Differential device

Abstract

[Problem] To provide a differential device in which a lubricating oil can be made to flow inside and outside an input rotating member through a tubular portion of the input rotating member into which an output rotating member is inserted, even when the input rotating member and the output rotating member rotate at the same speed. [Solution] This differential device 1 comprises: a differential case 2 rotates by the driving force of a drive source; and a differential mechanism 4 which is accommodated in the differential case 2, lubricated by a lubricating oil, and distributes the driving force inputted into the differential case 2 to first and second axle shafts 51, 52. The differential case 2 has a body 23 that accommodates the differential mechanism 4, and first and second tubular portions 21, 22 into which the first and second axle shafts 51, 52 are inserted, respectively. Oil grooves 20 extending in the axial direction are formed in the inner circumferential surfaces 21a, 22a of the first and second tubular portions 21, 22. The oil grooves 20 become deeper and wider proceeding from one side to the other side of the first and second cylindrical sections 21, 22 in the axial direction.

Description

Differential device

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

[0002] Conventionally, vehicles are equipped with a differential gear for distributing driving force from a driving source such as an engine to left and right wheels. The differential gear includes a case-shaped input rotary member to which driving force from the driving source is input, and a differential mechanism housed in the input rotary member. The differential mechanism includes a pair of left and right side gears and a plurality of pinion gears that mesh with the pair of side gears, and is lubricated with lubricating oil. Left and right output rotary members for transmitting driving force to the left and right wheels are respectively connected to the pair of side gears so as not to rotate relative to each other.

[0003] The differential device described in Patent Document 1 has cylindrical portions at both ends of a differential case serving as an input rotating member, through which left and right output rotating members are inserted, respectively. A lubrication groove is formed in a spiral shape on the inner circumferential surface of the cylindrical portions to allow lubricating oil to flow inside and outside the differential case as the output rotating members rotate relative to the differential case.

[0004] The differential device described in Patent Document 2 has a cylindrical portion at one end of a differential case that serves as an input rotating member that houses a differential gear mechanism, through which an output rotating member is inserted, and an oil groove having a right-handed spiral first groove portion and a left-handed spiral second groove portion is formed on the inner surface of this cylindrical portion.

[0005] JP 2006-83876 A JP 2020-106046 A

[0006] In the devices described in Patent Documents 1 and 2, when the rotational speeds of the left and right wheels are different, such as when the vehicle is turning, the output rotating member rotates relative to the input rotating member, and the spiral groove allows the lubricating oil to flow.However, when the input rotating member and the output rotating member rotate at the same speed, such as when driving straight ahead, the spiral groove does not have the full effect of allowing the lubricating oil to flow.

[0007] Therefore, the present invention aims to provide a differential device that can allow lubricating oil to flow inside and outside the input rotating member through the cylindrical portion of the input rotating member through which the output rotating member is inserted, even when the input rotating member and the output rotating member rotate at the same speed.

[0008] In order to achieve the above-mentioned object, the present invention provides a differential device comprising: a case-shaped input rotating member that rotates by the driving force of a vehicle's driving source; and a differential mechanism that is housed in the input rotating member and lubricated by lubricating oil, and that distributes the driving force input to the input rotating member to a pair of output rotating members that are coaxially rotatable relative to each other, wherein the input rotating member has a main body that houses the differential mechanism and a pair of cylindrical portions into which the pair of output rotating members are respectively inserted, and an oil groove extending in the axial direction of at least one of the pair of cylindrical portions is formed on the inner surface of the one cylindrical portion, and the oil groove becomes deeper and wider as it goes from one side to the other in the axial direction.

[0009] According to the differential device of the present invention, even when the input rotating member and the output rotating member rotate at the same speed, it is possible to cause lubricating oil to flow inside and outside the input rotating member through the cylindrical portion of the input rotating member through which the output rotating member is inserted.

[0010] FIG. 1 is a configuration diagram showing a differential gear according to a first embodiment of the present invention mounted on a vehicle. FIG. 2 is a perspective view showing a differential mechanism housed in a differential case with a portion of the case body of the differential case cut away. FIG. 3 is a perspective view showing a case cover of the differential case. FIG. 4 is a cross-sectional view of the case body of the differential case and the differential mechanism taken along line A-A in FIG. 1. FIG. 5 is a configuration diagram showing the case body as viewed in the axial direction from the case cover side of the differential case. FIG. 6 is a configuration diagram showing the case cover as viewed in the axial direction from the case body side of the differential case. FIG. 7 is a configuration diagram showing a portion of the first cylindrical portion and the first side wall of the differential case as viewed from the axial direction. FIG. 8 is a cross-sectional view of the first cylindrical portion and the first side wall in a cross section including the rotation axis of the differential case. FIG. 9 is an explanatory diagram showing the inner circumferential surface and oil groove of the first cylindrical portion as viewed from the rotation axis of the differential case. FIG. 10 is a cross-sectional view of the second cylindrical portion and the second side wall in a cross section including the rotation axis of the differential case. Fig. 11 is a structural diagram showing a core used to manufacture the case body of the differential case. Fig. 12 is a structural diagram showing a differential gear according to a second embodiment of the present invention. Fig. 13 is an explanatory diagram showing the inner circumferential surface and oil grooves of the first cylindrical portion as viewed from the rotation axis of the differential case according to the second embodiment. Fig. 14 is a structural diagram showing a core used to manufacture the case body of the differential case according to the second embodiment. Fig. 15 is a structural diagram showing a differential gear according to a third embodiment of the present invention. Fig. 16 is an explanatory diagram showing the inner circumferential surface and oil grooves of the second cylindrical portion as viewed from the rotation axis of the differential case.

