Gear motor, motor, and motor shaft production method

Abstract

Provided is a gear motor comprising a motor that has a motor shaft 16 and a speed reducer that has an input shaft 26. The motor shaft 16 is provided with a hollow part 64 into which the input shaft 26 is inserted. The gear motor comprises a connection structure 60 that is provided in a hollow space 66 inside the hollow part 64 and that connects the motor shaft 16 and the input shaft 26 in a manner enabling integral rotation, and a shaft seal member 62 that is disposed between the motor shaft 16 and the input shaft 26 and that seals the hollow space 66. The connection structure 60 may be a spline structure.

Description

Manufacturing Method of Gear Motor, Motor, and Motor Shaft

[0001] The present disclosure relates to a gear motor and a motor.

[0002] Patent Document 1 discloses a gear motor including a motor having a motor shaft and a speed reducer having an input shaft. This motor shaft has a hollow portion into which the input shaft is inserted. The input shaft is connected to the motor shaft so as to be rotatable integrally therewith by a connection structure such as a spline structure provided in the hollow space within the hollow portion of the motor shaft.

[0003] Japanese Patent Application Laid-Open No. 2022-024281

[0004] There may be a requirement for lubrication of a connection structure such as a spline structure. In this case, a means for lubricating the connection structure using a lubricant enclosed in the internal space of the speed reducer is assumed. However, in this case, there is a problem that the hollow space of the motor shaft and the internal space of the speed reducer need to be constantly communicated, and the structure of the gear motor is restricted.

[0005] One object of the present disclosure is to provide a technique for relaxing the restriction on the structure of a gear motor in lubricating a connection structure.

[0006] One aspect of the present disclosure is a gear motor. This gear motor is a gear motor including a motor having a motor shaft and a speed reducer having an input shaft, wherein the motor shaft has a hollow portion into which the input shaft is inserted, a connection structure provided in the hollow space within the hollow portion for connecting the motor shaft and the input shaft so as to be rotatable integrally therewith, and a seal member disposed between the motor shaft and the input shaft for sealing the hollow space.

[0007] Another aspect of the present disclosure is a motor. This motor is a motor having a motor shaft, wherein the motor shaft has a hollow portion into which an input shaft of a speed reducer is inserted, the motor shaft is connected to the input shaft so as to be rotatable integrally therewith by a connection structure provided in the hollow space within the hollow portion, and includes a seal member disposed between the input shaft and the motor shaft for sealing the hollow space.

[0008] According to this disclosure, constraints on the structure of the gear motor can be relaxed when it comes to lubricating the connection structure.

[0009] This is a side cross-sectional view of the gear motor of the first embodiment. This is an enlarged view of the area around the hollow portion of the motor shaft in Figure 1. Figure 3(A) is a schematic explanatory diagram showing the state before the forging die is inserted into the hollow portion of the motor shaft material, and Figure 3(B) is a schematic explanatory diagram showing the state after the forging die is inserted. This is a schematic explanatory diagram showing the cutting process of the outer circumference of the motor shaft material. This is a schematic explanatory diagram showing the cutting process of the motor shaft material by skiving. This is a schematic explanatory diagram showing the cutting process of the motor shaft material by gear shaping. This is a view of the gear motor of the second embodiment from the same viewpoint as in Figure 1.

[0010] Embodiments for implementing the gear motor of this disclosure are described below. The same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. For the sake of clarity, components are omitted, enlarged, or reduced in each drawing. The drawings should be viewed in accordance with the orientation of the reference numerals.

[0011] (First Embodiment) Refer to Figure 1. In this specification, the direction along the rotational centerline of the motor shaft 16 is simply referred to as the axial direction, and the radial and circumferential directions with respect to that rotational centerline are simply referred to as the radial direction and circumferential direction, respectively. In the axial direction, the side of the motor 12 with the reduction gear 14 (left side of Figure 1) is referred to as the load side, and the opposite side in the axial direction (right side of Figure 1) is referred to as the non-load side.

[0012] The gear motor 10 is incorporated into the master machine. The master machine is, for example, at least part of various machines such as (1) industrial machinery such as machine tools and construction machinery, (2) robots such as industrial robots and service robots, (3) transport equipment such as conveyors, and (4) vehicles.

[0013] The gear motor 10 comprises a motor 12 and a reduction gear 14. The gear motor 10 can drive a driven element that is part of the main machine by outputting the rotation generated by the motor 12, after the reduction gear 14 has reduced the rotation.

[0014] The motor 12 comprises a motor shaft 16, a stator 18 and rotor 20 that rotate the motor shaft 16, a motor casing 22 that houses the motor shaft 16 and the like, and at least two motor shaft bearings 24A, 24B that rotatably support the motor shaft 16. Details of the motor shaft 16 will be described later.

[0015] The stator 18 is fixed to the motor casing 22 by interference fit or the like, and is capable of generating a rotating magnetic field. The type of stator 18 is not particularly limited, and may be a core-type stator, a coreless stator, etc.

[0016] The rotor 20 is fixed to the motor shaft 16 by interference fit or the like. The rotor 20 can rotate together with the motor shaft 16 due to the rotating magnetic field generated by the stator 18. The type of rotor 20 is not particularly limited and may be a magnetic rotor, a wound rotor, a squirrel-cage rotor, a coreless rotor, etc.

[0017] A motor internal space 27 is provided inside the motor casing 22 for housing the stator 18 and rotor 20. The motor casing 22 comprises a motor casing body 22a and a load-side motor cover 22b provided on the load side relative to the motor casing body 22a. In this embodiment, the motor casing body 22a comprises a cylindrical motor frame 22c and a non-load-side motor cover 22d provided on the non-load side relative to the motor frame 22c. The load-side motor cover 22b is connected to the motor casing body 22a by bolts B1 and covers the motor internal space 27 from the load side.

