JPH0686040B2 - Hydraulic overload prevention device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic overload prevention device for a press. In particular, the set hydraulic pressure is kept constant so that an overload can be prevented [the metal seal portion is opened (broken)] by an arbitrary press load.

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

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

In the metal seal method, the metal seal portion 4 is formed between the piston 2 communicated with the point portion 1 and the cylinder 3 into which the piston 2 is fitted. Then, the pump 6 establishes a set hydraulic pressure (for example, Ps in FIG. 4) in the cylinder chamber 5.

At this time, the piston 2 and the 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 increases from the oil pressure Ps of the cylinder chamber 5 toward Po, and when the press load becomes Lb, the oil pressure of the cylinder chamber 5 becomes Pb. Then, the metal seal portion 4 is opened (broken), and the oil in the cylinder chamber 5 is released to the tank 8 via the oil drainage member 7. Therefore, the relative movement between the piston 2 and the cylinder 3 is allowed, and it is possible to prevent an overload that may damage the mold or the like.

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

[Problems to be Solved by the Invention] By the way, the above-mentioned conventional structures have the following drawbacks in any of the methods, and it is strongly desired to diversify and improve precision of various kinds of products by pressing various kinds of products in small amounts. Now, I am no longer able to satisfy my request.

Metal seal method As shown in FIG. 4, when the set overload prevention load [press load at which the metal seal part opens (breaks)] is set to Lb, the set hydraulic pressure with respect to the breaking hydraulic pressure Pb increases as the press load increases. Ps is lowered by the hydraulic pressure rising portion ΔP of the cylinder chamber 5. Therefore, when the breaking load is set to, for example, Lb ₁ according to the mold used, it is necessary to change the setting hydraulic pressure to Ps ₁ .

Therefore, by changing the set hydraulic pressure, the mechanical deformation of the cylinder 3 and the piston 2 (particularly the ball cup portion) changes, and the bottom dead center position changes. Moreover, since the gap of the point portion 1 is increased, the processing accuracy is deteriorated, and smooth press operation is difficult. This leads to shortening the life of the mold and the press. However, the set hydraulic pressure Ps cannot be lowered so much that the applicable range is narrow.

Furthermore, when changing from the high pressure to the low pressure by changing the set oil pressure Ps, it is necessary to once withdraw the oil pressure of the cylinder chamber 5 to the tank 8, and the setting work is troublesome and the production efficiency is reduced.

Packing seal method In this method, the relief setting hydraulic pressure Pb can be set arbitrarily and easily by adjusting the biasing force P ₁ (relief opening pressure Po) of the spring 11, but the hydraulic pressure increase Δ
The relationship between the set hydraulic pressure Ps regarding P and the relief hydraulic pressure Pb is the same as in the metal seal system. When the set oil pressure Ps is constant, the relief set oil pressure Po of the relief valve 10 cannot be set lower than the set oil pressure Ps as shown in FIG. 6, so the settable relief pressure Po is in the range from Pb to Ps. . When the set relief pressure is set to Po 'and the press load increases to Lb', the relief valve is opened to prevent the hydraulic pressure from becoming higher than Pb ', but the spring 11 keeps the hydraulic pressure at Pb'', The lifting load is Lb ″, and a load larger than the set load Lb ′ is applied to the mold.

Even with this method, the set pressure is the same as the metal seal method.
By changing to Ps ′ and changing the relief set pressure to Po ″, it is possible to prevent the load increase after the relief is released, but it is necessary to adjust both the set pressure and the relief pressure.
Similar to the metal seal system, the mechanical deformation is changed by changing the set pressure, and there is a drawback that the gap between the bottom dead center and the point portion is changed.

Here, an object of the present invention is to prevent the hydraulic overload which can set the hydraulic pressure to a constant value and variably set the breaking hydraulic pressure, thereby expanding the range of application, reducing the mechanical deformation change, facilitating handling and downsizing. To provide a device.