[0011] [First embodiment] A first embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and while there are some parts that specifically exemplify various technically preferable technical matters, the technical scope of the present invention is not limited to this specific embodiment.

[0012] Fig. 1 is a structural diagram showing a differential gear 1 according to a first embodiment of the present invention mounted on a vehicle. Fig. 1 shows a vertical cross section of the differential gear 1 as viewed horizontally from the rear to the front in the longitudinal direction of the vehicle, with the up-down direction in the drawing corresponding to the vertical direction and the left-right direction in the drawing corresponding to the horizontal direction.

[0013] The differential device 1 includes, as its main components, a differential case 2 as a case-shaped input rotating member that rotates due to the driving force of the vehicle's driving source, a ring gear 3 fixed to the differential case 2, a differential mechanism 4 housed in the differential case 2, first and second axle shafts 51, 52 as a pair of output rotating members, a differential housing 6 that houses the differential case 2, and bearings 71, 72 that rotatably support the differential case 2 relative to the differential housing 6. The driving source is, for example, an engine or a high-output electric motor. Cylindrical cover members 601, 620 that cover the first and second axle shafts 51, 52 are attached to the differential housing 6.

[0014] The differential case 2 rotates about a rotation axis O relative to the differential housing 6. The first and second axle shafts 51, 52 are coaxially rotatable relative to each other about the rotation axis O, and transmit the driving force distributed by the differential mechanism 4 to the left and right wheels of the vehicle, respectively. Hereinafter, the direction parallel to the rotation axis O will be referred to as the axial direction. Furthermore, the direction of rotation of the differential case 2 when the vehicle is traveling forward will be referred to as the main rotation direction of the differential case 2.

[0015] Bearings 71, 72 are rolling bearings and include inner rings 711, 721 and outer rings 712, 722, a plurality of rolling elements 713, 723 arranged between the inner rings 711, 721 and the outer rings 712, 722, and cages 714, 724 that hold the plurality of rolling elements 713, 723. In this embodiment, bearings 71, 72 are tapered roller bearings, and rolling elements 713, 723 are configured as part-conical rollers. However, bearings 71, 72 are not limited to tapered roller bearings, and may be, for example, ball bearings in which a plurality of spherical rolling elements are held in a cage between an inner ring and an outer ring.

[0016] The differential case 2 has a cylindrical case body 201 with a bottom, and a case lid 202 arranged to close an opening of the case body 201. The case body 201 and the case lid 202 are fastened together by a plurality of bolts 203. The case body 201 is formed with a plurality of screw holes 201a into which the bolts 203 are threaded. The case lid 202 is formed with a plurality of bolt insertion holes 202a into which the bolts 203 are inserted.

[0017] The ring gear 3 has a fixed portion 31 fixed to the differential case 2 and a gear portion 32 provided on the outer periphery of the fixed portion 31. The fixed portion 31 is fastened to the differential case 2 by a plurality of bolts 30. A plurality of threaded holes 31a into which the bolts 30 are threaded are formed in the fixed portion 31. A plurality of bolt insertion holes 201b, 202b into which the bolts 30 are inserted are formed in the case main body 201 and the case cover 202.

[0018] The gear portion 32 of the ring gear 3 meshes with a final gear (not shown) on the front side of the differential case 2 in the longitudinal direction of the vehicle. The driving force of the driving source is transmitted to the final gear via a transmission or a reducer, and is input from the final gear to the differential case 2 via the ring gear 3.

[0019] Fig. 2 is a perspective view showing the differential mechanism 4 housed in the differential case 2 with a portion of the case body 201 cut away. Fig. 3 is a perspective view showing the case cover 202. Fig. 4 is a cross-sectional view of the case body 201 and the differential mechanism 4 taken along line A-A in Fig. 1.

