JP2706671B2 - Secondary pressure casting equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary pressure casting apparatus of a type in which a secondary pressure is applied to a molten metal that has been pressure-filled into a mold cavity. . [Prior Art] A pressure die casting method in which a molten metal is cast into a cavity of a mold at a high pressure has been widely adopted and implemented as a method most suitable for mass production in an aluminum alloy casting technique. In this die-casting method, porosity tends to occur in the thick part of the product,
There is a tendency that the crystal structure is coarsened and the strength of the outer thick portion is reduced. In order to solve this problem, a secondary pressure casting method has been proposed in which an additional pressing force (secondary pressing pressure) is applied to the molten metal pressurized and filled in the mold cavity to reach solidification. (Eg, JP-B-48-7570, JP-B-49-36093). [Problem to be Solved] In the die casting method, the molten metal in the pressurized injection sleeve is injected and solidified into the mold cavity through an extremely narrow injection passage, so that the time until solidification is very short. There is a feature. 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 is the pressurizing effect not obtained, but also if the secondary pressurization is performed after the start of solidification, 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 accuracy of the position detection sensor, a change in the speed of the injection ram, a change in the detection accuracy due to a change in the amount of molten metal, and the like are large, and the secondary pressurization cannot be performed with high reliability. [Means for Solving the Problems and Effects] The present invention relates to an improvement of a secondary pressure casting apparatus which overcomes the above-mentioned difficulties, and pressurizes a molten metal in an injection sleeve into a cavity of a mold by an injection ram. Then, after the filling of the molten metal is completed, in a mold casting apparatus in which a pressure rod is pressed into the molten metal to apply a secondary pressing force to the molten metal, an injection hydraulic cylinder for driving the injection ram is driven by an accumulator for a low speed operation in a parallel relationship. Pressurizing rod driving means for receiving the supply of pressure oil only through the valve and the high-speed valve and applying a secondary pressure to the molten metal in the cavity of the mold detects pressure oil pressure in the accumulator or detects the pressure oil pressure in the accumulator. Controlled by secondary pressure control means operating by detecting a change in hydraulic oil pressure, the low-speed valve is opened at the beginning of hydraulic oil supply from the accumulator to the hydraulic cylinder for injection, The speed control valve is closed at the beginning of the pressurized oil supply, but is opened at the middle stage of the pressurized oil supply from the accumulator to the pressurized oil cylinder for injection, and the secondary pressurizing force control means controls the injection pressure from the accumulator from the accumulator. After the hydraulic oil pressure in the accumulator decreases due to the hydraulic oil discharge to the hydraulic cylinder, any hydraulic pressure or a change in the hydraulic pressure in the process of returning to the initial set pressure is detected. Is what you do. Since the present invention is configured as described above, when the molten metal in the injection sleeve is pressurized and filled into the cavity of the mold by the injection ram, the low-speed valve is initially opened, The pressure oil in the accumulator is gradually introduced by introducing the pressure oil in the accumulator into the injection hydraulic cylinder, the injection ram is advanced at a low speed, and then the closed high-speed valve is opened. Supplying rapidly to the injection hydraulic cylinder, advancing the injection ram at a high speed, and applying a secondary pressurizing pressure to the molten metal by advancing a pressure rod into the cavity of the mold after the filling of the molten metal is completed. Accordingly, it is possible to prevent the occurrence of a cavity in a cast product, and to improve strength and quality. Further, in the present invention, the pressure oil pressure in the accumulator connected to the injection hydraulic cylinder releases initial pressure oil energy in the accumulator so as to advance the injection ram at a high speed, causing a pressure drop. From
