JP6649057B2 - Differential device - Google Patents

Description

  The present invention relates to a differential device that distributes and transmits the rotational force of a differential case to a pair of output shafts.

  A pinion (differential gear) disposed in the differential case, a pinion shaft (differential gear support portion) supported by the differential case and rotatably penetrating and supporting the pinion, and a gear portion meshing with the pinion are provided on the outer peripheral portion. And a pair of side gears (output gears) opposed to each other across a pinion shaft and connected to a pair of output shafts, respectively, for distributing and transmitting the rotational force of the differential case to the pair of output shafts. Conventionally, for example, at an opposing portion of a pinion and a pinion shaft, an oil sump portion facing a space adjacent to a radially inward end surface of the side gear of the pinion is provided, and between the inner peripheral shaft portion of the side gear and the output shaft. A lubricating oil is introduced between the opposing surfaces of a pair of side gears from a lubricating oil supply passage provided in the differential gear, and a part of the introduced lubricating oil can be supplied to the oil reservoir. For example, it is known as described in Patent Document 1.

JP 2014-190374 A Japanese Patent No. 4803871 JP-A-2002-364728

  However, in the conventional device, the lubricating oil introduced between the opposing surfaces of the pair of side gears easily flows radially outward on the opposing surfaces by centrifugal force, so that most of the introduced lubricating oil is relatively It flows directly to the gear portion side on the outer periphery of the side gear connected to the facing surface. For this reason, the lubricating effect on the meshing portion between the side gear and the pinion is sufficiently obtained, but the amount of oil supplied to the oil reservoir is relatively small, and the fitting portion between the pinion and the pinion shaft, that is, There is a problem that the lubricating effect on the rotary sliding portion is not sufficient.

  The problem of insufficient lubrication of the rotary sliding portion between the pinion and the pinion shaft is, for example, that the side gear has a sufficiently large diameter with respect to the pinion so that the number of teeth of the side gear can be set sufficiently larger than the number of teeth of the pinion. In particular, such as in the case where the width of the output shaft of the differential case is reduced in the axial direction, there is a possibility that the difference will appear more remarkably in a severe operating condition in which the pinion rotates at high speed.

  The present invention has been made in view of such circumstances, and has as its object to provide a differential device that can solve the above problem with a simple structure.

In order to achieve the above object, a differential device according to the present invention is a differential device that distributes and transmits the rotational force of a differential case to a pair of output shafts, and a pinion disposed in the differential case, A pinion shaft supported by a differential case and rotatably penetrating and supporting the pinion; and a gear portion meshing with the pinion on an outer peripheral portion, and opposed to each other with the pinion shaft interposed therebetween and connected to the pair of output shafts, respectively. a pair of side gears to be an oil introduction path for introducing the lubricating oil to opposite surfaces of the pair of side gears, depression and of the pinion is formed on the opposite surface of the front Symbol pair of side gears, a radial direction of said side gears And a space formed between the pinion and the pinion shaft so as to face the space. Wherein the oil reservoir communicating with each other rotatably sliding fit portion of the pinion shaft, provided with on at least one of the opposing surfaces of the opposing surfaces of the pair of side gears, said of said space and A step portion is formed at an inner peripheral end in a radial direction to form an opening edge of the recess, and the step portion is an edge in which the opposed surface perpendicular to the axial direction of the side gear and a side surface of the recess are orthogonal to each other. Jo the Ru is formed (the first feature of this).

Also preferably, the side gears include a shaft portion connected to the pair of output shafts, the gear portion radially outwardly spaced from the shaft portion, and a gear portion radially outward from an inner end of the shaft portion. A flat intermediate wall portion extending in the direction of the axis, and the step portion is formed on an outer peripheral portion of the intermediate wall portion distant radially outward from the shaft portion (this is a second feature).

  In order to achieve the above object, a differential gear according to the present invention is a differential gear that distributes and transmits the rotational force of a differential case to a pair of output shafts, wherein the differential gear is disposed in the differential case. A differential gear supporting portion supported by the differential case and rotatably penetrating and supporting the differential gear; and a gear portion meshing with the differential gear on an outer peripheral portion, and sandwiching the differential gear supporting portion. A pair of output gears facing each other and respectively connected to the pair of output shafts, an oil introduction path for introducing lubricating oil to the facing surfaces of the pair of output gears, and a facing surface of the pair of output gears And a space between the differential gear and a radially inward end face of the output gear of the differential gear, and the differential gear and the differential gear support facing the space. And the differential gear and the An oil reservoir communicating with a fitting portion slidable with respect to the dynamic gear supporting portion, and at least one of the opposing surfaces of the pair of output gears has the above-described space of the space. A stepped portion is formed at an inner peripheral end in the radial direction and constitutes an opening edge of the recess. The number of teeth of the output gear is Z1, the number of teeth of the differential gear is Z2, and the differential gear support is provided. When the diameter of the part is d2 and the pitch cone distance is PCD,

The filling,
And Z1 / Z2> 2 is satisfied (this is a third feature) .

Good The suitable (and this fourth feature) satisfies the Z1 / Z2 ≧ 4.

Preferably, Z1 / Z2 ≧ 5.8 is satisfied (this is a fifth feature).

Preferably, the step portion is formed such that an imaginary plane passing through the top surface of the step portion and orthogonal to the rotation axis of the differential case passes through the internal space or the opening edge of the oil sump portion (this is referred to as a second step). 6 ).

According to the first feature, a stepped portion formed on at least one of the opposing surfaces of the opposing surfaces of the pair of side gears, the side gears flows along the opposing surface by centrifugal force radially outward of the side gears gear Part of the lubricating oil can be effectively separated from the lubricating oil flow toward the part, and the separated lubricating oil is guided to the space adjacent to the radially inward end face of the side gear of the pinion. Since the lubricating oil can be scattered, the scattered lubricating oil can be efficiently captured and stored in an oil reservoir formed at a portion facing the pinion and the pinion shaft so as to reach the space. As a result, the lubricating oil is sufficiently supplied to the fitting portion between the pinion and the pinion shaft, that is, the rotary sliding portion, so that even in a severe operating condition in which the pinion rotates at a high speed, etc. In addition to the lubrication of the meshing part between the shaft and the side gear, the lubrication of the rotating sliding part between the pinion and the pinion shaft can be sufficiently performed, and the seizing of the meshing part and the rotating sliding part is simple. Can be effectively prevented.

According to the second feature, the side gear includes a shaft portion connected to each of the pair of output shafts, a gear portion radially outwardly separated from the shaft portion, and a flat portion extending radially outward from the inner end of the shaft portion. The intermediate gear has a large intermediate wall, so the side gear can be made as large as possible with respect to the pinion so that the number of teeth of the side gear can be set sufficiently larger than the number of teeth of the pinion, reducing the load on the pinion shaft and extending the diameter The width of the output shaft of the differential case in the axial direction is reduced. Also, if the diameter of the side gear is increased as described above, the lubricating oil flow flowing radially outward of the side gear along the facing surface (that is, the intermediate wall portion that is relatively wide in the radial direction) receives a large centrifugal force. In addition, the effect of separating and scattering the lubricating oil by the step portion from the lubricating oil flow is increased, and the scattered lubricating oil can be more effectively captured in the oil reservoir.

According to the third feature, the step formed on at least one of the opposing surfaces of the pair of output gears flows radially outward of the output gear along the opposing surface by centrifugal force. Part of the lubricating oil can be effectively separated from the lubricating oil flow toward the gear section of the output gear, and the separated lubricating oil is applied to the radially inner end face of the differential gear in the radial direction of the output gear. Since the lubricating oil can be guided to the adjacent space and scattered, the scattered lubricating oil can be efficiently captured by the oil reservoir formed in the opposed portion between the differential gear and the differential gear support so as to face the space. Can be stored. As a result, not only the lubrication of the meshing portion between the differential gear and the output gear, but also the lubrication of the rotating sliding portion between the differential gear and the differential gear supporting portion is sufficiently performed. Seizure of the sliding portion can be effectively prevented with a simple structure. Moreover, according to the third feature, the differential device as a whole is sufficiently narrowed in the axial direction of the output shaft while securing the same strength (for example, static torsional load strength) and the maximum torque transmission amount as those of the conventional device. This makes it possible to easily and easily incorporate a differential device with a high degree of freedom into a transmission system that has many layout restrictions around the differential device, and is advantageous in reducing the size of the transmission system. .
(Delete)
Further, according to the fourth and fifth features, the differential device can be more sufficiently moved in the axial direction of the output shaft while securing the same strength (for example, static torsional load strength) and the maximum torque transmission amount as those of the conventional device. Can be narrowed.

