JP2011063345A - Sheet feeder and image forming device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a sheet feeder be in a state capable of retard paper feeding in a state of not causing transfer failure by minimizing productivity reduction, by releasing attraction force of coat paper and thick paper in the rising of an image forming device and after replenishing paper under a high humidity environment. <P>SOLUTION: A paper feeding part of the image forming device is provided with a suction fan, a dehumidifying means 200 by a dehumidifying filter and an air separation means by the suction fan 4, and an operation condition is changed in operation of the dehumidifying means and the air separation means based on a detection result by detecting humidity in a paper feeder by a humidity sensor 108. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sheet feeding apparatus for feeding a sheet and an image forming apparatus such as a copying machine, a printer, and a facsimile machine including the sheet feeding apparatus.

  Conventionally, in image forming apparatuses such as copying machines and printers, cut sheets that can be continuously fed are usually limited to high-quality paper and plain paper designated by the copying machine manufacturer. Conventionally, various separation methods have been adopted in order to reliably separate and feed such sheets one by one. For example, the pickup roller is brought into contact with and pressed against the uppermost sheet of the sheet bundle and the sheet is fed out from the uppermost sheet, and a separation roller that is provided downstream of the sheet conveying direction and driven in a direction opposite to the sheet conveying direction is fed with a predetermined torque. Various separation methods have been adopted, such as a retard separation method in which the roller is brought into contact with a predetermined pressure to prevent double feed, and a duplo method in which a friction member is brought into contact with the feed roller with a predetermined pressure to prevent double feed. Yes. In order to reliably separate and feed the paper by the above-described method, for example, in the case of the retard method, the return torque and pressurizing force are optimized in consideration of the frictional force of the paper to be fed. It was possible to separate them one by one.

  On the other hand, in recent years, with the diversification of recording media, there is a growing demand for image formation on coated paper in which the surface of the sheet is subjected to a coating treatment in order to obtain whiteness and gloss due to the market demand for colorization. However, coated paper has the property of adsorbing sheets when the sheets are stacked especially in a high humidity environment (detailed mechanism will be explained in the embodiment), so the conventional paper feed separation system Then, there still arises a problem that pickup cannot be performed or multiple feeds occur frequently. This is because the conventional separation method only considers the frictional force between the sheets. In the case of the coated paper as described above, the frictional force between the sheets itself is equivalent to that of the plain paper described above, but the adsorption force of the coated paper in a high humidity environment is the frictional force between the sheets. This is because the sheet is adsorbed with a force much higher than the force, and cannot be separated by the conventional paper feed separation method.

  Furthermore, even if paper feeding can be performed, the transfer paper has a greatly reduced insulation resistance, so that it tends to be a defective image with a reduced toner image transfer characteristic.

  Therefore, conventionally, in order to prevent moisture absorption, a method for preventing moisture absorption of the transfer paper by increasing the ambient temperature of the transfer paper has been proposed. In this method, a transfer paper placing tray or a heater that raises the air temperature inside the apparatus is turned on to prevent moisture absorption of the transfer paper. However, in such a method, since it is necessary to always turn on the heater and there is a lot of waste in terms of power, a system using a dehumidifying unit including a chemical moisture absorbent has been proposed (see Patent Document 1).

  On the other hand, as a dehumidifying device for indoor use, a dehumidifying member that can be regenerated by heating is used, and in order to remove moisture absorbed by the dehumidifying member, the dehumidifying member is dried by heating the dehumidifying member to regenerate the dehumidifying member (Desicant type dehumidifier) has been put into practical use. A material such as porous zeolite is used as the dehumidifying member that can be regenerated by heating.