[0018] The two motor shaft bearings 24A and 24B include a load-side motor shaft bearing 24A positioned on the load side and a non-load-side motor shaft bearing 24B positioned on the non-load side. Each motor shaft bearing 24A and 24B is supported by the motor casing 22. In this embodiment, the load-side motor shaft bearing 24A is supported by the load-side motor cover 22b, and the non-load-side motor shaft bearing 24B is supported by the non-load-side motor cover 22d.

[0019] The gearbox 14 includes an input shaft 26 to which rotation is input from the motor shaft 16, a reduction mechanism 28 that reduces the rotation of the input shaft 26, a gearbox casing 30 that houses at least a part of the reduction mechanism 28, an adapter 31 that connects the gearbox casing 30 and the motor casing 22, an output member 32 that outputs the rotation transmitted from the reduction mechanism 28, and at least two input shaft bearings 34A, 34B that rotatably support the input shaft 26. In this embodiment, the gearbox 14 includes a load-side member 36 provided on the load side relative to the reduction mechanism 28. In this embodiment, the load-side member 36 constitutes the output member 32. In addition, depending on the type of gearbox 14, the gearbox casing 30 may also serve as the output member 32.

[0020] The reduction gear 14 in this embodiment uses a center crank type eccentric oscillating reduction gear mechanism 28. The reduction gear 14 using this mechanism comprises a crankshaft 40 having an eccentric portion 38, an external gear 42 that oscillates due to the eccentric portion 38, and an internal gear 44 that meshes with the external gear 42.

[0021] In this embodiment, the input shaft 26 is composed of the shaft portion 46 (described later) of the crankshaft 40. Details of the input shaft 26 will be described later. The crankshaft 40 has at least one (two in this case) eccentric portion 38. The eccentric portion 38 has a circular shape that is eccentric with respect to the rotational centerline of the crankshaft 40. In this embodiment, the eccentric portion 38 is provided separately from the shaft portion 46 which is provided radially inward of the crankshaft 40 relative to the eccentric portion 38. Alternatively, the shaft portion 46 and the eccentric portion 38 may be provided integrally from the same material.

[0022] The reduction mechanism 28 in this embodiment is composed of an external gear 42 and an internal gear 44. The rotation of the input shaft 26 is transmitted to the reduction mechanism 28 directly or indirectly. The reduction mechanism 28 can reduce the rotation of the input shaft 26 that has been transmitted to it, and then transmit a rotation that is reduced even further than that of the input shaft 26 to the output member 32.

[0023] In this embodiment, the external gear 42 is provided in accordance with the eccentric portion 38 and is pivotable by the corresponding eccentric portion 38. A part of the internal gear 44 in this embodiment is provided on the inner circumference of the reduction gear casing 30. The internal gear 44 comprises a gear body 44a which is also the reduction gear casing 30, and an internal tooth portion 44b provided on the gear body 44a. In this embodiment, the internal tooth portion 44b is composed of a pin rotatably supported by the gear body 44a and a roller through which the pin is inserted. Alternatively, the internal tooth portion 44b may be integrally provided from the same material as the gear body 44a.

[0024] A reduction gear casing 30 is provided with an internal space 48 for the reduction gear 28, which houses at least a portion of the reduction mechanism 28. Various components of the reduction mechanism 28 are housed in the internal space 48, depending on the type of reduction mechanism 28. In this embodiment, the internal space 48 houses the external gear 42 as well as the pins and rollers that constitute the internal teeth 44b of the internal gear 44. For example, if the internal gear 44 is separate from the reduction gear casing 30, the internal space 48 may house the internal gear 44.

[0025] The internal space 48 of the reducer is sealed by a plurality of reducer sealing members 50A and 50B. The reducer sealing members 50A and 50B in this embodiment include a first reducer sealing member 50A positioned between the adapter 31 and the input shaft 26, and a second reducer sealing member 50B positioned between the reducer casing 30 and the load-side member 36. The number, position, etc., of the reducer sealing members 50A and 50B may vary depending on the type of reducer 14. At least a lubricant for lubricating the reduction mechanism 28 is sealed in the internal space 48 of the reducer.

[0026] The adapter 31 is connected to the gearbox casing 30 by bolts B3 or the like. The adapter 31 covers the internal space 48 of the gearbox from the non-load side.

[0027] A pin 52 protrudes from the load-side member 36. The pin 52 directly or indirectly contacts the external gear 42, enabling synchronization of the rotation component of the external gear 42 with the load-side member 36. In this embodiment, the load-side member 36 comprises a flange portion 36a provided on the load side relative to the reduction mechanism 28, and an output shaft portion 36b provided on the load side relative to the flange portion 36a and having a smaller diameter than the flange portion 36a. The output shaft portion 36b of the load-side member 36, which becomes the output member 32, is connected to a driven element (not shown).

[0028] The two input shaft bearings 34A and 34B include a load-side input shaft bearing 34A positioned on the load side and a non-load-side input shaft bearing 34B positioned on the non-load side. In this embodiment, the load-side input shaft bearing 34A is supported by a load-side member 36, and the non-load-side input shaft bearing 34B is supported by an adapter 31.

