[0060] The front cover 71 and the back cover 72 sandwich the two planet gears 51 and 52 mounted via the needlerollers with cages 12A and 12B on the eccentric portions 41 and 42 of the eccentric shaft 4, and support both sides (the upper side and the lower side in Fig. 6) of the two planet gears 51 and 52 on the eccentric shaft 4. This both-end support mechanism improves the torsional rigidity of the speed reducer 1 and increases the strength against overload.

[0061] On the circumference at a predetermined distance from the center of the through-hole 71A of the front cover 71, a plurality (for example, eight) of fastening holes 71B are formed at equal intervals, and positioning holes 71C are formed at positions intermediate between adjacent fastening holes 71B on the same circumference (see FIG. 7). The fastening holes 71B are holes for inserting a fastening member (for example, a bolt) for fastening the front cover 71 and the back cover 72 (see FIG. 8). The positioning holes 71C are holes for determining the position of the front cover 71 with respect to the back cover 72 when fastening the front cover 71 and the back cover 72 (see FIG. 8). As shown in FIG. 6, the positioning pins 10 are inserted into the positioning holes 71C.

[0062] On the circumference at a predetermined distance from the center of the through-hole 72A of the back cover 72, a plurality (for example, eight) of mounting holes 72B are formed at equal intervals (see FIG. 9). The mounting holes 72B are holes for attaching the rotation transmission member 8. On one surface of the back cover 72 (the upper surface in FIG. 6), fastening pins 72C project at positions intermediate between adjacent fastening holes 72B (see FIG. 9). A nut is provided on the tip surface of the fastening pin 72C (see FIG. 10). The fastening pin 72C is a member for fastening a fastening member (bolt) inserted into the fastening hole 71B of the front cover 71 when fastening the front cover 71 and the back cover 72.

[0063] On the circumference at a predetermined distance from the center of the first through-hole 51A of the first planetary gear 51, a plurality (for example, sixteen) of second through-holes 51B are formed at equal intervals (see FIGS. 11 and 12). Similarly to the first planetary gear 51, a plurality (for example, sixteen) of second through-holes 52B are formed at equal intervals on the circumference at a predetermined distance from the center of the first through-hole 52A of the second planetary gear 52 (not shown). The second through-holes 51B and 52B are holes for fitting the fastening pins 72C formed on one surface of the back cover 72 (the upper surface in FIGS. 6 and 10) and the reaction pins 81 attached to one surface when the first planetary gear 51 and the second planetary gear 52 are sandwiched between the front cover 71 and the back cover 72.

[0064] The rotation transmission member 8 is a member that transmits the rotation of the first planetary gear 51 and the second planetary gear 52 to the carrier 7. The rotation transmission member 8 is composed of reaction pins 81 each consisting of a plurality (for example, eight) of solid pins 81A (hereinafter referred to as "support pins 81A") and a plurality (for example, eight) of hollow pins 81B (hereinafter referred to as "hollow pins 81B") (see FIG. 6). The support pin 81A is a pin attached to the mounting hole 72B of the back cover 72. A step (base portion) for mounting on the mounting hole 72B of the back cover 72 is provided at one end of the support pin 81A. A fastening nut is formed on the end face of the support pin 81A where the step is provided, and a concave groove for fitting the positioning pin 10 is formed on the tip face of the support pin 81A (see FIGS. 6 and 10).

[0065] The plurality of support pins 81A are respectively attached to the plurality of mounting holes 72B of the back cover 72. Each support pin 81A is attached to each mounting hole 72B of the back cover 72 by inserting the base portion into the mounting hole 72B of the back cover 72 and fastening a fastening bolt inserted from the opposite side of the mounting hole 72B to the nut provided on the base portion. The reaction pin 81 is attached to the position of each mounting hole 72B of the back cover 72 by covering the support pin 81A fixed to the mounting hole 72B of the back cover 72 with the hollow pin 81B.

[0066] The planetary gears 5 (two planetary gears 51, 52) are fitted without clearance between the eccentric shaft 4 and the angular bearings 13A, 13B. The planetary gears 5 are sandwiched between the front cover 71 and the back cover 72 to which the reaction pins 81 are attached, and are integrated by fastening the front cover 71 and the back cover 72 with a fastening member. Specifically, eight reaction pins 81 attached to the back cover 72 and eight fastening pins 72C protruding from the back cover 72 are respectively inserted into the 16 second through holes 51B of the two planetary gears 51, 52 from the side of the second planetary gear 52, and the positions of the eight positioning holes 71C of the front cover 71 and the reaction pins 81 attached to the back cover 72 are aligned. Then, positioning pins 10 are inserted into the eight positioning holes 71C respectively, and fastening bolts (not shown) are inserted into the eight fastening holes 71B. Further, by fastening each bolt to the nut formed on the tip surface of the support pin 81A facing each fastening hole 71B, the two planetary gears 51, 52 are integrally sandwiched between the front cover 71 and the back cover 72.

