JP2015169227A - Universal joint and steering device having the universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a universal joint which is high in a holding force with respect to a shaft member to be fit, and can prevent the fletching wear of a serration tooth caused by a stress concentration, and a steering device having the universal joint.SOLUTION: At an internal peripheral face of a connecting part 30, a first toothless part 56 is arranged in a prescribed range at one side of a circumferential direction with a slit 42 sandwiched, and a second toothless part 58 is arranged in a prescribed range at the other side of the circumferential direction. When it is assumed that a female serration is formed over the whole periphery of the internal peripheral face, the range of the first toothless part 56 is set as a range which reaches a female serration tooth 52a having a tooth face at which one tooth face forms a right angle with respect to a center axial line of a bolt penetration hole 44, or one tooth face forms an inclination angle which is most approximate to a right angle from a portion corresponding to the slit 42, and the range of the second toothless part 58 is set as a range which reaches a range terminal end at which the bolt penetration hole 44 intersects with a fitting hole 36 from the portion corresponding to the slit 42 when viewed from the axial direction.

Description

  The present invention relates to a universal joint used in a steering apparatus and the like, and a steering apparatus including the universal joint.

  Conventionally, in a universal joint that is serrated at a fitting portion with a shaft member such as a steering shaft and is fastened to the shaft member by a bolt tightening force, a female serration forming region is formed on the inner peripheral surface of the shaft member fitting hole of the yoke. And a female serration non-formation region, that is, a missing tooth portion is disclosed.

For example, in Patent Document 1, the central angle θ corresponding to the female serration non-formation region centered on the central axis of the shaft member fitting hole of the yoke is set to a predetermined value within the range of 100 ° to 140 °. Universal joints are described.
Further, Patent Document 2 describes a universal joint in which a serrated portion formed in an inner peripheral surface of a shaft member fitting hole is formed with a missing tooth portion at a portion facing in the diameter direction perpendicular to the slit direction. Yes.
Further, Patent Document 3 discloses a universal joint in which a missing tooth portion where no female serration is formed is provided on the inner peripheral surface of the shaft member fitting hole, and the missing tooth portion is used as a space for accommodating a burr generated when a slit is formed. The yoke is described.

JP 2012-193798 A Japanese Utility Model Publication No. 52-169641 JP 2003-200238 A

  In the electric power steering device, when the steering shaft rotates left or right by steering, the torque sensor detects the steering torque applied to the steering shaft, and the auxiliary steering torque generated from the electric motor according to the detected steering torque. Is transmitted to the output shaft of the steering assist mechanism via the speed reduction mechanism. Excessive torque is applied to the steering shaft when the steering wheel is cut back or cut, and this excessive torque is repeatedly applied to the shaft member fitting portion of the universal joint, that is, the serration teeth via the output shaft of the steering assist mechanism. Entered. In particular, in a column assist type electric power steering apparatus, a large torque is input to the universal joint. Therefore, the yoke of the universal joint is required to have a high holding force for the shaft member to be fitted.

  FIG. 8 is an example of a conventional universal joint yoke used in a column assist type electric power steering apparatus, and is a cross-sectional view of the yoke as viewed from the axial direction. A yoke 320 shown in FIG. 8 is a yoke on the side to which the output shaft of the steering assist mechanism is fitted, out of a pair of yokes constituting the universal joint. As shown in FIG. 8, a female serration 338 and a missing tooth portion 354 in which the female serration 338 is not formed are provided on the inner peripheral surface of the shaft member fitting hole 336. The missing tooth portion 354 is a region of the root circle in a range where the bolt insertion hole 344 of the tightening bolt crosses the root circle of the female serration 338 around the slit 342 as viewed from the axial direction of the shaft member fitting hole 336. It is provided on the inner peripheral surface corresponding to the arc.

  In the column assist type electric power steering apparatus, since the torque input to the universal joint is large as described above, the yoke of the universal joint is not a press-formed product from a plate material but a cold forged product. . As a material for cold forging, carbon steel cast steel (SC material) or the like is used. Carbon steel cast steel has a lower elongation than cold-rolled steel sheets (SPCC, SPHC) used for press-molded sheets. In the clamped state, the teeth of the entire female serration are in contact with the male serration of the output shaft in the press-molded one, but in the cold-forged one, the elongation is small. There is a tendency that stress concentrates on the serrated teeth and the meshing in this range becomes strong. As a result, fretting wear occurs on the serration teeth of the portion.

  The present invention has been made in view of such a situation, and a universal joint that has a high holding force with respect to a shaft member to be fitted and can prevent fretting wear of serration teeth due to stress concentration, and the universal joint. It is an object to provide a steering device including a joint.

