JP2012226464A - Process temperature control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process temperature control method capable of neatly controlling temperature in a manufacturing process that requires processes of heating and cooling.SOLUTION: A process temperature control method in a manufacturing process of a melted material includes: a step for preliminarily determining minimum control output to a flow valve according to minimum flow that can stabilize supply of cooling water to a cooler of a container equipped with the cooler and a heater; a step for obtaining a difference between actually-measured temperature of the material, which is measured in the manufacturing process of the melted material, and predetermined target temperature; and a step for, when the difference is close to the target temperature, controlling temperature of the melted material in the container by adjusting heating by the heater while supplying the minimum flow of cooling water through the minimum control output.

Description

  The present invention relates to a process temperature control method for accurately performing temperature control during heating and cooling processing in a manufacturing process that requires heating and cooling processing in an industrial or chemical plant.

  Conventionally, process temperature control in an industrial / chemical plant, for example, consists of a heater with two heating functions with different maximum heating capacities and a cooler with two cooling functions with different maximum cooling capacities. An extruder equipped with a cylinder is used. In the extruder, the melting temperature is controlled in the process of friction and shearing while the pellet-shaped plastic is melted. That is, the temperature of the cylinder provided in the extruder is measured by a sensor, and threshold values are set on the plus side and the minus side with respect to the deviation between the actually measured value of the measurement result and a predetermined target value. The cooling control output decreases toward the positive threshold value, while the heating control output is controlled to decrease toward the negative threshold value. Therefore, heating and cooling are simultaneously performed within the threshold range (see Patent Document 1).

JP 2004-246773 A

  In the conventional process temperature control method, the temperature can be controlled if the deviation between the target temperature of the molten material and the measured temperature is about ± 4 to 5 ° C., but the temperature cannot be controlled if the deviation is within ± 1 ° C. Therefore, as a result of intensive studies by repeating experiments to solve the problem, the inventors have obtained the following knowledge.

  That is, it was found that if the amount of cooling water supplied into the cylinder is reduced near the target temperature, a small amount of cooling water cannot be continuously supplied by the flow valve provided in the cylinder. . Further, in the case of controlling the cooling of the melted material to be controlled at a target temperature higher than 100 ° C., the heat removal of the extruder is performed by the sensible heat action by the cooling water supplied to the cylinder and the cooling by the vaporization heat. Here, since the cooling by the heat of vaporization is larger than the cooling efficiency by the sensible heat action (the amount of heat removed per unit amount of cooling water), even if a slight change in the amount of cooling water supplied to the cylinder is caused by the heat of vaporization It was found that a large error occurred in the cooling accuracy, and as a result, the process temperature control near the target temperature could not be performed with high accuracy.

  The present invention has been made in view of such circumstances, and a main object thereof is to provide a process temperature control method capable of accurately controlling the temperature of a molten material in the vicinity of a target temperature.

In order to achieve such an object, the present invention has the following configuration.
That is, in the process temperature control method in the manufacturing process of the molten material,
The minimum control output to the flow valve according to the minimum flow rate that can keep the supply of the cooling water to the cooler of the container equipped with the cooler and the heater constant is determined in advance.
Find the deviation between the measured temperature of the material measured during the manufacturing process of the melted material and the predetermined target temperature,
When the deviation is in the vicinity of the target temperature, the temperature of the molten material in the container is controlled by adjusting the heating by the heater while supplying the cooling water with the minimum flow rate to the cooler by the minimum control output. It is characterized by that.

  (Operation / Effect) According to the above method, when the deviation obtained from the target temperature and the measured temperature of the melted material is in the vicinity of the target temperature, the minimum control output capable of supplying a certain amount of cooling water to the cooler. Fix the opening of the flow valve. When the molten material needs to be cooled, the cooler is always filled with a certain amount of cooling water, so that the cooling by the heat of vaporization can be stabilized. Therefore, in the process where the deviation converges to the target value, the heater is operated according to the deviation and the cooling action is offset by heating to adjust the temperature. As a result, the temperature of the molten material in the container can be accurately controlled near the target temperature.

  In the process temperature control method, the process temperature control near the target temperature may be performed as follows.

