Patent Description:
<CIT> discloses an eccentric oscillation type transmission includes an eccentric body, an external gear and an internal gear. The external gear is located radially outside of the eccentric body. The internal gear is arranged radially outside of the external gear and coaxially with a central axis. Part of a plurality of external teeth of the external gear and part of a plurality of internal teeth of the internal gear are engaged with each other on an extension line of a long diameter of the eccentric body. Also, between the eccentric body and the external gear, a bearing unit is interposed. The bearing unit includes a first bearing, a second bearing and a preload member. The first bearing and the second bearing are arranged side by side in the axial direction. The preload member is arranged between the first bearing and the second bearing.

<CIT> describes an eccentric oscillation type speed reducer includes: an internal gear; an external gear which meshes with the internal gear; an eccentric body shaft which oscillates the external gear; and a carrier disposed at a side portion of the external gear in an axial direction, in which the carrier includes a first carrier which is disposed on one side in the axial direction of the external gear, and a second carrier which is disposed on the other side in the axial direction of the external gear, a driven member is connected to the first carrier, the first carrier is made of metal, and the second carrier is made of resin.

<CIT> discloses a rotation mechanism, where a first and a second carrier of a metal shaft are made of resin.

As one type of robot, a cooperative robot that shares a work space with workers have been known. For example, a multi-joint cooperative robot, which is one of such cooperative robots, is provided with a speed reducing mechanism that serves as a rotation mechanism at a joint where two arms of the robot are connected to each other. The multi-joint cooperative robot and the like is provided with an electric motor or the like that imparts rotational force to the speed reducing mechanism. By decelerating and outputting the rotational force of the electric motor, one of the two arms is given a larger output torque relative to the other of the two arms.

As the speed reducing mechanism, for example, an eccentric oscillating speed reducing mechanism with high rotational position accuracy and high load resistance is used. This type of speed reducing mechanism includes, for example, a housing having an internal gear formed on its inner peripheral surface, an oscillating gear (external gear) meshed with the internal gear and oscillatory rotated, an input crankshaft (first rotating portion) that has an eccentric portion (eccentric body) rotatably supporting the oscillating gear and that transmits a rotational force to the oscillating gear, an output shaft (carrier pin) that transmits a rotational force of the oscillating gear, and a support member (carrier) connected to the output shaft. The support member is rotatably supported by the housing via a slide bearing. The output shaft is press-fitted into a hole (press-fitted hole) formed in the support member and formed integrally with the support member. Thus, when the rotational force of the oscillating gear is transmitted to the output shaft, the support member rotates relative to the housing.

However, in the conventional art described above, the output shaft is press-fitted into the support member, which increases the assembly work and disassembly work of the speed reducing mechanism. Further, since the output shaft is not freely rotated relative to the support member, the PV limits of the support member and the output shaft become low, and troubles such as seizure of the support member and the output shaft may occur. For this reason, it is difficult to stably operate the speed reducing mechanism, and there is a possibility that the product life of the speed reducing mechanism is shortened.

It is an object of the present invention to provide a rotation mechanism for which assembly and disassembly work efficiency can be improved and that can provide the stable operation and extended product life. According to the present invention said object is solved by a rotation mechanism having the features of the independent claim <NUM>. Preferred embodiments are laid down in the dependent claims.

According the invention, it is possible to improve work efficiency in assembling and disassembling the rotating member and the shaft. The surface roughness Ra of the inner peripheral surface of the rotating member is set to <NUM> or less, and the static friction coefficient of the inner peripheral surface of the rotating member against the shaft is set to <NUM> or less. Therefore, the sliding resistance of the shaft against the rotating member can be reduced, and the PV limit of the rotating member can be increased. Consequently, the speed reducing mechanism can be stably operated, which extends the product life.

The rotation mechanism for which assembly and disassembly work efficiency can be improved and that can provide the stable operation and extended product life.

The following describes embodiments of the present invention with reference to the drawings.

<FIG> schematically shows the configuration of a cooperative robot <NUM>. In the following description, the vertical and horizontal directions of the cooperative robot <NUM> are defined as the vertical and horizontal directions when the cooperative robot <NUM> is placed on an installation surface F.

As shown in <FIG>, the cooperative robot <NUM> includes a base portion <NUM> (an example of a first member or a second member in the claims) placed on an installation surface F, a rotating head <NUM> (an example of the first member or the second member in the claims), and an arm unit <NUM> (an example of the first member or the second member in the claims) rotatably attached to the top of the rotating head <NUM> (the example of the first member or the second member in the claims). The cooperative robot <NUM> further includes: speed reducing mechanisms 1A, 1B, and 1C (first speed reducing mechanism 1A, second speed reducing mechanism 1B, and third speed reducing mechanism 1C) provided in joint portions 106a, 106b, and 106c (first joint portion 106a, second joint portion 106b, and third joint portion 106c) of the base portion <NUM>, the rotating head <NUM>, and the arm unit <NUM>; servomotors <NUM>, <NUM> and <NUM> (first servomotor <NUM>, second servomotor <NUM>, and third servomotor <NUM> ) as drive sources; and an end effector <NUM> attached to the arm unit <NUM>.

The rotating head <NUM> is coupled to the base portion <NUM> such that it is rotatable around a first rotation axis L1. This coupling portion is the first joint portion 106a. The first speed reducing mechanism 1A and the first servomotor <NUM> are coupled to the first joint portion 106a. The first rotation axis L1 coincides with, for example, the vertical direction. Rotation of the first servomotor <NUM> is transmitted to the rotating head <NUM> via the first speed reducing mechanism 1A. In this way, the rotating head <NUM> is rotationally driven relative to the base portion <NUM> around the first rotation axis L1.

The arm unit <NUM> includes, for example, two arms <NUM> and <NUM> (first arm <NUM> and second arm <NUM>) that extend in one direction. One end of the first arm <NUM> of the two arms <NUM> and <NUM> is coupled to the upper portion of the rotating head <NUM> such that it is rotatable about a second rotation axis L2. This coupling portion is the second joint portion 106b, and the second speed reducing mechanism 1B and the second servomotor <NUM> are coupled to the second joint portion 106b.

