Patent Publication Number: US-2019193138-A1

Title: Method for manufacturing universal joint using pipe

Description:
TECHNICAL FIELD 
     The present invention relates to a method for manufacturing a universal joint using a pipe, in which the universal joint is applied to a steering apparatus for manipulating the traveling direction of a vehicle as desired, and more specifically to the provision of a method for manufacturing a universal joint using a pipe, which enables a shaft joint and a pipe joint integrated with yokes, respectively, to be each manufactured by using a method of forming, pressing and machining a material obtained by cutting a pipe to a predetermined length, thereby reducing manufacturing cost, improving production efficiency, and fulfilling durability while providing the effect of reducing the weight of a product. 
     BACKGROUND ART 
     In general, a steering apparatus for enabling a driver to change the traveling direction of a vehicle as desired is provided to the vehicle. The steering apparatus includes: a steering wheel disposed in front of a driver&#39;s seat, and configured to change the traveling direction of a vehicle through the manipulation of the driver; a steering column disposed beneath the steering wheel; a steering gearbox configured to switch the rotation of the steering wheel from rotation movement to rectilinear movement and to also change the directions of tires by increasing steering force; and a universal joint configured to transfer rotating force, transferred to the steering column, to the steering gearbox. 
     The universal joint includes a shaft joint and a pipe joint configured to transfer rotating force to the shaft joint. In this case, splines that are formed on the outer surface of the shaft joint in a protrusion and depression form are fitted into splines that are formed on the inner surface of the pipe joint in a protrusion and depression form so that the two members can slide in an axial direction while transferring rotating force. 
     Yokes are formed at ends of the shaft joint and the pipe joint, the yoke formed in the shaft joint is connected to the steering column, and the yoke formed in the pipe joint is connected to the gearbox. 
     A conventional technology regarding the above-described universal joint is a “universal joint for a vehicle and a method for manufacturing the same” disclosed in Korean Patent Application Publication No. 10-2006-0116099 (published on Nov. 14, 2006), and the method includes: a shaft joint formation step of forming a shaft portion and a yoke portion in an integrated form by inserting a material having a predetermined length and outer diameter into dies functioning as a mold and then plastically deforming the material by pressing the material with a punch; a hole formation step of forming a connection hole in the yoke portion of the shaft joint in order to connect another joint, such as a spider, with the yoke portion of the shaft joint; a step of forming a gear on the outer surface of the shaft portion; a pipe joint formation step of forming a pipe portion and a yoke portion in an integrated form by inserting a material having a predetermined length and outer diameter into dies functioning as a mold and then plastically deforming the material by pressing the material with a punch; a hole formation step of forming a connection hole in the yoke portion of the pipe joint in order to connect another joint, such as a spider, with the yoke portion of the pipe joint; a step of forming splines corresponding to the gear of the shaft portion on the inside of the formed pipe portion; and an assembly step of achieving the form of a completed universal joint by inserting the shaft portion of the manufactured shaft joint into the pipe portion of the manufactured pipe joint. 
     Another conventional technology is a “yoke manufacturing method” disclosed in Korean Patent No. 10-1322363 (published on Oct. 28, 2013), and the method includes: a first step of machining a yoke formation member by cutting a round rod raw material and subjecting the cut material to tube extrusion molding so that a knuckle portion and a shaft portion are formed; a second step of forming plate-shaped tensile portions on both sides of the knuckle portion by punching the knuckle portion of the yoke formation member machined at the first step; a third step of performing piercing and punching a connection hole across the insides of the tensile portions so that the inside of the shaft portion is pierced toward the knuckle portion on which the tensile portions have been formed at the second step; a fourth step of performing primary bending so that the tensile portions in which the connection hole has been formed at the third step are bent above the knuckle portion; a fifth step of performing secondary bending so that the tensile portions primarily bent at the fourth step is bent perpendicular to the knuckle portion; a sixth step of forming splines on the inner circumferential surface of the shaft portion that has been pierced at the third step. 