[0067] When the two planetary gears 51, 52 sandwiched between the front cover 71 and the back cover 72 rotate, the second through holes 51B, 52B contact the reaction pins 81 due to the rotation, and the rotation of the two planetary gears 51, 52 is transmitted to the front cover 71 and the back cover 72. When the second through holes 51B, 52B contact the reaction pins 81, a reaction force is generated from the reaction pins 81 to the second through holes 51B, 52B. Since the hollow pin 81B is rotatably attached to the support pin 81A, the reaction force to the second through holes 51B, 52B is absorbed by the smooth rotation of the hollow pin 81B, and the rotation of the two planetary gears 51, 52 is effectively transmitted to the front cover 71 and the back cover 72.

[0068] The centers of the front cover 71 and the back cover 72 are rotatably supported on the eccentric shaft 4 by the tapered roller bearings 11A and 11B, and the circumferential surfaces of the front cover 71 and the back cover 72 are rotatably supported on the case 9 by the angular bearings 13A and 13B. Therefore, the front cover 71 and the back cover 72 rotate smoothly in synchronization with the rotation of the two planetary gears 51, 52. The rotation of the front cover 71 and the back cover 72 is the rotation output from the second reduction unit 3 (reduction gear 1).

[0069] Next, the characteristic configuration of the speed reducer 1 according to the present invention will be described.

[0070] As shown in FIGS. 1 and 3, the speed reducer 1 used for the joint portion of an industrial robot has a disk shape. As shown in FIG. 6, the speed reducer 1 has a configuration in which a carrier 7 with two planetary gears 51 and 52 sandwiched between a front cover 71 and a rear cover 72 is housed in a cylindrical case 9, thereby realizing a disk shape. In order to further reduce the thickness in this configuration, it is necessary to reduce the thicknesses of the front cover 71, the rear cover 72, and the planetary gears 51 and 52, reduce the height of the case 9, and shorten the length of the eccentric shaft 4. However, even if the physical sizes of these components are simply reduced, problems such as a decrease in the torsional rigidity and other characteristics of the speed reducer 1 or a decrease in the performance such as backlash of the speed reducer 1 will occur.

[0071] Since the reduction in thickness of the speed reducer 1 and the improvement in the performance and characteristics of the speed reducer 1 are in an antinomic relationship, when reducing the thicknesses of components such as the front cover 71, the rear cover 72, the first planetary gear 51, and the second planetary gear 52 arranged in the case 9 and shortening the length of the eccentric shaft 4, it is necessary to fully consider the decrease in the torsional rigidity of the speed reducer 1 and the performance degradation of the rotating parts and friction parts in the speed reducer 1. In particular, since the gear mechanism of the speed reducer 1 is likely to experience a decrease in performance and characteristics, it is necessary to take measures to suppress or improve the performance and characteristics of the gear mechanism of the speed reducer 1.

[0072] The speed reducer 1 according to the present embodiment is made thinner than the conventional speed reducer by adjusting the size in the height direction of the components related to the reduction in thickness of the speed reducer 1. The components related to the reduction in thickness of the speed reducer 1 are components such as the eccentric shaft 4, the first spur gear 21, the second spur gear 22, the front cover 71, the rear cover 72, the first planetary gear 51, the second planetary gear 52, and the case 9. In the case of disk-shaped components such as the first spur gear 21, the second spur gear 22, the front cover 71, the rear cover 72, the first planetary gear 51, and the second planetary gear 52, the size in the height direction of the speed reducer 1 is the "thickness" of the disk, and in the case of the eccentric shaft 4 and the cylindrical case 9, the size in the height direction of the speed reducer 1 is the "height" or "length" of the cylinder.

[0073] Regarding the size of the components related to the thinning of the speed reducer 1, when a predetermined surface treatment (for example, shot peening) is performed on the components used in the conventional speed reducer (hereinafter referred to as "conventional components") to enhance the torsional rigidity, if the increase amount of the torsional rigidity is K [%], the size of the conventional components is adjusted to approximately the size reduced by K [%]. For example, if the torsional rigidity of the conventional component is θ1 and the torsional rigidity when shot peening is performed on the conventional component under a predetermined condition is θ2 (> θ1), the increase amount K [%] of the torsional rigidity is expressed as K = [(θ2 - θ1) / θ1] × 100. If the thickness (original thickness) of the conventional component is t' [mm] and the thickness (thickness after thinning adjustment) obtained by reducing its thickness by K [%] is t (< t') [mm], the thickness t of the components related to the thinning of the speed reducer 1 is set to have a relationship of t = t' × (1 - K / 100) with respect to the thickness t' of the conventional component.

[0074] Shot peening is a surface treatment that projects a large number of iron or non-ferrous metal projectiles (microspheres) onto the metal surface at high speed to increase the strength of the metal surface. When shot peening is performed on the surface of a metal component, the hardness of the component surface is enhanced, and the torsional rigidity of the metal component can be increased. Shot peening has effects such as an increase in the fatigue strength of the metal component, an improvement in wear resistance, and an improvement in stress corrosion cracking resistance due to the increase in torsional rigidity. Furthermore, since shot peening forms innumerable depressions (marks) on the surface of the metal component, it also has effects such as an improvement in heat dissipation, a reduction in weight, and a reduction in fluid resistance (oil pooling effect). Also, shot peening can remove impurities adhering to the component surface and fine burrs generated on the surface, and can eliminate the abnormal layer of the surface structure.

