Multistage gears, speed reducers, and electric motors with speed reducers

Abstract

To provide a multi-stage gear that can be easily manufactured without compromising gear precision. [Solution] A multi-stage gear comprises a first gear member formed of a first material and having a first gear, and a second gear member formed of a second material different from the first material and having a second gear with a different outer diameter from the first gear. The first gear and the second gear are connected with their respective centerlines coincide. The first gear has a hole extending in a direction along the centerline and having points on its inner circumferential surface at different distances from the centerline. The second gear has a columnar portion extending in a direction along the centerline and having points on its outer circumferential surface at different distances from the centerline that are inserted into the hole. When the columnar portion is inserted into the hole, at least a portion of the outer circumferential surface of the columnar portion contacts at least a portion of the inner circumferential surface of the hole.

Description

Technical Field

[0001] The present invention relates to a multi-stage gear, a speed reducer using the multi-stage gear, and an electric motor with a speed reducer.

Background Art

[0002] Conventionally, a speed reducer using a planetary gear mechanism is known. In this type of speed reducer, a configuration is disclosed in which a two-stage gear combining two gears of different sizes is used as a planetary gear. (See, for example, Japanese Patent Application Laid-Open No. 2012-121407)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The two-stage gear is often manufactured by integral molding of resin. When manufactured by integral molding of resin, high stress acts on the gear teeth of the small gear on which a large force acts, and the small gear is likely to be damaged. In addition, the two-stage gear may be manufactured by sintering or die casting, but the accuracy of the gear is low, which may cause abnormal noise.

[0005] An object of the present invention is to provide a multi-stage gear that can be easily manufactured without reducing the accuracy of the gear.

Means for Solving the Problems

[0006] An exemplary multi-stage gear of the present invention comprises a first gear member formed of a first material and having a first gear, and a second gear member formed of a second material different from the first material and having a second gear with a different outer diameter from the first gear. The first gear member and the second gear member are connected with their centerlines aligned. The first gear member has a hole extending in a direction along the centerline and having points on its inner circumferential surface at different distances from the centerline. The second gear member has a columnar portion extending in a direction along the centerline and having points on its outer circumferential surface at different distances from the centerline, which is inserted into the hole. When the columnar portion is inserted into the hole, at least a portion of the outer circumferential surface of the columnar portion contacts at least a portion of the inner circumferential surface of the hole. [Effects of the Invention]

[0007] According to an exemplary version of the present invention, it is possible to provide a multi-stage gear that can be easily manufactured without compromising the precision of the gear. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view taken from a plane containing the central axis of an electric motor with a gearbox. [Figure 2] Figure 2 shows the schematic arrangement of the sun gear, multi-stage gear, and internal gear. [Figure 3] Figure 3 is a perspective view of a multi-stage gear. [Figure 4] Figure 4 shows a multi-stage gear viewed from the axial direction. [Figure 5] Figure 5 is a cross-sectional view of the multi-stage gear shown in Figure 4, cut along the VV line. [Figure 6] Figure 6 is an exploded perspective view showing the first gear member and the second gear member disassembled. [Figure 7] Figure 7 is a view of the first gear member from the axial direction. [Figure 8] Figure 8 is a view of the second gear member from the axial direction. [Figure 9] Figure 9 is a view of the multi-stage gear of the second embodiment from the axial direction. [Figure 10]FIG. 10 is a view seen from the axial direction of the first gear member. [Figure 11] FIG. 11 is a view seen from the axial direction of the second gear member. [Figure 12] FIG. 12 is a view seen from the axial direction of the multi-stage gear of the third embodiment. [Figure 13] FIG. 13 is a view seen from the axial direction of the first gear member. [Figure 14] FIG. 14 is a view seen from the axial direction of the second gear member. [Figure 15] FIG. 15 is a view seen from the axial direction of the multi-stage gear of the fourth embodiment. [Figure 16] FIG. 16 is a view seen from the axial direction of the first gear member. [Figure 17] FIG. 17 is a view seen from the axial direction of the second gear member. [Figure 18] FIG. 18 is a view seen from the axial direction of the multi-stage gear of the fifth embodiment. [Figure 19] FIG. 19 is a view seen from the axial direction of the first gear member. [Figure 20] FIG. 20 is a view seen from the axial direction of the second gear member. [Figure 21] FIG. 21 is a view seen from the axial direction of the multi-stage gear of the sixth embodiment. [Figure 22] FIG. 22 is an enlarged view showing a part of the multi-stage gear shown in FIG. 21.

Embodiments for Carrying out the Invention

[0009] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In this specification, when explaining the motor 100 with a speed reducer, the state of the motor 100 with a speed reducer shown in FIG. 1 will be used as a reference. In the motor 100 with a speed reducer, the central axis J1 extends in the left-right direction. And the direction in which the central axis J1 extends is referred to as the "axial direction". The direction perpendicular to the central axis J1 is referred to as the "radial direction", and the direction along the arc centered on the central axis J1 is referred to as the "circumferential direction", respectively. And in the following description, in FIG. 1, the left side along the axial direction is defined as one side in the axial direction, and the right side is defined as the other side in the axial direction. Note that the above directions are defined for ease of explanation and may not coincide with the directions of the actual motor 100 with a speed reducer used.

[0010] <Motor 100 with a speed reducer> The motor 100 with a speed reducer according to the present embodiment is used, for example, as a power source for electric vehicles such as electric bicycles, electric assist bicycles, and electric wheelchairs. FIG. 1 is a cross-sectional view taken along a plane including the central axis J1 of the motor 100 with a speed reducer.

[0011] As shown in FIG. 1, the motor 100 with a speed reducer has a housing portion 10, a motor portion 20, a speed reduction mechanism 30, a first fixed shaft 41, and a second fixed shaft 42. That is, the motor 100 with a speed reducer has a speed reducer 30 and a motor 20 connected to the speed reducer.

[0012] <First fixed shaft 41 and second fixed shaft 42> The first fixed shaft 41 and the second fixed shaft 42 are fixing portions for fixing the motor 100 with a speed reducer to the above-described electric vehicle. The first fixed shaft 41 and the second fixed shaft 42 are substantially cylindrical and are arranged apart in the axial direction. As shown in FIG. 1, in the motor 100 with a speed reducer, the center of the first fixed shaft 41 and the center of the second fixed shaft 42 both coincide with the central axis J1.

[0013] The first fixed shaft 41 is fixed to the first holder portion 241 of the holder 24 of the motor unit 20, which will be described later. The second fixed shaft 42 is fixed to the main body portion 361 of the carrier 36 of the reduction mechanism 30. The first fixed shaft 41 and the second fixed shaft 42 are fixed parts that are fixed to the electric vehicle, etc. In other words, the motor with reduction gear 100 is fixed to the electric vehicle, etc. via the first fixed shaft 41 and the second fixed shaft 42.

[0014] <Housing Section 10> The housing portion 10 is cylindrical with respect to the central axis J1. In the motor with reduction gear 100, the motor portion 20 and the reduction mechanism 30 are housed in the internal space 14 of the housing portion 10. The housing portion 10 includes a first housing member 11, a second housing member 12, a first bearing 131, and a second bearing 132.

