JPH02108500A - Pneumatic die cushion device - Google Patents

Abstract

PURPOSE:To eliminate the need for a buffer tank of large capacity, etc., and to make the device small and light by forming a pneumatic die cushion device in a press mechanism of a closed cylinder and connecting the upper and the lower room of the cylinder through a check valve to control the difference of pressure between both rooms. CONSTITUTION:The die cushion device is composed of a cylinder device consisting of a cylinder 1 and a piston 2, a check valve and an on-off valve 20 and the upper 1U and the lower room 1L of the cylinder 1 are communicated through the check valve 10 and when the difference between the pressure in the upper room and that in the lower room reaches a specified value, the check valve is opened and when the piston 2 rises, the pressure Pu in the upper room 1U can be prevented from rising up, consequently, a large buffer tank, a compressor of high pressure and large capacity, a large quick exhaust valve, etc., which are used conventionally, are never required and the whole device can be made small and light.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a pneumatic die cushion device for a press.

[Prior Art] FIG. 4 shows a conventional pneumatic die cushion device. In the figure, 1 is an air cylinder separated by a piston 2 into an upper chamber IU and a lower chamber IL.

There is. The upper chamber IU is open to the atmosphere through an opening 5.

4 is a wear plate fixed to the upper end of the piston rod 3 and receives a cushion pin (not shown).

Further, 6 is a buffer tank which is connected to a lower chamber I via a connecting pipe 7.
It is connected to L.

In the die cushion device having such a configuration, the upper chamber IU is open to the atmosphere, so the upper chamber internal pressure PU is constant and equal to atmospheric pressure. Therefore, the ducting capacity F is determined from the lower chamber pressure PL and the cross-sectional area A1 of the piston 2 (F=PL
-AI), as the piston 2 descends, that is, as the volume of the lower chamber IL decreases, the pressure PL in the lower chamber increases, so the ducting capacity increases. On the other hand, the dictation capacity, that is, the appropriate wrinkle pressing force (F) necessary for press working, is determined based on the material of the material, etc., and therefore, excessive capacity is disadvantageous.

Here, conventionally, in order to increase the apparent volume of the lower chamber IL and suppress excessive fluctuations in the ducting capacity F, the lower chamber IL has a volume that is 5 to 8 times the volume of the cylinder 1. A buffer tank 6 is provided.

Therefore, as shown by the two-dot chain line in FIG. The necessary wrinkle pressing force FD is established at the same time as it starts to descend from the upper limit UL. After that,
It gradually increases as shown by the one-dot chain line in the figure. The ducting capacity when the piston 2 reaches the lower limit LL is FOe.

[Problems to be Solved by the Invention] As described above, the conventional duction device introduces a large-capacity buffer tank 6 to increase the apparent volume of the lower chamber IL, and attempts to stabilize the appropriate wrinkle pressing force. It was the composition.

Therefore, in today's world where presses are becoming larger, automation as seen in transfer presses, and high quality and productivity improvements are required, the following problems have become a problem.

- The installation space for the buffer tank 6 is large, which is not only uneconomical, but also limits the layout of other functional items as well as increasing the size of the press.

In particular, the influence is excessive in transfer presses and the like that have many molds.

■ It takes a long time to establish the initial pressure PLS or adjust the ducting capacity, resulting in a situation where the press cannot operate even though other initial conditions have been established in a short time. On the other hand, in order to establish a rapid initial pressure PLS, it is necessary to install a high-pressure, large-capacity compressor, which further disadvantages equipment economy and installation space.

In addition, when making adjustments to reduce the wrinkle holding force, it is necessary to install a large, rapid-acting exhaust valve, which also imposes a large economic burden.Moreover, a large amount of high-pressure air is released into the atmosphere or supplied for each adjustment. Therefore, the operational economy is also disadvantageous.

(2) Furthermore, even if the above-mentioned sacrifices (2) and (3) are accepted, it is impossible to make the capacity of the buffer tank 6 infinitely large. Therefore, as the piston 2 descends, the ducting capacity increases to varying degrees.

However, in today's world where ultimate high quality and cost reduction are required, it is no longer acceptable to increase or change the ductus capacity in the processing of many products.

The object of the present invention is to provide a simple structure, easy handling, low cost, small size and light weight, which can eliminate the conventional large capacity buffer tank, large compressor, rapid large exhaust valve, etc. and maintain a constant ductus capacity. The object of the present invention is to provide a pneumatic ductition device.

[Means for Solving the Problems] The present invention is constructed from a closed cylinder device, whereas the conventional device is composed of a cylinder device that is open to the atmosphere, and the ductus capacity of the closed cylinder device is equal to the lower chamber pressure and the upper chamber pressure. Based on the principle that the pressure is determined by the pressure difference between the chamber pressure and the indoor pressure, the lower chamber and upper chamber are communicated with each other and are designed to control the differential pressure.

