JP6827752B2 - Differential - Google Patents

Description

The present invention relates to a differential device suitable for a vehicle such as an automobile.

A conventional differential device, particularly a differential case (input member), is supported by the differential case to support a pinion (differential gear) of a differential mechanism in a differential device that also serves as a carrier plate that supports a shaft for supporting planetary gears. For example, Patent Document 1 discloses a shaft for supporting a differential gear and a shaft for supporting a planetary gear arranged at the same position in the circumferential direction of the differential case.

Japanese Unexamined Patent Publication No. 2001-121980 Japanese Patent No. 4803871 JP-A-2002-364728

By the way, in a differential device including a pinion (that is, a differential gear) and a pair of side gears (that is, output gears) that mesh with the pinion, the side gear is pinioned so that the number of teeth of the side gear can be set sufficiently larger than the number of teeth of the pinion. It is conceivable to make the differential device flat in the axial direction by increasing the diameter sufficiently.

In this case, if the above-described shaft arrangement configuration disclosed in Patent Document 1 is applied to the flat differential device as it is, the circumferential direction of the shaft for supporting the differential gear and the shaft for supporting the planetary gear in the flat differential case. The load tends to be concentrated on the parts where the positions match, and the durability of the differential case may decrease.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a differential device capable of solving the above problems with a simple structure.

In order to achieve the above object, the differential device according to the present invention includes an input member that can be coupled to a carrier that supports the plurality of planetary gears via a plurality of first shafts that each support the plurality of planetary gears. A differential gear that is supported by the input member via at least one second shaft, is rotatable with respect to the input member, and can revolve around the center of rotation of the input member, and meshes with the differential gear. The input member includes a pair of output gears, and the input member has a plurality of recesses into which the first shaft can be fitted, at positions that overlap with the output gears in the radial direction on the wall facing the carrier. The plurality of recesses are arranged at positions deviated from all the second shafts in the circumferential direction of the input member. Preferably, the pair of output gears has a shaft portion connected to the pair of output shafts, and the input member has a boss portion that concentrically surrounds the shaft portions and an outer surface of the output shaft. It has a side wall portion connected to the boss portion as an orthogonal flat surface.

Preferably, the pair of output gears has a shaft portion connected to the pair of output shafts, and the input member has a boss portion that concentrically surrounds the shaft portions and an outer surface of the output shaft. It has a side wall portion connected to the boss portion as an orthogonal flat surface.

Preferably, the plurality of recesses are arranged at positions shifted in the circumferential direction of the input member with respect to the welded portion connecting the carrier and the input member.

Preferably, the plurality of recesses are arranged at positions shifted in the circumferential direction of the input member with respect to the welded portion connecting the carrier and the input member.
Further, in order to achieve the above object, the differential device according to the present invention includes a carrier main body adjacent to a carrier cover that supports one end of a plurality of first shafts that each support a plurality of planetary gears, and the carrier main body. An input member having one cover portion having a wall portion integrally formed with the portion and the other cover portion that can be coupled to the one cover portion, and the input member via at least one second shaft. A differential gear that is supported by the input member and can rotate with respect to the input member and revolves around the center of rotation of the input member, and a pair of output gears that mesh with the differential gear. The cover portion has a plurality of recesses in which each of the other ends of the plurality of first shafts can be inserted at a position on the wall portion that overlaps with the output gear in the radial direction . It is arranged at a position deviated from all the second shafts in the circumferential direction of the input member.

Preferably, the pair of output gears has a shaft portion connected to the pair of output shafts, and each of the one cover portion and the other cover portion concentrically surrounds the shaft portion. It has a portion and a side wall portion connected to the boss portion with the outer surface as a flat surface orthogonal to the output axis.

Preferably, when the number of teeth of the output gear is Z1, the number of teeth of the differential gear is Z2, the diameter of the second shaft is d2, and the pitch cone distance is PCD,

を満たし、
且つＺ１／Ｚ２＞２を満たしている。

The filling,
And Z1 / Z2> 2 is satisfied.

Further, preferably, Z1 / Z2 ≧ 4 is satisfied.

Further, preferably, Z1 / Z2 ≧ 5.8 is satisfied.

According to the present invention, even when the differential case is flattened due to the flattening of the differential device in the axial direction, it is possible to effectively suppress a decrease in durability of the differential case due to the formation of recesses.

Skeleton diagram of the differential device and reduction gear mechanism according to the first embodiment of the present invention. Longitudinal sectional view of a main part of the differential device and the reduction gear mechanism according to the first embodiment of the present invention. Cross-sectional view of the differential device according to the first embodiment of the present invention as viewed from the center thereof to the first cover portion side (A3-A3 line sectional view of FIG. 2). A4-A4 line sectional view of FIG. Side view of the differential case (first cover portion) before joining the carriers as viewed from the carrier side. An enlarged cross-sectional view showing an enlarged view of the A6 arrow-viewing portion of FIG. An enlarged cross-sectional view showing a main part of the differential device according to the second embodiment of the present invention. Longitudinal sectional view of a main part of the differential device and the reduction gear mechanism according to the third embodiment of the present invention (corresponding to FIG. 2). Longitudinal sectional view of a main part of the differential device and the reduction gear mechanism according to the fourth embodiment of the present invention (corresponding to FIG. 2). Longitudinal sectional view of a main part of the differential device and the reduction gear mechanism according to the fifth embodiment of the present invention (corresponding to FIG. 2). Longitudinal section showing an example of a conventional differential device A graph showing the relationship between the rate of change in gear strength and the ratio of the number of teeth when the number of teeth of the pinion is 10. Graph showing the relationship between the rate of change in gear strength and the rate of change in pitch cone distance A graph showing the relationship between the rate of change of the pitch cone distance and the ratio of the number of teeth when the gear strength is maintained at 100% when the number of teeth of the pinion is 10. A graph showing the relationship between the ratio of the number of teeth when the number of teeth of the pinion is 10 and the ratio of the shaft diameter / pitch cone distance. A graph showing the relationship between the ratio of the number of teeth when the number of teeth of the pinion is 6 and the ratio of the shaft diameter / pitch cone distance. A graph showing the relationship between the ratio of the number of teeth when the number of teeth of the pinion is 12 and the ratio of the shaft diameter / pitch cone distance. A graph showing the relationship between the ratio of the number of teeth when the number of teeth of the pinion is 20 and the ratio of the shaft diameter / pitch cone distance.

Embodiments of the present invention will be described with reference to the drawings.

First, the first embodiment of the present invention will be described with reference to FIGS. 1 to 6. In FIG. 1, a differential device D is connected to an engine (not shown) as a power source mounted on an automobile via a reduction gear mechanism RG. The differential device D distributes and transmits the rotational force transmitted from the engine to the differential case DC via the reduction gear mechanism RG to the output shafts J1 and J2 connected to a pair of axles parallel to each other in the vehicle width direction (not shown). Therefore, both axles are driven while allowing differential rotation of both axles. For example, the reduction gear mechanism RG is adjacent to the transmission case M arranged next to the engine at the front of the vehicle body. It is housed together with the reduction gear mechanism RG in the state of being moved. A power disconnection / disconnection mechanism and a forward / reverse advance switching mechanism (neither of which is shown), which are well known in the art, are interposed between the engine and the reduction gear mechanism RG. Further, the rotation axis L of the differential case DC coincides with the central axis of the output axes J1 and J2.

In the present specification, the "axial direction" refers to a direction along the central axis of the output shafts J1 and J2 (that is, the rotation axis L of the differential case DC and the side gear S) and the axis of each gear of the reduction gear mechanism RG. Further, the "diametrical direction" means the radial direction of the differential case DC and the side gear S.

The reduction gear mechanism RG has, for example, a sun gear 20 that is concentrically rotatably fitted and supported at one end of a differential case DC, and a large diameter that concentrically surrounds the sun gear 20 and is fixed to the inner wall of the mission case M. It includes a ring gear 21, a plurality of (for example, four) planetary gears 22 interposed between the sun gear 20 and the ring gears 21 and meshing with the gears 20 and 21, and a carrier 23 that pivotally supports the planetary gears 22. The sun gear 20 is connected to the crankshaft of the engine via, for example, an interlocking mechanism (not shown), and the power input to the sun gear 20 is sequentially decelerated and transmitted to the differential case DC via the planetary gear 22 and the carrier 23. To.

The carriers 23 are, for example, a plurality of carrier bases 23b formed in a circular ring shape having a diameter smaller than that of the differential case DC, and a plurality of carriers 23 that are integrally connected to the end faces of the carrier bases 23b at intervals in the circumferential direction and extend in the axial direction. It has (for example, four) arm portions (carrier main body portions) 23a. Each arm portion 23a is formed in a fan shape when viewed from a projection plane orthogonal to the rotation axis L of the differential case DC, for example, and the tip end portion (that is, the axial end portion of the carrier 23) of each arm portion 23a is formed. , As will be described later, it is connected to the differential case DC by welding w.

