Reducer

Abstract

The present invention provides a speed reducer. The speed reducer (1) according to an embodiment of the present invention includes: a gear bracket (24) having a concave portion (50); a crankshaft (12) disposed in the concave portion (50); and a restricting member (60) disposed on the bottom surface (51) of the concave portion (50) to restrict the crankshaft (12) from moving in the direction toward the bottom surface (51) along the axis (A2) of the crankshaft (12).

Description

Technical Field

[0001] The present invention relates to a speed reducer. Background Art

[0002] Speed reducers are used in industrial robots, machine tools, and various other machines that operate due to an input torque. The speed reducer reduces the rotation input from a drive source such as an electric motor and outputs it to an object device to be driven. As one type of speed reducer, an eccentric swing type speed reducer is known. A conventional eccentric swing type speed reducer is described in Japanese Patent Laid-Open No. 5-180278.

[0003] The eccentric swing type speed reducer has: a crankshaft having an eccentric body; an external gear mounted on the crankshaft of the eccentric body; a housing having internal teeth meshing with the external gear; and a gear carrier provided to be rotatable relative to the housing. For such an eccentric swing type speed reducer, the rotation from the drive source is transmitted from the input gear to the crankshaft. When the crankshaft rotates, the external gear is pushed by the eccentric body and also rotates, and accordingly, the gear carrier rotates relative to the housing. Thus, the reduced rotation is output from the gear carrier or the housing to the object device.

[0004] A conventional swing type speed reducer, for example, as disclosed in Japanese Patent Laid-Open No. 2016-130536, has a cover fitted to the gear carrier in order to restrict the axial movement of the crankshaft. The outer peripheral surface of the cover has an external thread, and the inner peripheral surface of the through hole for accommodating the crankshaft that forms the gear carrier has an internal thread. By fastening the cover having the external thread to the inner peripheral surface of the gear carrier, the cover is mounted on the gear carrier, and the axial movement of the crankshaft is restricted by the threaded cover mounted on the gear carrier.

[0005] Prior art documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Laid-Open No. 5-180278

[0008] Patent Document 2: Japanese Patent Laid-Open No. 2016-130536 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] For a conventional speed reducer that restricts the movement of the crankshaft using a threaded cover, there is a gap between the external thread of the cover and the internal thread of the inner peripheral surface of the gear carrier. Therefore, sometimes the lubricant becomes insufficient for sealing the inside of the speed reducer. This problem applies not only to eccentric swing type speed reducers but also to other types of speed reducers having threaded covers.

[0011] An object of the present invention is to eliminate or mitigate the above problems of the prior art. One specific object of the present invention is to provide a new speed reducer having a crankshaft support mechanism with excellent sealing performance. Other objects of the present invention will become clear by referring to the entire specification.

[0012] Solutions for solving the problems

[0013] A speed reducer according to an embodiment of the present invention includes: a gear carrier having a recess; a crankshaft disposed in the recess; and a restricting member disposed on the bottom surface of the recess to restrict the crankshaft from moving in a direction toward the bottom surface of the crankshaft along the rotation axis of the crankshaft.

[0014] A speed reducer according to an embodiment of the present invention includes a crankshaft bearing that is provided on the inner peripheral surface of the recess at a position separated from the bottom surface in the direction along the rotation axis of the crankshaft and supports the crankshaft. In one embodiment, the restricting member restricts the crankshaft bearing from moving toward the bottom surface side in the rotation axis direction.

[0015] In one embodiment of the present invention, the inner peripheral surface has: a support surface that supports the crankshaft bearing; and a relief portion that is provided between the support surface and the bottom surface in the rotation axis direction, and the diameter of the relief portion is larger than the diameter of the support surface.

[0016] In one embodiment of the present invention, the relief portion is provided at a position separated from the bottom surface in the rotation axis direction.

[0017] In one embodiment of the present invention, the gear carrier has a through hole extending in the rotation axis direction. A speed reducer according to an embodiment of the present invention includes a sealing member provided in the through hole.

[0018] In one embodiment of the present invention, the outer peripheral surface diameter of the restricting member is smaller than the outer peripheral surface diameter of the crankshaft bearing.

[0019] In one embodiment of the present invention, the diameter of the through hole is smaller than the outer peripheral surface diameter of the restricting member.

[0020] In one embodiment of the present invention, the gear carrier has another recess. A speed reducer according to an embodiment of the present invention includes another restricting member that is provided on the bottom surface of the another recess to restrict the crankshaft from moving in a direction toward the bottom surface of the another recess in the rotation axis direction.

[0021] In one embodiment of the present invention, the crankshaft includes: an eccentric portion; and a journal having an end face opposite to the bottom face, and the restricting member supports the journal at the end face.

[0022] In one embodiment of the present invention, the restricting member is arranged not to rotate about the rotation axis relative to the gear housing.

[0023] In one embodiment of the present invention, the restricting member is arranged to be able to rotate about the rotation axis relative to the gear housing.

[0024] A speed reducer according to one embodiment of the present invention includes: a housing; a gear housing having a recess; a crankshaft bearing provided on a support surface which is a part of the inner peripheral surface of the recess and is located at a position separated from the bottom face of the recess; a crankshaft supported by the crankshaft bearing to relatively rotate one of the gear housing and the housing with respect to the other; and a restricting member arranged to face a relief portion and restrict the crankshaft and the crankshaft bearing from moving in a direction toward the bottom face in the axial direction of the crankshaft, the relief portion being a part of the inner peripheral surface and having a diameter larger than the diameter of the support surface.

