Eccentric swing type reduction gear

Abstract

To provide an eccentrically swinging speed reduction device that can be made lightweight.SOLUTION: The eccentrically swinging speed reduction device is provided that comprises: an internal gear 16; an external gear 14 meshing with the internal gear 16; an eccentric body shaft causing the external gear 14 to swing; and a carrier arranged at an axially side part of the external gear 14. The carrier has a first carrier 18 arranged on one axial side of the external gear 14, and a second carrier 20 arranged on the other axial side of the external gear 14, and a driven member 50 is coupled to the first carrier 18. The first carrier 18 is made of metal, and the second carrier 20 is made of resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an eccentric swing type reduction gear.

Background Art

[0002] The applicant of the present application disclosed in Patent Document 1 a planetary reduction mechanism including an external gear oscillated by an eccentric body and an internal gear that meshes with the external gear.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The planetary reduction mechanism described in Patent Document 1 includes, in addition to the external gear and the internal gear, two flanges, a casing, etc. as main components. In the conventional reduction mechanism, since these main components are made of steel materials, the weight of the reduction mechanism tends to increase. Regarding such a reduction mechanism, weight reduction is required to expand its applications.

[0005] An object of the present invention is to provide an eccentric swing type reduction gear capable of weight reduction in view of such problems.

Means for Solving the Problems

[0006] In order to solve the above problems, an eccentric swing type reduction gear according to an aspect of the present invention is an eccentric swing type reduction gear including an internal gear provided in a casing, an external gear that meshes with the internal gear, an eccentric body shaft that swings the external gear, a carrier disposed on an axial side portion of the external gear, and a main bearing disposed between the casing and the carrier, wherein the casing and the external gear are made of resin, and the main bearing is made of metal.

[0007] Another aspect of the present invention is also an eccentric swing type reduction gear. This device is an eccentric swing type reduction gear including an internal gear provided in a casing, an external gear meshing with the internal gear, an eccentric shaft for swinging the external gear, and an input shaft bearing for supporting the eccentric shaft, wherein the casing and the external gear are made of resin, and the input shaft bearing is made of metal.

[0008] Still another aspect of the present invention is also an eccentric swing type reduction gear. This device is an eccentric swing type reduction gear including an internal gear provided in a casing, an external gear meshing with the internal gear, an eccentric shaft for swinging the external gear, and a carrier disposed on an axial side portion of the external gear, wherein the casing and the external gear are made of resin, and the carrier is made of metal.

[0009] In addition, any combination of the above components, or those obtained by mutually replacing the components and expressions of the present invention among methods, systems, etc. are also effective as aspects of the present invention.

Effects of the Invention

[0010] According to the present invention, it is possible to provide an eccentric swing type reduction gear capable of weight reduction.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. In the embodiments, comparative examples, and modification examples, the same or equivalent components and members are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. In addition, the dimensions of the members in each drawing are enlarged or reduced as appropriate for easy understanding. Also, some of the members that are not important for explaining the embodiments in each drawing are omitted from the display. In addition, terms including ordinal numbers such as first and second are used to describe various components, but this term is used only for the purpose of distinguishing one component from another, and the components are not limited by this term.

[0013] [First Embodiment] Hereinafter, with reference to FIGS. 1 and 2, the configuration of the eccentric swing type reduction gear 10 according to the first embodiment will be described. FIG. 1 is a side sectional view showing the eccentric swing type reduction gear 10 of the first embodiment. FIG. 2 is a sectional view of the eccentric swing type reduction gear 10 taken along the line A-A of FIG. 1. In this figure, for easy understanding, one of the two external gear wheels 14 is shown, and the other is not shown. The other external gear wheel 14 differs in that it has a 180-degree phase difference from the one external gear wheel 14, and the other configurations are the same. The eccentric swing type reduction gear 10 of the present embodiment is an eccentric swing type gear device that causes one of the internal gear and the external gear to rotate by swinging the external gear that meshes with the internal gear, and outputs the generated motion component from the output member to the driven device.

