Differential device

Abstract

This reduces gear noise at the ring gear meshing point by suppressing rotational runout of the differential case. [Solution] A differential device 1 is provided in which a ring gear 8 is integrally provided on the outer circumference of a differential case 3, a pair of side gears 10a and 10b facing each other on the rotational axis of the differential case are arranged inside the differential case 3, pinion gears 11a and 11b that mesh with the side gears are arranged between the side gears, a pinion shaft 12 arranged perpendicular to the rotational axis passes through the pinion gears and holds the pinion gears rotatably, and the end of the pinion shaft is supported by the differential case, the differential case has a through hole into which the end of the pinion shaft is inserted, the end of the pinion shaft is press-fitted into the through hole, and further the pinion shaft has a protruding portion that extends outward from the through hole to the outside of the differential case, and the protruding portion is an enlarged portion 15a and 15b that is larger than the inner diameter of the through hole.

Description

Technical Field

[0001] The present invention relates to a differential device, and more particularly to a differential device that causes differential rotation in a pair of side gears by the rotation of pinion gears meshing with the pair of side gears.

Background Art

[0002] This type of differential device is disclosed in Patent Document 1. The differential device has a differential case integrated with a ring gear. A pair of side gears are arranged inside the differential case. The side gears are arranged facing each other on the rotation center axis of the differential case. A pair of pinion gears meshing with the side gears are arranged between the side gears. These pinion gears are rotatably held by a pinion shaft orthogonal to the rotation center axis of the differential case. The pinion shaft is press-fitted into an insertion hole for the shaft provided in the differential case and fixed to the differential case.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the differential device described in Patent Document 1, the pinion shaft is tightly attached to and integrated with the differential case, which not only increases the rigidity of the differential case but also increases the support rigidity of the differential case in supporting the pinion shaft. As a result, errors in the meshing between the pinion gear and the side gears are less likely to occur, and noise and vibration caused by the meshing of these gears can be suppressed. However, torque is input to the differential case from the ring gear which is integrated with it, and depending on the meshing state of the ring gear, gear noise may occur. That is, the differential case is supported by the vehicle body etc. via bearings, but the ring gear meshes at a point far away from the support point by the bearings, so the torque acting on the ring gear causes slight distortion in the differential case and its rotation. Such distortion is sometimes called rotational runout, and this rotational runout appears as a meshing error in the ring gear, and this meshing error can cause gear noise. The differential device described in Patent Document 1 is unable to reduce gear noise caused by such rotational runout, and there is still room for improvement.

[0005] This invention was made in view of the above technical problems, and aims not only to improve the support rigidity of the pinion shaft by the differential case and the rigidity of the differential case, but also to suppress rotational runout of the differential case and reduce gear noise at the meshing portion of the ring gear. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a differential device in which a ring gear is integrally provided on the outer circumference of a differential case, a pair of side gears facing each other on the rotational axis of the differential case are rotatably arranged about the rotational axis, a pinion gear meshing with the pair of side gears is positioned between the pair of side gears, a pinion shaft positioned perpendicular to the rotational axis passes through the pinion gear and holds the pinion gear rotatably, and the end of the pinion shaft is supported by the differential case, wherein the differential case has a through hole into which the end of the pinion shaft is inserted, the end of the pinion shaft is press-fitted into the through hole, and furthermore, the pinion shaft has a protruding portion that extends outward from the through hole to the outside of the differential case, and the protruding portion is an enlarged portion that is larger than the inner diameter of the through hole.

[0007] In the present invention, one of the ends of the pinion shaft may be made of a capping member which is integrally formed with the enlarged portion and is press-fitted into the through hole with the pinion shaft fitted inside.

[0008] In the present invention, the through hole and the end portion pressed into the through hole may be configured to have a circular cross-sectional shape.

