speed reduction device

Abstract

The present invention provides a reduction gear that effectively suppresses heat generation during operation while preventing lubricant leakage. [Solution] The reduction gear 1 of the embodiment comprises a case 2, a carrier 3 rotatably supported by the case 2, a plurality of crankshafts 13 rotatably supported by the carrier 3, and external gears 15, 16 housed in the carrier 3 and rotatably supported by the crankshafts 13, and meshing with internal tooth pins 5. The carrier 3 comprises center through holes 7a, 8a formed on a first rotation axis A1, a plurality of crank insertion holes 7b, 8b into which the plurality of crankshafts 13 are each inserted separately, a connecting recess 28 formed on the axial outer end surface 7d of the carrier 3 that allows the center through holes 7a, 8a and the crank insertion holes 7b, 8b to pass through, and a seal cap 30 attached to the connecting recess 28 that closes the connecting recess 28.

Description

Technical Field

[0001] The present invention relates to a speed reduction device.

Background Art

[0002] Conventionally, so-called eccentric oscillating speed reduction devices have been known as speed reduction devices. This type of device includes a cylindrical case (outer cylinder) having internal teeth gears, a carrier rotatably supported by the case, a plurality of crankshafts (crank shafts) rotatably supported by the carrier, and external teeth gears (oscillating gears) that are housed in the carrier and rotatably supported by the plurality of crankshafts.

[0003] The carrier is formed with a housing space (closed space) in which the external teeth gears are housed. Further, in the carrier, a plurality of crank center through-holes (crank shaft mounting holes) are formed at equal intervals in the circumferential direction on the same pitch circle centered on the rotation axis. Each of the crankshafts is inserted into a corresponding crank insertion hole and rotatably supported by the carrier. Furthermore, a center through-hole (through hole) is formed in the carrier coaxially with the rotation axis. The crank insertion holes and the center through-hole communicate with the housing space.

[0004] In order to improve the drive efficiency of such a speed reduction device, a lubricant is sealed in the housing space and the crank insertion holes. Thereby, the lubricity of the speed reduction device is improved, and the lubricant is intended to suppress heat generation during operation of the speed reduction device. The speed reduction device is provided with seal caps that close the crank insertion holes and the center through-hole in order to prevent the lubricant from leaking out (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of Invention

[0006] However, if the crank insertion hole and center through hole are sealed with a seal cap, as in the conventional technology described above, the flow of lubricant within the carrier is obstructed. As a result, the lubricant itself becomes hot, and there is a problem in that the heat generated when the reduction gear is driven cannot be effectively suppressed.

[0007] The present invention provides a reduction gear that can effectively suppress heat generation during operation while preventing lubricant leakage. [Means for solving the problem]

[0008] A reduction gear according to one aspect of the present invention comprises a cylindrical case having an internal gear, a carrier arranged radially inside the case and rotatably supported by the case, a plurality of crankshafts rotatably supported on a circle of the same pitch centered on the rotation axis of the carrier and to which an external rotational force is input, and an external gear housed in the carrier and rotatably supported on the crankshafts and meshing with the internal gear, wherein the carrier comprises a center through hole formed on the rotation axis, a plurality of crank insertion holes into which the plurality of crankshafts are each inserted separately, a connecting hole formed on the end face of the carrier in the direction of the rotation axis and passing through the center through hole and the crank insertion hole, and a seal cap attached to the connecting hole and closing the connecting hole.

[0009] This configuration allows the center through-hole and the crank insertion hole to be connected via the connecting hole. As a result, lubricant can flow smoothly between the center through-hole and the crank insertion hole through the connecting hole. Therefore, the lubricant can effectively suppress heat generation during the operation of the reduction gear. Furthermore, the connecting holes are sealed with seal caps. This prevents the lubricant sealed in the center through-hole and crank insertion hole from leaking out.