[0014] The eccentric swing type reduction gear 10 mainly includes an input shaft 12, an external gear wheel 14, an internal gear wheel 16, carriers 18 and 20, a casing 22, main bearings 24 and 26, an inner pin 40, and a carrier pin 38. Hereinafter, the direction along the central axis line La of the internal gear wheel 16 is referred to as the "axial direction", and the circumferential direction and the radial direction of the circle centered on the central axis line La are referred to as the "circumferential direction" and the "radial direction", respectively. Also, hereinafter, for convenience, one side in the axial direction (the right side in the figure) is referred to as the input side, and the other side (the left side in the figure) is referred to as the anti-input side.

[0015] (Input Shaft) The input shaft 12 is rotated around the rotation center line by the rotational power input from a driving device (not shown). The eccentric swing type reduction gear 10 of the present embodiment is of a center crank type in which the rotation center line of the input shaft 12 is provided on the same axis as the central axis La of the internal gear 16. The driving device is, for example, a motor, a gear motor, an engine, or the like.

[0016] The input shaft 12 of the present embodiment is an eccentric body shaft having a plurality of eccentric portions 12a for swinging the external gear 14. The input shaft 12 having such a configuration may be referred to as a crankshaft. The axis of the eccentric portion 12a is eccentric with respect to the rotation center line of the input shaft 12. In the present embodiment, two eccentric portions 12a are provided, and the eccentric phases of the adjacent eccentric portions 12a are shifted by 180°.

[0017] The input side of the input shaft 12 is supported by the second cover 23 via the input shaft bearing 34, and the anti-input side thereof is supported by the first carrier 18 via the input shaft bearing 34. That is, the input shaft 12 is rotatably supported with respect to the first carrier 18 and the second cover 23. The input shaft bearing 34 is not particularly limited in its configuration, but in this example, it is a ball bearing having spherical rolling elements. A preload may be applied to the input shaft bearing 34, but no preload is applied in this example.

[0018] (External gear) The external gear 14 is individually provided corresponding to each of the plurality of eccentric portions 12a. The external gear 14 is rotatably supported by the corresponding eccentric portion 12a via the eccentric bearing 30. As shown in FIG. 2, twelve through holes are formed at equal intervals in the external gear 14 at positions offset from its axis. Among them, carrier pins 38 are inserted into three holes arranged at equal intervals of 120 degrees, and inner pins 40 are inserted into the remaining nine holes. Therefore, the former is called the carrier pin hole 39, and the latter is denoted as the inner pin hole 41. These holes may have the same diameter, but in this example, the diameter of the carrier pin hole 39 is larger than the diameter of the inner pin hole 41.

[0019] The carrier pin hole 39 and the inner pin hole 41 are circular holes provided at the same radial position. The outer periphery of the external gear 14 is formed with corrugated teeth, and as these teeth move while contacting the internal teeth 16a of the internal gear 16, the external gear 14 can swing in a plane with the central axis as the normal. An inner pin hole 41 through which the inner pin 40 penetrates is formed in the external gear 14. A clearance serving as play for absorbing the swinging component of the external gear 14 is provided between the inner pin 40 and the inner pin hole 41. The inner pin 40 and the inner wall surface of the inner pin hole 41 are in partial contact.

[0020] (Internal gear) The internal gear 16 meshes with the external gear 14. The internal gear 16 of the present embodiment has internal teeth 16a integrally formed on the inner peripheral portion of the casing 22. That is, in this example, the internal teeth 16a are a portion provided seamlessly with the casing 22. The number of internal teeth 16a of the internal gear 16 is one more than the number of external teeth of the external gear 14 in the present embodiment.

[0021] (Carrier) The carriers 18 and 20 are arranged on the axial side portions of the external gear 14. The carriers 18 and 20 include a first carrier 18 arranged on the side portion of the external gear 14 on the non-input side and a second carrier 20 arranged on the side portion of the external gear 14 on the input side. The first carrier 18 and the second carrier 20 are rotatably supported by the casing 22 via the first main bearing 24 and the second main bearing 26. The carriers 18 and 20 are generally disk-shaped as a whole. The first carrier 18 rotatably supports the input shaft 12 via the input shaft bearing 34. The second carrier 20 may be configured to support the input shaft via an input shaft bearing, but in this example, it does not support the input shaft bearing 34 and the input shaft 12.

