Gear device and actuator

Abstract

To prevent damage when mounting a seal cap, and to secure sealing performance of the seal cap while suppressing coming-off.SOLUTION: A carrier 4 configured to be attachable to one of a first member and a second member, an oscillation gear 14 having an insertion hole into which an eccentric part of a crankshaft 10 provided on the carrier 4 is inserted and having a tooth part, and an outer cylinder 2 configured to be attachable to the other of the first member and the second member and having internal teeth that mesh with the tooth part of the oscillation gear 14, A seal cap 25 formed in a bottomed cylindrical shape is attached to the crank hole 40. The seal cap 25 includes a disk-shaped bottom plate portion 25b and a resin-made annular cylindrical portion 25b arranged to project from an outer circumferential portion of the bottom plate portion 25c. The 25c of the cylindrical portion is in close contact with the 40a of the first inner peripheral surface of the crank hole 40. A hole diameter of a second inner peripheral surface 40b of the crank hole 40 is larger than that of a first inner peripheral surface 40a with which the seal cap 25 comes into contact in the crank hole 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gear device and an actuator. [Background technology]

[0002] In a conventional gear device, which converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit driving force, a gear device is known which includes a carrier configured to be attachable to one of the first member and the second member, a crankshaft attached to a crank hole provided in the carrier, an oscillating gear having a through hole into which an eccentric portion of the crankshaft is inserted and having teeth, and an outer cylinder configured to be attachable to the other of the first member and the second member and having internal teeth that mesh with the teeth of the oscillating gear, and in which a seal cap formed in a cylindrical shape with a bottom is attached to the opening side of the crank hole (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-102221 Summary of the Invention [Problem to be solved by the invention]

[0004] In gear devices such as those described in Patent Document 1, the seal cap is fixed only by the fitting force of the interference with the crank hole. As a result, with the improvement in usage conditions in recent years, the internal pressure of the reducer increases, and the seal cap cannot withstand the fit with the crank hole, causing it to come loose. To address this issue, there is also a structure in which a retaining ring is provided in the crank hole to physically prevent the seal cap from slipping out. In this case, a retaining ring groove for attaching the retaining ring is formed on the inner peripheral surface of the crank hole. Therefore, when the seal cap is inserted from the opening side of the crank hole and attached to the back side of the retaining ring groove, the seal cap comes into contact with and gets caught as it passes through the open end of the retaining ring groove, causing tears in the surface of the seal cap and making it impossible to ensure sealing, which leaves room for improvement in this regard.

[0005] The present invention provides a gear device and an actuator that can prevent damage to a seal cap when it is attached and can ensure the sealing performance of the seal cap while suppressing slip-out. [Means for solving the problem]

[0006] A gear device according to one embodiment of the present invention is a gear device that converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit a driving force, and includes: a carrier configured to be attachable to one of the first member and the second member; a crankshaft attached to a crank hole provided in the carrier; an oscillating gear having a through hole into which an eccentric portion of the crankshaft is inserted and having a toothed portion; and an outer cylinder configured to be attachable to the other of the first member and the second member and having internal teeth that mesh with the toothed portion of the oscillating gear, wherein a seal cap formed in a cylindrical shape with a bottom is attached to the crank hole, the seal cap having a disk-shaped bottom plate portion and an annular cylindrical portion made of resin protruding from the outer periphery of the bottom plate portion, the cylindrical portion being in close contact with the inner circumferential surface of the crank hole, and the hole diameter of the crank hole being larger than the contact portion of the crank hole with which the seal cap comes into contact.

[0007] With this configuration, the diameter of the crank hole is larger than the contact portion of the crank hole with which the seal cap comes into contact, so when the seal cap is inserted from the opening side of the crank hole, the seal cap does not come into contact with the inner peripheral surface of the crank hole. This prevents damage such as tearing of the seal cap and prevents the seal cap from coming out. This ensures the sealing performance of the seal cap and prevents oil leakage from inside the carrier.

[0008] The crank hole is provided with a retaining ring groove for attaching a retaining ring that prevents the seal cap from slipping out, and the crank hole has a first inner circumferential surface that includes the contacted portion and a second inner circumferential surface on the opposite side of the retaining ring groove from the first inner circumferential surface, and it is desirable that the hole diameter of the second inner circumferential surface be larger than the hole diameter of the first inner circumferential surface.

[0009] It is desirable that a groove depth dimension D from the groove bottom of the retaining ring groove to the second inner circumferential surface in the radial direction of the crank hole satisfies the formula D≧{(d2−d1) / 2}×0.5, where d1 is the hole diameter of the first inner circumferential surface and d2 is the groove bottom diameter of the retaining ring groove.