The planetary gears 22 are arranged, for example, in the space between the arm portions 23a adjacent to each other in the circumferential direction of the carrier 23. Further, the planetary gear 22 is rotatably and supported by the pivot PL as the first shaft passing through the space. One end of the Axis PL (the other end of the Axis PL) is fitted and supported by, for example, a through hole H2 provided in the carrier 23 (more specifically, the carrier base 23b), and the fitting and supporting portion is fitted and supported. Is bonded by an appropriate bonding means (for example, welding, bonding, caulking, press fitting, etc.) so that one end of the Axis PL is fixed to the carrier 23. Further, the pivot PL may be fixed to the carrier 23 by using a pin for preventing the pivot PL from coming off, as in the fourth embodiment described later.

Further, the other end of the pivot PL (one end of the pivot PL) has a diameter with the side gear S on the wall facing the carrier 23 of the differential case DC (that is, the side wall Cs of the first cover portion C1 described later) as described later. It is fitted and supported in a bottomed concave hole H1 as a concave portion provided at a position where it overlaps in the direction . As a result, the pivot PL is supported by the carrier base 23b of the carrier 23 and the differential case DC.

One end of the differential case DC (in this embodiment, the right end when viewed on the paper in FIG. 2) is rotatably supported by the mission case M via, for example, a bearing 2. On the other hand, on the other end side of the differential case DC, for example, at least one of the sun gear 20, the carrier 23, or the output shaft J1 is rotatably supported by the mission case M, although not shown. As a result, the coupling of the differential case DC and the carrier 23 that rotate integrally with each other is rotatably supported by the mission case M.

Further, the mission case M is formed with through holes Ma into which the output shafts J1 and J2 are fitted. An annular sealing member 3 for sealing between the inner circumference of the through hole Ma and the outer circumference of the output shafts J1 and J2 is interposed. Further, at the bottom of the mission case M, for example, an oil pan (not shown) that faces the internal space 1 of the mission case M and stores a predetermined amount of lubricating oil is provided. Then, the lubricating oil stored in the oil pan is scraped up and scattered around by the rotation of the movable element of the reduction gear mechanism RG and the differential case DC in the internal space 1 of the mission case M, so that the machine exists inside and outside the differential case DC. It is designed to lubricate moving parts. The lubricating oil stored in the oil pan is sucked by an oil pump (not shown), and a specific part of the internal space 1 of the mission case M, for example, the reduction gear mechanism RG, the differential case DC, or the mission case M around it. It may be forced to spray or spray toward the inner wall of the.

The differential device D includes, for example, a differential case DC, a plurality of pinions P housed in the differential case DC, a pinion shaft PS housed in the differential case DC and rotatably supporting the pinion P, and a differential case DC. It is provided with a pair of side gears S that mesh with the pinion P from both the left and right sides and are connected to the pair of output shafts J1 and J2, respectively. Further, the side gear S is an example of an output gear, the pinion P is an example of a differential gear, the pinion shaft PS is an example of a differential gear support portion, and the differential case DC is an example of an input member.

The pinion (pinion gear) P is housed and supported by the differential case DC, and can rotate around the axial axis in the radial direction with respect to the differential case DC, and can revolve around the center of rotation of the differential case DC as the differential case DC rotates.

The differential case DC covers, for example, a short cylindrical (cylindrical) case portion (circumferential wall portion) 4 that supports the pinion shaft PS so that it can rotate together with the pinion shaft PS, and a case portion 4 that covers the outside of the pair of side gears S, respectively. It has a pair of cover portions C1 and C2 that rotate integrally with the cover portion C1 and C2.

Of the pair of cover portions C1 and C2, the first cover portion C1 on the reduction gear mechanism RG side is formed integrally with, for example, the case portion 4. The first cover portion C1 is connected to the carrier 23 by, for example, welding w. Further, the second cover portion C2 is detachably connected to the case portion 4 by, for example, a connecting means such as a bolt B. As the coupling means, an appropriate coupling means other than the bolt B, for example, a coupling means such as caulking, bonding, or welding may be adopted. Further, the first cover portion C1 may be formed separately from the case portion 4 like the second cover portion C2, and may be connected to the case portion 4 by a coupling means such as a bolt B.

The first and second cover portions C1 and C2 include, for example, a cylindrical boss portion Cb that concentrically surrounds and rotatably fits and supports the shaft portion Sj described later of the side gear S, and the entire outer surface or a large portion. The portion is provided with a plate-shaped annular side wall portion Cs integrally connected to the axial inner end of the boss portion Cb as a flat surface orthogonal to the rotation axis L of the differential case DC. Further, the outer peripheral end portion of the side wall portion Cs is integrally or detachably connected to the case portion 4. Since the side wall portion Cs has a flat surface as described above, it is possible to prevent the side wall portion Cs from protruding significantly outward in the axial direction, which is advantageous for flattening the differential device D in the axial direction.

The outer peripheral surface of the output shaft J1 is directly fitted to the inner peripheral surface of the boss portion Cb of one of the cover portions (the first cover portion C1 in the present embodiment) so as to be relatively rotatable. Then, a spiral concave groove 8 capable of forcibly supplying lubricating oil from the outer end in the axial direction to the inner end side of the boss portion Cb is formed on the inner peripheral surface of the boss portion Cb with the relative rotation. .. Further, the inner peripheral surface of the boss portion Cb of the other cover portion ( second cover portion C2 in the present embodiment) is the same as the other cover portion ( more specifically, the boss portion Cb of the second cover portion C2). A spiral concave groove 8'that can forcibly supply lubricating oil from the axially outer end to the inner end side of the boss portion Cb is formed along with the relative rotation of the side gear S with the shaft portion Sj. The cover.

The pinion shaft PS is, for example, arranged in the differential case DC so as to be orthogonal to the rotation axis L of the differential case DC, and is provided in a pair of through support holes 4a provided on one diameter line in the tubular case portion 4. , Both ends of the pinion shaft PS are inserted so that they can be inserted and removed. Then, the pinion shaft PS is fixed to the case portion 4 by a retaining pin 5 which penetrates one end portion of the pinion shaft PS and is inserted into the case portion 4. The retaining pin 5 is prevented from coming off from the case portion 4, for example, by applying the outer end of the retaining pin 5 to the second cover portion C2 bolted to the case portion 4.

By the way, in the present embodiment, the pinion shaft PS as the second shaft is formed in a straight rod shape so that the two pinion Ps are supported at both ends of the pinion shaft PS. Three or more may be provided. In that case, the pinion shaft PS has a cross-bar shape (for example, when there are four pinions P) that branches radially from the rotation axis L of the differential case DC in three or more directions corresponding to three or more pinions P. Is formed in a cross shape) so that each tip of the pinion shaft PS supports the pinion P. Further, the case portion 4 is divided into a plurality of case elements so that each end portion of the pinion shaft PS can be attached and supported.

A plurality of pinion shaft PSs as the second shaft (more specifically, the same number as a plurality of pinion Ps) are prepared and attached to the differential case DC separately, and a plurality of pinion shafts P are attached to the attached plurality of pinion shaft PSs. It may be supported individually.

Further, the pinion P may be fitted directly to the pinion shaft PS, or may be fitted via a bearing means such as a bearing bush. As shown in FIGS. 2 and 3, the pinion shaft PS may have a shaft shape having a substantially uniform diameter over the entire length, or may have a stepped shaft shape. Further, on the fitting surface of the pinion shaft PS with the pinion P, for example, a flat notched surface 6 (see FIG. 3) for sufficiently ensuring the flow of lubricating oil to the fitting surface is formed and cut. An oil passage through which lubricating oil can flow is secured between the notch surface 6 and the inner peripheral surface of the pinion P.

Further, the pinion P and the side gear S are formed on, for example, bevel gears, and the entire pinion P and the side gear S including the tooth portions are formed by plastic working such as forging. Therefore, the tooth portions can be formed with high accuracy with an arbitrary gear ratio without being restricted by machining as in the case of cutting the tooth portions of the pinion P and the side gear S. As the pinion P and the side gear S, other gears may be adopted instead of the bevel gear. For example, the side gear S may be a face gear and the pinion P may be a spur gear or an oblique tooth gear.

Further, the pair of side gears S are located, for example, at positions separated radially outward from the cylindrical shaft portion Sj in which the inner end portions of the pair of output shafts J1 and J2 are spline-fitted 7, respectively. An annular tooth portion Sg having a tooth surface that is present and meshes with the pinion P, and a flat ring plate shape extending radially outward from the inner end portion of the shaft portion Sj toward the inner peripheral end portion of the tooth portion Sg. The intermediate wall portion Sm is provided, and the shaft portion Sj and the inner peripheral end portion of the tooth portion Sg are integrally connected by the intermediate wall portion Sm. Of the back surface f of the side gear S, the back surface portion fg of the tooth portion Sg projects outward in the axial direction from the back surface portion fm of the intermediate wall portion Sm.

