JP4962037B2 - Universal joint, steering device using the same, and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a universal joint capable of preventing occurrence of large stress concentration in transmitting torque even when a connection hole formed with a spline, serration or the like is provided at a shaft connection position: and a steering device and an electric power steering device using it. <P>SOLUTION: This universal joint 17A is composed of a pair of yokes each formed into a U-shaped form by a pair of arm parts and a connection part connecting the arm parts to each other, and connected to a shaft, and a joint cross connecting the pair of yokes. The shape of a connection hole 23d to the shaft 21 formed on a connection part 23c at least in one-side yoke 23 is set at a rate of shape change suppressing stress concentration in high-stress regions A1-A4 in the vicinities of virtual lines L1-L4 deflected by 45&deg; with respect to both coordinate axes in an X-Y coordinate system using, as the coordinate axes, a first line connecting center parts of the pair of arm parts 23a and 23b to each other by passing through the center of the connection hole, and a second line orthogonal to the first line by passing through the center of the connection hole. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention comprises a pair of arm portions connected to a shaft, a pair of yokes formed in a U shape by a connecting portion connecting these arm portions, and a cross shaft connecting the pair of yokes. The present invention relates to a universal joint, a steering device using the same, and an electric power steering device.

As this kind of universal joint, for example, the cross shaft coupling member and the shaft coupling member constituting the first and second yokes are joined to each other by welding without forming through holes, spline teeth, or bolt holes. After this welding, through holes, spline teeth, and bolt holes are formed in the cross shaft coupling member and the shaft coupling member, and distortion caused by welding causes the relative positions of the through holes, spline teeth, and bolt holes to be distorted. There has been proposed a method for manufacturing a universal joint (see, for example, Patent Document 1).
JP-A-5-87152 (first page, fourth page, FIG. 1, FIG. 2, FIG. 4)

  However, in the conventional example described in Patent Document 1, when a universal joint is used in a steering device, a steering assist mechanism that applies a steering assist force to the column side is provided due to the recent development of an electric power steering device. The number of examples increases, and when a universal joint is provided on the steering shaft that transmits torque from the column side to the steering gear mechanism, the universal joint is required to have a high torque transmission function.

  Since the high torque transmission function of this universal joint is required, the stress generated in the yoke naturally increases. For this reason, as shown in FIGS. 17 and 18, a yoke 2 formed in a U-shape by a pair of arm portions 1a and 1b separated by a predetermined distance and a connecting portion 1c connecting the arm portions 1a and 1b. When the connecting hole 3 for connecting the shaft to the connecting portion 1c is formed, the portion where the maximum stress is generated is the base of the arms 1a and 1b, but the connecting portion 1c is also deformed along with the deformation of the arms 1a and 1b. The arm 1a, 1b side of the connecting hole 3 is deformed into an ellipse as shown in FIG. That is, the first line passing through the central part of the arms 1a and 1b and the central point of the connecting hole 3 is defined as the Y axis, and the second line passing through the central point of the connecting hole 3 and orthogonal to the first line is also defined. In the XY coordinate system as the X axis, an axis shifted by 45 degrees with respect to both coordinate axes is transformed into an ellipse having major axes L1, L3 and minor axes L2, L4, and the portions in contact with the minor axes L2, L4 are high. When a spline or serration is formed at this position, a greater stress concentration occurs. Since the rotation direction is forward and backward, there is an unsolved problem that there are four stress concentration sites.

  Therefore, the present invention has been made paying attention to the unsolved problems of the above-mentioned conventional example, and even when a connecting hole in which splines, serrations, etc. are formed at the shaft coupling position, a large stress concentration occurs during torque transmission. It aims at providing the universal joint which can suppress this, a steering device using the same, and an electric power steering device.

