Control method of hydraulic pinch roll and control unit thereof

A control method of hydraulic pinch rolls wherein a strip is held between upper and lower pinch rolls to guide the strip, the control method comprising the steps of:

• providing an upper pinch roll having end portions, and a lower pinch roll, with hydraulic cylinders that independently support each of the end portions in an axis direction of the upper pinch roll, wherein each hydraulic cylinder has a piston;
• adjusting an excurrent/incurrent amount of an operation oil of the hydraulic cylinders with servo values to move the pistons;
• detecting positions of the pistons of the hydraulic cylinders with position detectors to generate a first output;
• detecting a pressing force of the hydraulic cylinders with pressing force detectors to generate a second output used to calculate an actual pressing force value;
• processing the actual pressing force value to generate first set value input for a right control unit and a left control unit;
• and
• controlling the servo values with the right control unit and the left control unit to receive output from the position detectors and to receive the first set value input to generate a drive signal to control the servo values, whereby positional control and pressing force control of the upper pinch roll and the lower pinch roll are performed,
• wherein the first set value inputs of positional control are provided for the right control unit and the left control unit to move the upper pinch roll and the lower pinch roll parallelly so that a fluctuation in right and left gaps of the pinch rolls is suppressed.

A control unit of hydraulic pinch rolls, comprising:

• position detectors disposed to detect positions of pistons of hydraulic cylinders, wherein each position detector generates a first output signal;
• first add/subtract units connected to receive first output signals from the position detectors, wherein the first add/subtract units add or subtract each first output signal from the position detectors and a first set value;
• first controllers connected to receive input from the first add/subtract units, wherein the first controllers process deviation of a calculated positional control value and the first output signal from a respective position detector to form a drive signal for servo valves;
• servo valves disposed to control an excurrent/incurrent amount of oil to the hydraulic cylinders based on the drive signal;
• pressure detectors disposed to detect pressure of piping at a head side and a rod side, wherein each pressure detector generates a second output;
• arithmetical units connected to receive the second outputs from the pressure detectors, wherein the arithmetical units calculate pressing force based on the second outputs from the pressure detectors, and each arithmetical unit generates a third output;
• a second add-subtract unit connected to receive summed third outputs from the arithmetical units, wherein the second add-subtract unit operates to compare, by adding or subtracting, the summed third outputs from the arithmetical units and a third set value of pressing force, and the second add-subtract unit generates a deviation output;
• and
• a second controller connected to receive the deviation output from the second add-subtract unit, wherein the second controller processes the deviation output from the second add-subtract unit to form the first set value for the control unit, whereby the hydraulic cylinders move the pinch rolls parallelly in accordance with the first set value so that fluctuation in a difference in right and left gaps of the pinch rolls is suppressed.

A control unit of hydraulic pinch rolls comprising:

• first pressure detectors disposed in piping between a first hydraulic cylinder and a first servo valve, the first hydraulic cylinder having a first piston;
• a first arithmetical unit connected to receive input from the pressure detectors, wherein the first arithmetical unit performs an operation for calculating a pressing force generated by the first hydraulic cylinder using pressure of the first hydraulic cylinder at a head side and a rod side, wherein the pressure is detected by the pressure detectors and the first arithmetical unit generates a first calculated value output corresponding to the pressing force;
• a first controller connected to receive the first calculated value output from the first arithmetical unit and to send output to the first servo valve, the first controller operating to compare and process the first calculated value output corresponding to the pressing force and a pressing force set value, wherein the first servo valve is driven based on the output from the first controller and the first servo valve operates to control an excurrent/incurrent amount of oil to the first hydraulic cylinder in order to control the pressing force generated by the first hydraulic cylinder to a predetermined value;
• position detectors disposed to detect positions of the first piston of the first hydraulic cylinder and a second piston of a second hydraulic cylinder, each position detector generating an output;
• a second arithmetical unit connected to receive output from the position detectors, wherein the second arithmetical unit performs an operation for processing a difference of output from the position detectors, and generates a second calculated value output;
• and
• a second controller connected to receive the second calculated value output from the second arithmetical unit, wherein the second controller operates to process the second calculated value output to generate correction output, and the first controller includes a first add/subtract unit connected to receive the correction output from the second controller, wherein when the first add/subtract unit operates to add the correction output to the pressing force set value, the first controller drives the first servo to push an end portion of the pinch rolls having a wider first gap in a direction to push down the first gap, and the correction output is received by a second add/subtract unit of a third controller connected to drive a second servo valve, wherein the second servo valve operates to control an excurrent/incurrent amount of oil to the second hydraulic cylinder in order to control the pressing force generated by the second hydraulic cylinder to a predetermined value, wherein the second add/subtract unit operates to subtract the correction output from the pressing force set value, and the third controller drives the second servo to push lighter on an opposite end portion of the pinch rolls having a second gap, whereby set values of pressing force control provided for the first and second gaps are independently corrected.