[0010] It is desirable that the chamfer angle of the retaining ring groove be 45° or less with respect to the axial direction of the crank hole.

[0011] It is desirable that at least a portion of the second inner circumferential surface is flat along the axial direction of the crank hole.

[0012] A gear device according to another aspect of the present invention is a gear device that converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit a driving force, and includes: a carrier configured to be attachable to one of the first member and the second member; a crankshaft attached to a crank hole provided in the carrier; an oscillating gear having a toothed portion and having a through hole into which an eccentric portion of the crankshaft is inserted; and an outer cylinder configured to be attachable to the other of the first member and the second member and having internal teeth that mesh with the toothed portion of the oscillating gear; a seal cap formed in a cylindrical shape with a bottom is attached to the crank hole, the seal cap having a disk-shaped bottom plate portion and an annular cylindrical portion made of resin protruding from an outer periphery of the bottom plate portion, the cylindrical portion being in close contact with an inner circumferential surface of the crank hole, and the hole diameter of the crank hole is a retaining ring groove for attaching a retaining ring that prevents the seal cap from slipping out; the crank hole has a first inner circumferential surface that includes the contacted portion and a second inner circumferential surface that is on the opposite side of the retaining ring groove from the first inner circumferential surface, the diameter of the second inner circumferential surface being larger than the diameter of the first inner circumferential surface; a groove depth D from a groove bottom of the retaining ring groove to the second inner circumferential surface in the radial direction of the crank hole satisfies the formula D≧{(d2−d1) / 2}×0.5, where d1 is the diameter of the first inner circumferential surface and d2 is the groove bottom diameter of the retaining ring groove; a chamfer angle of the retaining ring groove is 45° or less with respect to the axial direction of the crank hole; and at least a portion of the second inner circumferential surface is flat along the axial direction of the crank hole.

[0013] With this configuration, the diameter of the crank hole is larger than the contact portion of the crank hole with which the seal cap comes into contact, so when the seal cap is inserted from the opening side of the crank hole, the seal cap does not come into contact with the inner peripheral surface of the crank hole. This prevents damage such as tearing of the seal cap and prevents the seal cap from coming out. This ensures the sealing performance of the seal cap and prevents oil leakage from inside the carrier. Furthermore, since the hole diameter of the second inner peripheral surface on the opening side of the retaining ring groove is larger than the hole diameter of the first inner peripheral surface on the seal cap side, there is no contact when the seal cap passes through the open end of the retaining ring groove, preventing the seal cap from being torn off. Furthermore, because the force that causes the seal cap to come out is less than half the force caused by the bearing pressure or thrust load, by setting the groove depth dimension D to satisfy the above formula, it is possible to prevent the force in the direction of the seal cap coming out from being unable to be suppressed by the retaining ring. Furthermore, since the chamfer angle of the retaining ring groove is 45° or less with respect to the axial direction of the crank hole, the corners at the boundary between the inner surface of the crank hole and the retaining ring groove do not become sharp and are prone to being torn off when the seal cap is inserted. Furthermore, by providing a straight portion where at least a portion of the second inner circumferential surface is flat along the axial direction of the crank hole, it is possible to further prevent the corners at the boundary between the second inner circumferential surface and the retaining ring groove, which have a significant impact on the insertion of the seal cap into the crank hole, from becoming sharp and being easily torn off when the seal cap is inserted.

[0014] An actuator according to one aspect of the present invention is an actuator including an electric motor and a gear device that converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit a driving force, wherein the gear device includes a carrier configured to be attachable to one of the first member and the second member, a crankshaft attached to a crank hole provided in the carrier, an oscillating gear having a through hole into which an eccentric portion of the crankshaft is inserted and having a toothed portion, and an outer cylinder configured to be attachable to the other of the first member and the second member and having internal teeth that mesh with the toothed portion of the oscillating gear, wherein a seal cap formed in a cylindrical shape with a bottom is attached to the crank hole, the seal cap having a disk-shaped bottom plate portion and an annular cylindrical portion made of resin protruding from the outer periphery of the bottom plate portion, the cylindrical portion being in close contact with the inner circumferential surface of the crank hole, and the hole diameter of the crank hole being larger than the contact portion of the crank hole with which the seal cap comes into contact.