[0029] The motor casing 22 of the motor 12 and the reduction gear casing 30 of the reduction gear 14 are detachably connected by bolts B2 or the like. In this embodiment, the motor casing 22 and the reduction gear casing 30 are connected via an adapter 31, but they may be connected without the adapter 31. In this embodiment, the load-side motor cover 22b of the motor casing 22 and the adapter 31 are fastened together by bolts B2. When these are connected, the motor shaft 16 and the input shaft 26 are connected so as to be able to rotate together via a connection structure 60, which will be described later. The motor 12 and the reduction gear 14 can be separated by releasing the fastening by bolts B2. When the motor 12 and the reduction gear 14 are separated, the internal space 48 of the reduction gear is kept sealed by a plurality of reduction gear sealing members 50A, 50B.

[0030] An example of the operation of the gear motor 10 described above will now be explained. The motor shaft 16 rotates together with the rotor 20 due to the rotating magnetic field generated by the stator 18. The input shaft 26 rotates together with the motor shaft 16. The rotation of the input shaft 26 is transmitted to the reduction mechanism 28, where it is reduced in speed, and then transmitted from the reduction mechanism 28 to the output member 32. As a result, the output member 32 rotates, and this rotation is output from the output member 32 to the driven body.

[0031] Refer to Figure 2. The motor shaft 16 and input shaft 26 will be described in detail. In addition to the motor shaft 16 and input shaft 26, the gear motor 10 in this embodiment includes a connection structure 60 that connects the motor shaft 16 and the input shaft 26 so that they can rotate together, and a shaft sealing member 62 that is positioned between the motor shaft 16 and the input shaft 26.

[0032] The motor shaft 16 has a hollow section 64 into which the input shaft 26 is inserted. The hollow section 64 opens at the load-side end of the motor shaft 16. The hollow section 64 does not penetrate axially and has a bottom on the non-load side, forming a bottomed hole.

[0033] The hollow portion 64 includes a motor shaft side connection portion 64a that is connected to the input shaft 26 by a connection structure 60. In this embodiment, the motor shaft side connection portion 64a is provided with a female spline portion 70 that is part of the connection structure 60. The hollow portion 64 in this embodiment includes a large inner diameter portion 64b that is provided on the load side of the motor shaft side connection portion 64a. The large inner diameter portion 64b has a larger inner diameter than the motor shaft side connection portion 64a. It can also be said that the large inner diameter portion 64b has a larger inner diameter than the female spline portion 70. Here, the inner diameter of the motor shaft side connection portion 64a and the female spline portion 70 refers to the diameter of the inscribed circle that is inscribed in the motor shaft side connection portion 64a, with the rotational center line of the motor shaft 16 as the center of the circle. The large inner diameter portion 64b extends straight in the axial direction. This condition only needs to be met in areas other than the mounting groove 74, if the mounting groove 74, which will be described later, is formed in the large inner diameter portion 64b.

[0034] The input shaft 26 is provided with an input shaft side connection portion 26a that is connected to the motor shaft 16 by a connection structure 60. In this embodiment, the input shaft side connection portion 26a is provided with a male spline portion 68 that is part of the connection structure 60. The input shaft 26 in this embodiment is provided with a large outer diameter portion 26b that is located on the load side of the input shaft side connection portion 26a. The large outer diameter portion 26b has a larger outer diameter than the input shaft side connection portion 26a. It can also be said that the large outer diameter portion 26b has a larger outer diameter than the male spline portion 68. Here, the outer diameter of the input shaft side connection portion 26a and the male spline portion 68 refers to the diameter of the circumscribed circle that circumscribes the input shaft side connection portion 26a, with the rotational center line of the input shaft 26 as the center of the circle. The large outer diameter portion 26b extends straight in the axial direction. This condition only needs to be met in areas other than the mounting groove 74, which will be described later, if the mounting groove 74 is formed in the large outer diameter portion 26b.

[0035] The input shaft 26 does not necessarily have a through hole that penetrates it axially. It can also be said that the input shaft 26 does not have a communication hole that connects the hollow space 66 located within the hollow portion 64 of the motor shaft 16 to the internal space 48 of the reduction gear.

[0036] The connection structure 60 is provided in the hollow space 66 within the motor shaft 16, between the hollow portion 64 of the motor shaft 16 and the input shaft 26. The connection structure 60 in this embodiment is a spline structure having a male spline portion 68 and a female spline portion 70 that mesh with each other. The specific example of the connection structure 60 is not particularly limited. For example, the connection structure 60 may be a key structure comprising a keyway provided in the input shaft side connection portion 26a of the input shaft 26 and the motor shaft side connection portion 64a of the motor shaft 16, and a key that fits into the keyway.

[0037] The male spline portion 68 is provided on the outer circumference of the input shaft 26, more specifically on the input shaft side connection portion 26a. The male spline portion 68 has a plurality of male spline teeth that protrude radially outward. The male spline teeth are spaced apart in the circumferential direction.

[0038] The female spline portion 70 is provided on the inner circumference of the hollow portion 64 of the motor shaft 16, more specifically, on the motor shaft side connection portion 64a. The female spline portion 70 has a plurality of female spline teeth that protrude radially inward. The plurality of female spline teeth are provided with spacing in the circumferential direction. Spline grooves 70a are formed between adjacent female spline teeth. Each of the plurality of male spline teeth is positioned within the spline grooves 70a, allowing each male spline tooth and each female spline tooth to mesh.

[0039] A radial gap 72 is provided between the hollow portion 64 of the motor shaft 16 and the input shaft 26 when their centerlines coincide. The radial gap 72 allows for relative radial movement of the input shaft 26 with respect to the motor shaft 16, assuming that all members other than the input shaft 26 are omitted from the reduction gear 14. The radial gap 72 is provided throughout the entire axial range where the motor shaft 16 and the input shaft 26 overlap radially. For example, the radial gap 72 is provided in the area including the space between the male spline portion 68 of the input shaft 26 and the female spline portion 70 of the motor shaft 16. Here, the radial gap 72 between these spline portions 68 and 70 is highlighted. This makes it easier to insert and remove the input shaft 26 from the hollow portion 64 of the motor shaft 16, improving workability during assembly and disassembly of the gear motor 10.

