JP6411921B2 - Differential gear lubrication structure - Google Patents

Description

  The present invention provides a differential gear in which a pair of pinions rotatably supported on a pinion shaft and a pair of side gears fixed to a pair of output shafts are engaged with each other inside a differential case to which a driving force of a driving source is input. The present invention relates to a differential gear lubrication structure that guides lubricating oil supplied between an output shaft and a side gear to a pinion shaft and a sliding portion of the pinion.

  A helical groove is formed on the outer peripheral surface of the pinion shaft where the inner peripheral surface of the pinion of the differential gear is slidably fitted, and the lubricating oil is fed along the helical groove from the axial center of the pinion shaft by the rotation of the pinion. Patent Document 1 below discloses that the lubricating oil is distributed to the pinion shaft and the sliding portion of the pinion to improve the lubricating performance by being guided toward the end.

JP 2007-51668 A

  FIG. 7A shows a cross section of the sliding portion of the pinion shaft 01 and the pinion 02 of the conventional differential gear. Although exaggerated in FIG. 7 (A), the inner diameter D2 of the pinion 02 is larger than the outer diameter D1 of the pinion shaft 01, and the pinion 02 is radially caused by a meshing reaction force F received from a side gear (not shown). Since the center of the pinion 02 is eccentric with respect to the center of the pinion shaft 01, the clearance α between the inner peripheral surface of the pinion 02 and the outer peripheral surface of the pinion shaft 01 is uneven in the circumferential direction. Thus, the gap α is minimized at the minimum gap portion P.

  In the lubricating state by the lubricating oil, a lubricating oil film is formed between the surfaces of the two objects, the two surfaces are completely separated by the lubricating oil, and the lubricating oil film is thinned. There is a boundary lubrication state in which two surfaces are partially in contact with each other, and the friction coefficient in the boundary lubrication state is significantly larger than the friction coefficient in the fluid lubrication state. And the load acting between the two surfaces is small, the sliding speed between the two surfaces is large, and the higher the viscosity of the lubricating oil, the easier it is to transition to the fluid lubrication state, and vice versa. The lower the sliding speed between the two surfaces and the lower the viscosity of the lubricating oil, the easier it is to transition to the boundary lubrication state.

  In FIG. 7A, when the pinion 02 rotates relative to the pinion shaft 01 in the direction of arrow A, the lubricating oil existing between the pinion 02 and the pinion shaft 01 is dragged by the pinion 02 and pushed into a portion where the gap α is small. Due to the wedge effect, the hydraulic pressure rises in that area. Thus, in the portion where the hydraulic pressure rises, an oil film is formed between the pinion 02 and the pinion shaft 01, and a fluid lubrication state is obtained.

  However, in the above-mentioned conventional one, the spiral groove 03 is formed on the surface of the pinion shaft 02, and the clearance α between the pinion 02 and the pinion shaft 01 becomes large at the portion of the spiral groove 03. The area where the hydraulic pressure is generated becomes smaller due to the hindrance, and the maximum value of the hydraulic pressure is also reduced. Moreover, since the hydraulic pressure is interrupted in the vicinity of the minimum clearance P, the lubricating oil is extremely insufficient on the downstream side in the rotational direction A from the minimum clearance P, and there is a boundary lubrication region in the sliding portions of the pinion 02 and the pinion shaft 01. Will occur.

  As a result, large frictional heat due to poor lubrication is generated in the boundary lubrication region, and the sliding portions of the pinion 02 and the pinion shaft 01 may be damaged or seized.

  As shown in FIG. 7 (B), two chamfered portions 04 and 04 which are two parallel planes for guiding the lubricating oil are generally formed on the surface of the pinion shaft 02 of the differential gear. Even when the two chamfered portions 04 and 04 are formed, a boundary lubrication region is generated in the sliding portion of the pinion 02 and the pinion shaft 01 as in the case of forming the spiral groove 03 described above, resulting in poor lubrication or burning. There is a possibility that it may become a cause.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to improve the lubrication performance of the pinion shaft of the differential gear and the sliding portion of the pinion.

