JPH0332500A - Hydraulic overload preventing device - Google Patents

Abstract

PURPOSE:To make set hydraulic pressure constant so that set rupture hydraulic pressure can be set variably and to contrive the enlargement of an application range, etc., by constituting the subject device so that after a relief valve is opened once, said valve is not closed again until hydraulic pressure drops to the set rupture hydraulic pressure or below. CONSTITUTION:A relief valve 20 consisting of a cylinder body having plural ports and a piston body 31 in which a valve part, etc., are formed integrally is allowed to communicate with a body cylinder chamber 5. Also, a seal area of a first port 22 and the valve part is formed to the same as a seal area of a fourth port 25 and a small diameter part 35. Moreover a ratio of the effective diameter of a valve part 32 and the diameter of a middle diameter part 33 is determined in advance to such a value as the valve part 32 does not seal a first port 22 until hydraulic pressure in the cylinder chamber 5 becomes smaller than set rupture hydraulic pressure based on set pressure of pressurized air after a first port 22 and a second port 23 communicate with each other once. In such a way, the set rupture hydraulic pressure can be set variably, and a hydraulic overload preventing device which can attain a slight mechanical deformation, facilitation for handling, etc., can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic overload prevention device for a press. In particular, it is configured so that the set oil pressure is kept constant and overload can be prevented [the metal seal part opens (@cut)] with an arbitrary press load.

[Prior Art] In a press, a hydraulic overload prevention device is provided between a slide and a connecting rod that communicates with a crankshaft.

As a typical structure of such a hydraulic overload prevention device, the third structure is
The metal seal method shown in the figure and the packing seal method shown in FIG. 5 are known.

In the metal seal method, a metal seal portion 4 is formed between a piston 2 communicating with a point portion l and a cylinder 3 into which the piston 2 is fitted. Then, a set oil pressure (for example, Ps in FIG. 4) is established in the cylinder chamber 5 by the pump 6.

At this time, the piston 2 and cylinder 3 are mechanically deformed by the hydraulic pressure in the cylinder chamber 5. As shown in Fig. 4, when the press load increases, the oil in the cylinder chamber 5 is compressed, and the oil pressure in the cylinder chamber 5 increases from Ps toward Po, and when the press load reaches Lb, the oil pressure in the cylinder chamber 5 becomes p
b, the metal seal portion 4 opens (breaks) and the oil in the cylinder chamber 5 escapes to the tank 8 via the oil drain system 7. Therefore, relative movement between the piston 2 and the cylinder 3 is allowed, and overload that may cause damage to the mold or the like can be prevented.

On the other hand, the packing seal method, as shown in Figure 5,
The piston 2 and cylinder 3 are sealed with a gasket 9 such as an O-ring, and the oil pressure in the cylinder chamber 5 is set to Ps. At this time, the piston 2 and cylinder 3 are mechanically deformed by the hydraulic pressure in the cylinder chamber 5, similar to the metal seal system. Cylinder chamber 5 is 1'F in response to increase in press load.
The oil is compressed and the hydraulic pressure rises. When the press load becomes a<Lb as shown in FIG. 6 and reaches the relief setting oil pressure Po of the relief valve 10, the relief valve 10 is opened and overload can be prevented. The relief setting oil pressure Po is set by setting the biasing force of the spring 11.

[Problem to be solved by the invention] By the way, all of the conventional structures described above have the following drawbacks, and there is a strong demand for diversification and high precision in pressing various products in small quantities. It is no longer possible to meet the current demands of the government.

■Metal seal system As shown in Figure 4, when the set overload prevention load t [the press load that causes the metal seal to open (break)] is Lb,
The set oil pressure is Ps, which is lower than the breaking oil pressure pb by the extraction pressure increase portion ΔP of the cylinder chamber 5 due to an increase in press load. Therefore, if the breaking load is set to nl or Lb depending on the mold used, it may be necessary to change the set oil pressure to Ps.

Therefore, by changing the set oil pressure, the mechanical deformation of the cylinder 3 and piston 2 (particularly the first part of the piston) changes, and the bottom dead center position changes. In addition, since the gap between the point portions 1 is increased, the machining accuracy is deteriorated, and the press circle Ht
make driving difficult.

This results in shorter lifespans of molds and presses. Therefore, the set oil pressure Ps cannot be made very low, and the range of application is narrow.

