Transaxle

Abstract

To ensure a large driving force and take a large deceleration ratio while suppressing enlargement of a physique.SOLUTION: This transaxle comprises: a planetary gear mechanism including a stepped pinion gear in which a large-diameter pinion gear and a small-diameter pinion gear are integrated; a differential gear disposed inside the small-diameter pinion gear in a radial direction; and a transaxle case that stores the planetary gear mechanism and the differential gear, and transmits power of a motor through the planetary gear mechanism and the differential gear to an axle. The planetary gear mechanism includes a sun gear provided in an output shaft of the motor to be engaged with the large-diameter pinion gear, a ring gear that rotates at the same rotation speed as that of a differential case of the differential gear, a carrier that is fixed to the transaxle case and that supports the stepped pinion gear so as to be self-rotatable, and an outer pinion gear self-rotatably supported on the carrier and engaged with the small-diameter pinion gear and the ring gear.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a transaxle. [Background technology]

[0002] Patent Document 1 discloses a transaxle that transmits power output from a motor to an axle via a planetary gear mechanism and a differential device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-110374 Summary of the Invention [Problem to be solved by the invention]

[0004] In a transaxle that transmits the power of a motor, a larger reduction ratio is sometimes required to ensure greater driving force or to make the motor more compact. In this case, with a structure in which a stepped pinion gear of a planetary gear mechanism revolves, as in the configuration described in Patent Document 1, the outermost diameter of the orbital path of the large-diameter pinion gear becomes large, which can increase the radial size of the transaxle.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a transaxle that can ensure a large driving force while suppressing an increase in size, and that can achieve a large reduction ratio. [Means for solving the problem]

[0006] The present invention is a transaxle comprising a planetary gear mechanism having a stepped pinion gear in which a large diameter pinion gear and a small diameter pinion gear are integrated, a differential device arranged radially inside the small diameter pinion gear, and a transaxle case that houses the planetary gear mechanism and the differential device, and which transmits power from an electric motor to an axle via the planetary gear mechanism and the differential device, wherein the planetary gear mechanism is provided on the output shaft of the electric motor and has a sun gear that meshes with the large diameter pinion gear, a ring gear that rotates at the same rotation speed as the differential case of the differential device, a carrier that is fixed to the transaxle case and rotatably supports the stepped pinion gear, and an outer pinion gear that is rotatably supported by the carrier and meshes with the small diameter pinion gear and the ring gear. [Effects of the Invention]

[0007] According to the present invention, it is possible to ensure a large driving force while suppressing an increase in size, and also possible to obtain a large reduction ratio. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view showing a transaxle according to the embodiment. [Figure 2] FIG. 2 is a diagram illustrating the structure of a planetary gear mechanism. [Figure 3] FIG. 3 is a collinear diagram showing the states of the elements of the planetary gear mechanism in a driving state. [Figure 4] FIG. 2 is a diagram schematically illustrating a transaxle. [Figure 5] FIG. 2 is a diagram for explaining the detailed structure of a planetary gear mechanism. [Figure 6] FIG. 2 is a diagram for explaining the size of a planetary gear mechanism when the gear ratio is 12.5. [Figure 7] FIG. 10 is a diagram for explaining that the radial size of the planetary gear mechanism can be further reduced when the gear ratio is 12.5. [Figure 8] FIG. 2 is a diagram for explaining the size of a planetary gear mechanism when the gear ratio is 15.7. [Figure 9] FIG. 1 is a diagram schematically illustrating a transaxle having a conventional structure. [Figure 10] FIG. 1 is a diagram for explaining the size of a planetary gear mechanism of a conventional structure when the gear ratio is 12.5. DETAILED DESCRIPTION OF THE INVENTION

[0009] A transaxle according to an embodiment of the present invention will be specifically described below, although the present invention is not limited to the embodiment described below.

[0010] 1 is a cross-sectional view showing a transaxle according to an embodiment. The transaxle 1 is a power transmission device mounted on a vehicle. The transaxle 1 includes a planetary gear mechanism 2, a differential 3, and a transaxle case 4.

