JP6742715B2 - Differential - Google Patents

Description

The present invention relates to a differential device provided in a vehicle such as an automobile.

Conventionally, in a differential device, a washer is interposed between the tooth back surface of each output gear and an input member (for example, a differential case), and lubricating oil is guided to the surface of the input member facing the back surface of the output gear. Patent Document 1 discloses a configuration in which an oil groove is recessed.

Utility model registration No. 2606235 Japanese Patent No. 4803871 JP 2002-364728 A

In the above-described conventional device, among the surfaces of the input member facing the back surface of the output gear, particularly in the area portion located on the back surface side of the meshing portion of the output gear and the differential gear, the meshing portion of the output gear A large thrust reaction force acts via the teeth and the washer.

However, the oil groove of the conventional device is formed in an area portion of the surface of the input member facing the rear surface of the output gear, which is located on the rear surface side of the meshing portion, that is, an area portion where the large thrust reaction force acts. Therefore, this may cause a reduction in support rigidity in the region where the load is heavy, and the durability of the region, and eventually the input member, may be reduced. Further, the load is concentrated on the edge portion of the oil groove, which may reduce the durability of the input member.

Such a problem is caused by, for example, increasing the diameter of the output gear with respect to the differential gear so that the number of teeth of the output gear can be set to be sufficiently larger than the number of teeth of the differential gear. In particular, in a differential device in which the input member is required to be thinned and lightened, such as in the differential device in which the flattening is performed, it may be particularly remarkable.

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

In order to achieve the above-mentioned object, a differential device according to the present invention is provided with an input member to which a driving force is input, a rotation of the input member supported by the input member, and rotation of the input member. Accordingly, a differential gear capable of revolving around the rotation center of the input member, a pair of output gears having a tooth portion meshing with the differential gear and a shaft portion located radially inward of the tooth portion, A washer interposed between the back surface of the tooth portion of each of the output gears and the input member, and a recess provided on a surface of the input member facing the back surface of a side wall portion facing the back surface of the output gear. being, and an oil groove extending to the back of the washer from the periphery of the shaft portion of the output gear, the side wall section has a plurality of through-holes or concave holes arranged at intervals in the circumferential direction, wherein The oil groove is arranged offset in the circumferential direction of the output gear with respect to the meshing portion of the tooth portion and the differential gear, and is formed of two through holes or concave holes that are adjacent in the circumferential direction. Arranged to pass through . (This is the first feature. )
The good suitable, of the input member, the inner peripheral portion of the facing surfaces of the output gear, the oil reservoir facing the outer periphery of the shaft portion of the output gear is recessed. (This is the second feature.)
Preferably, the oil groove is arranged in the vicinity of the meshing portion in the circumferential direction of the output gear. (This is the third feature.)
Preferably, the oil grooves are arranged in a pair so as to sandwich the meshing portion when viewed on a projection plane orthogonal to the rotation axis of the output gear. (This is the fourth feature.)
In order to achieve the above-mentioned object, a differential device according to the present invention is provided with an input member to which a driving force is input, a rotation of the input member supported by the input member, and rotation of the input member. Accordingly, a differential gear capable of revolving around the rotation center of the input member, a pair of output gears having a tooth portion meshing with the differential gear and a shaft portion located radially inward of the tooth portion, A washer interposed between the back surface of the tooth portion of each of the output gears and the input member, and the shaft of the output gear recessed in the surface of the input member facing the back surface of the output gear. An oil groove extending from the periphery of the portion to the back surface of the washer, wherein the oil groove is arranged offset in the circumferential direction of the output gear with respect to the meshing portion of the tooth portion and the differential gear, The differential gear is supported by the input member via a differential gear support portion supported by the input member, the number of teeth of the output gear is Z1, the number of teeth of the differential gear is Z2, and the difference is When the diameter of the dynamic gear support is d2 and the pitch cone distance is PCD,

The filling,
Further, Z1/Z2>2 is satisfied (this is the fifth characteristic).

Further, preferably, Z1/Z2≧4 is satisfied (this is a sixth feature).

Further, preferably, Z1/Z2≧5.8 is satisfied (this is the seventh feature).

According to the first feature of the present invention, the washer interposed between the tooth back surface of each output gear and the input member, and the face of the input member facing the back surface of the output gear are recessed and output. Since it has an oil groove extending from the periphery of the gear shaft to the back of the washer, it becomes possible to effectively supply the lubricating oil through the oil groove from the shaft periphery of the output gear to the back of the washer using centrifugal force. Therefore, even if a large thrust reaction force is applied to the washer from the differential gear through the output gear, the sliding portion between the washer and the back surface of the output gear can be sufficiently lubricated. Moreover, since the oil groove is arranged offset in the circumferential direction of the output gear with respect to the meshing portions of the tooth portion of the output gear and the differential gear, the oil groove on the surface of the input member facing the back surface of the output gear is offset. Of these, the oil groove can be displaced from the area portion where a particularly large thrust reaction force acts, that is, the area portion located on the back side of the meshing portion, and thus it is possible to suppress lowering of support rigidity in the area portion where the load is large, This can contribute to improving the durability of the input member.

Also, the input member has a rear and opposite side wall of the output gear, the side wall section has a plurality of through-holes or concave holes arranged at intervals in the circumferential direction, the oil groove is a circumferential direction Since it is arranged so as to pass between two adjacent through holes or concave holes, by specially providing the through holes or concave holes, the weight of the input member can be reduced while considering the weight balance of the input member. Moreover, it is possible to form the oil groove sufficiently long (that is, without interrupting the through hole or the like) while avoiding the through hole or the concave hole.

According to the second feature, in particular, since the oil reservoir facing the outer periphery of the shaft of the output gear is recessed in the inner periphery of the surface of the input member facing the output gear, The supply of lubricating oil to the oil groove can be adjusted appropriately. For example, at the beginning of the differential operation of the differential device, the lubricating oil in the oil reservoir is used to supply the lubricating oil to the oil groove, and thus to the washer. Can be smoothly performed, and the surplus lubricating oil can be temporarily stored in the oil reservoir to prepare for insufficient supply to the oil groove.

According to the third feature, in particular, the oil groove is arranged in the vicinity of the meshing portion in the circumferential direction of the output gear, so that a particularly large thrust reaction force of the surface of the input member facing the rear surface of the output gear is generated. It is possible to make the oil groove as close as possible to the acting area portion, that is, the area portion located on the back side of the meshing portion, thereby suppressing the reduction in support rigidity in the area portion where the load is heavy. Therefore, the area portion can be effectively lubricated.

According to the fourth feature, in particular, the oil grooves are arranged in a pair with the meshing portion sandwiched therebetween, so that it is possible to more effectively lubricate the area portion while suppressing a reduction in supporting rigidity in the area portion where the load is large. can do.

Further, in particular, according to the fifth feature, the differential device as a whole is sufficiently narrow in the axial direction of the output shaft while securing the same level of strength (eg, static torsional load strength) and maximum torque transmission amount as those of the conventional device. Therefore, it is possible to easily and easily install a differential gear in a transmission system that has many layout restrictions around the differential gear with a high degree of freedom, and is advantageous in downsizing the transmission system. Become.

