JP2018111873A - Gas wiping apparatus and gas wiping method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas wiping apparatus and a gas wiping method which are effective for appropriately controlling the gas discharge pressure according to the variation of the opening width of a gas wiping nozzle.SOLUTION: A gas wiping apparatus 3 comprises a gas wiping nozzle 41, a width adjusting unit 42 for changing the opening width of the gas wiping nozzle 41, an air blower 5, a first valve 7A and a second valve 7B, and a controller 100. The controller 100: controls the width adjusting unit to adjust the opening width according to the width of a steel strip 9; derives a command value for an operation speed of the air blower 5 according to a pressure target value and the opening width based on a data list 114 and outputs the command value to the air blower 5; and feedback-controls the first valve 7A and the second valve 7B to make the deviation between the pressure target value and a detected value smaller.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a gas wiping apparatus and a gas wiping method.

  Patent Document 1 discloses a gas wiping device capable of adjusting the opening width of a gas wiping nozzle in accordance with the width of a steel strip. In Patent Document 2, as a method for controlling the gas pressure in the gas wiping nozzle (hereinafter referred to as “discharge pressure of the gas wiping nozzle”), the deviation between the set value and the measured value of the discharge pressure of the gas wiping nozzle is reduced. Thus, there is disclosed a method of feedback-controlling the wiping nozzle control valve and feedback-controlling the blower so as to reduce the deviation between the set value of the blower discharge pressure and the measured value.

JP 2012-251237 A JP 2003-129206 A

  As disclosed in Patent Document 1, when adjusting the opening width of the gas wiping nozzle according to the width of the steel strip, it is necessary to adjust the discharge pressure of the gas wiping nozzle according to the change in the opening width. As a control method for adjusting the discharge pressure, a method disclosed in Patent Document 2 can be cited. However, in this method, since both the control valve of the gas wiping nozzle and the blower are feedback-controlled according to the pressure, there is a possibility that the fluctuation of the opening width cannot be followed and the discharge pressure cannot be adjusted appropriately.

  Therefore, an object of the present disclosure is to provide a gas wiping apparatus and a gas wiping method that are effective in appropriately controlling the gas discharge pressure in accordance with the variation in the opening width of the gas wiping nozzle.

  A gas wiping apparatus according to an aspect of the present disclosure includes a gas wiping nozzle that blows gas onto a steel strip to which molten metal for plating is attached, a width adjusting unit that changes an opening width of the gas wiping nozzle, and a gas that is applied to the gas wiping nozzle. A pressure adjusting valve that adjusts the opening degree of the gas flow path between the gas wiping nozzle and the blower, a pressure sensor that detects the pressure of the gas supplied to the gas wiping nozzle, and a controller. The controller has a data list including a plurality of data for deriving the operating speed of the blower according to the target value of the pressure of the gas supplied to the gas wiping nozzle and the opening width, and the steel strip Controlling the width adjusting unit to adjust the opening width according to the width of the fan, and the blower according to the target value of pressure and the opening width based on the data list Deriving the command value of the operation speed and outputting it to the blower, and performing feedback control of the pressure control valve so as to reduce the deviation between the target value of the pressure and the detected value of the pressure sensor It is configured as follows.

  According to this gas wiping apparatus, the pressure control valve is feedback controlled so as to reduce the deviation between the target value of the discharge pressure of the gas wiping nozzle and the detected value of the pressure sensor. On the other hand, the blower is controlled using a data list. That is, using the data list, the operating speed of the blower according to the target value of the pressure and the opening width is derived and output to the blower. If the blower is feedback controlled so as to reduce the control deviation of the blowing pressure, the feedback control in the blower and the feedback control in the pressure control valve may affect each other, and the stabilization of the discharge pressure may be delayed. On the other hand, by performing control using a data list for the blower, the operation speed of the blower is quickly stabilized in response to the command value without being affected by the operation of the pressure control valve. Further, the influence of fluctuations in the operating speed of the blower on the feedback control of the pressure control valve is reduced. For this reason, the discharge pressure of the gas wiping nozzle quickly follows the target value. Therefore, it is effective to appropriately control the gas discharge pressure in accordance with the variation in the opening width of the gas wiping nozzle.

  The steel strip includes a first steel strip and a second steel strip that are connected to each other and sequentially conveyed. The controller includes a first period during which the first steel strip passes through the gas wiping nozzle, and a second steel strip that is gas-wiped. In the transition period between the second period passing through the nozzle, controlling the width adjusting unit to increase the opening width of the gas wiping nozzle as compared with the first period and the second period; Prior to starting, the command value of the fan operating speed in the second period is derived based on the data list, and in the transition period, feedback control of the pressure control valve is stopped, and the fan operating speed in the second period It may be configured to further execute outputting a command value (hereinafter referred to as “second speed command value”) to the blower.

If the control for increasing the opening width of the gas wiping nozzle is not performed in the transition period as compared with the first period and the second period, the adhesion of molten metal to the gas wiping nozzle may increase. For example, when the width of the second steel strip is larger than that of the first steel strip, the expansion of the opening width of the gas wiping nozzle may be delayed in transition from the first period to the second period.
In this case, in the transition period, a state where the opening width of the gas wiping nozzle is smaller than the width of the steel strip may occur. In this state, a portion with a large amount of molten metal adhering to the vicinity of the edge of the steel strip is generated, and the molten metal is likely to scatter (splash) from the portion, so the scattered molten metal adheres to the gas wiping nozzle. It becomes easy. On the other hand, in the transition period, by increasing the opening width of the gas wiping nozzle as compared with the first period and the second period, the above-described splash is reduced and adhesion of molten metal to the gas wiping nozzle is suppressed. be able to.