After the filling of the molten metal is completed and the advance of the injection ram is stopped, the pressure oil pressure in the accumulator returns to the initial set pressure, but the pressure oil pressure in the accumulator is equal to the pressure oil pressure pressing the injection piston. It is a gradual pressure change that does not change sharply compared to the pressure change.Using this phenomenon, a change in the hydraulic pressure of the accumulator is detected, and when the hydraulic pressure reaches a predetermined set value. Or when the change value of the hydraulic pressure reaches a predetermined set value, the secondary pressurizing rod is operated to apply a secondary pressurizing pressure to the molten metal in the cavity of the mold. Therefore, secondary pressurization can be properly performed, and a high-quality cast product can be obtained. Further, in the present invention, since the pressurized oil is supplied to the injection hydraulic cylinder only with the pressurized oil discharged from the accumulator, the pressurized oil supply characteristics of the pressurized oil source can be stabilized and easily adapted to required characteristics, The advancement characteristics of the injection ram can be easily and appropriately matched with the characteristics of filling the molten metal into the cavity of the mold, and high-quality mold casting can be efficiently and appropriately performed, and the number of parts can be increased. Can be eliminated to reduce the size of the apparatus and reduce costs. EXAMPLES Hereinafter, specific examples in which the present invention is applied to a secondary pressure casting method will be described. FIG. 1 shows a die casting apparatus 10 capable of applying a secondary pressurizing pressure, together with a secondary pressurizing hydraulic control system 106 thereof. 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 intervals are fixedly provided. Further, a movable platen 20 which is guided between the fixed platens 14 and 16 and guided by the connecting rod 18 and slidably displaces 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. In view of the cavity A passing through the movable mold 24, a pair of extrusion pins 32 used to release the product after completion of casting from the movable mold 24 penetrate the movable mold 24 so as to be slidable and relatively displaceable. The extruding plate 28 is fixed to an extruding plate 28 having a pair of return pins 30. The extruding plate 28 has an end of a piston rod 35 fixed to the movable platen 20 and an extruding hydraulic pressure that moves relatively to the movable platen 20. cylinder
A push rod 36 connected to the substrate 34 moves the movable mold 24 in the product detaching direction relative to the movable mold 24. Also, a movable platen driving hydraulic cylinder 38 is fixed to the fixed platen 14, one end of which is fixed to the piston,
The movable platen 20 is moved by a push rod 40 having the other end fixed to the cross member 41. Further, the injection hydraulic cylinder 52 is fixed to the fixed platen 16 with a support rod 90, and an injection ram 88 connected to the injection piston 58 passes through the fixed platen 16 and a fixed mold 22.
After the molten metal is supplied into the injection sleeve 42 through the lubrication port 44, the injection ram 88 is moved in the forward direction by the operation of the injection piston 58. When moved, the molten metal in the injection sleeve 42 is pushed into the cavity A through the hot water passage. On the other hand, the movable mold 24 supports a secondary pressurizing hydraulic cylinder 48 via a pair of holding rods 46, and a pressurizing rod 50 connected to the piston of the secondary pressurizing hydraulic cylinder 48 has an extruding plate 28 and The movable mold 24 is configured to penetrate the movable mold 24 so that the movable mold 24 can slide freely and enter the cavity A. The hydraulic cylinder for injection 52 has a small-diameter chamber 54 in which an injection piston 58 is fitted, and a large-diameter chamber 56 in which a pressure-increasing piston 62 is fitted. The pressure-intensifying piston 62 integrally has a rod 68 that fits into the small-diameter chamber 54, a valve chamber 64 that stores a check valve 72, and an oil passage that communicates with the valve chamber 64 and penetrates the rod 68.
70 are formed (FIG. 2). The check valve 72 is an umbrella-shaped piece comprising a head portion 74 having a conical surface and a shaft portion 76 (third portion).