[0022] The first carrier 18 and the second carrier 20 are connected via carrier pins 38 and inner pins 40. The carrier pins 38 and the inner pins 40 penetrate through the plurality of external gear wheels 14 in the axial direction at positions radially offset from the axis of the external gear wheel 14. In this example, the carrier pins 38 and the inner pins 40 are provided separately from the carriers 18, 20, but some of these pins may be integrally formed as part of the carriers 18, 20. The carrier pins 38 and the inner pins 40 will be described later.

[0023] One of the first carrier 18 and the casing 22 functions as an output member that outputs rotational power to a driven device, and the other functions as a fixed member that is fixed to an external member for supporting the eccentric swing type reduction gear 10. The output member is rotatably supported by the fixed member via main bearings 24, 26. In the present embodiment, the output member is the first carrier 18, and the fixed member is the casing 22. A driven member 50 that is rotationally driven by the eccentric swing type reduction gear 10 is connected to the end face on the anti-input side of the first carrier 18 by bolts 50b.

[0024] (Casing) The casing 22 has a hollow cylindrical shape as a whole, and an internal gear 16 is provided on its inner peripheral portion. A flange or the like may be provided on the outer peripheral portion of the casing 22, but no flange is provided in this example. The casing 22 is provided with a first cover 21 that covers the anti-input side of the casing 22 and a second cover 23 that covers the input side of the casing 22. The first cover 21 and the second cover 23 are fixed to the casing 22 by a plurality of bolts arranged in the circumferential direction.

[0025] The casing 22 is provided with a recess for accommodating the input side of the outer ring of the first main bearing 24. The first cover 21 is provided with a recess for accommodating a part of the non-input side of the outer ring of the first main bearing 24. The outer ring of the first main bearing 24 is axially sandwiched and supported between the casing 22 and the first cover 21. The casing 22 is provided with a recess for accommodating the input side of the outer ring of the second main bearing 26. The second cover 23 is provided with a recess for accommodating a part of the non-input side of the outer ring of the second main bearing 26. The outer ring of the second main bearing 26 is axially sandwiched and supported between the casing 22 and the second cover 23. The second cover 23 is provided with a recess for accommodating the outer ring of the input shaft bearing 34 on the input side. That is, the second cover 23 rotatably supports the input side of the input shaft 12 via the input shaft bearing 34.

[0026] (Main bearing) The main bearings 24 and 26 include a first main bearing 24 disposed between the first carrier 18 and the casing 22 and a second main bearing 26 disposed between the second carrier 20 and the casing 22. The main bearings 24 and 26 of the present embodiment include a plurality of rolling elements 42 and a retainer (not shown). The plurality of rolling elements 42 are provided at intervals in the circumferential direction. The rolling elements 42 of the present embodiment are spherical bodies. The retainer holds the relative positions of the plurality of rolling elements 42 and rotatably supports the plurality of rolling elements 42.

[0027] The main bearings 24 and 26 of the present embodiment include an outer ring 48 and an inner ring 49 having rolling surfaces of the rolling elements 42. The inner ring rolling surface may be provided on the outer peripheral surfaces of the carriers 18 and 20 instead of the inner ring. The outer ring 48 is fixed to the casing 22 by fitting such as clearance fitting, interference fitting, or intermediate fitting. The fitting clearance may be set corresponding to the difference in the coefficient of thermal expansion. Preload may be applied to the main bearings 24 and 26, but in this example, no preload is applied.

[0028] (Inner pin) As shown in FIG. 1, the inner pin 40 is inserted into an inner pin hole 41 formed through the external gear 14 with a gap therebetween. One end of the inner pin 40 is fitted into a recess 18b of the first carrier 18, and the other end is fitted into a recess 20b of the second carrier 20. The inner pin 40 is press-fitted into the recesses 18b and 20b and is not fixed by bolts or the like. The inner pin 40 abuts against a part of the inner pin hole 41 formed in the external gear 14, restrains the rotation of the external gear 14, and allows only its oscillation. The inner pin 40 functions as a connecting member that contributes to the transmission of power between the first carrier 18 and the second carrier 20 and the external gear 14.