[0040] In this embodiment, the shaft seal member 62 is positioned between the radially opposing portions of the motor shaft 16 and the input shaft 26. More specifically, the shaft seal member 62 is positioned between the large inner diameter portion 64b of the hollow portion 64 of the motor shaft 16 and the large outer diameter portion 26b of the input shaft 26. In addition, the shaft seal member 62 may be positioned between the axially opposing portions of the motor shaft 16 and the input shaft 26. In this embodiment, the shaft seal member 62 is an O-ring. This specific example is not particularly limited, and may be a V-ring, rubber packing, etc.

[0041] The shaft seal member 62 seals the hollow space 66 of the motor shaft 16. The connection structure 60 will be provided in the hollow space 66 sealed by the shaft seal member 62. The shaft seal member 62 is mounted on one of the motor shaft 16 and the input shaft 26 by being housed in a mounting groove 74 formed in either one of them. The shaft seal member 62 of the present embodiment is housed in the mounting groove 74 formed in the large outer diameter portion 26b of the input shaft 26.

[0042] The effects of the gear motor 10 described above will be explained.

[0043] (A) The hollow space 66 of the motor shaft 16 is sealed by the shaft seal member 62 disposed between the motor shaft 16 and the input shaft 26. Thereby, even without connecting the internal space 48 of the speed reducer and the hollow space 66 of the motor shaft 16, the connection structure 60 can be lubricated using the lubricant enclosed in the hollow space 66. It can also be said that the shaft seal member 62 can make the internal space 48 of the speed reducer and the hollow space 66 of the motor shaft 16 independent of each other without communicating with each other. Therefore, in lubricating the connection structure 60, the constraints on the structure of the gear motor 10 can be relaxed.

[0044] For example, when considering the case of communicating the internal space 48 of the speed reducer and the hollow space 66 using the structure of the embodiment in order to lubricate the connection structure 60. In this case, the arrangement position of the speed reducer seal member 50A has to be changed from between the adapter 31 and the input shaft 26 to between the motor shaft 16 and the load side motor cover 22b, and the structure of the gear motor 10 is restricted in that regard. In this regard, according to the present embodiment, the arrangement position of the speed reducer seal member 50A may be between the motor shaft 16 and the load side motor cover 22b, or may be between the adapter 31 and the input shaft 26. That is, the constraints on the structure of the gear motor 10 can be relaxed.

[0045] The arrangement positions of the seal members other than the shaft seal member 62 described here (for example, the seal members 50A and 50B for the reduction gear) are merely examples, and may be variously changed according to the types of the motor 12 and the reduction gear 14. Also, in order to solve the problem of relaxing the restrictions on the structure of the gear motor 10, it is only necessary to seal the hollow space 66 with the shaft seal member 62, and it is not essential that a lubricant be enclosed in the hollow space 66.

[0046] When the connection structure 60 is a spline structure, fretting wear may occur at the meshing portion between the female spline portion 70 and the male spline portion 68. According to this embodiment, a lubricant (described later), which is a component effective as a countermeasure against fretting wear, can be enclosed in the hollow space 66. Also, the shaft seal member 62 can separate the internal space 48 of the reduction gear and the hollow space 66. Therefore, there is an advantage that a lubricant, which is a component effective as a countermeasure against fretting wear, can always be enclosed in the hollow space 66 regardless of the component of the lubricant enclosed in the internal space 48 of the reduction gear.

[0047] The hollow portion 64 of the motor shaft 16 opens at the load side end of the motor shaft 16 and does not penetrate in the axial direction. Therefore, compared with the case where the hollow portion 64 penetrates in the axial direction, the hollow space 66 can be easily sealed with a single shaft seal member 62. Also, compared with the case where the hollow portion 64 penetrates in the axial direction, the man-hours required for machining inside the motor shaft 16 can be reduced.

[0048] A through-hole is not formed in the input shaft 26. Therefore, the man-hours required for machining the input shaft 26 can be reduced.

[0049] Another feature of the gear motor 10 will be described. The shaft seal member 62 described above can separate the internal space 48 of the reduction gear and the hollow space 66 from each other. For this reason, depending on the lubrication targets provided in the internal space 48 of the reduction gear and the hollow space 66 respectively, a lubricant with an appropriate component can be adopted.

[0050] Based on this, in the gear motor 10 of this embodiment, the components of the lubricant sealed in the internal space 48 of the reduction gear (hereinafter referred to as the reduction gear lubricant) and the components of the lubricant sealed in the hollow space 66 (hereinafter referred to as the shaft lubricant) are different. Specifically, the components of the reduction gear lubricant can be determined according to the lubrication target, such as the reduction mechanism 28 provided in the internal space 48 of the reduction gear, while the components of the shaft lubricant can be determined according to the connection structure 60 provided in the hollow space 66.

[0051] For example, pitting may occur at the meshing points of the gear pairs constituting the reduction mechanism 28. For this reason, a lubricant containing molybdenum disulfide or the like, which is effective in preventing pitting, may be used as the lubricant for the reduction gear. Also, if the connection structure 60 is a spline structure, a key structure, etc., fretting wear may occur at the contact points between the components of the connection structure 60. For this reason, a grease containing a molybdenum-based additive, which is effective in preventing fretting wear, may be used as the lubricant for the shaft. The lubricants for the reduction gear and shaft mentioned here are just examples, and lubricants with various components may be applied depending on the required conditions. Furthermore, the components of the lubricant for the reduction gear and the lubricant for the shaft may be the same.

