Differential gear and manufacturing method of the same

Abstract

To provide a differential gear which can easily secure desired performance of a case member and an inner ring member, and to provide a manufacturing method of the differential gear.SOLUTION: A differential device 1 includes an input member 8, a case member 9, a one-way clutch 10 which is disposed between the input member 8 and the case member 9 and transmits torque between the input member 8 and the case member 9 only when the input member 8 rotates in a normal rotation direction relative to the case member 9; at least one pinion gear 11; and a pair of side gears 12. The one-way clutch 10 has: an outer diameter side engagement surface 47 which is formed on the inner peripheral surface of the input member 8 directly or through another member; an inner diameter side engagement surface 49 formed on the outer peripheral surface of the inner ring member 48 fixedly coupled to the case member 9; and an engagement element 50 disposed between the outer diameter side engagement surface 47 and the inner diameter side engagement surface 49. The hardness of the inner diameter side engagement surface 49 of the inner ring member 48 is higher than the hardness of the surface of the case member 9.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a differential device for distributing the power of a drive source to a pair of wheels.

Background Art

[0002] In a vehicle drive device, the torque of a drive source such as an engine or a drive motor is transmitted to a differential device (differential gear) via a speed reduction mechanism including a transmission and a power transmission mechanism such as a propeller shaft, and is distributed to a pair of wheels by the differential device.

[0003] There is room for improvement in a vehicle drive device as described above in terms of improving fuel consumption performance or electricity consumption performance. That is, when the accelerator is turned off during the running of a vehicle equipped with the vehicle drive device and the vehicle tries to coast, losses occur in the meshing portion of the speed reduction mechanism, the drive source, etc., so the coasting distance may be shortened.

[0004] International Publication No. 2022 / 215449 describes a differential device including an input member having a torque input portion to which torque from a power transmission mechanism is input, a case member rotatably supporting a pinion gear and a pair of side gears that mesh with each other, and a one-way clutch disposed between the input member and the case member and transmitting torque between the input member and the case member only when the input member tries to rotate relative to the case member in the forward rotation direction. Note that the forward rotation direction refers to the rotation direction of the input member with respect to the case member when torque is transmitted from the drive source to the wheels to move the vehicle forward.

[0005] According to the differential device described in International Publication No. 2022 / 215449, when a vehicle in forward travel switches from a non-inertial running state to an inertial running state, that is, when the rotational speed of the input member in the forward rotation direction decreases and becomes slower than the rotational speed of the case member in the forward rotation direction, and the input member rotates relative to the case member in the reverse rotation direction, the one-way clutch switches from the engaged state to the disengaged state, and the case member becomes rotatable idly with respect to the input member. In short, the wheels are disconnected from the power transmission mechanism and the drive source. As a result, the travel distance due to inertial running can be increased, and the fuel consumption performance or power consumption performance of the vehicle can be improved.

[0006] In addition, International Publication No. 2022 / 215449 describes, as the structure of the one-way clutch incorporated in the differential device, a structure including an outer diameter side engaging surface on the input member side, an inner diameter side engaging surface on the case member side, and an engaging element disposed between the outer diameter side engaging surface and the inner diameter side engaging surface. In such a one-way clutch, when the input member (outer diameter side engaging surface) attempts to rotate relative to the case member (inner diameter side engaging surface) in the forward rotation direction, the engaging element engages with each of the outer diameter side engaging surface and the inner diameter side engaging surface to enter the engaged state, whereas when the input member (outer diameter side engaging surface) attempts to rotate relative to the case member (inner diameter side engaging surface) in the reverse rotation direction, the engagement of the engaging element with each of the outer diameter side engaging surface and the inner diameter side engaging surface is disengaged, resulting in the disengaged state.

[0007] In addition, International Publication No. 2022 / 215449 describes a structure of the one-way clutch having the above structure, further including an inner ring member having an inner diameter side engaging surface on its outer peripheral surface, and the inner ring member is externally fitted and fixed to the case member.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] In the conventional differential device described in International Publication No. 2022 / 215449, since the inner ring member externally fitted and fixed to the case member has an inner diameter side engagement surface with which an engaging element engages (is pressed) on the outer peripheral surface, it is necessary to sufficiently ensure the hardness of the inner diameter side engagement surface from the viewpoint of ensuring durability.

[0010] On the other hand, the case member has a stepped cylindrical shape. That is, the case member has a shape change portion where the shape changes abruptly and stress tends to concentrate, such as a connecting portion between a substantially cylindrical tube portion and a substantially hollow circular plate-shaped connecting portion, for example. Therefore, in order to ensure the durability of the case member, it is necessary to ensure a certain degree of toughness.

[0011] Generally, hardness and toughness are in an inverse relationship. Therefore, if a heat treatment is performed on the whole of a case member and an inner ring member integrally formed by casting or the like to adjust the hardness of the entire surface to the range of the hardness required for the inner diameter side engagement surface, there is a possibility that the toughness of the case member cannot be sufficiently ensured.

[0012] In view of the above circumstances, an object of the present disclosure is to provide a differential device in which desired performance can be easily ensured for each of a case member and an inner ring member, and a manufacturing method thereof.

Means for Solving the Problems

[0013] The differential device according to the first aspect of the present disclosure is an input member having a torque input portion, a case member coaxially arranged with the input member and capable of relatively rotating with respect to the input member, a one-way clutch arranged between the input member and the case member and transmitting torque between the input member and the case member only when the input member attempts to relatively rotate in the normal rotation direction with respect to the case member, at least one pinion gear supported by the case member so as to be capable of rotating about an axis orthogonal to the central axis of the case member Coaxial with the central axis of the input member, a pair of side gears that are supported so as to be rotatable relative to the input member and the case member and mesh with the pinion gear, and comprising The one-way clutch has an outer diameter side engaging surface formed directly on the inner peripheral surface of the input member or via another member, an inner diameter side engaging surface formed on the outer peripheral surface of the inner ring member coupled and fixed to the case member, and an engaging element disposed between the outer diameter side engaging surface and the inner diameter side engaging surface. The hardness of the inner diameter side engaging surface of the inner ring member is harder than the hardness of the surface of the case member.

