JP2010188502A - Method for producing yoke for universal joint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a yoke for a universal joint in which a damage such as a crack is hardly generated at a portion in a severe condition even when the yoke is produced by applying press-processing to a thick-walled metal plate. <P>SOLUTION: A portion 33 between a pair of lingual parts 17a, 17a is folded back in a U shape at a middle part of a base plate part 16a to make the yoke for the universal joint, having the base plate part 16a as a base part 10a. Before folding back the in-between portion 33 in the U shape, surface roughness of a portion with a cross-hatched pattern, surrounded at three sides with the in-between portion 33 and base plate parts of the lingual parts 17a, 17a, is refined by removing metal materials existing on a surface of the portion. Accordingly, the damage such as the crack is hardly generated in the portion by folding back and usage afterwards. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a metal yoke among the yokes constituting a universal joint that connects ends of a pair of rotating shafts that do not exist on the same straight line and enables transmission of rotational force between the rotating shafts. The present invention relates to an improvement in a method for manufacturing a universal joint yoke manufactured by pressing a plate. Specifically, even when the thickness of the metal plate is increased to form a universal joint that transmits a large torque, the end portion of the rotary shaft is supported and the cross shaft is supported. It is intended to realize a manufacturing method capable of obtaining a yoke in which damage such as cracks is unlikely to occur in a pair of power arms.

  As a device for incorporating a universal joint configured to include a yoke that is a subject of the present invention, an automobile steering device as shown in FIG. 6 is widely known. This steering apparatus for an automobile transmits the movement of the steering wheel 1 to the steering gear unit 2, and the movement of the steering wheel 1 is transmitted to the steering shaft 3, the universal joint 4a, the intermediate shaft 5, and the universal joint 4b. Is transmitted to the input shaft 6 of the steering gear unit 2. When the input shaft 6 rotates as the steering wheel 1 is operated, the steering gear unit 2 pushes and pulls the pair of left and right tie rods 7 and 7 to give a desired steering angle to the steered wheels. In the example shown in FIG. 6, an electric power steering device is provided in which an electric motor 8 applies an assisting force corresponding to the force applied by the driver to the steering wheel 1 to the steering shaft 3.

  As is well known, each of the universal joints 4a and 4b incorporated in such an automobile steering apparatus is formed by freely combining torque transmission and swing displacement through a pair of yokes via a cross shaft. As a yoke that constitutes such a universal joint, a yoke formed by pressing a metal plate such as a steel plate can reduce the manufacturing cost. Therefore, for example, as described in Patent Documents 1 to 5, conventionally, Widely known. FIG. 7 shows an example of such a press-type yoke 9 that has been widely known. The yoke 9 includes a base 10 and a pair of arms 11 and 11 extending from one axial end edge of the base 10.

  Of these, the base 10 is formed in a not-cylindrical shape in which one end in the circumferential direction is discontinuous in order to insert the end of the rotating shaft to which the yoke 9 is to be fixed. A pair of opposing flanges 12, 12 are provided. Then, a through hole 13 for inserting a flange portion of a bolt (not shown) into one flange 12 and a flange portion of the bolt to be screwed into the other flange 12 are concentric with the through hole 13. Screw holes (not shown) are respectively formed. In the case of the yoke 9 shown in FIG. 7, flanges 12 and 12 are provided in which metal plates are folded 180 degrees to overlap each other. On the other hand, as shown in FIG. 8, which will be described later, a yoke having a flange made up of only one metal plate is also conventionally known. A yoke having a flange in which the thickness of a single metal plate is increased by fleshing is also conventionally known. Any structure yoke can be the object of the manufacturing method of the present invention.

  On the other hand, each of the arms 11 and 11 is slightly bent outwardly in the radial direction of the base 10 from a position opposite to the radial direction at one end edge in the axial direction of the base 10, and then extends in the axial direction of the base 10. Yes. Each of the arms 11 and 11 has a partially cylindrical concave surface facing each other. Further, concentric circular holes 14 and 14 are formed at the distal ends of the arm portions 11 and 11, respectively. When a universal joint is configured by combining the yoke 9 and a cross shaft (not shown), a bearing cup (not shown) is press-fitted into the circular holes 14 and 14. Each of these bearing cups functions as an outer ring of a radial needle bearing, and couples and supports the cross shaft with the yoke 9 so as to be swingable and displaceable.

