Oil seal and reduction gear

Abstract

The present application relates to an oil seal and a speed reducer. The oil seal is provided with a metal ring (34), a lip portion (33), and a cover portion (35). The metal ring (34) is provided with a metal fitting portion (36) and a metal flange portion (27). The cover portion (35) is provided with a cover fitting portion (38) covering the metal fitting portion (36) and a cover flange portion (39) covering the metal flange portion (37). In a state before the cover fitting portion (38) is fitted to the seal fitting inner peripheral surface (24), the thickness (TS1) in the radial direction of the metal fitting portion (36) is thicker than the thickness (TC) in the radial direction of the cover fitting portion.

Description

Technical Field

[0001] This invention relates to an oil seal and a speed reduction device. Background Technology

[0002] Conventionally, oil seals are known for sealing between a cylindrical first member (outer peripheral member) and a second member (inner peripheral member) inserted into the first member and rotatably disposed therein. The oil seal is disposed between the inner peripheral surface of the first member and the outer peripheral surface of the second member. The oil seal includes a metal ring, a lip disposed radially inward of the metal ring, and a rubber cover covering the metal ring. The metal ring includes a fitting portion and a flange extending radially inward from the axial end of the fitting portion.

[0003] Various techniques have been proposed to ensure the stable sealing performance of such oil seals. For example, a technique of providing an auxiliary sealing body on the radially inner side of the mating portion has been disclosed (see, for example, Patent Document 1). Thus, by using an auxiliary sealing body in addition to the oil seal for sealing, stable sealing performance can be ensured.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2023-144283 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, in the above-described embodiments, there are problems such as increased structural complexity and larger oil seal size, corresponding to the provision of auxiliary sealing bodies.

[0009] This invention provides an oil seal and a speed reduction device that can ensure stable sealing performance without being large in size.

[0010] Solution for solving the problem

[0011] An oil seal of one aspect of the present invention seals between a first member and a second member, the first member having an inner circumferential surface, the second member being inserted into the first member and having an outer circumferential surface radially opposite to the inner circumferential surface, wherein the oil seal comprises: a metal ring; a lip disposed radially inside the metal ring and supported by the metal ring, contacting the outer circumferential surface; and a rubber cover covering the metal ring, the metal ring comprising: a metal fitting portion fitting into the inner circumferential surface; and a metal flange portion extending radially inward from the axial ends of the first member and the second member of the metal fitting portion, connected to the lip, the cover comprising: a cover fitting portion covering the metal fitting portion; and a cover flange portion covering the metal flange portion, connected to the lip, wherein, before the cover fitting portion is fitted into the inner circumferential surface, the radial thickness of the metal fitting portion is greater than the radial thickness of the cover fitting portion on the side opposite to the lip across the metal fitting portion.

[0012] This configuration allows for maximizing the radial thickness of the metal fitting portion without increasing the size of the oil seal. This improves the rigidity of the metal fitting portion. Consequently, the metal fitting portion can forcefully press the covering fitting portion against the inner circumferential surface of the first member. This, in turn, enhances the pressure resistance of the oil seal with a simple structure and prevents it from detaching. Therefore, stable sealing performance is ensured.

[0013] In the above structure, the covering fitting portion is only provided on the outer peripheral surface of the metal fitting portion.

[0014] In the above configuration, the radial thickness of the metal fitting portion is 55% or more relative to the total thickness of the sum of the radial thickness of the metal fitting portion and the radial thickness of the covering fitting portion on the side opposite to the lip portion.

[0015] In the above structure, the radial thickness of the metal fitting portion is 59% or more relative to the total thickness.

[0016] Another aspect of the speed reduction device of the present invention comprises: a cylindrical housing having an internal gear; a gear carrier disposed radially inward of the housing and rotatably supported on the housing by means of a bearing; at least one crankshaft rotatably disposed on the gear carrier and subjected to an external rotational force; an oscillating gear rotatably disposed on the gear carrier and oscillatingly rotated by the crankshaft, meshing with the internal gear; and an oil seal sealing the space between the housing and the gear carrier, wherein the bearing is disposed axially outward of the internal gear, and the oil seal is disposed on the side of the bearing opposite to the internal gear, the oil seal comprising: a metal ring; and a lip disposed radially inward of the metal ring. And supported by the metal ring, in contact with the outer peripheral surface of the gear carrier; and a rubber cover covering the metal ring, the metal ring having: a metal fitting portion fitting into the inner peripheral surface of the housing; and a metal flange portion extending radially inward from the axial end of the metal fitting portion and connecting to the lip, the cover having: a cover fitting portion covering the metal fitting portion; and a cover flange portion covering the metal flange portion and connecting to the lip, wherein, before the cover fitting portion is fitted into the inner peripheral surface, the radial thickness of the metal fitting portion is greater than the radial thickness of the cover fitting portion on the side opposite to the lip across the metal fitting portion.

