Differential device

Abstract

To supply lubricant oil into a differential gear while suppressing a cover and a housing from increasing in volume.SOLUTION: A differential gear has: a pinion gear; a pinion shaft supporting the pinion gear rotatably; a pair of side gears engaging the pinion gear and fitted to a pair of drive shafts; a differential case supporting the pinion shaft, housing the pinion gear and the side gears, and having an opening part on one side of the drive shaft; and a differential cover having a hole that one of the drive shafts penetrates and fixed to the differential case to close the opening part, and the differential cover comprises an oil passage which penetrates along the hole from an inner surface opposed to the side gears to an outer surface on the opposite side from the differential case and in which lubricating oil circulates.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a differential device.

Background Art

[0002] Patent Document 1 discloses a power transmission device that transmits the rotation of an electric motor to drive wheels. This power transmission device has a structure in which the gears of a differential mechanism are covered by integrating a differential case and a differential cover. This differential cover has holes that penetrate from the outer peripheral surface to the inner peripheral surface of the differential cover and through which oil flows. The oil supplied to the holes of the differential cover from the housing on the outer peripheral surface side of the differential cover through an oil pump is supplied into the differential case through between the inner peripheral surface of the differential cover and the output shaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention disclosed in Patent Document 1, in order to prevent the oil supplied to the holes provided in the differential cover from leaking, it is necessary to provide a seal ring between the housing and the outer peripheral surface of the differential cover. However, by providing the seal ring, the rotating differential cover slides with respect to the seal ring, and resistance due to the sliding results in loss. Also, it is necessary to secure space for providing the seal ring, which causes an increase in volume in the output shaft direction and an increase in processing costs for securing space.

[0005] The present invention has been made in view of the above, and an object thereof is to supply lubricating oil to the inside of a differential device while suppressing an increase in the volume of a cover or a housing.

Means for Solving the Problems

[0006] The differential according to the present invention comprises a pinion gear, a pinion shaft that rotatably supports the pinion gear, a pair of side gears that mesh with the pinion gear and are fitted onto a pair of drive shafts, a differential case that supports the pinion shaft, houses the pinion gear and the side gears, and has an opening on one side of the drive shaft, and a differential cover that has a hole through which one of the drive shafts passes, is fixed to the differential case and closes the opening, the differential cover having an oil passage that penetrates from the inner surface facing the side gear along the hole to the outer surface opposite the differential case, through which lubricating oil flows.

[0007] This allows for the supply of lubricating oil to the inside of the differential gear while minimizing the increase in volume of the covers and housings of the pinion shaft, pinion gear, and side gear.

[0008] Furthermore, in the above, the phase difference between the hole supporting the pinion shaft and the oil passage in the differential case rotation direction may be offset.

[0009] This allows the differential to retain a large amount of lubricating oil, preventing seizure even when operating after being stopped for a long period of time.

[0010] Furthermore, in the above, the differential cover may have an oil groove through which the lubricating oil flows at a position on its inner surface facing the side gear, and the oil passage may open into the oil groove.

[0011] This allows for efficient supply of lubricating oil to the inside of the differential. [Effects of the Invention]

[0012] The differential gear according to the present invention has the effect of supplying lubricating oil to the inside of the differential gear while suppressing the increase in volume of the cover and housing. [Brief explanation of the drawing]

[0013] [Figure 1]Figure 1 is a schematic cross-sectional view showing the structure of a power transmission device 1 according to an embodiment. [Figure 2] Figure 2 is a perspective view of a cross-section of a differential. [Figure 3] Figure 3 is a perspective view of the differential cover from the inside. [Figure 4] Figure 4 is a plan view of the differential. [Figure 5A] Figure 5A is a cross-sectional view taken along line AA in Figure 4. [Figure 5B] Figure 5B is a cross-sectional view along line BB in Figure 4. [Figure 5C] Figure 5C is a version of Figure 5A with the differential side gears omitted. [Figure 6A] Figure 6A is a cross-sectional view showing the differential rotated 90 degrees from the state shown in Figure 5A. [Figure 6B] Figure 6B is a cross-sectional view showing the differential rotated 90 degrees from the state shown in Figure 5B. [Figure 6C] Figure 6C is a version of Figure 6A with the differential side gears omitted. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below. Furthermore, in the drawings, the same or corresponding elements are appropriately denoted by the same reference numerals. It should also be noted that the drawings are schematic, and the dimensional relationships of each element may differ from those in reality. Even between drawings, there may be parts where the dimensional relationships and ratios differ.

