Gear device and actuator

Abstract

The invention provides a gear device and an actuator. A gear device is provided with: a carrier (4) attached to one of a first member and a second member; a swing gear (14) having a through hole into which an eccentric portion of a crankshaft (10) provided on the carrier (4) is inserted, and having a tooth portion; an outer cylinder (2) that is attached to the other of the first member and the second member and has internal teeth that mesh with the teeth of the oscillating gear (14); and a bottomed cylindrical seal cover (25) attached to the crankshaft hole (40). The seal cover (25) has a circular-plate-shaped bottom plate portion (25b) and a resin circular-ring-shaped cylindrical portion (25c) protruding from the outer peripheral portion of the bottom plate portion (25b). The cylindrical portion (25c) is in close contact with a first inner peripheral surface (40a) of the crankshaft hole (40). The diameter of the second inner peripheral surface (40b) of the crankshaft hole (40) is larger than the diameter of the first inner peripheral surface (40a).

Description

Technical Field

[0001] This invention relates to gear mechanisms and actuators. Background Technology

[0002] Gear mechanisms that transmit driving force by changing the rotational speed between a first component and a second component at a predetermined speed ratio are known in the past. For example, gear mechanisms that include a gear carrier, a crankshaft, a oscillating gear, and an outer cylinder are known (see, for example, Patent Document 1).

[0003] The gear carrier is configured to be installed in either the first or second component. The crankshaft is mounted in a crankshaft bore provided in the gear carrier. The oscillating gear has a through hole for the eccentric portion of the crankshaft to be inserted and has teeth. The outer cylinder is configured to be installed in either the first or second component and has internal teeth that mesh with the teeth of the oscillating gear. Furthermore, a sealing cap formed as a bottomed cylinder is installed on the opening side of the crankshaft bore.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-102221 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In the gear mechanism described in Patent Document 1, the sealing cover is fixed solely by the fitting force based on the interference fit between the sealing cover and the crankshaft bore. Therefore, there is a possibility that the sealing cover may become unusable due to increased internal pressure in the reducer, causing it to detach from the crankshaft bore. In particular, with the increasing operating conditions in recent years, the internal pressure of the reducer tends to rise more easily. Therefore, there is a concern that the sealing cover may detach from the crankshaft bore.

[0009] There are known structures that physically suppress the seal cap from dislodging by providing a retaining ring in the crankshaft bore. In this case, a retaining ring groove for mounting the retaining ring is formed on the inner circumferential surface of the crankshaft bore. Therefore, when the seal cap is inserted from the opening side of the crankshaft bore and installed at a position closer to the inside of the crankshaft bore than the retaining ring groove, the seal cap contacts and hooks onto the opening end of the retaining ring groove. In this case, there is a problem that the surface of the seal cap may crack (surface breakage, peeling, etc.), and the sealing performance can no longer be guaranteed; there is room for improvement.

[0010] The present invention provides a gear device and actuator that can prevent damage to the sealing cap during assembly and ensure the sealing performance of the sealing cap while suppressing dislodgement.

[0011] Solution for solving the problem

[0012] (1) A gear device according to a technical solution of the present invention transmits driving force by changing the rotational speed between a first component and a second component at a predetermined rotational speed ratio. The gear device comprises: a gear carrier mounted on one of the first and second components; a crankshaft mounted in a crankshaft bore provided in the gear carrier; a oscillating gear having a through hole for inserting an eccentric portion of the crankshaft and having teeth; an outer cylinder mounted on the other of the first and second components and having internal teeth meshing with the teeth of the oscillating gear; and a bottom-cylindrical sealing cover mounted in the crankshaft bore. The sealing cover has a circular plate-shaped bottom plate portion and a resin-made annular cylindrical portion protruding from the outer periphery of the bottom plate portion. The cylindrical portion is in close contact with the inner circumferential surface of the crankshaft bore. A portion of the inner circumferential surface of the crankshaft bore is a contacted portion for contact with the sealing cover. The diameter of the portion of the inner circumferential surface of the crankshaft bore located on the side closer to the opening of the crankshaft bore than the contacted portion is formed to be larger than the diameter of the contacted portion.

[0013] With this configuration, the diameter of the portion of the crankshaft bore's inner circumferential surface located on the opening side of the crankshaft bore is larger than the diameter of the contact portion that the sealing cap contacts. Therefore, when the sealing cap is inserted from the opening side of the crankshaft bore, the sealing cap will not contact the inner circumferential surface of the crankshaft bore. This prevents damage such as cracking of the sealing cap and inhibits its dislodgement. Consequently, the sealing performance of the sealing cap is ensured, and oil leakage within the gear carrier is suppressed.

