Sheet manufacturing device control method

Abstract

To control a moisture amount adjustment part in a sheet manufacturing device in which a measurement part is disposed on the downstream side of the moisture amount adjustment part.SOLUTION: A sheet manufacturing device comprises: a conveyance part to convey a web formed of material containing fibers; a humidifier to humidify the web by atmospheric air mixed with water supplied from a tank; a heating roller that is positioned on the downstream side of the humidifier and forms a sheet from the web; a moisture meter that is positioned between the humidifier and the heating roller and measures moisture amount in the web; a thermometer to measure temperature of the water in the tank; and a hygrometer to measure humidity. A control method of the sheet manufacturing device includes, until a tip of the web reaches the moisture meter: a first mode to control driving of the humidifier based on measurement result by at least either the thermometer or the hygrometer; and a second mode to control driving of the humidifier based on the measurement result by the moisture meter after executing the first mode.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for controlling a sheet manufacturing apparatus. [Background technology]

[0002] Patent Document 1 discloses a sheet manufacturing apparatus that includes a measuring unit that acquires moisture content information of the defibrated material, and a moisture content adjustment unit that adjusts the moisture content of the defibrated material based on the moisture content information. According to Patent Document 1, moisture content information of the transported defibrated material is acquired by the measuring unit, and the moisture content of the defibrated material is adjusted by the moisture content adjustment unit located downstream of the measuring unit in the transport direction based on the acquired moisture content information. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-208923 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the sheet manufacturing apparatus described in Patent Document 1, the result of adjusting the moisture content of the defibrated material by the moisture content adjustment unit is not known. In other words, in this sheet manufacturing apparatus, feedback control of the moisture content of the defibrated material cannot be performed. In order to perform feedback control of the moisture content of the defibrated material, a configuration in which a measurement unit is arranged downstream of the moisture content adjustment unit in the conveying direction of the defibrated material is considered. With this configuration, the moisture content adjustment unit can be controlled based on the moisture content information acquired by the measurement unit. However, in a configuration in which a measurement unit is arranged downstream of the moisture content adjustment unit in the conveying direction of the defibrated material, feedback control cannot be performed during the period from when the conveyance of the defibrated material starts until the tip of the defibrated material reaches the measurement unit. In other words, in a sheet manufacturing apparatus in which a measurement unit is arranged downstream of the moisture content adjustment unit in the conveying direction of the defibrated material, it is difficult to control the moisture content adjustment unit during the period from when the conveyance of the defibrated material starts until the tip of the defibrated material reaches the measurement unit. [Means for solving the problem]

[0005] The control method for a sheet manufacturing apparatus is a control method for controlling a sheet manufacturing apparatus that manufactures a sheet from a material containing fibers, the sheet manufacturing apparatus including: a depositing unit that deposits the material to form a web from the material; a conveying unit having a conveying belt that conveys the web while supporting the web; a humidifier that humidifies the web by discharging air mixed with the water supplied from a tank that stores water; a heating roller that is located downstream of the humidifier in a conveying direction of the web and forms the sheet from the web by heating the web; and The sheet manufacturing apparatus is equipped with a moisture meter located between the tank and a roller for measuring the amount of moisture contained in the web, a thermometer for measuring the temperature of the water stored in the tank, and a hygrometer for measuring the humidity outside the sheet manufacturing apparatus, and the control method includes a first mode in which operation of the humidifier is controlled based on at least one of the measurement results of the water temperature by the thermometer and the measurement results of the humidity by the hygrometer until the tip of the web reaches the moisture meter, and a second mode in which operation of the humidifier is controlled based on the measurement results of the moisture amount by the moisture meter after execution of the first mode. [Brief description of the drawings]

[0006] [Figure 1] FIG. 2 is a schematic diagram showing a configuration of a sheet manufacturing apparatus. [Diagram 2] FIG. 4 is a schematic diagram showing a web transport section, a humidifying section, and a sheet forming section. [Diagram 3] FIG. 13 is a diagram showing a table for deriving a duty ratio. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] As shown in FIG. 1, the sheet manufacturing apparatus 1 includes a supply unit 3, a crushing unit 5, a defibrating unit 7, a mixing unit 9, a deposition unit 10, a web forming unit 11, a web conveying unit 13, a humidifying unit 15, a sheet forming unit 17, and a cutting unit 19. The sheet manufacturing apparatus 1 manufactures a sheet S from a raw material C. The raw material C changes into the form of a web W and the form of a sheet S in this order through various processes. The various processes for forming the sheet S from the raw material C are mainly executed by the above-mentioned respective processing units. That is, the supply unit 3, the crushing unit 5, the defibrating unit 7, the mixing unit 9, the deposition unit 10, the web forming unit 11, the web conveying unit 13, the humidifying unit 15, the sheet forming unit 17, and the cutting unit 19 are each a processing unit. The web conveying unit 13 is an example of a conveying unit. The humidifying unit 15 is an example of a humidifier.

[0008] The processing sections are not limited to these. Other processing sections may be added to these processing sections, some of these processing sections may be combined, or some of these processing sections may be omitted. In the process path in which the raw material C is formed into the sheet S, the direction toward the subsequent process is called downstream, and the direction toward the previous process is called upstream. In other words, the raw material C changes from upstream to downstream on the process path into the web W and the sheet S in this order. In the process path, the transport direction of the web W and the sheet S is called downstream, and the opposite direction to the transport direction is called upstream. The web W and the sheet S are transported from upstream to downstream on the transport path.

[0009] Furthermore, the sheet manufacturing apparatus 1 has a control unit 20 and a hygrometer 22. The control unit 20 is a controller that generally controls the operation of the sheet manufacturing apparatus 1. The control unit 20 controls the operation of each processing unit of the sheet manufacturing apparatus 1. The hygrometer 22 measures the humidity of the environment in which the sheet manufacturing apparatus 1 is placed. The hygrometer 22 may be placed either inside or outside a housing (not shown) of the sheet manufacturing apparatus 1. The hygrometer 22 is connected to the control unit 20 so as to be able to communicate with the control unit 20. The humidity measurement result by the hygrometer 22 is output to the control unit 20.