[0052] The features of the hollow portion 64 of the motor shaft 16 will now be described. The female spline portion 70 comprises a pair of end faces 70b on both sides in the axial direction, and a female spline body portion 70c that constitutes the portion of the female spline portion 70 excluding the pair of end faces 70b.

[0053] The hollow portion 64 includes a load-side tapered portion 70d provided on the load-side end face portion 70b of the female spline portion 70. The load-side tapered portion 70d has a tapered shape that continuously decreases in diameter towards the non-load side. The load-side tapered portion 70d is provided in the radial range from the tooth tip portion 70e to the tooth root portion 70f of the female spline portion 70. In addition, the load-side tapered portion 70d in this embodiment extends radially outward from the tooth root portion 70f of the female spline portion 70.

[0054] The hollow portion 64 includes a load-side recess 76 provided between the large inner diameter portion 64b and the spline groove portion 70a of the female spline portion 70. The load-side recess 76 is recessed radially outward from the large inner diameter portion 64b. The side surface of the load-side recess 76 that is not load-side constitutes part of the load-side tapered portion 70d. The load-side tapered portion 70d is continuous from the radially outward recessed bottom of the load-side recess 76 to the tooth tip portion 70e of the female spline portion 70.

[0055] The hollow portion 64 is provided on the non-load side relative to the female spline portion 70 and includes a non-load side recess 78 that is recessed radially outward from the female spline portion 70. The non-load side recess 78 is recessed radially outward from the inner diameter portion 80 adjacent to the non-load side relative to the female spline portion 70, in addition to the female spline portion 70. The non-load side end of the spline groove portion 70a of the female spline portion 70 is open on the load side surface of the non-load side recess 78.

[0056] The hollow portion 64 may include a non-load side tapered portion 70g provided on the non-load side end face portion 70b of the female spline portion 70. The non-load side tapered portion 70g has a tapered shape that continuously expands in diameter towards the non-load side. The non-load side tapered portion 70g is provided in the radial range from the tooth tip portion 70e to the tooth root portion 70f of the female spline portion 70. In this embodiment, the non-load side tapered portion 70g extends radially outward from the tooth root portion 70f of the female spline portion 70.

[0057] The hollow portion 64 comprises a first stage portion 82 provided on the opposite side of the load from the female spline portion 70 and facing the load side, and a second stage portion 84 provided on the opposite side of the load from the first stage portion 82 and facing the load side. The first stage portion 82 overlaps the female spline portion 70 in the axial direction. The second stage portion 84 is provided between the first stage portion 82 and the bottom surface portion 64c of the hollow portion 64. The second stage portion 84 is provided radially inward from the female spline portion 70 and the first stage portion 82.

[0058] Next, an example of a manufacturing method for producing a motor shaft will be described. This manufacturing method includes a preparation step of preparing a rod-shaped motor shaft material that will be used as the material for the motor shaft 16, a hollow portion forming step of forming a hollow portion 64 by processing the motor shaft material, and an outer circumference cutting step of obtaining the outer shape of the motor shaft 16 by cutting the outer circumference of the motor shaft material.

[0059] The hollow section formation process includes a rough machining process in which at least a portion of the hollow section 64 is formed by cutting the motor shaft material, and a spline machining process in which the female spline section 70 of the desired shape is formed. The desired shape here refers to a shape within a predetermined range of dimensional accuracy that must be satisfied in the finished motor shaft 16.

[0060] In the rough machining process, the motor shaft material is cut using a first machining tool such as a drill or boring bar. In the rough machining process, the motor shaft material is cut to form a hollow portion 64 having an internal shape that excludes at least the female spline portion 70 from the hollow portion 64. In the rough machining process, the load-side tapered portion 70d and the non-load-side tapered portion 70g of the hollow portion 64 are also formed by cutting the motor shaft material. As described later, when the female spline portion 70 is formed by casting in the spline machining process, the spline groove portion 70a of the female spline portion 70 is formed with a dimensional accuracy lower than that of the female spline portion 70 obtained by casting.

[0061] Refer to Figure 3(A). The spline machining process in this embodiment is performed by forging using a forging die 90. There are no particular limitations on the specific machining methods used to realize the spline machining process. For example, skiving, gear shaping, etc., which will be described later, may be used as these machining methods.

[0062] The forging die 90 includes a male spline portion 92 having a shape corresponding to the female spline body portion 70c, and a die tapered portion 94 having the same taper angle as the load-side tapered portion 70d of the hollow portion 64. In the forging process, in addition to this forging die 90, other dies are also used, although not shown, which receive the pressure applied to the motor shaft material 98 by the forging die 90 from the non-load side, and which restrain the radially outward plastic flow of the motor shaft material 98.

[0063] Refer to Figure 3(B). When forging, a forging die 90 is inserted into the hollow portion 64 of the motor shaft material 98 from the load side. The forging die 90 is inserted until it contacts a part of the hollow portion 64 from the non-load side. In this embodiment, the "part" is the second stage portion 84 of the hollow portion 64. This "part" is the part that can receive the axial force applied by the forging die 90.

[0064] In this state, pressure is applied to the motor shaft material 98 from the load side by the forging die 90, causing the motor shaft material 98 to undergo plastic flow. By bringing the plastically flowing motor shaft material 98 into close contact with the forging die 90, the external shape of the forging die 90, such as the male spline portion 92, can be transferred to the hollow portion 64 of the motor shaft material 98. As a result, the female spline body portion 70c of the female spline portion 70 of the desired shape can be formed in the hollow portion 64 of the motor shaft material 98. In this embodiment, by forging using the forging die 90, at least one of the load-side tapered portion 70d and the large inner diameter portion 64b of the desired shape is formed simultaneously. In this embodiment, both the load-side tapered portion 70d and the large inner diameter portion 64b are formed simultaneously with the female spline body portion 70c, but only one of them may be formed simultaneously.