The second rotation axis L2 coincides with, for example, the horizontal direction. Rotation of the second servomotor <NUM> is transmitted to the first arm <NUM> via the second speed reducing mechanism <NUM>. In this way, the first arm <NUM> is rotationally driven relative to the rotating head <NUM> around the second rotation axis L2. For example, the first arm <NUM> is driven to move swingably in the front and rear directions relative to the base portion <NUM>.

One end of the second arm <NUM> of the two arms <NUM> and <NUM> is coupled to the other end of the first arm <NUM> such that it is rotatable around a third rotation axis L3. This coupling portion is the third joint portion 106c, and the third speed reducing mechanism 1C and the third servomotor <NUM> are coupled to the third joint portion 106c. The third rotation axis L3 coincides with, for example, the horizontal direction. Rotation of the third servomotor <NUM> is transmitted to the second arm <NUM> via the third speed reducing mechanism 1C. In this way, the second arm <NUM> is rotationally driven relative to the first arm <NUM> about the third rotation axis L3. For example, the second arm <NUM> is driven to move swingable in the upper and lower directions relative to the first arm <NUM>.

The end effector <NUM> is coupled to the other end of the second arm <NUM>. By driving the rotating head <NUM>, the first arm <NUM>, and the second arm <NUM>, the end effector <NUM> is three-dimensionally driven.

The base portion <NUM>, the rotating head <NUM>, the first arm <NUM>, and the second arm <NUM> of the cooperative robot <NUM> are made of, for example, an aluminum alloy. The thermal conductivity of the aluminum alloy is about <NUM> [W/m·K]. Alternatively, they may be made of, for example, a magnesium alloy, carbon fiber reinforced plastic (CFRP), or a resin containing boron nitride to increase the thermal conductivity. The thermal conductivity of the magnesium alloy is, for example, about <NUM> [W/m·K].

The speed reducing mechanism 1A to 1C will be now described with reference to <FIG>. The basic configuration of each speed reducing mechanism 1A-1C is the same. Therefore, only the second speed reducing mechanism 1B among the speed reducing mechanisms 1A to 1C will be hereunder described, and description of the first speed reducing mechanism 1A and the third speed reducing mechanism 1C will be omitted.

<FIG> schematically shows the configuration of the second speed reducing mechanism 1B. As shown in <FIG>, the second speed reducing mechanism 1B is a so-called eccentric oscillating-type speed reducing mechanism. The second speed reducing mechanism 1B includes a cylindrical case <NUM> (an example of an internal gear in the claims), a carrier <NUM> (an example of a support member in the claims) rotatably supported by the case <NUM>, an input crankshaft <NUM> rotatably supported by the carrier <NUM>, a plurality of (for example, three) output shafts <NUM>, and oscillating gears <NUM> and <NUM> (first oscillating gear <NUM> and second oscillating gear <NUM>) rotatably supported by the input crankshaft <NUM>.

A central axis C1 of the case <NUM> coincides with the second rotation axis L2. In the following description, the direction parallel to the second rotation axis L2 may be referred to as an axial direction, the circumferential direction of the second rotation axis L2 may be referred to as a circumferential direction, and the direction orthogonal to the axial direction and the circumferential direction may be referred to as a radial direction.

The case <NUM> is made of, for example, an aluminum alloy. Alternatively, the case <NUM> may be made of, for example, a magnesium alloy, carbon fiber reinforced plastic (CFRP), a resin containing boron nitride to increase thermal conductivity, or the like. The thermal conductivity of the case <NUM> is preferably higher than the thermal conductivity of the internal tooth pin <NUM>, which will be described later. On the outer circumferential surface of the case <NUM>, an outer flange portion <NUM> projecting outward in the radial direction is integrally formed in the axially middle portion of the case <NUM>. The outer flange portion <NUM> has a rectangular section along the axial direction.

The outer flange portion <NUM> has a plurality of bolt holes 4a that penetrate therethrough in the axial direction and are arranged at equal intervals in the circumferential direction. For example, the rotating head <NUM> overlaps the outer flange portion <NUM> from the outside in the axial direction. A bolt <NUM> is inserted into each bolt hole 4a from the side opposite to the rotating head <NUM> of the outer flange portion <NUM>. The case <NUM> is fixed to the rotating head <NUM> by fastening the bolt <NUM> into a female thread portion 102a of the rotating head <NUM>.

On both sides in the axial direction of the inner peripheral surface 2b of the case <NUM>, radially enlarged portions 3a and 3b (first radially enlarged portion 3a and second radially enlarged portion 3b) are formed with stepped portions 3c, 3d (first stepped portion 3c and second stepped portion 3d) interposed therebetween, respectively. The inner diameters of the radially enlarged portions 3a and 3b are larger than the inner diameter of the inner peripheral surface 2b of the case <NUM>. The carrier <NUM> is provided on each of the radially enlarged portions 3a and 3b.

A plurality of internal tooth pins <NUM> (an example of the internal gear in the claims) are provided on the inner peripheral surface 2b of the case <NUM> between the two stepped portions 3c and 3d. Each of the internal tooth pins <NUM> is formed of, for example, metal. Alternatively, the internal tooth pins <NUM> may be made of a high-thermal-conductivity resin, a non-metallic material, or the like. The internal tooth pins <NUM> may be made of a resin containing carbon nanotubes (CNT) or boron nitride nanotubes (BNNT). The internal tooth pins <NUM> may be made of ferrous metal such as bearing steel. The internal tooth pins <NUM> may be made of carbon fiber reinforced plastic (CFRP).

Each of the internal tooth pins <NUM> is shaped like a column. The configuration of the internal tooth pin <NUM> is not limited this, but it may be a hollowed member. Each of the internal tooth pins <NUM> may have a multi-layered structure with a core material being wrapped in a surface material. For example, one of the core and surface material of the internal tooth pin <NUM> may be made of an iron-based metal, and the other may be made of a copper- or aluminum-based metal. Such a structure can eliminate the trade-off between the mechanical and thermal characteristics. As yet another example of the configuration of the internal tooth pin <NUM>, one of the core and surface material may be made of metal and the other may be made of resin. The internal tooth pins <NUM> may be made of sintered metal.