  In addition, in order to solve the high adsorption force due to moisture absorption in a high humidity environment, air is blown in advance from the side of the sheet bundle (hereinafter referred to as `` auxiliary air blowing means ''), and there is no adsorption between the sheets. In the printing industry and some copiers, a paper feed method that picks up one sheet at a time from the upper sheet and separates the sheets one by one at the separation section located downstream of the upper sheet is used. Has been. In the paper feeding method equipped with the auxiliary air blowing means, compared with the apparatus of only the friction separation method that is generally used, even a material having a high adsorbing power as described above, the sheet is rolled before the paper feeding and the suction is performed. Since it is unraveled, paper separation is possible. A number of proposals related to a paper feeding method provided with such auxiliary air blowing means have been made. However, as an example, the paper feeding device 155 shown in FIG. Sheet feeding tray 59, sheet feeding means for feeding sheets from the sheet feeding tray 59, air blowing means 71 for blowing air from the direction perpendicular to the side surface of the sheet to the side surface and top surface of the stacked sheets, A flow path moving means 157 for moving the flow path of the air blown from the air blowing means 71 in the direction perpendicular to the sheet surface is provided. The flow path moving means 157 includes a guide rail (not shown) that supports the air blowing means 71 so as to be movable in the vertical direction, an electric motor 121, and is fixed to the output shaft of the electric motor 121 and slides on the lower surface of the air blowing means 71. And a cam plate 123 that moves the air blowing means 71 in contact therewith. Therefore, when the cam plate 123 rotates due to the rotation of the electric motor 121, the entire air blowing means 71 moves in the vertical direction. In this sheet feeding device 155, the opening (air outlet) of the air blowing means 71 always has a constant opening area, and the entire air blowing means 71 moves in the vertical direction, so that the air is against the side surface of the paper 57. Thus, it is moved in the direction perpendicular to the paper surface. According to this sheet feeding device, the flow path can be moved in the vertical direction. Further, at this time, the opening area of the opening of the air blowing means 71 is constant, but the side surface of the paper 57 is arranged opposite to the opening, so that the area of the opening is reduced and blown out from the opening. The above-described air narrowing portion for narrowing the air flow is formed. As a result, it is possible to lift the upper sheet 57 and release the adsorption between all the sheets 57.

  Japanese Patent Application Laid-Open No. 2001-48366 describes that the sheet is dehumidified by heating the blown air with a heater, and the adsorbing power of the coated paper is reduced particularly in a high humidity environment.

JP-A-11-005643 Japanese Patent Laid-Open No. 9-44063 Japanese Patent Laid-Open No. 2001-48366

  However, the method of releasing adsorption using the above-described heater or dehumidifier has a problem in humidity responsiveness. For example, when the image forming apparatus using the retard paper feeding system is placed in a high humidity environment with a humidity of 80%, the paper storage is provided with a dehumidifying function, and the humidity is about 50 at which the adsorbing power is reduced and paper can be fed. When the heater is used, several minutes to several tens of minutes are required even when the dehumidifier is used. The time required for the humidity reduction greatly varies depending on the difference in the dehumidifying ability of the heater and the dehumidifier and the difference in the size of the paper storage. Even after the humidity in the paper storage is controlled to about 50% or less where paper can be fed, if the storage is opened due to paper replenishment, etc., high-humidity air will flow in, making it impossible to feed paper again. As a result, it becomes impossible to feed paper until the humidity becomes low, and the downtime of the image forming apparatus increases. In order to avoid this problem, if the dehumidifying capacity of the heater or the dehumidifying device is improved, problems such as an increase in the size of the device and an increase in power consumption occur.

  On the other hand, when the above-described auxiliary air blowing means is used, only the vicinity of the air blowing opening of the stacked sheets is partially dried, and only that portion causes a transfer defect, resulting in an image defect. . In particular, in an electrophotographic system in which a toner image is transferred onto a sheet using static electricity, the transfer performance is greatly influenced by the surface resistance value of the sheet surface. If the surface resistance value is uneven, transfer unevenness is generated, and the resulting image density unevenness is remarkable and very unsightly. As a means for avoiding the above problems, there is a method of lowering the heater temperature and the wind speed of the air to be blown, but there is a problem that productivity is lowered as an adverse effect. In particular, in a high-speed machine of 100 sheets per minute, it is difficult to achieve both uneven image density and productivity, and the productivity of coated paper is significantly reduced.