In order to achieve the above object, a universal joint according to a first aspect of the present invention includes a pair of yokes formed in a U shape and connected to a shaft by a pair of arm portions and a connecting portion connecting the arm portions, A universal joint composed of a cross shaft for connecting a pair of yokes, wherein the shape of the connecting hole with the shaft formed in the connecting part of at least one of the yokes is between the central parts of the pair of arm parts. A coordinate system having a first line connecting through the center of the connecting hole and a second line passing through the center of the connecting hole and perpendicular to the first line as coordinate axes, and 45 with respect to both coordinate axes. The shape change rate that suppresses stress concentration is set in a high stress region near the imaginary line that is deviated, and the connection hole is one of a serration hole and a spline hole, and the serration hole and spline in the high stress region Any one of the holes There has been characterized in that it is set to the missing tooth has been values shape change rate is small.

The universal joint according to claim 2 is characterized in that, in the invention according to claim 1, the shape having a shape change rate for suppressing stress concentration is one of a linear shape and an arc shape having a large curvature radius. It is said.
Furthermore, the universal joint according to claim 3 is the invention according to claim 1 or 2, wherein the region in the vicinity of the virtual line is each region in four quadrants divided by the first line and the second line in the coordinate system. In the range of ± 15 degrees across the virtual line.

Furthermore, the universal joint according to 請 Motomeko 4, in the invention according to any one of claims 1 to 3, it repeatedly seating in the end surfaces of the pair of arm side of the serration hole and the spline hole is formed It is characterized by.

The steering apparatus according to 請 Motomeko 5 is characterized in that using a universal joint according to any one of claims 1 to 4.

In addition, the electric power steering apparatus according to claim 6, the output of the steering assist mechanism for generating a steering assist force to the universal joint to a steering system provided on the steering column according to any one of claims 1 to 4 It is characterized by being interposed between the shaft and the steering gear mechanism.

According to the present invention, since the shape change rate that suppresses the stress concentration of the connecting hole with the shaft is set in the high stress region where the stress is easily concentrated during the torque transmission of the connecting portion in the yoke, the stress concentration in the high stress region is reduced. In addition to improving the durability of the universal joint by suppressing it, it is possible to achieve smooth torque transmission by suppressing torsion during high torque transmission.
In addition, when the universal joint according to the present invention is applied to a steering device, it is possible to improve the durability of the steering device itself and to improve the steering feeling.

  Furthermore, when applied to a steering apparatus equipped with a column-type electric power steering apparatus according to the present invention, even if a larger torque is transmitted, the torsion is suppressed and the steering feeling is improved without affecting the durability. The effect of being able to be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an embodiment when the universal joint of the present invention is applied to an electric power steering apparatus, an enlarged longitudinal sectional view of an intermediate shaft, and FIGS. 3 and 4 are side views showing a yoke of the universal joint. FIG. 5 is a side view of the yoke schematically showing a connecting hole showing a high stress portion during high torque transmission.

  In the figure, reference numeral 2 denotes a steering shaft having a steering wheel 1 mounted at the rear end (right end in FIG. 1). The steering shaft 2 is rotatably held by a steering column 3. A front end (left end in FIG. 1) of the steering shaft 2 includes a worm speed reducer 11 that applies a steering assist torque to the steering shaft 2 and an electric motor 12 that generates the steering assist torque in the worm speed reducer 11. A steering assist mechanism 4 is connected.

An intermediate shaft 18 is connected to the output shaft 14 of the worm reducer 11 via a universal joint 17A, and this intermediate shaft 18 is connected to a pinion shaft 19 of the rack and pinion type steering gear mechanism 6 via a universal joint 17B. ing.
A rack shaft (not shown) of the steering gear mechanism 6 is connected to a steered wheel (not shown) via a tie rod 5.

Here, the steering shaft 2 includes an outer shaft 7 and an inner shaft 8, and the front end portion of the outer shaft 7 and the rear end portion of the inner shaft 8 are spline-coupled and are coupled via a synthetic resin. . Therefore, the outer shaft 7 and the inner shaft 8 can shorten the total length by breaking the synthetic resin at the time of collision.
Further, the cylindrical steering column 3 inserted through the steering shaft 2 is formed by combining the outer column 9 and the inner column 10 in a telescope shape, and absorbs energy caused by the impact when an axial impact is applied. However, it has a so-called collapsible structure in which the overall length is reduced.