  In order to solve the above problems, a universal joint according to the present invention includes a cross shaft and a pair of yokes connected via the cross shaft, and the pair of yokes have an inner peripheral surface fitted with a shaft member. A pair of cylindrical connecting portions that form fitting holes, and at least one of the connecting portions forms a slit extending in the radial direction from the outer peripheral surface to the inner peripheral surface and extending in the axial direction. Are connected to the shaft member by being tightened in a direction in which the pair of facing portions approach each other by a screw member, and is fitted to the shaft member in a partial range in the circumferential direction of the inner peripheral surface. In the universal joint provided with the female serration and the missing tooth region in which the female serration is not formed in the remaining range in the circumferential direction, the missing tooth region is located on one side in the circumferential direction across the slit. Provided first It consists of a tooth part and a second missing tooth part provided on the other side in the circumferential direction, and the circumferential range of the first missing tooth part is different from the circumferential range of the second missing tooth part. It is characterized by.

  In a preferred aspect of the present invention, the one connecting portion has a screw hole into which the screw member is screwed, and the screw hole is orthogonal to a radial direction in which the slit penetrates the connecting portion, and While intersecting with the slit in a direction perpendicular to the axial direction of the connecting portion, a part thereof is provided to intersect with a part of the fitting hole, and the first missing tooth portion and the second missing tooth portion. The circumferential range having the larger circumferential range is the inner side that is closer to the slit than the center axis of the fitting hole when it is assumed that the female serration is formed on the entire circumference of the inner circumferential surface. Of the female serration portion formed on the peripheral surface portion, the tooth whose one tooth surface is inclined at a right angle or the angle closest to the central axis of the screw hole from the portion corresponding to the slit Range to female serrated teeth with face And wherein the door.

  In a preferred aspect of the present invention, a circumferential range having a smaller circumferential range of the first missing tooth portion and the second missing tooth portion has the female serration on the entire circumference of the inner circumferential surface. Assuming that it is formed, the female serration is a range from the portion corresponding to the slit to the end of the range where the screw hole intersects the fitting hole when viewed in the axial direction. To do.

  In a preferred aspect of the present invention, the second missing tooth portion is a blank having a cylindrical portion for forming the yoke, and the female serration and the missing portion are formed on an inner peripheral surface of the cylindrical portion. It is a space for accommodating a burr generated when the slit is formed in a state where a tooth region is formed.

  A steering apparatus according to the present invention includes the universal joint.

  According to the present invention, it is possible to provide a universal joint that has a high holding force with respect to a shaft member to be fitted and can prevent fretting wear of serration teeth due to stress concentration, and a steering apparatus including the universal joint. Can do.

It is a perspective view showing the whole steering device composition provided with the universal joint concerning a 1st embodiment. It is a side view of the universal joint which concerns on 1st Embodiment. It is an expansion perspective view of an upper side yoke, (a), (b), (c) has shown the state seen from a different angle, respectively. It is a 6th page figure of an upper side yoke. It is an AA arrow expanded sectional view of Drawing 4 (d). It is an expanded sectional view of the upper side yoke, and shows the pressing direction of the female serration against the shaft member inserted into the fitting hole. It is an expanded sectional view of the upper side yoke of the universal joint which concerns on 2nd Embodiment. It is an expanded sectional view of the yoke of the conventional universal joint.

  Embodiments of the present invention will be described below with reference to the drawings. In the present specification, the directions related to the steering device and the universal joint are the same as the front-rear and left-right directions of the vehicle body when attached to the vehicle body unless otherwise specified. Further, the upper side and the rear side refer to the same direction, and the lower side and the front side refer to the same direction.

(First embodiment)
FIG. 1 is a perspective view showing an overall configuration of a steering apparatus including an upper universal joint according to the first embodiment of the present invention. The steering device according to the present embodiment is a rack and pinion type column assist type electric power steering device.

  As shown in FIG. 1, the steering device 100 includes a steering shaft 2 having a steering wheel 1 mounted on a rear end, a cylindrical steering column 3 in which the steering shaft 2 is rotatably supported on the inner diameter side, And a steering assist mechanism 4 connected to the front end portion of the steering shaft 2.

  The steering assist mechanism 4 includes a torque sensor (not shown), an electric motor 5 that generates an auxiliary steering torque according to the steering torque detected by the torque sensor, and a speed reduction mechanism 6 that is connected to the electric motor 5 and accommodated in a housing 6A. The auxiliary steering torque generated by the electric motor 5 is applied to the output shaft 7 of the steering auxiliary mechanism 4 via the speed reduction mechanism 6.