[0010] In the above configuration, the connecting hole is formed coaxially with the rotation axis and in a circular shape when viewed from the direction of the rotation axis. When a virtual circle that tangent to the plurality of crank insertion holes on the inside on the rotation axis side is defined as the inscribed circle, the diameter of the connecting hole is larger than the diameter of the inscribed circle.

[0011] In the above configuration, the seal cap comprises a cylindrical portion that fits into the connecting hole, a bottom portion that closes the end of the cylindrical portion on the end face side of the carrier, and an elastic covering portion that covers the outer circumferential surface of the cylindrical portion and the outer surface of the bottom portion, and at least a part of the outer surface of the bottom portion is exposed through the elastic covering portion.

[0012] In the above configuration, the exposed portion of the outer surface of the bottom is in contact with the mating member to which the carrier is fixed.

[0013] In the above configuration, the exposed portion of the outer surface of the bottom is in contact with the mating member to which the carrier is fixed, via a heat conductive member. [Effects of the Invention]

[0014] The aforementioned reduction gear effectively suppresses heat generation during operation while preventing lubricant leakage. [Brief explanation of the drawing]

[0015] [Figure 1] This is a cross-sectional view of a speed reducer according to an embodiment of the present invention. [Figure 2] This is a plan view of the reduction gear in an embodiment of the present invention, as seen from the substrate side. [Figure 3] This is an enlarged cross-sectional view of a seal cap in an embodiment of the present invention. [Figure 4] This is an enlarged cross-sectional view of the connecting recess and the area surrounding the connecting recess of the speed reducer in a first modified embodiment of the present invention. [Figure 5]This is an enlarged cross-sectional view of the connection recess of the reduction gear and the periphery of the connection recess in the second modified example of the embodiment of the present invention. [Figure 6] This is an enlarged cross-sectional view of the seal cap of the reduction gear and the periphery of the seal cap in the third modified example of the embodiment of the present invention. [Figure 7] This is an enlarged cross-sectional view of the seal cap of the reduction gear and the periphery of the seal cap in the fourth modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] Next, embodiments of the present invention will be described based on the drawings.

[0017] <Reduction Gear> Figure 1 is a cross-sectional view of the reduction gear 1. As shown in Figure 1, the reduction gear 1 reduces and outputs the rotation of, for example, an unillustrated electric motor. The reduction gear 1 is a so-called eccentric oscillating type reduction gear. The reduction gear 1 includes a cylindrical case 2, a carrier 3 rotatably provided radially inward of the case 2, and a reduction mechanism 4 connected to the carrier 3. The central axis of the case 2 coincides with the rotational axis of the carrier 3.

[0018] In the following description, these central axis and rotational axis are collectively referred to as the first rotational axis A1. The direction parallel to the first rotational axis A1 is referred to as the axial direction. The rotational direction of the carrier 3 is referred to as the circumferential direction. The radial direction of the case 2 orthogonal to the axial direction and the circumferential direction is simply referred to as the radial direction. In addition, the axially central side of the case 2 may be referred to as the axially inner side, and the side opposite to the axially inner side may be referred to as the axially outer side in the description.

[0019] <Case> Case 2 is made of spheroidal graphite cast iron (ductile cast iron). For example, FCD450 is used as the spheroidal graphite cast iron. An outer flange portion 2a that protrudes radially outward is integrally molded on the outer surface of Case 2. Multiple bolt holes 2b are formed in the outer flange portion 2a. The bolt holes 2b are arranged at equal intervals in the circumferential direction. Bolts (not shown) are inserted into these bolt holes 2b and the reduction gear 1 is fixed to, for example, the fixing part 100 of an industrial robot by tightening the bolts.