[0075] The front cover 71 and the back cover 72 function as a protective member that sandwiches the two planetary gears 51 and 52 and protects the front and back surfaces of the second reduction unit 3. The case 9 functions as a protective member that covers the circumferential surfaces of the front cover 71 and the back cover 72 that sandwich the two planetary gears 51 and 52 and protects the outer circumferential surface of the second reduction unit 3. Further, the carrier 7 composed of the front cover 71 and the back cover 72 functions as an output unit that outputs the rotations of the first planetary gear 51 and the second planetary gear 52 to a load (for example, a link of an industrial robot) connected to the speed reducer 1. For this reason, high torsional rigidity is required for the front cover 71 and the back cover 72.

[0076] Since the carrier 7 and the case 9 function as protective members of the speed reducer 1, they are manufactured using cast iron that is excellent in mechanical strength, wear resistance, and heat resistance. The carrier 7 and the case 9 are manufactured using ductile cast iron, which is tough cast iron with enhanced tensile strength and ductility.

[0077] FIG. 13 is a diagram showing the manufacturing process of each component of the front cover 71, the back cover 72, and the case 9. Note that steps S5 and S6 are processes applied only to the case 9. FIG. 14 is a diagram showing the difference in thickness between the front cover 71 and the conventional front cover 71'. (a) is a front view of the front cover 71, and (b) is a front view of the conventional front cover 71'. Hereinafter, the manufacturing method of each component of the front cover 71, the back cover 72, and the case 9 will be described using the front cover 71 as an example.

[0078] Perform cutting on ductile cast iron to produce a component with the same shape as the conventional front cover 71' and a reduced thickness (step S1). The thickness t [mm] of the produced front cover 71 is set to t = t'×(1 - K / 100) with respect to the thickness t' [mm] of the conventional front cover 71' (see FIG. 14). For example, when K = 25 [%], the thickness t of the front cover 71 is set to approximately 75 [%] of the thickness t' [mm] of the conventional front cover 71' (0.75×t' [mm]).

[0079] On the surface of the manufactured watch case 71, shot peening is performed under the shot peening processing conditions (for example, conditions such as shot size, shot projection angle, collision speed, processing time, etc.) corresponding to the increase in torsional rigidity K [%] of the above formula (step S2). Note that the relationship between the increase in torsional rigidity K [%] for the conventional watch case 71' and the shot peening processing conditions has been obtained in advance.

[0080] Measure the torsional rigidity of the watch case 71 after shot peening (step S3). Determine whether the measured value of torsional rigidity exceeds the torsional rigidity value (current value) of the conventional watch case 71' (step S4). If the measured value of torsional rigidity does not exceed the torsional rigidity value of the conventional watch case 71' (NO in step S4), return to step S2 and perform shot peening again, repeating until the measured value of torsional rigidity exceeds the torsional rigidity value of the conventional watch case 71' (loop of steps S2 to S4). When the measured value of torsional rigidity exceeds the torsional rigidity value of the conventional watch case 71' (YES in step S4), end the manufacturing process of the watch case 71.

[0081] By the above manufacturing method, the watch case 71 has torsional rigidity equivalent to or more enhanced than that of the conventional watch case 71' while leaving the properties of ductile cast iron inside the part. For example, when K = 25 [%], the thickness t of the watch case 71 is approximately 25 [%] thinner than the thickness t' of the conventional watch case 71' without reducing the torsional rigidity or strength of the conventional watch case 71'. The back cover 72 and the case 9 are also manufactured in the same manner as the watch case 71, and the thickness t is approximately 25 [%] thinner than the thickness of the conventional back cover and case without reducing the torsional rigidity or strength of the conventional back cover and case. In addition, the watch case 71, the back cover 72, and the case 9 are also made lighter due to the reduced thickness.

[0082] The plurality of outer peripheral pins 6 rotatably attached to the plurality of concave grooves 902 of the case 9 function as internal gears for the first planetary gear 51 and the second planetary gear 52 (external gears). When the torsional rigidity of the case 9 is enhanced by shot peening, in order to make the rolling contact between the external teeth of the first planetary gear 51 and the second planetary gear 52 and the internal teeth (outer peripheral pins 6) of the case 9 as smooth as possible, a surface treatment of super-smooth polishing is performed on the portion of the semi-circular concave groove 902 (see FIG. 4) (step S5), and further a surface treatment of oil reservoir machining is performed (step S6).

[0083] Super-smooth polishing is a polishing method for creating a super-smooth optical surface of a high-precision optical element. For example, polishing methods such as Brot polishing, EEM (elastic emission machining), and pole feed polishing are known. Oil reservoir machining is a machining for creating depressions on the order of several μm for retaining lubricating oil on a flat plane using a scraper tool.

