JP7007870B2 - Universal joint - Google Patents

Description

The present invention relates to a universal joint.

Patent Document 1 includes a first yoke connected to an output shaft of a transmission, a second yoke fixed to a propeller shaft, and a cross shaft member that swingably supports the first yoke or the second yoke. The universal joint (first universal joint) is disclosed. The first yoke includes a mounting flange having four bolt insertion holes formed at four corners, and a bifurcated yoke portion protruding from the mounting flange. The mounting flange is fixed to the output shaft of the transmission by stud bolts and nuts, and four flat nut seating portions on which the nut is seated are formed around the bolt insertion hole on one side of the mounting flange. Further, the cross-shaped shaft member is formed with four shaft portions protruding in a cross shape, and the yoke portion is formed with a bearing hole into which the shaft portion is inserted.

Japanese Unexamined Patent Publication No. 2008-20919

In recent years, there has been a demand for miniaturization of parts. In order to reduce the size of the universal joint, it is necessary to reduce the distance between the four nut seating portions in order to reduce the mounting flange. Then, in order to narrow the space between the nut seating portions, it is necessary to reduce the width dimension of the yoke portion to avoid interference between the nut seated on the nut seating portion and the yoke portion.

However, the connection portion between the yoke portion and the mounting flange is the portion where the stress generated when the rotation of the output shaft of the transmission is transmitted to the cross shaft member is maximized, whereas the width dimension of the yoke portion is reduced. , The rigidity of the yoke portion is reduced, and the yoke cannot secure sufficient strength. As described above, it has been difficult for the conventional universal joint to achieve both strength assurance and miniaturization.

An object of the present invention is to provide a universal joint capable of miniaturization while maintaining strength.

The universal joint of the present invention includes a cross-shaped shaft member having four shaft portions protruding in a cross shape, and a pair of yokes swingably connected to the shaft portion. The yoke is a portion that is bifurcated from one surface side of the yoke base portion and a yoke base portion that is fixed to the end surface of the drive shaft or the driven shaft by a fastening member. It comprises a pair of arms with bearing holes provided. The yoke base portion is provided on both sides in the width direction of the arm as viewed from the central axis direction of the bearing hole, and includes a flat surface-shaped seating surface portion that serves as a seating surface of the fastening member, and the arm is formed of the bearing hole. Among them, an arm tip portion forming the protruding direction tip end side of the arm and an arm proximal end portion forming the protruding direction proximal end side of the arm among the bearing holes are provided. The arm base end portion includes a relief portion whose width dimension seen from the center axis direction of the bearing hole is smaller than the maximum width dimension of the arm tip portion seen from the center axis direction of the bearing hole, and the yoke base portion and the above. A first connecting portion having an arcuate first R surface formed on both side surfaces in the width direction when viewed from the central axis direction of the bearing hole, which is a portion connecting the relief portion, and the arm tip portion. A portion connecting the relief portion and having a second connecting portion having an arcuate second R surface formed on both side surfaces in the width direction when viewed from the central axis direction of the bearing hole. The ratio of the radius of curvature of the first R surface to the width dimension of the relief portion is 0.14 or more, and the distance between the bearing surface portions formed on both sides in the width direction sandwiching the arm is the distance between the tip portions of the arms. Greater than the maximum width dimension .

According to the universal joint of the present invention, the arm base end portion includes the first R surface and the second R surface, so that the yoke applies the stress generated in the relief portion to the first R surface and the second R surface. Can be distributed to and. Therefore, the yoke can suppress an increase in stress generated on the first R surface even if the width dimension of the relief portion is reduced. Further, the yoke forms the arm base end portion so that the ratio of the radius of curvature of the first R surface to the width dimension of the relief portion is 0.14 or more. As a result, the yoke can evenly disperse the stress generated in the relief portion with respect to the first R surface and the second R surface. Therefore, the universal joint can reduce the size of the yoke while maintaining the strength of the yoke.

It is a partially enlarged view of the universal joint in one Embodiment of this invention. It is a partially enlarged sectional view of the universal joint in the IB-IB line of FIG. 1A. It is the figure which looked at the yoke from the direction of the central axis of a bearing hole. It is a top view of the yoke. It is a graph which shows the relationship between the radius of curvature of the 1st R plane and the stress generated in the 1st R plane and the 2nd R plane. It is a graph which shows the relationship between the radius of curvature of the 1st R plane and the stress generated in the 1st R plane and the 2nd R plane.

