JP4052278B2 - Method for manufacturing universal joint yoke - Google Patents

Description

In the method for manufacturing a universal joint yoke according to the present invention, the ends of a pair of rotating shafts that do not exist on the same straight line are connected to each other so that rotational force can be transmitted between the rotating shafts. The present invention relates to a method for manufacturing a yoke constituting a joint.

  For example, an automobile steering apparatus is configured by connecting a plurality of rotating shafts such as a steering shaft and an intermediate shaft in series via a universal joint. Conventionally, as a universal joint used in such a case, a universal joint called a cardan joint, in which a pair of yokes are displaceably connected by a cross shaft, has been widely used. In addition, it has been widely practiced to produce a yoke that constitutes such a universal joint by plastic working a metal plate having sufficient rigidity, such as a steel plate.

  FIG. 11 shows an example of a universal joint yoke manufactured in this manner. The yoke 1 includes a base portion 2 and a pair of arm portions 3 and 3 extending from one end edge in the axial direction of the base portion 2. Of these, the base 2 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 1 is to be fixed. A pair of opposing flanges 5 and 6 are provided. A through hole 18 for inserting a flange portion of a bolt (not shown) into one flange 6 and a flange portion of the bolt to be screwed into the other flange 5 are concentric with the through hole 18. Screw holes 8 are respectively formed.

  On the other hand, each of the arms 3 and 3 extends in the axial direction of the base 2 from a position opposite to the diameter direction at one end edge in the axial direction of the base 2. Each of the arms 3 and 3 has a cylindrical concave surface that faces each other. Further, concentric circular holes 4 and 4 are formed at the distal end portions of the respective arm portions 3 and 3. When the universal joint is configured by combining the yoke 1 and the cross shaft 9, the bearing cups 10 and 10 are press-fitted into the circular holes 4 and 4. Each of these bearing cups 10 and 10 functions as an outer ring of a radial needle bearing, and couples and supports the cross shaft 9 to the yoke 1 so as to be swingable and displaceable.

  The manufacturing operation of the yoke 1 as described above has been conventionally performed as shown in FIG. First, a flat base plate 11 having a shape as shown in FIG. 12A is obtained by punching out a metal plate having sufficient rigidity, such as a steel plate, by press working. The base plate 11 includes a substantially rectangular substrate portion 12 and a pair of tongue-like portions 13 and 13 projecting from one end edge of the substrate portion 12 in a hook-like shape. Such a base plate 11 is pressed between a pair of press dies, and is plastically deformed into a shape as shown in FIG. The first intermediate material 14 is to be a pair of arms 3 and 3 (see FIG. 11). The tongue portions 13 and 13 are curved in a partial cylindrical shape, and the substrate portion is to be the base 2. 12 is provided with a protruding portion 15 by fleshing in a portion where a screw hole 8 (see FIG. 11) is to be formed. Next, as shown in FIGS. 12C and 12D, such a first intermediate material 14 is formed into a second intermediate material 16 by curving the central portion of the substrate portion 12 into a cylindrical shape.

  In the second intermediate material 16 configured in the shape as shown in FIG. 12D in this way, serrations 17 (see FIG. 11) are provided on the inner peripheral surface of the portion corresponding to the base 2, and the flanges 5, 6 are provided. A through hole 18 and a screw hole 8 (see FIG. 11) are respectively formed in portions corresponding to. In addition, circular holes 4 and 4 (see FIG. 11) are formed at the tip portions corresponding to the tongue-like portions 13 and 13, respectively. Conventionally, in order to form each of these circular holes 4 and 4, first, a pilot hole having a small diameter is first formed by a drill, then the inner diameter of the pilot hole is increased by an end mill, and the inner periphery of the pilot hole is finished by a reamer. These circular holes 4 and 4 are used.