(See FIG. 2) The coil spring 80, which is also stored in the valve chamber 64, urges the injection piston 58 to the opposite side (the right side in FIG. 2). The opening 66 of the valve chamber 64 is closed when the head 74 of the check valve 72 is pressed against the periphery of the opening 66. An oil passage 78 is formed in the shaft portion 76 of the check valve 72 so as to pass from the outer peripheral surface near the head portion 74 to the distal end, and the opening 66 of the valve chamber 64 → the oil passage
A flow of pressure oil 78 → oil path 70 is obtained. Inner chamber of injection hydraulic cylinder 52 (small diameter chamber 54, large diameter chamber 5
A part of 6) is composed of a chamber B facing the opening 66 of the valve chamber 64, a chamber C around the base of the rod 68 and defined by the pressure-intensifying piston 62 and the cylinder wall, and the rod 68 and the injection piston 58. It is convenient for the following description to grasp the room D that occurs when the user leaves. The wall of the hydraulic cylinder for injection 52 has C
A relief valve 86 is provided in communication with the chamber, and the relief valve 86 is opened by a detection signal of a pressure sensor 84 for detecting the pressure in the B chamber. Further, a position sensor 82 for detecting a displacement amount of the rod 60 integrated with the injection piston 58 is provided at a predetermined position, and the high-speed valve 102 opened by the position signal is connected to the accumulator 92.
Of the oil passages 96, 98 communicating with the oil chamber 96, the low-speed valve 10 is inserted into an oil passage 94 provided in parallel with the oil passage 96.
0 is interposed. The hydraulic control system 106 of the secondary pressurized hydraulic cylinder 48 extracts the operating pressure of the injection hydraulic cylinder 52 through the oil passage 104, 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 110, the sequence valve 110 capable of adjusting the starting pressure by using the urging spring force operates, and the hydraulic pump 1
Pressure oil discharged from 08 is oil passage 112, switching valve 114, flow control valve
116, the main part of the hydraulic control system 106 is configured so that the pressure rod 50 is guided to the secondary pressure hydraulic cylinder 48 through the pressure rod advancement oil passage 118, and the pressure rod 50 operates to enter the cavity A. I have. The switching valve 114 is switched from the state shown in the drawing at the same time when the pressure oil is supplied to the chamber B of the injection hydraulic cylinder 52 through the oil supply passage 98. In such a configuration, after the molten metal (eg, aluminum alloy) is injected into the injection sleeve 42 through the pouring port 44, the injection ram 88 is operated by the operation of the injection hydraulic cylinder 52.
Is advanced, the molten metal in the injection sleeve 42 is filled into the cavity A under pressure. After the filling of the cavity A is completed, the pressing rod 50 is pushed into the molten metal in the cavity A at a predetermined timing, and a secondary pressurizing pressure is applied to the molten metal. Hereinafter, the injection hydraulic cylinder 52 and the hydraulic control system 106
Will be described. Before the start of injection: The state of the hydraulic cylinder for injection 52 before the start of injection is shown in FIG. The low-speed valve 100 and the high-speed valve 102 are both closed. Injection piston 58,
The pressure-intensifying piston 62 is at the rearmost position, and the check valve 72 in the pressure-increasing piston 62 is urged by the coil spring 80 so that the opening 66 of the valve chamber 64 is opened.
Is closed. Injection start (low-speed injection): When the low-speed valve 100 is opened, the discharge oil of the accumulator 92 which is already in a standby state is sent to the B chamber through the oil passages 94 and 98, and the hydraulic pressure in the B chamber rises to check the valve. 72 is moved against the urging force of the coil spring 80, and B
The passage from the chamber to the oil passage 78 formed in the shaft portion 76 of the check valve 72 → the oil passage 70 formed in the rod 68 of the pressure-intensifying piston 62 becomes conductive, and the pressure between the injection piston 58 and the rod 68 becomes high. Oil (pressure P
₁₁ ) is supplied. Hydraulic pressure acting on the top surface (P ₁₁₎
Injection piston 58 is slow by: forward with (slow versus fast forward in the next step see curve I ₁ in FIG. 6), D chamber is formed between the injection piston 58 and the rod 68 (FIG. 4) . During this time, the discharge working pressure of the accumulator 92 is gradually decreased from the initial set pressure P _A1 by the energy release (see curve I _A in Figure 6). High-speed injection: When the injection piston 58 advances by a predetermined length (hence, when the injection ram 88 advances by a predetermined length), the position sensor is in contact with the injection piston 58 and the integral rod 60.