According to the sixth feature, the step portion is formed so that a virtual plane passing through the top surface of the step portion and orthogonal to the rotation axis of the differential case passes through the internal space or the opening edge of the oil reservoir portion. The lubricating oil that is separated by the step from the lubricating oil flow flowing radially outward of the side gear (output gear) along the opposing surface by force is guided into the space, and the lubricating oil scattered is effectively captured in the oil reservoir. As a result, lubricating oil can be more efficiently supplied to the rotary sliding portion between the pinion (differential gear) and the pinion shaft (differential gear support).

FIG. 2 is a longitudinal sectional view of a main part of a differential gear and a reduction gear mechanism according to an embodiment of the present invention (a sectional view taken along line 1A-1A in FIG. 2) Side view of one side in the axial direction with a part of the differential device cut away (cross-sectional view taken along line 2A-2A in FIG. 1). Side view of main part of the other side of the differential device in the axial direction (cross-sectional view taken along line 3A-3A in FIG. 1). FIG. 4 is a sectional view taken along line 4A-4A of FIG. 1, and only one cover portion C is indicated by a solid line. FIG. 5 is a cross-sectional view taken along line 5A-5A of FIG. 1, and only the other cover part C ′ and the differential case DC are indicated by solid lines. (A) is an enlarged view of the part viewed from arrow 6A in FIG. 1, and (B) is a cross-sectional view taken along the line BA-BA in (A). Longitudinal sectional view showing an example of a conventional differential device Graph showing the relationship between the gear ratio and the gear ratio when the number of teeth of the pinion is set to 10. Graph showing the relationship between the rate of change in pitch cone distance and the rate of change in gear strength A graph showing the relationship between the ratio of the number of teeth and the rate of change of the pitch cone distance when the gear strength is maintained at 100% when the number of teeth of the pinion is set to 10. Graph showing the relationship between the ratio of the number of teeth when the number of teeth of the pinion is set to 10, and the ratio of the 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 the 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 12 and the ratio of the 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 set to 20, and the ratio of the shaft diameter / pitch cone distance.

  Embodiments of the present invention will be described below based on preferred embodiments of the present invention shown in the accompanying drawings.

  First, 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 pair of left and right output shafts J connected to the pair of left and right axles, respectively. This is for driving while permitting the differential rotation of the left and right axles. For example, in a transmission case M arranged beside the engine at the front of the vehicle body, a reduction gear mechanism RG is provided adjacent to the reduction gear mechanism RG. It is housed with. Note that a conventionally known power connection / disconnection mechanism and a forward / reverse switching mechanism (both not shown) are interposed between the engine and the reduction gear mechanism RG. The rotation axis (center of rotation, center axis) L of the differential case DC coincides with the center axis of the output shaft J.

  In the illustrated example, the reduction gear mechanism RG includes a sun gear 50 that rotates in conjunction with the crankshaft of the engine, a ring gear 51 that concentrically surrounds the sun gear 50 and that is fixed to the inner wall of the transmission case M, and between the sun gear 50 and the ring gear 51. And a planetary gear mechanism having a plurality of planetary gears 52 interposed between the gears 50 and 51 and a carrier 53 rotatably supporting the planetary gears 52. 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 53 is rotatably supported by the transmission case M via a bearing (not shown). The carrier 53 is integrally rotatably coupled to one end of a differential case DC of the differential device D, and the other end of the differential case DC is rotatably supported by the transmission case M via the bearing 2. . Therefore, the combined body of the differential case DC and the carrier 53 that rotate integrally with each other is rotatably and stably supported by the transmission case M via the plurality of bearings.

  In the transmission case M, a through-hole Ma into which each output shaft J is inserted is formed, and between the inner periphery of the through-hole Ma and the outer periphery of each output shaft J, an annular sealing member 3 for sealing therebetween is provided. Is interposed. An oil pan (not shown) for storing a predetermined amount of lubricating oil facing the internal space 1 of the transmission case M is provided at the bottom of the transmission case M. In the internal space 1 of M, the movable elements of the reduction gear mechanism RG, the differential case DC, and the like are swept up and scattered around the rotating part by the rotation of the differential case DC, so that the mechanical motion parts existing inside and outside the differential case DC can be lubricated. . Note that lubricating oil is sucked by an oil pump (not shown) and is transmitted to a specific portion of the internal space 1 of the transmission case M, for example, the reduction gear mechanism RG and the differential case DC, or the transmission case around the reduction gear mechanism RG and the differential case DC. M may be forcibly scattered or scattered toward the inner wall of M.

  By the way, the ceiling wall Mt of the transmission case M has an inclined part which goes down to the upper part of the differential case DC as is clear from FIG. Part of the lubricating oil scattered in the transmission case M as described above also adheres to the ceiling wall Mt of the transmission case M, flows down the inclined inner surface Mtf of the ceiling wall Mt, and flows to the lower side. Mt is dropped from a specific portion of Mt, for example, a terminal portion of the inclined inner surface Mtf (that is, a boundary portion between the ceiling wall Mt and the horizontal plane) toward the differential case DC immediately below. Thereby, a part of the lubricating oil dropped can be taken into the oil intake holes H1 and H2 described later opened on the outer peripheral surface of the differential case DC. Even when the ceiling wall Mt of the transmission case M does not have the above-described inclined portion, a large amount of lubricant oil scatters and adheres to the ceiling wall Mt. , And a part of them can be taken into the oil intake holes H1 and H2.

  Referring also to FIGS. 2 to 6, the differential device D includes a differential case DC, a plurality of pinions (differential gears) P housed in the differential case DC, and a pinion P housed in the differential case DC. A pinion shaft (differential gear supporting portion) PS rotatably supported, and a pair of left and right side gears housed in a differential case DC and engaged with the pinion P from both left and right sides and connected to a pair of left and right output shafts J, respectively. Output gear) S. The differential case DC has a short cylindrical case main body 4 that supports the pinion shaft PS so as to be able to rotate together with the pinion shaft PS, and a pair of right and left that respectively cover the outer sides of both side gears S and rotate integrally with the case main body 4. And the case body 4 forms the outer peripheral wall of the differential case DC.

  The pinion shaft PS is arranged so as to pass through the rotation axis L of the differential case DC in the differential case DC, and is provided in a pair of through-support holes 4 a provided on the case main body 4 on one diameter line of the case main body 4. , Both ends of the pinion shaft PS are inserted so as to be able to be inserted and removed, respectively. The pinion shaft PS is fixed to the case main body 4 with a retaining pin 5 that penetrates one end of the pinion shaft PS and is inserted into the case main body 4. In a state where the pinion shaft PS is fixed to the case main body 4, both outer end surfaces PSf of the pinion shaft PS pass through an opening DCo in the outer peripheral surface of the differential case DC (that is, the outer end opening of the through-support hole 4a) to form the internal space of the transmission case M I am facing 1.

  In the present embodiment, the number of the pinions P is two, and the pinion shaft PS is formed in a linear rod shape extending along one diameter line of the case main body 4, and the two pinions P are supported at both ends of the pinion shaft PS. Although an example is shown in which the pinion P is provided, three or more pinions P may be provided. In this case, the pinion shaft PS is formed in a cross bar shape that is radially branched from the rotation axis L of the differential case DC in three or more directions corresponding to three or more pinions P (for example, in the case of four pinions P, The pinion P is formed at each tip of the pinion shaft PS, and the case body 4 is divided into two parts, and the pinion shaft PS is sandwiched between the divided elements. To do.

  Further, the pinion P may be directly fitted to the pinion shaft PS as shown in the figure, or may be fitted via a bearing means (not shown) such as a bearing bush. In the former case, the fitting portion between the pinion shaft PS and the pinion P becomes a rotary sliding portion rs between the pinion shaft PS and the pinion P. In the latter case, the bearing means is used. It becomes the rotary sliding part rs. The pinion shaft PS may have a shaft shape having a substantially uniform diameter over the entire length as shown in the illustrated example, or may have a stepped shaft shape.

  In this embodiment, the pinion P and the side gear S are formed as bevel gears, and the entirety including the teeth is formed by plastic working such as forging. For this reason, the teeth can be formed with an arbitrary ratio of the number of teeth with high precision without being restricted by machining such as when cutting the teeth of the pinion P and the side gear S. Note that another gear may be used 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.