[0010] The control unit 20 has a processor and a memory. The processor is composed of a CPU (Central Processing Unit), an MPU (Micro Processing Unit), etc. The memory has a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The RAM functions as a work area for the processor. The RAM is used for temporarily storing various control programs, various data, etc. The ROM stores control programs for controlling the operation of the sheet manufacturing apparatus 1, various setting information, etc.

[0011] The processor functions as various functional units by executing a control program stored in the memory. The functions performed by the processor include a function of controlling the operation of each processing unit of the sheet manufacturing apparatus 1. The functional units possessed by the processor include a supply control unit, a coarse crushing control unit, a defibration control unit, a mixing control unit, a deposition control unit, a web formation control unit, a web transport control unit, a humidification control unit, a sheet formation control unit, and a cutting control unit. The supply control unit controls the operation of the supply unit 3. The coarse crushing control unit controls the operation of the coarse crushing unit 5. The defibration control unit controls the operation of the defibration unit 7. The mixing control unit controls the operation of the mixing unit 9. The deposition control unit controls the operation of the deposition unit 10. The web formation control unit controls the operation of the web forming unit 11. The web transport control unit controls the operation of the web transport unit 13. The humidification control unit controls the operation of the humidification unit 15. The sheet formation control unit controls the operation of the sheet forming unit 17. The cutting control unit controls the operation of the cutting unit 19.

[0012] The supply unit 3 supplies the raw material C to the crushing unit 5. The supply unit 3 includes an automatic feed mechanism 25. The supply unit 3 automatically feeds the raw material C to the crushing unit 5 by the automatic feed mechanism 25. The raw material C includes various fibers or various fiber materials. The various fibers are not particularly limited, and a wide range of fibers can be used. For example, the fibers include natural fibers (animal fibers, plant fibers), chemical fibers (organic fibers, inorganic fibers, organic-inorganic composite fibers), etc. More specifically, fibers made of cellulose, silk, wool, cotton, hemp, kenaf, flax, ramie, jute, Manila hemp, sisal, coniferous trees, broadleaf trees, etc. can be used. These fibers may be used alone, may be appropriately mixed, or may be used as regenerated fibers that have been purified, etc.

[0013] Examples of fiber materials include pulp, waste paper, and old cloth. The fibers may be subjected to various surface treatments. The fiber material may be a pure substance, or may be a material containing multiple components such as impurities and other components. The fibers may be defibrated materials obtained by dry defibration of waste paper or pulp sheets. The length of the fibers is not particularly limited, but the length of an independent fiber along the longitudinal direction of the fiber is 1 μm or more and 5 mm or less, preferably 2 μm or more and 3 mm or less, and more preferably 3 μm or more and 2 mm or less.

[0014] In the sheet manufacturing apparatus 1, moisture is added to the web W in the humidifying section 15 described later. For this reason, if the fibers contained in the web W are fibers capable of forming hydrogen bonds between fibrils, the mechanical strength of the sheet S to be formed can be increased. An example of such a fiber is cellulose. In the following, the addition of moisture to the web W by the humidifying section 15 is also referred to as humidification. The fiber content in the sheet S is, for example, 50% by mass or more and 99.9% by mass or less, preferably 60% by mass or more and 99% by mass or less, and more preferably 70% by mass or more and 99% by mass or less. As described later, such a content can be achieved by performing a predetermined blending when forming a mixture in the mixing section 9.

[0015] The crushing unit 5 cuts the raw material C supplied by the supply unit 3 into small pieces in an atmosphere such as the atmosphere in a dry manner. The small pieces have a shape and size of, for example, several centimeters square. The crushing unit 5 has a crushing blade 31. The crushing unit 5 can cut the raw material C with the crushing blade 31. For example, a shredder can be used as the crushing unit 5. The small pieces of raw material C cut by the crushing unit 5 are transported to the quantitative supply unit 32. The quantitative supply unit 32 weighs the small pieces of raw material C and supplies them to the hopper 33 in a quantitative manner. The quantitative supply unit 32 is, for example, a vibrating feeder. The small pieces of raw material C supplied to the hopper 33 are transported through a pipe 34 to an inlet 35 of the defibration unit 7. The inlet 35 is a receiving port for introducing the small pieces of raw material C into the defibration unit 7.

[0016] The defibration unit 7 defibrates small pieces of raw material C in a dry manner. The defibration unit 7 includes a stator 36 and a rotor 37. The stator 36 has a cylindrical shape. The rotor 37 rotates along the inner surface of the cylindrical shape of the stator 36. The stator 36 and the rotor 37 constitute a so-called impeller mill. The small pieces of raw material C introduced from the inlet 35 are sandwiched between the stator 36 and the rotor 37 and rotate, and are defibrated by the shear force generated between them. The defibration unit 7 untangles the tangled fibers to generate a defibrated material.

[0017] Furthermore, the defibrating unit 7 can generate an airflow by the rotation of the rotor 37. The small pieces of raw material C are sucked into the inside of the defibrating unit 7 from the inlet 35 by the airflow generated by the rotation of the rotor 37. In addition, the defibrated material defibrated from the small pieces of raw material C is discharged from the outlet 38 to the inside of the pipe 41 by the airflow generated by the rotation of the rotor 37. The defibrated material defibrated in the defibrating unit 7 is transported from the outlet 38 through the pipe 41 to the deposition unit 10. Note that the airflow for transporting the defibrated material from the defibrating unit 7 to the deposition unit 10 is not limited to the airflow generated by the defibrating unit 7. By adding an airflow generating device such as a blower (not shown), the airflow generated by the airflow generating device can also be used.

[0018] One end of the pipe 41 communicates with the inside of the defibrating unit 7. The other end of the pipe 41 opposite the defibrating unit 7 communicates with the inside of the deposition unit 10. A mixing unit 9 is disposed between the defibrating unit 7 and the deposition unit 10. The mixing unit 9 is connected to the pipe 41. The mixing unit 9 mixes the defibrated material with a binder and the like in air such as the atmosphere. The mixing unit 9 has a hopper 42, a hopper 43, a supply pipe 44, a supply pipe 45, a valve 46, and a valve 47. The hopper 42 and the hopper 43 may each have a screw feeder or a disk feeder not shown.