  Also, the press yoke manufacturing method as described above has been widely known as shown in, for example, Patent Documents 2 to 4. FIG. 8 shows the manufacturing method described in Patent Document 3 among them as an example of a conventionally known manufacturing method in the order of steps. First, a flat base plate 15 having a shape as shown in FIG. 8A is obtained by punching out a metal plate having sufficient rigidity, such as a steel plate, by press working. The base plate 15 includes a substantially rectangular substrate portion 16 and a pair of tongue-like portions 17 and 17 projecting from one end edge of the substrate portion 16 in a hook-like shape. In addition, the lower holes 18 and 18 are punched and formed at the distal ends of the tongues 17 and 17 by press working.

  Such a base plate 15 is pressed between a pair of press dies, and is plastically deformed into a shape as shown in FIG. In the first intermediate material 19, the tongue-like portions 17, 17 to be a pair of arm portions 11, 11 (see FIG. 7) are curved in a partial cylindrical shape. Next, as shown in FIGS. 8C and 8D, such a first intermediate material 19 is formed by curving the central portion of the substrate portion 16 in the shape of a truncated cylinder, thereby forming second intermediate materials 20 to 3. The intermediate material 21 is used. Finally, both the lower holes 18 and 18 are enlarged to form circular holes 14 and 14 (see FIG. 7), and through holes and screw holes are formed in the pair of flanges 12a and 12a constituting the base 10a. Form.

  If a yoke for a universal joint is manufactured by the process as described above, the processing cost of this yoke can be reduced, but if the thickness dimension of the base plate 15 is increased to increase the transmittable torque, It becomes difficult to obtain a yoke having excellent durability. In particular, as shown in the aforementioned FIG. 6, the above-mentioned universal joint incorporated in an automobile steering apparatus incorporating a so-called column type electric power steering apparatus in which an electric motor 8 is provided on the steering wheel side of the universal joints 4a and 4b. In the case of 4a, 4b, the above tendency becomes remarkable. This is because it is necessary to transmit a large torque to the universal joints 4a and 4b, and it is necessary to increase the rigidity of the yokes constituting the universal joints 4a and 4b. This is to make it bigger. For example, it is necessary to increase the thickness dimension of about 6.5 mm to about 8 mm in the conventional case (not a column type electric power steering device).

  For example, when the yoke 9 shown in FIG. 7 is formed by folding a steel plate having a large thickness by 180 degrees, a large tensile stress is applied to the outer diameter portion of the folded portion 22 in the base portion 10 of the yoke 9. Occurs. That is, in order to form the folded portion 22 of the base portion 10, the substrate portion 16 is received by a receiving die having a partially cylindrical processing surface in the process shown in FIGS. 8B to 8D. It is bent around (or a cylindrical core). At this time, the amount of deformation of the base portion of the pair of arm portions 11 and 11 (the tongue portions 17 and 17 in FIG. 8) in a part of the substrate portion 16 becomes very large. The base plate 15 or the first intermediate material 19 including the substrate portion 16 is manufactured by punching (shearing) a metal plate as a material by a press. For this reason, a shear plane and a fracture surface exist at the outer peripheral edge of the base plate 15 or the first intermediate material 19. Of these, the fracture surface is a rough surface having a large surface roughness, and there may be defects such as microcracks and cracks on the surface.

  When a large tensile stress is applied to a portion where such a defect exists along with the processing of the folded portion 22, the stress is concentrated on the defective portion and the defect is increased. Large cracks that can lead to insufficient strength may occur. In particular, since the portion from the base 10 to the base of the arms 11 and 11 is repeatedly subjected to stress as the universal joint is used, it is necessary to prevent the crack from occurring in this portion. The yoke 9 with cracks must be discarded as a defective product, and it is important to suppress the frequency of crack generation from the viewpoint of improving the yield and reducing the manufacturing cost of the yoke 9. For this purpose, the folded surface 22 is conventionally provided with a fractured surface that is a rough surface positioned on the inner diameter side of the folded portion 22 and a shear surface having a relatively small surface roughness on the outer diameter side. Is formed. Prior to the processing of the folded portion 22, the surface of the outer peripheral edge of the substrate portion 16 is smoothed at a portion to be a portion of the base portion 10 and the base portions of the arm portions 11, 11. The surface roughness of this part is also improved by pressing the surface mold. However, as described above, when the thickness dimension of the steel plate constituting the yoke is increased, the amount of elongation of the metal material at the outer diameter side portion of the folded portion increases, so in the conventional technology as described above, the yield is increased. It is difficult to improve sufficiently.

