JP7754658B2 - Power transmission shaft - Google Patents

Description

The present invention relates to a power transmission shaft.

A driveshaft, which transmits the driving force of a vehicle engine to the wheels, typically consists of 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 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 the grease sealed inside the joint from leaking. 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.

A circular boot groove is formed on the outer periphery of the power transmission shaft, in the area 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 outside with a boot band, the inner periphery of the small diameter end of the boot bites into the boot groove, ensuring a seal.

When boot grooves are formed on the outer periphery 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, to reduce costs, there has been an increase in the number of cases where boot grooves are formed by plastic processing (e.g., rolling) (see Patent Document 1 below).

Patent No. 4122126

Incidentally, an annular identification groove is sometimes formed near the boot groove on the outer surface of a power transmission shaft to confirm the boot installation 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 lengthening the processing time. When such a shallow identification groove is formed by turning, runout of the shaft material during turning can result in the identification groove not being formed around the entire circumference, but only being formed along 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. This makes it difficult to check the identification groove when assembling the drive shaft, significantly reducing workability.

The present invention aims to reliably form an identification groove around the entire outer surface of a power transmission shaft.

To achieve the above objective, the present invention provides a power transmission shaft comprising a male spline portion inserted into a spline hole in 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 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.

When the boot mounting portion and identification groove are formed by plastic processing, 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 processing, 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.

It is preferable to mold the identification groove simultaneously with the boot attachment portion, which has an annular groove, using the same mold (e.g., a rolling mold). This reduces the number of steps compared to forming these separately, and also prevents the identification groove from being crushed by plastic processing of the boot attachment portion.

If the boot mounting portion has an annular groove and annular protrusions on both axial sides of the annular groove, it is preferable that the annular groove and annular protrusions of the boot mounting portion be formed as molded surfaces using a mold. This allows the dimensions of the annular groove and annular protrusions to be controlled with high precision.

The present invention can be applied, for example, to solid power transmission shafts.

As described above, according to the present invention, it is possible to reliably form an identification groove around the entire outer surface of the power transmission shaft.

1 is a cross-sectional view of a drive shaft having a power transmission shaft (intermediate shaft) according to an embodiment of the present invention. FIG. 2 is an enlarged side view of the vicinity of a boot attachment portion of the power transmission shaft. (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. FIG. 2 is a front view of the rolling die and the blank as viewed from the axial direction. 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. FIG. 1 is a cross-sectional view of a rolling die before it is brought into contact with a material. FIG. 1 is a cross-sectional view of a rolling die in contact with a material. FIG. 2 is a cross-sectional view showing the fiber flow in the surface layer of the power transmission shaft. FIG. 10 is a side view showing another example of the boot attachment portion. FIG. 10 is a side view showing still another example of the boot attachment portion. 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.

The following describes an embodiment of the present invention with reference to the drawings.

The drive shaft 1 shown in FIG. 1 comprises 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 thereof. One constant velocity universal joint 3 is a fixed-type constant velocity universal joint comprising 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 comprising 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; for example, the other constant velocity universal joint 4 may be a tripod-type sliding-type constant velocity universal joint.

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 ends 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 ends 5b, 6b fixed to the outer peripheral surface of the intermediate shaft 2, and bellows portions 5c, 6c provided between them. The boots 5, 6 are formed from resin, such as a thermoplastic polyester elastomer or a composition containing such. The surface hardness of the boots 5, 6 is HD38-50. The boots 5, 6 may also be formed from rubber (such as chloroprene rubber).

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 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. These 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 interior of the constant velocity universal joints 3, 4.

The intermediate shaft 2 has male spline portions 2a, 2b provided on both ends, a boot mounting 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 (axial center side) of the boot mounting 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 mate with 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 that torque can be transmitted.

As shown in Figure 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 radially inward relative to the 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 radially outward relative to the cylindrical surfaces 2c. The annular protrusion 12 is smoothly connected to 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.

