Differential gear device

Abstract

To provide a differential gear device capable of miniaturizing an outer diameter of a storage part in a differential case.SOLUTION: This differential gear device 1 is provided with a case member 2 having a storage part 5 formed in a cylindrical shape and rotatably held, a pinion gear 9 rotatably arranged and arranged inside the storage part 5 so as to revolve around the axis of the storage part 5, and two side gears 3 and 4 meshing with the pinion gear 9. Each of the pinion gears 9 includes a solid gear-portion 9a constituted by bevel gears meshing with the two side gears 3, 4, and a solid holding-shaft-portion 9a formed integrally with the gear-portion 9b and protruding toward the outer peripheral side of the housing portion 5, and the case member 2 is formed with a fitting hole 11 into which the holding-shaft-portion 9b is inserted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a differential gear device that connects left and right wheels so that they can rotate differentially. [Background technology]

[0002] A conventional differential gear device is composed of multiple pinion gears, two side gears that mesh with the pinion gears, and a cylindrical differential case that houses the pinion gears and side gears. The differential case has two radially opposed through holes. Pinion shafts are fitted into the through holes, and each pinion gear is rotatably fitted to the pinion shafts. Fixing pins are inserted radially through the pinion shafts to prevent them from slipping out of the differential case.

[0003] Patent Document 1 describes a differential gear device that can reduce the number of parts and assembly steps by rotatably holding the pinion gears without providing the above-mentioned pinion shaft. This differential gear device has two recesses formed 180 degrees apart in the rotational direction of the differential case. The recesses are composed of a concave spherical bottom portion and a circular cross-sectional hole portion into which a portion of the pinion gear fits. The pinion gear is composed of a bevel gear, and a cylindrical portion is formed on the side opposite the end where the teeth are formed in the axial direction, and the end face of the cylindrical portion is formed in a convex spherical shape that matches the bottom face of the recess. Therefore, this differential gear device is configured so that when a radial load acts on the pinion gears, the cylindrical portion comes into contact with the hole portion, thereby restricting movement of the pinion gears. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-275042 Summary of the Invention [Problem to be solved by the invention]

[0005] The differential gear device described in Patent Document 1 eliminates the need for pinion shafts to hold the pinion gears by positioning the pinion gears by accommodating portions of the pinion gears in recesses formed in the differential case. Therefore, the fitting length between the holes formed in the differential case and the cylindrical portions formed in the pinion gears must be long enough to support the load acting in the radial direction of the pinion gears. Furthermore, the thickness of the differential case where the recesses are formed must be thick enough to support the centrifugal force acting on the pinion gears as they revolve. Therefore, the differential case needs to be thick enough to form the holes and to support the centrifugal force acting on the pinion gears. Therefore, there is room for technical improvement to reduce the outer diameter of the differential case.

[0006] The present invention has been made in view of the above technical problems, and has an object to provide a differential gear device that can reduce the outer diameter of the differential case. [Means for solving the problem]

[0007] 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 portion and held rotatably around the central axis of the storage portion; a pinion gear provided inside the storage portion so as to be rotatable and revolve around the central axis of the storage portion; and two side gears provided opposite each other in the direction of the central axis of the storage portion and meshing with the pinion gear, wherein the pinion gear comprises a solid gear portion formed by bevel gears that mesh with the two side gears, and a solid retaining shaft portion formed integrally with the gear portion and protruding toward the outer periphery of the storage portion, and the case member is formed with a fitting hole into which the retaining shaft portion is inserted. [Effects of the Invention]