  On the other hand, if the control for expanding the opening width of the gas wiping nozzle is executed during the transition period, the response of the blower and the pressure control valve to the fluctuation of the opening width may be delayed. When such a delay occurs, the fluctuation of the discharge pressure continues even after the start of the second period, and there is a possibility that a desired weight per unit area (amount of molten metal attached to the steel strip) cannot be obtained. On the other hand, during the transition period, the command value for the operating speed of the blower is maintained at the second speed command value. Thereby, at the start of the second period, there is no need to change the command value of the operating speed of the blower. Further, during the transition period, the feedback control of the pressure control valve is stopped. Thereby, the opening degree of the pressure control valve in the transition period is maintained in or near the fluctuation range on the premise of the combined use of the blower control. For this reason, at the start of the second period, the discharge pressure of the gas wiping nozzle can quickly follow the target value. Therefore, it is possible to appropriately control the gas discharge pressure while changing the opening width of the gas wiping nozzle so as to reduce the splash.

  The data list may be configured such that the operating speed of the blower increases as the target value of pressure increases, and the operating speed of the blower increases as the opening width increases. In this case, when the target pressure value is reduced, the operating speed of the blower is reduced, and when the opening width is reduced, the operating speed of the blower is reduced, so that energy loss in the pressure control valve can be reduced.

  A gas wiping method according to another aspect of the present disclosure includes: adjusting an opening width of a gas wiping nozzle that blows gas to a steel strip to which a molten metal for plating is attached according to the width of the steel strip; It has a data list including a plurality of data for deriving the operating speed of the blower according to the target value of the pressure of the supplied gas and the opening width, and based on the data list, the target value of the pressure and the opening width Pressure target valve for deriving and outputting the command value of the operating speed of the blower according to the pressure, and outputting to the blower, and adjusting the opening of the gas flow path between the gas wiping nozzle and the blower. Feedback control of the pressure control valve to reduce a deviation between the value and a detected value of the pressure of the gas supplied to the gas wiping nozzle.

  According to the present disclosure, it is possible to provide a gas wiping apparatus and a gas wiping method that are effective in appropriately controlling the gas discharge pressure in accordance with the variation in the opening width of the gas wiping nozzle.

It is a schematic diagram which shows schematic structure of a gas wiping apparatus. It is a perspective view of a gas wiping nozzle. It is a schematic diagram which shows the structure of a width adjustment part. It is a figure which illustrates a data list. It is a block diagram which shows the hardware constitutions of a controller. It is a flowchart which shows the control procedure of a gas wiping apparatus. It is a schematic diagram which shows operation | movement of the gas wiping nozzle when a connection part passes. It is a schematic diagram which shows a mode that a molten metal adheres to a gas wiping nozzle. It is a graph which shows transition of the blower rotation speed when a connection part passes. It is a graph which shows transition of the discharge pressure when a connection part passes. It is a graph which shows transition of the fabric weight when a connection part passes.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the description, the same elements or elements having the same functions are denoted by the same reference numerals, and redundant description is omitted.

[Molten metal plating equipment]
A molten metal plating apparatus 1 shown in FIG. 1 is an apparatus for plating a surface of a steel strip by passing the steel strip through a plating bath containing molten metal. The molten metal plating apparatus 1 includes a plating pot 2 and a gas wiping apparatus 3.

  The plating pot 2 accommodates a plating bath containing molten metal for plating. Specific examples of the molten metal include molten zinc. A sink roll 21 that can rotate around a horizontal axis is provided in the plating pot 2. The sink roll 21 is located in the plating bath. The plating pot 2 receives the steel strip 9 to be plated from above. The steel strip 9 received in the plating pot 2 from above is immersed in the plating bath. The steel strip 9 immersed in the plating bath is folded upward by the sink roll 21 and fed upward from the plating pot 2 with the molten metal attached thereto. Hereinafter, the direction in which the steel strip 9 moves is referred to as “conveying direction”. Moreover, the part sent out upward from the inside of the plating pot 2 among the steel strips 9 is called "steel strip 9 after immersion".

  The gas wiping device 3 adjusts the basis weight by blowing gas to the steel strip 9 after immersion. The basis weight means the amount of molten metal adhering to the steel strip 9, and is represented by the weight of the molten metal adhering per unit area, for example. The gas may be an inert gas such as nitrogen gas or air.

  The gas wiping device 3 includes a first nozzle unit 4A, a second nozzle unit 4B, a blower 5, a first pipeline 6A, a second pipeline 6B, a first valve 7A, a second valve 7B, A first pressure sensor 8A, a second pressure sensor 8B, and a controller 100 are provided.

  The first nozzle unit 4 </ b> A and the second nozzle unit 4 </ b> B are provided so as to sandwich the steel strip 9 after immersion above the plating pot 2, and spray gas onto the steel strip 9 after immersion. The first nozzle unit 4A includes a gas wiping nozzle 41 that opens toward one surface of the steel strip 9, and the second nozzle unit 4B includes a gas wiping nozzle 41 that opens toward the other surface of the steel strip 9. Have

  The blower 5 supplies gas to the gas wiping nozzles 41 of the first nozzle unit 4A and the second nozzle unit 4B. The blower 5 includes a blower 51, a motor 52 that drives the blower 51, and an inverter 53 that supplies driving power to the motor 52.

