Differential gear device

Abstract

To provide a differential gear device capable of engaging a side gear with a pinion gear at an intended position and suppressing backlash of the gears.SOLUTION: A differential gear device (1) is provided with a case member (2) having a containing section (5) formed in a tubular shape and held so as to be capable of rotating about the center axis line (L) of the containing section (5), a pinion gear (21) provided so as to be capable of rotating and to revolve about the center axis line of the containing section and provided inside the containing section (5) so as to be capable of rotating, and two side gears provided facing each other in the direction of the center axis line (L) of the containing section (5), wherein the differential gear device (1) is provided with three pinion shafts (9) which extend from the center axis line (L) of the containing section (5) to the wall surface of the containing section (5), one end of which is connected to the wall surface, and which are provided at predetermined intervals from each other in the direction of rotation of the containing section (5), and the pinion gears (21) include three pinion gears (21) fitted to the three pinion shafts (9) so as to be capable of rotating.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] Patent Document 1 describes a differential mechanism in which a case member and two side gears are connected to each other so as to be capable of differential rotation. The case member is provided with two pinion shafts that are arranged in the diameter direction of the case member and intersect with each other, and both ends of the pinion shafts are fitted into the case member. Two pinion gears are fitted into each pinion shaft so as to be rotatable, facing each other. In other words, the differential gear mechanism is provided with four pinion gears. The four pinion gears are configured to mesh with the side gears that face each other in the direction of the rotation center axis of the case member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2009-505002 Summary of the Invention [Problem to be solved by the invention]

[0004] In a typical differential gear device, there is unavoidable backlash between the side gears and the case member that rotatably holds the side gears. Therefore, when the differential gear device is in operation, the radial position of the side gears is determined by balancing the radial loads acting on the side gears from the pinion gears. Furthermore, the axial position of the side gears is determined by the thrust loads acting from the pinion gears pressing the side gears against the case member. Furthermore, the axial position of each pinion gear is determined by the reaction force acting from the side gears pressing the pinion gears against the case member.

[0005] Therefore, as described above, the radial positioning of the side gear is achieved by balancing the radial load acting on the side gear. In a case where four pinion gears are provided, as in the differential gear device described in Patent Document 1, the radial positioning of the side gear is achieved by three pinion gears. In other words, one pinion gear may not mesh with the side gear, or the meshing position with the side gear may deviate from the intended position. This may result in abnormal noise due to the pinion gear rattling, or the durability of the pinion gear may be reduced due to the meshing position with the side gear deviating from the intended position.

[0006] The present invention has been made in light of the above technical problems, and aims to provide a differential gear device that can mesh side gears and pinion gears at intended positions and suppress rattle of these gears. [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 section and held rotatably around the central axis of the storage section; a pinion gear rotatably provided inside the storage section and revolvable around the central axis of the storage section; and a first side gear and a second side gear provided opposite each other in the direction of the central axis of the storage section and meshing with the pinion gear, wherein the differential gear device comprises three pinion shafts extending from the central axis of the storage section to a wall surface of the storage section, one end of which is connected to the wall surface, and which are provided at a predetermined interval from each other in the rotational direction of the storage section, and the pinion gear includes three pinion gears rotatably engaged with each of the three pinion shafts.

[0008] In addition, in the present invention, the case member may have a first positioning wall portion facing the surface of the first side gear facing away from the second side gear, and a second positioning wall portion facing the surface of the second side gear facing away from the first side gear, and may further include a first elastic member provided between the first side gear and the first positioning wall portion and pressing the first side gear toward the second side gear, and a second elastic member provided between the second side gear and the second positioning wall portion and pressing the second side gear toward the first side gear.

[0009] In addition, in the present invention, the surface of the pinion gear facing the accommodating portion may be formed in a convex spherical shape, and the portion of the inner surface of the accommodating portion facing the pinion gear may be formed in a concave spherical shape.

[0010] In addition, in the present invention, the case member may include an annular cover portion that abuts against an opening end on one side of the accommodating portion, and three first recesses may be formed in the opening end at a predetermined interval in the circumferential direction of the accommodating portion, and three second recesses may be formed in the surface of the cover portion that abuts against the opening end at the circumferential direction of the cover portion at the predetermined interval, and the ends of each of the three pinion shafts may be fitted into respective hole portions formed by the first recess and the second recess.

