Control method of hydaulic pinch roll and control unit thereof

Abstract: A control unit of hydraulic pinch rolls 1 comprises: position detectors 10c, 10d that detect position of right and left cylinder pistons 6c; an arithmetical unit 13 that calculates a difference of output 16c, 16d from the position detectors; a controller 14 that processes a calculated value to make correction output; and add-subtract units 18c, 18d that add/subtract the correction output from the controller such that the correction output 17 is added to an end portion of the pinch rolls having a wider gap in a direction to push the gap and the correction output of the same amount is subtracted from the opposite end portion, by which the set values of pressing force control provided for right and left independently are corrected. Thus, a defective winding shape can be suppressed.

Description: The present invention relates to a method of improving a winding shape of a coil to be wound by a down coiler by hydraulic pinch rolls controlled by a hydraulic cylinder and a servo valve and to a control unit thereof. Document JP(A) 09267126, on which the preambles of claims 1, 2, 4 and 5 are based, discloses a control method and a control unit for hydraulic pinch rolls. Description of the Related Art Fig. 1 shows pinch rolls 1 of a down coiler 2 of hot rolling equipment being a subject of the present invention. In the hot rolling equipment, a strip 4 that has been rolled to a predetermined plate thickness by a finishing mill is rolled by the down coiler to be an end item in a coil state. The pinch roll functions to guide a strip 4 run on a table roller 5 to the down coiler 2. Recently, as shown in Fig. 2, a hydraulic pinch roll that controls the position of upper and lower pinch rolls and a pressing force to the strip by a hydraulic cylinder 6 and a servo valve 7 has been commercialized. Function required to such pinch rolls 1 is stretching the strip 4 to guide to the down coiler 2 in an initial period of the winding and stretching the strip 4 in an opposite direction to maintain an appropriate tension with a mandrel 2e after the strip 4 has been wound to the mandrel 2e. Accordingly, an appropriate force is given to the pinch rolls 1 to press the strip 4. The hydraulic pinch rolls 1 shown in Fig. 2 is constituted as follows. Specifically, right/left chucks 1c and 1d of an upper pinch roll 1a is supported by the hydraulic cylinder 6 and control of excurrent/incurrent of oil to the hydraulic cylinder 6 is performed by the servo valve 7 connected via piping 8a and 8b. Pressure detector 9a and 9b are severally connected to the piping 8a and 8b so that the pressure of the hydraulic cylinder 6 at a head side 6a and a rod side 6b can be detected. Moreover, position detectors 10c and 10d can detect the position of a piston 6c of the hydraulic cylinder 6. In the hydraulic pinch rolls 1, an initial gap is set by detecting the position of the piston 6c of the hydraulic cylinder 6 by the position detectors 10c and 10d and by controlling the position of the upper pinch roll 1a based on the signal of the detection. After the strip 4 bounces into the pinch rolls 1 to be guided to the down coiler 2, a positional control is switched to a pressing force control in an appropriate timing, and a pressing force arithmetical unit 11 calculates the pressing force to the strip 4 of the upper pinch roll 1a based on the pressure of the head and rod sides 6a and 6b, which has been detected by the pressure detectors 9a and 9b, and then a servo controller 12 sends an instruction to a servo valve 7 based on the signal of the calculation to control the pressing force. In a conventional down coiler 2, a defective winding shape of the coil (a telescope), as shown in Fig.3, has occurred due to reasons such as the case where a plane shape of the strip 4 to be wound is bad and where the strip 4 enters the pinch rolls 1 in an off-center manner. Furthermore, recently, when a wide and hard material is wound, a problem of multiple defective winding shapes as shown in Fig. 4 in which an end surface of a wound coil has an iterative unevenness. SUMMARY OF THE INVENTION In consideration of the foregoing circumstances, the object of the present invention is to provide a control method of the hydraulic pinch rolls that can suppress the defective winding shape and a control unit thereof. The inventor of the present invention has found out that the right/left difference of a piston position of the hydraulic pinch rolls, that is, the output difference of the position detectors 10c and 10d shows a periodic fluctuation when the defective winding shape occurs where the end surface of the wound coil has an iterative unevenness, and that the output difference does not show the