Hereinafter, embodiments to which the universal joint according to the present invention is applied will be described with reference to the drawings. First, the outline of the universal joint 1 according to the embodiment of the present invention will be described with reference to FIGS. 1A and 1B. The universal joint 1 is connected between the drive shaft 2 and the driven shaft (not shown), and transmits the rotation of the drive shaft 2 to the driven shaft.

(1. Outline of universal joint 1)
As shown in FIGS. 1 and 2, the universal joint 1 mainly includes a cross-shaped shaft member 10, a pair of yokes 20, and four bearing cups 30. The cross-shaped shaft member 10 includes a body portion 11 and four shaft portions 12. The four shaft portions 12 are portions protruding from the body portion 11 in a cross shape. Each shaft portion 12 is formed in a columnar portion.

The pair of yokes 20 are fixed to the drive shaft 2 or the driven shaft (not shown). Specifically, of the pair of yokes 20, one yoke 20 has a bolt as a fastening member with respect to the end surface 2a of the drive shaft 2, and the other yoke 20 has a bolt with respect to the end surface (not shown) of the driven shaft. It is fixed by 3 and a nut 4. Further, two bearing holes 21 into which the shaft portion 12 can be inserted are formed through each yoke 20. The details of the yoke 20 will be described later with reference to FIGS. 2A and 2B.

The bearing cup 30 is formed in a bottomed cylindrical shape that can be press-fitted into the bearing hole 21. The four bearing cups 30 are covered on each of the four shaft portions 12. A needle bearing 40 is provided between the inner peripheral surface of the bearing cup 30 and the outer peripheral surface of the shaft portion 12. As a result, the pair of yokes 20 are swingably connected to each of the shaft portions 12 of the cross-shaped shaft member 10 via the bearing cup 30 and the needle bearing 40.

(2. About the shape of the yoke 20)
Next, the shape of the yoke 20 will be described in detail. As shown in FIGS. 2A and 2B, the yoke 20 includes a yoke base 60 and a pair of arms 70. The yoke base 60 is a plate-shaped portion fixed to the end surface 2a of the drive shaft 2 (see FIG. 1A) or the end surface of the driven shaft (not shown).

The yoke base portion 60 includes four seat surface portions 61 formed on one surface side (upper surface side of FIG. 3A) of the yoke base portion 60, and four bolt holes 62 formed through the central portion of each seat surface portion 61 in a plan view. To prepare for. The seat surface portion 61 is a flat surface portion that becomes the seat surface of the nut 4 when the yoke base portion 60 is fixed to the end surface 2a of the drive shaft 2 or the end surface of the driven shaft, and the four seat surface portions 61 are viewed in a plan view. It is provided at the four corners of the yoke base 60 in the above. Further, the seat surface portions 61 are located on both sides in the width direction (horizontal direction in FIG. 3A) sandwiching the arm 70 when viewed from the central axis O direction of the bearing hole 21.

The yoke base 60 has the end surface 2a or the end surface 2a of the drive shaft 2 in a state where the other surface side (lower surface side of FIG. 3A) of the yoke base 60 is in contact with the end surface 2a (see FIG. 1A) of the drive shaft 2 or the end surface of the driven shaft. The bolt 3 is inserted into the bolt hole 62 from the end face of the driven shaft. Then, by screwing the nut 4 onto the bolt 3 from one surface side of the yoke base 60, the yoke base 60 is fastened and fixed to the end surface 2a of the drive shaft 2 or the end surface of the driven shaft.

The pair of arms 70 are portions that project bifurcatedly from one side of the yoke base 60. Each arm 70 includes an arm tip portion 71 and an arm base end portion 72. The arm tip portion 71 is a C-shaped portion of the bearing hole 21 that forms the tip end side portion (upper portion of FIG. 3A) of the arm 70 in the protruding direction. The arm base end portion 72 is a portion formed between the yoke base portion 60 and the arm tip portion 71, and forms a protruding direction base end end side portion (lower portion in FIG. 3A) of the bearing hole 21 in the bearing hole 21. do.