[0029] (Carrier Pin) The carrier pin 38 is inserted into a carrier pin hole 39 formed through the external gear 14 with a gap therebetween. One end of the carrier pin 38 is fitted into a recess 18c of the first carrier 18, and the other end is fitted into a recess 20c of the second carrier 20. The carrier pin 38 is press-fitted into the recesses 18c and 20c and is not fixed by bolts or the like. The carrier pin 38 is surrounded by a tubular spacer 37. One end of the spacer 37 abuts against the first carrier 18, and the other end abuts against the second carrier 20. The spacer 37 functions as a spacer that maintains an appropriate axial distance between the first carrier 18 and the second carrier 20. The carrier pin 38 and the spacer 37 do not contact the carrier pin hole 39 of the external gear 14 and do not contribute to restraining the rotation of the external gear 14. The carrier pin 38 functions as a connecting member that contributes only to the connection between the first carrier 18 and the second carrier 20.

[0030] Next, the materials constituting each component of the present embodiment will be described. In recent years, the applications of speed reducers have been expanding to collaborative robots that operate near people. In order to expand the applications, weight reduction and low noise of speed reducers are desired. Conventional speed reducers are composed of components made of iron-based metals. In order to reduce the weight, it is conceivable to form the components with a material having a low specific gravity. As such a material, resin or the like is suitable. On the other hand, if the components are made of resin, it is conceivable that the temperature rises due to the decrease in heat dissipation, and the lifespan becomes short. Therefore, it is conceivable to keep the rotational speed and output torque low in consideration of the temperature rise.

[0031] Also, when a speed reducer is used in a robot, the carrier output may be easier to use due to its configuration. When resinifying the carrier on the load side, it is conceivable to embed an iron female thread by insert molding in order to ensure the strength of the tap for attaching the driven member. In this case, the weight increases due to the iron female thread, and the manufacturing man-hours increase due to insert molding.

[0032] From these viewpoints, the first carrier 18 of the present embodiment is made of metal, and the second carrier 20 is made of resin. In this case, since the first carrier 18 to which the driven member 50 is connected is made of metal, the strength of the mounting tap can be ensured. Further, since the second carrier 20 is made of resin, the weight of the second carrier 20 can be reduced.

[0033] Various resins can be used for the second carrier 20. In this example, the second carrier 20 is made of POM (polyacetal). POM is sometimes referred to as PO. From the viewpoint of mitigating the influence of temperature rise, the second carrier 20 of the present embodiment is not in direct contact with the input shaft bearing 34 and is provided in a non-contact manner.

[0034] Note that the resin used for each component member of the present embodiment may be a resin containing reinforcing fibers such as glass fibers and carbon fibers, may be a resin not containing reinforcing fibers, or may be a material obtained by impregnating a base material such as paper or cloth with a resin and laminating them.

[0035] High-speed rotation before deceleration is input to the input shaft 12, the first carrier 18, and the input shaft bearing 34 disposed between the input shaft 12. Therefore, the temperature rise of these components is relatively large. If their heat resistance is low, the allowable input rotation speed will be low. For this reason, the input shaft bearing 34 and the input shaft 12 may be made of metal. In this case, a decrease in the allowable input rotation speed can be suppressed. Since a large torsional stress is applied to the input shaft 12, it is desirable that the input shaft 12 be made of a material having higher rigidity than the first carrier 18. Therefore, in the present embodiment, the first carrier 18 is made of aluminum (including aluminum alloy; the same shall apply hereinafter) with high heat dissipation, and the input shaft 12 is made of an iron-based metal having higher torsional strength than aluminum.

[0036] Note that as the iron-based metal used for each component member of the present embodiment, carbon steel, bearing steel, stainless steel, etc. can be used according to desired characteristics.

[0037] Since the external gear 14 is disposed near the input shaft 12 where the temperature rise is large, it is desirable that the heat-resistant temperature of the external gear 14 be high. From this perspective, the external gear 14 may be made of a resin having a higher heat-resistant temperature than the second carrier 20. In this example, the external gear 14 is made of PEEK (polyetheretherketone).