  When calculating the control output for determining the opening of the flow valve based on the deviation at least on the minus side of the deviation, the minimum control output is set as a threshold, and the target temperature is reached from the time when the threshold is reached in the actual measurement calculation process. Heating by the heater is adjusted while supplying the cooling water with the lowest flow rate to the cooler until it reaches.

  That is, after the deviation becomes zero, the cooling water supply to the cooler and the heating by the heater are stopped, and then the control is switched to the heating control by the heater on the plus side of the deviation.

  According to this method, in the vicinity of the target temperature, temperature control by cooling and heating can be accurately performed within a necessary range from the minus threshold to the target temperature.

  In the range of deviation on the plus side of the target temperature that requires temperature control by active heating, temperature control is performed only by the heater. That is, when cooling is performed with cooling water in the above range and heating is performed using a heater, inconveniences such as poor energy efficiency that tend to occur in the process of increasing the heating control output can be avoided.

  In the above method, the threshold value may be set on the plus side of the difference, and the supply of the cooling water to the cooler may be stopped when the threshold value is exceeded in the actual measurement calculation process, and the control may be switched to the heating control by the heater. .

  According to this method, when temperature control by cooling and heating is performed in a range where active heating is performed, energy efficiency is deteriorated, but by accurately controlling cooling and heating by heat of vaporization, the temperature near the target temperature can be controlled. Temperature control can be performed with high accuracy. Furthermore, since the heating control functions continuously when switching from the range of the heating control with the cooling control to a range where the cooling control is unnecessary and only the heating control is required, the process temperature control can be performed efficiently.

  In the above method, a combination of a heater having a system having a different maximum heating amount and a cooler having a system having a different maximum cooling amount is used to reach a target temperature from when a predetermined temperature deviation threshold is reached. In this range, it is preferable to control the process temperature by simultaneously using the system having the smaller maximum heating amount and the maximum cooling amount.

  According to this method, since a dedicated system for heating and cooling can be used in a region where the temperature deviation is small, it is possible to cause hunting that tends to occur when temperature is controlled by a single device having only one function. Therefore, the process temperature control can be performed with high accuracy.

  According to the process temperature control method of the present invention, the process temperature control can be accurately performed in the vicinity of the target temperature of the material in the manufacturing process of the molten material.

It is a side view which shows schematic structure of the extruder used for an Example, and its periphery. It is a block diagram which shows the structure of a cylinder. It is the block diagram which showed the control process of the cylinder. It is a figure which shows the relationship between the heating control output and cooling control output in a temperature control process. It is a flowchart which shows the control processing by the 2nd PID controller for cooling. It is a flowchart which shows the control processing by the PID controller for 2nd heating. It is a figure which shows the relationship between the heating control output in the process temperature control of a modification, and a cooling control output. It is the block diagram which showed the control process of the cylinder of a modification. It is a figure which shows the relationship between the heating control output in the process temperature control of a modification, and a cooling control output.

  Embodiments of the present invention will be described below with reference to the drawings.

  In this embodiment, a case where the temperature of a material (resin) melted in the extruder is controlled in the process of manufacturing a film using the extruder will be described as an example. Therefore, this example is merely an example, and the process temperature control method of the present invention is not limited to film production, and can be used for temperature control of a material melted in the production process.

  FIG. 1 is a side view showing a schematic configuration of an extruder, and FIG. 2 is a block diagram showing a schematic configuration of a cylinder and its surroundings.

  An extruder 1 used in this embodiment shown in FIG. 1 includes a hopper 3 that supplies a material 2 such as a pellet-shaped plastic, a conveying unit 5 that conveys the material 2 while being frictionally and sheared by an internal screw 4, and a conveying It comprises a cylinder 6 that heats, cools or combines the material 2 in the part 5 and a die 7 that coats the surface of the cooling roll 8 that cools and hardens the material 2 melted in the transport part 5. Yes.

  The material 2 applied to the cooling roll 8 from the extruder 1 includes a thickness adjusting roll 9, a transport roll 10 group, and a surface treatment unit 11 that performs surface treatment (for example, corona treatment) of the material 2 formed into a film after adjusting the thickness. In this order, and is wound and collected by the collection destination turret 12. Hereinafter, the structure of each part is demonstrated concretely.

