Abstract:
The present invention provides a production apparatus for crankshaft, including: a die which has a lower die, an upper die, and plural side forming punches, the upper die being provided movably to the lower die, the side forming punches moving perpendicularly to a movement direction of the upper die; a press ram which moves the upper die to the lower die, closes a material of the crankshaft, and forms the material; cam mechanisms which are provided for the side forming punches and which move the side forming punches to an inside portion of the die in accordance with movement of the press ram; a grade separation structure which is provided to at least one of the side forming punches in order to prevent interference of the side forming punches with each other.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a production apparatus and a production method for crankshafts. In particular, it relates to an improvement in a technique for forming of plural hollow hole portions to a crankshaft for weight reduction thereof. 
         [0003]    2. Description of Related Art 
         [0004]    A crankshaft of internal-combustion engine has a journal shaft portion. A crankpin portion parallel to the journal shaft portion is connected to the journal shaft portion by arm portions. A counterweight portion is formed to the arm portion. In the arm portion, the formed position of the counterweight portion with respect to the journal shaft portion is opposite to the connected position of the crankpin portion. In the crankshaft, in order to improve fuel consumption, a hollow hole portion may be formed to the crankpin portion for weight reduction thereof. Even when the hole portion is formed to the crankpin portion, the influence on the stiffness of the crankshaft is small, so that it is desirable to form the hole portion to the crankpin portion. 
         [0005]    In formation of a hole portion to a crankpin portion, a forging apparatus may be used. The forging apparatus has a side forming punch which moves in a direction perpendicular to a movement direction of a press ram. A cam mechanism has been used as a driving source for the side forming punch of the forging apparatus as disclosed in Japanese Unexamined Patent Application Publication Nos. H1-104436 and 2003-343592. The cam mechanism has a mechanism which is simpler than that of servomotors and hydraulic apparatus, the cam mechanism is not provided outside a die set, and the cam mechanism allows the side forming punch to linearly follow the action of the press ram. 
         [0006]      FIG. 7  is a conceptual diagram for explanation of action of a side forming punch  20  (hereinafter referred to as “punch  20 ”) by a cam mechanism  10 . The cam mechanism  10  is equipped with a cam  11 , a cam driver  12 , and a cam holder  13 . The cam driver  12  drives the cam  11 . The cam  11  and the cam driver  12  are slidably supported by the cam holder  13 . The punch  20  is provided at a side surface of the cam  11  which faces an inside of a die, and a side surface of the cam  11  which faces an outside of a die is an inclined surface. A lower surface of the cam driver  12  is an inclined surface. In an initial condition, the lower surface of the cam driver  12  is positioned so as to be spaced a predetermined distance from the inclined surface of the cam  11 . In action of the cam  11 , the lower surface of the cam driver  12  slides on the inclined surface of the cam  11 . In the cam mechanism  10 , when an upper plate  31  moves a predetermined distance downwardly to a lower plate  32  by a press ram (not shown in the Figure), the inclined surfaces of the cam  11  and the cam driver  12  contact each other. When the upper plate  31  moves further downwardly, the inclined surfaces of the cam  11  and the cam driver  12  slide on each other, and the punch  20  moves toward the inside of the die in a horizontal direction. 
         [0007]    However, when a crankshaft is formed by the above forging apparatus, it is necessary that the punch  20  be inserted into the crankpin portion from an axial direction of the crankshaft since the crankshaft is disposed in the die such that the axial direction of the crankshaft should be perpendicular to a movement direction of the press ram. Due to this, when a hole portion is formed to each crankpin portion of the crankshaft having plural cylinders, punches collide with each other. 
         [0008]    Specifically, in side forming which uses the cam mechanism  10 , the cam  11  acts in accordance with the movement of the press ram, so that the inserted length of the punch  20  provided on the cam  11  is maximum when the press ram arrives at a bottom dead point. Next, when the press ram moves to a top dead point, the punch  20  is removed from the crankpin portion. Due to this, for example, as shown in  FIG. 8 , when a hole portion  44  is formed to each crankpin portion of crankshaft  40  which is used for four cylinders and has a full counterweight structure, punches  21  and  22  collide with each other, and punches  23  and  24  collide with each other (as shown in a portion surrounded by a dotted line in  FIG. 8 ). As a result, during one stroke of the press ram from the top dead point to the bottom dead point, plural hole portions, which are positioned such that the punches for forming of them interfere with each other, cannot be formed. Reference numerals  41  and  42  denote a journal shaft portion and a crank arm portion. 