[0020] Multiple pin grooves 2c are formed on the inner circumferential surface 2d of case 2, oriented along the axial direction. The pin grooves 2c are arranged at equal intervals in the circumferential direction. An internal tooth pin 5 is fitted into each pin groove 2c. The internal tooth pin 5 functions as an internal tooth that meshes with the external gears 15 and 16 of the reduction mechanism 4, which will be described later. Main bearings 6 are provided on both sides of the inner circumferential surface 2d of case 2 in the axial direction. The carrier 3 is rotatably supported by case 2 via the main bearings 6.

[0021] <Career> The carrier 3 comprises a disc-shaped base portion 7 and an end plate portion 8 arranged opposite each other in the axial direction, and three column portions 9 that protrude from the base portion 7 toward the end plate portion 8. Each column portion 9 is arranged at equal intervals in the circumferential direction. The end plate portion 8 is positioned on the tip 9a of the column portion 9. The end plate portion 8 is fixed to the column portion 9 by bolts 10. In this state, a storage space S having a constant width in the axial direction is formed between the axially inward inner end surface 7c of the base portion 7 and the axially inward inner end surface 8c of the end plate portion 8. A pin 11 is provided radially inward from the bolt 10 of the column portion 9. The pin 11 positions the end plate portion 8 relative to the base plate portion 7. The pin 11 is fitted into a pin hole 12 provided in the end plate portion 8.

[0022] The base plate portion 7, end plate portion 8, and column portion 9 are formed from spheroidal graphite cast iron (ductile cast iron). For example, FCD450 is used as the spheroidal graphite cast iron. The outer circumferential surfaces of the base plate portion 7 and the end plate portion 8 are rotatably supported by the case 2 via corresponding main bearings 6. A seal portion 25 is provided on the outer circumferential surface of the base plate portion 7, axially outward from the main bearings 6. The seal portion 25 seals the space between the outer circumferential surface of the base plate portion 7 and the inner circumferential surface 2d of the case 2.

[0023] Figure 2 is a plan view of the reduction gear 1 as seen from the substrate 7 side. As shown in Figures 1 and 2, center through-holes 7a and 8a (center through-hole 7a on the substrate, center through-hole 8a on the end plate; an example of a center through-hole in the claim) are formed at the radial center of the substrate portion 7 and the radial center of the end plate portion 8, respectively. The two center through-holes 7a and 8a are arranged coaxially. The two center through-holes 7a and 8a each lead to the storage space S.

[0024] The base plate portion 7 and the end plate portion 8 each have three crank insertion holes 7b and 8b (base plate crank insertion holes 7b and end plate crank insertion holes 8b) formed between adjacent column portions 9 in the circumferential direction. The three base plate crank insertion holes 7b formed on the base plate portion 7 are arranged on the same pitch circle Cp centered on the first rotation axis A1. The three end plate crank insertion holes 8b formed on the end plate portion 8 are also arranged on the same pitch circle Cp centered on the first rotation axis A1. In addition to these, each crank insertion hole 7b and 8b are arranged coaxially. That is, the central axis A2 of the crank insertion holes 7b and 8b facing each other in the axial direction is parallel to the first rotation axis A1.

[0025] Of the crank insertion holes 7b and 8b, the substrate crank insertion hole 7b on the substrate portion 7 side has an inner flange portion 26 formed on the axially outward side. A small-diameter crank hole 27a is formed on the inner circumferential surface of the inner flange portion 26. That is, the substrate crank insertion hole 7b has a small-diameter crank hole 27a formed on the inner circumferential surface of the inner flange portion 26, and a large-diameter crank hole 27b formed on the axially inward side of the small-diameter crank hole 27a.

[0026] The small-diameter crank hole 27a and the large-diameter crank hole 27b are connected. The large-diameter crank hole 27b is formed such that its inner diameter is larger than that of the small-diameter crank hole 27a via a step. The inner diameter of the large-diameter crank hole 27b is the same as the inner diameter of the end plate crank insertion hole 8b. Crank bearings 18 are provided in both the large-diameter crank hole 27b (base plate crank insertion hole 7b) and the end plate crank insertion hole 8b. The crank bearings 18 are, for example, tapered roller bearings.

