JPH0634019Y2 - Die cushion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a pneumatic die cushion for a press machine.

[Prior Art] A pneumatic die cushion is known as one of the means for generating a wrinkle holding pressure required when performing drawing with a press.

A conventional pneumatic die cushion is formed of a cylinder, a first piston, and a piston rod that connects the first piston and a mold, and a cushion pressure is obtained by applying a predetermined air pressure to the first piston. ing.

[Problems to be Solved by the Invention] However, since such a conventional pneumatic die cushion has a structure for achieving only the original purpose of generating wrinkle holding pressure, it has the following problems. Was.

That is, when the die cushion is drawn, for example, when a cup-shaped product is drawn, compressive stress in the circumferential direction is generated in the flange portion as the working progresses, and wrinkles occur if left unattended. It is intended to hold down. Therefore, it can be said that it is not necessary at the time when the upper die and the lower die (the concept including a blank holder in the present invention; the same applies hereinafter) and at a certain period thereafter.

However, according to the conventional die cushion, cushion pressure is applied from the moment when the upper die and the lower die abut. That is,
Upper mold. This means that heavy metal objects such as the lower mold are colliding with each other at the slide descending speed. For this reason, there is a problem that vibration and noise are severe and it is not preferable from the viewpoint of equipment life.

The present invention solves the above-mentioned problems by using the upper mold. (EN) A die cushion capable of generating a predetermined cushion pressure while reducing a collision force when a lower die is in contact.

[Means for Solving Problems] The present invention focuses on the structure of a conventional die cushion, and absorbs and alleviates a collision force by a skillful construction of incorporating a second piston that can be relatively displaced within a predetermined range. It is formed so that it can be done.

That is, in a die cushion formed of a cylinder, a first piston, and a piston rod that connects the first piston and a mold, the die cushion is fitted to the piston rod and is opposed to the first piston within a predetermined range. A movable second piston is provided, and the first piston is vertically movable within the predetermined range with respect to the second piston. One end of the first piston and the second piston is a second piston. It is characterized in that a flow path is provided that connects the upper surface side and the lower surface side of the first piston by connecting with a pin that is fixed.

[Operation] In the present invention having such a configuration, the piston rod and the first piston descend together with the slide in the cylinder immediately after the upper mold and the lower mold are brought into contact with each other. However, since the pressure fluid escapes to the second piston side through the flow path, the desired cushion pressure is not directly applied to the upper die or the like, and their collision force is absorbed and relaxed by the flow of the pressure fluid. After that, the desired cushion pressure is established.

[Embodiment] An embodiment of the die cushion according to the present invention will be described below in detail with reference to the drawings.

In FIG. 2, which is a schematic view of a press machine incorporating this die cushion, in the press machine 1, an upper mold 3 is attached to a slide 2 that is raised and lowered by a crankshaft, and a lower mold is attached to a bolster 8 bolted to a bed 9. 4 is attached and the die cushion is stored in the bed.

The die cushion mechanism includes a blank holder 5 (which forms a part of the lower die in this embodiment) for holding a blank fitted in the lower die 4, a cylinder device 11, a cylinder device 11, and a blank holder. 5 and a plurality of cushion pins 6 that connect the two. Cushion pin 6
Passes through the bolster 8 slidably and through the pad 7
Is connected to the pistons 22, 22 of.

The cylinder device 11 consists of a pair of left and right die cushions 10.
And is formed of a cylinder 12, a first piston 22, and a piston rod 19 directly connected to the first piston 22.

Here, a characteristic technical matter of the present invention is that the second piston 32 and the flow passage 39 are provided as shown in FIG.

In FIG. 1 (the left and right cross-sectional positions are different about the axis), the cylinder 12 is a hollow cylindrical body, and the piston rod 19 is penetrated through the upper plate 13 via a seal member 14 so as to be slidable in the axial direction. The lower plate 15 has a pipe 16 communicating with the tank 17.
Is provided.

The first piston 22 is fixed to the lower end of the piston rod 19 and slidably contacts the inner surface of the cylinder 12 via a seal member 23.

On the other hand, the second piston 32 slidably contacts the inner surface of the cylinder 12 via the seal member 33 similarly to the first piston 22, and has a piston rod in the hole 34 provided in the central portion.
19 is fitted.

That is, the second piston 32 is fitted on the piston rod 19 and is attached to the piston rod 19 so as to be movable in the axial direction. Reference numeral 35 is a seal member.

Here, the first piston 22 and the second piston 32 are connected by a pin 42 so as to be relatively displaceable in the axial direction.

A male screw 46 that engages with a female screw 36 provided on the second piston 32 is engraved at the tip (one end) of the pin 42, and a collar 43 is fixed to the base end. Further, the outer diameter D of the pin 42 is slightly smaller than the inner diameter of the through hole 24 formed in the first piston 22. Therefore, if the end of the pin 42 is threaded through the through hole 242 and the screws 36 and 46 are screwed together and the pin 42 is mounted and one end of the pin 42 is fixed to the second piston 32, the second piston 32 will have the length of the pin 42. It becomes possible to make relative displacement with respect to the first piston 22 within a predetermined range regulated by. The predetermined range is the dimension a shown in FIG. 1, and this dimension a is the upper surface 4U of the lower mold 4 shown in FIG.
Is equal to the dimension b of the upper surface U of the blank holder 5.

In addition, the first piston 22 is provided with a flow path 39 for circulating the air in the cylinder 12.

13L is the lower surface of the upper plate 13, 32U and 32L are the upper and lower surfaces of the second piston 32, and 22U and 22L are the upper and lower surfaces of the first piston 22.