Furthermore, when changing the set extraction pressure Ps from high pressure to low pressure, it is necessary to drain the hydraulic pressure in the -degree cylinder chamber 5 to the tank 8, which makes the setting work cumbersome and reduces production efficiency.

■ Packing seal method In this method, the relief setting oil pressure pb can be set arbitrarily and easily by adjusting the biasing force P+ (relief opening pressure P, o) of the spring 11, but the
The relationship between the set oil pressure Ps and the relief oil pressure pb regarding the oil pressure increase ΔP at' is the same as that of the metal seal system. When the set oil pressure Ps is constant, the relief pressure Po of the relief valve 10 can only be set lower than the set oil pressure Ps as shown in FIG. 6, so the relief pressure Po that can be set is in the range from pb to Ps. . When the set relief pressure is set to Po', the press load is L
When the pressure increases to b', the relief valve is opened and the oil pressure becomes P.
However, the spring 11 keeps the oil pressure at pb", and the load on the piston 2 is Lb".
Therefore, a load larger than the set load Lb' is applied to the mold.

Also, in this method, as with the metal seal method, by changing the set pressure to Ps' and the relief set pressure to PO'', it is possible to prevent the load from increasing after the relief is opened, but both the set pressure and the relief pressure Further, when the set pressure is changed, the mechanical deformation changes, similar to the metal seal method, and the bottom dead center and the gap between the points change.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hydraulic overload prevention device that can set the breaking oil pressure variably while keeping the set oil pressure constant, thereby expanding the range of application, minimizing changes in mechanical deformation, and facilitating handling. It's about doing.

[Means for Solving the Problems] The present invention has a clever structure that has the advantages of both the conventional metal seal system and the Para-Jin seal system equipped with a relief valve, so that the set rupture oil pressure can be arbitrarily set regardless of the set oil pressure. Once the relief valve is opened, the relief valve is not closed again until the oil pressure inside the cylinder falls below the set breakage oil pressure based on the set pressurized air pressure.

That is, a first port that communicates with the cylinder chamber of the metal seal type main body, a second port that forms a part of an oil drainage path that can communicate with this first port, and pressurized air that sets the set rupture oil pressure are supplied. a cylinder body having a third port connected to the first port via a check valve; a valve portion sealing the first port; a medium diameter portion housed in the second port; A relief valve is provided that includes a piston body in which a piston accommodated in three ports and a small diameter portion accommodated in a fourth port are integrally formed, and the sealing area between the first port and the valve portion and the fourth port are The sealing area with the small diameter part should be the same, and the ratio of the effective diameter of the valve part to the diameter of the middle diameter part should be set to either bleed pressure or pressurized air in the cylinder chamber once the first and second ports communicate. It is characterized in that the value is determined so that the valve portion does not seal the first port until the hydraulic pressure becomes lower than a set breakage oil pressure based on the pressure.

[Function] In the present invention, pressurized air is supplied to the third port of the relief valve, the first port is closed by the valve part, and the inside of the cylinder chamber, the first port, and the fourth port of the metal seal type main body is closed. Establish the set extraction pressure by the pump.

Here, the sealing area between the first port and the valve part and the sealing area between the fourth port and the small diameter part are assumed to be the same, and the internal pressures of the first port and the fourth port are assumed to be the same. The pressing force of the piston body for closing the first port is determined by the pressure receiving area of the third port and the set pressure of pressurized air.

Then, when the press load increases, the extraction pressure in the cylinder chamber increases to 1.
The bending pressure starts to rise from the set bending pressure. When this extraction pressure in the cylinder reaches a predetermined value, that is, the set breaking oil pressure (set by the pressure of the pressurized air), the oil pressure in the first port increases, so the pressing force of the piston body based on the pressurized air pressure increases. The valve portion opens the first port against this. Then, the oil pressure in the cylinder chamber (the oil pressure in the first port) gradually decreases due to the drainage action through the second port and the drainage passage.

At this time, the first
Once the port is opened, that is, once the first port and the second port are communicated, hunting (repetitive opening and closing of the first port) will not occur until the cylinder indoor hydraulic pressure becomes equal to or lower than the set rupture hydraulic pressure based on the set air pressure. The first port is not closed.

Therefore, the oil pressure in the fourth port also decreases because the oil is drained through the check valve, the first port, the second port, and the like. Here, even if the metal seal breaks and the first port is subsequently closed by the set air pressure, the oil pressure in the cylinder chamber will be released to the tank via the oil drainage system until it reaches almost zero value, preventing overload. .

