Injection device for die casting machine

Abstract

In a hybrid injection system of a die casting machine, the occurrence of a large electric power loss can be prevented by avoiding a large current at a pressure-holding step and the size of a motor is reduced. In an injection system comprising an injection cylinder ( 16 ) housing an injection piston ( 15 ) for injecting molten metal to a mold and an electric booster ( 8 ) of hydraulic cylinder type, a head chamber ( 8 H) to the electric booster communicates fluidly with a head chamber ( 16 H) of the injection cylinder, causing a booster piston rod ( 5 ) to be housed in the electric booster ( 8 ) to move linearly and thus pressing under pressure to move the injection piston to perform injection molding. Because a stop valve ( 25 ) is provided in a pipe that causes the head chamber ( 16 H) of the injection cylinder to communicate with a rod chamber ( 8 R) of the booster ( 8 ), it is possible for the pressure of the hydraulic oil to act on a head area of the electric booster at a pressure-increasing step for increasing pressure of the molten metal, and for pressure of the hydraulic oil to act on a rod area of the electric booster at a pressure-holding step for holding pressure of the molten metal.

1 . An injection system of a die casting machine, comprising:
 an injection cylinder housing an injection piston for injecting molten metal, such as aluminum, into a mold of the die casting machine; and   an electric booster of hydraulic cylinder type housing a booster piston rod for performing injection molding by supplying pressurized hydraulic oil to a head chamber of the injection cylinder and pressing under pressure to move the injection piston, wherein   a head chamber of the electric booster communicates fluidly with the head chamber of the injection cylinder; and   the electric booster has a structure in which pressure of the hydraulic oil acts on a head area of the electric booster at a pressure-increasing step for increasing pressure of the molten metal and pressure of the hydraulic oil acts on a rod area of the electric booster at a pressure-holding step for holding pressure of the molten metal in an injection molding process.   
   
   
       2 . The injection system according to  claim 1 , wherein
 communicating pipes for causing the head chamber of the injection cylinder to communicate fluidly with a rod chamber of the booster are provided and the communicating pipe is provided with a stop valve to cause hydraulic oil to flow intermittently.   
   
   
       3 . The injection system according to  claim 1 ,
 wherein the booster piston rod is driven to reciprocate by an electric motor.   
   
   
       4 . The injection system according to  claim 3 , wherein
 the electric motor is a servo motor.   
   
   
       5 . The injection system according to  claim 1 , further comprising an injection piston accumulator for supplying hydraulic oil to the head chamber of the injection cylinder. 
   
   
       6 . The injection system according to  claim 1 , wherein
 the rod chamber of the booster communicates fluidly with a tank and the communicating pipe that causes the rod chamber of the booster to communicate fluidly with the tank is provided with a stop valve.   
   
   
       7 . The injection system according to  claim 1 , wherein
 a rod chamber of the injection cylinder communicates fluidly with the tank and a hydraulic oil supply inlet from a pump etc.   
   
   
       8 . The injection system according to  claim 1 , wherein
 the booster further comprises a pressure detection sensor for detecting a head pressure, which is pressure in the head chamber of the injection cylinder.   
   
   
       9 . An injection system of a die casting machine, comprising:
 an injection cylinder housing an injection piston for injecting molten metal, such as aluminum, into a mold of the die casting machine;   an electric booster of a hydraulic cylinder type housing a booster piston rod for performing injection molding by supplying hydraulic oil to a head chamber of the injection cylinder and pressing under pressure to move the injection piston;   a piston accumulator formed so as to be capable of storing a predetermined amount of hydraulic oil at a predetermined maximum pressure and also capable of supplying hydraulic oil to the head chamber of the injection cylinder and pressing under pressure to move the injection piston, the piston accumulator performing injection molding in cooperation with the electric booster; and   a first switching valve provided on an exit side of the piston accumulator and capable of opening/closing a flow passage of hydraulic oil from an exit of the piston accumulator, wherein   the elimination of a logic valve is enabled, which would be provided originally at the exit of the piston accumulator in order to prevent leak of hydraulic oil through the first switching valve, by supplying hydraulic oil to the piston accumulator immediately before commencement of injection.   
   