[0015] The first housing member 11 is a bottomed cylindrical shape with an opening on one side in the axial direction, centered on the central axis J1. The first housing member 11 has a bottom portion 111 and a side wall portion 112. The bottom portion 111 is an annular shape that expands radially, centered on the central axis J1. A through hole 113 is formed in the center of the bottom portion 111 when viewed from the axial direction, penetrating in the axial direction. A first bearing 131 is installed in the through hole 113. The first housing member 11 is rotatably supported by the holder 24 of the motor unit 20 via the first bearing 131. The first bearing 131 is a ball bearing, but is not limited to this, and a wide range of bearing structures that can smoothly and accurately support the first housing member 11 can be adopted.

[0016] The side wall portion 112 is cylindrical in shape and extends axially with respect to the central axis J1. The side wall portion 112 is formed extending from the radial outer edge of the bottom portion 111 to one side in the axial direction. In other words, in the first housing member 11, the bottom portion 111 and the side wall portion 112 are formed integrally. The side wall portion 112 has a pair of connecting portions 114 arranged side by side in the axial direction.

[0017] The connecting portion 114 is flange-shaped and extends radially outward from the outer surface of the side wall portion 112. For example, spokes of a wheel (not shown) are connected to the connecting portion 114. By connecting the spokes of the electric vehicle's wheel to the connecting portion 114, the torque generated by the electric motor 20 is transmitted to the wheel, supplying power for the electric vehicle's operation.

[0018] The second housing member 12 is an annular shape that expands axially around the central axis J1. The second housing member 12 is fixed to one side of the first housing member 11 in the axial direction. The second housing member 12 is fixed to the first housing member 11 by screw fastening, but the fixing method is not limited to screw fastening. By fixing the second housing member 12 to the first housing member 11, an internal space 14 is formed inside the housing portion 10.

[0019] A through-hole 121 is formed in the center of the second housing member 12 when viewed from the axial direction. A second bearing 132 is installed in the through-hole 121. The second housing member 12 is fixed to the first housing member 11 and is rotatably supported on the second fixed shaft 42 via the second bearing 132. The second bearing 132 is a ball bearing, but is not limited to this, and a wide range of bearing structures that can smoothly and accurately support the second housing member 12 can be adopted.

[0020] With the configuration described above, the housing portion 10 is rotatably supported with respect to the first fixed shaft 41 and the second fixed shaft 42.

[0021] <Electric motor section 20> The motor unit 20 is a DC brushless motor. The motor unit 20 includes a motor shaft 21, a rotor 22, a stator 23, a holder 24, a third bearing 251, and a fourth bearing 252. The motor unit 20 is an inner rotor type motor in which the rotor 22 is arranged inside the stator 23. However, the motor unit 20 is not limited to an inner rotor type motor and may also be an outer rotor type motor.

[0022] <Electric motor shaft 21> The motor shaft 21 is substantially cylindrical in shape, extending axially around a central axis J1. The motor shaft 21 is rotatable circumferentially around the central axis J1. The motor shaft 21 is rotatably supported by a holder 24 via a third bearing 251 and a fourth bearing 252. The third bearing 251 and the fourth bearing 252 are positioned at two axially separated locations and rotatably support the motor shaft 21 at two axially separated locations. The third bearing 251 and the fourth bearing 252 are ball bearings, but are not limited to these, and a wide range of bearing structures that can smoothly and accurately support the motor shaft 21 can be adopted.

[0023] <Rotor 22> The rotor 22 is fixed to the outer circumference of the motor shaft 21. The rotor 22 has a rotor core 221 and a rotor magnet 222. The rotor 22 is rotatable in the circumferential direction about the central axis J1.

[0024] The rotor core 221 is formed by stacking thin sheets of electromagnetic steel in the axial direction. The rotor core 221 is a cylindrical body extending along the axial direction. Alternatively, the rotor core 221 may be formed by sintering magnetic powder. Multiple rotor magnets 222 are fixed to the rotor core 221. The multiple rotor magnets 222 are arranged in a line in the circumferential direction. The rotor 22 is positioned radially opposite the stator 23. The radially outer magnetic poles of adjacent rotor magnets 222 in the circumferential direction are different magnetic poles.

[0025] <Stata 23> The stator 23 comprises a stator core 231, an insulator 232, and a coil 233. The stator 23 is held by a holder 24. The stator core 231 has a plurality of teeth 234 that protrude radially inward from an annular core back and are arranged circumferentially. The stator core 231 is formed by laminating thin sheets of electromagnetic steel in the axial direction. Alternatively, it may be formed by sintering magnetic powder.

[0026] The insulator 232 is made of an insulating material such as resin, and covers at least the teeth 234. The coil 233 is formed by winding a conductor around the teeth 234, which are covered by the insulator 232.

[0027] <Holder 24> The holder 24 holds the stator 23 and rotatably supports the motor shaft 21. The holder 24 has a first holder portion 241 and a second holder portion 242. The first holder portion 241 and the second holder portion 242 face each other in the axial direction.

[0028] The first holder portion 241 is bottomed cylindrical. The first holder portion 241 has a first cylindrical portion 243 and a first projection portion 244. The first cylindrical portion 243 is substantially cylindrical and extends from the radial outer edge of the first holder portion 241 to one side in the axial direction. The first projection portion 244 protrudes from the central part of the first holder portion 241 to the other side in the axial direction when viewed in the axial direction. The first holder portion 241 has a first through hole 245 that penetrates the first projection portion 244 in the axial direction. A first fixed shaft 41 is fixed to the other end of the first through hole 245 in the axial direction. A third bearing 251 is attached to the one end of the first through hole 245 in the axial direction. As a result, the first holder portion 241 rotatably supports the motor shaft 21. Furthermore, the electric motor shaft 21, which is rotatably supported by the first holder portion 241, and the first fixed shaft 41, which is fixed to the first holder portion 241, have their centers aligned.

[0029] The first bearing 131 is then attached to the outer surface of the first projection 244. As a result, the first holder portion 241 rotatably supports the first housing member 11 of the housing portion 10. The center of rotation of the first housing member 11 coincides with the central axis J1.

[0030] The second holder portion 242 is bottomed cylindrical. The second holder portion 242 has a second cylindrical portion 246. The second cylindrical portion 246 is substantially cylindrical and extends from the radial outer edge of the second holder portion 242 to the other axial direction.

[0031] Furthermore, the second holder portion 242 has a second through hole 247 and a support projection 248. The second through hole 247 is located in the central part when the second holder portion 242 is viewed in the axial direction and passes through it in the axial direction. The fourth bearing 252 is attached to the second through hole 247. As a result, the second holder portion 242 rotatably supports the motor shaft 21. At this time, the motor shaft 21 passes through the second through hole 247, and the tip portion 211 of the motor shaft 21 protrudes from the second holder portion 242 to one side in the axial direction. The sun gear 31 of the reduction mechanism 30, which will be described later, is fixed to the tip portion 211 of the motor shaft 21.

[0032] The support projection 248 is a convex shape that protrudes in the axial direction from one axial side surface of the second holder portion 242. The other axial end of the support shaft 363 that supports the multi-stage gear 32, which will be described later, is fixed to the support projection 248. The support projection 248 then contacts the first contact surface 347 of the second gear member 34 of the multi-stage gear 32, which will be described later, thereby restricting the movement of the multi-stage gear 32 in the other axial direction. As shown in Figure 2, since the reduction mechanism 30 is provided with three multi-stage gears 32, there are also three support projections 248. The number of support projections 248 may be the same as the number of multi-stage gears 32, or it may be more than the number of multi-stage gears 32. If there are more than the number of multi-stage gears 32, the mounting position of the multi-stage gears 32 can be changed while maintaining balance.