The axial direction of the internal tooth pins <NUM> coincides with the central axis C1 of the case <NUM>. The internal tooth pins <NUM> are arranged at regular intervals in the circumferential direction. The internal tooth pins <NUM> serve as internal teeth that mesh with the oscillating gears <NUM> and <NUM>.

The carrier <NUM> includes a first carrier (shaft flange) <NUM> provided in the first radially enlarged portion 3a situated closer to the rotating head <NUM> among the two radially enlarged portions 3a and 3b formed in the case <NUM>, and a second carrier (hold flange) <NUM> provided in the second radially enlarged portion 3b situated opposite to the first radially enlarged portion 3a in the axial direction. Each of the carriers <NUM> and <NUM> is formed in a disc shape. The outer peripheral surfaces of the carriers <NUM> and <NUM> are slidably fitted to the radially enlarged portions 3a and 3b, respectively. The carriers <NUM> and <NUM> are arranged and fixed in the axial direction by abutting against the corresponding stepped portions 3c and 3d.

The carriers <NUM> and <NUM> are made of resir. For example, the carriers <NUM> and <NUM> may be made of POM (polyacetal). Each of the carriers <NUM> and <NUM> may be formed of a resin different from POM, such as PAEK (Polyaryl Ether Ketones) typified by PEEK (Poly Ether Ketone). The resin may be PPS (Polyphenylene sulfide) or a resin containing PPS. The carriers <NUM> and <NUM> may be formed of carbon fiber reinforced plastic (CFRP). For example, the thermal conductivity of PPS is about <NUM> [W/m·K]. The thermal conductivity of PPS containing boron nitride is, for example, about <NUM> [W/m·K]. It is preferable that the linear expansion coefficient of each carrier <NUM>, <NUM> is, for example, greater than that of aluminum alloy (<NUM> to <NUM> (×<NUM>-<NUM>/°C)).

Input shaft holes 13a and 14a that penetrate the carriers <NUM> and <NUM>, respectively, in the radial direction are formed at the radial center of the carriers <NUM> and <NUM>. The input crankshaft <NUM> is inserted into the input shaft holes 13a and 14a. Bearings 15a and 15b (first bearing 15a and second bearing 15b) are provided in the input shaft holes 13a and 14a, respectively. Ball bearings, for example, are used as the bearings 15a and 15b. The input crankshaft <NUM> is rotatably supported by the carriers <NUM> and <NUM> via the bearings 15a and 15b. The rotation axis of the input crankshaft <NUM> coincides with the central axis C1 of the case <NUM> (second rotation axis L2).

A plurality of (for example, three) output shaft holes 13b and 14b (an example of shaft insertion holes, support member-side shaft holes) are formed at equal intervals in the circumferential direction around the input shaft holes 13a and 14a in each of the carriers <NUM> and <NUM>, respectively. An output shaft <NUM> is inserted into the output shaft holes 13b and 14b. A surface roughness Ra of the inner peripheral surfaces of the carriers defining the output shaft holes 13b and 14b is equal to or lower than <NUM>. The static friction coefficient of the inner peripheral surfaces of the carriers defining the output shaft holes 13b and 14b against the output shaft <NUM> is equal to or lower than <NUM>.

Among the two carriers <NUM> and <NUM>, a shim receiving concave portion <NUM> is formed coaxially with the output shaft hole 13b in a surface 13c of the first carrier <NUM> facing away from the second carrier <NUM>. The shim receiving recess <NUM> opens on the surface 13c side and communicates with the output shaft hole 13b.

An annular elastic shim <NUM> (an example of a shim in the claims) is received in the shim receiving recess <NUM>. The inner diameter of the elastic shim <NUM> is approximately the same as or slightly larger than the inner diameter of the output shaft hole 13b. The elastic shim <NUM> is made of rubber or the like and elastically deforms. The elastic shim <NUM> may be made of a material other than rubber, provided that it is made of an elastically deformable material. For example, a wave washer may be used as the elastic shim <NUM> instead of rubber.

An annular spacer <NUM> (an example of the shim in the claims) is disposed on the elastic shim <NUM>. The inner diameter of the spacer <NUM> is approximately the same as or slightly larger than the inner diameter of the output shaft hole 13b. The spacer <NUM> is formed of, for example, metal. The elastic shim <NUM> and the spacer <NUM> are provided for positioning the output shaft <NUM> with respect to the carriers <NUM> and <NUM> (details will be described later).

Among the two carriers <NUM> and <NUM>, a concave portion <NUM> is formed coaxially with the output shaft hole 14b in a surface 14c of the second carrier <NUM> on the side opposite to the first carrier <NUM>. The concave portion <NUM> opens on the side of the surface 14c and communicates with the output shaft hole 14b. The concave portion <NUM> may be filled with grease (not shown), for example. The grease is used to release heat transferred to the output shaft <NUM>. The grease has the thermal conductivity higher than those of the oscillating gears <NUM> and <NUM> and the second carrier <NUM>. The thermal conductivity of the grease is <NUM> [W/m·K] or greater.

The output shaft <NUM> inserted in the output shaft holes 13b and 14b is made of, for example, an aluminum alloy. The output shaft <NUM> is not limited to the aluminum alloy, and may be made of stainless steel instead. The thermal conductivity of the stainless steel is about <NUM> [W/m·K]. Alternatively, the output shaft <NUM> may be made of a ferrous metal, for example. As the ferrous metal, carbon steel, bearing steel, etc. may be used depending on desired properties. For example, the thermal conductivity of S45C as iron is about <NUM> [W/m·K].

A first end portion 9a of the output shaft <NUM> on the first carrier <NUM> side protrudes slightly from a surface 13c of the first carrier <NUM> facing away from the second carrier <NUM>. The elastic shim <NUM> and the spacer <NUM> are attached to the first end portion 9a of the output shaft <NUM>. A first retaining ring 18a is provided on the spacer <NUM> at the first end portion 9a of the output shaft <NUM>. Axial movement of the output shaft <NUM> toward the second carrier <NUM> is restricted by the first retaining ring 18a that abuts against the spacer <NUM>.