82 moves, the high-speed valve 102 is opened by the detection signal, the hydraulic oil supply amount of the accumulator 92 to the B chamber and the D chamber increases, and the pressure in the B chamber and the D chamber sharply increases (curve
I ₂ , pressure P ₁₂ , time T ₂ ), and the injection piston 58 advances at high speed. During this time, the operating pressure of the accumulator 92 is a minimum value operating pressure (P _A2) in drops with a large gradient in comparison with the curve I _A (curve II _A), molten metal filling completion (T _2), start then rise (Recovery of operating pressure starts). Pressure increase stage: After filling of the molten metal, the oil pressure in the chambers B and D should rise rapidly, but the molten metal in the cavity A, the oil passage and the injection sleeve 42 begins to solidify and contract, and the injection ram 88 and the injection piston 58 is still moving forward (slightly moving forward) and has a slow rise in hydraulic pressure, so it initially rises slowly (curve I ₃ , pressure P ₁₂ ). B chamber pressure when (P _12, D equals the pressure in the chamber) rises to P _X (time T _3), a pressure sensor 84 the pressure (P _X) as the set pressure
The relief valve 86 is opened by the detection signal. The pressure oil in the C chamber is discharged to the outside through the opened relief valve 86, and the pressure-intensifying piston 62 starts to move forward. as a result,
The pressure in the chamber D becomes higher than the pressure in the chamber B (equal to the operating pressure of the accumulator 92), and the check valve 72 is pressed against the opening 66 of the valve chamber 64 to close the opening 66. The pressure increasing piston 62 advances in a state where the communication between them is interrupted (FIG. 5), and the pressure in the chamber D rises rapidly (curve I ₄ , pressure P
₁₃ ). The rising speed of the pressure (P ₁₃ ) in the chamber D after the point T ₃ is B
Sufficiently larger than the rising speed of the indoor pressure (P ₂₃₎ (curve I _4, I ₅ refer), the injection piston 58 is also in this period,
Intensified biston 62 advances slightly. The pressure (P ₂₃ ) in the chamber B coincides with the operating pressure of the accumulator 92 in the returning process at the time (T ₄ ), and thereafter, the pressure (P ₂₃ ) in the chamber B becomes equal to the operating pressure of the accumulator 92 (curve).
I ₆ ), the operating pressure of the accumulator 92 returns to the initial set pressure (P _A1 ) at the time (T ₅ ). The operating pressure of the accumulator 92 changes from the pressure (P _A1 ) to the pressure (P
_A2) was lowered to, it is described above to return, equal to the operating pressure of the booster-pressure-opening start point (T ₃₎ after the accumulator 92 B
By detecting an arbitrary pressure P _Y (preselected pressure) in the room B between the time (T ₄ ) at which the change in the room pressure (P ₂₃ ) is stabilized and the time (T ₅ ) (see the curve I ₆ ). ,
It is possible to know the timing of starting the secondary pressurization promptly after the filling of the melt into the cavity A. Start of secondary pressurization: The pressure in the B chamber (operating pressure of the accumulator 92) is guided to the sequence valve 110 in the hydraulic control system 106 by the oil passage 104, and the pressure in the B chamber is reduced to the constant pressure P
_{When Y} (where P _A2 ≦ P _Y <P _A1 ) is reached, the sequence valve 110 is opened. As a result, in a state where the switching valve 114 is displaced from the state shown in FIG. 1, the secondary pressurizing hydraulic cylinder 48 through the sequence valve 110, the oil passage 112, the switching valve 114, the flow regulating valve 116 and the pressurizing rod advancement oil passage 118. The discharge oil of the hydraulic pump 108 is sent to the high pressure chamber, and the pressurizing rod 50 moves forward and is pushed into the molten metal filling the cavity A, and the secondary pressurizing pressure is applied to the molten metal that has not been solidified. . The secondary pressurizing pressure is applied until the molten metal in the cavity A is completely solidified, and then the secondary pressurizing hydraulic cylinder 48 is passed through the pressurizing rod retreat passage 120 by switching the switching valve 114.