[0027] Multiple female threaded portions 29 are formed on the outer periphery of the outer end surface 7d of the substrate portion 7, which is axially outward. These female threaded portions 29 are used, for example, to fix the carrier 3 to a movable part (an example of a mating member in the claim) 101 of an industrial robot. Bolts (not shown) can be tightened into the female threaded portions 29.

[0028] A connecting recess (an example of a connecting hole in the claim) 28 is formed on the outer end surface 7d of the substrate portion 7 on the axial side, coaxial with the first rotation axis A1. The connecting recess 28 is formed in a circular shape when viewed from the axial direction.

[0029] Here, when we define the circumscribed circle Co as a virtual circle that tangent to the three crank small-diameter holes 27a (substrate crank insertion holes 7b) on the outer side opposite to the first rotation axis A1, the diameter D1 of the connecting recess 28 is larger than the diameter D2 of the circumscribed circle Co. As a result, the bottom surface 28a of the connecting recess 28 is connected to the substrate center through hole 7a and the three substrate crank insertion holes 7b. In other words, the substrate center through hole 7a and the three substrate crank insertion holes 7b are connected via the connecting recess 28. A seal cap 30 is fitted into such a connecting recess 28. The seal cap 30 closes the connecting recess 28.

[0030] <Seal Cap> Figure 3 is an enlarged cross-sectional view of the seal cap 30. As shown in Figures 1 and 3, the seal cap 30 comprises a bottomed cylindrical cap body 31 and an elastic covering portion 32 that covers the cap body 31. The cap body 31 is integrally molded with a cylindrical portion 33 that fits into the inner circumferential surface 28b of the connecting recess 28 and a bottom portion 34 that closes the axially outer end 33a of the cylindrical portion 33. The elastic covering portion 32 covers the outer circumferential surface 33b of the cylindrical portion 33 and the axially outer surface 34a of the bottom portion 34.

[0031] The elastic coating portion 32 is compressed and sandwiched between the outer circumferential surface of the cylindrical portion 33 and the inner circumferential surface 28b of the connecting recess 28. This improves the sealing performance of the seal cap 30. The seal cap 30 only closes the axially outer opening 28c of the connecting recess 28 with its bottom portion 34. Therefore, even when the seal cap 30 is fitted into the connecting recess 28, a passage P is maintained between the substrate center through hole 7a and the three substrate crank insertion holes 7b via the connecting recess 28.

[0032] Since the connecting recess 28 is formed coaxially with the first rotation axis A1, the length of the passage P between the substrate center through hole 7a and each substrate crank insertion hole 7b, that is, the creepage distance between the substrate center through hole 7a and each substrate crank insertion hole 7b, is the same. The size of the passage P between the substrate center through hole 7a and each substrate crank insertion hole 7b is also the same.

[0033] <Deceleration mechanism> The reduction mechanism 4 reduces the rotation of an electric motor (not shown) by a constant ratio, causing the carrier 3 to rotate relative to the case 2. The reduction mechanism 4 comprises three crankshafts 13 inserted into each crank insertion hole 7b, 8b, a transmission spur gear (an example of a gear in the claim) 14 provided at the axial end of each crankshaft 13, and two external gears 15, 16 (first external gear 15, second external gear 16) housed in the storage space S between the base plate portion 7 and the end plate portion 8.

[0034] External teeth 17 are formed on the outer circumference of each of the three transmission spur gears 14. These external teeth 17 simultaneously mesh with, for example, the motor shaft of an electric motor (not shown). As a result, when the motor shaft rotates, the three transmission spur gears 14 rotate simultaneously.