[0020] The differential mechanism 4 includes a first side gear 41 and a second side gear 42 arranged side by side in the direction of the rotation axis, a plurality of pinion gear sets 43, a center washer 44 arranged between the first side gear 41 and the second side gear 42, a first side washer 45 arranged between the first side gear 41 and the case main body 201, and a second side washer 46 arranged between the second side gear 42 and the case cover 202. The first side gear 41 and the second side gear 42 are helical gears with teeth formed in a spiral shape.

[0021] A splined hole 410 is formed in the center of the first side gear 41, to which the first axle shaft 51 is non-rotatably coupled. A splined hole 420 is formed in the center of the second side gear 42, to which the second axle shaft 52 is non-rotatably coupled. The pinion gear sets 43 are disposed on the outer peripheries of the first side gear 41 and the second side gear 42. In this embodiment, the differential mechanism 4 includes three pinion gear sets 43.

[0022] Each pinion gear set 43 is formed by meshing a plurality of pinion gears with each other. In the present embodiment, one pinion gear set 43 is formed by meshing one first pinion gear 431 with two second pinion gears 432. The first pinion gear 431 and the second pinion gear 432 are supported by the differential case 2 to be rotatable about a rotation axis parallel to the rotation axis O.

[0023] The first pinion gear 431 and the second pinion gear 432 are helical gears with spirally formed teeth. The axial length of the first pinion gear 431 corresponds to the combined axial length of the first side gear 41 and the axial length of the second side gear 42. The axial length of the second pinion gear 432 corresponds to the axial length of the second side gear 42.

[0024] The first pinion gear 431 meshes with the first side gear 41. The two second pinion gears 432 mesh with the second side gear 42 on the front and rear sides of the first pinion gear 431 in the main rotation direction of the differential case 2. The first pinion gear 431 and the two second pinion gears 432 mesh with each other on the outer periphery of the second side gear 42. The first pinion gear 431 has a large diameter portion 431a that meshes with the first side gear 41 and a small diameter portion 431b that meshes with the two second pinion gears 432, and the tip circle diameter D of the large diameter portion 431a is １ is the tip diameter D of the small diameter portion 431b ２ It is formed larger than

[0025] When the differential mechanism 4 transmits driving force from the differential case 2 to the first and second axle shafts 51, 52, an axial thrust force corresponding to the twist angle of the tooth trace is generated in the first and second side gears 41, 42 and the first and second pinion gears 431, 432.

[0026] The differential case 2 has a pair of cylindrical portions 21, 22 through which the first and second axle shafts 51, 52 are respectively inserted, and a main body portion 23 that houses the differential mechanism 4. The pair of cylindrical portions 21, 22 are provided at both axial ends of the differential case 2. The main body portion 23 has side walls 24, 25 on both axial sides, and has a holding portion 26 between the side walls 24, 25 that holds a plurality of pinion gear sets 43. The pair of cylindrical portions 21, 22 are provided to protrude axially from the side walls 24, 25, respectively.

[0027] In this embodiment, one cylindrical portion 21 and one side wall 24 and holding portion 26 of the main body portion 23 are included in the case main body 201, and the other cylindrical portion 22 and the other side wall 25 of the main body portion 23 are included in the case cover 202. Hereinafter, one cylindrical portion 21 included in the case main body 201 will be referred to as the first cylindrical portion 21, and one side wall 24 will be referred to as the first side wall 24. Further, the other cylindrical portion 22 included in the case cover 202 will be referred to as the second cylindrical portion 22, and the other side wall 25 of the main body portion 23 will be referred to as the second side wall 25. The inner circumferential surface 21a of the first cylindrical portion 21 functions as a guide surface that suppresses tilt of the first axle shaft 51 relative to the differential case 2. The inner circumferential surface 22a of the second cylindrical portion 22 functions as a guide surface that suppresses tilt of the second axle shaft 52 relative to the differential case 2.

[0028] The retaining portion 26 is formed with a plurality of first retaining holes 261 that respectively retain the plurality of first pinion gears 431, and a plurality of second retaining holes 262 that respectively retain the plurality of second pinion gears 432. When the first pinion gears 431 and the second pinion gears 432 rotate, the tooth tip surface of the first pinion gear 431 slides on the inner surface of the first retaining hole 261, and the tooth tip surface of the second pinion gear 432 slides on the inner surface of the second retaining hole 262. The frictional resistance force generated by these sliding movements serves as a differential limiting force that suppresses differential rotation of the left and right wheels and prevents the wheels from spinning.

[0029] An inner ring 711 of a bearing 71 that supports one axial end of the differential case 2 relative to the differential housing 6 is disposed on the outer periphery of the first cylindrical portion 21. An inner ring 721 of a bearing 72 that supports the other axial end of the differential case 2 relative to the differential housing 6 is disposed on the outer periphery of the second cylindrical portion 22. The differential housing 6 is formed with a first insertion hole 61 into which the first axle shaft 51 is inserted, and a second insertion hole 62 into which the second axle shaft 52 is inserted.