  In order to achieve the above object, according to the first aspect of the present invention, a differential case having an input gear to which driving force from a driving source is input is provided on the outer periphery and is rotatably supported around the first axis. And a pair of output shafts arranged on the first axis and facing each other and fitted in the differential case, and both end portions arranged on a second axis perpendicular to the first axis Is fixed to the mutually opposing ends of the pinion shaft supported by the differential case, the pair of pinions rotatably supported by the pinion shaft, and the pair of output shafts, and meshes with the pair of pinions, respectively. And a differential gear lubrication structure for guiding lubricating oil supplied between the output shaft and the side gear to the pinion shaft and the sliding portion of the pinion. In the pinion shaft, a portion supporting the pair of pinions is formed in a circular cross section, and a concave portion is formed on an outer peripheral surface of a portion sandwiched between the pair of pinions, and the pinion shaft is formed inside the pinion shaft. Is formed with a plurality of oil holes penetrating from the surface of the recess to the shaft end of the pinion shaft, and the radial positions of the plurality of oil holes are closer to the outer peripheral surface than the center of the pinion shaft. A differential gear lubrication structure is proposed.

  According to the invention described in claim 2, in addition to the configuration of claim 1, the pinion shaft is fixed to the differential case with a pin arranged in parallel with the first axis, and the plurality of oil holes are A differential gear lubrication structure is proposed in which the pair of output shafts open to positions facing opposite ends of the pair of output shafts.

  According to the invention described in claim 3, in addition to the structure of claim 1, the pinion shaft is supported by the differential case so as to be rotatable about the second axis, and the plurality of oil holes are formed in the pinion shaft. A differential gear lubrication structure is proposed, which is arranged at predetermined intervals in the circumferential direction along the outer peripheral surface of the differential gear.

  The final driven gear 14 of the embodiment corresponds to the input gear of the present invention, the drive shaft 16 of the embodiment corresponds to the output shaft of the present invention, and the two-chamfered portion 17b and the annular groove 17d of the embodiment are the main gear. This corresponds to the recess of the invention.

  According to the configuration of the first aspect, the differential gear has an input gear to which driving force from a driving source is input on the outer periphery and is rotatably supported around the first axis, and on the first axis. A pair of output shafts whose ends facing each other are fitted in the differential case, a pinion shaft that is disposed on a second axis perpendicular to the first axis and whose both ends are supported by the differential case, and A pair of pinions rotatably supported by the pinion shaft, and a pair of side gears fixed to the mutually opposing ends of the pair of output shafts and meshing with the pair of pinions, respectively, between the output shaft and the side gears The lubricating oil supplied through lubricates the pinion shaft and the sliding portion of the pinion.

  Since the pinion shaft has a circular cross section at the portion supporting the pair of pinions, the pinion shaft is not formed between the inner peripheral surface of the pinion and the outer peripheral surface of the pinion shaft urged in the radial direction by the meshing reaction force received from the side gear. When the lubricating oil dragged by the rotating pinion is pushed into the uniform gap by the wedge effect, a boundary lubrication area is generated where sufficient oil pressure is raised in a wide area in the gap and the film of the lubricating oil becomes thin By minimizing this, heat generation of the pinion shaft due to friction can be suppressed.

  In addition, the pinion shaft has a recess formed on the outer peripheral surface of the portion sandwiched between the pair of pinions, and a plurality of oil holes that penetrate from the surface of the recess to the end of the pinion shaft are formed inside the pinion shaft. Since the radial positions of the plurality of oil holes are closer to the outer peripheral surface than the center of the pinion shaft, it is possible to effectively cool the outer peripheral surface of the pinion shaft that tends to increase in temperature due to frictional heat.

  According to the second aspect of the present invention, the pinion shaft is fixed to the differential case by pins arranged in parallel with the first axis, and the plurality of oil holes are opened at positions facing the mutually opposed ends of the pair of output shafts. Therefore, the cooling performance of the pinion shaft can be ensured by opening a plurality of oil holes at a position where the flow rate of the lubricating oil supplied through the output shaft and the side gear is large.

  According to the configuration of claim 3, the pinion shaft is supported by the differential case so as to be rotatable around the second axis, and the plurality of oil holes are arranged at predetermined intervals in the circumferential direction along the outer peripheral surface of the pinion shaft. Even if the pinion receives a meshing reaction force from the side gear, any of the plurality of oil holes must be made of lubricating oil while preventing only a part of the outer peripheral surface from being knitted and worn by rotating the pinion shaft. It is possible to ensure the cooling performance of the pinion shaft by opening at a position where the flow rate is large.

The longitudinal cross-sectional view of a differential gear. (First embodiment) FIG. 2 is an enlarged view of part 2 of FIG. 1. (First embodiment) FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. (First embodiment) The figure corresponding to FIG. (Second Embodiment) FIG. 5 is a sectional view taken along line 5-5 of FIG. (Second Embodiment) The figure corresponding to FIG. (Third embodiment) Explanatory drawing of the lubrication state of the sliding part of a pinion and a pinion shaft. (Conventional example)

First embodiment

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, a differential gear D that distributes the driving force of an automobile engine to left and right drive wheels is a hollow differential case supported inside a mission case 11 via a pair of left and right angular roller bearings 12, 12. 13 is provided. An annular final driven gear 14 is fixed to the outer periphery of the differential case 13 with a plurality of bolts 15... And the driving force of the engine is transmitted from a final drive gear (not shown) to the final driven gear 14. It rotates around the first axis L1 extending in the width direction.