[0008] According to the present invention, a pinion gear is accommodated in a cylindrical accommodation portion. The pinion gear is composed of a solid gear portion formed by a bevel gear and a solid retaining shaft portion formed integrally with the gear portion, and the retaining shaft portion is inserted into a fitting hole formed in a case member. Therefore, axial movement of the pinion gear can be restricted without providing a fixing member such as a fixing pin, which eliminates the need to provide space in the case member for providing a fixing member, thereby allowing the case member to be made more compact in the radial direction. Furthermore, because the retaining shaft portion and the fitting hole are fitted together to restrict movement of the pinion gear in the longitudinal direction or circumferential direction of the case member, it is not necessary to form a step portion or the like on the inner surface of the case member for abutting against the outer peripheral surface of the pinion gear, which allows the case member to be made more compact in the radial direction. Furthermore, by forming the gear portion and the retaining shaft portion in a solid shape, there is no need to secure a plate thickness to ensure the strength of the fitting portion when fitting the pinion gear to a pinion shaft, etc., and the pinion gear can be made smaller (reduced in diameter).As a result, the plate thickness of the case member required to withstand the centrifugal force acting on the pinion gear can be reduced, and the case member can be made smaller in the radial direction. [Brief explanation of the drawings]

[0009] [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

[0010] 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 implementations of the present invention and are not intended to limit the present invention.

[0011] A cross-sectional view for explaining an example of a differential gear device according to an embodiment of the present invention is shown in Figure 1. The differential gear device 1 shown in Figure 1 is configured so that a case member (hereinafter referred to as a differential case) 2, a right side gear 3, and a left side gear 4 rotate differentially.

[0012] The differential case 2 is composed of a cylindrical housing portion 5 that houses each side gear 3, 4, an annular cap portion 6 that abuts against one open end of the housing portion 5 (the left side in Figure 1), and a ring gear 7 that meshes with the output gear of a power transmission device such as a transmission mechanism (not shown), all of which are integrated together with bolts 8.

[0013] The housing 5 is composed of a cylindrical portion 5a housing a pinion gear 9 (described later) and each of the side gears 3 and 4, a flange portion 5b formed at one end (the left end in FIG. 1) of the cylindrical portion 5a, a reduced-diameter portion 5c whose diameter gradually decreases from the other end of the cylindrical portion 5a, and a cylindrical right-side boss portion 5d extending from the end of the reduced-diameter portion 5c to the outside in the axial direction of the cylindrical portion 5a (the right side in FIG. 1). The flange portion 5b has a plurality of female threads 5e formed at predetermined intervals in the circumferential direction. The cylindrical portion 5a and the reduced-diameter portion 5c may have windows formed therein for inserting the pinion gear 9 (described later).

[0014] The cap portion 6 is configured to abut against the end face of the flange portion 5b, and a cylindrical left boss portion 6a is formed on its inner periphery, extending outward (to the left in FIG. 1) from the central axis of the cylindrical portion 5a. Furthermore, fitting boss portions 6b with an outer diameter substantially the same as the inner diameter of the flange portion 5b are formed on both sides of the cap portion 6, and the housing portion 5 and the cap portion 6 are positioned so that they are arranged on the same axis by fitting one side of the fitting boss portion 6b into the flange portion 5b. Furthermore, a through hole 6c is formed in the cap portion 6 corresponding to the female thread portion 5e formed in the flange portion 5b, and further, through holes 6d are formed at predetermined intervals in the circumferential direction of the cap portion 6 in the portion between the fitting boss portion 6b and the left boss portion 6a in the radial direction of the cap portion 6.

[0015] The inner diameter of the ring gear 7 is formed to be substantially the same as the outer diameter of the other side (left side) of the fitting boss portion 6b formed on the cap portion 6, and by fitting the ring gear 7 into the fitting boss portion 6b, the ring gear 7 and the cap portion 6 are positioned so that they are arranged on the same axis. The ring gear 7 also has a through hole 7a formed in correspondence with the female thread portion 5e formed on the flange portion 5b. Therefore, by assembling the accommodating portion 5, cap portion 6, and ring gear 7 side by side in the axial direction and inserting bolts 8 into the respective through holes 7a and 6c and tightening them into the female thread portion 5e formed on the flange portion 5b, the accommodating portion 5, cap portion 6, and ring gear 7 are positioned in the circumferential direction and integrated.