[0033] The first holder portion 241 holds the other axial side of the stator 23, and the second holder portion 242 holds the one axial side of the stator 23. Specifically, the first cylindrical portion 243 of the first holder portion 241 and the second cylindrical portion 246 of the second holder portion 242 sandwich the stator 23 from the axial direction. The second holder portion 242 and the first holder portion 241 are then fixed together with a screw. At this time, the screw passes through a through hole 235 provided in the stator core 231 of the stator 23.

[0034] In other words, the stator 23 is held axially by being sandwiched between the first holder portion 241 and the second holder portion 242. In addition, the fact that the screw passes through the through hole 235 suppresses the circumferential movement of the stator core 231.

[0035] The motor unit 20 is rotatably supported by a holder 24, which holds the motor shaft 21 and the rotor 22 fixed to the motor shaft 21, and also holds the stator 23. The motor unit 20 is positioned inside the internal space 14 of the housing unit 10. When the motor unit 20 is positioned inside the housing unit 10, the inner surface of the side wall 112 of the first housing member 11 and the radially outer surfaces of the holder 24 and stator 23 face each other radially with a gap in between. In other words, when the housing unit 10 rotates around the central axis J1, the housing unit 10 and the motor unit 20 do not come into contact.

[0036] <Other components of the electric motor unit 20> On the axial side of the motor unit 20 relative to the stator 23, auxiliary components such as a circuit board 26 are mounted. A control circuit for controlling the current supplied to the coil 233 is mounted on the circuit board 26.

[0037] In the motor unit 20, the coil 233 is excited by passing an electric current through it. When the coil 233 is excited, a magnetic force is generated between it and the rotor magnet 222. By exciting multiple coils 233 at appropriate timings, a circumferential torque is generated in the rotor 22 around the central axis J1. This torque causes the motor shaft 21 to rotate around the central axis J1.

[0038] <Deceleration mechanism 30> Figure 2 shows the schematic arrangement of the sun gear 31, the multi-stage gear 32, and the internal gear 35. The reduction mechanism 30 is a power transmission mechanism that increases torque by reducing the rotation of the shaft of the electric motor 20 and transmits it to the housing 10.

[0039] As shown in Figures 1 and 2, the reduction mechanism 30 is attached to the motor unit 20. More specifically, the reduction mechanism 30 is attached to one axial side of the motor unit 20. The reduction mechanism 30 includes a sun gear 31, a multi-stage gear 32, an internal gear 35, and a carrier 36. The reduction mechanism 30 is a so-called star-type planetary gear mechanism in which the internal gear 35 rotates with power output from the sun gear 31. Note that the reduction mechanism 30 is not limited to a star type, but may also be a solar type or a planetary type.

[0040] <Sun Gear 31> As shown in Figure 1, the sun gear 31 is positioned at the tip 211 of the motor shaft 21. The sun gear 31 rotates integrally with the motor shaft 21. Therefore, the sun gear 31 may be formed from a single component with respect to the motor shaft 21, or it may be attached to the motor shaft 21 and fixed by fixing methods such as adhesive, welding, screwing, crimping, or press-fitting. Other fixing methods may also be employed. Furthermore, a wide range of fixing methods can be used to fix the sun gear 31 so that it can rotate integrally with the motor shaft 21.

[0041] As shown in Figure 2, the reduction mechanism 30 has three multi-stage gears 32, which are planetary gears. The three multi-stage gears 32 are arranged at equal intervals in the circumferential direction. In this embodiment, the reduction mechanism 30 has three multi-stage gears 32, but it is not limited to this, and it is sufficient to have two or more multi-stage gears 32. Also, the circumferential arrangement of the multi-stage gears 32 is not limited to equal intervals.

[0042] <Career 36> As shown in Figure 1, the multi-stage gear 32 is rotatably supported on the carrier 36. As shown in Figure 1, the carrier 36 has a main body 361, legs 362, a support shaft 363, and a retaining portion 364.

[0043] The main body 361 is roughly annular in shape, expanding radially. The main body 361 is positioned on one axial side of the sun gear 31. The main body 361 has a fixed shaft hole 365 in its center, which penetrates axially when viewed from the axial direction. The second fixed shaft 42 is fixed to the fixed shaft hole 365. As a result, the center of the second fixed shaft 42 coincides with the central axis J1.

[0044] The leg portion 362 extends from the radially outer edge of the main body portion 361 to the other axial direction. The other axial end of the leg portion 362 forms a base portion 366 that is bent radially outward. The base portion 366 is screwed to the second holder portion 242 of the holder 24. In this way, the carrier 36 is fixed to the second holder portion 242 of the holder 24.

[0045] The support shaft 363 is cylindrical and extends along the planetary axis J2, which is parallel to the central axis J1. The support shaft 363 rotatably supports the multi-stage gear 32, which is used as a planetary gear.

[0046] As shown in Figure 1, the retaining portion 364 has a protruding shape that extends from the other axial side surface of the main body portion 361 toward the other axial side. The axial end of the support shaft 363 is fixed to the retaining portion 364. The retaining portion 364 restricts the movement of the multi-stage gear 32 toward one axial side by contacting the second contact surface 348 of the second gear member 34 of the multi-stage gear 32 attached to the support shaft 363. In other words, the multi-stage gear 32 is restricted from moving toward the axial side by being sandwiched from both sides in the axial direction by the support projection 248 and the retaining portion 364.

[0047] For example, the number of support protrusions 248 and pressing portions 364 may be equal, and they may be arranged to face each other in the axial direction when the carrier 36 is attached to the second holder portion 242. Alternatively, one of the support protrusions 248 or pressing portions 364 may be greater than the other. In this case as well, when the carrier 36 is attached to the second holder portion 242, the greater number will include those that face each of the lesser numbers in the axial direction. In other words, the three multistage gears 32 are supported by the carrier 36 so as to be rotatable and separated in the circumferential direction. When attached to the carrier 36, the first gear 331 of the first gear member 33 of each multistage gear 32 is positioned radially outward from the radial outer edge of the main body portion 361 of the carrier 36 when viewed from the axial direction.

[0048] <Multistage gear 32> Next, the details of the multi-stage gear 32 will be described with reference to the drawings. Figure 3 is a perspective view of the multi-stage gear 32. Figure 4 is a view of the multi-stage gear 32 from the axial direction. Figure 5 is a cross-sectional view of the multi-stage gear 32 shown in Figure 4, cut along the VV line. Figure 6 is an exploded perspective view of the first gear member 33 and the second gear member 34. Figure 7 is a view of the first gear member 33 from the axial direction. Figure 8 is a view of the second gear member 34 from the axial direction. Note that the support shaft 363 is also shown in Figure 5.

[0049] The multi-stage gear 32 comprises a first gear member 33 and a second gear member 34. The first gear member 33 and the second gear member 34 are connected in the axial direction. The multi-stage gear 32 is rotatably supported on a support shaft 363 attached to a second holder portion 242 and a carrier 36. In other words, the first gear member 33 and the second gear member 34 are supported so as to be able to rotate integrally in the circumferential direction about a planetary axis J2 parallel to the central axis J1.

[0050] <First gear member 33> As shown in Figures 3 to 7, the first gear member 33 has a first gear 331, a hole 332, a recess 333, and a cylindrical portion 334. The first gear 331 and the cylindrical portion 334 are connected in the axial direction. The first gear member 33 is made of a metal such as carbon steel or stainless steel. The material constituting the first gear member 33 is referred to as the first material. That is, the first gear member 33 is made of the first material and has a first gear 331.

