Die casting machine and die casting method

Abstract

A die casting machine that suppresses the occurrence of surge pressure, prevents the occurrence of burrs and spouting of molten metal, and further minimizes variations in the quality of a molded product on site. The die casting machine comprises a mold ( 101 ) that cast-molds a product, an injection cylinder ( 102 ) for injecting molten metal ( 15 ) to the mold, and a hydraulic device ( 103 ) for pressing under high pressure the injection cylinder. The hydraulic device comprises a piston ACC ( 20 ) that supplies hydraulic oil to press under pressure a piston ( 13 ) of the injection cylinder ( 102 ) and an injection cylinder inlet valve ( 31 ). The piston ACC comprises a high pressure fast pressure-raising piston accumulator ( 22, 322 ) and a low-pressure injection piston accumulator ( 21, 321 ).

1 . A die casting machine, comprising:
 a mold that cast-molds a product;   an injection cylinder for injecting molten metal to the mold; and   a hydraulic device for pressing under high pressure the injection cylinder,   
     wherein 
     the hydraulic device comprises:
 a piston accumulator (ACC) that supplies hydraulic oil, which presses under pressure a piston of the injection cylinder, to the injection cylinder; and 
 an injection cylinder inlet valve for releasing/closing a flow of the hydraulic oil from the piston accumulator (ACC) to the injection cylinder, and wherein 
 the piston accumulator (ACC) comprises a high pressure fast pressure-raising piston accumulator (ACC-B) and a low-pressure injection piston accumulator (ACC-A). 
 
   
   
       2 . The die casting machine according to  claim 1 , wherein
 the piston of the injection cylinder is first pressed under pressure by a high hydraulic oil pressure supplied by the fast pressure-raising piston accumulator (ACC-B) and operates at a fast injection speed, and then is pressed under pressure by a low hydraulic oil pressure supplied by the injection piston accumulator (ACC-A) and operates when the hydraulic oil pressure supplied by the fast pressure-raising piston accumulator (ACC-B) is shut off.   
   
   
       3 . The die casting machine according to  claim 1 , wherein
 the fast pressure-raising piston accumulator (ACC-B) comprises an ACC-B piston that separates/forms a gas chamber and a hydraulic oil chamber within the fast pressure-raising piston accumulator (ACC-B) and reciprocates therein, and a projection part fixed on the ACC-B piston and extending up to a side of the hydraulic oil chamber, and penetrating and extending through an end wall on a side of the hydraulic oil chamber of the fast pressure-raising piston accumulator (ACC-B), wherein   the injection piston accumulator (ACC-A) comprises an ACC-A piston that separates/forms a gas chamber and a hydraulic oil chamber within the injection piston accumulator (ACC-A) and reciprocates therein, and wherein   the projection part is capable of penetrating through an end wall on a side of the gas chamber of the injection piston accumulator (ACC-A), invading the gas chamber of the injection piston accumulator (ACC-A), and detachably coming into contact with and pressing under pressure the ACC-A piston.   
   
   
       4 . The die casting machine according to  claim 3 , wherein
 the fast pressure-raising piston accumulator (ACC-B) and the injection piston accumulator (ACC-A) are formed integrally into one unit.   
   
   
       5 . The die casting machine according to  claim 1 , further comprising a pressure-increasing accumulator for holding under pressure molten metal in the mold at a predetermined pressure for a predetermined period of time after the injection molding of the molten metal. 
   
   
       6 . The die casting machine according to  claim 1 , wherein
 the injection cylinder inlet valve is capable of adjusting the flow rate of the hydraulic oil from the piston accumulator (ACC) to the injection cylinder.   
   
   
       7 . The die casting machine according to  claim 1 , further comprising a stroke sensor for detecting a stroke of the piston of the injection cylinder. 
   
   
       8 . The die casting machine according to  claim 7 , wherein
 the injection of the molten metal is controlled by the stroke sensor.   
   
   
       9 . The die casting machine according to  claim 1 , wherein
 the hydraulic device further comprises a pump, and wherein   the pump is capable of supplying hydraulic oil to the injection cylinder and the piston accumulator (ACC).   
   
