JP5007752B2 - Method for manufacturing yoke for cross shaft type universal joint - Google Patents

Description

  The present invention relates to an improvement in a manufacturing method of a yoke that constitutes a cross-shaft universal joint (cardan joint) for connecting rotation shafts constituting a steering apparatus for an automobile so that torque can be transmitted. Specifically, the metal plate is subjected to press working such as punching and bending, and a method of manufacturing a yoke having a pair of flange portions having a thickness dimension corresponding to two metal plates is devised. Therefore, it is intended to realize a manufacturing method capable of manufacturing a yoke that is less likely to be damaged such as cracks in both flange portions at a low cost.

  The automobile steering device is configured as shown in FIG. 3, and transmits the rotation of the steering wheel 1 to the input shaft 3 of the steering gear unit 2, and a pair of left and right tie rods 4 as the input shaft 3 rotates. 4 is pushed and pulled to give a steering angle to the front wheels. The steering wheel 1 is supported and fixed to the rear end portion of the steering shaft 5, and the steering shaft 5 is rotatably supported by the steering column 6 with the cylindrical steering column 6 inserted in the axial direction. Has been. Further, the front end portion of the steering shaft 5 is connected to the rear end portion of the intermediate shaft 8 via a universal joint 7, and the front end portion of the intermediate shaft 8 is connected to the input shaft 3 via another universal joint 9. Connected to. The illustrated example incorporates an electric power steering device that reduces the force required to operate the steering wheel 1 using the electric motor 10 as an auxiliary power source. Therefore, the front end portion of the steering shaft 5 is connected to the input side of the electric power steering device, and the output shaft of the electric power steering device and the rear end portion of the intermediate shaft 8 are connected by the universal joint 7. Torque transmission is connected freely.

  The universal joint 7 connected to the steering shaft 5, the intermediate shaft 8, and the input shaft 3, which are rotating shafts that are incorporated in the above-described steering apparatus for an automobile and do not exist on the same straight line. Reference numeral 9 denotes a cross shaft type universal joint that incorporates a yoke that is the object of the manufacturing method of the present invention. Such universal joints have been conventionally known in various structures as described in Patent Documents 1 to 5, for example. FIG. 4 shows an example of the structure described in Patent Document 1 among them. The universal joint 11 shown in FIG. 4 is formed by connecting a pair of yokes 12a and 12b via a single cross shaft 13 so as to transmit torque. In the case of the illustrated example, both of the yokes 12a and 12b are made by stamping and bending a metal plate having sufficient strength and rigidity, such as a steel plate, respectively. 14a and 14b, and a pair of connecting arm portions 15a and 15b for each of the yokes 12a and 12b.

  Of these, the base portions 14a and 14b include first flange portions 16a and 16b and second flange portions 17a and 17b, respectively. The first flange portions 16a and 16b and the second flange portions 17a and 17b are provided with a discontinuous portion 18a and 18b provided at one place in the circumferential direction of the base portions 14a and 14b, respectively. . A pair of mounting holes for each of the two base portions 14a and 14b is provided at a position where the first and second flange portions 16a, 16b, 17a and 17b are paired with each other for the two base portions 14a and 14b. Each of these base portions 14a and 14b is formed in a direction that is a torsional positional relationship with respect to the axial direction. In addition, the seating surface portions 19a and 19b are provided on the outer shaft of the first flange portions 16a and 16b so as to surround the opening portions of the mounting holes formed in the first flange portions 16a and 16b. They are formed in the orthogonal direction.

  In addition, a pair of coupling arm portions 15a and 15b for each of the yokes 12a and 12b is rotated to be coupled and fixed to the base portions 14a and 14b at the front end edges of the base portions 14a and 14b of the yokes 12a and 12b, respectively. It extends in the axial direction from two positions on the diametrically opposite side with respect to the shafts 20a and 20b. Then, circular holes 21a and 21b are respectively formed at the distal ends of the respective connecting arm portions 15a and 15b so as to be concentric with each other between the pair of connecting arm portions 15a and 15b for each of the yokes 12a and 12b. ing. The four shaft portions provided on the cross shaft 13 inside the circular holes 21a and 21b are rotatably supported by radial bearings 22a and 22b, each of which is a shell type needle bearing. With such a structure, the yokes 12a and 12b are combined so that torque can be transmitted even when the central axes of the base portions 14a and 14b are inclined.

