Sun gear unit of planetary gear mechanism, speed changer

Abstract

The sun gear unit of the planetary gear mechanism comprises: a sun gear shaft having a first end for inputting and outputting rotational force and a second end opposite to the first end, and having a shaft track surface formed on its outer circumferential surface; a sun gear disposed at the second end and meshing with the planetary gear of the planetary gear mechanism; an outer ring mounted on a support portion supporting the sun gear shaft, disposed in a manner surrounding the shaft track surface, and having an outer ring track surface formed on its inner circumferential surface; and a plurality of rolling elements disposed between the shaft track surface and the outer ring track surface.

Description

Technical Field

[0001] This disclosure relates to a sun gear unit and a speed changer for a planetary gear mechanism. Background Technology

[0002] For example, as described in Patent Document 1, there is a speed reducer that reduces the rotational speed of the drive shaft of a drive unit. This speed reducer has multiple rotating shafts equipped with gears, and reduces the rotational speed by sequentially transmitting the rotation of the drive shaft to the multiple rotating shafts. Additionally, there are speed reducers that use a planetary gear mechanism to change the rotational speed.

[0003] Prior art literature Patent documents Patent Document 1: Japanese Patent Application Publication No. 2017-3048 Summary of the Invention The problem that the invention aims to solve In a transmission equipped with a planetary gear mechanism, the sun gear shaft of the sun gear unit of the planetary gear mechanism is rotatably supported on a support via a bearing. If this sun gear shaft vibrates, a reduction in rotational performance and durability is generally considered.

[0004] Therefore, the purpose of this disclosure is to provide a sun gear unit and a transmission that can support the sun gear shaft in a planetary gear mechanism capable of stable rotation.

[0005] Solution for solving the problem The sun gear unit disclosed herein is [1] "a sun gear unit, which is a sun gear unit of a planetary gear mechanism, the sun gear unit comprising: a sun gear shaft having a first end for inputting and outputting rotational force and a second end opposite to the first end, wherein an shaft track surface is formed on the outer peripheral surface between the first end and the second end; a sun gear disposed at the second end and meshing with a planetary gear of the planetary gear mechanism; an outer ring mounted on a support portion supporting the sun gear shaft, disposed in a manner surrounding the shaft track surface, and having an outer ring track surface formed on its inner peripheral surface; and a plurality of rolling elements disposed between the shaft track surface and the outer ring track surface." In this sun gear unit, the sun gear shaft is supported by a support portion via rolling elements and an outer ring. That is, the sun gear shaft also functions as the inner ring of a bearing. This reduces the number of components in the mechanism supporting the sun gear shaft and suppresses the decrease in support accuracy of the sun gear shaft caused by deviations in component precision. Therefore, in this sun gear unit, the sun gear shaft can be supported to rotate stably.

[0006] The sun gear unit disclosed herein may also be [2] "the sun gear unit according to [1] above, wherein a spline is formed on the outer or inner circumferential surface of the first end". Thus, the sun gear unit can transmit rotational force with other rotating components more reliably via the spline.

[0007] The sun gear unit disclosed herein can also be [3] "According to the sun gear unit described in [1] or [2] above, the sun gear shaft has: a shoulder surface forming portion having a shoulder surface adjacent to the shaft track surface on its outer peripheral surface at a position closer to the first end than the shaft track surface; and an insert portion adjacent to the shoulder surface forming portion at a position closer to the first end than the shoulder surface forming portion, wherein the size of the shoulder surface forming portion in the radial direction of the sun gear shaft is larger than the size of the insert portion in the radial direction of the sun gear shaft." In this case, a step is formed between the shoulder surface forming portion and the insert portion on the outer peripheral surface of the sun gear shaft. Thus, the sun gear unit can position the component embedded in the insert portion by abutting against the step portion.

[0008] The sun gear unit disclosed herein can also be [4] "the sun gear unit according to any one of [1] to [3] above, wherein the sun gear shaft has a first shoulder surface and a second shoulder surface adjacent to the shaft track surface in the axial direction of the sun gear shaft, the first shoulder surface and the second shoulder surface being respectively annular extending circumferentially along the sun gear shaft, and the outer diameters of the first shoulder surface and the second shoulder surface being different from each other." The rolling element disposed on the shaft track surface is less likely to climb onto the shoulder surface on the larger diameter side of the first shoulder surface and the second shoulder surface compared to the shoulder surface on the smaller diameter side. Thus, by making the outer diameters of the first shoulder surface and the second shoulder surface different from each other, the sun gear unit can suppress the rolling element from climbing onto the shoulder surface and can withstand axial loads.

[0009] The sun gear unit disclosed herein may also be [5] "the sun gear unit according to any one of [1] to [4] above, wherein the outer circumferential surface of the outer ring is provided with a engaging portion that engages with the support portion in the axial direction of the sun gear shaft." In this case, by means of the engaging portion provided on the outer ring, the axial displacement between the outer ring and the support portion of the sun gear shaft can be suppressed.

[0010] The sun gear unit disclosed herein can also be [6] "the sun gear unit according to any one of [1] to [5] above, wherein a gap is provided between the sun gear and the outer ring and the rolling element in the axial direction of the sun gear shaft." In this case, the design freedom can be increased in the sun gear unit, or the assemblability around the rolling element and the outer ring can be improved.