Further, in particular, according to the sixth and seventh characteristics, the differential device is more sufficiently provided in the axial direction of the output shaft while ensuring the same level of strength (eg, static torsion load strength) and maximum torque transmission amount as those of the conventional device. The width can be narrowed.

FIG. 2 is a longitudinal sectional view of a main part of a differential gear and a reduction gear mechanism according to the first embodiment of the present invention (a sectional view taken along line 1A-1A in FIG. 2). 2A-2A line sectional view of FIG. 3A-3A line sectional view of FIG. An enlarged view of the 4A arrow portion of FIG. 1, a partially enlarged view thereof, and a load distribution diagram An enlarged cross-sectional view showing a main part (a meshing part of a pinion and a side gear) of a differential gear device according to a second embodiment of the present invention. An enlarged sectional view showing a main part of a differential gear device according to a third embodiment of the present invention (a sectional view corresponding to a partially enlarged view of FIG. 4). A vertical cross-sectional view showing an example of a conventional differential device A graph showing the relationship of the gear strength change rate to the tooth number ratio when the number of teeth of the pinion is 10. Graph showing the relationship of the gear strength change rate to the pitch cone distance change rate A graph showing the relationship between the rate of change in 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. Graph showing the relationship between the number of teeth when the number of teeth of the pinion is 10, and the ratio of shaft diameter/pitch cone distance 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 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 shaft diameter/pitch cone distance. Graph showing the relationship between the number of teeth when the number of teeth of the pinion is 20, and the ratio of shaft diameter/pitch cone distance

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

First, a first embodiment of the present invention will be described with reference to FIGS. 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 the rotational force transmitted from the engine to the differential case DC through the reduction gear mechanism RG to the output shafts J and J′ connected to a pair of axles that are parallel to each other in the vehicle width direction to transmit the rotational force. , For driving both axles while allowing differential rotation, for example, in a mission case M arranged beside the engine at the front of the vehicle body, in a state adjacent to the reduction gear mechanism RG. It is housed together with the gear mechanism RG. A conventionally known power connecting/disconnecting mechanism and a forward/reverse switching mechanism (neither is shown) are interposed between the engine and the reduction gear mechanism RG. The rotation axis L of the differential case DC coincides with the center axes of the output shafts J and J'. In this specification, the “axial direction” means a direction along the central axis of the output shafts J, J′ (that is, the rotation axis L of the differential case DC and the side gear S), and the “radial direction” means the differential case. It refers to the radial direction of DC and the side gear S. Further, the “back surface” refers to a surface in the axial direction of the side gear (output gear) S, which is opposite to a pinion (differential gear) P described later, that is, a surface facing away from the differential gear.

The reduction gear mechanism RG includes, for example, a sun gear 20 that rotates in conjunction with the crankshaft of the engine, a ring gear 21 that concentrically surrounds the sun gear 20 and is fixed to the inner wall of the transmission case M, and between the sun gear 20 and the ring gear 21. The planetary gear mechanism includes a plurality of planetary gears 22 that are interposed and mesh with both gears 20 and 21, and a carrier 23 that rotatably supports the planetary gears 22. Note that, instead of such a planetary gear mechanism, a reduction gear mechanism including a gear train of a plurality of spur gears may be used.

The carrier 23 is rotatably supported by the mission case M via a bearing (not shown). Further, in the present embodiment, the carrier 23 is coupled to one end portion (a cover portion C′ described later) of the differential case DC of the differential device D so as to rotate integrally therewith, and the other end portion (a cover portion described later of the differential case DC is also coupled. C) is rotatably supported by the mission case M via the bearing 2. Therefore, the combined body of the differential case DC and the carrier 23, which rotate integrally with each other, is rotatably and stably supported by the mission case M via the plurality of bearings.

Further, the transmission case M is formed with a through hole Ma into which the output shafts J and J'are inserted, and a seal is provided between the inner circumference of the through hole Ma and the outer circumference of the output shafts J and J'. The annular sealing member 3 is interposed. In addition, 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 at the bottom of the mission case M, and the lubricating oil stored in the oil pan is used for the mission case. In the inner space 1 of M, the movable elements of the reduction gear mechanism RG, the differential case DC, etc. are scraped up and scattered around by the rotation of the differential case DC and the like, so that the mechanical movement parts existing inside and outside the differential case DC can be lubricated.

The lubricating oil stored in the oil pan is sucked by an oil pump (not shown), and a specific portion of the internal space 1 of the mission case M, for example, the reduction gear mechanism RG or the differential case DC, or the mission case M in the vicinity thereof. It may be forcibly jetted or sprayed toward the inner wall. Further, in the differential case DC of the present embodiment, a part of the outer peripheral portion of the differential case DC may or may not be immersed below the surface of the lubricating oil stored in the inner bottom portion of the mission case M.

2 to 4 as well, the differential device D rotatably supports the differential case DC, a plurality of pinions P housed in the differential case DC, and the pinion P housed in the differential case DC. A pinion shaft PS and a pair of side gears S that are housed in the differential case DC and mesh with the pinion P from both left and right sides and that are respectively connected to the pair of output shafts J and J′ are provided. The side gear S is an example of an output gear, the pinion P is an example of a differential gear, and the differential case DC is an example of an input member. Pinion P, like the well-known differential equipment and can revolve around the rotational center of the differential case DC with the rotation of the differential case DC with housed supported to the differential case DC to differential case DC is capable of rotating.

The differential case DC is, for example, a short cylindrical (cylindrical) case portion 4 that supports the pinion shaft PS so that it can rotate together with the pinion shaft PS, and covers the outside of each of the pair of side gears S and is integrally formed with the case portion 4. It has a pair of rotating cover parts C and C'.

Either one of the pair of cover parts C and C', for example, the cover part C'on the reduction gear mechanism RG side is formed separately from the case part 4 and is attached to the case part 4 by a bolt B or other parts. It is removably coupled by a suitable coupling means. Further, the carrier 23 of the reduction gear mechanism RG is coupled to the cover portion C'by welding or other suitable coupling means so that the carrier 23 of the reduction gear mechanism RG can rotate integrally with the cover portion C'. The cover portion C on the other side is formed integrally with, for example, the cylindrical case portion 4, but the cover portion C is formed separately from the case portion 4 like the cover portion C′ on the one side. Alternatively, the case portion 4 may be coupled with the bolt B or other suitable coupling means.

Each of the cover portions C and C′ has a cylindrical boss portion Cb that concentrically surrounds a shaft portion Sj of the side gear S, which will be described later, and is rotatably fitted and supported, and all or most of the outer side surface of the differential case DC. 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, and the outer peripheral end of the side wall portion Cs is provided on the case portion 4. It is integrally or detachably coupled. The side wall portion Cs of each of the cover portions C and C'is substantially flush with the axial end surface of the case portion 4 or slightly overhangs. As a result, it is possible to prevent the side wall portion Cs from largely protruding outward in the axial direction, which is advantageous in achieving flattening of the differential device D in the axial direction.