[0019] The hopper 42 communicates with the inside of the pipe 41 via a supply pipe 44. A valve 46 is provided in the supply pipe 44. The valve 46 is provided between the hopper 42 and the pipe 41. The hopper 42 supplies the binder to the inside of the supply pipe 44. The binder supplied to the supply pipe 44 is supplied to the inside of the pipe 41. The valve 46 adjusts the weight of the binder supplied from the hopper 42 to the pipe 41. This adjusts the mixing ratio of the defibrated material and the binder. The hopper 43 communicates with the inside of the pipe 41 via a supply pipe 45. A valve 47 is provided in the supply pipe 45. The valve 47 is provided between the hopper 43 and the pipe 41. The hopper 43 supplies additives other than the binder to the inside of the supply pipe 45. The additives supplied to the supply pipe 45 are supplied to the inside of the pipe 41. The valve 47 adjusts the weight of the additives supplied from the hopper 43 to the pipe 41. This adjusts the mixing ratio of the defibrated material and the additives. The mixture of the defibrated material, the binder, and the additives is transported to the deposition unit 10 via pipe 41.

[0020] The binder is, for example, starch or dextrin. Starch is a polymer in which a plurality of α-glucose molecules are polymerized by glycosidic bonds. Starch may be linear or may contain branches. Starch derived from various plants can be used. Examples of starch sources include cereals such as corn, wheat, and rice; beans such as broad beans, mung beans, and red beans; tubers such as potato, sweet potato, and tapioca; wild plants such as dogtooth violets, bracken, and kudzu; and palms such as sago palm.

[0021] In addition, processed starch or modified starch may be used as the starch. Examples of the processed starch include acetylated adipic acid cross-linked starch, acetylated starch, oxidized starch, sodium octenyl succinate starch, hydroxypropyl starch, hydroxypropylated phosphate cross-linked starch, phosphorylated starch, phosphate esterified phosphate cross-linked starch, urea phosphate esterified starch, sodium starch glycolate, and high amylose corn starch. In addition, dextrin obtained by processing or modifying starch can be suitably used as the modified starch.

[0022] In the sheet manufacturing apparatus 1, by using starch or dextrin as a binder, the sheet S produced can be given sufficient strength. This is because at least one of gelatinization of the binder and hydrogen bonding between the fiber fibrils occurs when moisture is added to the web W by the humidifying unit 15 described below and then pressurized and heated by the sheet forming unit 17. On the other hand, if sufficient strength can be imparted to the sheet S by hydrogen bonding only between the fiber fibrils, the addition of a binder may be omitted. When the addition of a binder is omitted, the hopper 42, the supply pipe 44, and the valve 46 can be omitted from the sheet manufacturing apparatus 1.

[0023] The content of starch or dextrin in the sheet S is, for example, 0.1% by mass or more and 50% by mass or less. Preferably, the content of starch or dextrin in the sheet S is 1% by mass or more and 40% by mass or less. More preferably, the content of starch or dextrin in the sheet S is 1% by mass or more and 30% by mass or less. Such a content can be achieved by adjusting the valve 46 of the mixing section 9. The additives supplied from the hopper 43 to the pipe 41 may contain a colorant for coloring the fibers, an aggregation inhibitor, a flame retardant, etc. The aggregation inhibitor inhibits the aggregation of the fibers and the aggregation of the binder. The flame retardant makes the fibers and the like less flammable. The additives are not essential components. When the additives are omitted, the hopper 43, the supply pipe 45, and the valve 47 can be omitted.

[0024] The defibrated material mixed with the binder and additives is transported to the deposition section 10 via pipe 41. Note that on the downstream side of the mixing section 9, the defibrated material mixed with the binder and additives is also simply referred to as the defibrated material. The deposition section 10 has a drum section 51, a housing section 52, and a web forming section 11. The housing section 52 contains the drum section 51. The defibrated material mixed with the binder and additives is introduced into the drum section 51 via pipe 41. The drum section 51 loosens tangled fibers and the like. The drum section 51 has a rotatable cylindrical sieve. The defibrated material is introduced into the cylindrical sieve.

[0025] The defibrated material introduced into the drum unit 51 is defibrated by a rotating cylindrical sieve. The cylindrical sieve is composed of a mesh. Fibers and particles smaller than the size of the mesh openings pass through the mesh and are discharged to the outside of the drum unit 51. The fibers and particles pass through the mesh of the cylinder rotated by a motor (not shown) and are deposited in the web forming unit 11 while being dispersed in air such as the atmosphere. This allows the drum unit 51 to deposit the defibrated material in the web forming unit 11 with good uniformity.

[0026] The direction from the drum unit 51 toward the web forming unit 11 is the downward direction of the sheet manufacturing apparatus 1. Conversely, the direction from the web forming unit 11 toward the drum unit 51 is the upward direction of the sheet manufacturing apparatus 1. The web forming unit 11 is located below the deposition unit 10. The drum unit 51 is located above the web forming unit 11. The "sieve" of the drum unit 51 does not need to have the function of selecting a specific object. In other words, the "sieve" used as the drum unit 51 means one equipped with a net, and the drum unit 51 may pour down all of the defibrated material introduced into the drum unit 51.

[0027] The web forming unit 11 has a first mesh belt 61, a plurality of tension rollers 62, and a first suction mechanism 63. The web forming unit 11 accumulates the defibrated material that falls from the drum unit 51 to form a web W. The defibrated material that has passed through the drum unit 51 is accumulated on the first mesh belt 61. The first mesh belt 61 is made of a mesh-like material. The first mesh belt 61 is stretched around the tension roller 62, and is difficult for the defibrated material to pass through but allows air to pass through easily. The first mesh belt 61 is a so-called endless belt, and rotates clockwise as viewed in FIG. 1 as the tension roller 62 rotates by a motor (not shown). The defibrated material continuously falls and accumulates on the rotationally driven first mesh belt 61 from the drum unit 51, forming a web W on the first mesh belt 61.