[0084] By performing the surface treatment of super-smooth polishing on the surface of the concave groove 902, the abnormal layer of the surface structure is removed, and it is finished into a super-smooth surface with an arithmetic mean roughness Ra of 0.0097. The surface of the concave groove 902 has a reduced frictional resistance compared to the concave grooves of the conventional case, and the surface roughness and fatigue strength are improved. Further, by performing oil reservoir machining on the surface of the concave groove 902, it is finished into a plateau structure surface, and the lubricating oil holding function (oil reservoir) is improved by approximately 20% compared to the concave grooves of the conventional case. Since the concave groove 902 maintains a good lubrication state when the outer peripheral pin 6 rotates within the concave groove 902, it is possible to suppress an increase in the oil temperature and the generation of noise in the speed reducer 1. As a result, the operating efficiency as the internal teeth of the case 9 can be improved, and the long life of the case 9 is also made possible.

[0085] As described above, while the case 9 contributes to the thinning of the speed reducer 1, the concave groove 902 of the case 9 greatly affects the performance of the speed reduction gear mechanism of the speed reducer 1. Therefore, shot peening is performed on the entire surface of the case 9 to not only strengthen the torsional rigidity of the case 9, but also surface treatment of super smooth polishing and oil reservoir processing is performed on the surface of the concave groove 902 to reduce the frictional resistance of the concave groove 902 and prevent oil drainage of the lubricating oil. When the outer peripheral pin 6 rotatably attached to the concave groove 902 rotates smoothly, the outer teeth 511, 521 (see FIG. 11) can be made to roll and contact the outer peripheral pin 6 (inner teeth) of the case 9 as smoothly as possible when the first planetary gear 51 and the second planetary gear 52 rotate, and the generation of noise during contact can be suppressed.

[0086] On the other hand, since the first spur gear 21, the second spur gear 22, the first planetary gear 51, the second planetary gear 52, the eccentric shaft 4, etc. are components that constitute the speed reduction gear mechanism, steel materials containing carbon used for components where strength and machinability are emphasized are used for manufacturing. For example, the first spur gear 21, the first planetary gear 51, the second planetary gear 52, and the eccentric shaft 4 are manufactured using structural steel materials that guarantee hardenability, and the second spur gear 22 is manufactured using high-carbon chromium bearing steel materials. Similar to the front cover 71, the back cover 72, and the case 9, the first spur gear 21, the second spur gear 22, the first planetary gear 51, the second planetary gear 52, and the eccentric shaft 4 also have the common point of performing shot peening to enhance torsional rigidity after performing processing to reduce the thickness by the amount of increase in torsional rigidity by K[%] compared to conventional components, but differ in the points of adding heat treatments of quenching, ultra sub-zero treatment, and tempering and performing surface treatments of super smooth polishing and oil reservoir processing. The reason for adding the heat treatment is that the material types are different from those of the carrier 7 and the case 9.

[0087] FIG. 15 is a diagram showing the manufacturing process of each component that constitutes the speed reduction gear mechanism such as the first spur gear 21, the second spur gear 22, the first planetary gear 51, and the second planetary gear 52. Hereinafter, the manufacturing method of each component that constitutes the speed reduction gear mechanism will be described taking the second spur gear 22 as an example.

[0088] For example, a high-carbon chromium bearing steel material is machined by cutting to produce a part with the same shape as the conventional second spur gear but with a reduced thickness (step S11). For example, when K = 25 [%], similar to the manufacturing process of the watch case 71, the thickness of the manufactured second spur gear 22 is set to approximately 75 [%] of the thickness of the conventional second spur gear. Subsequently, heat treatments such as quenching (step S12), cryogenic treatment (step S13), and tempering (step S14) are performed on the manufactured second spur gear 22 in this order. The reason for performing the heat treatments of quenching, cryogenic treatment, and tempering before shot peening is to improve the hardening, strength, and fatigue resistance of the structural steel material because a structural steel material with guaranteed hardenability is used.

[0089] Quenching is a process of heating a carbon-containing steel material to a temperature above the transformation point and then rapidly cooling it to transform the structure of the steel material into a martensite structure. Since the martensite structure is a very hard structure, hardening, strength, and fatigue resistance of the high-carbon chromium bearing steel material can be improved by quenching. Tempering is a process of reheating after quenching to adjust the hardness and increase the toughness (ductility) and toughness. Cryogenic treatment is a process of cooling the high-carbon chromium bearing steel material to -130 degrees Celsius or lower before tempering to transform the retained austenite structure remaining after quenching into a martensite structure. Further hardening, strength, and fatigue resistance of the high-carbon chromium bearing steel material can be improved by cryogenic treatment.

[0090] After the tempering heat treatment, shot peening described above is performed on the surface of the second spur gear 22 (step S15). In this shot peening, shot peening is performed under the processing conditions of shot peening corresponding to the increase percentage K [%] of torsional rigidity (for example, conditions such as the size of the shot, the projection angle of the shot, the collision speed, the processing time, etc.). This shot peening is performed until the measured value of torsional rigidity exceeds the torsional rigidity value of the conventional second spur gear (loop of steps S15 to S17). When the torsional rigidity of the second spur gear 22 is enhanced by shot peening, in order to make the meshing of the first spur gear 21 and the second spur gear 22 as smooth as possible, super smooth polishing surface treatment is performed on the outer peripheral surface of the external teeth 22A (see FIG. 2) of the second spur gear 22 (step S18), and further surface treatment of oil reservoir machining is performed (step S19).

