JP4217673B2 - Sheet feeding apparatus and image forming apparatus provided with the same - Google Patents

Description

  The present invention relates to a sheet feeding apparatus and an image forming apparatus including the same, and more particularly to a configuration for separating and feeding sheets having high adhesion between sheets.

  In conventional image forming apparatuses such as copiers and printers, sheets stacked on a sheet stacking unit are sequentially fed one by one from the top by a pickup roller that is a sheet feeding unit, and then one sheet is separated by a separation unit. A sheet feeding device that separates and feeds the image to the image forming unit is provided.

  Here, in such a sheet feeding apparatus, when continuous feeding is performed, a cut sheet is used. However, such a cut sheet is usually limited to high-quality paper or plain paper designated by the copier manufacturer. It was. Further, in order to reliably separate and feed such sheets one by one, various separation methods have been conventionally employed. As such a separation method, for example, a friction member is provided on a feed roller. There is a separation pad type that abuts with a pressure of 2 to prevent double feeding.

  As another separation method, the separation unit includes a feed roller that rotates in the sheet conveyance direction, and a separation roller that is driven with a predetermined torque in a direction opposite to the sheet conveyance direction and that contacts the feed roller with a predetermined pressure. This separation unit allows retarding to prevent double feeding by allowing only the uppermost sheet of the sheet bundle fed by the pickup roller to pass and returning the other sheet fed to the uppermost sheet to the sheet stacking means side. There is a separation method.

  Here, in order to reliably separate and feed the sheet by these separation methods, for example, in the case of the retard separation method, optimization is performed in consideration of the return torque of the separation roller and the frictional force of the sheet to be fed. By doing so, it was possible to reliably separate the sheets one by one.

  By the way, with the diversification of sheets (recording media) in recent years, in addition to ultra-thick paper, OHP sheets, art films, etc., a coating in which the surface of the sheet has been subjected to a coating treatment in order to produce whiteness and gloss due to the demand for colorization There is a growing demand for image formation on sheets such as paper.

  However, when trying to feed ultra-thick paper, the weight of the super-thick paper becomes a conveyance resistance and cannot be picked up, resulting in jamming. In addition, a sheet made of a resin material that is easily charged, such as an OHP sheet or an art film, is gradually charged when the sheets are rubbed during a feeding operation in a low-humidity environment. Because it sticks, pick-up is not possible or double feed occurs.

  Also, coated paper with a coating material such as paint on the paper surface has the property of adsorbing sheets when loaded in a highly humid environment. There is a problem that sending frequently occurs.

  In the case of a special sheet as described above, the frictional force between the sheets itself is equal to or less than that of plain paper, but in the case of a resin material sheet, the friction in a low humidity environment. Because of the adsorption force due to electrification, and in the case of coated paper, the adsorption force is higher than the friction force between the sheets due to the adsorption force in a high humidity environment. Because.

  In other words, in the case of the conventional separation method, only the frictional force between the sheets is taken into consideration, and therefore, when an adsorption force other than such a frictional force acts, the sheet cannot be reliably separated.

  Therefore, in order to solve such a very high adsorbing force between sheets, conventionally, by blowing air from the side of the sheet bundle in advance, the sheets are preliminarily blown and the adsorbing between the sheets is eliminated and the upper sheet is removed. A printer that employs a separation feeding system that picks up one sheet at a time and separates the sheets one by one at a separation section provided downstream thereof is used in the printing industry and some copying machines (for example, Patent Document 1).

  In the separation and feeding method provided with means for blowing air from the side of the sheet bundle (hereinafter referred to as auxiliary air blowing means), even a sheet (recording medium) having a high adsorbing power as described above is used. Separation performance is improved as compared with the method using only the frictional force described above, because the sheet is unwound by unwinding the sheet prior to feeding.