The arm base end portion 72 includes a relief portion 73, a first connection portion 74, and a second connection portion 75. The first connection portion 74 connects the yoke base portion 60 and the relief portion 73, and the second connection portion 75 connects the arm tip portion 71 and the relief portion 73. Further, the width dimension W1 of the relief portion 73 seen from the central axis O direction of the bearing hole 21 is set to be smaller than the maximum width dimension W2 of the arm tip portion 71. Further, arcuate first R surfaces 76 are formed on both side surfaces of the first connecting portion 74 in the width direction when viewed from the central axis O direction of the bearing hole 21, and are viewed from the central axis O direction of the bearing hole 21. An arcuate second R surface 77 is formed on both side surfaces of the second connecting portion 75 in the width direction.

Here, the distance I between the two bearing surface portions 61 provided on both sides in the width direction sandwiching the arm 70 when viewed from the central axis O direction of the bearing hole 21 is the width dimension W1 of the relief portion 73 and the first R surface 76. The dimensions are the sum of twice the radius of curvature R1 (I = W1 + R1 × 2). Therefore, in the arm base end portion 72, the larger the radius of curvature R1 of the first R surface 76 is, the smaller the width dimension W1 of the relief portion 73 is, while the width dimension W1 of the relief portion 73 is set to a larger dimension. The radius of curvature R1 of the first R surface 76 becomes smaller.

In this regard, the relationship between the radius of curvature R1 of the first R surface 76 and the stress generated on the first R surface 76 and the second R surface 77 will be described with reference to the graph shown in FIG. The graph shown in FIG. 3 shows that the radius of curvature R1 of the first R surface 76 is 1 mm, 2.5 mm in the yoke 20 in which the height H from one surface side of the yoke base 60 to the central axis O of the bearing hole 21 is 29 mm. The measurement results of the stress generated on the first R surface 76 and the second R surface 77 when set to 4 mm, 5.5 mm and 7 mm, respectively, are shown. The radius of curvature of the second R surface 77 is constant. The horizontal axis of the graph shown in FIG. 3 is the ratio (R1 / W1) of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73, and the larger the value, the more the radius of curvature R1 of the first R surface 76. Indicates that

According to the graph shown in FIG. 3, when the value of R1 / W1 is 0.03 (R1 is 1 mm), the stress generated on the first R surface 76 is 689 MPa, and the stress generated on the second R surface 77 is 146 MPa. there were. On the other hand, when the value of R1 / W1 was 0.09 (R1 is 2 mm), the stress generated on the first R surface 76 was 534 MPa, and the stress generated on the second R surface 77 was 313 MPa. As described above, the yoke 20 having a value of R1 / W1 of 0.09 has a stress generated in the relief portion 73 as that of the first R surface 76 as compared with the yoke 20 having a value of R1 / W1 of 0.03. It can be seen that the particles are evenly dispersed with respect to the second R surface 77.

Further, the yoke 20 having a value of R1 / W1 of 0.09 is first, although the width dimension of the relief portion 73 is smaller than that of the yoke 20 having a value of R1 / W1 of 0.03. It can be seen that the stress generated on the R surface 76 has decreased. In this respect, the yoke 20 can reduce the stress generated on the first R surface 76 by ensuring the radius of curvature R1 of the first R surface 76 even if the width dimension of the relief portion 73 is reduced. I can guess that it can be done.

When the value of R1 / W1 was 0.14 (R1 was 4 mm), the stress generated on the first R surface 76 was 552 MPa, and the stress generated on the second R surface 77 was 483 MPa. When the value of R1 / W1 was 024 (R1 was 5.5 mm), the stress generated on the first R surface 76 was 552 MPa, and the stress generated on the second R surface 77 was 528 MPa. When the value of R1 / W1 was 0.35 (R1 was 7 mm), the stress generated on the first R surface 76 was 615 MPa, and the stress generated on the second R surface 77 was 606 MPa. As described above, the yoke 20 having a value of R1 / W1 of 0.14, 0.24 or 0.35 is generated in the relief portion 73 as compared with the yoke 20 having a value of R1 / W1 of 0.09. It can be seen that the stress is more evenly distributed with respect to the first R surface 76 and the second R surface 77.