[0009] In the present invention, the enlarged portion of the crowning member may have an engaging portion for engaging a tool for pulling it out from the through hole. [Effects of the Invention]

[0010] In the differential device of the present invention, the pinion shaft is press-fitted into a through-hole in the differential case and integrated with the differential case. Therefore, the support rigidity of the pinion gear against the differential case and the rigidity of the differential case are increased, making it difficult for meshing errors between the pinion gear and the side gears and the resulting gear noise to occur. In addition, the enlarged portion provided at the end of the pinion shaft increases the inertial mass or moment of inertia of the differential case, so that rotational runout of the differential case can be prevented or suppressed. As a result, gear noise at the meshing portion of the ring gear, which is integrated with the differential case, can be reduced. Furthermore, since the area where the load is applied for press-fitting is the enlarged portion, which has a larger diameter than the through-hole, deformation of the end of the pinion shaft when a load is applied to the pinion shaft is less likely to occur, making it easier to apply the load for press-fitting.

[0011] Furthermore, by configuring one end of the pinion shaft with a capping member having an enlarged portion, the assembly of the differential device becomes easier. Specifically, the procedure for attaching the pinion shaft to the differential case is as follows: First, the pinion shaft, with the capping member removed, is inserted from one through-hole towards the other through-hole, thereby press-fitting one end of the pinion shaft into one through-hole, and then the capping member is press-fitted into the other through-hole, thereby fitting the capping member onto the pinion shaft.

[0012] In the differential device of the present invention, by making the cross-sectional shape of the through-hole in the differential case and the end of the pinion shaft that is press-fitted into the through-hole circular, the pressure-receiving area, which is the area over which the load acts between the differential case and the pinion shaft, can be increased. As a result, wear caused by repeated load application between the two can be suppressed or reduced.

[0013] Furthermore, in the differential device of the present invention, by providing an engaging portion on the enlarged part of the crowning member, when removing the crowning member from the through hole, the load for removal can be applied to the crowning member using the engaging portion, thereby improving the ease of disassembly and assembly of the differential device. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a cross-sectional view showing an embodiment of the present invention. [Figure 2] Figure 2 is a partially abbreviated exploded front view showing the pinion shaft. [Figure 3] Figure 3 is a schematic cross-sectional view showing the through-hole portion of the differential case. [Modes for carrying out the invention]

[0015] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the embodiments described below are merely examples of how the present invention can be implemented and do not limit the invention.

[0016] The embodiment described below is substantially the same as a conventionally known differential gear, except for the structure of the pinion shaft and the structure for attaching the pinion shaft to the differential case. That is, the differential device 1 shown in Figure 1 includes a differential case 3 housed inside a differential carrier 2 and rotatably held by the differential carrier 2. The differential case 3 has boss portions 4a and 4b extending to the left and right on the same axis, and a frame portion (or support plate portion) 5 connecting these boss portions 4a and 4b. The differential case 3 is supported by the differential carrier 2 via bearings 6a and 6b fitted to the outer circumference of its boss portions 4a and 4b. A flange 7 is integrally provided on the outer circumference of the frame portion 5 at a location closer to one of the boss portions 4a (or 4b). A ring gear 8 is fixed to this flange 7 with appropriate fastening means such as bolts 9, and the ring gear 8 is integrated with the differential case 3.

[0017] A pair of side gears 10a and 10b are arranged facing each other inside the frame portion 5 and on the same axis as the boss portions 4a and 4b. These side gears 10a and 10b have hollow portions aligned on the same axis as the boss portions 4a and 4b, and are configured to be spline-fitted with a rotating shaft (not shown) into these hollow portions. The side gears 10a and 10b are bevel gears, and a pair of pinion gears 11a and 11b that mesh with these side gears 10a and 10b are arranged between the side gears 10a and 10b. These pinion gears 11a and 11b are connected to the differential case 3 by a pinion shaft 12 and are rotatably held.

