Power transmission shaft

Abstract

To reliably form an identification groove on the whole circumference of an outer peripheral surface of a power transmission shaft.SOLUTION: A power transmission shaft (intermediate shaft 2) comprises: male spline parts 2a, 2b inserted into spline holes of inside joint members 3a, 4a of constant velocity universal joints 3, 4; a boot mounting part 10 having an annular groove 11; and an annular identification groove 20 provided on the opposite axial end side of the boot mounting part 10. A fiber flow on a surface layer in an area where the boot mounting part 10 and the identification groove 20 are formed extends continuously along the surfaces of the boot mounting part 10 and the identification groove 20.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a power transmission shaft. [Background technology]

[0002] A driveshaft that transmits the driving force of a vehicle engine to the wheels typically comprises a power transmission shaft and constant velocity universal joints attached to both ends of the power transmission shaft (see, for example, Figure 3 of Patent Document 1 listed below). A bellows-shaped boot is attached to the constant velocity universal joint to prevent foreign matter such as dust from entering the joint and to prevent leakage of grease sealed inside the joint. The large diameter end of the boot is fastened and fixed to the outer peripheral surface of the outer joint member of the constant velocity universal joint with a boot band, and the small diameter end of the boot is fastened and fixed to the outer peripheral surface of the power transmission shaft with a boot band.

[0003] An annular boot groove is formed in the outer peripheral surface of the power transmission shaft in a portion where the small diameter end of the boot is fixed. By fitting the boot onto the power transmission shaft and tightening the small diameter end of the boot from the outer periphery with a boot band, the inner peripheral surface of the small diameter end of the boot bites into the boot groove, thereby ensuring a seal.

[0004] When boot grooves are formed on the outer peripheral surface of a power transmission shaft by turning, a turning allowance is required, which increases the diameter of the material and leads to higher costs. Therefore, in order to reduce costs, there has been an increase in the number of cases where boot grooves are formed by plastic processing (for example, rolling) (see Patent Document 1 below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4122126 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, an annular identification groove is sometimes formed near the boot groove on the outer peripheral surface of a power transmission shaft to confirm the boot mounting position and the orientation (left / right) of the power transmission shaft. Because the identification groove only needs to be deep enough to be visible, it is typically very shallow to avoid reducing the strength of the power transmission shaft and increasing the processing time. When such a shallow identification groove is formed by turning, the influence of runout of the shaft material during turning can result in the identification groove not being formed over the entire circumference but only being formed on a portion of the circumference. In particular, if the identification groove is formed by turning and then the boot groove is formed by plastic processing, there is a risk that the identification groove will be crushed during plastic processing. In this case, it becomes difficult to check the identification groove during drive shaft assembly, significantly reducing workability.

[0007] An object of the present invention is to reliably form an identification groove around the entire outer periphery of a power transmission shaft. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a power transmission shaft comprising a male spline portion to be inserted into a spline hole of an inner joint member of a constant velocity universal joint, a boot mounting portion having an annular groove, and an annular identification groove provided on the anti-axial end side of the boot mounting portion, wherein the fiber flow of the surface layer in the formation area of ​​the boot mounting portion and the identification groove extends continuously along the surfaces of the boot mounting portion and the identification groove.

[0009] When the boot attachment portion and the identification groove are formed by plastic working, the fiber flow in the surface layer in these formation areas extends continuously along the surface without being cut. In this way, by forming the identification groove by plastic working, it is possible to reliably form the identification groove around the entire outer surface of the power transmission shaft without being affected by runout of the shaft material, as is the case with turning.

[0010] It is preferable to mold the identification groove simultaneously with the boot mounting portion having the annular groove using the same mold (e.g., rolling mold). This reduces the number of steps compared to forming them separately and also prevents the identification groove from being crushed by plastic processing of the boot mounting portion.

[0011] When the boot mounting portion has an annular groove and annular protrusions provided on both axial sides of the annular groove, the annular groove and the annular protrusions of the boot mounting portion are preferably formed as molded surfaces using a mold, which allows the dimensions of the annular groove and the annular protrusions to be controlled with high precision.

