Differential device

Abstract

To provide a pinion shaft and a differential gear provided with the same, capable of compatibly securing strength durability and reducing weight.SOLUTION: The pinion shaft SHP1 includes a shaft part 11 rotatably journaling the pinion gear GP and a body part 12 radially connecting the shaft parts 11 around the rotation axis AX3 of the differential case by the same number as the number of the pinion gears GP along the radial direction, and the body part 12 includes the same number of connection holes 14 as the shaft parts 11 into which the center side end part of each shaft part 11 can be inserted and fitted and a cylindrical shape having the same diameter as the connection hole 14 and a reinforcing cylindrical part 15 radially protruding from an opening edge part of the connection hole 14 along the radial direction.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a differential for a vehicle. [Background technology]

[0002] The differential is primarily incorporated into the final drive unit that drives the rear wheels of a vehicle. The differential device also includes a pair of side gears, pinion gears that mesh with the side gears, a differential case that houses the side gears and pinion gears, and a pinion shaft that supports the pinion gears. The differential case has a spherical shell shape, with side gears arranged coaxially with the rotation axis, and pinion gears arranged to mesh with the side gears at right angles to the inner circumferential surface of the spherical shell of the differential case. Conventionally, differential gears have been required to be smaller and lighter overall, and as part of this effort, the side gears and pinion gears have been made smaller. However, when the side gears and pinion gears are made smaller, tooth root stress due to gear meshing increases. To address this issue, the number of pinion gears has been increased to reduce the load on each pinion gear.

[0003] In conventional differential devices that use two pinion gears, the differential case is generally molded as a single unit, with the side gears and pinion gears installed inside through openings on the circumferential surface of the spherical shell. However, when there are three or more pinion gears, the pinion gears are arranged on the inner peripheral surface of the spherical shell portion of the differential case, making it impossible to provide a large opening. Therefore, in Patent Document 1, a configuration is adopted in which the differential case is divided in the direction of the rotation axis, and side gears, pinion gears, pinion shafts, etc. are installed inside through openings in the direction of the rotation axis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-185402 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the pinion shaft is composed of a cylindrical portion arranged coaxially with the differential case and a plurality of shaft portions oriented radially from the cylindrical portion along the rotation axis. One end of the shaft portion is fitted into the cylindrical portion, and the other end of the shaft portion has a pinion gear inserted therethrough and is fitted and supported by the differential case. In a pinion shaft configured in this manner, the gear meshing reaction force acts on the support portions at both ends, making it difficult to ensure strength and durability while also reducing weight. The present invention has been devised to solve the above-mentioned problems, and its object is to provide a differential device including a pinion shaft that ensures strength and durability while also being lightweight. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the differential device of the present invention has a hollow differential case, a pair of side gears supported within the differential case, and a plurality of pinion gears journalled to the differential case via pinion shafts and meshing with each of the pair of side gears, the pinion shaft having a shaft portion that journalled the pinion gears rotatably, and a body portion that radially connects the shaft portions, the number of which is equal to the number of pinion gears, around the rotation axis of the differential case, and the body portion has connecting holes into which the central end portions of the shaft portions can be inserted and which are the same number as the shaft portions, and a reinforcing cylindrical portion that has a cylindrical shape with the same diameter as the connecting holes and protrudes radially from the opening edge of the connecting holes in the radial direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a differential device including a pinion shaft that ensures strength and durability while also being lightweight. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a power transmission device for a vehicle equipped with a differential gear according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing a differential gear according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 1 is a plan view showing a pinion shaft according to a first embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view of a portion of FIG. [Figure 6] FIG. 5 is a side view seen from the direction IV in FIG. 4. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. [Figure 8] FIG. 10 is a plan view showing a pinion shaft according to a second embodiment of the present invention, with a portion shown in cross section. [Figure 9] 7 is a cross-sectional view showing a pinion shaft according to a third embodiment of the present invention, taken along a line VII-VII in FIG. 4. [Figure 10] 7 is a cross-sectional view showing a pinion shaft according to a fourth embodiment of the present invention, taken along a line VII-VII in FIG. 4. [Figure 11] FIG. 10 is a top view showing a pinion shaft according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] First Embodiment A vehicle power transmission device S having a differential gear DF1 according to a first embodiment of the present invention will be described in detail with reference to FIGS. In the description, the same elements are given the same reference numerals and redundant description will be omitted. The vehicle power transmission device S of this embodiment is mounted on a four-wheel drive vehicle (not shown) based on front-wheel drive.