  The steering shaft 2 has an outer shaft 8 that is an upper shaft and an inner shaft 9 that is a lower shaft, and the outer shaft 8 and the inner shaft 9 have a structure that can reduce the overall length in the event of a collision. Further, the steering column 3 is formed by combining an outer column 10 as an upper column and an inner column 11 as a lower column in a telescope shape, and when an axial impact is applied, the steering column 3 absorbs impact energy and has a total length. It has a collapsible structure that shrinks.

  The outer column 10 of the steering column 3 is supported on the vehicle body side member 13 by the upper vehicle body side bracket 12U so that the tilt position and the telescopic position can be adjusted. The housing 6A of the speed reduction mechanism 6 is supported so as to be pivotable in the vertical direction about a pivot shaft 14p that is rotatably provided on a lower vehicle body side bracket 12L attached to the vehicle body side member 13.

  The rear end of the intermediate shaft 16 is connected to the output shaft 7 of the steering assist mechanism 4 via the upper side universal joint 15. A front end of the intermediate shaft 16 is connected to a pinion shaft 19 of a rack and pinion type steering gear mechanism 18 via a lower side universal joint 17. The upper side universal joint 15 includes an upper side yoke 20, a lower side yoke 22, and a cross shaft 24 that couples the pair of yokes 20, 22.

  The pinion shaft 19 is connected to the lower end yoke 26 of the lower universal joint 17 at the upper end. A rack shaft (not shown) is supported in the gear housing 18A so as to be movable in the vehicle width direction, and a pinion (not shown) of the pinion shaft 19 is engaged with rack teeth (not shown) of the rack shaft. Both ends of the rack shaft are connected to steered wheels (not shown) via tie rods 28 and 28, respectively.

  Since the steering device 100 has such a configuration, when a driver rotates the steering wheel 1, a torque sensor (not shown) detects a steering torque applied to the steering shaft 2, and is generated from the electric motor 5 in accordance with the detected steering torque. The auxiliary steering torque is transmitted to the output shaft 7 via the speed reduction mechanism 6 and further transmitted to the pinion shaft 19 via the intermediate shaft 16. When the pinion shaft 19 rotates, a rack shaft (not shown) engaged with the pinion shaft 19 is driven in the axial direction, that is, the vehicle width direction, and the left and right steered wheels connected to the tie rods 28 and 28 are steered.

FIG. 2 is a side view of the upper side universal joint 15 according to the first embodiment of the present invention.
FIG. 3 is an enlarged perspective view of the upper side yoke 20 of the upper side universal joint 15, and (a), (b), and (c) each show a state viewed from different angles.
FIG. 4 is a six-side view of the upper side yoke 20. 4A shows a state where the upper side yoke 20 is viewed from the upper side end surface, that is, the end surface side on the steering shaft 2 side, and FIG. 4B is a view taken along the line bb in FIG. ) Is a view taken along the line cc of (a), (d) is a view taken along the line dd of (a), (e) is a view taken along the line ee of (a), ( f) is a view taken along line ff in (d).

  As shown in FIG. 2, the upper side universal joint 15 according to this embodiment includes an upper side yoke 20, a lower side yoke 22, and a cross shaft 24 that couples the pair of yokes 20 and 22. . The output shaft 7 and the intermediate shaft 16 of the steering assist mechanism 4 are connected to the upper side yoke 20 and the lower side yoke 22, respectively (see FIG. 1).

  As shown in FIGS. 3 and 4, the upper yoke 20 (hereinafter simply referred to as “yoke 20”) has a cylindrical shape that is externally fitted to the lower end of the output shaft 7 of the steering assist mechanism 4 and tightened. And a pair of arm portions 32, 32 that extend from the lower end of the connecting portion 30 outward in the axial direction of the connecting portion 30 and are connected to the lower yoke 22 via the cross shaft 24. I have. The pair of arm portions 32 and 32 are a pair of plate-like members arranged to face each other, and each arm portion 32 is formed with a through hole 34 for supporting the cross shaft 24.

  The inner peripheral surface of the connecting portion 30 of the yoke 20 is formed in a cylindrical shape, and the inner diameter side thereof is a fitting hole 36 into which the lower end of the output shaft 7 is inserted and fitted. That is, the inner peripheral surface of the connecting portion 30 forms a fitting hole 36 as a peripheral wall of the fitting hole 36. A female serration 38 is provided on the inner peripheral surface of the connecting portion 30, that is, on the peripheral wall of the fitting hole 36. A male serration (not shown) that engages with the female serration 38 is formed on the outer peripheral surface of the output shaft 7.