[0014] The differential device according to the second aspect of the present disclosure is the differential device according to the first aspect of the present disclosure, wherein the case member has at least one support hole penetrating the case member in the radial direction, the pinion gear is rotatably supported around a support shaft whose axial end portion is fitted and supported in the support hole, the case member has a fitting surface portion at a portion of the outer peripheral surface that is axially offset from the opening on the radially outer side of the support hole, the inner ring member is externally fitted to the fitting surface portion, and an end portion on the side farther from the support hole in the axial direction is welded and fixed to the case member.

[0015] The method for manufacturing a differential device according to the third aspect of the present disclosure is the method for manufacturing a differential device according to the first aspect or the second aspect of the present disclosure, and includes a step of manufacturing the case member, a step of manufacturing the inner ring member, a step of coupling and fixing the inner ring member to the case member, and comprising the step of manufacturing the case member includes a step of performing a heat treatment on the case member, the step of manufacturing the inner ring member includes a step of performing a heat treatment on the inner ring member under conditions different from the heat treatment performed on the case member.

[0016] The manufacturing method of the differential device according to the fourth aspect of the present disclosure is, in the manufacturing method of the differential device according to the third aspect of the present disclosure, at least one of the step of manufacturing the case member and the step of manufacturing the inner ring member includes a casting step.

Advantages of the Invention

[0017] According to the differential device and its manufacturing method of one aspect of the present disclosure, it is easy to ensure desired performance for each of the case member and the inner ring member.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0019] An example of an embodiment of the present disclosure will be described with reference to FIGS. 1 to 8(b).

[0020] FIG. 1 shows a vehicle drive device 2 incorporating the differential device 1 of this example. The vehicle drive device 2 increases the output torque of a drive source 3 such as an engine or a drive motor by a power transmission mechanism 4 and then transmits it to the differential device 1. The differential device 1 distributes it to a pair of drive shafts 5. As a result, a pair of wheels 6 connected to the tip ends of the pair of drive shafts 5 are rotationally driven.

[0021] The power transmission mechanism 4 can increase the torque input from the drive source 3 and output it from an output gear 4a that constitutes a torque output portion. The power transmission mechanism 4 can include a transmission of an appropriate type such as an automatic transmission (AT), a continuously variable transmission (CVT) such as a belt type or a toroidal type, an automated manual transmission (AMT), a dual clutch transmission (DCT), or a manual transmission (MT), or a propeller shaft.

[0022] In this example, each wheel 6 that constitutes the pair of wheels 6 functions as a drive wheel only when the vehicle is non-inertially traveling in the forward direction in an all-wheel drive (AWD) vehicle. This point will be described in more detail later.

[0023] The differential device 1 of this example includes a housing 7, an input member 8, a case member 9, a one-way clutch 10, a pinion gear 11, and a pair of side gears 12.

[0024] Regarding the differential device 1, the axial direction, the circumferential direction, and the radial direction refer to the axial direction, the circumferential direction, and the radial direction of the input member 8 unless otherwise specified. The axial direction, the circumferential direction, and the radial direction of the input member 8 coincide with the axial direction, the circumferential direction, and the radial direction of the case member 9, and also coincide with the axial direction, the circumferential direction, and the radial direction of the pair of side gears 12. One side with respect to the axial direction refers to the right side in FIGS. 2 to 4(b), and the other side with respect to the axial direction refers to the left side in FIGS. 2 to 4(b).

[0025] The housing 7 is supported and fixed to the vehicle body and does not rotate during use.

[0026] The input member 8 has a ring gear 13 that constitutes a torque input portion. The ring gear 13 is provided on the outer peripheral surface of the input member 8 and meshes with an output gear 4a that constitutes a torque output portion of the power transmission mechanism 4. In this example, the input member 8 has a stepped cylindrical shape and includes, in order from one axial side, an input small-diameter cylindrical portion 14a, an input connection portion 15a, an input large-diameter cylindrical portion 16, an input connection portion 15b, and an input small-diameter cylindrical portion 14b.

[0027] The input small-diameter cylindrical portion 14a on one axial side has a cylindrical shape.

[0028] The input connection portion 15a on one axial side has a substantially conical cylindrical shape that slopes in a direction in which the inner diameter and the outer diameter increase from one axial side toward the other side, and connects the end portion on the other axial side of the input small-diameter cylindrical portion 14a on one axial side and the end portion on one axial side of the input large-diameter cylindrical portion 16. That is, the end portion on one axial side of the input connection portion 15a is connected to the end portion on the other axial side of the input small-diameter cylindrical portion 14a, and the end portion on the other axial side of the input connection portion 15a is connected to the end portion on one axial side of the input large-diameter cylindrical portion 16.

[0029] The input large-diameter cylindrical portion 16 has a cylindrical shape. A ring gear 13 is provided on the outer peripheral surface of the input large-diameter cylindrical portion 16. In this example, the ring gear 13 is constituted by a helical gear. However, the ring gear 13 can also be constituted by a spur gear or a bevel gear. Alternatively, the torque input portion to which torque from the power transmission mechanism 4 is input can also be constituted by a pulley for passing a belt or a sprocket for passing a chain.