[0035] The crankshaft 13 is rotatably supported on the carrier 3 (base plate portion 7 and end plate portion 8) via each crank bearing 18. The crankshaft 13 has a shaft body 13c that rotates about a central axis A2, and a first eccentric portion 13a and a second eccentric portion 13b formed in the axial center of the shaft body 13c. Both axial sides of the shaft body 13c are rotatably supported on the carrier 3 (base plate portion 7 and end plate portion 8) via the crank bearings 18. The shaft body 13c and the transmission spur gear 14 are arranged coaxially and integrated. That is, the crankshaft 13 and the transmission spur gear 14 rotate together as a single unit around the central axis A2. Hereinafter, the central axis A2 will be referred to as the second rotation axis A2 of the crankshaft 13.

[0036] The first eccentric portion 13a and the second eccentric portion 13b are eccentric from the second rotation axis A2. The first eccentric portion 13a and the second eccentric portion 13b are positioned adjacent to each other in the axial direction between the two crank bearings 18. In other words, the first eccentric portion 13a and the second eccentric portion 13b are positioned adjacent to each other in the axial direction between the base portion 7 and the end plate portion 8. The first eccentric portion 13a and the second eccentric portion 13b are positioned with a phase angle difference of 180°. The inner circumferential surfaces of roller bearings 19 are fitted to each of the eccentric portions 13a and 13b. The roller bearings 19 are, for example, cylindrical roller bearings. The first external gear 15 and the second external gear 16 are rotatably supported on each crankshaft 13 via the roller bearings 19.

[0037] The first external gear 15 and the second external gear 16 are positioned in the space between the base plate portion 7 and the end plate portion 8. The first external gear 15 and the second external gear 16 have through holes 15a and 16a, respectively, into which the outer circumferential surfaces of the roller bearings 19 are fitted. As a result, when the first eccentric portion 13a and the second eccentric portion 13b oscillate due to the rotation of the crankshaft 13, the first external gear 15 and the second external gear 16 oscillate via the roller bearings 19.

[0038] The first external gear 15 and the second external gear 16 each have openings 15b and 16b, respectively, to avoid interference with the column portion 9. Center through holes 15c and 16c are formed in the radial center of the first external gear 15 and the second external gear 16. Each center through hole 15c and 16c leads to the storage space S. External teeth 15d and 16d are formed on the outer circumference of the first external gear 15 and the outer circumference of the second external gear 16, respectively. The number of teeth on each external tooth 15d and 16d is, for example, one less than the number of internal tooth pins 5 in case 2.

[0039] <Operation of the speed reducer> Next, the operation of the reduction gear 1 will be explained. First, before the reduction gear 1 is driven, a lubricant (not shown) is sealed inside the carrier 3. The lubricant is evenly distributed throughout the inside of the carrier 3. When the reduction gear 1 is driven, for example by an electric motor (not shown), the three crankshafts 13 rotate simultaneously. As a result, the two external gears 15 and 16 are rotated in an oscillating motion. As these external gears 15 and 16 rotate in an oscillating motion, some of the external teeth 15d and 16d of each external gear 15 and 16 engage with the internal tooth pins 5 of the case 2.

[0040] The number of teeth on each external gear 15d, 16d is, for example, one less than the number of internal gear pins 5. Therefore, each external gear 15, 16 rotates such that the meshing points of each external gear 15d, 16d are sequentially shifted in the circumferential direction relative to the internal gear pins 5 (case 2). This rotation is decelerated relative to the rotation of the crankshaft 13.

[0041] As each external gear 15 and 16 rotates, each crankshaft 13 also rotates on its own axis around the second rotation axis A2 while revolving around the first rotation axis A1. Each crankshaft 13 is rotatably supported on the carrier 3 (base plate portion 7, end plate portion 8). Therefore, the carrier 3 rotates as each crankshaft 13 revolves. As a result, the reduction gear 1 reduces the rotation of, for example, an electric motor (not shown) and outputs the reduced speed. This drives the movable portion 101 relative to the fixed portion 100 of the industrial robot. However, the reduction gear 1 can also move the fixed portion 100 relative to the movable portion 101. That is, if the movable portion 101 is fixed, the case 2 rotates relative to the carrier 3, and the fixed portion 100 is driven relative to the movable portion 101.

