Abstract:
Provided is a powder molding apparatus including: a die; an upper punch and a lower punch; a middle platen attached to the upper punch; an upper platen mounted on a press machine and the upper platen being attached to a push rod; a link mechanism connecting the upper platen and the middle platen; a first actuator that fixes the link mechanism and cancels a fixation of the link mechanism; a bolster attached to the lower punch, and a lower platen attached to the die, in which descending of the upper platen and the push rod causes the lower platen and the die to be pushed downward by the push rod, and along with a downward movement of the die, the lower punch makes a upward movement inside the hollow with respect to the die.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The disclosure of Japanese Patent Application No. 2015-185134 filed on Sep. 18, 2015 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a powder molding apparatus and a compact manufacturing method using the apparatus. 
         [0004]    2. Description of Related Art 
         [0005]    various types of sintered parts are manufactured by press-molding metal powder into a compact and sintering the compact. 
         [0006]    In the aforementioned press molding, using a powder molding apparatus including a die having a hollow and an upper punch and a lower punch that slide inside the hollow of the die and form a cavity jointly with the hollow, a metal powder body is charged into the cavity and is pressurized by pushing down, for example, the upper punch, whereby a powder compact is manufactured. 
         [0007]    Japanese Patent Application Publication No. 6-188138 discloses a molding apparatus in which when a compact is ejected from a die, the die is pulled down using an actuator provided below the die, and molding apparatuses of this type are in common use. 
         [0008]    Employment of the molding apparatus disclosed in JP 6-188138 A requires providing an actuator and a mechanism (e.g., a rod) that connects the actuator and the die below the die, causing a problem in that a position of the die from the ground is often high. 
         [0009]    Also, for the convenience of work, the height of the die needs to be a height that allows an upper surface of the die to be viewed by a worker, and thus, a problem also arises in that it is necessary to dig a pit at a site where a press is to be installed to embed a lower portion of the press under the ground or it is necessary for the worker to stand on a platform and perform work. 
         [0010]    Furthermore, in ejection of a compact from the die, in order to prevent cracking of the compact, it is necessary to apply a hold-down load (the compact is ejected from the die in a state in which the compact is held between the lower punch and the upper punch and a load for the holding the compact in this situation is referred to as “hold-down load”). 
         [0011]    In order to keep the hold-down load constant, it is necessary to provide a load cell to perform control; however, the load cell needs to withstand not only the hold-down load, but also a molding load, resulting in problems in that the molding apparatus itself tends to large in size and is often expensive. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention provides a powder molding apparatus that enables a manufactured compact to be ejected easily without the need to make a height of the molding apparatus to be high and the need to dig a pit at a site where a press is to be installed and, and a compact manufacturing method using the apparatus. 
         [0013]    A powder molding apparatus according to an aspect of the present invention includes: a die having a hollow; an upper punch and a lower punch that slide inside the hollow of the die and form a cavity jointly with an inner wall of the hollow; a middle platen attached to the upper punch; an upper platen attached to a push rod; a press machine that pushes down the upper platen; a link mechanism that connects the upper platen and the middle platen; a first actuator that fixes the link mechanism and cancels the fixation of the link mechanism; a bolster attached to the lower punch; and a lower platen attached to the die, the lower platen being biased upward from the bolster via a spring, and descending of the upper platen and the push rod causes the lower platen and the die to be pushed downward by the push rod, and along with a downward movement of the die, the lower punch makes a upward movement inside the hollow with respect to the die. 
         [0014]    The powder molding apparatus according to the aspect of the present invention employs the configuration in which the first actuator fixes, and cancels the fixation of, a link mechanism connecting the upper platen attached to the push rod (injection push rod), the push rod pushing down the lower platen equipped with the die, and the middle platen equipped with the upper punch that slides inside the die. 
         [0015]    At the time of molding for press-molding powder charged in the cavity, the link mechanism is fixed by the first actuator, a pressing force from the press machine is transmitted to the upper platen, the pressing force is transmitted to the middle platen via the fixed link mechanism, and the pressing force is then transmitted to the upper punch provided on the middle platen, whereby the powder is press-molded. 
         [0016]    On the other hand, when a molded compact is ejected from the cavity, the first actuator cancels the fixation of the link mechanism, and the pressing force from the press machine is transmitted to the upper platen, but the pressing force is not transmitted to the middle platen via the unfixed link mechanism. 
         [0017]    Instead, the pressing force transmitted to the upper platen is transmitted to the lower platen equipped with the die by the push rod, whereby the lower platen and the die are pushed down. As a result of the die being pushed down, the compact molded on the lower punch inside the hollow of the die is exposed above the die, enabling ejection of the compact. 