[Means for Solving the Problems] The present invention has a skillful configuration that has the advantages of both the conventional metal seal system and the packing seal system with a relief valve, so that the set break hydraulic pressure can be set arbitrarily regardless of the set hydraulic pressure. When the relief valve is once opened, the relief valve does not close again until the hydraulic pressure in the cylinder chamber falls below the set breaking hydraulic pressure based on the set pressurized air pressure.

That is, the first port that communicates with the cylinder chamber of the metal-sealed body, the second port that forms a part of the oil discharge passage that can communicate with the first port, and the pressurized air that sets the set breaking hydraulic pressure are supplied. A cylinder body having a third port and a fourth port connected to the first port via a check valve, a valve portion for sealing the first port, a medium diameter portion accommodated in the second port, and A relief valve including a piston body integrally formed with a piston housed in the 3rd port and a small diameter part housed in the 4th port is provided, and a sealing area between the 1st port and the valve part and the 4th port are provided. The seal area of the small diameter part is the same, and the ratio of the effective diameter of the valve part to the diameter of the medium diameter part is the set break hydraulic pressure between the first port and the second port. Is the installation breaking hydraulic pressure based on the set force of the pressurized air It is characterized in that the valve portion is set to a value that does not seal the first port until it becomes smaller than.

[Operation] In the present invention, pressurized air is supplied to the third port of the relief valve and the first port is closed by the valve portion, so that the cylinder chamber, the first port, and the fourth port of the metal-sealed body are closed. The set hydraulic pressure is established by the pump.

Here, since the seal area between the first port and the valve portion and the seal area between the fourth port and the small diameter portion are the same, and the respective room pressures of the first port and the fourth port are 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 the pressurized air.

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

At this time, depending on the ratio between the effective diameter of the valve portion and the diameter of the medium diameter portion, the first
Once the port is opened, that is, once the first port and the second port communicate with each other, hunting (repeating opening and closing of the first port) does not occur until the hydraulic pressure in the cylinder chamber becomes equal to or lower than the set breaking hydraulic pressure based on the set air pressure. The first port is not closed.

Therefore, the oil pressure in the fourth port is also reduced because it is discharged through the check valve, the first port, the second port, and the like. At this point, the metal seal breaks,
Even if the port is closed by the set air pressure, the hydraulic pressure in the cylinder chamber is discharged to the tank through the oil drainage system until the value reaches zero, and the overload is prevented.

Therefore, by appropriately setting the supply pressure of the pressurized air to the third port, the set rupture hydraulic pressure can be set to an arbitrary pressure between the set hydraulic pressure and the metal seal type conventional rupture hydraulic pressure while keeping the set hydraulic pressure constant. The pressure difference between the set hydraulic pressure and the breaking hydraulic pressure is small, and the mechanical deformation is also slight.

Further, since the oil pressure in the cylinder chamber can be reduced to the set oil pressure or less, the low pressure can be set.

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

As shown in FIG. 1, the main body of the hydraulic overload prevention device of the present press is the same as the conventional metal seal system shown in FIG. 3, and a relief valve 20 having a special structure is provided in its cylinder chamber 5. It is in communication.

Here, the relief valve 20 sets a set breaking hydraulic pressure (breaking load) by adjusting the pressurized air pressure, and once it becomes the set breaking hydraulic pressure, once released, the hydraulic pressure in the cylinder chamber 5 is set based on the set pneumatic pressure. It is formed so that it will not close again unless it falls below the breaking hydraulic pressure.

The relief valve 20 includes a first port 22, a second port 23,
A cylinder body 21 having a third port 24 and a fourth port 25,
In FIG. 1, from the left side, a valve portion 32 for sealing the first port 22, a medium diameter portion 33 accommodated in the second port 23, a piston 34 accommodated in the third port 24, and a fourth port 25 are accommodated. The small-diameter portion 35 is formed with the piston body 31 integrally arranged in this order.