[0014] (2) A retaining ring groove for mounting a retaining ring may also be provided in the crankshaft bore, which prevents the sealing cap from dislodging. The crankshaft bore may also have a first inner circumferential surface including the contacted portion and a second inner circumferential surface located on the opposite side of the first inner circumferential surface, separated by the retaining ring groove. The second inner circumferential surface may also be positioned closer to the opening of the crankshaft bore than the retaining ring groove. The diameter of the second inner circumferential surface may also be larger than the diameter of the first inner circumferential surface.

[0015] (3) When the diameter of the first inner circumferential surface is defined as d1 and the bottom diameter of the retaining ring groove is defined as d2, the retaining ring groove can also be formed such that the groove depth D from the bottom of the retaining ring groove to the second inner circumferential surface along the radial direction of the crankshaft hole satisfies the following mathematical formula: D≥{(d2-d1) / 2}×0.5.

[0016] (4) The chamfer angle of the retaining ring groove can also be formed to be less than 45° relative to the axial direction of the crankshaft hole.

[0017] (5) At least a portion of the second inner circumferential surface may also be formed flat along the axial direction of the crankshaft bore.

[0018] (6) An actuator according to one embodiment of the present invention comprises: an electric motor; and a gear assembly that transmits driving force by changing the rotational speed between a first member and a second member at a predetermined rotational speed ratio. The gear assembly comprises: a gear carrier mounted on one of the first member and the second member; a crankshaft mounted in a crankshaft bore provided in the gear carrier; a oscillating gear having a through hole for inserting an eccentric portion of the crankshaft and having teeth; an outer cylinder mounted on the other of the first member and the second member and having internal teeth meshing with the teeth of the oscillating gear; and a bottom-cylindrical sealing cap mounted in the crankshaft bore. The sealing cap has a circular plate-shaped bottom plate portion and a resin-made annular cylindrical portion protruding axially from the outer periphery of the bottom plate portion along the crankshaft bore. The cylindrical portion is in close contact with the inner circumferential surface of the crankshaft bore. A portion of the inner circumferential surface of the crankshaft bore is a contacted portion for contact with the sealing cap. The inner diameter of the portion of the inner circumferential surface of the crankshaft bore located on the side of the opening of the crankshaft bore that is closer to the contacted portion is formed to be larger than the bore diameter of the contacted portion.

[0019] With this configuration, the diameter of the portion of the crankshaft bore's inner circumferential surface located on the opening side of the crankshaft bore is larger than the diameter of the contact portion that the sealing cap contacts. Therefore, when the sealing cap is inserted from the opening side of the crankshaft bore, the sealing cap will not contact the inner circumferential surface of the crankshaft bore. This prevents damage such as cracking of the sealing cap and inhibits its dislodgement. Consequently, the sealing performance of the sealing cap is ensured, and oil leakage within the gear carrier is suppressed.

[0020] The effects of the invention

[0021] According to the present invention, damage to the sealing cap during assembly can be prevented, and the sealing performance of the sealing cap can be ensured while suppressing dislodgement. Attached Figure Description

[0022] Figure 1 This is a cross-sectional view showing the main part of the reducer with a sealing cover according to the embodiment.

[0023] Figure 2 Observation from the output side Figure 1 A 3D view of the speed reducer.

[0024] Figure 3 It means Figure 2 A three-dimensional view (partial sectional view) of the main part of the crankshaft bore.

[0025] Figure 4 This is a cross-sectional view showing the installation status of the sealing cap at the crankshaft bore.

[0026] Figure 5 It means Figure 4Enlarged sectional view of the main part.

[0027] Explanation of reference numerals in the attached figures

[0028] 1. Reducer (gear assembly); 2. Outer cylinder; 3. Internal gear pin; 3a. Internal gear; 4. Gear carrier; 4a. Base plate; 4d. Through hole; 5. Base; 7. End plate; 10. Crankshaft; 10a. First eccentric part; 10b. Second eccentric part; 10c. Shaft body; 14. First oscillating gear; 14a. First external gear; 16. Second oscillating gear; 16a. Second external gear; 25. Sealing cover; 25a. Outer peripheral surface; 25b. Base plate; 25c. Cylindrical part; 40. Crankshaft hole; 40a. First inner peripheral surface; 40b. Second inner peripheral surface; 40c. Opening; 40d. Straight part; 41. Retaining ring groove; 41a. Groove bottom; 41b. First chamfer; 41c. Second chamfer; 42. Retaining ring; X. Axial direction. Detailed Implementation

[0029] Embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the various embodiments and modifications described below, common parts are labeled with the same reference numerals, and repeated descriptions are omitted in certain instances.

[0030] Figure 1 This is a cross-sectional view of the main part of a reducer 1 equipped with a sealing cover 25, illustrating an example of an embodiment of the present invention. Figure 2 Observation from the output side Figure 1 The diagram shows a three-dimensional view of reducer 1. Figure 3 It means Figure 2 A perspective view (partial sectional view) of the main part of the crankshaft bore 40 shown. Figure 4 This is a cross-sectional view showing the installation state of the sealing cap 25 at crankshaft bore 40. Figure 5 It means Figure 4 Enlarged sectional view of the main part.