[0012] The present invention is applicable, for example, to solid power transmission shafts. [Effects of the Invention]

[0013] As described above, according to the present invention, it is possible to reliably form an identification groove around the entire outer circumferential surface of a power transmission shaft. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a drive shaft having a power transmission shaft (intermediate shaft) according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged side view of the vicinity of a boot attachment portion of the power transmission shaft. [Figure 3] (A) is a cross-sectional view showing a state in which a boot is attached to a power transmission shaft in the normal position, and (B) and (C) are cross-sectional views showing a state in which the boot is attached to a position shifted from the normal position. [Figure 4] FIG. 2 is a front view of the rolling die and the blank as viewed from the axial direction. [Figure 5] 5 is a side view (upper half) and a cross-sectional view (lower half) of the rolling die and the material as viewed from the X direction in FIG. 4. [Figure 6] FIG. 1 is a cross-sectional view of a rolling die before it is brought into contact with a material. [Figure 7] FIG. 1 is a cross-sectional view of a rolling die in contact with a material. [Figure 8] FIG. 2 is a cross-sectional view showing the fiber flow in the surface layer of the power transmission shaft. [Figure 9] FIG. 10 is a side view showing another example of the boot attachment portion. [Figure 10] FIG. 10 is a side view showing still another example of the boot attachment portion. [Figure 11] FIG. 10 is a cross-sectional view showing the fiber flow of the surface layer of a power transmission shaft according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] The drive shaft 1 shown in FIG. 1 includes an intermediate shaft 2 serving as a power transmission shaft according to one embodiment of the present invention, and constant velocity universal joints 3 and 4 attached to both ends of the intermediate shaft 2. One constant velocity universal joint 3 is a fixed-type constant velocity universal joint including an inner joint member 3a to which one end of the intermediate shaft 2 is attached, an outer joint member 3b connected to the wheel side, a plurality of balls 3c that transmit torque between them, and a cage 3d that holds the plurality of balls 3c. The other constant velocity universal joint 4 is a sliding-type constant velocity universal joint including an inner joint member 4a to which the other end of the intermediate shaft is attached, an outer joint member 4b connected to the differential side, a plurality of balls 4c that transmit torque between them, and a cage 4d that holds the plurality of balls 4c. Note that the constant velocity universal joints 3 and 4 are not limited to those described above, and for example, the other constant velocity universal joint 4 may be a tripod-type sliding-type constant velocity universal joint.

[0017] Boots 5, 6 are attached between the constant velocity universal joints 3, 4 and the intermediate shaft 2. The boots 5, 6 have large diameter end portions 5a, 6a fixed to the outer peripheral surfaces of the outer joint members 3b, 4b of the constant velocity universal joints 3, 4, small diameter end portions 5b, 6b fixed to the outer peripheral surface of the intermediate shaft 2, and bellows portions 5c, 6c provided therebetween. The boots 5, 6 are formed of resin, for example, a thermoplastic polyester elastomer or a composition containing same. The surface hardness of the boots 5, 6 is HD38 to 50. The boots 5, 6 may also be formed of rubber (for example, chloroprene rubber).

[0018] The large diameter ends 5a, 6a and small diameter ends 5b, 6b of the boots 5, 6 are fastened from the outer periphery by boot bands 7a, 8a, 7b, 8b, respectively, and are thereby fixed to the outer periphery of the outer joint members 3b, 4b of the constant velocity universal joints 3, 4 and the outer periphery of the intermediate shaft 2. The boots 5, 6 prevent the grease sealed inside the constant velocity universal joints 3, 4 from leaking out and prevent foreign matter from entering the inside of the constant velocity universal joints 3, 4.

[0019] The intermediate shaft 2 has male spline portions 2a, 2b provided on both ends, a boot attachment portion 10 to which the small diameter ends 5b, 6b of the boots 5, 6 are attached, and an annular identification groove 20 provided on the counter-axial end side (axial center side) of the boot attachment portion 10. The male spline portions 2a, 2b are inserted into spline holes provided in the inner joint members 3a, 4a of the constant velocity universal joints 3, 4, and the male spline portions 2a, 2b are fitted into the female spline portions of the inner joint members 3a, 4a. This connects the male spline portions 2a, 2b and the inner joint members 3a, 4a so as to be able to transmit torque.

[0020] As shown in FIG. 2, the boot mounting portion 10 has an annular groove 11 and annular protrusions 12 provided on both axial sides of the annular groove 11. The annular groove 11 is recessed toward the inner diameter side relative to cylindrical surfaces 2c provided on both axial sides of the boot mounting portion 10. The bottom surface of the annular groove 11 is a concave curved surface, and in the illustrated example, it is a concave curved surface with an arc-shaped cross section. The annular protrusion 12 protrudes toward the outer diameter side relative to the cylindrical surfaces 2c. The annular protrusion 12 is smoothly continuous with the bottom surface of the annular groove 11 and the cylindrical surfaces 2c. In the illustrated example, a cylindrical surface is provided at the top (outer diameter portion) of the annular protrusion 12.