Specifically, the lower chamber and upper chamber that sandwich the piston of the cylinder are opened when the pressure difference between the lower chamber pressure and the upper chamber pressure, which changes as the piston descends, exceeds a set differential pressure value. The pistons are characterized in that they are communicated through a stop valve and an on-off valve that prevents the pressure in the upper chamber from increasing when the piston moves upward.

[Function] In the present invention having the above configuration, when the piston descends from the upper limit due to a load, the pressure in the lower chamber increases and the pressure difference between the pressure in the lower chamber and the pressure in the upper chamber rapidly increases, and the ductus corresponds to the set differential pressure value. Competence is established.

Furthermore, when the piston attempts to descend, the pressure difference between the two chamber pressures becomes equal to or higher than the set differential pressure value, so the check valve opens and the upper chamber and the upper chamber are communicated with each other. Therefore, the pressure in the lower chamber is reduced and the differential pressure falls below the set differential pressure value, and at the same time the check valve closes.

Thereafter, as the piston descends, the check valve is repeatedly opened and closed, and the differential pressure between the two chamber pressures fluctuates within a minute range within the allowable range of the appropriate four-pressure force, but when the piston reaches the lower limit. The ductus ability can be maintained substantially constant until the end.

On the other hand, when the slide begins to rise, the piston rises from the lower limit toward the upper limit due to the differential pressure between the two chamber pressures. Along with this, the pressure in the upper chamber gradually increases, and when the pressures in both chambers become approximately equal, the on-off valve opens to communicate the upper chamber and the lower chamber. Therefore, the pressure in the upper chamber is prevented from increasing,
The pressures in both chambers become equal.

Even in this state, the piston moves upwards in a relatively smooth manner because the piston is pushed up due to the difference in effective area between the presence and absence of the piston rod (cross-sectional area).

Further, since residual pressure exists in the upper chamber, the piston reaches its upper limit without generating a large impact force.

Furthermore, by appropriately closing the on-off valve, the upper limit damper effect can be further strengthened.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is an overall configuration diagram, and FIG. 2 is a diagram for explaining the operation.

It should be noted that the same or common parts as those of the conventional duction device shown in FIG. 4 will be denoted by the same reference numerals, and the explanation thereof will be simplified or omitted.

As shown in FIG. 1, the duction device of the first embodiment is comprised of a cylinder device (cylinder 1, piston 2), a check valve 10, an on-off valve 20, and the like.

Pressurized air is supplied to the cylinder device via an air source 15 consisting of a small compressor, a pressure regulating valve 16, and a check valve 17. In the initial state where the piston 2 is at the upper limit UL, an initial pressure P[S is established in the lower chamber IL formed below across the piston 2 in the cylinder 1. is set. The movable stroke (ST) of the piston 2 is between the upper limit UL and the lower limit 11JiLL in the cylinder 1. Moreover, IU is an upper chamber formed on the upper side of the piston 2.

Therefore, if the cross-sectional area A2 of the piston rod 3 is ignored, the ducting capacity of this device consisting of a closed cylinder device is determined by the pressure difference between the lower chamber pressure PL and the upper chamber pressure Pu.

The check valve 10 is a means for communicating the lower chamber IL and the upper chamber IU, and the check valve 10 is a means for communicating the lower chamber IL and the upper chamber IU.
) reaches a set differential pressure value ΔS (for example, 3Kof/c+&). The check valve 10 is provided in the middle of a pipe 11 that connects both chambers IL and LU.

The check valve 10 of this embodiment is formed so that the magnitude of the ducting capacity can be changed to match the appropriate wrinkle pressing force.

That is, the check valve 10 receives the setting signal from the differential pressure setting device 12 and sets the set differential pressure value ΔS (for example, 2.8 Ko
f/a&, 3. OKQ f/d, 3°2! II f
/d, . . . ).

On the other hand, the on-off valve 20 is provided in the middle of a pipe 21 that communicates the upper chamber IU and the lower chamber IL, and is a means for communicating the upper chamber IU and the lower chamber IL in a timely manner. That is, this prevents the upper chamber pressure pu from increasing when the piston 2 moves up. It is closed when the piston 2 descends, and is opened at an appropriate time during the upward movement.

Here, high pressure in the present invention means that the upper chamber pressure Pu becomes higher than the lower chamber pressure PL, or when considering the cross-sectional area A2 of the piston rod 3, it means that the pressure in the upper chamber becomes higher than the pressure in the lower chamber PL, or when the cross-sectional area A2 of the piston rod 3 is taken into account, the pressure increases to a value at which the piston 2 cannot rise. This means that the indoor pressure Pu increases.