[0015] Figure 1 is a schematic cross-sectional view showing the structure of a power transmission device 1 according to an embodiment of the present invention. The power transmission device 1 is a power transmission device for an electric vehicle. The power transmission device 1 has a planetary gear type reduction mechanism 10 and a bevel gear type differential 20 arranged concentrically with the center line C. The reduction mechanism 10 and the differential 20 are housed inside a housing 2.

[0016] On the left side of the speed reduction mechanism 10, a motor (not shown in the figure) is arranged. This motor has a cylindrical output shaft 31. The motor is driven by a drive current supplied from an inverter to rotate the output shaft 31. At the end of the output shaft 31, a sun gear 31a is formed. The rotation of the output shaft 31 is decelerated by the speed reduction mechanism 10 meshed with the sun gear 31a, and the decelerated rotation is transmitted to a pair of drive shafts 32 and 33 via the differential device 20.

[0017] The speed reduction mechanism 10 includes a carrier 11, a compound planetary gear 12, and a ring gear 13. The carrier 11 is arranged to be rotatable about the center line C. A plurality of compound planetary gears 12 are arranged on the carrier 11 to be rotatable at equal angular intervals about an axis substantially parallel to the center line C. The compound planetary gear 12 integrally includes a large-diameter pinion 12a and a small-diameter pinion 12b in the axial direction, and is rotatable about an axis substantially parallel to the center line C via a planetary shaft 12c. The large-diameter pinion 12a is meshed with the sun gear 31a formed on the output shaft 31. The ring gear 13 is fixed to the housing 2 and is meshed with the small-diameter pinion 12b. When the output shaft 31 and the sun gear 31a are rotationally driven, the carrier 11 is rotationally decelerated at a predetermined reduction ratio with the ring gear 13 as a reaction force element. Each gear of the speed reduction mechanism 10 is a helical gear with meshing teeth twisted.

[0018] In addition, the carrier 11 integrally includes a differential case 11a on the side of the small-diameter pinion 12b, and is configured to form a differential case portion of the differential device 20. A differential cover 11b is attached to the opening of the differential case 11a so as to close the opening. When the differential cover 11b is attached to the opening of the differential case 11a to be integrated, a differential chamber R for housing the differential pinion gear 22 and the differential side gear 23 is formed. The carrier 11, with the differential cover 11b integrated, is supported by the housing 2 via a pair of bearings 41 and 42 at both left and right ends so as to be rotatable about the center line C and non-movable in the axial direction.

[0019] The differential gear 20 is positioned close to the reduction mechanism 10 on the small-diameter pinion 12b side of the compound planetary gear 12. The differential gear 20 comprises a differential pinion shaft 21, a differential pinion gear 22, and a differential side gear 23. The differential pinion shaft 21 is supported by the differential case 11a and is positioned perpendicular to the center line C. The differential pinion shaft 21 is an example of a pinion shaft according to the present invention. The differential pinion gear 22 and the differential side gear 23 are bevel gears. The differential pinion gear 22 is supported rotatably by the differential pinion shaft 21, which passes through it. The differential pinion gear is an example of a pinion gear according to the present invention. The differential side gear 23 is spline-fitted to a pair of drive shafts 32, 33 so as not to rotate relative to them, and meshes with the differential pinion gear 22. The differential side gear 23 is an example of a side gear according to the present invention.

[0020] Figure 2 is a cross-sectional perspective view of the differential gear 20. A shim 24 and a disc spring 25 are positioned between the differential side gear 23 and the differential cover 11b. Another shim 24 and a disc spring 25 are positioned between the differential case 11a and the differential side gear 23 on the motor side. The shim 24 and disc spring 25 apply a preload load to the differential side gear 23. Returning to Figure 1, a pair of drive shafts 32 and 33 are arranged concentrically with the center line C. Drive shaft 32 passes through the cylindrical output shaft 31 so as to be rotatable relative to it and reaches the opposite side of the motor. Drive shaft 33 protrudes to the outside of the housing 2 through a hole 11e formed in the differential cover 11b. Drive wheels are connected to the drive shafts 32 and 33, and the rotation of the drive shafts 32 and 33 is transmitted to the drive wheels. An oil seal 51 is positioned between the drive shaft 33 and the housing 2 to prevent oil leakage.