[0030] The input connection part 15b on the other side in the axial direction has a substantially hollow circular plate shape and connects the end part on the other side in the axial direction of the input large-diameter cylindrical part 16 and the end part on one side in the axial direction of the input small-diameter cylindrical part 14b on the other side in the axial direction. That is, the outer end part in the radial direction of the input connection part 15b is connected to the end part on the other side in the axial direction of the input large-diameter cylindrical part 16, and the inner end part in the radial direction of the input connection part 15b is connected to the end part on one side in the axial direction of the input small-diameter cylindrical part 14b.

[0031] The input small-diameter cylindrical part 14b on the other side in the axial direction has a cylindrical shape.

[0032] The input member 8 is rotatably supported with respect to the housing 7 by a pair of tapered roller bearings 17a and 17b provided with a contact angle of a face combination (DF) type. Specifically, by disposing the tapered roller bearing 17a on one side in the axial direction between the outer peripheral surface of the input small-diameter cylindrical part 14a on one side in the axial direction and the inner peripheral surface of the housing 7, and disposing the tapered roller bearing 17b on the other side in the axial direction between the outer peripheral surface of the input small-diameter cylindrical part 14b on the other side in the axial direction and the inner peripheral surface of the housing 7, the input member 8 is rotatably supported inside the housing 7.

[0033] In this example, the input member 8 is formed by coupling and fixing a first element 18 having the input small-diameter cylindrical part 14a on one side in the axial direction, the input connection part 15a on one side in the axial direction, and the input large-diameter cylindrical part 16, and a second element 19 having the input connection part 15b on the other side in the axial direction and the input small-diameter cylindrical part 14b on the other side in the axial direction with bolts 20. That is, bolts 20 inserted through through-holes provided at a plurality of circumferential positions of the input connection part 15b of the second element 19 are screwed into screw holes opened on the side surface on the other side in the axial direction of the input large-diameter cylindrical part 16 of the first element 18, and the first element 18 and the second element 19 are coupled to constitute the input member 8.

[0034] In this example, the input member 8 has an oil hole 58 for supplying lubricating oil to the one-way clutch 10. The oil hole 58 is provided so as to axially penetrate at least one circumferential position in the radial direction overlapping the one-way clutch 10 arranged radially inside the input large-diameter cylindrical portion 16 among the input connection portions 15b on the other axial side. In this example, the oil holes 58 are provided at eight equally spaced circumferential positions of the input connection portion 15b.

[0035] The case member 9 is arranged coaxially with the input member 8 and capable of relative rotation with respect to the input member 8. That is, the central axis O8 of the input member 8 and the central axis O9 of the case member 9 coincide with each other. In this example, the case member 9 is configured in a stepped cylindrical shape and is supported inside the input member 8 in the radial direction so as to be capable of relative rotation with respect to the input member 8. The case member 9 includes, in order from one axial side, a case small-diameter cylindrical portion 21a, a case connection portion 22a, a case large-diameter cylindrical portion 23, a case connection portion 22b, and a case small-diameter cylindrical portion 21b.

[0036] The case small-diameter cylindrical portion 21a on one axial side has a cylindrical shape.

[0037] The case connection portion 22a on one axial side has a substantially hollow circular plate shape and connects the end portion on the other axial side of the case small-diameter cylindrical portion 21a on one axial side and the end portion on one axial side of the case large-diameter cylindrical portion 23. That is, the inner end portion in the radial direction of the case connection portion 22a is connected to the end portion on the other axial side of the case small-diameter cylindrical portion 21a, and the outer end portion in the radial direction of the case connection portion 22a is connected to the end portion on one axial side of the case large-diameter cylindrical portion 23.

[0038] The large-diameter cylindrical portion 23 of the case has a substantially cylindrical shape. The case member 9 has at least one support hole 24 that penetrates the case member 9 in the radial direction. The support holes 24 are provided in the same number as the number of pinion gears 11. In this example, since two pinion gears 11 are provided, two support holes 24 are provided in the case member 9. The two support holes 24 are formed at two positions on the opposite sides in the radial direction of the axial intermediate portion of the large-diameter cylindrical portion 23 of the case so as to penetrate in the radial direction. The axial both-end portions of the support shaft 25 for supporting the two pinion gears 11 are internally fitted in the two support holes 24 without play in the radial direction.

[0039] The large-diameter cylindrical portion 23 of the case has a through hole 26 that penetrates in the axial direction in a portion adjacent to one (the lower side in FIGS. 2 and 3) of the support holes 24 in one axial direction, and has a concave hole 27 that opens to the inner peripheral surface of the one support hole 24 in a portion adjacent to the other side in the axial direction with respect to the one support hole 24. The axial both-end portions of the pin 28 are press-fitted and internally fitted in the through hole 26 and the concave hole 27. Further, the axial intermediate portion of the pin 28 is inserted into a through hole 29 that penetrates the end portion on one (the lower side in FIGS. 2 and 3) axial side of the support shaft 25 in the radial direction without play, thereby preventing the axial movement and rotation of the support shaft 25 with respect to each support hole 24.

[0040] The large-diameter cylindrical portion 23 of the case has window holes 30 that penetrate in the radial direction at at least one position (for example, two positions on the opposite sides in the radial direction) that is deviated from each support hole 24 in the circumferential direction in a portion from one end portion to the intermediate portion in the axial direction. When assembling the differential device 1, the pinion gear 11 and the side gear 12 are arranged inside the large-diameter cylindrical portion 23 of the case through the window holes 30.

[0041] The case member 9 has a fitting surface portion 31 at a portion of the outer peripheral surface that axially deviates from the opening on the radially outer side of the support hole 24. Specifically, in this example, the fitting surface portion 31 is provided on the outer peripheral surface of the end portion on the other axial side of the large-diameter case cylinder portion 23. In this example, the large-diameter case cylinder portion 23 bends radially outward from the end portion on one axial side of the fitting surface portion 31 and has a stepped surface 32 facing the other axial side.

