Motive power transmission shaft, yoke, and method for manufacturing yoke

Abstract

In the present invention, a protruding part (25) formed by cutting off a burr part (B) formed by forging is provided such that, in an axial direction that is the penetration direction of a bolt through-hole (203) in a flange outer peripheral surface (200), the center (Cb) of the protruding part (25) is shifted closer to a seating-surface (24) side than the center (Cf) of the flange outer peripheral surface (200). This makes it possible to maximally ensure the area of the seating surface (24) only through a step for forging a second yoke (2) without a process for cutting the flange outer peripheral surface (200), and to reduce the manufacturing cost for the second yoke (2) and thus also for a propeller shaft (PS).

Description

Power transmission shaft, yoke, and method of manufacturing the yoke

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

[0002] An example of a conventional power transmission shaft yoke is known from, for example, Patent Document 1 listed below.

[0003] In brief, the yoke of this power transmission shaft constitutes part of a Cardan joint and is formed integrally with a flange and a yoke body. The flange is formed by forging and fastened to a mating component by bolts and nuts through through holes provided on the outer periphery. Furthermore, the periphery of the through holes in the flange is formed by machining to have a flat seating surface on which the fastening member can rest.

[0004] The pitch circle diameter (P.C.D.) of the through hole of the yoke is set larger, and the outermost diameter portion of the flange portion that protrudes beyond the outer peripheral edge of the mating member is machined, thereby removing a portion of the flange portion that does not serve as a seating surface.

[0005] Japanese Patent Application Laid-Open No. 2008-208919

[0006] However, in the yoke of the conventional power transmission shaft, a portion of the flange portion that does not serve as a seating surface must be removed by cutting, which increases the manufacturing cost of the yoke due to the number of steps required for the cutting process, and there is still room for improvement.

[0007] The present invention has been devised in view of the technical problems with the conventional power transmission shaft, yoke, and yoke manufacturing method, and has an object to provide a power transmission shaft, yoke, and yoke manufacturing method that can reduce the manufacturing cost of the yoke.

[0008] In one aspect, the present invention comprises a flange portion extending radially relative to the rotation axis of a rotating member, a through hole provided in the flange portion and into which a fastening member is inserted, a seating surface provided on the periphery of the through hole and on which a seating portion of the fastening member seats, and a protrusion provided on the flange outer peripheral surface so as to extend in the hole diameter direction relative to the penetration direction of the through hole, and having a center closer to the seating surface than the center of the flange outer peripheral surface in the direction of the rotation axis of the rotating member.

[0009] According to the present invention, the manufacturing cost of the yoke can be reduced.

[0010] 1. A half sectional view of a power transmission shaft according to the present invention. 2. An enlarged half sectional view of a main portion of the power transmission shaft, showing the fastening state with the first rotating member of the vehicle. 3. A perspective view of the second yoke of the first universal joint shown in FIG. 2, viewed from the first yoke side. 4. A plan view of the first yoke shown in FIG. 3. 5. A diagram showing a method for manufacturing the first yoke shown in FIG. 3, where (a) is a diagram showing a hot forging process and (b) is a diagram showing a cutting process. 6. A diagram equivalent to FIG. 5, showing a manner in which a bolt is seated on the first yoke shown in FIG. 2. 7. A diagram showing a second embodiment of the power transmission shaft according to the present invention, and corresponding to the cross-sectional view of line A-A in FIG. 4.

[0011] Hereinafter, embodiments of a power transmission shaft, a yoke, and a method for manufacturing a yoke according to the present invention will be described in detail with reference to the drawings. In each of the following embodiments, the power transmission shaft, the yoke, and the method for manufacturing a yoke according to the present invention will be described, as applied to a propeller shaft for an automobile, as in the conventional method. For ease of explanation, the left side of FIGS. 1 and 2 will be referred to as the "front" and the right side as the "rear." In addition, the direction along the axis of rotation Z in each figure will be referred to as the "axial direction," the direction perpendicular to the axis of rotation Z as the "radial direction," and the direction around the axis of rotation Z as the "circumferential direction."

[0012] First Embodiment A first embodiment of a power transmission shaft, a yoke, and a method for manufacturing a yoke according to the present invention will be described below.

[0013] (Configuration of power transmission shaft) Figure 1 is a diagram showing the entire propeller shaft PS to which the power transmission shaft of the present invention is applied, and shows a half cross-sectional view of the propeller shaft PS cut along the rotation axis Z.

