JP2794016B2 - Secondary pressure casting method of die casting - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold casting method in which a molten metal is pressurized and filled into a mold cavity using an accumulator, and the molten metal is poured into the mold cavity. After the operating pressure of the accumulator has been reduced during the pressurized filling of the mold, a secondary pressing force is applied to the molten metal in the cavity based on the detection signal of the operating pressure in the return process. The present invention relates to a pressure casting method. 2. Description of the Related Art For example, in a secondary pressure casting method in which a secondary pressure is applied to a molten metal pressurized and filled in a cavity of a mold, the hydraulic pressure control method is employed. The pressure die casting method, in which molten metal is cast into a mold cavity at high pressure, is widely adopted and implemented as the most suitable method for mass production in aluminum alloy casting technology.This die casting method is used for thick parts of products. There is a tendency that cast cavities are easily formed, the crystal structure is coarsened, and the strength of the thick portion is reduced. In order to solve this problem, a secondary pressure casting method in which an additional pressing force (secondary pressing pressure) is applied to a molten metal pressurized and filled in a cavity of a mold to reach a pseudo-solid state. (Eg, JP-B-48-7570, JP-B-49-36093). In the die casting method, the molten metal in the pressurized injection sleeve is injected into the mold cavity in an injection shape through an extremely narrow injection passage and pseudo-solidified. It has the characteristic of being short. Therefore, there is little time margin for performing the secondary pressurization, and it is difficult to grasp the pressurization start timing. If this timing is incorrect, not only the pressurizing effect cannot be obtained, but also if the secondary pressurization is performed after the start of the indulgence, cracks may occur in the pressurized portion. Conventionally, various techniques have been proposed for detecting the position of an injection ram that pressurizes a molten metal in an injection sleeve with a position sensor or the like, and setting a secondary pressurization timing using a detection signal as a trigger signal. However, in this method, the detection accuracy fluctuates greatly due to the performance of the position detection sensor, a change in the speed of the injection ram, a change in the amount of molten metal, and the like, and the secondary pressurization cannot be performed with high reliability. The injection cylinder and the pressure-intensifying cylinder are used together to increase the pressure of the molten metal injected into the cavity and then pressurize the molten metal secondarily to detect the pressure in the injection cylinder. There is also known a method of setting the secondary pressurization timing by using the trigger signal as a trigger signal. However, in this method, since the pressure in the injection cylinder that rises rapidly after the filling of the molten metal is detected, the detection timing is unstable, and the time of starting the secondary pressurization cannot be accurately detected. Means for Solving the Problems and Effects The present invention relates to an improvement in a secondary pressure casting method for mold casting that overcomes such difficulties, and adds molten metal into a mold cavity using an accumulator. In the mold casting method for pressure filling, the working pressure of the accumulator is introduced into an injection hydraulic cylinder for pressurizing and filling the melt into the cavity of the mold, and the filling of the melt into the cavity is started. Then, after the operating pressure of the accumulator has once decreased, any operating pressure in the process of returning to the initial set pressure is detected, and based on the detection signal, the operating pressure is added to the molten metal in the mold cavity. It is characterized by applying a next pressing force. In the present invention, as described above, when the molten metal is pressurized and filled into the cavity of the mold by the injection hydraulic cylinder driven by the operating pressure of the accumulator, the operating pressure of the accumulator temporarily decreases. After that, any operating pressure in the process of returning to the initial set pressure is detected again, and based on the detection signal, a secondary pressure is applied to the molten metal in the cavity of the mold. The secondary pressurization can be performed with high timing accuracy and high reliability without being affected by the performance of the position detection sensor of the hydraulic cylinder or the detection accuracy due to a change in the amount of molten metal. Embodiment An embodiment of the present invention shown in FIGS. 1 to 5 will be described below. FIG. 1 shows a structure that embodies a hydraulic control method of the die casting apparatus 10 that controls the die casting apparatus 10 as an apparatus using an accumulator 90 in a hydraulic circuit. The die-casting apparatus 10 is provided with a first hydraulic circuit provided with an accumulator 90. The first hydraulic circuit includes an oil supply path 92, a sequence valve 94, and a hydraulic pump 96 outside the accumulator 90. Pressure oil is supplied to the opening 64 of the valve chamber 62 in the hydraulic cylinder for injection 52 described later. Further, the accumulator 90 of the first hydraulic circuit is started, and after the operating pressure once decreases, an arbitrary operating pressure in the process of returning to the initial set pressure is detected, and the accumulator 90 is started based on the detection signal. The second hydraulic circuit is shown as hydraulic control system 100. Further, on the base 12 of the die casting apparatus 10, fixed platens 14, 16 mutually connected by a plurality of connecting rods 18 and opposed to each other at an interval are immovably provided upright. The connecting rod 1 is located between the fixed platens 14 and 16.