  FIG. 18 is a diagram showing a configuration of a sheet feeding apparatus provided with such auxiliary air blowing means. The sheet feeding apparatus 155 includes a sheet feeding tray 59 on which sheets S are stacked, and a sheet feeding tray 59. A sheet feeding unit (not shown) that feeds the sheet S, an air blowing unit 71 that blows air onto the side surface of the stacked sheets S, and a flow path that moves the air blowing unit 71 in the vertical direction along the side surface of the sheet S. Moving means 157.

  Here, the flow path moving means 157 is fixed to 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 an output shaft of the electric motor 121. And a cam plate 123 for sliding the air blowing means 71 in the vertical direction.

  In such a flow path moving means 157, when the electric motor 121 rotates, the air blowing means 71 moves in the vertical direction by the cam plate 123, and accordingly, the air path moves in the vertical direction. Here, since the opening (air outlet) of the air blowing means 71 is always a constant opening area, when the air blowing means 71 descends, the side surface of the sheet S faces the opening, thereby opening the opening. The area of the part is reduced, and the air blown out from the opening is narrowed down. As a result, it is possible to lift the upper sheet S and release the adsorption between all the sheets.

  In addition, as a separation and feeding method in which air is blown from the side surface of the sheet bundle in this way, the sheet is dehumidified by heating the blown air with a heater, and the sheet (coated paper) particularly in a high humidity environment There is one in which the adsorption force is relaxed (see, for example, Patent Document 2).

JP-A-11-005643 JP 2001-48366 A

  However, in the sheet feeding apparatus adopting the separation feeding method in which air is blown from the side surface of such a sheet bundle, when air is blown, the air of the stacked sheets is aired particularly in a low humidity environment. Only the vicinity of the spray mouth is partially dried.

  When the sheet is partially dried in this way, the surface resistance value becomes uneven in the sheet surface. As a result, when the sheet is fed to the image forming unit of the image forming apparatus, the dried part causes a transfer failure. This will cause an image defect. In particular, in the case of an electrophotographic system in which the image forming unit uses a static electricity to transfer a toner image onto a sheet, transfer performance is greatly affected by the surface resistance value of the sheet surface, and thus unevenness in the surface resistance value occurs. Unevenness of transfer occurs, and the resulting image deterioration is remarkable, which is very unsightly.

  Accordingly, the present invention has been made in view of such a current situation, and includes a sheet feeding apparatus that can reliably separate and feed sheets without causing image defects such as transfer defects. An object of the present invention is to provide an image forming apparatus.

The present invention relates to a sheet feeding apparatus for feeding sheets stacked on a sheet stacking unit capable of moving up and down by a sheet feeding unit, and blowing means for blowing air to an end portion of a sheet bundle supported by the sheet stacking unit. And a sheet position detecting means for detecting that the upper surface of the sheet bundle has reached a position where the sheet feeding means can feed the sheet bundle, and the upper surface of the sheet bundle can be fed by the sheet position detecting means The sheet feeding operation by the sheet feeding means is performed even after a predetermined waiting time has elapsed since the sheet feeding operation by the sheet feeding means is detected. If not, you have rows blowing operation by the blowing means at the predetermined blowing time, and after the job ends, characterized in predetermined time line Ukoto the blowing operation by the blowing means.

In addition, the present invention provides a lifter base on which a sheet bundle is stacked, a pickup roller that feeds a sheet from the lifter base, a blower opening disposed to face an end portion of the sheet bundle on the lifter base, and the blower A fan for blowing air from the mouth, and a paper surface position detection sensor for detecting that the upper surface of the sheet bundle has reached a position where the upper surface of the sheet bundle can be fed by raising the lifter table, and the sheet surface position detection sensor After detecting that the upper surface of the bundle has reached a position where feeding is possible, or after the sheet feeding operation by the pickup roller is performed, the sheet feeding operation is performed even if a predetermined waiting time elapses. If no cracks are have rows blowing operation by the fan at a predetermined blowing time, and after the job ends, characterized in predetermined time line Ukoto the blowing operation by the fan.