[0042] Here, since lubricant is sealed inside the carrier 3, the driving resistance of the reduction gear 1 can be reduced as much as possible. The lubricant is prone to a force that tries to flow out from the outer end surface 7d of the substrate portion 7, which is the output side (opposite input side). However, a seal cap 30 is fitted into the connecting recess 28 formed on the outer end surface 7d of the substrate portion 7. Therefore, leakage of lubricant from the reduction gear 1 is suppressed.

[0043] Furthermore, since the connecting recess 28 is connected to the substrate center through hole 7a and the substrate crank insertion hole 7b, simply blocking the connecting recess 28 can suppress the leakage of lubricant from the substrate center through hole 7a and the substrate crank insertion hole 7b. The connecting recess 28 serves as a passage P leading to the substrate center through hole 7a and the three substrate crank insertion holes 7b. Lubricant flows back and forth between the center through holes 7a, 8a and the crank insertion holes 7b, 8b via this passage P. This allows for a good flow of lubricant.

[0044] As described above, the carrier 3 includes center through holes 7a, 8a, crank insertion holes 7b, 8b, connecting recesses 28 that allow these center through holes 7a, 8a and crank insertion holes 7b, 8b to pass through, and a seal cap 30 that closes the connecting recesses 28. Therefore, the center through holes 7a, 8a and crank insertion holes 7b, 8b can be connected via the connecting recesses 28. As a result, lubricant can flow smoothly between the center through holes 7a, 8a and crank insertion holes 7b, 8b via the connecting recesses 28. Consequently, the lubricant can effectively suppress the heat generated when the reduction gear 1 is driven. Furthermore, the connecting recess 28 is sealed by the seal cap 30. This prevents the lubricant sealed in each center through hole 7a, 8a and each crank insertion hole 7b, 8b from leaking out.

[0045] The connecting recess 28 is formed coaxially with the first rotation axis A1 and in a circular shape when viewed from the axial direction. The diameter D1 of the connecting recess 28 is larger than the diameter D2 of the circumscribed circle Co. Therefore, it can pass through the substrate center through hole 7a and each substrate crank insertion hole 7b. The length of the passage P between the substrate center through hole 7a and each substrate crank insertion hole 7b, that is, the creepage distance between the substrate center through hole 7a and each substrate crank insertion hole 7b, can be made the same. The size of the passage P between the substrate center through hole 7a and each substrate crank insertion hole 7b can also be made the same. Therefore, the lubricant can be distributed evenly and smoothly throughout the entire carrier 3. Uneven lubricant flow within the carrier 3 can also be suppressed. Furthermore, heat generation during the operation of the reduction gear 1 can be suppressed even more effectively.

[0046] [First variation] <Occlusion> Next, referring to Figure 2 and based on Figure 4, a first modified example of the reduction gear 1 will be described. Figure 4 is an enlarged cross-sectional view of the connecting recess 28 and the area surrounding the connecting recess 28 of the reduction gear 1 in the first modified example. In Figure 4, the seal cap 30 is shown removed for the sake of explanation. In the above-described embodiment, the case where the diameter D1 of the connecting recess 28 is larger than the diameter D2 of the circumscribed circle Co was explained. However, it is not limited to this, and the diameter D1 of the connecting recess 28 only needs to satisfy at least the following size.

[0047] In other words, as shown in Figures 2 and 4, when a virtual circle Ci is defined as the inscribed circle tangent to the three large-diameter crank holes 27b (substrate crank insertion holes 7b) on the inside of the first rotation axis A1 side, the diameter D1 of the connecting recess 28 should be larger than the diameter D3 of the inscribed circle Ci. The seal cap 30 should be formed to correspond to the size of the connecting recess 28. This configuration allows the connecting recess 28 to connect the center through holes 7a and 8a with the crank insertion holes 7b and 8b. Therefore, the same effects as in the above-described embodiment can be achieved.

