Power transmission shaft and method for manufacturing same

Abstract

The present invention provides a propeller shaft 10 (power transmission shaft) for transmitting rotational force from a power source of a vehicle to wheels of the vehicle, the propeller shaft 10 including: a shaft member 1 (pipe); and a stub shaft 2 (rotary member) which is spigot-fitted to the shaft member 1. The stub shaft 2 includes: a circumferential rib 25 (spigot part) fitted to an inner circumferential side of an end part of the shaft member 1; and a step surface 24 (annular step part) formed so as to rise radially outward from the root of the circumferential rib 25 and abutting on an end surface of the shaft member 1. A joint 8a (contact part) between the end surface of the shaft member 1 and the step surface 24 is welded along the circumferential direction of the propeller shaft 10. The propeller shaft 10 has a communication passage 7a for communicating between the welded part and an internal space of the shaft member 1.

Description

Power transmission shaft and its manufacturing method

[0001] The present invention relates to a power transmission shaft and a method for manufacturing the same.

[0002] Conventionally, a propeller shaft has been known as a power transmission shaft for a vehicle, in which an outer case body of a universal joint and its flange portion are spigot-jointed (see, for example, Patent Document 1). Specifically, the joint end (spigot portion) of the outer case body is formed in a cylindrical shape with a smaller diameter than the general portion of the outer case body. Meanwhile, the flange portion has a cylindrical body portion that fits the joint end (spigot portion) of the outer case body and a flange portion that extends radially outward from the body portion. The end face of the general portion, which appears to connect the step between the general portion of the outer case body and the joint end (spigot portion), abuts against the end face of the body portion of the flange portion when the outer case body and the flange portion are spigot-fitted. The seam between the end face of the outer case body and the end face of the flange portion is welded along the circumferential direction of the universal joint. With such a propeller shaft, spigot-fitting the outer case body and the flange portion facilitates positioning when joining these two components coaxially.

[0003] Japanese Patent Application Laid-Open No. 2020-085161

[0004] However, in a conventional propeller shaft (see, for example, Patent Document 1), when the outer case body and flange portion, which are fitted together, are welded, the air present in the gap formed between these two components thermally expands. The thermally expanded air can then be ejected from the molten portion of the weld to the outside, forming so-called blowholes in the weld. Such blowholes reduce the strength of the propeller shaft as a power transmission shaft.

[0005] An object of the present invention is to provide a power transmission shaft that can suppress the occurrence of blowholes in a welded portion formed at a spigot-fitting portion, and a method for manufacturing the same.

[0006] The power transmission shaft of the present invention, which solves the above-mentioned problems, is a power transmission shaft that transmits rotational force from a power source of a vehicle to wheels of the vehicle, and comprises a pipe extending in the axial direction, and a rotating member that is fitted into the inner periphery of the end of the pipe and is spigot-fitted to the pipe, rotating together with the pipe, wherein the rotating member comprises a spigot portion that is fitted into the inner periphery of the end of the pipe, and an annular step portion that is formed so as to rise radially outward from the base of the spigot portion and abuts against the end face of the pipe, the abutment portion between the end face of the pipe and the annular step portion is welded along the circumferential direction of the power transmission shaft, and a communication passage that connects the welded portion between the end face of the pipe and the annular step portion on the base side of the spigot portion with the internal space of the pipe.

[0007] Furthermore, a method for manufacturing a power transmission shaft of the present invention that solves the above-mentioned problem is a method for manufacturing the above-mentioned power transmission shaft, comprising the steps of fitting an end of the rotating member to the inner peripheral side of the end of the pipe in a spigot-fit manner, and welding the abutting portion between the end face of the pipe and the annular step in the circumferential direction of the power transmission shaft, wherein the start position of welding between the pipe and the annular step is set at a position that is different from the phase at which the communicating passage is formed as viewed in the axial direction of the power transmission shaft, and the welding is performed in a direction away from the communicating passage.

[0008] According to the power transmission shaft and the method for manufacturing the same of the present invention, it is possible to suppress the occurrence of blowholes in the welded portion formed in the spigot fitting portion.

[0009] 1. An explanatory diagram of the configuration of a power transmission shaft according to an embodiment of the present invention. An overall perspective view of a first collar member constituting the power transmission shaft of FIG. 1. A partially enlarged sectional view taken along line IIB-IIB of FIG. 2A. An overall perspective view of a second collar member constituting the power transmission shaft of FIG. 1. An overall perspective view of a stub shaft constituting the power transmission shaft of FIG. 1. A partially enlarged perspective view of portion IVB of FIG. 4A. A partially enlarged front view of the stub shaft as seen in the direction of arrow IVC of FIG. 4B. A partially enlarged sectional view of portion V of FIG. 1. An overall perspective view of a joint connecting member constituting the power transmission shaft of FIG. 1. A partially enlarged sectional view of portion VII of FIG. 1. An explanatory diagram of a manufacturing process for portion V of FIG. 1. An explanatory diagram of a manufacturing process as seen in the direction of arrow IX of FIG. 8. An explanatory diagram of a manufacturing process for portion VII of FIG. 1. An explanatory diagram of a welding process in a manufacturing method of a power transmission shaft according to a comparative example. An explanatory diagram of the configuration of a power transmission shaft according to another embodiment (modified example) of the present invention.