[0031] like Figure 1 As shown, reducer 1 (gear assembly) is connected to an electric motor (not shown) and serves as a part of a so-called geared motor. Reducer 1 is mounted on an actuator with an electric motor, such as the arm or hand of a robot (not shown).

[0032] In the reducer 1, the crankshaft 10 rotates via the rotation of the input shaft (not shown in the figure). Furthermore, it is configured such that the oscillating gears 14 and 16, in conjunction with the eccentric portions 10a and 10b of the crankshaft 10, oscillate and rotate, enabling the output rotation to be reduced in speed compared to the input rotation. This allows relative rotation to be generated between, for example, the robot's base (one object component) and the rotating component (another object component). Furthermore, the base is exemplified as the first component, and the rotating component is exemplified as the second component.

[0033] The reducer 1 includes an outer cylinder 2, a gear carrier 4, multiple (e.g., 3) crankshafts 10, a first oscillating gear 14, a second oscillating gear 16, multiple (e.g., 3) transmission gears 20, and a sealing cover 25.

[0034] The outer cylinder 2 is formed in a cylindrical shape, constituting the outer surface of the reducer 1. A plurality of pin grooves 2b are formed on the inner circumferential surface of the outer cylinder 2. Each pin groove 2b is configured to extend along the axial direction of the outer cylinder 2 (the axial direction X of the crankshaft bore 40 described later). Each pin groove 2b has a semi-circular cross-sectional shape in a section orthogonal to the axial direction X.

[0035] These pin slots 2b are arranged at equal intervals in the circumferential direction on the inner circumferential surface of the outer cylinder 2.

[0036] The outer cylinder 2 has a plurality of internal toothed pins 3. Each internal toothed pin 3 is respectively installed in a pin groove 2b. Specifically, each internal toothed pin 3 is embedded in a corresponding pin groove 2b. Each internal toothed pin 3 is formed to extend along the axial direction of the outer cylinder 2. Thus, a plurality of internal toothed pins 3 are arranged at equal intervals along the circumference of the outer cylinder 2. The internal teeth 3a are formed by these internal toothed pins 3.

[0037] The first external tooth 14a of the first oscillating gear 14 and the second external tooth 16a of the second oscillating gear 16 mesh with the internal tooth 3a composed of multiple internal tooth pins 3.

[0038] The outer cylinder 2 is provided with a flange portion. A through hole 2a is formed in the flange portion for fasteners (bolts) for fixing to, for example, a robot base.

[0039] The gear carrier 4 is housed within the outer cylinder 2, coaxially arranged with it. The gear carrier 4 rotates relative to the outer cylinder 2 about the same axis. Specifically, the gear carrier 4 is located radially inside the outer cylinder 2. The gear carrier 4 is supported by a pair of main bearings 6, which are axially separated from each other, enabling it to rotate relative to the outer cylinder 2.

[0040] like Figure 1 and Figure 2 As shown, the gear carrier 4 has a base portion 5 and an end plate portion 7. The base portion 5 has a base plate portion 4a and a plurality of (e.g., 3) shaft portions (not shown).

[0041] A base plate portion 4a is disposed at one end of the outer cylinder 2 along its axial direction. A circular through hole 4d is formed at the radial center of the base plate portion 4a. The through hole 4d is formed to penetrate the base plate portion 4a along its thickness direction. Furthermore, a plurality of (e.g., three) mounting holes (hereinafter referred to as crankshaft holes 40) are formed on the base plate portion 4a in a manner surrounding the through hole 4d. The plurality of crankshaft holes 40 are arranged at equal intervals in the circumferential direction. A plurality of crankshafts 10 are respectively mounted in the crankshaft holes 40. In addition, the crankshaft holes 40 are formed to penetrate the base plate portion 4a along its thickness direction.

[0042] Fastening holes are formed in the base plate portion 4a for fastening with fasteners (bolts) (not shown). The fasteners fix the gear carrier 4 to, for example, a rotating component of a robot.

[0043] like Figure 1 As shown, the end plate portion 7 is axially separated from the base plate portion 4a. The end plate portion 7 is disposed at the other end side of the outer cylinder 2 in the axial direction. A through hole 7a is formed at the radial center of the end plate portion 7. The through hole 7a is formed to penetrate the end plate portion 7 in the thickness direction. Moreover, a plurality of (e.g., 3) crankshaft mounting holes 7b (hereinafter simply referred to as mounting holes 7b) are formed on the end plate portion 7 in a manner disposed around the through hole 7a. The plurality of mounting holes 7b are arranged at equal intervals in the circumferential direction. Moreover, the plurality of mounting holes 7b are arranged face-to-face with the plurality of crankshaft holes 40 formed on the base plate portion 4a in the axial direction in a manner corresponding to the plurality of crankshaft holes 40 formed on the base plate portion 4a. Furthermore, the mounting holes 7b are formed to penetrate the end plate portion 7 in the thickness direction.