Therefore, by adjusting the supply pressure of pressurized air to the third port as appropriate, the breaking pressure can be set to any pressure between the set hydraulic pressure and the conventional breaking extraction pressure of the metal seal type, while keeping the set bending pressure constant. i! The Ji extraction pressure can be determined, the pressure difference between the set oil pressure and the rupture extraction pressure is small, and mechanical deformation is also slight.

Further, since the cylinder chamber hydraulic pressure can be lowered to below the set hydraulic pressure, it is possible to set a low pressure.

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

As shown in FIG. 1, the hydraulic overload prevention device of this press has the same main body as the conventional metal seal system shown in FIG. or are communicated.

Here, the relief valve 20 sets a set breaking extraction pressure (breaking load) by adjusting the pressurized air pressure, and once the set breaking extraction pressure is reached and the relief valve 20 is opened, the pressure is set based on the hydraulic pressure in the cylinder chamber 5 or the set air pressure. It is formed so that it will not close again unless the oil pressure drops below the set rupture oil pressure.

This relief valve 201, first port 22, second port 23. Third port 24. The cylinder body 21 having the fourth port 25 and the left side +l in FIG. 1! II to 1st port 2
2. Valve portion 32. Medium diameter portion 33 accommodated within the second port 23. Piston 3t1. accommodated in the third port 211. It consists of a small diameter portion 35 accommodated in the fourth port 25 and a piston body 31 integrally arranged in this order.

First, the sealing area A1 between the first port 22 and the valve part 32 is the product of the extraction pressure in the first port 22 (cylinder chamber 5), the pushing force in the direction of arrow X1 in FIG. 1, and the receiving pressure of the piston 34. It is determined to balance the pressing force in the direction of arrow X2 in FIG. 1, which is the product of the area and the pressurized air pressure into the third port 24.

The seal area A1 is determined by the effective diameter dl of the valve portion 32. Therefore, the value of the oil pressure in the cylinder chamber 5 when the piston body 31 moves in the direction of the arrow X1 to open the first port 22 depends on the pressure of the pressurized air supplied to the third port 24. 1 can be set. That is, the set breaking oil pressure (Pb) can be arbitrarily set by setting the supply air pressure.

Thus, in this configuration, a common air source 42 (e.g. two
~5 kg/cm) to rupture hydraulic pressure or 20
5 since it is 0 to 300 kg/cm2
The piston 34 must have an excessively large diameter, making it extremely difficult to put it into practical use.

Here, in the present invention, a small diameter portion 35 that fits into the fourth port 25 is provided on the opposite side of the valve portion 32 of the piston body 31, and the sealing area of the fourth port 25 is set to A1, which is the same as the sealing area of the first port 22. It is said that In other words, the effective diameter of the valve portion 32 and the diameter of the small diameter portion 35 are set to be the same d.

Therefore, the inside of the cylinder chamber 5 is pumped by the pump 6.

If the set extraction pressure Ps shown in FIG. 2 is established in the first port 22 and the fourth port 25, the extraction pressure in the cylinder chamber 5 (first port 22) will increase as the press load increases, and the arrow Xt Jr. When the suppression force in the direction of arrow X2/J- based on the pressurized air pressure is overcome, the valve portion 32
or move in the direction of arrow X1 at the first port 222
or be released. Then, the hydraulic pressure in the cylinder chamber 5 is released to the tank 8 through the first port 22 and the drain oil passage 27 (the second port 23 also forms a part of the jJF oil passage).

However, with this structure, like the conventional relief valve 10, the oil pressure in the cylinder chamber 5 cannot be lowered below the set extraction pressure PS, and the rupture characteristics of the metal seal system cannot be effectively exhibited.

Furthermore, the pressure of the pressurized air causes the valve portion 32 to close the first port 22 again within a short period of time, causing opening/closing hunting.