[0025] Effects of the invention

[0026] According to one embodiment of the present invention, a speed reducer having a support mechanism for a crankshaft with excellent sealing performance can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a cross-sectional view showing a cross-section taken along the rotation axis of a speed reducer according to one embodiment of the present invention.

[0028] Figure 2 is an enlarged view showing Figure 1 the crankshaft and its support structure of the speed reducer.

[0029] Figure 3 is a view in which the crankshaft is omitted from the enlarged cross-sectional view in Figure 2 above.

[0030] Figure 4 is a cross-sectional view showing a cross-section taken along the rotation axis of a speed reducer according to another embodiment of the present invention.

[0031] Explanation of reference numerals

[0032] 1, 101, Reducer; 12, Crankshaft; 20, Reduction mechanism; 23a, 23b, External gears; 24, Gear carrier; 24a, First gear carrier body; 24b, Second gear carrier body; 24b4, Recess; 24b5, Mounting surface; 27, Internal tooth pin; 28, Housing; 30a, 30b, 30c, 30d, Crankshaft bearings; 35, Cover; 50, 150, Recess; 52b, 152b, Second surface (tool withdrawal part); 60, 160, Limiting member; A1, Central axis; A2, Axis center. Detailed implementation mode

[0033] Hereinafter, various implementation modes of the present invention will be described with reference to the drawings. In addition, the same reference numerals are assigned to the constituent elements common to the respective drawings. It should be noted that for convenience of explanation, the respective drawings are not necessarily drawn to an accurate scale.

[0034] Refer to Figures 1 to 3 , and a reducer 1 according to an implementation mode of the present invention will be described. Figure 1 is a cross-sectional view showing a cross-section of the reducer 1 along the central axis A1, Figure 2 is a diagram showing an enlarged view of the crankshaft provided in the reducer 1 and its supporting structure. Figure 3 is from Figure 2 a diagram in which the crankshaft is omitted, showing a recess for accommodating the crankshaft.

[0035] In these diagrams, a reducer 1 of an eccentric swing type, which is one type of reducer to which the present invention can be applied, is shown. The reducer 1 includes: a spur gear 11, a crankshaft 12, and a reduction mechanism 20. The present invention can also be applied to reducers other than the eccentric swing type as understood by those skilled in the art.

[0036] The spur gear 11 is an example of a rotation transmission mechanism that transmits the rotation input from a drive source (not shown) to the crankshaft 12. The spur gear 11 can also be meshed with an input gear for inputting the rotation from the drive source. The rotation transmission mechanism applicable to the reducer 1 is not limited to the spur gear 11. As the rotation transmission mechanism for the reducer 1, any mechanism capable of transmitting the input from the drive source to the crankshaft 12 can be used.

[0037] The crankshaft 12 is a substantially cylindrical member extending along the axis center A2. In the illustrated implementation mode, the crankshaft 12 is spline-connected to the spur gear 11. Thus, the rotation input from the drive source is transmitted to the crankshaft 12 via the spur gear 11.

[0038] The speed reduction mechanism 20 reduces the rotation input from the crankshaft 12 and transmits it to the target device to be driven. The reduced rotation is output to the target device as rotation about the central axis A1. The speed reducer 1 may also be provided in an industrial robot. In this case, the target device to be driven is, for example, the arm of an industrial robot. The details of the speed reduction mechanism 20 will be described later.

[0039] Next, the crankshaft 12 will be described in more detail. The crankshaft 12 is a substantially cylindrical member extending along the axis A2 and rotates (self-rotates) about the axis A2 due to the rotation input transmitted from the spur gear 11. The crankshaft 12 has: a first journal 12a, a second journal 12b, an eccentric portion 12c, an eccentric portion 12d, and a head 12e. The first journal 12a, the second journal 12b, the eccentric portion 12c, the eccentric portion 12d, and the head 12e may also be formed integrally. In other words, the first journal 12a, the second journal 12b, the eccentric portion 12c, the eccentric portion 12d, and the head 12e may also have a single-piece structure that does not move relative to each other in the circumferential direction about the axis A2.

[0040] The first journal 12a and the second journal 12b each have a cylindrical shape extending in the direction of the axis A2. The eccentric portion 12c is disposed on the X2 side of the first journal 12a in the direction of the axis A2. The eccentric portion 12d is disposed on the X2 side of the eccentric portion 12c in the direction of the axis A2. In one embodiment, both the eccentric portion 12c and the eccentric portion 12d have a cylindrical shape. The eccentric portion 12c and the eccentric portion 12d are circular when viewed from the direction of the axis A2 and have centers at positions radially displaced from the axis A2. That is, the eccentric portion 12c and the eccentric portion 12d are eccentric with respect to the axis A2. The eccentric portion 12c and the eccentric portion 12d have different phases. For example, the phase of the eccentric portion 12c is offset from the phase of the eccentric portion 12d by 180°.

[0041] The head 12e is disposed on the X1 side of the first journal 12a in the direction of the axis A2. That is, the head 12e is disposed on the side opposite to the eccentric portion 12c with respect to the first journal 12a. The head 12e has a substantially cylindrical shape. The head 12e is spline-coupled to the spur gear 11.