The pressurizing rod 50 is retracted. The features of this embodiment are listed below. Accumulator 92 for driving injection piston 58
Operating pressure gradually decreases after the low-speed valve 100 is opened, continues to decrease at a higher speed after the high-speed valve 102 is opened, and returns when the molten metal filling is completed (T ₂ ). And between the time when the operating pressure of the accumulator 92 starts to return (T ₂ ) and the time when the recovery is completed (T ₅ ), particularly when the B chamber pressure (P ₂₃ ) and the operating pressure of the accumulator 92 match. By capturing the operating pressure ( _PY : can be detected in the B chamber) of the accumulator 92 from (T ₄ ) to the time (T ₅ ), the sequence valve 110 is opened at high accuracy with little fluctuation, and the secondary pressure Pressure can be started. If the operating pressure of the accumulator 92 is detected by the accumulator 92 instead of the B chamber from the time (T ₂ ) when the filling of the molten metal is completed to the time (T ₄ ) when the pressure in the B chamber (P ₂₃ ) and the operating pressure of the accumulator 92 match. For example, the start of the secondary pressurization is started at an earlier timing after the filling of the molten metal is completed as compared with the case where the operating pressure (P _Y ) of the accumulator 92 is detected from the time (T ₄ ) to the time (T ₅ ). Can capture points. Therefore, although the change in the operating pressure of the accumulator 92 cannot be detected in the room B in which the change in the molten metal pressure can be directly detected, the operating pressure of the accumulator 92 during the period from the time (T ₂ ) to the time (T ₄ ) is secondarily determined. It can be used as a starting pressure for starting pressurization. Since the operating pressure of the accumulator 92 returns relatively slowly, the sequence valve 110 set to start at the pressure (P _Y ) has little fluctuation at the time of starting, and after completion of filling of the molten metal, always at the scheduled correct timing. Secondary pressurization can be performed. Since the activation of the sequence valve 110 is performed by directly guiding the hydraulic pressure in the chamber B, the pressure in the chamber B is detected by a pressure detector, and the solenoid valve is activated based on the detection signal to thereby activate the hydraulic cylinder for secondary pressurization. , The time delay is small, 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 92 in advance, it is possible to adjust and change the speed of return of the operating pressure of the accumulator 92 after the pressure oil has once decreased. The point at which the operating pressure (P _Y ) is detected can be easily changed by the adjustment, and the secondary pressurization timing can be easily adjusted. The pressure oil supply speed to the secondary pressurizing hydraulic cylinder 48 can be selected and changed by adjusting the valve opening of the flow control valve 116, and therefore the material, shape,
The pressurizing rod 50 can be advanced at a speed suitable for the dimensions and the like, and appropriate secondary pressurization can be performed. In the present embodiment, the accumulator 92 in the return process
The operating pressure (P _Y ) was detected and the sequence valve 110 was started using this as a trigger signal.
₂ ) With reference to (lower limit operating pressure (P _A2 )), the sequence valve 110 may be opened after a certain time by a delay timer or the like. Next, a hydraulic control system 106A according to a modification shown in FIG. 7 will be described. In the figure, the same components as those shown in FIG. 1 are denoted by the same reference numerals. In the hydraulic control system 106A, in addition to the sequence valve 110, the switching valve 114, and the flow control valve 116 in the previous embodiment, a stop valve 122 and a flow control valve 116 between the hydraulic pump 108 and the switching valve 114 and a secondary pressurizing valve Pressure reducing valve 1 between hydraulic cylinders 48
You are using 24. According to the hydraulic control system 106A, the switching oil is simultaneously introduced from the accumulator 92 into the hydraulic cylinder 52 for injection.