  The differential case 13 includes a pair of left and right cylindrical shaft support portions 13a and 13a whose outer periphery is supported by the mission case 11 with angular roller bearings 12 and 12, and the left drive that penetrates the mission case 11 from the outside to the inside. The tip of the shaft 16 is fitted into the left shaft support portion 13 a of the differential case 13, and the tip of the right drive shaft 16 penetrating the transmission case 11 from the inside into the right case is fitted into the right shaft support portion 13 a of the differential case 13. .

  Inside the differential case 13, a pinion shaft 17 is disposed on a second axis L2 orthogonal to the first axis L1 extending in the vehicle width direction. Both ends of the pinion shaft 17 are fitted into a pair of support holes 13 b and 13 b formed in the differential case 13, and fitted into a pin hole 17 a formed in one shaft end of the pinion shaft 17 and a pin hole 13 c formed in the differential case 13. The pin 18 is fixed so that it cannot rotate but cannot move in the direction of the second axis L2.

  A pair of pinions 19, 19 are rotatably fitted on the outer periphery of the pinion shaft 17, and a pair of side gears 20, 20 that simultaneously mesh with the pair of pinions 19, 19 are mutually connected to the left and right drive shafts 16, 16. The spline is fitted to the opposite shaft ends.

  Spiral oil grooves 13d and 13d are formed on the inner peripheral surfaces of the shaft support portions 13a and 13a of the differential case 13 in which the left and right drive shafts 16 and 16 are rotatably fitted. The oil grooves 13d and 13d The outer end in the vehicle width direction communicates with the lubricating oil reservoirs 11a, 11a of the transmission case 11 formed between the angular roller bearings 12, 12 and the seal members 22, 22. The direction of inclination of the spiral oil grooves 13d and 13d is such that the lubricating oil in the lubricating oil reservoirs 11a and 11a is guided toward the side gears 20 and 20 when the drive shafts 16 and 16 rotate in the forward direction of the vehicle. Is set.

  The splines connecting the side gears 20 and 20 to the drive shafts 16 and 16 are missing teeth at a predetermined interval in the circumferential direction, and a plurality of oil passages 16a... Section). Accordingly, the lubricating oil guided inward in the vehicle width direction by the spiral oil grooves 13d, 13d is further driven by the oil passage 16a of the spline of the drive shafts 16, 16 and the lip portions 20a, 20a of the side gears 20, 20. It is guided inward in the direction and is supplied to the central portion of the pinion shaft 17 sandwiched between the pair of pinions 19 and 19.

  As shown in FIGS. 2 and 3, two parallel chamfered portions 17b and 17b, which are two parallel planes, are formed on the outer peripheral surface of the pinion shaft 17 where the shaft ends of the pair of drive shafts 16 and 16 face each other. The two chamfered portions 17b and 17b are formed only in a portion sandwiched between the pair of pinions 19 and 19, and the cross section of the pinion shaft 17 is a circular portion where the pinions 19 and 19 are fitted.

  Inside the pinion shaft 17 are formed four oil holes 17c extending in parallel with the second axis L2 from the surfaces of the two chamfered portions 17b, 17b toward the respective shaft ends of the pinion shaft 17. The four oil holes 17c are arranged closer to the surface of the circular cross section than the second axis L2 of the pinion shaft 17. Two of the four oil holes 17c are disposed at positions facing the shaft end of the left drive shaft 16, and the other two are disposed at positions facing the shaft end of the right drive shaft 16. The Further, two oil holes 17c passing through the vicinity of the pin hole 17a of the pinion shaft 17 are arranged so as to straddle both sides of the pin hole 17a.

  Next, the operation of the first embodiment of the present invention having the above configuration will be described.

  When the driving force of the engine is input from the final driven gear 14 to the differential case 13 and the differential case 13 rotates with respect to the transmission case 11, the driving force is supported by a pair of pinions 19 and 19 supported by a pinion shaft 17 that rotates integrally with the differential case 13. From the side gears 20 and 20 to the left and right drive wheels via the pair of drive shafts 16 and 16. Since the rotational speeds of the left and right drive wheels are different during the turning of the vehicle, a differential rotation occurs between the pair of side gears 20, 20. The differential rotation is absorbed by the relative rotation of the pinions 19, 19 with respect to the pinion shaft 17, The driving force of the engine is distributed to the left and right drive wheels without any problem.