[0042] Next, the details of the speed reduction mechanism 20 will be described in more detail. In the illustrated embodiment, the speed reduction mechanism 20 includes: external gears 23a, 23b, a gear carrier 24, and a housing 28. For the speed reduction mechanism 20, using the rotation input from the crankshaft 12, the gear carrier 24 rotates relative to the housing 28 about the central axis A1. The reduced rotation of the speed reduction mechanism 20 is transmitted from the gear carrier 24 or the housing 28 to the target device to be driven. Since the gear carrier 24 or the housing 28 rotates about the central axis A1, the central axis A1 is sometimes referred to as the rotation axis of the speed reducer 1.

[0043] Both the external gear 23a and the external gear 23b have a substantially annular shape. A through hole extending along the central axis A1 is provided at the center of each of the external gears 23a and 23b. For example, a cable is accommodated in the through hole extending along the central axis A1.

[0044] The external gear 23a has a crankshaft through hole 23a1, and the external gear 23b has a crankshaft through hole 23b1. For simplicity of explanation, hereinafter, the crankshaft through hole 23a1 will be simply referred to as the through hole 23a1, and the crankshaft through hole 23b1 will be simply referred to as the through hole 23b1. The through hole 23a1 is a through hole that penetrates the external gear 23a in the axial direction along the center axis A at a position offset radially outward from the center axis A1. The through hole 23b1 is a through hole that penetrates the external gear 23b in the axial direction along the center axis A at a position offset radially outward from the center axis A1. The external gear 23a may also have a plurality of through holes 23a1 arranged along the circumferential direction around the center axis A1. The external gear 23b may also have a plurality of through holes 23b1 arranged along the circumferential direction around the center axis A1.

[0045] The crankshaft 12 is provided in the through hole 23a1 and the through hole 23b1. The through hole 23a1 and the through hole 23b1 accommodate a part of the crankshaft 12. In the illustrated embodiment, the crankshaft 12 is arranged such that the eccentric portion 12c is located in the through hole 23a1 and the eccentric portion 12d is located in the through hole 23b1.

[0046] The external gears 23a, 23b have through holes for accommodating the raised portion 24b2 of the second gear carrier body 24b, which will be described later. Specifically, the external gear 23a has a through hole 23a3 radially outside the central axis A1, and the external gear 23b has a through hole 23b3 radially outside the central axis A1. The through hole 23a3 and the through hole 23b3 are provided at positions opposite to each other. Figure 1 A single through hole 23a3 and a single through hole 23b3 are shown, but the external gear 23a may also have a plurality of through holes 23a3, and the external gear 23b may also have a plurality of through holes 23b3.

[0047] The external gears 23a and 23b both have external teeth. Specifically, the external gear 23a has external teeth 23a2, and the external gear 23b has external teeth 23b2. The shapes of the external teeth 23a2 and 23b2 as observed from the direction of the central axis A1 are, for example, epicycloid curves. The number of external gears provided in the speed reducer 1 is arbitrary. The speed reducer 1 in the illustrated embodiment has two external gears (i.e., the external gear 23a and the external gear 23b), but the number of external gears provided in the speed reducer 1 can be either 1 or more than 3.

[0048] The housing 28 is provided on the radially outer side of the external gears 23a and 23b. The housing 28 has: a housing main body 28a having a hollow cylindrical shape; and a flange 28b provided on the radially outer side of the housing main body 28a. The flange 28b has bolt holes 28c extending parallel to the central axis A1. A part of, for example, a device to be driven (not shown) is connected to the flange 28b. The device to be driven is, for example, an industrial robot. When the device to be driven is an industrial robot, an arm or a base of the industrial robot is connected to the flange 28b. The device to be driven can be connected to the flange 28b by bolts. The base of the industrial robot is used to fix the industrial robot to a fixed surface such as the ground at the installation location of the industrial robot. When the flange 28b is connected to the base of the industrial robot, the rotation of the flange 28b (and thus the housing 28) is restricted.

[0049] A plurality of grooves 28a1 extending along the central axis A1 are formed on the inner peripheral surface of the housing main body 28a. In other words, the housing main body 28a has a plurality of grooves 28a1 extending along the central axis A1. Internal tooth pins 27 are provided in the plurality of grooves 28a1 respectively. The number of internal tooth pins 27 is different from the number of teeth of the external gears 23a and 23b. The number of internal tooth pins 27 is, for example, 1 more than the number of teeth of the external gears 23a and 23b. The internal tooth pins 27 are an example of internal teeth that mesh with the external teeth 23a2 of the external gear 23a and the external teeth 23b2 of the external gear 23b.

[0050] A gear carrier 24 is provided on the radially inner side of the housing 28. The gear carrier 24 is arranged to be rotatable relative to the housing 28 about the central axis A1. The gear carrier 24 has a first gear carrier body 24a and a second gear carrier body 24b. The first gear carrier body 24a is provided at a position on the X1 side with respect to the second gear carrier body 24b in the axial direction along the central axis A1. A gap is provided between the first gear carrier body 24a and the second gear carrier body 24b. The external gears 23a and 23b are arranged in the gap between the first gear carrier body 24a and the second gear carrier body 24b.