[0051] The first gear 331 of the first gear member 33 is an external gear centered on the planetary axis J2. The first gear member 33 is an external gear manufactured, for example, by hobbing. Hobbing is a process in which a gear is formed by rotating a cylindrical or other material and using a rotating hob to remove material from its surface. Hobbing can improve the precision of the gear, improve the rotational precision of the gear, and suppress abnormal noise generated by the gear.

[0052] The first gear member 33 has a sufficient axial length to mesh with the internal gear 35 as the first gear 331, and in the portion longer than that, it has a cylindrical portion 334 with an outer diameter smaller than the tooth root of the first gear 331. By providing the cylindrical portion 334, interference between the cylindrical portion 334 and the hob can be suppressed when hobbing is performed. This makes it possible to form the first gear 331 having gear teeth that are completely machined in the axial direction. Note that the method of manufacturing the first gear 331 is not limited to hobbing. Any other machining method that can accurately and reliably form the gear teeth can be widely adopted. When using a machining method other than hobbing, the cylindrical portion 334 may be omitted if no interference with the machining tool occurs.

[0053] The hole 332 is located in the center of the first gear member 33 when viewed from the axial direction, and penetrates it axially. A recess 333 is formed on the inner circumferential surface of the hole 332, which is recessed radially outward. As shown in Figures 3, 4, 6, and 7, the hole 332 of the first gear member 33 has a configuration in which eight recesses 333 are arranged at equal intervals in the circumferential direction. For example, the hole 332 has a shape in which multiple recesses 333 are recessed radially outward from the inner circumferential surface and extend axially, and are arranged in a circumferential direction.

[0054] In the hole 332, the radial inner edge of the recess 333 and the radial inner edge of the portion between adjacent recesses 333 in the circumferential direction have different distances from the centerline (planetary axis J2). That is, the first gear member 33 has a hole 332 that extends in a direction along the centerline (planetary axis J2) and has points on its inner circumferential surface that have different distances from the centerline (planetary axis J2).

[0055] Broaching is one possible method for forming the holes 332 and recesses 333, but it is not limited to this method. A wide range of processing methods that can accurately form the holes 332 and recesses 333 can be employed.

[0056] <Second gear member 34> As shown in Figures 3 to 6 and Figure 8, the second gear member 34 has a flange portion 340, a second gear 341, a column portion 342, and a protrusion portion 343. The second gear member 34 is made from a material with high rigidity and a low coefficient of friction, such as polyacetal resin. The material used to form the second gear member 34 is referred to as the second material. In the multi-stage gear 32, the first material and the second material are different. The second gear member 34 can be formed by injection molding of resin, but is not limited to this method. That is, the second gear member 34 is made of a second material different from the first material and has a second gear 341 with a different outer diameter than the first gear 331. In other words, the first material is a metal material and the second material is a resin material.

[0057] In the second gear member 34, the flange portion 340 is an annular shape that expands radially. The second gear 341 is positioned on the radial outer edge of the flange portion 340. In the multi-stage gear 32, the second gear 341 is larger than the first gear 331. One axial side of the flange portion 340 is the mounting surface 345 to which the first gear member 33 is attached, and the other side is the first contact surface 347.

[0058] The column portion 342 extends axially from the central part of the mounting surface 345 of the flange portion 340 when viewed from the axial direction. The column portion 342 has a plurality of protrusions 343 that project radially outward from the outer circumferential surface and extend axially, and are arranged in a circumferential direction. The protrusions 343 are formed integrally with the column portion 342. As shown in Figures 3, 4, 6, and 8, the column portion 342 of the second gear member 34 has a configuration in which eight protrusions 343 are arranged at equal intervals in the circumferential direction. In the second gear member 34, eight protrusions 343 are provided. The eight protrusions 343 are arranged at equal intervals in the circumferential direction.

[0059] For example, the radial outer edge of a protrusion 343 and the radial outer edge of the portion between adjacent protrusions 343 in the circumferential direction have different distances from the centerline (planetary axis J2). That is, the second gear member 34 has a columnar portion 342 that extends in a direction along the centerline (planetary axis J2) and has points on its outer circumferential surface that have different distances from the centerline (planetary axis J2). The circumferential width and radial height of the protrusion 343 are approximately the same as the circumferential width and radial depth of the recess 333 of the first gear member 33.

[0060] The column portion 342 has a sliding hole 344 that penetrates it in the axial direction. A support shaft 363 is positioned to pass through the sliding hole 344 (see Figures 1, 5, etc.).

[0061] Furthermore, a reference portion 346 is provided on one axial side surface of the flange portion 340. The reference portion 346 is a protrusion that projects in the axial direction from one axial side surface of the flange portion 340. As will be described in detail later, the reference portion 346 is a mark used to determine the reference for positioning the multi-stage gear 32 so that the second gear 341 of the second gear member 34 meshes with the sun gear 31 and the first gear 331 of the first gear member 33 meshes with the internal gear 35.

[0062] In this embodiment, the reference portion 346 is a convex portion, but it may also be a concave portion. Furthermore, the reference portion 346 is provided on one axial side of the flange portion 340, but it may also be provided on the other axial side. Moreover, the reference portion 346 is provided on the second gear member 34, but it may also be provided on the first gear member 33. In other words, the reference portion is formed at a predetermined position relative to the gear teeth of the first gear or the second gear.

[0063] The first contact surface 347 contacts the support projection 248 of the second holder portion 242 of the holder 24. The multi-stage gear 32 rotates with the first contact surface 347 in contact with the support projection 248. Therefore, the first contact surface 347 is a surface that requires high precision. On the other hand, the portion of the flange portion 340 radially outward from the first contact surface 347 on the other axial side does not contact the support projection 248, so it does not need to be as precise as the first contact surface 347. For this reason, a circumferential groove 3401 is formed radially outward from the first contact surface 347, recessed radially to one side of the first contact surface 347. In the circumferential groove 3401, the precision of the mold can be lower than that of the portion forming the first contact surface 347, thereby reducing manufacturing costs.

[0064] As described above, eight recesses 333 are arranged at equal intervals in the circumferential direction in the hole 332 of the first gear member 33, and eight protrusions 343 are arranged at equal intervals in the circumferential direction in the column portion of the second gear member 34. The circumferential width and radial depth of the recesses 333 arranged in the hole 332 of the first gear member 33 are approximately the same as the circumferential width and radial height of the protrusions 343 arranged in the column portion 342 of the second gear member 34. In other words, the cross-sectional shape perpendicular to the center line (planetary axis J2) of the hole 332 is approximately the same as the cross-sectional shape perpendicular to the center line (planetary axis J2) of the column portion 342. Therefore, the column portion 342 is inserted into the hole 332 by fitting the protrusions 343 into the recesses 333.

[0065] At this time, the protrusion 343 of the column portion 342 of the second gear member 34 fits into the recess 333 of the hole portion 332 of the first gear member 33. In other words, the hole portion 332 of the first gear member 33 and the column portion 342 of the second gear member 34 are connected by a so-called spline fitting. That is, when the column portion 342 is inserted into the hole portion 332, at least a part of the outer circumferential surface of the column portion 342 contacts at least a part of the inner circumferential surface of the hole portion 332. To explain further, at least a part of the outer surface of the protrusion 343 contacts at least a part of the inner surface of the recess 333. As a result, torque and rotation are transmitted stably and accurately between the first gear member 33 and the second gear member 34.