[0038] In order to ensure the connection strength between the first carrier 18 and the second carrier 20, it is desirable that the rigidity of the carrier pin 38 be high. From this perspective, the carrier pin 38 may be made of metal, and the spacer 37 may be made of resin for weight reduction. In this example, the carrier pin 38 is made of an iron-based metal, and the spacer 37 is made of POM.

[0039] Since a large torsional stress is applied to the input shaft 12 as an eccentric shaft, it is desirable that the input shaft 12 be made of a material with higher rigidity than that of the first carrier 18. For weight reduction, it is desirable that the first carrier 18 be made of a material with a specific gravity smaller than that of the input shaft 12. From this perspective, the first carrier may be made of a metal with a specific gravity of 5 or less, and the input shaft 12 may be made of a ferrous metal. The first carrier 18 may be made of a light metal such as aluminum, magnesium, beryllium, titanium (a metal with a specific gravity of 4 to 5 or less) or a composite material thereof. In this example, the first carrier 18 is made of aluminum.

[0040] From the perspective of weight reduction, the casing 22, the first cover 21 and the second cover 23 may be made of resin. These may be made of the same resin or different resins. In this example, the casing 22 is made of PEEK, and the first cover 21 and the second cover 23 are made of POM.

[0041] As described above, in this embodiment, the external gear 14, the second carrier 20, the casing 22, the first cover 21, the second cover 23 and the spacer 37 are made of resin. Also, the main bearings 24, 26, the eccentric bearing 30, the input shaft bearing 34, the carrier pin 38, the inner pin 40, the input shaft 12 and the bolt 50b are made of ferrous metal. Also, the first carrier 18 is made of a light metal such as aluminum. Some or all of these constituent members of this embodiment may be made of another material.

[0042] The operation of the eccentric swing type reduction gear 10 configured as described above will be described. When rotational power is transmitted from the drive device to the input shaft 12, the eccentric portion 12a of the input shaft 12 rotates around the rotation center line passing through the input shaft 12, and the external gear 14 swings due to the eccentric portion 12a. At this time, the external gear 14 swings so that its axis rotates around the rotation center line of the input shaft 12. When the external gear 14 swings, the meshing position between the external gear 14 and the internal gear 16 is sequentially displaced. As a result, every time the input shaft 12 makes one rotation, one of the external gear 14 and the internal gear 16 rotates by an amount corresponding to the difference in the number of teeth between the external gear 14 and the internal gear 16. In the present embodiment, the external gear 14 rotates, and the decelerated rotation is output from the first carrier 18.

[0043] [Second Embodiment] Next, the configuration of the eccentric swing type reduction gear 10 according to the second embodiment will be described. In the drawings and description of the second embodiment, the same or equivalent components and members as those in the first embodiment are denoted by the same reference numerals. Descriptions overlapping with those of the first embodiment are appropriately omitted, and the configurations different from those of the first embodiment will be mainly described. FIG. 3 is a side cross-sectional view showing the eccentric swing type reduction gear 10 of the second embodiment, corresponding to FIG. 1.

[0044] In the description of the first embodiment, a center crank type eccentric swing type gear device was shown as an example, but the eccentric swing type reduction gear of the present embodiment is a so-called distribution type eccentric swing type gear device. The eccentric swing type reduction gear 10 of the present embodiment is different from that of the first embodiment mainly in that it includes a plurality of input gears 70 and the configuration of the input shaft 12 is different.

[0045] The plurality of input gears 70 are arranged around the central axis line La of the internal gear 16. Only one input gear 70 is shown in this figure. The input gear 70 is supported by the input shaft 12 inserted through the central portion thereof, and is provided so as to be rotatable integrally with the input shaft 12. The input gear 70 meshes with the external tooth portion of a rotating shaft (not shown) provided on the central axis line La of the internal gear 16. Rotational power is transmitted from a drive device (not shown) to the rotating shaft, and the input gear 70 rotates integrally with the input shaft 12 due to the rotation of the rotating shaft.

[0046] The input shafts 12 of the present embodiment are arranged at positions offset from the central axis line La of the internal gear 16 with a circumferential interval therebetween in a plurality (for example, three) numbers. Only one input shaft 12 is shown in this figure.