  Incidentally, as a universal joint yoke having a cross shaft, in addition to the structure shown in FIG. 11, the structure shown in FIGS. 13 to 14 is also known. First, the yoke 1a of the second example shown in FIG. 13 has a base 2a formed in a U-shaped cross section. The rotating shaft for coupling the end of such a yoke 1a has an oval cross section at least at the end so that the yoke 1a and the rotating shaft do not rotate relative to each other during the coupling. In the case of the structure shown in FIG. 13, a screw hole for screwing a bolt is formed by press-fitting a nut 19 into a through hole 7 formed in the flange 5. In the yoke 1b of the third example shown in FIG. 14, the base 2b is formed in a cylindrical shape. In order to connect such a yoke 1b and the end of the rotating shaft, the end of the rotating shaft is press-fitted into the base 2b with an interference fit. As with the yoke 1 of the first example shown in FIG. 11 described above, a bearing cup 10 (see FIG. 11) is also provided at the distal ends of the arm portions 3 and 3 constituting the yoke of the second to third examples. Circular holes 4 and 4 for fitting and fixing are formed. Each of the circular holes 4 and 4 is also finished to a predetermined inner diameter by using a drill, an end mill, and a reamer in order as in the case of the yoke 1 shown in FIG.

In the case of the conventionally known yokes 1, 1a and 1b, the circular holes 4 and 4 are formed in the tip portions of the arm portions 3 and 3 by sequentially using a drill, an end mill and a reamer. For this reason, the processing of the circular holes 4 and 4 is troublesome, which causes the production costs of the yokes 1, 1 a, and 1 b to increase.
In addition, there was an idea of processing the circular holes 4 and 4 for inserting the cross shaft 9 with a press,
(1) Since the cross-sectional shape of the arm pieces 3 and 3 is curved, it is difficult to fit the hole punching punch and die to the curved portion of the arm pieces 3 and 3 exactly.
(2) Since the crosspieces at the tips of the arm pieces 3 and 3 are narrow, the crosspieces are crushed without being able to withstand the processing load when punching holes.
For these reasons, drilling with a press is inaccurate and has not been put into practical use. For this reason, with a press, it is only a grade which processes a prepared hole, and cutting processing could not be omitted finally.

The method for manufacturing a universal joint yoke of the present invention has been invented in order to reduce the cost of the universal joint yoke by simplifying the circular hole forming operation in view of the above-described circumstances.

The method for manufacturing a universal joint yoke according to the present invention is similar to the conventional method for manufacturing a universal joint yoke described above, and includes a base for coupling and fixing the end of the rotating shaft and a diameter at one end edge in the axial direction of the base. A universal joint yoke having a pair of arm portions extending in the axial direction of the base portion from opposite directions and a concentric circular hole formed at the tip portions of both arm portions is a flat metal. It is made from a board.
In particular, in the method for manufacturing a universal joint yoke of the present invention, first, a pilot hole having an inner diameter sufficiently smaller than the inner diameter of each of the circular holes in a portion of the flat metal plate to be the circular holes. Are formed by stamping. Then, by curving the flat metal plate to form an arm portion of the base portion and a pair, followed by a substantially rough finishing punching circular by pressing the lower hole portion. In this rough finishing process, a rough cored bar having a side shape and a rough punched hole matching the inner side surfaces of the two arm portions is inserted between the two arm portions, and the rough punched hole is aligned with the rough punched hole. This is done by pushing a rough punch into the pilot hole. Thereafter, a finishing process is performed in which the inner peripheral edge portion of each hole is cut by a small cutting allowance by pressing . This finishing process is obtained by the above rough finishing process in a state where a finishing metal core having a side shape and a finishing punching hole matching the inner side surfaces of the both arm parts is inserted between the both arm parts. This is done by pushing a finish punch into a rough punch hole aligned with the hole . The rough punched holes are referred to as the circular holes.

According to the method for manufacturing a universal joint yoke of the present invention configured as described above, the work of forming a circular hole in a pair of arm portions can be easily performed, and the cost of the universal joint yoke can be reduced.
For this reason, a quality universal joint can be obtained at low cost.