         [0018]    Examples of the first actuator can include, e.g., an air cylinder mechanism and an oil hydraulic cylinder mechanism. 
         [0019]    Also, examples of the press machine can include a slide and a unit body including an oil hydraulic cylinder or the like and a slide. 
         [0020]    According to the powder molding apparatus according to the aspect of the present invention, in molding of powder and ejection of a compact, fixation and cancellation of the fixation of a link mechanism are performed, respectively, by the first actuator, enabling the manufactured compact to be easily ejected without the need to make a height of the molding apparatus to be high and the need to dig a pit at a site where the press is installed. 
         [0021]    In the powder molding apparatus according to the aspect of the present invention, the link mechanism may include two links and three joints, the three joints connecting the links, the upper platen and the middle platen, respectively, and connecting the two links. 
         [0022]    In the powder molding apparatus according to the aspect of the present invention, the first actuator may include an air cylinder and a piston, and a distal end of the piston may be attached to the joint that is a middle joint among the three joints. 
         [0023]    Also, the powder molding apparatus according to the aspect of the present invention may further include a second actuator between the upper platen and the middle platen. 
         [0024]    As with the first actuator, the second actuator includes, e.g., an air cylinder mechanism or an oil hydraulic cylinder mechanism. 
         [0025]    After a compact is molded in the cavity, the fixation of the link mechanism is cancelled by the first actuator, and a pressing force from the press machine is thus transmitted to the lower platen equipped with the die, via the push rod to push the lower platen and the die down. Here, if the second actuator is not provided, no pressing force is applied to the upper punch, but because of the provision of the second actuator, the die can be pushed down while the compact being pressed by the second actuator with a pressing force that is smaller than a pressing force applied at the time of the molding. 
         [0026]    In the second actuator, for example, a relief valve is provided, enabling a compact to be pressed while a load applied on the upper punch (what is called “hold-down load”) being kept constant by the second actuator, and also a pressing force from the press machine to be transmitted to the lower platen equipped with the die, by the push rod to push the lower platen and the die down, whereby the compact is exposed from the cavity. 
         [0027]    Also, the aspect of the present invention also provides a compact manufacturing method, and the manufacturing method is a compact manufacturing method using the above powder molding apparatus, the method including: charging powder into the cavity; manufacturing a compact by fixing the link mechanism via the first actuator, and pushing down the upper platen, the middle platen and the upper punch via the press machine to mold the powder in the cavity; cancelling the fixation of the link mechanism via the first actuator, pushing down the upper platen via the press machine, and pushing down the lower platen and the die via the push rod to expose the compact from the cavity. 
         [0028]    The manufacturing method according to the aspect of the present invention employs the powder molding apparatus according to the aspect of the present invention, enabling manufacture of a compact and ejection of the manufactured compact from the cavity to be performed easily. 
         [0029]    Also, during exposure of the compact from the cavity, a first pressing force (hold-down load) is applied from the second actuator to the upper punch to expose the compact from the cavity while the compact being pressed by the first pressing force, the first pressing force being lower than a second pressing force applied to push down the upper platen, the middle platen and the upper punch via the press machine to mold the powder in the cavity. 
         [0030]    As can be understood from the above statement, with the powder molding apparatus according to the aspect of the present invention and the compact manufacturing method according to the aspect of the present invention, in molding of powder and ejection of a compact, fixation and cancellation of the fixation of the link mechanism are performed, respectively, by the first actuator, enabling the manufactured compact to be easily ejected without the need to make a height of the molding apparatus to be high and the need to dig a pit at a site where the press is installed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0032]      FIG. 1  is a schematic diagram of Embodiment 1 of a powder molding apparatus according to an aspect of the present invention; 
           [0033]      FIG. 2  is a schematic diagram illustrating a state in which a compact is being manufactured in Embodiment 1 of the powder molding apparatus; 
           [0034]      FIG. 3  is a schematic diagram illustrating a state in which a compact is exposed from a cavity so that the compact can be ejected in Embodiment 1 of the powder molding apparatus; 
           [0035]      FIG. 4  is a schematic diagram of Embodiment 2 of the powder molding apparatus; 
           [0036]      FIG. 5  is a schematic diagram illustrating a state in which a compact is being manufactured in Embodiment 2 of the powder molding apparatus; 
           [0037]      FIG. 6  is a schematic diagram illustrating a state in which a compact is exposed from a cavity in Embodiment 2 of the powder molding apparatus; and 
           [0038]      FIG. 7  is a schematic diagram illustrating a state in which the compact is exposed from the cavity so that the compact can be ejected in Embodiment 2 of the powder molding apparatus. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0039]    Embodiments 1 and 2 of a powder molding apparatus according to the present invention and compact manufacturing methods will be described below with reference to the drawings. 