The shaft portion Sj of each side gear S is rotatably and directly fitted to the boss portion Cb of each cover portion C1 and C2, for example, but may be fitted via a bearing.

A plurality of penetrating oil passages 9 penetrating the intermediate wall portion Sm of at least one of the left and right side gears (both in the present embodiment) so as to cross the intermediate wall portion Sm in the axial direction are formed at intervals in the circumferential direction. Will be done. Therefore, in the differential case DC, the lubricating oil is smoothly circulated between the inner side and the outer side of the side gear S through the through oil passage 9. Although not shown, a plurality of through holes that allow the flow of lubricating oil inside and outside the differential case DC are provided at least one of the cover portions C1 and C2 at intervals in the circumferential direction. You may.

Further, the back surface portion fg of the tooth portion Sg of the side gear S rotatably hits the inner surface of the side wall portion Cs of each cover portion C1 and C2, that is, the surface facing the back surface f of the side gear S via the washer W. Contact and support. The washer W is, for example, at least one of the inner side surfaces of the side wall portions Cs of the cover portions C1 and C2 and the back surface portion fg of the tooth portions Sg of the side gear S (in the side wall portion Cs in the present embodiment). It is fitted and held in the annular washer holding groove 10 formed on the side surface).

Further, on the inner surface of the side wall portions Cs of the cover portions C1 and C2, for example, as described above, the back surface portion fg of the tooth portion Sg of the side gear S projects outward in the axial direction from the back surface portion fm of the intermediate wall portion Sm. Correspondingly, the portion of the side wall portion Cs corresponding to the back portion fm of the intermediate wall portion Sm protrudes inward in the axial direction than the portion corresponding to the back portion fg of the tooth portion Sg (that is, the shaft). Formed (thick in the direction). As a result, the support rigidity of the side wall portion Cs with respect to the side gear S is effectively increased.

Of the back surface f of each side gear S, the outermost outermost end fe of the contact surface that comes into contact with the washer W is, for example, as shown in FIG. 6, the outermost outermost end of the mutual meshing portion I of the side gear S and the pinion P. On the other hand, the side gears S are at the same position in the radial direction, and the outer peripheral end portion We of the washer W extends outward in the radial direction than the outermost outer peripheral end fe of the contact surface.

Next, the welded structure of the carrier 23 and the differential case DC will be specifically described with reference to FIGS. 4 to 6. On the side surface of the outer peripheral end DCo of the differential case DC (more specifically, the first cover portion C1) on the carrier 23 side, for example, a recess is formed on the side opposite to the carrier 23, and the recess is formed in the outer peripheral end DCo of the differential case DC. An annular step portion 15 extending to the radial outer end surface DCoe is recessed. As is shown in FIGS. 4 and 5, for example, the step portion 15 is at a position that does not overlap with the planetary gear 22, that is, is first than the planetary gear 22 when viewed on a projection plane orthogonal to the rotation axis of the planetary gear 22. It is formed at a position on the outer side in the radial direction of the cover portion C1. In addition, in FIGS. 4 to 6, the step portion 15 shows the form before the welding process described later.

In the present specification, the outer peripheral end DCO of the differential case DC (more specifically, the first cover portion C1) is not only the radial outer end surface DCoe of the differential case DC but also the radial inner side of the radial outer end surface DCoe. This is a concept that includes a predetermined region close to the radial outer end surface DCoe.

Further, on the side surface of the first cover portion C1 on the carrier 23 side, for example, a plurality of arcuate recesses 16 deeper than the step portion 15 adjacent to the radial inward side of the step portion 15 are spaced apart from each other in the circumferential direction. It is recessed. The recess 16 is formed at a position corresponding to each of the plurality of arm portions 23a of the carrier 23. Moreover, each recess 16 extends outward from one end (both ends in this embodiment) of the tip end portion (that is, the protrusion 23af) of each arm portion 23a of the carrier 23 in at least the circumferential direction. .. Then, the peripheral end portions of the recesses 16 extending outward are formed on the gently rising gentle slopes 16s, respectively.

Further, on the side surface of the first cover portion C1 on the carrier 23 side, for example, an annular positioning protrusion 18 that engages with the inner peripheral surfaces of the plurality of arm portions 23a of the carrier 23 is integrally provided. By engaging the inner peripheral surfaces of the plurality of arm portions 23a with the positioning protrusions 18, the radial positioning of the carrier 23 with respect to the differential case DC can be easily and accurately performed.

On the other hand, the axial end of the carrier 23, that is, the tip of each arm 23a, extends from the tip surface of the arm 23a toward the differential case DC in the axial direction and has a diameter of the outer peripheral surface of the arm 23a in the radial direction. A flange-shaped protrusion 23af that projects outward in the direction is integrally formed. Of the axial tip surfaces of the respective protrusions 23af, the radial inner side portion faces the bottom surface of the recess 16 with a small gap 17 corresponding to the depth of the recess 16 interposed therebetween, and is a radial outer side portion. Is in contact with the stepped portion 15, and the abutting portion is welded w with the laser torch T (see FIG. 6), whereby the carrier 23 is connected to the differential case DC. The welded portion wa between the step portion 15 and the carrier 23 (specifically, the protrusion portion 23af) is included in the outer peripheral end portion DCo of the differential case DC. Further, in the present embodiment, the radial outer end surface of the protrusion 23af is formed so as to be continuous with the portion of the radial outer end surface DCoe of the outer peripheral end portion DCo of the differential case DC, which is adjacent to the step portion 15. , A slight height difference may be set between the step portion 15 and the adjacent portion.

Regarding the first cover portion C1 of the differential case DC, for example, the step portion 15 and the recess 16 are formed by a casting method or a forging method using a casting mold or a forging mold corresponding to the form of the step portion 15 and the recess 16.

By the way, as described above, the pivot PL supporting the planetary gear 22 is located at a position that radially overlaps the side gear S on the wall facing the carrier 23 of the differential case DC (that is, the side wall portion Cs of the first cover portion C1) . Recessed holes H1 are formed as a plurality of recesses into which the ends can be fitted, and the plurality of recessed holes H1 are formed in the pinion P as a differential gear and the pinion shaft PS supporting the pinion P. On the other hand, it is arranged at a position deviated in the circumferential direction of the differential case DC (that is, a position that does not overlap the pinion P and the pinion shaft PS when viewed from the projection plane orthogonal to the rotation axis L of the differential case DC). Further, in the present embodiment, the plurality of concave holes H1 are all in the circumferential direction of the differential case DC with respect to the welded portion wa that connects the carrier 23 (more specifically, the tip portion of the arm portion 23a) and the differential case DC. It is placed in a misaligned position.

Next, the operation of the first embodiment will be described.

In the differential device D of the present embodiment, when a rotational force is applied to the differential case DC from the engine via the reduction gear mechanism RG, the pinion P does not rotate around the pinion shaft PS and the rotation axis L of the differential case DC together with the differential case DC. When revolving around, the left and right side gears S are rotationally driven from the differential case DC via the pinion P at the same speed, and the driving force of the side gears S is evenly transmitted to the left and right output shafts J1 and J2. In addition, when there is a difference in rotational speed between the left and right output shafts J1 and J2 due to turning of an automobile or the like, the pinion P revolves while rotating, allowing differential rotation from the pinion P to the left and right side gears S. While doing so, the rotational driving force is transmitted. The above is the same as the operation of the conventionally known differential device.

By the way, in the present embodiment, the outer peripheral end portion DCo of the differential case DC has a recess on the side surface on the carrier 23 side, and the recess extends to the radial outer end surface DCoe of the outer peripheral end portion DCo of the differential case DC. , A step portion 15 that comes into contact with the axial end portion of the carrier 23 (that is, the protrusion 23af of each tip portion of the plurality of arm portions 23a) is recessed. Then, in a state where the step portion 15 and the axial end portion of the carrier 23 (more specifically, the protrusion 23af) are brought into contact with each other so as to abut against each other, the step portion 15 and the axial end portion of the carrier 23 are brought into contact with each other. By welding the tangent portion w, the differential case DC (more specifically, the first cover portion C1) and the reduction gear mechanism RG (more specifically, the carrier 23) are connected. At this time, the contact portion between the step portion 15 and the axial end portion (more specifically, the protrusion portion 23af) of the carrier 23 becomes the welded portion wa.

For example, as shown by the chain line in FIG. 6, the welding work is performed from the welding laser torch T provided outside the radial direction of the first cover portion C1, the step portion 15 and the axial end portion of the carrier 23. The laser is irradiated toward the radial outer end of the contact portion with the first cover portion C1 and one of the laser torch T (for example, the laser torch T) is applied to the other (for example, the first cover portion C1). This is done by gently rotating the differential case DC around the rotation axis L. As a result, the step portion 15 and the axial end portion of the carrier 23, that is, the axial tip surface of the protrusion 23af can be connected by welding w using the energy of the laser.

