Patent Publication Number: US-9884364-B2

Title: Molding apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a molding apparatus (molding machine). The molding apparatus is for example a die casting machine or injection molding machine. 
     BACKGROUND ART 
     A molding apparatus has a clamping device which holds, opens/closes, and clamps the molds and an injection device which injects and fills a molding material (for example metal in a molten state) into the clamped molds. 
     As the clamping device, for example, there is the one disclosed in Patent Literature 1. The clamping device in Patent Literature 1 is configured as a so-called two-platen clamping device which does not have a toggle mechanism. Further, the clamping device in Patent Literature 1 is configured as a so-called composite clamping device which opens/closes the molds by an electric motor and performs clamping by a hydraulic cylinder. 
     As the injection device, for example, there are those disclosed in Patent Literature 2 and Patent Literature 3. The injection devices in Patent Literature 2 and Patent Literature 3 are configured as so-called hybrid injection devices which perform low speed injection by electric motors and perform high speed injection by hydraulic cylinders. 
     Note that, there is also known a so-called full hydraulic type molding apparatus which performs all of the opening and closing of the molds, clamping, and injection by a hydraulic cylinder (for example Patent Literature 4). The full hydraulic type molding apparatus in Patent Literature 4 has a hydraulic power unit which is configured by partially combining a hydraulic device (for example tank, pump, valve etc.) supplying hydraulic oil to the hydraulic cylinder in the clamping device and hydraulic equipment supplying hydraulic oil to the hydraulic cylinder in the injection device. 
     CITATIONS LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Publication No. 2007-98799A 
     Patent Literature 2: Japanese Patent Publication No. 2012-91220A 
     Patent Literature 3: Japanese Patent Publication No. 2012-232330A 
     Patent Literature 4: Japanese Patent Publication No. 2010-264491A 
     SUMMARY OF INVENTION 
     Technical Problem 
     The patent literatures described above proposes each of composite clamping devices and hybrid injection devices of mode capable of suitably utilizing hydraulic cylinders and electric motors. However, the above patent literatures do not mention suitable utilization of hydraulic cylinders and electric motors from the viewpoint of saving space or saving energy in the clamping devices and injection devices as a whole. 
     Accordingly, it is desired to provide a molding apparatus which is capable of suitably utilizing a liquid pressure cylinder (hydraulic cylinder) and an electric motor in a clamping device and injection device as a whole. 
     Solution to Problem 
     A molding apparatus according to one aspect of the present invention is provided with a clamping device which has a fixed die plate which holds a fixed die, a movable die plate which holds a moving die, an electrically operated die opening and closing-use driving device which moves the movable die plate in an opening and closing direction, and a clamping cylinder which generates a clamping force and with an injection device which has a plunger which is capable of sliding in a sleeve, an electrically operated injection-use driving device which drives the plunger at least at the time of low speed injection, and an injection cylinder which drives the plunger at least at the time of high speed injection. 
     Preferably, it is further provided with a liquid pressure unit which has a tank for storing a hydraulic fluid, a pump for sending out the hydraulic fluid from the tank, a plurality of valves for controlling the flow of the hydraulic fluid, and a holding base for holding the tank, the pump, and the plurality of valves and which supplies the hydraulic fluid to both of the clamping cylinder and the injection cylinder. 
     Preferably, the clamping device further has a core cylinder for making a core advance or retract to or from a space between the fixed die and the moving die, and in each molding cycle, the retraction of the core by the core cylinder and the retraction of the plunger by the injection-use driving device are simultaneously carried out. 
     Preferably, it further has an accumulator for supplying the hydraulic fluid to the injection cylinder, and in each molding cycle, the die-opening by the die opening and closing-use driving device and filling of the accumulator are simultaneously carried out. 
     Advantageous Effects of Invention 
     According to the above configurations, the clamping device and injection device as a whole can suitably utilize the hydraulic cylinder and electric motor. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view which partially includes a cross-sectional view and schematically shows a configuration of principal parts of a die casting machine according to a first embodiment of the present invention. 
         FIG. 2  is a side view which partially includes a cross-sectional view and schematically shows a configuration of principal parts of a clamping device of the die casting machine in  FIG. 1 . 
         FIG. 3  is a plan view which partially includes a cross-sectional view and schematically shows a configuration of principal parts of an injection device of the die casting machine in  FIG. 1 . 
         FIG. 4  is a diagram which schematically shows a configuration of a hydraulic system of the die casting machine in  FIG. 1 . 
         FIG. 5  is a diagram for explaining the operation of the die casting machine in  FIG. 1 . 
         FIG. 6  is a plan view which schematically shows a configuration of principal parts of a clamping device of a die casting machine according to a second embodiment of the present invention 
         FIG. 7A  and  FIG. 7B  are diagrams which show consumed powers of die casting machines according to an example and a comparative example. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG. 1  is a plan view (partially including a cross-sectional view etc.) which schematically shows a configuration of principal parts of a die casting machine  1  according to a first embodiment of the present invention. 
     The die casting machine  1  for example has a clamping device  3  for opening and closing and clamping a fixed die  101  and a moving die  103 , an injection device  5  which injects and fills a molten metal (metal material in a molten state) as the molding material (material) into a cavity  105  (see  FIG. 2 ) which is configured by the fixed die  101  and the moving die  103  which are clamped by the clamping device  3 , and a not shown ejection device which ejects a molded die cast article (molded article) from the fixed die  101  or moving die  103 . Further, the die casting machine  1  has a liquid pressure unit  7  for supplying a hydraulic fluid (for example oil) to the devices in the die casting machine  1  such as the clamping device  3  and injection device  5  and a control device  9  for controlling the devices in the die casting machine  1 . 
     (Configuration of Clamping Device) 
       FIG. 2  is a side view which partially includes a cross-sectional view and schematically shows a configuration of principal parts of the clamping device  3 . 
     As shown in  FIG. 1  and  FIG. 2 , the clamping device  3 , for example, has a base  11  ( FIG. 2 ), a fixed die plate  13  which is fixed onto the base  11  and holds the fixed die  101 , a movable die plate  15  which is movable in the die opening and closing direction (right and left direction on the drawing sheet) above the base and holds the moving die  103 , and a plurality of (four in the present embodiment) tie bars  17  which extend so as to penetrate through the fixed die plate  13  and movable die plate  15 . 
     By the movable die plate  15  moving in the die opening and closing direction, the fixed die  101  and moving die  103  are closed or opened. Further, in a state where first end sides of the plurality of tie bars  17  are engaged with one of the fixed die plate  13  and the movable die plate  15  (movable die plate  15  in the present embodiment), the other end sides of the plurality of tie bars  17  are pulled with respect to the other of the fixed die plate  13  and the movable die plate  15  (fixed die plate  13  in the present embodiment), whereby the fixed die  101  and the moving die  103  are clamped. 
     The clamping device  3  is for example configured by a so-called composite type clamping device which opens and closes the dies by an electric driving operation and performs the clamping by a liquid pressure (oil pressure) driving operation. Specifically, for example, this is as follows. 
     The clamping device  3  for example has die opening/closing-use driving devices  19  ( FIG. 1 ) for driving the movable die plate  15  mainly for opening and closing the dies. Further, the clamping device  3 , mainly for clamping the dies, for example has a plurality of clamping cylinders  21  for driving the plurality of tie bars  17  and has a plurality of engagement devices  23  which are engaged with the plurality of tie bars  17 . 
     The die opening/closing-use driving devices  19  are for example provided as a pair of devices on the two sides of the right-left direction of the movable die plate  15 . Each die opening/closing-use driving device  19  for example has a rotary die opening/closing-use electric motor  25  and a die opening/closing-use screw mechanism  27  for converting the rotation of the die opening/closing-use electric motor  25  to a translational motion. 
     Each die opening/closing-use electric motor  25  may be a DC motor or AC motor or may be an induction motor or synchronous motor. The die opening/closing-use electric motor  25  is for example configured as a servo motor and configures a servo mechanism together with an encoder  25   e  for detecting the rotation of the die opening/closing-use electric motor  25  and a not shown servo driver which supplies electric power to the die opening/closing-use electric motor  25 . 
     Note that, in the explanation of the operation which will be given later, when the die opening/closing-use electric motor  25  is stopped, the die opening/closing-use electric motor  25  may be rendered a torque free state or may be controlled so as to stop at a constant position (in the case of a servo motor), or may be configured so as to include a brake and the brake may be used. A suitable stopping method may be selected in accordance with a situation for stopping the die opening/closing-use electric motor  25  and so on. 