  A pair of thick portions 40, 40 having a thickness in the radial direction and extending in the axial direction and facing each other are provided on the outer peripheral portion of the connecting portion 30. The slit 42 formed between the thick portions 40, 40 penetrates in a radial direction from the outer peripheral surface of the connecting portion 30 to the fitting hole 36, and extends from the upper end of the connecting portion 30 to the vicinity of the lower end. Extends in the direction.

FIG. 5 is an enlarged cross-sectional view taken along line AA in FIG.
As shown in FIGS. 4C, 4 </ b> D, and 5, in the vicinity of the upper side end of the thick portions 40, 40, the direction across the slit 42, that is, the diameter through which the slit 42 penetrates the connecting portion 30. A bolt insertion hole 44 is formed so as to intersect the slit 42 through the thick portions 40, 40 in a direction orthogonal to the direction and orthogonal to the axial direction of the connecting portion 30. A bolt (not shown) for tightening is inserted into the bolt insertion hole 44. The bolt insertion hole 44 is opened in a part of the fitting hole 36 on the slit 42 side. That is, the bolt insertion hole 44 and the fitting hole 36 partially intersect each other. Specifically, as shown in FIG. 5, the bolt insertion hole 44 is a bus on the center axis C side of the fitting hole 36 among the bus insertion holes 44 when viewed from the axial direction of the connecting portion 30. The inner circumferential surface of the connecting portion 30 is crossed and crossed.

  Further, as shown in FIG. 5, the bolt insertion hole 44 has an internal thread portion 46 (left side toward the paper surface) formed on the inner peripheral surface of one thick portion 40 with the slit 42 interposed therebetween and the other meat portion. The thick portion 40 is composed of a through-hole portion 48 (on the right side as viewed in the drawing) which is a cylindrical inner peripheral surface. The tightening bolt is inserted into the bolt insertion hole 44 from the through hole 48 side. A counterbore 50 against which the head of the bolt abuts is provided on the side of the thick portion 40 and the connecting portion 30 on the side corresponding to the through hole 48. By tightening the bolt inserted into the bolt insertion hole 44, the connecting portion 30 is tightened in a direction in which the pair of thick portions 40, 40 approach each other, and the output shaft 7 inserted into the fitting hole 36 (see FIG. 1). The male serration and the female serration 38 of the fitting hole 36 are engaged with each other, whereby the output shaft 7 and the connecting portion 30 are connected.

  As shown in FIG. 5, the inner peripheral surface of the connecting portion 30, i.e., the female serration 38 of the fitting hole 36, has a substantially triangular cross-sectional shape and a large number of protrusions extending in the axial direction are continuously formed in the circumferential direction. Has been. These ridges constitute a large number of female serration teeth 52. In the present embodiment, the female serration 38 is not provided over the entire circumference of the inner peripheral surface of the connecting portion 30. As shown in FIG. 5, the vicinity of the slit 42 on the inner peripheral surface of the connecting portion 30 is a missing tooth portion 54 in which the female serration 38 is not formed. The missing tooth portion 54 is on the inner circumferential surface of the cylinder having a curvature that matches the root circle of the female serration 38.

  The toothless portion 54 on the inner peripheral surface of the connecting portion 30 is provided in a predetermined range in the circumferential direction with the slit 42 interposed therebetween when the connecting portion 30 is viewed from the axial direction. That is, the missing tooth portion 54 is a straight line T extending through the slit 42 in the radial direction through the center line of the slit 42, that is, the center axis C of the fitting hole 36 when the connecting portion 30 is viewed from the axial direction. Of the intersections with the root circle of the female serration 38, from the intersection P on the slit side, it is provided on the inner peripheral surface corresponding to the arc in a predetermined range on both sides in the circumferential direction of the root circle. That is, the missing tooth portion 54 includes the first missing tooth portion 56 provided in a predetermined range on the through hole portion 48 side of the bolt insertion hole 44 on the inner peripheral surface of the connecting portion 30 with the slit 42 interposed therebetween, and the bolt. It consists of a second missing tooth portion 58 provided in a predetermined range on the female screw portion 46 side of the insertion hole 44.

  In the present embodiment, the first missing tooth portion 56 is provided over a wider range in the circumferential direction than the second missing tooth portion 58. Therefore, the length of the arc of the root circle of the female serration 38 corresponding to each range of the inner peripheral surface of the connecting portion 30 provided with the first and second missing teeth portions 56 and 58 is the first missing portion. The arc corresponding to the tooth portion 56 is longer than the arc corresponding to the second missing tooth portion 58.