[0091] After the second spur gear 22 is processed to have a smaller thickness than the conventional second spur gear, quenching, cryogenic treatment, and tempering are performed in this order, so that the hardness of the second spur gear 22 is enhanced, the dimensional and hardness uniformity is achieved, the wear resistance is improved, and the prevention of aging deterioration is achieved. Since the same heat treatment is performed on the first spur gear 21, the first planetary gear 51, the second planetary gear 52, and the eccentric shaft 4, the hardness of these parts is enhanced, the dimensional and hardness uniformity is achieved, the wear resistance is improved, and the prevention of aging deterioration is achieved.

[0092] Also, since shot peening is performed on the surface of the second spur gear 22 after tempering, the effects of the above-described shot peening treatment (increase in fatigue strength, improvement in wear resistance, improvement in stress corrosion cracking characteristics, improvement in heat dissipation, weight reduction, reduction in fluid resistance (oil reservoir effect, etc.)) are imparted to the second spur gear 22. Since the same shot peening is performed on the first spur gear 21, the first planetary gear 51, the second planetary gear 52, and the eccentric shaft 4, the effects of the above-described shot peening treatment are imparted. In addition, for the first spur gear 21, the second spur gear 22, the planetary gears 51, 52, and the eccentric shaft 4, impurities adhering to the part surface and fine burrs generated on the surface are removed, and abnormal layers of the surface structure are eliminated.

[0093] Each component of the first spur gear 21, the second spur gear 22, the first planetary gear 51, the second planetary gear 52, and the eccentric shaft 4 is subjected to quenching, cryogenic treatment, and tempering heat treatment after component manufacturing, and then shot peening is performed. Therefore, characteristics such as hardness, fatigue strength, and wear resistance are improved by at least 25% compared to each component of the conventional first spur gear, second spur gear, planetary gear, and eccentric shaft.

[0094] Also, for the first spur gear 21 and the second spur gear 22, super-smooth polishing and oil reservoir machining are performed on the outer peripheral surfaces of the external teeth 21A, 22A (see Fig. 2) where the two gears mesh. Therefore, compared to the conventional first spur gear and second spur gear, the effect of the above-mentioned super-smooth polishing is improved by at least 30%, and the effect of the above-mentioned oil reservoir machining is improved by at least 20%. For the first planetary gear 51 and the second planetary gear 52, super-smooth polishing and oil reservoir machining are performed on the outer peripheral surfaces of the external teeth 511, 521 (see Fig. 11) that rollingly contact the outer peripheral pins 6 of the case 9 and on the inner peripheral surfaces of the through holes 51A, 52A (see Fig. 11) where the needle rollers 12A, 12B with retainers are attached. Therefore, compared to the conventional planetary gear, the effect of the above-mentioned super-smooth polishing is improved by at least 30%, and the effect of the above-mentioned oil reservoir machining is improved by at least 20%.

[0095] The outer peripheral pin 6 functions as an internal tooth of the case 9 and is a component with which the external teeth 511, 521 of the first planetary gear 51 and the second planetary gear 52 rollingly contact. Therefore, it is manufactured using high-carbon chromium bearing steel material similar to the second spur gear 22. Also, the reaction pin 81 is a component that transmits the rotation of the planetary gear 5 to the carrier 7. Therefore, it is manufactured using high-carbon chromium bearing steel material similar to the second spur gear 22. The outer peripheral pin 6 and the reaction pin 81 are also manufactured in the same manufacturing process as the above-mentioned second spur gear 22 (the manufacturing process in Fig. 15).

[0096] The outer peripheral pin 6 is machined from a high-carbon chromium bearing steel material to produce a component having the same shape as the conventional outer peripheral pin (step S11). Subsequently, heat treatments of quenching (step S12), cryogenic treatment (step S13), and tempering (step S14) are performed on the produced outer peripheral pin 6 in this order. The support pin 81A and the hollow pin 81B are also machined from a high-carbon chromium bearing steel material to produce components having the same shapes as the conventional support pin and hollow pin (step S11). Note that the lengths of the support pin 81A and the hollow pin 81B are set shorter than the lengths of the conventional support pin and hollow pin in accordance with the thicknesses of the first planetary gear 51 and the second planetary gear 52 being made thinner than those of the conventional planetary gears. Subsequently, heat treatments of quenching (step S12), cryogenic treatment (step S13), and tempering (step S14) are performed on the produced support pin 81A and hollow pin 81B in this order.

[0097] After the tempering heat treatment, the above-described shot peening is performed on the surface of the outer peripheral pin 6 (step S15). This shot peening is performed until the measured value of the torsional rigidity exceeds the torsional rigidity value (current value) of the conventional outer peripheral pin (the loop of steps S15 to S17). After the tempering heat treatment of the support pin 81A and the hollow pin 81B, the above-described shot peening is performed on the surfaces of the support pin 81A and the hollow pin 81B until the measured values of the torsional rigidity exceed the torsional rigidity values (current values) of the conventional support pin and hollow pin (YES in step S17) (step S15).