[0010] A power transmission shaft and a manufacturing method thereof according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The power transmission shaft of the present invention will be described below using a propeller shaft as an example, which transmits driving force generated by an engine or motor disposed at the front of a vehicle to a differential gear at the rear via a transmission. The power transmission shaft of the present invention is not limited to a vehicle propeller shaft, but may also be applied to other power transmission shafts, such as a drive shaft that transmits driving force from a differential gear to wheels.

[0011] <Propeller Shaft> Figure 1 is a structural explanatory diagram of a propeller shaft 10 (power transmission shaft) according to an embodiment of the present invention. The front-to-rear direction indicated by the arrow in Figure 1 corresponds to the front-to-rear direction of the vehicle. In Figure 1, the upper half of the page is a cross-sectional view, and the lower half is a side view, with the rotation axis Ax of the propeller shaft 10 as the boundary. For convenience of drawing, Figure 1 is a partial structural explanatory diagram that omits the illustration of a driving propeller shaft that is disposed forward of the coupling member 5 and transmits driving force from the transmission, and a driven propeller shaft that is disposed rearward of the constant velocity joint 4 and transmits driving force to a differential gear.

[0012] As shown in Fig. 1, the propeller shaft 10 of this embodiment includes a coupling member 5, a joint connection member 3, a shaft member 1, a stub shaft 2, and a constant velocity joint 4, in addition to the drive propeller shaft and driven propeller shaft (not shown). The shaft member 1 corresponds to the "pipe" in the claims. The joint connection member 3 and the stub shaft 2 each correspond to the "rotating member" in the claims.

[0013] As will be described in detail later, the propeller shaft 10 (power transmission shaft) of this embodiment is formed by fitting a stub shaft 2 (rotating member) and a joint connection member 3 (rotating member) at both ends of a shaft member 1 (pipe) together with a spigot fitting, and welding them to each other. The propeller shaft 10 (power transmission shaft) of this embodiment is mainly characterized in that it has communication passages 7a, 7b (see FIGS. 8 and 10) that communicate these welded portions 9a, 9b (see FIGS. 8 and 10) with the internal space S1 (see FIGS. 8 and 10) of the shaft member 1 (pipe), as will be described in detail later.

[0014] The following will first describe the shaft member 1. As shown in Fig. 1, the shaft member 1 includes a cylindrical tube member 11 that is open at both axial ends, a cylindrical first collar member 12 that is connected to the rear end of the tube member 11, and a substantially cylindrical second collar member 13 that is connected to the front end of the tube member 11. The tube member 11 is made of CFRP (Carbon Fiber Reinforced Plastics). The first collar member 12 and the second collar member 13 are made of an iron-based metal.

[0015] In the embodiment, the shaft member 1 is formed by joining a first collar member 12, a tube member 11, and a second collar member 13 in this order so that they are integral with one another. The tube member 11 corresponds to the "pipe main body" in the claims. The first collar member 12 and the second collar member 13 each correspond to the "tubular member made of a metal material separate from the pipe main body" in the claims.

[0016] As shown in Figure 1, the tube member 11 has a reduced diameter section 11a at its front end. This reduced diameter section 11a gradually reduces in diameter from the front end of the general section 11c, which accounts for almost all of the tube member 11, toward the front, forming a tapered circumferential surface. The tube member 11 also has an expanded diameter cylindrical section 11b at its rear end. This expanded diameter cylindrical section 11b forms a cylinder with inner and outer diameters larger than those of the general section 11c.

[0017] Fig. 2A is an overall perspective view of the first collar member 12. As shown in Fig. 2A, the first collar member 12 includes a base end portion 12a that is fitted into the enlarged diameter cylindrical portion 11b (see Fig. 1) on the rear side of the tube member 11 (see Fig. 1), and a rearward extending cylindrical portion 12b that extends further rearward from the rear end of the base end portion 12a. Serrations 12a1 are formed on the outer peripheral surface of the base end portion 12a. These serrations 12a1 mesh with the inner peripheral side of the enlarged diameter cylindrical portion 11b (see Fig. 1) of the tube member 11 (see Fig. 1).

[0018] As shown in FIG. 2A , an expanded inner diameter portion Cf is formed on the inner circumferential side of the end of the rear cylindrical portion 12b of the first collar member 12. As shown in FIG. 2B , which is a cross-sectional view taken along the IIB-IIB line of FIG. 2A , this expanded inner diameter portion Cf is formed so that its inner diameter gradually increases toward the rear opening of the first collar member 12 along the axial direction (the front-to-rear direction in FIG. 2B ). This results in a chamfered corner formed between the rear end surface 12c of the first collar member 12 and the inner circumferential surface 12d of the first collar member 12. Note that this expanded inner diameter portion Cf (chamfered portion) can be configured as an inclined surface that is inclined at a predetermined angle with respect to the axial direction (the front-to-rear direction in FIG. 2B ) or an R-shaped surface that is curved at a predetermined curvature.