[0014] 1, the propeller shaft PS according to this embodiment is disposed in the longitudinal direction of the vehicle between a first rotating member 5 (see FIG. 2) as a rotating member disposed at the front of the vehicle and a second rotating member (not shown) as a rotating member disposed at the rear of the vehicle. For example, in a front engine, rear wheel drive (FR) vehicle, the first rotating member 5 is disposed at the front of the vehicle and corresponds to, for example, the output shaft of a transmission connected to the engine or the output shaft of a reducer attached to the motor, from which rotational force transmitted from a drive source such as an engine or a motor is output, and the second rotating member (not shown) is disposed at the rear of the vehicle and corresponds to, for example, the input shaft of a differential that transmits rotational force to the rear wheels of the vehicle.

[0015] In this embodiment, the propeller shaft PS has a two-piece structure in which a shaft member SH, which corresponds to the shaft member according to the present invention, is divided into two axially. That is, the propeller shaft PS includes a first shaft member S1 connected to a first rotating member 5 and a second shaft member S2 connected to a second rotating member (not shown) connected to the first rotating member 5 via a third universal joint J3, which is a constant velocity joint, so that the first shaft member S1 and the second shaft member S2 are rotatable together about the rotation axis Z. The propeller shaft PS is suspended from the underside of the floor of the vehicle body (not shown) via a bracket BKT disposed in front of the third universal joint J3, and is rotatably supported via a center bearing CB, which is supported by the vehicle body (not shown) via the bracket BKT.

[0016] The front end of the propeller shaft PS is connected to a first rotating member 5 (see FIG. 2) mounted on a vehicle (not shown) via a first universal joint J1 formed by a Cardan joint. Similarly, the rear end of the propeller shaft PS is connected to a second rotating member (not shown) mounted on a vehicle (not shown) via a second universal joint J2 formed by a Cardan joint.

[0017] (Configuration of the Yoke) FIG. 2 is an enlarged half-sectional view of a main portion of the propeller shaft PS, illustrating the fastened state between the second yoke 2 of the first universal joint J1 and the first rotating member 5. FIG. 3 is a perspective view of the second yoke 2 of the first universal joint J1, viewed from the first yoke 1 side. FIG. 4 is a plan view of the second yoke 2, showing the state in which the nut 62 (phantom line) is disposed on the seating surface 24. FIG. 5 is an enlarged sectional view of a main portion of the flange portion 20 taken along line A-A in FIG. 4. Note that the imaginary line V in FIG. 5 indicates the state of the forged flange portion 20 before cutting.

[0018] In this embodiment, for convenience, the yoke according to the present invention will be described using the first universal joint J1 as an example, but the second universal joint J2 also has a configuration similar to that of the first universal joint J1. In other words, the configuration of the second yoke 2 to which the yoke according to the present invention is applied can also be applied to the second universal joint J2.

[0019] For example, as shown in FIG. 2, the first universal joint J1 includes a pair of yokes consisting of a first yoke 1 connected to the first shaft member S1 of the propeller shaft PS and a second yoke 2 connected to the first rotating member 5, and a cross shaft (spider) 3 interposed between the pair of yokes (the first yoke 1 and the second yoke 2) to connect the pair of yokes, the first yoke 1 and the second yoke 2, so that they can rotate relative to each other.

[0020] The first yoke 1 has a cylindrical base 10 with a bottom that is fixed to the front end of the first shaft member S1 of the propeller shaft PS by, for example, friction welding, and a pair of arms, namely a first arm 11 and a second arm 12, that extend generally parallel to each other from a surface of the cylindrical base 10 that faces the second yoke 2 toward the second yoke 2 along the rotation axis Z of the propeller shaft PS. The cylindrical base 10 and the first arm 11 and second arm 12 are integrally formed by, for example, forging.

[0021] The first and second arm portions 11, 12 are arranged symmetrically with respect to the rotation axis Z. First and second arm through-holes 110, 120 are formed in the radial direction at the tips of the first and second arm portions 11, 12, facing each other across the rotation axis Z. Cylindrical needle bearings 4 are inserted between the first and second arm through-holes 110, 120 and the first and third shaft portions 31, 33 of the cross shaft 3 that are inserted into the first and second arm through-holes 110, 120, respectively, and the first and third shaft portions 31, 33 of the cross shaft 3 are rotatably supported by the needle bearings 4.

[0022] The second yoke 2 has a flange portion 20 formed in a generally plate shape, and a pair of arms, a first arm portion 21 and a second arm portion 22, which are a yoke main body according to the present invention, extending in parallel from a first flange end surface 201 of the flange portion 20 that faces the first yoke 1 toward the first yoke 1 along the rotation axis Z of the propeller shaft PS. The flange portion 20 and the first and second arm portions 21, 22 are integrally formed by forging (hot forging) as described below.