[0017] This configuration allows for maximizing the radial thickness of the metal fitting without increasing the size of the oil seal. This improves the rigidity of the metal fitting. Consequently, the metal fitting forcefully crushes the covering fitting against the inner circumferential surface of the housing. This, in turn, enhances the pressure resistance of the oil seal with a simple structure and prevents it from detaching. Therefore, it ensures stable sealing of the speed reduction device.

[0018] The effects of the invention

[0019] The aforementioned oil seal and speed reduction device have a simple structure and do not require large size to ensure stable sealing. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view of the deceleration device according to an embodiment of the present invention.

[0021] Figure 2 This is a partially enlarged axial cross-sectional view of the oil seal according to an embodiment of the present invention.

[0022] Figure 3 This is a graph showing the change in the shedding strength of the oil seal according to an embodiment of the present invention.

[0023] Explanation of reference numerals in the attached figures

[0024] 1. Reduction gear; 2. Housing (first component); 3. Gear carrier (second component); 5. Internal gear pin (internal gear); 6a. First main bearing (bearing); 6b. Second main bearing (bearing); 7. Base plate (second component); 13. Crankshaft; 15. First oscillating gear (oscillating gear); 16. Second oscillating gear (oscillating gear); 24. Sealing fitting inner circumferential surface (inner circumferential surface); 25. Sealing fitting outer circumferential surface (outer circumferential surface); 30. Oil seal; 33. Lip; 34. Metal ring; 35. Cover; 36. Metal fitting part; 37. Metal flange part; 38. Cover fitting part; 39. Cover flange part; Ta: Total thickness; TC: Radial thickness of the cover fitting part; TS1: Radial thickness of the metal fitting part. Detailed Implementation

[0025] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0026] <Speeding device>

[0027] Figure 1 This is a cross-sectional view of the speed reduction device 1.

[0028] like Figure 1 As shown, the reduction gear 1, for example, reduces the rotation of an input shaft 101 connected to an electric motor (not shown) and outputs the reduction speed. The reduction gear 1 is a so-called eccentric oscillating type reduction gear. The reduction gear 1 includes a cylindrical housing 2, a gear carrier 3, and a reduction mechanism 4. The gear carrier 3 is rotatably disposed radially inside the housing 2. The reduction mechanism 4 is connected to the gear carrier 3. The central axis of the housing 2 coincides with the rotation axis of the gear carrier 3.

[0029] In the following description, these central axes and axes of rotation are collectively referred to as the first axis of rotation A1. The direction parallel to the first axis of rotation A1 is called the axial direction. The direction of rotation of the gear carrier 3 is called the circumferential direction. The radial direction of the housing 2, which is orthogonal to both the axial and circumferential directions, is simply referred to as the radial direction.

[0030] <Shell>

[0031] An outer flange 2a extending radially outward is integrally formed on the outer peripheral surface of the housing 2. Multiple bolt holes 2b are formed in the outer flange 2a. The multiple bolt holes 2b are arranged at equal intervals in the circumferential direction. Bolts (not shown) are inserted into the multiple bolt holes 2b, for example, to fasten the bolts to the arm of an industrial robot to fix the reduction gear 1.

[0032] Multiple pin grooves 2c are formed along the axial direction on the inner circumferential surface of the housing 2. The multiple pin grooves 2c are arranged at equal intervals in the circumferential direction. Internal toothed pins 5 are respectively embedded in the multiple pin grooves 2c. The internal toothed pins 5 function as internal teeth that mesh with the swing gears 15 and 16 of the reduction mechanism 4, which will be described later.