[0051] The first gear housing 24a has a substantially disc shape. The second gear housing 24b has: a base portion 24b1 having a substantially disc shape; and a raised portion 24b2 that protrudes in the X1 direction at a position radially outward with respect to the central axis A1. A bolt hole for accommodating the bolt 26 is provided in the raised portion 24b2. The first gear housing 24a and the second gear housing 24b are connected by the bolt 26. The second gear housing 24b has two end faces that intersect the axial direction. An end face of the two end faces of the second gear housing 24b that is on the side opposite to the first gear housing 24a (i.e., the end face on the X2 side) is referred to as the mounting surface 24b5. The object device to be driven is mounted on the speed reducer 1 on the mounting surface 24b5. The second gear housing 24b has a recess 24b4 provided in the mounting surface 24b5. The recess 24b4 extends in the X1 direction from the mounting surface 24b5. The recess 24b4 is used to connect the object device to be driven to the second gear housing 24b. The object device to be driven can be connected to the gear housing 24b by inserting a bolt (not shown) into the recess 24b4. Desirably, the second gear housing 24b has a plurality of recesses 24b4. By fastening the object device to the mounting surface 24b5 using the plurality of recesses 24b4, the object device is fastened to the second gear housing 24b with a strong fastening force. As described above, the object device to be driven can be an industrial robot. When the arm of the industrial robot is connected to the flange 28b, the base of the industrial robot is connected to the gear housing 24b. On the contrary, when the base of the industrial robot is connected to the flange 28b, the arm of the industrial robot is connected to the gear housing 24b. When the gear housing 24b is connected to the base of the industrial robot, the rotation of the gear housing 24b (and thus the gear 24) is restricted.

[0052] The first gear housing 24a is supported by the housing 28 via the main bearing 29a. The second gear housing 24b is supported by the housing 28 via the main bearing 29b. Thus, the first gear housing 24a and the second gear housing 24b are mounted so as to be able to rotate relative to the housing 28. Since the first gear housing 24a and the second gear housing 24b are connected by the bolt 26, the first gear housing 24a and the second gear housing 24b rotate relative to the housing 28 integrally.

[0053] The first gear housing 24a has a through hole 40 for accommodating the crankshaft 12. The through hole 40 of the first gear housing 24a is defined by an inner peripheral surface 42 around the axis A2. The inner peripheral surface 42 extends along the circumferential direction around the axis A2. The first journal 12a of the crankshaft 12 is accommodated in the through hole 40. A crankshaft bearing 30a is provided between the first journal 12a and the inner peripheral surface 42. The first journal 12a of the crankshaft 12 is supported by the first gear housing 24a via the crankshaft bearing 30a.

[0054] A cover 35 that restricts the crankshaft 12 from moving in the X1 direction along the axis A2 is provided in the through-hole 40. The cover 35 has a disc shape. The cover 35 has a through-hole extending along the axis A2 at its radial center. The head 12e of the crankshaft 12 is inserted into this through-hole. External threads are provided on the outer peripheral surface of the cover 35, and internal threads are provided on a part of the inner peripheral surface 42 that defines the through-hole 40. By engaging the external threads of the cover 35 with the internal threads provided on the inner peripheral surface 42, the cover 35 is mounted on the first gear housing 24a. The lower surface of the cover 35 mounted on the first gear housing 24a contacts the end surface of the first journal 12a facing the X1 direction. Thus, the cover 35 mounted on the first gear housing 24a restricts the first journal 12a from moving in the X1 direction.

[0055] The second gear housing 24b has a recess 50 that houses the crankshaft 12. The recess 50 recesses from the end surface of the second gear housing 24b facing the X1 direction toward the X2 direction. As is clearly shown in the illustration where the crankshaft 12 is omitted Figure 3 the recess 50 is defined by a bottom surface 51 and an inner peripheral surface 52. The bottom surface 51 extends in a direction intersecting the axis A2. The bottom surface 51 may also be provided perpendicular to the axis A2.

[0056] The inner peripheral surface 52 extends along the circumferential direction around the axis A2. The inner peripheral surface 52 has: a first surface 52a that is connected to the bottom surface 51; a second surface 52b that is located on the X1 side of the first surface 52a; and a third surface 52c that is located on the X1 side of the second surface 52b. The dimension of the second surface 52b in the radial direction centered on the axis A2 is larger than the dimensions of the first surface 52a and the third surface 52c in the radial direction centered on the axis A2. Thus, the second surface 52b is recessed in a direction away from the axis A2 with respect to the first surface 52a and the third surface 52c. The third surface 52c is provided at a position separated from the bottom surface 51 in the axial direction along the axis A2. The shape of the recess 50 applicable to the present invention is not limited to the illustrated shape. For example, the inner peripheral surface 52 may also have surfaces other than the first surface 52a, the second surface 52b, and the third surface 52c.

[0057] The second gear housing 24b has a support portion 24b3 that protrudes from the first surface 52a toward the axis A2. At least a part of the bottom surface 51 is defined by the surface facing the recess 50 among the surfaces that define the outer shape of the support portion 24b3. The support portion 24b3 has a through-hole 53 that extends in the axial direction along the axis A2. The through-hole 53 may be provided coaxially with the axis A2. The through-hole 53 may have a circular shape when viewed from the direction of the axis A2. In one embodiment, the dimension of the through-hole 53 in the radial direction is smaller than the dimension of the restricting member 60 in the radial direction. That is, the diameter of the through-hole 53 is smaller than the outer diameter of the outer peripheral surface 60a of the restricting member 60.