The stress generated on the first R surface 76 and the second R surface 77 increases as the value of R1 / W1 increases. It is presumed that this is because the rigidity of the relief portion 73 is lowered due to the reduction of the width dimension W1 of the relief portion 73. However, in comparison between the yoke 20 having a value of R1 / W1 of 0.14 or 0.24 and the yoke 20 having a value of R1 / W1 of 0.09, the first is as the value of R1 / W1 increases. The increase in stress generated on the R surface 76 is smaller than the increase in stress generated on the second R surface 77. This is because the radius of curvature R1 of the first R surface 76 is increased, so that the stress concentration on the first R surface 77 is reduced and the stress generated on the second R surface 77 is increased. it is conceivable that. As described above, even if the width dimension of the relief portion 73 is reduced, the yoke 20 can suppress an increase in stress generated on the first R surface 76 by ensuring the radius of curvature R1 of the first R surface 76. Can be inferred.

On the other hand, the difference in stress generated on the first R surface 76 when the value of R1 / W1 is changed from 0.24 to 0.35 is that the value of R1 / W1 is changed from 0.14 to 0.24. In this case, it is considerably larger than the difference in stress generated on the first R surface 76. This is because the stress generated in the relief portion 73 can be evenly distributed to the first R surface 76 and the second R surface 77, while the width dimension W1 of the relief portion 73 becomes smaller, so that the relief portion 73 It is presumed that the cause is an increase in the stress generated in the entire 73. That is, if the width dimension W1 of the relief portion 73 is made excessively small, the absolute value of the stress generated on each of the first R surface 76 and the second R surface 77 becomes large, and the arm 20 secures sufficient strength. Is considered to be difficult.

As described above, the yoke 20 forms the second R surface 77 on the arm base end portion 72, so that even if the width dimension W1 of the relief portion 73 is reduced, the stress generated on the first R surface 76 is increased. It can be suppressed. As a result, the yoke 20 can maintain the strength of the yoke 20 even if the distance I between the two seating surfaces 61 formed on both sides of the arm 70 is reduced, and the universal joint 1 is compact while maintaining the strength. Can be achieved.

Subsequently, the relationship between the radius of curvature of the first R surface 76 and the stress generated on the first R surface 76 and the second R surface 77 will be described with reference to the graph shown in FIG. In the graph shown in FIG. 4, the radius of curvature R1 of the first R surface 76 is set to 1 mm, 2.5 mm, using yokes 20 having different heights H from one surface side of the yoke base 60 to the central axis O of the bearing hole 21. The measurement results of the stress generated on the first R surface 76 and the second R surface 77 when set to 4 mm, 5.5 mm and 7 mm, respectively, are shown. The vertical axis of the graph shown in FIG. 4 is the ratio of the stress generated on the first R surface 76 to the stress generated on the second R surface 77 (hereinafter, simply referred to as “stress ratio”), and the value on the vertical axis is The closer it is to 1, the more the stress generated in the relief portion 73 is shown to be evenly dispersed in the first R surface 76 and the second R surface 77.

Of the four graphs shown in FIG. 4, the graph shown on the upper left shows the results of measurement with the height H from one surface side of the yoke base 60 to the central axis O of the bearing hole 21 set to 23 mm. The graph shown in the upper right has a height H of 25 mm, the graph shown in the lower left has a height H of 27 mm, and the graph shown in the lower right has a height H of 29 mm. show. Further, in the four graphs, the measurement results using the yoke 20 having the radius of curvature R2 of the second R surface 77 as 3 mm are shown for each value of R1 / W1. In addition to this, in the graph shown in the upper left and the graph shown in the lower right, the radius of curvature R1 of the first R surface 76 is 2.5 mm (R1 / W1 = 0.09) and 7 mm (R1 / W1 = 0.35). ), The measurement result using the yoke 20 in which the radius of curvature R2 of the second R surface 77 is set to 2 mm and 5 mm is also shown.

As shown in FIG. 4, the stress ratio of the yoke 20, which is 0.03 of the value of R1 / W1, exceeds 3 regardless of the value of the height H. That is, in the yoke 20 having a value of R1 / W1 of 0.03, the stress generated in the relief portion 73 was concentrated on the first R surface 76, and the stress was not sufficiently dispersed on the second R surface 77. Is shown. It is considered that this is because the absolute value of the radius of curvature R1 of the first R surface 76 is small and the radius of curvature R1 of the first R surface 76 is smaller than the radius of curvature R2 of the second R surface 77.

The stress ratio of the yoke 20 which is 0.09 of the value of R1 / W1 is higher than the stress ratio of the yoke 20 which is 0.03 of the value of R1 / W1 regardless of the value of the height H. Also became smaller. This is because the radius of curvature R1 of the first R surface 76 is larger and the stress concentration on the first R surface 76 is reduced in comparison with the yoke 20, which has a value of R1 / W1 of 0.03. Is mentioned as.