[0033] On the inner circumferential surface of the housing 2, bearing mating inner circumferential surfaces 23a and 23b (first bearing mating inner circumferential surface 23a and second bearing mating inner circumferential surface 23b) are formed on both axial sides of each of the plurality of pin grooves 2c (internal tooth pins 5). The bearing mating inner circumferential surfaces 23a and 23b are respectively positioned slightly radially outward from the plurality of pin grooves 2c. A first main bearing 6a is mated on the first bearing mating inner circumferential surface 23a of the two bearing mating inner circumferential surfaces 23a and 23b. A second main bearing 6b is mated on the second bearing mating inner circumferential surface 23b of the two bearing mating inner circumferential surfaces 23a and 23b. The first main bearing 6a and the second main bearing 6b are, for example, angular contact ball bearings. The gear carrier 3 is rotatably supported on the housing 2 by means of the first main bearing 6a and the second main bearing 6b.

[0034] On the inner circumferential surface of the housing 2, a sealing fitting inner circumferential surface 24 is formed on the side opposite to the position of the plurality of pin grooves 2c, separated from the first bearing fitting inner circumferential surface 23a. The sealing fitting inner circumferential surface 24 is formed to be located radially outward relative to the first bearing fitting inner circumferential surface 23a, separated by a step portion 24a. An oil seal 30 is fitted into the sealing fitting inner circumferential surface 24. The oil seal 30 seals the space between the housing 2 and the gear carrier 3. Details of the oil seal 30 will be described later.

[0035] <Gear Carrier>

[0036] The gear carrier 3 includes a base plate portion 7, an end plate portion 8, and three pillar portions 9. The base plate portion 7 and the end plate portion 8 are arranged opposite each other in the axial direction. The base plate portion 7 and the end plate portion 8 are each formed in the shape of a circular plate. Each of the three pillar portions 9 is formed to protrude from the base plate portion 7 toward the end plate portion 8. In the following description, "each of the three pillar portions" will sometimes be simply referred to as "each pillar portion" or "pillar portion".

[0037] The three pillars 9 are arranged at equal intervals in the circumferential direction. Each of the three pillars 9 has a top end 9a. An end plate 8 is disposed on the top end 9a of each of the three pillars 9. The end plate 8 is fixed to each of the three pillars 9 by bolts 10. In this state, a space with a certain width in the axial direction is formed between the base plate 7 and the end plate 8.

[0038] A pin 11 is provided radially inward from each of the bolts 10 fixed to the three pillars 9. The pin 11 positions the end plate portion 8 relative to the base plate portion 7. The pin 11 engages with a pin hole 12 provided in the end plate portion 8.

[0039] The outer peripheral surface of the base plate 7 is rotatably supported on the housing 2 by means of the first main bearing 6a. A sealing outer peripheral surface 25 is formed on the outer peripheral surface of the base plate 7 at a position opposite to the sealing inner peripheral surface 24 in the radial direction. An oil seal 30 is fitted between the sealing outer peripheral surface 25 and the sealing inner peripheral surface 24. As a result, the space between the housing 2 and the gear carrier 3 is sealed.

[0040] The outer peripheral surface of the end plate 8 is rotatably supported on the housing 2 by means of the second main bearing 6b.

[0041] A shaft insertion hole 7a is formed at the radial center of the base plate portion 7. A shaft insertion hole 8a is formed at the radial center of the end plate portion 8. The two shaft insertion holes 7a and 8a are arranged coaxially. Three crankshaft insertion holes 7b are formed in the base plate portion 7. Each of the three crankshaft insertion holes 7b is located between two adjacent pillar portions 9 in the circumferential direction. Three crankshaft insertion holes 8b are formed in the end plate portion 8. Each of the three crankshaft insertion holes 7b is located between two adjacent pillar portions 9 in the circumferential direction. Each of the three crankshaft insertion holes 7b and each of the three crankshaft insertion holes 8b are arranged coaxially. That is, the central axis A2 of the crankshaft insertion holes 7b and 8b that are opposite each other in the axial direction is parallel to the first rotation axis A1. A crankshaft bearing 18 is provided in each of the crankshaft insertion holes 7b and 8b. The crankshaft bearing 18 is, for example, a tapered roller bearing. In the following description, "each of the three crankshaft insertion holes" is sometimes simply referred to as "each crankshaft insertion hole" or "crankshaft insertion hole".