A second end portion 9b of the output shaft <NUM> on the second carrier <NUM> side is situated slightly lower than the surface 14c of the second carrier <NUM>. That is, the second end portion 9b of the output shaft <NUM> is received in the concave portion <NUM> of the second carrier <NUM>. A second retaining ring 18b is provided on the second end portion 9b of the output shaft <NUM>. The second retaining ring 18b is also received in the concave portion <NUM>. Axial movement of the output shaft <NUM> toward the first carrier <NUM> is restricted by the second retaining ring 18b abutting against a bottom surface 16a of the concave portion <NUM>.

That is, the elastic shim <NUM>, the spacer <NUM>, and the retaining rings 18a and 18b help positioning of the output shaft <NUM> relative to the carriers <NUM> and <NUM>. Among them, the elastic shim <NUM> and the spacer <NUM> have the function of absorbing manufacturing errors of the case <NUM>, the carriers <NUM> and <NUM>, and the output shaft <NUM> and, adjusting the position of the output shaft <NUM> relative to the carriers <NUM> and <NUM>. Specifically, the axial thickness of the elastic shim <NUM> and spacer <NUM> are adjusted depending on the amount of play of the output shaft <NUM> in the axial direction against the carriers <NUM> and <NUM> to reduce the play of the output shaft <NUM> against the carriers <NUM> and <NUM>. The play is a space that allows the output shaft <NUM> to move in the axial direction relative to the carriers <NUM> and <NUM>, and caused by manufacturing errors of the case <NUM>, the carriers <NUM> and <NUM>, and the output shaft <NUM>.

The axial thickness of the elastic shim <NUM> is determined such that the elastic shim <NUM> is slightly compressed when fitted in the case. Thus, the first carrier <NUM> is biased toward the second carrier <NUM> by a restoring force of the elastic shim <NUM> fitted in the case. This prevents the carriers <NUM> and <NUM> and the output shaft <NUM> from moving and they can be stably secured. Even if the axial play of the output shaft <NUM> relative to the carriers <NUM> and <NUM> increases due to aged deterioration or the like, this play can be absorbed by the elastic shims <NUM>. By biasing the first carrier <NUM> toward the second carrier <NUM> side, preload can be applied to the bearings 15a and 15b disposed in the input shaft holes 13a and 14a of the carriers <NUM> and <NUM>, respectively.

Since the axial movement of the output shaft <NUM> relative to the carriers <NUM> and <NUM> is restricted, in other words, the axial movement of the carrier <NUM> and <NUM> is restricted. Thus, the carriers <NUM> and <NUM> are kept being fitted to the corresponding radially enlarged portions 3a and 3b of the case <NUM>, respectively. In this way, the carriers <NUM> and <NUM> and the output shafts <NUM> are integrated. Each output shaft <NUM> is inserted in the output shaft holes 13b and 14b of the carriers <NUM> and <NUM>, thus the output shafts <NUM> are arranged around the input crankshaft <NUM>. The input crankshaft <NUM>, like the output shafts <NUM>, is made of, for example, an aluminum alloy. Alternatively, similar to the output shaft <NUM>, the input crankshaft <NUM> may be made of, for example, stainless steel or various ferrous metals.

A first end portion 8a of the input crankshaft <NUM> on the first carrier <NUM> side protrudes axially outward through the first bearing 15a provided in the first carrier <NUM>. The second servomotor <NUM> is connected to the first end portion 8a. The rotation of the second servomotor <NUM> is transmitted to the input crankshaft <NUM>.

A second end 8b of the input crankshaft <NUM> on the second carrier <NUM> side is situated substantially flush with the end surface of the second bearing 15b provided in the second carrier <NUM> that faces away from the first carrier <NUM>. The input crankshaft <NUM> has a first eccentric portion 21a and a second eccentric portion 21b arranged axially between the bearings 15a and 15b provided in the carriers <NUM> and <NUM>, respectively. The input crankshaft <NUM> is formed with a radially enlarged portion <NUM> that has a larger diameter than the eccentric portions 21a and 21b and is disposed between the eccentric portions 21a and <NUM> b.

The first eccentric portion 21a is situated on the first carrier <NUM> side. The second eccentric portion 21b is situated on the second carrier <NUM> side. Each eccentric portion 21a, 21b is provided eccentrically with reference to the second rotation axis L2. The eccentric portions 21a and 21b are out of phase with each other. For example, the eccentric portions 21a and 21b are out of phase with each other by <NUM>°.

The bearings 15c and 15d (third bearing 15c and fourth bearing 15d) are provided on the eccentric portions 21a and 21b, respectively. Ball bearings, for example, are used for these bearings 15c and 15d as well as the first bearing 15a and the second bearing 15b. The axial distance between the bearings 15c and 15d is limited by abutment of the axial end surfaces of the bearings 15c and 15d against the radially enlarged portion <NUM>. The oscillating gears <NUM> and <NUM> (first oscillating gear <NUM> and second oscillating gear <NUM>) are rotatably supported by the eccentric portions 21a and 21b via the bearings 15c and 15d, respectively.

The two oscillating gears <NUM> and <NUM> are made of resin. For example, the oscillating gears <NUM> and <NUM> may be made of POM (polyacetal). Similarly to the material for the carriers <NUM> and <NUM> described above, various resins can be used for the oscillating gears <NUM> and <NUM>. Since the oscillating gears <NUM> and <NUM> are made of resin, the thermal conductivity of the output shaft <NUM> and the thermal conductivity of the input crankshaft <NUM> are higher than the thermal conductivity of the oscillating gears <NUM> and <NUM>. The thermal conductivity of the case <NUM> is higher than the thermal conductivity of the oscillating gears <NUM> and <NUM>. The thermal conductivity of the internal tooth pins <NUM> is higher than that of the oscillating gears <NUM> and <NUM>.

