JPH0790344B2 - Secondary pressure casting method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary pressure casting method of a type in which a secondary pressure is applied to a molten metal pressurized and filled in a cavity of a mold.

2. Description of the Related Art The pressure die casting method, in which a molten metal is cast into a cavity of a mold at high pressure, is widely adopted and practiced as a method most suitable for mass production in the aluminum alloy casting technology. In this die casting method, there is a tendency that cast holes are likely to occur in the thick portion of the product, the crystal structure becomes coarse, and the strength of the thick portion is reduced. In order to solve this problem, a secondary pressure casting method is proposed in which additional pressure (secondary pressure) is applied to the molten metal that is pressure-filled in the mold cavity to reach solidification. (Eg, Japanese Patent Publication No. 48-7570, Japanese Patent Publication No.
49-36093).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention 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. It has the characteristic of being short. Therefore, the time margin for performing the secondary pressurization is small, and it is difficult to accurately grasp the pressurization start timing. If this timing is incorrect, not only the pressurizing effect cannot be obtained, but also when secondary pressurization is performed after the start of solidification, cracks may occur in the pressed portion.

Conventionally, various methods have been proposed in which the position of the injection ram that pressurizes the molten metal in the injection sleeve is detected by a position sensor or the like, and the detection signal is used as a trigger signal to set the secondary pressurization timing. However, with this method, the detection accuracy fluctuates greatly due to the performance of the position detection sensor, changes in the speed of the injection ram, changes in the amount of molten metal, etc., and secondary pressurization cannot be performed with high reliability.

Further, the injection cylinder and the pressure boosting cylinder are used together to increase the pressure of the molten metal injected into the cavity and then perform the secondary pressure.The pressure in the injection cylinder is detected and the detection signal is detected. A method of setting a secondary pressurization timing as a trigger signal is also known. However, in this method, the pressure in the injection cylinder that rises rapidly after the completion of the molten metal filling is detected, so the detection timing is unstable, and the time point at which the secondary pressurization starts cannot be accurately captured.

Means and Actions for Solving Problems The present invention was created under such a technical background, and an object thereof is to improve the setting accuracy of the secondary pressurization timing.

This purpose is to fill the molten metal in the injection sleeve into the cavity of the mold by the injection ram, and to increase the forward pressure of the injection ram after the completion of the filling of the molten metal. Using the hydraulic cylinder for injection consisting of and the operating pressure of the accumulator installed in the hydraulic circuit, the injection ram is moved forward at low speed first and then at high speed, and the injection ram is much larger than the molten metal after the filling is completed. In the secondary casting method of operating the pressure rod while applying pressure to press the molten metal in the cavity,
After the completion of the molten metal filling into the cavity of the mold, the pressure in the high pressure chamber of the filling hydraulic cylinder that rises until the pressure intensification is started is detected, and the pressure oil from the hydraulic pressure source is used as a reference based on the detection signal. This is achieved by guiding the oil to the secondary pressurizing hydraulic cylinder to operate the pressurizing rod and applying the secondary pressurizing pressure to the molten metal in the cavity of the mold. In the present specification, the expression "the injection ram is initially advanced at low speed and then at high speed by utilizing the operating pressure of the accumulator provided in the hydraulic circuit" is inevitable when the injection ram is advanced at high speed. It is necessary to utilize the operating pressure of the accumulator, but it means that the operating pressure of the accumulator does not necessarily have to be utilized when advancing the injection ram at a low speed in the preceding stage.

A filling hydraulic cylinder for press-filling the molten metal in the injection sleeve into the cavity of the mold by the injection ram,
After using the hydraulic cylinder for injection, which consists of a hydraulic cylinder for boosting pressure to increase the forward pressure of the injection ram after the completion of the filling of the molten metal, the operating pressure of the accumulator provided in the hydraulic circuit is used to make the injection ram initially low speed, then Move forward at high speed,
The mold casting method, in which the pressurizing rod is actuated while applying a larger pressure by the injection ram to the molten metal after the completion of filling and the secondary pressure is applied to the molten metal in the cavity, is the formation of cavities in the cast product. This is a well-known method for preventing damage and improving strength and quality.