         [0040]    (Embodiment 1 of powder molding apparatus and compact manufacturing method)  FIG. 1  is a schematic diagram of Embodiment 1 of a powder molding apparatus according to the present invention,  FIG. 2  is a schematic diagram illustrating a state in which a compact is being manufactured in Embodiment 1 of the powder molding apparatus, and  FIG. 3  is a schematic diagram illustrating a state in which the compact is exposed from a cavity so that the compact can be ejected in Embodiment 1 of the powder molding apparatus. 
         [0041]    The illustrated powder molding apparatus  200  roughly includes a press machine  70  installed in a frame  100 , a die  10 , an upper punch  20  and a lower punch  30 , a middle platen  50  with the upper punch  20  attached thereto, an upper platen  40 , a link mechanism  90  connecting the upper platen  40  and the middle platen  50 , a first actuator  80  that fixes and cancels the fixation of the link mechanism  90 , a bolster  61  with the lower punch  30  attached thereto, and a lower platen  60  with the die  10  attached thereto. 
         [0042]    The lower punch  30  and the upper punch  20  are slidable inside a hollow  11  of the die  10 , and in  FIG. 1 , metal powder F to be press-molded is charged in a cavity defined by the hollow  11  and the lower punch  30 . 
         [0043]    The upper punch  20  is attached to a lower surface of the middle platen  50  via a retainer  53 , and first guide posts  54  are attached to an upper surface of the middle platen  50 . 
         [0044]    Also, a stopper  51  that holds a fixed position of the link mechanism  90  and a first actuator attachment portion  52  are provided on the upper surface of the middle platen  50 . 
         [0045]    First guide bushes  40   a  through which the respective first guide posts  54  extend are provided in the upper platen  40 , a slider  72  included in the press machine  70  is mounted on an upper surface of the upper platen  40 , and push rods  41  are attached to a lower surface of the upper platen  40 . 
         [0046]    The lower punch  30  is attached to an upper surface of the bolster  61  via a retainer  63 , and second guide posts  62  are also attached to the upper surface of the bolster  61 . 
         [0047]    Second guide bushes  60   a  through which the second guide posts  62  extend are provided in the lower platen  60 , and the die  10  is attached at the center of the lower platen  60 . 
         [0048]    A spring  64  is disposed around a periphery of each second guide post  62  projecting from the upper surface of the bolster  61 , and the springs  64  support the lower platen  60  while biasing the lower platen  60  upward. 
         [0049]    The press machine  70  includes an oil hydraulic cylinder  71  that slides a piston  71   a,  and a slider  72  that receives a pressing force from the piston  71   a.    
         [0050]    The components of the powder molding apparatus  200  are housed in the frame  100 , and the oil hydraulic cylinder  71  included in the press machine  70  is fixed on a top surface of the frame, and the piston  71   a  extends through the top surface and projects to the inside of the frame  100 , and a distal end of the piston  71   a  is fixed to the slider  72 . 
         [0051]    The link mechanism  90  includes two links  91  and three joints  92 , the three joints  92  connecting the links  91  to the upper platen  40  and the middle platen  50 , respectively, and connecting the two links  91  to each other. 
         [0052]    The first actuator  80  includes an air cylinder  81  and a piston  82 , and a distal end of the piston  82  is attached to the joint  92  that is a middle joint among the three joints  92 . 
         [0053]      FIG. 1  illustrates a state in which the piston  82  has moved to a left end of the air cylinder  81  (Z 1  direction) and fixes the two links  91 ,  91  linearly. 
         [0054]    As illustrated in  FIG. 1 , metal powder F is charged in the cavity, and the link mechanism  90  is fixed linearly by the first actuator  80 , and then, as illustrated in  FIG. 2 , the press machine  70  is activated to slide the piston  71   a  to provide a pressing force P to the upper platen  40  via the slider  72 . 
         [0055]    Upon receipt of the pressing force P, the upper platen  40  pushes down the middle platen  50  and the upper punch  20  fixed to the lower surface of the middle platen  50  (X 1  direction) via the link mechanism  90  fixed linearly by the first actuator  80 , and the metal powder F is molded in the cavity defined by the die  10  and the lower punch  30 , whereby a compact C is manufactured. 
         [0056]    After the manufacture of the compact C, next, the compact C is ejected from the cavity. 
         [0057]    More specifically, as illustrated in  FIG. 3 , the piston  82  moves rightward inside the air cylinder  81  of the first actuator  80  (Z 2  direction) to pivot the two links  91 ,  91  included in the link mechanism  90  around the respective joints  92  (respective Y 1  directions), whereby the linear fixation of the link mechanism  90  is cancelled. 