   
       10 . The die casting machine according to  claim 1 , wherein
 pressure of the fast pressure-raising piston accumulator (ACC-B) in its initial state is set to 14 to 21 MPa and pressure of the injection piston accumulator (ACC-A) in its initial state is set to 5 to 12 MPa.   
   
   
       11 . A die casting method using a die casting machine, the machine comprising:
 a mold that cast-molds a product;   an injection cylinder for injecting molten metal to the mold; and   a hydraulic device for pressing under high pressure the injection cylinder, wherein   the hydraulic device comprises a piston accumulator (ACC) that supplies hydraulic oil, which presses under pressure a piston of the injection cylinder, to the injection cylinder and an injection cylinder inlet valve for releasing/closing a flow of the hydraulic oil from the piston accumulator (ACC) to the injection cylinder, and wherein   the piston accumulator (ACC) comprises a high pressure fast pressure-raising piston accumulator (ACC-B) and a low-pressure injection piston accumulator (ACC-A), the die casting method comprising:
 a high-pressure injection step for supplying high-pressure hydraulic oil from the fast pressure-raising piston accumulator to the injection cylinder and pressing under pressure the piston of the injection cylinder to inject molten metal; and 
 a low-pressure injection step for supplying low-pressure hydraulic oil from the injection piston accumulator to the injection cylinder when shutting off hydraulic oil from the fast pressure-raising piston accumulator to the injection cylinder, and pressing under pressure the piston of the injection cylinder to continue injection of molten metal. 
   
   
   
       12 . The die casting method according to  claim 11 , wherein
 the hydraulic device of the die casting machine further comprises a pressure-increasing accumulator for holding under pressure molten metal in the mold at a predetermined pressure for a predetermined period of time, and wherein   the method further comprises a step for further continuing to apply pressure to the molten metal using the pressure-increasing accumulator after the injection of molten metal by the fast pressure-raising piston accumulator and the injection piston accumulator is completed.   
   
   
       13 . The die casting method according to  claim 11 , wherein
 the hydraulic device of the die casting machine further comprises a pump, and wherein   the method further comprises a step, before the high-pressure injection step and the low-pressure injection step, for supplying hydraulic oil from the pump to the injection cylinder to move forward the piston of the injection cylinder.   
   
   
       14 . The die casting method according to  claim 11 , wherein
 the hydraulic device of the die casting machine further comprises a stroke sensor for detecting a stroke of the piston of the injection cylinder, and wherein   the high-pressure injection step and the low-pressure injection step are commenced, respectively, based on the stroke of the piston detected by the stroke sensor.   
   
   
       15 - 16 . (canceled) 
   
   
       17 . A die casting machine comprising:
 a mold that cast-molds a product;   an injection cylinder for injecting molten metal to the mold by moving a piston comprised by the injection cylinder, the injection cylinder comprising a head chamber that moves forward the piston toward the mold when hydraulic oil is supplied to the head chamber and a rod chamber that moves back the piston so that it moves away from the mold when hydraulic oil is supplied to the rod chamber; and   a hydraulic device for supplying hydraulic oil to the injection cylinder, wherein   the hydraulic device comprises:
 an injection piston accumulator that supplies hydraulic oil, which presses under pressure the piston of the injection cylinder, to the injection cylinder, the injection piston accumulator comprising a hydraulic oil chamber that stores hydraulic oil and a gas chamber that stores gas, the hydraulic oil chamber and the gas chamber being partitioned in a fluidically tight manner; 
 a fast speed adjusting valve for controlling/closing a flow of hydraulic oil from the injection piston accumulator to the head chamber of the injection cylinder; and 
 at least one gas bottle installed so as to communicate fluidically with the gas chamber of the injection piston accumulator via a filling force pattern adjusting valve, and wherein 
 the filling force pattern adjusting valve is capable of variably setting its valve opening degree and adjusting the filling force of hydraulic oil to the injection cylinder by adjusting the opening degree of the filling force pattern adjusting valve. 
   