If the secondary pressure is applied very quickly after filling the mold cavity with the molten metal, the molten metal present in the passage from the injection sleeve to the cavity may not be completely solidified. A back flow of the molten metal may occur due to the action of the secondary pressurization pressure that is higher than the filling pressure.

In this sense, it is preferable that a pressure larger than the pressure at the time of completion of filling be applied to the molten metal in the injection sleeve before the secondary pressurization. By thus increasing the pressure after the completion of the molten metal filling, the secondary pressurizing effect can be secured and a cast product having a dense structure can be obtained.

Timing of applying a larger pressure by the injection ram to the molten metal after completion of the molten metal filling (timing to start increasing pressure)
Is set at a time when some time has passed after the completion of the molten metal filling. When the high-speed molten metal filling of the mold cavity is completed, the advance speed of the injection ram is significantly reduced, and the high pressure chamber pressure (injection ram drive pressure) of the filling hydraulic cylinder, which was kept almost constant during the molten metal injection process, is initially It rises relatively slowly and then rapidly. The transition point of this pressure increase rate is selected as the pressure increase start point. In the time period from the completion of filling to the start of increasing pressure, the injection ram advances at an extremely small speed because the solidification of the molten metal progresses, and the hydraulic pressure rapidly increases in response to a large decrease in the speed of the injection ram. Since it takes some time, the rate of pressure increase is relatively small. Therefore, it is possible to stably detect the high pressure chamber pressure of the filling hydraulic cylinder in this time zone as the set pressure (P _x ), and if the secondary pressurization is started based on this detection signal, The secondary pressurization can be performed sufficiently quickly after the completion of the molten metal filling and with expected high timing accuracy.

Examples Hereinafter, the present invention will be described with reference to specific examples.

FIG. 1 shows a die casting apparatus 10 capable of exerting a secondary pressurizing pressure together with a secondary pressurizing hydraulic control system 106. On the base 12 of the die-casting device 10, fixed platens 14 and 16 that are mutually connected by a plurality of connecting rods 18 and are opposed to each other with a space therebetween are fixedly erected. Further, a movable platen 20 which is positioned between the fixed platens 14 and 16 and which is guided by a connecting rod 18 and is slidably displaced on the base 12 is provided.

Then, 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. A pair of push-out pins 32, which penetrate the movable mold 24 and face the cavity A, and are used to separate the product after the completion of casting from the movable mold 24, are movable relative to each other by sliding relative displacement.
Extrusion plate 28 having a pair of return pins 30 extending through 24
The push-out plate 28 is fixed to the movable platen 20 with the tip of the piston rod 35 thereof fixed to the movable platen 20 by a push rod 36 connected to the base plate of the hydraulic cylinder 34 for push-out which moves relative to the movable platen 20. , Is moved relative to the movable mold 24 in the product separating direction.

Further, the movable platen driving hydraulic cylinder 38 is fixed to the fixed platen 14, one end of which is fixed to the piston, and the movable platen 20 is moved by the push rod 40 whose other end is fixed to the cross member 41. .

Further, the injection hydraulic cylinder 52 is fixed to the fixed platen 16 with the support rod 90, and the injection ram 88 connected to the injection piston 58 penetrates the fixed platen 16 and communicates with the hot water passage of the fixed mold 22. When the injection ram 88 moves forward due to the operation of the injection piston 58 after the molten metal is supplied to the injection sleeve 42 through the pouring port 44, 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 a piston of the hydraulic cylinder 48 is provided with a pushing plate 28 and a movable mold 24. Is configured so as to be slidably displaceable and enter into the cavity A.

