Differential gear device

Abstract

To provide a differential gear device capable of miniaturizing a side gear.SOLUTION: A differential gear device 1 includes a case member 2 having a housing portion 5 formed in a cylindrical shape and held so as to be rotatable about a central axis L of the housing portion 5, a pinion gear 13 provided inside the housing portion 5 so as to be rotatable and revolvable about the central axis L of the housing portion 5, and a side gear 3 (4) to which torque is transmitted from the pinion gear 13 to rotate and to which an output shaft 14 (15) is coupled. The side gear 3 (4) includes the gear portion 3a (4a) meshing with the pinion gear 13 and the boss portion 3a (4b) protruding toward the back surface side of the gear portion 4a (3b), and the outputting shaft 14 (15) is coupled to the side gear 3 (4) on the boss portion 3a (4a) side with respect to the boundary portion between the gear portion (3b) and the boss portion () in the rotation-center-axis-L direction of the side gear 3 (4). 4b 3b 4b.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a differential gear device that connects two opposing gears so that they can rotate differentially. [Background technology]

[0002] Patent Document 1 describes a differential gear mechanism that includes a rotatable case member, multiple pinion gears that revolve around the central axis of rotation of the case member and are rotatably held by the case member, and two side gears that are arranged opposite each other along the central axis of rotation of the case member and mesh with each pinion gear. The side gears include gear portions with meshing teeth that mesh with each pinion gear, and shaft portions that rotatably fit into the case member. Each side gear has a through hole formed along the central axis of rotation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-75109 Summary of the Invention [Problem to be solved by the invention]

[0004] The side gear described in Patent Document 1 is connected to, for example, a drive shaft or a propeller shaft, and torque transmitted between a rotating member on the input side of the differential gear mechanism and a rotating member on the output side of the differential gear mechanism, such as a drive shaft or a propeller shaft, acts on the side gear. Therefore, the rigidity (strength) of the gear portion of the side gear is determined based on the maximum value of torque expected to be transmitted through the differential gear mechanism. Therefore, the outer diameter of the side gear having a hollow portion described in Patent Document 1 is restricted by the inner diameter of the through hole and the wall thickness corresponding to the rigidity required for the gear portion of the side gear, leaving room for technical improvement to reduce the size of the side gear.

[0005] The present invention has been made in view of the above technical problems, and has as its object to provide a differential gear device that allows side gears to be made smaller. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present invention provides a differential gear device comprising: a case member having a cylindrically formed storage section and held rotatably around the central axis of the storage section; a pinion gear provided inside the storage section so as to be rotatable and revolve around the central axis of the storage section; and a side gear which rotates when torque is transmitted from the pinion gear and to which an output shaft is connected, wherein the side gear comprises a gear section having meshing teeth formed on its outer surface which mesh with the pinion gear, and a boss section protruding from the back side of the gear section, and the output shaft is connected to the side gear on the boss section side in the direction of the central axis of rotation of the side gear.

[0007] In addition, in the present invention, spline teeth may be formed on the outer peripheral surface of the end of the boss portion opposite the gear portion in the direction of the rotation center axis of the side gear, and the output shaft may have a recess on its inner surface with spline teeth that mesh with the spline teeth on the boss portion.

[0008] In addition, in the present invention, spline teeth may be formed on the outer peripheral surface of the end of the boss portion opposite the gear portion in the direction of the rotation center axis of the side gear, spline teeth may be formed on the outer peripheral surface of the tip portion of the output shaft, and a cylindrical member may be provided on its inner surface with spline teeth that mesh with the spline teeth formed on the boss portion and the spline teeth formed on the output shaft.

[0009] In addition, in the present invention, the case member may have a side wall portion facing the back surface of the gear portion of the side gear, the boss portion may be provided so as to penetrate the side wall portion, and the output shaft may be connected to the portion of the boss portion that penetrates through the side wall portion.

[0010] In the present invention, the gear portion may be formed in a solid shape. [Effects of the Invention]

[0011] According to the present invention, the side gear, to which torque is transmitted from the case member via the pinion gear, includes a gear portion that meshes with the pinion gear and a boss portion that protrudes from the rear side of the gear portion, and the output shaft is connected to the side gear on the boss portion side relative to the boundary between the gear portion and the boss portion. This eliminates the need to form a relatively large through hole inside the gear portion for engaging the output shaft, allowing the gear portion to be made more compact. Furthermore, the rigidity required of the gear portion is based on the rotational load and radial load acting from the pinion gear, and no rigidity is required for the engagement portion for transmitting torque between the gear portion and the output shaft. This reduces the rigidity required of the gear portion, allowing the gear portion to be made even more compact. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view illustrating an example of a differential gear device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples of specific embodiments of the present invention and are not intended to limit the present invention.