     Each die opening/closing-use screw mechanism (conversion mechanism, die opening/closing-use conversion mechanism)  27  for example has a die opening/closing-use screw shaft  29  which extends in the die opening and closing direction and a die opening/closing-use nut  31  which is screwed with the die opening/closing-use screw shaft  29 . The die opening/closing-use screw shaft  29  is for example supported by a not shown support member or the like which is provided on the base  11  or fixed die plate  13  so that it cannot move in the axial direction and can rotate around the axis. The die opening/closing-use nut  31  is for example fixed to the movable die plate  15  so that it cannot rotate around the axis. 
     When the rotation of the die opening/closing-use electric motor  25  is transmitted to the die opening/closing-use screw shaft  29  and the die opening/closing-use screw shaft  29  is rotated around the axis, the die opening/closing-use nut  31  moves in the die opening and closing direction. Due to this, the movable die plate  15  moves in the die opening and closing direction. Note that, the rotation of the die opening/closing-use electric motor  25  may be directly transmitted to the die opening/closing-use screw shaft  29  by connection of the die opening/closing-use screw shaft  29  and the output shaft of the die opening/closing-use electric motor  25  through a coupling or integral formation of the die opening/closing-use screw shaft  29  and the output shaft of the die opening/closing-use electric motor  25  (illustrated example) or may be indirectly transmitted to the die opening/closing-use screw shaft  29  through a pulley/belt mechanism or gear mechanism or another transmission mechanism. 
     Each clamping cylinder  21  for example has a clamping cylinder portion  33  which is provided at the fixed die plate  13  and a clamping piston  35  which is fixed to one end of the tie bar  17  and is accommodated in the clamping cylinder portion  33 . The clamping piston  35  divides the interior of the clamping cylinder portion  33  into a clamping rod side chamber  33   r  on the front face side (movable die plate  15  side) of the fixed die plate  13  and a clamping head side chamber  33   h  on the opposite side to the former. By selectively supplying the hydraulic fluid (for example oil) to these two cylinder chambers, the clamping piston  35  moves in the die opening and closing direction. 
     Each engagement device  23  is for example configured including a half nut or another split nut and is supported upon the movable die plate  15  so that it cannot move in the die opening and closing direction with respect to the movable die plate  15 . On the other hand, in the end part of a tie bar  17  on the movable die plate  15  side, an engaged portion  17   a  which can engage (can mesh) with the engagement device  23  in the die opening and closing direction is formed. 
     In a state where the moving die  103  contacts the fixed die  101  and the engagement devices  23  mesh with the engaged portions  17   a , the tie bars  17  are extended by supply of the hydraulic fluid to the clamping cylinders  21  so that the clamping pistons  35  move to the back face side of the fixed die plate  13 . Due to this, the fixed die  101  and moving die  103  are clamped. 
     Note that, the grooves or projected rims of the engagement devices  23  and engaged portions  17   a  may be spiral shaped or may be arranged perpendicular to the axial direction of the tie bars  17  in an array in the axial direction. The driving source of the engagement devices  23  is for example a linear motor, hydraulic cylinder, or pneumatic cylinder. 
     As shown in  FIG. 2 , the clamping device  3  has a core pullout device  37  for making the core  107  advance/retract with respect to the space between the fixed die  101  and the moving die  103 . 
     The core pullout device  37  for example has a core cylinder  39  which is supported upon the fixed die  101  or moving die  103  (moving die  103  in the present embodiment). 
     The core cylinder  39  has a core cylinder member  41 , a core piston  43  which can slide inside the core cylinder member  41 , and a core piston rod  45  which is fixed to the core piston  43  and extends outward from the core cylinder member  41 . 
     The core cylinder  39  is arranged so that the direction inclined (for example perpendicular) to the die opening and closing direction is the axial direction. The core cylinder member  41  is for example fixed to the moving die  103 . The core piston rod  45  is connected to the core  107 . The core piston  43  divides the interior of the core cylinder member  41  into a core rod side chamber  41   r  on the core piston rod  45  side and a core head side chamber  41   h  on the opposite side to the former. By selectively supplying the hydraulic fluid to these two cylinder chambers, the core  107  enters into or retracts from the space between the fixed die  101  and the moving die  103 . 
     (Configuration of Injection Device) 
       FIG. 3  is a cross-sectional view seen from the upper part and schematically shows a configuration of principal parts of the injection device  5 . 
     The injection device  5  has a sleeve  47  which is communicated with the cavity  105 , a plunger  49  which ejects the molten metal in the sleeve  47  into the cavity  105 , an injection cylinder  51  for driving the plunger  49 , and an electrically operated injection-use driving device  53  which drives the plunger  49 . 
     The configurations of the sleeve  47  and plunger  49  may be the same as the known configurations. The sleeve  47 , for example, as shown in  FIG. 1  and  FIG. 2 , is provided so as to be inserted into the fixed die plate  13  and fixed die  101 . The plunger  49  has a plunger tip  49   a  for sliding through the sleeve  47  and has a plunger rod  49   b  which is fixed to the plunger tip  49   a.    
     By sliding motion of the plunger  49  in the sleeve  47  toward the cavity  105  (movement forward) in a state where the molten metal is supplied to the sleeve  47  from a hot metal supply port  47   a  which is formed in the sleeve  47 , the molten metal is injected and filled into the cavity  105 . 
     Returning to  FIG. 3 , the injection cylinder  51  is for example configured by a direct coupled booster cylinder. That is, the injection cylinder  51  has an injection cylinder member  55 , an injection piston  57  and booster piston  59  which are capable of sliding inside the injection cylinder member  55 , and an injection piston rod  61  which is fixed to the injection piston  57  and is exposed from the injection cylinder member  55 . 
     The injection cylinder member  55  has an injection cylinder portion  55   a  and a booster cylinder portion  55   b  which is located on the back of the former and has a larger diameter than that of the injection cylinder portion  55   a . The injection piston  57  can slide through the injection cylinder portion  55   a  and divides the interior of the injection cylinder portion  55   a  into an injection rod side chamber  55   r  on the front side and an injection head side chamber  55   h  on the opposite side to the former. The booster piston  59  has a small diameter portion  59   a  capable of sliding through the injection cylinder portion  55   a  and a large diameter portion  59   b  capable of sliding through the booster cylinder portion  55   b . The large diameter portion  59   b  divides the interior of the booster cylinder portion  55   b  into a front side chamber  55   f  on the front side and a rear side chamber  55   e  on the rear side. 
     When the hydraulic fluid is supplied to the injection head side chamber  55   h , the injection piston  57  moves forward. Further, when the hydraulic fluid is supplied to the rear side chamber  55   e  in a state where the outflow of the hydraulic fluid from the injection head side chamber  55   h  is prohibited and the front side chamber  55   f  is rendered a tank pressure, the hydraulic fluid of the injection head side chamber  55   h  is boosted in accordance with a difference of pressurized areas in the front and back of the booster piston  59 . 
     The injection cylinder  51  is arranged coaxially (in series) on the back with respect to the plunger  49 . The tip end of the injection piston rod  61  is directly connected to the rear end of the plunger  49 . Accordingly, the plunger  49  advances and retracts as well along with the advance and retraction of the injection piston rod  61 . 
     The plunger  49  and the injection piston rod  61  are connected by a coupling  63 . The coupling  63  has for example a spacer  65  which is interposed between the rear end of the plunger  49  and the front end of the injection piston rod  61  and has a cover  67  which covers these. The cover  67  has an abutted portion  67   b  which is provided for connection with the injection-use driving device  53 . The abutted portion  67   b  is for example configured by a flange which is formed on the outer circumferential surface of the cover  67 . 
     The injection-use driving device  53  has injection-use electric motors  69  and detachable portions  71  which are driven in the front-back direction by the drive force of the injection-use electric motors  69  and are detachable with respect to the plunger  49  (injection piston rod  61 ). Between the injection-use electric motors  69  and the detachable portions  71 , for example, transmission mechanisms  73 , injection-use screw mechanisms  75 , and guide shafts  77  are interposed in that order from the injection-use electric motors  69  to the detachable portions  71 . The injection-use driving device  53  has for example two sets of these injection-use electric motors  69 , transmission mechanisms  73 , injection-use screw mechanisms  75 , guide shafts  77 , and detachable portions  71  right-left symmetrically. 