Further, a plurality of (for example, eight) through holes H penetrating the side wall portion Cs so as to traverse the side wall portion Cs in the axial direction are arranged in parallel in the side wall portion Cs of each of the cover portions C and C′ at intervals in the circumferential direction. It The formation site and size of the through hole H are appropriately set from the viewpoint of weight balance of the respective cover parts C and C′ and securing of necessary rigidity and strength. However, instead of or in addition to such through hole H, A bottomed concave hole opened only on one side may be formed on the inner surface of the side wall Cs of each cover C, C'. In particular, when the through hole H is adopted, the lubricating oil scattered in the transmission case M can be introduced into the differential case DC through the through hole H, so that the sliding parts between the movable elements in the differential case DC and the sliding parts can be introduced. Lubrication of the meshing portion can be performed more effectively.

The outer peripheral surface of the output shaft J is directly fitted to the inner peripheral surface of the boss portion Cb of the one cover portion C so as to be relatively rotatable. Along with the relative rotation, a spiral groove 8 is formed on the inner peripheral surface of the boss Cb so that the lubricating oil can be forcibly fed from the axially outer end to the inner end of the boss Cb. .. Further, on the inner peripheral surface of the boss portion Cb of the other cover portion C', from the axial outer end of the boss portion Cb due to the relative rotation of the other cover portion C'and the shaft portion Sj of the side gear S on the same side. A spiral recessed groove 8'for forcibly feeding the lubricating oil toward the inner end side is formed.

By the way, the pinion shaft PS is arranged in the differential case DC so as to be orthogonal to the rotation axis L of the differential case DC, and a pair of penetrating supports provided on the cylindrical case portion 4 on one diameter line of the case portion 4. Both ends of the pinion shaft PS are inserted into the holes 4a so that they can be removed. Then, the pinion shaft PS is fixed to the case portion 4 with a retaining pin 5 which penetrates one end of the pinion shaft PS and is inserted into the case portion 4. Retaining pin 5, retaining from the case portion 4 is made the outer end of the pin 5 by cormorants is applied to the cover portion C 'of the other side.

In the present embodiment, the pinion shaft PS is formed in the shape of a straight rod so that the two pinions P are supported at both ends of the pinion shaft PS, but three or more pinions P are provided. May be. In that case, the pinion shaft PS is branched from the rotation axis L of the differential case DC in three or more directions and radially extends corresponding to three or more pinions P (for example, when there are four pinions P). The pinion P is formed in a cross shape so as to support the pinion P at each tip of the pinion shaft PS, and the case portion 4 is provided in a plurality of case elements so that each end of the pinion shaft PS can be attached and supported. Divide and configure.

Further, the pinion P may be directly fitted to the pinion shaft PS, or may be fitted via a bearing means such as a bearing bush. The pinion shaft PS may have a shaft shape having a substantially uniform diameter over the entire length as shown in FIG. 2, or may have a stepped shaft shape. In addition, a flat cutout surface 6 (see FIG. 2) is formed on the fitting surface of the pinion shaft PS with the pinion P to ensure sufficient circulation of lubricating oil to the fitting surface. An oil passage through which lubricating oil can flow is secured between 6 and the inner peripheral surface of the pinion P.

The pinion P and the side gear S are formed, for example, in a bevel gear, and the whole of the pinion P and the side gear S, including the tooth portions, are each formed by plastic working such as forging. Therefore, the tooth portions can be formed with high accuracy with an arbitrary number of teeth without being subject to mechanical restrictions such as when 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 a bevel gear.

Further, the pair of side gears S are located at a position distant from the shaft portion Sj in the radial direction and a cylindrical shaft portion Sj to which the inner end portions of the pair of output shafts J and J′ are respectively spline fitted 7. A ring-shaped tooth portion Sg having a tooth surface that meshes with the pinion P, and a flat ring plate shape that extends 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 formed, 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. Then, of the back surface f of the side gear S, the back surface portion fg of the tooth portion Sg projects axially outwardly more than the back surface portion fm of the intermediate wall portion Sm.

Although the shaft portion Sj of each side gear S is rotatably directly fitted to the boss portion Cb of the cover portions C and C′, it may be fitted through a bearing.

A plurality of through oil passages 9 are formed in 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 circumferential direction at intervals. .. Therefore, in the differential case DC, the lubricating oil flows smoothly through the through oil passage 9 between the inner side and the outer side of the side gear S. The formation portion and the size of the through oil passage 9 are appropriately set from the viewpoint of the weight balance of the side gear S and ensuring the required rigidity strength.

In addition, on the inner surface of the side wall portion Cs of the cover portions C and C′, that is, on the surface facing the back surface f of the side gear S, the back surface portion fg of the tooth portion Sg of the side gear S (that is, the side gear of the back surface f of the side gear S). A portion of the meshing portion I of the S and the pinion P located on the back side of the meshing portion I is rotatably abutted and supported via a washer W. The washer W is formed on at least one of the inner surfaces of the side walls Cs of the covers C and C'and the rear surfaces of the teeth Sg of the side gear S (the inner surface of the side wall Cs in this embodiment). The ring-shaped washer holding groove 10 is fitted and held.

Further, at the inner peripheral end of the inner surface of the side wall Cs of the covers C and C'(that is, the surface facing the rear surface f of the side gear S), an annular oil reservoir T facing the outer periphery of the shaft Sj of the side gear S is formed. Are recessed respectively. Further, in particular, the oil sump portion T on the cover portion C side is located between the facing surfaces of the inner peripheral end portion of the boss portion Cb of the cover portion C and the outer peripheral portion and outer end surface of the shaft portion Sj of the side gear S on the cover portion C side. Is communicated with the inner end of the concave groove 8 on the inner peripheral surface of the boss portion Cb through the lubricating oil passage 11 formed in the inner side of the boss portion Cb. ing. The inner end of the concave groove 8 is also in communication with the spline fitting portion 7 between the inner peripheral portion of the shaft portion Sj of the side gear S and the inner peripheral portion of the output shaft J. Also, the lubricating oil can be supplied from the groove 8.

Further, the oil reservoir T on the other cover C′ side communicates with the inner end of the groove 8′ formed on the inner peripheral surface of the boss Cb of the cover C′, and the outer end of the groove 8′. Communicate with the internal space 1 of the mission case M.

As described above, the back surface portion fg of the tooth portion Sg of the side gear S projects axially outward from the back surface portion fm of the intermediate wall portion Sm on the inner surface of the side wall portion Cs of the cover portions C and C′. Correspondingly, the portion of the side wall portion Cs corresponding to the back surface portion fm of the intermediate wall portion Sm is projected axially inward (that is, the axial direction inward direction) rather than the portion of the side wall portion Cs corresponding to the back surface portion fg of the tooth portion Sg. Formed). As a result, the intermediate wall portion Sm of the side gear S can be formed as thin as possible while sufficiently securing the support rigidity of the covers C and C′ (and thus the differential case DC) to the back surface of the tooth portion Sg of the side gear S. Further weight reduction of the differential device D and flattening in the axial direction can be achieved.