The two oscillating gears <NUM> and <NUM> are arranged at a prescribed distance from each other between the two carriers <NUM> and <NUM>. At the radial center of the two oscillating gears <NUM> and <NUM>, formed are crankshaft insertion holes 24a and 24b (first crankshaft insertion hole 24a and second crankshaft insertion hole 24b) that penetrate the oscillating gears <NUM> and <NUM> in the thickness direction and receive outer peripheral surfaces of the bearings 15c and 15d, respectively. In this way, the oscillating gears <NUM> and <NUM> are rotatably supported by the eccentric portions 21a and 21b via the bearings 15c and 15d. The eccentric portions 21a and 21b cause the oscillating gears <NUM> and <NUM> to oscillatory rotate.

External teeth 23a and 23b that mesh with the internal tooth pins <NUM> provided on the case <NUM> are formed on the outer peripheral portions of the oscillating gears <NUM> and <NUM>, respectively. The number of the external teeth 23a, 23b is smaller than the number of the internal tooth pins <NUM> by, for example, one. The two oscillating gears <NUM> and <NUM> have output shaft insertion holes 25a and 25b (first output shaft insertion hole 25a and second output shaft insertion hole 25b; an example of a shaft insertion hole and an example of a gear-side shaft hole in the claims), respectively, at positions corresponding to the output shaft <NUM>. The inner diameters of the output shaft insertion holes 25a and 25b are large enough to allow the oscillatory rotation of the oscillating gears <NUM> and <NUM> with the output shaft <NUM> inserted in the output shaft insertion holes 25a and 25b. The surface roughness Ra of inner peripheral surfaces of the oscillating gears defining the output shaft insertion holes 25a and 25b is equal to or less than <NUM>. The static friction coefficient of the inner peripheral surfaces of the output shaft insertion holes 25a and 25b against the output shaft <NUM> equal to or less than <NUM>.

Of the two carriers <NUM> and <NUM> of the second speed reducing mechanism 1B configured in this way, the first arm <NUM>, for example, is disposed on the surface 14c of the second carrier <NUM> that faces away from the first carrier <NUM>. The first arm <NUM> is fixed to the first carrier <NUM> with bolts (not shown). The first arm <NUM> is formed with a convex portion 111a that fits into the input shaft hole 14a of the second carrier <NUM>. By fitting the convex portion, the first arm <NUM> is positioned with respect to the second carrier <NUM> in the radial direction. The convex portion 111a protrudes to such an extent that it faces the second bearing 15b and the second end portion 8b of the input crankshaft <NUM> with a minute gap therebetween.

Next, the operation and action of the second speed reducing mechanism 1B will be described. By driving the second servomotor <NUM>, the input crankshaft <NUM> is rotated. With the rotation of the crankshaft, the oscillating gears <NUM> and <NUM> rotatably supported by the eccentric portions 21a and 21b are oscillatory rotated. A part of the external teeth 23a and 23b of the oscillating gears <NUM> and <NUM> then mesh with the internal tooth pins <NUM> of the case <NUM>.

At this time, the meshing positions of the external teeth 23a and 23b with the internal tooth pins <NUM> (case <NUM>) are sequentially displaced in the circumferential direction since the number of teeth of each of the external teeth 23a and 23b is less than the number of the internal tooth pins <NUM> by, for example, one. Thus, the oscillating gears <NUM> and <NUM> rotate. This rotation is decelerated relative to the rotation of the input crankshaft <NUM>.

The output shaft <NUM> is inserted in the output shaft insertion holes 25a and 25b of the oscillating gears <NUM> and <NUM>. When the oscillating gears <NUM> and <NUM> rotate, the rotational force of the oscillating gears <NUM> and <NUM> in the rotational direction is transmitted to the output shafts <NUM>. Each output shaft <NUM> is rotatably supported by the carriers <NUM> and <NUM>. Thus, the rotational force of the oscillating gears <NUM> and <NUM> is transmitted to the carriers <NUM> and <NUM>.

The outer peripheral surfaces of the carriers <NUM> and <NUM> are slidably fitted to the corresponding radially enlarged portions 3a and 3b of the case <NUM>. Thus, each carrier <NUM> and <NUM> is rotated relative to the case <NUM>. That is, the rotation of the second servomotor <NUM> is decelerated and outputted to the carrier <NUM> (the first carrier <NUM> and second carrier <NUM>). The rotating head <NUM> is fixed to the case <NUM>. The first arm <NUM> is fixed to the second carrier <NUM> among the carriers <NUM> and <NUM>. Thus, the first arm <NUM> is rotated around the second rotation axis L2 relative to the rotating head <NUM>.

For example, when the rotation of the first arm <NUM> (the second carrier <NUM>) is restricted, the rotation of the second servomotor <NUM> is decelerated and outputted to the case <NUM>. In this case, the rotating head <NUM> is rotated around the second rotation axis L2 relative to the first arm <NUM>. That is, the speed reducing mechanisms 1A to 1C restrict the rotation of either the case <NUM> or the carrier <NUM>, so that the other of the case <NUM> and the carrier <NUM> serves as the output for the servomotors <NUM> to <NUM>. This operation principle also applies to the first speed reducing mechanism 1A and the third speed reducing mechanism 1C.

The output shaft <NUM> and the carriers <NUM> and <NUM> are integrated by the output shaft <NUM> inserted in the output shaft holes 13b and 14b formed in the carriers <NUM> and <NUM>, respectively. Thus, the output shaft <NUM> is freely rotated relative to the carriers <NUM> and <NUM>. Moreover, by forming the carriers <NUM> and <NUM> of resin, the output shaft <NUM> can be rotatably supported by the carriers <NUM> and <NUM> without providing bearings separately from the carriers <NUM> and <NUM>.

The surface roughness Ra of the inner peripheral surfaces of the carriers defining the output shaft holes 13b and 14b, respectively, is equal to or lower than <NUM>. The static friction coefficient of the inner peripheral surfaces of the carriers defining the output shaft holes 13b and 14b against the output shaft <NUM> is equal to or lower than <NUM>. Thus, the sliding resistance of the output shaft <NUM> against the carriers <NUM> and <NUM> can be reduced, and therefore the output shaft <NUM> can be smoothly rotated relative to the carriers <NUM> and <NUM>.