  When assembling a steering apparatus for an automobile as described above, the universal joint 11 as described above does not exist on the same straight line (the steering shaft 5, the intermediate shaft 8, and the input shaft 3 are mutually connected. A pair of rotating shafts 20a and 20b, which are any two adjacent to each other and whose central axes are inclined to each other, are coupled so as to be able to transmit torque. For this purpose, the bolts 23a are inserted into the bases 14a and 14b of the yokes 12a and 12b, and the mounting holes formed in the bases 14a and 14b are inserted into the ends of the rotary shafts 20a and 20b. 23b and nuts 24a and 24b are screwed together and further tightened. And the outer peripheral surface of the edge part of both the rotating shafts 20a and 20b is strongly suppressed by the inner surface of both the base parts 14a and 14b. In this state, these rotary shafts 20a and 20b are coupled via the universal joint 11 so as to be able to transmit torque.

  Of the pair of yokes 12a and 12b constituting the universal joint 11 shown in FIG. 4, one (left side in FIG. 4) yoke 12b has a female serration formed on the inner peripheral surface of the base portion 14b and the female serration. By engaging the male serration formed on the outer peripheral surface of the end portion of the rotating shaft 20b, a large torque can be transmitted between the base portion 14b and the rotating shaft 20b. Accordingly, when the base portion 14b and the rotary shaft 20b are coupled, the base portion 14b and the rotary shaft 20b are relatively displaced in the axial direction. On the other hand, the base portion 14a of the other yoke 12a (right side in FIG. 4) has a U-shaped cross section or a U-shaped cross section with a side opening, and the rotary shaft 20a is used as the base portion. 12a can be inserted from the side.

  As shown in FIGS. 5 to 6, one of the pair of mounting holes formed so as to be aligned with both the first and second flange portions 16c and 17c provided on the yoke 12c is a bolt 23c. A structure in which a nut is omitted as a through hole 25 for loosely inserting the nut and a screw hole 26 for screwing the bolt 23c into the other mounting hole has been conventionally used, for example, as described in Patent Documents 3 and 5. Widely known. The yoke 12c is a so-called press yoke in which a metal plate is sequentially punched and bent by a press. A female serration is formed on the inner peripheral surface of the base portion 14c except for the discontinuous portion 18c and the vicinity thereof. ing. Further, the first and second flange portions 16c and 17c are made to have a thickness dimension corresponding to two metal plates by folding the metal plate. In addition, a portion around the opening of the through hole 25 on the outer surface of the first flange portion 16c is a seating surface portion 19c. Such a structure and manufacturing method of a press yoke have been conventionally known, for example, as described in Patent Document 5. Since the present invention relates to an improvement in the manufacturing method of such a press yoke, the present invention is directed to a manufacturing method as a premise of the present invention, which is a slight improvement over the manufacturing method described in Patent Document 5. The explanation will be given with reference to FIG.

  In this manufacturing method, first, a metal plate having sufficient rigidity, such as a steel plate, is punched out by press working, so that a substrate portion 27 and a pair of tongue-like portions 28 and 28 as shown in FIG. A flat base plate 29 having the above is obtained. Among these, the board | substrate part 27 is made into a substantially rectangular shape, and the constriction parts 30 and 30 are provided in the part near both ends of a length direction, respectively.

  If the base plate 29 as described above is obtained by punching, then, in the base plate portion 27 constituting the base plate 29, both end portions protruding from the both tongue-like portions 28, 28 are respectively connected to the base plate 29. The two constricted portions 30, 30 located in the middle portion in the length direction are folded back 180 degrees and densely (with as much curvature as possible) in the same direction with respect to the thickness direction of the substrate portion 27. Overlapping parts 31, 31 are formed. Each of these overlapping portions 31, 31 is composed of a pair of flat plate portions 32 a, 32 b that overlap each other, and a folded portion 33 that connects the edges of the flat plate portions 32 a, 32 b. The width dimension of each folded portion 33 gradually decreases as the distance from the end edge of each flat plate portion 32a, 32b is based on the presence of the constricted portions 30, 30. In other words, the constricted portions 30 and 30 are formed by substantially V-shaped cutout portions present at both ends in the axial direction of one end edge in the width direction of the substrate portion 27. The end edge and the side edges of the two tongue-like portions 28 and 28 are portions corresponding to the both constricted portions 30 and 30 and are continuous by inclined edges. For this reason, both the width direction both ends of the folding | returning part 33 of both the said overlapping parts 31 and 31 become a shape inclined in the direction which decreases gradually as it leaves | separates from the edge of each said flat plate part 32a, 32b. As described above, the first intermediate material 34 as shown in FIG. 7B is obtained by folding back both end portions of the substrate portion 27.