[0015] With this configuration, the diameter of the crank hole is larger than the contact portion of the crank hole with which the seal cap comes into contact, so when the seal cap is inserted from the opening side of the crank hole, the seal cap does not come into contact with the inner peripheral surface of the crank hole. This prevents damage such as tearing of the seal cap and suppresses the seal cap from coming out. Therefore, an actuator can be provided that ensures the sealing performance of the seal cap and suppresses oil leakage from the carrier. [Effects of the Invention]

[0016] The above-described gear device and actuator can prevent damage to the seal cap when it is attached, and can ensure the sealing performance of the seal cap while suppressing slip-out. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing a main part of a reducer including a seal cap according to an embodiment. [Figure 2] FIG. 2 is a perspective view of the reducer of FIG. 1 as seen obliquely from the output side. [Figure 3] 3 is a partially cutaway perspective view showing a main part of the crank hole of FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view showing a state in which a seal cap is attached to a crank hole. [Figure 5] FIG. 5 is an enlarged cross-sectional view showing a main part of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, embodiments of the present invention will be described with reference to the drawings. In the embodiments and modifications described below, common parts are designated by the same reference numerals, and some overlapping descriptions will be omitted.

[0019] Fig. 1 is a cross-sectional view showing the main part of a reducer 1 equipped with a seal cap 25 according to an example embodiment of the present invention. Fig. 2 is a perspective view of the reducer 1 of Fig. 1 as seen obliquely from the output side. Fig. 3 is a partially cutaway perspective view showing the main part of the crank hole 40 of Fig. 2. Fig. 4 is a cross-sectional view showing the attachment state of the seal cap 25 in the crank hole 40. Fig. 5 is an enlarged cross-sectional view showing the main part of Fig. 4.

[0020] The reducer 1 (gear device) is connected to an electric motor (not shown) and is used as part of a so-called geared motor. The reducer 1 is attached to an actuator having an electric motor, such as an arm or hand of a robot (not shown).

[0021] The reducer 1 is configured to rotate an input shaft (not shown) to rotate a crankshaft 10, and to oscillate and rotate oscillating gears 14, 16 in conjunction with eccentric portions 10a, 10b of the crankshaft 10, thereby obtaining an output rotation that is reduced from the input rotation. This allows relative rotation to occur between, for example, a robot base (one mating member) and a rotating body (the other mating member). For example, the base is exemplified as the first member, and the rotating body is exemplified as the second member.

[0022] The reducer 1 includes an outer cylinder 2, a carrier 4, multiple (e.g., three) crankshafts 10, a first oscillating gear 14, a second oscillating gear 16, multiple (e.g., three) transmission gears 20, and a seal cap 25.

[0023] The outer cylinder 2 forms the outer surface of the reducer 1 and has a substantially cylindrical shape. A large number of pin grooves 2b are formed on the inner peripheral surface of the outer cylinder 2. Each pin groove 2b is arranged to extend in the axial direction of the outer cylinder 2 (axial direction X of a crank hole 40 described later), and has a semicircular cross-sectional shape in a cross section perpendicular to the axial direction X. These pin grooves 2b are arranged on the inner peripheral surface of the outer cylinder 2 at equal intervals in the circumferential direction.

[0024] The outer cylinder 2 has a large number of internally toothed pins 3. Each internally toothed pin 3 is attached to a pin groove 2b. Specifically, each internally toothed pin 3 is fitted into a corresponding pin groove 2b and is arranged in a position extending in the axial direction of the outer cylinder 2. As a result, the large number of internally toothed pins 3 are lined up at equal intervals along the circumferential direction of the outer cylinder 2. These internally toothed pins 3 form internal teeth 3a. The internal teeth 3a, which are made up of a plurality of internally toothed pins 3, mesh with the first external teeth 14a of the first oscillatory gear 14 and the second external teeth 16a of the second oscillatory gear 16.

[0025] The outer cylinder 2 is provided with a flange portion, and this flange portion is formed with an insertion hole 2a through which a fastener (bolt) for fixing to the base of a robot, for example, is inserted.

[0026] The carrier 4 is accommodated in the outer cylinder 2 while being disposed coaxially with the outer cylinder 2. The carrier 4 rotates relative to the outer cylinder 2 around the same axis. Specifically, the carrier 4 is disposed radially inside the outer cylinder 2, and in this state, is supported by a pair of main bearings 6 spaced apart from each other in the axial direction X so as to be rotatable relative to the outer cylinder 2.

[0027] The carrier 4 includes a base portion 5 having a base plate portion 4a and a plurality of (for example, three) shaft portions (not shown), and an end plate portion 7.

[0028] The base plate portion 4a is disposed near one end in the axial direction within the outer cylinder 2. A circular through-hole 4d is provided in the radial center of the base plate portion 4a. The through-hole 4d penetrates the base plate portion 4a in its thickness direction. A plurality of (e.g., three) mounting holes for the crankshaft 10 (hereinafter referred to as crank holes 40) are provided around the through-hole 4d at equal intervals in the circumferential direction. The crank holes 40 penetrate the base plate portion 4a in its thickness direction.

[0029] The base plate portion 4a is formed with fastening holes for fastening fasteners (bolts) (not shown) for fixing the carrier 4 to, for example, a rotating body of a robot.