[0048] [Second variation] <Occlusion> Next, a second modified example of the reduction gear 1 will be described based on Figure 5. Figure 5 is an enlarged cross-sectional view of the connecting recess 28 and the area surrounding the connecting recess 28 of the reduction gear 1 in the second modified example. Figure 5 corresponds to Figure 4 described above. In Figure 5, the seal cap 30 is shown removed for the sake of explanation. In the embodiments described above, the case in which the connecting recess 28 is formed coaxially with the first rotation axis A1 was described. The case in which the connecting recess 28 is formed in a circular shape when viewed from the axial direction was also described.

[0049] However, the design is not limited to this. As shown in Figure 5, the connecting recess 28 may pass through the substrate center through hole 7a and the substrate crank insertion hole 7b. The connecting recess 28 does not have to be formed coaxially with the first rotation axis A1. The shape of the connecting recess 28 does not have to be circular when viewed from the axial direction. The seal cap 30 may be formed to correspond to the shape of the connecting recess 28. By configuring it in this way, the same effects as the above-described embodiment can be achieved.

[0050] [Third variation] <Seal Cap> Next, a third modified example of the reduction gear 1 will be described based on Figure 6. Figure 6 is an enlarged cross-sectional view of the seal cap 30 and the area around the seal cap 30 of the reduction gear 1 in the third modified example. In the above-described embodiment, the case was explained in which the elastic covering portion 32 of the seal cap 30 of the reduction gear 1 covers the outer peripheral surface 33b of the cylindrical portion 33 and the outer surface 34a of the bottom portion 34 of the cap body 31. However, this is not the only option, and as shown in Figure 6, the elastic covering portion 32 does not need to cover the outer surface 34a of the bottom portion 34. With this configuration, the outer surface 34a of the bottom portion 34 is exposed to the outside. For example, a movable part 101 of an industrial robot is in contact with this outer surface 34a.

[0051] Therefore, according to the third modification described above, the bottom 34 of the cap body 31 is exposed to the outside, so that the heat transferred to the cap body 31 via a lubricant (not shown) can be actively dissipated from the bottom 34. As a result, the heat dissipation performance of the seal cap 30 can be improved, and the heat generated when the reduction gear 1 is driven can be suppressed even more effectively. Furthermore, the outer surface 34a of the bottom portion 34 is in contact with the movable part 101 of the industrial robot. Therefore, heat from the seal cap 30 can be transferred to the movable part 101. This further improves the heat dissipation performance of the seal cap 30.

[0052] In the third modification described above, the case in which the entire bottom portion 34 of the cap body 31 is exposed to the outside was explained. However, it is not limited to this, and it is sufficient if at least a part of the bottom portion 34 is exposed via the elastic coating portion 32. By exposing a part of the bottom portion 34, the heat dissipation performance of the seal cap 30 can be improved compared to the case in which the bottom portion 34 is completely covered by the elastic coating portion 32.

[0053] [Fourth variation] <Seal Cap> Next, a fourth modified example of the reduction gear 1 will be described based on Figure 7. Figure 7 is an enlarged cross-sectional view of the seal cap 30 and the area around the seal cap 30 of the reduction gear 1 in the fourth modified example. Figure 7 corresponds to Figure 6 described above. As shown in Figure 7, the difference between the third and fourth modified examples is that in the third modified example, the bottom 34 is in direct contact with the movable part 101, whereas in the fourth modified example, the bottom 34 is in contact with the movable part 101 via the heat conductive member 50.

[0054] Examples of heat conductive material 50 include aluminum, copper, and grease, which have high thermal conductivity. However, it is not limited to these, and various materials can be used as heat conductive material 50. Therefore, according to the fourth modification described above, in addition to the same effects as the third modification described above, the heat from the seal cap 30 can be more efficiently transferred to the movable part 101 via the heat conductive member 50.