The front end portion of the inner column 10 is fixed to the rear end surface of the housing 11a of the worm speed reducer 11, the inner shaft 8 is inserted into the housing 11a of the worm speed reducer 11, and the front end portion of the inner shaft 8 is The shaft 14 projects from the front end surface of the housing 11a of the speed reducer 11.
The outer column 9 of the steering column 3 is supported on the vehicle body side member 16 by the upper bracket 15U so that the tilt and telescopic position can be adjusted, and the housing 11a of the worm speed reducer 11 in the steering assist mechanism 4 is attached to the vehicle body side member 16. A pivot pin 15p pivotally supported by the attached lower bracket 15L is supported so as to be swingable in the vertical direction.

As shown in FIG. 2 showing the longitudinal sectional view of the intermediate shaft 18, a male shaft 21 connected to the universal joint 17A and a female connected serrated to the outer peripheral side of the male shaft 21 and connected to the universal joint 17B. A shaft 22 is provided.
Here, as shown in FIG. 2, the universal joint 17 </ b> A includes a pair of yokes 23 and 24 and a cross shaft 25 that connects the pair of yokes 23 and 24. The yoke 23 is formed in a U shape by a pair of arm portions 23a and 23b and a connecting portion 23c that connects the base portions of the arm portions 23a and 23b. Further, as shown in FIG. 3 showing a side view of the yoke 23, a connecting hole 23d is formed through the connecting portion 23c at the center position. On the inner peripheral surface of the connecting hole 23d, a first line connecting the center portions of the pair of arm portions 23a and 23b through the center of the connecting hole 23d is defined as a Y axis, and is orthogonal to the first line. In the XY coordinate system having the second line passing through the center of the connecting hole 23d as the X axis, the vicinity of the virtual lines L1 to L4 shifted by 45 degrees with respect to the XY coordinate axes in the first to fourth quadrants, for example, the virtual lines L1 to L1 If the range of ± 15 ° counterclockwise and clockwise, ie, the X axis is 0 ° across L4, the range of 30 ° -60 ° in the first quadrant, the range of 120 ° -150 ° in the second quadrant, Serration holes SH1 to SH4 are formed in regions excluding the high stress regions A1 to A4 set in the range of 210 ° to 240 ° in the three quadrants and in the range of 300 ° to 330 ° in the fourth upper limit, and the high stress regions A1. ~ A4, the shape change rate will be a small value to suppress stress concentration For example, cylindrical inner surfaces CI1 to CI4 are formed around the center point of the connection hole 23d.

  Serration shaft portions SS1 to SS4 meshing with serration holes SH1 to SH4 of the connection hole 23d of the male shaft 21, which will be described later, and cylindrical outer peripheral surfaces CO1 to CO4 engaged with the cylindrical inner peripheral surfaces CI1 to CI4. The connecting shaft portion 21c having the above is connected. And the connection part 23c and the connection shaft part 21c are integrally connected by fixing means, such as welding and caulking, for example.

Similarly to the yoke 23, the other yoke 24 is also formed in a U-shape with a pair of arm portions 24a and 24b and a connecting portion 24c connecting the base portions of the arm portions 24a and 24b. The output shaft 14 of the speed reducer 11 is clamped by a bolt 27.
Further, as shown in FIG. 2, the cross shaft 25 includes a body portion 25 a and four shaft portions 25 b formed on the body portion in a cross shape. Each shaft portion 25b has a spider pin 25c embedded at the tip thereof at the center axis position, a needle bearing 25d disposed on the outer peripheral surface, and a bearing cup 25e disposed so as to cover the spider pin 25c and the needle bearing 25d. It is installed. Each shaft portion 25b of the cross shaft 25 is inserted into a bearing cup insertion hole 26 formed in the arm portions 23a, 23b and 24a, 24b of the yokes 23 and 24.

On the other hand, the universal joint 17B has the same configuration as the universal joint 17A. The yoke 23 is connected to the female shaft 22 of the intermediate shaft 18, the yoke 24 is connected to the pinion shaft 19 of the steering gear mechanism 6, and these yokes. And a cross shaft 25 for connecting 23 and 24.
Further, as shown in FIG. 2, the male shaft 21 has a small-diameter central shaft portion 21a, a serration shaft portion 21b formed larger in diameter than the central shaft portion 21a formed at the left end thereof, and a connecting shaft formed at the right end. Part 21c. The serration shaft portion 21b is formed with a relatively long axial length, and the connecting shaft portion 21c is formed with a relatively short axial length. As described above, the serration shaft portions SS1 to SS4 and the cylindrical outer peripheral surfaces CO1 to CO4 shown in FIG. 3 are formed on the connecting shaft portion 21c.