[0030] The end plate portion 7 is provided axially spaced apart from the base plate portion 4a and is disposed within the outer cylinder 2 near the other axial end thereof. A through hole 7a is provided in the radial center of the end plate portion 7. The through hole 7a penetrates the end plate portion 7 in its thickness direction. Around the through hole 7a, multiple (e.g., three) crankshaft mounting holes 7b (hereinafter simply referred to as mounting holes 7b) are provided at positions corresponding to the multiple crank holes 40 in the base plate portion 4a. The mounting holes 7b penetrate the end plate portion 7 in its thickness direction. A closed space S is formed within the outer cylinder 2, surrounded by the inner surfaces of both the opposing inner surfaces of the end plate portion 7 and the base plate portion 4a and the inner circumferential surface of the outer cylinder 2. In other words, the closed space S is formed by the outer cylinder 2 and the carrier 4.

[0031] The through holes 4d, 7a and the crank holes 40, 7b are communication holes that connect the closed space S with the outside.

[0032] A seal cap 25 is attached to each of the multiple (here, three) crank holes 40 (see FIG. 2). The seal cap 25 closes the crank hole 40. The seal cap 25 has a disk-shaped bottom plate portion 25b and an annular cylindrical portion 25c protruding from the outer periphery of the bottom plate portion 25b, and is formed into a bottomed cylindrical shape. The cylindrical portion 25c is in close contact with the inner circumferential surface of the crank hole 40. This prevents the lubricating oil sealed inside the carrier 4 (inside the crank hole 40) from leaking.

[0033] The seal cap 25 is formed by an inner surface forming portion 26 that is a cylindrical, bottomed portion and is a rigid metal member that forms the inner surface, and an outer surface forming portion 27 that is made of resin and that covers the outer surface of the inner surface forming portion 26. In the seal cap 25, the rigidity (elasticity) of the inner surface forming portion 26 causes the cylindrical portion 25c to be pressed against the inner circumferential surface (first inner circumferential surface 40a) of the crank hole 40. The bottom of the inner surface forming portion 26 and the bottom of the outer surface forming portion 27 form a bottom plate portion 25b, and the cylindrical portion of the inner surface forming portion 26 and the cylindrical portion of the outer surface forming portion 27 form the cylindrical portion 25c.

[0034] The three shaft portions are integral with the base plate portion 4a and extend linearly from one main surface (inner surface) of the base plate portion 4a toward the end plate portion 7. The three shaft portions are arranged at equal intervals in the circumferential direction. Each shaft portion is fastened to the end plate portion 7 by a bolt (not shown). This integrates the base plate portion 4a, the shaft portions, and the end plate portion 7.

[0035] The three crankshafts 10 are, for example, arranged at equal intervals around the central axis of the carrier 4 inside the outer cylinder 2. Each crankshaft 10 is rotatably supported around its axis relative to the carrier 4 by a pair of crank bearings 12a, 12b. Specifically, a first crank bearing 12a is attached to one end of each crankshaft 10 in the axial direction X, and this first crank bearing 12a is attached to a crank hole 40 in the base plate 4a. Meanwhile, a second crank bearing 12b is attached to the other end of each crankshaft 10 in the axial direction X, and this second crank bearing 12b is attached to a mounting hole 7b in the end plate 7. In this way, the crankshafts 10 are rotatably supported by the base plate 4a and the end plate 7.

[0036] Each crankshaft 10 has a shaft body 10c and the above-mentioned eccentric portions 10a and 10b formed integrally with the shaft body 10c. The first eccentric portion 10a and the second eccentric portion 10b are arranged side by side in the axial direction between the portions supported by the crank bearings 12a and 12b. The first eccentric portion 10a and the second eccentric portion 10b each have a cylindrical shape and protrude radially outward from the shaft body 10c while being eccentric with respect to the axis of the shaft body 10c. The first eccentric portion 10a and the second eccentric portion 10b are each eccentric from the axis by a predetermined amount and are arranged to have a predetermined phase difference from each other.

[0037] The first oscillating gear 14 is disposed in the closed space S inside the outer cylinder 2 and is attached to the first eccentric portion 10a of each crankshaft 10 via a first roller bearing 18a. When each crankshaft 10 rotates and the first eccentric portion 10a rotates eccentrically, the first oscillating gear 14 oscillates and rotates while meshing with the internal tooth pin 3 in conjunction with this eccentric rotation.

[0038] The first oscillating gear 14 has a size slightly smaller than the inner diameter of the outer cylinder 2. The first oscillating gear 14 has the above-mentioned first external teeth 14a, a central through-hole 14b, a plurality (e.g., three) of first eccentric portion insertion holes 14c, and a plurality (e.g., three) of shaft portion insertion holes (not shown). The first external teeth 14a have a smoothly continuous wave shape over the entire circumferential direction of the oscillating gear 14.

