JP2006022869A - Universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an universal joint capable of being properly used at a place where large steering torque is added, resolving the loosening of a connecting part of a yoke and a shaft, and being easily disassembled and re-assembled, easily machined and manufactured at a low cost. <P>SOLUTION: A hot-rolled soft sheet steel is used as a material of the yoke 3, the material having tensile strength of 350N/mm<SP>2</SP>is optimum, and the material of the tensile strength of less than 370N/mm<SP>2</SP>is preferred to secure the strength of the yoke 3 and to secure the durability of press die. As parts where contact surface pressure of a pair of outer planes 14, 14 and control faces 10a, 10b becomes maximum in accompany with fastening of control bolts 33 are moved or increased to tip sides of control plate parts 9a, 9b, components are not plastically deformed until the fastening torque for fastening a nut is considerably increased. Accordingly, the connecting strength of the yoke 3 and the shaft 7 is sufficiently secured, and the undesired plastic deformation on the components can be prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a universal joint, and more particularly, to a horizontal insertion type universal joint used for a connecting portion of a steering shaft of a steering device to which a large steering torque is applied.

  In a steering device that steers the front wheels of a vehicle, the movement of a steering shaft that is rotated by the operation of a steering wheel is transmitted to an input shaft of a steering gear through a universal joint. In this universal joint, by connecting a pair of yokes via a cross shaft, the rotational force can be transmitted between the yokes even if the centers of the yokes are not located on the same straight line.

  In recent vehicles, the engine room is becoming narrower in order to secure a wide indoor space. For this reason, the steering column device must be assembled in a narrow space in the engine room. The universal joint that slides the shaft in the axial direction and is assembled to the yoke by serration requires a large assembly space, so it is not suitable for a narrow space in the engine room, and can be assembled simply by swinging the shaft Widely inserted universal joints are increasingly used.

  In addition, when a steering force assisting device such as an electric power steering device is attached to a steering device equipped with such a horizontal insertion type universal joint, the steering force assisting device and the input shaft of the steering gear are interposed between the steering force assisting device and the steering gear input shaft. A large steering torque is applied to the arranged universal joint. Even in a manual steering device that does not include a steering force assist device, a large steering torque is applied to the universal joint when the steering wheel is stationary. Conventional horizontal insertion type universal joints are used in places where steering torque is smaller on the steering wheel side than the steering force assist device (Patent Document 1, Patent Document 2, and Patent Document 3).

  Since the horizontal insertion type universal joint has a structure in which a pair of outer flat surfaces of the outer peripheral surface of the shaft are fastened by a holding surface of the yoke, the coupling strength between the shaft and the yoke tends to be insufficient as compared with the serration type. Therefore, when such a conventional horizontal insertion type universal joint is used between the steering force assist device and the input shaft of the steering gear, a large steering torque is applied to the universal joint, and due to deformation and wear due to insufficient coupling strength, The driver who operates the steering wheel feels uncomfortable. In addition, since a problem occurs in which the coupling portion between the yoke and the shaft is loosened, the tightening torque of the holding bolt is increased to increase the coupling force between the yoke and the shaft.

  9 to 11 show a conventional horizontal type universal joint, FIG. 9 is a partial side view of the conventional universal joint, and FIG. 10 is a view from the right side of FIG. 11 is a view showing a state when the holding bolt is tightened in FIG.

  The universal joint 1 is formed by connecting a pair of yokes 2 and 3 via a cross shaft 4. The four end portions provided on the cross shaft 4 are swingably supported by the respective arm portions 29 of the respective yokes 2 and 3 via needle bearings provided in the bearing cups 5 and 5, respectively. Has been. Therefore, even if the centers of the yokes 2 and 3 are not located on the same straight line, the rotational force can be transmitted between the yokes 2 and 3.

  The yokes 2 and 3 of the universal joint 1 have a base end portion 8 having a U-shaped cross section, and are of a lateral insertion type in which connection work can be performed without moving the shaft 7 in the axial direction. The base end portion 8 of the horizontal insertion type yoke 3 includes a pair of holding plate portions 9a and 9b. These holding plate portions 9a and 9b that are arranged apart from each other have the inner side surfaces as holding surfaces 10 and 10 that are parallel to each other. And the screw hole 12 is provided in the opening side edge part of one holding plate part 9a. In addition, a through hole 13 concentric with the screw hole 12 and having a diameter larger than that of the screw hole 12 is formed at the opening side end of the other holding plate 9b.