[0058] A sealing member 70 is provided in the through hole 53. The lubricant can be sealed inside the speed reducer 1 by the sealing member 70. As the sealing member 70, a sealing cover made of synthetic resin can be used.

[0059] The second shaft neck portion 12b of the crankshaft 12 and the restricting member 60 are received in the recess 50 of the second gear housing 24b. The crankshaft 12 is disposed in the recess 50 such that the second shaft neck portion 12b faces the third surface 52c of the inner peripheral surface 52 in the radial direction. The third surface 52c has a circular shape when viewed from the direction of the axis A2. A crankshaft bearing 30b is provided between the second shaft neck portion 12b and the third surface 52c of the inner peripheral surface 52. The crankshaft bearing 30b is supported by the third surface 52c of the inner peripheral surface 52. Therefore, in this specification, the third surface 52c is sometimes referred to as the supporting surface. Thus, the second shaft neck portion 12b of the crankshaft 12 is supported by the second gear housing 24b via the crankshaft bearing 30b.

[0060] The recess 50 may be provided by cutting. When the recess 50 is provided by cutting, the second surface 52b functions as a tool withdrawal portion during cutting. Due to the presence of the second surface 52b that functions as a tool withdrawal portion, the third surface 52c can be machined to have the same diameter from the end on the X1 side to the end on the X2 side in the axial direction along the axis A2 during cutting. In the case where there is no second surface 52b that functions as a tool withdrawal portion, since the cutting tool does not reach the end on the X2 side of the third surface 52c, a bent portion that bends toward the axis A2 remains at the end on the X2 side of the third surface 52c. If the crankshaft bearing 30b is installed in the recess having such a bent portion, the crankshaft bearing 30b interferes with the bent portion, and thus the crankshaft bearing 30b cannot be accurately installed in the recess 50. In one embodiment, by providing the second surface 52b that functions as a tool withdrawal portion, the third surface 52c can be made to have the same diameter up to its end on the X2 side in the axial direction along the axis A2, and thus the installation accuracy of the crankshaft bearing 30b can be improved.

[0061] The restricting member 60 is disposed on the bottom surface 51 of the recess 50. The restricting member 60 has, for example, an annular shape. In one embodiment, the restricting member 60 is formed of a material having a relatively high hardness, such as stainless steel. The restricting member 60 has: an outer peripheral surface 60a; an inner peripheral surface 60b; a first end surface 60c that connects the outer peripheral surface 60a and the inner peripheral surface 60b; and a second end surface 60d that connects the outer peripheral surface 60a and the inner peripheral surface 60b. The outer shape of the restricting member 60 is defined by the outer peripheral surface 60a, the inner peripheral surface 60b, the first end surface 60c, and the second end surface 60d. The second end surface 60d is located on the X2 side with respect to the first end surface 60c. The restricting member 60 contacts the bottom surface 51 of the recess 50 at the second end surface 60d. The second gear housing 24b supports the restricting member 60 by way of the bottom surface 51 (that is, by way of the supporting portion 24b3). The restricting member 60 is restricted from moving in the X2 direction in the axial direction since it is supported by the bottom surface 51.

[0062] In the recess 50, the restricting member 60 contacts the second journal portion 12b of the crankshaft 12 at its first end surface 60c. The restricting member 60 supports the second journal portion 12b by way of the first end surface 60c, thereby restricting the crankshaft 12 from moving in the direction toward the bottom surface 51 (that is, the X2 direction) in the axial direction.

[0063] In one embodiment, the restricting member 60 also contacts the crankshaft bearing 30b at its first end surface 60c. The restricting member 60 supports the crankshaft bearing 30b by way of the first end surface 60c, thereby restricting the crankshaft bearing 30b from moving in the direction toward the bottom surface 51 (that is, the X2 direction) in the axial direction.

[0064] In the illustrated embodiment, the diameter of the outer peripheral surface 60a of the restricting member 60 is smaller than the diameter of the outer peripheral surface of the crankshaft bearing 30b. That is, the dimension in the radial direction of the outer peripheral surface 60a of the restricting member 60 is smaller than the dimension in the radial direction of the outer peripheral surface of the retainer 31b of the crankshaft bearing 30b.

[0065] In one embodiment, the restricting member 60 is disposed in the recess 50 so as to be rotatable about the axis A2 relative to the second gear housing 24b. For example, the recess 50 is arranged such that the first surface 52a has a circular shape when viewed from the direction of the axis A2, and the restricting member 60 is arranged such that the outer peripheral surface 60a has a circular shape concentric with the first surface 52a when viewed from the direction of the axis A2. Thus, when the crankshaft 12 rotates about the axis A2, due to the force in the circumferential direction of the axis A2 acting from the crankshaft 12, the restricting member 60 rotates about the axis A2 in the same direction as the crankshaft 12. In other embodiments, the restricting member 60 may be arranged not to rotate about the axis A2 relative to the second gear housing 24b. For example, the recess 50 is arranged such that the first surface 52a has a polygonal shape (e.g., hexagonal shape) when viewed from the direction of the axis A2, and the restricting member 60 is arranged such that the outer peripheral surface 60a has a polygonal shape (e.g., hexagonal shape) that fits the first surface 52a when viewed from the direction of the axis A2. Thus, even when the crankshaft 12 rotates about the axis A2 and a force in the circumferential direction of the axis A2 acts on the restricting member 60 from the crankshaft 12, the restricting member 60 does not rotate about the axis A2.