[0011] The sun gear unit disclosed herein may also be [7] "the sun gear unit according to any one of [1] to [6] above, wherein the sun gear shaft is provided with a shaft through hole extending along the axis of the sun gear shaft and through which a rotating shaft passes." In this way, since other rotating shafts can be arranged inside the sun gear shaft, miniaturization of the device using the sun gear unit can be achieved.

[0012] The sun gear unit disclosed herein can also be [8] "According to the sun gear unit described above [7], a curing layer is provided on the surface portion of the sun gear shaft, the hardness of the portion with the curing layer is higher than the hardness of the portion of the sun gear shaft other than the curing layer, and the thickness of the curing layer is greater than half the wall thickness of the shaft guide surface of the sun gear shaft." Here, the inner circumferential surface of the shaft through hole of the sun gear shaft also becomes the surface of the sun gear shaft. Therefore, in addition to the portion of the sun gear shaft facing the radially outward side, a curing layer is also provided on the portion of the inner circumferential surface of the shaft through hole of the sun gear shaft. By making the thickness of the curing layer greater than half the wall thickness of the shaft guide surface, the portion of the shaft guide surface of the sun gear shaft becomes a state in which a curing layer is provided throughout the entire radial wall thickness area. As a result, the sun gear unit can further improve the internal hardness of the shaft guide surface.

[0013] The gearbox disclosed herein is [9] "a gearbox comprising: a planetary gear mechanism having a sun gear unit as described in [7] or [8] above; and a differential gear unit having a differential housing that transmits rotational force from the planetary gear mechanism, and a differential mechanism provided in the differential housing, wherein a drive shaft connected to the differential mechanism passes through the shaft through hole as the rotational shaft."

[0014] In this gearbox, the sun gear shaft is supported on a support via rolling elements and an outer ring. That is, the sun gear shaft also functions as the inner ring of a bearing. This sun gear unit reduces the number of components supporting the sun gear shaft and suppresses the decrease in support accuracy of the sun gear shaft caused by deviations in component precision. Therefore, in a gearbox with this sun gear unit, the sun gear shaft can be supported to rotate stably. Furthermore, in this gearbox, a drive shaft connected to the differential gear can be positioned inside the sun gear shaft. This enables miniaturization of the gearbox.

[0015] The effects of the invention According to this disclosure, the sun gear shaft can be supported to rotate stably. Attached Figure Description Figure 1 This is a cross-sectional view showing the main parts of the transmission in the embodiment.

[0017] Figure 2 Viewed from the spline side Figure 1 A three-dimensional view of the sun gear unit.

[0018] Figure 3 Viewed from the sun gear side Figure 1 A three-dimensional view of the sun gear unit.

[0019] Figure 4 yes Figure 1 An enlarged sectional view of the sun gear unit.

[0020] Figure 5 This diagram illustrates an example of a manufacturing embodiment of the sun gear shaft.

[0021] Figure 6 This is a cross-sectional view of the sun gear shaft in a modified example.

[0022] Figure 7 This is an enlarged sectional view around the shaft guide surface used to illustrate the formation of the shaft guide surface and the sun gear.

[0023] Figure 8 This is an enlarged sectional view around the shaft track surface of the sun gear unit in the first modified example.

[0024] Figure 9 This is an enlarged sectional view of the sun gear unit in the second variation.

[0025] Figure 10 This is a cross-sectional view showing the cured layer disposed on the surface of the sun gear unit in the second variation.

[0026] Figure 11 (a) ~ Figure 11 (c) is an enlarged sectional view of the sun gear unit of the third variation.

[0027] Figure 12 This is a cross-sectional view showing the main parts of a gearbox with a modified sun gear shaft. Detailed Implementation

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Furthermore, in the drawings, the same or equivalent elements are given the same reference numerals, and repeated descriptions are omitted. Additionally, the speed reducer used to reduce the rotational speed of the drive unit will be described below as the speed reducer of the present disclosure.

[0029] like Figure 1As shown, in this embodiment, as an example, the gearbox 1 is configured as a reduction gear for an EV (Electric Vehicle) equipped with a drive unit 30 having an electric motor. The gearbox 1 includes a planetary gear mechanism 10 and a differential gear unit 20. Furthermore, the gearbox 1... Figure 1 The middle part is omitted, but it has a frame that houses various mechanisms such as the planetary gear mechanism 10.

[0030] The drive unit 30 constitutes an electric motor unit that serves as the drive source for the vehicle. More specifically, the drive unit 30 includes a motor rotor 31 and a rotor shaft 32. The motor rotor 31 constitutes the rotor of the electric motor. Although not shown in the figure, the drive unit 30, as a drive mechanism, includes components such as magnets that constitute the electric motor. In addition, the drive unit 30 may also include electronic components such as an inverter.

[0031] The rotor shaft 32 is located at the center of the motor rotor 31. The rotor shaft 32 is driven by the rotation of the motor rotor 31. The rotor shaft 32 serves as the output shaft for the driving force (rotational force) of the drive unit 30. The rotor shaft 32 is connected to the planetary gear mechanism 10. The rotor shaft 32 is cylindrical. The first drive shaft 41 passes through the inner side of the rotor shaft 32. In the rotor shaft 32, a rotor spline 32a is formed on the inner circumferential surface of the end connected to the planetary gear mechanism 10.