     Each injection-use electric motor  69  is a rotary electric motor and is for example arranged so that its output shaft  69   a  is parallel to the injection piston rod  61  and faces backward. The injection-use electric motor  69  may be a DC motor or AC motor or may be an induction motor or synchronous motor. The injection-use electric motor  69  is preferably an electric motor with a brake. The injection-use electric motor  69  is for example configured as a servo motor and configures a servo mechanism together with an encoder  69   e  which detects the rotation of the injection-use electric motor  69  and a not shown servo driver for supplying electric power to the injection-use electric motor  69 . Note that, in the explanation of the operation which will be given later, when the injection-use electric motor  69  is to be stopped, the suitable stopping method may be selected in accordance with the situation in the same way as the die opening/closing-use electric motor  25 . 
     Each transmission mechanism  73  is for example configured by a pulley-belt mechanism and has a first pulley  79  which fixed to the output shaft  69   a  of the injection-use electric motor  69 , a second pulley  81  which is fixed to the injection-use screw mechanism  75 , and a belt  83  which is suspended between the first pulley  79  and the second pulley  81 . Accordingly, when the injection-use electric motor  69  is rotated, that rotation is transmitted through the transmission mechanism  73  to the injection-use screw mechanism  75 . 
     Each injection-use screw mechanism  75  (conversion mechanism and injection-use conversion mechanism) is for example configured by a ball screw mechanism and has an injection-use screw shaft  85  and an injection-use nut  87  which is screwed with the injection-use screw shaft  85  through a not shown ball. 
     Each injection-use screw shaft  85  is arranged parallel to the injection piston rod  61 , is fixed concentrically or coaxially with the second pulley  81 , and is restricted in movement in the axial direction and is allowed to rotate around the axis by an appropriate bearing. On the other hand, the injection-use nut  87  is allowed to move in the axial direction and is restricted in rotation around the axis. 
     Accordingly, when the injection-use electric motor  69  is rotated, that rotation is transmitted through the transmission mechanism  73  to the injection-use screw shaft  85 . Then, by rotation of the injection-use screw shaft  85 , the injection-use nut  87  moves in the direction parallel to the injection piston rod  61 . 
     Each guide shaft  77  extends in a direction parallel to the injection piston rod  61 , is fixed at one end to the injection-use nut  87 , and is fixed at the other end to the detachable portion  71 . Accordingly, when the injection-use nut  87  moves in the front-back direction, the guide shaft  77  and detachable portion  71  move in the front-back direction as well. 
     The guide shaft  77  is for example formed in a hollow state that accommodates the injection-use screw shaft  85 . The guide shaft  77 , for example, has a length long enough to cover the entire portion in the injection-use screw shaft  85  which is ahead of the injection-use nut  87  even when the injection-use nut  87  is located at the backward limit of the injection cycle with respect to the injection-use screw shaft  85  (over the injection cycle from another viewpoint). Preferably, the front end of the guide shaft  77  is closed. 
     The guide shaft  77  is for example slidably inserted into a bushing provided in an injection frame  89  which is fixed to the fixed die plate  13 . Due to this, the load etc. of the guide shaft  77  is supported by the injection frame  89 , and application of unnecessary force to the plunger  49  etc. is suppressed. 
     Each detachable portion  71  has a base  91 , a hook  93  slidably supported upon the base  91 , and an actuator  95  for driving the hook  93 . The detachable portions  71  share the base  91 . 
     The base  91  is fixed to the guide shafts  77 . Accordingly, the base  91  is driven in the front-back direction together with the injection-use nuts  87  and guide shafts  77  by the drive force of the injection-use electric motors  69 . Further, by the movement in front-back direction of the base  91 , the hooks  93  and actuators  95  which are supported upon the base  91  move in the front-back direction as well. Note that, fixation of the base  91  and two guide shafts  77  contributes to the restriction of rotation of each guide shaft  77  around the axis and consequently contributes to the restriction of rotation of the injection-use nut  87 . 
     The base  91  has for example a plate-shaped portion having a hole part formed therein into which the injection piston rod  61  is inserted and can abut against the abutted portion  67   b  of the coupling  63  from the back side. That is, the base  91  is, by abutment against the abutted portion  67   b , restricted in relative forward movement with respect to the plunger  49  (injection piston rod  61 ) and is allowed to relatively retract with respect to the plunger  49  backward from that abutment position. 
     Accordingly, by moving the base  91  forward in a state where the base  91  abut against the abutted portions  67   b , the plunger  49  can be moved forward. That is, the plunger  49  can be moved forward by the drive forces of the injection-use electric motors  69 . Further, by supplying the hydraulic fluid to the injection head side chamber  55   h  to move the injection piston rod  61  at a relatively high speed and so on, it is possible to make the plunger  49  relatively move forward with respect to the base  91 . 
     Each hook  93  is for example formed in a roughly L-shape and is rotatably supported at one end by the corresponding base  91 . Further, the hook  93  can move between the position at which it can engage with the abutted portion  67   b  in the retraction direction of the plunger  49  (“ON” position) and the position at which the engagement is released (“OFF” position). Note that, the hook  93  can grip the abutted portion  67   b  together with the base  91  at the “ON” position. 
     By setting the hooks  93  OFF (releasing engagement), it is possible to make the plunger  49  relatively move forward with respect to the base  91 . Further, by setting the hooks  93  ON (engagement), the plunger  49  can be retracted along with the retraction of the base  91 . That is, the plunger  49  can be retracted by the drive forces of the injection-use electric motors  69 . 
     The injection-use driving device  53  is configured and arranged so that it can make the hooks  93  engage with the abutted portions  67   b  over a stroke of the injection piston  57 . For example, the strokes of the injection-use screw mechanisms  75  are made equivalent to the stroke of the injection cylinder  51 , and the injection-use driving device  53  is arranged so that the injection-use nuts  87  are positioned at the backward limit as well when the injection piston  57  is positioned at the backward limit. 
     Each actuator  95  is for example configured by an actuator performing reciprocating action (expansion/contraction from another viewpoint). The actuator  95  is for example a linear motor, air pressure cylinder, or liquid pressure cylinder. By the reciprocating action of the actuator  95 , the corresponding hook  93  is rendered ON or OFF. 
     (Configuration of Liquid Pressure Unit  7 ) 
       FIG. 4  is a diagram which schematically shows the configuration of a hydraulic system of the die casting machine  1 . 
     The liquid pressure unit  7  for example has a tank  151  which stores the hydraulic fluid, a pump  153  which sends out the hydraulic fluid in the tank  151 , a pump-use electric motor  155  for driving the pump  153 , an accumulator  157  which supplies the accumulated hydraulic fluid, parts of passages which connect these elements and the hydraulic cylinders explained above ( 21 ,  39 ,  51 ) to each other, a plurality of valves ( 161 ,  163 ,  165 A to  165 F, and  167 ) which control the flow of the hydraulic fluid, and a holding base  159  for holding the parts of the liquid pressure unit  7 . 
     The tank  151  is for example an open tank and holds the hydraulic fluid under atmospheric pressure. The tank  151  for example eliminates excess and deficiency of the hydraulic fluid in each hydraulic cylinder. Further, it supplies the hydraulic fluid through the pump  153  to the accumulator  157 . 
     The pump  153  may be a gear pump, vane pump, or other rotary pump which discharges the hydraulic fluid by the rotation of a rotor or may be an axial type plunger pump, radial type plunger pump, or other plunger pump which discharges the hydraulic fluid by reciprocating action of a piston. The pump  153  may be configured by a constant capacity pump which is fixed in discharge amount in motion of the rotor or piston over one period or may be configured by a variable capacity pump which can change that discharge amount. Further, the pump  153  need only be able to discharge the hydraulic fluid in one direction, but may have the same structure as a bi-directional (2-direction) pump. 
     The pump-use electric motor  155  is a rotary electric motor. The pump-use electric motor  155  may be a DC motor or AC motor or may be an induction motor or synchronous motor. The pump-use electric motor  155  may function as a constant speed electric motor provided in an open loop or may function as a servo motor provided in a closed loop. In the present embodiment, the pump-use electric motor  155  is configured as a servo motor and configures a servo mechanism together with the encoder  155   e  detecting the rotation of the pump-use electric motor  155  and a not shown servo driver supplying electric power to the pump-use electric motor  155 . In the explanation of operation which will be given later, when the pump-use electric motor  155  is stopped, a suitable stopping method may be selected in accordance with the situation due to which the pump-use electric motor  155  is stopped in the same way as other electric motors. 
     The accumulator  157  may be configured by a gravimetric, spring type, gas pressure type (including pneumatic type), cylinder type, bladder type, or another accumulator having a suitable form. For example, the accumulator  157  is a gas pressure type, cylinder type, or bladder type accumulator, and the pressure is accumulated by compression of the gas (for example air or nitrogen) which is held in the accumulator  157 . The accumulated hydraulic fluid is supplied to the injection cylinder  51 . 