[0098] When the torsional rigidity of the outer peripheral pin 6 is enhanced by shot peening, in order to make the rolling contact with the outer teeth 511 and 521 of the first planetary gear 51 and the second planetary gear 52 as smooth as possible, a surface treatment of super-smooth polishing is performed on the outer peripheral surface of the outer peripheral pin 6 (step S18), and further a surface treatment of oil pocket machining is performed (step S19). When the torsional rigidity of the support pin 81A is enhanced by shot peening, in order to make the rotation of the hollow pin 81B as smooth as possible, a surface treatment of super-smooth polishing is performed on the outer peripheral surface of the support pin 81A (step S18), and further a surface treatment of oil pocket machining is performed (step S19). When the torsional rigidity of the hollow pin 81B is enhanced by shot peening, in order to make the rotation with respect to the support pin 81A as smooth as possible, a surface treatment of super-smooth polishing is performed on the entire hollow pin 81B (step S18), and further a surface treatment of oil pocket machining is performed (step S19).

[0099] After the production of the outer peripheral pin 6, quenching, cryogenic treatment and tempering heat treatment are performed, and further shot peening is performed on the part surface. Therefore, the properties such as hardness, fatigue strength and wear resistance are improved by at least 25% compared with the conventional outer peripheral pin. In addition, since the outer peripheral surface of the outer peripheral pin 6 is subjected to super-smooth polishing and oil pocket machining after shot peening, the effect of the above-mentioned super-smooth polishing is improved by at least 30% and the effect of the above-mentioned oil pocket machining is improved by at least 20% compared with the conventional outer peripheral pin.

[0100] After the production of the reaction force pin 81, quenching, cryogenic treatment and tempering heat treatment are performed, and further shot peening is performed on the part surface. Therefore, the properties such as hardness, fatigue strength and wear resistance are improved by at least 25% compared with the conventional reaction force pin. In addition, since the outer peripheral surface of the support pin 81A is subjected to super-smooth polishing and oil pocket machining after shot peening, and the inner peripheral surface of the hollow pin 81B is subjected to super-smooth polishing and oil pocket machining after shot peening, the effect of the above-mentioned super-smooth polishing is improved by at least 30% respectively compared with the conventional support pin and hollow pin, and the effect of the above-mentioned oil pocket machining is improved by at least 20%.

[0101] Each of the tapered roller bearings 11A and 11B, the needled rollers 12A and 12B with cages, and the angular bearings 13A and 13B includes two annular raceway rings (inner ring and outer ring) and a plurality of rollers or balls disposed between both raceway rings, and functions to smoothly rotate the member on the inner ring side and the member on the outer ring side respectively by rotating the plurality of rollers or balls in response to the rotation of the inner ring and the outer ring.

[0102] For the eccentric shaft 4, the planetary gear 5, and the carrier 7, shot peening is performed to strengthen the strength of the entire component, and super-smooth polishing and oil reservoir processing are carried out to reduce the frictional resistance and prevent oil starvation in the parts related to the gear mechanism of the component. Correspondingly, for these bearings 11A, 11B, 12A, 12B, 13A, and 13B, the strength of the entire component is strengthened by shot peening in the same procedure as the steps S15 to S19 in FIG. 15, and the frictional resistance in the parts related to the gear mechanism of the component is reduced and oil starvation is prevented by super-smooth polishing and oil reservoir processing.

[0103] In the tapered roller bearings 11A and 11B, shot peening is performed on the entire inner ring and the entire outer ring that provide the raceway surfaces of the frustum-shaped rollers, and super-smooth polishing and oil reservoir processing are performed on the surfaces (raceway surfaces) where the rollers of the inner ring and the outer ring roll. Due to these surface treatments, the tapered roller bearings 11A and 11B have characteristics such as hardness, fatigue strength, and wear resistance improved by at least 25% compared to conventional tapered roller bearings. Furthermore, the tapered roller bearings 11A and 11B have the effect of the above-mentioned super-smooth polishing improved by at least 30% and the effect of the above-mentioned oil reservoir processing improved by at least 20% compared to conventional tapered roller bearings.

[0104] In the case of the needle rollers 12A and 12B with cages, shot peening is performed on the entire parts of the needle rollers. Further, in the needle roller 12A with a cage, super-smooth polishing and oil reservoir processing are performed on the peripheral surface of the needle roller that contacts the eccentric portion 41 of the eccentric shaft 4 and the through-hole 51A of the first planetary gear 51. In the needle roller 12B with a cage, super-smooth polishing and oil reservoir processing are performed on the peripheral surface of the needle roller that contacts the eccentric portion 42 of the eccentric shaft 4 and the through-hole 52A of the second planetary gear 52. By these surface treatments, the characteristics such as the hardness, fatigue strength, and wear resistance of the needle rollers 12A and 12B with cages are improved by at least 25% compared to the conventional needle rollers with cages. Further, the peripheral surface of the needle rollers of the needle rollers 12A and 12B with cages has at least a 30% improvement in the effect of the above-described super-smooth polishing and at least a 20% improvement in the effect of the above-described oil reservoir processing compared to the conventional needle rollers with cages.

