JP2007055036A - Sheet molding apparatus and roll gap control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To automatically continue the molding of a sheet without causing trouble, such as the stop of the operation of a roll driving motor or the falling of a molten resin even if the extrusion amount of the molten resin from an extruder is varied under a state that the gap between rolls is kept constant to perform the molding of the sheet. <P>SOLUTION: In a case that the pressing load P acting on the rolls exceeds a preset upper limit value Pmax or a preset lower limit value Pmin under a state that the gap between the rolls is controlled by a roll gap constant control mode, control for changing over the roll gap constant control mode to a pressing load constant control mode is performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet forming apparatus and a roll gap control method, and in particular, a sheet forming apparatus by a touch roll that passes a sheet between two rolls and performs sheet forming in a state where the front and back surfaces of the sheet are in contact with the two rolls. The present invention relates to a roll gap control method for the sheet forming apparatus.

  As a sheet forming apparatus by an extrusion method, there are two rolls arranged in parallel with a gap, and a sheet (molten resin from a T-die) is passed between the two rolls that are rotationally driven. Some perform sheet forming in a state where the front and back surfaces of the sheet are in contact with the roll (for example, Patent Documents 1 and 2).

In the conventional sheet forming apparatus, a wedge member is inserted between roll support housings (bearing housings) of two rolls, and one roll support housing is pressed against the other roll support housing by a hydraulic cylinder device to support the two rolls. The roll gap is adjusted by the amount of the wedge member inserted between the housings. Thereby, sheet forming can be performed while keeping the roll gap constant.
JP-A-9-155948 Japanese Patent Laid-Open No. 10-34748

  However, in the sheet production process in which sheet forming is performed while keeping the roll gap constant, the amount of molten resin extruded from the extruder is reduced due to operational errors, material supply failures, maintenance failures such as filter clogging, temperature changes, etc. When it fluctuates, the following problems arise.

  If the extrusion amount of the molten resin increases even temporarily, the melt bank due to the molten resin between the rolls becomes excessive, and the roll driving load increases. For this reason, the roll drive motor becomes overloaded, and a trouble that stops operation due to torque over occurs. Moreover, in a rubber roll etc., there exists a possibility that a roll may be damaged.

  When the extrusion amount of the molten resin decreases, the molten resin does not properly contact the roll, and the molten resin falls below the gap between the rolls, so that the sheet cannot be formed.

  The problem to be solved by the present invention is that the roll drive motor is stopped or melted even if the amount of molten resin extruded from the extruder fluctuates in a state where sheet forming is performed with the roll gap kept constant. It is to be able to automatically continue sheet forming without causing trouble such as resin dropping.

  The sheet forming apparatus according to the present invention has two rolls arranged in parallel with a gap, and a sheet is passed between the two rolls that are rotationally driven, and the front and back surfaces of the sheet are in contact with the two rolls. In a sheet forming apparatus that performs sheet forming in a state where the sheet is formed, a roll gap adjusting unit that increases or decreases a roll gap by displacing an arrangement position of at least one of the two rolls, and a gap between the two rolls is a predetermined amount A roll gap constant control mode in which the roll gap is adjusted by the roll gap adjusting means so as to become a control target value, and the roll gap is adjusted by the roll gap adjusting means so that the pressing load acting on the roll becomes a predetermined control target value. There are two control modes, the constant pressing load control mode for adjusting the pressure, and one of the control modes is selectively executed between the rolls. A roll gap control means for controlling the roll gap, and the roll gap control means controls the roll gap in a roll gap constant control mode, and the pressing load acting on the roll is set to a predetermined upper limit value. Alternatively, when the lower limit value is exceeded, control to switch to the constant pressing load control mode is performed.