  The pair of side gears S are located at a cylindrical shaft portion Sj at which the inner ends of the pair of output shafts J are spline-fitted 6, and at a position radially outward of the differential case DC from the shaft portion Sj. An annular wall portion Sg meshing with the pinion P and an intermediate wall portion formed in a flat ring plate shape orthogonal to the axis L of the output shaft J and integrally connecting the shaft portion Sj and the tooth portion Sg. Sw. Although the shaft portion Sj of the side gear S is rotatably fitted directly to the boss portion Cb of the cover portions C and C 'in the illustrated example, it may be fitted via a bearing.

  In the middle wall portion Sw of at least one of the left and right side gears S (both in the present embodiment), a through oil passage 15 that opens at both ends on the inner side surface and the outer side surface of the middle wall portion Sw and crosses the middle wall portion Sw is provided. It is formed.

  The intermediate wall portion Sw of the side gear S has a width t1 in the radial direction of the intermediate wall portion Sw larger than the maximum diameter d1 of the pinion P, and the maximum thickness of the intermediate wall portion Sw in the axial direction of the output shaft J. The thickness t2 is formed so as to be smaller than the effective diameter d2 of the pinion shaft PS, that is, the outer diameter (see FIG. 1). Thereby, as will be described later, the diameter of the side gear S can be made sufficiently large 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 in the axial direction of the output shaft J, The side gear S can be made sufficiently thin.

  Further, one of the pair of left and right cover portions C and C ′ in the differential case DC, for example, the cover portion C on the opposite side to the reduction gear mechanism RG is formed separately from the case body portion 4 and is formed separately from the case body portion 4. It is detachably connected to the part 4 with a bolt B. As the connecting means, various connecting means other than the screw means, for example, welding means and caulking means can be used. In the illustrated example, the cover C 'on the other side is formed integrally with the case body 4 and is coupled to the carrier 53 of the reduction gear mechanism RG. Similarly, it may be formed separately from the case main body 4 and connected to the case main body 4 with bolts B or other connecting means.

  Each of the cover portions C and C ′ has a cylindrical boss portion Cb that surrounds the shaft portion Sj of the side gear S concentrically and rotatably fits and supports, and an outer surface thereof is orthogonal to the rotation axis L of the differential case DC. And a plate-shaped side wall Cs integrally connected to the inner end of the boss Cb in the axial direction as a flat surface to be formed. The side walls Cs of the covers C and C ′ are arranged in the axial direction of the output shaft J. It is arranged to fit within the width of the case body 4. This suppresses the side wall portion Cs of the cover portions C and C 'from protruding outward in the axial direction from the end face of the case main body portion 4, so that the width of the differential device D in the axial direction of the output shaft J is suppressed. This is advantageous for narrowing.

  In addition, the back surface of at least one of the intermediate wall portion Sw and the tooth portion Sg (in the illustrated example, the intermediate wall portion Sw) of the side gear S is disposed via the washer W by the inner side surface of the side wall portion Cs of the cover portions C and C ′. It is rotatably supported. Incidentally, such a washer W may be omitted, and the back surface of the side gear S may be directly supported rotatably by the inner surface of the side wall portion Cs.

  Thus, the side gear S of the present embodiment has a shaft portion Sj between the inner shaft portion Sj and the tooth portion Sg of the outer peripheral side gear S radially outwardly spaced from the shaft portion Sj. It has a flat ring-plate-shaped intermediate wall portion Sw that integrally connects with the tooth portion Sg, and the radial width t1 of the intermediate wall portion Sw is longer than the maximum diameter d1 of the pinion P. Therefore, the side gear S can have a sufficiently large diameter with respect to 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. Therefore, when transmitting torque from the pinion P to the side gear S, The load on the pinion shaft PS can be reduced, and the effective diameter d2 of the pinion shaft PS can be reduced, and the pinion P can be narrowed (reduced in diameter) in the axial direction of the output shaft J.

The support thus with load bearing of the pinion shaft P S is reduced, the reaction force is reduced according to the side gears S, moreover the back of the intermediate wall portion Sw side gears S cover section C, and the side wall portion Cs of C ' Therefore, it is easy to secure the necessary rigidity of the side gear S even when the thickness of the intermediate wall portion Sw is reduced. That is, it is possible to sufficiently reduce the thickness of the intermediate wall portion Sw of the side gear S while securing the support rigidity for the side gear S. Furthermore, in the present embodiment, the maximum thickness t2 of the intermediate wall portion Sw of the side gear S is formed smaller than the effective diameter d2 of the pinion shaft PS capable of reducing the diameter. Further thinning can be achieved. Moreover, since the side wall portion Cs of the cover portions C and C 'is formed in a plate shape whose outer surface is a flat surface orthogonal to the rotation axis L of the differential case DC, the thickness of the side wall portion Cs itself is also reduced.

  As a result, the differential device D is required to be sufficiently narrow as a whole in the axial direction of the output shaft J while ensuring the same strength (for example, static torsional load strength) and the maximum torque transmission amount as the conventional device. Is possible, the differential device D can be easily and easily incorporated with a high degree of freedom into a transmission system having many layout restrictions around the differential device D, and the transmission system can be downsized. It is very advantageous in doing so.

  By the way, the side gear Cs of the side wall portion Cs of the one cover portion C has a first predetermined region including a region overlapping with the pinion P in a side view when viewed from the outside of the output shaft J in the axial direction (that is, as viewed in FIG. 2). And a lightening portion 8 for exposing the back surface of the side gear S to the outside of the differential case DC in a second predetermined region that does not overlap the pinion P in the side view, and an oil holding portion. 7 and a connecting arm 9 extending in the circumferential direction of the case main body 4 and extending in the radial direction of the case main body 4 to connect the boss Cb and the case main body 4 together. In other words, the side wall portion Cs, which is basically in the shape of a disc, of the cover portion C is formed by forming a plurality of cutout portions 8 in the side wall portion Cs with a gap in the circumferential direction. The oil retaining portion 7 is formed on one side and the connecting arm portion 9 is formed on the other side with the cutout portion 8 sandwiched in the circumferential direction.

  The structure of the side wall portion Cs of the cover portion C, in particular, the oil holding portion 7 allows the lubricating oil, which tends to move radially outward due to the centrifugal force due to the rotation of the differential case DC, to the oil holding portion 7 and the case body. The lubricating oil can be easily retained in the space covered with the portion 4 and the pinion P and the peripheral portion of the pinion P can be easily retained.

  In this embodiment, as shown in FIG. 3, the lightening portion 8 is also formed on the side wall portion Cs of the other cover portion C 'as in the case of the one cover portion C. However, in the side wall portion Cs of the other cover portion C ′, the oil holding portion 7 and the connecting arm portion 9 are formed integrally with the case main body portion 4. The side wall portion Cs of one of the cover portions C and C 'is formed of a disk having no lightened portion (therefore covers the intermediate wall portion Sw of the side gear S and the entire back surface of the tooth portion Sg). It may be formed in a shape.

  Meanwhile, in the differential case DC, the opposing portion between the pinion P and the pinion shaft PS faces the space 60 adjacent to the end face Pfi of the pinion P on the radially inward side of the side gear S as shown in FIG. An oil sump 61 capable of catching and accumulating lubricating oil scattered in the space 60 is provided in a fitting portion (that is, a rotary sliding portion rs) between the pinion P and the pinion shaft PS that is slidable with respect to each other. 61 are formed so as to directly communicate with each other. In the illustrated example, the oil reservoir 61 is formed by performing an annular chamfer on an inner peripheral surface of the pinion P on a radially inner side edge of the side gear S. The space 60 includes a recess Swa formed on the opposing surface of the pair of left and right side gears S (in the illustrated example, an inner surface near the tooth portion Sg of the intermediate wall portion Sw of each side gear S), and a diameter of the side gear S of the pinion P. An edge-shaped stepped portion E is formed so as to be sandwiched between the end surface Pfi on the inner side in the direction and located at the inner peripheral end of the space 60 in the radial direction of the side gear S and constituting the opening edge of the depression Swa. Are formed on opposing surfaces of the pair of left and right side gears S.