Further, on the inner side surface of the side wall portion Cs of the cover portions C and C′ (that is, the surface facing the rear surface f of the side gear S), a plurality of oils that linearly extend from the periphery of the shaft portion Sj of the side gear S to the rear surface of the washer W. The groove G is recessed. As shown in FIG. 3 in particular, the plurality of oil grooves G are arranged to be offset in the circumferential direction of the side gear S with respect to the meshing portion I of the tooth portion Sg of the side gear S and the pinion P.

In particular, the oil groove G of the present embodiment is arranged so as to extend radially with respect to the rotation axis L of the differential case DC and pass between two through holes H that are adjacent to each other in the circumferential direction of the side gear S. That is, the oil groove G is arranged at a position that does not overlap the pinion P in the circumferential direction when viewed on the projection plane orthogonal to the rotation axis L of the side gear S. In addition, the oil grooves G are arranged in a V-shape one by one with the meshing portion I of the side gear S and each pinion P sandwiched therebetween, as viewed on the projection plane (FIG. 3) orthogonal to the rotation axis L of the side gear S, Moreover, it is arranged so as to be located in the vicinity of the meshing portion I. The inner end of each oil groove G directly communicates with the oil reservoir T. The pair of oil grooves G sandwiching the meshing portion I may be arranged in parallel to each other, for example, along the pinion shaft PS, instead of being arranged in a V shape as in the present embodiment.

By the way, as shown in FIG. 4, the outermost peripheral edge fwe of the washer contact surface fw that contacts the washer W on the rear surface f of each side gear S is the outermost periphery of the meshing portion I of the side gear S and the pinion P with each other. It is located at the same position in the radial direction of the side gear S with respect to the end Ie, and the outer peripheral end We of the washer W extends outward in the radial direction from the washer contact surface fw. Further, in the present embodiment, the outermost peripheral edge fwe of the washer contact surface fw of each side gear S is the maximum outer diameter portion of the side gear S.

Next, the operation of the first embodiment will be described. In the differential device D of the present embodiment, when the differential case DC receives a rotational force from the engine through 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 at the same speed from the differential case DC via the pinions P, and the driving force of the side gears S is evenly transmitted to the left and right output shafts J, J'. When a difference in rotational speed occurs between the left and right output shafts J, J'due to turning of the automobile, the pinion P revolves while revolving to rotate the pinion P differentially with respect to the left and right side gears S. The rotational driving force is transmitted while allowing it. The above is the same as the operation of the conventionally known differential device.

By the way, when the power of the engine is transmitted to the left and right output shafts J, J′ through the reduction gear mechanism RG and the differential device D, for example, in the forward running state of the automobile, each movable element of the reduction gear mechanism RG and the differential case DC. The lubricating oil vigorously scatters in various places in the mission case M as a result of the rotation of No. 1, but a part of the scattered lubricating oil flows into the differential case DC through the plurality of through holes H as described above. Then, a part of the lubricating oil that has flowed in travels through the gap between the side walls Cs of the covers C and C′ and the rear surface f of the side gear S by centrifugal force, and the rear surface of the tooth portion Sg of the side gear S and the washer W. Go to the sliding part between and lubricate the sliding part. The other part of the lubricating oil that has flowed into the differential case DC also flows into the inner space of the side gear S through the through oil passage 9 of the side gear S, and the inner surface of the side gear S is radially outwardly moved by centrifugal force. It flows along and flows to the tooth surface of the tooth portion Sg of the side gear S and to the meshing portion I of the tooth portion Sg of the side gear S and the pinion P to lubricate the meshing portion I.

Further, part of the lubricating oil that has scattered in the mission case M and has reached the vicinity of the outer end of the boss portion Cb of the one cover portion C of the differential case DC is accompanied by relative rotation between the boss portion Cb and the output shaft J. It is fed toward the axially inner end side of the boss portion Cb through the concave groove 8 on the inner peripheral surface of the boss portion Cb, and sequentially passes through the lubricating oil passage 11 and the oil reservoir portion T from the inner end of the concave groove 8. And flows into the inner end of the oil groove G. A part of the lubricating oil reaching the inner end of the groove 8 also flows into the spline fitting portion 7 and flows from the spline fitting portion 7 to the inner side surface side of the side gear S.

On the other hand, a part of the lubricating oil that has scattered in the mission case M and has reached the vicinity of the outer end of the boss portion Cb of the other cover portion C′ of the differential case DC has a portion relative to the boss portion Cb and the shaft portion Sj of the side gear S. Along with the rotation, the oil is fed toward the axially inner end side of the boss portion Cb through the groove 8'on the inner peripheral surface of the boss portion Cb, and from the inner end of the groove 8'through the oil reservoir T to the oil groove. It flows into the inner end of G.

According to the present embodiment, the side gear S has a flat ring that connects the inner peripheral shaft portion Sj and the outer peripheral side gear S tooth portion Sg that is radially outwardly separated from the shaft portion Sj. It has a plate-shaped intermediate wall portion Sm, and 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 to be sufficiently larger than the number of teeth Z2 of the pinion P, and the pinion at the time of torque transmission from the pinion P to the side gear S. The load on the shaft PS can be reduced, and the effective diameter d2 of the pinion shaft PS can be reduced, and consequently the width of the pinion P in the axial direction of the output shafts J, J′ can be narrowed (reduced diameter). it can.

Further, in this way, the load on the pinion shaft PS is reduced, the reaction force applied to the side gear S is reduced, and moreover, the rear surface f of the side gear S (particularly on the rear surface side of the meshing portion I of the side gear S and the pinion P). Since the rear surface portion fg) located is supported by the side wall portion Cs of the cover portions C, C′ via the washer W, the required rigidity strength of the side gear S can be secured even if the intermediate wall portion Sm is made thin. It is easy, that is, it is possible to sufficiently thin the intermediate wall portion Sm of the side gear S while ensuring the supporting rigidity for the side gear S. Furthermore, in the present embodiment, 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 reduction. Further thinning can be achieved. Moreover, the side wall portion Cs of the cover portions C and C'is formed into a flat plate shape in which the outer side surface of the side wall portion Cs is a flat surface orthogonal to the rotation axis L of the differential case DC. The thinning of the side wall portion Cs itself is also achieved.

Further, according to the present embodiment, of the back surface f of the side gear S, the back surface portion fg of the tooth portion Sg projects axially outwardly more than the back surface portion fm of the intermediate wall portion Sm. The intermediate wall portion Sm of the side gear S can be formed as thin as possible while sufficiently ensuring the rigidity of Sg, and the weight reduction and flattening of the differential device D in the axial direction can be achieved.

As a result, the differential device D can be sufficiently narrowed in the axial direction as a whole while ensuring strength (for example, static torsional load strength) and maximum torque transmission amount comparable to those of the conventional device. Therefore, even in a transmission system around the differential gear D, which has many layout restrictions, the differential gear D can be easily and easily installed with a high degree of freedom, and the transmission gear of the differential gear D can be downsized. It will be a great advantage in doing so.