periodic fluctuation when the defective winding shape does not occur. Accordingly, in a first embodiment of the present invention, the control unit of the hydraulic pinch rolls is constituted such that the pressing force of the right and the left of the pinch rolls is changed moment by moment in accordance with the output difference of the position detectors 10c and 10d and the fluctuation shown in the output difference of the position detectors 10c and 10d can be suppressed. As a result, a gap fluctuation that occurs alternately in right and left (a seesaw state) on the upper pinch roll 1a of the hydraulic pinch rolls 1 can be prevented. In a second embodiment of the present invention, since the control unit of the hydraulic pinch rolls 1 changes the gaps of the right and left of the pinch rolls by positional control moment by moment in accordance with the pressing force of the pinch rolls obtained from the output of the pressure detectors 9a and 9b, the gap of the pinch rolls is maintained parallelly. Accordingly, the gap fluctuation that occurs alternately in right and left on the upper pinch roll 1a can be prevented. As a result, the defective winding shape where the end surface of a wound coil iterates the periodical unevenness can be prevented. Other objects and advantageous characteristic of the present invention will be made clear by the following description with reference to the accompanied drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a constitutional view of a hot rolling equipment including conventional hydraulic pinch rolls. Fig. 2 is a constitutional view of conventional pinch rolls. Fig. 3 is an explanatory view of a defective winding shape (a telescope) of a coil. Fig. 4 is an explanatory view of another defective winding shape of the coil. Fig. 5 is an entire constitutional view of hydraulic pinch roll unit including a control unit of the present invention. Fig. 6 is a typical view of a case where the gap of one side of the pinch rolls is wide. Fig. 7 is a block diagram of the control unit of the present invention. Fig. 8A and Fig. 8B are examples of a main arithmetical unit of the control unit of the present invention. Fig. 9 is a block diagram showing a second embodiment of the control unit of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 5 shows the entire constitutional view of a first embodiment of the pinch rolls of the present invention, the same reference numerals are given to common portions to Fig. 2, and redundant explanation will be omitted. In the apparatus of the present invention, the pressing force of the upper pinch roll 1a to the strip 4 is controlled by pressing force control units C and D independently provided for right and left, similarly to the conventional apparatus of Fig. 2. Specifically, from the pressure of the head side 6a and the rod side 6b (P a and P b , respectively) of the hydraulic cylinder 6, the pressure having been detected by the pressure detectors 9a and 9b provided in mid course of the piping 8a and 8b, the arithmetical units 11 calculate a pressing force F generated by the hydraulic cylinders 6 as in F = P a ×A h -P b ×A 1 (where A h and A 1 show the area of the piston 6c in the head side and the rod side respectively). Then, a calculated value is compared with a set value by the controller 12, the servo valve 7 is driven based on the difference between the values to control the excurrent/incurrent of the oil to the hydraulic cylinder 6, and the pressing force F is controlled so as to be a predetermined value. In the conventional apparatus, the pressing force of the right and left was merely controlled independently. Accordingly, as shown in Fig. 6, since the pressing force in the right and left is severally controlled so as to be constant even if the thick strip 4 is tilted between the gap of the pinch rolls 1, the upper pinch roll 1a tilts accordingly, and thus the right and left difference of a roll gap could not eliminated. Therefore, occurrence of the gap fluctuation could not be suppressed because the strip 4 moves in the right and left direction between the gap of the pinch rolls, and thus the defective winding shape in which the end surface of the wound coil iterates unevenness periodically. In addition to the conventional apparatus, the apparatus of the present invention shown in Fig. 5 is constituted such that an arithmetical unit 13 performs an operation for the difference of output 16c and 16d from the position detection units 10c and 10d detecting the position of the right and left cylinder pistons 6c, a controller 14 processes a calculated value, and its output 17 is applied to the right and left pressing force controller 12. The control unit of the present invention will be described in more detail by the