[0042] The case connection portion 22b on the other axial side has a substantially hollow circular plate shape and connects the end portion on the other axial side of the large-diameter case cylinder portion 23 and the end portion on one axial side of the small-diameter case cylinder portion 21b on the other axial side. That is, the radially outer end portion of the case connection portion 22b is connected to the end portion on the other axial side of the large-diameter case cylinder portion 23, and the radially inner end portion of the case connection portion 22b is connected to the end portion on one axial side of the small-diameter case cylinder portion 21b.

[0043] The small-diameter case cylinder portion 21b on the other axial side has a cylindrical shape.

[0044] In this example, the case member 9 is made of an iron alloy such as chromium molybdenum steel (SCM material), and the surface hardness is adjusted to a predetermined range by heat treatment. Specifically, the surface of the case member 9 preferably has a surface hardness of HV300 or more and HV350 or less, although it is not limited thereto.

[0045] The differential device 1 of this example further includes two radial needle bearings 33a and 33b. The two radial needle bearings 33a and 33b rotatably support the input member 8 with respect to the case member 9.

[0046] One radial needle bearing 33a is disposed between the inner peripheral surface of the input small-diameter cylinder portion 14a of the input member 8 and the outer peripheral surface of the small-diameter case cylinder portion 21a of the case member 9. The other radial needle bearing 33b is disposed between the inner peripheral surface of the input small-diameter cylinder portion 14b of the input member 8 and the outer peripheral surface of the small-diameter case cylinder portion 21b of the case member 9.

[0047] In this example, each radial needle bearing 33a, 33b includes an outer ring 34 fitted inside the input small-diameter cylindrical portions 14a, 14b, an inner ring 35 fitted outside the case small-diameter cylindrical portions 21a, 21b, a plurality of needles 36 disposed between the inner peripheral surface of the outer ring 34 and the outer peripheral surface of the inner ring 35, and a cage 37 that holds the plurality of needles 36.

[0048] The differential device 1 of this example further includes two thrust needle bearings 38a, 38b. The two thrust needle bearings 38a, 38b rotatably support the input member 8 with respect to the case member 9.

[0049] One thrust needle bearing 38a is disposed between the side surface on the other axial side of the input connection portion 15a of the input member 8 and the side surface on one axial side of the case connection portion 22a of the case member 9. The other thrust needle bearing 38b is disposed between the side surface on one axial side of the input connection portion 15b of the input member 8 and the side surface on the other axial side of the case connection portion 22b of the case member 9.

[0050] In this example, each thrust needle bearing 38a, 38b includes a thrust race 39 and a plurality of needles 40.

[0051] As shown in FIGS. 8(a) and 8(b), the thrust race 39 is configured in a hollow circular plate shape. In this example, the thrust race 39 has notches 41 at a plurality of circumferential locations on the outer peripheral surface. In this example, the notches 41 are provided at 18 circumferentially equally spaced locations on the outer peripheral surface of the thrust race 39. The thrust race 39 has a thrust raceway surface 42 on the side surface closer to the case member 9 in the axial direction. The thrust race 39 has oil grooves 43 that cross the side surface in the radial direction and have radially outer ends opening into the notches 41 at a plurality of locations on the side surface farther from the case member 9 in the axial direction and having the same phase as the notches 41 in the circumferential direction. Note that when implementing the present disclosure, the notches and oil grooves of the thrust race can also be omitted.

[0052] The plurality of needles 40 are arranged radially along the thrust raceway surface 42. In this example, each of the thrust needle bearings 38a, 38b further includes a cage 44. The plurality of needles 40 are freely held by the cage 44 so as to rotate about their respective central axes.

[0053] In this example, each of the thrust needle bearings 38a, 38b further includes another thrust race 45. The other thrust race 45 is formed by bending a metal plate and is configured in an annular shape as a whole with a substantially L-shaped cross section, and has a thrust raceway surface 46 on the side far from the case member 9 in the axial direction. The plurality of needles 40 are sandwiched between the thrust raceway surface 42 of the thrust race 39 and the thrust raceway surface 46 of the other thrust race 45.

[0054] In this example, one thrust needle bearing 38a is brought into contact with the axially other side surface of the input connection portion 15a of the input member 8 at the axially one side surface of the thrust race 39 where a plurality of oil grooves 43 are provided, and the axially other side surface of the other thrust race 45, which is the surface opposite to the side where the thrust raceway surface 46 is provided, is brought into contact with the axially one side surface of the case connection portion 22a of the case member 9 and is installed in this state. The other thrust needle bearing 38b is brought into contact with the axially one side surface of the input connection portion 15b of the input member 8 at the axially other side surface of the thrust race 39 where a plurality of oil grooves 43 are provided, and the axially one side surface of the other thrust race 45, which is the surface opposite to the side where the thrust raceway surface 46 is provided, is brought into contact with the axially other side surface of the case connection portion 22b of the case member 9 and is installed in this state.

[0055] The one-way clutch 10 is arranged between the input member 8 and the case member 9, and transmits torque between the input member 8 and the case member 9 only when the input member 8 attempts to rotate relative to the case member 9 in the forward rotation direction. The forward rotation direction refers to the relative rotation direction of the input member 8 with respect to the case member 9 when torque is transmitted from the drive source 3 to the wheels 6 to move the vehicle forward.

[0056] In this example, the one-way clutch 10 is disposed between the input large-diameter cylindrical portion 16 of the input member 8 and the case large-diameter cylindrical portion 23 of the case member 9.

[0057] The one-way clutch 10 has an outer-diameter-side engaging surface 47 formed directly on the inner peripheral surface of the input member 8 or via another member, an inner-diameter-side engaging surface 49 formed on the outer peripheral surface of the inner ring member 48 fixedly coupled to the case member 9, and a plurality of engaging elements 50 disposed between the outer-diameter-side engaging surface 47 and the inner-diameter-side engaging surface 49.