[0044] A closed space S is formed inside the outer cylinder 2, which is enclosed by the inner surfaces of the end plate portion 7 and the base plate portion 4a that are opposite to each other and the inner circumferential surface of the outer cylinder 2. That is, the closed space S is formed by the outer cylinder 2 and the gear carrier 4.

[0045] Through hole 4d, through hole 7a, crankshaft hole 40 and mounting hole 7b function as connecting holes to connect the outside with the closed space S.

[0046] like Figures 1-4 As shown, sealing caps 25 are installed in multiple (3) crankshaft holes 40 respectively (see reference). Figure 2 ).

[0047] The sealing cap 25 seals the crankshaft bore 40. The sealing cap 25 has a circular plate-shaped base plate portion 25b and an annular cylindrical portion 25c protruding from the outer periphery of the base plate portion 25b along the axial direction X of the crankshaft bore 40. Thus, the sealing cap 25 is formed as a bottomed cylindrical shape. The cylindrical portion 25c is in close contact with the inner circumferential surface of the crankshaft bore 40.

[0048] Thus, the sealing cap 25 prevents the lubricating oil sealed inside the gear carrier 4 (inside the crankshaft bore 40) from leaking to the outside.

[0049] Detailed description of sealing cap 25.

[0050] The sealing cap 25 is integrally formed by a bottomed cylindrical inner surface forming portion 26 that forms the inner surface of the entire sealing cap 25 and an outer surface forming portion 27 that covers the outer surface of the inner surface forming portion 26. The inner surface forming portion 26 is made of metal and is a rigid member. In contrast, the outer surface forming portion 27 is made of resin.

[0051] In the sealing cover 25, the cylindrical portion 25c is pressed against the inner circumferential surface (first inner circumferential surface 40a) of the crankshaft hole 40 by the rigidity (elasticity) of the inner surface forming portion 26.

[0052] Furthermore, the bottom plate portion 25b, which serves as the sealing cover 25, is formed from the bottom of the inner surface forming portion 26 and the bottom of the outer surface forming portion 27. The cylindrical portion 25c, which serves as the sealing cover 25, is formed from the cylindrical portion of the inner surface forming portion 26 and the cylindrical portion of the outer surface forming portion 27.

[0053] The three shafts constituting the gear carrier 4 are integrally provided with the base plate portion 4a. The three shafts are formed to extend axially in a straight line from a main surface (inner surface) of the base plate portion 4a toward the end plate portion 7. The three shafts are arranged at equal intervals in the circumferential direction. Each shaft is fastened to the end plate portion 7 by bolts (not shown). Thus, the base plate portion 4a, the shafts, and the end plate portion 7 are integrated.

[0054] like Figure 1 As shown, three crankshafts 10 are arranged, for example, at equal intervals within the outer cylinder 2, around the central axis of the gear carrier 4. Each crankshaft 10 is supported by a pair of crankshaft bearings 12a, 12b, enabling it to rotate about its axis relative to the gear carrier 4.

[0055] Specifically, a first crankshaft bearing 12a is mounted at one end of each crankshaft 10 along the axial direction X. The first crankshaft bearing 12a is mounted in the crankshaft bore 40 of the base plate portion 4a. On the other hand, a second crankshaft bearing 12b is mounted at the other end of each crankshaft 10 along the axial direction X. The second crankshaft bearing 12b is mounted in the mounting hole 7b of the end plate portion 7. Thus, each crankshaft 10 is rotatably supported on the base plate portion 4a and the end plate portion 7.

[0056] Each crankshaft 10 has a shaft body 10c and eccentric portions 10a and 10b integrally formed on the shaft body 10c.

[0057] The first eccentric portion 10a and the second eccentric portion 10b are formed between the portions supported by two crankshaft bearings 12a and 12b in the shaft body 10c and are arranged axially. The first eccentric portion 10a and the second eccentric portion 10b are each cylindrical in shape. Both the first eccentric portion 10a and the second eccentric portion 10b extend radially outward from the shaft body 10c in a state of eccentricity relative to the axis of the shaft body 10c. The first eccentric portion 10a and the second eccentric portion 10b are respectively formed to be eccentrically positioned relative to the axis of the shaft body 10c by a predetermined amount of eccentricity and are arranged to have a predetermined angular phase difference with each other.

[0058] The first oscillating gear 14 is disposed in the closed space S inside the outer cylinder 2. The first oscillating gear 14 is mounted on the first eccentric portion 10a of each crankshaft 10 via the first roller bearing 18a. When the first eccentric portion 10a rotates eccentrically as each crankshaft 10 rotates, the first oscillating gear 14 oscillates and rotates in conjunction with the eccentric rotation, while meshing with the internal gear pin 3.