[0065] Refer to Figure 4. The outer circumference cutting process will be explained. In Figure 4, the area of ​​the motor shaft material 98 that will become the outer circumference of the motor shaft 16 is shown by a dashed line. In the outer circumference cutting process, the motor shaft material 98 is centered using centering jigs 100A and 100B. The centering jigs 100A and 100B include a load-side centering jig 100A positioned on the load side of the motor shaft material 98 and a non-load-side centering jig 100B positioned on the non-load side. Each of the centering jigs 100A and 100B in this embodiment is provided with a jig-side tapered surface 100a that faces the motor shaft material 98 in the axial direction.

[0066] In the outer circumference cutting process, the motor shaft material 98 is fixed by a chuck 102. Before or after this, a center hole 98a is formed on the non-load side end face of the motor shaft material 98 for positioning the non-load side centering jig 100B. A female screw hole may be formed in the center hole 98a after the outer circumference cutting process.

[0067] Next, a load-side centering jig 100A is inserted into the hollow portion 64 of the motor shaft material 98 formed in the hollow portion formation process from the load side, and the motor shaft material 98 is pressed against the non-load-side centering jig 100B by the load-side centering jig 100A. At this time, by pressing the jig-side tapered surface 100a of the load-side centering jig 100A against the load-side tapered portion 70d of the motor shaft material 98, centering is performed so that the center of the load-side tapered portion 70d of the motor shaft material 98 aligns with the center of each centering jig 100A, 100B. The load-side tapered portion 70d of the motor shaft material 98 is used as a reference surface, and the motor shaft material 98 is centered with respect to the center of the centering jigs 100A, 100B. At this time, the position of the motor shaft material 98 is adjusted using the chuck 102, and the center of the load-side tapered portion 70d of the motor shaft material 98 is aligned with the center of the centering jigs 100A and 100B.

[0068] With the motor shaft material 98 centered in this manner, the outer circumference of the motor shaft material 98 is cut using a cutting machine to obtain the outer shape of the motor shaft 16 with the desired shape. In this embodiment, a lathe is used as the cutting machine. The cutting machine is equipped with a chuck 102 for fixing the motor shaft material 98 and a spindle for rotating the motor shaft material 98. By centering the motor shaft material 98 using centering jigs 100A and 100B, the rotation center of the spindle of the cutting machine and the center of the load-side tapered portion 70d of the motor shaft material 98 are aligned. In this embodiment, the female spline body portion 70c, the load-side tapered portion 70d, and the large inner diameter portion 64b are formed simultaneously by forging, and the centers of the female spline body portion 70c, the load-side tapered portion 70d, and the large inner diameter portion 64b are precisely aligned. Since the outer circumference of the motor shaft material is cut using the load-side tapered portion 70d, whose center precisely coincides with the female spline body portion 70c, as the reference plane, it is advantageous in improving the accuracy of the coaxiality between the outer circumference of the motor shaft 16 and the female spline body portion 70c.

[0069] In relation to these effects, the large inner diameter portion 64b, which is formed simultaneously with the female spline body portion 70c by forging, may be used as a reference plane, and centering may be performed by aligning the centers of the centering jigs 100A and 100B with the center of the large inner diameter portion 64b of the motor shaft material 98 using centering jigs 100A and 100B. In this case, a dedicated centering jig capable of achieving this purpose may be used as the centering jig, or a commercially available collet may be used. Even in this case, since the outer circumference of the motor shaft material 98 is cut using the large inner diameter portion 64b, whose center accurately coincides with the female spline body portion 70c, as the reference plane, it is advantageous in improving the accuracy of the coaxiality between the outer circumference of the motor shaft 16 and the female spline body portion 70c. To summarize, the outer circumference of the motor shaft material 98 may be cut while centered using either the load-side tapered portion 70d or the large inner diameter portion 64b, which are formed simultaneously with the female spline portion 70, as the reference plane.

[0070] Next, we will explain the case where the spline machining process is performed by skiving. Refer to Figure 5. Skiving is a method in which both the skiving cutter 104 and the workpiece are rotated, and the tooth profile is formed by the relative motion of the two. When skiving is performed, in the rough machining process, a hollow portion 64 is formed that has an inner shape that excludes the spline groove portion 70a of the female spline portion 70 from the hollow portion 64. After this, the skiving cutter 104 is inserted into the hollow portion 64 of the motor shaft material 98, and by rotating both the skiving cutter 104 and the motor shaft material, each spline tooth of the female spline portion 70 is formed. In this process, the skiving cutter 104 continuously cuts the portions that will become each spline groove portion 70a of the female spline portion 70 from one end to the other end. At this time, since tapered portions 70d and 70g are provided at both ends of the female spline portion 70, there is an advantage that the cutting resistance of the motor shaft material 98 when cutting is started can be reduced.

[0071] Next, we will explain the case where the spline machining process is performed by gear shaping. Refer to Figure 6. Gear shaping is a method of forming a tooth profile by cutting a part of the workpiece through the axial reciprocating motion of a gear shaper 106. In the case of gear shaping, as in the case of skiving, a hollow portion 64 is formed in the rough machining process, which has an inner shape that excludes the spline groove portion 70a of the female spline portion 70 from the hollow portion 64. After this, the gear shaper 106 is inserted into the hollow portion 64 of the motor shaft material 98, and the spline teeth of the female spline portion 70 are formed by sequentially cutting the locations that will become each spline groove portion 70a of the female spline portion 70 through the reciprocating motion of the gear shaper 106.