[0042] <Speed ​​reduction mechanism>

[0043] The reduction mechanism 4 causes the gear carrier 3 to rotate at a speed reduced relative to the input shaft 101 by a certain ratio. The reduction mechanism 4 includes three crankshafts 13, a transmission spur gear 14, and two oscillating gears 15 and 16. Each of the three crankshafts 13 is inserted into crankshaft insertion holes 7b and 8b arranged coaxially. The transmission spur gear 14 is provided at the axial end of each of the three crankshafts 13. Each of the two oscillating gears 15 and 16 is provided between the base plate portion 7 and the end plate portion 8. Each of the two oscillating gears 15 and 16 oscillates and rotates as the crankshafts 13 rotate. In the following description, "each of the three crankshafts" is sometimes simply referred to as "each crankshaft" or "crankshaft".

[0044] External teeth 17 are formed on the outer periphery of the transmission spur gear 14. External teeth 17 mesh with external teeth 102 formed on the input shaft 101. Through the meshing of external teeth 17 and 102, the rotation of the input shaft 101 is transmitted to the transmission spur gear 14, and the transmission spur gear 14 rotates.

[0045] The crankshaft 13 is rotatably supported on the gear carrier 3 (base plate portion 7 and end plate portion 8) by means of crankshaft bearings 18. The crankshaft 13 has a shaft body 13c, a first eccentric portion 13a, and a second eccentric portion 13b. The shaft body 13c rotates about the central axis A2. The first eccentric portion 13a and the second eccentric portion 13b are formed at the axial center of the shaft body 13c. The axial sides of the shaft body 13c are rotatably supported on the gear carrier 3 (base plate portion 7 and end plate portion 8) by means of crankshaft bearings 18.

[0046] The crankshaft 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 as a whole around the central axis A2. Hereinafter, the central axis A2 will be referred to as the second axis of rotation A2 of the crankshaft 13.

[0047] The first eccentric portion 13a and the second eccentric portion 13b are eccentric relative to the second rotation axis A2. The first eccentric portion 13a and the second eccentric portion 13b are arranged axially adjacent between the two crankshaft bearings 18. In other words, the first eccentric portion 13a and the second eccentric portion 13b are arranged axially adjacent between the base plate portion 7 and the end plate portion 8. The first eccentric portion 13a and the second eccentric portion 13b are arranged with a 180° phase angle offset.

[0048] The inner circumferential surfaces of roller bearings 19 are fitted into the first eccentric portion 13a and the second eccentric portion 13b, respectively. The roller bearings 19 are, for example, cylindrical roller bearings. The first oscillating gear 15 and the second oscillating gear 16 are rotatably supported on the respective crankshafts 13 by means of the roller bearings 19.

[0049] The first oscillating gear 15 and the second oscillating gear 16 are disposed in the space between the base plate portion 7 and the end plate portion 8. Through holes 15a and 16a are respectively formed in the first oscillating gear 15 and the second oscillating gear 16 for fitting into the outer peripheral surface of the roller bearing 19. Thus, when the first eccentric portion 13a and the second eccentric portion 13b are oscillating and rotating due to the rotation of the crankshaft 13, the first oscillating gear 15 and the second oscillating gear 16 oscillate and rotate with the aid of the roller bearing 19.

[0050] An opening 15b is formed in the first oscillating gear 15 to avoid interference with the column portion 9. Similarly, an opening 16b is formed in the second oscillating gear 16 to avoid interference with the column portion 9. A shaft insertion hole 15c is formed at the radial center of the first oscillating gear 15. A shaft insertion hole 16c is formed at the radial center of the second oscillating gear 16. External teeth 15d are formed on the outer periphery of the first oscillating gear 15. External teeth 16d are formed on the outer periphery of the second oscillating gear 16. The number of teeth of each of the external teeth 15d and 16d is a predetermined number less than the number of internal toothed pins 5 in the housing 2.

[0051] <Oil seal>

[0052] Next, based on Figure 2 The oil seal 30 is described in detail.

[0053] Figure 2 This is a partially enlarged sectional view of oil seal 30 along the axial direction. Figure 2 and Figure 1 The enlarged image corresponds to Part II.

[0054] like Figure 1 , Figure 2As shown, the oil seal 30 has a fitting portion 31, a flange portion 32, and a lip portion 33. The oil seal 30 is obtained by integrally forming the fitting portion 31, the flange portion 32, and the lip portion 33.