As described above, according to the present embodiment, the outer peripheral end portion of the differential case DC (more specifically, the first cover portion C1) is recessed on the side surface of the outer peripheral end DCo on the carrier 23 side and on the side opposite to the carrier 23. The recess has a stepped portion 15 that extends to the radial outer end surface DCoe of the outer peripheral end portion DCo of the differential case DC (more specifically, the first cover portion C1) and can come into contact with the protrusion 23af of the carrier 23. There is. Therefore, in the welding work, the welding laser torch T can be easily opposed to the welded portion (that is, the outer end of the contact portion) from the radial outer side of the differential case DC. As a result, the degree of freedom of movement of the laser torch T for welding can be secured wider on the radial outer side of the differential case DC (more specifically, the first cover portion C1) than in the conventional technology, and the degree of freedom in processing and welding can be secured more than in the conventional technology. Workability can be improved.

Further, according to the present embodiment, the step portion 15 and the carrier 23 are welded together, and the welded portion wa of the step portion 15 and the carrier 23 is included in the outer peripheral end portion DCo of the differential case DC. Therefore, in the welding work, the welding laser torch T can be more easily opposed to the welded portion from the radial outer side of the differential case DC (more specifically, the first cover portion C1). Therefore, the degree of freedom of movement of the welding laser torch T can be secured wider on the radial outer side of the differential case DC (more specifically, the first cover portion C1), and the degree of freedom of processing and welding workability can be further improved. .. Moreover, since the welded portion washer is included in the outer peripheral end DCo of the differential case DC (more specifically, the first cover portion C1), the back surface of the side gear S of the differential case DC (more specifically, the first cover portion C1). The influence of welding heat (for example, thermal strain) on the portion supporting f (the contact surface with the washer W in this embodiment) can be avoided or reduced. This eliminates the need for finishing in consideration of the influence of welding heat. In addition, since there is no possibility that the weld bead and peripheral parts (for example, the ring gear 21 of the reduction gear mechanism RG) interfere with each other, the welding bead cutting work and finishing work are not required. As a result, the manufacturing cost can be effectively suppressed.

Further, according to the present embodiment, the side surface of the first cover portion C1 on the carrier 23 side has an arcuate concave portion 16 deeper than the step portion 15 adjacent to the radial inward side of the step portion 15. The recess 16 is at least one end of the arm portion 23a (more specifically, the tip portion of the arm portion 23a (the protrusion 23af of the arm portion 23a in the present embodiment)) in the circumferential direction of the carrier 23 (the present embodiment). Then, it extends to the outer side in the circumferential direction from both ends). Therefore, the gas generated around the welded portion during welding can be accurately discharged to the outside through the recess 16, which can contribute to the improvement of welding quality.

Further, according to the present embodiment, since a plurality of recesses 16 are arranged at intervals in the circumferential direction, the decrease in strength of the differential case DC due to the provision of the recesses 16 can be suppressed as much as possible. As a result, it is possible to achieve a thin wall weight reduction of the differential case DC (more specifically, the cover portion C1) while maintaining the strength of the differential case DC (more specifically, the first cover portion C1).

Further, according to the present embodiment, the step portion 15 is formed at a position that does not overlap with the planetary gear 22 when viewed on a projection plane orthogonal to the rotation axis of the planetary gear 22. Therefore, it can be avoided that the sliding support surface on the differential case DC (more specifically, the first cover portion C1) side with respect to the planetary gear 22 is reduced by specially providing the step portion 15, so that the sliding on the differential case DC side can be prevented. The area of the dynamic support surface (that is, the pressure receiving area with respect to the planetary gear 22) can be sufficiently secured.

Further, according to the present embodiment, in the first cover portion C1, the step portion 15 and the recess 16 are formed by a casting method or a forging method using a casting mold or a forging mold. Therefore, the cutting process for forming the step portion 15 and the recess 16 becomes unnecessary, and the processing man-hours can be reduced.

Further, according to the present embodiment, the stepped portion 15 formed on the side surface of the outer peripheral end portion DCo of the first cover portion C1 and recessed on the side opposite to the carrier 23 is the contact surface with the carrier 23 (that is, the surface to be welded). ). Therefore, although the side surface of the outer peripheral end DCo of the first cover portion C1 and the axial end portion of the carrier 23 are abutted in the axial direction and welded together, the first cover portion C1 and the carrier 23 are joined. The total width of the outer peripheral edge of the body in the axial direction can be made as small as possible. As a result, the differential device D can be downsized.

Further, according to the present embodiment, as described above, at a position that overlaps the side gear S in the radial direction on the wall facing the carrier 23 of the differential case DC (more specifically, the side wall portion Cs of the first cover portion C1). A plurality of concave holes H1 are formed as recesses into which the end portion of the pivot (first shaft) PL supporting the planetary gear 22 on the differential case DC side can be fitted. Moreover, the plurality of concave holes H1 are arranged at positions deviated from the pinion shaft (second shaft) PS supporting the pinion P as the differential gear in the circumferential direction of the differential case DC. As a result, the back surface f (more specifically, washer W) side of the side gear S is supported at a position corresponding to the meshing portion between the pinion P and the side gear S in the differential case DC where a particularly large load acts during torque transmission. It is avoided that the concave hole H1 into which the pivot PL supporting the planetary gear 22 can be fitted is formed in the portion). Therefore, even if the differential device D is flattened in the axial direction and the differential case DC is flattened as in the present embodiment, the decrease in durability of the differential case DC due to the formation of the concave hole H1 can be effectively suppressed.

Further, when the shaft arrangement configuration disclosed in Patent Document 1 is applied to the flat differential device, among the plurality of planetary gears, the circumferential position of the planetary gear support shaft and the differential gear support shaft is particularly high. A biased force acts only on specific planetary gears that match. Therefore, the balance of the force acting on the gear portion between the specific planetary gear and the other planetary gears is lost, and the load load of the plurality of planetary gears cannot be equalized. As a result, the strength of the gear portions of the plurality of planetary gears cannot be set accurately without excess or deficiency, and there is a problem that the performance of the gear portions of all the planetary gears cannot be optimally and sufficiently exhibited.

However, according to the present embodiment, by adopting the above configuration, it is possible to prevent a biased force from acting on some of the planetary gears 22 among the plurality of planetary gears 22. Therefore, the forces acting on the gear portions of all the planetary gears 22 can be equalized as much as possible. As a result, the strength of the gear portions of all the planetary gears 22 can be set accurately without excess or deficiency. Therefore, the performance of the gear portions of all the planetary gears 22 can be optimally and sufficiently exhibited.

Further, in the present embodiment, the differential case DC has a plate-shaped side wall connected to the boss portion Cb with the boss portion Cb surrounding the shaft portion Sj of the side gear S and the outer surface as a flat surface orthogonal to the output shafts J1 and J2. It has a part Cs. Therefore, the differential case DC, particularly the side wall portions Cs of the first and second cover portions C1 and C2, has an advantageous structure for thin-walling flattening, but the thin-walled flattening of the side wall portions Cs also causes as described above. By arranging the concave hole H1 at a position deviated from the pinion shaft PS in the circumferential direction of the differential case DC, the decrease in durability of the differential case DC due to the formation of the concave hole H1 is effectively suppressed.

Further, in the present embodiment, the concave hole H1 formed in the differential case DC (more specifically, the first cover C1) connects the carrier 23 (more specifically, the tip end portion of the arm portion 23a) and the differential case DC. It is arranged at a position deviated from the welded portion wa in the circumferential direction of the differential case DC. Therefore, the pinion support surface of the differential case DC (that is, the surface that supports the large-diameter side end surface of the pinion P with relative rotation via the washer W') and the side gear support surface near the pinion P (that is, the back surface f of the side gear S are washers). The surface that supports the surface so as to be relatively rotatable via the W) can be kept away from the welded portion, and the influence of heat during welding can be suppressed as much as possible. As a result, it is possible to effectively prevent the pinion support surface and the side gear support surface of the differential case DC from being distorted by welding heat and increasing the rotational sliding resistance.

Further, according to the present embodiment, the side gear S has a shaft portion Sj between the shaft portion Sj on the inner peripheral side and the tooth portion Sg of the side gear S on the outer peripheral side separated from the shaft portion Sj in the radial direction. It has a flat ring plate-shaped intermediate wall portion Sm connecting between the tooth portion Sg and the tooth portion Sg. Further, the radial width t1 of the intermediate wall portion Sm is longer than the maximum diameter d1 of the pinion P. Therefore, the diameter of the side gear S can be made sufficiently larger than that of the pinion P so that the number of teeth Z1 of the side gear S can be set sufficiently larger than the number of teeth Z2 of the pinion P. Further, the load load on the pinion shaft PS when the torque is transmitted from the pinion P to the side gear S can be reduced, whereby the effective diameter d2 of the pinion shaft PS can be reduced, and the output shafts J1 and J2 of the pinion P can be reduced. It is possible to narrow the width (smaller diameter) in the axial direction.