  On the other hand, the shaft 7 that joins the tip of the yoke 3 configured as described above forms a pair of outer flat surfaces 14 and 14 parallel to each other on the outer peripheral surface of the tip of the shaft 7. The outer planes 14 and 14 and the restraining surfaces 10 and 10 are brought into close contact with each other to prevent the shaft 7 from rotating with respect to the yoke 3.

  If the end portion of the shaft 7 is inserted into the base end portion 8 of the yoke 3 and the respective restraining surfaces 10 and 10 are opposed to the outer flat surfaces 14 and 14, the restraining bolts inserted through the through holes 13 (see FIG. A male screw formed at the tip of the screw (not shown) is screwed into the screw hole 12 and further tightened. Based on this tightening, the distance between the pair of restraining surfaces 10 and 10 is narrowed, the restraining surfaces 10 and 10 and the outer flat surfaces 14 and 14 are in strong contact, and the tip of the shaft 7 is The base end 8 is coupled and fixed.

  The base ends of the pair of holding plate portions 9a and 9b constituting the yoke 3 (the right end in FIGS. 10 and 11 on the side opposite to the opening side end portion of the base end portion 8) are connected by an arc-shaped connecting portion 25. Are connected to each other. When the holding bolts screwed into the screw holes 12 of the yoke 3 are tightened so that the yoke 3 and the shaft 7 are coupled and fixed, the holding surfaces 10 and 10 of the pair of holding plate portions 9a and 9b constituting the yoke 3 are Then, with the connecting portion center 25A of the connecting portion 25 as a fulcrum, it is inclined and deformed as shown in the restraining surfaces 101 and 101 shown by the two-dot chain line in FIG. Due to the inclined deformation, the holding surfaces 101 and 101 come into contact with the corner portions 7A and 7A of the shaft 7.

  Since the distance d between the corners 7A and 7A and the center of the through hole 13 is small, the bending moment acting on the corners 7A and 7A due to tightening of the holding bolt is small, and therefore the surface pressure acting on the corners 7A and 7A. Is small, the coupling force between the yoke 3 and the shaft 7 is insufficient.

  As a result, in order to sufficiently secure the coupling strength between the shaft 7 and the yoke 3, the torque for tightening the holding bolt must be further increased. Tightening the holding bolt with excessive torque is not preferable because it causes excessive plastic deformation in the holding plate portions 9a and 9b, and it becomes difficult to disassemble and reassemble the cover when attempting to disassemble it by inspection or vehicle inspection. On the contrary, if the torque for tightening the holding bolt is not sufficiently secured, the coupling strength between the shaft 7 and the yoke 3 is insufficient, and there is a possibility that rattling occurs at the coupling portion between the shaft 7 and the yoke 3. . Such rattling is undesirable because it gives the driver operating the steering wheel a feeling of strangeness.

JP-A-9-291910 Japanese Patent Laid-Open No. 10-2339 Japanese Patent Laid-Open No. 10-9281

  The present invention is suitable for use in a place where a large steering torque is applied, loosening of the joint between the yoke and the shaft is eliminated, disassembly and reassembly are facilitated, processing is easy, and manufacturing is performed at low cost. It is an object of the present invention to provide a horizontal insertion type universal joint that can be used.

  The above problem is solved by the following means. In other words, the first invention has a base end portion that is open on the side, a yoke that can couple a pair of outer flat surfaces of the shaft tip inserted from the opening side to the base end portion, and the base end. A pair of restraining plate portions that are spaced apart from each other and formed with restraining surfaces that are opposed to the respective outer flat surfaces on the respective inner surfaces, and the both restraining plate portions are opposite to the opening of the base end portion. A connecting portion that is connected to each other at the side portion, a substantially concentric through hole or screw hole formed in the both holding plate portions, and a male screw portion that is formed at the distal end portion of the male screw portion that is inserted into the through hole. In the universal joint provided with a screw bolt or a nut that is screwed into a nut and tightening the outer flat surface of the shaft with the holding surface of the holding plate portion, the yoke is a hot rolled mild steel plate, The pair of pairs before tightening the holding bolts The relationship between the clamping plate portion and the outer plane is made non-parallel to each other depending on the degree to which the tightening force of the holding bolt is strongly influenced. It is a universal joint characterized by raising the shaft holding force.