[0055] The fitting portion 31 fits into the sealing fitting inner peripheral surface 24. The fitting portion 31 is formed in a cylindrical shape. The flange portion 32 extends radially inward from the end of the fitting portion 31 opposite to the first main bearing 6a. The lip portion 33 is supported by the inner peripheral end 32a of the flange portion 32 opposite to the fitting portion 31. The lip portion 33 contacts the sealing fitting outer peripheral surface 25.

[0056] The fitting portion 31 and the flange portion 32 are provided with a metal ring 34 and a rubber cover portion 35 covering the metal ring 34.

[0057] The metal ring 34 is formed, for example, by bending a cold-rolled steel sheet (SPCC) through stamping. The metal ring 34 is formed in an L-shape in a cross-section along the axial direction. That is, the metal ring 34 has a metal fitting portion 36 and a metal flange portion 37. The metal ring 34 is obtained by integrally forming the metal fitting portion 36 and the metal flange portion 37. The metal fitting portion 36 constitutes the fitting portion 31 and is formed in a cylindrical shape. The metal flange portion 37 extends radially inward from the end of the metal fitting portion 36 on the side opposite to the first main bearing 6a.

[0058] The radial thickness TS1 of the metal fitting portion 36 is the same as the axial thickness TS2 of the metal flange portion 37. However, the present invention is not limited to the relationship between the thickness TS1 of the metal fitting portion 36 and the thickness of the metal flange portion 37 described in this embodiment. The thicknesses TS1 and TS2 may also be different from each other.

[0059] The cover portion 35 is formed, for example, of fluororubber (FKM). The cover portion 35 has a cover fitting portion 38 and a cover flange portion 39. The cover portion 35 is obtained by integrally molding the cover fitting portion 38 and the cover flange portion 39. The cover fitting portion 38 covers the outer peripheral surface 36a of the metal fitting portion 36. The cover flange portion 39 covers the outer surface 37a of the metal flange portion 37 on the side opposite to the first main bearing 6a.

[0060] Before the oil seal 30 (metal fitting portion 36) is fitted into the inner peripheral surface 24 of the sealing fitting, the radial thickness TC of the covering fitting portion 38 is thinner than the radial thickness TS1 of the metal fitting portion 36. Details regarding this thickness TS1 will be described later.

[0061] In the following description, the radial thicknesses TS1 and TC will be simply referred to as thicknesses TS1 and TC, respectively. Furthermore, when describing the magnitudes of thicknesses TS1 and TC, thicknesses TS1 and TC refer to the state before the oil seal 30 (metal fitting portion 36) is fitted onto the inner circumferential surface 24 of the sealing fitting. Here, "the state before the oil seal 30 (metal fitting portion 36) is fitted onto the inner circumferential surface 24 of the sealing fitting" in other words means "the state before the cover fitting portion 38 is fitted onto the inner circumferential surface 24 of the sealing fitting."

[0062] The lip 33 includes a main lip 41, a spring 43, and an auxiliary lip 42. The main lip 41 extends from the inner peripheral end 32a of the flange 32 toward the first main bearing 6a. The main lip 41 has a root 41a located near the flange 32. The spring 43 is mounted on the main lip 41. The spring 43 is formed in a ring shape. The auxiliary lip 42 protrudes from the root 41a. The main lip 41 and the auxiliary lip 42 are formed, for example, of fluororubber. The main lip 41 and the auxiliary lip 42 are integrally formed with the cover 35.

[0063] The main lip 41 is formed in a cylindrical shape resembling a frustum of a cone, gradually moving radially inward from the inner peripheral end 32a of the flange portion 32 toward the first main bearing 6a. The main lip 41 has a top portion 41b located on the side opposite to the root portion 41a. An annular ridge portion 44 protruding radially inward is integrally formed on the top portion 41b. The ridge portion 44 is formed to taper at the top towards the radial inward. The top of the ridge portion 44 contacts the sealing fitting outer peripheral surface 25.

[0064] The main lip 41 has an outer peripheral surface 41c located near the fitting portion 31. A spring 43 is mounted on the outer peripheral surface 41c. The spring 43 is positioned radially opposite the protrusion portion 44. The spring 43 elastically applies force to the main lip 41 toward the sealing fitting outer peripheral surface 25.