[0021] In this embodiment, an oil passage 11c is formed in the differential cover 11b to prevent seizure of the differential pinion gear 22 and differential side gear 23 of the differential 20. The oil passage 11c is a circular hole that penetrates from the outer surface opposite to the differential case 11a to the inner surface on the differential case 11a side, along the center line of the hole 11e. In addition, an oil passage for preventing seizure is also formed on the inner surface of the differential cover 11b facing the differential side gear 23. Figure 3 is a perspective view of the differential cover 11b from the inner side. On the inner surface of the differential cover 11b, the opening of the oil passage 11c is located at the position of the oil groove 11d. The oil groove 11d is a groove of a predetermined depth formed on the inner surface of the differential cover 11b from the opening of the hole 11e toward the radially outward side of the differential cover 11b. The oil groove 11d is a groove for supplying oil to the shim 24 and the disc spring 25, and for circulating oil to the outer circumference of the differential side gear 23.

[0022] As shown in Figure 1, the housing 2 has an oil passage 2a through which oil is supplied as lubricant from an oil pump (not shown). The oil flowing through the oil passage 2a in the direction of the arrow in the figure is supplied to the space between the bearing 41 and the oil seal 51. The oil supplied to the space between the bearing 41 and the oil seal 51 flows through the bearing 41, through the oil passage 11c located near the bearing 41 in the direction of the arrow in the figure, and further through the oil groove 11d to flow to the differential chamber R. The oil that has passed through the bearing 41 is also supplied to the space between the differential gear 20 and the housing 2 by passing between the bearing 41 and the differential cover 11b in the direction of the arrow in the figure.

[0023] Next, the operation and effects of this embodiment will be described. Figure 4 is a plan view of the differential 20. Figure 5A is a cross-sectional view along line AA of Figure 4, and Figure 5B is a cross-sectional view along line BB of Figure 4. Figure 5C is a view of Figure 5A with the differential side gear 23 omitted. As shown in Figure 5C, when the differential cover 11b is viewed from the inner side, if the differential pinion shaft 21 is vertical, the oil passage 11c is located at 0 degrees and 180 degrees around the center of rotation, and the phase difference between the rotation of the differential pinion shaft 21 and the rotation of the oil passage 11C is 90 degrees around the center line C.

[0024] When the differential pinion shaft 21 is vertical and the differential 20 stops, the oil passage 11c is higher than the lower differential side gear 23, as shown in Figure 5C, and the oil level inside the differential chamber R is at the position of the dashed line LS1 shown in Figures 5A, 5B, and 5C. When the differential pinion shaft 21 is vertical and the differential 20 stops, and the supply of oil to the differential chamber R is stopped, a small amount of oil leaks from the clearance between the differential pinion shaft 21 and the differential case 11a. However, in this embodiment, the oil level when the differential 20 stops is at the position of the dashed line LS1 shown in the figure, and since the amount of oil at the time of stopping is large, the period during which oil is retained inside the differential chamber R while stopped can be extended. Furthermore, even when the differential 20 is activated after being stopped for a long period of time, the oil is retained in the differential chamber R for a long period of time, so seizure of the differential pinion gear 22 and the differential side gear 23 can be prevented.

[0025] Next, Figure 6A shows a cross-section when the differential 20 is rotated 90 degrees from the state shown in Figure 5A, and Figure 6B shows the state when the differential 20 is rotated 90 degrees from the state shown in Figure 5B. Also, Figure 6C is a diagram from Figure 6A with the differential side gear 23 omitted.

