JPH043682Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a control circuit for a hydraulic system used in a rolling mill for iron, non-ferrous metals, etc.

(Prior art) In a rolling mill that rolls iron or other materials to produce steel plates of uniform thickness, a hydraulic device is used to adjust the load on the rolling rolls and the distance between their axes in order to roll the plate thickness to a desired set value. , has conventionally been configured as shown in FIGS. 2 and 3.

The work W to be rolled is rolled by two work rolls 1
and 2 to be rolled. Backup rolls 3 and 4 are arranged outside the work rolls 1 and 2, respectively.

Adjust the gap (distance between axes) between work rolls 1 and 2 by pressing on work rolls 1 and 2 from both outsides,
In order to control the thickness of the workpiece W to a predetermined value, a reduction cylinder 5 is provided that presses the support shafts of the backup rolls 3 and 4.

A balance cylinder 7 is interposed between the support shafts of the work rolls 1 and 2, and is opposed to the reduction cylinder 5 to maintain the initial distance between the upper and lower work rolls 1 and 2. Insert the work W in between.

Bending cylinders 9 and 10 are provided to prevent the plate thickness from changing at the center and both ends during rolling, and the bending cylinders 9 and 10 are connected to the support shafts of the work rolls 1 and 2 and the back-up rolls. By inserting it between the support shafts 3 and 4 and bending the opposing work rolls 1 and 2 into a drum shape,
To correct the thickness of a workpiece W to make it uniform across the entire width.

Note that FIG. 3 discloses the structure of the roll portion of FIG. 2.

(Problem to be solved by the invention) By the way, during rolling, hydraulic pressure from a hydraulic source is applied to the reduction cylinder 5 via the switching valve 22 so that the back up rolls 3 and 4 press the work rolls 1 and 2 from the outside. is supplied, and at the same time the left and right balance cylinders 7 are also supplied with the switching valve 2 to counteract this.
Hydraulic pressure is supplied via 0.

In this case, high pressure is supplied to the central piston chamber 12 of the balance cylinder 7 from the switching valve 20,
The rod chambers 13 and 14 on both sides are drained to the tank side via a switching valve 21.

When rolling is finished in this state and the work W comes out from between the work rolls 1 and 2, the work rolls 1 and 2 try to approach each other by the thickness of the work W at that moment. This is because the back up rolls 3 and 4 are pressed by the reduction cylinder 5, and as a result, the left and right balance cylinders 7 receive the driving force of the reduction cylinder 5, and the central piston chamber 12 is strongly compressed. At the same time, the rod chambers 13 and 14 on both sides rapidly expand.

In this case, the rod chamber 13 of the balance cylinder 7
Due to the expansion of 14 and 14, hydraulic oil is sucked from the tank line through the switching valve 21, but the pressure in the tank line is generally low, 1.0 kg/cm ² or less, and the pressure up to the rod chambers 13 and 14 is low. When the tank line piping is long, suction into the rod chambers 13 and 14 cannot be carried out smoothly, causing cavitation, and outside air or cooling water for cooling the rolling rolls may be sucked in through the sliding gap of the piston rod. Damage to the rod seals, hydraulic cylinders, piping, etc. due to suction of cooling water.
There was a problem with rust forming on switching valves, etc.

The present invention aims to solve such problems.

(Means for solving the problem) Therefore, the present invention provides back-up rolls located on both sides of the two work rolls,
In a rolling mill that is equipped with a reduction cylinder that rolls a back-up roll into contact with the work roll, and feeds the rolling material between the work rolls and rolls it to a predetermined thickness, the roll cylinder is interposed between the support shafts of the work rolls. A pump circuit and a tank circuit are selectively connected to the main circuit connected to the balance cylinder via a switching valve, and a bypass circuit branched from the switching valve is connected in the middle of this main circuit, and the switching valve is connected to the main circuit. When connected to the tank circuit, the bypass circuit is equipped with a pressure reducing valve that reduces the pressure and introduces the pressure oil from the pump circuit, and the main circuit is equipped with a pressure reducing valve that opens at a pressure slightly higher than the set pressure of this pressure reducing valve. A sequence valve was installed to do this.

(Function) If the pressure in the tank line is maintained at a predetermined value using the pressure reducing valve in this way, when an excessive compression force is applied to the balance cylinder, such as at the end of rolling, the expansion of the Hydraulic oil can be actively fed into the rod chamber, and negative pressure in the balance cylinder can be prevented.

In addition, when an external force is forcibly applied to the balance cylinder in the direction of extension due to a work W being caught, the sequence valve opens with the hydraulic oil discharged from both rod chambers, causing abnormally high pressure to occur in the piping. There isn't.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As shown in FIG. 1, a main circuit 3 connects the rod chambers 13 and 14 of the balance cylinder 7 and a switching valve 21 that controls the supply of hydraulic oil to the rod chambers 13 and 14.
0, a bypass circuit 31 is provided in parallel with this.

The switching valve 21 has an A position that supplies high pressure from the pump circuit 34 to the rod chambers 13 and 14, and a tank circuit 35 that also supplies the rod chambers 13 and 14 to the tank circuit 35.
There is a B position that is released.