  The first conduit 6A guides gas from the blower 51 to the gas wiping nozzle 41 of the first nozzle unit 4A. The second conduit 6B guides gas from the blower 51 to the gas wiping nozzle 41 of the second nozzle unit 4B.

  The first valve 7A (pressure control valve) is provided between the gas wiping nozzle 41 and the blower 51 in the first pipeline 6A, and adjusts the opening of the gas flow path. The second valve 7B (pressure control valve) is provided between the gas wiping nozzle 41 and the blower 51 in the second pipeline 6B, and adjusts the opening of the gas flow path. Specific examples of the first valve 7A and the second valve 7B include a globe valve.

  The first pressure sensor 8A detects the pressure of the gas supplied to the gas wiping nozzle 41 of the first nozzle unit 4A. For example, the first pressure sensor 8A is provided between the gas wiping nozzle 41 and the first valve 7A in the first pipeline 6A, and detects the pressure in the first pipeline 6A. The first pressure sensor 8A may be provided in the first nozzle unit 4A so as to detect the pressure in the gas wiping nozzle 41. The second pressure sensor 8B detects the pressure of the gas supplied to the gas wiping nozzle 41 of the second nozzle unit 4B. For example, the second pressure sensor 8B is provided between the gas wiping nozzle 41 and the second valve 7B in the second pipeline 6B, and detects the pressure in the second pipeline 6B. The second pressure sensor 8B may be provided in the second nozzle unit 4B so as to detect the pressure in the gas wiping nozzle 41.

  Next, the structure of the first nozzle unit 4A and the second nozzle unit 4B will be described with reference to FIGS. Since the first nozzle unit 4A and the second nozzle unit 4B have the same structure, they are hereinafter referred to as “nozzle unit 4” without distinction.

  As shown in FIGS. 2 and 3, the gas wiping nozzle 41 of the nozzle unit 4 includes a gas receiving portion 41 a that receives the gas supplied from the blower 5, and a slit 41 b that discharges the gas. The slit 41 b is along the width direction of the steel strip 9.

  The nozzle unit 4 further includes a width adjusting unit 42 that changes the opening width of the gas wiping nozzle 41. The width adjusting unit 42 includes two closing members 44 and two actuators 45. The two closing members 44 are arranged so as to close both ends of the slit 41 b, and the interval between the two closing members 44 is the opening width of the gas wiping nozzle 41.

  The two actuators 45 change the opening width of the gas wiping nozzle 41 by moving the two closing members 44 along the width direction of the steel strip 9. The actuator 45 is, for example, an electric linear actuator, and drives the closing member 44 via a transmission element 46 such as a wire and a pulley.

  Next, returning to FIG. 1, the controller 100 will be described. The controller 100 automatically controls the opening width of the gas wiping nozzle 41 and the pressure of the gas supplied to the gas wiping nozzle 41 (hereinafter referred to as “discharge pressure”).

  The controller 100 has a data list 114 including a plurality of data for deriving the operation speed of the blower 5 according to the target value of the pressure of the gas supplied to the gas wiping nozzle 41 and the opening width. The width adjusting unit 42 is controlled so as to adjust the opening width according to the width of 9, and the operating speed of the blower 5 according to the target value of the pressure and the opening width based on the data list (for example, the rotational speed of the blower 51) ) Is derived and output to the blower 5, and the first valve 7A is set so as to reduce the deviation between the target pressure value and the detected values of the first pressure sensor 8A and the second pressure sensor 8B. And feedback control of the second valve 7B.

  Here, the steel strip 9 includes a plurality of steel strips having different widths. The plurality of steel strips are arranged along the conveying direction, and adjacent steel strips are connected to each other by welding or the like. Hereinafter, of the two steel strips connected to each other, the one transported in advance is referred to as the “first steel strip”, and the one transported subsequently is referred to as the “second steel strip”. The space between the steel strip and the second steel strip is referred to as a “connection portion”. That is, the steel strip 9 includes a first steel strip and a second steel strip that are connected to each other and conveyed in order.

  The controller 100 includes a first period and a second period in a transition period between a first period in which the first steel strip passes the gas wiping nozzle 41 and a second period in which the second steel strip passes the gas wiping nozzle 41. Prior to the start of the second period, the command value of the operating speed of the blower 5 in the second period is set to the above-mentioned value by controlling the width adjusting unit 42 so as to increase the opening width of the gas wiping nozzle 41 compared to the period. Deriving based on the data list, and stopping the feedback control of the first valve 7A and the second valve 7B in the transition period and outputting the command value of the operating speed of the blower 5 in the second period to the blower 5. , May be further executed. “Passing through the gas wiping nozzle 41” means passing through a position where the gas discharged from the gas wiping nozzle 41 reaches.

  The controller 100 includes a steel strip information acquisition unit 111, a target pressure setting unit 112, a control mode switching unit 113, a data list 114, and a blower speed control as a functional configuration (hereinafter referred to as “functional block”). Part 115, first valve control part 116, second valve control part 117, and opening width control part 118.

  The steel strip information acquisition part 111 acquires the information regarding the steel strip 9 in conveyance from a high-order controller. The target pressure setting unit 112 sets a target value for the discharge pressure based on the information acquired by the steel strip information acquisition unit 111.

  The control mode switching unit 113 determines the start and end of the transition period based on the position of the connection portion between the steel strips, a control mode outside the transition period (hereinafter referred to as “normal mode”), and a transition period. The control mode in the middle (hereinafter referred to as “transition mode”) is switched.