     The plurality of valves include for example a clamping valve  161  for controlling the flow of the hydraulic fluid relating to the clamping cylinders  21 , a core-use valve  163  for controlling the flow of the hydraulic fluid relating to the core cylinder  39 , a first injection-use valve  165 A to sixth injection-use valve  165 F for controlling the flow of the hydraulic fluid relating to the injection cylinder  51 , and a filling valve  167  for controlling the flow of the hydraulic fluid relating to filling of the accumulator  157 . 
     The clamping valve  161  is for example configured by a 4-port 3-position switching valve. At one position, the clamping rod side chamber  33   r  and the pump  153  are connected and the clamping head side chamber  33   h  and the tank  151  are connected. At another position, the clamping head side chamber  33   h  and the pump  153  are connected and the clamping rod side chamber  33   r  and the tank  151  are connected. At the remaining positions, all of the connections described above are closed. 
     The core-use valve  163  is for example configured by a 4-port 3-position switching valve. At one position, the core rod side chamber  41   r  and the pump  153  are connected and the core head side chamber  41   h  and the tank  151  are connected. At another one position, the core head side chamber  41   h  and the pump  153  are connected and the core rod side chamber  41   r  and the tank  151  are connected. At the remaining positions, all of the connections described above are closed. 
     The first injection-use valve  165 A is for example configured by a pilot type check valve which permits or prohibits the flow of the hydraulic fluid relating to the injection head side chamber  55   h . The first injection-use valve  165 A is used to control the flow with the injection head side chamber  55   h  for example for the injection rod side chamber  55   r , pump  153 , and/or tank  151 . 
     The second injection-use valve  165 B is for example configured by a pilot type check valve which permits or prohibits the flow of the hydraulic fluid between the injection head side chamber  55   h  and the accumulator  157 . 
     The third injection-use valve  165 C is for example configured by a pilot type check valve which permits or prohibits the flow between the rear side chamber  55   e  and the accumulator  157 . 
     The fourth injection-use valve  165 D is for example configured by a servo valve which permits or prohibits the flow of the hydraulic fluid relating to the injection rod side chamber  55   r . The fourth injection-use valve  165 D is used to control the flow with the injection rod side chamber  55   r  for example for the injection head side chamber  55   h , tank  151 , and/or pump  153 . Note that, the fourth injection-use valve  165 D configures a meter-out circuit. 
     The fifth injection-use valve  165 E is for example configured by a pilot type check valve which permits or prohibits the flow of the hydraulic fluid according to the tank  151 . The fifth injection-use valve  165 E is used to control the flow with the tank  151  for example for the injection rod side chamber  55   r  and/or injection head side chamber  55   h.    
     The sixth injection-use valve  165 F is for example configured by a pilot type check valve which permits or prohibits the flow between the tank  151  and the front side chamber  55   f.    
     The filling valve  167  is for example configured by a pilot type check valve which permits or prohibits the flow between the pump  153  and the accumulator  157 . 
     The holding base  159  is a housing-shaped member or framework-shaped member which is configured by a metal or the like. The holding base  159  may be integrally formed or may be configured by a combination of a plurality of members. To the holding base  159 , for example, the tank  151 , pump  153 , pump-use electric motor  155 , accumulator  157 , and plurality of valves ( 161 ,  163 ,  165 A to  165 F, and  167 ) are fixed together. These elements may be accommodated in the housing-shaped holding base  159  or may be fixed to the framework-shaped holding base  159  and be exposed to the outside. The holding base  159  is provided at a suitable position, for example, the lateral side of the clamping device  3  or injection device  5 . 
     The control device  9  ( FIG. 1 ) includes, for example, although not particularly shown, a CPU, ROM, RAM, external memory device, input circuit, and output circuit. The control device  9  outputs control signals for controlling the portions based on various types of input signals which are input. 
     What input signals to the control device  9  are for example a not shown input device accepting the input operation by the user, encoders ( 25   e ,  69   e ,  155   e ) of various types of motors, a position sensor  169  ( FIG. 3 ) for detecting the position of the plunger  49 , and a not shown pressure sensor which detects the pressure of the hydraulic fluid at a suitable position in the hydraulic system. 
     What the control device  9  outputs signals to are for example a not shown display unit which displays information to the user, servo drivers of various types of motors, various types of valves, and an actuator  95  (or driver of that). 
     The position sensor  169  for example configures a linear encoder together with a not shown scale portion. For example, the position sensor  169  is provided in front of the injection cylinder member  55  in a fixed manner, and the scale portion is provided on the injection piston rod  61  and extends in its axial direction. The position sensor  169  indirectly detects the position of the plunger  49  by detecting the position of the scale portion which moves along with the movement of the injection piston rod  61 . Note that, by differentiating the detected position, the position sensor  169  or control device  9  can detect the speed. 
     The pressure sensor is provided at a suitable position in the hydraulic system. For example, although particularly not shown, a pressure sensor which detects the pressure of the clamping rod side chamber  33   r  is provided. The control device  9  can identify the clamping force based on the detection value of this pressure sensor. Note that, the clamping force may be identified from displacement of the clamping piston  35  or the amount of expansion of the tie bars  17 . Further, for example, a pressure sensor detecting the pressures of the injection head side chamber  55   h  and injection rod side chamber  55   r  is provided. The control device  9  can identify the pressure which is applied to the molten metal by the plunger  49  based on these detection values of the pressure sensor. Further, for example, though not particularly shown, a pressure sensor detecting the pressure of the accumulator  157  is provided. The control device  9  can judge completion of filling of the accumulator  157  based on that detection value. 
     (Operation of Die Casting Machine  1 ) 
       FIG. 5  is a table for explaining the operation of the die casting machine  1 . 
     In this table, the row of “LIQUID PRESSURE” of “CLAMPING DEVICE” shows the driving state of the hydraulic system (clamping cylinders  21  and core cylinder  39 ) of the clamping device  3 . The row of “ELECTRICALLY OPERATED” of “CLAMPING DEVICE” shows the driving state of the die opening/closing-use electric motor  25 . The row of “LIQUID PRESSURE” of “INJECTION DEVICE” shows the driving state of the injection cylinder  51 . The row of “ELECTRICALLY OPERATED” of “INJECTION DEVICE” shows the driving state of the injection-use electric motor  69 . The row of “PUMP” shows the driving state of the pump  153  (pump-use electric motor  155 ). The row of “ACC” shows the state of the accumulator  157 . 
     Further, each column corresponds to the process executed by the die casting machine  1 . They are shown from left to right in time sequence. 
     In the rows of “ELECTRICALLY OPERATED” of “CLAMPING DEVICE” and “ELECTRICALLY OPERATED” of “INJECTION DEVICE” and “PUMP”, “ON” shows the state where electric power is supplied to the electric motor and the motor is driven (rotated), while “OFF” shows the state where it is stopped. In “LIQUID PRESSURE” of each “CLAMPING APPARATUS” and “INJECTION DEVICE”, “P” shows the state where the hydraulic fluid is supplied from the pump  153 , “ACC” shows the state where the hydraulic fluid is supplied from the accumulator  157 , and “OFF” shows the state which is not any of the states described above. 
     Before the die closing process shown as the first process in this table, the movable die plate  15  is positioned at a predetermined die opening position (for example, a die open limit). The clamping piston  35  is for example positioned at the driving limit on the clamping rod side chamber  33   r  side. The core piston  43  is for example positioned at the backward limit. The plunger  49  (injection piston rod  61 ) and booster piston  59  are for example positioned at the backward limit. Various types of valves are for example controlled so as to prohibit the flow of the hydraulic fluid. Further, the various types of electric motors ( 25 ,  69 ,  155 ) are for example stopped. 
     (Die Closing Process) 
     In the die closing process, the control device  9  drives the die opening/closing-use electric motor  25  and moves the movable die plate  15  to the die closing direction. Then, the control device  9  for example stops the die opening/closing-use electric motor  25  when the detection value of the encoder  25   e  reaches a value which is set in advance corresponding to the die contact position or the position in the vicinity of that. Note that, a not shown position sensor which detects the position of the movable die plate  15  may be provided and the control may be carried out based on the detection value of that position sensor. 
     The control device  9  drives the pump-use electric motor  155  and sends out the hydraulic fluid from the pump  153  parallel to the movement of the movable die plate  15  described above. Further, the control device  9  switches the core-use valve  163  to supply the hydraulic fluid from the pump  153  to the core head side chamber  41   h  and permit the discharge of the hydraulic fluid from the core rod side chamber  41   r  to the tank  151 . Due to this, the core  107  is inserted between the fixed die  101  and the moving die  103 . After insertion, the control device  9  switches the core-use valve  163  to prohibit the flow of the hydraulic fluid relating to the core cylinder  39 . 