     Still another conventional technology is a “method for manufacturing a pipe joint for the steering apparatus of a vehicle” disclosed in Korean Patent No. 10-1632702 (published on Jun. 22, 2016), and there is provided the method for manufacturing a pipe joint for the steering apparatus of a vehicle, the method including: a center groove formation step of forming a center groove on one side of a material by pressing the material with a punch after obtaining the cut material by cutting a material fed from one side of a forming machine and supplying the cut material to center groove forming dies; a primary backward extrusion formation step of forming an inner diameter hole and a pipe on one side of the material by moving a die pin forward after locating the material in front of primary backward extrusion forming dies; a secondary backward extrusion formation step of further increasing the inner diameter hole by moving the die pin forward after locating the material in front of secondary backward extrusion forming dies; a yoke preliminary formation step of pressing the material with a punch after locating the material in front of yoke preliminary forming dies; a yoke formation step of forming a yoke across which a connection groove is formed by pressing the material with a yoke forming punch after locating the material in front of yoke forming dies via a transfer machine and completely forming the inner diameter hole with a die pin; and a spline formation step of forming splines on a pipe of the material; wherein the center groove formation step, the primary backward extrusion step, the secondary backward extrusion step, the yoke preliminary formation step, the yoke formation step, and the spline formation step are perform through cold rolling in a forming machine, wherein the yoke preliminary formation step is performed such that a preliminary yoke which is larger than the outer diameter of the material and at the center of which a guide groove is formed is formed on the opposite side of the material, in which the inner diameter hole has been formed, by pressing the material, formed at the secondary backward extrusion step, with a punch after placing the material in front of yoke preliminary forming dies, wherein the yoke formation step is performed such that the yoke across which the connection groove is formed is formed in the preliminary yoke by pressing the preliminary yoke with yoke forming dies, and wherein the spline formation step is performed such that splines are formed on a pipe in a protrusion and depression form by introducing the material, formed at the yoke formation step, into spline dies and pressing the material with a spline-shaped punch. 
     The above-described conventional technologies are based on round rods that are raw materials. The yoke portion is formed through the steps of flattening a rod-shaped material through rolling, bending the material, and then machining the material. Furthermore, a through hole needs to be formed across the center of the pipe joint through extrusion molding. Accordingly, their manufacturing process is complicated, and thus it is difficult to improve production efficiency. 
     Furthermore, the shaft joint is configured such that a spline shaft is formed on the outside of a rod-shaped material. Accordingly, it is difficult to provide the shaft joint in a lightweight form, and also it is difficult to contribute to the effort to reduce part weight in order to improve fuel efficiency in the automotive industry. 
     DISCLOSURE 
     Technical Problem 
     Accordingly, the present inventor has contrived and developed the present invention in order to overcome the problems of the conventional methods for manufacturing a universal joint. 
     In other words, the present invention enables a shaft joint and a pipe joint to be each manufactured by using a pipe as a raw material rather than using the conventional round rod-shaped raw material by means of a method of forming a shaft and a tube through forming and pressing and machining a yoke, thereby improving production efficiency and also reducing manufacturing cost. In particular, the present invention has been accomplished with a focus on the provision of a method for manufacturing a universal joint using a pipe, which enables weight to be considerably reduced by providing the inside of a shaft joint in a hollow state. 
     Technical Solution 
     First, when a universal joint including a combination of a shaft joint and a pipe joint integrated with yokes, respectively, is manufactured, the shaft joint is manufactured by: a material preparation step of preparing a material by cutting a pipe to a predetermined length; a shaft formation step of forming a shaft by reducing the outer diameter of a shaft formation portion, obtained by excluding a head formation portion from the material, by forming the outside of the shaft formation portion with a forming machine; a cutting step of bisecting the non-reduced head formation portion by forming a split across the non-reduced head formation portion in an axial direction; a yoke formation step of forming both opposite members of a yoke in a head by pressing the bisected head formation portion; a pinhole formation step of forming a pinhole across the yoke; and a spline shaft formation step of forming a spline shaft on the outer surface of the reduced hollow shaft. 