  The data list 114 includes a plurality of data for deriving the operation speed of the blower 5 according to the target value of the pressure of the gas supplied to the gas wiping nozzle 41 and the opening width. For example, the data list 114 includes a list of a plurality of combination patterns of the target value of the discharge pressure, the opening width of the gas wiping nozzle 41, and the operating speed of the blower 5. As illustrated in FIG. 4, the data list 114 is a table that defines the operating speed of the blower 5 for each combination of a plurality of types of discharge pressures and a plurality of types of opening widths. The operating speed of the blower 5 according to the discharge pressure and the opening width is, for example, a predetermined pressure margin for the discharge pressure under the condition of blowing the same flow rate as the gas flow rate when the discharge pressure is applied to the opening width. It sets so that the added ventilation pressure (pressure at the time of the air blower 5 sending out gas) is obtained. The predetermined pressure margin includes a pressure loss from the blower 5 to the gas wiping nozzle 41, a variation in the blowing pressure of the blower 5, and the like. The operating speed of the blower 5 according to the discharge pressure and the opening width may be set based on data actually measured with an actual machine in advance, or may be set based on a simulation result.

  The table in FIG. 4 is divided into a plurality of columns each corresponding to a plurality of types of discharge pressures (pressures 1 to 8) and a plurality of rows respectively corresponding to a plurality of types of opening widths (widths 1 to 6). The operating speed of the blower 5 is assigned to each of the cells. The data list 114 may be configured such that the operating speed of the blower 5 increases as the target value of the discharge pressure increases, and the operating speed of the blower 5 increases as the opening width increases. Good.

  The blower speed control unit 115 outputs an operation speed command value to the blower 5. For example, the blower speed control unit 115 outputs a command value for the rotational speed of the blower 51 to the inverter 53 of the blower 5. When the above-described control mode is the normal mode, the blower speed control unit 115 derives a command value for the operation speed of the blower 5 according to the target value of the discharge pressure and the opening width based on the data list 114, and sends it to the blower 5. Output. When the above-described control mode is the transition mode, the blower speed control unit 115 derives a command value for the operation speed of the blower 5 in the second period based on the data list 114 and outputs the command value to the blower 5.

  The first valve control unit 116 controls the first valve 7A so as to adjust the opening degree of the gas flow path in the first pipeline 6A. When the above-described control mode is the normal mode, the first valve control unit 116 feeds back the first valve 7A so as to reduce the deviation between the target value of the discharge pressure and the detected value of the first pressure sensor 8A. Control.

  Specific examples of feedback control include P control, PI control, or PID control. P control is control which outputs the opening degree command value proportional to the said deviation to the 1st valve | bulb 7A. The PI control is a control for adding the opening command value proportional to the deviation and the opening command value proportional to the time integral of the deviation and outputting the result to the first valve 7A. The PID control adds the opening command value proportional to the deviation, the opening command value proportional to the time integral of the deviation, and the opening command value proportional to the time derivative of the deviation to add the first valve 7A. It is the control which outputs to.

  When the above-described control mode is the transition mode, the first valve control unit 116 stops the feedback control of the first valve 7A. Thereafter, the first valve control unit 116 maintains the opening command value of the first valve 7A at a value immediately before the feedback control is stopped.

The second valve control unit 117 controls the second valve 7B so as to adjust the opening degree of the gas flow path in the second pipeline 6B. When the above-described control mode is the normal mode, the second valve control unit 117 feeds back the second valve 7B so as to reduce the deviation between the target value of the discharge pressure and the detected value of the second pressure sensor 8B. Control. When the above-described control mode is the transition mode, the second valve control unit 117 stops the feedback control of the second valve 7B.
Thereafter, the second valve control unit 117 maintains the opening command value of the second valve 7B at a value immediately before the feedback control is stopped.

  The opening width control unit 118 controls the width adjusting unit 42 so as to adjust the opening width of the gas wiping nozzle 41. When the above-described control mode is the normal mode, the opening width control unit 118 adjusts the opening width of the gas wiping nozzle 41 according to the width of the steel strip 9. When the above-described control mode is the transition mode, the opening width control unit 118 controls the width adjusting unit 42 so as to increase the opening width of the gas wiping nozzle 41 as compared with the first period and the second period.

  FIG. 5 is a block diagram illustrating a hardware configuration of the controller 100. As shown in FIG. 5, the controller 100 includes a circuit 120, and the circuit 120 includes one or more processors 121, a memory 122, a storage 123, and an input / output port 124.

  The input / output port 124 inputs and outputs electrical signals among the width adjusting unit 42, the first valve 7 </ b> A, the second valve 7 </ b> B, the first pressure sensor 8 </ b> A, the second pressure sensor 8 </ b> B, and the inverter 53. The storage 123 stores a program for configuring each functional block of the controller 100. The storage 123 may be anything that can be read by a computer. Specific examples include a hard disk, a nonvolatile semiconductor memory, a magnetic disk, and an optical disk. The memory 122 temporarily stores the program loaded from the storage 123, the calculation result of the processor 121, and the like. The processor 121 configures each functional block by executing a program in cooperation with the memory 122.

  Note that the hardware configuration of the controller 100 is not necessarily limited to the configuration of each functional block by a program. For example, at least a part of the functional block of the controller 100 may be configured by a dedicated logic circuit or an ASIC (Application Specific Integrated Circuit) in which the logic circuit is integrated.