  The sheet forming apparatus according to the present invention has two rolls arranged in parallel with a gap, and a sheet is passed between the two rolls that are rotationally driven, and the front and back surfaces of the sheet are in contact with the two rolls. In a sheet forming apparatus that performs sheet forming in a state of being performed, a roll gap adjusting unit that increases or decreases a roll gap by displacing an arrangement position of at least one of the two rolls, and a gap between the two rolls is measured. The roll gap measuring means, the pressing load measuring means for measuring the pressing load acting on the roll, and the roll gap adjusting means so that the roll gap measured by the roll gap measuring means becomes a predetermined control target value. The roll gap constant control mode for adjusting the gap, and the pressing load measured by the pressing load measuring means becomes a predetermined control target value. Roll pressure control means for controlling the roll gap by selectively executing either one of the control modes, ie, a constant pressing load control mode for adjusting the roll gap by the roll gap adjustment means. The roll gap control means has a preset upper limit value or lower limit value for the pressing load measured by the pressing load measurement means in a state where the roll gap is controlled by the roll gap constant control mode. When it exceeds, control to switch to the constant pressing load control mode is performed.

  In the sheet forming apparatus according to the present invention, preferably, the roll gap control means controls a roll gap in a roll gap constant control mode, and a pressing load acting on the roll is set to an upper limit value set in advance or The pressing load constant control mode to be executed when the lower limit value is exceeded is performed by a preset pressing load, or the upper limit value or the lower limit value of the pressing load.

  In the sheet forming apparatus according to the present invention, preferably, the roll gap control means controls a roll gap in a roll gap constant control mode, and a pressing load acting on the roll is set to an upper limit value set in advance or When the roll gap returns to the range between the preset upper limit value and lower limit value under the condition that the roll gap is controlled by the constant pressing load control mode due to exceeding the lower limit value, or the roll gap is When the roll gap immediately after switching from the constant roll gap control mode to the constant pressing load control mode changes to a value close to the preset roll gap, or when the roll gap returns to the control target value for the constant roll gap control Performs control to switch to the constant roll gap control mode.

  A roll gap control method for a sheet forming apparatus according to the present invention includes two rolls arranged in parallel with a gap, and a sheet is passed between the two rolls that are rotationally driven. In a roll gap control method for a sheet forming apparatus that forms a sheet in a state where the front and back surfaces are in contact with each other, the roll gap adjustment means displaces the arrangement position of at least one of the two rolls to increase or decrease the roll gap. The roll gap is controlled by a roll gap constant control mode in which the roll gap is adjusted by the roll gap adjusting means so that the gap between the two rolls becomes a predetermined control target value. When the pressing load exceeds a preset upper limit value or lower limit value, the pressing load acting on the roll is a predetermined control value. Controlling the roll gap by pressing load constant control mode for adjusting the roll gap by the roll gap adjusting means so that the value.

  A roll gap control method for a sheet forming apparatus according to the present invention includes two rolls arranged in parallel with a gap, and a sheet is passed between the two rolls that are rotationally driven. In a roll gap control method for a sheet forming apparatus that forms a sheet in a state where the front and back surfaces are in contact with each other, the roll gap adjustment means displaces the arrangement position of at least one of the two rolls to increase or decrease the roll gap. The gap between the two rolls is measured by the roll gap measuring means, the pressing load acting on the roll is measured by the pressing load measuring means, and the roll gap measured by the roll gap measuring means becomes a predetermined control target value. The roll gap is adjusted by a roll gap constant control mode in which the roll gap is adjusted by the roll gap adjusting means. When the pressing load acting on the roll exceeds a preset upper limit value or lower limit value under the controlled state, the pressing load measured by the pressing load measuring means becomes a predetermined control target value. The roll gap is controlled by a constant pressing load control mode in which the roll gap is adjusted by the roll gap adjusting means.

  In the sheet forming apparatus according to the present invention, the pressing load acting on the roll has a preset upper limit value or lower limit value in a state where the roll gap is controlled by a roll gap constant control mode for keeping the roll gap at a predetermined value. If exceeded, the roll gap is controlled by the constant pressing load control mode that controls the roll gap so that the pressing load acting on the roll becomes a predetermined control target value, so that the amount of molten resin extruded from the extruder varies. However, a constant pressing load control is performed to compensate for variations in the pressing load, and the roll gap increases when the extrusion amount increases, and the roll gap decreases when the extrusion amount decreases. Is maintained at an appropriate value.