  The present invention has been made in view of the above circumstances, and there is no wait time even when the image forming apparatus is started up in a high humidity environment or when it is restarted immediately after material replenishment. It is possible to reliably feed and separate materials that generate odors. It is another object of the present invention to provide a sheet feeding apparatus capable of high-speed sheet feeding and separation and an image forming apparatus including the same without causing image defects such as image density unevenness due to transfer defects while minimizing a decrease in productivity. And

In order to achieve the above object, a sheet feeding apparatus and an image forming apparatus including the sheet feeding apparatus according to the invention described in claim 1 are provided.
Sheet stacking means for stacking a plurality of sheets;
A sheet feeding means for feeding sheets one by one from the uppermost sheet stacked on the sheet stacking means;
A substantially sealed housing for storing the sheet stacking unit and the sheet feeding unit;
A humidity detecting means provided in the housing for detecting the humidity in the housing;
An air blowing means for blowing air from a direction substantially perpendicular to the upper side surface of the sheet bundle loaded on the sheet stacking means;
A heat regeneration type dehumidifying member;
A sheet feeding apparatus including a heating unit for heating and regenerating the dehumidifying member, and a dehumidifying device for dehumidifying the inside of the housing;
By the value detected by the humidity detecting means,
The operating conditions of the air blowing means and the dehumidifying means are changed.

  As is apparent from the above description, according to the present invention, the dehumidifying device is connected to the paper feeding unit, and the auxiliary air blowing means is further provided. The dehumidifying device and the auxiliary air blowing means are optimally suited to the humidity in the paper feeding unit. By selecting and operating the setting, it is possible to reliably feed the coated paper and the ultra-thick paper without causing poor feeding due to suction and uneven transfer due to partial drying of the paper. In addition, high-speed feeding of coated paper and ultra-thick paper can be performed while minimizing the time during which productivity decreases even in a high humidity environment.

1 is a main cross-sectional view of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention. FIG. 3 is a plan view of a sheet feeding device of the image forming apparatus. FIG. 3 is a plan view (small size) of a sheet feeding device of the image forming apparatus. FIG. 3 is a cross-sectional view of a sheet feeding device of the image forming apparatus. The block diagram of the said sheet feeding apparatus. Relationship between adsorption force and relative temperature. The operation | movement flowchart of an auxiliary air blowing means and a dehumidifier. Setting list of auxiliary air blowing means and dehumidifier. Humidity transition graph in the sheet feeding device. Explanatory drawing of adsorption mechanism of coated paper. Explanatory drawing of a prior art example.

Example 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the adsorption phenomenon occurred under high humidity, and the mechanism of adsorption of coated paper, which was unavoidable with problems such as misfeeding and double feeding, was clarified.

As shown in FIG. 10 (a), when the paper bundle of coated paper is exposed to a high humidity environment, only the surface of the uppermost paper and the paper tab absorb moisture. Then, as shown in FIG. 10 (b), the uppermost paper expands and the paper swell swells. At this time, since the back surface of the uppermost paper is less stretched, a convex deformation phenomenon occurs as shown in FIG. The coated paper has high smoothness and low air permeability, so that air hardly flows between the papers. For this reason, as shown in FIG. 10 (c), when the uppermost paper is stretched and convexly deformed, the volume between the papers expands and a negative pressure is generated and adsorbed (referred to as uppermost paper moisture absorption). Further, in the paper bundle other than the top paper, the paper dust absorbs moisture and the vicinity of the edge swells. Here, since the vicinity of the center does not swell, a volume expansion occurs in the sheet thickness direction, and a negative pressure is adsorbed (referred to as “paper paper hygroscopic adsorption”). Also, as shown in FIG. 10 (d), the second sheet also has a convex deformation between the second and third sheets due to the convex deformation of the top sheet, and the second and third sheets. Adsorption may occur due to negative pressure between the sheets. Similarly, this may be several tens of sheets from the third sheet. (Referred to as chain deformation adsorption)
As described above, there are three types of adsorption phenomena as the mechanism of coated paper adsorption under high humidity. These three types of adsorption phenomena are all caused by the negative pressure generated by the paper absorbing and swelling, so the humidity near the paper bundle is reduced and moisture is released from the absorbed and swollen paper. By drying, the negative pressure can be eliminated and the adsorption phenomenon can be eliminated. Similarly, the negative pressure can be eliminated by forcibly flowing air between the sheets. Further, since the paper can be dried by increasing the temperature of the air, the suction release ability is improved, and there is an effect of suppressing the phenomenon that the papers are again adsorbed.