  1 to 10 show an example of the best mode for carrying out the present invention. The universal joint yoke 1 of this example extends from the base 2 and one axial end edge of the base 2 as shown in FIG. 1, as in the first example of the conventional structure shown in FIG. And a pair of arm portions 3 and 3. Of these, the base 2 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 1 is to be fixed. A pair of opposing flanges 5 and 6 are provided. A through hole 18 for inserting a flange portion of a bolt (not shown) into one flange 6 and a nut 19 for screwing the flange portion of the bolt into the other flange 5 (see FIG. 13). ), And the through holes 7 concentric with the through holes 18 are respectively formed.

On the other hand, each of the arms 3 and 3 extends in the axial direction of the base 2 from the diametrically opposite position at one axial end edge of the base 2. Each of the arms 3 and 3 has a cylindrical concave surface that faces each other. Further, concentric circular holes 4 and 4 are formed at the distal end portions of the respective arm portions 3 and 3. When a universal joint is configured by combining the yoke 1 and the cross shaft 9, bearing cups 10 and 10 (see FIG. 11) are press-fitted into the circular holes 4 and 4, respectively. Each of these bearing cups 10 and 10 functions as an outer ring of a radial needle bearing, and couples and supports the cross shaft 9 to the yoke 1 so as to be swingable and displaceable. In particular, in the case of the yoke 1 obtained by the manufacturing method of the present invention, the circular holes 4 and 4 are formed only by pressing.

The yoke 1 configured as described above is manufactured as shown in FIGS. 2 to 10 by the manufacturing method of the present invention . First, steel plate, a metal plate having a sufficient rigidity By punching by press working, having a shape as shown in FIG. 2 (a), to obtain a flat material plate 11a. The base plate 11 a includes a substantially rectangular substrate portion 12 and a pair of tongue-like portions 13 and 13 that protrude from one end edge of the substrate portion 12 in the shape of a hook ear. Further, at the tip portions of the tongue-like portions 13 and 13, the portions to be the circular holes 4 and 4 (see FIG. 1) formed in the tip portions of the arm portions 3 and 3 of the yoke 1, The lower holes 20 and 20 having an inner diameter sufficiently smaller than the inner diameters of the holes 4 and 4 are formed by stamping. Since the inner diameter d ₁ of the lower holes 20 and 20 is sufficiently smaller than the inner diameter of the circular holes 4 and 4 after completion, when the tongue-like parts 13 and 13 are bent into a partial cylindrical shape in the subsequent process, The shape of the peripheral portion of the lower holes 20 and 20 is not distorted at the tips of the tongue portions 13 and 13.

  Such a base plate 11a is pressed between a pair of press dies, and is plastically deformed into a shape as shown in FIG. 2B to form a first intermediate material 14a. In the first intermediate material 14a, the tongue portions 13 and 13 which are to be the pair of arms 3 and 3 (see FIG. 1) are curved in a partial cylindrical shape. FIG. 3 shows a state in which the tongue 13 is sandwiched between the upper mold 21 and the lower mold 22 in order to bend the tongue 13 and 13 into a partial cylindrical shape. Of the lower surface 21a of the upper mold 21 and the upper surface 22a of the lower mold 22, the lower surface 21a is a concave surface having a partial cylindrical surface, and the upper surface 22a is a convex surface having a partial cylindrical surface shape.

The curvature radius R _P1 of the cross section of the lower surface 21a is smaller than the curvature radius R _o1 of the cross section of the upper surface 22a (R _P1 <R _o1 ). Further, in order to bend each of the tongue portions 13 and 13 into a partial cylindrical shape, the width direction central portion of the lower surface 21a and the upper surface 22a of the upper surface 21a are placed with the upper mold 21 and the lower mold 22 being brought closest to each other. The distance t from the center in the width direction is the same as the thickness t _{0 of the base} plate 11a {see FIG. 2 (a)} (t = t ₀ ). Therefore, when each tongue 13 is pressed between the lower surface 21a of the upper mold 21 and the upper surface 22a of the lower mold 22, the tongue 13 is plastically deformed into a partial cylindrical surface and at the same time both ends in the width direction. The thickness decreases toward the part. The dimensional relationship of each part is regulated in this way in consideration of the change in the plate thickness of each tongue-like part 13, 13, and the contact between the lower surface of each tongue-like part 13, 13 and the upper face 22 a of the lower mold 22. This is to stabilize the dimensional shape of the arms 3 and 3 (see FIG. 1) obtained by increasing the area and plastically deforming the tongues 13 and 13.