  In order to suppress the occurrence of cracks due to the above-described causes, it is conceivable to perform a punching process for forming a base plate from a metal plate by a precision shearing process as shown in FIG. 9, that is, so-called fine blanking. That is, the upper surface of the metal plate 24 placed on the receiving die 23 is punched into the shape of the base plate 15 by the punching die 26 in a state where the upper surface of the metal plate 24 is strongly held by the holding die 25. Of the lower surface of the holding die 25, at least the portion located between the tongue-like portions and the circumferential side edges of both tongue-like portions, which are continuous from both ends of this portion, A protrusion 27 having a triangular cross-sectional shape and a U-shaped or U-shaped planar shape is provided around a portion surrounded by three sides. When the metal plate 24 is punched out by the punching die 26 and used as the material 15 while the upper surface of the metal plate 24 is strongly suppressed by the holding die 25 as described above, the outer peripheral properties (surface roughness) of the base plate 15 are obtained. However, there is a possibility that it can be processed into a good (small surface roughness) surface as in the case of finishing by cutting such as shaving.

  However, even if the portion surrounded by the three sides is restrained by the restraining die 25, it is difficult to sufficiently increase the internal pressure, and the surface roughness cannot be sufficiently reduced. In addition, the structure of the mold constituted by the molds 23, 25, and 26 is complicated, which increases the manufacturing cost. Furthermore, since the molding load becomes large, the work hardening of the obtained base plate 15 becomes remarkable, and there is a concern that cracks are likely to occur along with the work hardening. For these reasons, the fine blanking cannot always be an optimal manufacturing method.

JP 58-193935 A JP 2000-320564 A JP 2004-223616 A Japanese Patent Publication No.7-88859 Utility Model Registration No. 2508575

  In view of the circumstances as described above, the present invention provides a universal joint yoke that is less prone to cracking or other damage in severe conditions even when it is manufactured by pressing a thick metal plate compared to the prior art. Invented to realize a production method capable of obtaining

The yoke for a universal joint, which is the object of the manufacturing method of the present invention, extends from the diametrically opposite position at the base end for coupling and fixing the end of the rotating shaft to the axial direction of the base at one end edge in the axial direction of the base. And a pair of arms that have been taken out.
The method for manufacturing a universal joint yoke according to the present invention is similar to the conventional method described above, in order to produce a universal joint yoke as described above, by first punching and forming a metal plate. And a pair of tongue-shaped portions protruding from two spaced apart positions on one end edge of the substrate portion, thereby forming a flat base plate.
Thereafter, a portion between the two tongue-like portions is folded in a U shape at an intermediate portion of the substrate portion, and this substrate portion is used as the base portion.

In particular, in the method for manufacturing a universal joint yoke according to the present invention, before the intermediate portion is folded back into a U-shape, the two arm portions of the one side edge of the substrate portion provided with the both arm portions are connected to each other. Except for the portion located between them and the circumferential side edge of the base half (proximal end portion) of both arms, the portion continuing from both ends of this portion, excluding the tips of these arms The surface roughness of the part surrounded by the three sides is improved by removing the metal material present on the surface of this part (reducing the value of the surface roughness, making it a smooth surface or a surface close to a smooth surface) Process.
The processing for improving the surface roughness is performed by shaving, for example, as in the invention described in claim 2, or by cutting, as in the invention described in claim 3.

  According to the method for manufacturing a universal joint yoke of the present invention configured as described above, even if it is manufactured by pressing a thick metal plate as compared with the conventional case, damage such as cracks may occur in severe conditions. It is possible to stably produce a universal joint yoke that does not easily occur.

The top view and end view which show one example of embodiment of this invention in order of a process. The top view (A) and end view (B) of a base plate for demonstrating the part which cuts off in order to improve surface roughness. FIG. 3 is an enlarged eye cross-sectional view of FIG. 2A showing a state (A) before shaving and a state (B) after shaving. The top view (A) and end view (B) for showing the position in the yoke after completion of the part which cut off in order to improve surface roughness. The top view which shows one example of the implementation condition of the shaving process performed in order to improve surface roughness. The partial cutting side view which shows an example of the steering device for motor vehicles incorporating a universal joint. The perspective view which shows an example of the yoke for universal joints. The top view and end view {(D) and a side view} which show an example of the conventional manufacturing method in order of a process. Sectional drawing for demonstrating the manufacturing method considered prior to this invention.