[0019] Fig. 3 is an overall perspective view of the second collar member 13. As shown in Fig. 3, the second collar member 13 includes a base end portion 13a that is fitted into the front side of the tube member 11 (see Fig. 1) from the reduced diameter portion 11a (see Fig. 1) to the general portion 11c (see Fig. 1), and a forward extending cylindrical portion 13b that extends further forward from the front end of the base end portion 13a.

[0020] Serrations 13a1 are formed on the outer peripheral surface of a portion of the base end 13a that corresponds to the general portion 11c (see FIG. 1) of the tube member 11 (see FIG. 1). These serrations 13a1 mesh with the inner peripheral side of the general portion 11c (see FIG. 1) of the tube member 11 (see FIG. 1). As shown in FIG. 3, an expanded inner diameter portion Cf (chamfered portion) is formed on the inner peripheral side of the front end of the extending cylindrical portion 13b of the second collar member 13, similar to the expanded inner diameter portion Cf (see FIG. 2A) of the extending cylindrical portion 12b of the first collar member 12 (see FIG. 2A).

[0021] Next, the stub shaft 2 (see FIG. 1) will be described. As shown in FIG. 1, the stub shaft 2 is welded to the rear end of the first collar member 12 that constitutes the shaft member 1 (pipe). As described above, the stub shaft 2, which is a rotating member, rotates together with the shaft member 1.

[0022] Fig. 4A is an overall perspective view of the stub shaft 2 (rotating member). As shown in Fig. 4A, the stub shaft 2 is configured as a substantially cylindrical body having a stepped shape in the axial direction (front-rear direction in Fig. 4A). In this embodiment, the stub shaft 2 is assumed to be made of an iron-based metal. The stub shaft 2 includes, in order from the front side, a large-diameter cylindrical portion 21, a medium-diameter cylindrical portion 22 having a smaller diameter than the large-diameter cylindrical portion 21, and a small-diameter cylindrical portion 23 having an even smaller diameter than the medium-diameter cylindrical portion 22.

[0023] As shown in Fig. 1, the outer diameter of the large-diameter cylindrical portion 21 of the stub shaft 2 is formed to be equal to the outer diameter of the extending cylindrical portion 12b of the first collar member 12. The large-diameter cylindrical portion 21 is welded to be coaxial with the extending cylindrical portion 12b (see Fig. 1). Also, as shown in Fig. 4A, a circumferential rib 25 is formed on the front end surface 21a of the large-diameter cylindrical portion 21 of the stub shaft 2. This circumferential rib 25 has a cylindrical shape that is short in the axial direction (front-to-back direction in Fig. 4A).

[0024] In this embodiment, the inner diameter of the circumferential rib 25 (see FIG. 4A) is equal to the inner diameter of the large-diameter cylindrical portion 21 (see FIG. 4A). The outer diameter of the circumferential rib 25 (see FIG. 4A) is equal to the inner diameter of the extending cylindrical portion 12b (see FIG. 2A) at a location where the expanded inner diameter portion Cf (see FIG. 2A) of the first collar member 12 (see FIG. 2A) is not formed.

[0025] As a result, the stub shaft 2 has a step surface 24 that connects the step between the outer peripheral surface of the large-diameter cylindrical portion 21 and the outer peripheral surface of the circumferential rib 25, as shown in Figure 4B, which is a partially enlarged perspective view of portion IVB in Figure 4A. The radial length of the step surface 24 on the stub shaft 2 is equal to the thickness of the extending cylindrical portion 12b (see Figure 2B) of the first collar member 12 (see Figure 2B). The circumferential rib 25 (see Figure 4A) corresponds to the spigot portion that constitutes the spigot fitting structure 6a (see Figure 5), which will be described later. The step surface 24 also corresponds to the "annular step" that constitutes the spigot fitting structure 6a (see Figure 5).

[0026] Figure 4C is a partially enlarged front view of the stub shaft 2 as viewed in the direction of arrow IVC in Figure 4B. As shown in Figure 4C, a flat surface 25b is partially formed on the outer peripheral surface 25a of the circumferential rib 25 of the stub shaft 2. This flat surface 25b forms one wall surface that defines a communicating passage 7a (see Figure 5) in a spigot fitting structure 6a (see Figure 5) described below between the stub shaft 2 and the first collar member 12 (see Figure 2A). This communicating passage 7a will be described in detail later.

[0027] 4A, it is desirable that a plurality of flat surfaces 25b of the stub shaft 2 in this embodiment are formed at equal intervals in the circumferential direction of the circumferential rib 25. Note that in this embodiment, four flat surfaces 25b are formed at equal intervals in the circumferential direction of the circumferential rib 25. However, the number of flat surfaces 25b of the stub shaft 2 in this embodiment is not limited to this and may be one.

[0028] Next, the spigot fitting structure 6a (see FIG. 5) between the first collar member 12 (see FIG. 1) and the stub shaft 2 (see FIG. 1) will be described. FIG. 5 is a partially enlarged cross-sectional view of portion V in FIG. 1. As shown in FIG. 5, the spigot fitting structure 6a between the first collar member 12 and the stub shaft 2 is formed by coaxially fitting a circumferential rib 25 (spigot portion) of the stub shaft 2 into the inner circumferential side of the extending cylindrical portion 12b of the first collar member 12. In other words, this circumferential rib 25 contacts the inner circumferential surface of the extending cylindrical portion 12b of the first collar member 12.