  Further, the female shaft 22 is formed in a cylindrical shape, and a serration hole 22a is formed over the entire inner peripheral surface thereof. The left end outer peripheral surface of FIG. 2 has a yoke of the universal joint 17B as shown in FIG. Serration shaft portions SS1 to SS4 meshing with serration hole portions SH1 to SH4 formed in the connection hole 23d of the cylinder 23, and cylindrical outer peripheral surfaces CO1 to CO4 engaged with the cylindrical inner peripheral surfaces CI1 to CI4 having a small shape change rate. A connecting shaft portion 22b is formed. Then, the serration shaft portions SS1 to SS4 of the connection shaft portion 22b are engaged with the serration holes SH1 to SH4 in the connection hole 23d of the yoke 23 of the universal joint 17B, and the cylindrical outer peripheral surfaces CO1 to CO4 of the connection shaft portion 22b are connected to the connection holes. As shown in FIG. 2, the connecting shaft portion 22b and the connecting portion 23c are connected to each other by fixing means such as welding or caulking in a state of being engaged with the cylindrical inner peripheral surfaces CI1 to CI4 of 23d.

Next, the operation of the first embodiment will be described.
Now, when the driver steers the steering wheel 1, the steering torque transmitted to the steering wheel 1 is detected by a steering torque sensor (not shown), and the vehicle speed is detected by a vehicle speed sensor (not shown), based on the steering torque and the vehicle speed. A drive assist control device (not shown) drives and controls the electric motor 12 so as to generate an optimum steering assist force in the steering state.

  Therefore, the steering assist force generated by the electric motor 12 is transmitted to the steering shaft 2 via the worm speed reducer 11. By transmitting the steering assist force to the steering shaft 2 in this way, a large steering torque is output from the output shaft 14 of the worm speed reducer 11, which is the steering gear via the universal joint 17A, the intermediate shaft 18 and the universal joint 17B. It is transmitted to the pinion shaft 19 of the mechanism 6. In the steering gear mechanism 6, the rotational motion transmitted to the pinion shaft 19 is converted into a linear motion in the vehicle width direction by a pinion constituting the steering gear and a rack meshing with the pinion, and is converted into a steered wheel (not shown) via the tie rod 5. This is transmitted to steer this steered wheel.

At this time, since the optimum steering assist force corresponding to the steering torque transmitted to the steering wheel 1 is generated by the electric motor 12 of the steering assist mechanism 4, the steering wheel 1 can be lightly steered.
As described above, since the steering assist mechanism 4 is provided on the output side of the steering column 3, a large steering torque acts on the output shaft 14 of the worm speed reducer 11, and this large steering torque is applied to the universal joint 17A. And 17B and the intermediate shaft 18 are transmitted to the steering gear mechanism 6.

  For this reason, as described above, a torsional force acts on the arm portions 23a and 23b of the yoke 23 of the universal joints 17A and 17B connected to both ends of the intermediate shaft 18. Thereby, for example, when the steering wheel 1 is turned to the right, the connecting hole 23d of the connecting portion 23c of the yoke 23 is shown in FIG. 5 schematically showing the connecting hole 23d by the torque in the arrow Z direction. The virtual lines L1 and L3 in the system are deformed into an elliptical shape having the major axes as the virtual axes L2 and L4, and the positions of the virtual lines L2 and L4 of the connecting hole 23d become the high stress part HS. At this time, as shown in FIG. 3, serration holes SH1 to SH4 having a large shape change rate are missing in the high stress regions A2 and A4 including the virtual lines L2 and L4 of the connection hole 23d corresponding to the high stress portion HS. Since the cylindrical inner peripheral surfaces CI2 and CI4 are centered on the center point of the connecting hole 23d having a small shape change rate, the concentration of stress on the cylindrical inner peripheral surfaces CI2 and CI4 is surely suppressed. In addition to improving durability, it is possible to prevent a phase shift due to torsion between the yoke 23 and the male shaft 21 of the intermediate shaft 18 connected thereto, thereby changing the steering feeling. Can be prevented.