  The embodiment of the present invention will be described with reference to FIGS. In the manufacturing method of this example, the yoke 9 as shown in FIG. 7 is manufactured in the steps (A) → (B) → (C) → (D) → (E) in FIG. First, a flat base plate 15a as shown in FIG. 1A is obtained by punching a metal plate having sufficient rigidity, such as a steel plate, by press working. The base plate 15a includes a substantially rectangular substrate portion 16a and a pair of tongue-shaped portions 17a and 17a that protrude from one end edge of the substrate portion 16a in a hook-like shape.

  Such a base plate 15a is formed by first folding back both ends of the substrate portion 16a 180 degrees at the narrow portions 28 and 28, respectively, so that a first intermediate material 29 as shown in FIG. And Next, the first intermediate material 29 is pressed between a pair of pressing dies to be plastically deformed, thereby forming a second intermediate material 30 as shown in FIG. The second intermediate material 30 is a pair of arms 11 and 11 (see FIG. 7). The tongues 17a and 17a are curved in a partial cylindrical shape, and the tongues 17a and 17a A portion near the base end is bent into a substantially crank shape, and an intermediate portion or a tip end portion of both tongue portions 17a and 17a is offset with respect to the substrate portion 16a. Next, such a second intermediate material 30 is slightly curved (over 90 degrees and less than 180 degrees, for example, about 130 to 150 degrees) at the center portion of the substrate portion 16a, and is shown in FIG. Such a third intermediate material 31 is used. Next, the substrate portion 16a of the third intermediate material 31 is further curved (from a flat plate state to 180 degrees) to form a fourth intermediate material 32 as shown in FIG. In this state, the base portion 10a and the pair of arm portions 11 and 11 provided in the completed yoke are formed. Therefore, finally, a through hole 13 and a screw hole are formed in the base portion 10a, and circular holes 14 and 14 (see FIG. 7) are formed in both the arm portions 11 and 11, respectively, and a yoke as shown in FIG. Completed as 9.

  The steps described above are basically described with reference to FIG. 8 except that both end portions of the substrate portion 16a are folded back closely at the narrow portions 28 and 28 to form a thick portion. This is the same as the conventional manufacturing method. In particular, in the case of the manufacturing method of this example, a metal plate is punched out by pressing to form the flat base plate 15a shown in FIG. 1A, and then the base 10a in the state of the yoke 9 after completion. 2 and the side edges of the base half of the pair of arm portions 11 and 11, that is, a portion surrounded by three sides, that is, FIGS. ) And the roughness-improved portion indicated by the broken line α in FIG. 4A, the surface roughness of the roughness-improved portion is improved (a smooth surface or a smooth surface that reduces the surface roughness value). To make the surface close to the surface). In addition, although the range which performs this process is determined by design in relation to the magnitude of the stress applied to the yoke 9 after completion, for example, in a general steering system for a passenger car incorporating an electric power steering device. In the case of a universal joint yoke to be incorporated, the distance L (see FIG. 2) from the edge of the base 10 is set to a range up to about 20 mm.

  In the processing for improving the surface roughness, the portion 33 between the two tongue-like portions 17a and 17a in the substrate portion 16a constituting the base plate 15a is shown in FIGS. 1D and 1E. However, in the case of this example, after the base plate 15a is punched and formed, it is performed before the narrow portions 28 and 28 are folded back. And by the said process, the surface layer part in which defects, such as a crack, may exist about the said roughness improvement part shown with the said oblique lattice and the broken line (alpha) is scraped off, and the new surface which does not have this defect is created. That is, as shown in FIG. 3A, the surface of the roughness improving portion composed of the shear surface 34 and the fracture surface 35 is scraped off. Such scraping work can be performed by general cutting using a cutting tool, for example. However, considering the combination with press working, the processing is troublesome and the processing time becomes long, so it is not always preferable processing. Not the way. For this reason, in the case of this example, the surface of the said roughness improvement part is scraped off by the shaving process using cutting tools, such as an end mill.