Specifically, as shown in FIG. 2, the opening/closing control means 22 in this embodiment, which is controlled to open and close by the opening/closing control means 22, lowers the lower chamber pressure PL as the piston 2 rises from the lower limit LL. , outputs an open signal to the on-off valve 20 when the upper chamber pressure Pu increases and both chamber pressures PL and Pu become approximately equal (lower chamber pressure PL is slightly higher);
Further, the closing signal is outputted immediately before the piston 2 reaches the upper limit UL.

Note that the output timing of the open signal may be determined from the viewpoint of regulating the rising speed of the piston 2, and the output timing of the open signal may be
), and it is preferable that the closing signal be output at any time within the range in which the piston 2 can reach the upper limit UL and at a timing that allows the upper limit damping effect to be made thicker.

Further, these timings are defined by the current position of the piston 2 (piston rod 3) detected by a position detector (not shown).

However, it may be configured to detect and define the upper chamber pressure Pu, the differential pressure between the lower chamber pressure PL and the upper chamber pressure, or the crankshaft angle.

In addition, the on-off valve 20. The opening/closing control means 22 is not limited to the above-mentioned structure, and may be constructed by, for example, a pilot check valve and the piping 21 etc. may be omitted.

Moreover, 19 is an exhaust valve used when reducing the wrinkle pressing force manually.

Next, the action will be explained.

When the piston 2 is at the upper limit UL, assuming that the cross-sectional area of the piston 2 is A1, the die cushion capacity F is determined by the following equation.

F=PL −AI −PU −(AI −A2) In this example, as shown in FIG. 2, at the upper limit UL, the upper chamber pressure PL and the lower chamber pressure Pu are equal, so the differential pressure Δ is based on the difference in effective area depending on the presence or absence of the cross-sectional area A2 of the piston rod 3.

In the conventional structure shown in FIG. 4, the upper chamber IU is open to the atmosphere, so the die cushion capacity gradually increases to Fpe at the lower limit LL, as shown by the dashed line in FIG. It is not possible to maintain the die cushion capacity Fp constant. At the lower limit LL, the wrinkle pressing force is 20~
This will be 25% excessive.

Here, in this embodiment, the T chamber IL is set in the differential pressure setting device 12 in advance.
By setting a differential pressure value ΔS for communicating between the upper chamber IU and the lower chamber IU, when the piston 2 is displaced downward, the lower chamber pressure PL increases and the differential pressure Δ between the upper chamber pressure Pu and the upper chamber pressure Pu increases. A predetermined die cushion capacity F1 can be established. When the differential pressure Δ becomes equal to the set differential pressure value ΔS, the check valve 10 opens and communicates the chambers LL and IU. the result,
The lower chamber pressure PL decreases, the upper chamber pressure Pu increases, the differential pressure Δ becomes smaller than the set differential pressure value ΔS, and the check valve 10 closes again. In this way, the check valve 10 is repeatedly opened and closed based on the differential pressure Δ until the piston 2 reaches the lower limit LL.

Therefore, although there are minute differential pressure fluctuations due to the opening and closing operations of the check valve 10, the die cushion capacity F1 remains constant in the band B.
controlled within.

The width of band B is within the allowable range of appropriate wrinkle pressing force. Note that the width of the band B can be selected by appropriately adjusting the check valve 10, the diameter of the pipe 10, the flow path resistance, etc. with respect to the volume of the cylinder 1.

Further, the die cushion capacity can be varied by setting the differential pressure value ΔS of the differential pressure setting device 12. When setting the capacity F2 shown in FIG. 2, the set differential pressure value ΔS may be set smaller than in the case of the capacity F1.

On the other hand, the raising operation of the piston 2 from the lower limit LL is initially adapted to the raising of the slide based on the pressure difference Δ between the two chamber pressures PL and PU, and thereafter is performed smoothly under no-load conditions. Since the lower chamber pressure PL becomes lower and the upper chamber pressure Pu becomes higher, the differential pressure Δ rapidly decreases.

Then, the on-off valve 20 is opened by a signal from the on-off control means 22, and both chambers IU and IL are communicated with each other.

Therefore, both chamber pressures PL and PU are equal, but
The piston 2 is further raised by the push-up blade generated based on the difference in effective area between the presence and absence of the cross-sectional area A2 of the piston rod 3.

Although the upper limit UL may be reached as is, in this embodiment, the on-off valve 20 is closed again just before the upper limit UL surface. Therefore, the upper chamber pressure PU increases slightly and the push-up blade of the piston 2 is rapidly lowered, so that the damper effect at the upper limit UL can be further enhanced.

It is also effective to configure and implement the on-off valve 20 so that it opens and closes again only momentarily when the piston 2 approaches the upper limit UL.