[0105] In the case of the angular bearings 13A and 13B, shot peening is performed on the entire inner ring and the entire outer ring that provide the raceway surfaces of the rollers, and super-smooth polishing and oil reservoir processing are performed on the surfaces (raceway surfaces) where the rollers of the inner ring and the outer ring roll. By these surface treatments, the characteristics such as the hardness, fatigue strength, and wear resistance of the angular bearings 13A and 13B are improved by at least 25% compared to the conventional angular bearings. Further, the angular bearings 13A and 13B have at least a 30% improvement in the effect of the above-described super-smooth polishing and at least a 20% improvement in the effect of the above-described oil reservoir processing compared to the conventional tapered roller bearings.

[0106] FIG. 16 is a table showing the relationship between the components of the speed reducer 1 described above and the surface treatments applied to each component. In the table, "material" indicates the type of steel used for each component, and specific examples are shown in parentheses. "Treatment 1" to "Treatment 6" indicate the order of the treatments when a plurality of treatments are applied to each component.

[0107] As shown in the table, for the speed reducer 1, the carrier 7 and the case 9 are made of spheroidal graphite cast iron, and the other components are made of carbon-containing steel. In order to make the speed reducer 1 thinner and lighter, it is necessary to strengthen the torsional rigidity of the speed reducer 1. Therefore, basically, shot peening is performed on the entire components that make up the speed reducer 1. In addition, for the components made of carbon-containing steel, heat treatments such as quenching, cryogenic treatment, and tempering are performed before shot peening to further increase the strength of the steel. And after increasing the strength of the components by shot peening, super-smooth polishing and oil reservoir processing are performed on the parts related to the speed reduction gear mechanism of the speed reducer 1 for each component (contact parts and meshing parts between components, rolling parts of bearings, etc.) to further reduce the frictional resistance, supply sufficient lubricating oil, and prevent oil starvation.

[0108] Figure 17 is a table comparing the product specifications of the speed reducer 1 according to the present embodiment with those of the conventional product.

[0109] As shown in Figure 17, as a result of prototyping the speed reducer 1 according to the present invention, the thickness of the speed reducer 1 can be made at least 20[%] thinner than that of the conventional speed reducer (the currently commercialized speed reducer), and the weight of the speed reducer 1 can be made at least 17[%] lighter than that of the conventional speed reducer. In addition, the torsional rigidity of the speed reducer 1 can also be improved by 5 to 50 [N·m] compared with the conventional speed reducer, and the thinning and weight reduction of the speed reducer 1 can be achieved without reducing the strength of the torsional rigidity.

[0110] Furthermore, super-smooth polishing and oil reservoir processing are performed on the parts related to the rotation, meshing, and contact of the components related to the speed reduction gear mechanism of the speed reducer 1 to significantly reduce the frictional resistance and surface roughness of the friction surface and sliding surface, and improve the oil reservoir of the lubricating oil. Therefore, significant performance improvement can also be achieved for each item such as the transmission efficiency, starting torque, no-load running torque, angular transmission error, backlash, lost motion, and noise (vibration) of the speed reducer 1 compared with the conventional speed reducer.

[0111] In the above-described embodiment, the two-stage reduction gear 1 in which the first reduction unit 2 is provided in front of the second reduction unit 3 has been described. However, the present invention can also be applied to a reduction gear in which the first reduction unit 2 is omitted. In the above-described embodiment, a spur gear reduction mechanism in which two spur gears 21 and 22 are combined is used as the first reduction unit 2. However, a reduction device using a planetary gear mechanism may be used as the first reduction unit 2.

Explanation of Signs

[0112] 1 Reduction gear 2 First reduction unit 21 First spur gear 22 Second spur gear 3 Second reduction unit 4 Eccentric shaft 41 First eccentric part 42 Second eccentric part 5 Planet gear 51 First planet gear 52 Second planet gear 51A, 52A First through hole 51B, 52B Second through hole 6 Pin (outer peripheral pin) 7 Carrier 71 Cover (front cover) 71A Through hole (of the front cover) 71B Fastening hole (of the front cover) 71C Positioning hole (of the front cover) 72 Cover (rear cover) 72A Through hole (of the rear cover) 72B Mounting hole (of the rear cover) 72C Fastening pin (of the rear cover) 8 Rotation transmission member 81 Reaction pin 81A Support pin 81B Hollow pin 9 Case 901 Protrusion 902 Groove 903 Flange 10 Positioning pin 11A, 11B Tapered roller bearing 12A, 12B Needle roller with retainer 13A, 13B Angular bearings M Electric motor