  As a result, the sheet forming can be automatically continued without causing troubles such as stoppage of operation of the roll drive motor or dropping of the molten resin.

  One embodiment of a sheet forming apparatus according to the present invention will be described with reference to FIG.

  The sheet forming apparatus includes a first roll 11 and a second roll 12 on a fixed base 10. The first roll 11 and the second roll 12 are arranged in parallel (parallel).

  The first roll 11 is supported by the left and right shaft end portions 15R and 15L so as to be rotatable by the left and right bearing housings 16R and 16L, and is rotatable about its own central axis. The bearing housings 16R and 16L are engaged with the left and right linear guides 17R and 17L provided on the fixed base 10 so as to be displaceable. Thereby, the first roll 11 can be displaced in the direction A in which the roll gap is increased or decreased with respect to the second roll 12. That is, the arrangement position of the first roll 11 can be displaced (changed) in the direction A in which the roll gap with the second roll 12 is increased or decreased.

  The second roll 12 is supported so that the left and right shaft end portions 23R and 23L can be rotated by left and right bearing housings 24R and 24L fixedly mounted on the fixed base 10, and can rotate about its own central axis. Yes.

  On the fixed base 10, left and right hydraulic cylinder devices 33R and 33L are attached by an attachment member 31 and connecting cylinders 32R and 32L. The piston rods 34R, 34L of the hydraulic cylinder devices 33R, 33L are fixedly connected to the bearing housings 16R, 16L at the tips. The hydraulic cylinder devices 33R and 33L are double-acting types having cylinder chambers 72 and 73 on both sides of the piston 71, respectively.

  As a result, the hydraulic cylinder devices 33R and 33L serve as roll gap adjusting means for increasing and decreasing the roll gap by displacing the arrangement position of the first roll 11, and the left and right bearing housings 16R and 16L are operated by the hydraulic operation of the hydraulic cylinder devices 33R and 33L. Are individually displaced in the roll gap increase / decrease direction A.

  Supply and discharge of hydraulic pressure to and from the cylinder chambers 72 and 73 of the hydraulic cylinder devices 33R and 33L are performed by bidirectional pumps 74R and 74L driven by servo motors 75R and 75L.

  The hydraulic cylinder devices 33R and 33L incorporate displacement meters (position sensors) 41R and 41L. The displacement meters 41R and 41L measure the piston positions of the hydraulic cylinder devices 33R and 33L, and measure the position of the first roll 11, and the roll gap between the first roll 11 and the fixedly arranged second roll 12. Functions as a roll gap measuring means.

  Displacement meters (linear scales) 42R and 42L for detecting the positions of the left and right bearing housings 16R and 16L are attached to the fixed base 10. The displacement meters 42R and 42 also function as roll gap measuring means for measuring the roll gap between the first roll 11 and the fixedly arranged second roll 12 by measuring the positions of the bearing housings 16R and 16L.

  As the roll gap measuring means, any one of displacement gauges 41R and 41L with a built-in hydraulic cylinder or displacement gauges 42R and 42L at the bearing section may be provided. When the displacement gauges 41R and 41L with a built-in hydraulic cylinder are used, the number of parts can be reduced by using an existing displacement cylinder built-in type hydraulic cylinder device. On the other hand, when the displacement gauges 42R and 42L of the bearing portion are used, the roll is not affected by the deformation of the fastening portions of the piston rods 34R and 34L and the piston rods 34R and 34L with the bearing housings 16R and 16L. The gap can be measured with high accuracy. These may be selected according to the required specifications.