  A plurality of cylinders 6 are arranged at substantially equal intervals from the base end of the transport unit 5 on the hopper 3 side toward the tip of the die 7. Each cylinder 6 is composed of a pipe that circulates cooling water and the like, and includes a cooler that cools the transport unit 5 and a heater that heats the transport unit 5.

  Moreover, as shown in FIG. 2, the PID controller 13 which transmits the various output signals for operating a heater and a cooler is provided. The PID controller 13 will be described later.

  The heater includes a heater 14, a power regulator 15 that regulates the amount of power supplied to the heater 14, and a semiconductor relay 16 (SSR: Solid State Relay) that controls the heating temperature by operating the on / off timing of the heater 14. ).

  The power regulator 15 allows different maximum heating amounts to be output by the heater 14. Specifically, two power adjusting resistors R1 and R2 having different resistance values are connected in parallel in combination with resistance switching relays 17a and 17b, and two heaters having different maximum heating capacities are provided. It is composed.

  That is, each of the resistance switching relays 17 a and 17 b is connected to the PID controller 13, and one of the resistance switching relays 17 a and 17 b is turned on in response to a signal from the PID controller 13. For example, when the resistance value is set to satisfy the relationship R1 <R2, and the resistor R1 is turned on and the first system is used, it is larger than the power supplied from the second system side provided with the resistor R2. Electric power is supplied to the heater 14. Conversely, when the resistor R2 is turned on and the second system side is used, electric power smaller than the electric power on the first system side is supplied to the heater 14. Therefore, a heater having two heating systems with different maximum heating capacities can be configured.

  The cooler has two cooling systems that can keep the amount of cooling water supplied to the cylinder 6 constant. The two cooling systems are supplied with different flow rates of cooling water. Specifically, a cooling unit 18 having a buffer tank as a cooling water supply source, a control valve 19 for switching the cooling water supply amount, and a first electromagnetic for each pipe branched downstream from the control valve 19. A valve 20 and a second electromagnetic valve 22 are provided. Further, a first manual valve 21 is provided on the downstream side of the first electromagnetic valve 20. A second manual valve 23 is provided on the downstream side of the second electromagnetic valve 22.

  The maximum cooling capacity is set larger on the first system side of the cooler than on the second system side. That is, the opening degree of the first manual valve 21 is set to be larger than the opening degree of the second manual valve 23 in advance. After the opening degree of the first manual valve 21 is set in advance, use / unuse is determined by turning on / off the first electromagnetic valve 20. However, the flow rate of the cooling water supplied from the first system side to the cylinder 6 is larger than the flow rate of the cooling water supplied from the second system to the cylinder 6.

  Similarly, on the second system side of the cooler, after the opening degree of the second manual valve 23 is set in advance, whether the second system is used or not is determined by turning on / off the second electromagnetic valve 22.

  Note that switching of the cooling water supply amount to the first system or the second system is performed by adjusting the control valve 19 using a signal transmitted from the PID controller 13.

  Further, the opening degree of the first manual valve 21 and the second manual valve 23, the on / off state of the first electromagnetic valve 20 and the second electromagnetic valve 22, and the opening degree of the control valve 19 are determined in advance by experiments and simulations. Each of these valves corresponds to the flow valve of the present invention.

  In addition, each cylinder 6 shown in FIG. 1 is equipped with the above-mentioned heater and cooler separately, and it is comprised so that temperature control can be carried out independently for every cylinder 6. FIG.

  The cooling roll 8 is configured such that cooling water circulates inside the roll. That is, in the process in which the material 2 melted on the cooling roll 8 is uniformly stretched to form a film, the film is cooled and cured. As the thickness adjusting roll 9, for example, a metal or rubber one is appropriately used.

  Next, a process temperature control method that is a feature of the present embodiment will be described with reference to FIGS.

  When the temperature of the molten material is measured directly or indirectly with a sensor, a deviation is obtained from a predetermined target value and an actual measurement value, and when the deviation falls within the target value range from the predetermined threshold value, the cooler The second system having the smaller maximum heating output and maximum cooling output is selected from each of the heaters and process temperature control is performed. In a deviation region other than the set range, process temperature control is performed using one of the first system having the largest maximum heating output and the largest cooling output.

  First, before starting film production, the film production conditions are set in the controller switch 24 shown in FIG. For example, a temperature suitable for each of various materials used for manufacturing a target film is obtained in advance through experiments and simulations as a target value SV and is set and input.