     Second, when a universal joint including a combination of a shaft joint and a pipe joint integrated with yokes, respectively, is manufactured, the shaft joint is manufactured by: a material preparation step of preparing a material by cutting a pipe to a predetermined length; a shaft formation step of forming a shaft by reducing the outer diameter of a shaft formation portion, obtained by excluding a head formation portion from the material, by forming the outside of the shaft formation portion with a forming machine; a preliminary yoke formation step of forming a preliminary yoke by means of a pressing method (rolling) of introducing the non-reduced head formation portion into a die and then pressing an upper press die into the inside of the head formation portion; a cutting step for the formation of a yoke of cutting away connection portions, other than the yoke, from a rectangular shape with an open top, which is formed by the preliminary yoke formation step; a pinhole formation step of forming a pinhole across the yoke; and a spline shaft formation step of forming a spline shaft on the outer surface of the reduced hollow shaft. 
     Third, when a universal joint including a combination of a shaft joint and a pipe joint integrated with yokes, respectively, is manufactured, the pipe joint is manufactured by: a material preparation step of preparing a material by cutting a pipe to a predetermined length; a tube formation step of reducing the outer diameter of a tube formation portion, obtained by excluding a head formation portion from the material, by forming the outside of the tube formation portion with a forming machine; a cutting step of bisecting the non-reduced head formation portion by forming a split across the non-reduced head formation portion in an axial direction; a yoke formation step of forming both opposite members of a yoke in a head by pressing the bisected head formation portion; a pinhole formation step of forming a pinhole across the yoke; and a spline boss formation step of forming a spline boss on the inner surface of the reduced hollow tube. 
     Fourth, when a universal joint including a combination of a shaft joint and a pipe joint integrated with yokes, respectively, is manufactured, the pipe joint is manufactured by: a material preparation step of preparing a material by cutting a pipe to a predetermined length; a tube formation step of reducing the outer diameter of a tube formation portion, obtained by excluding a head formation portion from the material, by forming the outside of the tube formation portion with a forming machine; a preliminary yoke formation step of forming a preliminary yoke by means of a pressing method (rolling) of introducing the non-reduced head formation portion into a die and then pressing an upper press die into the inside of the head formation portion; a cutting step for the formation of a yoke of cutting away connection portions, other than the yoke, from a rectangular shape with an open top, which is formed by the preliminary yoke formation step; a pinhole formation step of forming a pinhole across the yoke; and a spline boss formation step of forming a spline boss on the inner surface of the reduced hollow tube. 
     Fifth, the pipe prepared at the material preparation step is a seamless pipe without a seam. 
     Advantageous Effects 
     According to the method for manufacturing a universal joint using a pipe that is provided by the present invention, a shaft joint and a pipe joint integrated with yokes, respectively, are manufactured using seamless pipes, and thus a reduction in cost may be expected. 
     Furthermore, production efficiency may be improved by minimizing machining, and the weight of a completed universal joint may be reduced by providing the universal joint in a hollow state, thereby providing the effect of highly contributing to an effort to reduce the weight of a vehicle. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a perspective view showing the appearance of a universal joint that is provided and manufactured by the present invention; 
         FIG. 2  shows a view showing a process of manufacturing the shaft joint of the universal joint that is provided by the present invention; 
         FIG. 3  shows a process of manufacturing another example of the shaft joint of the universal joint that is provided by the present invention; 
         FIG. 4  shows a view showing a process of manufacturing the pipe joint of the universal joint that is provided by the present invention; and 
         FIG. 5  shows a process of manufacturing another example of the pipe joint of the universal joint that is provided by the present invention. 
     
    
    
     BEST MODE 
     A method for manufacturing a universal joint using a pipe, which is provided by the present invention, will be described based on the accompanying drawings below. 
       FIG. 1  shows a perspective view showing the appearance of a universal joint that is provided and manufactured by the present invention. 
     A steering apparatus that is provided to enable a driver to change the traveling direction of a vehicle as desired is applied to the vehicle. 
     The steering apparatus includes: a steering wheel disposed in front of a driver&#39;s seat and configured to change the traveling direction of a vehicle through the manipulation of the driver; a steering column disposed beneath the steering wheel; a steering gearbox configured to switch the rotation of the steering wheel from rotation movement to rectilinear movement and to also change the directions of tires by increasing steering force; and a universal joint  1  configured to transfer rotating force, transferred to the steering column, to the steering gearbox. 