The same can be said for the relation between the oscillating gears <NUM> and <NUM> and the output shaft <NUM>. That is, the oscillating gears <NUM> and <NUM> are made of resin. The surface roughness Ra of the inner peripheral surfaces the oscillating gears <NUM> and <NUM> defining the output shaft insertion holes 25a and 25b, respectively, is equal to or less than <NUM>. The static friction coefficient of the inner peripheral surfaces of the output shaft insertion holes 25a and 25b against the output shaft <NUM> equal to or less than <NUM>. Therefore, the output shaft <NUM> is smoothly brought into contact with the oscillating gears <NUM> and <NUM> without providing bearings separately from the oscillating gears <NUM> and <NUM>.

Each elements generate heat due to the meshing between the internal tooth pins <NUM> and the oscillating gears <NUM> and <NUM>, the sliding friction between the case <NUM> and the carriers <NUM> and <NUM>, the sliding friction between the carriers <NUM> and <NUM> and the output shaft <NUM>, and the sliding friction the bearings 15a to 15d, and the like. The input crankshaft <NUM> and the output shafts <NUM> are made of, for example, an aluminum alloy. The thermal conductivity of the input crankshaft <NUM> and the output shafts <NUM> is higher than that of the oscillating gears <NUM> and <NUM>.

Therefore, the heat trapped inside the second speed reducing mechanism 1B is actively transferred to the input crankshaft <NUM> and the output shafts <NUM>. For example, the heat of the bearings 15a to 15d and the heat of the oscillating gears <NUM> and <NUM> are actively transferred to the input crankshaft <NUM>. Heat is accumulated in the oscillating gears <NUM> and <NUM> by the heat of the internal tooth pins <NUM>, the third bearing 15c, and the fourth bearing 15d transferred to the oscillating gears <NUM> and <NUM> and the heat of the oscillating gears <NUM> and <NUM> themselves, but this heat is actively is transferred to the output shaft <NUM>.

The heat transferred to the input crankshaft <NUM> spreads over the entire axial length of the crankshaft and is transferred to the first end portion 8a and the second end portion 8b. Heat is dissipated through the end portions 8a and 8b. Since the second end portion 8b faces the convex portion 111a of the first arm <NUM> with the minute gap therebetween, the heat of the second end portion 8b is also transferred to the first arm <NUM>. Since the first arm <NUM> is made of, for example, an aluminum alloy, its thermal conductivity is higher than that of the input crankshaft <NUM> and the output shaft <NUM>. In this way, the heat transferred from the input crankshaft <NUM> to the first arm <NUM> is effectively released.

The heat transferred to the output shaft <NUM> spreads over the entire axial length of the shaft and is transferred to the first end portion 9a and the second end portion 9b. Heat is dissipated through the end portions 9a and 9b. The concave portion <NUM> is formed in the second carrier <NUM> around the second end portion 9b of the output shaft <NUM>. The concave portion <NUM> is filled with grease. The first arm <NUM> is arranged such that it blocks the opening of the concave portion <NUM> filled with the grease, that is, it overlaps the surface 14c of the second carrier <NUM>. Thus, the heat of the second end portion 9b of the output shaft <NUM> is efficiently transferred to the first arm <NUM> through the grease. Therefore, the heat transferred from the output shaft <NUM> to the first arm <NUM> is effectively released.

The case <NUM> is made of, for example, an aluminum alloy. The internal tooth pins <NUM> can be made of a metal material, a high-thermal-conductivity resin, a non-metallic material, or the like. The oscillating gears <NUM> and <NUM> are made of resin. The thermal conductivity of the case <NUM> is higher than the thermal conductivity of the oscillating gears <NUM> and <NUM>. The thermal conductivity of the internal tooth pins <NUM> is higher than the thermal conductivity of the oscillating gears <NUM> and <NUM>. Thus, the heat generated by the meshing between the internal tooth pins <NUM> and the oscillating gears <NUM> and <NUM> can be actively transferred to the case <NUM> and the internal tooth pins <NUM>. Therefore, it is possible to prevent the heat accumulation inside the second speed reducing mechanism 1B.

The heat dissipation effect as described above is the same for the first speed reducing mechanism 1A and the third speed reducing mechanism 1C. The heat accumulated inside the first speed reducing mechanism 1A and the third speed reducing mechanism 1C is released through the input crankshaft <NUM> and the output shafts <NUM>. The heat is transferred to the rotating head <NUM>, the second arm <NUM> and the like via the input crankshaft <NUM> and the output shafts <NUM>, and the heat is effectively released. The case <NUM> and the internal tooth pins <NUM> prevent heat from being trapped inside the speed reducing mechanisms 1A and 1C.

Thus, in the speed reducing mechanisms 1A, 1B, and 1C described above, the surface roughness Ra of the inner peripheral surfaces of the respective carriers <NUM> and <NUM>, which are rotating members, defining the output shaft holes 13b and 14b is equal to or less than <NUM>. The static friction coefficient of the inner peripheral surfaces of the output shaft holes 13b and 14b against the output shaft <NUM> is equal to or lower than <NUM>. Similarly, the surface roughness Ra of the inner peripheral surfaces of the oscillating gears <NUM> and <NUM>, which are the rotating members, defining the output shaft insertion holes 25a and 25b, respectively, is equal to or less than <NUM>. The static friction coefficient of the inner peripheral surfaces of the output shaft insertion holes 25a and 25b against the output shaft <NUM> equal to or less than <NUM>.

Therefore, the output shaft <NUM> can be smoothly rotatably supported by the carriers <NUM> and <NUM> without providing bearings separately from the carriers <NUM> and <NUM>. The output shaft <NUM> is smoothly brought into contact with the oscillating gears <NUM> and <NUM> without providing bearings separately from the oscillating gears <NUM> and <NUM>. The PV limit of each carrier <NUM>, <NUM> and each oscillating gear <NUM>, <NUM> can be increased. Therefore, the speed reducing mechanisms 1A, 1B, and 1C can be stably operated, which extends the product life.