[0059] The first oscillating gear 14 is formed with a size slightly smaller than the inner diameter of the outer cylinder 2. The first oscillating gear 14 has a first external tooth 14a, a central through hole 14b, a plurality of (e.g., 3) first eccentric through holes 14c, and a plurality of (e.g., 3) shaft through holes (not shown). The first external tooth 14a has a wave-shaped shape that is smoothly continuous throughout the circumference of the oscillating gear 14.

[0060] A central through hole 14b is provided in the radially central portion of the first oscillating gear 14. Three first eccentric through holes 14c are formed and equally spaced around the central through hole 14b in the circumferential direction. The first eccentric portion 10a of each crankshaft 10 passes through each first eccentric through hole 14c in a state where the first roller bearing 18a is clamped.

[0061] Multiple shaft through holes are formed and equally spaced around the central through hole 14b in the circumferential direction. Each shaft through hole is positioned, for example, between adjacent first eccentric through holes 14c in the circumferential direction. The corresponding shaft portion passes through each shaft through hole with a gap.

[0062] The second oscillating gear 16 is disposed in the closed space S inside the outer cylinder 2. The second oscillating gear 16 is mounted to the second eccentric portion 10b of each crankshaft 10 via the second roller bearing 18b. The first oscillating gear 14 and the second oscillating gear 16 are arranged axially in correspondence with the configuration of the first eccentric portion 10a and the second eccentric portion 10b. When the second eccentric portion 10b rotates eccentrically as each crankshaft 10 rotates, the second oscillating gear 16 oscillates and rotates in conjunction with this eccentric rotation, meshing with the internal gear pin 3.

[0063] The second oscillating gear 16 is formed with a size slightly smaller than the inner diameter of the outer cylinder 2. The second oscillating gear 16 is constructed in the same manner as the first oscillating gear 14.

[0064] That is, the second oscillating gear 16 has a second external tooth 16a, a central through hole 16b, a plurality of (e.g., 3) second eccentric through holes 16c, and a plurality of (e.g., 3) shaft through holes (not shown). They have the same structure as the first external tooth 14a, central through hole 14b, plurality of first eccentric through holes 14c, and plurality of shaft through holes of the first oscillating gear 14. The second eccentric portion 10b of the crankshaft 10 passes through each of the second eccentric through holes 16c in a state in which the second roller bearing 18b is clamped.

[0065] A transmission gear 20 is mounted on the portion of each crankshaft 10 located axially outward from the mounting hole 7b. Each transmission gear 20 has external teeth 20a that mesh with the input gear 8a. Rotational driving force is input from the input shaft to the input gear 8a. Furthermore, the input shaft functions as an input section for the driving force of a drive motor (not shown). Each transmission gear 20 transmits the rotation of the input gear 8a to the corresponding crankshaft 10.

[0066] Each transmission gear 20 is externally fitted to the end of the corresponding crankshaft 10's shaft body 10c. Each transmission gear 20 rotates integrally with the crankshaft 10 around an axis that is the same as the crankshaft 10's axis of rotation. If each transmission gear 20 is driven by the input gear 8a, each crankshaft 10 rotates around its axis. If each crankshaft 10 rotates, the oscillating gears 14 and 16 mounted on the eccentric portions 10a and 10b oscillate while meshing with the internal tooth pin 3 as the eccentric portions 10a and 10b rotate. As a result, the gear carrier 4 and the outer cylinder 2 rotate relative to each other.

[0067] like Figure 1 , Figure 3 , Figure 4 and Figure 5 As shown, a bottomed cylindrical sealing cap 25 is installed in the crankshaft bore 40. The sealing cap 25 is fitted into the crankshaft bore 40 by insertion from the opening 40c side of the crankshaft bore 40. As described above, the sealing cap 25 has a circular plate-shaped bottom plate portion 25b and a resin-made annular cylindrical portion 25c protruding from the outer periphery of the bottom plate portion 25b. The outer peripheral surface 25a of the cylindrical portion 25c is in close contact with the inner peripheral surface (first inner peripheral surface 40a) of the crankshaft bore 40.

[0068] The diameter d3 of the portion of the crankshaft bore 40 located on the side of the opening 40c (the second inner circumferential surface 40b) is larger than the diameter d1 of the contact portion (the first inner circumferential surface 40a) in the crankshaft bore 40 that is in contact with the sealing cap 25.

[0069] A retaining ring groove 41 is provided in the crankshaft bore 40 for mounting a retaining ring 42, which prevents the sealing cover 25 from dislodging (falling off). Furthermore, in Figure 3 The illustration of retaining ring 42 is omitted in the text.