[0010] In this four-wheel drive vehicle, in addition to a drive unit (not shown) for driving the front wheels, a rear wheel drive unit RWD (final reduction gear) for driving the rear wheels is provided. The vehicle power transmission device S of this embodiment, together with the motor M serving as a drive source, constitutes rear wheel drive means RWD (see FIG. 1). That is, the vehicle power transmission device S of this embodiment is configured to transmit the driving force generated by the motor M to the rear wheels. The rear wheel drive means RWD is installed on the vehicle so that the rotation shaft of the motor M is oriented in the vehicle width direction and the motor M is positioned on the right side of the vehicle power transmission device S.

[0011] The vehicle power transmission device S is housed in a housing H and configured as a single unit together with a motor M (see FIG. 1). The housing H is made up of a first housing H1 and a second housing H2. The first housing H1 and the second housing H2 form a box-like shape and define a space in which the vehicle power transmission device S is housed.

[0012] The vehicle power transmission device S includes a housing H, a reduction gear RD, and a differential gear DF1. The reducer RD is configured to reduce the rotation speed of the motor M at a set reduction ratio while increasing the torque and transmitting it to the differential device DF1. The reducer RD is configured with a two-stage gear mechanism consisting of a first gear mechanism RD1 and a second gear mechanism RD2. The first gear mechanism RD1 and the second gear mechanism RD2 are configured with spur gears whose respective rotation axes (first rotation axis AX1, second rotation axis AX2) are arranged in parallel.

[0013] When the vehicle travels straight, the differential device DF1 transmits driving force equally to the left and right drive shafts SD at the same rotation speed (see FIGS. 1 to 3). Furthermore, when the vehicle turns, the differential device DF1 transmits driving force to the left and right drive shafts SD with a rotation difference corresponding to the inner wheel difference that occurs between the left and right drive shafts SD. The drive shaft SD serves as the output portion of the differential device DF1 and is connected to the rear wheels of the vehicle to transmit driving force to the rear wheels. The drive shaft SD is made up of a right drive shaft SDR and a left drive shaft SDL, with the right drive shaft SDR driving the right rear wheel (not shown) and the left drive shaft SDL driving the left rear wheel (not shown).

[0014] The differential device DF1 includes a differential case CD, a pinion gear GP, a right side gear GSR (first side gear), and a left side gear GSL (second side gear). The differential case CD is supported within the housing H via bearings BR so as to be rotatable about a third rotation axis AX3 (the rotation axis of the differential case). The third rotation axis AX3 is set as the rotation center of the differential case CD, ring gear GR, right side gear GSR, and left side gear GSL. The third rotation shaft AX3 is located behind the reducer RD (the first gear mechanism RD1 and the second gear mechanism RD2) and is oriented in the vehicle width direction.

[0015] The differential case CD has a generally cylindrical shape with the third rotation shaft AX3 as its central axis, and accommodates the pinion gear GP, the right side gear GSR, and the left side gear GSL inside the cylinder.

[0016] The pinion gear GP is configured to transmit the rotational force of the differential case CD to the left and right side gears GSR and GSL by meshing with the left and right side gears GSR and GSL and rotating together with the differential case CD (see Figures 2 to 7). The pinion gear GP is rotatably supported via a pinion shaft SHP1 that is supported by a main case CD1 (to be described later) and that is perpendicular to the third rotation axis AX3. Three pinion gears GP are provided at equal angular intervals in the circumferential direction around the third rotation axis AX3. Each pinion gear GP is made up of a bevel gear of the same shape.