[0058] When implementing the present disclosure, the one-way clutch can be configured by a mechanism that switches between a connected state for transmitting torque and a disconnected state for not transmitting torque based on the engagement and disengagement of a plurality of engaging elements with respect to an outer-diameter-side engaging surface and an inner-diameter-side engaging surface, such as a sprag clutch or a roller clutch. In this example, the one-way clutch 10 is configured by a sprag clutch. That is, in this example, each of the plurality of engaging elements 50 is configured by a sprag.

[0059] In this example, the outer-diameter-side engaging surface 47 is formed directly on the inner peripheral surface of the input large-diameter cylindrical portion 16 of the input member 8. However, when implementing the present disclosure, the outer-diameter-side engaging surface can also be provided on the inner peripheral surface of the input member via another member. For example, the outer-diameter-side engaging surface can also be formed on the inner peripheral surface of an outer ring member that is fitted and fixed to the input member.

[0060] The hardness of the inner-diameter-side engaging surface 49 of the inner ring member 48 is harder than the hardness of the surface of the case member 9. Specifically, the inner-diameter-side engaging surface 49 preferably has a surface hardness of HV650 or more and HV750 or less, and an effective hardened layer depth of 0.5 mm or more and 0.9 mm or less, although it is not limited thereto.

[0061] In this example, the inner ring member 48 is entirely configured in an annular shape and has a substantially rectangular cross-sectional shape. The inner ring member 48 is made of an iron alloy such as chrome molybdenum steel (SCM material), and the hardness of the surface of the inner-diameter-side engaging surface 49 provided on the outer peripheral surface is adjusted to a predetermined range by heat treatment.

[0062] Incidentally, the material constituting the inner ring member 48 can be the same as or different from the material constituting the case member 9.

[0063] In any case, at least the surface hardness of the inner diameter side engaging surface 49 of the inner ring member 48 is adjusted to a predetermined range harder than the surface hardness of the case member 9. In this example, the surface hardness of the entire inner ring member 48 including the inner diameter side engaging surface 49 is adjusted to a predetermined range harder than the surface hardness of the case member 9.

[0064] The inner ring member 48 has a stepped surface 51 facing one axial side at a portion near the end on one axial side of the inner peripheral surface.

[0065] In this example, the inner ring member 48 has scraping grooves 52 at at least one circumferential position on each of the side surfaces on both axial sides. In this example, the scraping grooves 52 are provided at 18 equally spaced circumferential positions on the side surfaces on both axial sides of the inner ring member 48. In this example, each scraping groove 52 extends in the radial direction, and the radially outer end thereof opens to the outer peripheral surface of the inner ring member 48. In this example, the radially inner end of each scraping groove 52 does not open to the inner peripheral surface of the inner ring member 48. Incidentally, when implementing the present disclosure, the scraping grooves of the inner ring member can also be omitted.

[0066] The inner ring member 48 is externally fitted to the fitting surface portion 31 of the case member 9. Specifically, in this example, the portion of the inner peripheral surface of the inner ring member 48 located on the other axial side than the stepped surface 51 is externally fitted to the fitting surface portion 31 of the case member 9 by press-fitting, and the stepped surface 51 of the inner ring member 48 is in contact with the stepped surface 32 of the case member 9.

[0067] In this state, the inner ring member 48 is welded and fixed to the case member 9 at the end on the opposite side of each support hole 24 of the case member 9 in the axial direction, that is, at the end on the other side in the axial direction. Specifically, at least one location in the circumferential direction among the radially inner ends of the side surface on the other side in the axial direction of the inner ring member 48 is welded and fixed to the case member 9 by a welding bead 53 (shown only in FIG. 3). When implementing the present disclosure, the method of coupling and fixing the inner ring member to the case member is not limited to the method of this example, and any fixing method such as caulking and bolt fixing can be adopted.

[0068] In this example, the one-way clutch 10 further includes a retainer 54 and a biasing spring 55.

[0069] The engaging elements 50 are arranged in a plurality of locations in the circumferential direction within the cylindrical space between the outer diameter side engaging surface 47 and the inner diameter side engaging surface 49 while being held by the retainer 54.

[0070] The biasing spring 55 biases each engaging element 50 in a direction in which the engaging element 50 meshes with the outer diameter side engaging surface 47 and the inner diameter side engaging surface 49.

[0071] When the input member 8 attempts to rotate relative to the case member 9 in the forward rotation direction, each engaging element 50 swings in a predetermined direction and meshes with the outer diameter side engaging surface 47 and the inner diameter side engaging surface 49. As a result, the one-way clutch 10 switches to a locked state where it is in a connected state, and torque can be transmitted between the input member 8 and the case member 9. That is, the case member 9 can rotate integrally with the input member 8.

[0072] When the input member 8 attempts to rotate relative to the case member 9 in the reverse direction, the engaging element 50 swings in the direction opposite to the predetermined direction, and the one-way clutch 10 switches to an overrunning state in which the engagement between the engaging element 50 and the outer diameter side engaging surface 47 and the inner diameter side engaging surface 49 is disengaged. As a result, torque transmission between the input member 8 and the case member 9 becomes impossible. That is, the input member 8 idles relative to the case member 9, or the case member 9 idles relative to the input member 8.

[0073] The pinion gear 11 is supported by the case member 9 so as to be rotatable about an axis orthogonal to the central axis O9 of the case member 9. In this example, two pinion gears 11 are provided, and each pinion gear 11 is constituted by a bevel gear. That is, the pinion gear 11 has a substantially frustum shape and has a plurality of teeth on its outer peripheral surface. Further, the pinion gear 11 has a central hole 56 penetrating in the axial direction of the pinion gear 11 at its center. The pinion gear 11 is rotatably supported around a support shaft 25 whose both end portions in the axial direction are fitted and supported in two support holes 24 of the case member 9.

