Power transmission device

Abstract

The invention provides a power transmission device. A power transmission device is provided with: a sun gear fixed to a rotatable shaft; a ring gear disposed coaxially with the sun gear and fixed to a housing that accommodates the planetary gear mechanism; the planetary gear is meshed with the sun gear and the gear ring; and a carrier that rotatably supports the planetary gears, that is disposed coaxially with the sun gear, and that is rotatably supported by the housing, the sun gear and the ring gear being helical gears, respectively. The torsion angle of the teeth of the sun gear and the torsion angle of the teeth of the ring gear are set so that the directions of the axial thrust acting on the sun gear and the axial thrust acting on the ring gear are opposite, and a load transmission path for transmitting the axial thrust acting on the sun gear and the axial thrust acting on the ring gear is provided between the sun gear and the ring gear. The load transmission path is configured so as to include at least a portion of the carrier.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a power transmission device having a planetary gear mechanism and a housing that houses the planetary gear mechanism. Background Technology

[0002] As one of the power transmission devices, Patent Document 1 discloses a variable speed drive axle that transmits the power of an electric motor to the axle via a planetary gear reducer and a differential device. According to Patent Document 1, the planetary gear reducer is a planetary type planetary gear mechanism with a sun gear formed on the output shaft of the electric motor as the input element, a gear ring fixed on the housing housing the planetary gear reducer as the reaction force element, and a planetary carrier as the output element. The planetary carrier supports a stepped pinion capable of rotation and revolution, and the stepped pinion has a large-diameter pinion that meshes with the sun gear and a small-diameter pinion that meshes with the gear ring.

[0003] In addition, according to Patent Document 1, the case in which each gear constituting the planetary gear reducer is a helical gear is disclosed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-110374 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the aforementioned planetary gear mechanism, when the gear ring is a helical gear, an axial thrust is exerted on the gear ring. The housing that fixes the gear ring bears the axial thrust acting on the gear ring. Therefore, in order to withstand the axial thrust acting on the gear ring, it is necessary to ensure the strength of the housing, which presents a problem such as making the housing thicker, resulting in a larger housing size.

[0009] Solution for solving the problem

[0010] This specification discloses a power transmission device having a planetary gear mechanism and a housing housing the planetary gear mechanism. The planetary gear mechanism includes: a sun gear fixed to a rotatable shaft; a ring gear coaxially arranged with the sun gear and fixed to the housing; planet gears meshing with the sun gear and the ring gear; and a planet carrier supporting the planet gears for rotatability, coaxially arranged with the sun gear, and rotatably supported in the housing. The sun gear and the ring gear are both helical gears. The torsional angles of the teeth of the sun gear and the ring gear are set such that the axial thrust acting on the sun gear is opposite in direction to the axial thrust acting on the ring gear. The power transmission device further includes a load transmission path between the sun gear and the ring gear, the load transmission path transmitting the axial thrust acting on the sun gear and the axial thrust acting on the ring gear, the load transmission path being formed by including at least a portion of the planet carrier.

[0011] According to the structure described, the axial thrust acting on the ring gear and the force acting in the opposite direction to the axial thrust acting on the ring gear, i.e., the axial thrust acting on the sun gear, are transmitted to the load transfer path. Therefore, at least a portion of the axial thrust acting on the ring gear is offset by the axial thrust acting on the sun gear. This reduces the strength required of the housing to withstand the axial thrust acting on the ring gear, thus suppressing the increase in housing size. Furthermore, since the load transfer path is constructed including at least a portion of the planetary gear carrier, the increase in the number of components can be suppressed when the load transfer path is configured. Attached Figure Description

[0012] Figure 1 It is a simplified diagram illustrating the structure of a power transmission device.

[0013] Figure 2 It is a simplified three-dimensional diagram showing the appearance of the shell and the contents contained inside the shell.

[0014] Figure 3 This is a partial sectional view that mainly shows the planetary gear mechanism inside the housing.

[0015] Figure 4 This is a simplified side view of a vehicle equipped with a power transmission device.