     As shown in  FIG. 1 , the universal joint  1  includes a shaft joint  2  and a pipe joint  3  configured to transfer rotating force to the shaft joint  2 , a spline shaft  27  is formed on the outer surface of the shaft joint  2  in a protrusion and depression form and a spline boss  37  is formed on the inner surface of the pipe (A) joint  3  in a protrusion and depression form so that the two members can slide in an axial direction while transferring rotating force in the state of having been fitted into each other. In this case, there is provided a configuration in which a bearing  4  is interposed between the contact surfaces of the spline shaft  27  and the spline boss  37  in order to reduce frictional force. 
     The universal joint  1  using the pipe A, which is provided by the present invention, is characterized in that the shaft joint  2  and the pipe joint  3 , which are configured as described above, are each manufactured using the pipe A, rather than using the conventional round rod material, thereby reducing manufacturing cost, improving production efficiency, and fulfilling durability while providing the effect of reducing the weight of a product. 
     A method for manufacturing the shaft joint  2  using a pipe A and a method for manufacturing the pipe joint  3  using a pipe A will be described in greater detail below. 
     —Manufacture of the Shaft Joint— 
       FIG. 2  shows a view showing a process of manufacturing the shaft joint of the universal joint that is provided by the present invention. 
     The process of manufacturing the shaft joint  2  of a universal joint  1  using a pipe A according to the present invention, in which a yoke  25  is integrated with the shaft joint  2 , is performed in the sequence of: 1) a material preparation step S 11 ; 2) a shaft formation step S 12 ; 3) a cutting step S 13  for forming a head that corresponds to the yoke  25 ; 4) a yoke formation step S 14 ; 5) a pinhole formation step S 15 ; and 6) a spline shaft formation step S 16 , and these individual steps will be described in greater detail below. 
     1) Material Preparation Step S 11   
     A material B is prepared by cutting a pipe A having a predetermined diameter to a predetermined length by means of a cutting machine. In this case, a diameter that is suitable for a head formation portion  21  to be described later is used as the preferable diameter of the pipe A. Furthermore, when a cracking phenomenon in a manufacturing process, etc. are taken into account, it is preferable to use a seamless pipe A without a seam as the pipe A. 
     2) Shaft Formation Step S 12   
     The material B provided by cutting the pipe A to the predetermined length may be divided into the head formation portion  21  and a shaft formation portion  22 . The shaft ( 23 ) formation step is the step of forming the shaft formation portion  22  into a shaft  23  by reducing the diameter of the shaft formation portion  22 . 
     Preferably, the shaft  23  is formed by reducing the outer diameter of the shaft formation portion  22  by means of a method for introducing the shaft formation portion  22 , obtained by excluding the head formation portion  21  from the material B, into a forming machine and then forming the shaft  23 . 
     When the shaft  23  is formed using the forming machine, as described above, a hollow shape is provided in such a manner that the outer diameter of the shaft formation portion  22  is reduced, the length of the shaft formation portion  22  is increased, and the thickness of the shaft formation portion  22  is also increased. The effect of reducing weight while maintaining durability may be provided. 
     It is preferred that the outer diameter of the shaft formation portion  22  is gradually reduced by repeating the above-described formation process using the forming machine one or more times depending on the extent to which the outer diameter of the shaft  23  is reduced. 
     3) Cutting Step S 13   
     This step is the step that is performed before the formation of the yoke  25 , and is the step of forming a split  24  across the head formation portion  21  by means of a method for bisecting the non-reduced head formation portion  21  in an axial direction by means of a cutting machine, a metal laser cutting machine, or the like. 
     4) Yoke Formation Step S 14   
     The yoke formation step S 14  is the step of forming the yoke  25 . Both the opposite members of the yoke are formed by means of a pressing method (rolling) of introducing the bisected head formation portion  21  into a die and then pressing an upper press die into the inside of the head formation portion  21 . 
     5) Pinhole Formation Step S 15   
     The yoke  25  formed in the head formation portion  21  requires a pinhole  26  into which a needle roller bearing coupled to a neighboring counterpart yoke  25  via a cross axis is fitted. Accordingly, the pinhole  26  is formed across both the opposite members of the yoke  25 . 