[0074] A pair of side gears 12 are supported coaxially with the central axis O8 of the input member 8 so as to be rotatable relative to the input member 8 and the case member 9, and mesh with the pinion gear 11. The side gears 12 constituting the pair of side gears 12 are constituted by bevel gears. That is, the side gear 12 has a substantially frustum shape and has a plurality of teeth on its outer peripheral surface that mesh with the teeth of the pinion gear 11. Further, the side gear 12 has a spline hole 57 penetrating in the axial direction at its center. The side gear 12 is disposed inside the case large diameter cylinder portion 23 of the case member 9 and is coupled and fixed to the base end portion of the drive shaft 5 so as to enable torque transmission. That is, the spline shaft portion provided at the base end portion of the drive shaft 5 is spline-engaged with the spline hole 57.

[0075] <When the vehicle is non-inertially traveling in the forward direction> To move the vehicle forward, with the shift lever switched to the forward driving range, when torque in the forward driving direction of the vehicle is output from the drive source 3 based on an operation of the accelerator by the driver or the like, the torque is increased by the power transmission mechanism 4 and then transmitted to the input member 8. As a result, when the input member 8 attempts to rotate relative to the case member 9 in the forward rotation direction, the one-way clutch 10 switches to the connected state, and the input member 8 and the case member 9 rotate integrally.

[0076] When the case member 9 rotates, the two pinion gears 11 rotate, that is, revolve, about the central axis O9 of the case member 9. Further, based on the meshing of the teeth of the pinion gear 11 and the teeth of the side gear 12, a pair of side gears 12 rotate about their own central axes arranged coaxially with the central axis O8 of the input member 8. Thereby, a pair of drive shafts 5 coupled and fixed to the pair of side gears 12 are rotationally driven, and a pair of wheels 6 are rotationally driven in the direction of moving the vehicle forward.

[0077] <When the vehicle coasts in the forward direction> From the state where the vehicle is moving forward as described above, to perform coasting, such as called coasting driving or sailing driving, when the accelerator is turned off and the input of torque from the drive source 3 to the input member 8 stops, the rotational speed of the input member 8 in the forward rotation direction decreases and becomes slower than the rotational speed of the case member 9 in the forward rotation direction. That is, the input member 8 rotates relative to the case member 9 in the reverse rotation direction. As a result, the one-way clutch 10 switches to the disengaged state, and the case member 9 idles relative to the input member 8.

[0078] In short, a pair of wheels 6 are disconnected from the power transmission mechanism 4 and the drive source 3. Therefore, the traveling distance by coasting can be lengthened. In other words, the speed reduction during coasting can be moderated. As a result, the fuel consumption performance and the power consumption performance of the vehicle can be improved.

[0079] <When the vehicle moves backward> In the vehicle equipped with the drive device 2 for an automobile of this example, at least one pair of wheels, different from the pair of wheels 6, are rotationally driven in the direction of reversing the vehicle to reverse the vehicle. In this example, the pair of wheels 6 cannot be rotationally driven in the direction of reversing the vehicle.

[0080] That is, in order to reverse the vehicle, when the shift lever is switched to the reverse driving range and the torque output from the drive source 3 is increased by the power transmission mechanism 4 and then transmitted to the input member 8 based on an operation of the accelerator by the driver or the like, the input member 8 tends to relatively rotate in the reverse direction with respect to the case member 9. As a result, the one-way clutch 10 is switched to the disengaged state, and the case member 9 idles with respect to the input member 8. In short, since the pair of wheels 6 are disconnected from the power transmission mechanism 4 and the drive source 3, they are not rotationally driven in the direction of reversing the vehicle.

[0081] Note that in any driving state, the difference in rotational speed between the pair of wheels 6 that occurs during turning driving or the like is absorbed by the two pinion gears 11 rotating, that is, revolving, about the support shaft 25.

[0082] In the differential device 1 of this example, even when the rotation of the input member 8 stops during coasting, that is, even when the lubricating oil supplied to the lower part of the portion between the input member 8 and the case member 9 through the oil hole 58 cannot be scraped up by the rotation of the input member 8, it is easy to maintain a good lubrication state of the two radial needle bearings 33a, 33b and the two thrust needle bearings 38a, 38b.

[0083] That is, in the differential device 1 of this example, even when the rotation of the input member 8 stops during coasting, the case member 9 and the inner ring member 48 rotate, and through the oil hole 58 provided in the input connection portion 15b of the input member 8, it is supplied to the portion between the input member 8 and the case member 9, and the lubricating oil accumulated in the lower part of the portion can be scraped up by the scraping grooves 52 provided on the side surfaces on both axial sides of the inner ring member 48.

[0084] The lubricating oil lifted by the lifting groove 52 moves from the lower part to the upper part of the portion between the input member 8 and the case member 9 while being held by the lifting groove 52 as shown by the dashed arrow α1 in Fig. 2, and is flung off by the action of centrifugal force accompanying the rotation of the inner ring member 48.

[0085] A part of the flung-off lubricating oil adheres to the inner peripheral surface of the large-diameter input cylinder portion 16 of the input member 8 and lubricates the outer diameter side engagement surface 47 provided on the inner peripheral surface of the large-diameter input cylinder portion 16. The lubricating oil adhering to the outer diameter side engagement surface 47 moves so as to drip onto the surface of the engaging element 50 and the inner diameter side engagement surface 49, and lubricates these surfaces. The inner diameter side engagement surface 49 is also lubricated as the inner diameter side engagement surface 49 passes through the lubricating oil accumulated in the lower part of the portion between the input member 8 and the case member 9 as the inner ring member 48 rotates.