[0016] Explanation of reference numerals in the attached figures

[0017] 10: Power transmission device; 11: Housing; 20: Motor; 21: Stator; 22: Rotor; 23: Rotor shaft; 30: Planetary gear mechanism; 31: Sun gear; 32: Ring gear; 33: Planetary gear; 33a: Large diameter pinion; 33b: Small diameter pinion; 34: Planetary gear carrier; 35: Differential housing; 40: Load transmission path; 41: First part; 42: Second part; 43: Structure; 48: First bearing; 49: Second bearing; 50: Differential device; Ax: Shaft Detailed Implementation

[0018] The following are the main features of the embodiments to be described.

[0019] The load transmission path may include: a first bearing on the path between the sun gear and the planetary carrier; and a second bearing on the path between the ring gear and the planetary carrier.

[0020] According to the structure, whenever a load transmission path is formed, the smooth rotation of the sun gear and planetary gear carrier can be ensured and the increase in the number of components can be suppressed when the first bearing and the second bearing are used to form the load transmission path.

[0021] Alternatively, the planetary gear carrier may be connected to the differential housing that houses the differential device, and the first bearing may be held between the sun gear and the differential housing.

[0022] According to the structure described, in a power transmission device of the type in which the planetary gear carrier is connected to the differential housing housing the differential device, the load transmission path can be easily constructed using the differential housing.

[0023] Alternatively, the load transmission path may include a structure extending from the gear ring, and the second bearing may be held by the structure and the planetary gear carrier.

[0024] According to the structure, whenever a load transfer path is formed, the load transfer path can be easily formed by using the structure.

[0025] Alternatively, the structure may be integrally formed with the gear ring.

[0026] According to the structure, by pre-forming the gear ring into a shape that includes the structure, the assembly of the power transmission device can be simplified by eliminating the structure as a separate component.

[0027] Alternatively, the planetary gear may be a stepped pinion having a large-diameter pinion meshing with the sun gear on one side of an axial direction parallel to the shaft, and a small-diameter pinion meshing with the ring gear on the other side of the axial direction, wherein the load transmission path is positioned on the other side of the axial direction, closer to the large-diameter pinion.

[0028] According to the structure, the load transmission path can be constructed simply and compactly by effectively utilizing the shape of the planetary gear as a stepped pinion, and the enlargement of the housing that houses the load transmission path can be suppressed.

[0029] Alternatively, the torsional angles of the teeth of the sun gear and the teeth of the ring gear can be set such that the magnitude of the axial thrust acting on the sun gear is equal to the magnitude of the axial thrust acting on the ring gear.

[0030] According to the structure, the axial thrust acting on the sun gear and the axial thrust acting on the gear ring can be completely canceled out under ideal conditions through the load transfer path, so that the axial thrust input from the gear ring to the housing is 0.

[0031] Referring to the accompanying drawings, one embodiment of the present technology is described. The drawings are merely illustrative, and the embodiment is not limited to the depicted content. Furthermore, since the drawings are illustrative, some parts are sometimes omitted.

[0032] Figure 1 The structure of the power transmission device 10 is simply illustrated in the schematic diagram. Generally speaking, the housing 11 houses the motor 20, the planetary gear mechanism 30, and the differential device 50. The power transmission device 10 includes the planetary gear mechanism 30 and the housing 11. The concept of the power transmission device 10 may also include, for example, two or one of the motor 20 and the differential device 50.

[0033] The motor 20 includes a cylindrical stator 21 fixed within a housing 11, and a rotor 22 and a rotor shaft 23 disposed on the radially inner circumferential side of the stator 21. The rotor 22 and rotor shaft 23 are supported to rotate about an axis Ax. As is known, a coil (not shown) is wound on the stator 21, and by supplying power to the coil, the rotor 22 and rotor shaft 23 rotate about the axis Ax under the influence of a magnetic field. The direction parallel to the axis Ax is referred to as the axial direction.

[0034] A sun gear 31 is fixed to one end of the rotor shaft 23 in the axial direction. That is, the sun gear 31 is fixed to the rotor shaft 23 and rotates together with the rotor shaft 23. The rotor shaft 23 is an example of a shaft that can rotate relative to the housing 11.