[0066] The number of protrusions 343 and recesses 333, and their circumferential size, can be appropriately changed depending on the transmitted torque. For example, when a large torque is transmitted, this can be addressed by increasing the number of protrusions 343 and recesses 333 or by increasing the circumferential size of the protrusions 343 and recesses 333. When increasing the circumferential width of the protrusions 343, they may also be made larger in the radial direction. In this way, the contact area between the protrusions 343 and recesses 333 can be increased when torque is transmitted, thereby suppressing deformation, wear, etc., of the protrusions 343 and recesses 333.

[0067] The method for fixing the column portion 342 of the second gear member 34 to the hole 332 of the first gear member 33 can be, for example, press-fitting or light press-fitting. When fixing the column portion 342 of the second gear member 34 to the hole 332 of the first gear member 33 by press-fitting, a weak press-fitting force that restricts axial movement may be used. In other words, compared to press-fitting when a conventional cylindrical member is inserted into a cylindrical hole to transmit rotation, a small amount of press-fitting force is sufficient to achieve a good effect. Therefore, the force applied to the first gear member 33 and the second gear member 34 during press-fitting can be kept small, and problems such as deformation of the first gear member 33 and the second gear member 34 can be suppressed.

[0068] Furthermore, in the case where the column portion 342 is press-fitted into the hole portion 332, the end of the column portion 342 on one axial side may be formed in a tapered shape, with the outer diameter decreasing toward the axial side. This formation makes it easier to insert the column portion 342 into the hole portion 332. The tapered portion may be a convex portion 343, a portion between adjacent convex portions 343, or both.

[0069] Furthermore, even if the outer diameter of the column portion 342 of the second gear member 34 is small and it cannot be fixed by press-fitting into the hole portion 332 of the first gear member 33, it is still possible to fix it using fixing methods such as adhesive or screw fastening. Even in this case, it is possible to fix it with less force than conventional fixing methods, and deformation of the first gear member 33 and the second gear member 34 can be suppressed. Note that the first gear member 33 and the second gear member 34 do not necessarily have to be fixed together, as the structure has such that the convex portion 343 is in contact with the concave portion 333 and the carrier 36 presses against one axial side surface of the first gear member 33.

[0070] The multi-stage gear 32 is connected by a first gear member 33 and a second gear member 34, with their respective centerlines (planetary axis J2) aligned. The support shaft 363 is inserted into the sliding hole 344 of the second gear member 34, thereby rotatably supporting the multi-stage gear 32 on the support shaft 363. Because the second gear member 34 is made of polyacetal resin, friction between the inner surface of the sliding hole 344 and the outer surface of the support shaft 363 is reduced. In other words, the multi-stage gear 32 is rotatably supported on the support shaft 363 without the use of bearings. Furthermore, the multi-stage gear 32 can rotate smoothly without the use of lubricants. That is, the sliding hole 344 acts as a sliding bearing for the multi-stage gear 32 relative to the support shaft 363.

[0071] <Internal gear 35> As shown in Figure 2, the internal gear 35 is an annular gear. Internal teeth are formed on the radially inner surface. The internal gear 35 meshes with the first gear member 33 of the multi-stage gear 32.

[0072] As shown in Figure 2, the internal gear 35 is fixed to the second housing member 12 by screws. Because the internal gear 35 is fixed to the second housing member 12 in this way, the second housing member 12 rotates together with the internal gear 35.

[0073] To explain further, the rotation and torque output from the motor shaft 21 of the motor unit 20 are transmitted to the internal gear 35 via the sun gear 31 and the multi-stage gear 32, causing the internal gear 35 to rotate. As a result, the housing unit 10 to which the internal gear 35 is fixed rotates circumferentially around the central axis J1. The internal gear 35 is fixed by screws, but is not limited to this, and a wide range of fixing methods that can firmly fix the internal gear 35 to the second housing member 12 of the housing unit 10 can be employed.

[0074] <Assembly of the reduction gear mechanism 30> When installing the multi-stage gear 32, the reference portion 346 is positioned toward the central axis J1. This allows the position of the multi-stage gear 32 in the rotational direction to be determined. This enables the second gear 341 of the second gear member 34 of the multi-stage gear 32 to mesh with the sun gear 31. At the same time, the first gear 331 of the first gear member 33 of the multi-stage gear 32 can be meshed with the internal gear 35. The multi-stage gear 32 can be easily and reliably installed in the reduction mechanism 30.

[0075] <Operation of the motor 100 with a gearbox> By supplying current to the coil 233 of the motor unit 20, the motor unit 20 is driven. In other words, the motor shaft 21 of the motor unit 20 rotates around the central axis J1. As the motor shaft 21 rotates, the sun gear 31 fixed to the motor shaft 21 rotates.

[0076] As a result, the rotation and torque of the motor shaft 21 are transmitted from the sun gear 31 to the second gear 341. In the multi-stage gear 32, the second gear 341 and the first gear 331 rotate as a single unit. Therefore, the rotation and torque transmitted to the second gear 341 are transmitted to the internal gear 35 via the first gear 331.

[0077] As described above, the first fixed shaft 41 and the second fixed shaft 42 are fixed to equipment to which a motor 100 with a reduction gear, such as an electric vehicle, is attached. As a result, rotation and torque are transmitted to the internal gear 35, causing the internal gear 35 to rotate. Since the internal gear 35 is fixed to a housing portion 10 that is substantially rotatably supported with respect to the first fixed shaft 41 and the second fixed shaft 42, the housing portion 10 rotates with respect to the first fixed shaft 41 and the second fixed shaft 42 about a central axis J1.

[0078] As described above, in the multi-stage gear 32, the first gear 331 of the first gear member 33, which is subjected to a large force on its gear teeth, can be made of a different high-strength first material than the second gear 341 of the second gear member 34. This makes it possible to suppress wear on the first gear 331 of the first gear member 33 on the side subjected to the large force. Furthermore, the first gear 331 of the first gear member 33 on the side subjected to the large force can be formed by machining, such as hobbing, and by improving the machining accuracy of the gear teeth, it is possible to suppress the generation of abnormal noise.

[0079] Furthermore, since the first gear member 33 is made of a material with higher strength than the second gear member 34, and the second gear member 34 can be formed, for example, by resin injection molding, it is possible to reduce the amount of parts that are manufactured using machining, which takes time and effort, compared to when the entire multi-stage gear 32 is made of a high-strength metal material.

[0080] Furthermore, by forming the second gear member 34, which contacts the support shaft 363, from a resin with a low coefficient of friction, a bearing is unnecessary between the support shaft 363 and the second gear member 34, and even lubricant is unnecessary. This reduces the number of parts, eliminates the need to replenish lubricant, and allows for easy manufacturing. In addition, it enables stable and accurate operation over a long period of time.

[0081] In this embodiment, there are eight recesses 333 formed in the hole 332 of the first gear member 33 and eight protrusions 343 formed on the column 342 of the second gear member 34. In other words, the first gear member 33 and the second gear member 34 of the multi-stage gear 32 are fitted together by eight serrations. The first gear 331 of the first gear member 33 has 16 teeth. In other words, the number of teeth of the first gear 331 of the first gear member 33 is a multiple of the number of serrations. Therefore, even if the set of fitting serrations is misaligned when connecting the first gear member 33 and the second gear member 34, the position of the gear teeth of the first gear 331 of the first gear member 33 relative to the gear teeth of the second gear 341 of the second gear member 34 will be the same.