[0011] Transaxle 1 transmits power output from motor 5, which is the vehicle's power source, to axles 6 via planetary gear mechanism 2 and differential 3. Motor 5 and axles 6 are arranged on the same axis. Motor 5 is connected to planetary gear mechanism 2 so that power can be transmitted. Planetary gear mechanism 2, differential 3, and motor 5 are housed in transaxle case 4. The left and right axles 6 pass through transaxle case 4. Transaxle case 4 forms a motor chamber 10 that houses motor 5, and a gear chamber 11 that houses planetary gear mechanism 2 and differential 3.

[0012] The transaxle case 4 includes a case body 12 and a cover member 13. The case body 12 is a cylindrical case member. The cover member 13 is attached to the case body 12 from one axial side so as to cover the opening of the case body 12. The case body 12 and the cover member 13 are integrated by bolting. The case body 12 has a partition wall 14 that separates the motor chamber 10 and the gear chamber 11. The partition wall 14 is a wall portion.

[0013] The motor 5 includes a rotor 15, a stator 16, and an output shaft 17. The rotor 15 rotates at the same rotation speed as the output shaft 17. The stator 16 is fixed to the case body 12. The output shaft 17 outputs the power of the motor 5 to the planetary gear mechanism 2. The output shaft 17 extends from the motor chamber 10 to the gear chamber 11. A sun gear 21 of the planetary gear mechanism 2 is formed on the end of the output shaft 17 on the gear chamber 11 side.

[0014] The planetary gear mechanism 2 is a stepped pinion type and double pinion type planetary gear mechanism. As shown in FIGS. 1 and 2, the planetary gear mechanism 2 includes a sun gear 21, a ring gear 22, a stepped pinion gear 23, an outer pinion gear 24, and a carrier 25. The sun gear 21 is an input element. The ring gear 22 is an output element. The carrier 25 is a reaction element. The carrier 25 rotatably holds the stepped pinion gear 23 and rotatably holds the outer pinion gear 24. The carrier 25 is provided with three stepped pinion gears 23 and three outer pinion gears 24. The three stepped pinion gears 23 are arranged at equal intervals in the circumferential direction of the carrier 25. The three outer pinion gears 24 are arranged at equal intervals in the circumferential direction of the carrier 25.

[0015] The stepped pinion gear 23 includes a large-diameter pinion gear 26, a small-diameter pinion gear 27, and a pinion shaft 28. The large-diameter pinion gear 26, the small-diameter pinion gear 27, and the pinion shaft 28 are integrally formed. The large-diameter pinion gear 26 meshes with the sun gear 21. The small-diameter pinion gear 27 is a gear formed with a smaller diameter than the large-diameter pinion gear 26. The small-diameter pinion gear 27 meshes with the outer pinion gear 24. The pinion shaft 28 is disposed parallel to the output shaft 17 and the axle 6. The outer pinion gear 24 meshes with the small-diameter pinion gear 27 and the ring gear 22. The ring gear 22 rotates at the same rotational speed as a differential case 29 of the differential device 3. The differential case 29 of the differential device 3 is disposed radially inward of the small-diameter pinion gear 27.

[0016] The carrier 25 includes a carrier body 30, a carrier cover 31, and an outer pinion shaft 32. The carrier body 30 has a structure in which a carrier plate 33 and a bridge portion 34 are integrally formed. The carrier plate 33 is a disc-shaped plate member and is bolted to the transaxle case 4. The peripheral portion of the carrier plate 33 is sandwiched between the case body 12 and the cover member 13 and bolted to them. The bridge portion 34 protrudes from the carrier plate 33 to one side in the axial direction. The carrier plate 33 is provided with a first through hole 35 through which the pinion shaft 28 of the stepped pinion gear 23 is inserted, and a second through hole 36 that holds the outer pinion shaft 32. A needle bearing 37 is fitted into the first through hole 35. The needle bearing 37 is a bearing that supports the stepped pinion gear 23. A needle bearing 37 is attached to the pinion shaft 28 at a portion between the large diameter pinion gear 26 and the small diameter pinion gear 27. The needle bearing 37 is a bearing that supports the pinion shaft 28. The large diameter pinion gear 26 is disposed closer to the partition wall 14 than the carrier plate 33.