[0017] The pinion shaft SHP1 also includes three shaft portions 11 and one body portion 12. The shaft portions 11 are each made of a round bar-shaped member of the same shape. Each of the shaft portions 11 rotatably supports a separate pinion gear GP. The shaft portions 11 are arranged radially on a plane perpendicular to the third rotation axis AX3 along a radial direction (hereinafter referred to as the radial direction) centered on the third rotation axis AX3. The radially inner ends of the shaft portions 11 are connected together at the body portion 12 . Further, the radially outer end of each shaft portion 11 is supported by the main case CD1.

[0018] The body portion 12 is configured to connect the shaft portions 11 radially. The body portion 12 includes a body main body 13, a connecting hole 14, a reinforcing cylindrical portion 15, and a rib 16. The body main body 13 has a cylindrical shape with its center positioned on the third rotation axis AX3. A connecting hole 14 opens on the outer peripheral surface of the cylindrical body 13 .

[0019] The connecting holes 14 are holes into which the center side ends of the shaft portions 11 are inserted, and three holes of the same shape (the same number as the shaft portions 11) are provided. These three connecting holes 14 are open radially along the radial direction at equal angular intervals in the circumferential direction (hereinafter referred to as the circumferential direction) centered on the third rotation axis AX3. The reinforcing cylindrical portion 15 has a cylindrical shape with an inner diameter equal to that of the connecting hole 14, and protrudes radially from the opening edge of the connecting hole 14 along the radial direction by a height h1. The reinforcing cylindrical portion 15 has a cylindrical wall whose thickness is set to be constant regardless of the position in the circumferential direction of the reinforcing cylindrical portion. The ribs 16 are provided radially upright on a plane perpendicular to the third rotation axis AX3, and connect adjacent reinforcing cylindrical portions 15 together.

[0020] Next, the procedure for assembling the pinion shaft SHP1 will be described. With the body portion 12 positioned on the third rotation axis AX3, the three shaft portions 11 are inserted from the outside of the main case CD1 into the pinion support hole 25a, pinion washer 52, pinion gear GP, and body portion 12 in that order. Next, the roller pin 54 is inserted into the extension portion 25 set in the cylindrical wall of the main case CD1, and is fitted onto the shaft portion 11, thereby fixing the pinion shaft SHP1 to the extension portion 25.

[0021] The right side gear GSR is journalled to the differential case CD so as to be rotatable relative to the differential case CD about a third rotation axis AX3. The right side gear GSR is composed of a bevel gear that can mesh with the pinion gear GP and is located at the right end of the differential case CD. The right side gear GSR is formed at the inner end of the right drive shaft SDR in the vehicle width direction. A constant velocity joint (not shown) disposed at the end of the right drive shaft SDR is inserted into the center of the shaft of the right side gear GSR, and the right side gear GSR rotates integrally with the right drive shaft SDR.

[0022] The left side gear GSL is journaled to the differential case CD so as to be rotatable relative to the differential case CD about a third rotation axis AX3, while facing the right side gear GSR. The left side gear GSL is composed of the same bevel gear as the right side gear GSR, and is rotatably supported on the left end of the differential case CD while meshing with the pinion gear GP. The left side gear GSL is formed at the inner end of the left drive shaft SDL in the vehicle width direction. Furthermore, a constant velocity joint (not shown) disposed at the end of the left drive shaft SDL is inserted into the center of the shaft of the left side gear GSL, and the left side gear GSL rotates integrally with the left drive shaft SDL.

[0023] The differential case CD, which houses the pinion gear GP, right side gear GSR, and left side gear GSL, includes a main case CD1 (first differential case) and a sub-case CD2 (second differential case). The main case CD1 and the sub-case CD2 form a hollow box shape. The differential case CD is configured so as to be divided into a main case CD1 and a sub-case CD2 on the left and right sides in the vehicle width direction along a plane perpendicular to the third rotation axis AX3.

[0024] In the differential device DF1 configured as above, rotation of the ring gear GR causes the differential case CD and the pinion gear GP to rotate (revolve) around the third rotation axis AX3. As the pinion gear GP revolves, it transmits the rotation of the differential case CD (ring gear GR) to the meshing right side gear GSR and left side gear GSL. When the right side gear GSR rotates, the right drive shaft SDR rotates, and when the left side gear GSL rotates, the right drive shaft SDR rotates. Additionally, when the differential case CD rotates, the pinion gear GP rotates (spins) around the pinion shaft SHP1, transmitting rotation while creating a rotational difference between the left and right drive shafts SD.

