JP7609673B2 - Mold opening and closing device - Google Patents

Description

The present invention relates to a mold opening and closing device.

A mold opening and closing device is known that includes a fixed platen that supports a fixed mold, a movable platen that supports a movable mold, a number of tie bars each having one end connected to the fixed platen and the other end extending through the movable platen, male threads formed on the other ends of the tie bars, split nuts that are freely threadedly attached to the male threads, and a mold opening and closing cylinder that is attached to each tie bar and uses a reaction force from the split nuts to move the movable platen forward and backward relative to the fixed platen to open and close the movable platen (see, for example, Patent Document 1).

Patent No. 4254495

When opening and closing the mold, a large impact may occur due to collision between the male thread and the split nut caused by backlash. In order to mitigate this impact and make it easier to open the mold, it is possible to apply grease containing molybdenum as a lubricant to the contact area between the fixed and movable molds.

However, when grease containing molybdenum is applied to the contact area between the fixed and movable dies, the grease can seep into the cavity, affecting product quality and increasing the cleaning load during maintenance. Vibrations can also have an impact on the entire die-casting machine, causing damage to equipment welds and loosening of wiring terminal screws, which can lead to unexpected machine trouble and problems that affect the machine's lifespan.

In view of the above, the present invention aims to provide a mold opening and closing device that is easy to maintain and prevents violent collisions between the split nut and the male threaded portion, thereby reducing the occurrence of impacts without requiring new capital investment.

[1] In order to achieve the above object, the present invention provides
A fixed platen that supports the fixed mold, a movable platen that supports the movable mold,
a plurality of tie bars each having one end connected to the fixed platen and the other end extending through the movable platen;
A male thread portion formed on the other end of the tie bar;
A split nut that is detachably screwed onto the male thread portion;
a mold opening/closing cylinder provided for each of the tie bars, the mold opening/closing cylinder moving the movable platen forward and backward relative to the fixed platen by a reaction force from the split nut to open and close the movable platen;
In a mold opening and closing device comprising:
Among the plurality of tie bars, the tie bars that are subject to the difficulty of mold opening due to a specified cause are defined as "some tie bars",
The present invention is characterized in that, at the time of mold opening, mold opening control is executed in such a way that a mold opening command to the mold opening/closing cylinders provided on some of the tie bars is issued earlier than the mold opening command to the mold opening/closing cylinders provided on the remaining tie bars excluding some of the tie bars .

According to the present invention, by speeding up the mold opening instruction to the mold opening/closing cylinders installed on some of the tie bars, it is possible to prevent the split nut from colliding violently with the male threaded portion, thereby reducing the occurrence of impacts. In addition, there is no longer a need to apply grease as a lubricant to the contact area between the fixed and movable dies, making maintenance easier.

[2] In the present invention,
The mold opening and closing device is used in a die casting device,
The stationary platen is provided with an injection device for supplying molten metal into the cavity,
The part of the tie bars is
Of the tie bars, it is preferably the tie bar that is closer to the injection device .

With this configuration, the mold opening cylinder attached to the tie bar on the injection device side, which is easily affected by thermal expansion, is commanded to open earlier than the other mold opening and closing cylinders, so that the parts that are difficult to open can be opened earlier, and the split nut and the male threaded part are prevented from colliding violently, thereby suppressing the occurrence of impacts.

FIG. 2 is an explanatory diagram showing a mold closing state of the mold opening and closing device according to the embodiment of the invention. FIG. 4 is an explanatory diagram illustrating a mold opening and closing device according to the present embodiment in a mold open state. FIG. 13 is an explanatory diagram showing a schematic diagram of a state in which the split nut and the male thread portion of the diver are screwed together when the mold is closed in this embodiment. FIG. 13 is an explanatory diagram illustrating a state in which the split nut and the male thread portion of the diver are screwed together when the mold is in an open state in this embodiment.

The mold opening and closing device according to the embodiment of the invention will be described with reference to the drawings. With reference to Figs. 1 and 2, the mold opening and closing device 1 according to this embodiment includes a fixed mold 2, a movable mold 3 which is pressed against the fixed mold 2 to define a cavity 2a between the fixed mold 2 and the movable mold 3, a rectangular fixed platen 4 which supports the fixed mold 2, a rectangular movable platen 5 which supports the movable mold 3, four tie bars 6 each having one end connected to each of the four corners of the fixed platen 4, and an injection device 9 which is provided below the fixed mold 2 and which injects molten metal into the cavity 2a. Note that Fig. 1 shows a schematic diagram of the mold opening and closing device 1 in a mold-closing state, and Fig. 2 shows a schematic diagram of the mold opening and closing device 1 in a mold-opening state.