[0023] The flange portion 20 has a generally rectangular plate shape, and has bolt through holes 203 formed in its four corners (see FIGS. 3 and 4 ). The flange portion 20 is connected to the first rotating member 5 via bolts 61 and nuts 62 serving as fastening members that are inserted through the bolt through holes 203. The planar shape of the flange portion 20 can be freely changed, for example, to a circular shape or an irregular shape, depending on the shape of the flange portion 51 of the mating first rotating member 5, in addition to the rectangular shape exemplified in this embodiment. Also, as shown in FIG. 2 , a second flange end surface 202, which is an end surface of the flange portion 20 axially opposite the first and second arm portions 21, 22 and faces the first rotating member 5, has an annular fitting protrusion 23 that can fit into a fitting recess 512 (described later) of the first rotating member 5 and protrudes in the axial direction opposite the first and second arm portions 21, 22.

[0024] As shown in Fig. 2 , the first and second arm portions 21, 22 function as a pair with the first and second arm portions 11, 12 of the first yoke 1, are arranged symmetrically about the rotation axis Z, and are circumferentially shifted by 90° from the first and second arm portions 11, 12. As shown in Figs. 2 and 3 , first and second arm through-holes 210, 220 are formed in the distal ends of the first and second arm portions 11, 12 along the radial direction, facing each other across the rotation axis Z. Cylindrical needle bearings 4 are inserted between the first and second arm through-holes 210, 220 and the second and fourth shaft portions 32, 34 of the cross shaft 3 inserted into the first and second arm through-holes 210, 220, respectively, and the second and fourth shaft portions 32, 34 of the cross shaft 3 are rotatably supported by the needle bearings 4.

[0025] 3 and 5 , the first flange end face 201 of the flange portion 20 is formed with flat seating surfaces 24 on the periphery of each bolt through hole 203, at a position including a maximum outer diameter portion X that is the largest outer diameter Rx of the flange portion 20, on which a nut 62 serving as a fastening member can be seated. Note that, as shown in FIG. 2 , an inner end surface 620 corresponding to the seating portion of a nut 62 screwed onto a bolt 61 that is one of the fastening members according to the present invention may abut against the seating surface 24, or, as shown in FIG. 7 , a head 611 of the bolt 61 that is the other fastening member may abut against the seating surface 24. The seating surface 24 is concentrically cut out around the periphery of the bolt through hole 203, with a radially inner portion 241 facing a step portion 240 that forms the boundary with the first flange end face 201, and a radially outer portion 242 that is open in the radial direction. The seating surface 24 is formed by cutting a predetermined depth Dx from the first flange end surface 201, and is configured as a relatively precise flat surface.

[0026] Furthermore, in the present embodiment, the seating surface 24 is formed to overlap with a protrusion 25 (described later) in the axial direction. In other words, the seating surface 24 has a predetermined depth Dx, which is the axial distance from the first flange end face 201 to the seating surface 24, that is set to be greater than the axial distance D1 from the first flange end face 201 to a first end P1, which is the end of the protrusion 25 (described later) on the seating surface 24 side, and smaller than the axial distance D2 from the first flange end face 201 to a second end P2, which is the end of the protrusion 25 (described later) on the first rotating member 5 side. As a result, a portion of the seating surface 24 is formed by the protrusion 25 (described later) at a radially outer portion 242 of the seating surface 24. The area of ​​the seating surface 24 can be set arbitrarily depending on the specifications of the second yoke 2, such as the shape of the flange portion 20 and the pitch edge diameter of the bolt through hole 203. In this embodiment, however, the seating surface 24 is formed so that the entire inner end surface 620, which is the seating portion of the nut 62, seats on the seating surface 24, as shown in FIGS. 2 and 4, for example.

[0027] As described above, the second yoke 2 is formed by hot forging. Therefore, as shown in FIG. 3 , the flange outer peripheral surface 200 of the flange portion 20 has a protrusion 25 that protrudes radially outward and extends continuously along the circumferential direction at the parting line, i.e., the parting portion between the first and second forging dies FD1 and FD2 (described later). In other words, the protrusion 25 corresponds to the root of a flash B (described later) that remains after trimming the flash B formed during the forging of the second yoke 2. Specifically, the protrusion 25 protrudes radially outward from the flange outer peripheral surface 200 and along the circumferential direction of the flange outer peripheral surface 200. Furthermore, as shown in FIG. 5 , the center Cb of the protrusion 25 is offset toward the seating surface 24 in the axial direction relative to the center Cf of the flange outer peripheral surface 200, which corresponds to the central portion between the seating surface 24 and the second flange end face 202.