Further, in this way, the load load on the pinion shaft PS is reduced, the reaction force applied to the side gear S is reduced, and the back surface f of the side gear S (particularly, the back surface side of the mutual meshing portion I of the side gear S and the pinion P). Since the located back surface portion fg) is supported by the side wall portions Cs of the cover portions C1 and C2 via the washer W, it is easy to secure the required rigidity strength of the side gear S even if the intermediate wall portion Sm is thinned. Is. That is, it is possible to sufficiently thin the intermediate wall portion Sm of the side gear S while ensuring the support rigidity for the side gear S.

Further, according to the present embodiment, since the maximum wall thickness t2 of the intermediate wall portion Sm of the side gear S is formed to be smaller than the effective diameter d2 of the pinion shaft PS that enables the diameter to be reduced, the intermediate wall portion Sm of the side gear S is formed. Further thinning of the wall can be achieved.

Further, according to the present embodiment, the side wall portions Cs of the first and second cover portions C1 and C2 are formed in a flat plate shape in which the outer surface of the side wall portions Cs is a flat surface orthogonal to the rotation axis L of the differential case DC. By doing so, thinning of the side wall portions Cs itself of the first and second cover portions C1 and C2 is also achieved. Moreover, of the back surface f of the side gear S, the back surface portion fg of the tooth portion Sg projects outward in the axial direction from the back surface portion fm of the intermediate wall portion Sm. Therefore, it is possible to form the intermediate wall portion Sm of the side gear S as thin as possible while sufficiently ensuring the rigidity of the tooth portion Sg of the side gear S, and further weight reduction and axial flattening of the differential device D are achieved. ..

As a result, according to the present embodiment, the differential device D is sufficiently narrow in the axial direction as a whole while ensuring the same strength (for example, static torsional load strength) and the maximum torque transmission amount as the conventional device. It becomes possible to change. Therefore, even for a transmission system having many layout restrictions around the differential device D, the differential device D can be easily incorporated with a high degree of freedom, and the transmission system of the differential device D can be miniaturized. It will be a great advantage to do.

Next, the second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the first embodiment, a long pinion shaft PS is used as the second shaft for supporting the pinion P on the differential case DC, but in the second embodiment, the pinion P is coaxially and integrally coupled to the end face on the large diameter side. The support shaft PS'is used for the second shaft that supports the pinion P on the differential case DC. According to this configuration, since it is not necessary to provide the pinion P with a through hole for fitting the pinion shaft PS, the diameter of the pinion P can be reduced (the width in the axial direction is narrowed) by that amount, and the differential device D can be further axially oriented. Flattening can be achieved. That is, when the pinion shaft PS penetrates the pinion P, it is necessary to form a through hole having a size corresponding to the diameter of the pinion shaft PS in the pinion P, but the support shaft PS'is integrated with the end face of the pinion P. In this case, it is possible to reduce the diameter of the pinion P (narrow the width of the output shafts J1 and J2 in the axial direction) without depending on the outer diameter of the support shaft PS'(that is, the effective diameter d2).

Then, between the outer peripheral surface of the support shaft PS'and the outer peripheral wall of the differential case DC (more specifically, the first cover portion C1), that is, the inner peripheral surface of the through support hole 4a provided in the tubular case portion 4. A bearing bush 12 as a bearing means that allows relative rotation between the outer peripheral surface of the support shaft PS'and the inner peripheral surface of the through support hole 4a is inserted therein. As the bearing means, a bearing such as a needle bearing may be used. Further, the bearing may be omitted and the support shaft PS'may be directly fitted into the through support hole 4a of the differential case DC.

Further, since the second embodiment has the same configuration as the first embodiment except for the differences from the first embodiment described above, the second embodiment also has the configuration of the first embodiment shown above. As for the effect other than the effect obtained by the difference from the above, the same effect as that of the first embodiment can be obtained. That is, also in the second embodiment, the effect caused by the structure related to the welding between the first cover portion C1 of the differential case DC and the carrier 23 of the reduction gear mechanism RG, and the pivot shaft (first shaft) that supports the planetary gear 22. As for the effect based on the arrangement relationship between the PL and the support shaft (second shaft) PS'supporting the pinion P, the same effect as that of the first embodiment can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. In the first and second embodiments, one end of the pivot PL (the other end of the pivot PL) as the plurality of first shafts supporting the plurality of planetary gears 22 is provided with a differential case DC (more specifically, the first cover). as the recess for supporting the side wall Cs) parts C1, it is exemplified recess hole H1 of a bottom, in the third embodiment, as the recess, the differential case DC (more specifically the side wall portion of the first cover portion C1 ' A through hole H1'that penetrates Cs') is adopted, and a part of the back surface of the washer W faces the through hole H1'.

Since the other configurations of the third embodiment are the same as those of the first embodiment, each component of the third embodiment is given the same reference code as the corresponding component of the first embodiment. The above description of the structure will be omitted. Thus, in the third embodiment, as compared with the first embodiment, the recess for supporting one end of the pivot PL as the first shaft (the other end of the pivot PL) on the differential case DC is the through hole H1. Since the configuration is the same except for this, the same effect as the above-mentioned effect of the first embodiment can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the first to third embodiments, a carrier base 23b having an annular carrier 23 and a plurality of fan-shaped arm portions (carrier main body portions) 23a viewed from a projection plane orthogonal to the rotation axis L of the differential case DC are integrated. The end portion of each arm portion 23a is connected to the differential case DC by welding w. However, in the fourth embodiment, the carrier 123 corresponds to the carrier base 23b of the third embodiment. Is separated from the plurality of arm portions (carrier main body portions) 123a to form a carrier cover 123b.

Then, the carrier cover 123b and at least one (all in the present embodiment) arm portions 123a are connected, for example, through the coupling means (specifically, the carrier cover 123b) so that the carrier cover 123b and the arm portion 123a are adjacent to each other. It is detachably connected with a bolt 100) screwed into the arm portion 123a. The coupling means is not limited to the bolt 100, and various coupling means such as welding, clipping, and bonding can be selected.

Further, the plurality of arm portions (carrier main body portions) 123a of the fourth embodiment are integrally formed on the wall portion (more specifically, the side wall portion Cs'of the first cover portion C10) of the differential case DC. That is, the first cover portion C10 includes, for example, the above-mentioned boss portion Cb, the above-mentioned side wall portion Cs', and the above-mentioned plurality of arm portions (carrier main body portions) 123a. That is, the first cover portion C10 includes at least a side wall portion Cs'and an arm portion (carrier main body portion) 123a. Then, at a position that overlaps the side gear S in the radial direction on the side wall portion Cs'of the first cover portion C10, one end of a plurality of pivot PLs as the first shafts that support the plurality of planetary gears 22 (the pivot PL). A plurality of through holes H1'are provided as recesses for inserting and supporting the other end).

The other end of the pivot PL (one end of the pivot PL) is fitted and supported in the through hole H2 provided in the carrier cover 123b. Then, a pin hole 102 extending in a direction crossing the through hole H2 is provided so as to straddle the other end of the carrier cover 123b and the pivot PL. Then, the pin 101 is press-fitted into the pin hole 102 of the carrier cover 123b, and the tip of the pin 101 is engaged with the pivot PL. As a result, the pivot PL is prevented from coming off from the carrier cover 123b. For fixing the pin 101 to the carrier cover 123b, various coupling means such as welding, caulking, bonding, and screwing can be selected in addition to the above press fitting.

For fixing the other end of the Axis PL (one end of the Axis PL) to the carrier cover 123b, various coupling means such as welding, caulking, bonding, screwing, etc. are selected without using the pin 101. Alternatively, the other end of the pivot PL may be press-fitted directly into the through hole H2 of the carrier cover 123b.

Since the other configurations of the fourth embodiment are the same as those of the first embodiment, each component of the fourth embodiment is provided with the same reference code as the corresponding component of the first embodiment. The above description of the structure will be omitted.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the first to fourth embodiments, the case portion (peripheral wall portion) 4 is integrally formed on the side wall portions (Cs, Cs') of the first cover portion (C1, C1', C10) in the differential case DC, and the case portion 4 is formed. The side wall portion Cs of the second cover portion C2 is fastened to the end surface (specifically, the right end surface in FIGS. 2 and 9) with a bolt B to connect the first and second cover portions C1 and C2. However, in the fifth embodiment, the case portion (peripheral wall portion) 4 is integrally formed with the side wall portion Cs of the second cover portion C200, and the end surface of the case portion 4 (specifically, the left end surface in FIG. 10). By fastening the side wall portion Cs'of the first cover portion C100 with a bolt B', the first and second cover portions C100 and C200 are connected to each other.