First, the seal area A ₁ between the first port 22 and the valve portion 32 is
The product of the product of the hydraulic pressure in the port 22 (cylinder chamber 5) in the direction of arrow X 1 in FIG. ₁ , the pressure receiving area of the piston 34, and the compressed air pressure in the third port 24. 1 Arrow X ₂
It is decided to balance with the pressing force in the direction.

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

Therefore, in this structure, a general air source 42 (for example, 2 to
Since the breaking hydraulic pressure is 200 to 300 Kg / cm ² with respect to 5 Kg / cm ² ), the piston 34 must be made to have an excessively large diameter, which is extremely difficult to put into practical use.

Here, in the present invention, a small diameter portion 35 which is fitted into the fourth port 25 is provided on the side of the piston body 31 opposite to the valve portion 32, and the fourth port 25 is provided.
The seal area of 25 is A ₁ , which is the same as the seal area of the first port 22. That is, the effective diameter of the valve portion 32 and the small diameter portion 35
The diameter is the same as d ₁ .

Therefore, the set hydraulic pressure Ps shown in FIG. 2 is set in the cylinder chamber 5, the first port 22 and the fourth port 25 by the pump 6.
If the pressure is increased, the hydraulic pressure in the cylinder chamber 5 (first port 22) will increase as the press load increases, and the pressing force in the arrow X ₁ direction will overcome the pressing force in the arrow X ₂ direction based on the pressurized air pressure. The valve portion 32 moves in the direction of the arrow X _{1 in} FIG.
Port 22 is opened. Then, the hydraulic pressure in the cylinder chamber 5 is released to the tank 8 through the first port 22 and the oil drain passage 27 (the second port 23 also forms a part of the oil drain passage).

However, with this structure, the hydraulic pressure in the cylinder chamber 5 cannot be reduced to the set hydraulic pressure Ps or less, like the conventional relief valve 10. Moreover, the breaking characteristics of the metal seal method cannot be effectively exhibited. In addition, the pressure of the pressurized air causes the valve portion 32 to close the first port 22 again within a short time, causing open / close hunting.

Here, the most characteristic of the present invention is that the first port
When 22 is once opened, the first port 22 is not closed again unless the hydraulic pressure in the cylinder chamber 5 is lower than the set breaking hydraulic pressure based on the set pressurized air pressure, that is, the pressure in the cylinder chamber 5 is reduced. Is smaller than the breaking pressure, the diameter d ₂ larger than the effective diameter d ₁ of the valve 32 is
The medium diameter part 33 and the first port where this is accommodated
The second port 23 having a diameter larger than 22 is provided.
That is, once the first port 22 is open, the first port 22
Arrow X ₁ direction of the pressing force which is obtained as the product of the cross-sectional area A ₂ of diameter 33 within the 22 within the hydraulic and the diameter d ₂ is formed so as to generate.
Therefore, the first port 22 can be continuously opened against the pressing force in the direction of the arrow X ₂ accumulated by the set pressure of the pressurized air and the pressure receiving surface of the piston 34. The ratio of the diameters d ₁ and d ₂ can be arbitrarily selected in consideration of the structure of the metal seal portion 4 and the responsiveness.

Further, in this embodiment, in order to reduce the pressing force in the arrow X ₂ direction at this time, the oil in the fourth port 25 passes through the check valve 26, and the first and second ports 22, 23, the drain oil passage It is supposed to escape to the tank 8 by the route of 27.

In addition, 40 is a pressure setting means of the pressurized air, the air source 42,
It is formed of the pressure control valve 41 and the like. Further, 51 is a spring for setting the piston body 31 to the initial position. Therefore, in order to set the set breaking pressure, the third
It is necessary to slightly increase the set air pressure to the port 24 by the biasing force of the spring 51. However, the spring 51 may be omitted.

Next, the operation will be described.