[0065] The auxiliary lip 42 protrudes from the root 41a of the main lip 41 toward the side opposite to the first main bearing 6a. The auxiliary lip 42 is formed in a cylindrical shape approximating a frustum of a cone, gradually moving radially inward toward the side opposite to the first main bearing 6a. The tip of the auxiliary lip 42 on the side opposite to the main lip 41 is in elastic contact with the sealing outer peripheral surface 25.

[0066] <The Operation of the Speed ​​Reduction Device and the Function of the Oil Seal>

[0067] Next, the operation of the speed reduction device 1 and the function of the oil seal 30 will be explained.

[0068] For example, when the input shaft 101 connected to the electric motor is rotated by driving the motor (not shown), each crankshaft 13 is rotated via the transmission spur gear 14. Thus, the first oscillating gear 15 and the second oscillating gear 16 oscillate and rotate. As the first oscillating gear 15 and the second oscillating gear 16 oscillate and rotate, a portion of the external teeth 15d and 16d of the oscillating gears 15 and 16 meshes with the internal toothed pin 5 of the housing 2.

[0069] The number of teeth on each of the external teeth 15d and 16d is less than the number of internal tooth pins 5 by a predetermined number (e.g., one). Therefore, the oscillating gears 15 and 16 rotate in such a way that the meshing portions of each of the external teeth 15d and 16d relative to the internal tooth pins 5 (housing 2) are staggered in the circumferential direction. This rotation reduces the speed of rotation relative to the crankshaft 13.

[0070] As the oscillating gears 15 and 16 rotate, each crankshaft 13 also rotates on its own axis about the second rotation axis A2 and revolves around the first rotation axis A1. Each crankshaft 13 is rotatably supported on the gear carrier 3 (base plate 7 and end plate 8). Therefore, the gear carrier 3 rotates with the revolution of each crankshaft 13. As a result, the reduction gear 1 reduces the rotation of the input shaft 101 and outputs it from the gear carrier 3. Assuming that the gear carrier 3 is fixed to the arm of an industrial robot, the reduction gear 1 can reduce the rotation of the input shaft 101 and output it from the housing 2.

[0071] However, lubricant is sealed inside the gear carrier 3 to improve the lubrication of bearings 6a, 6b, 18, and 19 or to reduce the meshing resistance between the internal gear pin 5 and the oscillating gears 15 and 16. An oil seal 30 is used to prevent this lubricant from leaking out.

[0072] The fitting portion 31 of the oil seal 30 is fitted into the sealing fitting inner peripheral surface 24 of the housing 2. At this time, the metal fitting portion 36 is used to crush the covering fitting portion 38 by the desired amount. As a result, the tightness between the sealing fitting inner peripheral surface 24 and the fitting portion 31 is improved, and the sealing fitting inner peripheral surface 24 and the fitting portion 31 are reliably sealed.

[0073] On the other hand, the main lip 41 and the auxiliary lip 42 of the lip 33 are elastically pressed against the sealing and fitting outer peripheral surface 25 of the gear carrier 3. Therefore, even if the gear carrier 3 rotates relative to the housing 2, the lip 33 is always in contact with the sealing and fitting outer peripheral surface 25.

[0074] As a result, the housing 2 and the gear carrier 3 are sealed by an oil seal 30, preventing lubricant from leaking out between the housing 2 and the gear carrier 3.

[0075] Here, when the pressure inside the gear carrier 3 rises, the pressure exerts a force on the oil seal 30 in the direction of detachment from the housing 2. However, the thickness TC of the cover fitting portion 38 is thinner than the thickness TS1 of the metal fitting portion 36. In other words, the thickness TS1 of the metal fitting portion 36 is thicker than the thickness TC of the cover fitting portion 38. Furthermore, in other words, the thickness TS1 of the metal fitting portion 36 is thicker than the thickness TC of the cover fitting portion 38 on the side opposite to the lip 33 across the metal fitting portion 36. Therefore, the rigidity of the metal fitting portion 36 is increased, and the cover fitting portion 38 is strongly crushed by the metal fitting portion 36. As a result, the oil seal 30 is prevented from detaching from the housing 2. The thickness TS1 of the metal fitting portion 36 will be further described in detail below.

[0076] Figure 3 This is a graph showing the change in the detachment strength of oil seal 30. In Figure 3 In the figure, the vertical axis represents the detachment strength of the oil seal 30 from the housing 2, and the horizontal axis represents the ratio of the thickness TS1 of the metal fitting part 36 to the total thickness Ta of the fitting part 31 (metal fitting part thickness ratio).