     The pinhole  26  is formed to have a desired diameter through drilling in the state in which a sufficient thickness has been provided through drawing using a press so that a needle roller bearing can be stably fitted into the pinhole  26 . 
     6) Spline Shaft Formation Step S 16   
     The spline shaft  27  is formed on the outer surface of the hollow shaft  23  that has been reduced through forming using the forming machine, as described above. 
       FIG. 3  shows a process of manufacturing another example of the shaft joint of the universal joint that is provided by the present invention. 
     The process of manufacturing the shaft joint  2  of a universal joint  1  using a pipe A according to the present invention, in which a yoke  25  is integrated with the shaft joint  2 , is performed in the sequence of: 1) a material preparation step S 111 ; 2) a shaft formation step S 112 ; 3) a preliminary yoke formation step S 113 ; 4) a cutting-away step S 114  for the formation of a yoke; 5) a pinhole formation step S 115 ; and 6) a spline shaft formation step S 116 , and these individual steps will be described in greater detail below. 
     1) Material Preparation Step S 111   
     A material B is prepared by cutting a pipe A having a predetermined diameter to a predetermined length by means of a cutting machine. In this case, a diameter that is suitable for a head formation portion  21  to be described later is used as the preferable diameter of the pipe A. Furthermore, when a cracking phenomenon in a manufacturing process, etc. are taken into account, it is preferable to use a seamless pipe A without a seam as the pipe A. 
     2) Shaft Formation Step S 112   
     The material B provided by cutting the pipe A to the predetermined length may be divided into the head formation portion  21  and a shaft formation portion  22 . The shaft ( 23 ) formation step is the step of forming the shaft formation portion  22  into a shaft  23  by reducing the diameter of the shaft formation portion  22 . 
     Preferably, the shaft  23  is formed by reducing the outer diameter of the shaft formation portion  22  by means of a method for introducing the shaft formation portion  22 , obtained by excluding the head formation portion  21  from the material B, into a forming machine and then forming the shaft  23 . 
     When the shaft  23  is formed using the forming machine, as described above, a hollow shape is provided in such a manner that the outer diameter of the shaft formation portion  22  is reduced, the length of the shaft formation portion  22  is increased, and the thickness of the shaft formation portion  22  is also increased. The effect of reducing weight while maintaining durability may be provided. 
     It is preferred that the outer diameter of the shaft formation portion  22  is gradually reduced by repeating the above-described formation process using the forming machine one or more times depending on the extent to which the outer diameter of the shaft  23  is reduced. 
     3) Preliminary Yoke Formation Step S 113   
     The pipe A is configured to have a diameter that is suitable for a head formation portion. A preliminary yoke is formed by means of a pressing method (rolling) of introducing the head formation portion into a die and then pressing an upper press die into the inside of the head formation portion  21 . 
     In this case, the opposite members of the yoke are in the state of being connected to each other, and the preliminary yoke is formed in the shape of a rectangular container with an open top. 
     4) Cutting-Away Step S 114  for the Formation of a Yoke 
     The cutting step is the step of providing a yoke. The yoke that is formed at the preliminary yoke formation step is configured to have the connected members. At this cutting step, the portions other than the yoke are cut away. The cutting-away step may be performed by means of a machine tool, such as a milling machine, or a metal laser cutting machine. 
     5) Pinhole Formation Step S 115   
     The yoke  25  formed in the head formation portion  21  requires a pinhole  26  into which a needle roller bearing coupled to a neighboring counterpart yoke  25  via a cross axis is fitted. Accordingly, the pinhole  26  is formed across both the opposite members of the yoke  25 . 
     The pinhole  26  is formed to have a desired diameter through drilling in the state in which a sufficient thickness has been provided through drawing using a press so that a needle roller bearing can be stably fitted into the pinhole  26 . 
     6) Spline Shaft Formation Step S 116   
     The spline shaft  27  is formed on the outer surface of the hollow shaft  23  that has been reduced through forming using the forming machine, as described above. 
     The formation of the spline shaft may be performed by any one of a press method, a forming method using a forming machine, and a rolling method. These forming methods are commonly used methods, and thus detailed descriptions thereof will be omitted. 