  The predetermined range on the through-hole portion 48 side of the bolt insertion hole 44 in which the first missing tooth portion 56 is provided is as follows in detail. First, it is assumed that the female serration 38 is formed over the entire inner peripheral surface of the connecting portion 30. In this case, among the many female serration teeth 52 formed on the inner peripheral surface portion corresponding to the slit 42 side from the center axis C of the fitting hole 36 and the through hole 48 side from the straight line T, the connection When viewed from the axial direction of the portion 30, one tooth surface has a tooth surface that is inclined at a right angle or an angle closest to the central axis D of the bolt insertion hole 44, that is, the direction in which the axial force of the bolt acts. Female serration teeth 52a are contemplated.

  In the present embodiment, in the root circle of the female serration 38, the range of the inner peripheral surface corresponding to the arc from the intersection P to the portion including the female serration tooth 52 a is defined as the first missing tooth portion 56. In other words, the portion of the female serration 38 from the portion corresponding to the slit 42 to the female serration tooth 52 a is the first missing tooth portion 56. Note that the axial force of the bolt acts in a direction orthogonal to the axial direction of the connecting portion 30.

  On the other hand, the predetermined range on the female screw 46 side of the bolt insertion hole 44 in which the second missing tooth portion 58 is provided is as follows in detail. First, it is assumed that the female serration 38 is formed over the entire inner peripheral surface of the connecting portion 30 as in the case of the first missing tooth portion 56. In this case, of the multiple female serration teeth 52 formed on the inner peripheral surface portion corresponding to the slit 42 side from the center axis C of the fitting hole 36 and the female screw portion 46 side from the straight line T, the connecting portion. A female serration tooth 52b located at the end on the central axis C side in a range where the bolt insertion hole 44 intersects the fitting hole 36 when viewed from the axial direction of 30 can be considered.

  In the present embodiment, in the root circle of the female serration 38, the range of the inner peripheral surface corresponding to the arc from the intersection P to the portion including the female serration tooth 52b is defined as the second missing tooth portion 58. In other words, the portion from the portion corresponding to the slit 42 of the female serration 38 to the female serration teeth 52b, that is, the range where the bolt insertion hole 44 intersects with the fitting hole 36 is extended to the second end on the central axis C side. The missing tooth portion 58 is used.

  As described above, the yoke 20 of the upper universal joint 15 according to the present embodiment is formed with two missing tooth portions 56 and 58 having different circumferential ranges on the inner peripheral surface with the slit 42 interposed therebetween. In other words, on the inner peripheral surface of the yoke 20, the missing teeth 56 and 58 are formed on both sides of the slit 42 over the asymmetric circumferential region. And these two missing tooth parts 56 and 58 are located on the side of the through hole 48 of the bolt insertion hole 44, that is, the first missing tooth part 56 on the head side of the bolt, that is, on the side of the female screw part 46 of the bolt insertion hole 44. It is formed over a wider range in the circumferential direction than the second missing tooth portion 58 on the screw tip side of the bolt.

Next, a method for connecting the yoke 20 of the upper universal joint 15 and the output shaft 7 (see FIG. 1) according to the present embodiment will be described.
First, the output shaft 7 is inserted into the fitting hole 36 of the yoke 20. At this time, the female serration 38 of the yoke 20 and the male serration (not shown) of the output shaft 7 are clearance fits. Next, a bolt for tightening (not shown) is inserted into the bolt insertion hole 44 from the through hole 48 side, and the bolt is tightened.

FIG. 6 is an enlarged cross-sectional view of the upper yoke 20 and shows the pressing direction of the female serration 38 against the output shaft 7 inserted into the fitting hole 36. In FIG. 6, the output shaft 7 inserted into the fitting hole 36 is not shown.
As the bolt is tightened, the connecting portion 30 is tightened in a direction in which the pair of thick portions 40, 40 approach each other. That is, the connection part 30 becomes large in the bending of the outer peripheral surface side part at the front end side of the thick parts 40, 40. Then, as shown by a thin arrow K in FIG. 6, the pressing force of the bolt bearing surface against the side surface (the counterbore 50) of the connecting portion 30 is small in the thick portion 40 on the side close to the tip of the slit 42. As shown by the thick arrow L in FIG. 6, the thickness is increased in the thick portion 40 on the side close to the fitting hole 36.