       SUMMARY OF THE INVENTION 
       [0009]    An object of the present invention is to provide a production apparatus and a production method for crankshafts, which can perform formation of plural hole portions during one stroke of a press ram from a top dead point to a bottom dead point even when a cam mechanism is used as a driving source for side forming punches and the hole portions are positioned such that the punches interfere with each other. 
         [0010]    According to one aspect of the present invention, a production apparatus for crankshaft includes: a die which has a lower die, an upper die, and plural side forming punches, the upper die being provided movably to the lower die, the side forming punches moving perpendicularly to a movement direction of the upper die; a press ram which moves the upper die to the lower die, closes a material of the crankshaft, and forms the material; cam mechanisms which are provided for the side forming punches and which move the side forming punches to an inside portion of the die in accordance with movement of the press ram; a grade separation structure which is provided to at least one of the side forming punches in order to prevent interference of the side forming punches with each other. 
         [0011]    In the production apparatus of the one aspect of the present invention, the material of the crankshaft is closed and formed into a predetermined shape in the die by the movement of the press ram, and the cam mechanisms also move the side forming punches (hereinafter referred to as “punches”) to the inside portion of the die in accordance with the movement of the press ram, so that hole portions are formed to predetermined portions of the material by the punches. Since the grade separation structure is provided to at least one of the side forming punches in order to prevent the interference of the side forming punches with each other, the punches can cross each other in a grade separation manner when they move to and retreat from the inside portion of the die. Therefore, the formation of the hole portions can be simultaneously performed on the material of the crankshaft. Thus, the formation of the plural hole portions can be performed in one stroke of the press ram from a top dead point to a bottom dead point. 
         [0012]    As described above, since the cam mechanisms, which can be provided in a die set, can be used as a driving source for the punches, it is unnecessary to use a space at which external devices (for example, actuators) independently controlling the punches are disposed, so that a press apparatus can be compact, and workability and productivity can be improved. Since the grade separation structure, which is formed to at least one of the punches, is simple structures, the press apparatus can be more compact. Since the movement ranges of the punches can be set within the space of the dieset, safety of operators can be secured. 
         [0013]    The production apparatus for crankshaft can use various structures. According to one preferred embodiment of the present invention, the grade separation structure may be a through-hole portion formed to one of the side forming punches, and another of the side forming punches may move in the through-hole portion during forming of hole portions of the crankshaft. 
         [0014]    According to another aspect of the present invention, a production method for crankshaft includes the above side forming method of the plural hole portions by the production apparatus for crankshaft. That is, a production method for crankshaft uses: a die which has a lower die, an upper die, and plural side forming punches, the upper die being provided movably to the lower die, the side forming punches moving perpendicularly to a movement direction of the upper die. The production method includes: a preparing step of a material of the crankshaft; and a forming step that a press ram moves the upper die to the lower die so that the material of the crankshaft is closed and formed in the die, and cam mechanisms also move the side forming punches to an inside portion of the die in accordance with a movement of the press ram in forming of the material, so that hole portions are formed to predetermined portions of the material by the side forming punches, wherein when the material has a shape such that the side forming punches may interfere with each other in forming of the hole portions to the material by the side forming punches, the side forming punches cross each other in a grade separation manner. 
         [0015]    In the production method of the another aspect of the present invention, the same effects as those by the production apparatus using the grade separation structure can be obtained. 
         [0016]    According to the production apparatus or the production method for crankshaft of the present invention, when the material has a shape such that the side forming punches may interfere with each other in forming of the hole portions to the material by the side forming punches, the formation of the hole portions can be simultaneously performed on the material of the crankshaft, so that the formation of the plural hole portions can be performed in one stroke of the press ram from the top dead point to the bottom dead point. As a result, the press apparatus can be compact and another effect can be obtained. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a conceptual diagram which shows a construction of a portion of a production apparatus for crankshafts of one embodiment according to the present invention, and  FIG. 1  is a perspective view which shows a die. 