Further, according to the present embodiment, most of the lubricating oil that has flowed into the oil grooves G of the cover portions C and C′ smoothly flows radially outward in the oil grooves G by centrifugal force, and the washer W Efficiently supplied to the back of. Therefore, even if a large thrust reaction force acts on the washer W from the pinion P via the side gear S, the sliding portion between the washer W and the back surface f of the side gear S (particularly the back surface portion fg of the tooth portion Sg) is sufficiently moved. Can be lubricated. In addition, the oil groove G is arranged offset in the circumferential direction of the side gear S with respect to the meshing portion I of the tooth portion Sg of the side gear S and the pinion P, so that the differential case DC (that is, the cover portions C, C' To shift the oil groove G in the circumferential direction from an area portion of the side wall portion Cs) facing the rear surface f of the side gear S, on which an especially large thrust reaction force acts, that is, an area portion located on the rear surface side of the meshing portion I. You can As a result, it is possible to suppress a decrease in support rigidity in a region of the differential case DC where the load is large, and improve the durability of the differential case DC.

Further, according to the present embodiment, a plurality of through holes H are arranged side by side in the circumferential direction at the side wall portions Cs of the respective cover portions C and C′ in the differential case DC, and two adjacent through holes H are formed. Since the oil groove G passes between them, not only can the weight of the differential case DC be reduced by considering the weight balance of the differential case DC by the special provision of the through hole H, but the oil groove G can be sufficiently provided while avoiding the through hole H. This is convenient because it can be formed long (that is, without being interrupted by the through hole H or the like in the middle).

Moreover, according to the present embodiment, the back surface portion fg of the back surface f of the side gear S, which is present on the back surface side of the meshing portion I, and the washer W are projection planes (FIG. 3) orthogonal to the rotation axis L of the side gear S. It is arranged so as to partially overlap when viewed. Therefore, via the washer W, a region of the differential case DC facing the rear surface f of the side gear S (that is, the inner side surface of the side wall portion Cs of the cover portions C and C') where a particularly large thrust reaction force acts is provided. Since the thrust reaction force is transmitted from the side gear S, excessive load concentration on the area portion can be avoided. As a result, it is possible to more effectively suppress the decrease in support rigidity in the region where the load is large, and thus it is possible to further improve the durability of the differential case DC.

According to the present embodiment, the shaft of the side gear S is attached to the inner peripheral end of the surface of the differential case DC facing the side gear S (that is, the inner peripheral end of the inner side surface of the side wall Cs of the covers C and C′). Since the oil reservoir T facing the outer periphery of the portion Sj is recessed, the amount of lubricating oil supplied to the oil groove G can be appropriately adjusted by the oil reservoir T. For example, in the initial stage of the differential operation of the differential device D, the lubricating oil stored in the oil reservoir T is used to supply the lubricating oil to the oil groove G, and thus to the washer W and the rear surface f of the side gear S. Can be performed smoothly, and the surplus lubricating oil can be temporarily stored in the oil reservoir T to prepare for the situation of insufficient supply to the oil groove G.

Further, according to the present embodiment, the oil groove G is arranged in the vicinity of the meshing portion I in the circumferential direction of the side gear S, so that a particularly large thrust reaction force of the surface of the differential case DC facing the rear surface f of the side gear S. It is possible to move the oil groove G closer to the area portion on which the oil acts, that is, the area portion located on the back surface side of the meshing portion I. As a result, it is possible to effectively lubricate the area portion of the differential case DC while suppressing the reduction in support rigidity in the area portion where the load is large. Moreover, since a pair of such oil grooves G are arranged with the meshing portion I interposed therebetween, it is possible to more effectively lubricate the area portion while suppressing a decrease in support rigidity in the area portion where the load is large.

Further, according to the present embodiment, the case where the tooth portion Sg of the side gear S is far away from the output shafts J and J'by increasing the diameter of the side gear S and the severe operating condition in which the pinion P rotates at high speed can be achieved. Also, the lubricating oil can be efficiently supplied to the meshing portion I and the sliding portion between the back surface f of the side gear S and the washer W, and seizure of those portions can be effectively prevented.

In the present embodiment, the outermost peripheral edge fwe of the washer contact surface fw that contacts the washer W on the back surface f of each side gear S is meshed with the side gear S and the pinion P as shown in FIG. Since the outermost peripheral end Ie of the portion I is located at the same position in the radial direction of the side gear S, the outermost peripheral end of the washer contact surface fw of the side gear S passes from the pinion P to the tooth portion Sg of the outer periphery of the side gear S. There is no fear that a large thrust reaction force will be excessively concentrated, and the load burden on the tooth portion Sg itself on the outer periphery of the side gear S is also reduced. In the present invention, the washer contact surface fw is set so that the outermost peripheral edge fwe of the washer contact surface fw is located outward of the outermost peripheral edge Ie of the meshing portion I in the radial direction of the side gear S. However, in that case, the same effect as above can be expected.

Moreover, since the outer peripheral end portion We of the washer W extends radially outward from the washer contact surface fw of the side gear S, as is apparent from the load distribution chart of FIG. 4, the washer receiving portion of the differential case DC is provided. The load is distributed at the bottom portion of the washer holding groove 10 in the side wall portion Cs of the cover portions C and C', which effectively prevents the washer receiving portion from locally increasing the load. .. The comparative example (dotted line) in the load distribution chart of FIG. 4 shows a case where the outer peripheral end portion We of the washer W is not extended outward in the radial direction from the washer contact surface fw of the side gear S. An excessive load is applied to the washer receiving portion of the differential case DC that is in contact with the outermost peripheral end of the washer W.

According to the relational structure of the back surface f of the side gear S, the washer W, and the washer receiving portion of the differential case DC in this embodiment, the differential case DC (particularly the side wall portion Cs of the covers C and C′) and the side gear S (particularly, the side gear S). The outer peripheral tooth portion Sg) can be made thin and lightweight, which can contribute to flattening and weight saving of the differential device D in the axial direction. Moreover, since the outermost peripheral edge fwe of the washer contact surface fw is the maximum outer diameter portion of the side gear S, a large thrust reaction force is appropriately dispersed on the washer receiving surface of the differential case DC without increasing the diameter of the side gear S. Can be accepted. As a result, the side wall portion Cs of the differential case DC and the tooth portion Sg of the side gear S can be made thinner and lighter.

Next, a 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, the long pinion shaft PS is used as the support portion of the pinion P (that is, the differential gear support portion). However, in the second embodiment, the pinion P is coaxial with the end surface on the large diameter side. The support shaft PS' integrally connected to each other constitutes a support portion of the pinion P (that is, a differential gear support portion). According to this configuration, since it is not necessary to provide the pinion P with a through hole into which the pinion shaft PS is fitted, the diameter of the pinion P can be reduced (the axial width can be narrowed), and the axial direction of the differential device D can be further increased. It can be flattened. 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 J and J′ 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, that is, the inner peripheral surface of the through support hole 4a provided in the cylindrical case portion 4, the outer peripheral surface of the support shaft PS' penetrates. A bearing bush 12 is inserted as a bearing means that allows relative rotation with the inner peripheral surface of the support hole 4a. A bearing such as a needle bearing may be used as the bearing means. 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.