[0028] 5, the flange outer peripheral surface 200 is formed by a second inclined surface 262 such that the radial distance R2 from the rotation axis Z to the flange outer peripheral surface 200 increases as the distance approaches the protrusion 25 from the second flange end face 202 side in a radial cross section passing through the maximum outer diameter portion X. In this case, it is desirable that the second inclined surface 262 is formed so that the minor angle θ between the second inclined surface 262 and the rotation axis Z is 5 degrees.

[0029] 2, the first rotating member 5 connected to the second yoke 2 integrally includes a generally disk-shaped flange portion 51 provided opposite the flange portion 20 of the second yoke 2, and a generally cylindrical tubular portion 52 extending axially from a first end face 501, which is the front end face of the flange portion 51, toward the opposite side from the second yoke 2. In other words, the first rotating member 5 is connected to the second yoke 2 via the flange portion 51, and is linked to an engine or motor (not shown) via the tubular portion 52.

[0030] The flange portion 51 has bolt through holes 511 formed at positions axially opposite the bolt through holes 203 of the second yoke 2, through which shanks 612 of bolts 61 serving as fastening members can be inserted. The bolt through holes 511 have an inner diameter slightly larger than the outer diameter of the shanks 612 of the bolts 61. In this manner, the first rotating member 5 is fastened together by the bolt 61 inserted from the front (flange portion 51 side) in the axial direction and the nut 62 screwed from the rear (second yoke 2 side) onto a male threaded portion 613 formed on the outer periphery of the tip end of the shank 612 of the bolt 61. The flange portion 20 of the second yoke 2 and the flange portion 51 of the first rotating member 5 are clamped between the head 611 of the bolt 61 and the nut 62, whereby the bolt 61 and the nut 62 are fastened together.

[0031] Furthermore, a fitting recess 512, into which the fitting protrusion 23 of the second yoke 2 fits, is formed on the rear end surface of the flange portion 51, a second end surface 502 facing the second flange end surface 202 of the second yoke 2. The fitting recess 512 is recessed in the axially opposite direction from the second yoke 2. The fitting recess 512 is set to have a recess amount that is relatively larger than the protrusion amount of the fitting protrusion 23 of the second yoke 2. This prevents the flange portion 20 from floating relative to the flange portion 51 when the fitting protrusion 23 abuts against the bottom portion 512a of the fitting recess 512 due to processing errors (variations) in the fitting protrusion 23. This enables the flange portion 20 of the second yoke 2 and the flange portion 51 of the first rotating member 5 to be joined in close contact with each other.

[0032] (Method of Manufacturing Yoke) FIGS. 6A and 6B are diagrams illustrating a method of manufacturing the second yoke 2, in which (a) is a cross-sectional view of the forging dies (first forging die FD1 and second forging die FD2) in the hot forging process, and (b) is a perspective view of the second yoke 2 after the seating surface cutting process.

[0033] For example, as shown in FIG. 6( a), the second yoke 2 is hot forged by sandwiching the raw material M between a first forging die FD1, which is an upper die used to forge the flange portion 20, and a second forging die FD2, which is a lower die used to forge the first arm portion 21 and the second arm portion 22 (forging process). More specifically, a certain outer shape of the second yoke 2 is first formed in a roughing process, and then the outer shape of the second yoke 2 is finished to a predetermined precision in a finishing process. During the roughing and finishing processes, a flash B is formed at the parting line PL, which corresponds to the parting point between the first forging die FD1 and the second forging die FD2, as the raw material M is crushed during forging. Subsequently, after the finishing process, the flash B is removed in a trimming process. Specifically, while the second flange end surface 202 of the flange portion 20 is supported by the first trim die TD1, which is a fixed die, the second trim die TD2, which is a movable die, is moved relatively from the first flange end surface 201 side, whereby the burrs B are cut off at their bases and the protrusions 25 are formed on the flange outer peripheral surface 200. In this way, the second yoke prototype PF is formed.

[0034] Next, the second yoke prototype PF forged in the hot forging process is machined (cut). As shown in FIG. 6( b), the first and second arm through-holes 210, 220 and the bolt through-holes 203 are formed by drilling, and the seating surfaces 24 are formed around the peripheries of the bolt through-holes 203 in the first flange end face 201 by countersinking (seating surface cutting process), thereby completing the second yoke 2.

[0035] (Operation and Effect of the Present Embodiment) As a first conventional example, in a conventional power transmission shaft described in, for example, Japanese Patent Application Laid-Open No. 2008-208919, a portion of the flange portion 20 of the second yoke 2 that protrudes radially outward beyond the flange portion 51 of the first rotating member 5 and does not function as the seating surface 24 is removed by cutting. For this reason, the manufacturing cost of the second yoke 2 increases due to the number of steps involved in the cutting process, and there is still room for improvement.