[0028] The first suction mechanism 63 is provided below the first mesh belt 61. The first suction mechanism 63 can generate an airflow that faces downward. The first suction mechanism 63 can suck the defibrated material dispersed in the air by the drum unit 51 onto the first mesh belt 61. The first suction mechanism 63 can also increase the discharge speed of the defibrated material from the accumulation unit 10. Furthermore, the first suction mechanism 63 can form a downflow in the fall path of the defibrated material, preventing the fibers, binder, etc. from becoming entangled while falling.

[0029] In this way, the deposition unit 10 can deposit the mixture containing fibers by airflow to form the web W. By passing through the deposition unit 10, a binder and the like are further mixed with the fibers, and the web W containing a lot of air and in a soft and swollen state is formed. The web transport unit 13 is located downstream of the web forming unit 11. The web transport unit 13 is disposed downstream of the web W on the first mesh belt 61. The web W formed on the first mesh belt 61 is transferred from the first mesh belt 61 to the web transport unit 13. The web transport unit 13 transports the web W on the first mesh belt 61 in the transport direction T. Specifically, the web transport unit 13 peels the web W from the first mesh belt 61 and transports it toward the sheet forming unit 17.

[0030] The sheet forming section 17 is located downstream of the web transport section 13 on the transport path of the web W. The web W is transported from the web transport section 13 toward the sheet forming section 17. The sheet forming section 17 has a pressurizing and heating section 111. For example, a heating roller or a heat press molding machine can be applied to the pressurizing and heating section 111. In this embodiment, a heating roller pair 112 is applied to the pressurizing and heating section 111. The heating roller pair 112 is also simply referred to as the heating roller 112. The web W is in a state before being pressed or heated by the sheet forming section 17.

[0031] The sheet forming section 17 pressurizes and heats the web W at the same time. When the web W humidified by the humidifying section 15 is heated and pressurized by the sheet forming section 17, the fiber density is increased. This is because the moisture contained in the web W is evaporated after the temperature rises, and the thickness of the web W becomes thinner. The heat raises the temperature of the moisture and binder contained in the web W, and the pressure increases the fiber density. As a result, the binder is gelatinized, and the moisture evaporates, so that multiple fibers are bonded to each other via the gelatinized binder. Furthermore, the moisture evaporates due to the heat, and the fiber density is increased due to the pressure, so that multiple fibers are bonded to each other by hydrogen bonds between the fibrils. As a result, a sheet S with high mechanical strength and good quality can be formed.

[0032] The heating of the web W by the heating roller pair 112 is preferably performed so that the temperature of the web W is 60° C. or more and 100° C. or less. The pressure applied to the web W by the heating roller pair 112 is preferably 0.1 MPa or more and 15 MPa or less, more preferably 0.2 MPa or more and 10 MPa or less, and even more preferably 0.4 MPa or more and 8 MPa or less. If the pressure is within such a range, deterioration of the fibers can be suppressed, and a sheet S with good strength can be manufactured again by using the defibrated material obtained by defibrating the manufactured sheet S as a raw material.

[0033] The sheet forming unit 17 may be configured to perform at least one of heating and pressurizing. The sheet forming unit 17 can form the sheet S by performing at least one of heating and pressurizing. The sheet forming unit 17 can form the sheet S by performing at least one of heating and pressurizing, by binding a plurality of fibers together via a binder and compressing the fibers into a sheet shape.

[0034] The cutting section 19 is located downstream of the sheet forming section 17 on the transport path of the web W. The sheet S formed by the sheet forming section 17 is in a continuous sheet shape. As shown in FIG. 1, the cutting section 19 cuts the continuous sheet-shaped sheet S. The cutting section 19 has a first cutting section 122 and a second cutting section 124. The first cutting section 122 cuts the sheet S in the width direction, which is a direction intersecting the transport direction T of the sheet S. The second cutting section 124 cuts the sheet S in the length direction, which is a direction parallel to the transport direction T. After the first cutting section 122 cuts the sheet S in the width direction, the second cutting section 124 cuts the sheet S in the length direction. The cutting section 19 produces a single-sheet-shaped sheet S of a predetermined size. The cut single-sheet-shaped sheet S is discharged to the discharge receiving section 130.

[0035] As shown in FIG. 2, the web conveying section 13 has a second mesh belt 71, a plurality of rollers 72, and a second suction mechanism 73. The second mesh belt 71 is an example of a conveying belt. Note that the viewing direction of the sheet manufacturing apparatus 1 is different between FIG. 1 and FIG. 2. The viewing direction in FIG. 1 and the viewing direction in FIG. 2 are opposite to each other. This is also clear from the fact that the direction of the conveying direction T in FIG. 1 and the direction of the conveying direction T in FIG. 2 are opposite to each other. The second mesh belt 71 is made of a mesh-like material. As shown in FIG. 2, the second mesh belt 71 is stretched over a plurality of rollers 72 and can pass humidified air MA described later. The second mesh belt 71 is an endless belt, and rotates clockwise as viewed in FIG. 2 by rotating the rollers 72 by a motor not shown. The web W is conveyed in the conveying direction T by the second mesh belt 71 that is driven to rotate.

[0036] The second suction mechanism 73 is disposed at a position facing the web W from above with the second mesh belt 71 interposed therebetween. The second suction mechanism 73 includes a plurality of intake fans 74. The second suction mechanism 73 generates an upward airflow on the second mesh belt 71 in contact with the web W by the suction force of the plurality of intake fans 74. The direction of the airflow is also the thickness direction of the web W. This airflow sucks the web W from above through the second mesh belt 71, and the web W can be held below the second mesh belt 71. The direction from the second suction mechanism 73 to the web W is the downward direction of the sheet manufacturing apparatus 1. Conversely, the direction from the web W to the second suction mechanism 73 is the upward direction of the sheet manufacturing apparatus 1. The transport path of the web W is located below the second suction mechanism 73. The second suction mechanism 73 is located above the transport path of the web W.

[0037] The second suction mechanism 73 has a plurality of suction ports 75 for sucking in the humidified air MA described below. The second suction mechanism 73 also has suction ducts 76 connected to the plurality of suction ports 75, respectively. The suction ducts 76 are partitioned by walls that form the suction ports 75. The suction ducts 76 connected to the plurality of suction ports 75, respectively, can stabilize the amount of suction applied to the web W. The web transport unit 13 can peel the web W from the first mesh belt 61, transfer it to the second mesh belt 71, and transport it in the transport direction T.