In the first embodiment, the case has been described in which the serration hole portion is missing in the high stress regions A1 to A4 to form a circular arc surface with a small shape change rate that suppresses stress concentration. However, the present invention is not limited to this. Instead of a circular arc surface, it may be a straight line orthogonal to the imaginary lines L1 to L4, or a curved line wavy with a small shape change rate.
Moreover, in the said 1st Embodiment, although the case where it set to the range of +/- 15 degree which pinches | interposes virtual lines L1-L4 as high stress area | region A1-A4 was demonstrated, it is not limited to this, virtual Only the region near the lines L1 to L4, particularly the region where the stress concentration is large, may be missing, and the inner peripheral surface having a small shape change rate may be formed. Conversely, the high stress regions A1 to A4 are replaced with the virtual line L1. May be set to be larger than the range of ± 15 ° across L4, and the serration hole SH1 to the extent that the maximum steering torque can be transmitted by serration coupling between the serration holes SH1 to SH4 and the serration shaft portions SS1 to SS4. -SH4 formation region can be narrowed.

  Furthermore, in the first embodiment, the case where the serration holes SH1 to SH4 are formed in the connecting hole 23d has been described. However, the present invention is not limited to this, and instead of the serration holes SH1 to SH4, spline holes are provided. In this case, spline shaft portions may be formed on the male shaft 21 and the female shaft 22 instead of the serration shaft portions SS1 to SS4.

Next, a second embodiment of the present invention will be described with reference to FIG.
In the second embodiment, the stress concentration in the high stress region is suppressed by reducing the thickness of the high stress region to make it easy to twist.
On the other hand, in the second embodiment, the yoke 23 of the universal joint 17A (or 17B) is shown in FIGS. 6A and 6B which are a longitudinal sectional view and an arrow view seen from the direction of the arrow H. As shown, the serration hole SH0 is formed over the entire inner periphery of the connection hole 24d of the connection part 23c, and the counterbore having an inner diameter larger than the inner diameter of the connection hole 23d is formed on the arm 23a and 23b side end surfaces of the connection hole 24d. Except that the hole 30 is formed, it has the same configuration as that of the first embodiment described above.

  According to the second embodiment, the serration hole SH0 is formed on the inner peripheral surface of the connection hole 23d in the connection part 23c of the yoke 23 over the entire circumference, and the arm parts 23a and 23b side of the connection hole 23d. Since the countersink hole 30 having an inner diameter larger than the inner diameter of the connection hole 23d is formed on the end face, the thickness around the connection hole 23d in the connection part 23c is reduced by the depth of the countersink hole 30. An imaginary line L2 when the periphery of the connecting hole 23d is easily deformed and the steering wheel 1 is turned to the right when the periphery is easily deformed and a torsional force due to the steering torque is applied to the arm portions 23a and 23b of the yoke 23. And high stress areas A2 and A4 in the vicinity of L4, and high stress areas A1 and A3 in the vicinity of virtual lines L1 and L3 when the steering wheel 1 is turned to the left. There it is possible to suppress the occurrence.

As a result, durability can be improved, and a phase shift due to torsion between the yoke 23 and the male shaft 21 of the intermediate shaft 18 connected to the yoke 23 can be prevented, thereby changing the steering feeling. Can be prevented.
In the second embodiment, the case where the serration hole SH0 is formed on the inner peripheral surface of the connection hole 23d over the entire circumference has been described. However, the present invention is not limited to this, and the serration hole SH0 is formed in the serration hole SH0. Instead, a spline hole may be formed.

Moreover, in the said 2nd Embodiment, although the case where the serration hole SH0 was formed over the perimeter of the internal peripheral surface of the connection hole 23d was demonstrated, it is not limited to this, The 1st mentioned above Similarly to the embodiment, the stress concentration may be further suppressed by reducing the shape deformation rate by setting the high-stress regions A1 to A4 as missing teeth.
Next, a third embodiment of the present invention will be described with reference to FIG. 7 showing a side view of a yoke.