  As described above, the first intermediate material 14a in which the tongue portions 13 and 13 are curved is then cut into a cylindrical shape with the central portion of the substrate portion 12 as shown in FIGS. 2 (c) and 2 (d). To be a second intermediate material 16a. In this manner, the operation of plastically deforming a part of the first intermediate material 14a to form the second intermediate material 16a is performed in the same manner as in the conventional method for manufacturing a universal joint yoke.

  The second intermediate material 16a obtained as described above is subjected to rough finishing by punching the lower holes 20 and 20 into a substantially circular shape by a punching press device 24 as shown in FIGS. The third intermediate material 23 is as shown. The punching press device 24 includes a pair of left and right rough punching punches 25, 25 and pressing punches 26, 26, V blocks 27, 28 and a pressing arm 29 for positioning and holding the second intermediate material 16a, A cored bar 30 is provided.

As shown in FIGS. 4 (c) and 5, the left and right side surfaces of the rough core 30 are rough cores to match the inner surfaces of the pair of arms 3 and 3 provided on the second intermediate material 16a. A partial cylindrical surface having a radius of curvature R ₀₂ (≈R ₀₁ ) offset from the center of the gold 30 is used. In addition, a rough punching hole 31 is formed in a part of the rough cored bar 30 that is aligned with the lower holes 20 and 20 formed in the arm portions 3 and 3. The inner diameter D _d2 of the rough punch hole 31 is larger than the inner diameter d ₁ of the lower holes 20, 20 {see FIG. 2 (a)}, and the circular holes 4, 4 to be formed in the arms 3, 3 are formed. The inner diameter d ₃ is slightly smaller than {see FIG. 10 (c)} (d ₁ <D _d2 <d ₃ ).

The outer diameter D _p2 of the processed portion 32 provided at the tip of each of the rough punching punches 25, 25 is slightly smaller than the inner diameter D _d2 of the rough punching hole 31 (D _p2 <D _d2 ), A clearance C ₂ is set between the outer peripheral edge of the processed portion 32 and the inner peripheral surface of the rough punch hole 31. The size of the clearance C ₂ is slightly smaller than the clearance value in general punching. Further, the radius of curvature R _p2 (see FIG. 6) of the processed portion 32 is set so that the end surface of the processed portion 32 matches the outer surface of each of the arm portions 3 and 3 (see FIG. 3). The radius of curvature R _p1 is substantially the same (R _p2 ≈R _p1 ). Further, the machining portion 32 is provided with a rake angle α, and the tip edge is curved with a small radius of curvature R _s2 . The rake angle α is determined by design in the range of 5 to 40 °.

  As described above, the rake angle α of the processing portion 32 is regulated within the range of 5 to 40 ° because the punched-out debris 33 generated in the punching process is efficiently discharged to the front in the punching direction (right side in FIG. 6). Because of that. In this way, by providing the rake angle α and curving the tip edge, and efficiently discharging the scraper 33 forward in the punching direction, the rough finishing holes are formed in the arms 3 and 3 by the rough punching punches 25 and 25, respectively. Deformation resistance when forming 34 and 34 (see FIG. 7) is suppressed, the deformation of the arm portions 3 and 3 is prevented, and the dimensional accuracy and shape accuracy of the resulting rough finishing holes 34 and 34 are ensured. .