[0036] Furthermore, as a second conventional example, a conventional power transmission shaft described in JP 2016-133212 A further cold forging is performed on the second yoke base form PF formed by hot forging, in which the side surface of the maximum outer diameter portion X of the flange portion 20 is restricted and the base form PF is crushed in the axial direction, thereby enlarging the portion formed by the hot forging that does not function as the seating surface 24, i.e., the seating surface 24 that has been reduced in size due to the draft taper and corner radius portions of the first forging die FD1. For this reason, the manufacturing cost of the second yoke 2 increases due to the number of steps involved in the cold forging, and there is still room for improvement.

[0037] In contrast, the second yoke 2 of the propeller shaft PS according to this embodiment provides the following effects, thereby solving the technical problems of the conventional power transmission shaft.

[0038] Specifically, the propeller shaft PS includes a shaft member SH connected to a rotated part (a second rotating member not shown) that rotates based on a rotational force input from a rotating member (a first rotating member 5), and a yoke provided between the rotating member (first rotating member 5) and the shaft member SH, the yoke having a flange portion 20, a yoke main body portion (first and second arm portions 21, 22), a through hole (a bolt through hole 203), a seating surface 24, a flange outer peripheral surface 200, and a protruding portion 25, the flange portion 20 being formed to extend in a radial direction relative to the rotation axis Z of the rotating member (first rotating member 5), and a through hole (a bolt through hole 203) into which a fastening member (a shaft portion 612 of a bolt 61) for fastening to the rotating member (first rotating member 5) is inserted, the through hole being provided in the axial direction along the rotation axis Z. Both yokes have a protruding yoke main body (first and second arm portions 21, 22) connected to the shaft member SH on the opposite side of the rotating member (first rotating member 5) in the axial direction, and the seating surface 24 is formed flat on the periphery of the through hole (bolt through hole 203) so that the seating portion of the fastening member (head 611 of the bolt 61 or inner end surface 620 of the nut 62) can seat thereon, and the protruding portion 25 is formed on a flange outer peripheral surface 200 formed in the circumferential direction with respect to the penetration direction of the through hole (bolt through hole 203) so as to extend in the hole diameter direction with respect to the penetration direction of the through hole (bolt through hole 203), and the center Cb of the protruding portion 25 is located closer to the seating surface 24 than the center Cf of the flange outer peripheral surface 200 in the axial direction.

[0039] In other words, the manufacturing method of the yoke (second yoke 2) of the propeller shaft PS is a manufacturing method of the yoke (second yoke 2) provided between the rotating member (first rotating member 5) and the shaft member SH connected to the rotated part (second rotating member not shown) that rotates based on the rotational force input from the rotating member (first rotating member 5), and the yoke (second yoke 2) is a flange part formed so as to extend in the radial direction with respect to the rotation axis Z of the rotating member (first rotating member 5), A through hole (bolt through hole 203) into which a fastening member (shank 612 of bolt 61) for fastening to the first rotating member 5 is inserted is provided so as to penetrate in the axial direction along the rotation axis Z, and a flange portion 20 from which a yoke main body portion (first and second arm portions 21, 22) connected to the shaft member SH is provided to protrude on the opposite side of the rotating member (first rotating member 5) in the axial direction, and a seat portion for a fastening member (head portion 611 of bolt 61) is provided on the periphery of the through hole (bolt through hole 203) and a protrusion 25 provided on a flange outer peripheral surface 200 formed in a circumferential direction relative to the penetration direction of a through hole (bolt through hole 203) in the flange portion 20, the protrusion 25 extending in a hole diameter direction relative to the penetration direction of the through hole (bolt through hole 203), and having a center Cb of the protrusion 25 located closer to the seating surface 24 than a center Cf of the flange outer peripheral surface 200 in the axial direction, the protrusion 25 having a center Cb of the protrusion 25 located closer to the seating surface 24 than a center Cf of the flange outer peripheral surface 200 in the axial direction, the protrusion 25 including a first forging process and a second forging process. The first forging process and the second forging process have a split portion (parting line PL) located closer to the seating surface 24 than the center Cf of the flange outer peripheral surface 200 in the axial direction.

[0040] As described above, in this embodiment, the protrusion 25 formed by removing the flash B formed by forging is provided at a position offset toward the seating surface 24 from the center Cf of the flange outer peripheral surface 200 in the penetration direction of the bolt through hole 203. This makes it possible to maximize the area of ​​the seating surface 24 only through the hot forging process of the second yoke 2, without requiring cutting of the flange outer peripheral surface 200 as in the first conventional example, thereby reducing the manufacturing costs of the second yoke 2 and, ultimately, the propeller shaft PS.