A movable platen 20 guided by 8 and slidably displaced on the base 12 is provided. The fixed mold 22 is fixed to the fixed platen 16, and the movable mold 24 is fixed to the movable platen 20 via the holder 26. It faces the cavity A through the movable mold 24,
The extrusion pin 32 used to separate the product after completion of casting from the movable mold 24 is movable relative to the movable mold 24 so as to be slidable relative to each other.
Is fixed to an extruding plate 28 supported by a holding rod 30 penetrating the hydraulic cylinder for extruding.
A push rod connected to the piston 34 moves the movable mold 24 relative to the movable mold 24 in the product separating direction. Further, a movable platen driving hydraulic cylinder 38 is fixed to the fixed platen 14, and the movable platen 20 is moved by a push rod 40 integrated with the piston. Further, the injection pressing cylinder 52 is fixed to the fixed platen 16 with a support rod 88, and an injection ram 86 connected to the injection piston 58 penetrates the fixed platen 16 and the fixed mold 22
The injection ram 86 moves in the forward direction by the operation of the injection piston 58 after the molten metal is supplied into the injection sleep 42 through the pouring port 44 and is slidably displaceably fitted to the injection sleep 42 communicating with the runner. Then, the molten metal in the injection sleep 42 is pushed into the cavity A through the hot water passage. On the other hand, a hydraulic cylinder 48 for secondary pressurization is supported on the movable mold 24 via a holding rod 46.
A pressure rod 50 connected to the piston of FIG. 1 is configured to penetrate the extruding plate 28 and the movable mold 24 so as to be slidable and enter the cavity A. The injection hydraulic cylinder 52 has a small-diameter chamber 54 into which an injection piston 58 is inserted and a large-diameter chamber 56 into which a pressure-increasing piston 60 is inserted. The pressure-intensifying piston 60 integrally has a rod 66 that fits into the small-diameter chamber 54, a valve chamber 62 that stores a check valve 70, and an oil passage that communicates with the valve chamber 62 and penetrates the rod 66.
68 are formed (FIG. 2). The check valve 70 is an umbrella-shaped piece comprising a head portion 72 having a conical surface and a shaft portion 74 (third part).
(See FIG. 2) The coil spring 78 is also urged to the side opposite to the injection piston 58 (to the right in FIG. 2) by the coil spring 78 stored in the valve chamber 62. The opening 64 of the valve chamber 62 is
When the head 72 of the check valve 70 is pressed against the peripheral portion of the check valve 70, the check valve 70 is closed. The shaft portion 74 of the check valve 70 is formed with an oil portion 76 that passes from the outer peripheral surface near the head portion 72 to the distal end portion.
Thus, a flow of the pressure oil in the order of opening 64 → oil passage 76 → oil passage 68 can be obtained. Inner chamber of injection hydraulic cylinder 52 (small diameter chamber 54, large diameter chamber 5
6), a part of the chamber B facing the opening 64 of the valve chamber 62, a part of the C chamber around the base of the rod 66 and defined by the pressure-intensifying piston 60 and the cylinder wall, and the rod 66 and the injection piston 58. It is convenient for the following explanation to grasp the room D that occurs when the user leaves the room. A relief valve 84 is provided on the wall of the injection hydraulic cylinder 52 so as to communicate with the chamber C, and the relief valve 84 is opened by a detection signal of a pressure sensor 82 that detects the pressure in the defined chamber D. It has become. Further, a position sensor 80 for detecting a displacement amount of a rod 59 integrated with the injection piston 58 is provided at a predetermined position, and a sequence valve 94 opened by the position signal provides a refueling for communicating the accumulator 90 with the B chamber. A hydraulic pump 96 is connected to the oil supply passage 92 between the sequence valve 94 and the B chamber. The hydraulic control system 100 of the secondary pressurizing hydraulic cylinder 48 extracts the operating pressure of the injection hydraulic cylinder 52 through the oil passage 98, and operates using this as a guide. That is, when the operating pressure of the injection hydraulic cylinder 52 is guided to the sequence valve 104, the sequence valve 104 capable of adjusting the starting pressure by using the urging spring force operates, and the hydraulic pump 1
The pressure oil discharged from 02 is guided to the secondary pressurizing hydraulic cylinder 48 through the oil passage 106, the switching valve 108, the flow control valve 110, and the pressurizing rod advancement oil passage 112, and the pressurizing rod 50 operates to The main part of the hydraulic control system 100 is configured to enter the tee A. The switching valve 108 is switched from the illustrated state at the same time when the pressure oil is supplied to the chamber B of the hydraulic cylinder 52 for injection through the oil supply passage 92. In such a configuration, after the molten metal (eg, aluminum alloy) is injected into the injection sleep 42 through the pouring port 44, the injection ram 86 is operated by the operation of the injection hydraulic cylinder 52.