[0086] Also, a part of the flung-off lubricating oil moves toward both axial sides as shown by the dashed arrow α2, passes through the installation locations of the two thrust needle bearings 38a and 38b and the installation locations of the two radial needle bearings 33a and 33b in order, lubricates the two thrust needle bearings 38a and 38b and the two radial needle bearings 33a and 33b, and then is returned to the lower part of the portion between the housing 7 and the input member 8. The lubricating oil returned to the lower part of the portion between the housing 7 and the input member 8 is supplied again to the lower part of the portion between the input member 8 and the case member 9 through the oil hole 58 and is lifted by the lifting groove 52.

[0087] As can be understood from the above description, in the differential device 1 of this example, when the entire two radial needle bearings 33a, 33b and two thrust needle bearings 38a, 38b arranged in the portion between the input member 8 and the case member 9 are located above the oil level S which is the upper surface of the lubricating oil supplied to the lower portion of the portion between the input member 8 and the case member 9, that is, even when the two radial needle bearings 33a, 33b and the two thrust needle bearings 38a, 38b are not immersed in the lubricating oil, if the lower portion of the inner ring member 48 is immersed in the lubricating oil supplied to the lower portion of the portion between the input member 8 and the case member 9, the lubricating oil can be continuously supplied to the two radial needle bearings 33a, 33b and the two thrust needle bearings 38a, 38b by scraping up the lubricating oil by the scraping grooves 52 provided on the side surfaces on both axial sides of the inner ring member 48. Therefore, it is easy to maintain a good lubrication state of the one-way clutch 10, the two radial needle bearings 33a, 33b, and the two thrust needle bearings 38a, 38b.

[0088] Furthermore, in this example, as shown by the arrow α2 in FIG. 2, when the lubricating oil flowing passes through the installation locations of the two thrust needle bearings 38a, 38b, a part of it passes through the notch 41 and the oil groove 43 of the thrust race 39, and the rest passes through the portion between the thrust races 39 and 45. That is, a part of the lubricating oil passes through the installation locations of the thrust needle bearings 38a, 38b without being used for lubricating the rolling contact portions between the needles 40 and the thrust raceway surfaces 42, 46. Therefore, even when the relative rotational speed of the case member 9 with respect to the input member 8 is high, since the supply amount of the lubricating oil to the two radial needle bearings 33a, 33b is sufficiently ensured, seizure of each of the radial needle bearings 33a, 33b can be prevented, and the durability of the differential device 1 can be improved.

[0089] In this example, the inner diameter side engaging surface 49 of the one-way clutch 10 is not directly formed on the outer peripheral surface of the case member 9, but is formed on the outer peripheral surface of the inner ring member 48 which is separately configured from the case member 9 and is coupled and fixed to the case member 9. The hardness of the inner diameter side engaging surface 49 of the inner ring member 48 is harder than the hardness of the surface of the case member 9. Therefore, it is easy to ensure the desired performance for each of the case member 9 and the inner ring member 48.

[0090] That is, in this example, by sufficiently hardening the hardness of the inner diameter side engaging surface 49 with which a plurality of engaging elements 50 engage in the state where the one-way clutch 10 is switched to the connected state, the durability of the inner ring member 48 can be easily ensured. Further, by sufficiently ensuring the toughness of the case member 9, it is possible to effectively prevent damage due to stress concentration from occurring at the shape change portion existing in the case member 9. Therefore, the durability of the case member 9 can be easily ensured.

[0091] In this example, the inner ring member 48 is externally fitted to the fitting surface portion 31 of the case member 9, and the end portion on the side far from the support hole 24 in the axial direction is welded and fixed to the case member 9. Therefore, even if deformation due to welding occurs in the peripheral portion of the welding fixed portion in the case member 9, it is possible to effectively prevent the deformation from reaching the respective support holes 24. Accordingly, it is possible to effectively prevent inconveniences such as the central axis of the support shaft 25 supported by the end portions on both sides in the axial direction of each support hole 24 tilting with respect to the virtual plane orthogonal to the central axis O9 of the case member 9 from occurring.

[0092] Next, a manufacturing method of the differential device 1 of this example will be described. The manufacturing method of the differential device 1 of this example includes a step of manufacturing the case member 9, a step of manufacturing the inner ring member 48, and a step of coupling and fixing the inner ring member 48 to the case member 9. That is, after separately manufacturing the case member 9 and the inner ring member 48, the inner ring member 48 is coupled and fixed to the case member 9.

[0093] The step of manufacturing the case member 9 includes a step of performing heat treatment on the case member 9.

[0094] That is, when manufacturing the case member 9, a forging process of performing forging on a metal material that is the raw material of the case member 9, that is, an iron alloy such as a chromium molybdenum steel material (SCM material), or a casting process of performing casting using the iron alloy, after obtaining an intermediate body having a rough shape of the case member 9, the intermediate body is sequentially subjected to cutting for shaping, heat treatment such as carburizing and quenching for imparting mechanical properties such as required hardness, and finishing for finishing to the final shape and surface roughness.

[0095] The process of manufacturing the inner ring member 48 includes a process of performing heat treatment on the inner ring member 48 under conditions different from those of the heat treatment performed on the case member 9.

[0096] That is, when manufacturing the inner ring member 48, a forging process of performing forging on a metal material that is the raw material of the inner ring member 48, that is, an iron alloy such as a chromium molybdenum steel material (SCM material), or a casting process of performing casting using the iron alloy, after obtaining an intermediate body having a rough shape of the inner ring member 48, the intermediate body is sequentially subjected to cutting for shaping, heat treatment such as carburizing and quenching for imparting mechanical properties such as required hardness, and finishing for finishing to the final shape and surface roughness.

[0097] At this time, the heat treatment conditions for the case member 9 and the heat treatment conditions for the inner ring member 48 are made different from each other so that the hardness of the inner diameter side engagement surface 49 of the inner ring member 48 becomes harder than the hardness of the surface of the case member 9.