  When the pressing force of the bolt against the side surface (counterbore 50) of the connecting portion 30 increases in a portion close to the fitting hole 36, the center axis of the fitting hole 36 among the female serration teeth 52 on the inner peripheral surface of the connecting portion 30. The female serration teeth 52 in the region closer to the through hole 48 than C strongly presses the output shaft 7 in a direction (arrow V direction) parallel to the axial force direction of the bolt. Here, since the first peripheral tooth portion 56 is provided on the inner peripheral surface of the connecting portion 30, the portion of the inner peripheral surface of the connecting portion 30 where the female serration teeth 52 are formed is connected to the output shaft 7. It is particularly strongly pressed in the direction parallel to the axial force direction of the bolt. That is, when the connecting portion 30 is viewed from the axial direction and the straight line E passing through the central axis C of the fitting hole 36 and intersecting the straight line T at a right angle is defined as a straight line E, the female serration adjacent to the first missing tooth portion 56 is obtained. The female serration teeth 52 formed in the circumferential region from the teeth 52c to the female serration teeth 52d symmetrical to the female serration teeth 52c centering on the straight line E push the output shaft 7 more strongly. This region is indicated by an arc M in FIG.

  As shown in FIG. 6, the arc M is located in the middle part of the fitting hole 36 in the direction in which the straight line T extends. Therefore, the female serration tooth 52 formed in the range of the arc M pushes the central portion of the output shaft 7 inserted into the fitting hole 36 in a direction parallel to the axial direction of the bolt (arrow V direction), and the central axis line The output shaft 7 is pressed against the portion of the female serration 38 on the opposite side across C. As described above, by providing the first missing tooth portion 56 on the inner peripheral surface of the connecting portion 30, the pressing portion of the inner peripheral surface of the connecting portion 30 against the output shaft 7 corresponds to the central portion of the output shaft 7. Will be formed.

  Here, on the inner peripheral surface of the connecting portion 30, the second missing tooth portion 58 is provided on the side opposite to the arc M across the central axis C, that is, on the female thread portion 46 side of the bolt insertion hole 44 with respect to the straight line T. Is provided. As described above, the second missing tooth portion 58 has a narrower circumferential range than the first missing tooth portion 56. That is, on the female threaded portion 46 side of the straight line T, the inner peripheral surface of the connecting portion 30 is larger than the inner peripheral surface portion of the through hole 48 side of the straight line T and extends to the vicinity of the slit 42. Serration teeth 52 are formed.

  Since the output shaft 7 is pressed in the direction of arrow V as described above, the output shaft 7 is pressed against the portion of the female serration 38 in the circumferential region N wider than the arc M in the portion opposite to the arc M. It will be. The circumferential region N is formed in a circumferential region from the female serration tooth 52e adjacent to the second missing tooth portion 58 to the female serration tooth 52f that is symmetric with the female serration tooth 52e, centered on the straight line E. Female serration teeth 52. As the bolt is tightened, the female serration tooth 52 in the range of the arc N also pushes the output shaft 7 in a direction (arrow Y direction) parallel to the axial force direction of the bolt due to the axial force of the bolt. At this time, the female serration teeth 52e and 52f respectively push the output shaft 7 in the direction (arrow X, Z direction) toward the approximate center of the output shaft 7, and press the output shaft 7 against the portion of the female serration 38 on the opposite side. .

  Thus, the male serration of the output shaft 7 meshes with the female serration 38 of the connecting portion 30 within the range of the arc M and the arc N of the connecting portion 30. As a result, the holding range for holding the output shaft 7 of the connecting portion 30, that is, the range in meshing contact with the output shaft 7 is increased, and the holding force is increased.

  As described above, according to the present embodiment, the first serrated portion 56 having a wide circumferential range is provided on the inner peripheral surface of the connecting portion 30, so that the female serration on one side portion of the inner peripheral surface of the connecting portion 30 is provided. The tooth 52 pushes the central portion of the output shaft 7 in a direction parallel to the axial force direction of the bolt, and the second missing tooth portion 58 has a narrower circumferential range than the first missing tooth portion 56. The output shaft 7 can be meshed over a wide circumferential range of the female serration 38 on the other side. As a result, even in a cold forged yoke, the shaft holding force of the connecting portion 30 can be increased.

  Further, by providing the first missing tooth portion 56, it is possible to prevent the fretting wear of the serration tooth in the vicinity of the slit 42 where the stress is concentrated.

Further, by providing the second missing tooth portion 58, it is possible to omit the step of removing burrs generated when the slit 42 is formed in the blank (not shown) for forming the yoke 20.
A blank integrally including a cylindrical portion and a yoke portion for forming the yoke 20, wherein a female serration 38 and first and second toothless portions 56 and 58 are formed on the cylindrical portion. In order to form the slit 42 in the cylindrical portion, cutting is performed from the outer peripheral side to the inner peripheral side of the cylindrical portion. When such cutting is performed, burrs are generated when the cutting tool protrudes toward the inner peripheral side of the cylindrical portion, that is, the female serration 38 side.