[0025] Next, the effects of the differential device DF1 of this embodiment will be described. In the differential device DF1 of this embodiment, a reinforcing cylindrical portion 15 is provided on a body portion 12 that constitutes the pinion shaft SHP1. By adopting such a configuration, it is possible to ensure a large fitting length of the shaft portion 11 while reducing the size of the body portion 12. This increases the support rigidity with which the body portion 12 supports the shaft portion 11, and also prevents stress from concentrating in a local area. Furthermore, it is possible to reduce the weight of the pinion shaft SHP1 while ensuring sufficient strength and durability.

[0026] In the differential device DF1 of this embodiment, a rib 16 is provided on the outer circumferential surface of the trunk main body 13, extending in the rotational axis direction of the pinion shaft SHP1 and connecting adjacent reinforcing cylindrical portions 15 together. With this configuration, the support rigidity with which the body portion 12 supports the shaft portion 11 can be increased. This makes it possible to reduce the weight of the pinion shaft SHP1 while ensuring more sufficient strength and durability.

[0027] Second Embodiment Next, a differential device DF1 according to a second embodiment of the present invention will be described with reference to FIG. In the description, the same elements as those in the first embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted. In the differential device DF1 of this embodiment, the shape of the body portion 12 constituting the pinion shaft SHP2 is different from that of the first embodiment, but the other configurations are the same as those of the first embodiment.

[0028] The body 12 of this embodiment has a cylindrical body main body 13 with a through-hole 17 opening along the third rotation axis AX3. That is, the body main body 13 has a cylindrical shape with a through hole 17 opening along the third rotation axis AX3. The configuration of the body portion 12, which includes the connecting hole 14, the reinforcing cylindrical portion 15, and the rib 16, is the same as in the first embodiment.

[0029] The through holes 17 have a cross section of an approximately equilateral triangle formed by a surface perpendicular to the radial direction for each of the three connecting holes 14, and open while penetrating the body main body 13 along the third rotation axis AX3. That is, the through-hole 17 is a hole whose cross-sectional shape is a regular polygon formed by hole walls perpendicular to the radial direction of each connecting hole 14 .

[0030] By adopting such a configuration, it is possible to ensure a larger fitting length with the shaft portion 11 compared to when a through hole having a circular cross section is provided. This makes it possible to increase the support rigidity with which body portion 12 supports shaft portion 11, and also to prevent stress from concentrating in a local area. Furthermore, it is possible to reduce the weight of the pinion shaft SHP2 while ensuring sufficient strength and durability.

[0031] <Third embodiment> Next, a differential device DF1 according to a third embodiment of the present invention will be described with reference to FIG. In the description, the same elements as those in the first embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted. In the differential device DF1 of this embodiment, the shape of the body portion 12 constituting the pinion shaft SHP3 is different from that of the first embodiment, but the other configurations are the same as those of the first embodiment. In the present embodiment, the body portion 12 has a body main body 13 that is a sphere of radius r1 with its center located away from the third rotation axis AX3, so that the axial central portion of the third rotation axis AX3 has a barrel shape that is more bulging than the ends. The configuration of the body portion 12, which includes the connecting hole 14, the reinforcing cylindrical portion 15, and the rib 16, is the same as in the first embodiment. With this configuration, it is possible to obtain the same effects as in the first embodiment.

[0032] <Fourth embodiment> Next, a differential device DF1 according to a fourth embodiment of the present invention will be described with reference to FIG. In the description, the same elements as those in the first embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted. In the differential device DF1 of this embodiment, the shape of the body portion 12 constituting the pinion shaft SHP4 is different from that of the first embodiment, but the other configurations are the same as those of the first embodiment. In the body 12 of this embodiment, the body main body 13 has a spherical shape with a radius r2 and a center on the third rotation axis AX3. The configuration of the body portion 12, which includes the connecting hole 14, the reinforcing cylindrical portion 15, and the rib 16, is the same as in the first embodiment. With this configuration, it is possible to reduce the weight of the pinion shaft SHP4 while ensuring sufficient strength and durability.