And Thus, the fifth side wall portion of the first cover portion C100 Cs embodiment ', the arm portions of the carrier 1 23 on one side in the axial direction (carrier body portion) 123a is integrally projected. Further, a case portion (peripheral wall portion) 4 is integrally projected on one side in the axial direction on the side wall portion Cs of the second cover portion C200 of the fifth embodiment. Further, the retaining pin 5 of the pinion shaft PS is fixed to the side wall portion Cs of the second cover portion C200 by press fitting, but is fixed by a coupling means other than press fitting, for example, welding, caulking, adhesion, screwing or the like. May be good.

Since the other configurations of the fifth embodiment are the same as those of the fourth embodiment, each component of the fifth embodiment is given the same reference code as the corresponding component of the fourth embodiment. The above description of the structure will be omitted.

Thus, in the fourth and fifth embodiments described above, the arm portion (carrier main body portion) 123a of the carrier 123 is integrated with the differential case DC (more specifically, the side wall portions Cs'of the first cover portions C10 and C100). Be made. Therefore, among the above-mentioned effects of the first to third embodiments, the effect related to connecting the arm portion 23a of the carrier 23 to the differential case DC by welding w cannot be obtained, but the other effects are the first. The same can be obtained in the fourth and fifth embodiments. That is, in the first to third embodiments, a plurality of concave holes (recesses) H1 or through holes (recesses) H1'supporting the ends of the pivot (first shaft) PL, and a pinion shaft (second shaft) PS. The above-mentioned effect based on the fact that the differential case DC is displaced in the circumferential direction and the above-mentioned effect on the weight reduction and the axial flattening of the differential device D are similarly obtained in the fourth and fifth embodiments. Is something that can be done.

By the way, in the conventional differential device as illustrated in Patent Documents 1 to 3 described above, the number of teeth Z1 of the side gear (output gear) and the number of teeth Z2 of the pinion (differential gear) are usually set to, for example, Patent Document 3. The 14 × 10, 16 × 10 or 13 × 9 shown are used, and in this case, the number of teeth ratio Z1 / Z2 of the output gear to the differential gear is 1.4, 1.6, and 1.44, respectively. Further, in the conventional differential device, it is also known that the number of teeth Z1 and Z2 is, for example, 15 × 10, 17 × 10, 18 × 10, 19 × 10, or 20 × 10 as another combination. In this case, the tooth number ratios Z1 / Z2 are 1.5, 1.7, 1.8, 1.9, and 2.0, respectively.

On the other hand, today, the number of transmission devices with layout restrictions around the differential device is increasing, and the width of the differential device is sufficiently narrowed in the axial direction of the output shaft while ensuring the gear strength of the differential device (that is,). Flattening) is required in the market. However, in the conventional existing differential device, as is clear from the combination of the number of teeth ratios, the structure is wide in the axial direction of the output shaft, so that it is difficult to meet the above market demands. It is in.

Therefore, a configuration example of the differential device D capable of sufficiently narrowing (that is, flattening) the width of the differential device in the axial direction of the output shaft while ensuring the gear strength of the differential device is described from a viewpoint different from the above-described embodiment. , Specifically specified below. The structure of each component of the differential device D according to this configuration example is the structure of the differential device D of the above-described embodiment described with reference to FIGS. 1 to 10 (particularly, FIGS. 1 to 6 and 8 to 10). Since it is the same as each component, the reference code of each component uses the same code as that of the above embodiment, and the structural description will be omitted.

First, the basic concept for sufficiently narrowing (that is, flattening) the differential device D in the axial direction of the output shafts J1 and J2 will be described with reference to FIG.
[1] The tooth number ratio Z1 / Z2 of the side gear S, that is, the output gear to the pinion P, that is, the differential gear is increased as compared with the tooth number ratio of the conventional differential device. (This reduces the gear module (and therefore the tooth thickness) and reduces the gear strength, while increasing the pitch circle diameter of the side gear S increases the transmission load at the gear meshing portion and increases the gear strength. As a whole, the gear strength decreases as described later.)
[2] The pitch cone distance PCD of the pinion P is increased from the pitch cone distance of the conventional differential device. (As a result, the number of gear modules increases and the gear strength increases, and at the same time, the pitch circle diameter of the side gear S increases, the transmission load at the gear meshing portion decreases, and the gear strength increases. The gear strength is greatly increased.)
Therefore, the amount of decrease in gear strength due to the above [1] is equal to the amount of increase in gear strength due to the above [2], or the amount of decrease in gear strength due to the above [1] is larger than the amount of decrease in gear strength due to the above [2]. By setting the number of teeth ratio Z1 / Z2 and the pitch cone distance PCD so that the amount of increase in strength exceeds, the gear strength as a whole can be equal to or increased as compared with the conventional differential device.

Next, the mode of change in gear strength based on the above [1] and [2] is specifically verified by a mathematical formula. The verification will be described in the following embodiments. First, the differential device D'when the number of teeth Z1 of the side gear S is 14 and the number of teeth Z2 of the pinion P is 10, is referred to as a "reference differential device". The "rate of change" is the rate of change of various variables when the reference differential device D'is used as a reference (that is, 100%).
[1] Bevel gear when the module of the side gear S is MO, the pitch circle diameter is PD ₁ , the pitch angle is θ ₁ , the pitch cone distance is PCD, the transmission load at the gear meshing part is FO, and the transmission torque is TO. From the general formula of
MO = PD ₁ / Z1
PD ₁ = 2PCD ・ sinθ ₁
θ ₁ = tan ^-1 (Z1 / Z2)
From these formulas, the gear module
MO = 2PCD ・ sin {tan ^-1 (Z1 / Z2)} / Z1 ・ ・ ・ (1)
Next,
The module of the reference differential D'is 2PCD · sin {tan ^-1 (7/5)} / 14
Will be.

Therefore, by dividing the right term of both equations, the module change rate with respect to the reference differential device D'is as shown in equation (2) below.

Further, the cross-sectional coefficient of the tooth portion corresponding to the gear strength (that is, the bending strength of the tooth portion) has a relationship proportional to the square of the tooth thickness, while the tooth thickness has a substantially linear relationship with the module MO. Therefore, the square of the module change rate corresponds to the change rate of the cross-sectional coefficient of the tooth portion, and by extension, the change rate of the gear strength. That is, the gear strength change rate is expressed by the following equation (3) based on the equation (2). Equation (3) is shown by L1 in FIG. 12 when the number of teeth Z2 of the pinion P is 10, and it can be seen that the gear strength decreases due to the decrease in modules as the number of teeth ratio Z1 / Z2 increases.

By the way, according to the general formula of the bevel gear described above, the torque transmission distance of the side gear S is as shown in the following equation (4).

_{PD 1/2 = PCD · sin} {tan -1 (Z1 / Z2)} ··· (4)
The transmission load FO due to the torque transmission distance PD _1/2 is FO = 2TO / PD ₁ . Therefore, in the side gear S of the reference differential device D', if the torque TO is constant, the transmission load FO and the pitch circle diameter PD ₁ have an inversely proportional relationship. Further, since the rate of change of the transmission load FO is also inversely proportional to the rate of change of the gear strength, the rate of change of the gear strength is equal to the rate of change of the pitch circle diameter PD ₁ .

As a result, the rate of change of the pitch circle diameter PD ₁ is as shown in the following equation (5) using the equation (4).

Equation (5) is shown by L2 in FIG. 12 when the number of teeth Z2 of the pinion P is 10, and it can be seen that the gear strength is increased by reducing the transmission load as the number of teeth ratio Z1 / Z2 increases.

After all, the rate of change in gear strength due to the increase in the number of teeth ratio Z1 / Z2 depends on the rate of change in gear strength due to the decrease in module MO (the right item in equation (3) above) and the reduction in transmission load. It is expressed as the following equation (6) by multiplying it with the rate of increase / change in gear strength (the right term of equation (5) above).

Equation (6) is shown by L3 in FIG. 12 when the number of teeth Z2 of the pinion P is 10, and it can be seen that the gear strength as a whole decreases as the number of teeth ratio Z1 / Z2 increases.
Regarding [2] When the pitch cone distance PCD of the pinion P is increased from the pitch cone distance of the reference differential device D', when the PCD before the change is PCD1 and the PCD after the change is PCD2, before and after the change of the PCD. According to the general formula of the bevel gear described above, the module change rate of is (PCD2 / PCD1) if the number of teeth is constant.

On the other hand, the rate of change in the gear strength of the side gear S corresponds to the square of the module change rate, as is clear from the process of deriving Eq. (3).
Gear strength change rate due to module increase = (PCD2 / PCD1) ² ... (7)
Equation (7) is shown by L4 in FIG. 13, and it can be seen that the gear strength increases due to the increase in modules as the pitch cone distance PCD increases.