  A second invention has a base end portion that is open on the side, a yoke that can be coupled to the base end portion with a pair of outer flat surfaces of the shaft tip inserted from the opening side, and the base end portion. A pair of restraining plate portions that are spaced apart from each other and formed with restraining surfaces facing the respective outer flat surfaces on the respective inner surfaces, and the both restraining plate portions that are opposite to the opening of the base end portion A connecting portion that is connected to each other, a substantially concentric through hole or screw hole formed in each of the holding plate portions, and a male screw portion formed at the tip of the screw hole that is inserted into the through hole. Alternatively, in a universal joint provided with a holding bolt that is screwed into a nut and tightens the outer flat surface of the shaft with a holding surface of the holding plate portion, the yoke is made of a hot-rolled mild steel plate and the holding plate is pressed. Before the bolts are tightened, the pair of holding plate parts The gap between the front surfaces is narrow on the side close to the connecting portion, wide on the opening side of the base end portion where the through hole or screw hole is formed, and is screwed to the holding bolt or the holding bolt. When the nuts are tightened, the pair of outer flat surfaces and the respective restraining surfaces start to come into contact with each other on the side close to the connecting portion, and as the tightening operation of the restraining bolt proceeds, the base end portion opens. The universal joint is characterized in that the portion where the contact surface pressure becomes maximum is shifted or increased.

A third invention is characterized in that in the universal joint of the first or second invention, the yoke is formed of a material having a tensile strength of 370 N / mm ² or less. Universal joint.

  A fourth invention is a universal joint according to any one of the first to third inventions, wherein a steering force assisting device is attached between the yoke and the steering wheel. It is.

  The universal joint of the present invention can be manufactured at a low cost because the yoke is formed of a hot-rolled mild steel sheet having good formability, so that it is easy to process and can be mass-produced by pressing.

  Also, before tightening the retaining bolt, the retaining plate of the yoke is not parallel to the shaft outer plane depending on the degree to which it is strongly affected by the tightening force of the retaining bolt, or before the retaining bolt is tightened. The spacing between the restraining surfaces of the yoke restraining plate is narrow on the side close to the connecting portion of the yoke and wide on the opening side. Accordingly, the tightening force of the yoke with respect to the shaft is improved, and the looseness of the coupling portion between the yoke and the shaft is eliminated. Therefore, it is suitable for use in a place where a large steering torque is applied.

  Moreover, since excessive tightening of the holding bolt is not required, deformation to the inside of the holding plate portion of the yoke is suppressed, so that disassembly and reassembly is facilitated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall front view of a steering column apparatus equipped with a universal joint according to an embodiment of the present invention. FIG. 2 is a side view showing a state in which the base end portion of the yoke according to the embodiment of the present invention is coupled to the end portion of the shaft.

  FIG. 1 shows an example in which a universal joint according to an embodiment of the present invention is mounted on a column type electric power steering apparatus. In a column 43 fixed to the vehicle body, a steering shaft 44 having a steering wheel 45 attached to the rear side of the vehicle body (upward in FIG. 1) is pivotally supported. Below the column 43, a reduction gear box 47 of an electric steering force assisting device 49 is attached.

  The steering force assisting device 49 detects the steering torque of the steering wheel 45, rotates a motor 46 that generates an auxiliary steering force proportional to the detected steering torque, and decelerates the rotation of the motor 46 with a reduction gear box 47. It is transmitted to the shaft (output shaft) 6. The steering force transmitted to the shaft 6 is transmitted to the shaft (intermediate shaft) 7 via the upper universal joint 1, and the pinion of the rack and pinion motion conversion mechanism 48 is transmitted from the shaft 7 via the lower universal joint 1. It is transmitted to a shaft (not shown) to steer the wheels.

  As shown in detail in FIG. 2, the universal joint 1 according to the embodiment of the present invention is formed by connecting a pair of yokes 2 and 3 via a cross shaft 4. The four end portions provided on the cross shaft 4 swing to the pair of arm portions 29 at the tip portions of the yokes 2 and 3 via needle bearings provided in the bearing cups 5 and 5, respectively. It is supported freely. Accordingly, the rotational force is transmitted between the yokes 2 and 3 even if the centers of the yokes 2 and 3 are not located on the same straight line.