     After the completion of die closing as in the above-described way, though not particularly shown, the control device  9  closes the engagement devices  23  and engages the movable die plate  15  and the tie bars  17 . Note that, meshing between the engagement devices  23  and the engaged portions  17   a  at this time may be adjusted by the stopping position of the movable die plate  15  described above being set at a position which enables meshing or may be carried out by movement of the tie bars  17  by the clamping cylinders  21  after the stopping of the movable die plate  15 . 
     (Clamping Process) 
     After closing the engagement devices  23 , the control device  9  drives the pump-use electric motor  155  and sends out the hydraulic fluid from the pump  153 . Further, the control device  9  switches the position of the clamping-use valve  161  to supply the hydraulic fluid from the pump  153  to the clamping rod side chamber  33   r  and permit the flow of the hydraulic fluid from the clamping head side chamber  33   h  to the tank  151 . Due to this, the clamping piston  35  moves to the back of the fixed die plate  13 , the tie bars  17  are extended, and thus the clamping is carried out. 
     When the desired clamping force is obtained, the control device  9  switches the position of the clamping-use valve  161  to prohibit the flow of the hydraulic fluid relating to the clamping cylinders  21  and stops the pump-use electric motor  155 . That is, the control device  9  maintains the intended clamping force. Note that, considering leakage of the hydraulic fluid, until the later explained pressure holding operation is completed, the supply of the hydraulic fluid from the pump-use electric motor  155  to the clamping cylinders  21  may be continued at a suitable timing and/or supply rate. 
     (Low Speed Injection Process) 
     Low speed injection is the process of moving the plunger forward at a relatively low speed (so-called critical speed) to inject the molten metal into the cavity  105  in order to reduce entrainment of air into the molten metal. That injection speed is suitably set in accordance with the diameter of the sleeve  47  or amount of hot metal in one shot or the like. However, for example, it is less than 1 m/s, more specifically it is for example 0.2 m/s to 0.5 m/s. 
     When the clamping is completed and the molten metal is supplied to the sleeve  47  by a not shown hot metal supply device, the control device  9  drives the injection-use electric motor  69  and moves the detachable portion  71  forward. The detachable portion  71  (base  91 ) is restricted in relative forward movement with respect to the plunger  49 , therefore the plunger  49  moves forward as well. Due to this, the low speed injection is carried out. 
     By the forward movement of the detachable portion  71 , the injection piston  57  moves forward as well. The control device  9  suitably controls the liquid pressure unit  7  so that the discharge of the hydraulic fluid from the injection rod side chamber  55   r  and the supply of the hydraulic fluid to the injection head side chamber  55   h  are suitably carried out along with the forward movement of the injection piston  57 . 
     For example, the first injection-use valve  165 A and fourth injection-use valve  165 D permit the flow of the hydraulic fluid from the injection rod side chamber  55   r  to the injection head side chamber  55   h . Due to this, the hydraulic fluid discharged from the injection rod side chamber  55   r  is refluxed to the injection head side chamber  55   h . Note that, a passage connecting the injection rod side chamber  55   r  and the injection head side chamber  55   h  configures a run-around circuit. 
     The pressurized area of the injection head side chamber  55   h  is larger than the pressurized area of the injection rod side chamber  55   r  by a difference equivalent to the cross-sectional area of the injection piston rod  61 . Therefore, even when the hydraulic fluid of the injection rod side chamber  55   r  is refluxed to the injection head side chamber  55   h , shortage of the hydraulic fluid occurs. The shortage of the hydraulic fluid is for example made up for by supply of the hydraulic fluid from the tank  151  to the injection head side chamber  55   h . Specifically, for example, the fifth injection-use valve  165 E prohibits the flow from the injection cylinder  51  to the tank  151  and permits the flow in an inverse direction to that. 
     Note that, the shortage of the hydraulic fluid may be made up for by the supply of the hydraulic fluid from the pump  153  in place of the supply of the hydraulic fluid from the tank  151 . The amount of supply of the hydraulic fluid at this time may be of an extent where formation of negative pressure in the injection head side chamber  55   h  is resolved or may be magnitude such several fractions of the drive force for driving the plunger  49  are borne by the injection cylinder  51  (the injection cylinder  51  assists the injection-use electric motor  69 ). 
     The speed of the plunger  49  is controlled by the adjustment of the rotation speed of the injection-use electric motor  69 . Specifically, the control device  9  controls the rotation speed of the injection-use electric motor  69  by feedback based on the speed of the plunger  49  which is detected by the position sensor  169 . An electric motor has a higher controllability than a hydraulic cylinder, therefore the speed of the low speed injection can be controlled with a high accuracy. 
     In low speed injection, the detachable portion  71  may be set ON or OFF. Note, when it is set ON, for example, when multistage control including deceleration is carried out, the plunger  49  advancing so as to separate from the base  91  due to inertial force can be prevented. 
     (High Speed Injection Process) 
     High speed injection is the process of moving the plunger forward at a relatively high speed and injecting the molten metal into the cavity  105  for the purpose of filling the molten metal in the cavity without delay in solidification of the molten metal. The injection speed is suitably set in accordance with the diameter of the sleeve  47  or amount of hot metal of one shot. However, for example, it is 1 m/s or more, more specifically, it is for example 2 m/s to 10 m/s. 
     The control device  9  opens the second injection-use valve  165 B and supplies the hydraulic fluid from the accumulator  157  to the injection head side chamber  55   h  when the position of the plunger  49  according to the detection value of the position sensor  169  reaches the predetermined high speed switching position. Further, the control device  9  adjusts the servo valve constituting the fourth injection-use valve  165 D to a suitable degree of opening. Further, the control device  9  sets the detachable portion  71  OFF (releases engagement) continuously from the low speed injection or sets OFF the detachable portion  71  which was ON in the low speed injection. 
     Due to this, the injection piston  57 , injection piston rod  61 , and plunger  49  move forward at a relatively high speed. At this time, the engagement of the detachable portion  71  is released, therefore the plunger  49  etc. move forward while leaving behind the detachable portion  71 , guide shaft  77 , and injection-use nut  87  which move at a relatively low speed. Accordingly, the injection-use driving device  53  does not become a load preventing the forward movement of the plunger  49  etc. Then, the molten metal in the sleeve  47  is injected into the cavity  105  at a high speed. 
     The speed of the plunger  49  is controlled by adjustment of the degree of opening of the fourth injection-use valve  165 D which is the servo valve. Note that, the control device  9  may control by feedback the degree of opening of the fourth injection-use valve  165 D as well based on the speed of the plunger  49  which is detected by the position sensor  169 . 
     After that, though not particularly shown, decelerated injection is carried out. That is, when the molten metal is filled in the cavity  105  to a certain extent, the plunger  49  receives a counterforce from that filled molten metal and is decelerated while the injection pressure suddenly rises. Note that, the operations of the portions are the same as those at the time of high speed injection. Note, in order to mitigate the shock at the time of filling, suitable deceleration control may be carried out as well. For example, the degree of opening of the fourth injection-use valve  165 D as the servo valve may be made small when predetermined deceleration start conditions such as arrival of the plunger  49  at a predetermined deceleration position are satisfied. 
     (Boosting/Holding Process) 
     When the predetermined boosting start conditions are satisfied, the control device  9  controls the liquid pressure unit  7  so as to start the boosting process. The boosting start conditions are for example that the injection pressure based on the detection value of a not shown pressure sensor which detects the pressure of the injection head side chamber  55   h  (and, according to need, a not shown pressure sensor which detects the pressure of the injection rod side chamber  55   r ) reaches a predetermined value or that the detection position of the plunger  49  detected by the position sensor  169  reaches a predetermined position. 
     In the boosting process, for example, the fourth injection-use valve  165 D and fifth injection-use valve  165 E permit the discharge of the hydraulic fluid from the injection rod side chamber  55   r  to the tank  151 . The first injection-use valve  165 A and second injection-use valve  165 B prohibit the outflow of the hydraulic fluid from the injection head side chamber  55   h . The sixth injection-use valve  165 F permits the discharge of the hydraulic fluid from the front side chamber  55   f  to the tank  151 . The third injection-use valve  165 C permits the release of the hydraulic fluid from the accumulator  157  to the rear side chamber  55   e.    
     By operations of the various types of valves as described above, the pressure of the injection head side chamber  55   h  is raised by the boosting piston  59  and the injection pressure rises. Then, the injection pressure reaches the final pressure. Further, the injection speed becomes zero by complete filling of the molten metal in the cavity  105 . 