[0029] Furthermore, the stepped surface 24 (annular stepped portion) of the stub shaft 2 is formed so as to rise radially outward (upper side of the paper surface in FIG. 5 ) from the base of the circumferential rib 25 (spigot portion). In this spigot fitting structure 6 a, the stepped surface 24 abuts against the end surface 12 c of the first collar member 12 (pipe).

[0030] In such a spigot fitting structure 6a, as will be described in detail later, a joint 8a (abutment portion) between the end face 12c of the first collar member 12 (pipe) and the stepped surface 24 of the stub shaft 2 (rotating member) is laser welded along the circumferential direction of the propeller shaft 10. In addition, in Figure 5, reference numeral 7a denotes a communication passage, which will be described in detail later.

[0031] 1, although not shown, an inner ring of a tubular bracket that supports the propeller shaft 10 on the vehicle body is attached to the medium diameter cylindrical portion 22 of the stub shaft 2. The small diameter cylindrical portion 23 of the stub shaft 2 is fixed to an inner race 42 of the constant velocity joint 4, which will be described next.

[0032] The constant velocity joint 4 (see FIG. 1) is fixed to the front end of the driven propeller shaft (not shown) as described above. As shown in FIG. 1, the constant velocity joint 4 is mainly composed of a casing 41 which is an outer race formed in a substantially cylindrical shape, an inner race 42 which is arranged on the inner periphery of the casing 41, a plurality of torque transmission balls 43 which are provided so as to be able to roll between the casing 41 and the inner race 42, and a cage 44 which holds the torque transmission balls 43. In FIG. 1, reference numeral 45 denotes a rubber boot which seals the inside of the casing 41 which is filled with lubricating oil such as grease.

[0033] Next, the joint connection member 3 (see FIG. 1) as a rotating member will be described. As shown in FIG. 1, this joint connection member 3 (stub yoke) is welded to the front end of the second collar member 13 that constitutes the shaft member 1. The joint connection member 3 rotates together with the shaft member 1.

[0034] FIG. 6 is an overall perspective view of the joint connection member 3. As shown in FIG. 6, the joint connection member 3 has a cylindrical base 31 and a flange yoke 32. As shown in FIG. 1, the outer diameter of the cylindrical base 31 is formed to be equal to the outer diameter of the forward extending cylindrical portion 13b of the second collar member 13. The cylindrical base 31 is welded to be coaxial with the forward extending cylindrical portion 13b of the second collar member 13. Returning to FIG. 6, a circumferential rib 34 is formed on the rear end surface 31a of the cylindrical base 31. This circumferential rib 34 has a cylindrical shape that is short in the axial direction (the front-to-rear direction in FIG. 6). The inner diameter of the circumferential rib 34 is formed to be equal to the inner diameter of the cylindrical base 31.

[0035] The outer diameter of the circumferential rib 34 (see Figure 6) is formed to be equal to the inner diameter of the forward extending cylindrical portion 13b (see Figure 3) at a location where the inner diameter enlarged portion Cf (see Figure 3) of the second collar member 13 (see Figure 3) is not formed.

[0036] As shown in Figure 6, the joint connection member 3 has a step surface 33 that connects the step between the outer peripheral surface of the cylindrical base portion 31 and the outer peripheral surface of the circumferential rib 34. The length of the step surface 33 in the radial direction of the cylindrical base portion 31 is equal to the thickness of the forward extending cylindrical portion 13b (see Figure 3) of the second collar member 13 (see Figure 3). The circumferential rib 34 (see Figure 6) corresponds to the "spigot joint portion" in the claims, and the step surface 33 corresponds to the "annular step portion" in the claims.

[0037] 6, a flat surface 34b is partially formed on the outer circumferential surface 34a of the circumferential rib 34. This flat surface 34b forms one wall surface that defines a communicating passage 7b (see FIG. 7) in a spigot fitting structure 6b (see FIG. 7) described below between the cylindrical base portion 31 of the joint connection member 3 and the second collar member 13 (see FIG. 3). This communicating passage 7b will be described in detail later.

[0038] As shown in Fig. 6, in this embodiment, it is desirable that a plurality of flat surfaces 34b are formed at equal intervals in the circumferential direction of the circumferential rib 34. Note that in this embodiment, four flat surfaces 34b are formed at equal intervals in the circumferential direction of the circumferential rib 34. However, this does not exclude the joint connection member 3 in this embodiment in which the number of flat surfaces 34b of the circumferential rib 34 is one or five or more.

[0039] Next, the spigot fitting structure 6b (see FIG. 7) between the second collar member 13 (see FIG. 1) and the joint connection member 3 (see FIG. 1) will be described. FIG. 7 is a partially enlarged cross-sectional view of part VII in FIG. 1. As shown in FIG. 7, the spigot fitting structure 6b between the second collar member 13 and the joint connection member 3 is formed by coaxially fitting the circumferential rib 34 of the joint connection member 3 into the inner circumferential side of the forward extending cylindrical portion 13b of the second collar member 13. In other words, this circumferential rib 34 (spigot portion) is in contact with the inner circumferential surface of the forward extending cylindrical portion 13b of the second collar member 13.