  Load cells 43R and 43L are attached to the connecting cylinders 32R and 32L. The load cells 43 </ b> R and 43 </ b> L are pressing load measuring means, and measure the load acting on the connecting cylinders 32 </ b> R and 32 </ b> L as a load equivalent to the pressing load acting on the first roll 11. Note that the load cells 43R and 43L may be provided at a connecting portion with the bearing housings 16R and 16L at the ends of the piston rods 34R and 34L (see FIG. 4). The pressing load measuring means may be pressure sensors 45R and 45L that measure the hydraulic pressure supplied to the hydraulic cylinder devices 33R and 33L instead of the load cells 43R and 43L.

  Although not shown in the figure, each of the first roll 11 and the second roll 12 is individually connected to an electric motor for driving the rotation of the roll, and the first roll 11 is rotated in the counterclockwise direction in the second direction. Each of the rolls 12 is driven to rotate in the clockwise direction.

  A T die 100 that is long in the roll axis direction is provided above the roll gap between the first roll 11 and the second roll 12. The T-die 100 discharges the molten resin from the lip toward the roll gap between the first roll 11 and the second roll 12. As a result, a melt bank MB made of a molten resin is formed in the upper part of the gap between the first roll 11 and the second roll 12.

  The first roll 11 is driven to rotate in the counterclockwise direction and the second roll 12 is driven to rotate in the clockwise direction, so that both the rolls are disposed at the roll gap portion between the first roll 11 and the second roll 12. With the front and back surfaces of the sheet S in contact with each other, sheet forming is performed in a touch roll manner.

  An electronically controlled roll gap control device 50 using a microcomputer is provided as a roll gap control means. The roll gap control device 50 receives sensor signals (measurement information) from the displacement meters 41R, 41L or 42R, 42L, the load cells 43R, 43L, or the pressure sensors 45R, 45L, and the first roll 11 and the second roll 12 are input. Servo motors 75R and 75L are controlled to control the roll gap.

  The roll gap control device 50 has an executable control mode so that the roll gap between the first roll 11 and the second roll 12 measured by the displacement meters 41R, 41L or 42R, 42L becomes a predetermined control target value. The roll gap constant control mode in which the roll gap is adjusted by the servo motors 75R and 75L, and the pressing load of the first roll 11 measured by the load cells 43R and 43L or the pressure sensors 45R and 45L respectively become predetermined control target values. As described above, there are two control modes of a constant pressing load control mode in which the roll gap is adjusted by the servo motors 75R and 75L, and either one of the control modes is selectively executed.

  The roll gap control device 50 measures the pressing load of the first roll 11 by the load cells 43R and 43L or the pressure sensors 45R and 45L in a state where the roll gap is controlled by the roll gap constant control mode. When the measured value of the pressing load of one roll 11 exceeds the preset upper limit value Pmax or lower limit value Pmin in the roll gap constant control, control is performed to switch to the pressing load constant control mode with a predetermined time constant. .

  The pressing load constant control at this time is performed by setting the control target value of the pressing load to a preset pressing load, or the upper limit value Pmax or the lower limit value Pmin of the pressing load.

Here, the preset pressing load may be an intermediate value between the upper limit value Pmax and the lower limit value Pmin.

  The roll gap control device 50 switches (returns) to the constant roll gap control mode when the return condition to the constant roll gap control mode is satisfied in the state where the roll gap is controlled by the constant pressing load control mode as described above. Take control. The return conditions include the following (1) to (3).

(1) When the roll gap returns to the range between the preset upper limit value and lower limit value.

(2) When the roll gap immediately after switching from the roll gap constant control mode to the constant pressing load control mode changes to a value close to the preset roll gap.

(3) When the roll gap returns to the control target value of the roll gap constant control.

  Next, an example of a processing flow of this roll gap control will be described with reference to FIG.

  In a state where the roll gap is controlled by the roll gap constant control by the predetermined roll gap Gtag (step S101), the pressing load P of the first roll 11 is measured by the load cells 43R and 43L or the pressure sensors 45R and 45L (step S101). S102). That is, the pressing load P of the first roll 11 is monitored while the roll gap constant control is being executed.