In the die used in the die casting machine such as the die opening and closing device 1 of this embodiment, a sliding core 3a is used to extract the shape of the product. A total of four sliding cores 3a are arranged in the movable die 3, one pair on the left and right, and one pair on the top and bottom, and each has a product shape surface to which the top, bottom, left and right shapes of the product are transferred. The sliding cores 3a are subjected to a force that opens in a direction 90 degrees different from the mold opening direction of the movable die 3 during casting. The fixed die 2 is provided with a backup part 2b that prevents the sliding cores 3a from opening due to the pressure during casting. The casting pressure acts on the sliding cores 3a in a direction 90 degrees different from the force that acts in the direction of opening the movable die 3, and a force that tries to push the opposing sliding cores 3a apart acts. Therefore, the sliding cores 3a and the backup part 2b of the fixed die 2 come into strong contact with each other, which may be one of the factors that prevent the movable die 3 from quickly separating from the fixed die 2 when the die is opened.

The injection device 9 has a pressing function to press the casting (not shown) in the cavity 2a toward the movable mold 3 after the molten metal in the cavity 2a has solidified, i.e., it has a function to assist in mold opening. In addition, the injection device 9 is generally provided below the fixed mold 2 to prevent air from remaining in the cavity 2a. Insertion holes 5a are provided at the four corners of the movable platen 5 to correspond to the positions of the tie bars 6 and to allow the other ends of the tie bars 6 to pass through.

The other end of the tie bar 6 is provided with a male threaded portion 6a that is exposed to the outside from the movable platen 5 and is located on the side farther away from the fixed platen 4 than the movable platen 5. A split nut 7 is provided so as to be freely screwed onto the male threaded portion 6a.

The insertion hole 5a is provided with a mold opening/closing cylinder 8 formed in a cylindrical shape so that the tie bar 6 can be inserted therethrough. The mold opening/closing cylinder 8 has a cylindrical cylinder body 8a and a piston 8b that can move forward and backward relative to the cylinder body 8a. The cylinder body 8a is provided with a mold closing side hydraulic chamber 8c to which hydraulic pressure is transmitted to cause the piston 8b to protrude relative to the cylinder body 8a, and a mold opening side hydraulic chamber 8c to which hydraulic pressure is transmitted to cause the piston 8b to retract relative to the cylinder body 8a. Hydraulic pressure is transmitted to the mold closing side hydraulic chamber 8c and the mold opening side hydraulic chamber 8c, and oil is discharged, via a hydraulic circuit 10.

The cylinder body 8a is fixed to the movable platen 5. The piston 8b is joined to the split nut 7.

Next, the mold opening and closing operation of the mold opening and closing device 1 of this embodiment will be described. First, in the mold opening and closing device 1 of this embodiment, when opening the mold, the split nut 7 is released from the tie bar 6, and an electric motor (not shown) moves the movable platen 5 and movable mold 3 close to the fixed mold 2 and fixed platen 4 to a predetermined distance where the mold can be clamped by the mold opening and closing cylinder 8.

After the electric motor (not shown) moves the movable platen 5 and the movable mold 3 to a predetermined distance from the fixed mold 2 and the fixed platen 4, the split nut 7 is screwed onto the male thread 6a of the tie bar 6. Then, hydraulic pressure is transmitted to the mold closing hydraulic chamber 8c, and the piston 8b and the cylinder body 8a receive the reaction force from the split nut 7, moving the movable platen 5 toward the fixed platen 4, and pressing the movable mold 3 against the fixed mold 2 with a pressure stronger than that of the electric motor (not shown). Then, molten metal is poured from the injection device 9 into the cavity 2a. In high-speed high-pressure die casting (hereinafter referred to as HPDC), the quality of the product is established by the casting pressure. When the casting pressure is applied to the cavity 2a, it acts in a direction that pushes the fixed mold 2 and the movable mold 3 open, but in the sliding core 3a provided in the movable mold 3, a force acts to firmly press the sliding core 3a against the backup part 2b of the fixed mold 2. Then, once the molten metal in cavity 2a has solidified, the oil in the mold closing hydraulic chamber 8c can be discharged, and the injection device 9 presses the casting in cavity 2a toward the movable mold 3, assisting in the mold opening of the movable mold 3 and the movable platen 5.