Further, when the pitch cone distance PCD is increased more than the pitch cone distance PCD1 of the reference differential device D', the transmission load FO is reduced, and the rate of change in gear strength due to this is the pitch circle as described above. Equal to the rate of change of diameter PD ₁ . Further, the pitch circle diameter PD ₁ of the side gear S and the pitch cone distance PCD are in a proportional relationship. Therefore,
Gear strength change rate due to transmission load reduction = PCD2 / PCD1 ... (8)
Equation (8) is shown in L5 of FIG. 13, and it can be seen that as the pitch cone distance PCD increases, the gear strength increases due to the reduction of the transmission load.

The rate of change in gear strength due to the increase in pitch cone distance PCD is the rate of change in gear strength due to the increase in module MO (the right item of equation (7) above) and the increase in pitch circle diameter PD. It is expressed as the following equation (9) by multiplying it with the rate of increase / change in gear strength due to the reduction of the transmitted load (the right item of equation (8) above).

Gear strength change rate due to increase in pitch cone distance = (PCD2 / PCD1) ³ ... (9)
Equation (9) is shown by L6 in FIG. 13, and it can be seen that the gear strength is significantly increased as the pitch cone distance PCD increases.

Then, the decrease in gear strength due to the method [1] (increase in the number of teeth ratio) is sufficiently compensated for by the increase in gear strength due to the method [2] (increase in pitch cone distance), and the differential device as a whole The combination of the number of teeth ratio Z1 / Z2 and the pitch cone distance PCD is determined so that the gear strength is equal to or higher than the gear strength of the conventional differential device.

For example, when maintaining 100% of the gear strength of the side gear S of the reference differential device D', the rate of change of the gear strength with the increase in the number of teeth ratio obtained in [1] (the right term of the above equation (6)). ) And the gear strength change rate due to the increase in the pitch cone distance obtained in [2] (the right item of (9) above) may be set to be 100%. From this, the relationship between the number of teeth ratio Z1 / Z2 and the rate of change of the pitch cone distance PCD when the gear strength of the reference differential device D'is maintained at 100% is obtained by the following equation (10). Equation (10) is shown by L7 in FIG. 14 when the number of teeth Z2 of the pinion P is 10.

As described above, in the equation (10), the change in the number of teeth ratio Z1 / Z2 and the pitch cone distance PCD when the gear strength of the reference differential device D'with the number of teeth ratio Z1 / Z2 = 14/10 is maintained at 100%. The relationship with the rate (see FIG. 14) is shown. The rate of change of the pitch cone distance PCD on the vertical axis of FIG. 14 is such that the shaft diameter of the pinion shaft PS (that is, the pinion support portion) supporting the pinion P is d2. In the case of, it can be converted to the ratio of d2 / PCD.

That is, in the conventional differential device, the increase change of the pitch cone distance PCD has a correlation with the increase change of d2 as shown in Table 1 above, and when d2 is constant, the ratio of d2 / PCD decreases. It can be expressed. Moreover, in the conventional existing differential device, as shown in Table 1 above, when the reference differential device D'is used, d2 / PCD is within the range of 40 to 45%, and when the PCD is increased, the gear strength is increased. Since it increases, if the shaft diameter d2 of the pinion shaft PS and the pitch cone distance PCD are determined so that at least d2 / PCD is 45% or less at the time of the reference differential device D', the gear strength will be different from the conventional one. It can be equal to or greater than the gear strength of the moving device. That is, in the case of the reference differential device D',
It suffices to satisfy d2 / PCD ≦ 0.45. In this case, if the PCD after the increase / decrease change is PCD2 with respect to the pitch cone distance PCD1 of the reference differential device D',
d2 / PCD2 ≤ 0.45 / (PCD2 / PCD1) ... (11)
It means that it is sufficient to satisfy. Then, if the equation (11) is applied to the equation (10) described above, the relationship between the d2 / PCD and the tooth number ratio Z1 / Z2 can be converted as in the following equation (12).

When the equal sign of the equation (12) holds, when the number of teeth Z2 of the pinion P is 10, it can be expressed as L8 in FIG. When the equal sign of Eq. (12) holds, it is the relationship between d2 / PCD and the tooth number ratio Z1 / Z2 when the gear strength of the reference differential device D'is maintained at 100%.

By the way, in the conventional differential device, as described above, not only the device in which the tooth number ratio Z1 / Z2 is 1.4 as in the reference differential device D', but also the tooth number ratio Z1 / Z2 is usually 1. Those having a tooth number ratio of 6.6 and those having a tooth number ratio Z1 / Z2 of 1.44 are also adopted. Based on this fact, if it is assumed that the reference differential device D'(Z1 / Z2 = 1.4) can obtain the necessary and sufficient gear strength, that is, 100% gear strength, the conventional differential device has teeth. As is clear from FIG. 12, in the differential device having a number ratio Z1 / Z2 of 16/10, it can be seen that the gear strength is reduced to 87% as compared with the reference differential device D'. However, the gear strength lowered to this extent is allowed as a practical strength in the conventional differential device and is put into practical use. Therefore, even in a differential device that is flat in the axial direction, if the gear strength is at least 87% with respect to the reference differential device D', it is considered that the gear strength is sufficiently secured and allowed.

From this point of view, when the relationship between the number of teeth ratio Z1 / Z2 and the rate of change of the pitch cone distance PCD when the gear strength of the reference differential device D'is maintained at 87% is first obtained, the relationship is ( Calculations following the process of deriving Eq. 10) (that is, the rate of change in gear strength due to an increase in the number of teeth ratio (the right term of Eq. By calculating so that the product of 9) and the right term) is 87%, it can be expressed as the following equation (10').

Then, if the above equation (11) is applied to the above equation (10'), d2 / PCD when the gear strength of the reference differential device D'is maintained at 87% or more and the tooth number ratio Z1 / Z2. The relationship with can be converted as shown in the following equation (13). However, in the process of calculation, except for the terms expressed using variables, significant figures are calculated with 3 digits, and the other digits are rounded down so that they are actually almost equal due to calculation error. However, in the expression of the formula, it is expressed by the equal sign.

When the equal sign of the equation (13) holds, when the number of teeth Z2 of the pinion P is 10, it can be represented as shown in FIG. 15 (more specifically, as shown by the L9 line in FIG. 15). In the case, the region corresponding to the equation (13) is the region on the L9 line and below the L9 line in FIG. The specific region (hatching region in FIG. 15) that satisfies the equation (13) and that the number of teeth ratio Z1 / Z2 on the right side of the L10 line in FIG. 15 exceeds 2.0 is particularly the pinion P. In an axially flat differential device in which the number of teeth Z2 is 10 and the number of teeth ratio Z1 / Z2 exceeds 2.0, Z1 / Z2 and Z1 / Z2 capable of ensuring a gear strength of at least 87% with respect to the reference differential D'. This is a setting area for d2 / PCD. For reference, if an example is shown in FIG. 15 when the number of teeth ratio Z1 / Z2 is set to 40/10 and d2 / PCD is set to 20.00%, it becomes like a rhombus point. An example in which the tooth number ratio Z1 / Z2 is set to 58/10 and d2 / PCD is set to 16.67% is shown in FIG. 15 as a triangular point, and these are in the above specific region. It fits. As a result of strength analysis by simulation for these examples, a gear strength equal to or higher than that of the conventional one (more specifically, a gear strength of 87% or higher with respect to the reference differential device D'). ) Was obtained.

Thus, the flat differential device in the specific region as a whole secures the same gear strength (for example, static torsional load strength) and maximum torque transmission amount as the conventional non-flat differential device. It is configured as a differential device that is sufficiently narrow in the axial direction of the output shaft. Therefore, the differential device has a high degree of freedom even for a transmission system with many layout restrictions around the differential device. Therefore, it can be easily incorporated without difficulty, and it is possible to achieve effects such as a great advantage in miniaturizing the transmission system.

Further, preferably, if Z1 / Z2 ≧ 4 is satisfied, and more preferably Z1 / Z2 ≧ 5.8 is satisfied, the gear strength is about the same as that of the conventional non-flat differential device. The width of the differential device can be further narrowed in the axial direction of the output shaft while ensuring (for example, static torsional load strength) and the maximum torque transmission amount.

Further, when the structure of the flat differential device in the specific region is, for example, the structure of the above-described embodiment (more specifically, the structure shown in FIGS. 1 to 10), the specific region Some flat differentials can also achieve the effects associated with the structures shown in the embodiments described above.

The above description (particularly the description relating to FIGS. 12, 14 and 15) describes the differential device when the number of teeth Z2 of the pinion P is 10, but the present invention is not limited thereto. Absent. For example, even when the number of teeth Z2 of the pinion P is 6, 12, 20, a flat differential device capable of achieving the above effect is shown by hatching in FIGS. 16, 17, and 18 (13). It can be expressed by an expression. That is, the equation (13) derived as described above can be applied regardless of the change in the number of teeth Z2 of the pinion P, for example, when the number of teeth Z2 of the pinion P is 6, 12, 20. However, as in the case where the number of teeth Z2 of the pinion P is 10, the number of teeth Z1 of the side gear S, the number of teeth Z2 of the pinion P, the shaft diameter d2 of the pinion shaft PS, and the pitch cone distance PCD so as to satisfy the equation (13). The above effect can be obtained by setting.