[0016] Furthermore, bearings 10 are fitted to the bosses 5d and 6a, and the differential case 2 is rotatably held by a transmission housing (not shown) or the like. In other words, the differential case 2 is arranged to rotate about the central axis of the accommodation portion 5.

[0017] In the central portion of the axial direction of the above-mentioned accommodating section 5, two through holes 11 are formed 180 degrees apart in the circumferential direction of the accommodating section 5, and a pinion gear 9 is rotatably fitted into each of these through holes 11.

[0018] Since each pinion gear 9 is formed to have the same shape, the following description will only explain the configuration of one of the pinion gears 9, and will omit a description of the configuration of the other pinion gear 9. The pinion gear 9 is composed of a solid gear portion 9a having a bevel gear formed thereon that meshes with each of the side gears 3 and 4, and a solid retaining shaft portion 9b that is formed integrally with the gear portion 9a and protrudes toward the outer periphery of the accommodating portion 5, and the retaining shaft portion 9b is rotatably fitted into a through hole 11 formed in the accommodating portion 5. In other words, the radial movement of the pinion gear 9 is limited by the accommodating portion 5.

[0019] The outer diameter of gear portion 9a is larger than the outer diameter of retaining shaft portion 9b. Therefore, by fitting retaining shaft portion 9b into through hole 11, the inner wall surface of housing portion 5 and the bottom surface of gear portion 9a face each other. The inner wall surface of housing portion 5 facing the bottom surface of gear portion 9a is formed in a concave spherical shape, and the bottom surface of gear portion 9a is formed in a convex spherical shape that matches the inner wall surface of housing portion 5. In order to reduce sliding resistance between the inner wall surface of housing portion 5 and the bottom surface of gear portion 9a, a spherical washer 12 having a through hole 12a through which retaining shaft portion 9b passes is provided between housing portion 5 and gear portion 9a.

[0020] The right side gear 3 is a bevel gear arranged to rotate about the central axis of the housing portion 5 so as to mesh with the above-mentioned pinion gears 9. The right side gear 3 is composed of a gear portion 3a that meshes with the pinion gears 9, and a cylindrical portion 3b whose tip fits into the rear end portion (the left end portion in FIG. 1) of the right boss portion 5d.

[0021] The outer diameter of the gear portion 3a is larger than the inner diameter of the rear end of the right boss portion 5d. That is, the bottom surface (the right side surface in FIG. 1) of the gear portion 3a faces the rear end of the right boss portion 5d. An annular shim 13 and an annular disc spring (conical spring) 14 are disposed between the bottom surface of the gear portion 3a and the rear end of the right boss portion 5d. Therefore, the disc spring 14 presses the right side gear 3 toward the pinion gear 9 in the direction of the rotational center axis of the housing portion 5 so that the meshing length between the right side gear 3 and each pinion gear 9 is appropriate.

[0022] The outer diameter of the cylindrical portion 3b is formed to be substantially the same as the inner diameter of the rear end of the right boss portion 5d, and by fitting the cylindrical portion 3b into the right boss portion 5d, the right side gear 3 and the housing portion 5 are positioned so as to be arranged on the same axis. The cylindrical portion 3b is configured to be engaged with the tip of a drive shaft (not shown). Specifically, spline teeth 3c are formed on the inner peripheral surface of the cylindrical portion 3b, and spline teeth formed on the tip of the drive shaft are configured to mesh with the spline teeth 3c.

[0023] The left side gear 4 has the same configuration as the right side gear 3 and is disposed opposite the right side gear 3. That is, the left side gear 4 is a bevel gear disposed to rotate about the central axis of the accommodating portion 5 so as to mesh with each of the pinion gears 9 described above, and the number of teeth of the gear portion 3a of the right side gear 3 is the same as the number of teeth of the gear portion 4a (described later) of the left side gear 4. The left side gear 4 is composed of the gear portion 4a which meshes with each of the pinion gears 9 and a cylindrical portion 4b whose tip fits into the rear end portion (the right end portion in FIG. 1 ) of the left boss portion 6a.