[0033] Fifth Embodiment Next, a differential device DF1 according to a fifth embodiment of the present invention will be described with reference to FIG. In the description, the same elements as those in the first embodiment are denoted by the same reference numerals, and duplicated descriptions will be omitted. In the differential device DF1 of this embodiment, the shape of the body portion 12 constituting the pinion shaft SHP5 differs from that of the first embodiment, but the other configurations are the same as those of the first embodiment. In the body portion 12 of this embodiment, the reinforcing tube portion 15 is not circular and has a uniform thickness, and the dimension t2 of the tube wall along the circumferential direction of the third rotation axis AX3 is set larger than the dimension t1 of the tube wall along the axial direction of the third rotation axis AX3.

[0034] With this configuration, when a meshing reaction force acts on the pinion shaft SHP5, a bending load acts on the shaft portion 11 in the rotational direction of the third rotation axis AX3. Therefore, the thickness of the reinforcing cylinder portion 15 is increased in the direction of rotation, thereby increasing the support rigidity with which the body portion 12 supports the shaft portion 11. This makes it possible to reduce the weight of the pinion shaft SHP5 while improving its strength and durability.

[0035] In FIG. 11, the end of the reinforcing cylindrical portion 15 along the circumferential direction of the rotation axis AX3 is sharply pointed, but the present invention is not limited to this shape. For example, the reinforcing cylindrical portion 15 may have an elliptical shape, and the same effects as those of this embodiment can be obtained. It is also possible to connect adjacent reinforcing cylindrical portions 15 with ribs 16, which further increases the strength and durability. [Explanation of symbols]

[0036] DF1...Differential device CD...Differential case AX3...Differential case rotating shaft (third rotating shaft) GS...Side gear GP...Pinion gear SHP1...Pinion shaft 11...Shaft portion 12...Body portion 14...Connecting hole 15...Reinforcing cylinder portion 16...Rib 17...Through hole

Claims

1. A differential case having a hollow shape and supported rotatably around a rotation axis; a pair of side gears supported within the differential case so as to be rotatable relative to the differential case around a rotation axis of the differential case; a plurality of pinion gears journalled to the differential case via pinion shafts and meshing with the pair of side gears, respectively; and The pinion shaft a shaft portion formed of a rod-shaped member and rotatably supporting the pinion gear; a body portion that radially connects the shaft portions, the number of which is equal to the number of the pinion gears, along a radial direction around a rotation axis of the differential case; Equipped with The body portion is the center end of each of the shaft portions can be inserted into a connecting hole, and the number of the connecting holes is the same as the number of the shaft portions; a reinforcing cylindrical portion having a cylindrical shape with the same diameter as the connecting hole and protruding radially from an opening edge portion of the connecting hole along the radial direction of the rotation shaft of the differential case; A differential equipped with a differential gear.

2. 2. The differential device according to claim 1, The body portion is A cylindrical shape having a center on the rotation axis of the differential case Differential device.

3. 2. The differential device according to claim 1, The body portion is The differential case has a cylindrical shape with a through hole opening along the rotation axis. Differential device.

4. 2. The differential device according to claim 1, The body portion is The rotor has a substantially spherical shape with its center positioned on the rotation axis of the differential case. Differential device.

5. 4. The differential device according to claim 3, The through hole is The cross-sectional shape is formed as a polygon composed of planes perpendicular to the radial direction of each of the connecting holes. Differential device.

6. The differential device according to any one of claims 1 to 5, The pinion shaft A rib is provided on the outer peripheral surface of the body portion in a radial direction relative to the rotation axis of the differential case, and connects adjacent reinforcing cylindrical portions. Differential device.

7. The differential device according to any one of claims 1 to 5, The reinforcing cylindrical portion is A dimension t2 of the cylindrical wall along the circumferential direction of the rotation shaft of the differential case is set larger than a dimension t1 of the cylindrical wall along the axial direction of the rotation shaft of the differential case. Differential device.

8. The differential device according to any one of claims 1 to 5, The pinion shaft At least three of the shaft portions are provided. Differential device.

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