[0011] In the present invention, the three pinion gears and the two side gears may be configured by bevel gears. [Effects of the Invention]

[0012] According to the present invention, a differential gear device is configured with a rotatable case member, three pinion gears housed in the case member, and two side gears meshing with each pinion gear. Therefore, each pinion gear and each side gear are positioned by thrust loads and radial loads acting on each other. In other words, there are no gears, such as pinion gears, that are not positioned due to improper loads. This prevents situations such as a deterioration in gear root stress due to misalignment of teeth, and prevents a decrease in the durability of each pinion gear and each side gear. Furthermore, because it prevents situations such as rattle of misaligned gears during operation of the differential gear device, it also prevents the generation of abnormal noise and increased vibration during operation of the differential gear device. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view illustrating an example of a differential gear device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a longitudinal cross-sectional view taken along line II-II in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] 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.

[0015] Fig. 1 shows a cross-sectional view illustrating an example of a differential gear device according to an embodiment of the present invention, and Fig. 2 shows a longitudinal cross-sectional view taken along line II-II in Fig. 1. The differential gear device 1 shown in Figs. 1 and 2 is configured such 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. The right side gear 3 and the left side gear 4 correspond to the "first side gear" and the "second side gear" in the embodiment of the present invention.

[0016] The differential case 2 is composed of a cylindrical housing portion 5 that houses the right side gear 3, and a cylindrical cover portion 6 that abuts against one open end (the left side in FIG. 1) of the housing portion 5 and houses the left side gear 4. This cover portion 6 is configured to transmit torque from a driving force source (not shown).

[0017] The housing 5 is composed of a cylindrical portion 5a, inside which a part of the pinion gear 21 (described later) and the right side gear 3 are housed, and an annular side wall portion 5b formed at one end (the right end portion in FIG. 2) of the cylindrical portion 5a. The cylindrical portion 5a is provided with notches 5c at predetermined intervals in the circumferential direction. In other words, three outer wall portions 5d are formed to protrude from the side wall portion 5b in the axial direction of the housing 5 and at predetermined intervals in the circumferential direction of the housing 5, and these outer wall portions 5d form the cylindrical portion 5a. The notches 5c are formed to ensure space for components provided on the outer periphery of the differential gear device 1.

[0018] The cover portion 6 is composed of a cylindrical portion 6a having approximately the same outer and inner diameters as the cylindrical portion 5a of the accommodation portion 5, an annular side wall portion 6b formed at one end (the left end portion in FIG. 2 ) of the cylindrical portion 6a, and a cylindrical shaft portion 6c protruding from the inner peripheral portion of the side wall portion 6b. The cylindrical portion 6a is provided with notches 6d at predetermined intervals in the circumferential direction, similar to the cylindrical portion 5a. The outer diameter of the cylindrical shaft portion 6c on the side of the side wall portion 6b is larger than the outer diameter of the remaining portion. A bearing 7 is fitted into this portion, 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 L of the accommodation portion 5 and the cover portion 6.

[0019] The housing portion 5 and the cover portion 6 configured as described above are fixed by abutting the end faces of the cylindrical portions 5a and 6a. Specifically, the housing portion 5 and the cover portion 6 are formed with flange portions (not shown) that partially protrude outward from the outside, and the housing portion 5 and the cover portion 6 are integrated by fixing these flange portions with bolts 8.

[0020] A hole 10 into which the pinion shaft 9, which will be described later, fits is formed at the contact portion between the accommodating portion 5 and the cover portion 6. Specifically, three recesses 11 are formed at a predetermined interval in the circumferential direction on the end surface of the cylindrical portion 5a of the accommodating portion 5, and similarly, three recesses 12 are formed at a predetermined interval in the circumferential direction on the end surface of the cylindrical portion 6a of the cover portion 6. By fixing the accommodating portion 5 and the cover portion 6 so that the recesses 11, 12 face each other, hole 10 into which the pinion shaft 9 fits is formed. In other words, the accommodating portion 5 and the cover portion 6 are fixed so as to abut on a plane passing through any point on the central axis of each pinion shaft 9.