  The burr generated in this manner becomes an obstacle when the male serration of the output shaft 7 is fitted to the yoke 20 or the blank female serration 38. In the present embodiment, by providing the second missing tooth portion 58 connected to the slit 42, the burr generated by the cutting process is not applied to the fitting portion between the male serration and the female serration 38. That is, the second missing tooth portion 58 is a space for accommodating such a burr. Thereby, when fitting the output shaft 7 to the female serration 38, the step of removing burrs can be omitted. As a result, the manufacturing cost can be reduced. Note that the same effect can be obtained at the connection portion of the first missing tooth portion 56 with the slit 42.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment will be described with a focus on a different configuration from the first embodiment, and a redundant description of the same configuration as the first embodiment will be omitted. The same members as those in the first embodiment will be described using the same reference numerals. The upper side universal joint which concerns on 2nd Embodiment is a form which made the structure of a connection part different from 1st Embodiment.

FIG. 7 is an enlarged cross-sectional view of an upper side yoke 220 (hereinafter simply referred to as “yoke 220”) of the upper side universal joint according to the second embodiment.
The yoke 220 according to the second embodiment includes a circumferential range of the first missing tooth portion 56 on the through hole portion 48 side of the bolt insertion hole 44 and a circumferential range of the second missing tooth portion 58 on the female screw portion 46 side. Is the reverse of the first embodiment. That is, the second missing tooth portion 58 is provided over a wider range in the circumferential direction than the first missing tooth portion 56.

  In the present embodiment, the circumferential range of the first missing tooth portion 56 is as follows. First, as in the first embodiment, it is assumed that the female serration 38 is formed over the entire inner peripheral surface of the connecting portion 230. In this case, of the multiple female serration teeth 52 formed on the inner peripheral surface portion corresponding to the slit 42 side from the center axis C of the fitting hole 36 and the through hole 48 side from the straight line T, the connection A female serration tooth 52g located at the end on the central axis C side in a range where the bolt insertion hole 44 intersects the fitting hole 36 when viewed from the axial direction of the portion 30 is conceivable.

  In the present embodiment, in the root circle of the female serration 38, the range of the inner peripheral surface corresponding to the arc from the intersection P to the portion including the female serration tooth 52g is defined as the first missing tooth portion 56. In other words, the portion of the female serration 38 from the portion corresponding to the slit 42 to the female serration teeth 52g, that is, the end of the center portion C side in the range where the bolt insertion hole 44 intersects the fitting hole 36 is the first. The missing tooth portion 56 is used.

  On the other hand, the circumferential range of the second missing tooth portion 58 is as follows. First, as in the first embodiment, it is assumed that the female serration 38 is formed over the entire inner peripheral surface of the connecting portion 230. In this case, of the large number of female serration teeth 52 formed on the inner peripheral surface portion corresponding to the slit 42 side from the central axis C of the fitting hole 38 and the female screw portion 46 side from the straight line T, the connecting portion. A female surface having a tooth surface whose one tooth surface is inclined at a right angle or an angle close to the right angle with respect to the central axis D of the bolt insertion hole 44, that is, the direction in which the axial force of the bolt acts, as viewed from the axial direction of 30. A serration tooth 52h is conceivable.

  In the present embodiment, in the root circle of the female serration 38, the range of the inner peripheral surface corresponding to the arc from the intersection P to the portion including the female serration tooth 52h is defined as the second missing tooth portion 58. In other words, the portion of the female serration 38 from the portion corresponding to the slit 42 to the female serration tooth 52 h is the second missing tooth portion 58. Other configurations are the same as those of the first embodiment.

  Next, a method of connecting the yoke 220 of the upper universal joint according to the present embodiment and the shaft member (in this embodiment, the output shaft 7, see FIG. 1) will be described.

  In the present embodiment, the circumferential range of the first missing tooth portion 56 is narrower than the circumferential range of the second missing tooth portion 58. Therefore, when the fastening bolt is tightened, the inner circumference of the connecting portion 30 is increased. Of the surface, the portion of the female serration 38 on the side where the first missing tooth portion 56 is provided, that is, the female serration tooth 52 formed over a wide range, the central portion of the output shaft 7 is connected to the central axis C. It will be pushed in the opposite direction across. That is, the output shaft 7 is pressed against the portion of the female serration 38 on the side where the second missing tooth portion 58 is provided on the inner peripheral surface of the connecting portion 30.