[0066] A crankshaft bearing 30c is provided between the eccentric portion 12c and the through hole 23a1, and a crankshaft bearing 30d is provided between the eccentric portion 12d and the through hole 23b1. Thus, the outer gear 23a is supported by the crankshaft bearing 30c on the eccentric portion 12c of the crankshaft 12, and the outer gear 23b is supported by the crankshaft bearing 30d on the eccentric portion 12d of the crankshaft 12.

[0067] In the illustrated embodiment, the crankshaft bearings 30a to 30d are all needle bearings. The crankshaft bearing 30c and the crankshaft bearing 30d may also be bearings of other types than needle bearings. The crankshaft bearing 30a has a retainer 31a and rolling elements 32a held by the retainer 31a. The crankshaft bearing 30b has a retainer 31b and rolling elements 32b held by the retainer 31b. The crankshaft bearing 30c has a retainer 31c and rolling elements 32c held by the retainer 31c. The crankshaft bearing 30d has a retainer 31d and rolling elements 32d held by the retainer 31d.

[0068] The shapes, structures, and arrangements of the constituent components that make up the speed reducer 1 are not limited to the shapes, structures, and arrangements clearly shown in this specification and the accompanying drawings. In particular, the shape, structure, and arrangement of the restricting member 60 are not limited to the illustrated form, the shapes, structures, and arrangements clearly described in this specification. At least one of the crankshaft bearings 30a to 30d may also be a type of bearing other than a needle bearing that can support the crankshaft 12. The shapes, structures, and arrangements of the gear carrier 24 and the housing 28 are also not limited to the illustrated form, the shapes, structures, and arrangements clearly described in this specification.

[0069] Next, the operation of the speed reducer 1 will be described. When the spur gear 11 rotates due to the rotational driving force from the drive source, this rotation is transmitted from the head 12e that meshes with the spur gear 11 to the crankshaft 12. Due to the rotation input from this drive source, the eccentric portions 12c and 12d of the crankshaft 12 eccentrically rotate about the axis A2. Due to the rotation of the crankshaft 12, the eccentric portions 12c and 12d respectively push the external gears 23a and 23b in the circumferential direction. Therefore, when the crankshaft 12 rotates one revolution, the external gears 23a and 23b relatively rotate with respect to the housing 28 by an amount corresponding to the difference between the number of internal tooth pins 27 of the housing 28 and the number of teeth of the external gears 23a and 23b. In this way, the rotation of the crankshaft 12 is decelerated at a reduction ratio of (the number of teeth of the external gears 23a and 23b) / (the number of internal tooth pins 27 - the number of teeth of the external gears 23a and 23b) and transmitted to the gear carrier 24 or the housing 28. When the self-rotation of the gear carrier 24 is restricted, the housing 28 rotates about the central axis A1 by an amount corresponding to one tooth, which is the difference between the number of internal tooth pins 27 and the number of teeth of the external gears 23a and 23b. When the self-rotation of the housing 28 is restricted, the gear carrier 24 rotates about the central axis A1.

[0070] As described above, the rotation input from the drive source is decelerated by the speed reduction mechanism 20 at the above reduction ratio and output from the gear carrier 24 or the housing 28 to the target device.

[0071] Next, with reference to Figure 4 Another embodiment of the speed reducer 101 of the present invention will be described. Another embodiment of the speed reducer 101 of the present invention differs from the speed reducer 1 in that a recess 150 is provided in the first gear carrier body 24a, and a restricting member 160 that restricts the movement of the crankshaft 12 in the X1 direction is provided in this recess 150. That is, in the speed reducer 1, the movement of the crankshaft 12 in the X1 direction is restricted by the cover 35, whereas in the speed reducer 101, the movement of the crankshaft 12 in the X1 direction is restricted by the restricting member 160. For Figure 4 Among the constituent elements of the speed reducer 101 shown, those that are the same as or similar to the Figure 1 constituent elements of the speed reducer 1 shown are labeled the same asFigure 1 For these components with the same or similar reference numerals, detailed descriptions thereof are omitted.

[0072] The first gear housing 24a has a recess 150 that houses the crankshaft 12. The recess 150 is recessed from the end face of the first gear housing 24a facing the X2 direction toward the X1 direction. The recess 150 is defined by a bottom surface 151 and an inner peripheral surface 152. The bottom surface 151 extends in a direction intersecting the axis A2. The bottom surface 151 may be set orthogonal to the axis A2. The inner peripheral surface 152 extends along the circumferential direction around the axis A2. The inner peripheral surface 152 has: a first surface 152a that is connected to the bottom surface 151; a second surface 152b that is located on the X2 side of the first surface 152a; and a third surface 152c that is located on the X2 side of the second surface 152b. The dimension of the second surface 152b in the radial direction centered on the axis A2 is larger than the dimensions of the first surface 152a and the third surface 152c in the radial direction centered on the axis A2. The third surface 152c is disposed at a position separated from the bottom surface 151 in the axial direction along the axis A2. The recess 150 may also have the same or substantially the same shape as the recess 50.