  A part of the lubricating oil for the transmission is stored in the lubricating oil reservoirs 11a and 11a of the transmission case 11, and when the drive shafts 16 and 16 rotate as the vehicle travels forward, the lubricating oil in the lubricating oil reservoirs 11a and 11a is It is guided by spiral oil grooves 13d and 13d facing the outer peripheral surfaces of the drive shafts 16 and 16 and flows to the center in the vehicle width direction, and from there there is a spline toothless portion between the drive shafts 16 and 16 and the side gears 20 and 20. By passing through the oil passages 16a, the oil flows into the two chamfered portions 17b and 17b of the pinion shaft 17.

  When the vehicle is traveling backward, the rotational direction of the drive shafts 16, 16 is opposite to the rotational direction when traveling forward, so that the lubricating oil in the lubricating oil reservoirs 11 a, 11 a faces the outer peripheral surface of the drive shafts 16, 16. However, the frequency of the vehicle traveling backward is much smaller than the frequency of traveling forward, and the time for which the vehicle continuously travels backward is short, so that the differential gear D There is no risk of trouble with lubrication.

  A part of the lubricating oil flowing into the two chamfered portions 17b and 17b of the pinion shaft 17 is urged radially outward by centrifugal force to flow into the oil holes 17c of the pinion shaft 17, and the diameter of the oil holes 17c. The pinion shaft 17 is cooled while flowing outward in the direction, and then discharged from the shaft end of the pinion shaft 17 into the mission case 11.

  Since the inlet opening of the oil holes 17c is opposed to the shaft ends of the drive shafts 16 and 16 to which the lubricating oil from the lubricating oil reservoirs 11a and 11a is supplied, lubrication from the shaft ends of the drive shafts 16 and 16 is performed. The pinion shaft 17 can be cooled by efficiently introducing oil into the oil holes 17c. Further, since the pinion shaft 17 generates heat on the outer peripheral surface that rotatably supports the pinions 19, 19, the temperature of the outer peripheral surface is particularly likely to rise, but the oil holes 17 c are arranged at positions close to the surface of the pinion shaft 17. Therefore, the cooling efficiency of the pinion shaft 17 is improved.

  As is clear from FIG. 3, the pinion 19 is urged in the direction of arrow F by the meshing reaction force received from the side gear 20, so that the clearance α between the inner peripheral surface of the pinion 19 and the outer peripheral surface of the pinion shaft 17 is in the circumferential direction. It becomes non-uniform and becomes minimum at the minimum gap P. The lubricating oil in the clearance α dragged by the pinion 19 rotating in the direction of arrow A is pushed toward the minimum clearance P due to the wedge effect. In this embodiment, the pinion shaft 17 has a circular cross section at the portion that supports the pinion 19. In addition, since no groove or notch is formed, the wedge effect is effectively exhibited, and sufficient hydraulic pressure rises in a wide area in the gap α. Particularly, the region where the hydraulic pressure rises extends beyond the minimum gap P to the downstream side in the rotation direction A, and the boundary lubrication region where the film of lubricating oil between the pinion 19 and the pinion shaft 17 becomes thin is the conventional example shown in FIG. As a result, the frictional force between the pinion 19 and the pinion shaft 17 is reduced, and the durability of the pinion shaft 17 is improved by reducing the heat generation amount and the wear.

  As described above, according to the present embodiment, the boundary lubrication region in the sliding portions of the pinions 19 and 19 and the pinion shaft 17 is minimized to suppress heat generation, and the oil formed inside the pinion shaft 17 By improving the cooling performance through the holes 17c, the sliding portions of the pinions 19 and 19 and the pinion shaft 17 are prevented from being heated without special processing such as a special wear-resistant coating. Durability can be improved.

Second embodiment

  Next, a second embodiment of the present invention will be described based on FIG. 4 and FIG.

  The pinion shaft 17 of the differential gear D of the second embodiment includes an annular groove 17d whose diameter is reduced over 360 ° instead of the two chamfered portions 17b and 17b of the first embodiment. The pinion shaft 17 is formed with a plurality of oil holes 17c that extend in the second axis L2 direction and connect the surface of the annular groove 17d and the shaft end of the pinion shaft 17, these oil holes. 17c... Are arranged at equal intervals in the circumferential direction at a portion close to the outer peripheral surface of the pinion shaft 17. The pinion shaft 17 is not fixed to the differential case 13 in a non-rotatable manner, but is supported by the support holes 13b and 13b of the differential case 13 so as to be rotatable about the second axis L2, and is prevented from being detached by a pair of circlips 31 and 31. Is done.