  The controller 100 is divided into a controller that controls the first nozzle unit 4A and the second nozzle unit 4B (controls the width adjusting unit 42) and a controller that controls the first valve 7A, the second valve 7B, and the blower 5. These may be connected by a communication line.

[Gas wiping method]
Subsequently, a control procedure executed by the controller 100 will be described as an example of the gas wiping method. It is assumed that the control mode is the normal mode at the start of the following procedure.

  As shown in FIG. 6, the controller 100 first executes step S01. In step S01, the steel strip information acquisition part 111 acquires the information regarding the steel strip 9 in conveyance from a high-order controller. For example, the steel strip information acquisition unit 111 is referred to as information on the widths of a plurality of steel strips continuous in the transport direction, information on the position of the connection portion between the steel strips, and the transport speed of the steel strip 9 (hereinafter referred to as “line speed”). ) Information and the target value of the basis weight.

  Next, the controller 100 executes step S02. In step S02, the target pressure setting unit 112 sets a target value for the discharge pressure. For example, the target pressure setting unit 112 acquires the target value of the basis weight and the line speed from the steel strip information acquisition unit 111, and sets the target value of the discharge pressure according to these. The target value of the basis weight and the target value of the discharge pressure according to the line speed are derived based on a theoretical formula, past operation data or experimental data, a regression formula based on these data, or a feedback calculation of the actual value of the basis weight. Is possible.

  Next, the controller 100 executes step S03. In step S <b> 03, the opening width control unit 118 adjusts the opening width of the gas wiping nozzle 41 according to the width of the steel strip 9. For example, the opening width control unit 118 sets a value obtained by adding the first margin to the width of the steel strip 9 acquired by the steel strip information acquisition unit 111 as a command value for the opening width, and outputs the command value to the width adjustment unit 42. . The first margin is set in advance by preconditioning.

  Next, the controller 100 executes step S04. In step S <b> 04, the blower speed control unit 115 derives a command value for the operation speed of the blower 5 according to the target value and opening width of the discharge pressure based on the data list 114, and outputs the command value to the blower 5. That is, the data list 114 does not perform feedback control of the blower 5 for reducing the control deviation of the blowing pressure. For example, the blower speed control unit 115 searches the data list 114 for the operating speed of the blower 5 corresponding to the discharge pressure target value set in step S02 and the opening width command value derived in step S03. Use command value. Further, the blower speed control unit 115 may derive the operation speed of the blower 5 by interpolating between data in the data list 114 by a method such as linear interpolation.

  Next, the controller 100 executes step S05. In step S05, the first valve control unit 116 acquires the detection value of the first pressure sensor 8A, and the second valve control unit 117 acquires the detection value of the second pressure sensor 8B.

  Next, the controller 100 performs step S06. In step S06, the first valve control unit 116 derives an opening command value corresponding to the deviation between the target value of the discharge pressure and the detected value of the first pressure sensor 8A, and outputs it to the first valve 7A. The second valve control unit 117 derives an opening command value corresponding to the deviation between the target value of the discharge pressure and the detected value of the second pressure sensor 8B, and outputs it to the first valve 7A. The opening command value according to the deviation may be a value proportional to the deviation, or may be a value obtained by adding a value proportional to the deviation and a value proportional to the time integration of the deviation. A value obtained by adding a proportional value, a value proportional to the time integral of the deviation, and a value proportional to the time derivative of the deviation may be used.

  Next, the controller 100 executes step S07. In step S07, the steel strip information acquisition part 111 acquires again the information regarding the steel strip 9 in conveyance from a high-order controller, and updates it.

  Next, the controller 100 executes step S08. In step S08, the control mode switching unit 113 confirms whether the transport of the steel strip 9 has stopped.

  When it determines with conveyance of the steel strip 9 not having stopped, the controller 100 performs step S09. In step S09, the control mode switching unit 113 confirms whether or not the transition period has started based on the information updated in step S07. For example, the control mode switching unit 113 determines that the transition period has started when the distance from the connection portion (connection portion not passing through the gas wiping nozzle 41) to the gas wiping nozzle 41 is equal to or less than a predetermined value. .

  If it is determined in step S09 that the transition period has not started, the controller 100 returns the process to step S03. Thereafter, the adjustment of the opening width and the control of the blower 5, the first valve 7A, and the second valve 7B in the normal mode are repeated until the transition period starts.

  If it is determined in step S09 that the transition period has started, the controller 100 executes step S10. In step S10, the control mode switching unit 113 changes the control mode from the normal mode to the transition mode.

  Next, the controller 100 performs step S11. In step S11, the first valve control unit 116 stops the feedback control of the first valve 7A, and the second valve control unit 117 stops the feedback control of the second valve 7B. Thereafter, the first valve control unit 116 maintains the opening command values for the first valve 7A and the second valve 7B at the values derived in step S07.

  Next, the controller 100 performs step S12. In step S12, the opening width control unit 118 controls the width adjusting unit 42 so as to increase the opening width of the gas wiping nozzle 41 as compared with the first period and the second period. For example, the opening width control unit 118 acquires the widths of the first steel strip and the second steel strip from the steel strip information acquisition unit 111, and adds a second margin larger than the first margin to the larger one of them. The obtained value is set as a command value for the opening width, and the command value is output to the width adjusting unit 42. For this reason, as shown in FIG. 7, the opening width W3 of the gas wiping nozzle 41 in the transition period T3 is larger than the opening width W1 in the first period T1 and the opening width W2 in the second period T2. The second margin is set in advance by preconditioning.