[0098] As described above, the material constituting the inner ring member 48 can be the same as or different from the material constituting the case member 9. For example, when the inner ring member 48 is constituted of the same material as the material constituting the case member 9, by adjusting heat treatment conditions such as the carbon concentration of the atmospheric gas, the heating time, and the heating temperature, the hardness of the surface of the inner diameter side engagement surface 49 can be made harder than the hardness of the surface of the case member 9.

[0099] In this example, at least one of the process of manufacturing the case member 9 and the process of manufacturing the inner ring member 48 includes a casting process. However, when implementing the present disclosure, it is also possible that neither the process of manufacturing the case member 9 nor the process of manufacturing the inner ring member 48 includes a casting process.

[0100] In the process of coupling and fixing the inner ring member 48 to the case member 9, a portion of the inner circumferential surface of the inner ring member 48 that is located on the other axial side of the stepped surface 51 is externally fitted to the fitting surface portion 31 of the case member 9 by press-fitting, and the stepped surface 51 of the inner ring member 48 is brought into contact with the stepped surface 32 of the case member 9. Then, in this state, at least one location in the circumferential direction of the radially inner end portion of the side surface on the other axial side of the inner ring member 48 is welded and fixed to the case member 9 by a welding bead 53 (only shown in FIG. 3).

[0101] According to the manufacturing method of this example, the differential device 1 having a configuration in which the hardness of the inner diameter side engaging surface 49 of the inner ring member 48 is harder than the hardness of the surface of the case member 9 can be appropriately manufactured.

[0102] When implementing the differential device of the present disclosure, a structure provided with a clutch device that is disposed between the input member and the case member and can switch the connection and disconnection state between the input member and the case member can be adopted.

[0103] In a differential device having such a structure, when the shift lever is switched to the forward travel range and the clutch device is in the disengaged state, when the vehicle coasts, that is, when the input member rotates relative to the case member in the reverse direction, the one-way clutch switches to the disengaged state, and the case member can be idled relative to the input member. Further, when the shift lever is switched to the reverse travel range and the clutch device is in the engaged state, when the vehicle is traveling in reverse, the input member and the case member can be integrally rotated by the torque input to the input member from the drive source via the power transmission mechanism. Thereby, a pair of wheels connected to the differential device can be rotationally driven in the direction in which the vehicle is reversed.

Description of Symbols

[0104] 1 Differential device 2 Vehicle drive device 3 Drive source 4 Power transmission mechanism 4a Output gear 5 Drive shaft 6 Wheel 7 Housing 8 Input member 9 Case member 10 One-way clutch 11 Pinion gear 12 Side gear 13 Ring gear 14a, 14b Input small-diameter cylindrical part 15a, 15b Input connection part 16 Input large-diameter cylindrical part 17a, 17b Tapered roller bearing 18 First element 19 Second element 20 Bolt 21a, 21b Case small-diameter cylindrical part 22a, 22b Case connection part 23 Case large-diameter cylindrical part 24 Support hole 25 Support shaft 26 Through hole 27 Concave hole 28 Pin 29 Through hole 30 Window hole 31 Fitting surface part 32 Step surface 33a, 33b Radial needle bearing 34 Outer ring 35 Inner ring 36 Needle 37 Retainer 38a, 38b Thrust needle bearing 39 Thrust race 40 Needle 41 Notch 42 Thrust raceway surface 43 Oil groove 44 Retainer 45 Thrust race 46 Thrust raceway surface 47 Outer diameter side engaging surface 48 Inner ring member 49 Inner diameter side engaging surface 50 Engager 51 Step surface 52 Scraper groove 53 Weld bead 54 Retainer 55 Biasing spring 56 Central hole 57 Spline hole 58 Oil hole

Claims

1. An input member having a torque input portion; A case member coaxially arranged with the input member and capable of relative rotation with respect to the input member; A one-way clutch arranged between the input member and the case member and transmitting torque between the input member and the case member only when the input member attempts to rotate relative to the case member in the forward rotation direction; At least one pinion gear supported by the case member and capable of rotating about an axis orthogonal to the central axis of the case member; A pair of side gears supported coaxially with the central axis of the input member and capable of relative rotation with respect to the input member and the case member and meshing with the pinion gear; Comprising; The one-way clutch has an outer diameter side engaging surface formed directly on the inner peripheral surface of the input member or via another member, an inner diameter side engaging surface formed on the outer peripheral surface of an inner ring member fixedly coupled to the case member, and an engaging element disposed between the outer diameter side engaging surface and the inner diameter side engaging surface; The hardness of the inner diameter side engaging surface of the inner ring member is harder than the hardness of the surface of the case member; Differential device.

2. The case member has at least one support hole penetrating the case member in the radial direction; The pinion gear is rotatably supported around a support shaft whose axial end is fitted and supported in the support hole; The case member has a fitting surface portion at a portion of the outer peripheral surface that is axially offset from the opening on the radially outer side of the support hole; The inner ring member is externally fitted to the fitting surface portion, and an end portion on the side farther from the support hole in the axial direction is welded and fixed to the case member; The differential device according to claim 1.

3. A method for manufacturing the differential device according to claim 1 or 2, comprising: A step of manufacturing the case member; A step of manufacturing the inner ring member; A step of coupling and fixing the inner ring member to the case member; Comprising; The step of manufacturing the case member includes a step of performing heat treatment on the case member; The step of manufacturing the inner ring member includes a step of performing heat treatment on the inner ring member under conditions different from the heat treatment performed on the case member; Method for manufacturing a differential device.

4. The method for manufacturing a differential device according to claim 3, wherein at least one of the step of manufacturing the case member and the step of manufacturing the inner ring member includes a casting step.

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