  That is, on the opposing surfaces of the pair of left and right side gears S (in the illustrated example, the inner surfaces of the intermediate wall portions Sw of the side gears S near the teeth Sg), the radial direction is transmitted along the inner surface of the intermediate wall portion Sw by centrifugal force. A part of the lubricating oil that is separated from the outwardly flowing lubricating oil flow is guided to the space 60, and an edge-shaped annular step E that can be scattered is formed. The top surface of the step portion E is continuous with the inner surface of the intermediate wall portion Sw on the inner side of the step portion E in the radial direction of the side gear S.

  Incidentally, the side gear S can be manufactured by forging or other various forming methods. For example, when the side gear S is forged, the outer peripheral surface (step surface) connected to the top surface of the step E and the step E is formed. ) May form roundness due to so-called forging. In that case, a sharp edge can be formed between the top surface and the outer peripheral surface (step surface) by performing machining on the outer peripheral surface (step surface).

  In a state where the vehicle rotates in the forward direction and the differential case DC is driven to rotate in the normal rotation direction R, the lubricating oil flows through the oil passage 15 of the side gear S and the diameter of the inner surface of the intermediate wall portion Sw as described later. The lubricating oil supplied near the intermediate portion in the radial direction travels on the inner surface of the intermediate wall portion Sw due to centrifugal force, that is, the lubricating oil is supplied to the vicinity of the intermediate portion in the radial direction. Attempts to flow to the Sg side, and reaches the step portion E in the middle.

Thus, the step portion E effectively separates a part of the lubricating oil from the lubricating oil flow flowing radially outward along the inner surface of the intermediate wall portion Sw by centrifugal force at the edge portion of the step portion E. Thus, a part of the lubricating oil can be guided to the space 60 and scattered in the space 60. As a result, the scattered lubricating oil can be efficiently captured and stored in the oil reservoir 61 facing the space 60, so that the rotary sliding portion rs between the pinion P and the pinion shaft PS passes through the oil reservoir 61 to be lubricated. Oil is adequately supplied. At the same time, the remaining portion of the lubricating oil flow flows toward the tooth portion Sg of the side gear S along the step surface of the step portion E without scattering from the edge portion of the step portion E, and meshing between the tooth portion Sg and the pinion P. The part can be lubricated sufficiently. Thus, even in a severe operating condition in which the pinion P rotates at a high speed due to a reduction in the diameter of the pinion P, the lubrication of the meshing portion and the rotational sliding portion between the pinion P and the pinion shaft PS can be achieved. Lubrication to rs is sufficiently performed together.

  In addition, the edge-shaped step portion E of the present embodiment passes through the top surface of the step portion E and the imaginary plane fe orthogonal to the rotation axis L of the differential case DC passes through the internal space 61s or the opening edge 61e of the oil reservoir 61. Formed. Thereby, the lubricating oil separated from the lubricating oil flow at the stepped portion E and guided to the space 60 and scattered can be effectively captured by the oil sump 61 and easily stored in the oil sump 61. Therefore, lubricating oil can be more efficiently supplied to the rotary sliding portion rs between the pinion P and the pinion shaft PS. Further, in the differential device D of the present embodiment, the side gear S has a sufficiently large diameter with respect to the pinion P in order to reduce the width of the differential case DC in the axial direction of the output shaft J as described above. However, due to the increase in the diameter of the side gear S, the lubricating oil flow flowing radially outward along the inner surface of the intermediate wall portion Sw receives a greater centrifugal force. Therefore, the effect of partly separating and scattering the lubricating oil from the lubricating oil flow at the step portion E is increased, so that the scattered lubricating oil can be more effectively captured in the oil reservoir 61.

  By the way, in this embodiment, both outer end surfaces PSf of the pinion shaft PS pass through the opening DCo on the outer peripheral surface of the differential case DC (that is, the outer end opening of the through support hole 4a of the case main body 4) as described above. Although facing the internal space 1, at both ends of the pinion shaft PS, as shown in FIG. 6, a bottomed hollow portion T having one end opened and the other end closed is formed on both outer end surfaces of the pinion shaft PS. It is formed so as to be recessed from PSf. The bottomed hollow portion (hollow cylindrical portion) T is formed in the shape of a bottomed cylindrical hole extending in the axial direction of the pinion shaft PS, and the depth of the hole of the bottomed hollow portion T is determined by the pinion shaft PS and the pinion shaft. It is set deep so as to extend further inward past the rotary sliding portion rs between P. Therefore, the bottomed hollow portion T has an arrangement in which at least the intermediate portion of the bottomed hollow portion T is concentrically surrounded by the rotary sliding portion rs.

  A plurality of oil guide holes G that can guide the lubricating oil stored in the bottomed hollow portion T to the rotary sliding portion rs by centrifugal force are provided on the peripheral wall of the bottomed hollow portion T of the pinion shaft PS. The oil guide holes G are formed so as to be inclined from the inner periphery to the outer periphery of the peripheral wall of the bottomed hollow portion T toward the outside in the axial direction of the pinion shaft PS so as to cross the peripheral wall. The plurality of oil guide holes G are formed so as to be arranged at intervals in the longitudinal direction of the bottomed hollow portion T. Further, an array group of such oil guide holes G is formed by the bottomed hollow portion T. Are arranged radially from the central axis of the bottomed hollow portion T at intervals in the circumferential direction. The open end Gi of the oil guide hole G to the inner periphery of the peripheral wall of the bottomed hollow portion T is separated from the bottom surface b of the bottomed hollow portion T in the longitudinal direction of the bottomed hollow portion T. The hollow portion Ta of the hollow portion T, which is closer to the bottom surface b than the open end Gi, can function as an oil reservoir capable of storing a required amount of lubricating oil.

  According to such a special structure of the bottomed hollow portion T in the pinion shaft PS, when the engine is stopped, the lubricating oil scattered in the transmission case M due to the operation of the differential device D or the like before the stop or the transmission case of the transmission case M is stopped. The lubricating oil adhering to the ceiling wall Mt and dripping from the ceiling wall Mt can be stored and held in the bottomed hollow portion T that is in the upward posture when stopped. Then, the lubricating oil stored in the bottomed hollow portion T is promptly supplied to the rotary sliding portion rs between the pinion P and the pinion shaft PS from the oil guide hole G by centrifugal force when the operation of the differential device D is started. can do. In this case, the oil guide hole G extends from the inner periphery of the peripheral wall of the bottomed hollow portion T toward the outer periphery in the axially outward direction of the pinion shaft PS. While the lubricating oil stored and held in the portion T can be effectively suppressed, the stored lubricating oil can be removed from the rotary sliding portion rs from the oil guide hole G using centrifugal force when the differential device D starts operating. Can be supplied efficiently.

  In addition, depending on the stop position of the differential device D, the bottomed hollow portion T may be in a horizontal position, and it may be difficult to store the lubricating oil. However, in most cases, any one of the plurality of bottomed hollow portions T may be used. Is in the upward vertical posture or the inclined posture, and the lubricating oil scattered in the transmission case M or the ceiling wall Mt of the transmission case M is dropped into the bottomed hollow portion T in the upward vertical posture or the inclined posture. Lubricating oil can be stored.

  Further, in the present embodiment, the lubricating oil in the transmission case M, for example, dripping from the ceiling wall Mt of the transmission case M, penetrates through the inside and outside of the case main body 4 on the outer peripheral wall of the differential case DC, that is, the case main body 4. Each of the plurality of first and second oil intake holes H1 and H2 capable of taking lubricating oil into the differential case DC is formed in a circular cross section and at intervals in the circumferential direction of the differential case DC. Moreover, the first and second oil intake holes H1 and H2 are located at positions offset from the intermediate point m of two adjacent pinions P in the circumferential direction of the differential case DC toward the respective pinions P as shown in FIG. Be placed.

  When viewed on a projection plane orthogonal to the rotation axis L of the differential case DC, each of the oil intake holes H1 and H2 has an axis extending from the inner opening end Hi to the outer opening end of the oil intake holes H1 and H2. It is formed to incline toward Ho in the rotation direction R front side of the differential case DC when the vehicle advances. In addition, each of the pinions P includes a first imaginary line L1 connecting one end in the circumferential direction of the inner opening end Hi of each of the oil intake holes H1 and H2 and the rotation axis L, as viewed on the projection plane, and each of the oils. The intake holes H1 and H2 are arranged outside a region A sandwiched between a second imaginary line L2 connecting the other end in the circumferential direction of the inner open end Hi and the rotation axis L.