[0030] A seal member 83 that prevents leakage of lubricating oil from the first insertion hole 61 is disposed between the inner circumferential surface of the first insertion hole 61 and the outer circumferential surface of the first axle shaft 51. The tip end surface 21b of the first cylindrical portion 21 faces the seal member 83 in the axial direction. A seal member 84 that prevents leakage of lubricating oil from the second insertion hole 62 is disposed between the inner circumferential surface of the second insertion hole 62 and the outer circumferential surface of the second axle shaft 52. The tip end surface 22b of the second cylindrical portion 22 faces the seal member 84 in the axial direction.

[0031] Fig. 5 is a structural diagram showing the case body 201 as viewed in the axial direction from the case cover 202 side. Fig. 6 is a structural diagram showing the case cover 202 as viewed in the axial direction from the case body 201 side. In Figs. 5 and 6, the main rotation direction of the differential case 2 is indicated by arrow A. １ , A ２ is shown.

[0032] A plurality of recesses 241 having bottom surfaces 241a axially facing the plurality of first pinion gears 431 are formed on the inner surface 24a of the first side wall 24 of the case body 201. A portion of the inner surface 24a of the first side wall 24 closer to the rotation axis O than the plurality of recesses 241 faces the first side washer 45 in the axial direction. The recesses 241 are formed by being recessed in the axial direction from the inner surface 24a of the first side wall 24. When a thrust force toward the first side wall 24 is generated in the first pinion gear 431, the end surface of the first pinion gear 431 facing the first side wall 24 abuts against the bottom surface 241a of the recesses 241.

[0033] A plurality of recesses 251 are formed on the inner surface 25a of the second side wall 25 of the case cover 202. The recesses 251 have bottom surfaces 251a axially facing the first pinion gear 431 and bottom surfaces 251b axially facing the second pinion gear 432. A portion of the inner surface 25a of the second side wall 25 closer to the rotation axis O than the plurality of recesses 251 faces the second side washer 46 in the axial direction. The recesses 251 are recessed in the axial direction from the inner surface 25a of the second side wall 25. The axial depth of the recesses 251 in the bottom surface 251a and the axial depth of the recesses 251 in the bottom surface 251b are, for example, the same, but these depths may be different.

[0034] When a thrust force toward second side wall 25 is generated in first pinion gear 431, the end face of first pinion gear 431 facing second side wall 25 abuts against bottom surface 251 a of recess 251. When a thrust force toward second side wall 25 is generated in second pinion gear 432, the end face of second pinion gear 432 facing second side wall 25 abuts against bottom surface 251 b of recess 251.

[0035] The differential mechanism 4 is lubricated by lubricating oil introduced into the differential case 2, and distributes the driving force input to the differential case 2 to the first and second axle shafts 51, 52. Shaft holes 510, 520 are formed in the centers of the first and second axle shafts 51, 52 to supply lubricating oil to the inside of the differential case 2. Lubricating oil 80 pumped up from the bottom of the differential housing 6 by an oil pump 81 mounted on the vehicle is supplied to the shaft holes 510, 520.

[0036] The oil pump 81 draws in and discharges the lubricating oil 80 through a strainer 82 that removes foreign matter mixed in the lubricating oil 80. The lubricating oil 80 discharged from the oil pump 81 is supplied to the axial holes 510, 520 of the first and second axle shafts 51, 52 via a rotary joint. The lubricating oil 80 supplied to the axial holes 510, 520 flows into the differential case 2 from the ends of the first and second axle shafts 51, 52 that are fitted to the first and second side gears 41, 42, to lubricate the differential mechanism 4, and is then discharged from the first and second cylindrical portions 21, 22. The lubricating oil 80 discharged from the first and second cylindrical portions 21, 22 flows back to the bottom of the differential housing 6 through gaps between the inner rings 711, 721 and outer rings 712, 722 of the bearings 71, 72 and the cages 714, 724.

[0037] In this embodiment, a plurality of oil grooves 20 are formed in the first and second cylindrical portions 21, 22 so that the lubricating oil 80 that flows in from the first and second axle shafts 51, 52 and lubricates the differential mechanism 4 can be smoothly discharged from the first and second cylindrical portions 21, 22. Next, the configuration of the oil grooves 20 will be described with reference to Figures 7 to 10. Note that in this embodiment, a plurality of oil grooves 20 are formed in each of the first cylindrical portion 21 and the second cylindrical portion 22, but the oil grooves 20 may be formed in only one of the first cylindrical portion 21 and the second cylindrical portion 22. In other words, it is sufficient that the oil grooves 20 are formed in at least one of the first and second cylindrical portions 21, 22.