[0041] Furthermore, in this embodiment, the second yoke 2 can be formed only by hot forging, eliminating the need for cold forging after hot forging as in the second conventional example, thereby reducing the manufacturing costs of the second yoke 2 and, ultimately, the propeller shaft PS.

[0042] In addition, in this embodiment, the seating surface 24 is formed on the periphery of the through hole (bolt through hole 203) including the protrusion 25, and includes the maximum outer diameter portion X where the flange portion 20 expands most in the radial direction.

[0043] In this manner, in this embodiment, the seating surface 24 is formed to include the maximum outer diameter portion X of the flange portion 20 on the periphery of the bolt through hole 203, including the protrusion 25. This makes it possible to ensure a larger area of ​​the seating surface 24 on which the head 611 of the bolt 61 or the inner end surface 620 of the nut 62, which serves as the seating portion, can be seated.

[0044] In addition, in this embodiment, when viewed in a cross section cut in the axial direction and passing through the maximum outer diameter portion X (see Figure 5), the flange outer peripheral surface 200 is formed so that the radial distance R2 from the rotation axis Z to the flange outer peripheral surface 200 increases as it approaches the protrusion 25 in the axial direction from the end (second end P2) on the rotating member (first rotating member 5) side.

[0045] Thus, in this embodiment, the flange outer peripheral surface 200 is formed so that the radial distance R2 from the rotation axis Z to the flange outer peripheral surface 200 increases as it approaches the protruding portion 25 in the axial direction from the end (second end P) on the first rotating member 5 side. This makes it possible to use the second inclined surface 262 formed from the end (second end P2) of the flange outer peripheral surface 200 on the first rotating member 5 side to the protruding portion 25 as a draft gradient for the second forging die FD2, improving mold releasability during forging and contributing to good forging (hot forging).

[0046] In this embodiment, the flange outer peripheral surface 200 is formed so that the minor angle θ between the flange outer peripheral surface 200 and the rotation axis Z is 5 degrees.

[0047] In this manner, in this embodiment, the minor angle θ of the flange outer peripheral surface 200 with respect to the rotation axis Z is set to 5 degrees. This makes it possible to ensure a relatively large pitch circle diameter of the bolt through holes 203 while also ensuring good mold releasability during forging, thereby achieving both an increase in the pitch circle diameter of the bolt through holes 203 and good mold releasability during forging.

[0048] In this embodiment, the protrusion 25 is provided so as to protrude in the circumferential direction from the flange outer peripheral surface 200 .

[0049] As described above, in this embodiment, the protrusion 25 is formed to protrude in the circumferential direction from the flange outer peripheral surface 200. Therefore, even if a circumferential positional deviation occurs due to a radial gap between the shank 612 of the bolt 61 and the bolt through-hole 203 when the fastening members, ie, the bolt 61 and the nut 62, are fastened together, it is possible to ensure a larger seating area for the inner end surface 620 of the nut 62 to seat, thereby ensuring good fastening strength of the fastening members, ie, the bolt 61 and the nut 62.

[0050] In this embodiment, the fastening members are a bolt 61 and a nut 62, and the nut 62 is seated on the seating surface 24 (see FIG. 2).

[0051] As described above, in this embodiment, the fastening members are composed of the bolts 61 and the nuts 62. This makes it possible to easily fasten the second yoke 2, and also makes it possible to refasten the second yoke 2 during maintenance, making it easy to attach and detach the second yoke 2.

[0052] In another embodiment, the fastening members may be a bolt 61 and a nut 62, and the head 611 of the bolt 61 may be seated on the seating surface 24 (see FIG. 7).

[0053] In this way, even if the positions of the bolts 61 and nuts 62 are reversed, the fastening members are composed of the bolts 61 and nuts 62, which makes it easy to fasten the second yoke 2 and also makes it possible to refasten it during maintenance, making it easy to attach and detach the second yoke 2.

[0054] In this embodiment, the entire seating portion of the fastening member (the head 611 of the bolt 61 or the inner end surface 620 of the nut 62 ) is seated on the seating surface 24 .

[0055] In this manner, in this embodiment, the head 611 of the bolt 61 (see FIG. 8) or the entire inner end surface 620 of the nut 62 (see FIG. 2), which is the seating portion of the fastening member, is configured to be able to seat on the seating surface 24. This makes it possible to effectively prevent the bolt 61 and the nut 62 from loosening.

[0056] 8 shows a second embodiment of the power transmission shaft, yoke, and yoke manufacturing method according to the present invention, in which the configuration of the protrusion 25 according to the first embodiment is modified. Note that the basic configuration other than the modified points is the same as that of the first embodiment, and therefore the same components as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

[0057] FIG. 8 is a diagram showing a second embodiment of the power transmission shaft, yoke, and yoke manufacturing method according to the present invention, and shows a diagram equivalent to an enlarged cross-sectional view of a main part of the flange portion 20 taken along line A-A in FIG.