[0035] The planetary gear mechanism 30 includes a sun gear 31, a ring gear 32, planet gears 33, and a planet carrier 34. The ring gear 32 is coaxially configured with the rotor shaft 23 and fixed to the housing 11. The planet gears 33 mesh with the sun gear 31 and the ring gear 32, and are capable of rotation and revolution. The revolution of the planet gears 33 is a rotation centered on the axis Ax. Figure 1In the example, for simplicity, the planetary gears 33 are shown at positions above and below the axis Ax. The number of planetary gears 33 in the planetary gear mechanism 30 is not particularly limited; for example, it can have three.

[0036] The planetary gear carrier 34 supports the planetary gears 33 so that they can rotate. Furthermore, the planetary gear carrier 34 is coaxially arranged with the sun gear 31 and the ring gear 32, and is supported so that it can rotate relative to the housing 11. Thus, the planetary gear carrier 34 is configured to rotate about axis Ax together with the revolution of the planetary gears 33. In other words, the planetary gear carrier 34 is a rotating element that supports each planetary gear 33 so that it can rotate on its own axis and outputs the revolutionary motion of the planetary gears 33.

[0037] according to Figure 1 Planetary gear 33 is a stepped pinion, which has one side (in the axial direction) Figure 1 The large-diameter pinion 33a, which meshes with the sun gear 31 (left side) and the other side (in the axial direction) Figure 1 (The middle one is on the right) The small-diameter pinion 33b meshes with the gear ring 32. The terms "major diameter" and "minor diameter" are relative; the diameter of the small-diameter pinion 33b is smaller than that of the major-diameter pinion 33a.

[0038] according to Figure 1 The planetary gear carrier 34 is connected to the differential housing 35, which houses the differential device 50. The differential housing 35 is located axially opposite to the sun gear 31 on the opposite side of the motor 20. The differential device 50 is referred to as a differential gear, or simply a differential. The differential housing 35 houses left and right half-shaft gears 51 and 52, which are connected to the left and right drive shafts 1 and 2, and pinions 53 and 54 that mesh with the half-shaft gears 51 and 52, thus serving as the differential device 50. Drive shafts 1 and 2 are both mounted on shaft Ax and are connected to left and right wheels (not shown) outside the housing 11. Figure 1 In the example, the interior of the rotor shaft 23 is a hollow cylindrical shape, and the left drive shaft 1 of the drive shafts 1 and 2 passes through the interior of the rotor shaft 23 and extends out of the housing 11.

[0039] Half-shaft gear 51, connected to drive shaft 1, and half-shaft gear 52, connected to drive shaft 2, are located coaxially facing each other, with pinion shaft 55 passing between them along a radial direction orthogonal to the axial direction. Pinion shaft 55 is fixed inside differential housing 35. A pair of pinions 53 and 54 facing each other radially are supported on pinion shaft 55.

[0040] Here's a simplified explanation of the power transmission process in this power transmission device 10. The rotational force of the rotor shaft 23 is transmitted to the planetary gear 33 as input from the rotation of the sun gear 31. The planetary gear 33, receiving this input, rotates on its own axis while simultaneously receiving the reaction force from the fixed gear ring 32, causing it to revolve around the inner circumference of the gear ring 32. The revolving motion of the planetary gear 33 becomes the output rotation of the planet carrier 34. Within the differential housing 35, which rotates integrally with the planet carrier 34, power is transmitted from the pinions 53 and 54 to the half-shaft gears 51 and 52, driving the half-shaft gears 51 and 52 to rotate the drive shafts 1 and 2.

[0041] Figure 2 A perspective view is provided to simply illustrate the appearance of the housing 11 and the contents contained within it. The motor 20 and gear set 60 are arranged axially within the housing 11. Figure 2 In this context, the structure including the planetary gear mechanism 30 and the differential device 50 is collectively referred to as gear set 60. Furthermore, as... Figure 2 As shown, the inverter 3 can be housed in the housing 11. The inverter 3 supplies AC power to the motor 20 by converting DC power supplied from outside the housing 11 into AC power, thereby driving the motor 20. The housing 11 can be appropriately divided into multiple compartments to accommodate the inverter 3, the motor 20, the gear set 60, and other components.