[0014] Fig. 1 shows a cross-sectional view illustrating an example of a differential gear device according to an embodiment of the present invention. The differential gear device 1 shown in Fig. 1 is configured such that a case member (hereinafter referred to as a differential case) 2, a left side gear 3, and a right side gear 4 rotate differentially. The left side gear 3 and the right side gear 4 correspond to the "side gears" in the embodiment of the present invention.

[0015] The differential case 2 is composed of a cylindrical housing portion 5 that houses the side gears 3 and 4, an annular left side wall portion 6 formed at one end (the left end in FIG. 1) of the housing portion 5, and an annular right side wall portion 7 formed at the other end (the right end in FIG. 1) of the housing portion 5. The left side wall portion 6 and the right side wall portion 7 correspond to the "side wall portion" in the embodiment of the present invention.

[0016] In the housing portion 5, window holes 5a are formed at predetermined intervals in the circumferential direction to ensure mounting space for members provided around the differential case 2 and to allow for insertion of the side gears 3, 4 therein. In addition, through holes 5b into which one end of a pinion shaft 8 (described later) fits are formed at predetermined intervals in the circumferential direction in the wall portion of the housing portion 5. The pinion shafts 8 shown in FIG. 1 are configured as so-called spider shafts, three of which are formed radially from the central axis L of the differential case 2.

[0017] The left side wall portion 6 is integrally formed with a cylindrical portion 6a that protrudes from the outer surface of its inner periphery in the direction of the rotation axis L of the accommodating portion 5, and the cylindrical portion 6a is rotatably held in the transmission housing 10 via a tapered needle bearing 9a.

[0018] Similarly, a cylindrical portion 7a is integrally formed on the right side wall portion 7, protruding from the outer surface of the inner circumferential side thereof in the direction of the rotation axis L of the accommodation portion 5, and the cylindrical portion 7a is rotatably held in the transmission housing 10 via a tapered needle bearing 9b. In other words, the differential case 2 is held by the transmission housing 10 so as to be rotatable about the rotation central axis L of the accommodation portion 5.

[0019] A flange portion 7b is formed on the right side wall portion 7, and an annular input member 11 is fixed to the flange portion 7b with bolts 12. The input member 11 may be a ring gear or the like that inputs torque to a conventional differential gear mechanism.

[0020] A pinion gear 13 is rotatably fitted to the pinion shaft 8. Therefore, when the differential case 2 rotates, the pinion gear 13 revolves around the central axis of rotation L of the housing 5. The pinion gear 13 is formed of a bevel gear. A surface (back surface) 13a of the pinion gear 13 facing the wall surface of the differential case 2 is formed in a convex spherical shape. Similarly, the inner surface of the differential case 2 facing the pinion gear 13 is formed in a concave spherical shape with approximately the same curvature as the back surface 13a of the pinion gear 13. In order to reduce frictional resistance between the back surface 13a of the pinion gear 13 and the inner surface of the differential case 2, a spherical washer or the like may be provided.

[0021] The differential case 2 is not limited to being formed as a single unit, but may be formed by fastening multiple components together with bolts or the like, taking into consideration the ease of assembly of the pinion gear 13, pinion shaft 8, and each side gear 3, 4, etc.

[0022] The left side gear 3 is a solid member integrally formed with a left gear portion 3a and a left boss portion 3b protruding from the back side of the left gear portion 3a in the direction of the axis L (left side in FIG. 1 ). The left gear portion 3a is configured as a bevel gear with meshing teeth formed on a conical surface that mesh with the pinion gears 13, and its back surface faces the left side wall portion 6. Note that an elastic member such as an annular shim for adjusting the meshing length between the left side gear 3 and each pinion gear 13, or an annular disc spring for pressing the left side gear 3 toward each pinion gear 13 to maintain meshing between the left side gear 3 and each pinion gear 13, may be provided between the back side of the left gear portion 3a and the left side wall portion 6.

[0023] The left boss portion 3b has an outer diameter that is substantially the same as the inner diameter of the cylindrical portion 6a, and is rotatably held by the cylindrical portion 6a. A bearing such as a bushing may be provided between the cylindrical portion 6a and the left boss portion 3b.

[0024] The rear end of the left boss portion 3b (the end on the left side in FIG. 1) is formed to protrude from the cylindrical portion 6a. In other words, the left boss portion 3b is provided so as to penetrate the left side wall portion 6. The left drive shaft 14 is connected to the portion protruding from the cylindrical portion 6a so as to be rotatable integrally with the left boss portion 3b. In other words, the left drive shaft 14 is connected to the left side boss portion 3b side of the boundary between the left gear portion 3a and the left boss portion 3b in the direction of the rotational center axis L of the left side gear 3.