  Returning to FIG. 6, the controller 100 next executes step S13. In step S13, the target pressure setting unit 112 sets a target value for the discharge pressure in the second period. For example, the target pressure setting unit 112 acquires the target value of the basis weight in the second period (target value of the basis weight on the second steel strip) and the line speed from the steel strip information acquisition unit 111, and according to these Set the target value for the discharge pressure.

  Next, the controller 100 performs step S14. In step S14, the blower speed control unit 115 derives the opening width of the gas wiping nozzle 41 in the second period. For example, the blower speed control unit 115 acquires the width of the second steel strip from the steel strip information acquisition unit 111, adds a first margin to the width, and derives the opening width of the gas wiping nozzle 41 in the second period.

  Next, the controller 100 performs step S15. In step S <b> 15, the blower speed control unit 115 derives a command value for the operation speed of the blower 5 in the second period based on the data list 114 and outputs the command value to the blower 5. For example, the blower speed control unit 115 searches the data list 114 for the operation speed of the blower 5 corresponding to the target value of the discharge pressure set in step S12 and the opening width derived in step S13, and uses this as the command value. To do. Further, the blower speed control unit 115 may derive the operation speed of the blower 5 by interpolating between data in the data list 114 by a method such as linear interpolation.

  Since the derivation of the opening width of the gas wiping nozzle 41 in step S14 and the derivation of the command value of the operation speed in step S15 need only be executed at least prior to the start of the second period, the controller 100 These may be performed prior to the start of the transition period.

  Next, the controller 100 performs step S16. In step S16, the steel strip information acquisition part 111 acquires again the information regarding the steel strip 9 in conveyance from a high-order controller, and updates it.

  Next, the controller 100 performs step S17. In step S17, the control mode switching unit 113 confirms whether or not the transition period has been completed based on the information updated in step S16. For example, the control mode switching unit 113 determines that the transition period has been completed when the distance from the connection portion (connection portion that has passed through the gas wiping nozzle 41) to the gas wiping nozzle 41 is equal to or greater than a predetermined value.

  If it is determined in step S17 that the transition period has not been completed, the controller 100 returns the process to step S16. Thereafter, the update of the information on the steel strip 9 and the confirmation of the completion of the transition period are repeated until the transition period is completed.

  If it is determined in step S17 that the transition period has been completed, the controller 100 executes step S18. In step S18, the control mode switching unit 113 changes the control mode from the transition mode to the normal mode. Thereafter, the controller 100 returns the process to step S03. Thereby, control in the normal mode is resumed.

  If it is determined in step S08 that the conveyance of the steel strip 9 has stopped, the controller 100 ends the process. This completes the gas wiping procedure.

[Effect of this embodiment]
As described above, the gas wiping device 3 includes the gas wiping nozzle 41 that blows gas onto the steel strip 9 to which the molten metal for plating is attached, the width adjusting unit 42 that changes the opening width of the gas wiping nozzle 41, The blower 5 that supplies gas to the gas wiping nozzle 41, the first valve 7A and the second valve 7B that adjust the opening degree of the gas flow path between the gas wiping nozzle 41 and the blower 5, and the gas wiping nozzle 41 The controller 100 includes a first pressure sensor 8A and a second pressure sensor 8B that detect the pressure of the supplied gas, and the controller 100 includes a target value of the pressure of the gas supplied to the gas wiping nozzle 41, and an opening. It has a data list 114 including a plurality of data for deriving the operating speed of the blower 5 according to the width, and according to the width of the steel strip 9 Control the width adjusting unit 42 so as to adjust the opening width, and derive a command value of the operating speed of the blower 5 according to the target value of pressure and the opening width based on the data list 114, and output to the blower 5 And feedback controlling the first valve 7A and the second valve 7B so as to reduce the deviation between the target value of the pressure and the detected values of the first pressure sensor 8A and the second pressure sensor 8B. Is configured to run.

  According to this gas wiping device 3, the first valve 7A and the second valve 7B are provided between the target value of the discharge pressure of the gas wiping nozzle 41 and the detection values of the first pressure sensor 8A and the second pressure sensor 8B. Feedback control is performed to reduce the deviation. On the other hand, the blower 5 is controlled using the data list 114. That is, using the data list 114, the operating speed of the blower 5 corresponding to the target pressure value and the opening width is derived and output to the blower 5. If the blower 5 is feedback controlled so as to reduce the control deviation of the blowing pressure, the feedback control in the blower 5 and the feedback control in the first valve 7A and the second valve 7B influence each other, and the gas wiping nozzle 41 There is a case where the stabilization of the discharge pressure becomes slow. On the other hand, by controlling the blower 5 using the data list 114, the operation speed of the blower 5 is immediately responded to the command value without being affected by the operation of the first valve 7A and the second valve 7B. Stabilize early. Moreover, the influence which the fluctuation | variation of the operating speed of the air blower 5 has on the feedback control of the 1st valve 7A and the 2nd valve 7B becomes small. For this reason, the discharge pressure of the gas wiping nozzle 41 quickly follows the target value. Therefore, it is effective for appropriately controlling the gas discharge pressure in accordance with the variation in the opening width of the gas wiping nozzle 41.

  The data list 114 may be configured such that the operating speed of the blower 5 increases as the target value of pressure increases, and the operating speed of the blower 5 increases as the opening width increases. In this case, the operating speed of the blower 5 decreases when the target pressure value decreases, and the operating speed of the blower 5 decreases when the opening width decreases, so that energy loss in the first valve 7A and the second valve 7B can be reduced.