[0082] Hereinafter, the position of the gear teeth of the first gear 331 relative to the gear teeth of the second gear 341 will be referred to as the phase. In other words, in the multi-stage gear 32 according to the first embodiment, when the first gear member 33 and the second gear member 34 are connected, the phases of the first gear 331 and the second gear 341 coincide, even if the combination of the convex portion 343 and the concave portion 333 is not particularly limited.

[0083] On the other hand, there may be cases where the number of teeth of the first gear 331 of the first gear member 33 is not a multiple of the number of serrations. In such cases, if the designated protrusion 343 is not fitted into the designated recess 333, the phase of the first gear 331 of the first gear member 33 and the second gear 341 of the second gear member 34 will be misaligned. If the phase is misaligned, there is a risk that the first gear 331 of the first gear member 33 will not mesh with the internal gear 35 while the sun gear 31 and the second gear 341 of the second gear member 34 are meshed.

[0084] In other words, in such a configuration, the combination of serrations to be fitted is fixed, but when inserting a column 342 having a protrusion 343 of the same size into a hole 332 having a recess 333 of the same size, work is required to align the phases, making the work complicated. Therefore, the multi-stage gear of the following embodiment has a structure that aligns the phases of the first gear 331 and the second gear 341.

[0085] <Second Embodiment> Figure 9 is a view of the multi-stage gear 32a of the second embodiment from the axial direction. Figure 10 is a view of the first gear member 33a from the axial direction. Figure 11 is a view of the second gear member 34a from the axial direction. The multi-stage gear 32a of the second embodiment differs from the multi-stage gear 32 in that a first phase-aligning portion 335 is provided in the hole 332a of the first gear member 33a, and a second phase-aligning portion 349 is provided in the column portion 342a of the second gear member 34a. In all other respects, the multi-stage gear 32a has the same configuration as the multi-stage gear 32. Therefore, parts of the multi-stage gear 32a that are substantially the same as those of the multi-stage gear 32 are given the same reference numerals, and detailed descriptions of these same parts are omitted.

[0086] As shown in Figures 9 and 10, the first gear 331 in the first gear member 33a has 17 teeth. Therefore, if the number of serrations is 8, and the recesses 333 and protrusions 343 are misaligned, the phase of the first gear 331 of the first gear member 33 and the second gear 341 of the second gear member 34 will be misaligned. For this reason, the hole 332a of the first gear member 33a shown in Figures 9 and 10 has a first phase alignment portion 335. The hole 332a has seven recesses 333 arranged in the circumferential direction. There is one portion where the circumferential spacing between adjacent recesses 333 is wide. This wide portion is the first phase alignment portion 335. That is, the hole 332a has a first phase alignment portion 335 provided on its inner circumferential surface. In the multi-stage gear 32a, the first phase alignment portion 335 is planar, but it may also be curved.

[0087] Furthermore, as shown in Figures 9 and 11, in the second gear member 34a, the column portion 342a has a second phase-aligning portion 349. The column portion 342a has seven protrusions 343, and the seven protrusions 343 are formed in positions that can fit into the recesses 333 of the first gear member 33a. In other words, there is one section where the circumferential spacing between the seven protrusions 343 is wide. This section with wide spacing is the second phase-aligning portion 349. Note that in the multi-stage gear 32a, the second phase-aligning portion 349 is planar, but it may also be curved.

[0088] The second phase-aligning portion 349 is provided at a position corresponding to the first phase-aligning portion 335. That is, the column portion 342a has a second phase-aligning portion 349 provided at a position corresponding to the first phase-aligning portion 335. Furthermore, the second phase-aligning portion 349 is shaped to be in contact with the first phase-aligning portion 335.

[0089] As a result, when the first phase-aligning portion 335 and the second phase-aligning portion 349 are fitted together, the column portion 342a is inserted into the hole portion 332a. Therefore, the phases of the first gear 331 of the first gear member 33a and the second gear 341 of the second gear member 34a can be precisely aligned. This makes it easier to manufacture the multi-stage gear 32a and the reduction mechanism 30.

[0090] In this embodiment, the first phase-aligning portion 335 and the second phase-aligning portion 349 are in contact with each other. However, for example, a gap may be formed between the hole 332a and the column portion 342a to such an extent that the column portion 342a cannot be inserted when it rotates. From the viewpoint of transmitting rotation and torque, it is preferable that the first phase-aligning portion 335 and the second phase-aligning portion 349 are in contact.

[0091] <Third Embodiment> Figure 12 is a view of the multi-stage gear 32b of the third embodiment from the axial direction. Figure 13 is a view of the first gear member 33b from the axial direction. Figure 14 is a view of the second gear member 34b from the axial direction. The multi-stage gear 32b of the third embodiment differs from the multi-stage gear 32 in that a first phase-aligning portion 335b is provided in the hole 332 of the first gear member 33b, and a phase-aligning portion 349b is provided in the column portion 342b of the second gear member 34b. In all other respects, the multi-stage gear 32b has the same configuration as the multi-stage gear 32. Therefore, parts of the multi-stage gear 32b that are substantially the same as those of the multi-stage gear 32 are given the same reference numerals, and detailed descriptions of these same parts are omitted.

[0092] The hole 332b of the first gear member 33b shown in Figures 12 and 13 has seven recesses 333 and a first phase alignment portion 335b. The first phase alignment portion 335b has a concave shape that is recessed radially outward, similar to the recesses 333, but has a larger circumferential width and greater radial depth than the recesses 333. That is, the first phase alignment portion 334b ​​has a concave shape that is recessed radially outward, and the cross-sectional shape when cut by a plane perpendicular to the center line (planetary axis J2) is different from the cross-sectional shape of the recesses 333. The seven recesses 333 are arranged in a line in the circumferential direction, and the first phase alignment portion 335b is adjacent to each of the recesses 333 at both ends in the circumferential direction. The circumferential distance between the first phase alignment portion 335b and the adjacent recess 333 is the same as the circumferential distance between adjacent recesses 333. In this embodiment, the first phase alignment portion 335b has a larger cross-sectional shape than the recess 333, but it may have a smaller cross-sectional shape or a shape other than rectangular.

[0093] Furthermore, the column portion 342b of the second gear member 34b shown in Figures 12 and 14 has seven protrusions 343 and a second phase-aligning portion 349b. The second phase-aligning portion 349b protrudes radially outward, similar to the protrusions 343. The seven protrusions 343 are arranged in a line in the circumferential direction, and the second phase-aligning portion 349b is adjacent to each of the protrusions 343 at both ends in the circumferential direction. The circumferential distance between the second phase-aligning portion 349b and the adjacent protrusion 343 is the same as the circumferential distance between adjacent protrusions 343.

[0094] Even with this configuration, the second phase-aligning portion 349b has a shape corresponding to the first phase-aligning portion 335b and is provided in a corresponding position. That is, the second phase-aligning portion 349b has a convex shape with a cross-sectional shape corresponding to the first phase-aligning portion 335b. As a result, when the first phase-aligning portion 335b and the second phase-aligning portion 349b are fitted together, the column portion 342b is inserted into the hole portion 332b. Therefore, the phases of the first gear 331 of the first gear member 33b and the second gear 341 of the second gear member 34b can be precisely aligned. This makes it easier to manufacture the multi-stage gear 32b and the reduction mechanism 30.