  FIG. 1 is a cross-sectional view of a printer that is an example of an image forming apparatus including a sheet feeding device according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 1000 denotes a printer. The printer 1000 includes a printer main body 900 and a scanner 2000 disposed on the upper surface of the printer main body 900.

  Here, a scanner 2000 that reads a document is processed by a scanning optical system light source 201, a platen glass 202, a document pressure plate 203 that opens and closes, a lens 204, a light receiving element (photoelectric conversion) 205, an image processing unit 206, and an image processing unit 206. A memory unit 208 for storing the image processing signals.

  When reading the original, the original (not shown) placed on the platen glass 202 is read by irradiating light with the scanning optical system light source 201. Then, the read document image is processed by the image processing unit 206, converted into an electrically encoded electric signal 207, and transmitted to the laser scanner 111 a serving as an image forming unit. Note that image information processed and encoded by the image processing unit 206 may be temporarily stored in the memory unit 208 and transmitted to the laser scanner 111a as necessary by a signal from the controller 120 described later.

  The printer main body 900 includes a sheet feeding device 1001 to 1004 that feeds the sheet S, a sheet feeding device 902 that feeds the sheet S fed by the sheet feeding device 1001 to 1004 to the image forming unit 901, and a printer 1000. A controller 120, which is a control means for controlling

  Here, the sheet feeding apparatuses 1001 to 1004 all have the same configuration. The sheet feeding apparatus 1001 will be described as a representative. The sheet feeding apparatus 1001 includes a separation unit including a cassette 10, a pickup roller 11, a feed roller 12, and a retard roller 13, and a sheet S in the cassette 10 is a pickup roller that moves up and down / rotates at a predetermined timing. 11 and the separating part are separated and fed one by one. A paper feed sensor 14 is provided in the vicinity of the feed roller 12 and the retard roller 13 on the downstream side in the sheet conveying direction, and the paper feed sensor 14 can detect the passage of the sheet S.

  The sheet conveying device 902 includes a conveying roller pair 15 and a registration roller unit having a pre-registration roller pair 130 and a registration roller pair 110, and the sheet S fed from each of the sheet feeding devices 1001 to 1004 is conveyed. The roller pair 105 is guided to the registration roller pair 110 after passing through the sheet conveyance path 108 constituted by a guide plate. Further, the sheet S is thereafter conveyed to the image forming unit 901 by the registration roller pair 110.

  The image forming unit 901 includes a photosensitive drum 112, a laser scanner 111a, a developing unit 114, a transfer charging unit 115, a separation charging unit 116, and the like. During image formation, laser light from the laser scanner 111a is reflected by a mirror 113. The latent image formed on the photosensitive drum in this way is formed by irradiating the exposure position 112a on the photosensitive drum that is folded back and rotated clockwise. Thereafter, the toner image is developed by the developing device 114.

  The toner image on the photosensitive drum is then transferred to the sheet S by the transfer charger 115 in the transfer unit 112b. Further, the sheet S on which the toner image is transferred in this manner is electrostatically separated from the photosensitive drum 112 by the separation charger 116 and then conveyed to the fixing device 118 by the conveyance belt 117 to fix the toner image. Thereafter, the paper is discharged by a discharge roller 119. Further, a paper discharge sensor 119a is provided in the conveyance path between the fixing device 118 and the paper discharge roller 119, and the passage of the sheet S discharged by the paper discharge sensor 119a can be detected.

  Next, a detailed description of the sheet feeding apparatus unit 1001 will be given with reference to FIGS.

  2 and 3 are plan views of the sheet feeding apparatus according to the present invention, FIG. 4 is a main sectional view thereof, and FIG. 5 is a block diagram thereof.