Claims

1. an eccentric shaft having an eccentric part on a shaft, the shaft being rotated by rotation of a motor, and the eccentric part performing eccentric motion; a planetary gear that is rotatably supported by an eccentric portion of the eccentric shaft and that performs eccentric motion around an axial center of the eccentric shaft due to the eccentric motion of the eccentric portion; a case disposed around the planetary gear and having a plurality of outer circumferential pins rotatably attached to an inner circumferential surface thereof, the outer circumferential pins functioning as internal teeth corresponding to the external teeth of the planetary gear; a carrier including two lid bodies that sandwich the planetary gears and are rotatably supported on both ends of the shaft relative to the eccentric portion, and that outputs the rotation of the planetary gears based on the eccentric motion of the eccentric portion to the outside; In a reducer having At least the planetary gear and carrier components are manufactured by processing materials to manufacture each component, with the thickness of each component being made smaller than the original thickness by an amount corresponding to the increase in torsional rigidity of each component due to shot peening under predetermined conditions, and each manufactured component is subjected to shot peening under the predetermined conditions to increase the torsional rigidity of each component. A reducer characterized by:

2. After the shot peening, the case is subjected to a surface treatment of ultra-smooth polishing and oil pool processing on the grooves in which the outer peripheral pins are attached. The reducer according to claim 1 .

3. The material of the carrier and the case is ductile iron.

3. The reducer according to claim 1 or 2.

4. The eccentric shaft, the planetary gears, and the outer circumferential pins are made of structural steel having guaranteed hardenability.

3. The reducer according to claim 1 or 2.

5. After the eccentric shaft, the planetary gears and the multiple outer peripheral pins are manufactured by processing the material, the heat treatments of quenching, ultra-subzero and tempering are performed in this order, and then the surface treatments of shot peening, ultra-smooth polishing and oil-reservoir processing are performed in this order.

3. The reducer according to claim 1 or 2.

6. The two lid bodies are disk-shaped with a first through hole drilled in the center, the two lid bodies are rotatably attached to the eccentric shaft with first bearings interposed between the first through holes and the eccentric shaft, and are rotatably attached to the case with second bearings interposed between an outer periphery of each lid body and an inner periphery of the case, The first bearing and the second bearing have their raceways entirely shot peened, and the parts of the raceways that come into contact with the rollers are surface-treated by ultra-smooth polishing and oil-sump processing in that order. The reducer according to claim 5 .

7. The planetary gear has a disk shape with a second through hole drilled in the center, the planetary gear is rotatably attached to the eccentric shaft with a third bearing interposed between the second through hole and the eccentric portion, In the third bearing, the rollers are entirely subjected to shot peening, and the peripheral surfaces of the rollers are subjected to surface treatments of ultra-smooth polishing and oil reservoir processing in this order. The reducer according to claim 6 .

8. The first bearing is a tapered roller bearing, the second bearing is an angular bearing, and the third bearing is a needle roller with a cage. The reducer according to claim 7 .

9. A second spur gear is fixed to one end of the eccentric shaft, the second spur gear being engaged with a first spur gear connected to a rotor of the motor and transmitting the rotational speed of the first spur gear to the eccentric shaft by reducing the rotational speed of the first spur gear; When the first spur gear and the second spur gear are manufactured by processing a material to manufacture each component, the thickness of each component is made smaller than the original thickness by an amount corresponding to an increase in the torsional rigidity of each component by shot peening under predetermined conditions, and each manufactured component is subjected to shot peening under the predetermined conditions to increase the torsional rigidity of each component.

3. The reducer according to claim 1 or 2.

10. A second spur gear is fixed to one end of the eccentric shaft, the second spur gear being engaged with a first spur gear connected to a rotor of the motor and transmitting the rotational speed of the first spur gear to the eccentric shaft by reducing the rotational speed of the first spur gear; When the first spur gear and the second spur gear are manufactured by processing a material to manufacture each component, the thickness of each component is made smaller than the original thickness by an amount corresponding to an increase in the torsional rigidity of each component by shot peening under predetermined conditions, and each manufactured component is subjected to shot peening under the predetermined conditions to increase the torsional rigidity of each component. The reducer according to claim 5 .

11. A second spur gear is fixed to one end of the eccentric shaft, the second spur gear being engaged with a first spur gear connected to a rotor of the motor and transmitting the rotational speed of the first spur gear to the eccentric shaft by reducing the rotational speed of the first spur gear; When the first spur gear and the second spur gear are manufactured by processing a material to manufacture each component, the thickness of each component is made smaller than the original thickness by an amount corresponding to an increase in the torsional rigidity of each component by shot peening under predetermined conditions, and each manufactured component is subjected to shot peening under the predetermined conditions to increase the torsional rigidity of each component. The reducer according to claim 7 .

12. The first spur gear and the second spur gear are subjected to heat treatments of quenching, ultra-subzero and tempering in this order, and then surface treatments of shot peening, ultra-smooth polishing and oil-retaining processing in this order. The reducer according to claim 9 .

13. The first spur gear and the second spur gear are subjected to heat treatments of quenching, ultra-subzero and tempering in this order, and then surface treatments of shot peening, ultra-smooth polishing and oil-retaining processing in this order. The reducer according to claim 10 .

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