  Next, the first intermediate material 34 is pressed between a pair of pressing dies to be plastically deformed, whereby a second intermediate material 35 as shown in FIG. 8C is obtained. The second intermediate material 35 is to be a pair of connecting arm portions 15b, 15b (see FIG. 5), and the tongue portions 28, 28 are curved in a partial cylindrical shape, and the tongue portions 28, 28 are both curved. The base end portion of the tongue portion 28 is bent in a substantially crank shape, and the middle portion or the tip end portion portion of the two tongue-like portions 28, 28 is offset with respect to the substrate portion 27.

Next, the second intermediate material 35 as described above is slightly curved (over 90 degrees and less than 180 degrees, for example, about 130 to 150 degrees) at the central portion of the substrate portion 27, and is shown in FIG. The third intermediate material 36 as shown is used.
Next, the substrate portion 27 of the third intermediate material 36 is further curved (from a flat plate state to 180 degrees) to form a fourth intermediate material 37 as shown in FIG. In this state, a base portion 14c and a pair of arm portions 15b and 15b provided in the completed yoke 12c (see FIG. 6) are formed. Therefore, finally, through holes 25 and screw holes 26 are formed in the first and second flange portions 16c and 17c constituting the base portion 14c, and circular holes 21b and 21b (see FIG. 5) in the both arm portions 15b and 15b. 6) are formed to complete a yoke 12c as shown in FIGS.

  When the yoke 12c as shown in FIGS. 5 to 6 is manufactured by the manufacturing method as described above, in the process of using the base plate 29 as the first intermediate material 34 as shown in FIGS. The processing amount of the metal plate increases. That is, in the process of forming the overlapping portions 31, 31, both end portions of the substrate portion 27 are folded back 180 degrees with a large curvature (small curvature radius). For this reason, a large tensile stress is applied to the outer diameter side with respect to the folding direction, and in the obtained first intermediate material 34, there is a residual tensile stress in the outer diameter side portions of the folded portions 33, 33. It becomes a state. As is well known in the field of metal processing, the residual tensile stress is likely to lead to damage such as cracks, and if the processing is continued as it is, damage such as cracks occurs in the outer diameter side portions of the folded portions 33 and 33. easy. In particular, in recent years, as shown in FIG. 3 described above, there is an increasing number of cases where an electric power steering device is provided on the upstream side of the universal joint with respect to the direction of force transmission, and it is necessary to ensure the strength of the universal joint. As a metal plate constituting the yoke, there is an increasing demand to use a relatively thick plate having a thickness of about 6 to 8 mm, for example. When a metal plate having a large thickness is folded back with a large curvature as described above, the residual tensile stress increases, and damage such as cracks is likely to occur. Even if such a crack does not occur in the process of manufacturing the yoke, it may occur in the process of using the yoke after it has been incorporated into the cross shaft universal joint.

  For this reason, when the yoke 12c is made of a metal plate having a large thickness by the conventional method as shown in FIG. 7, after the base plate 29 is obtained, the two folded portions are formed at any stage. 33, 33, or the constricted portions 30, 30 to be the folded portions 33, 33 must be annealed. For example, in order to prevent the occurrence of cracks in the processing stage after the formation of the folded portions 33 and 33, the residual tensile stress inside the folded portions 33 and 33 is released, and then the subsequent machining is performed. Need to proceed. Even when cracking can be suppressed in the processing stage, it is necessary to anneal the folded portions 33 and 33 after the yoke 12c is manufactured and before the cross shaft is assembled to the yoke 12c. However, the annealing process, which is a kind of heat treatment, increases the amount of energy used, and is contrary to the trend of energy saving in recent years. Further, not only does the annealing process itself take a long time, but it is also necessary to perform the process in a place outside of a series of other processes, both of which can be performed by pressing, and therefore the degree of deterioration of the processing efficiency is significant. Furthermore, the rigidity is originally required to be rigid and does not need to be annealed, such as the base end portions of the tongue portions 28 and 28, and the portions other than the folded portions 33 and 33. This is also disadvantageous from the standpoint of maintaining the quality of the obtained yoke (securing necessary rigidity).