[0038] One side WA, which is the upper surface of the web W, contacts the second mesh belt 71. The other side WB, which is the lower surface of the web W, does not contact the second mesh belt 71. In other words, one side WA of the web W was not in contact with the first mesh belt 61, but is in contact with the second mesh belt 71. The other side WB of the web W was in contact with the first mesh belt 61, but is not in contact with the second mesh belt 71. When the web W is transferred from the first mesh belt 61 to the second mesh belt 71, the surface in contact with each of them switches from the other side WB to the one side WA.

[0039] The surface of the second mesh belt 71 that contacts one side WA of the web W is referred to as one side. The surface of the second mesh belt 71 that does not contact the web W is referred to as the other side. The one side of the second mesh belt 71 is the outer peripheral surface of the endless second mesh belt 71. The other side of the second mesh belt 71 is the inner peripheral surface of the endless second mesh belt 71. When the one side of the second mesh belt 71 faces downward, the web W is sucked by the second suction mechanism 73 and adsorbed to the one side of the second mesh belt 71. That is, the one side of the second mesh belt 71 facing downward can hold the web W against gravity. Such a second mesh belt 71 is also called a back conveyor belt.

[0040] The web W is transported in the transport direction T below the second mesh belt 71 with one side WA in contact with one side of the second mesh belt 71. At this time, the second suction mechanism 73 can stably suck the web W from the other side of the second mesh belt 71. This causes the web W to be adsorbed to the second mesh belt 71. When the web W is transported by the second mesh belt 71, it does not peel off from the second mesh belt 71 and fall off.

[0041] As shown in FIG. 2, the humidifying section 15 is disposed on one side of the second mesh belt 71 of the web transport section 13. That is, the humidifying section 15 is disposed below the web transport section 13. The humidifying section 15 is disposed below the web transport section 13 across the transport path of the web W. The transport path of the web W is between the web transport section 13 and the humidifying section 15. A moisture meter 80 is disposed downstream of the humidifying section 15 in the transport direction T. The humidifying section 15 and the moisture meter 80 are disposed at a position facing the second mesh belt 71 from below the second mesh belt 71. The humidifying section 15 and the moisture meter 80 are adjacent to each other in the transport direction T. The moisture meter 80 measures the moisture contained in the web W. The moisture meter 80 is communicably connected to the control section 20 shown in FIG. 1. The measurement result by the moisture meter 80 is output to the control section 20.

[0042] As shown in FIG. 2, the humidifying unit 15 has a case 91, a duct 92, a tank 93, a thermometer 94, a mist generating unit 95, and an air duct 97. The tank 93, the mist generating unit 95, and the air duct 97 are housed in the case 91. The duct 92 is provided above the case 91. The duct 92 covers the case 91. The tank 93, the mist generating unit 95, and the air duct 97 are surrounded by the case 91 and the duct 92. The tank 93 is capable of storing water L. The thermometer 94 measures the temperature of the water L inside the tank 93. The thermometer 94 is communicably connected to the control unit 20 shown in FIG. 1. The measurement result of the temperature of the water L by the thermometer 94 is output to the control unit 20.

[0043] As shown in FIG. 2, the mist generating unit 95 is disposed inside the tank 93. As the mist generating unit 95, various devices can be applied, such as an ultrasonic mist generator, a heated steam generator, and an evaporative humidifier using air blowing. In this embodiment, an ultrasonic mist generator having a piezoelectric vibrator is applied as the mist generating unit 95. With the ultrasonic mist generator having a piezoelectric vibrator, ultrasonic waves are generated in the water L to generate mist M from the water L. The generated mist M rises from the surface of the water L in the tank 93.

[0044] An air intake port 97A is formed in the case 91. The air intake port 97A is connected to an air duct 97. An exhaust port 97B is formed in the air duct 97. The exhaust port 97B opens toward the inside of the tank 93. An exhaust port 99 is formed in the duct 92. The exhaust port 99 opens toward the second mesh belt 71 of the web transport unit 13. The transport path of the web W passes between the exhaust port 99 and the web transport unit 13. That is, the exhaust port 99 opens toward the web W transported by the web transport unit 13.

[0045] When the second suction mechanism 73 is operated, the suction force of the intake fan 74 draws in the air inside the duct 92 through the exhaust port 99. When the air inside the duct 92 is drawn in through the exhaust port 99, the air pressure inside the duct 92 drops. As the air pressure inside the duct 92 drops, the air outside the humidifying unit 15 is drawn into the inside of the humidifying unit 15 through the intake port 97A. The air drawn into the inside of the humidifying unit 15 through the intake port 97A is exhausted through the air duct 97 and out through the exhaust port 97B towards the inside of the tank 93.

[0046] The air exhausted toward the inside of the tank 93 becomes an air current and flows inside the duct 92 toward the exhaust port 99. At this time, when the mist generating unit 95 is driven, the mist M generated from the water L inside the tank 93 mixes with the air current flowing inside the duct 92, generating humidified air MA. The humidified air MA rides on the air current flowing inside the duct 92 and is blown onto the web W from the exhaust port 99. This allows the web W to be appropriately humidified. In this embodiment, the humidifying unit 15 is located below the web transport unit 13, so that even if condensation occurs at or near the humidifying unit 15, water droplets do not fall onto the web W.

[0047] The exhaust port 99 has a rectangular shape. The side of the exhaust port 99 in the direction intersecting with the conveying direction T is longer than the width of the web W, and the humidified air MA can be exhausted across the entire width of the web W being conveyed. The exhaust port 99 is covered with a mesh surface made of a wire mesh of aluminum or the like. The mesh surface of the exhaust port 99 allows the humidified air MA to pass through while preventing foreign matter such as fibers from entering the exhaust port 99. The humidifying unit 15 also has a tray 101. Foreign matter such as fibers that falls from the exhaust port 99 and enters the humidifying unit 15 is received and captured by the tray 101.