[0070] The crankshaft bore 40 has a first inner circumferential surface 40a including a contact portion and a second inner circumferential surface 40b located on the opposite side of the first inner circumferential surface 40a in the axial direction X, separated by a retaining ring groove 41. The second inner circumferential surface 40b is positioned closer to the opening 40c of the crankshaft bore 40 than the retaining ring groove 41. To allow the sealing cap 25 to be inserted into the crankshaft bore 40 and to install the sealing cap 25, as previously described, the diameter d3 of the second inner circumferential surface 40b of the crankshaft bore 40 is formed to be larger than the diameter d1 of the first inner circumferential surface 40a.

[0071] The retaining ring groove 41 is formed such that the groove depth dimension D from the bottom 41a of the retaining ring groove 41 to the second inner circumferential surface 40b along the radial direction of the crankshaft hole 40 satisfies mathematical formula (1).

[0072] Furthermore, in mathematical formula (1), the aperture of the first inner circumferential surface 40a is defined as d1, and the bottom diameter of the retaining ring groove 41 is defined as d2. Moreover, the aperture d1 of the first inner circumferential surface 40a and the bottom diameter d2 of the retaining ring groove 41 are specified within the scope of Japanese Industrial Standards (JIS).

[0073] D≥{(d2-d1) / 2}×0.5…(1)

[0074] In mathematical formula (1), {(d2-d1) / 2} corresponds to the first groove depth dimension D1 along the radial direction of the crankshaft hole 40 from the bottom 41a of the retaining ring groove 41 to the first inner circumferential surface 40a. That is, the groove depth dimension D (denoted as the second groove depth dimension D2) along the radial direction of the crankshaft hole 40 from the bottom 41a of the retaining ring groove 41 to the second inner circumferential surface 40b is set to be more than 50% of the first groove depth dimension D1 (D2 / D1≥50%).

[0075] Since the force that causes the sealing cap 25 to detach from the crankshaft bore 40 is less than half of the bearing preload and thrust load, D2 / D1 can be set to 50% or more. Assuming that D2 / D1 is less than 50%, it can be envisioned that the retaining ring 42 cannot overcome the force in the detachment direction of the sealing cap 25.

[0076] The chamfer angle θ of the chamfered portions 41b and 41c of the retaining ring groove 41 is set to 45° or less relative to the axial direction X of the crankshaft bore 40.

[0077] Specifically, a first chamfered portion 41b is formed in the portion of the retaining ring groove 41 that connects the groove bottom 41a to the first inner circumferential surface 40a. Furthermore, the chamfer angle θ1 of the first chamfered portion 41b is set to 30° relative to the axial direction X. On the other hand, a second chamfered portion 41c is formed in the portion of the retaining ring groove 41 that connects the groove bottom 41a to the second inner circumferential surface 40b. Furthermore, the chamfer angle θ2 of the second chamfered portion 41c is set to 45° relative to the axial direction X. Therefore, the second chamfered portion 41c undergoes a so-called C-chamfering process.

[0078] Therefore, in this embodiment, the dimension of the first chamfered portion 41b located on the sealing cover 25 side along the axial direction X is set to be larger than the dimension of the second chamfered portion 41c along the axial direction X.

[0079] Furthermore, at least a portion of the second inner circumferential surface 40b has a straight portion 40d formed flatly along the axial direction X of the crankshaft bore 40. The length of the straight portion 40d in the axial direction X is, for example, 0.7 mm or more.

[0080] The reducer 1 of this embodiment, configured as described above, transmits driving force by changing the rotational speed between the first member and the second member at a predetermined speed ratio. Figure 1 As shown, the reducer 1 includes: a gear carrier 4, which is mounted on one of the first and second components; a crankshaft 10, which is mounted in a crankshaft bore 40 provided in the gear carrier 4; oscillating gears (first oscillating gear 14, second oscillating gear 16), which have through holes (first eccentric part through hole 14c, second eccentric part through hole 16c) for inserting the eccentric parts (first eccentric part 10a, second eccentric part 10b) of the crankshaft 10 and have teeth (first external tooth 14a, second external tooth 16a); an outer cylinder 2, which is mounted on the other of the first and second components and has internal teeth (3a) that mesh with the teeth of the oscillating gears; and a bottomed cylindrical sealing cover 25, which is mounted in the crankshaft bore 40.

[0081] The sealing cap 25 has a circular plate-shaped base plate portion 25b and a resin-made annular cylindrical portion 25c protruding from the outer periphery of the base plate portion 25b. The cylindrical portion 25c is in close contact with the first inner peripheral surface 40a of the crankshaft bore 40. A portion of the inner peripheral surface of the crankshaft bore 40 is the contacted portion (first inner peripheral surface 40a) for the sealing cap 25 to contact. Furthermore, the aperture (d3) of the second inner peripheral surface 40b of the crankshaft bore 40 is formed to be larger than the aperture (d1) of the contacted portion (first inner peripheral surface 40a).