  When the steering device is assembled using such a universal joint 1, for example, one (right side in FIG. 2) yoke 2 is connected and fixed to the end of one shaft 6 in advance by a holding bolt 11, and the other (see FIG. The yoke 3 on the left side of 2 is coupled to the end of the other shaft 7. In order to perform such an assembling operation, usually, the one shaft 6 is supported on the vehicle body, and then the shaft 6 and the other shaft 7 are coupled by the universal joint 1.

  The pair of yokes 2 and 3 and the shafts 6 and 7 constituting the universal joint 1 is a so-called lateral insertion type in which connection work can be performed without moving the shafts 6 and 7 in the axial direction. Since the yokes 2 and 3 and the shafts 6 and 7 have the same structure, in the following description regarding the detailed structure of the yoke and the shaft, only one yoke 3 and the shaft 7 will be described, and the other yoke. 2. Description of the shaft 6 is omitted.

  FIG. 3 shows a detailed structure of the yoke 3 and the shaft 7 of the first example of the embodiment of the present invention. FIG. 3 is a cross-sectional view of the base end portion 8 of the yoke 3 of FIG. 2 taken along line AA, and the base end portion 8 is a horizontal insertion type having a U-shaped cross section. The base end portion 8 of the horizontal insertion type yoke 3 has a pair of holding plate portions 9a and 9b. Before the holding plate portions 9a and 9b are tightened with the holding bolt 11 shown in FIG. They are not parallel to each other. The base ends of the pair of holding plate portions 9 a and 9 b (the right end in FIG. 3 on the side opposite to the opening side end portion of the base end portion 8) are connected to each other by an arc-shaped connecting portion 25.

  The holding plate portions 9a and 9b that are spaced apart from each other have their inner side surfaces as holding surfaces 10 and 10 that are non-parallel to each other. And the screw hole 12 is provided in the opening side edge part of the holding | suppressing board part 9a of one side (below FIG. 3). In addition, a through hole 13 that is substantially concentric with the screw hole 12 and has a larger diameter than the screw hole 12 is formed at the opening side end of the other holding plate 9b. In place of the screw hole 12, a nut may be fitted and fixed to the holding plate portion 9a. Further, a structure in which the nut is not fitted and fixed to the yoke 3 may be used.

  On the other hand, the shaft 7 whose tip is coupled to the yoke 3 configured as described above has a substantially oval cross-sectional shape as shown in FIG. That is, a pair of outer flat surfaces 14 and 14 parallel to each other are formed on the outer peripheral surface of the distal end portion of the shaft 7, and the outer flat surfaces 14 and 14 and the holding surfaces 10 and 10 are brought into close contact with each other at the time of connection. The rotation of the shaft 7 with respect to the yoke 3 is prevented.

  When the end portion of the shaft 7 having the above-described shape is connected and fixed to the base end portion 8 of the yoke 3 as described above, first, as shown by a solid line in FIG. Is arranged on the opening side of the base end portion 8. From this state, by rotating the yoke 3 about the cross shaft 4, the yoke 3 is swung clockwise from the solid line state to the chain line state in FIG. 7 is inserted into the base end 8 of the yoke 3.

  Note that the end of the shaft 7 may be inserted into the base end 8 of the yoke 3 by moving the end of the shaft 7 without moving the yoke 3. In any case, before the end portion of the shaft 7 is inserted into the base end portion 8, the restraining bolt 11 is not inserted into the through hole 13.

  If the end portion of the shaft 7 is inserted into the base end portion 8 of the yoke 3 as described above and the respective restraining surfaces 10, 10 and the outer flat surfaces 14, 14 (FIG. 3) are opposed to each other, The male screw portion 11a formed at the tip end portion of the holding bolt 11 inserted through the hole 13 is screwed into the screw hole 12 and further tightened. Based on this tightening, the distance between the pair of restraining surfaces 10 and 10 is narrowed, the restraining surfaces 10 and 10 and the outer flat surfaces 14 and 14 are in strong contact, and the tip of the shaft 7 is The base end 8 is coupled and fixed.

  A notch 15 is formed at one edge of the end portion of the shaft 7 to prevent interference between the shaft 7 and the outer periphery 11b of the shaft portion of the retaining bolt 11, and the restraining bolt 11 is loosened by any chance. Even in this case, the yoke 3 is prevented from coming off in the axial direction of the shaft 7.