  Further, in the present embodiment, as described above, since the pinion P has a flat differential structure capable of sufficiently reducing the diameter of the pinion P with respect to the side gear S, the oil intake holes H1 and H2 are arranged on the pinion P side from the intermediate point m in the circumferential direction of the differential case DC. Even if the pinion P is arranged offset (that is, closer to the pinion P), the pinion P can be easily arranged outside the region A corresponding to the inner opening ends Hi of the oil intake holes H1 and H2. In other words, the pinion P is formed to have a sufficiently small diameter with respect to the side gear S so that even if the oil intake holes H1 and H2 are offsetly arranged on the pinion P side, the pinion P can be easily arranged outside the area A. Is done.

  According to the special configuration of the oil intake holes H1 and H2 in the outer peripheral wall of the differential case DC, when the vehicle is moving forward and the differential case DC is rotating at a relatively low speed in the normal rotation direction R, the transmission case M The lubricating oil dropped from the ceiling wall Mt can be efficiently taken into the differential case DC through the plurality of first and second oil intake holes H1 and H2 inclined in a specific direction (that is, a direction that can be efficiently taken into the differential case DC). Becomes In addition, among the oil intake holes H1 and H2, the first oil intake hole H1, which is arranged on the pinion P side from the intermediate point m on the front side in the normal rotation direction R of each pinion P, is taken into the differential case DC and dropped. Lubricating oil can be efficiently supplied to the meshing portion between the pinion P and the side gear S near the first oil intake hole H1. On the other hand, the second oil intake hole H2, which is arranged on the pinion P side from the intermediate point m behind the forward rotation direction R of each pinion P, allows the lubricating oil taken in and dropped into the differential case DC to the pinion P. The pinion shaft PS can be supplied to the outer peripheral portion of the pinion shaft PS near the rotation center L of the differential case DC without obstruction (that is, without the pinion P acting as an obstacle and standing on the lubricating oil path), from which the lubricating oil is centrifugally driven. As it travels along the outer peripheral surface of the pinion shaft PS to the outer end side, that is, the rotary sliding portion rs between the pinion shaft PS and the pinion P, the lubricating oil can be efficiently supplied also to the rotary sliding portion rs. It is. As a result, the lubricating oil dropped from the ceiling wall Mt of the transmission case M is efficiently supplied not only to the meshing portion of the pinion P with the side gear S but also to the rotary sliding portion rs with the pinion shaft PS. Lubrication efficiency can be increased as a whole. In addition, a part of the lubricating oil taken in and dropped into the differential case DC from the oil intake holes H1 and H2 also reaches the inner surface of the intermediate wall portion Sw of the side gear S and travels along the inner surface of the intermediate wall portion Sw. Due to the centrifugal force, it flows to the radially outward side, that is, to the tooth portion Sg side.

  By the way, the washer W is interposed between the inner surface of the side wall Cs of the cover portions C and C 'and the outer surface of the side gear S in the differential case DC as described above. In order to position and maintain the lubricating oil path to the path 15 at an appropriate fixed position, at least one of the opposing surfaces of the inner surface of the side wall portion Cs and the outer surface of the side gear S (the outer surface of the side gear S in the illustrated example). 5), an annular washer holding groove 16 is formed, and a washer W is fitted into the washer holding groove 16. Then, the relative positions of the washer W and the penetration oil passage 15 are set such that the inner peripheral portion of the washer W faces the opening of the penetration oil passage 15 to the outside surface of the intermediate wall portion Sw. Thereby, the flow of the lubricating oil that tends to flow radially outward due to centrifugal force in the gap between the inner surface of the side wall portion Cs of the cover portions C and C ′ and the outer surface of the side gear S is suppressed by the washer W, Since it can be guided from the inner peripheral side of the washer W to the inward side of the side gear S via the penetrating oil passage 15, it passes through the penetrating oil passage 15 and travels radially outward on the inner side surface of the side gear S to the tooth portion Sg side. The amount of lubricating oil going can be increased.

  4 and 5, the inner surface of the side wall portion Cs of the cover portions C and C 'is connected to the washer W and the through oil passage 15 from the periphery of the lightening portion 8 when the differential case DC rotates. An oil guide groove 17 that can guide the inflow of lubricating oil is provided in a recessed manner. The oil guide groove 17 is oblique to the tangential direction of the oil holding portion 7 from the peripheral edge of the lightening portion 8 (more specifically, toward the center axis L side in the forward rotation direction of the differential case DC, which will be described later). A first inner wall 17a extending inclining, a second inner wall 17b extending in a tangential direction of the oil holding portion 7 from a peripheral edge of the lightening portion 8, and a rear wall connecting the inner ends of both inner walls 17a, 17b. 17c form a substantially triangular shape. Moreover, the inner inner groove 17i of the oil guide groove 17 facing the inner wall 17c always overlaps with a part of the washer W when viewed on a projection plane orthogonal to the rotation axis L of the differential case DC, and the rotation of the differential case DC. Accordingly, the through oil passage 15 is disposed at a position where it can temporarily overlap with the opening on the outer side surface of the intermediate wall portion Sw.

  Thus, when the differential case DC is rotated in the normal rotation direction R by the rotational force transmitted from the engine via the reduction gear mechanism RG to advance the vehicle, the differential case DC scatters around the differential case DC in the transmission case M. The lubricating oil flows into the oil holding portion 7 (that is, the oil guide groove 17) from the periphery of the lightening portion 8 due to a relative speed difference between the lubricating oil and the rotating cover portions C and C '. In this case, the lubricating oil that has flowed into the oil guide groove 17 is efficiently collected by the guide action of the first inner wall 17a toward the innermost groove 17i at the rearmost position of the oil guide groove 17 in the rotation direction. From the inner groove 17i to the washer W and the through oil passage 15 side. The lubricating oil that has passed through the oil passage 15 and reached the inner surface of the intermediate wall portion Sw of the side gear S flows radially outward through the inner surface of the intermediate wall portion Sw by centrifugal force as described above. I do. A series of oil passages extending from the lightening portion 8 to the through oil passage 15 through the oil guide groove 17 supplies lubricating oil to the inner side surface of the intermediate wall portion Sw of the side gear S (that is, the opposing surfaces of the pair of side gears S). The oil introduction path Os to be introduced is configured.

  Further, the cover portions C and C ′ of the present embodiment have an oil guiding slope f at the peripheral edge of the lightening portion 8 that can guide the inflow of lubricating oil into the case body 4 during rotation of the differential case DC. Have. The inlet of the oil guide groove 17 is open to the oil guide slope f. The oil guide slope f is viewed in a cross section (see the partial cross-sectional views of FIGS. 4 and 5) crossing the oil holding portion 7 and the connecting arm portion 9 in the circumferential direction of the differential case DC. The oil holding portion 7 and the connecting arm portion 9 are each formed with a slope inclined toward the center in the circumferential direction from the outer surface to the inner surface of each of the portions 9. Thus, according to the oil guiding action of the oil guiding slope f, the lubricating oil can smoothly flow from the outside to the inside of the cover portions C and C 'with the rotation of the differential case DC. Lubricating oil can efficiently flow in from the inlet opening on the oil guide slope f.

  Next, the operation of the above embodiment will be described. When the differential device D of this embodiment receives rotational force from the engine via the reduction gear mechanism RG to the differential case DC, the pinion P does not rotate around the pinion shaft PS, and the rotational axis L of the differential case DC together with the differential case DC. When revolving around, the left and right side gears S are driven to rotate at the same speed, and the driving force is transmitted evenly to the left and right output shafts J. Further, when a rotational speed difference occurs between the left and right output shafts J due to turning of the automobile or the like, the pinion P revolves while rotating, thereby allowing differential rotation from the pinion P to the left and right side gears S. The rotational driving force is transmitted. The above is the same as the operation of the conventionally known differential.

  By the way, when the power of the engine is transmitted to the left and right output shafts J via the reduction gear mechanism RG and the differential device D in the forward running state of the automobile, the rotation of each movable element of the reduction gear mechanism RG and the differential case DC is accompanied. Although the lubricating oil scatters vigorously at various points in the transmission case M, a part of the scattered lubricating oil flows into the inside of the cover portions C and C 'from the lightening portion 8 as described above.