The injection hydraulic cylinder 52 includes a filling hydraulic cylinder 54 in which an injection piston 58 is inserted and an injection hydraulic cylinder 56 in which a booster piston 62 is inserted. Booster piston 62
Has integrally a rod 68 that fits into the filling hydraulic cylinder 54, and has a valve chamber 64 for accommodating the check valve 72 and the valve chamber 6
An oil passage 70 communicating with 4 and penetrating the rod 68 is formed (Fig. 2). The check valve 72 includes a head portion 74 having a conical surface and a shaft portion.
An umbrella-shaped piece composed of 76 (Fig. 3), also a valve chamber
The coil spring 80 stored in 64 urges the injection piston 58 to the opposite side (right side in FIG. 2). Valve chamber
The opening 66 of 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 from its outer peripheral surface close to the head portion 74 to the tip end. The flow is getting.

A part of the inner chamber of the injection hydraulic cylinder 52 (small diameter chamber 54, large diameter chamber 56) is a chamber B facing the opening 66 of the valve chamber 64, the booster piston 62 and the cylinder wall around the base of the rod 68. It is convenient for the following description to understand the C chamber defined by (1) and the D chamber generated when the rod 68 and the injection piston 58 are separated from each other. A relief valve 86 is provided on the wall of the injection hydraulic cylinder 52 so as to communicate with the chamber C, and the relief valve 86 is opened by a detection signal of a pressure sensor 84 for detecting the pressure in the chamber B. .

Further, a position sensor 82 that detects the amount of displacement of the rod 60 that is integral with the injection piston 58 is disposed at a predetermined position, and the low speed valve 100 that is opened by the position signal is used as an accumulator 92.
The high speed valve 102 is installed in the oil passage 94 of the oil passages 94, 98 communicating with the chamber B and is provided in parallel with the oil passage 94.
Is installed.

The hydraulic control system 106 of the secondary pressurizing hydraulic cylinder 48 takes out the operating pressure of the injection hydraulic cylinder 52 through the oil passage 104, and operates using this as a pointer. 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 its starting pressure using the urging spring force operates and the hydraulic pump 1
The pressure oil discharged from 08 is the oil passage 112, the switching valve 114, the flow rate adjusting valve.
116, the main part of the hydraulic control system 106 is configured so that it is guided to the secondary pressurizing hydraulic cylinder 48 through the pressurizing rod advancing oil passage 118, and the pressurizing rod 50 operates and enters into the cavity A. There is. The switching valve 114 is switched from the state shown in the figure at the same time as 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, the injection sleeve 42 through the pouring port 44
When the injection ram 88 is moved forward by the operation of the injection hydraulic cylinder 52 after injecting the molten metal (for example, aluminum alloy) into the cavity A, the molten metal in the injection sleeve 42 is pressurized and filled in the cavity A. Then, after the filling of the molten metal in the cavity A is completed, the pressing rod 50 is moved to the cavity A at a predetermined timing.
The secondary pressurization pressure is applied to the molten metal inside the molten metal.

The operations of the injection hydraulic cylinder 52 and the hydraulic control system 106 will be described below.

Before the start of injection: The state of the injection hydraulic cylinder 52 before the start of injection is shown in FIG. The low speed valve 100 and the high speed valve 102 are both closed. The injection piston 58 and the pressure boosting piston 62 are in the rearmost retracted position, and the check valve 72 in the pressure boosting piston 62 is biased by the coil spring 80 to close the opening 66 of the valve chamber 64.

Injection start (low speed injection): When the low speed valve 100 is opened,
The oil discharged from the accumulator 92 that is already in the standby state
After being sent to the B chamber via 4,98, the hydraulic pressure in the B chamber rises and the check valve 72 is moved against the biasing force of the coil spring 80.
Oil passage 78 formed in shaft 76 of check valve 72 → booster piston 62
The oil passage 70 formed on the rod 68 of the rod 68 becomes conductive, and pressure oil (pressure) is applied between the injection piston 58 and the rod 68.
P ₁₁ ) is supplied. Hydraulic pressure acting on the parietal surface (P ₁₁ )
Causes the injection piston 58 to move forward at a low speed (a low speed in comparison with the high speed forward movement in the next stage: see the curve I _{1 in} FIG. 6), and a D chamber is formed between the injection piston 58 and the rod 68 (FIG. 4). . During this period, the discharge operating pressure of the accumulator 92 gradually decreases from the initial set pressure P _A1 due to the energy release (see the curve I _{A in} FIG. 6).