As a material of the yoke 3, a hot rolled mild steel plate (SPHC, SPHD, SPHE) is used. In order to ensure the strength of the yoke 3 and to ensure the durability of the press die in consideration of the strength of the press die for forming the yoke 3, a material having a tensile strength of 350 N / mm ² is most suitable. A tensile strength of 370 N / mm ² or less is desirable. Since the yoke 3 is formed of a hot-rolled mild steel plate having good formability, it is easy to process, can be mass-produced by pressing, and can be manufactured at low cost.

  As shown in FIG. 3, when the distance between the pair of holding plate portions 9a and 9b constituting the yoke 3 having a U-shaped cross section is reduced by the holding bolt 11, the influence of the tightening force of the holding bolt 11 is as described above. It becomes stronger at the distal end side of the pair of holding plate portions 9a, 9b and weaker at the proximal end side. For this reason, if the pair of holding plate portions 9a and 9b are parallel to each other before the holding bolt 11 is tightened, the tightening that should provide the maximum moment tightening (maximum shaft holding force) on the base end side is the moment. The ratio at the tip side with a small tightening force will increase.

  Therefore, in the case of the first example, the pair of restraining plate portions 9a and 9b are made non-parallel to each other in a direction in which the interval between the portions that are strongly influenced by the tightening force by the restraining bolt 11 becomes wider. As the holding bolts 11 are tightened, the holding surfaces 10 and 10 of the holding plates 9a and 9b become parallel to each other, and a pair of outer sides formed on the holding surfaces 10 and 10 and the shaft 7 are formed. The flat surfaces 14 and 14 are in contact with each other uniformly.

  More specifically, the distance between the pair of holding surfaces 10 and 10 is wide on the opening side of the yoke 3 and narrow on the connecting portion 25 side. When the shaft 7 is inserted into the yoke 3 and the center lines of the cross sections of the members 7 and 3 are made to coincide with each other, a wedge shape is formed between the holding surfaces 10 and 10 and the outer flat surfaces 14 and 14. Gaps 27, 27 are formed. The inclination angle θ of the gaps 27 and 27 is determined by design according to the rigidity of each part, but if the angle is about 1 to 2 °, the contact state between the restraining surfaces 10 and 10 and the outer flat surfaces 14 and 14 is determined. The shaft holding force can be sufficiently increased by making it uniform.

  4 to 8 show second to third examples of the embodiment of the present invention, and the right half of FIG. 4 and FIGS. 5 to 6 show the second embodiment of the present invention. For example, the left half of FIG. 4 and FIGS. 7 to 8 show the third example. The yoke 3 constituting each example is symmetrical with respect to the center line α except for a through hole for inserting the holding bolt 33 in FIG. 6. The material of the yoke 3 in the second to third examples also uses hot rolled mild steel sheets (SPHC, SPHD, SPHE).

  The base ends of the pair of holding plate portions 9a and 9b constituting the base end portion 8 of the yoke 3 (the end opposite to the opening side end portion of the base end portion 8 and the lower end in FIG. 4) are arc-shaped. The connecting portions 25 are connected to each other. In addition, thin portions 34, 34 are formed at the continuous portion between the width direction both end edges of the connecting portion 25 and the base end edges of the holding plate portions 9a, 9b to reduce the rigidity of these continuous portions. ing.

  Therefore, based on the tightening of the holding bolt 33 in FIG. 6 and a nut (not shown), the distal ends of the pair of holding plates 9a and 9b (the opening side end of the base end 8 and the upper end in FIG. 4) When the distance between the pair of restraining plate portions 9a and 9b is reduced, the distance between the restraining surfaces 10a and 10b of the pair of restraining plate portions 9a and 9b is reduced by a relatively small tightening force.

  In order to form such thin portions 34, 34, in the illustrated example, concave portions 35, 35 extending in the axial direction of the shaft 7 (direction perpendicular to the paper surface of FIG. 4) are formed on the inner surface of the connecting portion 25. Is forming. In addition to forming the thin-walled portions 34, 34, the concave portions 35, 35 interfere with the inner surface of the base end portion 8 and the corner portions 36, 36 of the shaft 7 when the holding bolt 33 and the nut are tightened. To prevent it.

  Of the pair of holding plate portions 9a and 9b, the third example of the embodiment is shown, and the overall shape in the free state of one holding plate portion 9a (left side in FIG. 4) is (next It is flat) except for the convex portions 37 and 37 described below. Further, a part of the holding surface 10a which is the inner side surface of the one holding plate portion 9a and a portion facing the outer flat surface 14 of the shaft 7 are provided with a plurality of convex portions 37 and 37 and the holding plate portion 9a. It is formed by plastically deforming a part of.