114 is switched from the state shown in the figure, the pressure oil from the hydraulic pump 108 enters a standby state at the inlet port of the sequence valve 110, and when the sequence valve 110 is opened, the pressure oil in the standby state is quickly changed to the flow control valve. The pressure is guided to the secondary pressurizing hydraulic cylinder 48 via the pressure reducing valve 124. The advance speed of the pressurizing rod 50 can be selected and changed to an appropriate value by adjusting the flow control valve 116, and the secondary pressurizing pressure can be selected and changed to an appropriate value by adjusting the pressure reducing valve 124. can do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway schematic view showing an embodiment of a secondary pressure casting apparatus according to the present invention, FIG. FIG. 3 is a perspective view of the check valve shown in FIG. 2, FIG. 4 and FIG. 5 are views similar to FIG. 7 is a graph showing a change in hydraulic pressure in an injection hydraulic cylinder and a change in operating pressure of an accumulator in the secondary pressure casting apparatus, and FIG.
The figure shows a hydraulic control system in which the hydraulic control system of the secondary pressure casting apparatus is partially modified. 10 ... Die-casting device, 12 ... Base, 14,16 ... Fixed platen, 18 ... Connection rod, 20 ... Movable platen, 22 ... Fixed mold, 24 ... Movable mold, 26 ... Holding Body, 28 ... extrusion plate, 30 ... return pin, 32 ... extrusion pin, 34 ... extrusion hydraulic cylinder, 36 ... push rod, 38 ... hydraulic platen drive hydraulic cylinder, 40 ... push rod, 42 ... injection sleeve, 44 ... pouring port, 46 ... holding rod, 48 ... hydraulic cylinder for secondary pressurization, 50 ... pressurizing rod, 52 ... hydraulic cylinder for injection, 54 ... small diameter part, 56 …… Large diameter part, 58 …… Injection piston, 60 …… Rod, 62 …… Pressure increasing piston, 64 ……
Valve chamber, 66 ... Opening, 68 ... Rod, 70 ... Oil passage, 72 ...
Check valve, 74 Head, 76 Shaft, 78 Oil passage, 80
Coil spring, 82 Position sensor, 84 Pressure sensor 86
... relief valve, 88 ... injection ram, 90 ... support rod, 92 ...
Accumulator, 94, 96, 98… Oil passage, 100… Low speed valve, 102… High speed valve, 104… Oil passage, 106… Hydraulic control diameter, 108… Hydraulic pump, 110… Sequence valve , 11
2 Oil passage 114 Switching valve 116 Flow control valve 118
… Pressure rod forward oil passage, 120 …… Pressure rod retreat passage, 122…
... Stop valve, 124 ... Reducing valve.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Fujito Mugi               1-4-1 Chuo, Wako-shi, Saitama               Inside Honda Technical Research Institute (72) Inventor Kosuke Kikuchi               22-30 Honcho, Wako-shi, Saitama               Within Industries                (56) References JP-A-1-40158 (JP, A)                 JP-A-62-183954 (JP, A)

Claims (1)

(57) [Claims] In a mold casting apparatus in which the molten metal in the injection sleeve is pressure-filled into the cavity of the mold by the injection ram, and after the completion of the filling of the molten metal, a pressure rod is pressed into the molten metal to apply a secondary pressing force to the molten metal. The injection hydraulic cylinder that drives the injection ram receives pressurized oil only from the accumulator through the parallel low-speed valve and high-speed valve, and applies a secondary pressure to the molten metal in the mold cavity. The pressure rod driving means is controlled by secondary pressure control means operating by detecting the pressure oil pressure in the accumulator or detecting a change in the pressure oil pressure, and the low speed valve is provided by the injection valve from the accumulator. Is opened at the initial stage of the supply of hydraulic oil to the hydraulic cylinder for use, and the high-speed valve is closed at the initial stage of the supply of the hydraulic oil, but is supplied from the accumulator to the hydraulic cylinder for injection. The secondary pressurizing force control means may be configured to return to the initial set pressure after the pressure oil pressure in the accumulator decreases due to the discharge of the pressure oil from the accumulator to the injection hydraulic cylinder. A secondary pressure casting apparatus configured to detect a hydraulic pressure or a change in the hydraulic pressure.