Other than that, in the second embodiment, substantially the same effects as in 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, the outermost peripheral edge fwe of the washer contact surface fw that contacts the washer W on the rear surface f of the side gear S is located at the outermost peripheral edge Ie of the meshing portion I of the side gear S and the pinion P. On the other hand, at the same position in the radial direction of the side gear S or at the radially outer position, and the outermost peripheral edge fwe of the washer contact surface fw was the maximum outer diameter portion of the side gear S. However, in the third embodiment, The outer peripheral end surface of the tooth portion Sg of the side gear S and the back surface of the tooth portion Sg (particularly the washer contact surface fw) are smoothly connected by a radius r having an arc cross section. Therefore, although the outermost peripheral end fwe of the washer contact surface fw is located radially inward of the maximum outer diameter portion of the side gear S (that is, the outer peripheral end surface), the outer peripheral end We of the washer W has the first and second positions. Similar to the embodiment, the washer contact surface fw extends outward in the radial direction from the washer contact surface fw, and the washer contact surface fw is located on the rear surface side of the meshing portion I.

In the third embodiment, the other configurations are the same as those in the first embodiment. Therefore, each component is given the same reference numeral as that of the corresponding component in the first embodiment. The above description is omitted.

Therefore, also in the third embodiment, it is possible to achieve substantially the same operational effects as those of the first and second embodiments. In the third embodiment, between the outer peripheral end surface of the tooth portion Sg and the back surface of the tooth portion Sg (particularly the washer contact surface fw) of the side gear S, not the radius r, but a flat tapered surface having a linear cross section. You may make it connect with.

By the way, a conventional differential device as exemplified in the above-mentioned Patent Documents 2 and 3 (in particular, a pinion (differential gear) in the input member and a pair of side gears (output gear) meshing with the pinion (differential gear)) In the conventional differential device provided, the number of teeth Z1 of the side gear (output gear) and the number of teeth Z2 of the pinion (differential gear) are normally set to 14×10 or 16×10 shown in Patent Document 3, or 16×10 or 13x9 is used. In this case, the gear ratios Z1/Z2 of the output gear to the differential gear are 1.4, 1.6 and 1.44, respectively. In addition, in the conventional differential device, it is known that other combinations of the numbers of teeth Z1 and Z2 are, for example, 15×10, 17×10, 18×10, 19×10, or 20×10. The tooth number ratios Z1/Z2 in this case are 1.5, 1.7, 1.8, 1.9 and 2.0, respectively.

On the other hand, nowadays, transmission devices accompanied by layout restrictions around differential devices are also increasing, and the differential devices are sufficiently narrowed in the axial direction of the output shaft (that is, while securing the gear strength of the differential device). Flattening is required in the market. However, in the existing existing differential device, as is clear from the combination of the tooth number ratios, the structure is wide in the axial direction of the output shaft, and thus 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 (i.e., flattening) the differential device in the axial direction of the output shaft while ensuring the gear strength of the differential device, from a viewpoint different from the above-described embodiment. , Will be specifically specified below. The structure of each component of the differential device D according to this configuration example is the same as each component of the differential device D of the above-described embodiment described with reference to FIGS. 1 to 6 (particularly FIGS. 1 to 4 and 6). The same reference numerals as those of the above-described embodiment are used as the reference numerals of the respective constituent elements, 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 J and J′ will be described with reference to FIG. 7 as well.
[1] To increase the gear ratio Z1/Z2 of the pinion P, that is, the side gear S to the differential gear, that is, the output gear, more than the gear ratio of the existing differential device. (Thus, while the gear module (thus, tooth thickness) is reduced and the gear strength is reduced, the pitch circle diameter of the side gear S is increased and the transmission load at the gear meshing portion is reduced, and the gear strength is increased. , As a whole, the gear strength decreases as described later.)
[2] The pitch cone distance PCD of the pinion P is made larger than the pitch cone distance of the conventional existing differential device. (As a result, the number of modules of gears increases and the gear strength increases, and the pitch circle diameter of the side gear S increases to reduce the transmission load at the gear meshing portion and increase the gear strength. As you can see, the gear strength is greatly increased.)
Therefore, the amount of gear strength reduction due to the above [1] is equal to the amount of gear strength increase due to the above [2], or the amount of gear strength reduction due to the above [1] is greater than the amount of gear strength reduction due to the above [1]. By setting the tooth ratio Z1/Z2 and the pitch conical distance PCD so that the amount of increase in strength is greater, the gear strength as a whole can be made equal to or increased as compared with the conventional existing differential device.

Next, the manner of changing the gear strength based on the above [1] and [2] will be specifically verified by mathematical expressions. The verification will be described in the following embodiment. First, 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, the differential device D'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%).
Regarding [1] 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 mesh portion is FO, and the transmission torque is TO, the bevel gear From the general formula of
MO=PD ₁ /Z1
PD ₁ =2PCD・sin θ ₁
θ ₁ = tan ^-1 (Z1/Z2)
From these equations, the gear module is
MO=2PCD·sin{ tan ⁻¹ (Z1/Z2)}/Z1 (1)
Next to
The module of the reference differential D'is 2PCD·sin{ tan ^-1 (7/5)}/14.
Becomes

Therefore, by dividing the right-hand terms of both equations, the module change rate for the reference differential device D'is given by the following equation (2).

Further, the cross-sectional modulus 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-section coefficient of the tooth portion, and thus 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). Expression (3) is shown by L1 in FIG. 8 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 module decrease as the number of teeth ratio Z1/Z2 increases.

By the way, according to the above general formula of the bevel gear, the torque transmission distance of the side gear S is expressed by 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, if the torque TO is constant in the side gear S of the reference differential device D′, the transmission load FO and the pitch circle diameter PD ₁ have an inversely proportional relationship. Further, the rate of change of the transmission load FO is also inversely proportional to the rate of change of the gear strength, so the rate of change of the gear strength becomes 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 given by the following equation (5) using the equation (4).

Equation (5) is shown by L2 in FIG. 8 when the number of teeth Z2 of the pinion P is 10, and it can be understood that the gear strength increases due to the reduction of the transmission load as the number of teeth ratio Z1/Z2 increases.

After all, the rate of change of gear strength due to the increase of the tooth ratio Z1/Z2 depends on the rate of decrease of gear strength due to the decrease of the module MO (right side of the above equation (3)) and the reduction of transmission load. It is expressed as the following expression (6) by being multiplied by the rate of increase in the change in gear strength (the right side of the expression (5) above).

Equation (6) is shown by L3 in FIG. 8 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 made larger than the pitch cone distance of the reference differential D′, when the PCD before the change is PCD1 and the PCD after the change is PCD2, the PCD before and after the change From 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, since the rate of change of the gear strength of the side gear S corresponds to the square of the rate of change of the module, as is clear from the process of deriving the equation (3), after all,
Gear strength change rate due to module increase = (PCD2/PCD1) ² (7)
Expression (7) is shown by L4 in FIG. 9, and it can be seen that the gear strength increases due to the increase in the module as the pitch cone distance PCD increases.