Further, the stress ratio of the yoke 20 which is 0.09 of the value of R1 / W1 is less than 2 when taking any value of H = 23 mm, 25 mm and 27 mm, while the height H is H = 29 mm. The stress ratio at the time is much higher than 2. It is considered that the larger the height H, the easier it is for stress to concentrate on the first R surface 76. Therefore, the yoke 20 having a value of R1 / W1 of 0.09 is generated in the relief portion 73 when the height H is 27 mm or less in comparison with the yoke 20 having a value of R1 / W1 of 0.03. It is considered that there is an effect of dispersing the stress to be applied to the first R surface 76 and the second R surface 77.

In the yoke 20 having a height H of 29 mm and a value of R1 / W1 of 0.09, the yoke 20 having a radius of curvature R2 of the second R surface 77 of 5 mm has a radius of curvature R2 of the second R surface 77 of 2 mm or The stress ratio was larger than that of the yoke 20 having a radius of 3 mm. On the other hand, in the yoke 20 having a height H of 23 mm and a value of R1 / W1 of 0.09, the difference in the radius of curvature R2 of the second R surface 77 had almost no effect on the stress ratio. This is because, as the height H increases, the stress tends to concentrate on the first R surface 76, and the radius of curvature R2 of the second R surface 77 is increased, so that the stress generated in the relief portion 73 becomes the first. It is considered that the degree of stress concentration on the first R surface 76 increased as a result of the difficulty in being dispersed on the second R surface 77.

The stress ratio of the yoke 20, which is the value of R1 / W1 of 0.14, 0.24 or 0.35, is 0.09 of the value of R1 / W1 regardless of the value of the height H. The value was closer to 1 than the stress ratio of the yoke 20. At this point, when the radius of curvature R1 of the first R surface 76 becomes a certain size or more, it is estimated that the radius of curvature R1 is substantially close to 1. Specifically, when the ratio of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73 is 0.14 or more, the yoke 20 applies the stress generated in the relief portion 73 to the first R surface 76. It can be inferred that it can be dispersed almost evenly on the second R surface 77.

The yoke 20, which has a value of R1 / W1 of 0.35, has almost no effect on the stress ratio due to the difference in the radius of curvature R2 of the second R surface 77 even when the heights H are 23 mm and 29 mm. I couldn't see it. This is because the absolute value of the radius of curvature R1 of the first R surface 76 is large, and the radius of curvature R1 of the first R surface 76 is larger than the radius of curvature R2 of the second R surface 77, so that the stress generated in the relief portion 73 is generated. Is more likely to be dispersed on the second R surface 77.

In this way, the universal joint 1 forms the arm base end portion 72 so that the ratio of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73 is 0.09 or more. As a result, even if the width dimension of the relief portion 73 is reduced in the arm 70, the stress generated in the relief portion 73 is dispersed in the second R surface 77, so that the stress generated in the first R surface 76 increases. Can be suppressed. Then, in the universal joint 1, the ratio of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73 is set to 0.14 or more, so that the stress generated in the relief portion 73 is set to the first R surface 76. It can be more evenly dispersed with respect to the second R surface 77. As a result, the universal joint 1 can maintain the strength of the yoke 20 and reduce the size at the same time.

Further, it is desirable to set the ratio of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73 to 0.35 or less. That is, when the ratio of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73 exceeds 0.35, the width dimension W1 of the relief portion 73 becomes excessively small, and the rigidity of the arm base end portion 72 is reduced. It will not be possible to secure enough. Therefore, the arm 70 can maintain the strength of the arm 70 by setting the ratio of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73 to 0.35.

Further, since the width dimension W1 of the relief portion 73 of the arm 70 is set to be smaller than the maximum width dimension W2 of the arm tip portion 71 seen from the central axis O direction of the bearing hole 21, the nut 4 (FIG. 1A). A gap can be provided between the relief portion 73 and the relief portion 73). Therefore, the universal joint 1 can improve the work efficiency when fixing the yoke 20 to the end surface 2a of the drive shaft 2 or the end surface (not shown) of the driven shaft.