[0024] The outer diameter of the gear portion 4a is larger than the inner diameter of the rear end of the left boss portion 6a. That is, the bottom surface (the left side surface in FIG. 1 ) of the gear portion 4a faces the rear end of the left boss portion 6a. An annular shim 15 and an annular disc spring (conical spring) 16 are disposed between the bottom surface of the gear portion 4a and the rear end of the left boss portion 6a. Therefore, the disc spring 16 presses the left side gear 4 toward the pinion gear 9 in the direction of the rotational center axis of the housing portion 5 so that the meshing length between the left side gear 4 and each pinion gear 9 is appropriate.

[0025] The outer diameter of the cylindrical portion 4b is formed to be substantially the same as the inner diameter of the rear end of the left boss portion 6a, and by fitting the cylindrical portion 4b into the left boss portion 6a, the left side gear 4 and the accommodating portion 5 are positioned so as to be arranged on the same axis. The cylindrical portion 4b is configured to engage with the tip of a drive shaft (not shown). Specifically, spline teeth 4c are formed on the inner peripheral surface of the cylindrical portion 4b, and spline teeth formed on the tip of the drive shaft are configured to mesh with the spline teeth 4c.

[0026] In the differential gear device 1 configured as described above, for example, the right side gear 3, each pinion gear 9, and left side gear 4 are inserted into the accommodating portion 5 in this order. Specifically, the shim 13, the disc spring 14, and the right side gear 3 are inserted into the accommodating portion 5 in this order, and while pressing the right side gear 3, each pinion gear 9 is inserted and the retaining shaft portion 9b of the pinion gear 9 is inserted into the through hole 11. By inserting the retaining shaft portion 9b of the pinion gear 9 into the through hole 11 in this manner, the right side gear 3 and pinion gear 9 are positioned in the direction of the rotation center axis of the accommodating portion 5. Next, the left side gear 4, the disc spring 16, and the shim 15 are inserted into the accommodating portion. Then, the cap portion 6 and the ring gear 7 are assembled into the accommodating portion 5 and fixed with bolts 8, thereby assembling the differential gear device 1. It should be noted that the differential gear device 1 may be assembled by inserting the pinion gear 9 through a window formed in the differential case 2 after assembling components other than the pinion gear 9.

[0027] 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 rotational speed, and therefore the differential case 2 and the side gears 3 and 4 rotate at the same rotational speed. Meanwhile, torque transmitted to the differential case 2 from a driving force source (not shown) is transmitted equally to the side gears 3 and 4. When the vehicle is turning, the rotational speed of the outer drive wheel is higher than the rotational speed of the inner drive wheel. In such a case, the rotation of the pinion gears 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. That is, the differential case 2 rotates at a rotational speed based on the rotational speed of the driving force 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. The torque transmitted from a driving force source (not shown) to the differential case 2 is equally distributed and transmitted to each of the side gears 3 and 4.

[0028] As described above, the pinion gear 9 is formed of a bevel gear and meshes with each of the side gears 3 and 4. Therefore, when the differential gear device 1 is assembled, movement of the pinion gear 9 toward the inner periphery of the accommodating portion 5 can be restricted. Furthermore, the retaining shaft portion 9b of the pinion gear 9 is configured to fit into the through hole 11 formed in the accommodating portion 5, and the outer diameter of the gear portion 9a is larger than the outer diameter of the retaining shaft portion 9b. Therefore, when the differential gear device 1 is assembled, movement of the pinion gear 9 toward the outer periphery of the accommodating portion 5 can be restricted. Furthermore, when centrifugal force acts on the pinion gear 9 as the differential case 2 rotates, the gear portion 9a comes into contact with the wall surface of the accommodating portion 5, thereby restricting movement of the pinion gear 9 toward the outer periphery of the accommodating portion 5. In other words, movement of the pinion gear 9 in the axial direction is restricted.