[0042] Figure 3 The planetary gear mechanism 30 housed in the first chamber 12 within the housing 11 is shown primarily through a partial sectional view. Figure 3 The configuration and shape of each structure shown are Figure 1 The configurations and shapes of the structures shown may not be identical, but these inconsistencies will not pose a problem in understanding this embodiment. For example, one side of the axial direction may differ. Figure 1 The middle is on the left, but in Figure 3 The middle is on the right. The other side of the axis is... Figure 1 The middle is on the right, but in Figure 3 The middle is on the left. Figure 3 The image primarily shows the area above the ax axis in the first chamber 12. According to... Figure 3 The space within the housing 11 is axially divided into a first chamber 12 and a second chamber 14 by a partition 13 that is part of the housing 11. Figure 3 Although omitted in the middle, motor 20 is housed in the second chamber 14.

[0043] The rotor shaft 23 is supported by a bearing 45 fixed to the partition 13 and is rotatable. A sun gear 31 is fixed to the end of the rotor shaft 23 that extends beyond the partition 13 and enters the first chamber 12. The planetary gear 33, which has a large-diameter pinion 33a and a small-diameter pinion 33b, is a stepped pinion, and its relationship to the sun gear 31 and the ring gear 32 has been explained. The outer circumferential surface of the ring gear 32 is fixed relative to the inner surface 12a that defines the first chamber 12.

[0044] The specific structure of the planetary gear carrier 34 for supporting the planetary gears 33 is not particularly limited. The planetary gear carrier 34, for example, has multiple support shafts 34a parallel to the axial direction. The number of support shafts 34a is the same as the number of planetary gears 33. One support shaft 34a passes through the center of one planetary gear 33. The planetary gear 33 is capable of rotating about the support shaft 34a. Furthermore, according to… Figure 3 For example, the planetary gear carrier 34 has bosses 34b and 34c at both ends of the support shaft 34a to restrict the axial movement of the planetary gear 33 and support the support shaft 34a.

[0045] The planetary gear carrier 34, including support shaft 34a, boss portions 34b and 34c, rotates around axis Ax. On one side of the axial direction (in... Figure 3 (The middle is on the right), the planetary gear carrier 34 is supported by a bearing 46 disposed between the boss portion 34c and the partition wall 13, enabling it to rotate. Furthermore, on the other side of the axial direction (in... Figure 3 (The middle one is on the left). The planetary gear carrier 34 is supported by a bearing 47 disposed between the end of the planetary gear carrier 34 and the housing 11 so that it can rotate.

[0046] Sun gear 31 and ring gear 32 are both helical gears. A helical gear is a gear in which the teeth (tooth line) are twisted (inclined) relative to the gear axis. Planet gear 33, which meshes with sun gear 31 and ring gear 32 respectively, can also be understood as a helical gear. In this embodiment, the torsion angles of the teeth of sun gear 31 and ring gear 32 are set such that the axial thrust acting on sun gear 31 and the axial thrust acting on ring gear 32 are opposite in direction.

[0047] Axial thrust is a load applied in a direction parallel to the axial direction. That is, in the planetary gear mechanism 30, the helical gears are designed such that the direction of the axial thrust acting on the sun gear 31 when it meshes with the planetary gear 33 is opposite to the direction of the axial thrust acting on the ring gear 32 when it meshes with the planetary gear 33. Figure 3 In the diagram, arrow A indicates the direction of the axial thrust acting on the sun gear 31, and arrow B indicates the direction of the axial thrust acting on the gear ring 32.

[0048] According to this embodiment, the power transmission device 10 further includes a load transmission path 40 between the sun gear 31 and the ring gear 32, which transmits the axial thrust acting on the sun gear 31 and the axial thrust acting on the ring gear 32. The load transmission path 40 is configured to include at least a portion of the planetary gear carrier 34.