The identification groove 20 is provided around the entire outer circumferential surface of the intermediate shaft 2. The axial width and depth of the identification groove 20 are uniform around the entire circumference. The bottom surface of the identification 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 identification groove 20 only needs to have a minimum depth that can be visually confirmed. Therefore, the depth D2 of the identification 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 identification groove 20 is set to, for example, a range of 0.1 to 0.5 mm. The shape of the identification groove 20 is not limited to the above, and may be, for example, rectangular in cross section or a combination of cylindrical and curved surfaces.

The identification groove 20 is provided near the boot mounting portion 10. The identification groove 20 allows the small diameter ends 5b, 6b of the boots 5, 6 to be accurately mounted at the predetermined positions on the outer circumferential surface of the intermediate shaft 2. Specifically, as shown in FIG. 3(A), the end face 5b1 of the small diameter end 5b of the boot 5 is positioned axially at the end on the axial end side (left side in the figure) of the identification groove 20, thereby positioning the small diameter end 5b of the boot 5 in the correct position on the outer circumferential surface of the intermediate shaft 2. In other words, the axial position of the identification groove 20 is set so that when the small diameter end 5b of the boot 5 is positioned 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 positioned axially at the end on the axial end side of the identification groove 20. In the illustrated example, the annular groove 11 of the boot mounting portion 10 is positioned approximately in the axial center of the small diameter end 5b of the boot 5 when it is positioned in the correct position.

In contrast, if the small diameter end 5b of the boot 5 covers the identification groove 20, making it invisible, 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 (to the right in the figure). Also, if the small diameter end 5b of the boot 5 and the identification groove 20 are axially separated 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 (to the left 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).

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. However, 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 axially inverted, so detailed explanation will be omitted.

The intermediate shaft 2 in this embodiment is solid and is manufactured through the following process.

First, a shaft-shaped material is formed, and then its outer periphery is turned. In this embodiment, the entire surface of the material (outer periphery and end faces) is turned. This removes the oxide film (black scale) that has 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.

Next, the boot attachment portion 10 and identification 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 identification groove 20 are simultaneously formed on the outer peripheral surface of the material 2' using rolling dies 31 and 32 shown in Figures 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 identification groove-forming die 50 for forming the identification groove 20. As shown in Figure 6, the boot attachment portion-forming die 40 has an annular protrusion 41 and annular recesses 42 provided on both axial sides thereof. The identification 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 identification groove-forming die 50. In the illustrated example, a cylindrical surface 60 is provided over the entire axial area between the boot mounting portion molding die 40 and the identification groove molding die 50. Each cylindrical surface 60 has the same diameter.

Flat surfaces 31a, 32a are provided on portions of the outer periphery of the rolling dies 31, 32 in the circumferential direction (see Figure 4). With these flat surfaces 31a, 32a facing each other, the blank 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 Figure 4), the boot mounting portion molding die 40 and identification groove molding die 50 provided on these outer peripheries are pressed against the outer periphery of the blank 2', and the shapes of the boot mounting portion molding die 40 and identification groove molding die 50 are transferred to the outer periphery of the blank 2' (see Figure 5).

Specifically, as shown in FIG. 7 , the annular protrusion 41 of the boot attachment portion molding die 40 is pressed against the cylindrical outer peripheral surface of the blank 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 raised portions are pressed against the annular recess 42 of the boot attachment portion molding die 40 to form a protrusion (part of the annular protrusion 12). At the same time, the identification groove molding die 50 is pressed against the cylindrical outer peripheral surface of the blank 2' to form a groove (part of the identification groove 20). While the boot attachment portion molding die 40 and the identification groove molding die 50 of the rolling dies 31 and 32 are pressed against the outer peripheral surface of the blank 2', the blank 2' is rotated in the opposite direction to the rolling dies 31 and 32 (see arrow B in FIG. 4 ), thereby forming the boot attachment portion 10 and the identification groove 20 around the entire outer peripheral surface of the blank 2' (intermediate shaft 2). The entire boot attachment portion 10 and identification groove 20 thus formed are plastically processed surfaces, specifically molded surfaces.