[0039] The central through-hole 14b is provided in the radial center of the first oscillating gear 14. Three first eccentric portion insertion holes 14c are provided at equal intervals in the circumferential direction around the central through-hole 14b in the first oscillating gear 14. The first eccentric portions 10a of the crankshafts 10 are inserted into the respective first eccentric portion insertion holes 14c with first roller bearings 18a mounted therebetween.

[0040] The multiple shaft portion insertion holes are provided at equal intervals in the circumferential direction around the central through-hole 14b of the first oscillating gear 14. Each shaft portion insertion hole is disposed, for example, at a position between the first eccentric portion insertion holes 14c in the circumferential direction. A corresponding shaft portion is inserted into each shaft portion insertion hole with some play.

[0041] The second oscillating gear 16 is disposed in the closed space S within the outer cylinder 2 and is attached to the second eccentric portion 10b of each crankshaft 10 via a second roller bearing 18b. The first oscillating tooth 14 and the second oscillating gear 16 are arranged side by side in the axial direction in accordance with the arrangement of the first eccentric portion 10a and the second eccentric portion 10b. When each crankshaft 10 rotates and the second eccentric portion 10b rotates eccentrically, the second oscillating gear 16 oscillates and rotates while meshing with the internal tooth pin 3 in conjunction with this eccentric rotation.

[0042] The second oscillating gear 16 has a size slightly smaller than the inner diameter of the outer cylinder 2 and has a similar configuration to the first oscillating gear 14. That is, the second oscillating gear 16 has the above-mentioned second external teeth 16a, a central through-hole 16b, a plurality (e.g., three) of second eccentric portion insertion holes 16c, and a plurality (e.g., three) of shaft portion insertion holes (not shown). These have the same structures as the first external teeth 14a, central through-hole 14b, a plurality of first eccentric portion insertion holes 14c, and a plurality of shaft portion insertion holes of the first oscillating gear 14. The second eccentric portion 10b of the crankshaft 10 is inserted into each of the second eccentric portion insertion holes 16c with a second roller bearing 18b interposed therebetween.

[0043] A transmission gear 20 is attached to the axially outer side of the portion of each crankshaft 10 that is attached to the mounting hole 7b of the end plate 7. Each transmission gear 20 has external teeth 20a that mesh with the input gear 8a. The input gear 8a receives rotational driving force from an input shaft that functions as an input portion to which the driving force of a drive motor (not shown) is input. Each transmission gear 20 transmits the rotation of the input gear 8a to the corresponding crankshaft 10.

[0044] Each transmission gear 20 is fitted onto the end of the shaft body 10c of the corresponding crankshaft 10. Each transmission gear 20 rotates integrally with the crankshaft 10 around the same axis as the rotational axis of the crankshaft 10. When each transmission gear 20 is driven by the input gear 8a, each crankshaft 10 rotates around its axis. When each crankshaft 10 rotates, the oscillating gears 14, 16 attached to the eccentric portions 10a, 10b oscillate while meshing with the internally toothed pin 3 in accordance with the rotation of the eccentric portions 10a, 10b, causing the carrier 4 and the outer cylinder 2 to rotate relative to each other.

[0045] 1, 3, 4, and 5, the seal cap 25 is formed in a cylindrical shape with a bottom and is attached to the crank hole 40. The seal cap 25 is attached to the crank hole 40 by being inserted from the opening 40c side of the crank hole 40. As described above, the seal cap 25 has a disk-shaped bottom plate portion 25b and an annular resin cylindrical portion 25c that protrudes from the outer periphery of the bottom plate portion 25b. The outer periphery 25a of the cylindrical portion 25c is in close contact with the inner periphery of the crank hole 40 (first inner periphery 40a).

[0046] The diameter d1 of the crank hole 40 on the opening 40c side (position of the second inner circumferential surface 40b) is larger than the contacted portion (first inner circumferential surface 40a) of the crank hole 40 with which the seal cap 25 comes into contact.

[0047] The crank hole 40 is provided with a retaining ring groove 41 for attaching a retaining ring 42 that prevents the seal cap 25 from slipping out. The retaining ring 42 is omitted from FIG. 3. The crank hole 40 has a first inner circumferential surface 40a that includes a contacted portion, and a second inner circumferential surface 40b that is located on the opposite side of the retaining ring groove 41 from the first inner circumferential surface 40a in the axial direction X. That is, the hole diameter d3 of the second inner circumferential surface 40b in the crank hole 40 is larger than the hole diameter d1 of the first inner circumferential surface 40a.

