JPH0234253B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to forming in a press forming method in which a metal plate or the like is drawn between a die and a punch whose molding cavity is filled with a highly viscous substance such as silicone. Regarding how to set the pressure.

(Prior Art) Generally, in order to mold a metal plate into a predetermined shape, a means of pressurizing the metal plate between a pair of molds is used. However, in order to obtain a deep-drawn product, both convex and concave shapes must be manufactured with high precision, and even if they can be manufactured with high precision, variations in the thickness of the metal plate may cause problems during forming. Cracks, wrinkles, etc. occur.

For this purpose, liquid is filled into a die as in JP-B No. 36-20010, or a bag is filled with liquid as in JP-B No. 55-21603, and products with complex shapes are formed using this liquid pressure. There are known ways to do this. However, such a hydroforming method has disadvantages in that it is difficult to control the hydraulic pressure and handling in consideration of liquid leakage is also troublesome.

Furthermore, Japanese Patent Publication No. 57-55493 is an example of a die in which an elastic body such as rubber is provided in place of the above-mentioned hydraulic pressure. However, compared to hydraulic pressure, elastic bodies such as rubber have a poor ability to follow the shape of the punch, so when molding products with complex shapes,
There is a problem that cracks, wrinkles, etc. are likely to occur.

Therefore, the present applicant filed Japanese Patent Application No. 58-241644 (Japanese Unexamined Patent Publication No.
60-133933), the cavity of the die facing the punch is filled with a highly viscous substance that loses fluidity due to sudden external force and regains fluidity when the external force is reduced. We proposed a method for pressure forming workpieces such as metal plates between a highly viscous substance and a punch.

(Problem to be Solved by the Invention) When press-forming a workpiece using the above-mentioned highly viscous substance with a punch, in order to always obtain a product with excellent dimensional accuracy, the final pressure during molding must be equalized. However, since it is not possible to fill the cavity with a highly viscous substance using a pump as in the case of conventional hydraulic molding, the problem is how to set the final molding pressure.

(Means for Solving the Problems) In order to solve the above problems, the present invention leaves a space in the cavity of a die to hold a highly viscous substance through a pressure sheet, and allows a punch to relatively enter the cavity. The final molding pressure is set by discharging a part of the air in the space inside the cavity to the outside of the cavity while the amount of inflow reaches the top dead center or bottom dead center position where it reaches its maximum value.

(Example) Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view of the die. The die 1 is formed with a cavity 2 that is open on one side, and a groove 3 is formed around this opening into which the peripheral edge of a pressure sheet made of urethane or the like, which will be described later, is fitted. There is. In the cavity 2, one end of a discharge pipe 4, one end of a pressure gauge 5, and one end of a rod 6 for finely adjusting molding pressure are respectively exposed. A valve 7 is provided on the part of the discharge pipe 4 exposed to the outside of the die 1, and a male threaded part is carved in a part of the rod 6, and the rod 6 is fixed to the side surface of the die 1 with this male threaded part. By screwing into the nut 8 and rotating the rod 6, the rod 6 moves forward and backward into the cavity 2, increasing and decreasing the internal volume of the cavity 2.

In the molding pressure setting method according to the present invention, first, as shown in FIG. 2, a high viscosity substance 9 is filled into the cavity 2 of the die 1, for example, at about the 8th minute. The highly viscous substance 9 has a so-called dilatancy property in which it loses fluidity due to sudden external force and regains fluidity by reducing the external force, and examples thereof include two-component silicone or vinyl chloride sealant.

After filling the cavity 2 with the high viscosity substance 9 while leaving a space S in the cavity 2, the opening of the cavity 2 is covered with a flexible pressure sheet 10 made of two stacked urethane sheets, etc. It is held between the opening periphery and the die face plate 11. That is, the groove 3 is formed on the periphery of the opening of the cavity 2 as described above, and the groove 12 is also formed on the surface of the die face plate 11 facing the opening of the cavity 2, while the thick part is formed on the periphery of the pressure sheet 10. 13 is formed, and this thick part 13 is connected to the groove part 3,
Pressure sheet 1 by inserting it into 12
Hold 0.

After filling the die 1 with the highly viscous substance 9 leaving the space S as described above, the die 1 is placed in the third
As shown in the figure, the pressure sheet 10 is attached to the movable die base 14 so as to face downward, and the high viscosity substance 9 is pushed downward by its weight inside the cavity 2.
With the space S facing upward, press molding machine M
Configure.

That is, the press molding machine M consists of a die 1 and a punch 15 located below the cavity 2 of the die 1. The punch 15 is attached to a fixed die base 16, and the surface shape of the upper half of the punch 15 is shaped like the desired product shape. I am doing it.

A blank holder 17 is provided around the punch 15, and this blank holder 17 is supported by the upper ends of rods 18 and 18 which are urged upward by a spring or the like (not shown). The die face plate 19 is installed. This die face plate 19 is for holding the peripheral edge of a workpiece such as a metal plate between it and the die face plate 11.

A method of setting the final molding pressure in the molding machine configured as above will be described below.

First, the movable die base 14 is lowered from the state shown in FIG. 3, the punch 15 is relatively inserted into the cavity 2 of the die 1, and finally the movable die base 14 is moved to the bottom dead center position as shown in FIG. let it go down to

By the way, since the punch 15 enters the cavity 2 of the die 1 by the above operation, the volume inside the cavity 2 decreases and the pressure inside the cavity 2 increases. The final molding position is reached when the movable die base 14 descends to the bottom dead center position. In this case, the air in the space S is completely exhausted from the cavity 2, and the space S no longer exists within the cavity 2.