[0018] The pinion shaft 12 is positioned between the side gears 10a and 10b in a direction perpendicular to the central axis of the boss portions 4a and 4b, i.e., the rotational axis of the differential case 3. The pinion shaft 12 has a length that connects the frame portions 5 and is fixed to the frame portions 5, i.e., the differential case 3, at both ends. Inside the differential case 3, the pinion shaft 12 is rotatably fitted to the pinion gears 11a and 11b. In other words, each pinion gear 11a and 11b is connected to the differential case 3 by the pinion shaft 12.

[0019] FIG. 2 shows an example of the pinion shaft 12 in an embodiment of the present invention, and FIG. 3 shows a through hole 13 for attaching the pinion shaft 12 to the differential case 3. The pinion shaft 12 is a metal round bar-shaped member, and has an intermediate portion 12a that fits into the pinion gears 11a and 11b to hold the pinion gears 11a and 11b, and end portions 12b and 12c on both sides thereof. Those end portions 12b and 12c have press-fitting portions 14a and 14b that are press-fitted into the through hole 13 in the differential case 3, and enlarged portions 15a and 15b. Each of the press-fitting portions 14a and 14b has an outer diameter greater than or equal to the outer diameter of the intermediate portion 12a. Further, the through hole 13 and each of the press-fitting portions 14a and 14b are portions where the cross-sectional shape when cut by a plane perpendicular to their respective central axes is circular, and the through hole 13 and each of the press-fitting portions 14a and 14b are configured to be in close contact without a gap. Therefore, since the through hole 13 and each of the press-fitting portions 14a and 14b are circular in cross-section, the pressure-receiving area for receiving the load acting between them is widened.

[0020] The enlarged portions 15a and 15b are protruding portions that protrude from the through hole 13 to the outside of the differential case 3, and are portions having a larger diameter than the through hole 13. When press-fitting the pinion shaft 12 into the through hole 13, a pressing force or load is applied to the enlarged portions 15a and 15b. However, due to the large diameter of the enlarged portions 15a and 15b, the pressing force or load can be easily applied without causing deformation in the edge portion or the like, and the assembly workability is improved. Note that the enlarged portions 15a and 15b only need to be integral with the press-fitting portions 14a and 14b. The enlarged portions 15a and 15b may be formed or attached during the process of assembling the pinion shaft 12 to the differential case 3, or the enlarged portions 15a and 15b may be integrated with the pinion shaft 12 after the pinion shaft 12 is assembled to the differential case 3.

[0021] Figure 2 shows an example of a pinion shaft 12 in which one end 12c is configured to be detachably attached to an intermediate portion 12a. The end 12c is composed of a press-fit plug 16, which is a capping member that integrates a press-fit portion 14b and an enlarged portion 15b. The press-fit portion 14b is cylindrical in shape and is configured to fit or press-fit the intermediate portion 12a into its interior in a tight fit. Furthermore, an engagement portion 17 is provided on the outer circumference of the enlarged portion 15b. This engagement portion 17 is the part into which a suitable tool 18 for removing the press-fit plug 16 from the through hole 13 is engaged. The engagement portion 17 may be formed by partially cutting out a so-called jaw portion such as a corner portion on the outer circumference of the enlarged portion 15b, or it may be a portion formed by separating a part of the enlarged portion 15b from the outer surface of the differential case 3, or it may be a recess provided on a part of the outer surface of the enlarged portion 15b. The presence of such an engaging portion 17 facilitates the attachment and detachment of the press-fit plug 16, and thus facilitates the disassembly and assembly of the differential device 1.

[0022] In the embodiment of the present invention with the configuration described above, the differential device 1 rotates as a whole, including the differential case 3 and the gears 10a, 10b, 11a, and 11b inside it, due to torque being transmitted to the ring gear 8. As the differential case 3 rotates, the pinion shaft 12, which is integrated with the differential case 3, rotates about its longitudinal center, so the pair of pinion gears 11a and 11b held by the pinion shaft 12 revolve around the rotational axis of the differential case 3. Since the pinion gears 11a and 11b mesh with the left and right side gears 10a and 10b, the revolving of the pinion gears 11a and 11b transmits torque to the side gears 10a and 10b, causing the side gears 10a and 10b to rotate. In this case, when the pinion gears 11a and 11b rotate on their own, the side gears 10a and 10b rotate differentially.