  In this case, the lubricating oil that has flowed into the oil guide groove 17 formed on the inner side surface of the side wall portion Cs of the cover portions C and C ′ is directed to the inner depth groove portion 17i by the guide action of the first inner side wall 17a as described above. And is efficiently collected therefrom, and is efficiently guided to the washer W and the through oil passage 15 side therefrom. Therefore, the lubricating effect on the washer W can be enhanced, and the amount of lubricating oil that passes through the through oil passage 15 and reaches the inner side surface of the intermediate wall portion Sw of the side gear S can be sufficiently ensured. The lubricating oil that has reached flows radially outward along the inner surface of the intermediate wall portion Sw due to centrifugal force as described above, and a part of the lubricating oil flow is separated from the edge-shaped step portion E into the space. The oil is scattered to the oil reservoir 60 and is captured and stored in the oil reservoir 61 to lubricate the rotary sliding portion rs between the pinion shaft PS and the pinion P, but the rest of the lubricating oil flow travels along the step surface of the step E. The gear reaches the tooth portion Sg of the side gear S, and lubricates the meshing portion between the tooth portion Sg and the pinion P. As a result, even when the tooth portion Sg of the side gear S is far away from the output shaft J due to the increase in the diameter of the side gear S or in a severe operating condition in which the pinion P rotates at a high speed, the above-described meshing portion and the rotary sliding portion rs are not removed. Since the lubricating oil can be supplied efficiently, seizure of the meshing portion and the rotary sliding portion rs can be effectively prevented.

  Further, in the present embodiment, since the bottom end hollow portion T which is open to the internal space 1 of the transmission case M and can function as an oil reservoir is recessed in the outer end face PSf of the pinion shaft PS, the engine stops when the engine stops. The lubricating oil scattered in the transmission case M due to the operation of the preceding differential device D and the like and the lubricating oil adhering to the ceiling wall Mt of the transmission case M and dripping from the ceiling wall Mt are provided with the bottomed hollow portion in the upward posture. It can be stored and held in T. Therefore, the lubricating oil stored in the bottomed hollow portion T is supplied from the oil guide hole G in the peripheral wall of the bottomed hollow portion T by centrifugal force between the pinion P and the pinion shaft PS when the operation of the differential device D is started. Since it can be quickly supplied to the rotary sliding portion rs, the rotary sliding portion rs between the pinion P and the pinion shaft PS can be sufficiently lubricated without delay from the beginning of the operation.

  Further, in the present embodiment, a plurality of first and second oil intake holes H1 and H2 are formed on the outer peripheral wall of the differential case DC so that the lubricating oil dropped from the ceiling wall Mt of the transmission case M can be taken into the differential case DC. The formation positions and directions of the first and second oil intake holes H1 and H2 are as described above. Therefore, when the vehicle is moving forward and the differential case DC is rotating at a relatively low speed in the normal rotation direction R, the lubricating oil dripping from the ceiling wall Mt of the transmission case M receives the first and second oil intake holes H1, The first oil intake hole H1 that can be efficiently taken into the differential case DC through H2 and that is offset toward the pinion P side from the intermediate point m between the adjacent pinions P in the forward direction R of each pinion P and The lubricating oil taken into the differential case DC can be efficiently supplied to the meshing portion between the pinion P and the side gear S near the first oil intake hole H1. On the other hand, the second oil intake hole H2, which is disposed behind the pinion P in the forward rotation direction R and offset from the intermediate point m to the pinion P side, allows the lubricating oil taken in and dropped into the differential case DC to pass through the pinion P The lubricating oil can be supplied to the outer peripheral portion of the pinion shaft PS near the rotation center L of the differential case DC without being disturbed by the lubricating oil flowing from the outer peripheral surface of the pinion shaft PS to the outer end side by centrifugal force. Also, it is possible to efficiently supply the lubricating oil to the rotary sliding portion rs between the pinion shaft PS and the pinion P. As a result, the lubricating oil dropped from the ceiling wall Mt of the transmission case M is efficiently supplied not only to the meshing portion of the pinion P with the side gear S but also to the rotary sliding portion rs with the pinion shaft PS. As a result, the lubrication efficiency can be further increased.

  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 oil level of the lubricating oil stored in the inner bottom of the transmission case M. In particular, when the vehicle is immersed below the oil level, the vehicle is stored in the differential case DC from the first and second oil intake holes H1 and H2 while the differential case DC is rotating in the normal rotation direction R when the vehicle is moving forward. Since the lubricating oil thus obtained can be efficiently scooped up, each part in the differential case DC can be more efficiently lubricated.

By the way, a conventional differential device as exemplified in Patent Documents 2 and 3 described above (in particular, a differential case is provided with a pinion (differential gear) and a pair of side gears (output gears) meshed with the pinion (differential gear)). In the conventional differential device, the number of teeth Z1 of the side gear (output gear) and the number of teeth Z2 of the pinion (differential gear) are usually 14 × 10, 16 × 10 or 13 shown in Patent Document 3, for example. × 9 is used. In this case, the ratio of the number of teeth Z1 / Z2 of the output gear to the differential gear is 1.4, 1.6, and 1.44, respectively. Further, in a conventional differential device, there are known other combinations of the number of teeth Z1 and Z2, for example, 15 × 10, 17 × 10, 18 × 10, 19 × 10, or 20 × 10. 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 power transmission devices accompanied by layout restrictions around the differential device is increasing, and the differential device is sufficiently narrowed in the axial direction of the output shaft while securing the gear strength of the differential device (ie, Flattening) is required in the market. However, the conventional existing differential has a structure that is wide in the axial direction of the output shaft, as is clear from the combination of the above-mentioned tooth number ratios. It is in.

  Therefore, a configuration example of the differential device D capable of sufficiently narrowing (ie, flattening) the differential device in the axial direction of the output shaft while securing the gear strength of the differential device will be described from a viewpoint different from the above-described embodiment. , Are specified below. Note that 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 embodiment described with reference to FIGS. The reference numerals are the same as those in the above embodiment, and the description of the structure is omitted.

First, the basic concept for sufficiently narrowing (ie, flattening) the differential device D in the axial direction of the output shaft J will be described with reference to FIG.
[1] The ratio of the number of teeth Z1 / Z2 of the pinion P, that is, the side gear S, that is, the output gear to the differential gear, is made larger than that of the conventional differential. (Thus, while the gear module (and thus the tooth thickness) decreases and the gear strength decreases, the pitch circle diameter of the side gear S increases and the transmission load at the gear meshing portion decreases and the gear strength increases. As a whole, the gear strength decreases as described later.)
[2] The pitch cone distance PCD of the pinion P is increased more than the pitch cone distance of the conventional differential. (Thus, the number of gear modules increases, the gear strength increases, and 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 like this.)
Therefore, the amount of reduction in gear strength due to [1] is equal to the amount of increase in gear strength according to [2], or the amount of reduction in gear strength according to [2] is greater than the amount of reduction in gear strength according to [1]. By setting the tooth number ratio Z1 / Z2 and the pitch cone distance PCD so that the amount of increase in strength is greater, the gear strength can be made equal to or greater than that of a conventional differential device as a whole.

Next, the manner in which the gear strength changes based on the above [1] and [2] will be specifically verified by mathematical expressions. The verification will be described in the following embodiment. First, the differential 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". The "rate of change" is the rate of change of various variables when the reference differential D 'is used as a reference (that is, 100%).
[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 meshing portion is F, 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)
Becomes
The module of the reference differential D 'is 2PCD · sin {tan ^-1 (7/5)} / 14
Becomes

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

  Further, the section 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, and 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 section modulus of the tooth portion, and hence 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 indicated by L1 in FIG. 8 when the number of teeth Z2 of the pinion P is 10, which indicates that the gear strength decreases as the number of teeth Z1 / Z2 increases due to a decrease in the number of modules.

  By the way, according to the general formula of the bevel gear described above, 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 F based on the torque transmission distance PD _1/2 is F = 2TO / PD ₁ . Thus, the side gears S standard differential D ', if constant torque TO, the transmitted load F and pitch circle diameter PD ₁ is the inverse relationship. Further, since the change rate of the transmission load F is inversely proportional to the change rate of the gear strength, the change rate of the gear strength is the pitch circle diameter PD _1.
Change rate.

As a result, the change rate of the pitch circle diameter PD _1, using the equation becomes: (5) formula (4).

  Equation (5) is indicated by L2 in FIG. 8 when the number of teeth Z2 of the pinion P is 10, and it can be seen that the gear strength increases by reducing the transmission load as the number of teeth Z1 / Z2 increases.

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

Equation (6) is indicated by L3 in FIG. 8 when the number of teeth Z2 of the pinion P is 10, which indicates that the gear strength decreases as the number of teeth Z1 / Z2 increases.
[2] When the pitch cone distance PCD of the pinion P is increased beyond the pitch cone distance of the reference differential device D ′, if the PCD before the change is PCD1 and the PCD after the change is PCD2, before and after the change of the PCD Is given by (PCD2 / PCD1) from the general formula of the bevel gear described above, when the number of teeth is fixed.