  In the third embodiment, the connecting hole 23d formed in the connecting portion 23c of the yoke 23 has a two-sided width shape, and the linear inner peripheral surfaces LI1 and LI2 that are parallel to each other by a predetermined distance, and these inner peripheral surfaces LI1 and The boundary portions BP1 to BP4 having a large shape change rate at the connecting positions with the arcuate inner peripheral surfaces CI1 and CI2 connecting between the end portions of the LI2 are regions deviated from the high stress regions A1 to A4 in the first embodiment described above. Except that the connecting shaft portion 21c of the male shaft 21 or the connecting shaft portion 22b of the female shaft 22 has a two-face width shape that can be inserted into the connecting hole 23d. It has the same configuration as the embodiment.

According to the third embodiment, the connecting hole 23d of the yoke 23 constituting the universal joints 17A and 17B is formed in a two-sided width shape, and the connecting shaft portion 21c of the male shaft 21 or the female shaft is connected to the connecting hole 23d. Since the shaft portion 22b is inserted, it is possible to reliably transmit the steering torque between the male shaft 21 or the female shaft 22 and the yoke 23.
Further, the boundary portions BP1 to BP4 between the linear inner peripheral surfaces LI1 and LI2 and the arcuate inner peripheral surfaces CI1 and CI2 having a large shape change rate in the two-surface-width connecting hole 23d are out of the high stress regions A1 to A4. Therefore, the stress can be reliably prevented from concentrating on the boundary portions BP1 to BP4, the durability can be improved, and the yoke 23 and the intermediate shaft 18 connected thereto can be improved. It is possible to prevent a phase shift due to torsion between the male shaft 21 and the male shaft 21, thereby preventing a change in steering feeling.

  In the third embodiment, the case where the connecting hole 23d in the connecting portion 23c of the yoke 23 has a two-sided width shape has been described. However, the present invention is not limited to this, and although not illustrated, the straight portion LI1 and LI2 has an oval shape formed in an arc shape, a rectangular shape as shown in FIG. 8 showing a side view of the yoke, or a regular octagonal shape as shown in FIG. 9 showing a side view of the yoke. In any shape, by setting the boundary portions BP1 to BP4 between the straight portions where the shape change rate is large to deviate from the high stress regions A1 to A4, stress concentration is caused in the high stress regions A1 to A4. It is possible to suppress the occurrence and improve the durability, and the phase shift caused by the twist between the yoke 23 and the male shaft 21 or the female shaft 22 of the intermediate shaft 18 connected thereto. It is possible to prevent occurring, it is possible to prevent a change in the steering feeling.

  Next, a fourth embodiment of the present invention will be described with reference to FIGS. Here, FIG. 10 is a view showing the yoke, wherein (a) and (b) are a front view and a side view in cross section of the upper half portion showing the yoke after hot forging, and (c) is an arm portion. FIG. 11 is a side view showing the assembled state after cutting. FIG. FIG. 12 is an enlarged side view, FIG. 12 is a view showing a conventional yoke, and (a) and (b) are a front view and a side view with the upper half section showing the yoke after hot forging as a cross section, and (c). FIG. 13 is a side view showing an assembled state after cutting the arm portion, and FIG. 13 is a side view showing a cross section of the lower arm portion for explaining the problems of the conventional example.

In the fourth embodiment, the bearing cup insertion holes in the yokes of the universal joints 17A and 17B are reinforced.
That is, in the fourth embodiment, when forming the yoke 24 of the universal joints 17A and 17B by hot forging, as shown in FIGS. 10A and 10B, the arm portion of the yoke 24 shown in FIG. In order to reinforce the mechanical strength of the bearing cup insertion hole 26 through which the bearing cup 25e of the cross shaft 25 formed on the distal end side of 24a and 24b is inserted, the bearing cup insertion in both arm portions 24a and 24b at the end of hot forging. The wall around the hole 26 is formed thicker.