[0017] Bearings 38 are provided on the inner periphery of the carrier plate 33. The bearings 38 support the differential case 29. The carrier body 30 rotatably supports the differential case 29 via the bearings 38 provided on the inner periphery of the carrier plate 33. The bridge portion 34 connects the carrier plate 33 and the carrier cover 31. The carrier cover 31 is attached to the tip of the bridge portion 34. This integrates the carrier body 30 and the carrier cover 31.

[0018] The carrier cover 31 is a disk-shaped member disposed axially opposite the carrier plate 33. The carrier cover 31 has a structure in which a disk-shaped plate portion 39 and a bottomed, cylindrical boss portion 40 are integrally formed. The boss portion 40 protrudes from the plate portion 39 to one side in the axial direction. The boss portion 40 supports one end of the pinion shaft 28. A needle bearing 41 is attached to one end of the pinion shaft 28. The needle bearing 41 is provided on the inner periphery of the boss portion 40 and supports the pinion shaft 28.

[0019] The plate portion 39 is provided with a third through hole 42 that holds the outer pinion shaft 32. The outer pinion shaft 32 is a fixed shaft that is arranged parallel to the pinion shaft 28. One end of the outer pinion shaft 32 is held in the third through hole 42 of the carrier cover 31, and the other end is held in the second through hole 36 of the carrier body 30. A needle bearing 43 is attached to the outer pinion shaft 32. The needle bearing 43 is provided on the inner periphery of the outer pinion gear 24 and supports the outer pinion gear 24. The outer pinion shaft 32 rotatably supports the outer pinion gear 24 via the needle bearing 43.

[0020] The differential device 3 includes a differential case 29, a differential pinion gear 44, a differential pinion shaft 45, and a differential side gear 46. The differential case 29 has a flange portion 47. The flange portion 47 is connected to the ring gear 22. The differential case 29 is rotatably supported on the transaxle case 4 via bearings 48. The differential pinion gear 44, the differential pinion shaft 45, and the differential side gear 46 are housed inside the differential case 29. The differential pinion gear 44 meshes with the differential side gear 46. The differential side gear 46 is fixed to the axle 6. The differential pinion shaft 45 is fixed to the differential case 29. A pair of differential pinion gears 44 are rotatably supported on the differential pinion shaft 45. When the ring gear 22 rotates, the ring gear 22 and the differential case 29 rotate together with the differential pinion shaft 45, and the left and right differential side gears 46 are driven by the differential pinion gear 44, causing the left and right axles 6 to rotate.

[0021] As shown in FIG. 3, when the vehicle is in a driving state, torque output from the motor 5 acts on the sun gear 21, causing the sun gear 21 to rotate. In this case, since the carrier 25 is fixed, torque acts on the ring gear 22, and the torque is transmitted to the axle 6. The rotation speed of the ring gear 22, which is the output element, is smaller than the rotation speed of the sun gear 21, which is the input element. The planetary gear mechanism 2 functions as a reducer. In FIG. 3, the motor 5 is designated "MG", the differential case 29 is designated "OUT", the sun gear 21 is designated "S", the ring gear 22 is designated "R", the carrier 25 is designated "C", the stepped pinion gear 23 is designated "P", and the outer pinion gear 24 is designated "P". O "It is stated.

[0022] As shown in FIGS. 2, 4, and 5, the size and arrangement of the planetary gear mechanism 2 are such that the ring gear 22 has a large diameter that extends to a position close to the outermost diameter of the large-diameter pinion gear 26. The outermost diameter of the large-diameter pinion gear 26 is located radially outward of the ring gear 22. As shown in FIG. 4, the position of the outermost diameter of the large-diameter pinion gear 26 can be expressed by the radial distance Y from the rotational axis of the sun gear 21 to the outermost diameter of the large-diameter pinion gear 26. The distance between the rotational axis of the sun gear 21 and the rotational axis of the large-diameter pinion gear 26 is defined as the inter-axial distance a. As shown in FIG. 5, when the planetary gear mechanism 2 is viewed from the axial direction, the outer pinion gear 24 is arranged at a circumferential position where the angle with respect to a line passing through the rotational axis of the sun gear 21 and the rotational axis of the large-diameter pinion gear 26 is an arrangement angle θ. The arrangement angle θ of the outer pinion gear 24 can be set to any value. The central axis of rotation of sun gear 21 is the same as the central axis of rotation of ring gear 22. Sun gear 21, ring gear 22, and axle 6 rotate on the same central axis of rotation. The central axis of rotation of large-diameter pinion gear 26 is synonymous with the central axis of rotation of small-diameter pinion gear 27, and is synonymous with the central axis of rotation of stepped pinion gear 23.