[0032] The planetary gear mechanism 10 of the transmission 1 reduces the rotational force transmitted from the rotor shaft 32 of the drive unit 30 and transmits it to the differential gear unit 20. The planetary gear mechanism 10 includes a sun gear unit 11, multiple planetary gear units 12, a support 13, and an external gear 14. The sun gear unit 11 is connected to the rotor shaft 32 of the drive unit 30. Rotational force is transmitted from the rotor shaft 32 to the sun gear unit 11. The axis of rotation of the sun gear unit 11 is the same as the axis of rotation of the rotor shaft 32. The sun gear unit 11 has a sun gear 111. Details regarding the sun gear unit 11 will be described later.

[0033] Multiple planetary gear units 12 are arranged circumferentially at predetermined intervals around the sun gear 111 of the sun gear unit 11. Each planetary gear unit 12 transmits rotational force from the sun gear 111. Each planetary gear unit 12 includes a first planetary gear (planetary gear) 121, a second planetary gear 122, and a planetary gear shaft 123. The first planetary gear 121 and the second planetary gear 122 are arranged on the same axis of rotation and are connected to each other. That is, the first planetary gear 121 and the second planetary gear 122 rotate integrally. The diameter of the first planetary gear 121 is larger than the diameter of the second planetary gear 122. The first planetary gear 121 meshes with the sun gear 111 of the sun gear unit 11. The planetary gear shaft 123 serves as the axis of rotation for both the first planetary gear 121 and the second planetary gear 122. The planetary gear shaft 123 supports the first planetary gear 121 and the second planetary gear 122 so that they can rotate.

[0034] The support 13 supports the ends of the drive unit 30 on the planetary gear shafts 123 of the multiple planetary gear units 12, respectively. The axis of rotation of the support 13 is the same as the axis of rotation of the sun gear unit 11. The ends of the planetary gear shafts 123 of the multiple planetary gear units 12, opposite to the side supported on the support 13, are supported by the differential housing 21 of the differential gear unit 20.

[0035] The external gear 14 is ring-shaped and has gears on its inner circumferential surface. The external gear 14 is arranged to surround a plurality of second planetary gears 122 and meshes with each of the plurality of second planetary gears 122. In this embodiment, the external gear 14 is, for example, fixed to the frame of the transmission 1.

[0036] Thus, multiple planetary gear units 12 rotate around the sun gear unit 11 as the sun gear unit 11 rotates. As the planetary gear units 12 rotate around the sun gear unit 11, the differential gear unit 20 rotates.

[0037] The differential gear unit 20 transmits rotational force from the planetary gear mechanism 10. The rotation axis of the differential gear unit 20 is the same as the rotation axis of the planetary gear mechanism 10 and the rotor shaft 32. The differential gear unit 20 includes a differential housing 21 and a differential mechanism 22.

[0038] Rotational force is transmitted from the planetary gear unit 12 of the planetary gear mechanism 10 to the differential housing 21. The differential housing 21 has internal space.

[0039] A differential mechanism 22 is disposed within the differential housing 21. The differential mechanism 22 is, for example, a differential mechanism of a vehicle differential gear unit including a pinion and a spur gear. Various known mechanisms can be used as the differential mechanism 22. A first insertion port h1 and a second insertion port h2 are provided on the differential housing 21 along the rotation axis of the sun gear unit 11. A first drive shaft (rotation shaft) 41 is inserted into the differential mechanism 22 via the first insertion port h1, and a second drive shaft 42 is inserted into the differential mechanism 22 via the second insertion port h2. The first drive shaft 41 and the second drive shaft 42 are respectively disposed on the rotation axis of the sun gear unit 11.

[0040] Next, the sun gear unit 11 will be described in detail. For example... Figures 2-4 As shown, the sun gear unit 11 includes a sun gear shaft 110, a sun gear 111, an outer ring 112, a plurality of balls (rolling elements) 113, and a retainer 114. The sun gear shaft 110 is disposed on the rotation axis of the rotor shaft 32. The sun gear shaft 110 has a first end 110a connected to the rotor shaft 32 and a second end 110b opposite to the first end 110a. Rotational force is input from the rotor shaft 32 to the first end 110a. In this embodiment, a sun gear spline (spline) 110c is formed on the outer peripheral surface of the first end 110a. The sun gear spline 110c meshes with the rotor spline 32a of the rotor shaft 32. Thus, rotational force is transmitted from the rotor shaft 32 to the sun gear unit 11.

[0041] A sun gear 111 is provided on the outer peripheral surface of the second end 110b of the sun gear shaft 110. The sun gear 111 rotates integrally with the sun gear shaft 110. In this embodiment, the sun gear 111 is integrally disposed with the sun gear shaft 110. The sun gear 111 transmits the rotational force transmitted to the sun gear unit 11 to the first planetary gear 121 of the planetary gear unit 12.