[0082] By configuring it in this way, the diameter of the second inner circumferential surface 40b of the crankshaft bore 40 can be larger than the diameter of the contacted portion (first inner circumferential surface 40a) that the sealing cap 25 contacts. Therefore, it is possible to prevent the sealing cap 25 from contacting the second inner circumferential surface 40b of the crankshaft bore 40 when it is inserted from the opening 40c side of the crankshaft bore 40. Therefore, damage such as cracking of the sealing cap 25 can be prevented. Therefore, the quality of the sealing cap 25 can be maintained, and it is possible to prevent the sealing cap 25 from falling out of the crankshaft bore 40. Therefore, the sealing performance of the sealing cap 25 can be ensured, and oil leakage within the gear carrier 4 can be appropriately suppressed.

[0083] Furthermore, in the reducer 1 of this embodiment, a retaining ring groove 41 for mounting a retaining ring 42 is provided in the crankshaft bore 40, and the retaining ring 42 prevents the sealing cover 25 from dislodging. The crankshaft bore 40 has a first inner circumferential surface 40a including a contact portion and a second inner circumferential surface 40b located axially across the retaining ring groove 41 on the side opposite to the first inner circumferential surface 40a. The bore diameter d3 of the second inner circumferential surface 40b is larger than the bore diameter d1 of the first inner circumferential surface 40a.

[0084] Therefore, the sealing cap 25 can be prevented from contacting the retaining ring groove 41 when passing through the open end of the retaining ring groove 41. Therefore, damage such as cracking of the sealing cap 25 can be prevented.

[0085] Furthermore, in the reducer 1 of this embodiment, the retaining ring groove 41 is formed such that the groove depth dimension D satisfies the mathematical formula "D≥{(d2-d1) / 2}×0.5".

[0086] Therefore, since the force that causes the sealing cover 25 to fall off is less than half of the bearing preload and thrust load, by setting the groove depth dimension D to satisfy the mathematical formula, it is possible to prevent the retaining ring 42 from being unable to overcome the force in the direction of the sealing cover 25 falling off.

[0087] Furthermore, in the reducer 1 of this embodiment, the chamfer angle θ of the retaining ring groove 41 is formed to be 45° or less relative to the axial direction X of the crankshaft bore 40.

[0088] Therefore, it is possible to prevent the corners of the junction between the inner circumferential surfaces 40a and 40b of the crankshaft bore 40 and the retaining ring groove 41 from becoming sharp. Therefore, it is possible to prevent damage such as cracking of the sealing cover 25 when it is inserted.

[0089] Furthermore, in the reducer 1 of this embodiment, at least a portion of the second inner circumferential surface 40b is a straight portion 40d formed flatly along the axial direction X of the crankshaft bore 40.

[0090] Therefore, it is possible to prevent the corner of the junction between the second inner circumferential surface 40b and the retaining ring groove 41 from becoming sharp when the sealing cap 25 is inserted into the crankshaft hole 40, which has a significant impact on the sealing cap 25. Therefore, it is possible to further suppress damage such as cracking of the sealing cap 25 when it is inserted.

[0091] In addition, the actuator of this embodiment includes: an electric motor; and a reducer 1, which transmits driving force by changing the rotational speed between the first member and the second member at a predetermined rotational speed ratio.

[0092] The reducer 1 includes: a gear carrier 4, which is mounted on one of the first and second components; a crankshaft 10, which is mounted in a crankshaft bore 40 provided in the gear carrier 4; oscillating gears (first oscillating gear 14, second oscillating gear 16), which have through holes (first eccentric part through hole 14c, second eccentric part through hole 16c) for inserting the eccentric parts (first eccentric part 10a, second eccentric part 10b) of the crankshaft 10 and have teeth (first external tooth 14a, second external tooth 16a); an outer cylinder 2, which is mounted on the other of the first and second components and has internal teeth (3a) that mesh with the teeth of the oscillating gear 14; and a bottomed cylindrical sealing cover 25, which is mounted in the crankshaft bore 40.

[0093] The sealing cap 25 has a circular base plate portion 25b and a resin-made annular cylindrical portion 25c protruding from the outer periphery of the base plate portion 25b. The cylindrical portion 25c is in close contact with the first inner peripheral surface 40a of the crankshaft bore 40. The diameter (d3) of the second inner peripheral surface 40b of the crankshaft bore 40 is formed to be larger than the diameter (d1) of the contacted portion (first inner peripheral surface 40a).

[0094] With this configuration, the diameter d3 of the second inner circumferential surface 40b of the crankshaft bore 40 can be larger than the diameter d1 of the contacted portion (first inner circumferential surface 40a) that contacts the sealing cap 25. Therefore, contact between the sealing cap 25 and the second inner circumferential surface 40b of the crankshaft bore 40 can be prevented when the sealing cap 25 is inserted from the opening 40c side of the crankshaft bore 40. Consequently, damage such as cracking of the sealing cap 25 can be prevented. Therefore, the quality of the sealing cap 25 can be maintained, and the dislodgement of the sealing cap 25 from the crankshaft bore 40 can be suppressed. Therefore, an actuator that ensures the sealing performance of the sealing cap 25 and appropriately suppresses oil leakage within the gear carrier 4 can be provided.