  The convex portions 37 and 37 may be embossed in a discontinuous shape in the axial direction of the shaft 7 (see FIG. 7 described later) or in a bank shape continuous in the axial direction (see FIG. 8 described later). See).

  In any case, the height of the plurality of convex portions 37, 37 (the amount of protrusion from the holding surface 10a) is close to the connecting portion 25 so as to contact the outer plane 14 from the side close to the connecting portion 25. When the adjustment bolts 33 are appropriately adjusted such as by raising the side, and the holding bolts 33 are sufficiently tightened, the tips of all the convex portions 37, 37 abut against the outer flat surface 14. However, the direction in the free state of the one holding plate portion 9a is inclined in a direction away from the center line α as the distance from the connecting plate portion 25 increases.

  On the other hand, of the pair of restraining plate portions 9a and 9b, the overall shape in the free state of the restraining plate portion 9b of the other (right side in FIG. 4) showing the second example of the embodiment is as follows. The holding surface 10b, which is the inner side surface of the holding plate 9b, is formed in a circular arc shape with a convex surface. The shape of the restraining surface 10b may be a single curved surface, but in the illustrated example, it is a complex curved surface in which cylindrical surfaces having different radii of curvature are smoothly connected.

  That is, FIG. 5 is an enlarged view of part A in FIG. 4, and as shown in FIG. 5, the portion near the base end of the restraining surface 10b is a first cylindrical curved surface 38 having a relatively small radius of curvature R1, A portion closer to the tip from the intermediate portion of the holding surface 10b is a second cylindrical curved surface 39 having a relatively large radius of curvature R2 (R1 <R2). It should be noted that the radius of curvature R2 is not prevented from being substantially infinite, that is, a substantially straight line.

  By forming the pair of holding plate portions 9a and 9b as described above, the pair of holding plates 9a and 9b before the tightening of the holding bolt 33 is performed in both the second and third examples. The space between the restraining surfaces 10a and 10b of the plate portions 9a and 9b is narrow on the proximal end side close to the connecting portion 25 and wide on the distal end side which is the opening side of the proximal end portion 8.

  A through hole (not shown) through which the holding bolt 33 is inserted is formed at the tip side portion of each holding plate portion 9a, 9b, and the holding bolt 33 is inserted into each through hole with the shaft 7 and It can be inserted without interference. However, when the holding bolt 33 is rotated based on the tightening of the nut screwed into the male threaded portion 40 provided at the distal end portion of the holding bolt 33 inserted into both the through holes, The outer peripheral surface of the formed cam portion 41 having an elliptical cross section is configured to hold the shaft 7 toward the inner peripheral surface of the connecting portion 25.

  Of the pair of substantially concentric through holes formed in the pair of holding plate portions 9a and 9b, one through hole has a relatively large diameter so that the cam portion 41 can be inserted, and the other The through hole has a relatively small diameter that allows the male screw portion 40 to be inserted therethrough.

  According to the universal joints of the second to third examples of the present invention configured as described above, the base end portion of the shaft 7 and the yoke 3 can be obtained without strictly controlling the tightening torque of the holding bolt 33. The holding force over the axial direction with 8 can be increased. That is, in order to connect the shaft 7 and the yoke 3, first, the shaft 7 is inserted into the base end portion of the yoke 3, and the restraining bolt 33 is inserted into the distal end portions of the pair of restraining plate portions 9 a and 9 b. It is inserted through the through-hole formed.

  Then, a nut is screwed into the male screw portion 40 protruding from the outer surface of the holding plate portion 9a (or 9b) at the tip end portion of the holding bolt 33. Then, by tightening the nut while rotating it, the interval between the nut and the head portion 42 of the holding bolt 33 is reduced, and the pair of holding plate portions 9a, The tip portions of 9b are held down.

  As described above, when the nuts are tightened so as to hold down the tip portions of the pair of holding plate portions 9a and 9b, first, the cam portion 41 is moved to the shaft based on the rotation of the holding bolt 33. 7 is held down to the inner peripheral surface of the connecting portion 25. As a result, the shaft 7 and the inner peripheral surface of the connecting portion 25 are in contact with each other at a portion B in FIG.