[0095] <Fourth Embodiment> Figure 15 is a view of the multi-stage gear 32c of the fourth embodiment from the axial direction. Figure 16 is a view of the first gear member 33c from the axial direction. Figure 17 is a view of the second gear member 34c from the axial direction. The multi-stage gear 32c of the fourth embodiment differs from the multi-stage gear 32 in that a first phase-aligning portion 335c is provided in the hole 332 of the first gear member 33b, and a second phase-aligning portion 349c is provided in the column portion 342c of the second gear member 34c. In all other respects, the multi-stage gear 32c has the same configuration as the multi-stage gear 32. Therefore, parts of the multi-stage gear 32c that are substantially the same as those of the multi-stage gear 32 are given the same reference numerals, and detailed descriptions of these same parts are omitted.

[0096] The hole 332c of the first gear member 33c shown in Figures 15 and 16 has eight recesses 333 and a first phase alignment portion 335c. In the first gear member 33c, the eight recesses 333 are arranged in a circumferential direction. In the first gear member 33c, there is one section where the circumferential spacing between adjacent recesses 333 is narrow. In the hole 332c, the section where the recesses 333 are closely spaced is the first phase alignment portion 335c.

[0097] Furthermore, as shown in Figures 15 and 17, in the second gear member 34c, the column portion 342c has a second phase alignment portion 349c. The column portion 342c has eight protrusions 343, and the eight protrusions 343 are formed in positions that can fit into the recesses 333 of the first gear member 33c. In other words, there is one section where the circumferential spacing between the eight protrusions 343 is narrow. This section with narrow spacing is the second phase alignment portion 349c.

[0098] The second phase-aligning portion 349c is provided at a position corresponding to the first phase-aligning portion 335c. As a result, when the second phase-aligning portion 349c is fitted into the first phase-aligning portion 335c, the column portion 342c is inserted into the hole portion 332c. Therefore, the phases of the first gear 331 of the first gear member 33c and the second gear 341 of the second gear member 34c can be precisely aligned. This makes it easier to manufacture the multi-stage gear 32c and the reduction mechanism 30.

[0099] <Fifth Embodiment> Figure 18 is a view of the multi-stage gear 32d of the fifth embodiment from the axial direction. Figure 19 is a view of the first gear member 33d from the axial direction. Figure 20 is a view of the second gear member 34d from the axial direction. The multi-stage gear 32d of the fifth embodiment differs from the multi-stage gear 32 in the shape of the hole 332 of the first gear member 33d and the column portion 342 of the second gear member 34d. In all other respects, the multi-stage gear 32d has the same configuration as the multi-stage gear 32. Therefore, parts of the multi-stage gear 32d that are substantially the same as those of the multi-stage gear 32 are given the same reference numerals, and detailed descriptions of these parts are omitted.

[0100] As shown in Figure 18, the first gear member 33d has 18 teeth on the first gear 331. Therefore, the number of teeth on the first gear 331 is a multiple of 3. In other words, the first gear member 33d is triplicately symmetrical, so that parts overlap even when shifted by 120 degrees. Therefore, the cross-section of the plane perpendicular to the planetary axis J2 of the hole 332d can be any shape other than a circle, such that it does not rotate in the circumferential direction when the column 342d is fitted into it. In this embodiment, the cross-section of the plane perpendicular to the planetary axis J2 of the hole 332d of the first gear member 33d shown in Figures 18 and 19 is a triangular shape with rounded corners.

[0101] Furthermore, as shown in Figures 18 and 20, in the second gear member 34d, the cross-section of the plane perpendicular to the planetary axis J2 of the column portion 342d is triangular in shape with rounded corners to match the hole portion 332d. As a result, the column portion 342d is inserted into the hole portion 332d when it aligns with the shape of the hole portion 332d. As described above, the first gear 331 of the first gear member 33d is 3-fold symmetrical so that they coincide when rotated 120 degrees. Therefore, when the column portion 342d is fitted into the hole portion 332d, the phases of the first gear 331 of the first gear member 33d and the second gear 341 of the second gear member 34d can be precisely aligned. This facilitates the manufacture of the multi-stage gear 32c and the reduction mechanism 30. In addition, since the cross-sectional shape of the hole portion 332d and the column portion 342d is not circular, circumferential slippage is suppressed. As a result, rotation and torque are transmitted safely and accurately.

[0102] The shape of the cross-section of the hole 332d and column 342d perpendicular to the planetary axis J2 is determined by the shape of the first gear 331 of the first gear member 33d. For example, if the first gear 331 is symmetrical five times, a pentagonal shape can be adopted as the cross-sectional shape of the plane perpendicular to the planetary axis J2 of the hole 332d and column 342d. Also, if the first gear 331 is not rotationally symmetric, such as when the number of teeth is a prime number, a non-rotationally symmetric shape can be adopted as the cross-sectional shape of the hole 332d and column 342d perpendicular to the planetary axis J2. In this way, the positions of the first gear member 33d and the second gear member 34d are uniquely determined. Therefore, the phases of the first gear 331 of the first gear member 33d and the second gear 341 of the second gear member 34d can be precisely aligned.

[0103] <Sixth Embodiment> Figure 21 is a view of the multi-stage gear 32e of the sixth embodiment as seen from the axial direction. Figure 22 is an enlarged view of a part of the multi-stage gear 32e shown in Figure 21. As shown in Figures 21 and 22, the shape of the internal teeth 336e between adjacent recesses 333e in the circumferential direction of the hole 332e of the first gear member 33e of the multi-stage gear 32e, and the shape of the convex portion 343e of the column portion 342e of the second gear member 34e may be involute. That is, the convex portion 343e is involute. In addition, the portion between the recesses 333e of the hole 332e of the first gear member 33e is configured as an involute internal teeth portion 336.

[0104] By making the internal teeth 335e and the protrusions 343e involute, machining accuracy can be improved, and the strength of the axial root of the protrusions 343e can be increased, thereby increasing the rigidity when the first gear member 33e and the second gear member 34e are combined. As a result, a larger torque can be transmitted stably and accurately. Stable torque transmission means that a constant torque can be transmitted over a long period of time.

[0105] As shown in Figure 22, by making the internal teeth 336 and the protrusions 343e of the first gear member 33e involute, the involute internal teeth and external teeth mesh together. In other words, the contact portion 37 between the recess 333e and the protrusion 343e becomes a point contact (line contact). As a result, the first gear member 33e and the second gear member 34e can be fitted together without placing an excessive load on the recess 333e and the protrusion 343e, compared to the case where the recess and the protrusion are in surface contact.

[0106] Furthermore, a gap 321e is formed between the convex portion 343e and the concave portion 333e. Also, a gap 322e is formed between the portion 3410 between the circumferentially aligned convex portions 343e and the internal tooth portion 336. With this configuration, the machining accuracy of the parts facing each other via the gap 321e and the parts facing each other via the gap 322e can be set lower than that of the parts in contact. This reduces the effort and time required for manufacturing.

[0107] In the embodiments described above, a configuration is given in which the first gear member and the second gear member are connected by inserting a column portion provided on the second gear member having a large-diameter second gear into a hole provided on the first gear member having a small-diameter first gear. However, the invention is not limited to this configuration. The connection may also be made by inserting a column portion provided on the first gear member having a small-diameter first gear into a hole provided on the second gear member. However, when a column portion is provided on the second gear member and inserted into a hole provided on the first gear member, the length of the column portion can be made approximately the same as the length of the first gear member. As a result, the area of ​​the spline fitting portion can be increased, enabling the transmission of high torque and suppressing damage to the spline fitting portion.