[0038] Fig. 7 is a configuration diagram of a portion of the first cylindrical portion 21 and the first side wall 24 as viewed from the axial direction. Fig. 8 is a cross-sectional view of the first cylindrical portion 21 and the first side wall 24 taken along a plane including the rotation axis O. Fig. 9 is an explanatory diagram showing the inner circumferential surface 21a of the first cylindrical portion 21 and the oil groove 20 as viewed from the rotation axis O. In Fig. 9, the up-down direction in the drawing corresponds to the circumferential direction of the first cylindrical portion 21. Note that a similar oil groove 20 is also formed in the second cylindrical portion 22.

[0039] 7 to 9 , the oil grooves 20 are formed to extend in the axial direction on the inner circumferential surface 21 a of the first cylindrical portion 21. The number of oil grooves 20 formed in the first cylindrical portion 21 is the same as the number of pinion gear sets 43 in the differential mechanism 4, and in this embodiment, three oil grooves 20 are formed in the first cylindrical portion 21.

[0040] The oil groove 20 has a groove depth D that increases and a groove width W that increases from one axial side to the other axial side of the first cylindrical portion 21. In this embodiment, the groove depth D gradually increases and the groove width W gradually increases from the base end 211 on the first side wall 24 side of the first cylindrical portion 21 to the tip end 212 on the tip face 21b side of the first cylindrical portion 21. Here, the groove depth D is the radial depth from the inner circumferential surface 21a of the first cylindrical portion 21 to the groove bottom surface 20a of the oil groove 20. The groove width W is the width between one groove side surface 20b and the other groove side surface 20c of the oil groove 20 in the circumferential direction of the inner circumferential surface 21a of the first cylindrical portion 21.

[0041] 7 and 9, the main rotation direction of the differential case 2 is indicated by an arrow A. ３ , A ４ In this embodiment, the angle of inclination θ of one groove side surface 20b of the oil groove 20, which is on the front side in the main rotation direction of the differential case 2, with respect to the axial direction is １ and an inclination angle θ of the other groove side surface 20c of the oil groove 20, which corresponds to the rear side in the main rotation direction of the differential case 2, with respect to the axial direction. ２ The center line C of the oil groove 20 shown in FIG. 9 is parallel to the rotation axis O, but the inclination angle θ １ and the tilt angle θ ２ The inclination angle θ ２ may be 0°.

[0042] Inclination angle θ １ , θ ２ The desirable range of the inclination angle θ is, for example, 5° to 30°. １ , θ ２ If the inclination angle θ is small, the effect of promoting the flow of lubricating oil in the oil groove 20 by the rotation of the differential case 2 is not necessarily sufficient, and １ , θ ２ If the inclination angle θ is too large, the groove width W becomes large and the area of ​​the inner peripheral surface 21a of the first cylindrical portion 21 becomes small. １ , θ ２ By setting the above range, the flow of lubricating oil in the oil groove 20 can be promoted by the rotation of the differential case 2 when the vehicle is moving forward and backward.

[0043] The inclination angle θ of the groove bottom surface 20a with respect to the axial direction shown in FIG. ３ The inclination angle θ is preferably, for example, 1° or more and 5° or less. ３ If the inclination angle θ is small, the centrifugal force acting on the lubricating oil during rotation of the differential case 2 does not necessarily promote the flow of the lubricating oil in the oil groove 20 sufficiently. ３ If the distance is too large, the thickness of the first cylindrical portion 21 at the portion where the oil groove 20 is formed becomes thin.

[0044] 8 and 5 , an inner wall groove 242 that extends radially and communicates with the oil groove 20 is formed on the inner surface 24a of the first side wall 24 of the case body 201. The inner wall groove 242 extends in a position aligned with the first side gear 41 in the axial direction, with an inner diameter side end of the first side wall 24 communicating with the oil groove 20 and an outer diameter side end communicating with the recess 241. The depth of the inner wall groove 242 from the inner surface 24a of the first side wall 24 is deeper than the depth of the recess 241. Note that, in the present embodiment, the inner wall groove 242 extends perpendicular to the circumferential direction of the first side wall 24 centered on the rotation axis O. However, the present invention is not limited to this, and the inner wall groove 242 may extend radially at an angle relative to the circumferential direction of the first side wall 24.

[0045] 10 is a cross-sectional view of the second cylindrical portion 22 and the second side wall 25 taken along a plane including the rotation axis O. Similar to the oil groove 20 of the first cylindrical portion 21, the oil groove 20 of the second cylindrical portion 22 gradually becomes deeper and wider from the base end 221 of the second cylindrical portion 22 on the second side wall 25 side toward the tip end 222 on the tip surface 22b side.