     After that, the control device  9  maintains the state where the injection pressure has become the final pressure. That is, the holding process is carried out. For example, the various types of valves are maintained in the states at the time of the boosting process described above. During the holding process, the molten metal is cooled and solidified. When the molten metal solidifies, the control device  9  closes the third injection-use valve  165 C and ends application of the liquid pressure from the accumulator  157  to the rear side chamber  55   e  and so on thereby ending the holding process. 
     Note that, the control device  9  suitably judges whether the molten metal has solidified. For example, the control device  9  judges whether the molten metal has solidified according to whether a predetermined time has passed from a predetermined point of time such as the point of time when the final pressure was obtained. 
     (Operation of Detachable Portion in High Speed Injection Process to Holding Process) 
     As explained above, when high speed injection is started, the plunger  49  and injection piston rod  61  move forward while leaving the detachable portions  71  behind. On the other hand, even after the start of the high speed injection, the forward movement of the detachable portions  71  by the injection-use electric motors  69  is continued. After that, the boosting starts and the speed of the plunger  49  falls and further the holding action is started and the plunger  49  stops, whereby the detachable portions  71  (base  91 ) catch up with the abutted portions  67   b . In other words, the detachable portions  71  become states where they can engage with the abutted portions  67   b . The point of time when the detachable portions  71  reach the abutted portions  67   b  is preferably before the completion of the holding action. 
     The control device  9  stops the injection-use electric motor  69  when detecting the arrival of the detachable portions  71  at the abutted portions  67   b  based on the detection values of the position sensor  169  and encoder  69   e . Note that, the positions of the detachable portions  71  may be detected by providing a position sensor (linear encoder) the same as the position sensor 169 and so on. 
     The speed of the detachable portions  71  from the start of the high speed injection up to the arrival of the detachable portions  71  at the abutted portions  67   b  may be the same as the speed at the time of the low speed injection or may be different from the latter. Further, the deceleration control may be suitably carried out as well so that the base  91  does not strike the plunger  49 . 
     (Die Opening Initial Step) 
     After ending of the holding action, the control device  9  switches the clamping-use valve  161  to connect the clamping rod side chamber  33   r  and the tank  151  and connect the clamping head side chamber  33   h  and the pump  153 . Due to this, the clamping cylinders  21  are depressurized and the extension of the tie bars  17  is canceled. After that, the control device  9  for example switches the clamping-use valve  161  so as to prohibit the flow of the hydraulic fluid relating to the clamping cylinders  21 . 
     Next, the control device  9  drives the die opening/closing-use electric motor  25  and moves the movable die plate  15  to the die opening direction. Due to this, the moving die  103  is separated from the fixed die  101  together with the molded article. 
     At this time, the control device  9  performs control for ejecting the biscuit by the plunger  49  along with the movement of the moving die  103 , that is, what may be called a “tracking ejection” action. For example, the control device  9  drives the pump-use electric motor  155  and sends out the hydraulic fluid from the pump  153 , controls the first injection-use valve  165 A so as to permit the flow of the hydraulic fluid from the pump  153  to the head side chamber  55   h , and controls the fourth injection-use valve  165 D and fifth injection-use valve  165 E so as to permit the flow of the hydraulic fluid from the injection rod side chamber  55   r  to the tank  151 . After that, when the plunger  49  moves up to a predetermined position, the control device  9  controls the above-described valves so as to prohibit the flow of the hydraulic fluid relating to the injection cylinder  51  and ends the ejection tracking action. Note that, the tracking ejection action may be carried out by driving the plunger  49  by the injection-use driving device  53  or may be carried out by driving the plunger  49  as a whole or partially by both of the injection cylinder  51  and the injection-use driving device  53 . 
     (Die Opening Process) 
     Even after the end of the tracking ejection action, the control device  9  continues the movement of the movable die plate  15  by the die opening/closing-use electric motor  25  in the die opening direction. Then, when the movable die plate  15  reaches the predetermined die opening position, the control device  9  stops the die opening/closing-use electric motor  25  and ends the die opening process. 
     Note that, the die opening position is generally made the die open limit (driving limit on the die opening side) of the movable die plate  15 . Note, the electrically operated die opening/closing-use driving devices  19  can easily hold the position of the movable die plate  15  at any position, therefore the die opening position may be made nearer the die closing side than the die open limit. In this case, the time required for opening and closing the die can be shortened. 
     The control device  9  fills the accumulator  157  parallel to the opening of the dies. That is, the control device  9  drives the pump-use electric motor  155  and controls the filling-use valve  167  so as to permit the flow of the hydraulic fluid from the pump  153  to the accumulator  157 . After that, when the detection value of the not shown pressure sensor detecting the pressure of the accumulator  157  reaches a predetermined value, the control device  9  closes the filling-use valve  167  and so on and ends the filling of the accumulator  157 . 
     (Core Return and Injection Return) 
     For example, when the die opening and filling of the accumulator  157  are completed, the control device  9  performs control for retracting the core  107  from the space between the fixed die  101  and the moving die  103  (core return). For example, the control device  9  drives the pump-use electric motor  155  and switches the core-use valve  163  to permit the flow of the hydraulic fluid from the pump  153  to the core rod side chamber  41   r  and permit the flow from the core head side chamber  41   h  to the tank  151 . When the core  107  ends the retraction, for example, the control device  9  switches the core-use valve  163  so as to prohibit the flow of the hydraulic fluid according to the core cylinder  39 . 
     Further, the control device  9  performs control for retracting the plunger  49  (injection return) parallel to the core return. For example, the control device  9  sets the hooks  93  of the detachable portions  71  to the ON position to engage them with the plunger  49 . Note that, this engagement may be carried out at any timing so far as the detachable portions  71  have caught up with the plunger  49 . Then, the control device  9  drives the injection-use electric motors  69  to retract the plunger  49 . That is, the injection return is carried out not by the injection cylinder  51 , but by the injection-use driving device  53 . 
     Note that, during a period where the injection return is carried out by the injection-use driving device  53 , for example, the injection cylinder  51  is brought to a state where the drive force is not generated and is returned to the initial state by the drive force of the injection-use driving device  53 . 
     For example, the control device  9  controls the fourth injection-use valve  165 D and fifth injection-use valve  165 E so as to permit the flow of the hydraulic fluid from the tank  151  to the injection rod side chamber  55   r , controls the first injection-use valve  165 A so as to prohibit the discharge of the hydraulic fluid from the injection head side chamber  55   h , controls the sixth injection-use valve  165 F so as to permit the flow of the hydraulic fluid from the tank  151  to the front side chamber  55   f , and controls a not shown valve so as to permit the discharge of the hydraulic fluid from the rear side chamber  55   e  to the tank  151  (the passage for this purpose is not shown). Due to this, along with the retraction of the plunger  49 , the injection piston  57  and the booster piston  59  retract. When the booster piston  59  reaches the backward limit, the first injection-use valve  165 A is controlled so as to permit the discharge of the hydraulic fluid from the injection head side chamber  55   h  to the tank  151 , and the retraction of the injection piston  57  is continued. 
     After that, when the plunger  49  reaches the backward limit, the control device  9  stops the injection-use electric motor  69  and prohibits the flow of the hydraulic fluid relating to the injection cylinder  51 . 
     (Ejection Process and Extraction Process) 
     When the core return and injection return are completed, the control device  9  drives a not shown ejection device to eject the molded article from the moving die  103 . Then, a not shown conveyor device takes out the ejected molded article from the clamping device  3  (dies). The not shown ejection device is for example driven by supply of the hydraulic fluid from the pump  153  to an ejection cylinder which is included in the ejection device. 
     As described above, in the present embodiment, the die casting machine  1  has the clamping device  3  and the injection device  5 . The clamping device  3  has the electrically operated die opening/closing-use driving devices  19  which move the movable die plate  15  in the die opening and closing direction and has the clamping cylinders  21  which generate the clamping force and is a 2-platen type. The injection device  5  has the electrically operated injection-use driving device  53  which drives the plunger  49  in the low speed injection and the injection cylinder  51  which drives the plunger  49  in the high speed injection. 