Moreover, the reason why the tip edge is curved is to reduce the inner diameter change of the rough finishing holes 34, 34. That is, the punching allowance δ ₂ at the time of punching of the rough finishing holes 34 and 34 by the punching press device 24 is relatively large, so that a fracture occurs in the processed part during punching and the rough finishing hole 34 obtained is obtained. , 34 is likely to change in the punching direction (left-right direction in FIG. 6). Therefore, in the illustrated example, by curving the tip edge of the processed portion 32, the inner peripheral surfaces of the rough finish holes 34, 34 obtained at the tip edge are handled, and the inner diameter of each of the rough finish holes 34, 34 is determined. Prevents changes in the punching direction.

  Further, when the rough finishing holes 34, 34 are punched by the punching press 24, the second intermediate material 16a is not only pressed against the pair of V blocks 27, 28 by the pressing arm 29, With a pair of pressing punches 26 and 26, a part to be the flanges 5 and 6 is pressed from the left and right by a part of the second intermediate material 16a. And between the end surface of both these press punches 26 and 26 and the part inserted between the parts which should become the said flanges 5 and 6 in a part of said rough core metal 30, these flanges 5 and 6 and Apply surface pressing on the part that should be. By this surface pressing, the shapes of the portions to be the flanges 5 and 6 are finished to a desired shape, and the twist or the like when the second intermediate material 16a is formed is corrected. Accordingly, the shape of the third intermediate material 23 shown in FIG. 7 obtained by completing the processing by the punching press device 24 is appropriate without distortion.

As described above, the third intermediate material 23 obtained by processing by the punching press device 24 is subsequently subjected to finish processing by press processing. That is, the rough core 30 (used when the second intermediate material 16a is pressed into the third intermediate material 23 between the pair of arms 3 and 3 constituting the third intermediate material 23. A finishing mandrel 35 having substantially the same shape as in FIG. 5 is inserted. As shown in FIG. 8, the left and right side surfaces of the finishing core 35 are centered on the finishing core 35 so as to match the inner surfaces of the pair of arms 3 and 3 provided on the third intermediate material 23. A partial cylindrical surface having a radius of curvature R ₀₃ (≈R ₀₁ ) that is offset with respect to the surface is used. In addition, a finish punching hole 36 is formed in a part of the finishing core 35 which is aligned with the rough finishing holes 34 and 34 formed in the arm portions 3 and 3. The inner diameter D _d3 of the finish punching hole 36 is larger than the inner diameter of the rough finishing holes 34, 34, and the inner diameter d _{3 of the} circular holes 4, 4 to be formed in the respective arm portions 3, ₃ {FIG. Slightly larger than the reference} (D _d3 > d ₃ ).

Further, the outer diameter D _p3 (see FIG. 9) of the processed portion 38 provided at the tip of each finish punching punch 37, 37 for finishing the inner diameter of each rough finish hole 34, 34 to a desired size is the above-mentioned finish. A clearance C ₃ is set between the outer peripheral edge of the processed portion 38 and the inner peripheral surface of the finish punch hole 36 slightly smaller than the inner diameter D _d3 of the punch hole 36 (D _p3 <D _d3 ). ing. The clearance C ₃ is also set to be smaller than typical in clearance punching. The outer diameter D _p3 of the processed portion 38 is substantially the same as the inner diameter of the circular holes 4 and 4 provided at the distal ends of the arm portions 3 and 3 of the yoke 1 after completion. Further, the radius of curvature R _p3 of the processed portion 38 is the same as that of the processed portion 32 (see FIGS. 4 to 6) of the rough punching punches 25 and 25. In order to match the outer surface, the curvature radius R _p1 of the lower surface 21a (see FIG. 3) of the upper mold 21 is substantially matched (R _p3 ≈R _p1 ). Further, the machining portion 38 is provided with a rake angle β. This rake angle β is determined by design within a range of 5 to 40 °. However, unlike the processing portion 32 of the rough punching punches 25, 25, the leading edge of the processing portion 38 of the finishing punching punches 37, 37 is a sharp edge (the radius of curvature of the leading edge is zero).