[0048] The groove depth D from the groove bottom 41a of the retaining ring groove 41 to the second inner circumferential surface 40b in the radial direction of the crank hole 10 satisfies formula (1), where d1 is the hole diameter of the first inner circumferential surface 40a and d2 is the groove bottom diameter of the retaining ring groove 41. The hole diameter d1 of the first inner circumferential surface 40a and the groove bottom diameter d2 of the retaining ring groove 41 are specified within the ranges of the JIS standard. D≧{(d2-d1) / 2}×0.5 ···(1)

[0049] In Equation (1), {(d2-d1) / 2} corresponds to the first groove depth D1 from the groove bottom 41a of the retaining ring groove 41 to the first inner circumferential surface 40a in the radial direction of the crankshaft bore 40. In other words, the groove depth D from the groove bottom 41a of the retaining ring groove 41 to the second inner circumferential surface 40b in the radial direction of the crankshaft bore 40 (referred to as the second groove depth D2) is set to 50% or more of the first groove depth D1 (D2 / D1≧50%). Because the force of the seal cap 25 to come out is half or less than the bearing pressure and thrust load, it is sufficient for D2 / D1 to be 50% or more. If D2 / D1 is less than 50%, it is expected that the force of the retaining ring 42 in the direction of coming out of the seal cap 25 will not be suppressed.

[0050] The chamfer angle θ of the chamfered portions 41b, 41c of the retaining ring groove 41 is 45° or less with respect to the axial direction X of the crank hole 40. Specifically, the chamfer angle θ1 of the first chamfered portion 41b that connects to the first inner circumferential surface 40a of the retaining ring groove 41 is set to 30° with respect to the axial direction X. On the other hand, the chamfer angle θ2 of the second chamfered portion 41c that connects to the second inner circumferential surface 40b of the retaining ring groove 41 is set to 45° with respect to the axial direction X (C-chamfer). That is, in this embodiment, the dimension of the first chamfered portion 41b on the seal cap 25 side in the axial direction X is greater than the dimension of the second chamfered portion 41c in the axial direction X.

[0051] At least a portion of the second inner circumferential surface 40b has a straight portion 40d that is flat along the axial direction X of the crank hole 40. The length of the straight portion 40d in the axial direction X is, for example, 0.7 mm or more.

[0052] As described above, the reducer 1 of this embodiment converts the rotational speed between the first member and the second member at a predetermined rotational speed ratio to transmit driving force. The reducer 1 includes a carrier 4 configured to be attachable to one of the first member and the second member, a crankshaft 10 attached to a crank hole 40 provided in the carrier 4, an oscillating gear 14 having a toothed portion and an insertion hole into which an eccentric portion of the crankshaft 10 is inserted, and an outer cylinder 2 configured to be attachable to the other of the first member and the second member and having internal teeth that mesh with the teeth of the oscillating gear 14. A seal cap 25 formed in a cylindrical shape with a bottom is attached to the crank hole 40. The seal cap 25 has a disk-shaped bottom plate portion 25b and an annular resin cylindrical portion 25c protruding from the outer periphery of the bottom plate portion 25b. The cylindrical portion 25c is in close contact with a first inner circumferential surface 40a of the crank hole 40. The diameter of the second inner circumferential surface 40b of the crank hole 40 is larger than the contacted portion (first inner circumferential surface 40a) of the crank hole 40 with which the seal cap 25 comes into contact.

[0053] With this configuration, the diameter of the crank hole 40 is larger than the contacted portion (first inner circumferential surface 40a) of the crank hole 40 with which the seal cap 25 comes into contact, so that when the seal cap 25 is inserted from the opening side of the crank hole 40, the seal cap 25 does not come into contact with the second inner circumferential surface 40b of the crank hole 40. This makes it possible to prevent damage to the seal cap 25, such as tearing, and to prevent the seal cap 25 from coming out. This ensures the sealing performance of the seal cap 25 and prevents oil leakage from inside the carrier 4.

[0054] In the reducer 1 of this embodiment, the crank hole 40 is provided with a retaining ring groove 41 for attaching a retaining ring 42 that prevents the seal cap 25 from slipping out. The crank hole 40 has a first inner circumferential surface 40a that includes a contacted portion, and a second inner circumferential surface 40b that is on the opposite side of the retaining ring groove 41 from the first inner circumferential surface 40a. The hole diameter of the second inner circumferential surface 40b is larger than the hole diameter of the first inner circumferential surface 40a. Therefore, there is no contact when the seal cap 25 passes over the open end of the retaining ring groove 41, and the seal cap 25 can be prevented from being torn off.