block diagram of Fig. 7. In Fig. 7, the control unit is constituted such that correction output 17 by the controller 14 of the present invention is added to pressing values 20 of the foregoing right and left pressing force control units C and D independently provided. Regarding the correction output 17, in the case where the left gap of the pinch roll 1 is wide, as shown in Fig.6, add-subtract units 18c and 18d built in the controller 12 perform addition-subtraction to a pressing force set value 20 such that the correction output 17 is added to push down the gap and the correction out put 17 of the same amount is subtracted from the gap of the other side. Accordingly, the wider gap is pushed down by the correction output 17 and the other gap is lightened by the amount of the correction output 17 without changing a total load to press the strip 4. Thus, fluctuation does not occur in the difference of the right and left gaps. Fig. 8A and Fig. 8B show a constitutional examples of a main arithmetical unit 15 in the controller 14 of the present invention. Fig. 8A shows a basic constitution in which the difference of the right and left cylinder piston positions 19 is multiplied by a spring constant K M of a tilt of a mechanical system of the pinch rolls 1 in the right and left directions to convert to a change 21 of force, and a proper control gain K G is further multiplied to make the correction value 17 of the right and left pressing force set values. Fig. 8B is a constitution where a high-pass filter 22 and a clamping circuit 23 are added to an input side and an output side respectively. The high-pass filter 22 takes out only a fluctuation amount from the right and left difference of the cylinder piston positions, and the clamping circuit 23 is a safety circuit to prevent the correction output 17 from exceeding a previously set value ±F C . Fig. 9 shows a second embodiment of the present invention. In the embodiment, positional control units C' and D', which control the position of the cylinder pistons 6C, that is, the right and left roll gaps based on the output from the position detectors 10c and 10d detecting the position of the cylinder pistons 6c, are provided independently for the right and left. Then, output 31 obtained by processing the difference between a set value 28 of the pressing force of the pinch rolls and a pressing force 27 actually detected by a controller 30 is supplied to the positional control units as the instruction value of the positional control. Specifically, regarding the gaps at the right and left of the hydraulic pinch rolls, add-subtract units 25c and 25d perform an operation for output signals 16c and 16d of the position detectors 10c and 10d attached to the pistons 6c of the cylinders 6 and the set value 28, and its deviation is processed by controllers 24 to be the drive signal of the servo valves 7. The servo valves 7, based on the drive signal, control the excurrent/incurrent of the oil to the hydraulic cylinders 6 via the piping 8 to move the pistons 6c of the hydraulic cylinders 6 until the deviation becomes "0". As a result, the right and left roll gaps are set to predetermined values. Herein, the arithmetical units 11 calculates the pressing force based on the output from the pressure detectors 9a and 9b provided on the head side and rod side of the piping 8, an adding unit 26 calculates the sum of the right and left pressing force, that is, the actual pressing force 27 of the pinch rolls 1, and it is subject to comparative operation with the pressing force set value 28 by an add-subtract unit 29 to obtain the deviation. The deviation is processed by the controller 30, and the processed value is made to be a set value 31 for the foregoing right and left control units C' and D'. With this set value, since the pinch rolls 1 are parallelly moved by the position control such that the right and left gaps of the pinch rolls 1 becomes the set pressing force 38, the fluctuation of the difference in the right and left gaps can be suppressed. As described above, according to the control unit of the hydraulic pinch rolls of the present invention, the fluctuation of the roll gaps caused by the shift of the strip 4 either to the right or the left can be suppressed more certainly. As a result, the shift of the strip 4 to the right or left can be prevented and the deterioration of the coil winding shape can be prevented. Although the present invention has been described based on a few preferred embodiments, it should be understood that the scope of right incorporated in the present invention is not limited to the embodiments. On the contrary, the present invention should include all improvements, modifications and equivalents within the scope of the appended claims.

