JP2011012793A - Power transmission shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce maximum bending stress in a spline fitting part while minimizing an increase in the weight of the spline fitting part.SOLUTION: This power transmission shaft includes a first shaft 6 with an end formed with a male spline groove 6a, and a second shaft 5 with an end formed with a female spline groove 5aa insert-fitted to the male spline groove 6a. In both end positions 15a1, 15a2 of an overlap part 15a where the first shaft 6 and the second shaft 5 overlap with each other by spline fitting, a first protrusion 23 and a second protrusion 24 projected radially outward are formed on the outer peripheral part of the second shaft 5.

Description

  The present invention relates to a power transmission shaft connected by spline fitting.

  A power transmission shaft that transmits the power of an engine such as an automobile is configured by connecting a plurality of shaft members. For example, a male spline groove is formed at the end of one shaft, a female spline groove is formed at the end of the other shaft, and the male spline is inserted and fitted into the female spline so as to be integrally rotated. Is used as a power transmission shaft of a vehicle (see, for example, Patent Documents 1 and 2).

  FIG. 3 shows a transaxle 51, a transfer 52, etc. of a conventional four-wheel drive vehicle. Reference numeral 57 is a differential gear, and reference numeral 55 is a differential case of the differential gear 57. Reference numeral 10 denotes a drive shaft connected to the front wheel of the vehicle. The transaxle case 61 is fixed to an engine (not shown), and the transfer case 62 is fixed to an engine (not shown) via a stiffener 64.

  The transfer 52 includes a hollow shaft-shaped ring gear mounting case 56, a ring gear 66 fixed to the ring gear mounting case 56, and a driven gear 67 meshed with the ring gear 66. The ring gear 66 and the driven gear 67 form a hypoid gear. The driven gear 67 is connected to a propeller shaft (not shown) so as to rotate together.

  FIG. 4 is an enlarged view of the spline fitting portion 65 shown in FIG. As shown in FIG. 4, a hollow shaft 55a is formed on one side of the differential case 55, and a female spline groove 55aa is formed at the end of the hollow shaft 55a. A male spline groove 56a formed at the end of the ring gear mounting case 6 is inserted and fitted into the female spline groove 55aa of the hollow shaft portion 55a.

  Since the ring gear 54 fixed to the differential case 55 employs a helical gear, when power is transmitted from the engine side to the drive wheel side, the ring gear 54 is indicated by an arrow F1 as shown in FIG. Receives direction force (reaction force). Further, since a hypoid gear is employed for the transfer 52, the ring gear 66 of the transfer 52 receives a force (reaction force) in the direction indicated by the arrow F2. Therefore, a bending moment in the direction indicated by the arrow M is generated in the differential case 55 and the ring gear mounting case 56.

Japanese Patent Laid-Open No. 7-117504 Japanese Patent Laid-Open No. 2005-199890

  When a bending moment is generated in the power transmission shaft (the differential case 55 and the ring gear mounting case 56) having the spline fitting portion 65, the maximum stress is easily generated in the spline fitting portion 65. Particularly recently, the bending moment has increased with the increase in the driving force of the engine. If the strength of the spline fitting portion 65 is insufficient, the differential case 55 side of the spline fitting portion 65 expands the inner diameter. There is a risk of deformation.

  In order to prevent such deformation, the transaxle case 61 is fixed to the engine, and as shown in FIG. 3, the transfer case 62 is also fixed to the engine using a stiffener 64 or the like. It was. Thereby, the bending moment and the maximum bending stress in the spline fitting portion 65 are reduced.

  Further, it is possible to uniformly increase the thickness of the spline fitting portion 65 of the hollow shaft portion 55a of the differential case 55 to reduce the maximum bending stress of the portion.

  However, when the stiffener 64 is provided, there is a problem that an increase in weight and an increase in assembly man-hours are caused. Further, in the FF4WD vehicle, it is difficult to secure a space for attaching the stiffener 64 around the transfer case 62, and the shape of the transfer case 62 may be restricted.