Since it is not necessary to provide bearings for the contact between the carriers <NUM> and <NUM> and the oscillating gears <NUM> and <NUM> and the output shaft <NUM>, the speed reducing mechanisms 1A, 1B and 1C can be made smaller in size. Further, the linear expansion coefficient of each carrier <NUM>, <NUM> is, for example, greater than that of aluminum alloy (<NUM> to <NUM> (×<NUM>-<NUM>/°C)). Whereas the output shaft <NUM> is made of, for example, an aluminum alloy. Therefore, even if the temperature of each carrier <NUM>, <NUM> rises by driving the speed reducing mechanisms 1A, 1B and 1C, the outer diameter of the output shaft <NUM> may become too large for the inner diameter of the output shaft holes 13b, 14b. The output shaft <NUM> can be smoothly rotatably supported by the carriers <NUM> and <NUM>.

The output shaft <NUM> is inserted into the output shaft holes 13b and 14b of the carriers <NUM> and <NUM>, respectively. Therefore, compared to the case where the output shaft <NUM> is press-fitted into the carriers <NUM> and <NUM> and fixed therein, the work efficiency in assembling and disassembling the speed reduction mechanisms 1A, 1B and 1C can be improved.

By forming the carriers <NUM> and <NUM> and the oscillating gears <NUM> and <NUM> of resin, the surface roughness Ra of the inner peripheral surfaces of the carriers and the oscillating gears defining the output shaft holes 13b and 14b and the output shaft insertion holes 25a and 25b, respectively, can be easily adjusted to equal to or less than <NUM>. The static friction coefficient of the inner peripheral surfaces of the carriers and the oscillating gears defining the output shaft holes 13b and 14b and the output shaft insertion holes 25a and 25b against the output shaft <NUM> equal to or less than <NUM>. By forming the output shaft <NUM> of metal, the rigidity of the output shaft <NUM> can be increased. Therefore, the speed reducing mechanisms 1A, 1B, and 1C can be operated more stably, and the product life can be extended.

In the eccentric oscillating-type speed reducing mechanism (speed reducing mechanism 1A, 1B, 1C), the first carrier <NUM> having the output shaft holes 13b, 14b and the second carrier <NUM> having the output shaft insertion holes 25a, 25b as described above are used. As a result, the drive efficiency can be improved while downsizing the speed reducing mechanisms 1A, 1B, and 1C. Moreover, the PV limit of each carrier <NUM>, <NUM> and each oscillating gear <NUM>, <NUM> can be easily increased, and the rigidity of the output shaft <NUM> can also be increased. Therefore, the speed reducing mechanisms 1A, 1B, and 1C can be stably operated. The product life of the speed reducing mechanisms 1A, 1B, and 1C can be extended.

The elastic shim <NUM> and the spacer <NUM> are attached to the first end portion 9a of the output shaft <NUM>. Therefore, positioning of the output shaft <NUM> relative to the carriers <NUM> and <NUM> can be performed easily and accurately. The elastic shims <NUM> and the spacers <NUM> can absorb manufacturing errors of the case <NUM>, the carriers <NUM> and <NUM>, and the output shaft <NUM>. The elastic shim <NUM> and the spacer <NUM> help positional adjustment of the output shaft <NUM> relative to the carriers <NUM> and <NUM>.

Since two members (the elastic shim <NUM> and the spacer <NUM>) are used for adjusting the position of the output shaft <NUM>, it is possible to increase the variety of positional adjustment methods by combining these two members. Therefore, it is possible to more easily and accurately arrange the output shaft <NUM> relative to the carriers <NUM> and <NUM>, and to reduce unnecessary movement of the output shaft.

Among other things, the elastic shim <NUM> is elastically deformable. By compressing and deforming the elastic shim <NUM> slightly in the axial direction and attaching it, the restoring force of the elastic shim <NUM> can bias the first carrier <NUM> toward the second carrier <NUM>. This prevents unnecessary movement or rattling of the carriers <NUM> and <NUM> and the output shaft <NUM>. Even if the axial play of the output shaft <NUM> relative to the carriers <NUM> and <NUM> increases due to aged deterioration or the like, this play can be absorbed by the elastic shims <NUM>. By biasing the first carrier <NUM> toward the second carrier <NUM> side, preload can be applied to the bearings 15a and 15b disposed in the input shaft holes 13a and 14a of the carriers <NUM> and <NUM>, respectively.

In the speed reducing mechanisms 1A, 1B, and 1C, the thermal conductivity of the case <NUM> is higher than the thermal conductivity of the oscillating gears <NUM> and <NUM>. Therefore, the heat inside the speed reducing mechanisms 1A, 1B, and 1C can be efficiently released via the case <NUM>. By making the thermal conductivity of the case <NUM> higher than that of the internal tooth pins <NUM>, the heat trapped in the internal tooth pins <NUM> can be actively transferred to the case <NUM>. Thus, the heat inside the speed reducing mechanisms 1A, 1B, and 1C can be efficiently released via the case <NUM>.

By using the speed reducing mechanisms 1A, 1B, and 1C as described above for the joints 106a, 106b, and 106c, respectively, of the cooperative robot <NUM>, the operation of the cooperative robot <NUM> can be stabilized. The product life of the cooperative robot <NUM> can be extended.

In the above first embodiment, the elastic shim <NUM> and the spacer <NUM> are provided on the first end portion 9a side of the output shaft <NUM> has been described. However, the configuration is not limited to this. The elastic shim <NUM> and the spacer <NUM> may be provided on the second end portion 9b side of the output shaft <NUM>. The elastic shim <NUM> and spacer <NUM> may be provided on both ends 9a and 9b of the output shaft <NUM>. Either only the elastic shim <NUM> or the spacer <NUM> may be provided.

The following describes a second embodiment of the present invention with reference to <FIG> and by referring to <FIG>. <FIG> schematically illustrates the configuration of a speed reducing mechanism <NUM> in the second embodiment. Elements and components similar to those of the first embodiment are referred to using the same referral numerals. In the following description of the second embodiment, the same labels as the first embodiment are used description thereof will be omitted.