[0048] The second suction mechanism 73 is disposed on the other surface side of the second mesh belt 71. The second suction mechanism 73 is disposed at a position facing the humidification unit 15 with the second mesh belt 71 in between. The suction port 75 of the second suction mechanism 73 and the exhaust port 99 of the humidification unit 15 face each other with the second mesh belt 71 in between. By driving the intake fan 74, the humidified air MA exhausted from the exhaust port 99 of the humidification unit 15 is sucked through the suction duct 76. The humidified air MA exhausted from the exhaust port 99 is sucked through the suction duct 76 from the suction port 75 facing the exhaust port 99 via the second mesh belt 71. The humidified air MA passes through the web W in contact with one surface of the second mesh belt 71. As a result, the web W is uniformly humidified by the humidified air MA.

[0049] The plurality of suction ports 75 are formed in the corresponding suction ducts 76. The plurality of intake fans 74 are provided for each of the corresponding suction ducts 76. The plurality of intake fans 74 can be driven independently. The second suction mechanism 73 can keep the air volume of the humidified air MA passing through the web W constant. This makes the amount of moisture imparted to the web W being transported more uniform. As a result, it is easy to suppress variations in the strength of the sheet S, and the quality of the sheet S can be ensured.

[0050] An air injection unit 150 is disposed downstream of the second suction mechanism 73 on the transport path of the web W. The air injection unit 150 is disposed at a position facing the web W across the second mesh belt 71. The air injection unit 150 is disposed at a position adjacent to the outlet side roller 72A, which is disposed at a position closest to the sheet forming unit 17 among the multiple rollers 72 in the web transport unit 13. The air injection unit 150 is disposed between the downstream end of the second suction mechanism 73 in the transport direction T and the outlet side roller 72A. The air injection unit 150 injects compressed air onto one side WA of the web W through the second mesh belt 71. The air injection unit 150 efficiently peels off the web W from the second mesh belt 71 by injecting compressed air toward the web W.

[0051] The air injection unit 150 has a compression unit (not shown) that compresses the air, and an opening 151 that exhausts the compressed air. For example, an air compressor is used as the compression unit that compresses the air. The opening 151 is provided at a position adjacent to the outlet side roller 72A and at a position facing the other surface of the second mesh belt 71. The opening 151 has a long and narrow rectangular shape. The opening 151 can inject compressed air over the entire width of one surface WA of the web W that is in contact with the second mesh belt 71.

[0052] Since the web W is humidified by the humidifying unit 15, the adhesive force of the web W to the second mesh belt 71 increases, and the web W may stick to the second mesh belt 71. If the web W does not peel off from the second mesh belt 71 due to gravity alone, the web W may not be transported smoothly to the sheet forming unit 17, which may cause poor transport of the web W or damage to the web W. To address this issue, in this embodiment, the air injection unit 150 injects compressed air toward the web W, so that the web W is blown downward. As a result, the web W is smoothly peeled off from the second mesh belt 71 and smoothly delivered to the sheet forming unit 17. Therefore, poor transport of the web W and damage to the web can be suppressed.

[0053] The moisture meter 80 is disposed downstream of the humidifier 15 on the transport path of the web W. The moisture meter 80 measures the moisture contained in the web W. The moisture meter 80 measures the moisture of the web W without contacting the web W. For example, a moisture meter using infrared rays or microwaves can be used as such a moisture meter 80. In this embodiment, an infrared moisture meter is used as the moisture meter 80. The moisture meter 80 can measure the moisture contained in the web W by irradiating infrared rays from the other side WB of the web W and receiving the returned infrared rays. The measurement result by the moisture meter 80 is output to the control unit 20 shown in FIG. 1.

[0054] The control unit 20 controls the moisture content of the web W based on the moisture content of the web W obtained from the moisture meter 80. The control of the moisture content of the web W is feedback control. The moisture content of the web W is controlled by controlling the driving of the mist generating unit 95 of the humidifying unit 15. The control unit 20 controls the mist generating unit 95 of the humidifying unit 15 to control the amount of mist M contained in the humidified air MA. As a result, the moisture content of the web W can be controlled. The moisture content of the web W is preferably 12% by mass or more and 40% by mass or less. By controlling the moisture content of the web W to be within this range, hydrogen bonds between the fiber fibrils of the web W can be effectively formed. As a result, the strength of the sheet S can be increased.

[0055] The amount of mist M generated can be controlled by changing the strength of the drive of the mist generating unit 95. As described above, an ultrasonic mist generator having a piezoelectric vibrator is applied as the mist generating unit 95. The strength of the drive of the mist generating unit 95 can be changed by changing the strength of the drive of the piezoelectric vibrator. The drive of the piezoelectric vibrator of the mist generating unit 95 is controlled by a PWM (Pulse Width Modulation) method. The drive of the piezoelectric vibrator can be strengthened by lengthening the pulse width of the voltage waveform that drives the piezoelectric vibrator. Conversely, the drive of the piezoelectric vibrator can be weakened by shortening the pulse width of the voltage waveform that drives the piezoelectric vibrator.

[0056] In PWM control, increasing the pulse width of the drive voltage waveform is expressed as increasing the duty ratio. Similarly, decreasing the pulse width of the drive voltage waveform is expressed as decreasing the duty ratio. By increasing the duty ratio of the drive voltage waveform, the drive of the mist generation unit 95 can be strengthened. By increasing the drive of the mist generation unit 95, the amount of mist M generated can be increased. By decreasing the duty ratio of the drive voltage waveform, the drive of the mist generation unit 95 can be weakened. By decreasing the drive of the mist generation unit 95, the amount of mist M generated can be reduced.

[0057] If the moisture content of the web W can be measured by the moisture meter 80, the moisture content of the web W can be feedback-controlled. However, before the web W reaches the moisture meter 80, the moisture content of the web W cannot be feedback-controlled. Such a case may occur, for example, between the start of formation of the web W and the end of the web W reaching the moisture meter 80. Before the web W reaches the moisture meter 80, how to control the amount of mist M generated becomes an issue. Note that the web W reaching the moisture meter 80 means that the web W reaches a position facing the moisture meter 80. The web W reaching the moisture meter 80 means that the web W and the moisture meter 80 face each other. The web W facing the moisture meter 80 means that the web W overlaps the moisture meter 80 when the moisture meter 80 is viewed vertically from above toward below.