  Even in the second embodiment, the outer peripheral surface of the pinion shaft 17 on which the inner peripheral surfaces of the pinions 19 and 19 are supported has a circular cross section having no grooves or notches, so that the boundary lubrication region is minimized. Heat generated by frictional heat can be minimized. In addition, since the pinion shaft 17 is rotatable around the second axis L2, the pinion shaft 17 is rotated by the rotation of the pinions 19 and 19, so that the pinion shaft 17 is rotated by the meshing reaction force F from the side gears 20 and 20. Only a part of the outer peripheral surface of the steel plate is prevented from being unevenly worn, and its life is further extended.

  Further, when the pinion shaft 17 rotates around the second axis L2, the positional relationship between the shaft ends of the drive shafts 16 and 16 to which the lubricating oil is supplied and the inlet openings of the oil holes 17c changes, but the pinion shaft 17 has a plurality of oil holes 17c at equal intervals in the circumferential direction, so that any oil hole 17c ... is formed at the shaft end of the drive shaft 16, 16 regardless of the phase of the pinion shaft 17. The lubricating oil can be reliably supplied by always facing each other.

Third embodiment

  Next, a third embodiment of the present invention will be described with reference to FIG.

  In the second embodiment, the circlips 21 and 21 are used to support the pinion shaft 17 so that the differential case 13 can rotate and cannot move in the direction of the second axis L2. However, in the third embodiment, other pinions are used. Means are used.

  That is, a shallow annular pin engaging groove 17e is formed on the outer peripheral surface of one shaft end of the pinion shaft 17, and two retaining pins 23 that are slidably fitted into the pin holes 13c of the differential case 13, 23 is urged by the springs 25, 25 that are contracted between the spring seats 24, 24 screwed into the pin hole 13c, and fits into the pin engaging groove 17e. As a result, the retaining pins 23 and 23 slide along the pin engaging groove 17e, whereby the rotation of the pinion shaft 17 is allowed, and the retaining pins 23 and 23 engage with the pin engaging groove 17e. This prevents the pinion shaft 17 from coming off in the direction of the second axis L2.

  Other configurations and operational effects of the third embodiment are the same as the configurations and operational effects of the second embodiment.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, the number and arrangement of the oil holes 17c are not limited to the embodiment and can be changed as appropriate.

13 Differential case 14 Final driven gear (input gear)
16 Drive shaft (output shaft)
17 Pinion shaft 17b Chamfered part (recessed part)
17c oil hole 17d annular groove (concave)
18 pin 19 pinion 20 side gear L1 first axis L2 second axis

Claims (3)

A differential case (13) having an input gear (14) to which driving force from a driving source is input is provided on the outer periphery and rotatably supported around the first axis (L1), and on the first axis (L1). Arranged end portions facing each other are arranged on a pair of output shafts (16) fitted in the differential case (13) and a second axis (L2) orthogonal to the first axis (L1). The pinion shaft (17) having both ends supported by the differential case (13), the pair of pinions (19) rotatably supported by the pinion shaft (17), and the pair of output shafts (16) And a pair of side gears (20) fixed to the mutually opposing ends and meshing with the pair of pinions (19), respectively, and supplied between the output shaft (16) and the side gear (20) The lubricating oil Nshafuto (17) and a lubrication structure of a differential gear for guiding the sliding portion of the pinion (19),
The pinion shaft (17) has a circular cross section at a portion supporting the pair of pinions (19), and a recess (17b, 17d) on the outer peripheral surface of the portion sandwiched between the pair of pinions (19). And a plurality of oil holes (17c) penetrating from the surface of the recesses (17b, 17d) to the shaft end of the pinion shaft (17) are formed inside the pinion shaft (17), The differential gear lubrication structure, wherein the radial positions of the plurality of oil holes (17c) are closer to the outer peripheral surface than the center of the pinion shaft (17).   The pinion shaft (17) is fixed to the differential case (13) by a pin (18) disposed in parallel with the first axis (L1), and the plurality of oil holes (17c) are connected to the pair of output shafts (16 The differential gear lubrication structure according to claim 1, wherein the structure is opened to a position facing the opposite ends of each other.   The pinion shaft (17) is supported by the differential case (13) so as to be rotatable about the second axis (L2), and the plurality of oil holes (17c) surround the outer peripheral surface of the pinion shaft (17). The differential gear lubricating structure according to claim 1, wherein the lubricating structure is arranged at predetermined intervals in the direction.

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