   
   
       18 . The die casting machine according to  claim 17 , further comprising an automatic control device, wherein
 the automatic control device comprises an operation circuit for selecting a filling force pattern using a fast injection stroke and a fast injection speed of the injection cylinder as parameters, and wherein   the opening degree of the filling force pattern adjusting valve is adjusted so as to match with a filling force pattern selected by the operation circuit.   
   
   
       19 . The die casting machine according to  claim 17 , wherein the hydraulic device further comprises:
 a pressure-increasing accumulator that communicates fluidically with the head chamber of the injection cylinder and increases pressure of molten metal in the mold for holding the molten metal at a predetermined pressure for a predetermined period of time after an injection filling of molten metal;   a pressure-increasing opening/closing valve installed between the pressure-increasing accumulator and the injection cylinder and releasing/shutting off a flow of hydraulic oil from the pressure-increasing accumulator to the injection cylinder; and   a pressure-increasing time adjusting valve installed in series to the pressure-increasing opening/closing valve between the pressure-increasing accumulator and the injection cylinder and adjusting pressure-increasing time of injected molten metal by changing its opening degree.   
   
   
       20 . The die casting machine according to  claim 17 , wherein the hydraulic device further comprises:
 a hydraulic pump that communicate fluidically with the head chamber and the rod chamber of the injection cylinder; and   an injection switching valve installed between the hydraulic pump and the injection cylinder and switching between guiding a flow of hydraulic oil from the hydraulic pump to the head chamber of the injection cylinder and guiding it to the rod chamber.   
   
   
       21 - 22 . (canceled) 
   
   
       23 . A die casting method using the die casting machine according to  claim 17 , the die casting method comprising:
 a low-speed injection step for pressing under pressure molten metal in the injection cylinder at a low speed; and   a fast injection step for pressing under pressure and injecting the molten metal in the injection cylinder at a high speed into the mold, wherein   the fast injection step comprises an opening setting procedure for setting the opening degree of the filling force pattern adjusting valve in accordance with a fast injection speed and an injection filling force.   
   
   
       24 . The die casting method according to  claim 23 , wherein
 the die casting machine further comprises an automatic control device comprising an operation circuit for determining an opening degree of the filling force pattern adjusting valve using a fast injection stroke, a fast injection speed, and a final filling force of the injection cylinder as parameters; and wherein   the opening setting procedure comprises a stage for determining an opening degree of the filling force pattern adjusting valve by the operation circuit.   
   
   
       25 . The die casting method according to  claim 23 , wherein the hydraulic device further comprises:
 a pressure-increasing accumulator that communicates fluidically with the head chamber of the injection cylinder and increases a pressure of molten metal in the mold for holding the molten metal at a predetermined pressure for a predetermined period of time after an injection filling of molten metal;   a pressure-increasing opening/closing valve installed between the pressure-increasing accumulator and the injection cylinder and releasing/shutting off a flow of hydraulic oil from the pressure-increasing accumulator to the injection cylinder;   a pressure-increasing time adjusting valve installed in series to the pressure-increasing opening/closing valve between the pressure-increasing accumulator and the injection cylinder and adjusting a pressure-increasing time of injected molten metal by changing its opening degree;   a hydraulic pump that communicate fluidically with the head chamber and the rod chamber of the injection cylinder; and   the injection switching valve installed between the hydraulic pump and the injection cylinder and switching between guiding a flow of hydraulic oil from the hydraulic pump to the head chamber of the injection cylinder and guiding it to the rod chamber, wherein   in the low-speed injection step, the hydraulic oil is supplied by the hydraulic pump to the head chamber of the injection cylinder to move forward the piston of the injection cylinder toward the mold, wherein   the fast injection step further comprises a procedure for controlling an opening degree of the fast speed adjusting valve, wherein   after the fast injection step, a pressure-increasing step is performed, and wherein   the pressure-increasing step comprises:
 a procedure for closing the fast speed adjusting valve; 
 a procedure for opening the pressure-increasing opening/closing valve; and 
 a procedure for holding an open state of the pressure-increasing opening/closing valve until a predetermined pressure is reached.