  Under the roll gap constant control, it is determined whether or not the pressing load P exceeds a preset upper limit value Pmax (step S103). When the pressing load P exceeds the upper limit value Pmax, the control target load Ptag is set to the same value as the upper limit value Pmax (Ptag ← Pmax), and the pressing load constant control is started (step S104). That is, the control mode is switched from the constant roll gap control mode to the constant pressing load control mode.

  If the pressing load P does not exceed the upper limit value Pmax, it is determined whether or not the pressing load P has exceeded a preset lower limit value Pmin (step S105). When the pressing load P exceeds the preset lower limit value Pmin, the control target load Ptag is set to the same value as the lower limit value Pmin (Ptag ← Pmin) and the pressing load constant control is started (step S106). . That is, the control mode is switched from the constant roll gap control mode to the constant pressing load control mode.

  If the pressing load P does not exceed both the upper limit value Pmax and the lower limit value Pmin, the process returns to step S101 to continue the roll gap constant control.

  As described above, when the pressing load P exceeds the upper limit value Pmax or the lower limit value Pmin, the pressing load constant control is performed, and the supply amount of the molten resin from the T die 100 due to the fluctuation of the extrusion amount of the molten resin from the extruder. Even if fluctuates, the pressing load constant control is performed so as to compensate for the fluctuation of the pressing load, and the roll gap increases as the extrusion amount increases, and the roll gap decreases as the extrusion amount decreases.

  As a result, the size of the melt bank MB due to the molten resin between the rolls is maintained at an appropriate value, and sheet forming automatically continues without causing troubles such as stoppage of the roll drive motor or dropping of the molten resin. Is done.

  While this pressing load constant control is being executed, it is determined whether or not a condition for returning to the constant roll gap control is satisfied (step S107). This return condition may be any one of (1) to (3) described above. Until the return condition is satisfied, the pressing load constant control is continued. However, when the return condition is satisfied, the process returns to step S101 to return to the roll gap constant control by the roll gap Gtag.

  As a result, when the amount of extrusion is restored, the control is automatically switched to the constant roll gap control at the preset roll gap at the time of initial production, and sheet forming is continued.

  In the above-described embodiment, hydraulic pressure is supplied to and discharged from the cylinder chambers 72 and 73 of the hydraulic cylinder devices 33R and 33L by the bidirectional pumps 74R and 74L driven by the servo motors 75R and 75L. As shown in FIG. 3, the supply and discharge of hydraulic pressure to and from the cylinder chambers 72 and 73 of 33R and 33L can be performed by electric servo valves 35R and 35L. In this case, the electric servo valves 35R and 35L are connected to oil tanks 36 and oil supply pipes 39R and 39L by a hydraulic pump 38 driven by a servo motor 37, and drain pipes 40R and 40L, which are connected to the left and right hydraulic cylinder devices. An electro-hydraulic servo system that individually controls the supply and discharge of hydraulic pressure to and from 33R and 33L is configured.

  Even in this embodiment, the same control as in the above-described embodiment is performed, so that troubles such as operation stop of the roll drive motor and dropping of the molten resin occur even if the amount of the molten resin extruded from the extruder fluctuates. Sheet forming will continue automatically.

  Further, as shown in FIG. 4, a feed screw type driven by a servo motor can be adopted as the roll gap adjusting means. An embodiment using a feed screw system driven by a servo motor will be described with reference to FIG. 4, parts corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted.

  The front ends of the left and right feed screw members 18R, 18L are fixedly connected to the bearing housings 16R, 16L via load cells 43R, 43L which are pressing load measuring means for measuring the pressing load acting on the first roll 11, respectively. In this embodiment, the pressing load acting on the first roll 11 can also be detected from a current value equivalent to output torque values of servo motors 21R and 21L described later.

  On the fixed base 10, left and right feed nut support bases 19R and 19L are fixedly arranged. The feed nut support bases 19R and 19L rotatably support the left and right feed nut members 20R and 20L. The feed screw members 18R and 18L are individually screw-engaged with the feed nut members 20R and 20L. Left and right servo motors 21R and 21L are mounted on the feed nut support bases 19R and 19L. The servo motors 21R and 21L are drivingly connected to the feed nut members 20R and 20L by the gear trains 22R and 22L, and rotationally drive the feed nut members 20R and 20L.