[0055] Furthermore, in the reducer 1 of this embodiment, the groove depth dimension D from the groove bottom 41a of the retaining ring groove 41 to the second inner surface 40b in the radial direction of the crank hole 40 satisfies the formula D≧{(d2-d1) / 2}×0.5, where d1 is the hole diameter of the first inner surface 40a and d2 is the groove bottom diameter of the retaining ring groove 41. Therefore, since the force that causes the seal cap 25 to come out is less than half the force caused by the bearing pressure or thrust load, by setting the groove depth dimension D to satisfy the above formula, it is possible to prevent the force acting in the direction of the seal cap 25 coming out by the retaining ring from being unable to be suppressed.

[0056] Furthermore, in the reducer 1 of this embodiment, the chamfer angle θ of the retaining ring groove 41 with respect to the axial direction X of the crank hole 40 is 45° or less. This prevents the corners at the boundary between the inner circumferential surfaces 40a, 40b of the crank hole 40 and the retaining ring groove 41 from becoming sharp and being easily torn off when the seal cap 25 is inserted.

[0057] Furthermore, in the reducer 1 of this embodiment, at least a portion of the second inner circumferential surface 40b is flat along the axial direction X of the crank hole 40. This further prevents the corners at the boundary between the second inner circumferential surface 40b and the retaining ring groove 41, which have a large effect on the insertion of the seal cap 25 into the crank hole 40, from becoming sharp and being easily torn off when the seal cap 25 is inserted.

[0058] The actuator of this embodiment also includes an electric motor and a reducer 1 that converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit driving force. The reducer 1 includes a carrier 4 that is configured to be attachable to one of the first member and the second member, a crankshaft 10 that is attached to a crank hole 40 provided in the carrier 4, an oscillating gear 14 that has a through-hole into which an eccentric portion of the crankshaft 10 is inserted and that has teeth, and an outer cylinder 2 that is configured to be attachable to the other of the first member and the second member and that has internal teeth that mesh with the teeth of the oscillating gear 14. A seal cap 25 formed in a cylindrical shape with a bottom is attached to the crank hole 40. The seal cap 25 has a disk-shaped bottom plate portion 25b and an annular resin cylindrical portion 25c that protrudes from the outer periphery of the bottom plate portion 25b. The cylindrical portion 25c is in close contact with a first inner circumferential surface 40a of the crank hole 40. The diameter of the second inner circumferential surface 40b of the crank hole 40 is larger than the contacted portion (first inner circumferential surface 40a) of the crank hole 40 with which the seal cap 25 comes into contact.

[0059] With this configuration, the diameter of the second inner circumferential surface 40b of the crank hole 40 is larger than the contacted portion (first inner circumferential surface 40a) of the crank hole 40 with which the seal cap 25 comes into contact, so that the seal cap 25 does not come into contact with the second inner circumferential surface 40b of the crank hole 40 when the seal cap 25 is inserted from the opening side of the crank hole 40. This makes it possible to prevent damage to the seal cap 25, such as tearing, and to suppress the seal cap 25 from coming out. Therefore, it is possible to provide an actuator that ensures the sealing performance of the seal cap 25 and suppresses oil leakage from within the carrier.

[0060] The present invention is not limited to the above-described embodiment, and various design modifications are possible without departing from the spirit of the present invention. For example, in the above embodiment, the crank hole 40 is provided with a retaining ring groove 41 for attaching a retaining ring 42 that prevents the seal cap 25 from slipping out, but it is also possible to apply this to a crank hole that is not provided with a retaining ring groove 41 and a retaining ring 42.

[0061] In addition, in this embodiment, the groove depth dimension D from the groove bottom 41a of the retaining ring groove 41 to the second inner surface 40b in the radial direction of the crank hole 40 is set to satisfy the above formula (1), but is not limited to this.

[0062] Furthermore, in this embodiment, the chamfer angle θ of the retaining ring groove 41 is set to 45° or less with respect to the axial direction X of the crank hole 40, but this is not limited to this, and the retaining ring groove 41 may have no chamfered portion.

[0063] In addition, in this embodiment, at least a portion of the second inner circumferential surface 40b is configured to be flat along the axial direction X of the crank hole 40, but the present invention is not limited to a configuration in which such a straight portion is provided.