           [0018]      FIG. 2  is a conceptual diagram which schematically shows a construction of the production apparatus for crankshafts of one embodiment according to the present invention, and  FIG. 2  is a schematic cross sectional view taken at line of A-A′ shown in  FIG. 1 . 
           [0019]      FIG. 3  is a perspective view which schematically shows structures of side forming punches shown in  FIG. 1 . 
           [0020]      FIGS. 4A and 4B  are perspective views which schematically show structures of side forming punches shown in  FIG. 1 .  FIG. 4A  shows a condition of the side forming punches before grade separation, and  FIG. 4B  shows a condition of the side forming punches in grade separation. 
           [0021]      FIGS. 5A and 5B  are side views which show examples of the side forming punches shown in  FIGS. 4A and 4B . 
           [0022]      FIG. 6  is a schematic top view which shows one layout example of the production apparatus for crankshafts of one embodiment according to the present invention. 
           [0023]      FIG. 7  is a side cross sectional view which schematically shows a cam mechanism of conventional production apparatus for crankshafts. 
           [0024]      FIG. 8  is a schematic top view for explanation of problems of conventional production apparatus for crankshafts. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     1. Construction of Embodiment 
       [0025]    One embodiment of the present invention will be described hereinafter with reference to Figures.  FIG. 1  is a conceptual diagram which shows a construction of a portion of a crankshaft production apparatus  100  of one embodiment according to the present invention, and  FIG. 1  is a perspective view which shows a lower die  103 A of a die  103 .  FIG. 2  is a conceptual diagram which schematically for action explanation of the crankshaft production apparatus  100  of one embodiment according to the present invention, and  FIG. 2  is a cross sectional view taken at line of A-A′ shown in  FIG. 1 .  FIG. 3  is a perspective view which schematically shows structures of side forming punches  112   p  and  117   p  shown in  FIG. 1 .  FIGS. 4A and 4B  are perspective views which schematically show structures of side forming punches  114   p  and  115   p  shown in  FIG. 1 , and  FIG. 4A  shows a condition of the side forming punches  114   p  and  115   p  before grade separation and  FIG. 4B  shows a condition of the side forming punches  114   p  and  115   p  in grade separation. In  FIG. 1 , cam mechanisms are not shown for illustration convenience. 
         [0026]    For example, the crankshaft production apparatus  100  is used for formation of hole portions to a crankshaft which is used for four cylinders and has a full counterweight structure. For example, the crankshaft production apparatus  100  is equipped with a press bolster  101 , and a press ram  102  is supported on the press bolster  101 . A die  103  is disposed between the press bolster  101  and the press ram  102 . The die  103  is equipped with a lower die  103 A, an upper die  103 B, and side forming punches  111 P to  118   p  (hereinafter referred to as “punches  111 P to  118   p ”). A preform  200  is disposed in the die  103 . 
         [0027]    The preform  200  has a journal shaft portion  201 , and arm portions  202  are provided to the journal shaft portion  201 . The arm portions  202  proximate to each other are connected by crankpin portions  203 . The crankpin portions  203  are parallel to the journal shaft portion  201 . The die  103  has a cavity surface having a shape corresponding to the preform  200 . The upper die  103 B is provided so as to be movable to the lower die  103 A. Reference numeral  105  in  FIG. 2  denotes a load adjustment device (hydraulic apparatus, air pressure device, or the like). 
         [0028]    The punches  111 P to  118   p  are provided so as to be movable perpendicularly to a movement direction of the upper die  103 B. The punches  111 P to  118   p  are insertable into an inside portion of the die  103  via punch passages  111   q  to  118   q  which are formed at side portions of the die  103 . The punches  111 P to  118   p  have cam mechanisms which move the punches  111 P to  118   p  to the inside portion of the die  103  in accordance with movement of the press ram  102 . 
         [0029]    As shown in  FIG. 2 , cam mechanisms  111  and  112 , which move the punches  111 P and  112   p , are equipped with cams  111   c  and  112   c  and cam drivers  111   d  and  112   d  which drive the cams  111   c  and  112   c . Cam mechanisms, which move the punches  1113  and  118   p , have the almost same structures and actions as those of the punches  111 P and  112   p , and explanation for the cam mechanisms of the punches  1113  and  118   p  is thereby omitted. 