[0058] In this embodiment, before the web W reaches the moisture meter 80, a method is adopted in which the drive of the humidifier 15 is controlled based on at least one of the measurement results by the thermometer 94 and the measurement results by the hygrometer 22. The thermometer 94 measures the temperature of the water L. The hygrometer 22 measures the humidity of the environment in which the sheet manufacturing apparatus 1 is placed. A mode in which the drive of the humidifier 15 is controlled based on at least one of the measurement results by the thermometer 94 and the measurement results by the hygrometer 22 is called a first mode. Moreover, a mode in which the drive of the humidifier 15 is controlled based on the measurement results by the moisture meter 80 after the first mode is called a second mode.

[0059] In this embodiment, when the web W reaches the moisture meter 80, the drive control of the humidifier 15 is switched from the first mode to the second mode. The switching from the first mode to the second mode is executed by the controller 20. Also, whether or not the web W has reached the moisture meter 80 is determined by the controller 20. That is, the control method of the sheet manufacturing apparatus 1 in this embodiment includes switching from the first mode to the second mode based on the determination that the leading end of the web W has reached the moisture meter 80.

[0060] The arrival of the web W at the moisture meter 80 can be detected, for example, by providing a sensor. The detection result by the sensor is transmitted to the control unit 20. As the sensor for detecting that the web W has reached the moisture meter 80, for example, an optical sensor such as a photosensor or an ultrasonic sensor can be applied. The arrival of the web W at the moisture meter 80 can also be determined by counting the elapsed time from the start of conveyance of the web W. Note that the timing of switching from the first mode to the second mode is not limited to the above-mentioned embodiment, and may be, for example, the timing when the web W has reached the sheet forming unit 17.

[0061] The control method of the sheet manufacturing apparatus 1 includes a first mode. The first mode is a mode in which the drive of the humidifier 15 is controlled based on at least one of the measurement result of the temperature of the water L by the thermometer 94 and the measurement result of the humidity by the hygrometer 22 until the leading end of the web W reaches the moisture meter 80. According to this control method, the moisture content of the web W can be controlled until the leading end of the web W reaches the moisture meter 80.

[0062] In the control method for the sheet manufacturing apparatus 1, for example, in the first mode, the driving of the humidifier 15 can be controlled based on a function having the measurement result by the thermometer 94 and the measurement result by the hygrometer 22 as variables. As a function applicable to the first mode, for example, a function having the measurement result of the temperature of the water L by the thermometer 94 as a variable can be adopted. The function having the measurement result of the temperature of the water L by the thermometer 94 as a variable is called the first function. As a function applicable to the first mode, for example, a function having the measurement result of the humidity by the hygrometer 22 as a variable can also be adopted. The function having the measurement result of the humidity by the hygrometer 22 as a variable is called the second function.

[0063] Furthermore, as a function applicable to the first mode, for example, a function can be adopted in which both the measurement result of the temperature of the water L by the thermometer 94 and the measurement result of the humidity by the hygrometer 22 are variables. A function in which both the measurement result of the temperature of the water L by the thermometer 94 and the measurement result of the humidity by the hygrometer 22 are variables is referred to as a third function. The moisture content of the web W can be controlled by any of the above first function, second function, and third function until the leading end of the web W reaches the moisture meter 80.

[0064] In drive control of the humidifier 15 based on the measurement result of the temperature of the water L by the thermometer 94, the piezoelectric vibrator is driven at a duty ratio derived from the following formula (1): Formula (1) corresponds to the above-mentioned first function. Duty ratio % = (65 - (water temperature - 23) × 2) ÷ 100 (1) The water temperature in formula (1) is the temperature of the water L measured by the thermometer 94, and is expressed in degrees Celsius. If the calculation result is 100% or more, it is set to 100%. If the calculation result is 20% or less, it is set to 20%.

[0065] In the drive control of the humidifier 15 based on the humidity measurement result by the hygrometer 22, the piezoelectric vibrator is driven at a duty ratio derived from the following formula (2): Formula (2) corresponds to the above-mentioned second function. Duty ratio % = (65 - (humidity - 50) × 1.6) ÷ 100 (2) The humidity in formula (2) is the relative humidity measured by the hygrometer 22, and is expressed in units of %RH. If the calculation result is 100% or more, it is set to 100%. If the calculation result is 20% or less, it is set to 20%.

[0066] In the drive control of the humidifier 15 based on the measurement result of the temperature of the water L by the thermometer 94 and the measurement result of the humidity by the hygrometer 22, the piezoelectric vibrator is driven with a duty ratio derived from the following formula (3). Formula (3) corresponds to the above-mentioned third function. Duty ratio % = (65 - (water temperature - 23) x 1 - (humidity - 50) x 0.8) ÷ 100 (3) The water temperature in formula (3) is the temperature of the water L measured by the thermometer 94, and is expressed in °C. The humidity in formula (3) is the relative humidity measured by the hygrometer 22, and is expressed in %RH. If the calculation result is 100% or more, it is set to 100%. If the calculation result is 20% or less, it is set to 20%.

[0067] The moisture content of the web W can be controlled by controlling the drive waveform of the piezoelectric vibrator of the humidifier 15 based on any one of the calculation formulas (1), (2), and (3) above. The formulas (1), (2), and (3) above are stored in the memory of the control unit 20. The control unit 20 reads any one of the formulas (1), (2), and (3) above from the memory, and then calculates the duty ratio by substituting the measured values ​​by the thermometer 94 and the hygrometer 22. As a result, the drive of the humidifier 15 can be controlled based on at least one of the measurement result of the temperature of the water L by the thermometer 94 and the measurement result of the humidity by the hygrometer 22.

[0068] The method of deriving the duty ratio is not limited to the above-mentioned function. The duty ratio can also be derived by, for example, tabulating the temperature, humidity, and duty ratio of the water L. FIG. 3 shows a table for deriving the duty ratio. The duty ratio can be derived by comparing the measurement results by the thermometer 94 and the measurement results by the hygrometer 22 with the table shown in FIG. 3. In the table shown in FIG. 3, a duty ratio is defined for each of conditions 1 to 7. When the measurement results by the thermometer 94 and the measurement results by the hygrometer 22 are compared with the table shown in FIG. 3, they match any one of conditions 1 to 7. The duty ratio can be derived from the matching condition.