[0046] 10 and 6 , an inner wall groove 252 is formed on the inner surface 25a of the second side wall 25 of the case cover 202. The inner wall groove 252 extends in the radial direction and communicates with the oil groove 20 formed in the second cylindrical portion 22. The inner wall groove 252 extends to a position aligned with the second side gear 42 in the axial direction, with an inner diameter side end of the second side wall 25 communicating with the oil groove 20 and an outer diameter side end communicating with the recess 251. The depth of the inner wall groove 252 from the inner surface 25a of the second side wall 25 is deeper than the depth of the recess 251. The inner wall groove 252 extends to a position aligned with the second pinion gear 432, one of the two second pinion gears 432 in the pinion gear set 43, which is located rearward of the first pinion gear 431 in the main rotation direction of the differential case 2.

[0047] The multiple inner wall grooves 242 of the first side wall 24 and the multiple inner wall grooves 252 of the second side wall 25 guide the lubricating oil 80 that is supplied into the differential case 2 from the axial holes 510, 520 of the first and second axle shafts 51, 52 and flows into the first retaining hole 261 and the second retaining hole 262 from between the first side gear 41 and the second side gear 42 to the oil grooves 20 of the first cylindrical portion 21 and the second cylindrical portion 22, thereby contributing to smooth the flow of the lubricating oil 80 within the differential case 2.

[0048] The case body 201 is formed by casting using a core. FIG. 11 is a structural diagram showing the core 9 used to manufacture the case body 201. The core 9 is a set core configured by combining a core body 91 for forming the retaining portion 26 and the first side wall 24 of the case body 201 with a segment 92 for forming the first cylindrical portion 21. The core body 91 is formed with a recess 910 into which a protrusion 920 provided on the segment 92 fits. The core body 91 is also provided with a first protrusion 911 for forming the first retaining hole 261, a second protrusion 912 for forming the second retaining hole 262, and a third protrusion 913 for forming the inner wall groove 242. The segment 92 is provided with a protrusion 921 for forming the oil groove 20.

[0049] The core body 91 and the divided bodies 92 are each manufactured by a mold casting method using a mold. Note that the inner surfaces of the first retaining holes 261 and the second retaining holes 262 in the retaining portions 26 of the differential case 2 and the bottom surfaces 241 a of the recesses 241 in the first side walls 24 are subjected to finishing after the core 9 is removed.

[0050] According to the first embodiment described above, even when the differential case 2 and the first and second axle shafts 51, 52 rotate at the same speed and in the same direction, the rotation of the differential case 2 relative to the differential housing 6 allows lubricating oil to flow inside and outside the differential case 2 via the oil grooves 20. Furthermore, since the oil grooves 20 become deeper and wider from one axial side to the other in the first cylindrical portion 21 and the second cylindrical portion 22, the oil grooves 20 can be easily formed by casting.

[0051] [Second embodiment] Figure 12 is a configuration diagram showing a differential 1A according to a second embodiment. Similar to Figure 1, Figure 12 shows a vertical cross section of the differential 1A when viewed horizontally from the rear to the front in the vehicle's longitudinal direction, with the up-down direction in the drawing corresponding to the vertical direction and the left-right direction in the drawing corresponding to the horizontal direction. In Figure 12, components common to those described in the first embodiment are designated by the same reference numerals as those in Figure 1, and redundant description will be omitted.

[0052] In the first embodiment, the lubricating oil 80 is supplied into the differential case 2 from the axial holes 510, 520 of the first and second axle shafts 51, 52 using the oil pump 81, and is discharged from the first and second cylindrical portions 21, 22. In the second embodiment, the oil pump 81 is not used, and the lubricating oil 80 is scooped up inside the differential housing 6 by the rotation of the ring gear 3, and is supplied into the differential case 2 from the first cylindrical portion 21 by the rotation of the differential case 2, and is discharged from the second cylindrical portion 22.

[0053] The inner surface 6a of the upper portion 63 of the differential housing 6, which is vertically above the differential case 2, is inclined so that the lubricating oil 80 scooped up by the ring gear 3 flows toward the first cylindrical portion 21. In Figure 12, multiple arrows indicate the direction of flow of the lubricating oil 80 scooped up by the ring gear 3 along the inner surface 6a of the differential housing 6. The lubricating oil 80 that has flowed along the inner surface 6a of the differential housing 6 flows from between the inner ring 711 and the outer ring 712 of the bearing 71 and the cage 714 toward the tip end portion 212 of the first cylindrical portion 21, and then flows into the differential case 2 through the multiple oil grooves 20 in the first cylindrical portion 21.

[0054] 13 is a cross-sectional view of the first cylindrical portion 21 and the first side wall 24 taken along a plane including the rotation axis O. In this embodiment, the oil groove 20 in the first cylindrical portion 21 gradually deepens in depth D and gradually widens in width from the distal end 212 of the first cylindrical portion 21 toward the proximal end 211 of the first side wall 24, as opposed to the first embodiment. The inner wall groove 242 of the first side wall 24 communicates with the oil groove 20 at the proximal end 211 of the first cylindrical portion 21. As in the first embodiment, three oil grooves 20 are formed in the first cylindrical portion 21. As in the first embodiment, the oil groove 20 in the second cylindrical portion 22 gradually deepens in depth and gradually widens in width from the proximal end 221 of the second side wall 25 toward the distal end 222.