High-speed injection: When the injection piston 58 moves forward by a predetermined length (hence, the injection ram 88 moves forward by a predetermined length), the position sensor is brought into contact with the injection piston 58 and the rod 60 integrated with the injection piston 58.
82 operates, 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 rapidly increases (curve I ₂ , pressure P ₁₂ At time T ₁ ), the injection piston 58 advances at high speed. During this period, the operating pressure of the accumulator 92 decreases with a larger gradient than the curve I _A (curve II _A ), and the operating pressure (P _A2 ) at the time of completion of the molten metal filling (T ₂ ) is set to the minimum value, and then the rise is started. (Restart of operating pressure).

Pressure increasing stage: After the completion of the filling of the molten metal, the hydraulic pressures 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 continues to move forward (moving speed is extremely small), and because there is a delay in the increase in hydraulic pressure, the pressure rises gradually at the beginning (curve I ₃ , pressure P ₁₃ ). When the pressure in the B chamber (P ₁₃ : equal to the pressure in the D chamber) rises to P ₁₄ (time point T ₃ ), the pressure (P ₁₄ ) is detected as the set pressure by the pressure sensor 84, and it is released by the detection signal. The valve 86 is opened.

The hydraulic pressure in the C chamber is released to the outside through the opened relief valve 86, and the pressure boosting piston 62 starts to move forward. As a result, D
The pressure in the chamber becomes higher than the pressure in the chamber B (equal to the operating pressure of the accumulator 92), and the check valve 72 opens the valve chamber 64.
The opening 66 is pressed by the 66 portion to close the opening 66, and the pressure boosting piston 62 advances with the communication between the B chamber and the D chamber blocked (Fig. 5), and the pressure in the D chamber rises rapidly ( Curve I ₄ , pressure P
₁₄ ).

The rising speed of the pressure (P ₁₅ ) in the D chamber after time T ₃ is sufficiently larger than the rising speed of the pressure (P ₂₃ ) in the B chamber (see curves I ₄ and I ₅ ), and the injection piston 58 Therefore, the booster piston 62 moves slightly forward.

The pressure in the B chamber (P ₂₃ ) coincides with the operating pressure of the accumulator 92 in the returning process at the time point (T ₄ ), and thereafter the pressure in the B chamber (P ₂₃ ) becomes equal to the operating pressure of the accumulator 92 (curve).
I ₆ ), the operating pressure of the accumulator 92 returns to the initial setting pressure (P _A1 ) at the time point (T ₅ ).

Start of secondary pressurization: The pressure in the B chamber (P ₁₃ : equal to the pressure in the D chamber) between the time point (T ₂ ) and the time point (T ₃ ) is the set pressure (P
_x : However, when P ₁₂ <P _x <P ₁₄ ) is reached, the sequence valve 110 is opened. As a result, when the switching valve 114 is displaced from the state shown in FIG.
The discharge oil of the hydraulic pump 108 is sent to the high pressure chamber of the secondary pressurizing hydraulic cylinder 48 through the 112, the switching valve 114, the flow control valve 116, and the pressurizing rod advancing oil passage 118, and the pressurizing rod 50 moves forward to move to the cavity. The secondary pressurization pressure is applied to the molten metal which is pushed into the molten metal which satisfies A and whose solidification is not completed. The secondary pressurization pressure is applied until the molten metal in the cavity A is completely solidified, and then the switching valve 114 is switched to supply the pressure oil to the secondary pressurizing hydraulic cylinder 48 through the pressurizing rod retreating oil passage 120. The pressure rod 50 is retracted.

The features of this embodiment are as follows.