Is advanced, the molten metal in the injection sleep 42 is pressurized and filled into the cavity A, and after the filling of the molten metal in the cavity A is completed, the pressurizing rod 50 is moved into the cavity A at a predetermined timing. And a secondary pressurizing pressure is applied to the molten metal. The operation of the injection hydraulic cylinder 52 and the flow control valve 110 will be described below with reference to FIG. Before the start of injection: The state of the hydraulic cylinder for injection 52 before the start of injection is shown in FIG. The hydraulic pump 96 has not been operated yet, and the sequence valve 94 has been closed. Then, the injection piston 58 and the booster piston 60 are at the rearmost positions, and the check valve 70 in the booster piston 60 is a coil spring.
Energized at 78, the opening 64 of the valve chamber 62 is closed. Injection start (low-speed injection): The hydraulic pump 96 is started while the sequence valve 94 is closed. The discharge oil of the hydraulic pump 96 is sent to the chamber B via the oil supply passage 92, and the oil pressure in the chamber B rises, and the check valve 70 is moved against the bias of the coil spring 78,
The path from the chamber B to the oil passage 76 formed in the shaft portion 74 of the check valve 70 → the oil passage 68 formed in the rod 66 of the pressure-intensifying piston 60 becomes conductive, and the path between the injection piston 58 and the rod 66 becomes conductive. Pressurized oil (pressure
P ₁ ) is supplied. The hydraulic pressure (P ₁ ) acting on the top of the head causes the injection piston 58 to advance at a low speed (low speed as compared with the high speed advance in the next stage: see curve I in FIG. 6). A chamber is formed (FIG. 4). High-speed injection: When the injection piston 58 advances by a predetermined length (hence, when the injection ram 86 advances by a predetermined length), the position sensor 80 is brought into contact with the injection piston 58 and the rod 59 which is integral.
Works, the sequence valve 94 is opened by the detection signal, and the operating pressure of the accumulator 90 (P _A1 ; P _A1 > P ₁ )
Is introduced into the room B (time T ₁ ). The pressure in the chamber B rises, the check valve 70 moves, the opening 64 of the valve chamber 62 is opened, and the pressure oil is sent to the chamber D via the path of the chamber B → the oil passage 76 → the oil passage 68, and the injection piston 58 Moves forward at high speed. In the meantime, the accumulator 90 operating pressure decreases as shown by the curve II and decreases to the pressure (P _A2 ) (time point ₃ ), and then the initial set pressure (P _A1 )
To rise. On the other hand, the pressure (P _D ) in the D chamber immediately before the time point (T ₃ ) (time point T ₂ ) is detected by the pressure sensor 82 as the set pressure, and the relief valve 84 is opened by the detection signal. The pressure oil in the C chamber is discharged outside through the opened relief valve 84, and the pressure-intensifying piston 60 starts to move forward. As a result, the pressure in the chamber D becomes larger than the pressure in the chamber B (equal to the operating pressure of the accumulator 90), and the check valve 70 is pressed against the opening 64 of the valve chamber 62 to close the opening 64,
When the communication between the chambers B and D is cut off,
Moves forward (FIG. 5), and the pressure in the chamber D rises rapidly. As described above, the return after the operating pressure of the accumulator 90 has decreased from P _A1 to P _A2 , but the return start time (T ₃ )
Thereafter, the secondary pressurization may be started immediately. The time of the second pressurization can be known by detecting the arbitrary pressure (P _AX ) (preselected pressure) in the chamber B in the process of returning the operating pressure of the accumulator 90 from P _A2 to P _A1. it can. The pressure in the B chamber (operating pressure of the accumulator 90) is an oil passage
Sequence valve 104 in hydraulic control system 100 by 98
And the pressure in the room B is P _AX (where P _A2 ≤ P _AX
When <P _A1 ) is reached, the sequence valve 104 is opened. As a result, when the switching valve 108 is displaced from the state shown in FIG.
8. The discharge oil of the hydraulic pump 102 is sent to the high-pressure chamber of the secondary pressurizing hydraulic cylinder 48 through the flow control valve 110 and the pressurizing rod advancement oil passage 112, and the pressurizing rod 50 moves forward to fill the cavity A. The secondary pressurizing pressure is applied to the molten metal that has been pressed into the molten metal and has not been completely solidified. The secondary pressurizing pressure is applied until the molten metal in the cavity A is in doubt, and then the switching valve 108 is switched to allow the secondary pressurizing oil passage cylinder 4 to pass through the pressurizing rod retreating oil passage 114.