As shown in <FIG>, the second embodiment is similar to the above-described first embodiment in that the speed reducing mechanism <NUM> is used in the cooperative robot <NUM>. As shown in <FIG>, the speed reducing mechanism <NUM> of the second embodiment is an eccentric oscillating-type speed reducing mechanism, and includes the case <NUM>, the carrier <NUM>, the input crankshaft <NUM>, the output shaft <NUM>, and the oscillating gears <NUM> and <NUM>, similarly to the speed reduction mechanisms 1A, 1B and 1C of the first embodiment described above.

The difference between the above-described first embodiment and the second embodiment is that the elastic shim <NUM> is provided on the first end portion 9a side of the output shaft <NUM> in the first embodiment, whereas the elastic shim <NUM> is not provided in the second embodiment. That is, the shim receiving recess <NUM> (see <FIG>) is not formed in the surface 13c of the first carrier <NUM>, and the whole surface 13c of the first carrier <NUM> is flat. Only the spacer <NUM> is provided on the first end portion 9a side of the output shaft <NUM>. Even in this case, the same effect as that of the above-described first embodiment is obtained.

The present invention s not limited to the above embodiments but encompasses various modifications of the above embodiments not departing from the purport of the present invention. For example, the above-described embodiment described the case where the reducing mechanisms 1A to 1C and <NUM> are used in the cooperative robot <NUM> as a robot. However, the embodiments are not intended to this. The configurations of the above-described embodiments can be adopted for various robots having different configurations provided that the robot includes two members (first member and second member), and a speed reducing mechanisms 1A to 1C and <NUM> disposed between the two members, and the second member rotates relative to the first member.

In the above embodiments, the speed reducing mechanisms 1A to 1C and <NUM> have been described as an example of the gear mechanism. However, the gear mechanism is not limited to these. In place of the speed reducing mechanisms 1A to 1C, the configuration of the above-described embodiments can be adopted for various gear mechanisms that have two gears meshed with each other and the rotational force is transmitted to one of the two gears, or have the shaft to which the rotational force of the one gear is transmitted.

In the above-described embodiments, the speed reducing mechanisms 1A to 1C and <NUM> are so-called eccentric oscillating-type speed reducing mechanisms, and each speed reducing mechanism has the single center crankshaft (input crankshaft <NUM>) coaxial with the central axis C1 of the case <NUM>. However, the embodiments are not limited to this. The eccentric oscillating-type speed reducing mechanism may be configured to oscillatory rotate the oscillating gears <NUM> and <NUM> by rotating two or more input crankshafts <NUM> in conjunction with each other. In this case, the input crankshafts <NUM> rotate while they revolve around the center axis C1 at the same time.

The cooperative robot <NUM> described above uses the servomotors <NUM>, <NUM>, and <NUM> as drive sources. However, the drive source is not limited to this, and various drive sources such as other electric motors, hydraulic motors, engines, or the like may be used in place of the servomotor.

In the above-described embodiment, the elastic shim <NUM> and the spacer <NUM> have the annular shapes. They are provided on the first end portion 9a of the output shaft <NUM> in the above embodiment. However, the configuration is not limited to this, and they can have any shape as long as manufacturing errors of the case <NUM>, the carriers <NUM> and <NUM>, and the output shaft <NUM> can be absorbed by the elastic shim <NUM> and the spacer <NUM>. Any shape may be adopted as long as the position of the output shaft <NUM> relative to the carriers <NUM> and <NUM> can be adjusted by the elastic shim <NUM> and the spacer <NUM>. For example, the elastic shim <NUM> and the spacer <NUM> may be formed in a U-shape. In this case, for example, the shim receiving recess <NUM> formed in the first carrier <NUM> may be configured to accommodate not only the elastic shim <NUM> but also the spacer <NUM>. Such a configuration can prevent the elastic shim <NUM> and the spacer <NUM> from coming off regardless of the shapes of the elastic shims <NUM> and the spacers <NUM>.

Claim 1:
A rotation mechanism (1B), comprising:
a shaft (<NUM>); and
a rotating member (<NUM>, <NUM>, <NUM>, <NUM>) having a shaft insertion hole (13b, 14b, 25a, 25b) in which the shaft (<NUM>) is inserted, the shaft (<NUM>) contacting an inner peripheral surface of the rotating member (<NUM>, <NUM>, <NUM>, <NUM>),
wherein the rotating member (<NUM>, <NUM>, <NUM>, <NUM>) is rotatable relative to the shaft (<NUM>),
wherein a surface roughness Ra of the inner peripheral surface is equal to or less than <NUM>, and
wherein a static friction coefficient of the inner peripheral surface against the shaft (<NUM>) is equal to or less than <NUM>,
wherein a portion of the rotating member (<NUM>, <NUM>, <NUM>, <NUM>) that at least includes the inner peripheral surface and surrounds the shaft (<NUM>) is made of resin, and
wherein the shaft (<NUM>) is made of metal, wherein the rotation mechanism (1B) further comprising:
an internal gear (<NUM>) having internal teeth (<NUM>);
an oscillating gear (<NUM>, <NUM>) having external teeth (23a, 23b) meshing with the internal teeth (<NUM>) and being oscillatory rotated;
an input crankshaft (<NUM>) having an eccentric portion (21a, 21b) that rotatably supports the oscillating gear (<NUM>, <NUM>);
an output shaft (<NUM>) to which a rotational force of the oscillating gear (<NUM>, <NUM>) is transmitted; and
a support member (<NUM>, <NUM>) supporting each axial end portion of the output shaft (<NUM>) rotatably,
wherein the input crankshaft (<NUM>) transmits a rotational force to the oscillating gear (<NUM>, <NUM>),
wherein the shaft (<NUM>) includes the output shaft (<NUM>),
wherein the rotating member (<NUM>, <NUM>, <NUM>, <NUM>) includes the oscillating gear (<NUM>, <NUM>) and the support member (<NUM>, <NUM>),
wherein the shaft insertion hole (13b, 14b, 25a, 25b) includes a gear-side shaft hole (25a, 25b) formed in the oscillating gear (<NUM>, <NUM>) and a support member-side shaft hole (13b, 14b) formed in the support member (<NUM>, <NUM>).