[0049] The details of the load transmission path 40 are explained below. As described above, the load transmission path 40 is the path for transmitting load between the sun gear 31 and the ring gear 32. That is, the load transmission path 40 is the path between the sun gear 31 and the ring gear 32. The load transmission path 40 includes a path between the sun gear 31 and the planet carrier 34, and a path between the ring gear 32 and the planet carrier 34. A first bearing 48 is provided in the path between the sun gear 31 and the planet carrier 34. That is, the load transmission path 40 includes a first bearing 48 provided in the path between the sun gear 31 and the planet carrier 34. Furthermore, a structure 43 extending from the ring gear 32 and a second bearing 49 are provided in the path between the ring gear 32 and the planet carrier 34. That is, the load transmission path 40 includes a structure 43 extending from the ring gear 32 and a second bearing 49 provided in the path between the ring gear 32 and the planet carrier 34.

[0050] The first bearing 48 is disposed between the sun gear 31 and the first portion 41 of the differential housing 35. That is, the first bearing 48 is held between the sun gear 31 and the differential housing 35. The first bearing 48 is a bearing that bears axial thrust. The second bearing 49 is disposed between the structure 43 and the second portion 42 of the planetary gear carrier 34. That is, the second bearing 49 is held between the structure 43 and the planetary gear carrier 34. The second bearing 49 is also a bearing that bears axial thrust.

[0051] The first part 41 and the second part 42 are axially separated, but as described above, they are connected as objects because the planetary gear carrier 34 is connected to the differential housing 35. Figure 3 In the diagram, the connection between the first part 41 and the second part 42 is simply illustrated by dashed lines. The first part 41 is the portion of the differential housing 35 that is axially close to the sun gear 31. The second part 42 is, for example, the portion of the planetary gear carrier 34 that is axially located on the other side than the minor pinion 33b (in... Figure 3 A portion of the support shaft 34a and / or a portion of the boss 34b located on the left side (in the middle), or a nearby portion of the support shaft 34a and / or the boss 34b. Furthermore, according to... Figure 3 The second part 42 can be said to be located on the axial side of the end of the planetary gear carrier 34 on the opposite side of the axis (in Figure 3 The middle position is on the right.

[0052] Structure 43 extends axially from the other side of gear ring 32 (in...) Figure 3 The end of the planetary gear carrier 34 (left side) extends out to cover a portion of the planetary gear carrier 34 from the other side, such as the end of the support shaft 34a, the boss 34b, etc.

[0053] The structure 43 is fixed relative to the gear ring 32. Various methods can be used to fix the structure 43 to the gear ring 32. For example, the structure 43 and the gear ring 32 can be fixed by welding. Furthermore, the structure 43 can be fixed to the gear ring 32 while being pressed between the inner surface 12a of the first chamber 12 that fixes the gear ring 32 and the recess formed in the gear ring 32. The structure 43 and the gear ring 32 can also be fixed by other fixing members not shown.

[0054] Alternatively, the structure 43 can be integrally formed with the gear ring 32. That is, the structure 43 and the gear ring 32 can be a single component. By pre-forming the gear ring 32 into a shape that includes the structure 43, the assembly of the power transmission device 10 can be simplified by eliminating the structure 43 as a separate component. It should be noted that the end 43b of the structure 43 opposite to the end 43a connected to the gear ring 32 is separated from the housing 11.

[0055] According to this load transmission path 40, the axial thrust acting on the sun gear 31 in the direction indicated by arrow A is borne by the first bearing 48. The axial thrust borne by the first bearing 48 is transmitted from the first part 41 to the planetary gear carrier 34. This axial thrust is also transmitted along the second part 42 of the planetary gear carrier 34, the second bearing 49, and the structure 43 to the ring gear 32.

[0056] On the other hand, an axial thrust acts on the gear ring 32 in the direction indicated by arrow B. Conventionally, this axial thrust is supported by the housing 11, but in this embodiment, the axial thrust acting on the sun gear 31 is also transmitted to the gear ring 32. Therefore, in the gear ring 32 or the load transmission path 40, the axial thrust acting on the sun gear 31 cancels out the axial thrust acting on the gear ring 32, and only the remaining axial thrust that is not canceled out is input to the housing 11.