[0042] A shaft guide surface 110e is formed on the outer peripheral surface of the sun gear shaft 110 between the first end 110a and the second end 110b. That is, the shaft guide surface 110e is formed on the outer peripheral surface of the sun gear shaft 110 between the sun gear spline 110c and the sun gear 111. The shaft guide surface 110e is provided over the entire circumferential region of the outer peripheral surface of the sun gear shaft 110. The shaft guide surface 110e is a groove extending circumferentially along the sun gear shaft 110. In this embodiment, the cross-sectional shape of the shaft guide surface 110e is approximately arc-shaped.

[0043] Additionally, on the outer peripheral surface of the sun gear shaft 110, a shaft track surface 110e is formed in the track surface forming portion 110f between the sun gear spline 110c and the sun gear 111 (see reference). Figure 4The track surface forming portion 110f is the part of the sun gear shaft 110 that faces the inner circumferential surface of the outer ring 112. In this embodiment, as an example, the outer diameter of the track surface forming portion 110f is larger than the outer diameter of the first end portion 110a forming the sun gear spline 110c. In this embodiment, as an example, the outer diameter of the track surface forming portion 110f is smaller than the outer diameter of the sun gear 111. However, the size relationship between the track surface forming portion 110f and other portions is not limited to this relationship, and may be the opposite of the relationship described herein.

[0044] The outer ring 112 is mounted on the shaft support portion (support portion) 50 that supports the sun gear shaft 110. In this embodiment, the shaft support portion 50 is constituted by the bracket (support portion) 13 of the planetary gear mechanism 10. However, the shaft support portion 50 may also be constituted, for example, by a part of a frame housing the planetary gear mechanism 10, etc.

[0045] The outer ring 112 is provided to surround the shaft track surface 110e formed on the sun gear shaft 110. An outer ring track surface 112a is formed on the inner circumferential surface of the outer ring 112. The outer ring track surface 112a is provided throughout the entire circumferential region of the inner circumferential surface of the outer ring 112. The outer ring track surface 112a is a groove extending circumferentially along the outer ring 112. In this embodiment, the cross-sectional shape of the outer ring track surface 112a is approximately arc-shaped. The outer ring track surface 112a of the outer ring 112 faces the shaft track surface 110e of the sun gear shaft 110.

[0046] Multiple balls 113 are disposed between the outer raceway surface 112a of the outer raceway 112 and the shaft raceway surface 110e of the sun gear shaft 110. The balls 113 are spherical. A retainer 114 holds each of the multiple balls 113 between the outer raceway surface 112a and the shaft raceway surface 110e to allow them to roll freely.

[0047] The sun gear shaft 110 has a through hole 110d extending along the axis of the sun gear shaft 110. The first drive shaft 41, which is connected to the differential mechanism 22 of the differential gear unit 20, passes through the through hole 110d. That is, the rotation axis of the sun gear shaft 110 and the rotation axis of the first drive shaft 41 are the same line.

[0048] As described above, in the sun gear unit 11 of the planetary gear mechanism 10, the sun gear shaft 110 is supported on the shaft support portion 50 via balls 113 and an outer ring 112. That is, the sun gear shaft 110 also functions as the inner ring of a bearing. In this way, the sun gear unit 11 can reduce the number of components in the mechanism supporting the sun gear shaft 110 and can suppress the decrease in the support accuracy of the sun gear shaft 110 caused by deviations in component precision. Therefore, in the sun gear unit 11, the sun gear shaft 110 can be supported to rotate stably.

[0049] Furthermore, axial loads are sometimes applied to this sun gear unit 11. For example, when the sun gear shaft is supported by a bearing with an inner ring, a retaining ring needs to be installed on the sun gear shaft or a spacer for abutting the inner ring against the sun gear to prevent the inner ring from shifting. However, in this sun gear unit 11, the sun gear shaft 110 also functions as the inner ring of the bearing, positioning the bearing portion, so there is no need to provide a retaining ring or spacer to prevent the inner ring from shifting.

[0050] In the sun gear unit 11 of this embodiment, the sun gear shaft 110 also functions as the inner ring of a bearing, thus eliminating the need for a separate inner ring. Therefore, radial miniaturization and weight reduction can be achieved in the sun gear unit 11.

[0051] A sun gear spline 110c is provided at the first end 110a of the sun gear shaft 110, which meshes with the rotor spline 32a of the rotor shaft 32. As a result, the sun gear unit 11 can transmit rotational force to the rotor shaft 32, which is another rotating component, more reliably via the sun gear spline 110c.

[0052] A shaft through hole 110d is provided on the inner side of the sun gear shaft 110. Other rotating shafts can be arranged inside the sun gear unit 11. In this embodiment, a first drive shaft 41 connected to the differential gear unit 20 is arranged in the shaft through hole 110d of the sun gear shaft 110. Therefore, the device having the sun gear unit 11 (in this embodiment, a transmission 1) can be miniaturized.