Here, the most characteristic feature of the present invention is that once the first port 22 is opened, the hydraulic pressure in the cylinder chamber 5 must be lower by an appropriate value than the set rupture hydraulic pressure based on the set pressurized air pressure. In order to prevent the first port 22 from being closed again, that is, to reduce the internal pressure of the cylinder chamber 5 to the rupture pressure or less, the intermediate diameter portion 33 has a diameter d2 larger than the effective diameter dl of the valve portion 32. A second port 23 having a larger diameter than the first port 22 that accommodates the second port 22 is provided. That is, it is formed so that, once the first port 22 is opened, a pressing force in the direction of arrow X1 is generated, which is determined as the product of the extraction pressure inside the first port 22 and the cross-sectional area A2 of the middle diameter portion 33 having the diameter d2. There is. Therefore, the first port 22 can be kept open against the pressing force in the direction of arrow X2, which is the sum of the set pressure of the pressurized air and the pressure receiving surface of the piston 34. The ratio between the diameters dl and d2 can be arbitrarily selected by taking into consideration the structure and responsiveness of the metal seal portion 4.

Furthermore, in this embodiment, in order to reduce the pressing force in the direction of arrow X2 at this time, the hole in the fourth port 25 is
6 through the first and second ports 22, 23, and the drain passage 2.
It is assumed that the water is released to tank 8 through route 7.

In addition, 40 is a pressure setting means for pressurized air, and the air source 4
2. It is formed from a pressure regulating valve 41'W. Also, 5
Reference numeral 1 denotes a sliding ring for setting the piston body 31 to the force position t. Therefore, in order to set the set breaking pressure, it is necessary to increase the set air pressure to the third port 24 by one minute of the biasing force of the spring 51. However, this spring 51 may be excluded.

Next, the effect will be explained.

(Setting the set oil pressure) First, a small air pressure is supplied to the third port 24 by the pressure regulating valve 41, and the first port 22 is closed by the valve portion 32.

Then, the pump 6 is started, and the cylinder chamber 5 of the main body. The first port 22 and the fourth port 25 of the relief valve 20
Set the extraction pressure Ps shown in FIG. 2 to .

Here, pressing forces of the same pressure and in opposite directions are applied to the piston body 31 from the first port 22 and the fourth port 25, so that the piston body 31 is dynamically balanced.

Therefore, the pressure A regulating valve 41 is operated again to supply pressurized air at a set pressure Pa such that the first port 22 is opened when the set breaking oil pressure Pb (breaking load Lb) shown in FIG. 2 is reached. Add to 3 port 24.

In other words, the pressure of pressurized air to the third port is P in Fig. 2.
By setting a, the set breaking pressure Pb(
It is understood that the breaking load Lb) can be set.

(Normal press operation) Although the oil pressure in the cylinder chamber 5 increases as the press load increases, it does not reach the set breaking oil pressure pb, so the relief valve 20 is never opened.

(4 overload occurs) Press load increases due to mold jamming, etc., resulting in 4 overload. In other words, when the oil pressure in the cylinder chamber 5 (first port 22) reaches the set breaking oil pressure pb as shown in FIG. Arrow X1 based on the product of the oil pressure inside the first port 22 and the sealing area A (according to the effective diameter dl) of the valve part 32
Since the pressing force in the direction increases, the first port 222 opens.

At the same time as opening, the first port 22 and the second port 23 communicate with each other, so the piston body 31 has the second port 23
First port 22) internal extraction pressure and cross-sectional area A2 (
Due to the diameter d2), a large pressure in the direction of arrow X1 is generated, so the set air pressure P in the third port 24
Even if the oil pressure in the cylinder chamber 5 slightly decreases, the first port 22 will not be closed even if the oil pressure a is approximately constant.

Therefore, the water inside the cylinder chamber 5 is released into the tank 8 through the first and second ports 22, 23 and the υ1 oil passage 27. Therefore, the oil pressure in the cylinder chamber 5 is
As shown in Figure 1, the Pb' concentration decreases. At this time, the bolt of the 11th port 25 is also released to the tank 8 through the check valve 26 and the like.

Then, whether it is the pressure inside the cylinder chamber 5 or the press load weight is Lb (
When the breaking load (breaking load) later decreases to Pb', the metal seal portion 4 breaks, and the oil in the cylinder chamber 5 is rapidly returned to the tank 8 through the oil drain system 7.

Here, the press load does not become larger than the set breaking load Lb, and overload is prevented.

At this stage, the cylinder chamber 5. 1st port 22.
Since the oil pressure in the fourth port 25 becomes almost zero, the first port 22 is closed by the pressing force in the direction of the arrow X2 by the set pressurized air Pa. That is, the relief valve 20 returns to its initial state.

(Setting change) In FIG. 2, in order to set the breaking load to Lb2, the pressure of the supplied pressurized air may be set to Pa2.