[0040] The stepped surface 33 (annular stepped portion) of the joint connection member 3 is formed so as to rise radially outward (upper side of the paper in FIG. 7 ) from the base of the circumferential rib 34 (spigot portion). In this spigot fitting structure 6b, the stepped surface 33 abuts against the end face 13c of the second collar member 13 (pipe).

[0041] In such a spigot fitting structure 6b, laser welding is performed along the circumferential direction of the propeller shaft 10 at a joint 8b (contact portion) between an end face 13c of the second collar member 13 (pipe) and the stepped surface 33 of the joint connection member 3. In Fig. 7, reference numeral 7b denotes a communication passage, which will be described in detail later.

[0042] Returning to Figure 6, the flange yokes 32 of the joint connection member 3 are formed so that they extend radially outward from the outer periphery of the cylindrical base 31. In this embodiment, three flange yokes 32 are formed at equal intervals around the circumference of the cylindrical base 31, but the number is not limited to this and may be two, four, or more. A bolt insertion hole 32a is formed at the tip of the flange yoke 32. As shown in Figure 1, the flange yoke 32 is fastened to the joint member 5 via a bolt B inserted into the bolt insertion hole 32a. As described above, the joint member 5 is fixed to the rear end of the drive propeller shaft (not shown).

[0043] <Method of Manufacturing Propeller Shaft> Next, a method of manufacturing the propeller shaft 10 (power transmission shaft) of this embodiment will be described. The method of manufacturing the propeller shaft 10 shown in Fig. 1 includes a fitting step of fitting a stub shaft 2 (rotating member) into a shaft member 1 (pipe) by spigot fitting, and a welding step of laser welding the shaft member 1 (pipe) and the stub shaft 2 (rotating member) together at a joint 8a (see Fig. 5) of the spigot fitting.

[0044] Figure 8 is an explanatory diagram of the manufacturing process of the V portion of Figure 1. Figure 9 is an explanatory diagram of the manufacturing process as viewed in the direction of arrow IX in Figure 8. In the fitting process, as shown in Figure 8, the circumferential rib 25 of the stub shaft 2 is press-fitted into the inner periphery of the trailing cylindrical portion 12b of the first collar member 12 that constitutes the shaft member 1 (pipe). At this time, the enlarged inner diameter portion Cf (chamfered portion) formed on the inner periphery of the trailing cylindrical portion 12b facilitates press-fitting of the circumferential rib 25 into the trailing cylindrical portion 12b.

[0045] As described above, this fitting process also forms the joint 8a (contact portion) between the stub shaft 2 and the first collar member 12. The outer peripheral surface 25a of the circumferential rib 25 is then pressed against the inner peripheral surface 12d of the trailing cylindrical portion 12b. This temporarily fastens the stub shaft 2 (rotating member) to the shaft member 1 (pipe).

[0046] In addition, in this fitting process, as shown in Figure 9, the flat surface 25b of the circumferential rib 25 defines a communication passage 7a between itself and the inner circumferential surface 12d of the trailing cylindrical portion 12b. In a cross section perpendicular to the axial direction of the stub shaft 2 (rotating member), this communication passage 7a has a bow shape surrounded by an arc having the same diameter as the outer diameter of the circumferential rib 25 (spigot portion) and a chord connecting both ends of this arc. In Figure 9, the spigot fitting joint 8a (abutment portion), which becomes the welded portion 9a, is shown hatched for ease of drawing.

[0047] As shown in Fig. 8 , the communicating passage 7a formed in the circumferential rib 25 (spigot portion) along the axial direction (front-rear direction in Fig. 8 ) has one end facing the joint 8a (abutment portion) at the base side of the circumferential rib 25 (spigot portion), and the other end facing the internal space S1 of the extending cylindrical portion 12b (pipe). That is, the communicating passage 7a communicates the internal space S2 formed between the expanded inner diameter portion Cf (chamfered portion) formed on the inner peripheral side of the extending cylindrical portion 12b and the stepped surface 24 (annular stepped portion) of the stub shaft 2 with the internal space S1 of the extending cylindrical portion 12b (pipe). As shown in Fig. 9 , the internal space S2 circles around the outer peripheral surface 25a of the circumferential rib 25 (spigot portion) and communicates with the communicating passage 7a.

[0048] Next, in the welding process, laser welding is performed on the seam 8a (abutment portion) as shown in Fig. 8. The laser welding is performed along the circumferential direction of the propeller shaft 10 where the seam 8a (abutment portion) is formed. In Fig. 8, reference numeral 9a denotes a weld formed on the seam 8a (abutment portion) by a laser beam 50a irradiated from a laser irradiation unit 50. Note that the weld 9a is shaded in Fig. 8 for convenience of illustration. In this laser welding, a heat-affected zone is formed locally, concentrated on the weld 9a formed on the seam 8a (abutment portion), as shown in Fig. 8.

[0049] In this welding process, the welding start position indicated by the symbol W1 in FIG. 9 is set at a position that differs from the circumferential phase (angle range θ) in which the communicating passage 7a is formed, as viewed in the axial direction of the propeller shaft 10 (the direction perpendicular to the paper surface of FIG. 9 ). Specifically, the welding start position W1 is set at a position that is circumferentially spaced a predetermined angle α from the phase (angle range θ) of the communicating passage 7a. This angle α is preferably set in the range of 0 degrees < α < 5 degrees. Alternatively, the welding start position W1 can be set at the boundary (α = 0) of the phase (angle range θ) in which the communicating passage 7a is formed.