[0077] The total thickness Ta of the fitting portion 31 is the sum of the thickness TS1 of the metal fitting portion 36 and the thickness TC of the covering fitting portion 38. In other words, the total thickness Ta of the fitting portion 31 refers to the sum of the thickness TS1 of the metal fitting portion 36 and the radial thickness TC of the covering fitting portion 38 on the side opposite to the lip 33 of the metal fitting portion 36. In the following description, the ratio of the thickness TS1 of the metal fitting portion 36 to the total thickness Ta of the fitting portion 31 will be simply referred to as the ratio of the thickness TS1 of the metal fitting portion 36. Furthermore, in Figure 3 In the diagram, line L represents the desired intensity, for example, 0.3 MPa.

[0078] like Figure 3 As shown, it can be confirmed that when the thickness TS1 of the metal fitting portion 36 is thicker than the thickness TC of the covering fitting portion 38 (the proportion of thickness TS1 is greater than 50%), the detachment strength of the oil seal 30 is increased compared with the case where the thickness TS1 of the metal fitting portion 36 is less than or equal to the thickness TC of the covering fitting portion 38.

[0079] Furthermore, when the thickness TS1 of the metal fitting portion 36 is 55% or more, it can be confirmed that the detachment strength of the oil seal 30 almost meets the desired strength. Preferably, the thickness TS1 of the metal fitting portion 36 is 59% or more. In this case, it can be confirmed that the detachment strength of the oil seal 30 sufficiently meets the desired strength.

[0080] Thus, in the oil seal 30 described above, the thickness TS1 of the metal fitting portion 36 is thicker than the thickness TC of the covering fitting portion 38. Therefore, the oil seal 30 can have a simple structure, and the thickness TS1 of the metal fitting portion 36 can be increased as much as possible without increasing the size of the oil seal 30. This improves the rigidity of the metal fitting portion 36. Consequently, the metal fitting portion 36 can forcefully crush the covering fitting portion 38 against the sealing fitting inner peripheral surface 24 of the housing 2. This improves the pressure resistance of the oil seal 30 and prevents the oil seal 30 from detaching from the housing 2. Therefore, stable sealing performance can be ensured.

[0081] The covering fitting portion 38 is only provided on the outer peripheral surface 36a of the metal fitting portion 36. Therefore, the total thickness Ta of the fitting portion 31 can be made as thin as possible, and the crushing amount of the covering fitting portion 38 can be sufficiently ensured. Therefore, the pressure resistance of the oil seal 30 can be further improved, and stable sealing performance can be further ensured.

[0082] If the thickness TS1 of the metal fitting portion 36 is 55% or more, the detachment strength of the oil seal 30 can almost meet the desired strength. Therefore, the pressure resistance of the oil seal 30 can be reliably improved.

[0083] Furthermore, the thickness TS1 of the metal fitting portion 36 can be 59% or more. In this case, the detachment strength of the oil seal 30 can fully meet the desired strength. Therefore, the pressure resistance of the oil seal 30 can be further improved.

[0084] As described above, the oil seal 30 is applicable to the so-called eccentric oscillating type speed reducer, i.e., speed reducer 1.

[0085] This invention is not limited to the embodiments described above, but includes embodiments that make various modifications to the above embodiments without departing from the spirit of this invention.

[0086] For example, in the above embodiment, the oil seal 30 for the speed reduction device 1 was described using the above structure. However, the present invention is not limited to such a structure. Oil seals for various devices can adopt the above structure. An oil seal is any member that seals between a first member having an inner circumferential surface and a second member inserted into the first member and having an outer circumferential surface that is radially opposite to the inner circumferential surface.

[0087] In the above embodiment, the case where an internal toothed pin 5 is provided on the inner circumferential surface of the housing 2 has been described. The internal toothed pin 5 is explained as functioning as an internal tooth meshing with the external teeth 15d and 16d of the oscillating gears 15 and 16. However, the present invention is not limited to this structure. An arcuate tooth profile that meshes with the external teeth 15d and 16d in place of the internal toothed pin 5 can be formed on the inner circumferential surface of the housing 2.