[0026] When the differential pinion shaft 21 is horizontal and the differential 20 stops, one of the oil passages 11c is lower than the differential pinion shaft 21, as shown in Figure 6C. Inside the differential chamber R, the oil level supplied to the differential chamber R is at the position of the dashed line LS2 shown in Figures 6A, 6B, and 6C, depending on the position of the oil passage 11c. When the differential pinion shaft 21 is horizontal and the differential 20 stops, and the supply of oil to the differential chamber R is stopped, the oil level is lower than when the differential pinion shaft 21 is vertical. However, since the differential pinion shaft 21 is above the dashed line LS2 and no oil leaks from the clearance between the differential pinion shaft 21 and the differential case 11a, the oil can be retained in the differential chamber R even when stopped. Furthermore, since no oil leaks from within the differential chamber R, even when the vehicle is activated after being stationary for a long period of time, the oil in the differential chamber R prevents seizure of the differential pinion gear 22 and the differential side gear 23. Also, as shown in Figures 6A and 6B, when the differential pinion shaft 21 is horizontal, the differential pinion gear 22 is not submerged in oil, allowing the differential chamber R to retain a larger amount of oil.

[0027] Furthermore, according to this embodiment, since the oil passage 11c is provided along the hole 11e through which the drive shaft 33 passes, a seal ring is not required on the outer circumferential surface side of the differential cover 11b, thereby suppressing the increase in the axial volume of the drive shaft 33 and eliminating the need for machining to secure space for a seal ring. In addition, according to this embodiment, since the opening of the oil passage 11c is located at the position of the oil groove 11d provided on the inner surface of the differential cover 11b, an oil path is secured on the inner surface side of the differential cover 11b, and oil can be efficiently supplied to the differential chamber R. Furthermore, compared to a configuration in which the opening of the oil passage 11c is not located at the position of the oil groove 11d, machining costs can be reduced.

[0028] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above and can be implemented in various other forms. For example, the present invention may be implemented by modifying the embodiments described above as follows. The embodiments described above and the following modifications may be combined with each other. The present invention is also included in configurations that appropriately combine the components of each embodiment and each modification described above. Furthermore, further effects and modifications can be easily derived by those skilled in the art. Therefore, broader embodiments of the present invention are not limited to the embodiments and modifications described above, and various modifications are possible.

[0029] In the embodiment described above, there are two oil passages 11c, and the phase difference between the rotation of the differential pinion shaft 21 and the rotation of the oil passage 11C around the center line C is 90 degrees. However, this phase difference is not limited to 90 degrees. In the state shown in Figure 5C, where the differential pinion shaft 21 is vertical, the lower end of the lower oil passage 11c may be positioned above the upper end of the lower differential pinion gear 22. With this phase difference, the oil level can be set to the same height as shown in Figure 5C.

[0030] In the embodiment described above, there are two oil passages 11c formed in the differential cover 11b, but three or more oil passages 11c may be formed. When there are three or more oil passages 11c, it is preferable to form the oil passages 11c such that, when viewing the differential 20 in the direction of the center line C, the oil passages 11c are located between the lower end of the upper differential pinion gear 22 and the upper end of the lower differential pinion gear 22 in the state shown in Figure 5C where the differential pinion shaft 21 is vertical, so that the phase difference between the rotation of the differential pinion shaft 21 and the rotation of the oil passages 11C is different. [Explanation of symbols]

[0031] 1. Power transmission device 2 Housing 10 Reduction mechanism 11 Careers 11a Differential Case 11b Differential Cover 11c oil passage 11d Oil groove 20 Differential device 21 Differential pinion shaft 22 Differential pinion gear 23 Differential side gear 32, 33 Drive shafts

Claims

1. Pinion gear and, A pinion shaft that rotatably supports the aforementioned pinion gear, A pair of side gears that mesh with the aforementioned pinion gear and are fitted onto a pair of drive shafts, A differential case that supports the pinion shaft, houses the pinion gear and the side gear, and has an opening on one side of the drive shaft, A differential cover having a hole through which one of the drive shafts passes, fixed to the differential case and closing the opening, It has, The differential cover has an oil passage through which lubricating oil flows, extending from the inner surface facing the side gear along the hole to the outer surface opposite the differential case. The phase difference between the hole supporting the pinion shaft and the oil passage in the differential case rotation direction is 90 degrees. Differential device.

2. The differential cover has an oil groove through which the lubricating oil flows, located on its inner surface opposite to the side gear. The oil passage opens into the oil groove. The differential device according to claim 1.

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