  Further, the holding bolt 33 does not rotate any more based on the engagement between the cam portion 41 and the shaft 7. When the nut is further tightened, a pair of outer flat surfaces 14, 14 formed on the shaft 7 on the proximal end side close to the connecting portion 25 among the restraining surfaces 10 a, 10 b of the pair of restraining plate portions 9 a, 9 b. Start to suppress. In this state, the holding surfaces 10a and 10b and the outer flat surfaces 14 and 14 are in contact with each other at portions C and D in FIG.

  When the nut is further tightened from this state, the portion where the contact surface pressure between the restraining surfaces 10a, 10b and the outer flat surfaces 14, 14 is maximum is the opening side of the base end portion 8 of the yoke 3. FIG. Move to the E and F parts. When the tightening torque of the restraining bolt 33 based on the tightening of the nut becomes sufficiently large, the outer flat surfaces 14 and 14 and the restraining surfaces 10a and 10b become substantially parallel, and the contact pressure at the E and F portions increases. On the contrary, the contact pressures of the C and D portions are slightly reduced, and finally the outer planes 14 and 14 are held down by the holding surfaces 10a and 10b substantially uniformly at the E and F portions and the C and D portions.

  As described above, the universal joints of the second to third examples of the present invention have the restraining plate portions 9a, 9a, The contact pressure between the restraining surfaces 10a and 10b of 9b and the pair of outer flat surfaces 14 and 14 formed on the shaft 7 increases.

  Accordingly, the pair of outer flat surfaces 14 and 14 and the respective restraining surfaces 10a and 10b are brought into close contact with each other with sufficient contact pressure, and the coupling strength between the shaft 7 and the yoke 3 can be ensured. In addition, as the nuts are tightened, the portion where the contact surface pressure between the pair of outer flat surfaces 14, 14 and the respective restraining surfaces 10a, 10b is maximized moves to the distal end side of the restraining plate portions 9a, 9b. Or, since it increases, the constituent parts do not undergo plastic deformation until the tightening torque for tightening the nut becomes considerably large.

  Therefore, in the case of the universal joints of the second to third examples of the present invention, the coupling strength between the yoke 3 and the shaft 7 is sufficiently ensured, and undesired plastic deformation does not occur in the constituent members.

  Next, FIGS. 7 to 8 show the overall shape of the yoke 3 constituting the third example of the embodiment of the present invention. The configuration and operation of the universal joint incorporating the yoke 3 are as described above. The holding bolt used in the universal joints of the second to third examples of the present invention does not necessarily need to be a cam bolt as shown in FIG. When the cam bolt is not used, a screw hole for screwing the holding bolt into one of the holding plate portions 9a and 9b can be formed, or a nut can be fixed.

  Since the universal joint of the present invention uses a hot-rolled mild steel plate with good formability as the material of the yoke, mass production by press working is possible, and it can be manufactured at low cost. In addition, since hot rolled mild steel sheet has little spring back during forming, the gap between the yoke restraining surface and the shaft outer plane can be manufactured with high accuracy and minimum error, so that the tightening force of the yoke against the shaft is stable. .

  Furthermore, before the tightening bolts are tightened, the yoke restraining plate is not parallel to the shaft outer plane depending on the degree to which it is strongly affected by the tightening force of the retaining bolts, or before the retaining bolts are tightened. The spacing between the restraining surfaces of the yoke restraining plate is narrow on the side close to the connecting portion of the yoke and wide on the opening side. Accordingly, the tightening force of the yoke with respect to the shaft is improved, and the looseness of the coupling portion between the yoke and the shaft is eliminated. Therefore, it is suitable for use in a place where a large steering torque is applied.

  In addition, hot rolled mild steel sheets are prone to plastic deformation when the restraining bolts are tightened excessively, but the universal joint of the present invention does not require excessive tightening of the restraining bolts. Deformation is suppressed and disassembly and reassembly become easy.

  In particular, in combination with a steering force assisting device having severe use conditions, a large torque is generated on the restraining surface, so that both securing of tightening force and difficulty in plastic deformation are required.