  Moreover, the opening degree of the control valve 19 which determines the minimum flow rate at which a constant amount of cooling water can be continuously supplied to the cylinder 6 is determined using the second system of the cooler. Here, the minimum flow rate is determined from the amount of cooling water that is circulated and discharged by supplying a predetermined amount of cooling water into the cylinder 6 at room temperature. That is, the minimum flow rate at which the supply amount of the cooling water to the cylinder 6 and the discharge amount from the cylinder 6 continuously match each other is obtained in advance by experiments.

  When the minimum flow rate using the second system is determined, the minimum control output Mc2 is obtained from the characteristics of the control valve 19. In the present embodiment, the minimum control output is set to 10% from the comparison with the opening degree of the control valve 19 using the second system.

  Next, the switching timing to the 2nd system of a cooler and the 2nd system of a heater is determined. That is, the process temperature control range in the vicinity of the target value SV of the present invention is determined. For example, a negative deviation from the target value SV is determined by opening degree = deviation (target value SV−actual value PV) × gain of the control valve 19 that satisfies the minimum control output of the first system of the cooler by PID control calculation, The deviation is used as a threshold value. In the present embodiment, the threshold value is set to −3 ° C., and the process temperature control is set to be performed using the second system of the cooler in the range from the target value SV to the threshold value −3 ° C.

  In the process of using the second system of the cooler, the second system of the heater is activated when the cooling control output sequentially obtained by the PID control calculation reaches 10% of the predetermined minimum control output. It sets so that process temperature control may be performed using heating.

  The switching timing of the heater to the first system is set to 3 ° C. as a threshold value.

  In this embodiment, the deviation is set to + 10 ° C. when the heating control output is 100%, and is set to −10 ° C. when the cooling control output is 100%. If the deviation exceeds ± 10 ° C., the control output of 100% is maintained. It is set to do.

  When the input of the condition setting is completed, the production of the film is started. As the film is manufactured, the temperature of the cylinder 6 is sequentially measured by a temperature sensor or the like. That is, the correlation between the temperature change of the molten material 2 in the conveyance path 5 and the temperature change of the cylinder 6 is obtained in advance, and the temperature of the material 2 is indirectly measured. The actual measurement value PV and the target value SV are input to the controller switch 24 shown in FIG.

  In the controller switch 24, the deviation e = target value SV−actual value PV is obtained. When deviation e <threshold (−3 ° C.), process temperature control is performed using the first system of the cooler. Here, when the deviation e exceeds −10 ° C., that is, when maximum cooling is required, the conveyance path is supplied while supplying the cooling water to the cylinder 6 with a predetermined cooling control output 100% as shown in FIG. 5 is removed.

  When the deviation e is smaller than −10 ° C. and within the range up to the threshold value, the first cooling PID controller corresponds to the opening of the control valve 19 capable of supplying the cooling water supply amount corresponding to the deviation e to the cylinder 6. The cooling control output Mc1 to be obtained is sequentially obtained by the following equation (1).

ここで、ＰＢは比例帯、Ｔ_Iは積分時間、Ｔ_Dは微分時間、１００／ＰＢはゲインである。

Here, PB is a proportional band, T _I is an integration time, T _D is a differentiation time, and 100 / PB is a gain.

  As the deviation e becomes smaller, the opening degree of the control valve 19 corresponding to the cooling control output Mc1 obtained by the above equation (1) is reduced, and the amount of cooling water supplied to the cylinder 6 is reduced. When the deviation e reaches the threshold in the process, the controller switch 24 turns on the second cooling PID controller. And the 2nd cooling PID controller performs the process according to the flowchart shown in FIG.

  The second cooling PID controller sequentially obtains the deviation e from the target value (SV) of the cylinder temperature and the actually measured value (PV) of the cylinder. Similarly, the cooling control output corresponding to the opening degree at which the supply amount of the cooling water corresponding to the deviation e can be supplied to the cylinder 6 is sequentially obtained by the above equation (1) (step S1).

  It is monitored whether or not the obtained cooling control output Mc2 reaches a preset 10% (step S2). If the cooling control output Mc2 is 10% or more, the opening of the control valve 19 is adjusted using the value as it is (step S3).