According to this embodiment, the pressure difference between the lower chamber IL and the upper chamber IU is PL, and the differential pressure Δ between the lower chamber IL and the upper chamber IU is the set differential pressure value Δ.
Since they are configured to communicate through a check valve 10 that opens when S is reached, the differential pressure between the upper chamber pressure Pu and the lower chamber pressure PL is constant, and the ductus capacity can be maintained constant during the press operation. Can be done.

In addition, it has a sealed structure in which the upper chamber IU and the lower chamber IL are communicated with each other by a check valve 10, a pipe 11, an on-off valve 20, and a pipe 21,
In addition, when the piston 2 descends, the air in the lower chamber IL is released into the upper chamber IU, so there is no need to provide an oversized buffer tank (6) in the conventional device, which is economical, saves installation space, and saves air. It is also very advantageous in terms of consumption.

In addition, the ductus capacity is achieved by adjusting the cracking pressure (differential pressure) of the check valve 11, so there is no need to provide a conventional high-pressure, large-capacity compressor or large exhaust valve, making it possible to significantly reduce the size and speed up the process. Able to accomplish coordination tasks. Therefore, the production time can be shortened and press production efficiency can be increased. Operational economy is also advantageous because large amounts of high-pressure air are not released into the atmosphere.

Furthermore, the upper chamber pressure Pu can remain near the upper limit UL of the piston 2, that is, the differential pressure can be reduced by appropriately closing the on-off valve 20, but the impact force at the upper limit UL can be reduced. can be significantly reduced.

Further, since the cracking pressure of the check valve 11 can be easily set and changed using the differential pressure setting device 12, the necessary wrinkle pressing force can be quickly and accurately established.

Moreover, since the wrinkle holding force is constant regardless of the downward displacement of the piston 2, the inconvenience of causing wrinkles or damage to the flange can be avoided, and it is possible to stably produce high-quality products. .

Furthermore, although the opening/closing valve 20 is configured to be opened/closed as appropriate by the opening/closing control means 22, it is possible to operate it by setting the return speed of the piston 2 to the upper limit UL, the upper limit damping effect, etc. to desired characteristics. can.

(Second Embodiment) As shown in FIG. 3, this embodiment has a check valve 10 in which the cracking pressure can be set and changed using a differential pressure setting device 12 in the first embodiment. A switching valve 13 consisting of check valves 10 (10A, IOB, TOC) with different king pressures arranged in parallel and correspondingly arranged solenoid valves.
(13A, 13B, 13C) is configured to select one check valve by switching the selection switching means 14. The rest of the configuration is the same as that of the first embodiment, so a description thereof will be omitted.

Therefore, in addition to producing the same functions and effects as in the first embodiment, since the cracking pressure of each check valve 11 is constant, the ducting capacity can be set even more accurately, and the switching valve only needs to be opened and closed. Settings can be changed even more quickly.

In addition, in the above embodiment, a completely sealed cylinder device (
It consisted of cylinder 1, piston 2), but the third
As shown by the two-dot chain line in the figure, this can also be implemented by providing a release valve 25 that temporarily opens the upper chamber IU to the atmosphere at an appropriate time. For example, if the opening/closing control means 22 opens the piston 2 only at the moment when it descends from the upper limit UL, the set traction capacity [F] is reached.

(F2)] can be started up rapidly, etc.
It becomes possible to further promote the action and effect of the present invention.

Of course, in the case of a special press or the like in which there is no need to change or adjust the ductus capacity, there is no need for the check valve 10 to be of the variable cracking pressure type, and the present invention is also applicable to this case.

[Effects of the Invention] The present invention communicates the upper and lower chambers of a cylinder via a check valve, opens the check valve when the pressure difference between the upper and lower chambers reaches a set differential pressure value, and opens and closes the check valve when the piston rises. Since the valve prevents the pressure in the upper chamber from increasing, it eliminates the need for conventional large buffer tanks, high-pressure large-capacity compressors, large rapid-acting exhaust valves, etc. It is small and lightweight, has low operating costs, and maintains a constant ductus capacity. We can provide a pneumatic ductition device that can.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing the first embodiment of the present invention, Fig. 2 is a diagram for explaining the operation in comparison with the operation of the same (conventional structure), and Fig. 3 is an overall diagram showing the second embodiment. The configuration diagram and FIG. 4 are overall configuration diagrams of a conventional duction device. 1...Cylinder, IU...Upper chamber, IL...Lower chamber,
2...Piston, 10...Check valve, 11...Piping, 20...Opening/closing valve, 21...Piping.

Claims (1)

[Claims] (1) A check valve that opens the lower and upper chambers that sandwich the piston of the cylinder when the differential pressure between the lower chamber pressure and the upper chamber pressure, which changes as the piston descends, exceeds a set differential pressure value. 1. A pneumatic die cushion device, characterized in that the pneumatic die cushion device is connected through an on-off valve that prevents the pressure in the upper chamber from increasing when the piston moves upward.