   
       10 . The injection system according to  claim 9 , wherein
 a head chamber of the electric booster communicates fluidly with the head chamber of the injection cylinder and also communicates fluidly with the exit of the piston accumulator;   a flow passage that causes the head chamber of the electric booster to communicate fluidly with the head chamber of the injection cylinder is provided with a second switching valve; and   the second switching valve connects fluidly, on one side of flow passage connections, to a flow passage that communicates with the head chamber of the electric booster and to a flow passage that communicates with the tank in which hydraulic oil is stored, and on the other side of the flow passage connections, connecting fluidly to a flow passage that communicates with the head chamber of the injection cylinder and to a flow passage that communicates with the piston accumulator.   
   
   
       11 . The injection system according to  claim 9 , wherein
 supply of hydraulic oil to the piston accumulator is performed by the electric booster and hydraulic oil in the head chamber of the electric booster is pressed under pressure and supplied.   
   
   
       12 . The injection system according to  claim 9 , wherein
 the booster is driven to supply hydraulic oil to the rod chamber of the injection cylinder in order to return the injection piston to an end part on a head side of the injection cylinder after an injection operation is completed.   
   
   
       13 . The injection system according to  claim 10 , further comprising a third switching valve provided in a flow passage that causes the rod chamber of the electric booster to communicate fluidly with the head chamber of the injection cylinder, wherein
 the first switching valve connects fluidly, on one side of flow passage connections, to a flow passage that communicates with the piston accumulator and to a flow passage that communicates with the tank in which hydraulic oil is stored, and on the other side of the flow passage connections, connecting fluidly to a flow passage that communicates with the head chamber of the injection cylinder and to a flow passage that communicates with the rod chamber of the injection cylinder; and   a third switching valve connects fluidly, on one side of flow passage connections, to a flow passage that communicates with the tank and to a flow passage that communicates with the rod chamber of the electric booster, and on the other side of the flow passage connections, connecting fluidly to a flow passage that communicates with the rod chamber of the injection cylinder and to a flow passage that communicates with the head chamber of the injection cylinder.   
   
   
       14 . The injection system according to  claim 9 , wherein
 a molten metal supply process is performed immediately before commencement of injection and supply of hydraulic oil to the piston accumulator is completed during the molten metal supply process.   
   
   
       15 . The injection system according to  claim 9 , wherein
 the booster piston rod is driven to reciprocate by the electric motor.   
   
   
       16 . The injection system according to  claim 15 , wherein
 the electric motor is a servo motor.   
   
   
       17 . A hybrid high-speed injection system excellent in controllability, which is an injection system that drives a plunger to fill a mold cavity with molten metal, in which a piston rod controlled by a back-and-forth movement control mechanism is provided behind a hydraulic cylinder that incorporates a plunger rod controlled by a hydraulic control mechanism. 
   
   
       18 . The hybrid high-speed injection system excellent in controllability according to  claim 17 , wherein
 the back-and-forth movement control mechanism is a ball screw mechanism.   
   
   
       19 . The hybrid high-speed injection system excellent in controllability according to  claim 18 , wherein
 the ball screw mechanism is driven by a servo motor.   
   
   
       20 . A hybrid high-speed injection control method for controlling filling of a mold cavity with molten metal by providing a piston rod controlled by a back-and-forth movement control mechanism behind a hydraulic cylinder that incorporates a plunger rod controlled by a hydraulic control mechanism and driving the hydraulic control mechanism and the back-and-forth movement control mechanism in conjunction with each other, the method comprising steps of:
 (i) driving the back-and-forth movement control mechanism to move forward the plunger rod integrated with the piston rod until a low-speed/high-speed switching position is reached, and after its arrival,   (ii) driving the hydraulic control mechanism to move forward the plunger rod at a high speed in cooperation with the back-and-forth movement control mechanism.   
   
   
       21 . The hybrid high-speed injection control method according to  claim 20 , wherein
 drive of the hydraulic control mechanism is feedback-controlled in real time according to an increasing curve up to a preset injection pressure.