  In step S2, when the cooling control output Mc2 falls below 10%, the minimum control output Mc2 is fixed to 10% in this state (step S4). At the same time, a flag is turned on from the second cooling PID controller to the second heating PID controller (step S5).

  Here, one of the second cooling PID controllers supplies the cylinder 6 with the cooling water having the lowest flow rate with the cooling control output Mc2 being 10%.

  On the other hand, the second heating PID controller obtains the control output Mh2 of the second system of the heater and adjusts the amount of electric power to the heater 14 according to the result to perform process temperature control. That is, as shown in FIG. 6, the second heating PID controller performs reception determination of a signal for turning on the flag from the second cooling PID controller in Step 10. When reception is confirmed, it is determined whether or not the signal is the first time (step S11).

If the received signal is the first time, the second heating PID controller stores the deviation e calculated at the present time as an initial deviation e _{0 in the} internal memory (step S12). At this time, since the deviation e is an initial value, e = e ₀ is set (step S13), and the heating control output Mh2 corresponding to the value is obtained using the above equation (1) (step S14).

In the subsequent heating control process by the second heating PID controller, the processing from step S10 to step S14 is repeatedly executed. In the second and subsequent processes, the deviation in step S13 is sequentially changed to deviation e ′. Therefore, the second and subsequent heating control outputs Mh2 are sequentially obtained as e ′ = e−e _{0 in} the above equation (1).

  That is, when the process temperature control by cooling is performed using only the second cooling PID controller, the cooling capacity is kept constant and the deviation e does not easily converge to the target value SV. The actual measurement value PV is controlled to approach the target value SV while adjusting the heating of the heater 14 to offset the cooling capacity.

  When the second heating PID controller receives a signal for turning off the flag from the second cooling PID controller, the deviation e turns to the plus side (e> 0) and it is determined that active heating is necessary. That is, the controller switching unit 24 turns off the cooler, obtains the control output Mh2 using the above formula (1) by the second heating PID controller (step S14), and the electric energy of the heater 14 according to the result The process temperature is controlled while adjusting and heating. In addition, the process temperature control using the 1st system | strain of a heater is performed by switching to the 1st heating PID controller from the time of the deviation e exceeding the threshold value 3 degreeC in a heating control process.

  As described above, in the process of manufacturing a film from the melted material 2, the temperature of the material 2 is close to the target value SV, and the predetermined minimum range of the second cooler system in the predetermined range where cooling is necessary. When the control output falls below the control output, the minimum control output obtained from the combination of the second manual valve 23 and the control valve 19 is supplied to the cylinder 6 while keeping the minimum flow rate of cooling water constant. By offsetting the cooling capacity using the second system of the heater, the amount of cooling water vaporized in the cylinder 6 can be kept constant without error. That is, by continuously supplying a certain amount of cooling water that can be controlled to the minimum into the cylinder 5, the amount of heat removal can be stabilized without error. Since the temperature is controlled while offsetting the excessive cooling effect by heating with a heater with a small maximum control output in a stable state of vaporization heat, fine temperature adjustment is possible and the measured value PV can be brought close to the target value SV. . Therefore, it is possible to perform delicate temperature control within the range of ± 1 ° C. of the target value.

  Moreover, since it is not necessary to provide an expensive and special system for each of the plurality of cylinders 6 that can supply a small amount of cooling water while keeping it constant, the cost of the apparatus can be reduced.

  The present invention is not limited to the embodiment described above, and can be modified as follows.

  In the above-described embodiment apparatus, a threshold value is provided on the minus side from the target value SV, and the minimum flow rate is maintained using the second system of the cooler within the range from the threshold value to the target value. Thus, process temperature control may be performed.

  (1) In the case where the deviation e tends to approach the target value SV, the process temperature control may be performed so that the cooling water having the lowest flow rate is supplied to the cylinder 6 when the actual measurement value PV matches the target value SV. . For example, as shown in FIG. 7, the cooling control output is decreased from a cooling control output of 100% at a deviation of −10 ° C. toward a target value SV having a deviation of zero.

  In this case, a cooler having two systems shown in FIG. 2 may be used, or a cooler having only one system shown in FIG. 8 may be used. In the case of this configuration, an electromagnetic valve is not necessary because the system is switched.