[0021] The discrimination groove 20 is provided around the entire outer circumferential surface of the intermediate shaft 2. The discrimination groove 20 has a uniform axial width and depth around the entire circumference. The bottom surface of the discrimination groove 20 is a concave curved surface, and in the illustrated example, it is a concave curved surface with an arc-shaped cross section. The discrimination groove 20 only needs to have a minimum depth that can be visually confirmed. Therefore, the depth D2 of the discrimination groove 20 is shallower than the radial depth D1 of the annular groove 11 of the boot attachment portion 10, and is set to, for example, 1 / 2 or less of D1. Specifically, the depth D2 of the discrimination groove 20 is set to, for example, a range of 0.1 to 0.5 mm. The shape of the discrimination groove 20 is not limited to the above, and may be, for example, a rectangular cross section or a combination of a cylindrical surface and a curved surface.

[0022] The discrimination groove 20 is provided near the boot attachment portion 10. By providing the discrimination groove 20, the small diameter ends 5b, 6b of the boots 5, 6 can be accurately attached to predetermined positions on the outer circumferential surface of the intermediate shaft 2. Specifically, as shown in FIG. 3(A), by arranging the end face 5b1 of the small diameter end 5b of the boot 5 in the axial position of the end on the axial end side (left side in the figure) of the discrimination groove 20, the small diameter end 5b of the boot 5 is arranged in the correct position on the outer circumferential surface of the intermediate shaft 2. In other words, the axial position of the discrimination groove 20 is set so that when the small diameter end 5b of the boot 5 is arranged in the correct position on the outer circumferential surface of the intermediate shaft 2, the end face 5b1 of the small diameter end 5b of the boot 5 is arranged in the axial position of the end on the axial end side of the discrimination groove 20. In the illustrated example, the annular groove 11 of the boot attachment portion 10 is arranged in approximately the axial center of the small diameter end 5b of the boot 5 arranged in the correct position.

[0023] In contrast, if the small diameter end 5b of the boot 5 covers the identification groove 20 and the identification groove 20 is not visible, as shown in Figure 3(B), it can be recognized that the boot 5 has shifted from its correct position toward the opposite axial end (the right side in the figure). Also, if the small diameter end 5b of the boot 5 and the identification groove 20 are spaced apart in the axial direction and the cylindrical surface 2c is visible between them, as shown in Figure 3(C), it can be recognized that the boot 5 has shifted from its correct position toward the axial end (the left side in the figure). Therefore, by adjusting the axial position of the boot 5 relative to the identification groove 20, the boot 5 can be easily positioned in the correct position shown in Figure 3(A).

[0024] Note that Figures 2 and 3 show the boot mounting portion 10 to which the boot 5 on the fixed constant velocity universal joint 3 side is attached and the adjacent identification groove 20, but the boot mounting portion 10 to which the boot 6 on the sliding constant velocity universal joint 4 side is attached and the adjacent identification groove 20 have the same configuration except for being reversed in the axial direction, so detailed explanations will be omitted.

[0025] The intermediate shaft 2 of this embodiment is solid and is manufactured through the following steps.

[0026] First, after forming a shaft-shaped material, the outer peripheral surface is turned. In this embodiment, the entire surface of the material (outer peripheral surface and end faces) is turned. This removes the oxide film (black scale) formed on the surface of the material, and sets the outer diameter of the material, particularly the lower diameter of the male spline portions 2a and 2b, to a predetermined value.

[0027] Next, the boot attachment portion 10 and the discrimination groove 20 are formed on the outer peripheral surface of the material by plastic processing, such as die forming, particularly cold rolling. In this embodiment, the boot attachment portion 10 and the discrimination groove 20 are simultaneously formed on the outer peripheral surface of the material 2' using rolling dies 31 and 32 shown in FIGS. 4 and 5. The outer peripheral surfaces of the rolling dies 31 and 32 are provided with a boot attachment portion-forming die 40 for forming the boot attachment portion 10 and an discrimination groove-forming die 50 for forming the discrimination groove 20. As shown in FIG. 6, the boot attachment portion-forming die 40 has an annular protrusion 41 and annular recesses 42 provided on both axial sides thereof. The discrimination groove-forming die 50 is composed of an annular protrusion. Cylindrical surfaces 60 are provided on the outer peripheral surfaces of the rolling dies 31 and 32 in regions adjacent to both axial sides of the boot attachment portion-forming die 40 and in regions adjacent to both axial sides of the discrimination groove-forming die 50. In the illustrated example, a cylindrical surface 60 is provided over the entire area between the boot mounting portion molding die 40 and the identification groove molding die 50 in the axial direction. Each cylindrical surface 60 has the same diameter.