  Here, as shown in FIG. 11, in consideration of the draft angle of hot forging, the opposing surfaces of the arm portions 24a and 23b are connected to the outer end portion of the seal ring 25f of the cross shaft 25 from the center point O of the connecting hole 25d. In order to form a flat surface that maintains the dimension C, which is obtained by adding the dimension B required to avoid the contact between the seal ring 25f and the inner surfaces of the arm portions 24a and 24b and to ensure the sealing performance. In addition, the dimension from the both end positions in the width direction of the arm portions 24a and 24b to the center point O of the connecting hole 25d when the draft angle (about 5 °) in hot forging is formed is the dimension C described above. The arms 24a and 24b are hot forged to a large thickness (see FIGS. 10A and 10B).

Thereafter, as shown in FIG. 10 (c), the outer end surfaces and the inner end surfaces of the arm portions 24a and 24b are each cut so as to cut out portions where draft angles are formed, and finished to a flat surface.
By this cutting, the maximum thickness of the arm portions 24a and 24b can be ensured in the entire region, and the mechanical strength around the bearing cup insertion hole 26 of the arm portions 24a and 24b can be ensured. .

  Incidentally, conventionally, as shown in FIGS. 12A to 12C, the outer end surfaces of the arm portions 24a and 24b are cut to cut the draft portion, but the inner end surfaces are cut. Since the hot forging is maintained, the dimension C is the dimension from the apex position of the draft (about 5 °) to the center point of the connecting hole 24d as shown in FIG. The thicknesses of the inner end surfaces of the arm portions 24a and 24b decrease from the apex position of the draft angle to both sides in the width direction due to the draft, and the minimum thickness D of the left and right ends of the arm parts 24a and 24b is There is an unsolved problem that the mechanical strength around the bearing cup insertion hole 26 is reduced due to the thinning.

  However, in the above-described fourth embodiment, the dimension between the flat surface after cutting after cutting the draft and the center point of the connecting hole 24d is set to the dimension C. As shown by the hatched area in FIG. 11, the thickness can be increased compared to the conventional example, and the mechanical strength around the bearing cup insertion hole 26 can be sufficiently secured.

  In the fourth embodiment, the case where a draft of about 5 ° is formed at the time of hot forging has been described. However, the present invention is not limited to this, and FIG. 14A similar to FIG. As shown in (c) to (c), the inner and outer peripheral surfaces of the arm portions 24a and 24b can be replaced with draft angles to form cylindrical surfaces 24f and 24g having relatively large curvatures. In this case, when the outer dimensions of the arm portions 24a and 24b are not restricted, the outer end surfaces of the arm portions 24a and 24b are not cut, and the counterbore hole 40 is formed at the outer end surface position of the bearing cup insertion hole 26. The dimension E between the bottoms of the counterbore holes 40 (see FIG. 14 (b)) is such that the bearing cup 25e is added by the caulking portion 24h as shown in FIG. When tightening, the required dimension is set to be longer than the required dimension F between the end faces of the bearing cup 25e of the cross shaft 25 (see FIG. 14C). Thus, by leaving the outer end surfaces of the arm portions 24a and 24b as the cylindrical surface 24g, the thickness of the arm portions 24a and 24b can be increased by the rising amount of the cylindrical surface 24g, and the mechanical strength of the arm portions 24a and 24b is increased. Strength can be improved.

  In the first to fourth embodiments, the case where the universal joints 17A and 17B according to the present invention are applied to the electric power steering apparatus has been described. However, the present invention is not limited to this, and the entire configuration of the steering apparatus. As shown in FIG. 16, the present invention can also be applied to a normal steering device in which the steering assist mechanism 4 is omitted and the steering shaft 2 is directly connected to the universal joint 17A. The universal joints 17A and 17B of the present invention can be applied to any power transmission device incorporated.