  In the cassette 100, a front side regulating plate 1 and a side regulating plate back 2 for regulating the position of the sheet S in the depth direction are provided. These are configured to be movable in a direction substantially perpendicular to the sheet conveying direction in the cassette 100 in accordance with the size of the sheet S in the depth direction. Further, a rear end regulating plate 3 for regulating the position of the sheet S in the width direction (sheet conveyance direction) is provided. Similarly, the sheet S moves in the sheet conveyance direction in the cassette 100 according to the size of the sheet S in the width direction. It has a possible configuration. On the back side 2 of the side regulating plate, there are provided air blowing ports 2a, 2b, and ducts 9, 12 are provided in communication therewith. Fans 4 and 5 are provided in the ducts 9 and 12, respectively, so that the fans 4 and 5 can blow air to the sheet S through the air blowing ports 2a and 2b. The fans 4 and 5 can be independently driven by fan driver circuits 4a and 5a in accordance with signals from the controller 120, respectively.

  The fans 4 and 5 can be selectively rotated at two rotational speeds by changing the applied voltage, and the strength of the air from the fans 4 and 5 is provided in two ways: strong and weak.

  Further, shutters 10 and 11 that can be driven up and down by a swing motor 13 (not shown) are provided between the fan and the air blowing ports 2a and 2b. By the action of the shutters 10 and 11, the air blown from the air blowing ports 2a and 2b can be swung to enhance the sheet rolling effect. (The details are described in Japanese Patent Laid-Open No. 11-005643, which is a conventional example, and the description thereof is omitted.) The swing motor 13 can be driven by a signal from the controller 120 by a swing motor driver circuit 13a. Further, the duct 9 is extended in the opposite direction to the air blowing port 2a of the fan 5, and air heating means including a heater 6 and a heat sink 7 is provided therein, and the air sucked from the air intake port 9a is warmed. 2a can be blown out. Further, a thermistor 8 is attached to the heat sink 7, and the temperature of the surface of the heat sink can be detected, and the detection signal is transmitted to the controller 120, whereby the driver circuit 6a of the heater 6 controls the ON / OFF of the heater 6. This makes it possible to control the temperature of the hot air from the air outlet 2a. As described above, the fans 4 and 5, the ducts 9 and 12, the heater 6 and the heat sink 7, the thermistor 8, and the shutters 10 and 11 are all attached to the back side of the side regulating plate 2, as shown in FIG. 3. Even if the size of the sheet changes from S to S2, the positional relationship with the end portion of the sheet S can always be maintained. Further, in the case of the size of the sheet S2 shown in FIG. 3, since the sheet end face is smaller than the position of the air blowing port 2b, the air blowing by the fan 4 is wasted. In this case, the signal from the sheet size sensor 14 (not shown) is used. The driving of the fan 4 can be stopped independently.

  The cassette 100 can be pulled out along the rails 19 and 20 in the front-rear direction (substantially perpendicular to the sheet conveying direction) in FIG. 4. When the user sets the sheet S, the cassette 100 moves from the main body to the front side. It can be pulled out. Further, the cassette 100 is provided with a protrusion 100a, and a cassette attachment / detachment sensor 17 is provided at a position opposed to the protrusion 100a. The cassette attachment / detachment detection sensor 17 can detect whether the cassette 100 is attached to the apparatus or pulled out.

  A lifter base 16 for stacking sheets is provided in the cassette 100 and can be moved up and down by a lifter motor 18 (not shown). When the user pulls out the cassette 100 from the apparatus for setting a sheet, the cassette attachment / detachment detection sensor 17 detects the cassette 100, and the lifter motor 18 operates so that the lifter base 16 is lowered to the lower limit position. When the cassette 100 is stored in the apparatus, the lifter base 16 is configured to rise. A paper surface position detection sensor 15 is provided above the cassette 100, and the lifter motor 18 is controlled by a signal from the paper surface position detection sensor 15. That is, when the cassette 100 is housed, the lifter motor 18 acts so that the lifter base 16 is raised, but when the proper paper surface height is detected by the paper surface position detection sensor 15, the lifter motor 18 stops and the proper paper surface is detected. The height can be maintained. Further, as the sheet S is sequentially fed from the top along with the paper feeding operation, the paper surface height gradually decreases. When the paper surface position detection sensor 15 is turned off, the lifter motor 18 is lifted again by the lifter base 16. The paper height is always controlled within a certain range. Reference numeral 17 denotes an attachment / detachment detection sensor for the sheet storage unit, and a humidity sensor 108 is provided in the sheet storage unit.