[0073] The first gear housing 24a has a support portion 24a3 that protrudes from the first surface 152a toward the axis A2. The support portion 24a3 has a through hole 153 that extends in the axial direction along the axis A2. The through hole 153 may be disposed coaxially with the axis A2. The through hole 153 may have a circular shape when viewed from the direction of the axis A2. In one embodiment, the dimension of the through hole 153 in the radial direction is smaller than the dimension of the restricting member 160 in the radial direction. That is, the diameter of the through hole 153 is smaller than the outer diameter of the outer peripheral surface of the restricting member 160.

[0074] The first shaft neck 12a of the crankshaft 12 and the restricting member 160 are housed in the recess 150 of the first gear housing 24a. The crankshaft 12 is disposed in the recess 150 such that the first shaft neck 12a faces the third surface 152c of the inner peripheral surface 152 in the radial direction. The third surface 152c has a circular shape when viewed from the direction of the axis A2. A crankshaft bearing 30a is provided between the first shaft neck 12a and the third surface 152c of the inner peripheral surface 152. The crankshaft bearing 30b is supported by the third surface 152c of the inner peripheral surface 152. Thus, the first shaft neck 12a of the crankshaft 12 is supported by the first gear housing 24a via the crankshaft bearing 30a.

[0075] The recess 150 can also be provided by machining in the same manner as the recess 50. When the recess 150 is provided by machining, the second surface 152b functions as a tool withdrawal surface during the machining. Thereby, the third surface 152c can be machined to have the same diameter from the end on the X1 side to the end on the X2 side in the axial direction along the axis A2. Thereby, the crankshaft bearing 30a can be accurately mounted in the recess 150.

[0076] The restricting member 160 is provided on the bottom surface 151 of the recess 150. The restricting member 160 is an annular member. The restricting member 160 may have the same or substantially the same shape as the restricting member 60. The restricting member 160 contacts the bottom surface 151 of the recess 150 at one of its end faces. The first gear housing 24a supports the restricting member 160 at the bottom surface 151. The restricting member 160 is supported on the bottom surface 151 so as to be restricted from moving in the X1 direction in the axial direction. The restricting member 160 contacts the first shaft neck portion 12a of the shaft 12 at the other end face thereof. The restricting member 60 supports the first shaft neck portion 12a by the end face facing the X2 direction, thereby restricting the crankshaft 12 from moving in the direction toward the bottom surface 151 (i.e., the X1 direction) in the axial direction. In one embodiment, the restricting member 160 also contacts the crankshaft bearing 30a at the other end face thereof. The restricting member 160 supports the crankshaft bearing 30a at its end face, thereby restricting the crankshaft bearing 30a from moving in the direction toward the bottom surface 151 (i.e., the X1 direction) in the axial direction.

[0077] In one embodiment, the diameter of the outer peripheral surface of the restricting member 160 is smaller than the diameter of the outer peripheral surface of the crankshaft bearing 30a. That is, the dimension in the radial direction of the outer peripheral surface of the restricting member 160 is smaller than the dimension in the radial direction of the outer peripheral surface of the retainer 31a of the crankshaft bearing 30a.

[0078] In one embodiment, the restricting member 160 is provided in the recess 150 so as to be rotatable about the axis A2 relative to the first gear housing 24a. In other embodiments, the restricting member 160 is provided so as not to rotate about the axis A2 relative to the first gear housing 24a.

[0079] Next, the effects of the above-described embodiments will be described. According to one of the above embodiments, the restricting member 60 provided on the bottom surface 51 of the recess 50 of the second gear housing 24b can restrict the movement of the crankshaft 12 in one direction (X2 direction) along the axis A2. The movement of the restricting member 60 in the axial direction with respect to the second gear housing 24b is restricted by the bottom surface 51 (that is, the supporting portion 24b3). Therefore, there is no need to provide an external thread on the outer peripheral surface 60a of the restricting member 60 in order to mount the restricting member 60 on the second gear housing 24b. Thus, compared with a conventional speed reducer that supports the crankshaft 12 by a threaded cover, the speed reducer 1 of one embodiment of the present invention can achieve higher sealing performance.

[0080] According to one of the above embodiments, the restricting member 60 is provided in contact with the crankshaft bearing 30b. Thereby, the restricting member 60 can restrict the movement of the crankshaft bearing 30b in one direction (X2 direction) along the axis A2. According to one of the above embodiments, the restricting member 60 supports the end surface of the second shaft neck portion 12b of the crankshaft 12 facing the X2 side direction. Thereby, the restricting member 60 can restrict the movement of the crankshaft 12 in one direction (X2 direction) along the axis A2.

[0081] According to one of the above embodiments, the inner peripheral surface 52 of the recess 50 has a second surface 52b (relief portion) having an inner diameter larger than the inner diameters of the first surface 52a and the third surface 52c between the first surface 52a and the third surface 52c. The second surface 52b that functions as a relief portion in the cutting process is provided between the first surface 52a and the third surface 52c, so that the third surface 52c can be machined to have the same diameter from the end on the X1 side to the end on the X2 side in the axial direction along the axis A2. Thereby, the installation accuracy of the crankshaft bearing 30b can be improved.

[0082] According to one of the above embodiments, the supporting portion 24b3 of the second gear housing 24b has a through hole 53, and a sealing member 70 is provided in the through hole 53. The lubricant can be sealed inside the speed reducer 1 by using the sealing member 70.