     Accordingly, the die casting machine  1  as a whole suitably utilizes the hydraulic cylinders and electric motors. Specifically, for example, the electrically operated driving devices are used for both of the clamping device  3  and the injection device  5 , therefore the instances where the electric motors drive the pump to send out the hydraulic fluid can be reduced in the die casting machine  1  as a whole. The electrically operated driving devices directly transmit the drive force without using hydraulic fluid, therefore are efficient, and the consumed power is reduced in the die casting machine  1  as a whole. On the other hand, by utilizing the hydraulic cylinders for the clamping needing a large power and for the high speed injection needing a high speed, the quality of the molded article can be improved. Also by stabilization of the control of the speed of the low speed injection by the electrically operated injection-use driving device  53 , an improvement of quality of the molded article is expected. A hybrid type injection device  5  needs space for arrangement of the injection-use driving device  53  compared with a full hydraulic type injection device. However, if the injection-use driving device  53  is arranged on the lateral side of the injection cylinder  51 , the increase in length and increase in size of the die casting machine  1  are reduced. Rather, due to the clamping device  3  being a 2-platen type, the die casting machine  1  can be made shorter as a whole. That is, the arrangement space can be made smaller. 
     Further, in the present embodiment, the die casting machine  1  has the liquid pressure unit  7 . The liquid pressure unit  7  has the tank  151  for storing the hydraulic fluid, the pump  153  which sends out the hydraulic fluid from the tank  151 , the plurality of valves which control the flow of the hydraulic fluid, and the holding base  159  which holds these and the unit supplies the hydraulic fluid to both of the clamping cylinders  21  and the injection cylinder  51 . 
     Accordingly, the clamping device  3  and the injection device  5  are integrated or standardized in parts of the hydraulic systems, so space is saved. Since the clamping device  3  does not have hydraulic cylinders for opening and closing the dies, so compared with the full hydraulic type clamping device, the amount of the hydraulic fluid used, the frequency of use of the pump, and the number of valves are smaller. Accordingly, even when parts of the hydraulic systems are integrated, extreme enlargement of the tank  151 , the use of the pump-use electric motor  155  under extremely severe conditions, and extreme enlargement of the holding base  159  are prevented. As a result, the concerned increase of costs of these parts is reduced. 
     Further, in the present embodiment, the clamping device  3  further has the core cylinder  39  which advances and retracts the core  107  to and from the space between the fixed die  101  and the moving die  103 . In each molding cycle, the retraction of the core  107  by the core cylinder  39  and the die-opening by the injection-use driving device  53  are simultaneously carried out. 
     Accordingly, the cycle time is shortened. Specifically, this is as follows. A spray process of coating a mold releasing agent is carried out after the die-opening and core return. At this time, in general, to prevent the mold releasing agent from entering into the sleeve  47 , the plunger  49  is not retracted but stands by at the position in front of the sleeve  47  until the spray process ends. Accordingly, the core return and the injection return are not simultaneously carried out. Further, in the full hydraulic type die casting machine, if the core return and the injection return are simultaneously carried out, the hydraulic fluid must be supplied from the pump  153  to both of the core cylinder  39  and the injection cylinder  51 . As a result, in the full hydraulic type die casting machine, even when trying to simultaneously perform the core return and the injection return, the hydraulic fluid flows to only the one of the core cylinder  39  or injection cylinder  51  which has a lower pressure. In the end, the operations are carried out in succession or the speeds of the two fall. That is, the effect of shortening the cycle time is not obtained. In the present embodiment, however, the core return and the injection return are simultaneously carried out by different driving sources, therefore the cycle time is shortened. 
     Note that, either of the core return or injection return may be started earlier. Further, either may be completed earlier as well. So far as at least a portion of the period of either of the core return or injection return and at least a portion of the other period overlap each other, the cycle time is shortened. 
     Further, in the present embodiment, the die casting machine  1  further has the accumulator  157  which supplies the hydraulic fluid to the injection cylinder  51 . In each molding cycle, the die-opening by the die opening/closing-use driving devices  19  and filling of the accumulator  157  are simultaneously carried out. 
     Accordingly, the cycle time is shortened. Note that, in the full hydraulic type die casting machine, even if trying to simultaneously perform the die-opening and filling, the hydraulic fluid flows to only the one of the die opening/closing-use hydraulic cylinder or accumulator  157  which has the lower pressure. In the end, the die-opening and filling are carried out in succession or the speeds of the two fall. That is, the effect of shortening the cycle time is not obtained. 
     Note that, either of the die-opening or filling of the accumulator may be started earlier, and either may be completed earlier. So far as at least a portion of the period of either of the die-opening or filling of the accumulator and at least a portion of the other period overlap each other, the cycle time is shortened. 
     Second Embodiment 
       FIG. 6  is a plan view schematically showing a configuration of principal parts of a clamping device  203  of a die casting machine according to a second embodiment of the present invention. 
     Although not particularly shown, in the second embodiment, configurations other than the clamping device  3  are the same as those in the first embodiment. Further, in the clamping device  203  in the second embodiment, configurations which are the same as or resemble those of the clamping device  3  in the first embodiment will be assigned the same notations as the notations in the first embodiment and explanations will be omitted. 
     The clamping device  203  differs from the clamping device  3  in the first embodiment in the point that a plurality of tie bars  217  can be pulled out of the fixed die plate  13  by the movable die plate  15 . Specifically, this is as follows. 
     The clamping device  203  has fixed side engagement devices  223  capable of connecting the clamping pistons  35  and the tie bars  217  and releasing the connections. The fixed side engagement devices  223  are configured including half nuts or other split nuts and are connected with respect to the clamping pistons  35  so that they cannot move in the die opening and closing direction. 
     In the tie bars  217 , in the same way as the first embodiment, engaged portions  217   a  which engage with engagement devices  23  are formed at ends on the movable die plate  15  side. Further, in the tie bars  217 , ends on the fixed die plate  13  side are formed with fixed side engaged portions  217   b  which engage with the fixed side engagement devices  223 . 
     Accordingly, by engaging the fixed side engagement devices  223  with the fixed side engaged portions  217   b  all the time in the molding cycle, the same operation as that of the clamping device  3  in the first embodiment becomes possible. 
     Further, at the time of exchange of the dies, the movable die plate  15  is moved in the die-closing direction (for example moved up to the die contact position). Next, the engagement devices  23  are engaged with the engaged portions  217   a , and the engagement between the fixed side engagement devices  223  and the fixed side engaged portions  217   b  is released. After that, the movable die plate  15  is moved to the die-opening direction, whereby the tie bars  217  can be pulled out of the fixed die plate  13 . 
     Note that, the base  11  and the die opening/closing-use driving devices  19  etc. must be configured longer than those in the first embodiment so that it is possible to move the movable die plate  15  in the die-opening direction more than the die open position of the molding cycle. Further, the movable die plate  15  has cylindrical guide members  218  which extend to the die-opening direction from the front face thereof so that the pulled-out tie bars  217  can be suitably supported. 
     According to the above second embodiment, the die casting machine has a 2-platen type composite type clamping device  203  and a hybrid type injection device  5 , therefore the same effects as those in the first embodiment are exhibited. Further, it is not necessary to provide large-scale equipment for pulling out the tie bars  217 , therefore space is further saved. 
     Example 
     A die casting machine according to the embodiments was fabricated, and the consumed power in the molding cycle was measured. Further, as a comparative example, the consumed power in the molding cycle of a full hydraulic type die casting machine was measured. Note, the molding cycles were for experiments. Molten metal was not supplied to the sleeves  47 . 
     The measurement conditions of the consumed power will be shown next. 
     Cycle time: Four kinds of 25, 30, 35, and 40 seconds 
     Pressure when filling accumulator: 13.5 MPa 
     Dies: None 
     Extrusion: Drive hydraulic cylinder for extrusion by full stroke 
     Stroke of high speed injection: About ⅓ of full stroke of injection cylinder 
     Temperature of oil as hydraulic fluid: About 40° C. 
     The measurement results of the consumed power will be shown below. Note that, the consumed powers which are shown below are the consumed powers in only the machine bodies, and the consumed powers concerned with the advance and retraction of the core, supply of hot metal, and spraying are excluded. Further, “REDUCTION RATE” is (consumed power in comparative example−consumed power in example)/(consumed power in comparative example)×100(%). 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                   
                 Comparative 
                   