  In addition, in order to obtain an optimal image according to the paper type, the apparatus main body operation unit (not shown) is provided with a sheet type input unit 21 (not shown), which allows a paper type other than plain paper (thick paper, super-thick paper, When coated paper, thin paper, OHT, and the like are selected, the variable setting values of the paper feeding device, the fixing device, and the transfer unit are set to predetermined values for each paper type via the controller 120. Although detailed description of the variable setting values of the fixing device and the transfer unit is omitted, the paper type and variable setting values of the paper feeding device will be described in detail later.

  Further, since the sheet feeding device sections 1002 to 1004 are the same as the above-described 1001, description thereof will be omitted.

  The sheet feeding apparatuses 1001 to 1004 are partitioned by partition plates 130, 131, and 132. The partition plates 130, 131, and 132 are provided with a large number of ventilation holes (not shown), and air in the sheet feeding device is provided. Circulates, making it difficult for temperature and humidity variations to occur.

  Next, the configuration of the dehumidifying unit 200 disposed adjacent to the sheet feeding apparatuses 1001 to 1004 in FIG. 1 will be described.

  The sheet feeding unit including the sheet feeding devices 1001 to 1004 and the dehumidifying device 200 are connected by dehumidifying air ducts 210 and 211.

  The air ducts 210 and 211 are provided with a suction fan 207 and a discharge fan 208 controlled by fan driver circuits 207a and 208a (not shown). Further, the sheet feeding unit and the dehumidifying device are substantially sealed, and are configured so that air does not enter and exit from the outside of the apparatus and other parts of the image forming apparatus main body.

  The dehumidifying unit 200 includes a dehumidifying filter 201 formed of porous zeolite, a heater 202 that is ON / OFF controlled by a heater driver circuit 202a (not shown), and a dehumidifying filter fan 203 that is controlled by a signal from a fan driver circuit 203a (not shown). , A heat exchanger 204, a water tank 205, and an air duct 206 that connects and seals them. Also, the heater 202 is provided so that the heater temperature can be set in two ways by changing the applied voltage.

Next, the dehumidification process of the dehumidifier 200 will be described.
The following description will be made on the assumption that the image forming apparatus main body is arranged in a high humidity environment.

  First, the suction fan 207 rotates, takes in high-humidity air in the paper feed unit into the dehumidifying unit 200, passes through the air duct 210, and reaches the dehumidifying filter 201. The air dehumidified by the dehumidifying filter 201 passes through the air duct 211 and is discharged into the paper feeding unit by the discharge fan 208.

  Next, the function regeneration process of the dehumidifying filter 201 that has absorbed moisture will be described.

  The dehumidifying filter 201 is always rotated at a constant rotation speed around the rotation shaft 201a by the filter motor 212 (not shown) driven by a filter motor driver circuit 212a (not shown) during the operation of the dehumidifying unit. The heater 202 is provided in the vicinity of the dehumidifying filter 201 and heats the dehumidifying filter 201. The heated dehumidifying filter 201 releases moisture, and the air moistened by the moisture release is sent to the heat exchanger 204 by the air flow formed by the dehumidifying filter fan 203. The heat exchanger 204 separates high-humidity air into low-humidity air and water, and the water is stored in the water tank 205. As a result, the dehumidifying filter 201 is dried immediately even after absorbing moisture, so that the dehumidifying function is maintained.

  Next, the sheet feeding apparatus according to the present invention will be described with reference to FIGS. FIG. 6 shows the result of the measurement of the attractive force of the coated paper performed by the applicants in determining the configuration and control of the sheet feeding apparatus. The adsorption power of two types of coated paper (coated paper A and B) is measured by changing the environment. At the same time, data on uncoated thin paper and thick paper is also included. The horizontal axis is the relative humidity when the experiment is performed, and the vertical axis is the adsorption force. The temperature is measured at a fixed temperature of 30 ° C. As is clear from this result, the adsorptive power of coated paper is very humidity-dependent, unlike in non-coated paper. It can be seen that the adsorption power increases linearly when the relative humidity exceeds 40%. In addition, the same experiment was performed under the conditions of 20 ° C. and 40 ° C., and the same result was obtained. In other words, it has been found that the adsorptive power of the coated paper depends more strongly on the relative humidity than on the absolute moisture content in the air.