  The steel strip 9 includes a first steel strip and a second steel strip that are connected to each other and sequentially conveyed. The controller 100 includes a first period during which the first steel strip passes through the gas wiping nozzle 41, and a second steel strip. The width adjusting unit 42 is controlled so that the opening width of the gas wiping nozzle 41 is larger than that in the first period and the second period in the transition period between the first period and the second period in which the gas wiping nozzle 41 passes. Prior to the start of the second period, the command value of the operating speed of the blower 5 in the second period is derived based on the data list 114, and the feedback of the first valve 7A and the second valve 7B in the transition period The control is stopped, and a command value (hereinafter referred to as “second speed command value”) of the operation speed of the blower 5 in the second period is further output to the blower 5. It may be.

  If the control for increasing the opening width of the gas wiping nozzle 41 is not performed in the transition period as compared with the first period and the second period, the adhesion of the molten metal to the gas wiping nozzle 41 may increase. For example, when the width of the second steel strip is larger than that of the first steel strip, the expansion of the opening width of the gas wiping nozzle 41 may be delayed in transition from the first period to the second period. In this case, in the transition period, a state where the opening width of the gas wiping nozzle 41 is smaller than the width of the steel strip 9 may occur. In this state, as shown in FIG. 8, a portion Mp with a large amount of adhesion of the molten metal M occurs in the vicinity of the edge of the steel strip 9, and the molten metal is likely to be scattered (splash) from the portion Mp. The scattered molten metal Ms is likely to adhere to the gas wiping nozzle 41. On the other hand, in the transition period, by increasing the opening width of the gas wiping nozzle 41 compared to the first period and the second period, the above-mentioned splash is reduced, and adhesion of molten metal to the gas wiping nozzle 41 is prevented. Can be suppressed.

  On the other hand, if the control for expanding the opening width of the gas wiping nozzle 41 is executed during the transition period, the response of the blower 5, the first valve 7A, and the second valve 7B to the variation in the opening width may be delayed. If such a delay occurs, the discharge pressure continues to change even after the start of the second period, and the desired basis weight may not be obtained. On the other hand, during the transition period, the command value for the operating speed of the blower 5 is maintained at the second speed command value. Thereby, it is not necessary to change the command value of the operating speed of the blower 5 at the start of the second period. Further, during the transition period, feedback control of the first valve 7A and the second valve 7B is stopped. Thereby, the opening degree of the 1st valve | bulb 7A and the 2nd valve | bulb 7B in a transition period is maintained in the fluctuation | variation area | region on the assumption that combined use of control of the air blower 5, or its vicinity. For this reason, at the start of the second period, the discharge pressure of the gas wiping nozzle 41 can quickly follow the target value. Therefore, it is possible to appropriately control the gas discharge pressure while changing the opening width of the gas wiping nozzle 41 so as to reduce the splash.

  FIG. 9 shows the number of rotations of the blower 51 (hereinafter referred to as “blower rotation”) when the blower 5, the first valve 7A, and the second valve 7B are controlled in the transition mode and in the normal mode during the transition period. It is a graph comparing actual values of “number”. FIG. 9A is a graph showing the transition of the opening width of the gas wiping nozzle 41. The opening width of the gas wiping nozzle 41 in the transition period T3 gradually increases from the opening width in the first period T1, maintains a constant value, and then gradually decreases to the opening width in the second period T2. doing. FIG. 9B is a graph showing the transition of the measured value of the blower rotational speed when the blower 5, the first valve 7A, and the second valve 7B are controlled in the transition mode during the transition period T3. (C) of FIG. 9 is a graph which shows transition of the measured value of the blower rotational speed when the control of the blower 5, the first valve 7A, and the second valve 7B in the transition period T3 is performed in the normal mode.

  As shown in FIG. 9C, when the blower 5, the first valve 7A, and the second valve 7B are controlled in the normal mode in the transition period T3, the blower rotational speed overshoots in the latter half of the transition period T3. However, the blower rotational speed fluctuates even after the start of the second period T2. This change is considered to be caused by delays in the responses of the blower 5, the first valve 7A, and the second valve 7B with respect to the change in the opening width of the gas wiping nozzle 41 in the transition period T3. On the other hand, as shown in FIG. 9B, when the blower 5, the first valve 7A, and the second valve 7B in the transition period T3 are controlled in the transition mode, the blower rotational speed is set to the second period. Prior to the start of the second period, it converges to the target value R1 of the rotational speed in the second period, and is kept substantially constant after the start of the second period.

  FIG. 10 shows measured values of the discharge pressure (first pressure sensor 8A) when the blower 5, the first valve 7A, and the second valve 7B are controlled in the transition mode and in the normal mode during the transition period. Or a detection value of the second pressure sensor 8B). (A) of FIG. 10 is a graph which shows transition of the opening width of the gas wiping nozzle 41 similarly to (a) of FIG. FIG. 10B is a graph showing the transition of the measured value of the discharge pressure when the blower 5, the first valve 7A, and the second valve 7B are controlled in the transition mode during the transition period T3. (C) of FIG. 10 is a graph which shows transition of the measured value of the discharge pressure when the control of the blower 5, the first valve 7A, and the second valve 7B in the transition period T3 is performed in the normal mode.