When the pressure in the mold opening/closing hydraulic chambers 8c and 8d is discharged, the movable mold 3 is pulled away from the fixed mold 2 by the injection device 9 pressing against the movable mold 3. However, in a situation where the sliding core 3a of the movable mold 3 is firmly pressed against the backup part 2b of the fixed mold 2, the movable mold 3 cannot be pulled away from the fixed mold 2. After that, hydraulic pressure is transmitted to the mold opening hydraulic chamber 8d, and the cylinder body 8a is moved toward the split nut 7 relative to the piston 8b, moving the movable mold 3 and the movable platen 5 in a direction away from the fixed mold 2 and the fixed platen 4 to open the mold. If the backup part 2b of the fixed mold 2 and the sliding core 3a of the movable mold 3 can be opened by the force of the injection device 9 alone, the mold opening/closing cylinder 8 will not transmit the mold opening force even if it is operated, and the initial mold opening operation will be performed by the injection device 9 alone.

If the mold cannot be opened by the force of the injection device 9 alone, the mold opening and closing cylinder 8 operates to separate the movable mold 3 from the fixed mold 2 with a combined force of the injection device 9 and the injection device 9. Since there is a gap between the split nut 7 and the male thread portion 6a of the tie bar 6, which is the amount of backlash in the direction of movement of the movable platen 5, the split nut 7, which was located on the fixed platen 4 side of the male thread portion 6a by the amount of backlash, moves away from the fixed platen 4 by the amount of backlash, transmitting the mold opening force to the movable platen 5. When the fixed mold 2 and the movable mold 3 including the sliding core 3a are separated by the combined force of the injection device 9 and the mold opening and closing cylinder 8, the movable platen 5 becomes free and runs free through the backlash of the split nut due to the pressure of the injection device 9, and the split nut 7 and the male thread portion 6a come into contact again. Figure 3 shows an enlarged cross-sectional view of the female threaded portion 7a of the split nut 7 and the male threaded portion 6a of the diver 6 when the mold is closed, and Figure 4 shows an enlarged cross-sectional view of the female threaded portion 7a of the split nut 7 and the male threaded portion 6a of the diver 6 when the mold is open. If the impact when the split nut 7 and the male threaded portion 6a move from the state shown in Figure 3 to the state shown in Figure 4 and come into contact again is too strong, this may cause problems such as a decrease in durability of the mold opening and closing device 1.

In this embodiment, an experiment was conducted to determine whether a strong impact would occur while measuring the distance between the fixed platen 4 and the movable platen 5 at three locations, two above the mold opening/closing device 1 and one below, using a distance measuring device (not shown) and an accelerometer (not shown) for measuring impact. As a result, it was found that a strong impact occurs when the fixed platen 4 and the movable platen 5 separate relatively smoothly on the upper side, whereas the fixed platen 4 and the movable platen 5 do not separate as smoothly on the lower side as on the upper side. This is because, in the mold opening/closing device 1 of this embodiment, the injection device 9 is disposed below the fixed mold 2, and the lower part of the mold opening/closing device 1 is deformed by thermal expansion, so that the relative separation between the fixed mold 2 and the movable mold 3 is not performed smoothly on the lower part, and the movable platen 5 is tilted and cannot move smoothly, and the movable platen 5 moves suddenly after the pressure of the injection device 9 and the mold opening/closing cylinder 8 increases.

Then, in order to make the distances between the fixed platen 4 and the movable platen 5 at three points (two at the top and one at the bottom) the same or substantially the same, the timing of the hydraulic pressure transmission to the mold opening hydraulic chamber 8d of the mold opening/closing cylinders 8 located on the two lower tie bars 6 was advanced relative to the two upper tie bars 6, and we were successful in suppressing the occurrence of strong impacts.