     —Manufacture of the Pipe Joint— 
       FIG. 4  shows a view showing a process of manufacturing the pipe joint of the universal joint that is provided by the present invention. 
     The process of manufacturing the pipe joint  3  of a universal joint  1  using a pipe A according to the present invention, in which a yoke  35  is integrated with the pipe joint  3 , is performed in the sequence of: 1) a material preparation step S 21 ; 2) a tube formation step S 22 ; 3) a cutting step S 23  for the formation of a head corresponding to a yoke  35 ; 4) a yoke formation step S 24 ; 5) a pinhole formation step S 25 ; and 6) a spline boss formation step S 26 . 
     1) Material Preparation Step S 11   
     A material B is prepared by cutting a pipe A having a predetermined diameter to a predetermined length by means of a cutting machine. In this case, a diameter that is suitable for a head formation portion  31  to be described later is used as the preferable diameter of the pipe A. Furthermore, when a cracking phenomenon in a manufacturing process, etc. are taken into account, it is preferable to use a seamless pipe A without a seam as the pipe A. 
     2) Tube Formation Step S 22   
     The material B provided by cutting the pipe A to the predetermined length may be divided into the head formation portion  31  and a shaft formation portion  32 . The tube formation step is the step of forming the tube formation portion  32  into a tube  33  by reducing the diameter of the tube formation portion  32 . 
     Preferably, the tube  33  is formed by reducing the outer diameter of the tube formation portion  32  by means of a method for introducing the tube formation portion  32 , obtained by excluding the head formation portion  31  from the material B, into a forming machine and then forming the tube  33  so that the spline shaft  27  of the above-described shaft joint  2  can be inserted into the tube  33 . 
     When the tube  33  is formed using the forming machine, as described above, a hollow shape is provided in such a manner that the outer diameter of the tube formation portion  32  is reduced, the length of the tube formation portion  32  is increased, and the thickness of the tube formation portion  32  is also increased. The effect of reducing weight while maintaining durability may be provided. 
     It is preferred that the outer diameter of the tube formation portion  32  is gradually reduced by repeating the above-described formation process using the forming machine one or more times depending on the extent to which the outer diameter of the tube  33  is reduced. 
     3) Cutting Step S 13   
     This step is the step that is performed before the formation of the yoke  35 , and is the step of forming a split  34  across the head formation portion  31  by means of a method for bisecting the non-reduced head formation portion  31  in an axial direction by means of a cutting machine, a metal laser cutting machine, or the like. 
     4) Yoke Formation Step S 14   
     The yoke formation step S 14  is the step of forming the yoke  25 . Both the opposite members of the yoke are formed by means of a pressing method (rolling) of introducing the bisected head formation portion  31  into a die and then pressing an upper press die into the inside of the head formation portion  31 . 
     5) Pinhole Formation Step S 15   
     The yoke  35  formed in the head formation portion  31  requires a pinhole  36  into which a needle roller bearing coupled to a neighboring counterpart yoke  35  via a cross axis is fitted. Accordingly, the pinhole  36  is formed across both the opposite members of the yoke  35 . 
     The pinhole  36  is formed to have a desired diameter through drilling in the state in which a sufficient thickness has been provided through drawing using a press so that a needle roller bearing can be stably fitted into the pinhole  36 . 
     6) Spline Boss Formation Step S 16   
     A spline boss  37  is formed on the inner surface of the hollow tube  33  that has been reduced through forming using the pipe (A) forming machine, as described above. 
       FIG. 5  shows a process of manufacturing another example of the pipe joint of the universal joint that is provided by the present invention. 
     The process of manufacturing the pipe joint  3  of a universal joint  1  using a pipe A according to the present invention, in which a yoke  35  is integrated with the pipe joint  3 , is performed in the sequence of: 1) a material preparation step S 211 ; 2) a tube formation step S 212 ; 3) a preliminary yoke formation step S 213 ; 4) a cutting step S 214  for the formation of a yoke; 5) a pinhole formation step S 215 ; and 6) a spline boss formation step S 216 . 