  As shown in FIG. 10C, when the blower 5, the first valve 7A, and the second valve 7B are controlled in the normal mode in the transition period T3, the discharge pressure overshoots in the latter half of the transition period T3. The discharge pressure fluctuates even after the start of the second period. This change is also considered to be caused by delays in the responses of the blower 5, the first valve 7A, and the second valve 7B with respect to the change in the opening width of the gas wiping nozzle 41 in the transition period T3. On the other hand, as shown in FIG. 10B, when the control of the blower 5, the first valve 7A, and the second valve 7B in the transition period T3 is performed in the transition mode, the discharge pressure is the second period T2. The value converges to the target value R2 with the start of, and remains substantially constant thereafter.

  FIG. 11 is a graph comparing measured values of the basis weight with the case where the control of the blower 5, the first valve 7A and the second valve 7B in the transition period is performed in the transition mode and the case where the control is performed in the normal mode. . (A) of FIG. 11 is a graph which shows transition of the opening width of the gas wiping nozzle 41 similarly to (a) of FIG. FIG. 11B is a graph showing the transition of the actual measurement value of the basis weight when the control of the blower 5, the first valve 7A, and the second valve 7B in the transition period T3 is performed in the transition mode. (C) of FIG. 11 is a graph which shows transition of the actual value of the basis weight when the blower 5, the first valve 7A, and the second valve 7B are controlled in the normal mode in the transition period T3.

  As shown in FIG. 11C, when the control of the blower 5, the first valve 7A, and the second valve 7B in the transition period T3 is performed in the normal mode, the basis weight overshoots in the latter half of the transition period T3. The basis weight varies even after the start of the second period. This variation is also considered to be caused by delays in the responses of the blower 5, the first valve 7A, and the second valve 7B with respect to the variation in the opening width of the gas wiping nozzle 41 during the transition period. On the other hand, as shown in FIG. 11B, when the control of the blower 5, the first valve 7A, and the second valve 7B in the transition period T3 is performed in the transition mode, the weight per unit area is the second period. It quickly converges to the target value R3 after the start, and is kept substantially constant thereafter.

  Although the embodiment has been described above, the present invention is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  In the above-described embodiment, the configuration in which the gas is supplied to both the first nozzle unit 4 </ b> A and the second nozzle unit 4 </ b> B from one blower 5 has been described, but the blower 5 may be provided for each nozzle unit 4. . That is, the gas wiping device 3 may include two blowers 5 that supply gas to the first nozzle unit 4A and the second nozzle unit 4B, respectively (hereinafter referred to as blowers that supply gas to the first nozzle unit 4A). 5 is referred to as “first blower 5A”, and the blower 5 that supplies gas to the second nozzle unit 4B is referred to as “second blower 5B”. In this case, the controller 100 is divided into a controller that controls the first nozzle unit 4A, the first valve 7A, and the first blower 5A, and a controller that controls the second nozzle unit 4B, the second valve 7B, and the second blower 5B. It may be.

  DESCRIPTION OF SYMBOLS 3 ... Gas wiping apparatus, 9 ... Steel strip, 5 ... Blower, 7A ... 1st valve (pressure control valve), 7B ... 2nd valve (pressure control valve), 8A ... 1st pressure sensor, 8B ... 2nd pressure sensor , 100... Controller, 41... Gas wiping nozzle, 42.

Claims (4)

A gas wiping nozzle that blows gas onto a steel strip to which molten metal for plating is attached;
A width adjusting unit for changing an opening width of the gas wiping nozzle;
A blower for supplying the gas to the gas wiping nozzle;
A pressure control valve for adjusting an opening degree of the gas flow path between the gas wiping nozzle and the blower;
A pressure sensor for detecting the pressure of the gas supplied to the gas wiping nozzle;
A controller, and
The controller is
A data list including a plurality of data for deriving an operating speed of the blower corresponding to a target value of the pressure of the gas supplied to the gas wiping nozzle and the opening width;
Controlling the width adjusting portion to adjust the opening width according to the width of the steel strip;
Deriving a command value of the operating speed of the blower according to the target value of the pressure and the opening width based on the data list, and outputting the command value to the blower;
A gas wiping apparatus configured to perform feedback control of the pressure control valve so as to reduce a deviation between a target value of the pressure and a detection value of the pressure sensor. The steel strip includes a first steel strip and a second steel strip that are connected to each other and conveyed in order,
The controller is
In the transition period between the first period in which the first steel strip passes through the gas wiping nozzle and the second period in which the second steel strip passes through the gas wiping nozzle, the first period and the second period Controlling the width adjusting unit to increase the opening width of the gas wiping nozzle as compared to a period;
Prior to the start of the second period, deriving a command value for the operating speed of the blower in the second period based on the data list;
In the transition period, the feedback control of the pressure control valve is stopped, and a command value of the operating speed of the blower in the second period is further output to the blower. Item 2. A gas wiping apparatus according to Item 1. The data list is:
The operation speed of the blower increases as the target value of the pressure increases, and the operation speed of the blower increases as the opening width increases. The gas wiping apparatus as described. Adjusting the opening width of the gas wiping nozzle that blows the gas supplied from the blower to the steel strip to which the molten metal for plating adheres, according to the width of the steel strip;
Based on a data list including a plurality of data for deriving an operating speed of the blower corresponding to a target value of the pressure of the gas supplied to the gas wiping nozzle and the opening width, the target value of the pressure And deriving a command value of the operating speed of the blower according to the opening width, and outputting the command value to the blower,
Targeting a pressure control valve that adjusts the opening degree of the gas flow path between the gas wiping nozzle and the blower, detection of the target value of the pressure and the pressure of the gas supplied to the gas wiping nozzle Feedback control of the pressure control valve so as to reduce a deviation between the values.

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