[0055] 14 is a structural diagram showing a core 93 used to manufacture the case body 201 of the differential case 2 according to the second embodiment. The core 93 includes a first convex portion 931 for forming the first retaining hole 261, a second convex portion 932 for forming the second retaining hole 262, a third convex portion 933 for forming the inner wall groove 242, and a fourth convex portion 934 for forming the oil groove 20, which are provided integrally with a body portion 930 for forming a space for accommodating the first and second side gears 41, 42.

[0056] As with the first embodiment, the second embodiment described above also makes it possible to cause lubricating oil to flow inside and outside the differential case 2 via the oil grooves 20 due to the rotation of the differential case 2 relative to the differential housing 6, even when the differential case 2 and the first and second axle shafts 51, 52 rotate at the same speed and in the same direction. Furthermore, since it is possible to cause lubricating oil to flow inside and outside the differential case 2 without using the oil pump 81, this can also contribute to reducing the weight and cost of the vehicle.

[0057] [Third embodiment] Figure 15 is a configuration diagram showing a differential 1B according to a third embodiment. Similar to Figure 1, Figure 15 shows a vertical cross section of the differential 1B when viewed horizontally from the rear to the front in the vehicle's longitudinal direction, with the up-down direction in the drawing corresponding to the vertical direction and the left-right direction in the drawing corresponding to the horizontal direction. In Figure 15, components common to those described in the first embodiment are designated by the same reference numerals as those in Figure 1, and redundant description will be omitted.

[0058] In the third embodiment, similar to the second embodiment, the differential device 1B is configured so that the lubricating oil 80 is supplied into the differential case 2 without using the oil pump 81 and is smoothly discharged from the differential case 2, but the direction of supply and discharge of the lubricating oil 80 is opposite to that of the second embodiment. That is, in the third embodiment, the lubricating oil 80 scooped up inside the differential housing 6 by the rotation of the ring gear 3 is supplied into the differential case 2 from the second cylindrical portion 22 by the rotation of the differential case 2 and is discharged from the first cylindrical portion 21.

[0059] The inner surface 6a of the upper portion 64 of the differential housing 6, which is vertically above the differential case 2, is inclined so that the lubricating oil 80 scooped up by the ring gear 3 flows toward the second cylindrical portion 22. In Figure 15, multiple arrows indicate the direction of flow of the lubricating oil 80 scooped up by the ring gear 3 along the inner surface 6a of the differential housing 6. The lubricating oil 80 that has flowed along the inner surface 6a of the differential housing 6 flows from between the inner ring 721 and the outer ring 722 of the bearing 72 and the cage 724 toward the tip end portion 222 of the second cylindrical portion 22, and then flows into the differential case 2 through the multiple oil grooves 20 of the second cylindrical portion 22.

[0060] 16 is a cross-sectional view of the first cylindrical portion 21 and the first side wall 24 taken along a plane including the rotation axis O. In this embodiment, the oil groove 20 in the second cylindrical portion 22 gradually deepens in depth D and gradually widens in width from the distal end 222 of the second cylindrical portion 22 toward the proximal end 221 of the second side wall 25, as opposed to the first embodiment. The inner wall groove 252 of the second side wall 25 communicates with the oil groove 20 at the proximal end 221 of the second cylindrical portion 22. As in the first embodiment, three oil grooves 20 are formed in the second cylindrical portion 22. As in the first embodiment, the oil groove 20 in the first cylindrical portion 21 gradually deepens in depth and gradually widens in width from the proximal end 211 of the first side wall 24 toward the distal end 212.

[0061] As described with reference to Fig. 6 in the first embodiment, the inner wall groove 252 of the second side wall 25 extends to a position that is aligned in the axial direction with the second pinion gear 432, of the two second pinion gears 432 in the pinion gear set 43, which is located on the rear side of the first pinion gear 431 in the main rotation direction of the differential case 2. The second pinion gear 432 located on the rear side in the main rotation direction of the differential case 2 transmits a larger driving force from the differential case 2 to the second side gear 42 and is subjected to a higher load than the second pinion gear 432 located on the front side in the main rotation direction of the differential case 2. Since the inner wall groove 252 of the second side wall 25 extends from the oil groove 20 toward the second pinion gear 432, which is located on the rear side of the main rotational direction of the differential case 2, the tooth tip surface and axial end surface of the second pinion gear 432, which are subjected to a relatively high load, can be properly lubricated, thereby making it possible to suppress the generation of heat and wear due to friction.