[0047] The operation of the eccentric swing type reduction gear 10 of the present embodiment described above will be described. When rotational power is transmitted from the drive device to the rotating shaft, the rotational power is distributed from the rotating shaft to the plurality of input gears 70, and each input gear 70 rotates in the same phase. When each input gear 70 rotates, the eccentric portion 12a of the input shaft 12 rotates around the rotation center line passing through the input shaft 12, and the external gear 14 swings due to the eccentric portion 12a. When the external gear 14 swings, as in the first embodiment, the meshing position between the external gear 14 and the internal gear 16 is sequentially shifted, and rotation of one of the external gear 14 and the internal gear 16 occurs. The rotation of the input shaft 12 is decelerated at a reduction ratio corresponding to the tooth number difference between the external gear 14 and the internal gear 16, and is output from the output member to the driven device. The output member of the present embodiment is also the first carrier 18.

[0048] In the present embodiment, the external gear 14, the second carrier 20, the casing 22, the first cover 21, the second cover 23, and the spacer 37 are made of resin. Further, the main bearings 24, 26, the eccentric bearing 30, the input shaft bearing 34, the carrier pin 38, the input shaft 12, and the bolt 50b are made of ferrous metal. The first carrier 18 is made of a light metal such as aluminum. Some or all of these constituent members of the present embodiment may be made of other materials. In particular, the second carrier 20 may be made of a resin having high heat resistance such as PEEK.

[0049] The above has described in detail examples of embodiments of the present invention. All of the above-described embodiments are merely specific examples for implementing the present invention. The content of the embodiments does not limit the technical scope of the present invention, and many design changes such as component changes, additions, deletions, etc. are possible without departing from the inventive concept defined in the claims. In the above-described embodiments, regarding the content for which such design changes are possible, explanations are given with notations such as "in the embodiment" and "in the embodiment", but design changes are not necessarily not allowed for the content without such notations. Also, the hatching attached to the cross-section of the drawing does not limit the material of the object to which the hatching is attached.

[0050] Hereinafter, modified examples will be described. In the drawings and descriptions of the modified examples, the same or equivalent components and members as those in the embodiments are denoted by the same reference numerals. Descriptions overlapping with those of the embodiments are appropriately omitted, and the configurations different from those of the first embodiment will be mainly described.

[0051] [Modified Example] In the description of the first embodiment, an example in which the internal gear 16 has internal teeth 16a integrally formed on the inner peripheral portion of the casing 22 is shown, but the present invention is not limited thereto. Instead of the internal teeth 16a, the internal gear 16 may be provided with internal tooth pins each made of the same number of metal pin members. In this case, the internal gear has an internal gear main body integrated with the casing and pin members rotatably supported by the internal gear main body. When using metal pin members, the casing 22 may be made of a resin such as POM having lower heat resistance than PEEK.

[0052] In the description of the first embodiment, an example in which two external gears 14 are provided is shown, but the present invention is not limited thereto. Three or more external gears 14 may be provided. For example, the input shaft may be provided with three eccentric portions 12a each having a phase shift of 120°, and three external gears 14 swung by the three eccentric portions 12a may be provided. Also, there may be one external gear 14.

[0053] In the description of the first embodiment, an example in which the second main bearing 26 and the first main bearing 24 have inner rings has been shown, but the present invention is not limited thereto. At least one of the second main bearing 26 and the first main bearing 24 may be a bearing without an inner ring.

[0054] In the description of the first embodiment, an example in which each bearing is a ball bearing having spherical rolling elements has been shown, but the present invention is not limited thereto. Some or all of these bearings may be roller bearings having cylindrical rolling elements.

[0055] In the description of the first embodiment, an example in which the output member is the carrier 18 and the fixed member is the casing 22 has been shown, but the present invention is not limited thereto. The fixed member may be the carrier 18 and the output member may be the casing 22.

[0056] In the description of the first embodiment, an example in which the first carrier 18 and the second carrier 20 are provided has been shown, but the present invention is not limited thereto. Only the first carrier may be provided on one axial side of the external gear.