[0053] Furthermore, as mentioned above, the sun gear unit 11 originally did not have an inner ring as another component, nor did it require a retaining ring or spacer to prevent the inner ring from shifting. Since no space is needed for a retaining ring, the axial length of the sun gear shaft 110 can be shortened. Generally, with the inner ring of the bearing held by a magnetic chuck at its axial end face, a track groove (track surface) is formed on the outer circumferential surface of the inner ring by a grinding slide. For example, when the length of the sun gear shaft 110 is short, a shaft track surface 110e can be formed on the outer circumferential surface of the sun gear shaft 110 using the same device as the device for forming a track groove in the inner ring of the bearing. Specifically, as... Figure 5As shown, for example, the second end 110b of the sun gear shaft 110 is held by a magnetic chuck G1. With the sun gear shaft 110 held by the magnetic chuck G1, a shaft track surface 110e is formed on the track surface forming portion 110f of the outer circumferential surface of the sun gear shaft 110 using a grinding slipper G2. Thus, the shaft track surface 110e can be formed on the track surface forming portion 110f of the sun gear shaft 110 using a device similar to that used for forming the inner ring of a general bearing.

[0054] In this case, when a bearing with an inner ring is mounted on the sun gear shaft, the inner ring of the bearing is sometimes positioned by abutting against the end of the sun gear. In this situation, the sun gear and the inner ring are related, which restricts their placement and the size of the sun gear. On the other hand, in the sun gear unit 11 of this embodiment, the sun gear shaft 110 also functions as the inner ring of the bearing. Therefore, in the sun gear unit 11, it is not necessary to position the inner ring through the sun gear 111. That is, the sun gear 111 is not related to the shaft track surface 110e, which functions as the inner ring of the bearing, and there are no restrictions on their placement or the size of the sun gear 111.

[0055] Therefore, as Figure 4 As shown, a gap is provided between the sun gear 111 and the outer ring 112 and the ball bearing 113 in the axial direction of the sun gear shaft 110. Additionally, as... Figure 6 As shown, a large clearance of a desired size can also be provided between the sun gear 111 and the outer ring 112 and the ball bearings 113 in the axial direction of the sun gear shaft 110. For example... Figure 6 As shown, a ball clamp G3, used for positioning the ball 113 between the outer ring 112 and the shaft track surface 110e, can also be positioned in the gap between the sun gear 111, the outer ring 112, and the ball 113. In this case, the ball clamp G3 is positioned in the gap between the sun gear 111 and the outer ring 112. Furthermore, the ball 113 is positioned between the outer ring 112 and the shaft track surface 110e from the first end 110a side of the sun gear shaft 110. When positioning the ball 113, the ball clamp G3 functions as a clamp to prevent the ball 113 from falling out between the outer ring 112 and the shaft track surface 110e. In this way, the sun gear unit 11 can increase the design flexibility by making the sun gear 111 and the shaft track surface 110e independent. In addition, since the ball clamp G3 can be positioned in the gap between the sun gear 111 and the outer ring 112, the assemblability of the sun gear unit 11 can be improved.

[0056] For example, in a structure where the inner ring is mounted on the sun gear shaft, the width of the sun gear (the axial length of the sun gear shaft) is sometimes extended in order to position the inner ring against the sun gear. In the sun gear unit 11 of this embodiment, as described above, the position of the sun gear 111 is not related to the position of the shaft track surface 110e. Therefore, in the sun gear unit 11, it is not necessary to extend the width of the sun gear 111 simply to abut against the inner ring. In the sun gear unit 11, the width of the sun gear 111 can be only the width required to transmit rotational force. Thus, the width of the sun gear 111 is not unnecessarily extended in the sun gear unit 11, thereby achieving weight reduction. Furthermore, since the width of the sun gear 111 is not unnecessarily extended in the sun gear unit 11, the processing time for forming the sun gear 111 can be shortened, and the life of the tool used to form the sun gear 111 can be extended.

[0057] For example, such as Figure 7 As shown, the shaft raceway surface 110e is sometimes ground using a grinding wheel G4. As mentioned above, the position of the sun gear 111 is not related to the position of the shaft raceway surface 110e. Therefore, the positions of the sun gear 111 and the shaft raceway surface 110e can be adjusted so that the tool forming the shaft raceway surface 110e, such as the grinding wheel G4, does not interfere with the sun gear 111. Similarly, the tooth surface of the sun gear 111 is sometimes ground using a gear grinding wheel. In this case, the positions of the sun gear 111 and the shaft raceway surface 110e can also be adjusted so that the tool forming the sun gear 111, such as the gear grinding wheel, does not interfere with the shoulder of the shaft raceway surface 110e. Thus, the sun gear unit 11 can increase the design freedom of the sun gear 111 and the shaft raceway surface 110e, and a sun gear shaft 110 having the sun gear 111 and the shaft raceway surface 110e can be easily formed.

[0058] In this embodiment, the sun gear 111 is integrally formed with the sun gear shaft 110. Furthermore, the shaft raceway surface 110e is formed on the outer peripheral surface of the sun gear shaft 110 (raceway surface forming portion 110f). That is, the sun gear shaft 110, the sun gear 111, and the shaft raceway surface 110e are integrally formed. Therefore, when forming the sun gear 111 and the shaft raceway surface 110e, the same machining reference can be used to form the sun gear 111 and the shaft raceway surface 110e. As a result, the sun gear unit 11 can ensure the coaxiality of the sun gear 111 and the shaft raceway surface 110e with higher precision.

[0059] The transmission 1 includes a planetary gear mechanism 10 having the aforementioned sun gear unit 11 and a differential gear unit 20 that transmits rotational force from the planetary gear mechanism 10. In this way, the transmission 1 with the sun gear unit 11 can support the sun gear shaft 110 to rotate stably.

