JPH0120006Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic system, and more particularly to a hydraulic system suitable for use in a hydraulic lowering device employed to improve plate thickness accuracy in a rolling mill.

In general, in rolling mills such as hot strip mills, cold strip mills, and plate mills, hydraulic rolling machines, which are more responsive than conventional electric rolling machines, are often used to improve plate thickness accuracy. There is. FIG. 1 shows a schematic diagram of a rolling mill with a hydraulic rolling device.

As shown in the figure, the rolling mill has a rolling mill housing 1.
a work roll bearing box 2 that supports a work roll 4;
It is generally constructed by supporting a reinforcing roll bearing box 3 that supports a reinforcing roll 5 via a hydraulic lowering device 6.

The hydraulic lowering device 6 supplies pressure oil through various servo valves, but in order to improve the responsiveness of the servo valves, it has a structure that applies back pressure to the piston and always applies a load to the servo valves. There are many. The area of action of the back pressure is 1/5 to 1/10 of the main pressure due to the difference between the main pressure of the piston and the area of the back pressure side, and the pressure is also 1/5 of the main pressure.
~1/10, so the load on the servo valve caused by back pressure is 1/25 to 1/1/2 of the output caused by main pressure.
It is about 100. Therefore, the effect of providing the rear chamber on the entire device is small, and it is effective in improving the responsiveness of the servo valve. Further, the hydraulic lowering device has a magnetic position measuring device in its center, and is controlled while constantly applying position feedback.

Next, the configuration of a conventional hydraulic system will be explained using FIG. 2. As shown in the figure, a main pressure chamber 18 is constituted by the bottom of the cylinder 7 and the head of the piston 8, and the cylinder 7, the piston 8, and the protrusion 9a of the cover 9 provided at the end of the cylinder 7
A back pressure chamber 19 is constituted by. cover 9
is tightened to the end of the cylinder 7 by a bolt 10, while the main pressure chamber 18 and the back pressure chamber 19 are sealed by a packing 11, and the back pressure chamber 19 and the outside are sealed by a packing 12, respectively. Further, the position measuring device 13 is installed between the cylinder 7 and the ram, and measures the displacement of the cylinder 7. The main pressure is led to the main pressure chamber 18 by the servo valve 14 .
The back pressure is led to the back pressure chamber 19 via the pressure reducing valve 15 from the same hydraulic line as the main pressure.

In a hydraulic system with such a configuration, if a space is created above the cylinder 7 and there is no mechanical stopper that regulates the cylinder stroke, such as when changing rolls or testing outside the hydraulic line, the position measurement circuit is turned off. This is often the case.
If pressure oil is sent into the main pressure chamber 18 at such a time, the cylinder 7 will rise and the distance a between the piston 8 and the cover 9 will become zero. At this time, the cover 9 and bolt 10 have a diameter of 1000 mm and a pressure of 210 kg/
^cm2 , it is pulled under a load of 1650TON, deforms,
causing damage.

The present invention has been made in view of the above points, and its purpose is to provide a hydraulic device that does not apply a heavy load to the cover etc. even in the event of erroneous operation, and does not cause deformation or damage.

This invention is designed so that when the cylinder is operating at a normal stroke, the main pressure chamber and back pressure chamber are not communicated, the cylinder rises, and the distance between the piston and the cover protrusion becomes zero. become,
A bypass circuit is provided so that the main pressure chamber and the back pressure chamber are connected during an abnormal stroke such as when a tensile load is applied to the cover protrusion, and the oil supplied to the main pressure chamber is guided to the back pressure chamber, and Installed in the back pressure chamber supply oil line, detects the pressure increase in the back pressure chamber supply oil line during an abnormal stroke, opens an oil drain circuit, and drains the main pressure chamber supply oil led to the back pressure chamber. By providing a relief valve, the intended purpose is achieved.

Hereinafter, the present invention will be explained based on the embodiments shown in the drawings. Note that the same reference numerals are used for the same parts as in the past.