[0088] In the above embodiment, the case where the reduction device 1, as an eccentric oscillating type reduction device, has three crankshafts 13 and two oscillating gears 15 and 16 has been described. The case where the two oscillating gears 15 and 16 are oscillating and rotating using the three crankshafts 13 has been described. However, this is not a limitation; at least one crankshaft 13 is sufficient. At least one oscillating gear 15 and 16 is also sufficient.

[0089] In the above embodiments, the case where the cover portion 35 and the lip portion 33 (main lip 41, auxiliary lip 42) of the oil seal 30 are formed of, for example, fluororubber has been described. However, the present invention is not limited to such a structure. Various rubbers can be used. For example, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), etc., can be used instead of fluororubber. In order to increase the crushing amount of the cover fitting portion 38 and suppress detachment from the housing 2 and gear carrier 3, a rubber with high tensile strength is preferred. Therefore, fluororubber, nitrile rubber, and hydrogenated nitrile rubber are preferred as the rubber used for the oil seal 30.

[0090] In the above embodiment, the case where the covering fitting portion 38 of the oil seal 30 only covers the outer peripheral surface 36a of the metal fitting portion 36 has been described. However, the present invention is not limited to such a structure. The covering fitting portion 38 may also cover the entire circumference of the metal fitting portion 36. In this case, the total thickness Ta of the fitting portion 31 is the thickness TS1 of the metal fitting portion 36 plus the radial thickness of the portion of the covering fitting portion 38 that is on the side opposite to the lip 33 of the metal fitting portion 36.

[0091] In the embodiments disclosed in this specification, a component composed of multiple objects can be integrated into one object; conversely, a component composed of a single object can be divided into multiple objects. Whether integrated or not, it is acceptable as long as the configuration achieves the purpose of the invention.

Claims

1. An oil seal for sealing between a first member and a second member, the first member having an inner circumferential surface, the second member being inserted into the first member and having an outer circumferential surface radially opposite to the inner circumferential surface, wherein... This oil seal has the following features: Metal ring; A lip, which is disposed radially inside the metal ring and supported by the metal ring, and contacts the outer peripheral surface; and A rubber cover that covers the metal ring. The metal ring comprises: A metal fitting portion that fits into the inner peripheral surface; and A metal flange portion, extending radially inward from the axial ends of the first and second members of the metal fitting portion, connects with the lip portion. The covering portion includes: Covering the fitting portion, which covers the metal fitting portion; and A cover flange portion, which covers the metal flange portion and connects to the lip portion. Before the cover fitting is fitted onto the inner circumferential surface, the radial thickness of the metal fitting is greater than the radial thickness of the cover fitting on the side opposite to the lip, separated by the metal fitting.

2. The oil seal according to claim 1, wherein, The covering fitting portion is only provided on the outer peripheral surface of the metal fitting portion.

3. The oil seal according to claim 1 or 2, wherein, The radial thickness of the metal fitting portion is 55% or more relative to the total thickness of the sum of the radial thickness of the metal fitting portion and the radial thickness of the covering fitting portion on the side opposite to the lip portion.

4. The oil seal according to claim 3, wherein, The radial thickness of the metal fitting portion is 59% or more relative to the total thickness.

5. A speed reduction device, wherein, The speed reduction device has the following features: A cylindrical shell with internal gears; A gear carrier, which is disposed radially inside the housing and is rotatably supported on the housing by means of bearings; At least one crankshaft is rotatably mounted on the gear carrier and is subjected to an external rotational force; A oscillating gear, rotatably mounted on the gear carrier, and oscillating and rotating by the crankshaft, meshes with the internal gear; and An oil seal is used to seal the space between the housing and the gear carrier. The bearing is located on the axial outer side of the internal gear. The oil seal is located on the side of the bearing opposite to the internal gear. The oil seal has the following features: Metal ring; A lip, which is located radially inside the metal ring and supported by the metal ring, contacts the outer peripheral surface of the gear carrier; and A rubber cover that covers the metal ring. The metal ring comprises: A metal fitting portion that fits into the inner circumferential surface of the housing; and A metal flange portion, which extends radially inward from the axial end of the metal fitting portion, connects with the lip portion. The covering portion includes: Covering the fitting portion, which covers the metal fitting portion; and A cover flange portion, which covers the metal flange portion and connects to the lip portion. Before the cover fitting is fitted onto the inner circumferential surface, the radial thickness of the metal fitting is greater than the radial thickness of the cover fitting on the side opposite to the lip, separated by the metal fitting.

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