It is a whole block diagram at the time of applying this invention to an electric power steering device. It is a longitudinal cross-sectional view which shows the intermediate shaft to which this invention is applied. It is a side view which shows the yoke of one universal joint of FIG. It is a side view which shows the yoke of the other universal joint of FIG. It is a side view of the yoke which shows typically the connecting hole which shows the stress generation state at the time of a high torque effect | action. It is a figure which shows the yoke of the universal joint which shows the 2nd Embodiment of this invention, Comprising: (a) is a longitudinal cross-sectional view, (b) is a side view. It is a side view which shows the yoke of the universal joint which shows the 3rd Embodiment of this invention. It is a side view which shows the modification of the yoke of the universal joint which shows the 3rd Embodiment of this invention. It is a side view which shows the further another modification of the yoke of the universal joint which shows the 3rd Embodiment of this invention. It is a figure which shows the yoke which shows the 4th Embodiment of this invention, Comprising: (a) And (b) is the front view and side view which made the upper half part which shows the yoke after hot forging a cross section, (c) FIG. 4 is a side view showing an assembled state after cutting an arm part. It is a side view of the yoke which made the lower arm part for an explanation of an effect in a 4th embodiment a section. It is a figure which shows the yoke of a prior art example, Comprising: (a) And (b) is the front view and side view which made the cross section the upper half part which shows the yoke after hot forging, (c) is after cutting an arm part It is a side view which shows the assembly state of. It is a side view of the yoke which made the cross section the lower arm part for the description of the problem of a prior art example. It is a figure which shows the modification of the 4th Embodiment of this invention, Comprising: (a) And (b) is the front view and side view which made the upper half part which shows the yoke after hot forging a cross section, (c) FIG. 4 is a side view showing an assembled state after cutting an arm part. It is a bottom view of the principal part of the yoke which shows the crimping state of the cross shaft of FIG. 1 is an overall configuration diagram showing a normal steering apparatus to which the present invention can be applied. It is a perspective view which shows the twisted state at the time of the high torque transmission of a yoke. It is a side view which shows the twist state at the time of the high torque transmission of a yoke. It is a side view of the yoke which shows the stress generation state at the time of high torque action.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Steering column, 4 ... Steering assist mechanism, 6 ... Steering gear mechanism, 17A, 17B ... Universal joint, 18 ... Intermediate shaft, 21 ... Male shaft, 21c ... Connection shaft part, 22 ... Female shaft, 22b ... Connection shaft portion, 23 ... Yoke, 23a, 23b ... Arm portion, 23c ... Connection portion, 23d ... Connection hole, 24 ... Yoke, 24a, 24b ... Arm portion, 24c ... Connection portion, 24e ... Bearing cup insertion hole, 25 ... cross shaft, 25a ... needle bearing, 25b ... bearing cup, 30 ... counter bore, A1-A4 ... high stress region, L1-L4 ... virtual line, SH1-SH4 ... serration hole, CI1 -CI4 ... arc-shaped inner peripheral surface, SS1-SS4 ... serration shaft, CO1-CO4 ... arc-shaped outer peripheral surface

Claims (6)

A universal joint comprising a pair of yokes formed in a U shape by a pair of arm portions and a connecting portion connecting these arm portions and connected to a shaft, and a cross shaft connecting the pair of yokes. And
The first line connecting the center of the pair of arm portions through the center of the connection hole and the center of the connection hole, the shape of the connection hole with the shaft formed in the connection portion in at least one of the yokes A shape change that suppresses stress concentration in a high-stress region in the vicinity of an imaginary line shifted by 45 degrees with respect to the two coordinate axes in a coordinate system having a second line orthogonal to the first line through the coordinate axis Rate is set ,
The connection hole is one of a serration hole and a spline hole, and either the serration hole or the spline hole is missing in the high stress region, and the shape change rate is set to a small value. Universal joint. 2. The universal joint according to claim 1, wherein the shape having a shape change rate that suppresses stress concentration is one of a linear shape and an arc shape having a large curvature radius. The region in the vicinity of the imaginary line is within a range of ± 15 degrees sandwiching the imaginary line in each of the four quadrants divided by the first line and the second line in the coordinate system. Item 3. The universal joint according to Item 1 or 2. The universal joint according to any one of claims 1 to 3, wherein countersinks are formed on end faces of the pair of arms of the serration hole and the spline hole . Steering apparatus characterized by using a universal joint according to any one of the請Motomeko 1 to 4. The universal joint according to any one of claims 1 to 4 is interposed between an output shaft of a steering assist mechanism that generates a steering assist force in a steering system provided in a steering column and a steering gear mechanism. An electric power steering device .

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