Further, for reference, when the number of teeth Z2 of the pinion P is set to 12, the number ratio Z1 / Z2 is set to 48/12 and d2 / PCD is set to 20.00%, respectively. An example in which the tooth number ratio Z1 / Z2 is set to 70/12 and d2 / PCD is set to 16.67% is illustrated by a triangular point in FIG. As a result of strength analysis by simulation for these examples, a gear strength equal to or higher than that of the conventional one (more specifically, a gear strength of 87% or higher with respect to the reference differential device D'). ) Was obtained. Further, these examples are contained in the specific area as shown in FIG.

As a comparative example, in an example that does not fit in the specific range, for example, when the number of teeth Z2 of the pinion P is 10, the number ratio Z1 / Z2 is set to 58/10 and d2 / PCD is set to 27.50%, respectively. When the number of teeth Z2 of the pinion P is 10 at the star point in FIG. 15, the number ratio Z1 / Z2 is set to 40/10 and d2 / PCD is set to 34.29%, respectively. In the example shown in FIG. 15, when the number of teeth Z2 of the pinion P is 12, the number ratio Z1 / Z2 is set to 70/12 and d2 / PCD is set to 27.50%, respectively. In the example of the time, when the number of teeth Z2 of the pinion P was 12 at the star point in FIG. 17, the number ratio Z1 / Z2 was set to 48/12 and d2 / PCD was set to 34.29%, respectively. Examples of the time are shown by the circles in FIG. As a result of performing strength analysis by simulation for these examples, the gear strength equal to or higher than the conventional one (more specifically, the gear strength is 87% or higher than that of the reference differential device D'). Was not obtained. That is, it was confirmed that the above effect cannot be obtained in the examples that do not fall within the above specific range.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the gist thereof.

For example, in the above-described embodiment, the differential device D allows a difference in rotational speed between the left and right axles, but the differential device of the present invention also has a center differential that absorbs the difference in rotational speed between the front wheels and the rear wheels. Is feasible.

Further, in the above-described embodiment, the number of planetary gears 22 installed (hence, the number of pivot PLs as the first shaft supporting the planetary gears 22) is set to 4, but in the present invention, the planetary gears 22 are As for the number of installations, two or more (for example, two, three, six, etc.) can be appropriately selected.

Further, in the first to third embodiments described above, the tip portions (more specifically, the flange-shaped protrusions 23af) of the plurality of arm portions 23a of the carrier 23 are replaced with the differential case DC (more specifically, the first cover portion C1). ) Is directly welded, but in the present invention, an annular second carrier base different from the carrier base 23b is integrally connected to the tips of the plurality of arm portions 23a to form the carrier 23. The axial end, that is, the end of the second carrier base may be welded to the differential case DC.

Further, in the first to third embodiments described above, the stepped portion 15 recessed in the side surface of the differential case DC (more specifically, the first cover portion C1) on the carrier 23 side is continuously provided over the entire circumference of the differential case DC. In the present invention, a plurality of arcuate step portions may be arranged at intervals in the circumferential direction, and in this case, the step portions 15 are formed in the differential case DC. It is possible to reduce the thickness and weight of the differential case DC while maintaining the strength of the differential case DC by suppressing the decrease in strength due to the provision as much as possible.

Further, in the first to third embodiments described above, the recess 16 formed on the side surface of the differential case DC (more specifically, the first cover portion C1) on the carrier 23 side adjacent to the step portion 15 is formed on the carrier 23. Although the one composed of a plurality of arcuate recesses 16 corresponding to the plurality of arm portions 23a is shown, in the present invention, the recess 16 is composed of a single annular recess (that is, an annular groove) continuous in the circumferential direction. You may.

Further, in the first and second embodiments described above, one end of the pivot PL as the plurality of first shafts each supporting the plurality of planetary gears 22 is provided with a differential case DC (more specifically, a side wall portion of the first cover portion C1). as the recess for supporting the cs), while illustrating the concave hole H1 of a bottom, in the third to fifth embodiments have been illustrated through hole H1 'as the recess, first, in the second embodiment, the The concave hole H1 as the concave portion may be replaced with the through hole H1', or in the third to fifth embodiments, the through hole H1'as the concave portion may be replaced with the concave hole H1.

C1, C1', C10, C100 ... 1st cover part (opposing wall, one cover part)
C2, C200 ... 2nd cover (the other cover)
Cb ... Boss part Cs, Cs' ... Side wall part (wall part)
D ... Differential device DC ... Diff case (input member)
d2 ... Diameter of pinion shaft, diameter of support shaft (diameter of second shaft)
H1 ... concave hole (recess)
H1'... Through hole (recess)
P: Pinion (pinion gear, differential gear)
PCD ・ ・ ・ Pitch cone distance PL ・ ・ ・ ・ Axis (1st shaft)
PS ... Pinion shaft (second shaft)
PS'... Support shaft (second shaft)
S: Side gear (output gear)
Sj ・ ・ ・ ・ Shaft part wa ・ ・ ・ ・ Welded part 22 ・ ・ ・ ・ Planetary gear 23 ・ ・ ・ ・ Carrier 123a ・ ・ Arm part (carrier body part)
123b ... Carrier cover

Claims (8)

An input member (DC) that can be coupled to a carrier (23) that supports the plurality of planetary gears (22) via a plurality of first shafts (PL) that each support the plurality of planetary gears (22).
It is supported by the input member (DC) via at least one second shaft (PS, PS'), is rotatable with respect to the input member (DC), and is around the center of rotation of the input member (DC). Revolving differential gear (P) and
A pair of output gears (S) that mesh with the differential gear (P) are provided.
The input member (DC) has the plurality of first shafts (PL) at positions that radially overlap the output gear (S) on the wall (C1, C1') facing the carrier (23). Each has a plurality of recesses (H1, H1') that can be fitted, and the plurality of recesses (H1, H1') have the input member (DC) with respect to all the second shafts (PS, PS'). ) Is a differential device that is placed at a position offset in the circumferential direction. The pair of output gears (S) have shaft portions (Sj) connected to the pair of output shafts (J1, J2).
The input member (DC) has a boss portion (Cb) that concentrically surrounds the shaft portion (Sj) and a boss portion (Cb) having an outer surface as a flat surface orthogonal to the output shafts (J1, J2). The differential device according to claim 1, further comprising side wall portions (Cs, Cs') connected to the same. The plurality of recesses (H1, H1') are located at positions displaced in the circumferential direction of the input member (DC) with respect to the welded portion (wa) that connects the carrier (23) and the input member (DC). The differential device according to claim 1 or 2, which is arranged. Together with the carrier body (123a) and the carrier body (123a) adjacent to the carrier cover (123b) that supports one end of the plurality of first shafts (PL) that each support the plurality of planetary gears (22). One cover portion (C10, C100) having a wall portion (Cs, Cs') to be formed and the other cover portion (C2, C200) capable of being coupled to the one cover portion (C10, C100). Input member (DC) to have
It is supported by the input member (DC) via at least one second shaft (PS, PS'), is rotatable with respect to the input member (DC), and is around the center of rotation of the input member (DC). Revolving differential gear (P) and
A pair of output gears (S) that mesh with the differential gear (P) are provided.
The other cover portion (C10, C100) of the one cover portion (C10, C100) is the other end of the plurality of first shafts (PL) at a position that radially overlaps with the output gear (S) on the wall portion (Cs, Cs'). It has a plurality of recesses (H1, H1') into which each of the portions can be inserted.
A differential device in which the plurality of recesses (H1, H1') are arranged at positions deviated from all the second shafts (PS, PS') in the circumferential direction of the input member (DC). The pair of output gears (S) have shaft portions (Sj) connected to the pair of output shafts (J1, J2).
Each of the one cover portion (C10, C100) and the other cover portion (C2, C200) has a boss portion (Cb) concentrically surrounding the shaft portion (Sj) and an output shaft on the outer surface. The differential device according to claim 4, further comprising a side wall portion (Cs, Cs') connected to the boss portion (Cb) as a flat surface orthogonal to (J1, J2). The number of teeth of the output gear (S) was Z1, the number of teeth of the differential gear (P) was Z2, the diameter of the second shaft (PS, PS') was d2, and the pitch cone distance was PCD. sometimes,

The filling,
And satisfying the Z1 / Z2> 2, differential device according to any one of claims 1 to 5. The differential device according to claim 6, which satisfies Z1 / Z2 ≥ 4. The differential device according to claim 6, wherein Z1 / Z2 ≥ 5.8 is satisfied.

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