[0025] 1, the outer diameter of the left drive shaft 14 is larger than the outer diameter of the left boss 3b, and a recess 14a with a circular cross section and a predetermined depth is formed in the end face of the left drive shaft 14. The left boss 3b is inserted into the recess 14a and is spline-engaged. That is, spline teeth 14b, 3c that mesh with each other in the rotational direction of the left drive shaft 14 are formed on the inner peripheral surface of the left drive shaft 14 and the outer peripheral surface of the left boss 3b.

[0026] The left drive shaft 14 is rotatably held in the transmission housing 10 via a bushing or the like (not shown).

[0027] Like the left side gear 3, the right side gear 4 is a solid member integrally formed with a right gear portion 4a and a right boss portion 4b protruding from the back side of the right gear portion 4a in the direction of the axis L (to the right in FIG. 1 ). The right gear portion 4a is configured as a bevel gear with meshing teeth formed on a conical surface that mesh with the pinion gears 13, and its back surface faces the right side wall portion 7. Note that an elastic member such as an annular shim for adjusting the meshing length between the right side gear 4 and each pinion gear 13 or an annular disc spring for pressing the right side gear 4 toward each pinion gear 13 to maintain meshing between the right side gear 4 and each pinion gear 13 may be provided between the back side of the right gear portion 4a and the right side wall portion 7.

[0028] The right boss 4b has an outer diameter that is substantially the same as the inner diameter of the cylindrical portion 7a, and is rotatably held by the cylindrical portion 7a. A bearing such as a bushing may be provided between the cylindrical portion 7a and the right boss 4b.

[0029] The rear end of the right boss portion 4b (the end on the right side in FIG. 1) is formed to protrude from the cylindrical portion 7a. In other words, the right boss portion 4b is provided so as to penetrate the right side wall portion 7. The right drive shaft 15 is connected to the portion protruding from the cylindrical portion 7a so as to be rotatable integrally therewith. That is, in the direction of the rotational center axis L of the right side gear 4, the right drive shaft 15 is connected on the right boss portion 4b side of the boundary portion between the right gear portion 4a and the right boss portion 4b.

[0030] In the example shown in Fig. 1, the outer diameter of the right drive shaft 15 is formed to be the same as the outer diameter of the right boss portion 4b. Spline teeth 4c, 15a of the same phase are formed on the outer peripheral surface of the rear end of the right boss portion 4b and on the outer peripheral surface of the tip end (the right end in Fig. 1) of the right drive shaft 15, respectively. The left drive shaft 14 and right drive shaft 15 described above correspond to the "output shaft" in the embodiment of the present invention.

[0031] 1, a cylindrical sleeve 16 is provided that meshes with the spline teeth 4c, 15a. That is, spline teeth 16a that are in phase with the spline teeth 4c, 15a are formed on the inner circumferential surface of the sleeve 16, and the spline teeth 16a of the sleeve 16 are engaged across the spline teeth 4c formed on the right boss portion 4b and the spline teeth 15a formed on the right drive shaft 15, thereby connecting the right side gear 4 and the right drive shaft 15 so that they rotate integrally. This sleeve 16 corresponds to the "cylindrical member" in this embodiment of the present invention.

[0032] In the example shown in FIG. 1, a cylindrical portion 10a is formed in the transmission housing 10, and a sleeve 16 is fitted into the cylindrical portion 10a with a seal member 17 interposed therebetween.

[0033] In the differential gear device 1 configured as described above, three rotating elements, namely, the differential case 2 and the side gears 3 and 4, rotate differentially. That is, when a vehicle equipped with this differential gear device 1 is traveling straight, the left and right wheels rotate at the same rotation speed, and therefore the differential case 2 and the side gears 3 and 4 rotate at the same rotation speed. Furthermore, torque transmitted to the differential case 2 from a driving force source (not shown) is divided and acts on the side gears 3 and 4 in accordance with the resistance torque acting on the left and right drive shafts 14 and 15 from the drive wheel side.

[0034] On the other hand, when a vehicle equipped with the differential gear device 1 configured as described above is turning, the rotation speed of the outer drive wheel is higher than the rotation speed of the inner drive wheel. In such a case, the rotation of the pinion gear 13 allows relative rotation between the side gear 3 (4) connected to the outer wheel and the side gear 4 (3) connected to the inner wheel. In other words, the differential case 2 rotates at a rotation speed based on the rotation speed of the driving power source, while the side gears 3 and 4 rotate relative to each other. In other words, the differential case 2 and the side gears 3 and 4 rotate differentially.