Pressure oil is supplied to 8, and the pressure rod 50 is retracted. The features of this embodiment are listed below. The operating pressure of the accumulator 90 for advancing the injection piston 58 at a high speed is reduced at the same time when the sequence valve 94 is opened, and the phenomenon that the return is started when the filling of the molten metal is completed (T ₃ ) is used. By capturing the operating pressure (P _A ) of the accumulator 90 from the time when the operating pressure of the accumulator 90 starts to return to the completion of the recovery, the sequence valve 104 is opened at a highly accurate timing with little fluctuation, and the secondary pressurization is performed. Can be started. It should be noted here that the operating pressure of the accumulator 90 is still introduced into the chamber B even after the completion of the filling of the molten metal (T ₃ ). Since the operating pressure of the accumulator 90 returns relatively slowly, there is little variation in the starting point of the sequence valve 104 set to start at the pressure (P _AX ). Can perform secondary pressurization. Since the activation of the sequence valve 104 is performed by directly guiding the oil pressure in the chamber B, the pressure in the chamber B is detected by a pressure detector, and based on the detection signal, the solenoid valve is activated and the hydraulic pressure for secondary pressurization is increased. The time delay is less than when the cylinder is operated, and the secondary pressurization timing can be set correctly. By adjusting the valve opening of the pressure oil supply valve with respect to the accumulator 90 in advance, it is possible to adjust and change the return speed of the operating pressure of the accumulator 90 after the pressure oil has once decreased. The time at which the operating pressure (P _A ) is detected can be easily changed by adjusting the valve, and the secondary pressurization timing can be easily adjusted. In the present embodiment, the accumulator 90 in the return process
The operating pressure (P _A ) was detected and the sequence valve 104 was started using this as a trigger signal.
₃ ) The sequence valve 104 may be opened after a predetermined time by a delay timer or the like based on the (lower limit operating pressure (P _A2 )).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway schematic view showing an example of a suitable secondary pressure casting apparatus for carrying out a method of controlling the hydraulic pressure of equipment according to the present invention, and FIG. FIG. 3 is a perspective view of the check valve shown in FIG. 2, FIG.
FIG. 5 is a view similar to FIG. 2 showing an operation mode of the secondary pressure casting apparatus, and FIG. 6 is a hydraulic pressure change in an injection hydraulic cylinder and an accumulator in the secondary pressure casting apparatus. 6 is a graph showing a change in the operating pressure of FIG. 10 ... die-casting device, 12 ... base, 14 ... fixed platen, 16 ... fixed platen, 18 ... connecting rod, 20 ... movable platen, 22 ... fixed mold, 24 ... movable mold, 26 ... Holder, 28 ... Extruded plate, 30 ... Holder rod, 32 ... Pusher pin, 34 ... Hydraulic cylinder for extrusion, 36 ... Push rod, 38
…… Hydraulic cylinder for driving the movable platen, 40 …… Push rod, 42 …… Injection sleep, 44 …… Pouring port, 46 …… Holding rod, 48 …… Hydraulic cylinder for secondary pressurization, 50 …… Pressure rod,
52 …… Injection hydraulic cylinder, 54 …… Small diameter chamber, 56 …… Large diameter chamber, 58 …… Injection piston, 59 …… Rod, 60 …… Pressure increasing piston, 62 …… Valve chamber, 64 …… Opening, 66 …… Rod, 68
... oil passage, 70 ... check valve, 72 ... head, 74 ... shaft, 76
... oil passage, 78 ... coil spring, 80 ... position sensor, 82 ...
... pressure sensor, 84 ... relief valve, 86 ... injection ram, 88 ...
… Supporting rod, 90 …… Accumulator, 92 …… Refueling channel, 94
…… Sequence valve, 96… Hydraulic pump, 98 …… Hydraulic passage, 100 …… Hydraulic control system, 102 …… Hydraulic pump, 104 ……
Sequence valve, 106: Oil passage, 108: Switching valve, 110
…… Flow control valve, 112… Pressure rod forward oil passage, 114… Pressure rod retreat oil passage.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B22D 17/22 B29C 45/26 B29C 45/77

Claims (1)

(57) [Claims] In a mold casting method of pressurizing and filling molten metal into a mold cavity using an accumulator, the operating pressure of the accumulator is applied to an injection hydraulic cylinder that pressurizes and fills molten metal into the cavity of the mold. Introduce and start filling the cavity with molten metal.After the operating pressure of the accumulator has once decreased, detect any operating pressure in the process of returning to the initial set pressure. A secondary pressure casting method for die casting, wherein a secondary pressure is applied to the molten metal in the cavity of the die. 2. The operating pressure of the accumulator is guided to a sequence valve that operates at an arbitrary operating pressure in the return process, and based on the operation of the sequence valve, the operating pressure of a hydraulic pressure source is introduced into a secondary pressurizing hydraulic cylinder. 2. The method according to claim 1, wherein a secondary pressure is applied to the molten metal in the cavity of the mold.