[0057] Thus, in the power transmission device 10 according to this embodiment, the sun gear 31 and the ring gear 32 are both helical gears. The torsional angles of the teeth of the sun gear 31 and the ring gear 32 are set such that the axial thrust acting on the sun gear 31 and the axial thrust acting on the ring gear 32 are opposite in direction. Furthermore, by providing a load transmission path 40 between the sun gear 31 and the ring gear 32, the axial thrust input to the housing 11 is reduced compared to the past. Therefore, the strength required by the housing 11 to withstand the axial thrust acting on the ring gear 32 is reduced, the enlargement of the housing 11 is suppressed, or the freedom of housing shape is increased. Moreover, since the load transmission path 40 includes at least a portion of the planet carrier 34 originally required by the planetary gear mechanism 30, the increase in the number of components can be suppressed when the load transmission path 40 is provided.

[0058] Furthermore, according to this embodiment, the load transmission path 40 includes a first bearing 48 disposed on the path between the sun gear 31 and the planetary carrier 34, and a second bearing 49 disposed on the path between the ring gear 32 and the planetary carrier 34. According to this structure, when the load transmission path 40 is configured, by using the first bearing 48 and the second bearing 49, smooth rotation of the sun gear 31 and the planetary carrier 34 can be ensured, and the load transmission path 40 is configured to suppress the increase in the number of components.

[0059] Furthermore, according to this embodiment, the planetary gear carrier 34 is connected to the differential housing 35 housing the differential device 50, and the first bearing 48 is held by the sun gear 31 and the differential housing 35. According to this structure, in a power transmission device 10 of the type where the planetary gear carrier 34 is connected to the differential housing 35 housing the differential device 50, the load transmission path 40 can be easily constructed using the differential housing 35.

[0060] Furthermore, according to this embodiment, the load transmission path 40 includes a structure 43 extending from the gear ring 32, and the second bearing 49 is held by the structure 43 and the planetary gear carrier 34. According to this structure, when the load transmission path 40 is configured, it can be easily configured by using the structure 43.

[0061] In addition, refer to Figure 3 The load transmission path 40 can be said to be axially positioned on the other side than the large-diameter pinion 33a (in Figure 3 The position is on the left side (the middle position), that is, on the side of the small diameter pinion 33b. In other words, when the planetary gear 33 is a stepped pinion with a large diameter pinion 33a and a small diameter pinion 33b, the shape of the stepped pinion is effectively utilized to position the load transmission path 40 axially closer to the small diameter pinion 33b side than the large diameter pinion 33a. Therefore, the load transmission path 40 can be easily constructed, and the enlargement of the housing 11 accommodating the load transmission path 40 can be suppressed.

[0062] According to this embodiment, the torsional angles of the teeth of the sun gear 31 and the ring gear 32 are set such that the direction of the axial thrust acting on the sun gear 31 is opposite to the direction of the axial thrust acting on the ring gear 32. Alternatively, the torsional angles of the teeth of the sun gear 31 and the ring gear 32 can be set such that the magnitude of the axial thrust acting on the sun gear 31 is equal to the magnitude of the axial thrust acting on the ring gear 32. For example, through experiments or simulations of operating the power transmission device 10 under standard operating conditions, the axial thrust acting on the sun gear 31 and the axial thrust acting on the ring gear 32 are measured or calculated, and various parameters, including the torsional angles of the teeth of the sun gear 31 and the ring gear 32, are set such that their magnitudes are equal. With this structure, the axial thrust acting on the sun gear 31 and the axial thrust acting on the ring gear 32 can be completely canceled out under ideal conditions via the load transmission path 40, thereby making the axial thrust input from the ring gear 32 to the housing 11 zero.

[0063] The specific structure of the load transmission path 40 is not limited to the structure shown in the figure. The load transmission path 40 can be any path that connects the sun gear 31 and the ring gear 32, includes at least a portion of the planet carrier 34, and transmits the axial thrust acting on the sun gear 31 and the axial thrust acting on the ring gear 32. Furthermore, the structure of the power transmission device 10 can include various modifications. For example, the functions of the planet carrier 34 and the differential housing 35 can be separated. Moreover, the relative positional relationship of the rotor shaft 23, planet carrier 34, differential housing 35, etc., is not limited to the positional relationship shown in the figure. Furthermore, it is also possible that instead of setting the sun gear 31 as the input and the planet carrier 34 as the output, the planet carrier 34 is set as the input and the sun gear 31 as the output. The planetary gears also do not have to be of the stepped pinion type.