[0069] For example, an example in which the temperature of the water L is 16°C and the humidity is 30% RH conforms to condition 3. Therefore, in this example, a duty ratio of 100% determined in condition 3 is derived. In an example in which all of conditions 1, 3, and 4 are satisfied, condition 1 takes precedence. In an example in which all of conditions 2, 5, and 6 are satisfied, condition 2 takes precedence. The table shown in FIG. 3 is stored in the memory of the control unit 20. The control unit 20 derives a duty ratio from the conforming condition by comparing the measured values ​​from the thermometer 94 and the hygrometer 22 with the table shown in FIG. 3.

[0070] 3 illustrates a table in which both the measurement result of the temperature of the water L by the thermometer 94 and the measurement result of the humidity by the hygrometer 22 are variables. However, the variable of the table may be only the measurement result of the temperature of the water L by the thermometer 94. Also, the variable of the table may be only the measurement result of the humidity by the hygrometer 22. By determining a table suitable for each, it is possible to derive an appropriate duty ratio. As described above, it is possible to control the driving of the humidifier 15 based on at least one of the measurement result of the temperature of the water L by the thermometer 94 and the measurement result of the humidity by the hygrometer 22.

[0071] In this embodiment, the arrival of the web W at the moisture meter 80 is determined by counting the time that has elapsed since the start of conveyance of the web W. As shown in FIG. 1, the defibrated material that has passed through the drum unit 51 is deposited on a first mesh belt 61. The first mesh belt 61 is an example of a deposition belt. In the sheet manufacturing apparatus 1, after the deposition of the defibrated material starts on the first mesh belt 61, the rotational driving of the first mesh belt 61 starts. The control unit 20 counts the time that has elapsed since the rotational driving of the first mesh belt 61 starts.

[0072] The control unit 20 starts driving the humidifier unit 15 in the first mode after a first period has elapsed since the rotational driving of the first mesh belt 61 was started. At this time, the first period is the time from the start of the rotational driving of the first mesh belt 61 to the arrival of the leading end of the web W at the exhaust port 99 of the humidifier unit 15. In other words, the control unit 20 starts driving the humidifier unit 15 in the first mode based on the determination that the leading end of the web W has reached the humidifier unit 15. This makes it possible to start humidifying the web W at an appropriate timing, and makes it easy to avoid imparting humidity to the web transport unit 13 before the web W has arrived.

[0073] Then, the control unit 20 switches from the first mode to the second mode after the first period has elapsed and then after the second period has elapsed. The second period is the time from the first period elapsed until the leading end of the web W reaches the moisture meter 80. In other words, the control unit 20 switches from the first mode to the second mode after the first period and the second period have elapsed since the rotational driving of the first mesh belt 61 is started. This allows the web W to be humidified in the first mode from the leading end of the web W over a predetermined length of the web W. [Explanation of symbols]

[0074] 1...sheet manufacturing apparatus, 3...supply section, 5...crushing section, 7...defibration section, 9...mixing section, 10...accumulation section, 11...web forming section, 13...web conveying section, 15...humidification section, 17...sheet forming section, 19...cutting section, 20...control section, 22...hygrometer, 25...automatic feed mechanism, 31...crushing blade, 32...quantitative supply section, 33...hopper, 34...pipe, 35...inlet, 36...stator, 37...rotor, 38...discharge port, 41...pipe, 42...hopper, 43...hopper, 44...supply pipe, 45...supply pipe, 46...valve, 47...valve, 51...drum section, 52...housing section, 61...first mesh belt, 62...tension roller, 63...first suction mechanism, 7 1...second mesh belt, 72...roller, 72A...exit roller, 73...second suction mechanism, 74...intake fan, 75...suction port, 76...suction duct, 80...moisture meter, 91...case, 92...duct, 93...tank, 94...thermometer, 95...mist generating section, 97...air duct, 97A...intake port, 97B...exhaust port, 99...exhaust port, 101...tray, 111...pressurizing and heating section, 112...heating roller pair, 122...first cutting section, 124...second cutting section, 130...discharge receiving section, 150...air injection section, 151...opening, C...raw material, L...water, MA...humidified air, S...sheet, T...conveying direction, W...web, WA...one side, WB...other side.

Claims

1. A method for controlling a sheet manufacturing apparatus for producing a sheet from a material containing fibers, comprising the steps of: The sheet manufacturing apparatus includes: a depositing section for depositing the material to form a web from the material; a conveying section having a conveying belt that conveys the web while supporting the web; a humidifier that humidifies the web by discharging air mixed with water supplied from a tank that stores water; a heating roller positioned downstream of the humidifier in a conveying direction of the web, the heating roller heating the web to form the sheet from the web; a moisture meter located between the humidifier and the heating roller for measuring the amount of moisture contained in the web; A thermometer that measures the temperature of the water stored in the tank; A hygrometer for measuring humidity outside the sheet manufacturing apparatus, The control method includes: a first mode in which the operation of the humidifier is controlled based on at least one of a result of measuring the temperature of the water by the thermometer and a result of measuring the humidity by the hygrometer until the leading end of the web reaches the moisture meter; and a second mode in which, after the first mode is executed, the operation of the humidifier is controlled based on a result of the measurement of the moisture content by the moisture meter. A method for controlling a sheet manufacturing apparatus.

2. In the first mode, the driving of the humidifier is controlled based on a function having a result of measuring the temperature of the water by the thermometer and a result of measuring the humidity by the hygrometer as variables. A method for controlling the sheet manufacturing apparatus according to claim 1.

3. switching from the first mode to the second mode based on a determination that the leading edge of the web has reached the moisture meter. A method for controlling the sheet manufacturing apparatus according to claim 1.

4. the deposition unit has a deposition belt that is rotated while depositing the material, starting the driving of the humidifier in the first mode after a first period has elapsed since the start of rotational driving of the deposition belt; switching from the first mode to the second mode at a timing when a second period has elapsed after the first period has elapsed; A method for controlling the sheet manufacturing apparatus according to claim 1.

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