  That is, as shown in FIG. 5, while rotating a rotary cutting tool 36 such as an end mill, the roughness improving portion is copied, and the cutting surface as shown in FIG. 37 is formed. The value of the surface roughness of the cutting surface 37 is smaller than the value of the surface roughness of the fracture surface 35 (which is a smoother surface), as well as from the shearing surface 34 formed by press punching. Can also reduce the value of the surface roughness. In addition, since the load applied to the base plate 15a is very low when the roughness improving portion is scraped off by the cutting tool 36, a part of the base plate 15a is almost always hardened by the scraping. Absent. For this reason, even if the yoke 9 is manufactured by pressing a thick metal plate as compared with the conventional case, damages such as cracks occur in the base portions of the arms 11 and 11 which are severe in conditions. It is possible to stably produce a yoke 9 that is difficult to perform. That is, not only does the roughness-improved portion have no micro unevenness that is the starting point of cracks, but the toughness is not reduced due to work hardening associated with the scraping operation performed prior to the folding process. For this reason, the yoke 9 which does not easily cause the damage can be stably formed. Further, since the processing load for the above-mentioned scraping is small, and the mold for holding the base plate 15a at the time of this processing is also small, this mold is included, and ( A) → (B) → (C) → (D) → (E) The present invention can be easily applied to so-called transfer molding in which the molds used in the steps shown in FIG. Therefore, the yoke 9 having excellent durability can be manufactured at low cost.

  Even when the roughness improving portion is scraped off by the cutting tool 36, the inclination angle θ of the fracture surface 35 is large, and the height difference H between the both end edges of the fracture surface 35 {see FIG. If it is larger, as shown in FIG. 3B, a part of the fracture surface 35 may remain without being cut off. Further, considering that the fracture surface 35 is completely scraped off, the amount of processing by the cutting tool 36 is increased, the processing time is increased, and the manufacturing cost is increased. On the other hand, when the intermediate portion 33 is folded back into a U-shape, only a compressive stress that does not bind to the crack (rather, suppresses cracking) is applied to the inner diameter side of the folded back, and tensile stress associated with the crack is applied. Absent. Therefore, in the case of this example, after the roughness improving portion is scraped off by the cutting tool 36, the side where the shearing surface 34 originally existed is positioned on the outer diameter side of the folded portion, and the intermediate portion 33 is placed. Is folded into a U-shape.

  In the above description, the present invention has been described in connection with the case of making a universal joint yoke to be incorporated in an automobile steering apparatus incorporating an electric power steering apparatus. On the other hand, the present invention is not limited to the case of making a universal joint yoke used for such applications, but is applied to the case of making a yoke by pressing a thick metal plate compared to the conventional case. it can.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering gear unit 3 Steering shaft 4a, 4b Universal joint 5 Intermediate shaft 6 Input shaft 7 Tie rod 8 Electric motor 9 Yoke 10, 10a Base part 11 Arm part 12, 12a Flange 13 Through-hole 14 Circular hole 15, 15a Base plate 16, 16a Substrate part 17, 17a Tongue part 18 Pilot hole 19 First intermediate material 20 Second intermediate material 21 Third intermediate material 22 Folded part 23 Receiving die 24 Metal plate 25 Suppression die 26 Punching die 27 Projection 28 Narrow Part 29 First intermediate material 30 Second intermediate material 31 Third intermediate material 32 Fourth intermediate material 33 Intersection 34 Shear surface 35 Fracture surface 36 Cutting tool 37 Cutting surface

Claims (3)

  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 fabricate, a flat plate having a substantially rectangular substrate part and a pair of tongues protruding from two spaced apart positions on one end edge of the substrate part by punching and forming a metal plate In the method of manufacturing a universal joint yoke using the base plate portion as the base portion, the intermediate portion of the base plate portion is folded back into a U shape at the intermediate portion of the base plate portion. Before turning back into a U-shape, the portion located between the arms of the one side edge of the substrate portion provided with the arms, and the circumferential direction of the base half of the arms Except for the tip side of these arms, which is the part of the side edge that is continuous from both ends of this part. Method for producing a universal joint yoke, characterized in that it has a step for improving the the surface roughness of the portion surrounded by, possible to remove the metal material present on the surface of this portion.   The method for manufacturing a universal joint yoke according to claim 1, wherein the surface roughness is improved by shaving.   The method for manufacturing a universal joint yoke according to claim 1, wherein the surface roughness is improved by cutting.

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