On the other hand, the change rate of the gear strength of the side gear S is equivalent to the square of the module change rate, as is clear from the process of deriving the equation (3).
Gear strength change rate due to module increase = (PCD2 / PCD1) ² (7)
Equation (7) is indicated by L4 in FIG. 9, and it can be seen from this that the gear strength increases as the pitch cone distance PCD increases as the number of modules increases.

When the pitch cone distance PCD is increased beyond the pitch cone distance PCD1 of the reference differential D ', the transmission load F is reduced. As a result, the change rate of the gear strength is reduced by the pitch circle as described above. equal to the rate of change of the diameter PD _1. Also there is a proportional relationship with the pitch diameter PD ₁ and a pitch cone distance PCD side gear S. Therefore,
Gear strength change rate due to transmission load reduction = PCD2 / PCD1 (8)
The equation (8) is indicated by L5 in FIG. 9, and it can be seen that the gear strength increases due to the reduction of the transmission load as the pitch cone distance PCD increases.

  The rate of change in gear strength with an increase in pitch cone distance PCD is the rate of change in gear strength with the increase in module MO (the right term in equation (7) above) and with the increase in pitch circle diameter PD. By multiplying the change rate of the gear strength by the transmission load reduction (the right term of the above-mentioned equation (8)), it is expressed as the following equation (9).

Gear strength change rate due to increase in pitch cone distance = (PCD2 / PCD1) ³ ··· (9)
Equation (9) is indicated by L6 in FIG. 9, and it can be seen that the gear strength is greatly 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) is sufficiently compensated for by the increase in gear strength according to the method [2] (increase in pitch cone distance), so that the differential device as a whole is improved. 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 conventional differential.

  For example, when maintaining the gear strength of the side gear S of the reference differential device D 'at 100%, the change rate of the gear strength accompanying the increase in the number of teeth determined in [1] (the right term of the above equation (6)) ) Is multiplied by the gear strength change rate due to the increase in the pitch cone distance obtained in [2] (the above-mentioned right item of (9)). Thus, the relationship between the ratio of the number of teeth 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 represented by L7 in FIG. 10 when the number of teeth Z2 of the pinion P is 10.

  As described above, the equation (10) shows the change in the tooth number ratio Z1 / Z2 and the pitch cone distance PCD when maintaining the gear strength of the reference differential device D 'with the tooth number ratio Z1 / Z2 = 14/10 at 100%. 10 shows the relationship with the ratio (see FIG. 10). The rate of change of the pitch cone distance PCD on the vertical axis in FIG. 10 is obtained by setting the shaft diameter of the pinion shaft PS (that is, the pinion support) supporting the pinion P to d2. Can be converted to a ratio of d2 / PCD.

That is, in the conventional existing differential device, the increase change of the pitch cone distance PCD is correlated with the increase change of d2 as shown in Table 1 above, and when d2 is fixed, the ratio of d2 / PCD decreases. It is expressible. Moreover, in the conventional differential device, as shown in Table 1 above, d2 / PCD is in the range of 40 to 45% in the case of the reference differential device D ', and the gear strength is increased by increasing the PCD. Therefore, 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 in the case of the reference differential device D ', the gear strength can be reduced by the conventional difference. It can 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 sufficient that d2 / PCD ≦ 0.45 is satisfied. In this case, if the PCD after the increase / decrease is changed to PCD2 with respect to the pitch cone distance PCD1 of the reference differential device D ′,
d2 / PCD2 ≦ 0.45 / (PCD2 / PCD1) (11)
It suffices to satisfy If the equation (11) is applied to the above-described equation (10), the relationship between d2 / PCD and the tooth number ratio Z1 / Z2 can be converted as in the following equation (12).

  When the equation (12) holds, when the number of teeth Z2 of the pinion P is 10, it can be expressed as L8 in FIG. The time when the equality 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 D 'is maintained at 100%.

  By the way, in the conventional existing differential device, as described above, the tooth number ratio Z1 / Z2 is usually not only 1.4 like the reference differential device D ', but also the tooth number ratio Z1 / Z2 is 1 as described above. .6, and a tooth number ratio Z1 / Z2 of 1.44. Based on this fact, if it is assumed that the reference differential D ′ (Z1 / Z2 = 1.4) can provide a necessary and sufficient gear strength, that is, 100% of the gear strength, the conventional differential can be used in the conventional differential. As can be seen from FIG. 8, in the differential having the number ratio Z1 / Z2 of 16/10, the gear strength is reduced to 87% as compared with the reference differential D '. However, the gear strength reduced to this extent is conventionally accepted as a practical strength in the existing differential, and is practically used. Therefore, it is considered that even in a differential device that is flat in the axial direction, if the gear strength is at least 87% of that of the reference differential device D ', the gear strength is sufficiently secured and allowed.

  From this point of view, the relationship between the tooth number ratio Z1 / Z2 and the rate of change of the pitch cone distance PCD when maintaining the gear strength of the reference differential device D 'at 87% is first obtained. Following the process of deriving the equation (10), the calculation (that is, the change rate of the gear strength with the increase in the number of teeth ratio (the right term of the above-mentioned equation (6))) and the change rate of the gear strength due to the increase of the pitch cone distance (the above 9) is calculated by multiplying the right term by 9) with 87% to obtain the following equation (10 ').

  Applying the above equation (11) 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 Can be converted as in the following equation (13). However, in the calculation process, except for terms expressed using variables, significant figures are calculated in three digits, and the remaining digits are rounded down. However, it is expressed by an equal sign in the expression.

  In the case where the equality 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, like the L9 line in FIG. 11). In this case, the region corresponding to the expression (13) is a region above the line L9 and below the line L9 in FIG. A specific area (hatched area in FIG. 11) satisfying the expression (13) and satisfying that the tooth number ratio Z1 / Z2 on the right side of the line L10 in FIG. In an axially flat differential having a tooth count Z2 of 10 and a tooth count ratio Z1 / Z2 exceeding 2.0, Z1 / Z2 and G1 / Z2 capable of securing at least 87% gear strength with respect to the reference differential D '; d2 / PCD setting area. For reference, FIG. 11 shows an example in which the ratio of the number of teeth Z1 / Z2 is set to 40/10 and d2 / PCD is set to 20.00%. 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%. Fits. As a result of performing a simulation-based strength analysis on 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 D ′) was obtained. ) Was obtained.

  Thus, the flat differential device in the specific region as a whole can secure the same gear strength (for example, static torsional load strength) and the maximum torque transmission amount as the conventional non-flat differential device, and as a whole, It is configured as a differential device with a sufficiently narrow width 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. Accordingly, it is possible to easily and easily install the power transmission system, and it is possible to achieve effects such as extremely advantageous in reducing the size of the transmission system.

  When the structure of the flat differential device in the specific area is, for example, the structure of the above-described embodiment (more specifically, the structure shown in FIGS. 1 to 6), the specific area The flat differential device described above can also achieve the effects of the structure shown in the above-described embodiment.

  Although the above description (especially the description relating to FIGS. 8, 10, and 11) has been made with respect to 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, and 20, the flat differential device capable of achieving the above-mentioned effect is, as shown by hatchings in FIGS. It can be represented by an equation. That is, the equation (13) derived as described above can be applied regardless of a 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, similarly to the case where the number of teeth Z2 of the pinion P is set to 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 Expression (13). Is set, the above effect can be obtained.

  For reference, FIG. 13 shows an example in which the number of teeth Z2 of the pinion P is set to 12 and the ratio of the number of teeth Z1 / Z2 is set to 48/12 and d2 / PCD is set to 20.00%. FIG. 13 illustrates an example in which the ratio of the number of teeth Z1 / Z2 is set to 70/12, and the ratio of d2 / PCD is set to 16.67%. As a result of performing a simulation-based strength analysis on 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 D ′) was obtained. ) Was obtained. In addition, these embodiments fall within the specific area as shown in FIG.