[0021] The right side gear 3 is configured as a bevel gear like a side gear provided in a conventional differential gear device, and is held in the housing 5 so as to rotate about the central axis of the housing 5. Specifically, the right side gear 3 is provided with a gear portion 3a on the left side in FIG. 2 in the direction of the central axis of the housing 5, and a boss portion 3b protruding from the back side of the gear portion 3a. The outer diameter of the boss portion 3b is formed to be approximately the same as the inner diameter of the annular side wall portion 5b of the housing 5, and the boss portion 3b is fitted into the side wall portion 5b.

[0022] The right side gear 3 is hollow, and the right drive shaft 13 is spline-engaged with its inner peripheral surface. That is, spline teeth 3c are formed along the central axis of the right side gear 3 on its inner peripheral surface, and spline teeth 13a that mesh with the spline teeth 3c are formed on the outer peripheral surface of the right drive shaft 13. An annular groove 13b is formed at the tip of the right drive shaft 13, and a snap ring 13c is engaged with the groove 13b, preventing the right drive shaft 13 from coming off the right side gear 3. The tip of the right drive shaft 13 protrudes from the gear portion 3a of the right side gear 3.

[0023] An annular right conical spring 14 and an annular right shim 15 are fitted to the boss portion 3b of the right side gear 3. Specifically, the right conical spring 14 and the right shim 15 are provided, in this order, from the gear portion 3a side between the back surface of the gear portion 3a of the right side gear 3 and the side wall portion 5b. The right conical spring 14 is provided so as to generate an elastic force in a direction that separates the gear portion 3a from the side wall portion 5b. In other words, the right conical spring 14 is provided so as to press the right side gear 3 toward the left side gear 4 in the direction of the central axis of the accommodation portion 5.

[0024] The right shim 15 is used to adjust backlash at the meshing portion between the right side gear 3 and each pinion gear described later, and a right shim 15 with an appropriate thickness is selected and assembled during the assembly process depending on the manufacturing error and assembly error of each component.

[0025] The left side gear 4 is formed similarly to the right side gear 3 and is held by the cover 6 so as to rotate about the central axis of the cover 6. Specifically, the left side gear 4 has a gear portion 4a on the right side in FIG. 2 in the direction of the central axis of the cover 6, and a boss portion 4b protruding from the back side of the gear portion 4a. The outer diameter of the boss portion 4b is formed to be substantially the same as the inner diameter of the annular side wall portion 6b of the cover 6, and the boss portion 4b is fitted into the side wall portion 6b.

[0026] The left side gear 4 is hollow, and the left drive shaft 16 is spline-engaged with its inner peripheral surface. That is, spline teeth 4c are formed on the inner peripheral surface of the left side gear 4 along its central axis, and spline teeth 16a that mesh with the spline teeth 4c are formed on the outer peripheral surface of the left drive shaft 16. An annular groove 16b is formed at the tip of the left drive shaft 16, and a snap ring 16c engages with the groove 16b to prevent the left drive shaft 16 from coming off the left side gear 4. The tip of the left drive shaft 16 protrudes from the gear portion 4a of the left side gear 4.

[0027] An annular left-side conical spring 17 and an annular left-side shim 18 are fitted to the boss portion 4b of the left side gear 4. Specifically, the left-side conical spring 17 and the left-side shim 18 are provided, in this order, from the gear portion 4a side between the back surface of the gear portion 4a of the left side gear 4 and the side wall portion 6b. The left-side conical spring 17 is provided so as to generate an elastic force in a direction that separates the gear portion 4a from the side wall portion 6b. In other words, the left-side conical spring 17 is provided so as to press the left side gear 4 toward the right side gear 3 in the direction of the central axis of the cover portion 6.

[0028] The left shim 18 is used to adjust backlash at the meshing portion between the left side gear 4 and each pinion gear described later, and a left shim 18 with an appropriate thickness is selected and assembled during the assembly process depending on the manufacturing error and assembly error of each component.