[0058] 8 , in the propeller shaft PS according to this embodiment, the seating surface 24 is provided so as not to overlap the protruding portion 25 in the axial direction, and the protruding portion 25 does not form part of the seating surface 24. In other words, in this embodiment, the seating surface 24 has a predetermined depth Dx, which is the axial distance from the first flange end face 201 to the seating surface 24, set to be smaller than the axial distance D1 from the first flange end face 201 to a first end P1, which is the end of the protruding portion 25, described later, on the seating surface 24 side.

[0059] In this way, the present invention only requires that the protrusion 25 is offset toward the seating surface 24 in the axial direction so that the center Cb of the protrusion 25 is located closer to the seating surface 24 than the center Cf of the flange outer peripheral surface 200, which corresponds to the center between the seating surface 24 and the second flange end face 202. Depending on the processing error related to the predetermined depth Dx of the seating surface 24, the present invention also includes a configuration in which the protrusion 25 does not form part of the seating surface 24.

[0060] 8 , in a radial cross section passing through the maximum outer diameter portion X, the flange outer peripheral surface 200 is formed by a first inclined surface 261 such that the radial distance R1 from the rotation axis Z to the flange outer peripheral surface 200 increases as the flange outer peripheral surface 200 approaches the protruding portion 25 from the first flange end face 201 side. Similarly, the flange outer peripheral surface 200 is formed by a second inclined surface 262 such that the radial distance R2 from the rotation axis Z to the flange outer peripheral surface 200 increases as the flange outer peripheral surface 200 approaches the protruding portion 25 from the second flange end face 202 side. In this case, it is desirable that the first inclined surface 261 and the second inclined surface 262 are formed so that the minor angle θ between them and the rotation axis Z is 5 degrees.

[0061] As described above, in this embodiment, the protrusion 25 is provided in the axial direction between the center Cf of the flange outer peripheral surface 200 and the end (first end P1) of the flange outer peripheral surface 200 on the seating surface 24 side, and the flange outer peripheral surface 200 is formed such that, when viewed in a cross section cut in the axial direction (see Figure 8), the radial distance R2 from the rotation axis Z to the flange outer peripheral surface 200 increases as the end (second end P2) on the rotating member (first rotating member 5) side approaches the protrusion 25 in the axial direction, and the radial distance R1 from the rotation axis Z to the flange outer peripheral surface 200 increases as the end (first end P1) on the seating surface 24 side approaches the protrusion 25 in the axial direction.

[0062] Thus, in the present embodiment, the flange outer peripheral surface 200 is formed such that the radial distance R2 from the rotation axis Z to the flange outer peripheral surface 200 increases axially from the end (second end P2) on the first rotating member 5 side toward the protruding portion 25, and the radial distance R1 from the rotation axis Z to the flange outer peripheral surface 200 increases axially from the end (first end P1) on the seating surface 24 side toward the protruding portion 25. This makes it possible to set the first inclined surface 261 and the second inclined surface 262 formed on the flange outer peripheral surface 200 as the draft angles of the first forging die FD1 and the second forging die FD2, respectively, which improves mold releasability during forging and contributes to good forging (hot forging).

[0063] The present invention is not limited to the configurations and aspects exemplified in the above-described embodiments, and can be freely modified depending on the specifications, costs, and the like of the target application as long as the above-described operational effects of the present invention can be achieved. For example, in the above-described embodiments, hot forging, which is the optimal method for implementing the present invention, has been described as an example of a method for manufacturing the power transmission shaft (propeller shaft PS) and yoke (second yoke 2) according to the present invention. However, the power transmission shaft (propeller shaft PS) and yoke (second yoke 2) according to the present invention can also be manufactured by cold forging in addition to the hot forging. In other words, the method for manufacturing the power transmission shaft (propeller shaft PS) and yoke (second yoke 2) according to the present invention includes cold forging in addition to the hot forging.