  When the feed nut member 20R is rotated by the servo motor 21R, the feed screw member 18R moves in the axial direction (roll gap increasing / decreasing direction A), and the right bearing housing 16R corresponds to the rotation angle (rotation amount) of the servo motor 21R. To displace in the roll gap increasing / decreasing direction A. Further, when the feed nut member 20L is rotated by the servo motor 21L, the feed screw member 18L moves in the axial direction (roll gap increasing / decreasing direction A), and the left bearing housing 16L is separated from the right bearing housing 16R. Then, it is displaced in the roll gap increasing / decreasing direction A according to the rotation angle (rotation amount) of the servo motor 21L.

  As a result, individual roll gap adjusting means are formed at the left and right shaft end portions of the first roll 11.

  Even in this embodiment, the same control as in the above-described embodiment is performed, so that troubles such as operation stop of the roll drive motor and dropping of the molten resin occur even if the amount of the molten resin extruded from the extruder fluctuates. Sheet forming will continue automatically.

It is a whole lineblock diagram showing one embodiment of a sheet forming device by this invention. It is a flowchart which shows the processing flow of the roll clearance control in the sheet forming apparatus of this embodiment. It is a whole block diagram which shows other embodiment of the sheet forming apparatus by this invention. It is a whole block diagram which shows other embodiment of the sheet forming apparatus by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fixed base 11 1st roll 12 2nd roll 16R, 16L Bearing housing 17R, 17L Linear guide 18R, 18L Feed screw member 19R, 19L Feed nut support base 20R, 20L Feed nut member 21R, 21L Servo motor 22R, 22L Gear Row 23R, 23L Shaft end 24R, 24L Bearing housing 33R, 33L Hydraulic cylinder device 41R, 41L, 42R, 42L Displacement meter 43R, 43L Load cell 45R, 45L Pressure sensor 50 Roll gap control device 74R, 74L Bidirectional pump 75R, 75L Servo motor 100 T die

Claims (9)