[0035] Also, when the vehicle is turning, just as when it is traveling straight, the torque transmitted from a driving force source (not shown) to the differential case 2 is divided and acts on each side gear 3, 4 in accordance with the resistance torque acting on the left and right drive shafts 14, 15 from the drive wheel side.

[0036] By connecting the drive shafts 14, 15 to the boss portions 3b, 4b as described above, there is no need to form a relatively large through hole inside the gear portions 3a, 4a in the direction of the rotational center axis L of the side gears 3, 4 to engage with the drive shafts 14, 15, so the gear portions 3a, 4a can be made smaller (reduced in diameter).

[0037] Furthermore, the rigidity (strength) required of the gear portions 3a, 4a is determined based on the rotational load acting from the pinion gear 13 and the radial load. On the other hand, when a through hole is formed as in a conventional side gear and the drive shaft is spline-engaged with the through hole, rigidity based on the load acting on the spline teeth is required in addition to the rigidity based on the load described above. In other words, the thickness between the tooth bottoms of the gear portions 3a, 4a and the tooth bottoms of the spline teeth must be increased. Therefore, the rigidity required of the gear portions 3a, 4a can be reduced compared to conventional side gears with through holes, allowing the gear portions 3a, 4a to be further miniaturized.

[0038] In order to reduce the weight of the side gears 3, 4, through holes may be formed in the side gears 3, 4 while maintaining rigidity based on the rotational load and radial load acting from the pinion gear 13. Specifically, through holes may be formed with an inner diameter determined so that the thickness between the tooth bottom of the gear portions 3 a, 4 a and the inner wall surface of the through holes can satisfy the rigidity.

[0039] The outer diameter of the boss portions 3b, 4b may be determined to a size that satisfies the torsional rigidity for transmitting torque and the rigidity against the load acting on the spline teeth.

[0040] As described above, the gear portions 3a, 4a housed in the differential case 2 can be made smaller, so the outer diameter dimension of the differential case 2 can be reduced, and the mountability of the differential gear device 1 can be improved.

[0041] In the above example, the configuration for connecting the left boss portion 3b and the left drive shaft 14 is different from the configuration for connecting the right boss portion 4b and the right drive shaft 15, but the configuration for connecting the left boss portion 3b and the left drive shaft 14 and the configuration for connecting the right boss portion 4b and the right drive shaft 15 may be the same configuration that employs either one of the above configurations. In addition, the configuration for connecting the boss portion 3b (4b) and the drive shaft 14 (15) is not particularly limited, and may be, for example, by forming a hollow portion in the rear end of the boss portion 3b (4b) and spline-engaging the drive shaft 14 (15) into the hollow portion. [Explanation of symbols]

[0042] 1 Differential gear unit 2 Differential case 3,4 Side gear 3a, 4a gear section 3b, 4b boss part 4c, 14b, 15a, 16a spline teeth 5. Storage section 6,7 Side wall 6a, 7a, 10a Cylindrical part 8 Pinion shaft 13 Pinion gear 14,15 Drive shaft 14a Recess 16 sleeve

Claims

1. A differential gear device comprising: a case member having a cylindrically formed housing portion and held rotatably about a central axis of the housing portion; a pinion gear provided inside the housing portion rotatably and revolvable about the central axis of the housing portion; and a side gear which rotates by torque transmitted from the pinion gear and is connected to an output shaft, the side gear includes a gear portion having meshing teeth formed on an outer peripheral surface thereof to mesh with the pinion gear, and a boss portion protruding from a rear side of the gear portion, The output shaft is connected to the side gear on the boss side of the boundary between the gear portion and the boss portion in the direction of the rotational center axis of the side gear. A differential gear device characterized by:

2. 2. The differential gear device according to claim 1, spline teeth are formed on an outer peripheral surface of an end portion of the boss portion opposite to the gear portion in the direction of the rotation center axis of the side gear, The output shaft has a recess on the inner surface of which spline teeth are formed to mesh with the spline teeth on the boss portion. A differential gear device characterized by:

3. 2. The differential gear device according to claim 1, spline teeth are formed on an outer peripheral surface of an end portion of the boss portion opposite to the gear portion in the direction of the rotation center axis of the side gear, spline teeth are formed on the outer peripheral surface of the tip end of the output shaft, a cylindrical member having spline teeth formed on the inner surface thereof, the spline teeth engaging with the spline teeth formed on the boss portion and the spline teeth formed on the output shaft; A differential gear device characterized by:

4. 2. The differential gear device according to claim 1, the case member has a side wall portion facing a back surface of the gear portion of the side gear, The boss portion is provided to penetrate the side wall portion, The output shaft is connected to a portion of the boss portion that penetrates through the side wall portion. A differential gear device characterized by:

5. 5. A differential gear device according to claim 1, The gear portion is formed in a solid shape. A differential gear device characterized by:

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