[0072] If the load-side tapered portion 70d and the large inner diameter portion 64b of the desired shape are not formed in the spline machining process, a finishing process to obtain the load-side tapered portion 70d and the large inner diameter portion 64b of the desired shape may be performed before or after the spline machining process. In this case, the desired shape may be obtained by machining the load-side tapered portion 70d and the large inner diameter portion 64b using a second machining tool that can machine with higher dimensional accuracy than the first machining tool used in the rough machining process. The second machining tool may be, for example, a cutting tool such as a reamer, or a grinding tool such as a grinder or honing tool.

[0073] The effects of the above features will now be explained. The hollow section 64 is equipped with a load-side tapered section 70d. Therefore, when inserting the input shaft 26 into the hollow section 64, the load-side tapered section 70d can guide the input shaft 26 to move closer to the center line of the hollow section 64, thereby facilitating radial alignment of the motor shaft 16 and the input shaft 26.

[0074] Furthermore, when inserting a machining tool used to process the motor shaft 16 into the hollow portion 64 of the motor shaft material 98, the load-side tapered portion 70d can guide the machining tool toward the center line. As a result, the machining tool can be smoothly inserted to the back of the hollow portion 64 without getting caught on the female spline portion 70 of the motor shaft material 98, thereby improving machining efficiency. The machining tools referred to here include, for example, forging dies 90 for forging processes, as well as cutting tools for cutting processes. The cutting tools referred to here include, for example, the skiving cutter 104 for skiving processes and the gear shaper 106 for gear shaping processes mentioned above. It can also be said that this is advantageous when employing forging processes, gear shaping processes, skiving processes, etc., in the spline machining process.

[0075] Let's consider the case where the large inner diameter portion 64b of the hollow portion 64 and the load-side tapered portion 70d are continuous. In this case, the relative axial positions of the large inner diameter portion 64b and the load-side tapered portion 70d become very close. Therefore, when attempting to finish the non-load-side end of the large inner diameter portion 64b by polishing with an abrasive tool, interference between the abrasive tool and the load-side tapered portion 70d occurs, making it difficult to polish the large inner diameter portion 64b all the way to the end of the non-load-side end with the abrasive tool. Consequently, at the non-load-side end of the large inner diameter portion 64b, a step occurs where the diameter narrows between the finished portion on the load side and the unfinished portion on the non-load side as it approaches the non-load side. If such a step occurs, there is a risk that the machining tool will get caught when using the load-side tapered portion 70d as a guide, reducing the potential for improvement in machining workability provided by the load-side tapered portion 70d.

[0076] In this respect, the hollow portion 64 of this embodiment is provided with a load-side recess 76 between the large inner diameter portion 64b and the female spline portion 70, which is recessed more than the large inner diameter portion 64b. Therefore, the relative positions of the large inner diameter portion 64b and the load-side tapered portion 70d in the axial direction can be appropriately separated. As a result, when attempting to finish the non-load-side end of the large inner diameter portion 64b with a grinding tool, interference between the grinding tool and the load-side tapered portion 70d can be avoided, and it becomes possible to grind the large inner diameter portion 64b all the way to the end of the non-load-side end with the grinding tool. Consequently, the occurrence of a step at the non-load-side end of the large inner diameter portion 64b can be avoided, and the reduction in the amount of improvement in machining workability due to the load-side tapered portion 70d caused by this can be avoided.

[0077] When the gear shaper 106 cuts the portion of the female spline portion 70 that will become the spline groove portion 70a, it is necessary to move the cutting edge 106a of the gear shaper 106 to the non-load side of the portion that will become the spline groove portion 70a. In this embodiment, a non-load side recess 78 is provided on the non-load side of the female spline portion 70. Therefore, when the cutting edge 106a of the gear shaper 106 is moved to the non-load side of the portion that will become the spline groove portion 70a, the cutting edge 106a can be positioned within the non-load side recess 78, thereby avoiding interference between the cutting edge 106a and the motor shaft material 98. Furthermore, the non-load side recess 78 can be used as a space to push out burrs generated at the non-load side end of the portion that will become the spline groove portion 70a during gear shaping, making it less likely for burrs to remain at the non-load side end of the female spline portion 70. In other words, it is advantageous to select gear shaping in the spline machining process.

[0078] (Second Embodiment) Refer to Figure 7. In the following embodiments, the same content as in the first embodiment may apply to components that were described in the first embodiment but are not described below.

[0079] The gear motor 10 of this embodiment differs in the position of the shaft seal member 62. In the first embodiment, an example was described in which the shaft seal member 62 is mounted on the input shaft 26. Instead, in this embodiment, the shaft seal member 62 is mounted on the hollow portion 64 of the motor shaft 16. To achieve this, a mounting groove 74 for mounting the shaft seal member 62 is provided in the hollow portion 64. According to this embodiment, it can also be considered that the motor 12 is equipped with the shaft seal member 62.

[0080] The gear motor 10 of this embodiment can achieve the same effects as the first embodiment, within a range that is not inconsistent with the first embodiment. In particular, the motor 12 of this embodiment is equipped with a shaft sealing member 62 for sealing the hollow space 66 of the motor shaft 16. Therefore, as with (A) described above, when used in combination with the reduction gear 14, the constraints on the structure of the gear motor 10 in terms of lubricating the connection structure 60 can be relaxed.

[0081] Next, we will describe the transformation forms of each component described so far.