[0064] Figure 4 A vehicle 70 equipped with a power transmission device 10 is shown simplified from the side. A rechargeable battery 72 is mounted under the floor of the passenger compartment 71. The vehicle 70 is driven by an electric motor 20 powered by electricity supplied from the battery 72, as is the case with, for example, a BEV (Battery Electric Vehicle) or a PHEV (Plug-in Hybrid Electric Vehicle). Figure 4 A power transmission device 10 is mounted coaxially with the front wheel 73 of the vehicle 70, and a power transmission device 10 is mounted coaxially with the rear wheel 74 of the vehicle 70. If the vehicle 70 is a two-wheel drive vehicle, then only... Figure 4Either of the front and rear power transmission devices 10 shown, if the vehicle 70 is a four-wheel drive vehicle, requires Figure 4 The front and rear power transmission devices 10 are shown.

[0065] By Figure 2 The power transmission device 10 shown as a unit is coaxially configured with the wheels, which allows for a relatively lower height position of the unit. As a result, the freedom of arrangement of various structures on the front side of the vehicle 70, such as the radiator 75, the air conditioning control system 76 that controls heating, ventilation, and air conditioning, and the EPS (Electric Power Steering) 77, is increased, ensuring more space in the passenger compartment 71. Moreover, on the rear side of the vehicle 70, for example, it helps to ensure luggage space and increases the freedom of rear seat design.

[0066] The above-described specific examples of the disclosed technology are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations to the specific examples described above. Furthermore, the technical elements illustrated in this specification or drawings are elements that exert technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Moreover, the technology illustrated in this specification or drawings is technology that achieves multiple objectives simultaneously, and the achievement of one of these objectives is itself technically useful.

Claims

1. A power transmission device, the power transmission device comprising a planetary gear mechanism and a housing housing the planetary gear mechanism, wherein, The planetary gear mechanism has the following features: A sun gear, which is fixed to a rotatable shaft; A gear ring, which is coaxially configured with the sun gear and fixed to the housing; A planetary gear that meshes with the sun gear and the ring gear; and A planetary gear carrier that supports the planetary gears for rotatability, is coaxially arranged with the sun gear, and is rotatably supported on the housing. The sun gear and the gear ring are both helical gears. The torsional angles of the sun gear teeth and the ring gear teeth are set such that the axial thrust acting on the sun gear is opposite in direction to the axial thrust acting on the ring gear. The power transmission device also includes a load transmission path between the sun gear and the ring gear, the load transmission path transmitting the axial thrust acting on the sun gear and the axial thrust acting on the ring gear. The load transfer path is formed by including at least a portion of the planetary gear carrier.

2. The power transmission device according to claim 1, wherein, The load transfer path includes: A first bearing, the first bearing being disposed in the path between the sun gear and the planetary gear carrier; and The second bearing is located in the path between the gear ring and the planetary gear carrier.

3. The power transmission device according to claim 2, wherein, The planetary gear carrier is connected to the differential housing that houses the differential device. The first bearing is held by the sun gear and the differential housing.

4. The power transmission device according to claim 2, wherein, The load transfer path includes a structure extending from the gear ring. The second bearing is held by the structure and the planetary gear carrier.

5. The power transmission device according to claim 4, wherein, The structure is integrally formed with the gear ring.

6. The power transmission device according to claim 1, wherein, The planetary gear is a stepped pinion with a large-diameter pinion and a small-diameter pinion. The large-diameter pinion meshes with the sun gear on one side of the axial direction parallel to the shaft, and the small-diameter pinion meshes with the ring gear on the other side of the axial direction. The load transfer path is positioned on the opposite side of the large-diameter pinion in the axial direction.

7. The power transmission device according to claim 1, wherein, The torsional angles of the sun gear teeth and the gear ring teeth are set such that the magnitude of the axial thrust acting on the sun gear is equal to the magnitude of the axial thrust acting on the gear ring.

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