  In view of the circumstances as described above, the present invention can reduce or eliminate the residual tensile stress inside the folded portion constituting the overlapped portion without performing an annealing process, and damage such as a crack in the folded portion. The invention has been invented to realize a method for manufacturing a yoke for a cross shaft type universal joint, which can prevent the occurrence of the problem.

The method of manufacturing the yoke for a cross shaft type universal joint according to the present invention includes a base for coupling and fixing the end of the rotary shaft, and an axial end of the base extending from the diametrically opposite position in the axial direction of the base. A universal joint yoke having a pair of arm portions is formed.
For this purpose, first, by punching and forming a metal plate, the substrate portion in which the constricted portion is formed in a substantially rectangular shape at both end portions in the length direction, and two spaced apart positions on one end edge in the width direction of the substrate portion. And forming a flat base plate having a pair of tongues protruding from the base plate.
After that, both end portions of the substrate portion that protrude from both tongue-shaped portions are 180 degrees in the same direction with respect to the thickness direction of the substrate portion at the both constricted portions located at the intermediate portions in the length direction. Each of the flat plate portions is folded and each has a pair of overlapping flat plate portions, and the end portions of the respective flat plate portions are connected to each other, and the return portions are gradually reduced in width as they are separated from the end edges of the respective flat plate portions. A pair of overlapping portions is formed.
Next, both end surfaces in the width direction of both folded portions are pressed in directions toward each other and toward the flat plate portions, and a force in the compression direction is applied to both folded portions. Preferably, as in the invention described in claim 2, after applying a force in the compression direction, a portion between the two tongue-shaped portions of the substrate portion is folded back into a U-shape, and the substrate portion is turned into the base portion. And

According to the method of manufacturing a cross shaft type universal joint yoke of the present invention configured as described above, a high quality yoke can be obtained at low cost. The reason for this is as follows.
First, in the case of the present invention, after forming a pair of overlapped portions, pressing the both end surfaces in the width direction of both folded portions at any stage, the residual tension existing inside these folded portions. Stress can be reduced or eliminated. That is, when both end surfaces in the width direction of both folded portions are pressed toward each other and toward each flat plate portion, residual compressive stress tends to be generated inside these folded portions. The residual compressive stress and the residual tensile stress are forces in opposite directions, and cancel each other, so that the residual tensile stress can be reduced or eliminated. For this reason, even after the processing of the both folded portions, even if the subsequent processing is performed without performing the annealing process, or the obtained yoke is incorporated in the cross shaft universal joint, Damage such as cracks is less likely to occur.

  Further, pressing both end surfaces in the width direction of the folded portions can be easily performed by surface pressing with a press, and the magnitude of the force applied to each of the end surfaces (will tend to occur inside the folded portions, The magnitude of the residual compressive stress can also be adjusted freely. Also, the amount of energy to be used is much less than that of annealing treatment, and the processing time can be shortened, so that the processing efficiency is deteriorated by solving the problem based on the residual tensile stress. Can be suppressed to a small extent. Furthermore, since the rigidity of the portions other than the two folded portions is not lowered, it is advantageous from the viewpoint of maintaining the quality of the obtained yoke.

The figure which shows the manufacturing method of the yoke which shows an example of embodiment of this invention in order of a process. Similarly, the perspective view of a yoke which shows the part which should be pressed by a surface pressing process in order to generate a compressive stress inside the folding | returning part of an overlapping part. The partial cutting side view which shows an example of the steering device for motor vehicles incorporating the cross-type universal joint. The partially cut side view which shows the 1st example of the cross-shaped universal joint conventionally known. The perspective view which shows the 2nd example in the state which took out only the yoke. The same figure as FIG. 1 which shows the state (A) before assembling | attaching a bolt after inserting a rotating shaft in this yoke simple substance, and the state (B) after assembling | attaching a bolt. The figure which shows the manufacturing method of this yoke in order of a process.

  1 and 2 show an example of an embodiment of the present invention. The feature of this example is that the first and second flange portions 16c and 17c constitute the folded portions 33 and 33 for connecting the edges of the pair of flat plate portions 32a and 32b, respectively. In order to prevent the occurrence of damage such as cracks based on the residual tensile stress, a process of generating a compressive stress is added to the folded portions 33 and 33. The other steps are the same as those in the manufacturing method described with reference to FIG. 7, and the structure and operation of the yoke 12c obtained are the same as those shown in FIGS. The description of the equivalent part is omitted, and the characteristic part of this example will be described below.