[0060] (First variation) The first variation of the sun gear unit will be explained. For example... Figure 8 As shown, the sun gear unit 11A of this modified example includes a sun gear shaft 110A instead of the sun gear shaft 110 of the embodiment. The sun gear shaft 110A has a first shoulder surface (shoulder surface) S1 and a second shoulder surface S2, which are adjacent to the shaft raceway surface 110e in the axial direction of the sun gear shaft 110A, separated by the shaft raceway surface 110e. The first shoulder surface S1 is adjacent to the shaft raceway surface 110e on the side closer to the first end 110a than the shaft raceway surface 110e. The second shoulder surface S2 is adjacent to the shaft raceway surface 110e on the side closer to the sun gear 111 (the side of the second end 110b opposite to the first end 110a) than the shaft raceway surface 110e.

[0061] The first shoulder surface S1 and the second shoulder surface S2 are radially outward surfaces facing the sun gear shaft 110A, extending in a circular shape along the circumference of the sun gear shaft 110A. In this modified example, the first shoulder surface S1 and the second shoulder surface S2 are cylindrical surfaces with the rotation axis of the sun gear shaft 110A as their axis. The outer diameter (diameter of the cylindrical surface) of the first shoulder surface S1 and the outer diameter (diameter of the cylindrical surface) of the second shoulder surface S2 are different from each other. In this modified example, the outer diameter of the first shoulder surface S1 is larger than the outer diameter of the second shoulder surface S2.

[0062] Furthermore, the sun gear shaft 110A has a first shoulder surface forming portion (shoulder surface forming portion) 110g and an insert portion 110h. The first shoulder surface forming portion 110g is the portion of the sun gear shaft 110A located on the side closer to the first end 110a than the shaft track surface 110e. The first shoulder surface forming portion 110g, located on the side closer to the first end 110a than the shaft track surface 110e, has a first shoulder surface S1 on its outer peripheral surface adjacent to the shaft track surface 110e. The insert portion 110h is adjacent to the first shoulder surface forming portion 110g on the side closer to the first end 110a than the first shoulder surface forming portion 110g. A sun gear spline 110c is formed on the portion of the outer peripheral surface of the first shoulder surface forming portion 110g on the side of the first end 110a. Other components B are inserted into the outer peripheral surface of the insert portion 110h. The components B inserted into the insert portion 110h are not particularly limited.

[0063] In the radial direction of the sun gear shaft 110A, the size of the first groove shoulder forming portion 110g is larger than the size of the insert portion 110h. That is, a step D is formed at the connection between the first groove shoulder forming portion 110g and the insert portion 110h.

[0064] As described above, in this modified example, the diameter of the first shoulder surface S1 is larger than the diameter of the second shoulder surface S2. Therefore, the ball 113 disposed between the outer ring 112 and the shaft track surface 110e is unlikely to climb onto the first shoulder surface S1 on the larger diameter side, which is larger than the diameter of the second shoulder surface S2 on the smaller diameter side. In this way, the sun gear unit 11A can suppress the ball 113 from climbing onto the shoulder surface on the larger diameter side by making the outer diameters of the first shoulder surface S1 and the second shoulder surface S2 different from each other, and can withstand axial loads. In addition, in this modified example, the diameter of the first shoulder surface S1 is larger than that of the second shoulder surface S2, but it is also possible for the diameter of the second shoulder surface S2 to be larger than that of the first shoulder surface S1. It is only necessary to set the outer diameters of the first shoulder surface S1 and the second shoulder surface S2 according to the direction of the axial load to be borne.

[0065] Furthermore, a step D is formed on the outer peripheral surface of the sun gear shaft 110A between the first groove shoulder surface forming portion 110g and the insert portion 110h (connecting portion). As a result, the sun gear unit 11A can position the member B inserted into the insert portion 110h by abutting against the step D.

[0066] (Second variation) A second variation of the sun gear unit will be described. For example... Figure 9 As shown, the sun gear unit 11B of this modified example has a sun gear shaft 110B instead of the sun gear shaft 110 of the embodiment. As... Figure 10 As shown, a cured layer F is provided on a portion of the surface of the sun gear shaft 110B. The hardness of the portion with the cured layer F is higher than that of the portion of the sun gear shaft 110B other than the cured layer F. For example, the cured layer F can also be provided on the surface of the sun gear shaft 110B by carburizing. However, the method of providing the cured layer F is not limited to carburizing.

[0067] The cured layer F is provided from the surface of the sun gear shaft 110B to a predetermined depth. Furthermore, the inner circumferential surface of the shaft through-hole 110d of the sun gear shaft 110B also becomes a surface of the sun gear shaft 110B. Therefore, in addition to the portion of the sun gear shaft 110B facing radially outward, the cured layer F is also provided on the portion of the inner circumferential surface of the shaft through-hole 110d of the sun gear shaft 110B.