At the same time, the cylindrical surfaces 60 on 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. In other words, 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 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 of the discrimination groove 20 (cylindrical surface 2c) become plastically processed surfaces, specifically molded surfaces.

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 surface of the intermediate shaft 2 without being affected by axial runout, as is the case with turning. In particular, in this embodiment, the identification groove 20 is formed simultaneously with the boot attachment portion 10, thereby reducing processing costs.

In addition, in this embodiment, not only the annular groove 11 of the boot mounting portion 10, but also the annular protrusions 12 on both sides of it are molded. This allows the dimensions of the annular protrusions 12, specifically the amount of protrusion relative to the cylindrical surface 2c, to be controlled with high precision, thereby stabilizing the sealing performance when the boots 5 and 6 are attached.

When the boot attachment portion 10 and the discrimination groove 20 are formed by turning, a portion of the surface of the intermediate shaft 2 is removed, and as shown in FIG. 11 , the fiber flow in the surface layer is cut by the boot attachment portion 10 and the discrimination groove 20. In contrast, by forming the boot attachment portion 10 and the discrimination groove 20 by plastic processing 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 and the discrimination groove 20, as shown in FIG. 8 , and extends continuously along the surfaces of the boot attachment portion 10 and the discrimination groove 20. 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 processing.

Furthermore, by forming the boot attachment portion 10 and the identification groove 20 by plastic processing, no turning marks remain on the surface and the fiber flow is continuous without being cut, resulting in a stronger intermediate shaft 2 than if the boot attachment portion 10 and the identification groove 20 were formed by a turning process. 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 is the weakest part of the intermediate shaft 2. Therefore, it is particularly effective to increase the strength of the boot attachment portion 10 by plastic processing.

Then, the male spline portions 2a and 2b are formed on the shaft end of the blank 2 by plastic processing (e.g., rolling). The blank is then heat treated to complete the intermediate shaft 2.

The present invention is not limited to the above embodiment. Other embodiments of the present invention will be described below, but explanations of points similar to the above embodiment will be omitted.

The boot mounting portion 10 may not have an annular protrusion 12 and may be composed only of an annular groove 11. The boot mounting portion 10 shown in Figure 9 is composed only of an annular groove 11 that is recessed radially inward from the cylindrical surface 2c. The boot mounting portion 10 shown in Figure 10 is composed only of an 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.

In the above embodiment, the boot attachment 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, or swaging.

In addition, while in the above embodiment, the identification grooves 20 are provided near the inboard and outboard boot mounting portions 10, the identification grooves 20 may be provided only near one of the boot mounting portions 10. In this case, the position of the identification grooves 20 can be used to confirm the orientation of the intermediate shaft 2, i.e., which end is the side to which the fixed constant velocity universal joint 3 is attached and which end is the side to which the sliding constant velocity universal joint 4 is attached, thereby preventing the inner joint members 3a, 4a from being attached to the male spline portions 2a, 2b at the ends of the intermediate shaft 2.

The present invention is not limited to solid intermediate shafts 2, but may also be applied to hollow intermediate shafts. In this case, after a diameter-reducing process such as swaging is performed near both ends of the material, the boot mounting portion 10 and identification groove 20 are formed by plastic processing (e.g., rolling). Then, the male spline portions 2a, 2b are formed by rolling or other processes, and the intermediate shaft 2 is manufactured by heat treatment.

Furthermore, the present invention is not limited to intermediate shafts in drive shafts, but can also be applied to intermediate shafts in propeller shafts, for example.

1 Drive shaft 2 Intermediate shaft (power transmission shaft)
2' Material 2a Male spline portion 3 Fixed type constant velocity universal joint 3a Inner joint member 4 Sliding type constant velocity universal joint 4a Inner joint member 5 Boot 5a Large diameter end portion 5b Small diameter end portion 5c Bellows portion 6 Boot 10 Boot mounting portion 11 Annular groove 12 Annular protrusion 20 Identification groove 31 Rolling die 40 Boot mounting portion molding die 41 Annular convex portion 42 Annular concave portion 50 Identification groove molding die

Claims (3)

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