In addition to this, the distance I between the seat surface portions 61 formed on both sides of the arm 70 in the width direction when viewed from the central axis O direction of the bearing hole 21 may be larger than the maximum width dimension W2 of the arm tip portion 71. desirable. As a result, the yoke 20 can easily avoid interference between the tool used when tightening the nut to the bolt from one side of the yoke base 60 and the yoke 20. Therefore, the universal joint 1 can improve the work efficiency when fixing the yoke 20 to the end surface 2a of the drive shaft 2.

As described above, since the arm base end portion 72 includes the first R surface 76 and the second R surface 77, the yoke 20 causes the stress generated in the relief portion 73 to be the first R surface 76 and the second. It can be dispersed on the second R surface 77. Therefore, the yoke 20 can suppress an increase in stress generated on the first R surface 76 even if the width dimension W1 of the relief portion 73 is reduced.

Further, the yoke 20 forms the arm base end portion 72 so that the ratio of the radius of curvature R1 of the first R surface 76 to the width dimension W1 of the relief portion 73 is 0.14 or more. In this case, since the yoke 20 can evenly disperse the stress generated in the relief portion 73 with respect to the first R surface 76 and the second R surface 77, the universal joint 1 increases the strength of the yoke 20. The size of the yoke 20 can be reduced while maintaining the size.

(3. Others)
Although the present invention has been described above based on the above embodiment, the present invention is not limited to the above embodiment, and it is easy that various modifications and improvements can be made without departing from the spirit of the present invention. It can be inferred from.

For example, in the above embodiment, when the yoke 20 is fixed to the end surface 2a of the drive shaft 2, the bolt 3 is inserted into the bolt hole 62 from the drive shaft 2 side, and the nut 4 is screwed into the bolt 3 from the yoke 20 side. The case has been described, but it is not limited to this. That is, when fixing the yoke 20 to the end surface 2a of the drive shaft 2, the bolt 3 may be inserted into the bolt hole 62 from the yoke 20 side, and the nut 4 may be screwed into the bolt 3 from the drive shaft 2 side.

1: Universal joint, 2: Drive shaft, 3: Bolt (part of fastening member), 4: Nut (part of fastening member), 10: Cross shaft member, 12: Shaft, 20: York, 21: Bearing Hole, bearing cup, 60: yoke base, 61: seat surface, 70: arm, 71: arm tip, 72: arm base end, 73: relief, 74: first connection, 75: second connection , 76: 1st R surface, 77: 2nd R surface, I: Spacing of bearing surfaces formed on both sides in the width direction across the arm, O: Central axis of the bearing hole, R1: Radius of curvature of the 1st R surface , W1: Width dimension of relief part, W2: Maximum width dimension of arm tip

Claims (2)

A cross-shaped shaft member having four shafts protruding in a cross shape,
A pair of yokes swingably connected to the shaft portion,
It is a universal joint equipped with
The yoke is
A yoke base fixed by a fastening member to the end face of the drive shaft or driven shaft,
A pair of arms having bearing holes formed through the shaft portion so as to be a portion protruding from one surface side of the yoke base portion in a bifurcated manner.
Equipped with
The yoke base portion is provided on both sides in the width direction of the arm as viewed from the central axis direction of the bearing hole, and includes a flat surface-shaped seating surface portion that serves as a seating surface for the fastening member.
The arm
Of the bearing holes, the arm tip portion forming the tip side of the arm in the protruding direction and the arm tip portion.
Of the bearing holes, the arm base end portion forming the protrusion direction base end side of the arm, and
Equipped with
The base end of the arm
A relief portion whose width dimension seen from the center axis direction of the bearing hole is smaller than the maximum width dimension of the arm tip portion seen from the center axis direction of the bearing hole.
A first connecting portion having an arcuate first R surface formed on both side surfaces in the width direction when viewed from the central axis direction of the bearing hole, which is a portion connecting the yoke base portion and the relief portion.
A portion that connects the tip of the arm and the relief portion, and has a second connecting portion having an arcuate second R surface formed on both side surfaces in the width direction when viewed from the central axis direction of the bearing hole. ,
Equipped with
The ratio of the radius of curvature of the first R surface to the width dimension of the relief portion is 0.14 or more .
A universal joint in which the distance between the seating surfaces formed on both sides of the arm in the width direction is larger than the maximum width dimension of the arm tip . The universal joint according to claim 1, wherein the ratio of the radius of curvature of the first connecting portion to the lateral width dimension of the relief portion is 0.35 or less.

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