When the third intermediate material 23 is punched by a press using the pair of finish punching punches 37, 37 as described above, and the circular holes 4, 4 are formed at the distal ends of the arms 3, 3, respectively. Takes the pair of finish punches 37, 37 closer together. Then, the processed portions 38, 38 provided at the tip portions of the finish punching punches 37, 37 are pushed into the finish punching holes 36 provided in the finishing core 35. As a result, the inner peripheral edge portions of the rough finishing holes 34, 34 are scraped off with a cutting allowance of δ ₃ to form circular holes 4, 4 having a desired dimension (inner diameter d ₃ ). Since the allowance δ ₃ in the finishing process is small, the operation of forming the circular holes 4 and 4 can be performed without causing distortion in the yoke 1. In this finishing process, the third intermediate material 23 is held and fixed as necessary in the same manner as in the rough finishing process. At the same time as the finishing process, through holes 7 and 18 are also formed in the portions to be the flanges 5 and 6 by punching with a press to form a fourth intermediate material 39 as shown in FIG.

  In the fourth intermediate material 39 obtained in this way, serrations 17 are formed by broaching in the final step to obtain the yoke 1 as shown in FIG. As described above, according to the universal joint yoke and the method of manufacturing the same according to the present invention, the time-consuming cutting process is only the broaching process for forming the serrations 17 on the inner peripheral surface of the base portion 2. And reduction of processing costs. It is obvious that the present invention can be applied not only to the yoke 1 as shown in FIG. 1, but also to the yokes 1, 1a and 1b as shown in FIGS.

An example of specific dimensions when the yoke 1 as shown in FIG. 1 is manufactured by the manufacturing method of the present invention will be described. In addition, the meaning of each code | symbol is used in embodiment mentioned above, and is as having shown in FIGS.
(1) First step (step of obtaining the first intermediate material 14a)
d ₁ = 12 mm
R _p1 = 20.5mm
R _o1 = 22.7mm
t = 6mm
t ₀ = 6 mm
(2) Second process (rough finish hole 34 punching process)
D _d2 = 14.84 mm
R _o2 = 22.7 mm
D _p2 = 14.6 mm
R _p2 = 20.75mm
α = 30 °
R _S2 = 0.4mm
δ ₂ = 1.3mm
C ₂ = 2%
(3) Third process (finish punching process of circular hole 4)
D _d3 = 15.27 mm
R _o3 = 22.7 mm
D _p3 = 15.03 mm
R _p3 = 20.75mm
d ₃ = 15.01 mm
β = 30 °
R _S3 = 0mm
δ ₃ = 0.2mm
C ₃ = 2%

  Under the above-mentioned conditions, when the circular holes 4 and 4 are formed in the tip portions of the pair of arm portions 3 and 3 constituting the yoke 1, the concentricity of both the circular holes 4 and 4 is 0.02 mm or less and is a perfect circle. The yoke 1 having a high dimensional accuracy such as a degree of 0.03 mm or less and a variation in hole diameter of 0.02 mm or less and having a stable quality could be obtained. Such dimensional accuracy and shape accuracy are almost equal to the dimensional accuracy and shape accuracy obtained when the circular holes 4 and 4 are formed by cutting. It was also confirmed that the workpiece (first to fourth intermediate materials) was stable in machining the circular holes 4 and 4 and was sufficiently suitable for mass production.