[0108] Various technical features disclosed herein can be modified in various ways without departing from the spirit of the technical creation. Furthermore, the multiple embodiments and modifications shown herein may be combined as possible.

[0109] <Summary> The present invention has the following configuration.

[0110] (1) A first gear member formed of a first material and having a first gear, A second gear member having a second gear which is formed of a second material different from the first material and has a different outer diameter from the first gear, The first gear member and the second gear member are connected with their centerlines aligned. The first gear member extends in a direction along the center line and has holes on its inner circumferential surface at points at different distances from the center line. The second gear member extends in a direction along the center line, has points on its outer circumferential surface at different distances from the center line, and has a column portion that is inserted into the hole. A multi-stage gear in which, when the column portion is inserted into the hole, at least a portion of the outer circumferential surface of the column portion contacts at least a portion of the inner circumferential surface of the hole.

[0111] (2) The aforementioned hole has a plurality of recesses that are recessed radially outward from the inner circumferential surface and extend axially, and are arranged in a circumferential direction. The column portion has a plurality of protrusions that project radially outward from the outer surface and extend axially, and are arranged in a circumferential direction. The multi-stage gear according to (1), wherein at least a portion of the outer surface of the protrusion is in contact with at least a portion of the inner surface of the recess.

[0112] (3) The aforementioned hole has a first phase alignment portion provided on its inner circumferential surface. The column portion has a second phase-aligning portion provided at a position corresponding to the first phase-aligning portion, as described in (1) or (2).

[0113] (4) The multi-stage gear according to (3), wherein the second phase-aligning portion has a shape that allows it to contact the first phase-aligning portion.

[0114] (5) The aforementioned hole has a first phase alignment portion provided on its inner circumferential surface. The column portion has a second phase-aligning portion provided at a position corresponding to the first phase-aligning portion, The first phase alignment portion has a concave shape that is recessed radially outward, and the cross-sectional shape obtained by cutting it with a plane perpendicular to the center line is different from the cross-sectional shape of the recess. The multi-stage gear described in (2), wherein the second phase-aligning portion has a convex cross-sectional shape corresponding to the first phase-aligning portion.

[0115] (6) The multi-stage gear according to any one of (3) to (5), wherein the convex portion has an involute shape, and the concave portion has an involute shape that can contact at least a portion of both sides in the circumferential direction of the convex portion.

[0116] (7) A multi-stage gear according to any one of (1) to (6), wherein the second gear has a larger diameter than the first gear.

[0117] (8) A multi-stage gear according to any one of (1) to (8), wherein the first material is a metal material and the second material is a resin material.

[0118] (9) A multi-stage gear according to any one of (1) to (8), wherein a reference portion is formed at a predetermined position relative to the gear teeth of the first gear or the second gear.

[0119] (10) A multi-stage gear described in any of (1) to (9) is a planetary gear. A gearbox having internal gears and a sun gear that mesh with the aforementioned planetary gears.

[0120] (11) (10) The gearbox described above, A motor with a reduction gear, comprising a motor connected to the aforementioned reduction gear. [Explanation of symbols]

[0121] 100 Electric motor with gearbox 10 Housing section 11. First housing member 111 Bottom 112 Side wall section 113 Through hole 114 Connection part 12. Second housing member 121 Through hole 131 First bearing 132 Second bearing 14 Interior space 20 Electric motor section 21 Electric motor shaft 211 Tip 22 rotors 221 Rotor Core 222 Rotor Magnet 23 Status 231 Stator Core 232 Insulators 233 coils 234 Teeth 235 Through hole 24 Holder section 241 First holder section 242 Second holder section 243 First cylindrical part 244 1st protrusion 245 First through hole 246 Second cylindrical part 247 Second through hole 248 Support protrusion 25 circuit boards 251 Third bearing 252 Fourth bearing 30 Reduction mechanism 31 Sun Gear 32, 32a, 32b, 32c, 32d, 32e multi-stage gear 33, 33a, 33b, 33c, 33d, 33e First gear member 331 First gear 332, 332a, 332b, 332c, 332d, 332e holes 333, 333e recess 334 Cylindrical section 335, 335b, 335c First phase alignment section 336 Internal teeth 34, 34a, 34b, 34c, 34d, 34e Second gear member 340 Flange section 3401 Circumferential groove 341 Second gear 342, 342a, 342b, 342c, 342d, 342e Column section 343, 343e protrusion 344 sliding holes 345 Mounting surface 346 Reference section 347 1st contact surface 348 Second contact surface 349, 349b, 349c Second phase alignment section 35 Internal gear 36 Careers 361 Main body 362 Legs 363 Support shaft 364 Pressing part 365 Fixed shaft holes 366 Base 41. First fixed shaft 42. Second fixed shaft

Claims

1. A first gear member formed of a first material and having a first gear, A second gear member having a second gear which is formed of a second material different from the first material and has a second gear which has a different outer diameter from the first gear, The first gear member and the second gear member are connected with their centerlines aligned. The first gear member extends in a direction along the center line and has holes on its inner circumferential surface at points that are at different distances from the center line. The second gear member extends in a direction along the center line, has points on its outer circumferential surface at different distances from the center line, and has a column portion that is inserted into the hole. A multi-stage gear in which, when the column portion is inserted into the hole, at least a portion of the outer circumferential surface of the column portion contacts at least a portion of the inner circumferential surface of the hole.

2. The aforementioned hole has a plurality of recesses that are recessed radially outward from the inner circumferential surface and extend axially, and are arranged in a circumferential direction. The column portion has a plurality of protrusions that project radially outward from the outer surface and extend axially, and are arranged in a circumferential direction. The multi-stage gear according to claim 1, wherein at least a portion of the outer surface of the protrusion is in contact with at least a portion of the inner surface of the recess.

3. The aforementioned hole has a first phase alignment portion provided on its inner circumferential surface. The multi-stage gear according to claim 1, wherein the column portion has a second phase-aligning portion provided at a position corresponding to the first phase-aligning portion.

4. The multi-stage gear according to claim 3, wherein the second phase-aligning portion has a shape that allows it to contact the first phase-aligning portion.

5. The aforementioned hole has a first phase alignment portion provided on its inner circumferential surface. The column portion has a second phase-aligning portion provided at a position corresponding to the first phase-aligning portion, The first phase alignment portion has a concave shape that is recessed radially outward, and the cross-sectional shape obtained by cutting it with a plane perpendicular to the center line is different from the cross-sectional shape of the recess. The multi-stage gear according to claim 2, wherein the second phase-aligning portion has a convex cross-sectional shape corresponding to the first phase-aligning portion.

6. The multi-stage gear according to claim 2, wherein the convex portion is involute in shape, and the concave portion is involute in shape so as to be able to contact at least a portion of both sides in the circumferential direction of the convex portion.

7. The multi-stage gear according to claim 1, wherein the second gear has a larger diameter than the first gear.

8. The multi-stage gear according to claim 7, wherein the first material is a metal material and the second material is a resin material.

9. The multi-stage gear according to claim 1, wherein a reference portion is formed at a predetermined position relative to the gear teeth of the first gear or the second gear.

10. The multi-stage gear according to any one of claims 1 to 9 is a planetary gear, A gearbox having internal gears and a sun gear that mesh with the aforementioned planetary gears.

11. The gearbox according to claim 10, A motor with a reduction gear, comprising a motor connected to the aforementioned reduction gear.

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