(Set hydraulic pressure) First, a small air pressure is supplied to the third port 24 by the pressure adjusting valve 41, and the first port 22 is closed by the valve portion 32.

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

Here, the piston body 31 has a first port 22 and a fourth port 25.
Therefore, the same pressure and the pressing force in the opposite directions are applied, and they are mechanically balanced.

Therefore, when the pressure regulating valve 41 is operated again to reach the set breaking hydraulic pressure Pb (breaking load Lb) in FIG. 2, the first port 22
The pressure Pa is set so that the air will be released.
Add to.

That is, the pressure of the pressurized air to the 3rd port is changed to Pa of FIG.
Setting the hydraulic pressure Ps and the conventional breaking pressure Po
Set breaking hydraulic pressure Pb (breaking load at any pressure between
It is understood that Lb) can be set.

(Normal press operation) Although the hydraulic pressure in the cylinder chamber 5 rises as the pressing load increases, the relief valve 20 does not open because it does not reach the set breaking hydraulic pressure Pb.

(Generation of quasi-overload) The press load increases due to biting of the mold, etc., resulting in quasi-overload. In other words, when the hydraulic pressure in the cylinder chamber 5 (first port 22) reaches the set breaking hydraulic pressure Pb as shown in FIG. 2, the piston body 31 has a pressure greater than the pressing force in the arrow X ₂ direction based on the set air pressure Pa. The pressing force in the direction of the arrow X ₁ due to the product of the oil pressure in the 1st port 22 and the seal area A ₁ of the valve portion 32 (depending on the effective diameter d ₁ ) becomes large, so that the 1st port 22 is opened.

Simultaneously with opening, the first port 22 and the second port 23 communicate with each other, so that the piston body 31 has a hydraulic pressure in the second port 23 (first port 22) and a cross-sectional area A ₂ (diameter d ₂ Therefore, even if the set air pressure Pa in the third port 24 is almost constant, a large pressing force is generated in the direction of the arrow X ₁ based on the product of
Even if the hydraulic pressure in the cylinder chamber 5 is slightly lowered, the first port 22 is not closed.

Therefore, the oil in the cylinder chamber 5 escapes to the tank 8 through the first and second ports 22 and 23 and the oil drain passage 27. Therefore, the hydraulic pressure in the cylinder chamber 5 decreases to Pb ', as indicated by the arrow X in FIG. At this time, the oil in the fourth port 25 also escapes to the tank 8 through the check valve 26 and the like.

When the hydraulic pressure in the cylinder chamber 5 decreases to Pb 'under the pressing load of Lb (breaking load), the metal seal portion 4 breaks, and the oil in the cylinder chamber 5 rapidly passes through the oil drainage system 7 to the tank 8 Returned to.

Here, the overload is prevented without the pressing load becoming larger than the set breaking load Lb.

At this stage, cylinder chamber 5, first port 22, fourth
Since the oil pressure in the port 25 becomes zero, the first port 22 is closed by the pressing force of the set pressurized air Pa in the arrow X ₂ direction. That is, the relief valve 20 returns to the initial state.

(Change of Settings) In FIG. ₂ , the pressure of the supply pressurized air may be set to Pa _{2 in order} to set the breaking load to Lb ₂ .

Then, the first port 22 is opened when the hydraulic pressure in the first port 22 is the set break hydraulic pressure Pb ₂ . The hydraulic pressure drops to Pb ₂ ′ and the metal seal portion 4 is broken.

On the other hand, in the case of using a delicate and relatively low-strength die, when the breaking load is set to Lb ₁ , the pressurized air pressure may be set to Pa ₁ .

Then, the relief valve 20 is opened at the set breakage hydraulic pressure Pb ₁ , decreases to the hydraulic pressure Pb ₁ ′ lower than the set hydraulic pressure Ps, and the metal seal portion 4 breaks at the press load (Lb ₁ ).