  Further, evenly increasing the thickness of the spline fitting portion 65 of the hollow shaft portion 55a of the differential case 55 has a problem in that the weight is increased.

  The present invention was devised in view of the above problems, and the maximum bending stress in the spline fitting portion can be reduced while suppressing the increase in the weight of the spline fitting portion as much as possible without fixing the transfer case to the engine. An object is to provide a power transmission shaft.

  As means for solving the above-described problems, the power transmission shaft of the present invention is configured as follows. That is, the power transmission shaft of the present invention includes a first shaft having a male spline groove formed at an end thereof, a second shaft having a female spline groove inserted and fitted into the male spline groove formed at an end thereof, and On both ends of the overlapping portion where the first shaft and the second shaft overlap with each other by spline fitting, and a convex portion protruding radially outward is formed on the outer peripheral portion of the second shaft. It is characterized by.

  According to the power transmission shaft having such a configuration, the deformation of the spline fitting portion can be suppressed only by partially increasing the thickness of the outer peripheral portion of the second shaft, and the weight in the spline fitting portion can be suppressed. The increase can be minimized.

  According to the power transmission shaft of the present invention, it is possible to suppress deformation of the spline fitting portion while minimizing the weight increase in the spline fitting portion without fixing the transfer case to the engine.

It is sectional drawing which cut | disconnected and showed the transaxle, transfer, etc. which concern on embodiment of this invention by the plane containing the axis line of a drive shaft. It is an expanded sectional view of the spline fitting part of FIG. Illustration of the drive shaft is omitted. It is sectional drawing which cut | disconnected and showed the transaxle, transfer, etc. which concern on the prior art example by the plane containing the axis line of a drive shaft. It is an expanded sectional view of the spline fitting part of FIG. Illustration of the drive shaft is omitted. It is a schematic diagram for demonstrating the bending moment which acts on the power transmission shaft which connects the transaxle and transfer which concern on a prior art example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a transaxle 1 and a transfer 2 for a four-wheel drive vehicle. FIG. 2 is an enlarged view of a spline fitting portion 15 described later. The power transmission shaft 3 of the present invention is applied to a differential case 5 and a ring gear mounting case 6 that are spline-fitted to each other.

  Reference numeral 7 denotes a differential gear. The differential gear 7 includes the differential case 5, a ring gear 4 including a helical gear fixed to the differential case 5, a pair of pinion gears 8 and 8, and a pair of side gears 9 and 9.

  Reference numerals 10 and 10 denote drive shafts, and respective end portions are spline-fitted to the side gears 9 and 9.

  The transaxle case 11 is fixed to an engine (not shown), and the transfer case 12 is fixed to the transaxle case 11. As described in the conventional example, the transfer case 12 may be fixed to the engine using a stiffener. However, in this embodiment, the transfer case 12 is fixed only to the transaxle case 11 and is not fixed to the engine. .

  The ring gear 4 and the differential case 5 of the differential gear 7 are rotationally driven via a transmission by an engine (not shown). The rotational driving force of the differential case 5 is transmitted to the drive shafts 10 and 10 through the pinion gears 8 and 8 and the side gears 9 and 9, and rotates the front wheels of the vehicle (not shown). The differential case 5 is rotatably supported in the transaxle case 11 by bearings 18 and 19.

  On one side of the differential case 5, a hollow shaft portion 5a extends along the periphery of the drive shaft 10, and a female spline groove 5aa (see FIG. 2) is formed at the end of the hollow shaft portion 5a. Yes. A hollow shaft-like ring gear mounting case 6 having a male spline groove 6a formed at the end thereof is spline-fitted to the hollow shaft portion 5a. That is, the male spline groove 6a is inserted and fitted into the female spline groove 5aa. The drive shaft 10 and the ring gear mounting case 6 are rotatable relative to each other.