The bypass circuit 31 includes a check valve 32 and a pressure reducing valve 3.
3 to the main circuit 30.

When the switching valve 21 is switched to the B position, the pressure reducing valve 33 reduces the high pressure supplied from the pump circuit 34 to the main circuit 30 and sends the reduced pressure to, for example, 10 kg/cm ² .

The main circuit 30 includes a pressure reducing valve 36 that controls the pressure oil sent to the rod chambers 13 and 14 to, for example, 70 kg/cm ² when the switching valve 21 is switched to the A position.
is interposed. In addition, sequence valve 3 is connected in series with this.
7 is interposed, and when the switching valve 21 is in the B position, it opens when the pressure of the discharged oil from the rod chambers 13 and 14 exceeds, for example, 15 kg/cm ² .

In addition, 38 in the figure is a high pressure relief valve that sets the upper limit pressure of the main circuit 30.

The operation of the structure as described above will be explained next. When the rod chambers 13 and 14 of the balance cylinder 7 are opened to the tank line during rolling, the switching valve 21 is switched to the B position as shown in the figure.

Then, the main circuit 30 is connected to the tank circuit 35, and at the same time, the bypass circuit 31 is connected to the pump circuit 34.
communicate with.

Therefore, the main circuit 30 is supplied with hydraulic pressure reduced to, for example, 10 kg/cm ² by the pressure reducing valve 33 from the bypass circuit 31 .

On the other hand, the return oil from both rod chambers 13 and 14 is
A check valve 36 in parallel with the pressure reducing valve 36 of the main circuit 30
A, but does not flow into the tank circuit 35 unless the pressure exceeds the pressure specified by the sequence valve 37, for example 15 kg/cm ² .

For this reason, the pressure in the main circuit 30 is at least constantly maintained at, for example, 10 kg/cm ² ,
As a result, when the workpiece W is removed from the balance cylinder 7 and the rod chambers 13 and 14 suddenly expand, the hydraulic oil is smoothly sucked into the rod chambers 13 and 14 due to the maintained pressure, and the negative pressure is reduced. It is possible to reliably prevent such occurrences.

Note that the pressure oil from the pump circuit 34 sent to the bypass circuit 31 is controlled by the pressure reducing valve 33, for example.
Since the pressure in the pump circuit 34 is controlled at 10 Kg/cm ² , the pressure in the pump circuit 34 is maintained at a high pressure regardless of this, and the supply pressure to other circuits connected in tandem will not be reduced.

When the balance cylinder 7 bites the workpiece W, it operates in the extension direction and hydraulic oil is discharged from both rod chambers 13 and 14. At this time, the sequence valve 37 opens when the pressure reaches, for example, 15 kg/cm ² Therefore, the hydraulic oil flows out smoothly and abnormally high pressure in the circuit is avoided.

On the other hand, the rod chambers 13, 1 of the balance cylinder 7
When high pressure is to be supplied to the pressure reducing valve 3 by switching the switching valve 21 to the A position, the main circuit 30 passes through the sequence valve 37 and the parallel check valve 37A.
For example, pressure oil with a pressure of 70 kg/cm ² specified in 6.
It is supplied to rod chambers 13 and 14.

In this case, a check valve 32 is interposed in the bypass circuit 31 to prevent backflow from the main circuit 30, so that the pressure in the rod chambers 13 and 14 is maintained at the specified value.

(Effects of the invention) As described above, according to the invention, when the rod chamber of the balance cylinder is released to the tank line, a predetermined pressure is secured by the pressure reducing valve and the sequence valve, so that the suction into the rod chamber is reduced. This can be done smoothly, reliably prevents the generation of negative pressure in the balance cylinder, and prevents damage to the rod seal and rust on the cylinder, piping, etc. due to suction of water from the outside.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram of a conventional device, and FIG. 3 is an explanatory diagram showing the configuration of a rolling roll. 1, 2... Work roll, 3, 4... Backup roll, 5... Reduction cylinder, 7... Balance cylinder, 9, 10... Bending cylinder, 12... Piston chamber, 13, 14... Rod Chamber, 20, 21, 22...Switching valve, 30...Main circuit, 31...Bypass circuit, 32...Check valve, 33...Pressure reducing valve, 34...Pump circuit, 35
... Tank circuit, 36 ... Pressure reducing valve, 37 ... Sequence valve.

Claims (1)

[Scope of utility model registration request] Backup rolls are provided on both sides of the two work rolls, and a reduction cylinder is provided to roll the backup rolls into rolling contact with the work rolls, and the rolling material fed between the work rolls is rolled to a predetermined thickness. In such a rolling mill, a pump circuit and a tank circuit are selectively connected to a main circuit connected to a balance cylinder interposed between support shafts of work rolls via a switching valve,
A bypass circuit branched from the switching valve is connected in the middle of the main circuit, and a pressure reducing valve is provided to reduce the pressure and introduce pressure oil from the pump circuit into the bypass circuit when the switching valve connects the main circuit to the tank circuit. A control circuit for a hydraulic system for a rolling mill, characterized in that the main circuit is equipped with a sequence valve that opens at a pressure slightly higher than the set pressure of the pressure reducing valve.