[0023] Since the torque is transmitted from the differential case 3 to the pinion gears 11a and 11b via the pinion shaft 12, a load acts between the inner peripheral surface of the through hole 13 of the differential case 3 and the outer peripheral surfaces of the press-fitting portions 14a and 14b on the pinion shaft 12. The surfaces that receive this load are the entire inner peripheral surface of the through hole 13 and the entire outer peripheral surfaces of the press-fitting portions 14a and 14b. Therefore, since the so-called pressure receiving area is wide, wear of these surfaces can be suppressed. Further, the pinion shaft 12 is firmly attached to the differential case 3 without any gaps or looseness. Moreover, since the pinion shaft 12 is press-fitted into the through hole 13 and integrated with the differential case 3, the rigidity of the differential case 3 is increased, so misalignment or error is unlikely to occur in the meshing between the pinion gears 11a, 11b and the side gears 10a, 10b. Therefore, gear noise at the meshing portions of these gears 11a, 11b, 10a, 10b is reduced.

[0024] In particular, in the differential device 1 according to the embodiment of the present invention described above, as described above, the pinion shaft 12 has enlarged portions 15a and 15b at both ends thereof, and the inertial mass or the moment of inertia is increased according to the mass of the enlarged portions 15a and 15b. Therefore, the rotational runout of the differential case 3 is suppressed, and the differential case 3 maintains smooth or stable rotation. Therefore, almost no meshing error occurs in the ring gear 8, and gear noise at the meshing portion of the ring gear 8 is suppressed.

[0025] Note that the present invention is not limited to the above-described embodiment, and a plurality of pairs or more of pinion gears may be provided. In that case, the pinion shaft may have a shape bifurcated from a single shaft portion or a cross shape.

Explanation of Reference Numerals

[0026] 1 Differential device 2 Differential carrier 3 Differential case 4a, 4b Boss portions 5 Frame portion 6a, 6b Bearings 7 Flange 8 Ring gear 9 volts 10a, 10b Side gears 11a, 11b pinion gear 12 pinion shaft 12a middle part 12b,12c end 13 Through hole 14a, 14b Press-fit section 15a,15b ampulla 16. Press-fit plug (crown component) 17 Engaging part 18 Tools

Claims

1. A differential device comprising a ring gear integrally provided on the outer circumference of a differential case, a pair of side gears facing each other on the rotational axis of the differential case, rotatably arranged around the rotational axis, a pinion gear meshing with the pair of side gears positioned between the pair of side gears, a pinion shaft positioned perpendicular to the rotational axis passing through the pinion gear and rotatably holding the pinion gear, and the end of the pinion shaft supported by the differential case, The differential case has a through hole into which the end of the pinion shaft is inserted. The end of the pinion shaft is press-fitted into the through hole, and further, The pinion shaft has a protruding portion that extends from the through hole to the outside of the differential case. The aforementioned protrusion is a swollen portion that is larger than the inner diameter of the through hole. A differential device characterized by the following features.

2. A differential device according to claim 1, One of the ends of the pinion shaft is formed by a capping member, which is integrally formed with the enlarged portion and is press-fitted into the through hole with the pinion shaft fitted inside. A differential device characterized by the following features.

3. A differential device according to claim 1 or 2, The through-hole and the end portion pressed into the through-hole are configured to have a circular cross-sectional shape. A differential device characterized by the following features.

4. A differential device according to claim 2 or claim 3 referencing claim 2, The enlarged portion of the crowning member has an engagement portion for engaging a tool for pulling it out from the through hole. A differential device characterized by the following features.

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