A sheet having two rolls arranged in parallel with a gap, passing a sheet between the two rolls that are rotationally driven, and performing sheet forming in a state where the front and back surfaces of the sheet are in contact with the two rolls In the molding equipment,
Roll gap adjusting means for increasing or decreasing the roll gap by displacing the arrangement position of at least one of the two rolls;
A roll gap constant control mode in which the roll gap adjusting means adjusts the roll gap so that the gap between the two rolls becomes a predetermined control target value, and the pressing load acting on the roll becomes a predetermined control target value. Two control modes of a constant pressing load control mode for adjusting the roll gap by the roll gap adjusting means, and a roll gap control means for controlling the roll gap by selectively executing one of the control modes. Have
The roll gap control means, when the roll gap is controlled by the roll gap constant control mode, when the pressing load acting on the roll exceeds a preset upper limit value or lower limit value, A sheet forming apparatus that performs control to switch to a constant control mode. A sheet having two rolls arranged in parallel with a gap, passing a sheet between the two rolls that are rotationally driven, and performing sheet forming in a state where the front and back surfaces of the sheet are in contact with the two rolls In the molding equipment,
Roll gap adjusting means for increasing or decreasing the roll gap by displacing the arrangement position of at least one of the two rolls;
Roll gap measuring means for measuring the gap between the two rolls;
A pressing load measuring means for measuring a pressing load acting on the roll;
A roll gap constant control mode for adjusting the roll gap by the roll gap adjusting means so that the roll gap measured by the roll gap measuring means becomes a predetermined control target value, and a pressing load measured by the pressing load measuring means. Has two control modes of a constant pressing load control mode in which the roll gap is adjusted by the roll gap adjustment means so that the roll gap adjustment means becomes a predetermined control target value, and either one of the control modes is selectively executed. Roll gap control means for controlling
When the roll load is controlled by the roll gap constant control mode and the pressing load measured by the pressing load measuring means exceeds a preset upper limit value or lower limit value, the roll gap control means A sheet forming apparatus that performs control to switch to the constant pressing load control mode.   The roll gap control means performs a pressing load that is executed when a pressing load acting on the roll exceeds a preset upper limit value or lower limit value in a state in which the roll gap is controlled by a roll gap constant control mode. The sheet forming apparatus according to claim 1, wherein the constant control mode is performed by a preset pressing load.   The roll gap control means performs a pressing load that is executed when a pressing load acting on the roll exceeds a preset upper limit value or lower limit value in a state in which the roll gap is controlled by a roll gap constant control mode. The sheet forming apparatus according to claim 1 or 2, wherein the constant control mode is performed by the upper limit value or the lower limit value of the pressing load.   The roll gap control means has a constant pressing load when the pressing load acting on the roll exceeds a preset upper limit value or lower limit value in a state where the roll gap is controlled by a roll gap constant control mode. In a state where the roll gap is controlled by the control mode, when the roll gap returns to the range between the upper limit value and the lower limit value set in advance, control to switch to the roll gap constant control mode is performed. The sheet forming apparatus according to any one of 4.   The roll gap control means has a constant pressing load when the pressing load acting on the roll exceeds a preset upper limit value or lower limit value in a state where the roll gap is controlled by a roll gap constant control mode. When the roll gap changes to a value closer to the preset roll gap than the roll gap immediately after switching from the constant roll gap control mode to the constant pressing load control mode while the roll gap is controlled by the control mode. The sheet forming apparatus according to claim 1, wherein control for switching to a constant roll gap control mode is performed.   The roll gap control means has a constant pressing load when the pressing load acting on the roll exceeds a preset upper limit value or lower limit value in a state where the roll gap is controlled by a roll gap constant control mode. 5. The control for switching to the constant roll gap control mode is performed when the roll gap returns to the control target value of the constant roll gap control in a state where the roll gap is controlled by the control mode. The sheet forming apparatus according to claim 1. A sheet having two rolls arranged in parallel with a gap, passing a sheet between the two rolls that are rotationally driven, and performing sheet forming in a state where the front and back surfaces of the sheet are in contact with the two rolls In the method for controlling the roll gap of the molding apparatus,
The roll gap adjusting means displaces the arrangement position of at least one of the two rolls by the roll gap adjusting means to increase or decrease the roll gap, and the roll gap adjusting means so that the gap between the two rolls becomes a predetermined control target value. When the pressing load acting on the roll exceeds a preset upper limit value or lower limit value while the roll gap is controlled by the roll gap constant control mode in which the roll gap is adjusted by the A roll gap control method for a sheet forming apparatus, wherein the roll gap is controlled by a constant pressing load control mode in which the roll gap is adjusted by the roll gap adjusting means so that an applied pressing load becomes a predetermined control target value. A sheet having two rolls arranged in parallel with a gap, passing a sheet between the two rolls that are rotationally driven, and performing sheet forming in a state where the front and back surfaces of the sheet are in contact with the two rolls In the method for controlling the roll gap of the molding apparatus,
The roll gap adjustment means is used to displace the roll gap by displacing the arrangement position of at least one of the two rolls,
The gap between the two rolls is measured by the roll gap measuring means, and the pressing load acting on the roll is measured by the pressing load measuring means,
In a state where the roll gap is controlled by the roll gap constant control mode in which the roll gap is adjusted by the roll gap adjustment means so that the roll gap measured by the roll gap measurement means becomes a predetermined control target value. When the pressing load acting on the roll exceeds a preset upper limit value or lower limit value, the roll gap adjusting means adjusts the pressing load measured by the pressing load measuring means to a predetermined control target value. A roll gap control method for a sheet forming apparatus, wherein the roll gap is controlled by a constant pressing load control mode for adjusting the roll gap.

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