Further, when the pitch cone distance PCD is made larger than the pitch cone distance PCD1 of the reference differential device D′, the transmission load FO is reduced, but the change rate of the gear strength by this is as described above. It becomes equal to the change rate of the 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 reduction of transmission load=PCD2/PCD1 (8)
Equation (8) is shown by L5 in FIG. 9, and it can be seen from this that as the pitch cone distance PCD increases, the transmission load decreases and the gear strength increases.

The rate of change of the gear strength with the increase of the pitch cone distance PCD is the rate of increase of the gear strength due to the increase of the module MO (the right side of the above formula (7)) and the increase of the pitch circle diameter PD. It is expressed as the following expression (9) by being multiplied by the rate of increase in the change in gear strength due to the reduction of the transmission load (the right term in the above expression (8)).

Gear strength change rate due to increased pitch cone distance = (PCD2/PCD1) ³ ··· (9)
Expression (9) is shown by L6 in FIG. 9, 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] (increasing the number of teeth) is sufficiently compensated by the increase in gear strength due to the method [2] (increasing the pitch cone distance), and as a whole, the differential device The combination of the tooth 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 existing differential device.

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

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

That is, in the existing differential device of the related art, an increase change in the pitch cone distance PCD is correlated with an increase change in d2 as shown in Table 1 above, and when d2 is kept constant, the ratio of d2/PCD decreases. It is expressible. Moreover, in the conventional existing differential device, as shown in Table 1 above, when the reference differential device D′, d2/PCD is in the range of 40 to 45%, and the gear strength increases when PCD is increased. Therefore, if the shaft diameter d2 and the pitch conical distance PCD of the pinion shaft PS are determined so that at least d2/PCD is 45% or less when the reference differential D'is used, the gear strength is different from that of the existing gear. It may be equal to or higher than the gear strength of the moving device. That is, in the case of the reference differential device D',
It is only necessary 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 above equation (10), the relationship between d2/PCD and the tooth number ratio Z1/Z2 can be converted as the following equation (12).

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

By the way, in the conventional existing differential device, as described above, not only is the gear number ratio Z1/Z2 set to 1.4 as in the reference differential device D′, but the tooth number ratio Z1/Z2 is set to 1 in general. And a tooth number ratio Z1/Z2 of 1.44 are also adopted. Based on this fact, if it is assumed that the reference differential D'(Z1/Z2=1.4) can obtain a necessary and sufficient gear strength, that is, 100%, it is possible to use the conventional differential gears. In the differential gear having the numerical ratio Z1/Z2 of 16/10, it is clear from FIG. 8 that the gear strength is 87% lower than that of the reference differential gear D'. However, the gear strength reduced to this extent has been accepted as a practical strength and has been put to practical use in the existing differential device. Therefore, it is considered that even in the axially flat differential gear, if the gear strength of at least 87% with respect to the reference differential gear D', the gear strength is sufficiently secured and allowed.

From this point of view, when the relationship between the tooth number ratio Z1/Z2 and the rate of change in 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 ( According to the process of deriving the equation (10) (that is, the rate of change in gear strength with an increase in the tooth number ratio (right side of the above equation (6)) and the rate of change in gear strength due to an increase in pitch cone distance (see the above ( By calculating so that the product of (9) and the right term) becomes 87%, it can be expressed as the following equation (10').

By applying the above equation (11) to the above equation (10'), d2/PCD and gear ratio Z1/Z2 when the gear strength of the reference differential device D'is maintained at 87% or more. The relationship with and can be converted as in the following expression (13). However, in the process of calculation, except for terms expressed using variables, significant figures are calculated with 3 digits and other digits are rounded down. However, the expression will be represented by an equal sign.

In the case where the equal sign of the equation (13) is satisfied, when the number of teeth Z2 of the pinion P is 10, it can be expressed as shown in FIG. 11 (more specifically, as line L9 in FIG. 11). In this case, the region corresponding to the equation (13) is the region above the L9 line and below the L9 line in FIG. Then, the specific region (hatched region in FIG. 11) that satisfies the expression (13) and that the tooth number ratio Z1/Z2 on the right side of the L10 line in FIG. In the axially flat differential having the number of teeth Z2 of 10 and the number of teeth Z1/Z2 exceeding 2.0, Z1/Z2 capable of ensuring at least 87% gear strength with respect to the reference differential D'and This is a setting area of d2/PCD. For reference, an example in which the tooth number ratio Z1/Z2 is set to 40/10 and d2/PCD is set to 20.00% is shown as a rhombus point in FIG. 11 shows an example in which the tooth number ratio Z1/Z2 is set to 58/10 and d2/PCD is set to 16.67%, it becomes like a triangular point, and these are in the above-mentioned specific region. It is settled. As a result of performing strength analysis by simulation for these examples, a gear strength equal to or higher than the conventional one (more specifically, a gear strength of 87% or more with respect to the reference differential device D′) ) Was obtained.

Thus, the flat differential gear in the above-mentioned specific region as a whole while securing the same level of gear strength (for example, static torsion load strength) and maximum torque transmission amount as the existing non-flat differential gear in the past. It is configured as a differential gear that is sufficiently narrowed in the axial direction of the output shaft. Therefore, the differential gear has a high degree of freedom even for a transmission system that has many layout restrictions around the differential gear. Therefore, it is possible to easily and easily install the device, and it is possible to achieve effects such as a great advantage in downsizing the transmission system.

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 6), the specific region is The flat differential device in 1) can also achieve the effects associated with the structures shown in the above-described embodiments.

Although the above description (especially the description relating to FIGS. 8, 10, and 11) has been made for the differential device when the number of teeth Z2 of the pinion P is 10, the present invention is not limited to this. Absent. For example, even when the number of teeth Z2 of the pinion P is set to 6, 12, 20, the flat differential device that can achieve the above effect is as shown by the hatching in FIGS. It can be represented by a formula. 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 expression (13). If is set, the above effect can be obtained.

Further, for reference, in the case where the number of teeth Z2 of the pinion P is 12, and the number of teeth ratio Z1/Z2 is set to 48/12 and d2/PCD is set to 20.00%, the embodiment shown in FIG. 13 shows an example in which the tooth number ratio Z1/Z2 is set to 70/12 and the d2/PCD is set to 16.67% in FIG. As a result of performing strength analysis by simulation for these examples, a gear strength equal to or higher than the conventional one (more specifically, a gear strength of 87% or more with respect to the reference differential device D′) ) Was obtained. In addition, these embodiments are included in the specific area as shown in FIG.