  As shown in FIG. 1, the ring gear mounting case 6 is rotatably supported by bearings 20 and 21 in the transfer case 12. A ring gear 16 is fixed to the ring gear mounting case 6, and the ring gear 16 and a driven gear 17 meshed with the ring gear 16 form a hypoid gear to constitute the transfer 2. The driven gear 17 is connected to a propeller shaft (not shown) so as to rotate together.

  At both end positions 15a1 and 15a2 in a portion where the hollow shaft portion 5a of the differential case 5 and the ring gear mounting case 6 are overlapped by spline fitting (hereinafter referred to as “overlapping portion 15a”), a diameter is formed on the outer periphery of the hollow shaft portion 5a. The 1st convex part 23 and the 2nd convex part 24 which protruded to the direction outer side are formed. These 1st convex parts 23 and 2nd convex part 24 are formed over the whole circumferential direction. The projecting height of the first convex portion 23 and the second convex portion 24 to the radially outer side is set so that the maximum stress generated by a bending moment described later is equal to or less than the allowable stress of the material used for the differential case 5. It is desirable.

  Since the ring gear 4 fixed to the differential case 5 employs a helical gear, when power is transmitted from the engine side to the drive wheel side, the ring gear 4 and the differential case 5 are forced in the direction indicated by the arrow F1. (Reaction force) is received from the drive side gear (gear meshed with the ring gear 4). Further, since a hypoid gear is adopted for the transfer 2 (ring gear 16 and driven gear 17), the ring gear 16 and the ring gear mounting case 6 receive a force (reaction force) in the direction indicated by the arrow F2 from the driven gear 17.

  For this reason, a bending moment acts on the differential case 5 and the ring gear mounting case 6 in the direction indicated by the arrow M. When a bending moment acts on the differential case 5 (hollow shaft portion 5a) having the spline fitting portion 15 and the ring gear mounting case 6, maximum stress is generated at both end positions 15a1 and 15a2 of the overlapping portion 15a of the spline fitting portion 15. However, the outer peripheral portion of the hollow shaft portion 5a of the differential case 5 is formed with the first convex portion 23 and the second convex portion 24 protruding outward in the radial direction at both end positions 15a1 and 15a2 of the overlapping portion 15a. Since it increases, the maximum bending stress which arises in the hollow shaft part 5a is suppressed. Thereby, the deformation | transformation which the hollow shaft part 5a of the differential case 5 is pushed and expanded by the ring gear mounting case 6 is prevented.

  The inventor of the present application confirmed by CAE analysis that when the bending moment M is generated, the stress at the root of the female spline groove 5aa at both end positions 15a1 and 15a2 of the overlapping portion 15a is the highest. Yes. According to the present invention, the stress at the root can be reduced.

  As is clear from the above description, according to the power transmission shaft 3 including the differential case 5 and the ring gear mounting case 6 in the embodiment of the present invention, the thickness of the hollow shaft portion 5a of the differential case 5 is partially increased. Only by increasing the thickness, deformation and breakage of the spline fitting portion 15 can be prevented, and the weight increase in the spline fitting portion 15 can be minimized.

  Further, according to the present invention, it is not necessary to fix the transfer case 12 to the engine using a stiffener or the like in order to suppress the bending moment.

  The present invention can be applied to, for example, a power transmission shaft of an automobile, in particular, a power transmission shaft having a spline fitting portion.

3 Power transmission shaft 5 Differential case (second shaft)
5aa Female spline groove 6 Ring gear mounting case (first shaft)
6a Male spline groove 15 Spline fitting part 15a Superposition part 15a1 End position of superposition part 15a2 End position of superposition part 23 1st convex part 24 2nd convex part

Claims (1)

A first shaft having a male spline groove formed at the end;
A second shaft having a female spline groove inserted and fitted in the male spline groove formed at an end;
In a power transmission shaft comprising:
At both end positions of the overlapping portion where the first shaft and the second shaft overlap by spline fitting, a convex portion protruding radially outward is formed on the outer peripheral portion of the second shaft.
A power transmission shaft characterized by that.

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