[0050] Laser welding by the laser irradiation unit 50 is performed on the seam 8a (contact portion) by moving circumferentially from the welding start position W1 away from the communicating passage 7a. The welding end position can be set to the position indicated by symbol W2 within the range of the phase (angle range θ) of the communicating passage 7a by rotating the welding.

[0051] In this manufacturing method, the welding start position can be set to the position indicated by the symbol W2, which is within the range of the phase (angle range θ) in which the communication passage 7a is formed. The welding end position can be set to a position where the welding is completed by rotating the welding and returning to the welding start position W2, i.e., a position that overlaps with the welding start position W2.

[0052] The method for manufacturing the propeller shaft 10 shown in FIG. 1 includes a fitting step of fitting a joint connection member 3 (rotating member) to the shaft member 1 (pipe) by spigot fitting, and a welding step of laser welding the shaft member 1 (pipe) and the joint connection member 3 (rotating member) together at a joint 8b (abutment portion) of the spigot fitting shown in FIG. 7 .

[0053] Figure 10 is an explanatory view of the manufacturing process of part VII in Figure 1. In the fitting process, as shown in Figure 10, the circumferential rib 34 of the joint connection member 3 is press-fitted into the inner periphery of the extended cylindrical portion 13b of the second collar member 13 that constitutes the shaft member 1 (pipe). At this time, the enlarged inner diameter portion Cf (chamfered portion) formed on the inner periphery of the extended cylindrical portion 13b facilitates press-fitting of the circumferential rib 34 into the extended cylindrical portion 13b.

[0054] As described above, in this fitting process, the joint 8b (contact portion) is formed between the joint connection member 3 and the second collar member 13. The outer peripheral surface 34a of the circumferential rib 34 is then pressed against the inner peripheral surface 13d of the extended cylindrical portion 13b. This temporarily fastens the joint connection member 3 (rotating member) to the shaft member 1 (pipe).

[0055] 10, the flat surface 34b of the circumferential rib 34 defines a communication passage 7b between itself and the inner circumferential surface 13d of the extended cylindrical portion 13b. Although not shown, in a cross section perpendicular to the axial direction of the joint connection member 3 (rotating member), the communication passage 7b has a bow shape surrounded by an arc having the same diameter as the outer diameter of the circumferential rib 34 (spigot portion) and a chord connecting both ends of the arc.

[0056] 10 , the communicating passage 7b formed in the circumferential rib 34 (spigot portion) along the axial direction (front-rear direction in FIG. 10 ) has one end facing the seam 8b (abutment portion) at the base of the circumferential rib 34 (spigot portion) and the other end facing the internal space S1 of the forward extending cylindrical portion 13b (pipe). That is, the communicating passage 7b communicates the internal space S1 of the forward extending cylindrical portion 13b (pipe) with the internal space S3 formed between the expanded inner diameter portion Cf (chamfered portion) formed on the inner periphery of the forward extending cylindrical portion 13b and the stepped surface 33 (annular stepped portion) of the joint connecting member 3. Although not shown, the internal space S3 circles around the outer circumferential surface 34a of the circumferential rib 34 (spigot portion) and communicates with the communicating passage 7b.

[0057] Next, in the welding process, laser welding is performed on the seam 8b (abutment portion) as shown in Fig. 10 . Laser welding is performed along the circumferential direction of the propeller shaft 10 where the seam 8b (abutment portion) is formed. In Fig. 10 , reference numeral 9b denotes a weld formed on the seam 8b (abutment portion) by laser light 50a irradiated from the laser irradiation unit 50. Note that the weld 9b is shaded in Fig. 10 for convenience of illustration. In this laser welding, a heat-affected zone is formed locally, concentrated on the weld 9b formed on the seam 8b (abutment portion), as shown in Fig. 10 .

[0058] Furthermore, although not shown, the process of welding the seam 8b (contact portion) in the circumferential direction can be performed in the same manner as the process of welding the seam 8a (contact portion) in the circumferential direction shown in Fig. 9. Then, a driving propeller shaft (not shown) is connected to the joint connection member 3 (see Fig. 1) via the joint member 5 (see Fig. 1), and a driven propeller shaft (not shown) is connected to the stub shaft 2 (see Fig. 1) via the constant velocity joint 4, thereby completing the series of manufacturing processes for the propeller shaft 10.

[0059] <Operations and Effects> Next, operations and effects achieved by the propeller shaft 10 of this embodiment will be described. Fig. 11 is an explanatory view of the welding process of the propeller shaft 100 according to a comparative example. As shown in Fig. 11, unlike the propeller shaft 10 of this embodiment (see Fig. 8), the propeller shaft 100 does not have the communicating passage 7a (see Fig. 8) in the circumferential rib 25 (spigot portion) of the stub shaft 2 (rotating member).