Therefore, according to this embodiment, the first to fourth ports 22 to
A relief valve 20 including a cylinder body 21 having 25 and a piston body 31 integrally provided with valve portions 32 to 35 is communicated with the main body cylinder chamber 5, and the effective diameter d ₁ and the medium diameter portion of the valve portion 32 are connected. 33
Smaller than the set breaking pressure the ratio of the diameter d ₂ of the first port 22 after the second port 23 is communicated once communicated cylinder chamber 5 in the hydraulic pressure based on the pressurized air set pressure (Pa) (Pb) Since the valve portion 32 is set to a value that does not close or seal the first port 22 until the value reaches the set value, the set hydraulic pressure (P
The breaking pressure (Pb) can be set between s) and the breaking pressure (Po) by the conventional metal seal method, and low pressure can be set, and high precision press working can be performed while keeping the die height constant due to the constant gap between points. Therefore, it can respond to diversification.

Further, since the set breaking hydraulic pressure (Pb) only needs to set the pressurized air pressure (Pa) to the third port 24, it is extremely easy to change the setting work and has wide applicability. At the same time, the fourth port 25 for providing a counter force to the first port 22 is provided and the sealing areas of these are the same (A ₁ ), so that the piston 34 (relief valve 20) can be miniaturized.

Further, since the relief valve (20) type is used, the hydraulic pressure in the cylinder chamber 5 can be made equal to or lower than the breaking hydraulic pressure.
The characteristics of the metal seal method can be fully exerted.

Furthermore, the pressurized air pressure to the third port 24 only needs to have a pressing force corresponding to the hydraulic pressure increase ΔP at the time of pressing load, so that it is not necessary to increase the diameter of the cylinder body 21 and the device can be easily downsized. Can be planned.

[Effects of the Invention] As is apparent from the above description, the present invention allows a relief valve, which is composed of a cylinder body having a plurality of ports and a piston body having a valve portion and the like integrated with each other, to be communicated with the main body cylinder chamber, and has the same seal area to provide the piston The balance pressure is applied to the body, and once the relief valve is opened, the relief valve will not close again unless it becomes a value smaller than the set break hydraulic pressure based on the set air pressure. It is possible to provide a hydraulic overload prevention device capable of variably setting hydraulic pressure, expanding the range of application, reducing changes in mechanical deformation, facilitating handling, and downsizing.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the same operation, and FIGS. 3 to 6 show a conventional hydraulic overload prevention device. FIG. 4 is a schematic diagram of the metal seal system, FIG. 4 is a diagram for explaining the operation of the methyl seal system, FIG. 5 is a schematic diagram of the packing seal system, and FIG. 6 is a diagram for explaining the operation of the packing seal system. It is a figure. 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 drainage path, 31 …… Piston body, 32 …… Valve section, 33 …… Medium diameter section, 34… … Piston, 35 …… Small diameter part, 40 …… Pressure air pressure setting means, 41 …… Pressure adjusting valve.

Claims (1)

[Claims] 1. A first port communicating with a cylinder chamber of a metal-sealed main body, a second port forming a part of an oil discharge passage communicable with the first port, and pressurized air for setting a set breaking hydraulic pressure. A cylinder body having a third port to which is supplied and a fourth port connected to the first port via a check valve;
A piston body in which a valve portion for sealing the first port, a medium diameter portion accommodated in the second port, a piston accommodated in the third port, and a small diameter portion accommodated in the fourth port are integrally formed. Is provided, the sealing area between the first port and the valve portion and the sealing area between the fourth port and the small diameter portion are the same, and the ratio of the effective diameter of the valve portion to the diameter of the medium diameter portion is the first. Port and second
After the port becomes the set break hydraulic pressure and once communicates with the port, a value is determined so that the valve does not seal the first port until the cylinder hydraulic pressure becomes smaller than the set break hydraulic pressure based on the set pressure of the pressurized air. Hydraulic overload prevention device characterized in that