     1) Material Preparation Step S 111   
     A material B is prepared by cutting a pipe A having a predetermined diameter to a predetermined length by means of a cutting machine. In this case, a diameter that is suitable for a head formation portion  31  to be described later is used as the preferable diameter of the pipe A. Furthermore, when a cracking phenomenon in a manufacturing process, etc. are taken into account, it is preferable to use a seamless pipe without a seam as the pipe A. 
     2) Tube Formation Step S 212   
     The material B provided by cutting the pipe A to the predetermined length may be divided into the head formation portion  31  and a shaft formation portion  32 . The tube formation step is the step of forming the tube formation portion  32  into a tube  33  by reducing the diameter of the tube formation portion  32 . 
     Preferably, the tube  33  is formed by reducing the outer diameter of the tube formation portion  32  by means of a method for introducing the tube formation portion  32 , obtained by excluding the head formation portion  31  from the material B, into a forming machine and then forming the tube  33  so that the spline shaft  27  of the above-described shaft joint  2  can be inserted into the tube  33 . 
     When the tube  33  is formed using the forming machine, as described above, a hollow shape is provided in such a manner that the outer diameter of the tube formation portion  32  is reduced, the length of the tube formation portion  32  is increased, and the thickness of the tube formation portion  32  is also increased. The effect of reducing weight while maintaining durability may be provided. 
     It is preferred that the outer diameter of the tube formation portion  32  is gradually reduced by repeating the above-described formation process using the forming machine one or more times depending on the extent to which the outer diameter of the tube  33  is reduced. 
     3) Preliminary Yoke Formation Step S 213   
     The pipe A is configured to have a diameter that is suitable for a head formation portion. A preliminary yoke is formed by means of a pressing method (rolling) of introducing the head formation portion into a die and then pressing an upper press die into the inside of the head formation portion. 
     In this case, the opposite members of the yoke are in the state of being connected to each other, and the preliminary yoke is formed in the shape of a rectangular container with an open top. 
     4) Cutting-Away Step S 214  for the Formation of a Yoke 
     The cutting step is the step of providing a yoke. The yoke that is formed at the preliminary yoke formation step is configured to have the connected members. At this cutting step, the portions other than the yoke are cut away. 
     The cutting-away step may be performed by means of a machine tool, such as a milling machine, or a metal laser cutting machine. 
     5) Pinhole Formation Step S 215   
     The yoke  35  formed in the head formation portion  31  requires a pinhole  36  into which a needle roller bearing coupled to a neighboring counterpart yoke  35  via a cross axis is fitted. Accordingly, the pinhole  36  is formed across both the opposite members of the yoke  35 . 
     The pinhole  36  is formed to have a desired diameter through drilling in the state in which a sufficient thickness has been provided through drawing using a press so that a needle roller bearing can be stably fitted into the pinhole  36 . 
     6) Spline Boss Formation Step S 216   
     A spline boss  37  is formed on the inner surface of the hollow tube  33  that has been reduced through forming using the pipe (A) forming machine, as described above. 
     The formation of the spline boss  37  may be performed by any one of a press method, a forming method using a forming machine, and a rolling method. These forming methods are commonly used methods, and thus detailed descriptions thereof will be omitted. 
     Meanwhile, although not mentioned in connection with the present invention, it is apparent that a heat treatment step may be additionally applied to the spline shaft  27  and the spline boss  37  formed on the shaft joint  2  and the pipe joint  3 , respectively, and the yokes  25  and  35  for the purpose of increasing abrasion resistance. 
     When the shaft joint  2  and the pipe joint  3  are manufactured using the method for manufacturing the universal joint  1  using the pipe A, as described above, the method may considerably reduce the cost of the materials B than the conventional methods for rolling a round rod. In particular, the shaft joint  2  may be provided in a hollow form, and thus the weight of a product may be considerably reduced, which will also contribute to the effort to reduce part weight in order to improve fuel efficiency in the automotive industry. 
     Although the specific embodiments have been described in the detailed description of the present invention, it will be apparent that various modifications may be made within a range that does not depart from the scope of the present invention. Therefore, the range of protection of the present invention should not be defined based on only the described embodiments, and should be defined based on not only the attached claims but also equivalents thereto.