  In the case of this example, the base plate 29 shown in FIG. 1A is used as the first intermediate material 34 shown in FIG. It is a width direction both end surface of a pair of folding | returning parts 33 and 33 which comprise a pair of overlapping parts 31 and 31, and it shows by the thick line in FIG. Further, the slope portions 38a and 38b are pressed in a direction perpendicular to the slope portions 38a and 38b. As a result, both end portions in the width direction of the folded portions 33, 33 are pressed toward each other and in the direction toward the flat plate portions 32a, 32b, and the folded portions 33, 33 are subjected to force in the compression direction. Is added. Thereafter, as shown in (B) → (C) → (D) → (E) in FIG. 1, the portion between the pair of tongue-shaped portions 28, 28 of the substrate portion 27 is folded back into a U-shape. The board part 27 is referred to as a base part 14c. In addition, if it is possible to suppress the occurrence of damage such as cracks based on the tensile stress during the processing steps shown in (B) → (C) → (D) → (E) in FIG. The operation of pressing the slope portions 38a and 38b may be performed after the yoke 12c is completed as shown in FIG.

  According to the method of manufacturing a yoke for a cross shaft type universal joint of the present example configured as described above, as described above, the residual tensile stress existing in the folded portions 33 and 33 can be reduced or eliminated, Damage such as cracks is less likely to occur at both folded portions. Further, the amount of energy to be used is reduced, the processing time is shortened and the degree of deterioration of processing efficiency is suppressed to a small extent, and a high quality yoke can be obtained without lowering the rigidity of portions other than the folded portions 33 and 33. Obtained stably.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering gear unit 3 Input shaft 4 Tie rod 5 Steering shaft 6 Steering column 7 Universal joint 8 Intermediate shaft 9 Universal joint 10 Electric motor 11 Universal joint 12a, 12b, 12c, 12d Yoke 13 Cross shaft 14a, 14b, 14c Base 15a, 15b Coupling arm portion 16a, 16b, 16c First flange portion 17a, 17b, 17c Second flange portion 18a, 18b, 18c Discontinuous portion 19a, 19b, 19c Seat surface portion 20a, 20b, 20c Rotating shaft 21a, 21b Circle Hole 22a, 22b Radial bearing 23a, 23b, 23c Bolt 24a, 24b Nut 25 Through hole 26 Screw hole 27 Substrate part 28 Tongue part 29 Base plate 30 Constricted part 31 Overlapping part 32a, 32b Flat plate part 33 Folded part 3 The first intermediate material 35 a second intermediate material 36 a third intermediate material 37 a fourth intermediate material 38a, 38b slope portion

JP-A-8-284968 Japanese Patent Laid-Open No. 10-2343 JP 2000-320564 A JP 2004-223616 A Japanese Patent Publication No.7-88859

Claims (2)

  A universal joint yoke comprising a base for coupling and fixing the end of the rotating shaft, and a pair of arms extending in the axial direction of the base from a position opposite to the diametrical direction at one axial end edge of the base In order to manufacture the substrate, by punching and forming a metal plate, the substrate portion having a substantially rectangular shape with constricted portions formed at both ends in the longitudinal direction, and two spaced apart positions on one end edge in the width direction of the substrate portion. After forming a flat base plate having a pair of protruding tongue-shaped portions, both end portions of the base plate that protrude from both tongue-shaped portions are positioned in the middle portions in the length direction. These two constricted portions are folded 180 degrees in the same direction with respect to the thickness direction of the substrate portion, respectively, and each of the overlapping flat plate portions and the edges of each flat plate portion are connected to each other. As you move away from the edge of each flat plate After forming a pair of overlapped portions each having a folded portion whose size gradually decreases, both end surfaces in the width direction of both folded portions are pressed toward each other and in the direction toward each flat plate portion. A method for manufacturing a universal joint yoke, wherein a force in the compression direction is applied to both folded portions.   The universal joint according to claim 1, wherein a portion between both tongue-like portions of the substrate portion is folded back into a U shape, and processing using the substrate portion as a base portion is performed after a force in the compression direction is applied to both folded portions. Method for manufacturing a magnetic yoke.

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