[0082] The specific examples of the reduction mechanism 28 of the reducer 14 are not particularly limited. If the reduction mechanism 28 is a gear mechanism, the gear mechanism may be an eccentric oscillating type reduction mechanism, a deflection meshing type reduction mechanism, or, for example, a simple planetary gear mechanism, an orthogonal axis gear mechanism, a parallel axis gear mechanism, etc. Also, the specific type of deflection meshing type reduction mechanism is not particularly limited and may be cylindrical, top hat type, cup type, etc. The specific type of eccentric oscillating type reduction mechanism is not particularly limited and, for example, in addition to the center crank type described above, it may be a distribution type in which multiple crankshafts 40 are arranged at positions offset from the rotation centerline of the output member 32. Furthermore, the reduction mechanism 28 is not limited to a gear mechanism and may also be a friction transmission mechanism, etc.

[0083] The hollow portion 64 of the motor shaft 16 does not necessarily have to include the load-side tapered portion 70d, the load-side recess 76, the non-load-side recess 78, the non-load-side tapered portion 70g, and each of the stepped portions 82 and 84. Furthermore, the hollow portion 64 may have any combination of these. Also, in relation to these features, the shaft seal member 62 is not essential. The hollow portion 64 of the motor shaft 16 may penetrate axially. In this case, the hollow space 66 can be sealed by shaft seal members 62 positioned on both axial sides relative to the connection structure 60.

[0084] The contents of each component described in the embodiments above are illustrative. The abstract technical ideas derived from these should not be interpreted restrictively to the contents of this specification. Many design changes, such as modifications, additions, and deletions, are possible for the contents of each component described in the embodiments. Such modifications are emphasized by the notation "this form" and "embodiment." However, design changes are also permitted for contents without such notation. Any combination of the above components is also valid. For example, any explanatory items from other embodiments may be combined with an embodiment, and any explanatory items from an embodiment and other modified forms may be combined with a modified form. The hatching applied to the cross-section in the drawings does not limit the material of the object to which the hatching is applied. The structures and numerical values ​​mentioned in the embodiments and modified forms naturally include those that can be considered identical when considering manufacturing tolerances, etc. Components composed of a single member in the description in this specification may be composed of multiple members. Similarly, components composed of multiple members may be composed of a single member.

[0085] This disclosure relates to gear motors and motors.

[0086] 10...Gear motor, 12...Motor, 14...Reduction gear, 16...Motor shaft, 26...Input shaft, 60...Connection structure, 62...Shaft seal member, 64...Hollow section, 64b...Large inner diameter section, 66...Hollow space, 68...Male spline section, 70...Female spline section, 70b...End face section, 70c...Female spline body section, 70d...Load side tapered section, 76...Load side recess, 78...Non-load side recess, 80...Inner diameter section, 98...Motor shaft material.

Claims

1. A gear motor comprising a motor having a motor shaft and a reduction gear having an input shaft, wherein the motor shaft has a hollow portion into which the input shaft is inserted, a connecting structure provided in the hollow space within the hollow portion and connecting the motor shaft and the input shaft so as to be able to rotate integrally, and a sealing member disposed between the motor shaft and the input shaft and sealing the hollow space.

2. The gear motor according to claim 1, wherein the connection structure is a spline structure.

3. The gear motor according to claim 2, wherein the connection structure comprises a female spline portion provided in the hollow portion, and the hollow portion comprises a load-side tapered portion provided on the load-side end face of the female spline portion.

4. The gear motor according to claim 3, wherein the hollow portion is provided on the load side of the female spline portion and comprises a large inner diameter portion having a larger inner diameter than the female spline portion, and a load-side recess provided between the large inner diameter portion and the spline groove portion of the female spline portion and recessed radially outward from the large inner diameter portion.

5. The gear motor according to any one of claims 2 to 4, wherein the connection structure comprises a female spline portion provided in the hollow portion, and the hollow portion comprises a non-load side recess provided on the non-load side with respect to the female spline portion and recessed radially outward from the female spline portion.

6. A gear motor according to any one of claims 1 to 5, wherein the components of the lubricant sealed in the internal space of the reduction gear are different from the components of the lubricant sealed in the hollow space.

7. The gear motor according to any one of claims 1 to 6, wherein the hollow portion is open at the load-side end of the motor shaft and does not penetrate axially.

8. The gear motor according to any one of claims 1 to 7, wherein the input shaft does not have a through hole that penetrates in the axial direction.

9. A motor having a motor shaft, wherein the motor shaft has a hollow portion into which the input shaft of a reduction gear is inserted, the motor shaft is connected to the input shaft so as to be able to rotate integrally with the input shaft by a connecting structure provided in the hollow space within the hollow portion, and the motor has a sealing member disposed between the input shaft and the motor shaft for sealing the hollow space.

10. A method for manufacturing a motor shaft according to claim 3 or 4, wherein the hollow portion comprises a large inner diameter portion provided on the load side of the female spline portion and having a larger inner diameter than the female spline portion, the female spline portion comprises a pair of end faces on both axial sides and a female spline body portion that constitutes the portion of the female spline portion excluding the pair of end faces, and the method includes: a hollow portion forming step of forming the hollow portion by processing a motor shaft material that will be the material for the motor shaft; and an outer circumference cutting step of obtaining the outer shape of the motor shaft by cutting the outer circumference of the motor shaft material, wherein in the hollow portion forming step, at least one of the load side tapered portion and the large inner diameter portion and the female spline body portion are formed simultaneously by forging, and in the outer circumference cutting step, the outer circumference of the motor shaft material is cut while the motor shaft material is centered with one of the load side tapered portion and the large inner diameter portion formed simultaneously with the female spline body portion as a reference surface.

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