  Further, the sheet feeding apparatuses 1001 to 1004 can reliably feed the sheet feeding device with an adsorption force of 5 N or less.

  Therefore, from the above results, in order to reliably feed the coated paper, the inside of the sheet feeding device 1001 to 1004 is humidity 40% or less, or when the humidity exceeds 40%, the auxiliary air firing is activated, It is necessary to forcibly release the adsorption force.

  FIG. 7 is an operation flowchart of the auxiliary air blowing means and the dehumidifying device of the image forming apparatus, and the operation when the coated sheet or ultra-thick paper is fed by the sheet feeding apparatus 1001 will be described.

  First, whether or not the cassette 100 is inserted is determined by a signal from the cassette attachment / detachment detection sensor 17. Next, it is determined whether the sheet type input unit 21 is set to coated paper or ultra-thick paper. If the paper is set to coated paper or ultra-thick paper, the signal from the sensor 108 is detected next. If the humidity value h detected from the sensor 108 is h> H1, the auxiliary air blowing means and the dehumidifying unit are operated with setting 1. Details of setting 1 are shown in FIG. Humidity value: Variable setting items linked to h are productivity of the image forming apparatus (ratio when paper is fed to 100%), ON / OFF of fans 207 and 208 of the dehumidifier 200, heater 202 The settings of the settings 1 to 5 are summarized. If the setting is not set to coated paper or ultra-thick paper, setting 5 is selected, and setting 5 is maintained unless changed to coated paper or ultra-thick paper setting. Next, when the humidity value h is h <H1, it is determined whether or not h> H2, and if h> H2, setting 2 is selected. Hereinafter, setting 1 to setting 5 are selected in the flow shown in FIG. After the selection is completed, the auxiliary air blowing means and the dehumidifying device operate according to each setting condition, and the above-described paper feeding operation becomes possible.

  In addition, even after the selection is completed, the humidity value 108 is detected by the humidity sensor 108 every predetermined time, and the setting selection is repeated.

  Next, productivity items in FIG. 8 will be described.

As shown in FIG. 8, in the settings 1 and 2, the productivity is 70% and 80%, respectively, and 100% cannot be maintained. This is because the humidity is high, so the adsorbing power is high, and even if the auxiliary air blowing means is operated, the paper cannot be drawn. This is because the image forming apparatus of this embodiment is a high-speed machine having a productivity of about 100 sheets per minute. An apparatus with high productivity has a short paper feeding interval, so that the time per sheet (time for receiving the air) is shortened. For example, in the case of a 100-sheet machine per minute, the time per page is 60000 (ms) / 100 (sheets) = 600 ms.

  In the image forming apparatus according to the present embodiment, it was obtained that a sheeting time of 850 ms or more per sheet was required under a condition where the paper type having a particularly high adsorbing power and humidity exceeding 80% was obtained. In addition, the productivity is reduced to 70% and the sheeting time is secured to prevent a paper feed failure. Similarly, when the humidity is between 70% and 80%, a time of 750 ms or more per sheet is required, so the productivity is set to 80%.

  Next, FIG. 9 is a graph showing the humidity and productivity in the sheet feeding apparatus when the image forming apparatus of the present embodiment is placed in an 80% humidity environment in time series from the main body power ON.

  The flow of FIG. 7 is executed at the same time as the main body power is turned on, the dehumidifying device is operated according to the setting 1, and the humidity in the paper feeding unit rapidly decreases.