Next, the operation will be described.

It is assumed that the slide 2 is at the top dead center as shown in FIG. In this case, both the first piston 22 and the second piston 32 are close to the lower surface 13L of the upper plate 13.
Due to the difference in area of the piston rod 19, the first piston 22
Is pushed up by air pressure.

Here, when the slide 2 descends from the state shown in FIG. 2 and the upper die 3 contacts the upper surface 5U of the blank holder 5 via the blank W, the first piston 22 descends together with the cushion 6 and the piston rod 19. To do. At the moment of this contact, the push-up force by pneumatic pressure is only the area difference.
Therefore, the impact of the abutment is only due to the impact of the lower die, the piston rod 19, the first piston 22, etc., and the cushion lifting force does not act. At the beginning of the descent, the air in the cylinder 12 passes through the flow path 39 until the state shown in FIG. 3 (A) to FIG. 3 (B) is reached, and the lower surface 32L of the second piston 32 and the upper surface of the first piston 22. It flows into the space C formed between 22U.

Therefore, the total air pressure in the cylinder 12 is
It does not join the lower surface 22L of 22. That is, the collision force between the upper mold 3 and the blank holder 5 (lower mold 4) can be absorbed and relaxed. The degree of absorption relaxation depends on the outer diameter of the first piston 22 (the lower surface 22
It is determined by the ratio of the area of L) and the cross-sectional area of the flow channel 39.

Then, when the drawing process starts, the first piston 22 is displaced by the dimension a with respect to the second piston 32, so that the slide 2 descends and the drawing process progresses as shown in FIG. 3 (B). As shown in FIG. 3 (C), the second piston 32 descends together with the first piston 22 via the pin 42.

Therefore, the original purpose of preventing wrinkles from occurring in the die cushion due to the cushion pressure applied as the processing starts can be achieved.

On the other hand, when the slide 2 rises from the bottom dead center toward the top dead center, the piston rod 19 and the first piston 22 move to the third position.
While rising from the state shown in FIG. 3C to the state shown in FIG.
The second piston 32 rises together with the first piston 22 while maintaining a space substantially equal to the dimension a of the first piston 22 by the action of the air pressure in the gap C.

Then, after the upper surface 32U of the second piston 32 is brought into contact with the lower surface 13L of the cylinder 12, the air in the gap C passes through the flow path 39 as the first piston 22 rises and the inside of the cylinder 12 on the lower side in FIG. Is discharged to. That is, the collision force of the first piston 22, the cylinder 12 or the pad 7 and the bolster 8 in the ascending limit can be absorbed and eased even when ascending.

Therefore, according to this embodiment, the second piston 32 which is movable relative to the first piston 22 is provided, and the gap C between the two pistons 22 and 32 communicates with the inside of the cylinder 12. Is provided so that the pressure in the cylinder 12 is released into the gap C when the first piston 22 descends, and thereafter the pressure in the cylinder is entirely applied to the first piston 22. When the blank holder 5 and the lower die 4 are brought into contact with each other and immediately thereafter, a predetermined cushion pressure does not act, and the collision force thereof is absorbed and relaxed, so that vibration and noise can be significantly reduced. This lowers the maximum value of the repeated load, so that the life of the press machine as a whole is extended and stable operation can be guaranteed.

Further, since the air in the cylinder 12 is made to flow through the flow passage 39 provided in the first piston 22 to absorb the collision force, even if the cylinder internal air pressure is changed to adjust the cushion pressure, the cushion pressure is not changed. The corresponding collision force can be absorbed.

Further, the degree of absorption and relaxation of the collision force can be adjusted by changing the cross-sectional area ratio of the first piston 22 and the flow passage 39, and the range thereof is also the length of the pin 42 connecting both pistons 22 and 32. Since it can be adjusted, it has a very wide range of application.

In the above embodiment, the flow path 39 is formed by the hole formed in the first piston 22, but the point is that the upper surface 22U side and the lower surface 22L side of the first piston 22 fixed to the piston rod 19 are formed. As shown in FIG. 4, for example, the diameter of the first piston 22 is made smaller than the inner diameter of the cylinder 12 to form a gap between the cylinder 12 and the first piston 22. Can be implemented as

Further, the length of the channel 39 and the pin 42 may be variable.

[Effects of the Invention] As is apparent from the above description, the present invention is provided with the second piston movable relative to the first piston, and the flow path that bypasses the first piston, and the inside of the cylinder is passed through the flow path. Since it is configured to flow the pressure fluid, it can absorb and mitigate the collision force at the time of contacting the mold to significantly reduce vibration and noise, and can exert a predetermined cushion force during machining, which is of high practical value. Can provide die cushion.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an essential part showing an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view showing a case where the same is incorporated in a press machine, and FIG. 3 is a view for explaining the operation, And FIG. 4 is a vertical cross-sectional view of a main part showing another modification. 10 …… Die cushion, 11 …… Cylinder, 19 …… Piston rod, 22 …… First piston, 32 …… Second piston, 39 …… Flow path, 42 …… Pin.

Claims (1)

[Scope of utility model registration request] 1. A cylinder, a first piston and the first piston.
In a die cushion formed from a piston rod connecting a piston and a die, a second piston fitted to the piston rod and movable relative to the first piston within a predetermined range is provided,
The first piston and the second piston are connected to each other with a pin having one end fixed to the second piston so that the first piston can move up and down within the predetermined range with respect to the second piston; 1. A die cushion, characterized in that a flow path that connects the upper surface side and the lower surface side of the first piston is provided.