[0029] Furthermore, because the retaining shaft portion 9b of the pinion gear 9 is fitted into the through hole 11 formed in the accommodating portion 5, the load acting on the pinion gear 9 from the side gears 3 and 4 when the differential gear device 1 is in operation can be received by the wall surface of the accommodating portion 5. This makes it possible to prevent the pinion gear 9 from moving in the longitudinal direction or circumferential direction of the accommodating portion 5.

[0030] As described above, it is possible to restrict the axial movement of the pinion gear 9 when the pinion gear 9 is assembled or driven without providing a fixing pin or the like. Therefore, it is not necessary to provide a space in the housing portion 5 for providing a fixing member such as a fixing pin, and it is possible to make the housing portion 5 smaller in the radial direction.

[0031] Furthermore, because movement of the pinion gear 9 in the longitudinal direction and circumferential direction of the accommodating portion 5 is restricted by the engagement between the retaining shaft portion 9b and the through hole 11, there is no need to form a stepped portion or the like on the inner surface of the accommodating portion 5 that comes into contact with the outer peripheral surface of the gear portion 9a of the pinion gear 9. Therefore, since no stepped portion or the like for restricting movement of the pinion gear 9 is formed, the accommodating portion 5 can be made smaller in the radial direction. In other words, the plate thickness of the portion of the accommodating portion 5 facing the pinion gear 9 only needs to be thick enough to withstand the load of the pinion gear 9 in the radial direction of the accommodating portion 5, such as centrifugal force acting on the pinion gear 9, and the plate thickness of the accommodating portion 5 can be reduced.

[0032] Furthermore, the gear portion 9a and the retaining shaft portion 9b of the pinion gear 9 are formed solid. Therefore, the diameter of the pinion gear 9 can be reduced compared to when the pinion gear 9 is configured to be fitted to a pinion shaft. This is because it is possible to prevent the outer diameter of the pinion gear 9 from being increased in order to ensure the thickness of the portion of the pinion gear 9 that fits to the pinion shaft (the tip end of the gear portion 9a). By reducing the diameter of the pinion gear 9 in this way, in other words, by making it smaller, the centrifugal force acting on the pinion gear 9 can be reduced. Therefore, the thickness of the housing portion 5 required to withstand this centrifugal force can be reduced, and the housing portion 5 can be made smaller in the radial direction. Furthermore, by reducing the diameter of the pinion gear 9, the spacing between the side gears 3 and 4 can be narrowed, thereby shortening the axial length of the differential case 2.

[0033] In the above-described differential gear device 1, two pinion gears 9 are provided in the circumferential direction of the accommodating portion 5, but three or more pinion gears 9 may be provided in the circumferential direction of the accommodating portion 5. Furthermore, it is sufficient that the accommodating portion 5 has a portion formed therein into which the retaining shaft portion 9b is fitted, and instead of the through hole 11, a recess (fitting hole) into which the retaining shaft portion 9b is fitted may be formed on the inner surface of the accommodating portion 5. [Explanation of symbols]

[0034] 1 Differential gear unit 2 Differential case 3,4 Side gear 3a, 4a Gear section 5. Storage section 5a Cylindrical part 6 Cap part 6c,6d,7a,11,12a through hole 7 Ring Gear 9 Pinion gear 9a Gear section 9b Holding shaft part

Claims

[Claim 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 so as to be rotatable and revolve around the central axis of the housing portion; and two side gears provided opposite each other in the direction of the central axis of the housing portion and meshing with the pinion gear, the pinion gear includes a solid gear portion formed by bevel gears that mesh with the two side gears, and a solid holding shaft portion that is formed integrally with the gear portion and protrudes toward the outer periphery of the accommodating portion, The case member has a fitting hole formed therein into which the holding shaft portion is inserted. A differential gear device characterized by:

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