[0064] Furthermore, in this embodiment, the planetary gear mechanism is shown as an example of the reducer 1, but the reducer 1 is not limited to a planetary gear mechanism. [Explanation of symbols]

[0065] DESCRIPTION OF SYMBOLS 1...reduction gear (gear device), 2...outer cylinder, 3...internal tooth pin, 3a...internal teeth, 4...carrier, 4a...base portion, 4d...through hole, 5...base portion, 7...end plate portion, 10...crankshaft, 10a...first eccentric portion, 10b...second eccentric portion, 10c...shaft body, 14...first oscillating gear, 14a...first external teeth, 16...second oscillating gear, 16a...second external teeth, 25...seal cap, 25a...outer peripheral surface, 25b...bottom plate portion, 25c...cylindrical portion, 40...crank hole, 40a...first inner peripheral surface, 40b...second inner peripheral surface, 40c...opening, 40d...straight portion, 41...retaining ring groove, 41a...groove bottom, 41b...first chamfered portion, 41c...second chamfered portion, 42...retaining ring, X...axial direction

Claims

1. A gear device that converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit driving force, a carrier configured to be attachable to one of the first member and the second member; a crankshaft attached to a crank hole provided in the carrier; an oscillating gear having a through hole into which the eccentric portion of the crankshaft is inserted and having a toothed portion; an outer cylinder configured to be attachable to the other of the first member and the second member, and having internal teeth that mesh with the tooth portion of the oscillating gear; A seal cap formed in a cylindrical shape with a bottom is attached to the crank hole, The seal cap has a disk-shaped bottom plate portion and an annular cylindrical portion made of resin protruding from an outer periphery of the bottom plate portion, the cylindrical portion is in close contact with the inner circumferential surface of the crank hole, a diameter of the crank hole is larger than a contacted portion of the crank hole with which the seal cap comes into contact.

2. The crank hole is provided with a retaining ring groove for attaching a retaining ring that prevents the seal cap from slipping out, the crank hole has a first inner circumferential surface including the contacted portion and a second inner circumferential surface on the opposite side of the retaining ring groove from the first inner circumferential surface, The gear device according to claim 1 , wherein the hole diameter of the second inner peripheral surface is larger than the hole diameter of the first inner peripheral surface.

3. 3. The gear device according to claim 2, wherein a groove depth dimension D from a groove bottom of the retaining ring groove to the second inner circumferential surface in the radial direction of the crank hole satisfies a formula: D≧{(d2−d1) / 2}×0.5, where d1 is a hole diameter of the first inner circumferential surface and d2 is a groove bottom diameter of the retaining ring groove.

4. 3. The gear device according to claim 2, wherein a chamfer angle of the retaining ring groove is 45 degrees or less with respect to the axial direction of the crank hole.

5. The gear device according to claim 2 , wherein at least a portion of the second inner peripheral surface is flat along the axial direction of the crank hole.

6. A gear device that converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit driving force, a carrier configured to be attachable to one of the first member and the second member; a crankshaft attached to a crank hole provided in the carrier; an oscillating gear having a through hole into which the eccentric portion of the crankshaft is inserted and having a toothed portion; an outer cylinder configured to be attachable to the other of the first member and the second member, and having internal teeth that mesh with the tooth portion of the oscillating gear; A seal cap formed in a cylindrical shape with a bottom is attached to the crank hole, The seal cap has a disk-shaped bottom plate portion and an annular cylindrical portion made of resin protruding from an outer periphery of the bottom plate portion, the cylindrical portion is in close contact with the inner circumferential surface of the crank hole, a hole diameter of the seal cap is larger than a contact portion of the crank hole with which the seal cap comes into contact, The crank hole is provided with a retaining ring groove for attaching a retaining ring that prevents the seal cap from slipping out, the crank hole has a first inner circumferential surface including the contacted portion and a second inner circumferential surface on the opposite side of the retaining ring groove from the first inner circumferential surface, The hole diameter of the second inner circumferential surface is larger than the hole diameter of the first inner circumferential surface, a groove depth dimension D from a groove bottom of the retaining ring groove to the second inner circumferential surface in the radial direction of the crank hole satisfies the formula D≧{(d2−d1) / 2}×0.5, where d1 is a hole diameter of the first inner circumferential surface and d2 is a groove bottom diameter of the retaining ring groove; a chamfer angle of the retaining ring groove is 45° or less with respect to the axial direction of the crank hole; At least a portion of the second inner circumferential surface is flat along the axial direction of the crank hole.

7. An electric motor; a gear device that converts rotational speeds at a predetermined rotational speed ratio between a first member and a second member to transmit a driving force, The gear device is a carrier configured to be attachable to one of the first member and the second member; a crankshaft attached to a crank hole provided in the carrier; an oscillating gear having a through hole into which the eccentric portion of the crankshaft is inserted and having a toothed portion; an outer cylinder configured to be attachable to the other of the first member and the second member, and having internal teeth that mesh with the tooth portion of the oscillating gear; A seal cap formed in a cylindrical shape with a bottom is attached to the crank hole, The seal cap has a disk-shaped bottom plate portion and an annular cylindrical portion made of resin protruding from an outer periphery of the bottom plate portion, the cylindrical portion is in close contact with the inner circumferential surface of the crank hole, The actuator, wherein the hole diameter of the seal cap is larger than the diameter of a contacted portion of the crank hole with which the seal cap comes into contact.

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