[0029] The above-mentioned side wall portions 5b and 6b correspond to the "first positioning wall portion" and "second positioning wall portion" in the embodiment of the present invention, the right-side disc spring 14 and the left-side disc spring 17 correspond to the "first elastic member" and "second elastic member" in the embodiment of the present invention, and the recesses 11 and 12 correspond to the "first recess" and "second recess" in the embodiment of the present invention.

[0030] The side gears 3, 4 and drive shafts 13, 16 are arranged facing each other at a predetermined interval in the direction of the central axis L of the housing portion 5 or the cover portion 6. A spider shaft 19 is provided in the gap. The spider shaft 19 is composed of a center portion 20 on the central axis L of the housing portion 5 or the cover portion 6, and three pinion shaft portions 9 extending from the center portion 20 in the radial direction of the housing portion 5 or the cover portion 6.

[0031] The pinion shaft portions 9 are arranged at predetermined intervals (120 degrees) in the circumferential direction (rotational direction) of the housing portion 5 and the cover portion 6, and their tips are fitted into the holes 10. That is, as the differential case 2 rotates, the spider shaft 19 rotates about the central axis L. In other words, the differential case 2 and the spider shaft 19 rotate integrally.

[0032] A pinion gear 21 is rotatably fitted to each of the pinion shaft portions 9. That is, three pinion gears 21 are provided at predetermined intervals (120 degrees) in the circumferential direction of the housing portion 5 or the cover portion 6.

[0033] The pinion gear 21 can be configured in the same manner as pinion gears provided in conventional differential gear devices, and is configured as a bevel gear so as to mesh with each of the side gears 3 and 4. The back surface of the pinion gear 21 facing the housing portion 5 and the cover portion 6 is formed in a convex spherical shape, and the inner surfaces of the housing portion 5 and the cover portion 6 are formed in a concave spherical shape.

[0034] In order to suppress frictional resistance between the pinion gear 21 and the housing portion 5 or the cover portion 6, a spherical washer 22 is provided between the pinion gear 21 and the housing portion 5 or the cover portion 6.

[0035] The differential gear device 1 configured as described above can be assembled by assembling the right side gear 3 and each pinion gear 21 into the accommodating portion 5, and then assembling the left side gear 4 so that it meshes with each pinion gear 21, or by meshing the left side gear 4 assembled into the cover portion 6 with each pinion gear 21.

[0036] Specifically, the right shim 15, the right disc spring 14, and the right side gear 3 are inserted into the housing 5 in this order. Next, the spider shaft 19, with the pinion gears 21 fitted to the pinion shaft portions 9, is assembled into the housing 5. That is, the housing 5 and the spider shaft 19 are aligned in phase so that the tip ends of the pinion shaft portions 9 engage with the recesses 11, and the spider shaft 19 is assembled into the housing 5. Next, for example, the left side gear 4 is assembled into the cover 6; that is, the boss portion 4b of the left side gear 4 is fitted into the side wall portion 6b of the cover 6, and the cover 6 is brought into contact with the housing 5 by aligning the phases of the spider shaft 19 and the housing 5 so that the tip ends of the pinion shaft portions 9 engage with the recesses 12. Thereafter, the housing 5 and the cover 6 are fixed together with the bolts 8.

[0037] 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, so that the differential case 2 and the side gears 3 and 4 rotate at the same rotation speed, and torque transmitted from a driving force source (not shown) to the differential case 2 is transmitted equally to the side gears 3 and 4.

[0038] Furthermore, when the vehicle 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 pinion gear 21 rotates, allowing 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, while the differential case 2 rotates at a rotation speed based on the rotation speed of the driving power source, the side gears 3, 4 rotate relative to each other. In other words, the differential case 2 and the side gears 3, 4 rotate differentially. The torque transmitted to the differential case 2 from the driving power source (not shown) is equally distributed and transmitted to each side gear 3, 4.

[0039] As described above, each pinion gear 21 and each side gear 3, 4 is configured by a bevel gear. Therefore, a thrust load acts on each side gear 3, 4 when torque is transmitted, and the axial position of each side gear 3, 4 is determined at a position where the thrust load and the elastic force of the disc springs 14, 17 are balanced.