  In the image forming apparatus according to the present embodiment, it takes about 4 minutes to prepare the main body for image formation. Therefore, when the image formation preparation is completed, the humidity in the paper feeding unit is reduced to 60% or less where the productivity can be maintained at 100%. So there is no decrease in productivity. Further, as can be seen from the humidity transition during the dehumidifying device stop time of 8 minutes to 12 minutes in FIG. Further, a rapid increase in humidity after the lapse of 12 minutes is a change in humidity when the cassette 100 is pulled out by paper replacement. At this time, since the humidity rises to 65% in 2 minutes, the productivity is reduced to 80% when restarting after the paper replacement. The decreasing time is the enclosed area in FIG. However, since the dehumidifier again operates after inserting the cassette 100, the humidity is reduced to 60% or less within 1 minute as shown in FIG. 9, and the productivity can be recovered to 100%. As described above, the productivity is set to decrease when the humidity of the image forming apparatus is 70% or more. However, in actual use, the productivity is reduced only for a short time immediately after the cassette 100 is inserted and removed by paper replacement or the like. This is not a big problem in terms of productivity.

(Other examples)
In the first embodiment, dehumidification is performed on the four sheet feeding device units. However, the sheet feeding device unit to be dehumidified may be, for example, only the sheet feeding device unit 1001. In that case, the ventilation hole of the partition plate 130 is abolished, and the inside of the sheet feeding apparatus unit 1001 is made substantially sealed. Further, the dehumidifying air ducts 210 and 211 of the dehumidifying device 200 are connected to the sheet feeding device unit 1001, and the dehumidifying air generated by the dehumidifying device 200 is fed only to the sheet feeding device unit 1001. The auxiliary air blowing means described in the first embodiment is also provided only in the sheet feeding apparatus unit 1001. In this embodiment, the paper feeding that causes the adsorption of coated paper, ultra-thick paper, and the like is limited to the sheet feeding unit 1001. Since the dehumidifying area is about 1/4 compared to the configuration of the first embodiment that dehumidifies all four stages of the paper feeding device, the humidity response speed during the operation of the dehumidifying device is about four times that of the first embodiment. Also, the productivity drop time after inserting and removing the cassette is shortened. In addition, since the dehumidifying region is small, the operation time of the dehumidifying device can be shortened and the power consumption can be reduced.

4, 5 Fan 6 Heater 8 Thermistor 9, 12 Duct 17 Cassette attachment / detachment detection sensor 15 Paper surface position detection sensor 100 Cassette 108 Humidity sensor 110 Sheet conveyance path 120 Controller 130 Pre-registration roller pair 200 Dehumidifier 201 Dehumidification filter 201
202 Heater 207, 208 Duct 204 Heat exchanger 1000 Printer 1001 Sheet feeding device

Claims (5)

Sheet stacking means for stacking a plurality of sheets;
A sheet feeding means for feeding sheets one by one from the uppermost sheet stacked on the sheet stacking means;
A sealed housing for storing the sheet stacking unit and the sheet feeding unit;
A humidity detecting means provided in the housing for detecting the humidity in the housing;
Air blowing means for blowing air from a direction perpendicular to the upper side surface of the sheet bundle loaded on the sheet stacking means;
A heat regeneration type dehumidifying member;
A sheet feeding apparatus including a heating unit for heating and regenerating the dehumidifying member, and a dehumidifying device for dehumidifying the inside of the housing;
By the value detected by the humidity detecting means,
The sheet feeding apparatus according to claim 1, wherein operating conditions of the air blowing means and the dehumidifying means are changed. The air blowing means is
A wind speed variable means for changing the wind speed of air;
A temperature variable means for changing the temperature of the air,
By the value detected by the humidity detecting means,
ON / OFF of the air blowing means;
The sheet feeding apparatus according to claim 1, wherein the variable wind speed and temperature are changed. The dehumidifying means includes
A heater for heating and drying the heating regeneration type dehumidifying member;
Temperature variable means for changing the temperature of the heater,
By the value detected by the humidity detecting means,
ON / OFF of the dehumidifying means,
The sheet feeding apparatus according to claim 1, wherein the temperature of the heater is changed.   The sheet feeding apparatus according to claim 1, wherein a sheet feeding interval of sheets fed from the sheet feeding unit is changed according to a value detected by the humidity detecting unit.   An image forming apparatus comprising the sheet feeding device according to claim 1.

Images