[0068] The thickness L of the cured layer F is greater than half the wall thickness of the axial surface 110e of the sun gear shaft 110B. In this modified example, the shaft track surface 110e is groove-shaped. In this modified example, the thickness L of the cured layer F is greater than half the wall thickness of the bottom of the groove in the groove-shaped shaft track surface 110e. Figure 9As shown, the wall thickness at the bottom of the groove on the shaft track surface 110e is the wall thickness T of the smallest diameter portion of the shaft track surface 110e. This wall thickness T is the length from the smallest diameter portion of the shaft track surface 110e to the shaft through hole 110d. Additionally, the thickness L of the cured layer F can also be a target value (design value) for the thickness of the cured layer F when performing the process of setting the cured layer F on the sun gear shaft 110B.

[0069] In this configuration, a cured layer F is provided at the bottom of the groove on the shaft guide surface 110e of the sun gear shaft 110B, covering the entire radially thick wall region T. This further enhances the internal hardness of the shaft guide surface 110e of the sun gear shaft 110B. Alternatively, this cured layer F can also be provided on the sun gear 111. This allows for increased internal hardness of the shaft guide surface 110e while ensuring the strength and toughness of the sun gear 111.

[0070] (Third variation) The third variation of the sun gear unit will be explained. For example... Figure 11 As shown in (a), the sun gear unit 11C of this modified example has an outer ring 112C instead of the outer ring 112 of the embodiment. A recess (engaging portion) 112b is provided on the outer peripheral surface of the outer ring 112C. The recess 112b may be provided throughout the entire circumferential area of ​​the outer ring 112C, or it may be provided only in a portion of the circumferential direction. In this example, the recess 112b is provided on the outer peripheral surface of the outer ring 112C at the end on the sun gear 111 side in the axial direction of the outer ring 112C.

[0071] The shaft support portion 50 supporting the outer ring 112C has a protrusion 50a protruding towards the outer ring 112C. The protrusion 50a of the shaft support portion 50 is embedded in the recess 112b of the outer ring 112C. The recess 112b of the outer ring 112C engages with the shaft support portion 50 in the axial direction of the sun gear shaft 110. In this case, by providing the recess 112b of the outer ring 112C, the axial displacement of the outer ring 112C and the shaft support portion 50 on the sun gear shaft 110 can be suppressed.

[0072] In addition, such as Figure 11 As shown in (b), the recess 112b of the outer ring 112C can also engage with the shaft support portion 50 via a retaining ring or other engaging member W. Specifically, a recess 50b is provided on the inner circumferential surface of the shaft support portion 50 (the mounting surface of the outer ring 112C). The engaging member W is respectively inserted into the recess 112b of the outer ring 112C and the recess 50b of the shaft support portion 50 to engage. Figure 11 As shown in (b), the recess 112b of the outer ring 112C into which the engaging member W is embedded can also be provided on the outer peripheral surface of the outer ring 112C, excluding the two axial ends. Figure 11As shown in (c), the recess 112b of the outer ring 112C into which the engaging member W is embedded can also be provided at the axial end of the outer circumferential surface of the outer ring 112C.

[0073] A recess 112b is provided on the outer peripheral surface of the outer ring 112C as an engaging portion that engages with the shaft support portion 50. However, it is not limited to this; a protrusion may also be provided on the outer peripheral surface of the outer ring 112C as an engaging portion that engages with the shaft support portion 50. The shape of the engaging portion (e.g., recess 112b, protrusion) provided on the outer ring 112C is not limited as long as it can engage with the shaft support portion 50. Furthermore, the engaging portion provided on the outer ring 112C can be as follows: Figure 11 As shown in (a), it can be directly engaged with the shaft support 50, or as shown in (a). Figure 11 As shown in (b), it engages with the shaft support portion 50 via the engaging member W, etc.

[0074] The embodiments and modifications of this disclosure have been described above, but this disclosure is not limited to the above embodiments and modifications. For example, the sun gear spline 110c formed on the first end 110a of the sun gear shaft 110 is not limited to being formed on the outer peripheral surface of the sun gear shaft 110. The sun gear spline formed on the first end 110a may also be formed on the inner peripheral surface of the sun gear shaft 110. In this case, it is sufficient that the rotor spline is formed on the outer peripheral surface of the rotor shaft 32.

[0075] Furthermore, the sun gear shaft 110 is not limited to a structure with a sun gear spline 110c at the first end 110a. The rotational force of the drive unit 30 can also be directly transmitted to the first end of the sun gear shaft. Specifically, as... Figure 12 As shown, the sun gear unit 11D has a sun gear shaft 110D instead of the sun gear shaft 110 in the embodiment. In the sun gear unit 11D, the structure other than the sun gear shaft 110D is the same as that of the sun gear unit 11 described above.

[0076] A first end 110a, from which rotational force is input from the drive unit 30, is provided at one end of the sun gear shaft 110D. The first end 110a extends into the interior of the motor rotor 31. The motor rotor 31 of the drive unit 30 is mounted on the first end 110a. The sun gear shaft 110D rotates integrally with the motor rotor 31. That is, the sun gear shaft 110D combines the functions of the sun gear shaft 110 and the rotor shaft 32 in the above embodiment. Thus, the rotational force of the drive unit 30 is directly input to the first end 110a of the sun gear shaft 110D.

[0077] Similar to the sun gear shaft 110 in the embodiment, the sun gear shaft 110D has a shaft track surface 110e between the first end 110a and the second end 110b. The sun gear shaft 110D is rotatably supported on the shaft support portion 50 via balls 113 and retainers 114. A sun gear 111 is provided at the second end 110b. Even in this case, the sun gear unit 11D with the sun gear shaft 110D can achieve the same effect as the sun gear unit 11 in the embodiment.