[0057] Each of the above-described modifications has the same operations and effects as those of the first embodiment.

[0058] Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. The new embodiment resulting from the combination has the effects of each of the combined embodiments and modifications.

[0059] This specification also discloses the inventions described in Items 1 to 7 below.

[0060] [Item 1] An eccentric swing type reduction gear comprising an internal gear provided on a casing, an external gear meshing with the internal gear, an eccentric shaft for swinging the external gear, a carrier disposed on an axial side portion of the external gear, and a main bearing disposed between the casing and the carrier, wherein the casing and the external gear are made of resin, and the main bearing is made of metal.

[0061] [Item 2] The eccentric swing type reduction gear according to Item 1, wherein the carrier is made of metal. [Item 3] The eccentric swing type reduction gear according to Item 1 or 2, further comprising an input shaft bearing for supporting the eccentric shaft, wherein the input shaft bearing is made of metal.

[0062] [Item 4] An eccentric swing type reduction gear comprising an internal gear provided on a casing, an external gear meshing with the internal gear, an eccentric shaft for swinging the external gear, and an input shaft bearing for supporting the eccentric shaft, wherein the casing and the external gear are made of resin, and the input shaft bearing is made of metal.

[0063] [Item 5] An eccentric swing type reduction gear comprising an internal gear provided on a casing, an external gear meshing with the internal gear, an eccentric shaft for swinging the external gear, and a carrier disposed on an axial side portion of the external gear, wherein the casing and the external gear are made of resin, and the carrier is made of metal.

[0064] [Item 6] The eccentric swing type reduction gear according to any one of Items 1 to 5, wherein the internal gear has an internal gear body integrated with the casing and a pin member rotatably supported by the internal gear body, the internal gear body is made of resin, and the pin member is made of metal.

[0065] [Item 7] The eccentric body shaft is made of metal, and the eccentric swing type reduction gear according to any one of Items 1 to 6, characterized in that.

[0066] [Item 8] The eccentric swing type reduction gear according to any one of Items 1 to 7, characterized in that it has an eccentric bearing disposed between the eccentric body shaft and the external gear, and the eccentric bearing is made of metal.

Explanation of Signs

[0067] 10 ··· Eccentric swing type reduction gear, 12 ··· Input shaft, 14 ··· External gear, 16 ··· Internal gear, 18 ··· First carrier, 20 ··· Second carrier, 21 ··· First cover, 22 ··· Casing, 23 ··· Second cover, 24 ··· First main bearing, 26 ··· Second main bearing, 30 ··· Eccentric bearing, 34 ··· Input shaft bearing, 37 ··· Spacer, 38 ··· Carrier pin, 40 ··· Inner pin, 50 ··· Driven member, 70 ··· Input gear.

Claims

1. An eccentric swing type reduction gear comprising an internal gear, an external gear meshing with the internal gear, an eccentric shaft for swinging the external gear, and a carrier disposed on an axial side portion of the external gear, wherein: the external gear is made of resin and provided with an internal pin hole at a position offset from the axis; it has an internal pin inserted through the internal pin hole and connected to the carrier; the internal pin is made of metal; the eccentric swing type reduction gear is characterized by having a metal eccentric bearing disposed between an eccentric body provided on the eccentric shaft and the external gear.

2. The eccentric swing type reduction gear according to claim 1, wherein the carrier is made of resin or light metal.

3. The eccentric swing type reduction gear according to claim 1, wherein the internal pin is made of ferrous metal.

4. The eccentric swing type reduction gear according to claim 1, wherein the internal gear has an internal gear body made of resin and a metal pin member rotatably supported by the internal gear body.

5. As the carrier, it has a first carrier disposed on one axial side of the external gear and a second carrier disposed on the other axial side; the external gear is provided with a carrier pin hole at a position offset from the axis; it has a carrier pin that is inserted without contacting the carrier pin hole and connects the first carrier and the second carrier; the internal pin abuts against the internal pin hole; the eccentric swing type reduction gear according to claim 1, wherein the carrier pin is made of metal.

6. The eccentric swing type reduction gear according to claim 5, having a resin spacer externally fitted to the carrier pin.

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