[0083] In one of the above embodiments, the diameter of the outer peripheral surface 60a of the restricting member 60 is smaller than the diameter of the outer peripheral surface of the crankshaft bearing 30b. In a conventional speed reducer with a threaded cover, since the movement of the crankshaft bearing in the axial direction is restricted and the external thread on the outer peripheral surface of the threaded cover meshes with the internal thread on the inner peripheral surface of the gear housing, the diameter of the outer peripheral surface of the threaded cover is larger than the outer diameter of the crankshaft bearing. In contrast, in one embodiment of the present invention, since the movement of the restricting member 60 in the axial direction is restricted by the supporting portion 24b3 of the second gear housing 24b, the diameter of the outer peripheral surface 60a of the restricting member 60 can be made smaller than the diameter of the outer peripheral surface of the crankshaft bearing 30b. Thereby, the radial dimension of the restricting member 60 can be miniaturized.

[0084] According to the above-described embodiment, the diameter of the through-hole 53 of the support portion 24b3 of the second gear housing 24b is smaller than the diameter of the outer peripheral surface 60a of the restricting member 60. Thus, the through-hole 53 provided in the second gear housing 24b at a position facing the crankshaft 12 can be made to have a small diameter. Therefore, a wider area for providing the recess 24b4 can be ensured on the mounting surface 24b5 of the second gear housing 24b. Thus, the target device can be more reliably mounted on the mounting surface 24b5 of the second gear housing 24b.

[0085] According to the above-described embodiment, the restricting member 160 provided on the bottom surface 151 of the recess 150 of the first gear housing 24a can restrict the movement of the crankshaft 12 in the other axial direction. Thus, the airtightness of the speed reducer can be further improved.

[0086] The dimensions, materials, and arrangements of the respective components described in this specification are not limited to the dimensions, materials, and arrangements of the respective components clearly described in the embodiments, and each of these components can be deformed into any dimensions, materials, and arrangements that can be included in the scope of the present invention. In addition, components not clearly described in this specification can be added to the described embodiments, and a part of the components described in each embodiment can also be omitted.

[0087] The above-described embodiments can also be appropriately combined. A form achieved by combining a plurality of embodiments can also be an embodiment of the present invention.

Claims

1. A speed reducer, wherein, the speed reducer includes: a gear carrier having a recess; a crankshaft disposed in the recess, the crankshaft having an eccentric portion and a journal, the journal having an end face opposite to the bottom face of the recess; and a restricting member disposed on the bottom face of the recess, the restricting member having a first end face and a second end face, the restricting member contacting the end face of the journal of the crankshaft at the first end face and contacting the bottom face of the recess at the second end face, thereby restricting the crankshaft from moving in a direction toward the bottom face along the rotation axis of the crankshaft.

2. The speed reducer according to claim 1, wherein, the speed reducer includes a crankshaft bearing disposed on the inner peripheral surface of the recess at a position separated from the bottom face in a direction along the rotation axis of the crankshaft and supporting the crankshaft, the restricting member restricts the crankshaft bearing from moving toward the bottom face side in the rotation axis direction.

3. The speed reducer according to claim 2, wherein, the inner peripheral surface has: a supporting surface for supporting the crankshaft bearing; and a relief portion disposed between the supporting surface and the bottom face in the rotation axis direction, the diameter of the relief portion being larger than the diameter of the supporting surface.

4. The speed reducer according to claim 3, wherein, the relief portion is disposed at a position separated from the bottom face in the rotation axis direction.

5. The speed reducer according to claim 4, wherein, the gear carrier has a through hole extending in the rotation axis direction, the speed reducer includes a sealing member disposed in the through hole.

6. The speed reducer according to claim 5, wherein, the outer peripheral surface diameter of the restricting member is smaller than the outer peripheral surface diameter of the crankshaft bearing.

7. The speed reducer according to claim 6, wherein, the diameter of the through hole is smaller than the outer peripheral surface diameter of the restricting member.

8. The speed reducer according to any one of claims 2 to 7, wherein, the gear carrier has another recess, the speed reducer includes another restricting member disposed on the bottom face of the another recess, restricting the crankshaft from moving in a direction toward the bottom face of the another recess in the rotation axis direction.

9. The speed reducer according to any one of claims 1 to 7, wherein, the restricting member supports the journal at the end face.

10. The speed reducer according to any one of claims 1 to 7, wherein, the restricting member is arranged not to rotate about the rotation axis relative to the gear carrier.

11. The speed reducer according to any one of claims 1 to 7, wherein, the restricting member is arranged to be able to rotate about the rotation axis relative to the gear carrier.

12. A speed reducer, wherein, the speed reducer includes: a housing; a gear carrier having a recess; a crankshaft bearing disposed on a supporting surface, the supporting surface being a part of the inner peripheral surface of the recess and located at a position separated from the bottom face of the recess; A crankshaft supported by the crankshaft bearings to relatively rotate one of the gear bracket and the housing with respect to the other, the crankshaft including an eccentric portion and a journal, the journal having an end face facing the bottom face of the recess; and A restricting member provided to face the relief portion, the restricting member having a first end face and a second end face, the restricting member contacting the end face of the journal of the crankshaft at the first end face and contacting the bottom face of the recess at the second end face, thereby restricting the crankshaft and the crankshaft bearings from moving in a direction toward the bottom face in the axial direction of the crankshaft, the relief portion being a part of the inner circumferential surface and having a diameter larger than the diameter of the support surface.

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