Therefore, in the present invention, between the time when the punch 15 relatively enters the cavity 2 and the punch 15 reaches the most advanced position (bottom dead center position),
The valve 7 of the discharge pipe 4 is opened and closed appropriately to discharge part of the air in the space S inside the cavity 2 to the outside of the cavity 2, and the final molding pressure is, for example, 200 kg/cm ²
After that, the rod 6 is advanced into or retreated from the cavity 2 to set the desired final molding pressure.

Once the final forming pressure is set as described above, a workpiece such as a metal plate is press-formed, and the procedure will be explained based on FIGS. 5 and 6.

First, as shown in FIG. 5, the movable die base 14 is raised and the die 1 is placed on standby above the punch 15. In this state, a workpiece W such as a metal plate is placed on the die face plate 19. do.

Next, as shown in FIG. 6, the movable die base 14
lower. Then, die face plate 1
The peripheral edge of the workpiece W is held between the lower surface of the die face plate 19 and the upper surface of the die face plate 19. When the movable die base 14 is further lowered, the blank holder 1
Since the rods 18, 18 supporting the blank holder 7 are biased by a spring or the like, the blank holder 1
7 is lowered, and along with this, the workpiece W is also lowered while being held between the die face plates 11 and 19. As a result of this descent, the upper end of the punch 15 forms the workpiece W and presses the presser sheet 10.
It enters into the cavity 2 through. Then, the highly viscous material 9 is deformed to follow the surface shape of the upper end of the punch 15, and the workpiece W is press-formed between the punch 15 and the pressure sheet 10, that is, punched by the back pressure of the highly viscous material 9. It is molded into a shape that matches the shape of No. 15. The molding pressure at this time is, for example, 200 kg/cm ² as described above.

Thereafter, the molded workpiece W is left on the punch 15, the movable die base 14 is raised, and when the die 1 is completely separated from the workpiece W, a cylinder unit (not shown) is operated, and the rod 1 is
The blank holder 17 is raised by activating the elastic force of the spring urging the parts 8 and 18 upward, and the workpiece W is released from the punch 15, and then the workpiece W is discharged from the molding machine M. .

FIG. 7 is a graph comparing the molding pressure setting method according to the present invention and the conventional molding setting method using hydraulic pressure forming. As can be seen from this figure, in press molding using hydraulic pressure, The pressure reaches close to the final forming pressure before the punch reaches the bottom dead center, making it impossible to form deep-drawn products with high precision.However, if the forming pressure is set using the method of the present invention, the pressure will reach close to the final forming pressure. Since the final molding pressure is reached at , the back pressure of the highly viscous material acts evenly on the entire surface of the workpiece, and even deep-drawn products can be made with high precision.

In the embodiment, the die 1 is fixed to the movable die base 14 and the punch 15 is fixed to the fixed die base 16, but the movable die base and the fixed die base may be replaced. In this case, the punch 15 will be moved up and down, so the final molding pressure will be the same as the punch 15.
It will be determined based on the top dead center of 5.

(Effects of the Invention) As explained above, according to the present invention, a space is left in the cavity of the die and a high viscosity substance is filled, and the high viscosity substance is sealed in the cavity with a flexible pressure sheet. However, when forming the workpiece between the pressure sheet and the punch, as a means of setting the final pressure for forming, the punch or die is moved relatively into the cavity of the die until the punch or die reaches the bottom dead center or Before the top dead center is reached, part of the air left in the cavity is exhausted to adjust the pressure inside the cavity, making it easy and accurate to set the final molding pressure. The molding itself can be performed with high precision, and compared to the case where the cavity is completely filled with a highly viscous substance such as silicone,
It is economical since only a small amount of the high viscosity substance is used, and the pressure adjustment is also simple since air can be removed without removing the high viscosity substance.

In the embodiment, when setting the final molding pressure, the air in the space S is completely exhausted from the cavity, but some space may be left in the cavity.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of the die, Fig. 2 is a longitudinal sectional view showing the cavity of the die filled with a highly viscous substance leaving a space, and Fig. 3 is a longitudinal sectional view of the press molding machine. Figure 4 is a longitudinal sectional view of the press molding machine with the die lowered to the bottom dead center and the final molding pressure set, and Figures 5 and 6 show the procedure for molding a workpiece with the press molding machine. FIG. 7, which is a longitudinal sectional view of the press molding machine, is a graph showing the relationship between die stroke and molding pressure. In the drawing, 1 is a die, 2 is a cavity, 4 is a discharge pipe, 5 is a pressure gauge, 6 is a pressure fine adjustment rod, and 7
1 is a valve, 9 is a high viscosity substance, 10 is a pressure sheet, 11 and 19 are die face plates, 14
1 is a movable die base, 15 is a punch, 16 is a fixed die base, S is a space, and W is a workpiece.

Claims (1)

[Claims] 1 Fill the molding cavity of a press molding die with a highly viscous substance such as silicone or vinyl chloride sealant via a flexible pressure sheet, leaving a space, and seal it, place a punch below the die, and then While the punch is relatively advanced into the cavity and reaches the position of the bottom dead center or top dead center where the punch has entered the most, part of the air in the space inside the cavity is discharged outside the cavity to increase the final molding pressure. A molding pressure setting method characterized in that the molding pressure is set.