  As a comparative example, in an embodiment that does not fall within the above specific range, for example, when the number of teeth Z2 of the pinion P is set to 10, the ratio of the number of teeth Z1 / Z2 is set to 58/10 and d2 / PCD is set to 27.50%. FIG. 11 shows an example in which the number of teeth Z2 of the pinion P is set to 10, and the ratio of the number of teeth Z1 / Z2 is set to 40/10, and the ratio of d2 / PCD is set to 34.29%. In the case where the number of teeth Z2 of the pinion P is 12, the ratio of the number of teeth Z1 / Z2 is set to 70/12, and the ratio of d2 / PCD is set to 27.50% when the example shown in FIG. When the number of teeth Z2 of the pinion P is set to 12 at the star point of FIG. 13 in the example at the time, the ratio of the number of teeth Z1 / Z2 is set to 48/12 and d2 / PCD is set to 34.29%, respectively. The embodiment at the time is indicated by a dot in FIG.As a result of simulation-based strength analysis of these examples, the same or higher gear strength (more specifically, 87% or higher gear strength with respect to the reference differential D ') was obtained. Could not be obtained. In other words, it was confirmed that the effects described above cannot be obtained in the examples that do not fall within the specific range.

  The embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the gist of the present 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, and the output side element (carrier 53) of the reduction gear mechanism RG is connected to the differential case DC (cover portion C ′). And the power from the power source is transmitted to the differential case DC via the reduction gear mechanism RG, but the output side elements of the reduction gear mechanism other than the planetary gear mechanism are coupled to the differential case DC. You may do so.

  Further, instead of the reduction gear mechanism as described above, an input tooth portion (final driven gear) for receiving power from a power source is integrally formed or fixed to the outer peripheral portion of the differential case DC, and is fixed via the input tooth portion. The power from the power source may be transmitted to the differential case DC. In this case, specific portions of the outer peripheral surface of the differential case DC, for example, the openings of the hollow cylindrical portion T and the openings of the first and second oil intake holes H1 and H2 are not covered with the input teeth portion but are inside the transmission case M. It is always exposed to the space 1.

  Further, in the above-described embodiment, as the oil introduction path Os through which the lubricating oil is guided to the inner side surface of the intermediate wall portion Sw of the side gear S (that is, the opposing surfaces of the pair of side gears S), for example, the side wall portions of the cover portions C and C ′ Although the oil path from the lightening portion 8 formed in Cs to the through oil path 15 via the oil guide groove 17 has been described, other oil introduction paths can be implemented instead of or in addition to such an oil path. is there. As another oil introduction path Os, for example, the boss portion Cb of the cover portions C and C ′ of the differential case DC is extended more axially outward than the shaft portion Sj of the side gear S, and If the output shaft J is rotatably fitted on the peripheral surface and a spiral groove is formed in at least one of the fitting surfaces (for example, the inner peripheral surface of the extension of the boss Cb), the extension of the boss Cb can be formed. The lubricating oil existing in the internal space 1 of the transmission case M around the spline fitting portion 6 between the shaft portion Sj of the side gear S and the output shaft J through the spiral groove during the relative rotation between the boss portion Cb and the output shaft J, Consequently, it can be efficiently supplied to the inner surface side of the intermediate wall portion Sw. In this case, if a part of the spline teeth of the spline fitting portion 6 is formed as a missing tooth to form an axial lubricating oil passage, the lubricating oil is further supplied to the inner side surface of the intermediate wall portion Sw of the side gear S. It can be supplied efficiently.

  Further, instead of or in addition to the spiral groove, lubricating oil is fed and supplied from the oil pump to the spline fitting portion 6 between the shaft portion Sj of the side gear S and the output shaft J. The lubricating oil may be supplied to the inner surface of the intermediate wall portion Sw of the side gear S via the spline fitting portion 6.

  In the above-described embodiment, the rear surfaces of the pair of side gears S are respectively covered with the pair of cover portions C and C ′. However, in the present invention, the cover portions are provided only on the rear surface of the one side gear S. Is also good. In this case, for example, a drive member (for example, the carrier 53 of the reduction gear mechanism RG) located upstream of the power transmission path is provided on the side where the cover is not provided, and the drive member and the differential case DC are coupled. You may do so.

  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 of the present invention is also applied to a center differential that absorbs the rotational speed difference between the front wheel and the rear wheel. It is feasible.

  In the above-described embodiment, a plurality of pinions P are supported by one pinion shaft PS. However, the present invention is also applicable to a case in which each pinion is individually supported by a separate pinion shaft. is there.

D: Differential device DC: Differential case d2: Diameter of pinion shaft, diameter of support shaft (diameter of pinion support, diameter of differential gear support)
E ···· Step fe ··· Virtual plane J ····· Output shaft P ····· Pinion (differential gear)
PCD: pitch cone distance Pfi: radially inner end surface PS of the pinion in the side gear PS: pinion shaft (pinion support, differential gear support)
PS ': Support shaft (pinion support, differential gear support)
S ... side gear (output gear)
Sg: Tooth Sj: Shaft Sw: Intermediate wall
Swa: recess rs: fitting part (rotary sliding part)
60 space 61 oil reservoir 61s internal space 61e of oil reservoir opening edge of oil reservoir

Claims (6)

A differential device that distributes and transmits the rotational force of a differential case (DC) to a pair of output shafts (J),
A pinion (P) arranged in the differential case (DC), a pinion shaft (PS) supported by the differential case (DC) and rotatably penetrating and supporting the pinion (P); and a pinion (P). A pair of side gears (S) each having an engaging gear portion (Sg) on an outer peripheral portion thereof and opposed to each other across the pinion shaft (PS) and connected to the pair of output shafts (J); An oil introduction path (Os) for introducing lubricating oil to the opposing surfaces of the side gears (S), a depression (Swa) formed on the opposing surfaces of the pair of side gears (S), and the pinion (P). A space (60) sandwiched between a radially inward end surface (Pfi) of the side gear (S), and the pinion (P) and the pinion shaft (PS) facing the space (60). )When Oil reservoir communicating with each other rotatably sliding fit portion of and the pinion is formed between the opposing portions (P) and said pinion shaft (PS) (rs) and (61), provided with,
At least one of the opposing surfaces of the pair of side gears (S) is located at the radially inner end of the space (60) and forms an opening edge of the depression (Swa). A step (E) is formed, and the step (E) is formed in an edge shape in which the facing surface perpendicular to the axial direction of the side gear (S) and the side surface of the recess (Swa) are orthogonal to each other. A differential device characterized by the above-mentioned. The side gear (S) includes a shaft portion (Sj) connected to the pair of output shafts (J), the gear portion (Sg) spaced radially outward from the shaft portion (Sj), and A flat intermediate wall portion (Sw) extending radially outward from the inner end of the shaft portion (Sj);
The stepped portion (E) is characterized Rukoto formed on the outer peripheral portion of the shaft portion and the intermediate wall portion remote from (Sj) in the radially outward (Sw), the differential of claim 1 apparatus. A differential device for distributing and transmitting the rotational force of a differential case (DC) to a pair of output shafts (J),
A differential gear (P) arranged in the differential case (DC), and a differential gear support (PS) supported by the differential case (DC) and rotatably penetrating and supporting the differential gear (P). A gear portion (Sg) meshing with the differential gear (P) is provided on an outer peripheral portion, and is opposed to each other with the differential gear support portion (PS) interposed therebetween and connected to the pair of output shafts (J). A pair of output gears (S), an oil introduction path (Os) for introducing lubricating oil to opposing surfaces of the pair of output gears (S), and an opposing surface of the pair of output gears (S). depression is formed in the (S w a) and the differential gear (P), and space (60) sandwiched between the end face of the radially inner side of said output gear (S) (Pfi), Opposing portion between the differential gear (P) and the differential gear support (PS) so as to face the space (60) Comprising oil reservoir communicating with the formed and differential gear (P) and the differential gear support portion mutually rotatable sliding fit portion between the (PS) (rs) and (61),
At least the one of the opposing surfaces, the opening edge of said space (60) located on the inner peripheral end in the radial direction recess wherein the (S w a) of the opposing surfaces of the pair of output gears (S) A step (E) is formed,
When 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 (PS) is d2, and the pitch cone distance is PCD. To

The filling,
A differential device characterized by satisfying Z1 / Z2> 2.   The differential device according to claim 3, wherein Z1 / Z2 ≧ 4 is satisfied.   The differential device according to claim 3, wherein Z1 / Z2 ≧ 5.8 is satisfied. The step (E) has a virtual plane (fe) passing through the top surface of the step (E) and orthogonal to the rotation axis (L) of the differential case (DC). The differential device according to any one of claims 1 to 5 , wherein the differential device is formed so as to pass through the (61s) or the opening edge (61e).

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