In this embodiment, the two lower mold opening and closing cylinders 8 were controlled to transmit hydraulic pressure to the mold opening side hydraulic chamber 8d 0.4 seconds earlier than the two upper mold opening and closing cylinders 8, which successfully prevented the occurrence of strong impacts. However, since the specific time when hydraulic pressure is transmitted varies depending on the operating speed and backlash of the mold opening and closing cylinders 8, it is desirable to verify the timing at which impacts can be prevented for each mold opening and closing device 1.

According to the mold opening and closing device 1 of this embodiment, the mold opening command to the mold opening and closing cylinders 8 attached to each of the two lower tie bars 6 is sent earlier than the mold opening command to the mold opening and closing cylinders 8 attached to each of the two upper tie bars 6, thereby preventing the split nut and the male threaded portion from colliding violently and reducing the occurrence of impact.

In addition, because impact can be suppressed, there is no longer a need to apply molybdenum-containing grease to the fixed die 2 and the movable die 3 including the sliding core 3a, and this also eliminates the problem of the fixed die 2 and the movable die 3 becoming dirty due to the grease applied to the sliding core 3a seeping into the cavity 2a, making maintenance easier.

In this embodiment, the mold opening control is performed to issue a mold opening command to the two lower mold opening/closing cylinders 8 earlier than the two upper mold opening/closing cylinders 8, but the mold opening control of the mold opening/closing device of the invention is not limited to this. For example, if it is found from the measurement of the distance between the fixed platen and the movable platen that it is difficult to open the upper part of the fixed mold 2 and the movable mold 3 due to the structural reasons of the mold, the mold opening control may be performed so that the mold opening command of the upper mold opening/closing cylinder is earlier than the mold opening command of the lower mold opening/closing cylinder. The same may be performed for the left and right. In addition, it is important to keep the length of the time lag to the shortest time at which the impact is eliminated by testing from the same time for a short time. Although the mold opening is basically performed in parallel and at the same time, a time lag longer than necessary will induce troubles in the mold and HPDC machine because it is a measure to firmly press the fixed mold 2 and the movable mold 3 including the sliding core 2a.

In addition, in this embodiment, the mold opening and closing device 1 having four tie bars 6 has been described, but the number of tie bars in the mold opening and closing device of the invention is not limited to four, and may be any number. For example, the number of tie bars in the mold opening and closing device of the invention may be three or five or more. Furthermore, as a method for eliminating or mitigating the mold opening shock, there is a method of slowing down the pushing speed of the movable mold 3 of the injection device 9 or reducing the pressure to mitigate the shock, but this method does not eliminate the strong imbalance in the pressure between the fixed mold 2 and the movable mold 3 including the sliding core 3a even if it mitigates the shock, and does not fundamentally solve the problem of impeding the durability of the mold opening and closing device 1.

1 Mold opening and closing device 2 Fixed mold 2a Cavity 2b Backup section 3 Movable mold 3a Sliding core 4 Fixed platen 5 Movable platen 5a Insertion hole 6 Tie bar 6a Male thread section 7 Split nut 7a Female thread section 8 Mold opening and closing cylinder 8a Cylinder body 8b Piston 8c Mold closing hydraulic chamber 8d Mold opening hydraulic chamber 9 Injection device 10 Hydraulic circuit

Claims (2)

A fixed platen that supports the fixed mold, a movable platen that supports the movable mold,
a plurality of tie bars each having one end connected to the fixed platen and the other end extending through the movable platen;
A male thread portion formed on the other end of the tie bar;
A split nut that is detachably screwed onto the male thread portion;
a mold opening/closing cylinder provided for each of the tie bars, the mold opening/closing cylinder moving the movable platen forward and backward relative to the fixed platen by a reaction force from the split nut to open and close the movable platen;
In a mold opening and closing device comprising:
Among the plurality of tie bars, the tie bars that are subject to the difficulty of mold opening due to a specified cause are defined as "some tie bars",
A mold opening and closing device characterized in that, during mold opening, mold opening control is executed to issue a mold opening command to the mold opening and closing cylinders provided on some of the tie bars earlier than the mold opening commands to the mold opening and closing cylinders provided on the remaining tie bars excluding the some of the tie bars. The mold opening and closing device is used in a die casting device,
The stationary platen is provided with an injection device for supplying molten metal into the cavity,
The part of the tie bars is
2. The mold opening and closing device according to claim 1, wherein the tie bars are located closer to the injection unit .

Images