Claims: A control method of hydraulic pinch rolls (1) in which a strip (4) is held between upper and lower pinch rolls (1a,1b) to guide the strip (4), the pinch rolls (1a,1b) being provided with hydraulic cylinders (6) which independently support both axial end portions of the upper pinch roll (1a); servo valves (7) that adjust an excurrent/incurrent amount of an operation oil in the hydraulic cylinders (6); position detectors (10c, 10d) that detect the piston positions of the hydraulic cylinders (6); pressing force detectors (9a,9b) that detect the pressing force of the hydraulic cylinders (6); and control units (12) that control the servo valves (7), whereby positional control and pressing force control of the pinch rolls are performed. characterized in that set values (20) of the pressing force control (12) provided for the right and left hydraulic cylinders (6) are independently corrected by a correction value (17) calculated based on a right and left difference (16c) of the piston positions of the hydraulic cylinders (6) A control unit of hydraulic pinch rolls in which pressure detectors (9a,9b) are provided for piping (8a,8b) between hydraulic cylinders (6) which independently support both axial end portions of said pinch rolls and servo valves (7), arithmetical units (11) are provided to perform an operation for pressing force generated by the hydraulic cylinders (6) using pressure of the hydraulic cylinders (6) at a head side (6a) and a rod side (6b) of a piston (6), the pressure being detected by the pressure detectors (9a,9b), and a controller (12) to compare and process a pressing force obtained and a set pressing value (20) provided, in which the servo valve (7) is driven based on the output from the controller (12) to control an excurrent/incurrent amount of oil to the hydraulic cylinders (6) in order to control the pressing force to said set pressing value (20), further comprising: position detectors (10c,10d) that detect the positions of right and left cylinder pistons (6c); characterized by : an arithmetical unit (13) that outputs a difference value (19) of output (16c,16d) from the position detectors (10c,10d); a further controller (14) that processes the difference value (19) to generate a correction output (17); and add-subtract units (18c,18d) that add/subtract the correction output (17) of the further controller (14) to/from the set pressing value (20) such that the correction output (17) is added to the set pressing value (20) for an end portion of the pinch rolls (1) having a wider gap in a direction to push the gap and the correction output (17) of the same amount is subtracted from the set pressing value (20) for the opposite end portion of the pinch roll (1), whereby the set pressing values (20) of pressing force control (11) provided for right and left end portions of the pinch rolls (1) are independently corrected. The control unit according to claim 2, wherein a main arithmetical unit (15) in said controller (14) is constituted of a high-pass filter, a control gain and a clamping circuit A control method of hydraulic pinch rolls (1) in which a strip (4) is held between upper and lower pinch rolls (1a,1b) to guide the strip (4), the pinch rolls (1a,1b) being provided with: hydraulic cylinders (6) which independently support both axial end portions of the upper pinch roll (1a); servo valves (7) that adjust an excurrent/incurrent amount of an operation oil of the hydraulic cylinders (6); position detectors (10c,10d) that detect the piston positions of the hydraulic cylinders (6); pressing force detectors (9a,9b) that detect the pressing force of the hydraulic cylinders (6); and control units (24) that control the servo valves (7), whereby positional control and pressing force control of the pinch rolls are performed, characterized in that : set values of positional control provided for right and left are independently corrected by a correction value (31) calculated based on a difference between pressure force (27) of the hydraulic cylinders (6) and set values (28) thereof. A control unit of hydraulic pinch rolls (1). provided with: position detectors (10d, 10c) for detecting position of pistons (6c) of hydraulic cylinders (6) which independently support both axial end portions of said pinch rolls; add-subtract units (25c,25d) that add/subtract output signal (16c, 16d) from the position detectors to/from a set value (31); controllers (24) that process deviation of a calculated value to form a drive signal for servo valves (7) which control an excurrent/incurrent amount of oil to the hydraulic cylinders (6) based on the drive signal, further comprising: pressure detectors (9a,9b) that detect the pressure of a piping (8) at a head side (6a) and a rod side (6b) of the piston (6c); arithmetical units (11) that output a pressing force value based on the output from the pressure detectors (9a,9b); characterized by : an add-subtract unit (29) that adds/subtracts the output from the arithmetical units (11) to/from a set value (28) of the pressing force (27); and a further controller (30) that processes the output from the add-subtract unit (29) to form a set value (31) for the control unit, whereby the set values of pressing force control provided for right and left are independently corrected.

Inventors: KUWANO HIROAKI, SHIRAKAWA KOUJI, KUWANO, HIROAKI, SHIRAKAWA, KOUJI
Applicants: ISHIKAWAJIMA HARIMA HEAVY IND, ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES CO., LTD.
Application year: 2001
Main classification: B21C47
IPC codes: B21B37, B21C47, B21B41, B21B39, B21B15