                 Reduction rate 
               
               
                 Cycle time (s) 
                 Example (kW) 
                 Example (kW) 
                 (%) 
               
               
                   
               
             
            
               
                 25 
                 16.0 
                 8.5 
                 46.8 
               
               
                 30 
                 15.9 
                 7.4 
                 53.4 
               
               
                 35 
                 15.5 
                 6.8 
                 56.1 
               
               
                 40 
                 15.1 
                 6.0 
                 60.2 
               
               
                   
               
            
           
         
       
     
     As described above, in the example, compared with the comparative example, the consumed power is reduced by roughly 40 to 60%. 
       FIG. 7A  shows the measurement results of consumed power in the example, and  FIG. 7B  shows the measurement results of consumed power in the comparative example. All are values at the time when the cycle time is 30 s. As shown in this table, in the injection return or die-closing (included in “CLAMPING” in this diagram) or the like wherein the drive force of the electric motor is directly transmitted without using hydraulic fluid, the consumed power is effectively reduced. 
     Further, other than the consumed power, in the example, compared with the comparative example, the following effects were confirmed. 
     Arrangement space of machine: Reduced by about 30% 
     Productivity: Increased by 10 to 30% (since overlap operation is possible or the like) 
     Used hydraulic fluid: Reduced by about 80% (tank capacity becomes about ⅕) 
     Improvement of casting quality/reduction of defect rate (since stabilization of low speed injection speed or the like) 
     The present invention is not limited to the above embodiments and may be executed in various aspects. 
     The molding machine is not limited to a die casting machine. For example, the molding machine may be another metal molding machine, may be an injection molding machine which molds resin, or may be a molding machine which molds a material obtained by mixing a thermoplastic resin or the like with sawdust. Further, the molding machine is not limited to a horizontal clamping/horizontal injection type. For example, it may be a vertical clamping/vertical injection, vertical clamping/horizontal injection, or horizontal clamping/vertical injection type. The molding machine may be one without an injection frame as well. The hydraulic fluid is not limited to oil and may be for example water. 
     In the molding machine, the liquid pressure unit which combines parts of the hydraulic systems relating to the clamping device and the injection device need not be provided either. The core may be driven by an electrically operated driving device as well. 
     The die opening and closing-use driving devices has only to be electrically operated types and are not limited to ones which convert the rotation of rotary electric motors to translational motion by screw mechanisms. For example, the die opening and closing-use electric motors are not limited to rotating types and may be linear motors as well. Further, for example, the mechanisms of converting the rotation of the die opening and closing-use electric motors to translational motion are not limited to screw mechanisms and may be for example rack and pinion mechanisms as well. Further, for example, in the die opening and closing-use driving devices, the transmission routes of drive force may be provided with suitable gear mechanisms or pulleys and belts mechanisms as well. 
     The injection device has only to be hybrid type and is not limited to one which attaches/detaches an electrically operated injection-use driving device to/from a plunger (injection piston rod). For example, the injection device may be one which moves a cylinder member of an injection cylinder by an electrically operated injection-use driving device or may be one which uses an electrically operated injection-use driving device to move a press member inserted into the cylinder member of the injection cylinder from the back and presses (pressurizes) the injection piston or the hydraulic fluid behind this by the press member described before. 
     Further, in a case where the drive force of an electrically operated injection-use driving device is transmitted to the plunger (injection piston rod) outside the injection cylinder member as in the embodiments, the injection device need not be provided with detachable portion either if the relative forward movement of the movable member (for example the base  91 ) of the injection-use driving device with respect to the plunger is restricted. For example, the hooks  93  and actuators  95  in the embodiments need not be provided either. Note that, in this case, retraction of the plunger is carried out by the injection cylinder. Further, when detachable portion is provided, the detachable portion is not limited to one utilizing engagement and may be one using frictional force or one using magnetic force. 
     Further, the injection-use driving device has only to be electrically operated and is not limited to one converting the rotation of a rotary electric motor to translational motion by a screw mechanism. For example, the injection-use electric motor is not limited to a rotating type and may be a linear motor as well. Further, for example, the mechanism for converting the rotation of the injection-use electric motor to translational motion is not limited to a screw mechanism and may be for example a rack and pinion mechanism as well. Further, the transmission mechanism for transmitting the rotation of the injection-use electric motor is not limited to a pulley and belt mechanism and may be a gear mechanism or the transmission mechanism may be omitted. 
     The liquid pressure unit may be configured by including suitable portions among a plurality of elements of the hydraulic system which are necessary for the clamping device and injection device etc. For example, in the embodiments, the case where all valves relating to the clamping device and injection device were included in the liquid pressure unit was exemplified, but part of the valves may be provided separately from the liquid pressure unit as well. Further, for example, the accumulator may be provided separately from the liquid pressure unit and may be provided above the injection cylinder as well. 
     The configuration of the hydraulic system shown in the embodiments is only one example. the arrangement of the passages and valves may be suitably changed. For example, the run-around circuit connecting the injection rod side chamber and the injection head side chamber need not be provided either. Further, for example, in place of or in addition to the servo valve configuring the meter-out circuit, a servo valve configuring a meter-in circuit may be provided as well. 
     The operation shown in the embodiments may be suitably changed. For example, in the embodiments, the case where the core return and the injection return were simultaneously carried out was exemplified. However, in the same way as a general operation, the die-opening and core return, spraying, and injection return may be carried out in that order. Further, for example, the die-opening and the filling of the accumulator need not be carried out parallel. Further, for example, the injection-use driving device may be utilized also for the boosting process. The injection return may be carried out by the drive force of the injection cylinder as well. 
     Note that, from the present application, for example, the following inventions can be extracted: An invention of a molding machine having a composite type clamping device and hybrid type injection device, having a liquid pressure unit capable of supplying a hydraulic fluid to the clamping device and the injection device. An invention wherein retraction of a core by a core cylinder and retraction of a plunger by an electrically operated injection-use driving device are simultaneously carried out. An invention wherein, in each molding cycle, die-opening by an electrically operated die opening and closing-use driving device and filling of an accumulator for injection cylinder are simultaneously carried out. In these inventions, suitable changes may be made within the scope where the inventions stand. For example, the clamping device or injection device may be changed to a fully electrically operating type or full hydraulic type, or the clamping device may be changed to a toggle type. 
     A priority is claimed on Japanese application No. 2014-136608 filed on Jul. 2, 2014, the contents of which are incorporated herein by reference. 
     REFERENCE SIGNS LIST 
       1  . . . die casting machine,  3  . . . clamping device,  5  . . . injection device,  13  . . . fixed die plate,  15  . . . movable die plate,  19  . . . die opening/closing-use driving device,  21  . . . clamping cylinder,  47  . . . sleeve,  49  . . . plunger,  51  . . . injection cylinder,  53  . . . injection-use driving device,  101  . . . fixed die,  103  . . . moving die, and  105  . . . cavity.