[0060] In such a propeller shaft 100, when welding is performed at the joint 8a (contact portion) between the stub shaft 2 and the first collar member 12, the air present in the gap between the stub shaft 2 and the first collar member 12 thermally expands. The thermally expanded air A may then be ejected to the outside from the molten welded portion 9a. This causes so-called blowholes to form in the welded portion 9a. Such blowholes reduce the strength of the propeller shaft 100.

[0061] In contrast, the propeller shaft 10 of this embodiment has communication passages 7a, 7b that connect the welded portions 9a, 9b with the internal space S1 of the shaft member 1 (pipe), as shown in Figures 8 and 10. With this propeller shaft 10, air A that thermally expands during welding is released into the internal space S1 of the shaft member 1 (pipe) through the communication passages 7a, 7b. The propeller shaft 10 can prevent the thermally expanded air A from escaping from the molten welded portions 9a, 9b. This makes it possible for the propeller shaft 10 to suppress the occurrence of blowholes in the welded portions 9a, 9b.

[0062] Furthermore, in this propeller shaft 10, the communication passages 7a, 7b communicate with the internal space S1 of the shaft member 1 (pipe) and are not open to the outside of the shaft member 1 (pipe). With this propeller shaft 10, water will not enter the shaft member 1 (pipe) from the outside through the communication passages 7a, 7b when washing the vehicle or due to mud splashing.

[0063] In this propeller shaft 10, the shaft member 1 (pipe) includes a tube member 11 (pipe body) and a first collar member 12 (cylindrical member) and a second collar member 13 (cylindrical member) made of a metallic material and connected to the ends of the tube member 11 (pipe body). With this propeller shaft 10, the shaft member 1 (pipe) can be formed from the tube member 11 (pipe body) made of a lightweight material such as CFRP, without being affected by the heat of the welded portions 9a, 9b. As a result, the propeller shaft 10 can reduce the vehicle weight and improve fuel efficiency.

[0064] Furthermore, in this propeller shaft 10, the first collar member 12 and the second collar member 13 constituting the shaft member 1 (pipe) have an expanded inner diameter portion Cf (chamfered portion) on the inner circumferential sides of their ends. This propeller shaft 10 improves the insertability of the circumferential rib 25 (spigot portion) of the stub shaft 2 (rotating member) and the circumferential rib 34 (spigot portion) of the joint connection member 3 (rotating member) into the inner circumferential sides of the ends of the first collar member 12 and the second collar member 13. Furthermore, in this propeller shaft 10, the expanded inner diameter portion Cf (chamfered portion) circumferentially connects the multiple communicating passages 7a and the multiple communicating passages 7b. This allows the propeller shaft 10 to release thermally expanded air to the communicating passages 7a and 7b even in areas where the communicating passages 7a and 7b are not provided.

[0065] In this propeller shaft 10, the communicating passage 7a is formed in the outer peripheral surface 25a of the circumferential rib 25 (spigot portion) of the stub shaft 2 (rotating member). In addition, the communicating passage 7b is formed in the outer peripheral surface 34a of the circumferential rib 34 (spigot portion) of the joint connection member 3 (rotating member). With this propeller shaft 10, the communicating passages 7a, 7b are formed in the outer peripheral surface 25a of the circumferential rib 25 and the outer peripheral surface 34a of the circumferential rib 34, which makes it easy to fabricate the communicating passages 7a, 7b.

[0066] Furthermore, in this propeller shaft 10, a plurality of communicating passages 7a, 7b are formed at equal intervals in the circumferential direction of the circumferential ribs 25, 34 (spigot portions). According to this propeller shaft 10, the dynamic balance and static balance in the circumferential direction of the propeller shaft 10 are improved.

[0067] Furthermore, in the manufacturing method of the propeller shaft 10 of this embodiment, the start position of welding at the joints 8a, 8b (contact portions) between the shaft member 1 (pipe) and the step surfaces 24, 33 (annular step portions) is set to a position different from the phase angle range θ in which the communicating passages 7a, 7b are formed. The welding is performed in a direction away from the communicating passages 7a, 7b. This manufacturing method prevents the communicating passages 7a, 7b from being blocked by molten material during welding when welding the joints 8a, 8b (contact portions) circumferentially around the shaft member 1 (pipe). Thermally expanded air A is effectively released from the communicating passages 7a, 7b. This manufacturing method more reliably prevents the occurrence of blowholes in the welded portions 9a, 9b.

[0068] Furthermore, in this manufacturing method, the end position of welding at the joints 8a, 8b (contact portions) is set within the phase angle range θ in which the communicating passages 7a, 7b are formed. This manufacturing method prevents the communicating passages 7a, 7b from being blocked by molten material during welding until welding of the joints 8a, 8b (contact portions) is completed. This manufacturing method can more reliably prevent the occurrence of blowholes in the welded portions 9a, 9b.

[0069] In this manufacturing method, the step of welding the seams 8 a, 8 b (contact portions) is performed by laser welding. This manufacturing method allows the welds 9 a, 9 b to be formed locally, concentrating on the seams 8 a, 8 b (contact portions). This manufacturing method thereby reduces thermal distortion around the welds 9 a, 9 b, allowing the propeller shaft 10 to be manufactured with high precision.