[0023] The relational expression for the reduction ratio (gear ratio) X is expressed by the following equation (1): The relational expression for the center distance a is expressed by the following equation (2): In the arrangement shown in FIG. 5, the relational expression for the diameter Dr of the ring gear 22 using the arrangement angle θ of the outer pinion gear 24 is expressed by the following equation (3): X=Dr / Ds×Dlp / Dsp...Formula (1) 2a=Ds+Dlp...Equation (2) Dr={a 2 +(Dsp / 2+Dp / 2) 2 +2a(Dsp / 2+Dp / 2)cosθ} 0.5 +Dp / 2...Equation (3)

[0024] In the above formula (1), X is the reduction ratio (gear ratio), Dr is the diameter of the ring gear 22, Ds is the diameter of the sun gear 21, Dlp is the diameter of the large-diameter pinion gear 26, and Dsp is the diameter of the small-diameter pinion gear 27. In the above formula (2), a is the center distance. In the above formula (3), Dp is the diameter of the outer pinion gear 24, and θ is the arrangement angle of the outer pinion gear 24.

[0025] The relational expression transformed using the above formulas (2) and (3) is expressed by the following formula (4). Dr={(Ds / 2+Dlp / 2) 2 +(Dsp / 2+Dp / 2) 2 +2(Ds / 2+Dlp / 2)(Dsp / 2+Dp / 2)cosθ} 0.5 +Dp / 2...Equation (4)

[0026] In order to increase the reduction ratio X without reducing the strength capacity of the transaxle 1, it is necessary to increase the diameter Dr of the ring gear 22 or the diameter Dlp of the large-diameter pinion gear 26. From equation (4) above, it is possible to increase the diameter Dr of the ring gear 22 by increasing the arrangement angle θ or the diameter Dp of the outer pinion gear 24, without increasing the diameter Dlp of the large-diameter pinion gear 26. Therefore, it is possible to suppress the increase in the diameter Dlp of the large-diameter pinion gear 26, which is necessary to ensure a larger reduction ratio X. As a result, as shown in Figures 6 and 10, the radial size of the transaxle 1 can be made smaller than that of the conventional structure.

[0027] As shown in Figures 9 and 10, a transaxle with a conventional structure includes a planetary gear mechanism 200 and a differential gear 300. The planetary gear mechanism 200 includes a sun gear 201, a ring gear 202, a carrier 203, and a stepped pinion gear 204. The ring gear 202 is fixed to the transaxle case. The carrier 203 holds the stepped pinion gear 204 so that it can rotate and revolve. The stepped pinion gear 204 includes a large-diameter pinion gear 205 that meshes with the sun gear 201, and a small-diameter pinion gear 206 that meshes with the ring gear 202. The differential gear 300 is disposed radially inside the small-diameter pinion gear 206. The revolution orbit Q of the large-diameter pinion gear 205 is drawn at a position where the radial distance from the rotational center axis of the sun gear 201 is Y1. The raceway diameter of the large diameter pinion gear 205 is approximately the same as the height direction length H. Figure 10 shows the structure of the planetary gear mechanism 200 when the gear ratio is 12.5.

[0028] When the gear ratio of the transaxle 1 is 12.5, the radial size of the planetary gear mechanism 2 is smaller than that of the conventional structure, as shown in Figure 6. The radial size can be divided into the height dimension and the front-to-rear dimension. The height dimension of the planetary gear mechanism 2 is smaller than the length H.

[0029] In transaxle 1, carrier 25 is a fixed element, so large diameter pinion gear 26 rotates on its axis but does not revolve. As shown in Figure 7, the height dimension can be reduced by shifting the phase of large diameter pinion gear 26 from the 12 o'clock phase. Diameter Dr of ring gear 22 shown in Figure 7 is the same as diameter Dr of ring gear 22 shown in Figure 6. Similarly, the longitudinal dimension can be reduced according to needs. Transaxle 1 offers design freedom depending on the phase arrangement of large diameter pinion gear 26. Note that the height direction is the height direction of a vehicle equipped with transaxle 1, and the longitudinal direction is the fore-and-aft direction of the vehicle.