As a comparative example, when the number of teeth Z2 of the pinion P is set to be 10 and the ratio of the number of teeth 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 set to 10 and the tooth number ratio Z1/Z2 is set to 40/10 and d2/PCD is set to 34.29% in the example of FIG. When the number of teeth Z2 of the pinion P is set to 12 in FIG. 11 and the tooth number ratio Z1/Z2 is set to 70/12 and d2/PCD is set to 27.50%, respectively. When the number of teeth Z2 of the pinion P is set to 12 at the star point of FIG. 13 in the example of the above case, the tooth number ratio Z1/Z2 is set to 48/12 and the d2/PCD is set to 34.29%. An example at that time is shown by a circle in FIG. As a result of strength analysis by simulation for these examples, a gear strength equal to or higher than the conventional one (more specifically, a gear strength of 87% or higher with respect to the reference differential device D′). It was confirmed that was not obtained. In other words, it was confirmed that the above effects could not be obtained in the examples that did not fall within the 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 scope of the invention.

For example, in the above-described embodiment, the reduction gear mechanism RG including the planetary gear mechanism is disposed adjacent to one side of the differential case DC as the input member, and the output side element (carrier 23) is provided in the differential case DC (cover portion C′). Although the power transmission from the power source is transmitted to the differential case DC via the reduction gear mechanism RG, the output side elements of the reduction gear mechanism other than the planetary gear mechanism are coupled to the differential case DC. You can

Further, instead of such a reduction gear mechanism, an input tooth portion (final driven gear, final gear) that receives power from a power source is integrally formed on the outer peripheral portion of the differential case DC or is fixed afterwards, and the input tooth portion is interposed. Alternatively, the power from the power source may be transmitted to the differential case DC.

Further, in the above-described embodiment, the lubricating oil existing around the outer end of the boss portion Cb in the mission case M is bossed by utilizing the concave grooves 8 and 8′ on the inner periphery of the boss portion Cb of the cover portions C and C′. Although the oil reservoir portion T on the inner end side of the portion Cb and further the oil reservoir portion G can be fed to the oil groove portion G, the transmission case can be replaced with or added to the concave grooves 8 and 8'. An oil supply path for guiding the scattered lubricating oil in M to the inner end of the oil reservoir T or the oil groove G may be provided at an appropriate position of the differential case DC (for example, the side wall Cs or the boss Cb). In that case, the lubricating oil scattered in the mission case M may be allowed to naturally flow into the oil supply passage, or the lubricating oil may be positively supplied by an oil pump (not shown). Good.

Further, in the above-described embodiment, with respect to the washer W, the radially inner end of the washer W is on the radially outer side than the radially inner end of the back surface portion fg of the tooth portion Sg of the side gear S, The present invention is not limited to this. For example, the radially inner end of the washer W may extend to the same position as the radially inner end of the back surface portion fg of the tooth portion Sg of the side gear S. As a result, it is possible to more effectively suppress a decrease in support rigidity of the tooth portion Sg of the side gear S, which bears a large load, on the back surface portion fg.

Further, in the above-described embodiment, the back surface of the pair of side gears S is covered with the pair of dedicated cover portions C and C′ of the differential case DC, respectively. However, in the present invention, only the back surface of the one side gear S is dedicated. You may make it provide a part. In this case, for example, a drive member (for example, the carrier 23 of the reduction gear mechanism RG) located upstream of the power transmission path is disposed on the side of the differential case DC where the dedicated cover portion is not provided, and the drive member and the differential case are arranged. You may make it couple|bond with DC. In that case, the drive member also serves as the cover portion C′, and the drive member and the differential case DC form the input member of the present invention.

Further, in the above-described embodiment, the differential device D allows the rotational speed difference between the left and right axles, but the differential device according to the present invention is also applied to the center differential that absorbs the rotational speed difference between the front wheels and the rear wheels. Can be implemented.

Cs... Side wall D... Differential device DC... Differential case (input member)
G: Oil groove H: Through hole I: Interlocking portion P: Pinion (differential gear)
PCD・・・Pitch cone distance PS・・・・・・Pinion shaft (Differential gear support)
PS'... Support shaft (differential gear support)
S: Side gear (output gear)
Sg...・Tooth portion Sj・・・・Shaft portion T・・・Oil sump portion d2・・・・Pinion shaft diameter, support shaft diameter (differential gear support portion diameter)
f. Rear of side gear (rear of output gear)

Claims (7)

An input member (DC) to which driving force is input,
A differential gear that is supported by the input member (DC) and can rotate about the input member (DC) and revolve around the rotation center of the input member (DC) as the input member (DC) rotates. (P),
A pair of output gears (S) having a tooth portion (Sg) meshing with the differential gear (P) and a shaft portion (Sj) located radially inward of the tooth portion (Sg);
A washer (W) interposed between the back surface of the tooth portion (Sg) of each output gear (S) and the input member (DC);
Of said input member (DC), said recessed in the surface facing the back (f) of the back (f) and opposing side wall portions of said output gear (S) (Cs), the output gear (S) An oil groove (G) extending from the periphery of the shaft portion (Sj) to the back surface of the washer (W),
The side wall portion (Cs) has a plurality of through holes (H) or concave holes arranged at intervals in the circumferential direction,
The oil groove (G) is arranged offset from the meshing portion (I) of the tooth portion (Sg) and the differential gear (P) in the circumferential direction of the output gear (S) , and A differential device characterized in that it is arranged so as to pass between two through holes (H) or concave holes that are adjacent to each other in the circumferential direction . An oil reservoir (T) facing the outer periphery of the shaft (Sj) of the output gear (S) is recessed in the inner periphery of the surface of the input member (DC) facing the output gear (S). The differential device according to claim 1, wherein the differential device is provided. The oil groove (G) is characterized in that is disposed in the vicinity of the engagement portion (I) in the circumferential direction of the output gear (S), differential of claim 1 or 2. The oil groove (G), when viewed in a projection plane perpendicular to the axis of rotation of said output gear (S), characterized in that it is a pair sandwiching the engagement portion (I), according to claim 1 to 3 The differential device according to claim 1. An input member (DC) to which driving force is input,
A differential gear that is supported by the input member (DC) and can rotate about the input member (DC) and revolve around the rotation center of the input member (DC) as the input member (DC) rotates. (P),
A pair of output gears (S) having a tooth portion (Sg) meshing with the differential gear (P) and a shaft portion (Sj) located radially inward of the tooth portion (Sg);
A washer (W) interposed between the back surface of the tooth portion (Sg) of each output gear (S) and the input member (DC);
The input member (DC) is recessed in the surface facing the back surface (f) of the output gear (S), and the washer (W) is removed from the periphery of the shaft portion (Sj) of the output gear (S). With an oil groove (G) extending to the back,
The oil groove (G) is arranged offset in the circumferential direction of the output gear (S) with respect to the meshing portion (I) of the tooth portion (Sg) and the differential gear (P).
The differential gear (P) is supported by the input member (DC) via a differential gear support portion (PS, PS′) supported by the input member (DC),
The number of teeth of the output gear (S) is Z1, the number of teeth of the differential gear (P) is Z2, the diameter of the differential gear support portion (PS, PS') is d2, and the pitch cone distance is PCD. And when

The filling,
And differential device you and satisfies the Z1 / Z2> 2.
The differential device according to claim 5 , wherein Z1/Z2≧4 is satisfied. The differential device according to claim 5 , wherein Z1/Z2≧5.8 is satisfied.

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