  As described above, as in the present invention, even after a predetermined waiting time elapses after it is detected that the sheet has reached a position where the sheet can be fed or the sheet feeding operation is performed, the sheet feeding is performed. When the feeding operation is not performed, the air suction operation is performed for a predetermined time to eliminate the sheet adsorption that occurs while waiting for the sheet feeding operation. Sheets can be fed separately. Further, the next sheet feeding operation can be performed smoothly.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  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 an embodiment of the present invention.

  In FIG. 1, reference numeral 1000 denotes a printer. The printer 1000 includes a printer main body 1001 and a scanner 2000 disposed on the upper surface of the printer main body 1001.

  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 1001 controls the sheet feeding apparatus 1002 that feeds the sheet S, the sheet conveying apparatus 1004 that conveys the sheet S fed by the sheet feeding apparatus 1002 to the image forming unit 1003, and the printer 1000. And a controller 120 as control means.

  Here, the sheet feeding apparatus 1002 includes a separation unit including a cassette 100, a pickup roller 101, a feed roller 102, and a retard roller 103, and the sheet S in the cassette 100 moves up and down / rotates at a predetermined timing. The pick-up roller 101 and the separating unit are separated and fed one by one. A paper feed sensor 104 is provided in the vicinity of the feed roller 102 and the retard roller 103 on the downstream side in the sheet conveyance direction. The paper feed sensor 104 can detect the passage of the sheet S.

  A cassette storage unit 1005 for storing the cassette 100 is provided at the lower part of the printer main body 1001. The cassette storage unit 1005 is partitioned by the partition plates 106 and 107 and sealed with a predetermined sealing degree. . The cassette 100 is provided with a temperature / humidity sensor 108 which is a temperature / humidity detection means for detecting the temperature and humidity in the vicinity of the cassette inside the storage unit, and the temperature and humidity in each cassette storage unit 1005 are independent of each other. It can be detected.

  Reference numeral 1010 denotes a large-capacity paper deck that is detachable as an option. The paper deck 1010 is provided with a sheet feeding device 1002 having the same configuration as the printer main body 1001 and a lifter base (not shown) that can be moved up and down. The paper deck 1010 is sealed with a predetermined sealing degree, and a temperature / humidity sensor 108 for detecting the temperature and humidity inside the deck unit is provided.

  The sheet conveying apparatus 1004 includes a conveying roller pair 105 and a registration roller unit having a pre-registration roller pair 130 and a registration roller pair 110, and the sheet S fed from the sheet feeding apparatus 1002 is conveyed to the conveying roller pair 105. Thus, after passing through the sheet conveyance path 108 constituted by the guide plate, it is guided to the registration roller pair 110. Further, the sheet S is thereafter conveyed to the image forming unit 1003 by the registration roller pair 110.

  The image forming unit 1003 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.

  In this embodiment, the printer main body 1001 and the scanner 2000 are separate, but the printer main body 1001 and the scanner 2000 may be integrated. In addition, the printer main body 1001 functions as a copying machine when a processing signal of the scanner 2000 is input to the laser scanner 111a, and functions as a FAX when a FAX transmission signal is input. Furthermore, if an output signal of a personal computer is input, it functions as a printer.

  Conversely, if the processing signal of the image processing unit 206 of the scanner 2000 is transmitted to another FAX, it functions as a FAX. Further, in the scanner 2000, if an automatic document feeder 250 as shown by a two-dot chain line is installed instead of the pressure plate 203, the document can be automatically read.

  2 is a plan view showing the configuration of the sheet feeding apparatus 1002, and FIG. 3 is a side sectional view thereof. In the present embodiment, the cassette 100 is attached to and detached from the cassette storage unit 1005 from the width direction orthogonal to the sheet conveyance direction.