[0028] Flat surfaces 31a, 32a are provided on parts of the outer circumferential surfaces of the rolling dies 31, 32 in the circumferential direction (see FIG. 4). With these flat surfaces 31a, 32a facing each other, the raw material 2' is placed between them. Then, by rotating the rolling dies 31, 32 in the same direction at the same speed (see arrow A in FIG. 4), the boot attachment portion forming die 40 and the identification groove forming die 50 provided on these outer circumferential surfaces are pressed against the outer circumferential surface of the raw material 2', and the shapes of the boot attachment portion forming die 40 and the identification groove forming die 50 are transferred to the outer circumferential surface of the raw material 2' (see FIG. 5).

[0029] 7, the annular protrusion 41 of the boot attachment portion-forming die 40 is pressed against the cylindrical outer peripheral surface of the raw material 2' to form a groove (part of the annular groove 11). Due to the plastic flow of the material caused by the formation of this groove, both axial sides of the groove rise outward, and these rises are pressed against the annular recess 42 of the boot attachment portion-forming die 40 to form a protrusion (part of the annular protrusion 12). At the same time, the discrimination groove-forming die 50 is pressed against the cylindrical outer peripheral surface of the raw material 2' to form a groove (part of the discrimination groove 20). While the boot attachment portion-forming die 40 and the discrimination groove-forming die 50 of the rolling dies 31, 32 are pressed against the outer peripheral surface of the raw material 2', the raw material 2' is rotated in the direction opposite to the rolling dies 31, 32 (see arrow B in FIG. 4), whereby the boot attachment portion 10 and the discrimination groove 20 are formed around the entire outer peripheral surface of the raw material 2' (intermediate shaft 2). The entire area of ​​the boot mounting portion 10 and the discrimination groove 20 thus formed is a plastically worked surface, specifically a molded surface.

[0030] At the same time, the cylindrical surfaces 60 of the outer peripheral surfaces of the rolling dies 31, 32 are pressed against the outer peripheral surface of the blank 2' to form the cylindrical surface 2c. That is, on the outer peripheral surface of the intermediate shaft 2, not only the boot attachment portion 10 and the discrimination groove 20, but also the region adjacent to the axial end side of the boot attachment portion 10 (cylindrical surface 2c), the region between the boot attachment portion 10 and the discrimination groove 20 in the axial direction (cylindrical surface 2c), and the region adjacent to the anti-axial end side of the discrimination groove 20 (cylindrical surface 2c) become plastically processed surfaces, specifically molded surfaces.

[0031] As described above, by forming the identification groove 20 by plastic processing, specifically die forming, and especially rolling, the identification groove 20 can be reliably formed around the entire outer circumferential surface of the intermediate shaft 2 without being affected by axial runout, as occurs with turning. In particular, in this embodiment, the identification groove 20 is formed simultaneously with the boot attachment portion 10, thereby reducing processing costs.

[0032] In this embodiment, not only the annular groove 11 of the boot attachment portion 10 but also the annular protrusions 12 provided on both sides thereof are molded. This allows the dimensions of the annular protrusions 12, specifically the amount of protrusion from the cylindrical surface 2c, to be controlled with high precision, thereby stabilizing the sealing performance when the boots 5, 6 are attached.

[0033] When the boot attachment portion 10 and the discrimination groove 20 are formed by turning, a portion of the surface layer of the intermediate shaft 2 is removed, and as a result, the fiber flow in the surface layer is cut by the boot attachment portion 10 and the discrimination groove 20, as shown in Fig. 11. In contrast, when the boot attachment portion 10 and the discrimination groove 20 are formed by plastic working as described above, the fiber flow in the surface layer of the intermediate shaft 2 (a region approximately 2 mm deep from the surface) is not cut by the boot attachment portion 10 or the discrimination groove 20, but extends continuously along the surfaces of the boot attachment portion 10 and the discrimination groove 20, as shown in Fig. 8. Therefore, if the fiber flow in the surface layer of the intermediate shaft 2 is continuous in the boot attachment portion 10, the discrimination groove 20, and the cylindrical surface 2c adjacent to them, it can be confirmed that they were formed by plastic working.