1 is an overall front view of a steering column device equipped with a universal joint according to an embodiment of the present invention. It is a side view which shows the state which couple | bonds the base end part of the yoke of the universal joint of embodiment of this invention with the edge part of a shaft. It is a fragmentary sectional view which shows the 1st example of embodiment of this invention, Comprising: It is AA sectional drawing of FIG. It is sectional drawing which shows the base end part of the yoke of embodiment of this invention, and the edge part of a shaft in the state before tightening a holding | suppressing volt | bolt, and the right half of the embodiment of this invention is centered on a centerline. A second example is shown, and the left half with respect to the center line indicates a third example of the embodiment of the present invention. It is the A section enlarged view of FIG. The 2nd example of embodiment of this invention is shown. It is the side view and top view of a holding bolt used for tightening the yoke of the 2nd example. It is a perspective view which shows the whole structure of the yoke which comprises the 3rd example of embodiment of this invention. It is a perspective view which shows the whole structure of the yoke of the modification of the 3rd example of embodiment of this invention. It is a partial side view of the conventional universal joint. It is the figure seen from the right side of FIG. It is a figure which shows a state when the clamp bolt is tightened in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Universal joint 2, 3 Yoke 4 Cross shaft 5 Bearing cup 6, 7 Shaft 7A Corner | angular part 8 Base end part 9a, 9b Holding plate part 10, 10a, 10b, 101 Holding surface 11 Holding bolt 11a Male thread part 11b Shaft part outer periphery 12 Screw hole 13 Through hole 14 Outer plane 15 Notch 25 Connection portion 25A Connection portion center 27 Gap 29 Arm portion 33 Retaining bolt 34 Thin wall portion 35 Recess portion 36 Corner portion 37 Convex portion 38 First cylindrical curved surface 39 Second cylindrical curved surface 40 Male thread part 41 Cam part 42 Head part 43 Column 44 Steering shaft 45 Steering wheel 46 Motor 47 Reduction gear box 48 Rack and pinion motion conversion mechanism 49 Steering force assist device

Claims (4)

A yoke having a base end portion that is open on the side, and a pair of outer flat surfaces of the shaft tip inserted from the opening side that can be coupled to the base end portion;
A pair of holding plate portions that are spaced apart from each other at the base end portion, and formed with holding surfaces facing the respective outer flat surfaces on the respective inner side surfaces;
A connecting part that connects the two holding plate parts to each other at the opposite side of the opening of the base end part;
A through hole or a screw hole formed substantially concentrically with each other, formed on the two holding plate parts,
Freely provided with a holding bolt that is screwed into the screw hole or nut with the male screw portion formed at the tip thereof inserted into the through hole and tightens the outer flat surface of the shaft with the holding surface of the holding plate portion. In the joint,
The yoke is made of hot-rolled mild steel sheet,
Before tightening the holding bolt, the relationship between the pair of holding plate portions and the outer plane is made non-parallel to each other according to the degree to which it is strongly affected by the tightening force of the holding bolt,
A universal joint characterized in that the holding force of the holding surface and the outer flat surface of each of the holding plate portions increases with tightening of the holding bolt. A yoke having a base end portion that is open on the side, and a pair of outer flat surfaces of the shaft tip inserted from the opening side that can be coupled to the base end portion;
A pair of holding plate portions that are spaced apart from each other at the base end portion, and formed with holding surfaces facing the respective outer flat surfaces on the respective inner side surfaces;
A connecting part that connects the two holding plate parts to each other at the opposite side of the opening of the base end part;
A through hole or a screw hole formed substantially concentrically with each other, formed on the two holding plate parts,
Freely provided with a holding bolt that is screwed into the screw hole or nut with the male screw portion formed at the tip thereof inserted into the through hole and tightens the outer flat surface of the shaft with the holding surface of the holding plate portion. In the joint,
The yoke is made of hot-rolled mild steel sheet,
Before the tightening bolts are tightened, the spacing between the restraining surfaces of the pair of restraining plate portions is narrow on the side close to the connecting portion, and the opening side of the base end portion in which the through hole or screw hole is formed Widely formed in each
When tightening the holding bolt or the nut screwed to the holding bolt, the pair of outer flat surfaces and the holding surfaces start to come into contact with each other on the side close to the connecting portion, and the tightening operation of the holding bolt proceeds. Accordingly, the universal joint is characterized in that the portion where the contact surface pressure is maximized moves or increases toward the opening side of the base end portion. In the universal joint according to claim 1 or 2,
The universal joint according to claim 1, wherein the yoke is formed of a material having a tensile strength of 370 N / mm ² or less. In the universal joint according to any one of claims 1 to 3,
A universal joint, wherein a steering force assisting device is attached between the yoke and the steering wheel.

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