         [0058]    Upon the press machine  70  being activated (pressing force P′) concurrently with the cancellation of the fixation of the link mechanism  90 , the lower platen  60  and the die  10  are pushed down against the biasing force from the spring  64 , via the push rods  41  (X 2  direction) while the pressing of the compact C by the upper punch  20  being cancelled. 
         [0059]    As a result of the die  10  being pushed down, the compact C in the cavity moves upward relative to the die  10  (X 3  direction) and the compact C is then exposed to the outside of the cavity and the compact C can thus be ejected. 
         [0060]    As described above, according to the powder molding apparatus  200 , in molding of metal powder F and ejection of a compact C, fixation and cancellation of the fixation of the link mechanism  90  are performed, respectively, by the first actuator  80 , enabling a manufactured compact to be easily ejected without the need to make a height of the powder molding apparatus  200  to be high and the need to dig a pit at a site where the press is installed. 
         [0061]    (Embodiment 2 of powder molding apparatus and compact manufacturing method)  FIG. 4  is a schematic diagram of Embodiment 2 of the powder molding apparatus, and  FIG. 5  is a schematic diagram illustrating a state in which a compact is being manufactured in Embodiment 2 of the powder molding apparatus. Also,  FIG. 6  is a schematic diagram illustrating a state in which the compact is exposed from a cavity in Embodiment 2 of the powder molding apparatus, and  FIG. 7  is a schematic diagram illustrating a state in which the compact is exposed from the cavity so that the compact can be ejected in Embodiment 2 of the powder molding apparatus. 
         [0062]    A powder molding apparatus  200 A, which is illustrated in  FIG. 4 , is an apparatus obtained by adding two second actuators  80 A connecting the upper platen  40  and the middle platen  50  to the powder molding apparatus  200 . 
         [0063]    As illustrated in  FIG. 4 , the two second actuators  80 A each include an air cylinder  81 A and a piston  82 A, and is disposed in such a manner that the piston  82 A moves up/down vertically. 
         [0064]    In each of the second actuators  80 A, a non-illustrated relief valve is provided, whereby a compact C is pressed while a load applied on an upper punch  20  (what is called “hold-down load”) being kept constant by the second actuators  80 A (see  FIG. 6 ), and a pressing force from a press machine  70  is transmitted to a lower platen  60  equipped with a die  10  by push rods  41 , thereby the compact C being exposed to the outside of the cavity. 
         [0065]    In other words, the second actuators  80 A are actuators for applying a constant hold-down load to a compact C when the compact C is ejected. 
         [0066]    Here, a compact manufacturing method using the powder molding apparatus  200 A will generally be described. 
         [0067]    As illustrated in  FIG. 5 , the press machine  70  is activated to apply a pressing force P to a middle platen  50  and the upper punch  20  fixed to a lower surface of the middle platen  50  via a link mechanism  90  fixed linearly by the first actuator  80  to push down the middle platen  50  and the upper punch  20  (X 1  direction), whereby a compact C is manufactured in the cavity defined by the die  10  and a lower punch  30 . 
         [0068]    Next, as illustrated in  FIG. 6 , a piston  82  is moved rightward (Z 2  direction) inside an air cylinder  81  of the first actuator  80  to pivot two links  91 ,  91  included in the link mechanism  90  around respective joints  92  (respective Y 1  directions), whereby the linear fixation of the link mechanism  90  is cancelled. 
         [0069]    Furthermore, the pistons  82 A are moved upward inside the air cylinders  81 A of the respective second actuators  80 A (Z 3  direction) to apply a constant hold-down load from the second actuators  80 A to the middle platen  50  (X 4  direction) and apply the constant hold-down load to the upper punch  20  via the middle platen  50  (X 5  direction). 
         [0070]    With the compact C held by the constant hold-down load, a pressing force V from the press machine  70  pushes down the lower platen  60  and the die  10  against a biasing force of the spring  64 , via the push rods  41  (X 2  direction). 
         [0071]    As illustrated in  FIG. 6 , as a result of the die  10  being pushed down, the compact C in the cavity moves upward relative to the die  10  (X 3  direction). 
         [0072]    As illustrated in  FIG. 7 , the pistons  82 A are moved further upward inside the air cylinders  81 A of the respective second actuators  80 A (Z 4  direction) to move the middle platen  50  and the upper punch  20  upward (X 6  direction), whereby the compact C exposed to the outside of the cavity can be ejected. 
         [0073]    In addition to the effects provided when the powder molding apparatus  200  is used, the powder molding apparatus  200 A can prevent a compact C from cracking when the compact C is ejected from the die  10 . 
         [0074]    Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configurations are not limited to those of these embodiments, and alternations in design and the like of such specific configurations without departing from the spirit of the present invention also fall within the scope of the present invention.