[0034] Furthermore, by forming the boot attachment portion 10 and the discrimination groove 20 by plastic processing, no turning marks remain on the surface and the fiber flow is continuous without being cut, which increases the strength of the intermediate shaft 2 compared to when the boot attachment portion 10 and the discrimination groove 20 are formed by turning. In particular, in this embodiment, the axial region between the boot attachment portion 10 and the male spline portion 2a is made of a cylindrical surface of uniform diameter, and no small-diameter cylindrical surface is provided in this portion, so the male spline portion 2a or the annular groove 11 of the boot attachment portion 10 becomes the weakest part of the intermediate shaft 2. For this reason, it is particularly effective to subject the boot attachment portion 10 to plastic processing to increase its strength.

[0035] Thereafter, the male spline portions 2a, 2b are formed by plastic processing (for example, rolling) on ​​the shaft end of the material 2. Thereafter, the material is subjected to heat treatment, and the intermediate shaft 2 is completed.

[0036] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but explanations of the same points as those in the above-described embodiment will be omitted.

[0037] The boot attachment part 10 may not have the annular protrusion 12 and may be configured only with the annular groove 11. The boot attachment part 10 shown in Fig. 9 is configured only with the annular groove 11 that is recessed radially inward from the cylindrical surface 2c. The boot attachment part 10 shown in Fig. 10 is configured only with the annular groove 11 that has a small-diameter cylindrical surface 11a that is smaller in diameter than the cylindrical surface 2c and inclined surfaces 11b provided on both axial sides of the small-diameter cylindrical surface 11a.

[0038] In the above embodiment, the boot mounting portion 10 and the identification groove 20 are formed by rolling, but they may also be formed by other plastic processes such as rolling, spinning, forging, swaging, etc.

[0039] Furthermore, in the above embodiment, the identification grooves 20 are provided near the inboard and outboard boot attachment portions 10, but the identification grooves 20 may be provided only near one of the boot attachment portions 10. In this case, the position of the identification groove 20 makes it possible to confirm the orientation of the intermediate shaft 2, i.e., which end is the side to which the fixed type constant velocity universal joint 3 is attached and which end is the side to which the sliding type constant velocity universal joint 4 is attached. This makes it possible to prevent the inner joint members 3a, 4a from being attached to the male spline portions 2a, 2b at the ends of the intermediate shaft 2 in error.

[0040] The present invention is not limited to being applied to a solid intermediate shaft 2, but may also be applied to a hollow intermediate shaft. In this case, after a diameter-reducing process such as swaging is performed near both ends of the material, the boot attachment portion 10 and the discrimination groove 20 are formed by plastic processing (for example, rolling). Then, the male spline portions 2a, 2b are formed by rolling or the like, and the intermediate shaft 2 is manufactured by performing a heat treatment.

[0041] Furthermore, the present invention is not limited to application to intermediate shafts of drive shafts, but can also be applied to intermediate shafts of propeller shafts, for example. [Explanation of symbols]

[0042] 1 drive shaft 2 Intermediate shaft (power transmission shaft) 2' Material 2a Male spline part 3 Fixed constant velocity universal joint 3a Inner joint member 4. Sliding constant velocity universal joint 4a Inner joint member 5. Boots 5a Large diameter end 5b Small diameter end 5c Bellows 6. Boots 10 Boot attachment part 11 Annular groove 12 Annular protrusion 20 Identification groove 31 Rolling mold 40 Boots mounting mold 41 Annular convex part 42 Annular recess 50 Identification groove forming mold

Claims

1. A power transmission shaft comprising: a male spline portion to be inserted into a spline hole of an inner joint member of a constant velocity universal joint; a boot mounting portion having an annular groove; and an annular identification groove provided on the counter-axial end side of the boot mounting portion, A power transmission shaft in which the fiber flow of the surface layer in the formation area of ​​the boot attachment portion and the identification groove extends continuously along the surfaces of the boot attachment portion, the identification groove, and the axial area between them.

2. the boot attachment portion has the annular groove and annular protrusions provided on both axial sides of the annular groove, 2. The power transmission shaft according to claim 1, wherein the annular groove and the annular projection of the boot mounting portion are formed with molded surfaces.

3. 3. A power transmission shaft according to claim 1 or 2, which is solid.

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