         [0030]    The punches  111   p  and  112   p  are provided at side surfaces of the cam  111   c  and  112   c  which face the inside of the die  103 , and side surfaces of the cams  111   c  and  112   c  which face an outside of the die  103  are inclined surfaces. Lower surfaces of the cam drivers  111   d  and  112   d  are inclined surfaces. In an initial condition, the lower surfaces of the cam drivers  111   d  and  112   d  are positioned so as to be spaced a predetermined distance from the inclined surfaces of the cams  111   c  and  112   c . The cam drivers  111   d  and  112   d  move downwardly in accordance with the downward movement of the press ram  102 . The lower surfaces (inclined surfaces) of the cam drivers  111   d  and  112   d  contact the inclined surfaces of the cams  111   c  and  112   c , and these inclined surfaces slide on each other. 
         [0031]    Retreat members  111   s  and  112   s  are provided to the cam mechanisms  111  and  112 . After side forming by the punches  111   p  and  112   p  at a bottom dead point of the press ram  102 , when the cam drivers  111   d  and  112   d  move upwardly in accordance with the movement of the press ram  102  to a top dead point thereof, the punches  111   p  and  112   p  are retreated to the outside of the die  103  by the retreat members  111   s  and  112   s , and return to initial positions thereof. 
         [0032]    In order not to interfere the punches  112   p  and  117   p  with each other at a region X shown in  FIG. 1  and not to interfere the punches  114   p  and  115   p  with each other at a region Y shown in  FIG. 1 , a grade separation structure  121  is provided to the punches  112   p  and  117   p , and a grade separation structure  122  is provided to the punches  114   p  and  115   p.    
         [0033]    Specifically, at the interference region X for the punches  112   p  and  117   p , the arm portions  202  of the preform  200 , into which the punches  111   p  and  117   p  are inserted, are away from each other, so that the grade separation structure  121  are provided so as to be away from the cavity of the die  103 . The grade separation structure  121  has a through hole portion  121 A and a flat portion  121 B. The through hole portion  121 A is formed to the punch  117   p , and the flat portion  121 B is formed to the punch  112   p . In the grade separation structure  121 , the flat portion  121 B is movably disposed in the through hole portion  121 A, and the punches  112   p  and  117   p  can cross each other in a grade separation manner. In this case, each axial direction length of the through hole portion  121 A and the flat portion  121 B is designed such that the punches  112   p  and  117   p  do not interfere with each other when the punches  112   p  and  117   p  move to and retreat from the die  103 . 
         [0034]    At the interference region Y for the punches  114   p  and  115   p , the arm portions  202  of the preform  200 , into which the punches  114   p  and  115   p  are inserted, are proximate to each other, so that the grade separation structure  122  are provided so as to be proximate to the cavity of the die  103 . The grade separation structure  122  has a through hole portion  122 A and a flat portion  122 B. The through hole portion  122 A is formed to the punch  115   p , and the flat portion  122 B is formed to the punch  114   p . In the grade separation structure  122 , the flat portion  122 B is movably disposed in the through hole portion  122 A, and the punches  114   p  and  115   p  can cross each other in a grade separation manner when the punches  112   p  and  117   p  are inserted into the crankpin portions  203 . In this case, each axial direction length of the through hole portion  122 A and the flat portion  122 B is designed such that the punches  114   p  and  115   p  do not interfere with each other when the punches  114   p  and  115   p  move to and retreats from the die  103 . 
         [0035]      FIGS. 5A and 5B  are side views which show examples of the punches  114   p  and  115   p  provided at a portion proximate to the cavity. In the punch  114   p , the flat portion  122 B is formed between a main body portion  114   m  and a leading end portion  114   n . The leading end portion  114   n  performs side forming, and the leading end portion  114   n  has a width wider than that of the flat portion  122 B. The flat portion  122 B has a shape so as to be movable in the through-hole portion  122 A of the punch  115   p.    