  On the other hand, as the bolt is tightened, due to the axial force of the bolt, the portion of the female serration 38 on the side where the second toothless portion 58 is provided makes the central portion of the output shaft 7 parallel to the axial force direction of the bolt. The output shaft 7 is pressed against the portion of the female serration 38 on the opposite side across the central axis C. As a result, as in the first embodiment, the holding range for holding the output shaft 7 of the connecting portion 220, that is, the range in meshing contact with the output shaft 7 is increased, and the holding force is increased. Therefore, also in this embodiment, the shaft holding force of the connecting portion 230 can be increased.

  In the present embodiment, the wall thickness between the spot facing 50 and the inner peripheral surface of the connecting portion 30 can be secured. Therefore, as in the first embodiment, when a notched portion having a wide circumferential width is formed on the inner peripheral surface of the connecting portion 30 on the through hole portion 48 side of the bolt insertion hole 44, the counterbore 50 and the connecting portion 30 This is effective when the thickness between the inner peripheral surface is thinned. Other effects are the same as those of the first embodiment.

  In the above embodiments, the present invention is applied to the upper universal joint of the steering device 100. However, the present invention can also be applied to a lower universal joint. In each of the above embodiments, the tooth missing portion is provided in the upper side yoke. However, the tooth missing portion similar to that in each of the above embodiments may be provided in both the upper side yoke and the lower side yoke.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Steering column 4 Steering assist mechanism 5 Electric motor 6 Deceleration mechanism 6A Housing 7 Output shaft 8 Outer shaft 9 Inner shaft 10 Outer column 11 Inner column 12U Upper bracket 12L Lower bracket 13 Car body side member 14P Pivot shaft 15 Upper side universal joint 16 Intermediate shaft 17 Lower side universal joint 18 Steering gear mechanism 18A Gear housing 19 Pinion shaft 20 Upper side yoke 22 Lower side yoke 24 Cross shaft 28 Tie rod 30 Connecting portion 32 Arm portion 34 Through hole 36 Fitting hole 38 Female Serration 40 Thick part 42 Slit 44 Bolt insertion hole 46 Female thread part 48 Through hole part 50 Counterbore 52 Female serration tooth 54 Missing tooth part 56 First missing tooth part 58 Second missing tooth part 10 Steering system

Claims (5)

The crosshair,
A pair of yokes connected via the cross shaft,
Each of the pair of yokes includes a cylindrical connection portion that forms a fitting hole whose inner peripheral surface is fitted to the shaft member,
At least one of the connecting portions has a pair of facing portions that form a slit extending in the radial direction from the outer peripheral surface to the inner peripheral surface and extending in the axial direction, and the pair of facing portions approach by a screw member. A female serration that is coupled to the shaft member by being tightened in a direction and is fitted to the shaft member in a partial range of the inner peripheral surface in the circumferential direction, and the female serration in the remaining circumferential range In a universal joint provided with a missing tooth region in which is not formed,
The missing tooth region includes a first missing tooth portion provided on one side in the circumferential direction with the slit interposed therebetween, and a second missing tooth portion provided on the other side in the circumferential direction. A universal joint characterized in that a circumferential range of the missing tooth portion is different from a circumferential range of the second missing tooth portion. The one connecting portion has a screw hole into which the screw member is screwed, and the screw hole is perpendicular to a radial direction in which the slit penetrates the connecting portion and perpendicular to an axial direction of the connecting portion. Crossing the slit, a part thereof is provided to cross a part of the fitting hole,
When it is assumed that the circumferential direction range having the larger circumferential range among the first missing tooth part and the second missing tooth part has formed the female serration on the entire circumference of the inner circumferential surface, Of the portions of the female serration formed on the inner peripheral surface portion on the slit side with respect to the center axis of the fitting hole, one tooth surface from the portion corresponding to the slit becomes the center axis of the screw hole. The universal joint according to claim 1, wherein the universal joint is in a range up to a female serration tooth having a tooth surface having a right angle or an angle of inclination closest to the right angle.   When it is assumed that the circumferential direction range having the smaller circumferential range among the first missing tooth portion and the second missing tooth portion has formed the female serration on the entire circumference of the inner circumferential surface, The female serration is a range from a portion corresponding to the slit to an end of a range where the screw hole intersects the fitting hole as viewed from the axial direction. Universal joint.   The second missing tooth portion is a blank having a cylindrical portion for forming the yoke, and the female serration and the missing tooth region are formed on the inner peripheral surface of the cylindrical portion. The universal joint according to any one of claims 1 to 3, wherein the universal joint is a space for accommodating a burr generated when the slit is formed.   A steering apparatus comprising the universal joint according to any one of claims 1 to 4.

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