[0055] The present invention is not limited to the embodiments described above, but includes various modifications to the embodiments described above, without departing from the spirit of the invention. For example, the above embodiment described a case in which the reduction gear 1 is used in an industrial robot. However, it is not limited to this, and the reduction gear 1 can be used in various devices.

[0056] In the above-described embodiment, the case in which the reduction gear 1 comprises three crankshafts 13 was explained. The case in which each external gear 15, 16 is oscillating and rotating by the three crankshafts 13 was explained. However, it is not limited to this, and when configured as a reduction gear 1, it is sufficient to have multiple crankshafts 13. The number of crankshafts 13 is two or more, and the carrier 3 is sufficient to have center through holes 7a, 8a formed therein.

[0057] The embodiments described above and their respective modifications can be combined as appropriate.

[0058] Among the embodiments disclosed herein, those composed of multiple objects may be integrated, and conversely, those composed of a single object may be divided into multiple objects. Whether or not they are integrated, the invention can be constructed in a way that achieves its objective. [Explanation of Symbols]

[0059] 1...Reduction device 2…case 3… Career 5…Internal gear pin (internal gear) 7a...Center through-hole on the circuit board (center through-hole) 7b... Circuit board crank insertion hole (crank insertion hole) 7d…Outer end face (end face) 8a... Center through hole in end plate (center through hole) 8b...End plate crank insertion hole (crank insertion hole) 13…Crankshaft 15…First external gear (external gear) 16…Second external gear (external gear) 27a... Small diameter hole for crank (crank insertion hole) 27b...Large diameter crank hole (crank insertion hole) 28…Connecting recess (connecting hole) 30... Seal cap 31…Cap body 32...Elastic coating 33...Cylinder part 33a...end 33b…Outer peripheral surface 34...Bottom 34a…External surface 101...Movable part (opposing member) A1…First axis of rotation (axis of rotation) Ci... Inscribed circle Co...Circumcircle Cp... Pitch Circle S...Storage space

Claims

1. A cylindrical case having an internal gear, A carrier is positioned radially inside the case and is rotatably supported by the case, Multiple crankshafts are rotatably supported on a circle of the same pitch centered on the rotation axis of the carrier, and to which an external rotational force is input, An external gear housed in the carrier and rotatably supported on the crankshaft, and meshing with the internal gear, Equipped with, The aforementioned carrier, A center through hole formed on the rotation axis, Multiple crank insertion holes into which each of the aforementioned multiple crankshafts is inserted separately, A connecting hole is formed on the end face in the direction of the rotation axis of the carrier, and the center through hole and the crank insertion hole are connected, A seal cap that is attached to the connecting hole and closes the connecting hole, Equipped with, Reduction device.

2. The connecting hole is formed coaxially with the axis of rotation and in a circular shape when viewed from the direction of the axis of rotation. When a virtual circle that tangent to the inner side of the rotation axis side of the plurality of crank insertion holes is defined as an inscribed circle, The diameter of the connecting hole is larger than the diameter of the inscribed circle. The speed reduction device according to claim 1.

3. The aforementioned seal cap is A cylindrical portion that fits into the aforementioned connecting hole, The bottom portion of the cylindrical portion closes the end face side of the carrier, An elastic covering portion that covers the outer circumferential surface of the cylindrical portion and the outer surface of the bottom portion, and has elasticity, Equipped with, At least a portion of the outer surface of the bottom is exposed through the elastic covering portion. The speed reduction device according to claim 1 or claim 2.

4. The exposed portion of the outer surface of the bottom is in contact with the mating member to which the carrier is fixed. The speed reduction device according to claim 3.

5. The exposed portion of the outer surface of the bottom is in contact with the mating member to which the carrier is fixed, via a heat conductive member. The speed reduction device according to claim 3.

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