An embodiment of the present invention will be described with reference to FIG.
In this figure, the schematic configuration of the hydraulic system is almost the same as in Figure 2, but a bypass circuit 17 is added inside the end of the body of the cylinder 7, and a relief valve 16 is added to the back pressure line. ing. The set value of the relief valve 16 is set slightly higher than the set value of the pressure reducing valve 15. For example, pressure oil line 210Kg/cm ²
If the set value of the pressure reducing valve 15 is 40 kg/cm ² , then the set value of the relief valve 16 is 50 kg/cm ² . If this is done, the relief valve 16 will not operate under normal conditions. Next, the operation of the bypass circuit 17 will be explained with reference to FIG. Normally, the hydraulic cylinder operates between strokes 0 and max as shown in a and b. Therefore,
The bus pass circuit 17 is filled with back pressure. However, as described above, in the event of a malfunction, the cylinder 7 moves up to the abnormal maximum stroke as shown in c. At this time, the bypass circuit 17 connects the main pressure chamber 18 and the back pressure chamber 19 as shown in the figure, and the main pressure flows into the back pressure chamber 19 where the pressure is lower. Then, the pressure in the back pressure line increases, so the relief valve 16 opens, and the main pressure flows into the oil return line and is drained. Since this operation is stabilized by the set value of the relief valve 16, in the state shown in FIG. According to the above example, the set value of the relief valve 16 is 50 kg/cm ² . Therefore, the load on the bolts 9 and cover 10 shown in Fig. 3 is reduced to 390 TON by a hydraulic cylinder with a diameter of 1000 mm, which increases safety against deformation and breakage.

According to the hydraulic system of the present invention described above, when the cylinder is operating at a normal stroke, the main pressure chamber and the back pressure chamber are not communicated, and the cylinder rises. At the time of an abnormal stroke in which the distance between the piston and the cover protrusion becomes zero and a tensile load is applied to the cover protrusion, the main pressure chamber and the back pressure chamber are connected and the oil supplied to the main pressure chamber is guided to the back pressure chamber. A bypass circuit configured as shown in FIG. Since it is equipped with a relief valve that drains the main pressure chamber supply oil, even in the event of an erroneous operation, the main pressure will flow into the oil return line through the bypass circuit and be drained, so there will be no heavy load on the cover. Since no pressure is applied, the cover, bolts, etc. will not be deformed or damaged.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a rolling mill equipped with a hydraulic cylinder, Figure 2 is a system diagram showing the configuration of a conventional hydraulic cylinder, Figure 3 is a system diagram showing the configuration of the hydraulic cylinder of the present invention, and Figure 4 is a system diagram showing the configuration of the hydraulic cylinder of the present invention. FIG. 3 is a cross-sectional view showing the operating state of the present invention. DESCRIPTION OF SYMBOLS 1...Rolling mill housing, 2...Work roll bearing box, 3...Reinforcement roll bearing box, 4...Work roll, 5...Reinforcement roll, 6...Hydraulic system, 7...
Cylinder, 8... Piston, 9... Cover, 1
0... Bolt, 11... Packing, 12... Packing, 13... Position measuring device, 14... Servo valve, 15... Pressure reducing valve, 16... Relief valve, 17
...Bypass circuit, 18...Main pressure chamber, 19...Back pressure chamber.

Claims (1)

[Scope of utility model registration request] The cover includes a cylinder, a piston housed in the cylinder, and a cover provided at an end of the cylinder and having a protrusion that protrudes inside the cylinder to regulate the stroke of the cylinder. A hydraulic device, wherein a main pressure chamber is formed between the bottom of the cylinder, a back pressure chamber between the end of the cylinder, the piston, and a protrusion of the cover, and the main pressure chamber and the back pressure chamber are sealed by a packing. When the cylinder is operating at a normal stroke, the main pressure chamber and the back pressure chamber are not communicated with each other, and the cylinder rises to increase the distance between the piston and the cover protrusion. a bypass circuit formed to connect the main pressure chamber and the back pressure chamber and guide the main pressure chamber supply oil to the back pressure chamber at the time of an abnormal stroke such that a tensile load is applied to the cover protrusion when the and installed in the back pressure chamber supply oil line,
The main pressure chamber supply oil line is characterized by comprising a relief valve that detects a pressure increase in the back pressure chamber supply oil line at the time of an abnormal stroke, opens an oil drain circuit, and drains the main pressure chamber supply oil led to the back pressure chamber. hydraulic system.