[0078] Furthermore, the sun gear shaft 110 and the like are not limited to being rotatably supported by the balls 113. The sun gear shaft 110 and the like can also be rotatably supported by "rollers" other than the balls 113. In this case, the shaft track surface 110e formed on the outer peripheral surface of the sun gear shaft 110 and the like, and the outer ring track surface 112a formed on the inner peripheral surface of the outer ring 112, can be formed in shapes corresponding to the rollers that are the rolling elements.

[0079] The structure of the planetary gear mechanism 10 is not limited to the structure described above. At least the planetary gear mechanism 10 needs to include the sun gear unit 11 and a planetary gear unit that rotates around the sun gear unit 11. In the above embodiments and variations, the planetary gear mechanism 10 indicates that rotational force is transmitted from the drive unit 30 to the sun gear unit 11, etc. That is, the rotational force is transmitted to the first end 110a of the sun gear shaft 110, etc., of the sun gear unit 11, etc. However, it is not limited to this; rotational force can also be transmitted from the first end 110a of the sun gear shaft 110, etc., to other mechanisms. That is, rotational force can also be output from the first end 110a of the sun gear shaft 110, etc., of the sun gear unit 11, etc. The planetary gear mechanism 10 is not limited to decelerating the rotational speed. The planetary gear mechanism 10 can also increase the rotational speed. In this case, the speed changer 1 functions as a speed increaser.

[0080] At least some of the above-described embodiments and various modifications can also be combined arbitrarily.

[0081] Explanation of reference numerals in the attached figures 1… Gearbox, 10… Planetary gear mechanism, 11, 11A~11D… Sun gear unit, 13… Bracket (support part), 20… Differential gear unit, 21… Differential housing, 22… Differential mechanism, 41… First drive shaft (rotating shaft), 50… Shaft support (support part), 110, 110A, 110B, 110D… Sun gear shaft, 110a… First end, 110b… Second end, 110c… Sun gear spline 110d…shaft through hole, 110e…shaft track surface, 110g…first groove shoulder surface forming part (groove shoulder surface forming part), 110h…embedded part, 111…sun gear, 112, 112C…outer ring, 112a…outer ring track surface, 112b…recess (engaging part), 113…ball (rolling element), 121…first planetary gear (planetary gear), F…cured layer, S1…first groove shoulder surface (groove shoulder surface), S2…second groove shoulder surface.

Claims

1. A sun gear unit of a planetary gear mechanism, the sun gear unit comprising: The sun gear shaft has a first end for inputting and outputting rotational force and a second end opposite to the first end, and a shaft track surface is formed on the outer peripheral surface between the first end and the second end. The sun gear is disposed at the second end and meshes with the planetary gears of the planetary gear mechanism; An outer ring, mounted on a support portion supporting the sun gear shaft, is disposed such that it surrounds the shaft's raceway surface, and an outer ring raceway surface is formed on its inner circumferential surface; and Multiple rolling elements are disposed between the shaft track surface and the outer ring track surface.

2. The sun gear unit according to claim 1, A spline is formed on the outer or inner circumferential surface of the first end.

3. The sun gear unit according to claim 1, The sun gear shaft has: The groove shoulder forming portion has a groove shoulder surface adjacent to the shaft track surface on its outer peripheral surface at a position closer to the first end than the shaft track surface; and The embedding portion is located adjacent to the groove shoulder surface forming portion at a position closer to the first end than the groove shoulder surface forming portion. The size of the groove shoulder forming portion in the radial direction of the sun gear shaft is larger than the size of the embedding portion in the radial direction of the sun gear shaft.

4. The sun gear unit according to claim 1, The sun gear shaft has a first shoulder surface and a second shoulder surface that are adjacent to the shaft track surface in the axial direction of the sun gear shaft, separated by the shaft track surface. The first and second shoulder surfaces are respectively annular, extending circumferentially along the sun gear shaft. The outer diameter of the first groove shoulder surface is different from that of the second groove shoulder surface.

5. The sun gear unit according to claim 1, The outer circumferential surface of the outer ring is provided with a engaging portion that engages with the support portion in the axial direction of the sun gear shaft.

6. The sun gear unit according to claim 1, In the axial direction of the sun gear shaft, there is a gap between the sun gear and the outer ring and the rolling element.

7. The sun gear unit according to any one of claims 1-6, The sun gear shaft is provided with a through hole that extends along the axis of the sun gear shaft and through which the rotating shaft passes.

8. The sun gear unit according to claim 7, A curing layer is provided on a portion of the surface of the sun gear shaft. The portion with the cured layer has a higher hardness than the portion of the sun gear shaft outside the cured layer. The thickness of the cured layer is greater than half the wall thickness of the shaft track surface of the sun gear shaft.

9. A speed changer, the speed changer comprising: Planetary gear mechanism, having the sun gear unit as described in claim 7; and A differential gear unit has a differential housing that transmits rotational force from the planetary gear mechanism, and a differential mechanism is provided within the differential housing. The drive shaft connected to the differential mechanism passes through the shaft through hole as the rotation axis.

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