[0040] Furthermore, since the pinion gears 21 mesh with the side gears 3, 4 at a predetermined interval (120 degrees) in the circumferential direction, the radial position of each side gear 3, 4 is determined by the radial load received from the pinion gears 21. In other words, the radial loads received from the pinion gears 21 cancel each other out, thereby restricting the radial movement of each side gear 3, 4. In other words, each side gear 3, 4 is aligned by each pinion gear 21.

[0041] Furthermore, each pinion gear 21 is pressed against the inner surfaces of the housing portion 5 and the cover portion 6 by the reaction forces from each of the side gears 3 and 4, thereby being positioned in the axial direction. The back surface of the pinion gear 21 is formed into a convex spherical shape, and the inner surfaces of the housing portion 5 and the cover portion 6 are formed into a concave spherical shape. Therefore, when the pinion gear 21 is pressed in the axial direction by the reaction forces received by each of the side gears 3 and 4, the reaction forces received from the housing portion 5 and the cover portion 6 (more specifically, the washer 22) act in the direction of the rotational center axis of the pinion gear 21, thereby positioning the pinion gear 21 in the radial direction.

[0042] As described above, by meshing the three pinion gears 21 with the side gears 3 and 4, the pinion gears 21 and the side gears 3 and 4 are positioned. In other words, there are no other gears, such as pinion gears, that are not positioned because a load is not applied appropriately. This prevents situations such as a deterioration in gear tooth root stress due to misalignment of the teeth, and prevents a decrease in the durability of the pinion gears 21 and the side gears 3 and 4. Furthermore, since it is possible to prevent situations such as rattle of unpositioned gears during operation of the differential gear device 1, it is possible to prevent the generation of abnormal noise and increased vibration during operation of the differential gear device 1. [Explanation of symbols]

[0043] 1 Differential gear unit 2 Differential case 3,4 Side gear 3a, 4a Gear section 5. Storage section 5a, 6a Cylindrical part 5b,6b Side wall part 5c,6c Notch 5d,6d Exterior wall 6 Cover 9 Pinion shaft 10 Hole 11,12 Recess 14,17 Disc spring 15,18 Sim 19 Spider Shaft 20 Center 21 Pinion gear 22 Washer L center axis

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 to be rotatable and to be revolvable about the central axis of the housing portion; and a first side gear and a second side gear provided opposite each other in the direction of the central axis of the housing portion and meshing with the pinion gear, three pinion shafts extending from a central axis of the accommodating portion to a wall surface of the accommodating portion, one end of which is connected to the wall surface, and which are provided at predetermined intervals from each other in a rotation direction of the accommodating portion, The pinion gear includes three pinion gears rotatably fitted to the three pinion shafts, respectively. A differential gear device characterized by:

2. 2. The differential gear device according to claim 1, the case member has a first positioning wall portion opposed to a surface of the first side gear facing away from the second side gear, and a second positioning wall portion opposed to a surface of the second side gear facing away from the first side gear, a first elastic member provided between the first side gear and the first positioning wall portion and pressing the first side gear toward the second side gear; The second side gear is provided with a second elastic member that is disposed between the second side gear and the second positioning wall portion and that presses the second side gear toward the first side gear. A differential gear device characterized by:

3. 2. The differential gear device according to claim 1, The surface of the pinion gear facing the housing portion is formed into a convex spherical shape, A portion of the inner surface of the accommodating portion that faces the pinion gear is formed in a concave spherical shape. A differential gear device characterized by:

4. 2. The differential gear device according to claim 1, the case member includes an annular cover portion that abuts against one open end of the storage portion, Three first recesses are formed at the opening end at predetermined intervals in the circumferential direction of the housing portion, three second recesses are formed at predetermined intervals in the circumferential direction of the cover portion on a surface of the cover portion that abuts against the opening end, The ends of the three pinion shafts are fitted into the holes formed by the first recess and the second recess. A differential gear device characterized by:

5. 2. The differential gear device according to claim 1, The three pinion gears and the two side gears are configured by bevel gears. A differential gear device characterized by:

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