  In the case of a cooler having two systems, a threshold value is determined in advance as a timing for simultaneously using the second system of the heater. For example, when the threshold is set to −3 ° C. as in the above embodiment, the amount of cooling water supplied to the cylinder 6 is larger than that in the above embodiment at −3 ° C. It is necessary to increase the control output of the heater 14 on the two systems as compared with the case of the above embodiment.

Therefore, unlike the above embodiment, this embodiment does not depend on a signal from the second cooling controller, and the second heating controller itself monitors the deviation e sequentially. In the process, from the point where the cooling control output Mc2 calculated by the second cooling controller deviation e at the time of the previous high value to be 10% preset as a fixed deviation e _0, it reaches the deviation e ₀ Heat control is performed. In addition, switching to the 2nd system | strain of a cooler is set to a threshold value (-3 degreeC) similarly to the said Example.

  As shown in FIG. 8, in the case of a cylinder configuration in which the cooler has only one cooling function, the opening degree of the manual valve 21A is determined and fixed in advance, and the cooling control output is controlled within a range of 100% to 10%. The opening degree of the valve 19 may be adjusted. Further, the process temperature may be controlled by adjusting the heating using the second system of the heater from the time when the threshold is reached.

  (2) As another modification, for example, as shown in FIG. 9, a threshold value is provided on the plus side of the deviation, and the second system of the cooler and the second system of the heater are within the range of the minus side to the plus side threshold value. Are used simultaneously to control the process temperature. According to this method, since positive heating is performed in the range of the threshold value on the plus side from the target value, the amount of the cooling water having the minimum flow rate that is guaranteed in the minus region tends to increase. Therefore, since temperature control by cooling and heating is performed within the range where active heating is performed, energy efficiency is deteriorated, but temperature control near the target temperature can be performed by accurately controlling cooling and heating by heat of vaporization. It can be performed with high accuracy. Furthermore, since the heating control functions continuously when switching from the range of the heating control with the cooling control to a range where the cooling control is unnecessary and only the heating control is required, the process temperature control can be performed efficiently.

DESCRIPTION OF SYMBOLS 1 ... Extruder 2 ... Material 3 ... Hopper 6 ... Cylinder 13 ... PID controller 14 ... Heater 15 ... Power regulator 16 ... SSR
17a, b ... Resistance switching relay 18 ... Cooling unit 19 ... Control valve 20 ... First electromagnetic valve 21 ... First manual valve 22 ... Second electromagnetic valve 23 ... Second manual valve 24 ... Controller switch R1, R2 ... Resistor

Claims (5)

In the process temperature control method in the manufacturing process of the molten material,
The minimum control output to the flow valve according to the minimum flow rate that can keep the supply of the cooling water to the cooler of the container equipped with the cooler and the heater constant is determined in advance.
Find the deviation between the measured temperature of the material measured during the manufacturing process of the melted material and the predetermined target temperature,
When the deviation is in the vicinity of the target temperature, the temperature of the molten material in the container is controlled by adjusting the heating by the heater while supplying the cooling water with the minimum flow rate to the cooler by the minimum control output. A process temperature control method characterized by the above. The process temperature control method according to claim 1,
When calculating the control output for determining the opening of the flow valve based on the deviation at least on the minus side of the deviation, the minimum control output is set as a threshold, and the target temperature is reached from the time when the threshold is reached in the actual measurement calculation process. A process temperature control method characterized by adjusting the heating by the heater while supplying the cooling water with the lowest flow rate to the cooler in a range until it reaches. The process temperature control method according to claim 2, wherein
A process temperature control method characterized by switching to heating control by a heater after stopping the supply of cooling water to the cooler and heating by the heater from the time when the deviation becomes larger than zero. The process temperature control method according to claim 2, wherein
The process temperature control is characterized in that the threshold value is also set on the plus side of the deviation, the supply of the cooling water to the cooler is stopped from the time when the threshold value is exceeded in the actual measurement calculation process, and the control is switched to the heating control by the heater. Method. In the process temperature control method according to any one of claims 2 to 4,
Using a combination of a heater with a system with a different maximum heating amount and a cooler with a system with a different maximum cooling amount, the maximum heating amount in the range from the point at which a predetermined temperature deviation threshold is reached to the target temperature And a process temperature control method using the system with the smaller maximum cooling amount simultaneously to control the process temperature.

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