[0095] Furthermore, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from its spirit.

[0096] For example, in the above embodiment, a retaining ring groove 41 for mounting a retaining ring 42 to prevent the sealing cap 25 from dislodging was described, but the invention is not limited to this case. For example, the invention can also be applied to crankshaft bores that do not have a retaining ring groove 41 and a retaining ring 42.

[0097] In addition, in this embodiment, the groove depth dimension D from the bottom 41a of the retaining ring groove 41 to the second inner circumferential surface 40b along the radial direction of the crankshaft hole 40 is set to satisfy mathematical formula (1), but is not limited to this.

[0098] Furthermore, in this embodiment, the chamfer angle θ of the retaining ring groove 41 is described as being set to 45° or less relative to the axial direction X of the crankshaft bore 40, but it is not limited to this. For example, the retaining ring groove 41 may not have a chamfered portion.

[0099] In addition, in this embodiment, the structure in which the second inner circumferential surface 40b has at least partially a straight portion 40d that is formed flatly along the axial direction X of the crankshaft hole 40 is described as an example, but the structure is not limited to having such a straight portion 40d.

[0100] In addition, a planetary gear mechanism is shown as an example of a reducer 1 in this embodiment, but it is not limited to a planetary gear mechanism.

Claims

1. A gear mechanism that transmits driving force by changing the rotational speed between a first component and a second component at a predetermined speed ratio, wherein, The gear mechanism has the following features: A gear carrier, which is mounted on one of the first component and the second component; A crankshaft, which is mounted in a crankshaft bore provided in the gear carrier; A oscillating gear having a through hole for insertion of an eccentric portion of the crankshaft and having teeth; The outer cylinder is mounted on another component of the first component and the second component, and has internal teeth that mesh with the teeth of the oscillating gear; as well as A bottomed cylindrical sealing cap is installed in the crankshaft bore. The sealing cap has a circular plate-shaped base plate portion and a resin-made annular cylindrical portion that protrudes axially from the outer periphery of the base plate portion along the crankshaft bore. The cylindrical portion is in close contact with the inner circumferential surface of the crankshaft bore. A portion of the inner circumferential surface of the crankshaft bore is the contacted part that the sealing cap contacts. The diameter of the portion of the inner circumferential surface of the crankshaft bore located on the side closer to the opening of the crankshaft bore than the contacted portion is formed to be larger than the diameter of the contacted portion.

2. The gear device according to claim 1, wherein, The crankshaft bore is provided with a retaining ring groove for installing a retaining ring, which prevents the sealing cap from falling out. The crankshaft bore has a first inner circumferential surface including the contacted portion and a second inner circumferential surface located on the opposite side of the first inner circumferential surface, separated by the retaining ring groove. The second inner circumferential surface is positioned closer to the opening of the crankshaft bore than the retaining ring groove. The aperture of the second inner circumferential surface is larger than the aperture of the first inner circumferential surface.

3. The gear device according to claim 2, wherein, When the diameter of the hole on the first inner circumferential surface is defined as d1 and the bottom diameter of the retaining ring groove is defined as d2, The retaining ring groove is formed such that the groove depth D from the bottom of the retaining ring groove to the second inner circumferential surface along the radial direction of the crankshaft hole satisfies the following mathematical formula: D≥{(d2-d1) / 2}×0.

5.

4. The gear device according to claim 2, wherein, The chamfer angle of the retaining ring groove is less than 45° relative to the axial direction of the crankshaft bore.

5. The gear device according to claim 2, wherein, The second inner circumferential surface is at least partially formed flat along the axial direction of the crankshaft bore.

6. An actuator comprising: Electric motor; as well as A gear mechanism that transmits driving force by changing the rotational speed between a first component and a second component at a predetermined speed ratio, wherein... The gear device includes: A gear carrier, which is mounted on one of the first component and the second component; A crankshaft, which is mounted in a crankshaft bore provided in the gear carrier; A oscillating gear having a through hole for insertion of an eccentric portion of the crankshaft and having teeth; An outer cylinder, which is mounted on another component of the first and second components, and has internal teeth that mesh with the teeth of the oscillating gear; and A bottomed cylindrical sealing cap is installed in the crankshaft bore. The sealing cap has a circular plate-shaped base plate portion and a resin-made annular cylindrical portion that protrudes axially from the outer periphery of the base plate portion along the crankshaft bore. The cylindrical portion is in close contact with the inner circumferential surface of the crankshaft bore. A portion of the inner circumferential surface of the crankshaft bore is the contacted part that the sealing cap contacts. The diameter of the portion of the inner circumferential surface of the crankshaft bore located on the side closer to the opening of the crankshaft bore than the contacted portion is formed to be larger than the diameter of the contacted portion.

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