Then, the first port 22 opens when the hydraulic pressure inside the first port 22 reaches the set breaking hydraulic pressure Pb2. The oil pressure drops to Pb2' and the metal seal portion 4 is broken.

On the other hand, when using a sophisticated mold with relatively low strength, the pressurized air pressure may be set to Pa when applying a breaking load to bl.

Then, the relief valve 20 operates at the set breaking oil pressure P b
When the pressure is +, the pressure is opened, and the pressure drops to Pb1', which is lower than the set pressure Ps, and the metal seal portion 4 breaks under the press load (Lb, ).

According to this embodiment, the first to fourth ports 22
Cylinder body 21 having ~25 and -J+' portion etc. 32~3
A relief valve 20 consisting of a piston body 31 integrally provided with a piston body 5 is communicated with the main body cylinder chamber 5, and the valve part 3
Once the first port 22 and the second port 23 are communicated, the oil pressure in the cylinder chamber 5 is set to the set pressure (a) of the pressurized air. The valve part 32 until the value becomes smaller than the set breakage oil pressure (Pb) based on
Since the configuration is such that the first port 22 is determined to a value that does not close or seal the first port 22, the set rupture oil pressure (Pb) is set between the set IF (PS) and the rupture extraction pressure (PO) of the conventional metal seal method. It is possible to set a low pressure, and high-precision press processing can be performed while keeping the die-hide constant by setting the gap at the point. Therefore, it can respond to diversification.

Moreover, since the set breaking oil pressure (Pb) only needs to be set by the pressurized air pressure (Pa) to the third port 24, setting work and setting changes are extremely easy and have wide applicability.

At the same time, since the second port 25 that exerts a counterforce to the first port 22 is provided and the sealing areas thereof are the same (A1), the piston 34 (relief valve 20) can be downsized.

Furthermore, although the relief valve (20) type is used, the extraction pressure in the cylinder chamber 5 can be made lower than the rupture oil pressure, so that the characteristics of the metal seal system can be fully exhibited.

[Effects of the Invention] As is clear from the above description, the present invention allows a relief valve consisting of a cylinder body having a plurality of ports and a piston body in which a valve portion, etc. In addition to applying a balance of hydraulic pressure to the body, once the relief valve is opened, the set hydraulic pressure is cut off based on the set air pressure.It is configured so that the relief valve will not close again unless the main hydraulic pressure becomes a small value, but the set hydraulic pressure is set as a constant. It is possible to provide a hydraulic overload prevention device that can set the rupture hydraulic pressure to a different value, expand the range of application, and achieve a slight change in R mechanical deformation, which is easy to handle.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining the operation, FIGS. 3 to 6 show a conventional hydraulic overload prevention device, and FIG. The figure is a schematic diagram of the metal seal system, Figure 4 is a diagram for explaining the operation of the metal seal system, Figure 5 is a schematic diagram of the seal seal system, and Figure 6 is a diagram for explaining the operation of the seal seal system. It is a diagram. DESCRIPTION OF SYMBOLS 1... Piston of main body, 3... Cylinder of main body, 5... Cylinder chamber, 6... Pump, 20... Relief valve, 21... Cylinder body, 22... First port , 23... Second port, 24... Third port, 25... Fourth port, 26... Check valve, 27... Oil drain path, 31... Piston body, 32... ...Valve part, 33...Medium diameter part, 34...Piston, 35...Small diameter part, 40...Pressure setting means for pressurized air, 41...Pressure adjustment valve.

Claims (1)

[Claims] (1) A first port that communicates with the cylinder chamber of the metal seal type main body, a second port that forms part of the oil drainage path that can communicate with this first port, and pressurized air that sets the set rupture oil pressure are supplied. a cylinder body having a third port connected to the first port and a fourth port connected to the first port via a check valve; a valve portion sealing the first port; and a medium diameter portion accommodated in the second port. A relief valve is provided, which includes a piston body in which a piston accommodated in a third port and a small diameter portion accommodated in a fourth port are integrally formed, and the sealing area between the first port and the valve portion and the fourth port are Once the first port and second port are in communication, the sealing area of the small diameter portion and the small diameter portion should be the same, and the ratio of the effective diameter of the valve portion to the diameter of the medium diameter portion should be set such that the cylinder indoor hydraulic pressure is equal to that of the pressurized air. A hydraulic overload prevention device, characterized in that the value is determined so that the valve part does not seal the first port until the hydraulic pressure becomes smaller than a set breakage oil pressure based on a set pressure.