When the operating pressure of accumulator 92 starts to return (T ₂ )
To the time (T ₅ ) when the recovery is completed, especially from the time (T ₄ ) to the time (T ₅ ) when the B room pressure (P ₂₃ ) and the working pressure of the accumulator 92 match.
It is necessary to capture the selected working pressure of 92 (which can be detected in the chamber B) and use this as the starting pressure to open the sequence valve 110 in order to quickly perform the secondary pressurization with high accuracy after the completion of the filling of the molten metal. Is the recommended method. However, as in the present embodiment, the pressure in the chamber B (P ₁₃ : D) is reached in the time zone from the completion of molten metal filling (T ₂ ) to the start of pressure increase (T ₃ ).
When the (equal to the pressure in the room) reaches the set pressure (P _x ), the sequence valve 110 set to the pressure (P _x ) is opened and the secondary pressurization is started in comparison with the above method. This is a preferable method in the sense that the secondary pressurization can be performed at a faster timing after the completion of the molten metal filling.

Next, the hydraulic control system 106A according to the modification shown in FIG. 7 will be described. In the figure, the same components as those shown in FIG. 1 are designated 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 rate control valve 116 in the previous embodiment, the hydraulic pump 1
08 and the stop valve 122 between the switching valve 114, and the pressure reducing valve 124 between the flow control valve 116 and the secondary pressurizing hydraulic cylinder 48.
Are using.

According to the hydraulic control system 106A, the discharge oil of the accumulator 92 is introduced into the injection hydraulic cylinder 52, and at the same time, the switching valve 11
4 is switched from the state shown in the figure, the pressure oil from the hydraulic pump 108 is in 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 quickly flows into the flow control valve. It is guided to the secondary pressurizing hydraulic cylinder 48 via 116 and the pressure reducing valve 124. The forward speed of the pressurizing rod 50 can be selected and changed to an appropriate value by adjusting the flow rate adjusting valve 116, and the secondary pressurizing pressure is set to the pressure reducing valve 12.
This can be selected and changed to an appropriate value by adjusting 4.

As another modified example, the pressure in the B chamber is detected by the pressure switch, the timer is started based on the time when the set pressure (P _x ) is detected, and the secondary pressurizing hydraulic cylinder 48 is delayed by a predetermined time. It is also possible to adopt a method of supplying pressure oil to the.

EFFECTS OF THE INVENTION As is apparent from the above description, the filling hydraulic cylinder for press-filling the molten metal in the injection sleeve into the cavity of the mold by the injection ram, and the advance pressure of the injection ram after the completion of the molten metal filling are increased. A hydraulic cylinder for injection consisting of a hydraulic cylinder for boosting pressure is used to advance the injection ram at low speed first and then at high speed by using the operating pressure of the accumulator provided in the hydraulic circuit, and the molten metal after filling is completed. On the other hand, it is a secondary pressure casting method in which a pressure rod is operated while applying a larger pressure by the injection ram to pressurize the molten metal in the cavity. Detects the pressure in the high-pressure chamber of the filling hydraulic cylinder that rises up to the point when the pressure signal from the hydraulic pressure source is used as the secondary pressurizing hydraulic cylinder based on the detection signal. A secondary pressure casting method has been proposed which is characterized in that the pressure rod is operated to apply a secondary pressure to the molten metal in the cavity of the mold.

A filling hydraulic cylinder for press-filling the molten metal in the injection sleeve into the cavity of the mold by the injection ram,
After using the hydraulic cylinder for injection, which consists of a hydraulic cylinder for boosting pressure to increase the forward pressure of the injection ram after the completion of the filling of the molten metal, the operating pressure of the accumulator provided in the hydraulic circuit is used to make the injection ram initially low speed, then Move forward at high speed,
In the secondary pressure casting method in which the molten metal in the cavity is pressurized by operating the pressure rod while applying a larger pressure by the injection ram to the molten metal after the filling is completed, it is almost constant in the high-speed injection process. The pressure in the high-pressure chamber of the hydraulic cylinder for filling, which changes in magnitude, initially rises relatively slowly after the completion of the filling of the molten metal, and then rises rapidly. In the present invention in which the pressure increase transition point is the pressure increase start time, the high pressure chamber pressure that rises at the slow speed of the filling hydraulic cylinder after the completion of the molten metal filling until the pressure increase start time is selected and set. The secondary pressurization can be performed as soon as possible after the completion of the molten metal filling and with high timing accuracy because the secondary pressurization is started with the detected signal.