1 shows an example of the best mode for carrying out the present invention, where (a) is a plan view of a yoke, (b) is a sectional view taken along line AA of (a), and (c) is also viewed from below. Side view. The figure which shows the state which press-processes the 2nd intermediate material through a 1st intermediate material from a metal plate in order of a process. Sectional drawing which shows the state which pressed this tongue-shaped part between upper and lower mold | types, in order to curve a tongue-shaped part, when pressing a 1st intermediate material. The state which has set the 2nd intermediate raw material to the punching press apparatus in order to form a rough finishing hole is shown, (a) is a top view, (b) is a side view seen from the lower part of (a), (c) Is a view from the right with some parts omitted. The figure equivalent to the BB cross section of FIG.4 (b). FIG. 6 is a view seen from the same direction as FIG. 5 in order to show the dimensional relationship between the rough punching punch and the second intermediate material. The 3rd intermediate material is shown, (a) is a top view, (b) is CC sectional drawing of (a), (c) is a side view seen from the lower part of (a). The figure similar to FIG. 5 which shows the punching apparatus for forming a finish punching hole. FIG. 9 is a view seen from the same direction as FIG. 8 in order to show the dimensional relationship between the finish punching punch and the third intermediate material. The 4th intermediate material is shown, (a) is a top view, (b) is DD sectional drawing of (a), (c) is the side view seen from the lower part of (a). 1 shows a first example of a conventionally known yoke, (a) is a plan view, (b) is a sectional view taken along line EE of (a), and (c) is a side view as viewed from below (a). Figure. The figure which shows the state which produces the yoke of the said 1st example from a metal plate by press work in order of a process. The 2nd example of the yoke known conventionally is shown, (a) is a top view, (b) is a figure seen from the right of (a), (c) is a side view seen similarly from the lower part. FIG. 3 shows a third example of a yoke that is conventionally known, in which (a) is an end view, (b) is a side view as viewed from the right side of (a), and (c) is viewed from above of (b). Side view.

Explanation of symbols

1, 1a, 1b Yoke 2, 2a, 2b Base part 3 Arm part 4 Circular hole 5, 6 Flange 7 Through hole 8 Screw hole 9 Cross shaft 10 Bearing cup 11, 11a Base plate 12 Substrate part 13 Tongue part 14, 14a First One intermediate material 15, projecting portion 16, 16a Second intermediate material 17 Serration 18 Through hole 19 Nut 20 Lower hole 21 Upper die 21a Lower surface 22 Lower die 22a Upper surface 23 Third intermediate material 24 Punching press device 25 Rough punching punch 26 Press punch 27, 28 V block 29 Pressing arm 30 Rough cored bar 31 Rough punched hole 32 Machining part 33 Punching 34 Rough finishing hole 35 Finishing cored bar 36 Finished punching hole 37 Finished punching punch 38 Processed part 39 Fourth intermediate material

Claims (2)

A base for coupling and fixing the ends of the rotary shaft, a pair of arms extending in the axial direction of the base from the diametrically opposite position at one axial edge of the base, and tips of these arms A universal joint yoke is formed from a flat metal plate, and the universal joint yoke having concentric circular holes formed in a portion is formed on each of the flat metal plates. A pilot hole having an inner diameter sufficiently smaller than the inner diameter of each of these circular holes is formed by punching in a portion to be a hole, and then the flat metal plate is bent to form a pair of arm portions with the base portion. Next, rough finishing processing is performed by punching the lower hole portion into a substantially circular shape by pressing, and a rough cored bar having a side shape and a rough punching hole that matches the inner surface of the both arm portions is formed between the two arm portions. In this state, it is inserted into the rough punch hole. After performing by pushing the rough boring punch into the lower hole is, the machining finish scraping with a small machining allowance of an inner peripheral edge of each hole by press working, the side surface shape and finish to match the inner surface of both arms the core metal finish having punched holes in a state in which inserted between each other the two arms, the performed by pushing the punch finishing the rough punched holes obtained aligned with the finish punching holes by the rough finishing A method for manufacturing a universal joint yoke, wherein each circular hole is formed. The opposed surfaces of the pair of arms are cylindrical concave surfaces, and a rough punching punch having a curved tip edge with a small radius of curvature and a rake angle of the leading edge of 5 to 40 ° is used. The method for producing a yoke for a universal joint according to claim 1 , wherein a finish punching punch having a sharp edge and a rake angle of 5 to 40 ° is used .

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