         [0036]      FIG. 6  is a schematic top view which shows one layout example of the crankshaft production apparatus  100 . In the example, reference numeral  113  denotes a cam mechanism which moves the punches  113   p  and  115   p . Reference numeral  114  denotes a cam mechanism which moves the punches  114   p  and  116   p . Reference numerals  117  and  118  denote cam mechanisms which move the punches  117   p  and  118   p . Reference numeral  104  denotes a surface of bed on which the press bolster  101  is mounted. Another components are the same components as those shown by reference numerals in  FIGS. 1 to 4 . In the example shown in  FIG. 6 , in the above manner, the one cam mechanism  113  is used for the movements of the two punches  113   p  and  115   p , and the one cam mechanism  114  is used for the movements of the two punches  114   p  and  116   p . Alternatively, one cam mechanism may be used for each movement of the punches  113   p  to  116   p  in the same manner as for the other punches. 
       2. Action of Embodiment 
       [0037]    The action of the crankshaft production apparatus  100  will be explained hereinafter with main reference to  FIGS. 2 to 4 . Since actions of the punches  113   p  to  118   p  by the cam mechanisms are almost the same as those of the punches  111   p  and  112   p  using the cam mechanisms  111  and  112 , in the following explanation, the actions of the punches  111   p  and  112   p  are mainly used. 
         [0038]    First, in the cavity of the die  103 , the preform  200  of the crankshaft is disposed. Next, when the press ram  102  starts moving downwardly from the top dead point, the cam drivers (in the cam mechanisms  111  and  112 , reference numerals  111   d  and  112   d  in  FIG. 2 ) moves downwardly in accordance with the downward movement of the press ram  102 , and the inclined surfaces of the cam drivers contact the inclined surfaces of the cams (in the cam mechanisms  111  and  112 , reference numerals  111   c  and  112   c  in  FIG. 2 ). When the press ram  102  moves further downwardly, the above inclined surfaces slide on each other, and the punches  111   p  and  112   p  move to the inside of the die  103  in a horizontal direction. Then, hole portions are formed to the crankpin portions  203  of the preform  200  by the punches  111   p  to  118   p.    
         [0039]    Next, when the press ram  102  arrives at the bottom dead point, stroke length of the cams are maximum, and side forming by the punches  111   p  to  118   p  are completed. Next, when the cam drivers start moving upwardly in accordance with the upward movement of the press ram  102  to the top dead point, the cams are retreated to the outside of the die  103  by the retreat members (in the cam mechanisms  111  and  112 , reference numerals  111   s  and  112   s  in  FIG. 2 ). After the cams return to initial positions thereof, a release pin of the die is acted, so that a crankshaft having the hole portions formed thereat is removed from the die. 
         [0040]    In the formation of the hole portions to the preform  200  described above, the punches  112   p  and  117   p  and the punches  114   p  and  115   p  having the regions X and Y at which they may interfere with each other in the conventional technique, they can cross each other in a grade separation manner by the grade separation structures  121  and  122 . 
         [0041]    Specifically, in the grade separation structure  121 , as shown in  FIG. 3 , the flat portion  121 B can move in the through hole portion  121 A, and the punches  112   p  and  117   p  can cross each other in a grade separation manner. In the grade separation structure  122 , the flat portion  122 B of the punch  114   p  shown in  FIG. 4A  is inserted into the through hole portion  122 A of the punch  115   p , and the punches  114   p  and  115   p  can cross each other in a grade separation manner. 
         [0042]    In the above manner, the punches  112   p  and  117   p  can cross each other in a grade separation manner and the punches  114   p  and  115   p  can cross each other in a grade separation manner when they move to and retreat from the inside portion of the die  103 . Therefore, the formation of the hole portions can be simultaneously performed on the preform  200  of the crankshaft. Thus, the formation of the plural hole portions can be performed in one stroke of the press ram  102  from the top dead point to the bottom dead point. The cam mechanisms, which can be provided in a die set, can be used as a driving source for the punches  111   p  to  118   p , it is unnecessary to use a space at which external devices (for example, actuators) independently controlling the punches  111   p  to  118   p  are disposed, so that a press apparatus can be compact, and workability and productivity can be improved. Since the grade separation structures, which are formed to the punches, are simple structures, the press apparatus can be more compact. Since the movement ranges of the punches  111   p  to  118   p  can be set within the space of the dieset, safety of operators can be secured.