[0030] FIG. 8 shows the structure of the planetary gear mechanism 2 when the gear ratio is 15.7. As shown in FIG. 8, the transaxle 1 allows for a larger radial size, but can instead have a larger reduction ratio X. The diameter Dr of the ring gear 22 shown in FIG. 8 is larger than the diameter Dr of the ring gear 22 shown in FIGS. 7 and 6. The reduced lamination thickness of the motor 5 allows for a reduction in the axial dimension. This makes it possible to reduce the axial size of the transaxle 1 while ensuring a larger driving force. The axial direction is the same as the width direction of the vehicle.

[0031] Because the large-diameter pinion gear 26 does not revolve in the transaxle 1, as shown in FIG. 2, it is possible to place other components in the space 49 in the phase where the large-diameter pinion gear 26 is not located. In the gear chamber 11, where the planetary gear mechanism 2 is located, a space 49 is formed in the phase where the large-diameter pinion gear 26 is not located, allowing other components to be placed in addition to the planetary gear mechanism 2. For example, an electric oil pump, a strainer, parking components, and actuators for operating these components can be placed in the space 49. Other components are placed in at least a portion of the space 49. This allows for the overall size of the transaxle 1 to be reduced. In a structure such as the planetary gear mechanism 2 that does not have a ring gear that meshes with the large-diameter pinion gear 26, even if the size of the other components slightly protrudes from the space 49 shown in FIG. 2, it is easy to utilize the space 49 because this does not directly result in component interference.

[0032] As described above, according to the embodiment, it is possible to reduce the size of the transaxle 1 while ensuring a larger reduction ratio X. The transaxle 1 can obtain a larger driving force while simultaneously ensuring a large reduction ratio X and reducing the size of the motor 5.

[0033] Although the structure in which the outermost diameter portion of the large diameter pinion gear 26 is located radially outward from the ring gear 22 has been described, the present invention is not limited to this. In the planetary gear mechanism 2, the outer diameter position of the ring gear 22 may be located radially outward from the outermost diameter portion of the large diameter pinion gear 26. In other words, it does not matter whether the outermost diameter portion of the ring gear 22 or the large diameter pinion gear 26 is located radially outward. [Explanation of symbols]

[0034] 1 transaxle 2 Planetary gear mechanism 3 Differential device 4 Transaxle case 5 motors 6 axles 10 Motor Room 11 Gear room 12 Case body 13 Cover member 14 Bulkhead 17 Output shaft 21 Sun gear 22 Ring gear 23 Stepped pinion gear 24 outer pinion gear 25 Career 26 Large diameter pinion gear 27 Small diameter pinion gear 28 Pinion shaft 29 Differential case 30 Carrier body 33 Carrier Plate 47 Flange 49 spaces

Claims

1. a planetary gear mechanism having a stepped pinion gear in which a large diameter pinion gear and a small diameter pinion gear are integrated; a differential device disposed radially inside the small diameter pinion gear; a transaxle case that houses the planetary gear mechanism and the differential; Equipped with A transaxle that transmits power of an electric motor to an axle via the planetary gear mechanism and the differential device, The planetary gear mechanism includes: a sun gear provided on an output shaft of the electric motor and meshing with the large diameter pinion gear; A ring gear that rotates at the same rotation speed as a differential case of the differential device; a carrier fixed to the transaxle case and rotatably supporting the stepped pinion gear; an outer pinion gear rotatably supported by the carrier and meshing with the small diameter pinion gear and the ring gear; A transaxle characterized by:

2. the transaxle case defines a motor chamber that houses the electric motor, and a gear chamber that houses the planetary gear mechanism and the differential device, a space in which a component other than the planetary gear mechanism can be disposed is formed in a phase in which the large-diameter pinion gear is not disposed in the gear chamber where the planetary gear mechanism is disposed; The other component is disposed in at least a portion of the space.

2. The transaxle of claim 1.

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