[Brief description of drawings]

FIG. 1 is a partially cutaway schematic view showing an example of a suitable secondary pressure casting apparatus for carrying out the method of the present invention, and FIG. 2 is an enlarged explanatory view of an essential part including its working hydraulic circuit, FIG. FIG. 4 is a perspective view of the check valve shown in FIG. 2, FIGS. 4 and 5 are views similar to FIG. 2 showing an operation mode of the secondary pressure casting apparatus, and FIG. FIG. 7 is a graph showing changes in the hydraulic pressure in the injection hydraulic cylinder and changes in the operating pressure of the accumulator in the secondary press casting apparatus, and FIG. 7 shows a hydraulic control system in which the hydraulic control system of the secondary press casting apparatus is partially modified. It is a figure. 10 …… Die casting device, 12 …… Base, 14,16 …… Fixed platen, 18 …… Connecting 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 ... Movable platen drive hydraulic cylinder, 40 ... Push rod, 42 …… Injection sleeve, 44 …… Pouring spout, 46 …… Holding rod, 48 …… Secondary pressurizing hydraulic cylinder, 50 …… Pressurizing rod, 52 …… Injection hydraulic cylinder, 54 …… Filling hydraulic cylinder , 56 …… Injection hydraulic cylinder, 58 …… Injection piston, 60 …… Rod, 62 …… Boosting 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, 94,9
6,98 …… Oil passage, 100 …… Low speed valve, 102 …… High speed valve, 10
4 …… Oil passage, 106 …… Hydraulic control system, 108 …… Hydraulic pump, 1
10 …… Sequence valve, 112 …… Oil passage, 114 …… Switching valve, 116 …… Flow control valve, 118 …… Pressurizing rod advance oil passage, 12
0 …… Pressurizing rod retracting oil passage, 122 …… Stop valve, 124
...... Reducing valve, A ... Cavity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mugigo Fujito, 1-4-1 Chuo, Wako-shi, Saitama Stock Research Institute, Honda R & D Co., Ltd. (72) Inventor Kosuke Kikuchi, 22-30 Honmachi, Wako, Saitama Company Teisan Industries

Claims (2)

[Claims] 1. A filling hydraulic cylinder for pressurizing and filling the molten metal in an injection sleeve into a cavity of a mold by an injection ram, and a pressure increasing hydraulic cylinder for increasing a forward pressure of the injection ram after the completion of the molten metal filling. Using the hydraulic cylinder for injection consisting of and the operating pressure of the accumulator installed in the hydraulic circuit, the injection ram is moved forward at low speed first and then at high speed, and the injection ram is much larger than the molten metal after the filling is completed. In the secondary pressure casting method in which the pressure rod is operated while applying pressure to press the molten metal in the cavity, the pressure rises after the completion of the molten metal filling into the cavity of the mold and before the start of the pressure increase. Detecting the pressure in the high pressure chamber of the filling hydraulic cylinder, guiding the pressure oil from the hydraulic pressure source to the secondary pressurizing hydraulic cylinder based on the detection signal, and operating the pressurizing rod, A secondary pressure casting method comprising applying a secondary pressure to the molten metal in the cavity of the mold. 2. A pressurizing rod by opening a sequence valve by the detection signal obtained by detecting the pressure in the high pressure chamber of the filling hydraulic cylinder and guiding the pressure oil from the hydraulic pressure source to the secondary pressurizing hydraulic cylinder. The secondary pressure casting method according to claim 1, wherein the secondary pressure casting method is operated.