[0062] As with the first embodiment, the third embodiment described above also makes it possible to cause lubricating oil to flow inside and outside the differential case 2 via the oil grooves 20 due to the rotation of the differential case 2 relative to the differential housing 6, even when the differential case 2 and the first and second axle shafts 51, 52 rotate at the same speed and in the same direction. Also, as with the second embodiment, it is possible to cause lubricating oil to flow inside and outside the differential case 2 without using the oil pump 81, which can contribute to reducing the weight and cost of the vehicle.

[0063] (Note) The present invention has been described above based on the first to third embodiments, but these embodiments do not limit the scope of the claimed invention. It should be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention. Furthermore, the present invention can be implemented by omitting some components, adding or substituting components, and by modifying it in the following ways, for example, without departing from the spirit of the invention.

[0064] In the first to third embodiments, the differential mechanism 4 has been described as having first and second pinion gears 431, 432 that can rotate around a rotation axis parallel to the rotation axis O and meshed with first and second side gears 41, 42. However, this is not limited to this, and a differential mechanism may also be used in which, for example, a pinion shaft extending in a direction perpendicular to the rotation axis O is fixed to the differential case 2, and multiple pinion gears journaled on this pinion shaft are meshed with a pair of side gears.

[0065] In the first to third embodiments, the first and second axle shafts 51, 52 are respectively connected to the first and second side gears 41, 42 so as not to rotate relative to each other, but this is not limiting, and one of the constant velocity joint coupling members of a drive shaft having constant velocity joints at both ends of an intermediate shaft may be connected to the first and second side gears 41, 42 so as not to rotate relative to each other. In this case, the left and right constant velocity joint coupling members connected to the first and second side gears 41, 42, respectively, correspond to the output rotating member of the present invention.

[0066] DESCRIPTION OF SYMBOLS 1, 1A, 1B... Differential device 2... Differential case (input rotating member) 20... Oil groove 21... First cylindrical portion 22... Second cylindrical portion 23... Main body portion 24... First side wall 242... Inner wall groove 25... Second side wall 252... Inner wall groove 4... Differential mechanism 41... First side gear 42... Second side gear 431... First pinion gear 432... Second pinion gear 51... First axle shaft (output rotating member) 52... Second axle shaft (output rotating member) 80... Lubricating oil O... Rotation axis D... Groove depth W... Groove width

Claims

1. A differential device comprising: a case-shaped input rotating member that rotates by the driving force of a vehicle's driving source; and a differential mechanism that is housed in the input rotating member and lubricated with lubricating oil, and distributes the driving force input to the input rotating member to a pair of output rotating members that are coaxially rotatable relative to each other, wherein the input rotating member has a main body that houses the differential mechanism and a pair of cylindrical portions into which the pair of output rotating members are respectively inserted, and an oil groove is formed on the inner surface of at least one of the pair of cylindrical portions, extending in the axial direction of the one cylindrical portion, and the oil groove becomes deeper and wider as it goes from one side to the other side in the axial direction.

2. The differential device according to claim 1, wherein the oil groove is formed in each of the pair of cylindrical portions.

3. A differential device as described in claim 1, wherein the main body portion has side walls on both sides in the direction of the rotation axis of the input rotating member, the pair of cylindrical portions are arranged to protrude from each of the side walls along the direction of the rotation axis, and the oil groove becomes deeper and wider as it moves from the side wall side toward the tip side of at least one of the cylindrical portions.

4. A differential device as described in claim 3, wherein the oil groove is formed in each of the pair of cylindrical portions, and the oil groove formed in the inner surface of one of the pair of cylindrical portions becomes deeper and wider in width from the side wall side toward the tip side of the one of the pair of cylindrical portions, and the oil groove formed in the inner surface of the other of the pair of cylindrical portions becomes deeper and wider in width from the tip side of the other of the pair of cylindrical portions toward the side wall side.

5. A differential device as set forth in claim 3 or 4, wherein an inner wall groove is formed on the inner surface of said side wall, said inner wall groove communicating with said oil groove and extending in the radial direction.

6. A differential device as claimed in claim 5, wherein said differential mechanism comprises a pair of side gears to which said pair of output rotating members are respectively connected so as not to rotate relative to one another, and a plurality of pinion gears supported by said input rotating member and meshing with said pair of side gears, and said inner wall groove extends in a position aligned in the direction of the rotation axis with at least one of said pair of side gears.

7. The differential device according to claim 6, wherein said multiple pinion gears include a first pinion gear meshing with one of said pair of side gears and two second pinion gears meshing with the other side gear, said first pinion gear and said two second pinion gears meshing with the outer periphery of said other side gear to form a pinion gear set, and said inner wall groove extends at a position aligned in the direction of the rotation axis with the second pinion gear on the rear side of said first pinion gear in the main rotation direction of said input rotating member.

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