[0064] 2...second yoke (yoke), 20...flange portion, 200...flange outer peripheral surface, 203...bolt through-hole (through-hole), 21...first arm portion (yoke main body), 22...second arm portion (yoke main body), 24...seating surface, 25...protrusion, 61...bolt (fastening member), 62...nut (fastening member), SH...shaft member, PS...propeller shaft (power transmission shaft), Z...rotation axis, B...burr portion, Cf...center of flange portion, Cb...center of protrusion, FD1...first forging die (forging die), FD2...second forging die (forging die),

Claims

1. A power transmission shaft comprising: a shaft member connected to a rotated part that rotates based on rotational force input from a rotating member; and a yoke provided between the rotating member and the shaft member, the yoke having a flange portion, a yoke main body portion, a through hole, a seating surface, a flange outer peripheral surface, and a protruding portion, the flange portion being formed to extend radially relative to the rotation axis of the rotating member, the through hole being formed to pass through in an axial direction along the rotation axis, and a fastening member being inserted therein for fastening the rotating member, and the yoke main body portion connected to the shaft member being protruding on the opposite side of the rotating member in the axial direction, the seating surface being formed flat on the periphery of the through hole so that the seating portion of the fastening member can seat on it, the protruding portion being provided on the flange outer peripheral surface which is formed circumferentially relative to the penetration direction of the through hole, extending in the hole diameter direction relative to the penetration direction of the through hole, and the center of the protruding portion being located closer to the seating surface than the center of the flange outer peripheral surface in the axial direction.

2. A power transmission shaft as set forth in claim 1, wherein the seating surface is formed on the periphery of the through hole including the protrusion, and includes the maximum outer diameter portion where the flange portion expands most in the radial direction.

3. A power transmission shaft as claimed in claim 2, characterized in that the flange outer peripheral surface is formed so that, when viewed in a cross section cut in the axial direction and passing through the maximum outer diameter portion, the radial distance from the rotation axis to the flange outer peripheral surface increases as it approaches the protruding portion from the end on the rotating member side in the axial direction.

4. A power transmission shaft according to claim 3, characterized in that the outer peripheral surface of the flange is formed so that the minor angle between it and the rotation axis is 5 degrees.

5. A power transmission shaft according to claim 2, characterized in that the protrusion is provided so as to protrude in the circumferential direction from the outer peripheral surface of the flange.

6. A power transmission shaft as claimed in claim 1, characterized in that the protrusion is provided in the axial direction between the centre of the flange outer peripheral surface and the end of the flange outer peripheral surface on the seating surface side, and the flange outer peripheral surface is formed so that, when viewed in a cross section cut in the axial direction, the radial distance from the rotation axis to the flange outer peripheral surface increases the closer it is to the protrusion in the axial direction from the end on the rotating member side, and the radial distance from the rotation axis to the flange outer peripheral surface increases the closer it is to the protrusion in the axial direction from the end on the seating surface side.

7. A power transmission shaft according to claim 1, wherein the fastening members are a bolt and a nut, and the head of the bolt is seated on the seating surface.

8. A power transmission shaft according to claim 1, wherein the fastening members are a bolt and a nut, and the nut is seated on the seating surface.

9. A power transmission shaft according to claim 1, characterized in that the entire seating portion of the fastening member is seated on the seating surface.

10. A yoke provided between a rotating member and a shaft member connected to a rotated part that rotates based on rotational force input from the rotating member, comprising: a flange portion formed to extend radially relative to the rotation axis of the rotating member, the flange portion having through holes formed axially along the rotation axis for inserting fastening members to fasten the rotating member, the flange portion having a yoke main body connected to the shaft member that protrudes on the opposite side of the rotating member in the axial direction; a flat seating surface provided on the periphery of the through hole on which a seating portion of the fastening member can be seated; and a protruding portion provided on an outer peripheral surface of the flange formed circumferentially relative to the through hole penetration direction of the flange portion, the protruding portion extending in the hole diameter direction relative to the through hole penetration direction, and the center of the protruding portion being located closer to the seating surface than the center of the outer peripheral surface of the flange in the axial direction.

11. A method for manufacturing a yoke provided between a rotating member and a shaft member connected to a rotated part that rotates based on a rotational force input from the rotating member, the yoke having: a flange portion formed to extend in a radial direction relative to the rotation axis of the rotating member, the flange portion having through holes formed in an axial direction along the rotation axis for inserting fastening members to be used for fastening the rotating member, the flange portion having a yoke main body connected to the shaft member that protrudes on the opposite side of the rotating member in the axial direction; a seating surface provided on the periphery of the through hole and formed flat on which a seating portion of the fastening member can be seated; and a protruding portion provided on an outer peripheral surface of a flange of the flange portion that is formed in a circumferential direction relative to the penetration direction of the through hole, the protruding portion extending in a hole diameter direction relative to the penetration direction of the through hole, the center of the protruding portion being located closer to the seating surface than the center of the outer peripheral surface of the flange in the axial direction. a forging step in which an outer shape of the yoke is formed and flash is formed on the outer peripheral surface of the flange using a plurality of forging dies having split portions closer to the seating surface than the center of the outer peripheral surface of the flange in the axial direction, and then the flash is removed to form the protrusion; and a seating surface cutting step in which the seating surface is machined onto the flange portion.

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