[0070] Although the present invention has been described above with reference to an embodiment thereof, it is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. Fig. 12 is an explanatory diagram of the configuration of a propeller shaft 10A (power transmission shaft) according to another embodiment (modified example) of the present invention. Note that in the propeller shaft 10A according to this modified example, components similar to those in the above embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in Fig. 12, the propeller shaft 10A according to the modified example has a shaft member 1A instead of the shaft member 1 (see Fig. 1) serving as a pipe in the propeller shaft 10 (see Fig. 1) of the above embodiment, but is otherwise configured similarly to the propeller shaft 10 (see Fig. 1).

[0071] Unlike the shaft member 1 (see FIG. 1), the shaft member 1A (pipe) of the propeller shaft 10A is formed solely from a tube member 11A made of an iron-based metal. Also, as shown in FIG. 5, the circumferential rib 25 (spigot portion) of the stub shaft 2 in the above embodiment fits into the inner circumferential side of the first collar member 12 to form a spigot fitting structure 6a. In contrast, in the propeller shaft 10A according to the modified example, as shown in FIG. 12, the circumferential rib 25 (spigot portion) of the stub shaft 2 fits into the inner circumferential side of the tube member 11A to form a spigot fitting structure 6c.

[0072] 7, the circumferential rib 34 (spigot portion) of the joint connection member 3 in the above embodiment is fitted into the inner circumferential side of the second collar member 13 to form a spigot fitting structure 6b. In contrast, in a propeller shaft 10A according to a modified example, as shown in FIG. 12, the circumferential rib 34 (spigot portion) of the joint connection member 3 is fitted into the inner circumferential side of the tube member 11A to form a spigot fitting structure 6d. Although not shown in FIG. 12, the circumferential rib 25 (spigot portion) and the circumferential rib 34 (spigot portion) have communicating passages 7a, 7b formed in the same manner as those shown in FIGS. 5 and 7. In the propeller shaft 10A, the joint 8c between the tube member 11A and the stub shaft 2 is laser welded in the circumferential direction, and the joint 8d between the tube member 11A and the joint connection member 3 is laser welded in the circumferential direction.

[0073] According to the propeller shaft 10A of this modified example, it is possible to suppress the occurrence of blowholes in the welded portion formed in the inlay fitting portion, and it is possible to reduce the number of parts compared to the propeller shaft 10 (see Figure 1).

[0074] DESCRIPTION OF SYMBOLS 1 Shaft member (pipe) 2 Stub shaft (rotating member) 3 Joint connection member (rotating member) 7a Communication passage 7b Communication passage 8a Joint (contact portion) 8b Joint (contact portion) 9a Welded portion 9b Welded portion 10 Propeller shaft (power transmission shaft) 11 Tube member (pipe main body) 12 First collar member (cylindrical member) 13 Second collar member (cylindrical member) 24 Step surface (annular step portion) 25 Circumferential rib (spigot joint portion) 33 Step surface (annular step portion) 34 Circumferential rib (spigot joint portion) Cf Inner diameter expansion portion S1 Internal space of shaft member (pipe)

Claims

1. A power transmission shaft that transmits the rotational force from the power source of a vehicle to the wheels of the vehicle, comprising: a pipe extending in the axial direction; and a rotating member that is fitted into the inner peripheral side of the end portion of the pipe and is in an inlay fit with respect to the pipe and rotates together with the pipe. The rotating member includes an inlay portion that is fitted into the inner peripheral side of the end portion of the pipe, and an annular step portion that is formed so as to rise radially outward from the base of the inlay portion and abuts against the end face of the pipe. The contact portion between the end face of the pipe and the annular step portion is welded along the circumferential direction of the power transmission shaft, and there is a communication passage that communicates the welded portion between the end face of the pipe and the annular step portion on the root side of the inlay portion with the internal space of the pipe.

2. The power transmission shaft according to claim 1, wherein the pipe has a pipe body and a cylindrical member made of a metal material that is connected to the end portion of the pipe body and is a separate member from the pipe body.

3. The power transmission shaft according to claim 1, wherein the inner peripheral side of the end portion of the pipe has an inner diameter increasing portion whose inner diameter gradually increases toward the opening side of the pipe along the axial direction.

4. The power transmission shaft according to claim 1 or claim 2, wherein the communication passage is formed on the outer peripheral surface of the inlay portion along the axial direction of the rotating member.

5. The power transmission shaft according to claim 4, wherein a plurality of the communication passages are formed at equal intervals in the circumferential direction of the inlay portion.

6. A method for manufacturing the power transmission shaft according to claim 1, comprising: a step of inlay-fitting the end portion of the rotating member into the inner peripheral side of the end portion of the pipe; and a step of welding the contact portion between the end face of the pipe and the annular step portion in the circumferential direction of the power transmission shaft. The starting position of the welding of the contact portion is set at a position different from the phase where the communication passage is formed when viewed in the axial direction of the power transmission shaft, and the welding is performed in a direction away from the communication passage.

7. The method for manufacturing the power transmission shaft according to claim 6, wherein the ending position of the welding of the contact portion is set within the range of the phase where the communication passage is formed when viewed in the axial direction of the power transmission shaft.

8. The method for manufacturing the power transmission shaft according to claim 6 or claim 7, wherein the step of welding the contact portion is performed by laser welding.

Images