  In FIG. 2, reference numerals 1 and 2 denote side regulating plates that are regulating members that regulate the position in the width direction of the sheets S stacked and stored in the cassette 100, and these side regulating plates 1 and 2 correspond to the size of the sheet S. In addition, it is configured to be movable in the width direction. Reference numeral 3 denotes a rear end regulating plate for regulating the rear end position of the sheet S in the sheet conveying direction. The rear end regulating plate 3 is configured to be movable in the sheet conveying direction according to the size of the sheet S. ing.

  The cassette 100 can be pulled out along the rails 19 and 20 shown in FIG. 3, and when the user sets the sheet S, the cassette 100 can be pulled out from the printer main body 1001 to the front side. It has become. Further, as shown in FIG. 2, the cassette 100 is provided with a protrusion 100a. When the cassette 100 is stored in the cassette storage section 1005, the cassette attachment / detachment sensor provided with the protrusion 100b in the cassette storage section 1005 is provided. 17 is detected.

  Then, a detection signal from the cassette attachment / detachment detection sensor 17 is transmitted to the controller 120, and the controller 120 is in a state where the cassette 100 is mounted in the cassette storage unit 1005 based on the detection signal from the cassette attachment / detachment detection sensor 17. It is possible to detect whether it is pulled out.

  In addition, as shown in FIG. 3, a lifter base 16 that is a sheet stacking means that can be moved up and down for stacking sheets S is provided in the cassette 100. The lifter motor 18 shown in FIG.

  For example, when the user stores the cassette 100 on which the sheet S is set and detects this by a signal from the cassette attachment / detachment detection sensor 17, the controller 120 drives the lifter motor 18 to raise the lifter base 16. Yes. Further, when the cassette 100 is pulled out for setting a sheet and this is detected by a signal from the cassette attachment / detachment detection sensor 17, the lifter motor 18 operates to lower the lifter base 16 to the lower limit position.

  In the upper part of the cassette storage unit 1005, it is confirmed that the paper surface position of the uppermost sheet stacked on the lifter table 16 is at an appropriate height for feeding, that is, the position where feeding is possible has been reached. A paper surface position detection sensor 15 for detection is provided.

  When the lifter table 16 is raised, the lifter motor 18 rotates until the paper surface position detection sensor 15 as the sheet position detection means detects the paper surface position of the uppermost sheet S1, but the paper surface position detection sensor 15 is When the uppermost sheet S1 is detected, the controller 120 stops the lifter motor 18 based on the detection signal from the paper surface position detection sensor 15. Thereby, an appropriate paper surface height can be maintained.

  In addition, when the sheet S is sequentially fed from the top along with the feeding operation, the paper surface height is gradually lowered, and the paper surface position detection sensor 15 is turned off, the controller 120 causes the lifter motor 18 to move the lifter motor 18 again. Drive in the direction of ascending. As a result, the paper surface height can always be controlled within a certain range.

  By the way, as described above, when the sheet is a coated paper, an adsorption phenomenon occurs under high humidity. Next, the elucidation of the adsorption mechanism performed by the present inventor will be described.

  FIG. 5 shows the results of an adsorption force measurement experiment conducted in advance for the elucidation of the adsorption mechanism. Here, in this adsorption force measurement experiment, the adsorption force of two types of coated paper (coated paper A and B) and plain paper was measured by changing the environment. In the figure, the horizontal axis is the relative humidity during the experiment, the vertical axis is the adsorption force, and the temperature is fixed at 30 ° C. for measurement.

  As is apparent from the results shown in the figure, the adsorptive power of coated papers A and B is very humidity-dependent and is almost the same as that of plain paper in an environment where the relative humidity is 40% or less. It can be seen that no adsorption force is generated, but the adsorption force increases linearly when the relative humidity exceeds 40%. Moreover, although the same measurement was performed on the conditions of temperature 20 degreeC and 40 degreeC, the same result was obtained. From this, it was found that the adsorptive power of the coated paper strongly depends on the relative humidity rather than the absolute moisture content in the air.

  The adsorption mechanism of the coated paper has been elucidated as follows by various experiments by the present inventors.

  As shown in FIG. 6A, when the paper bundle SA of the coated paper is exposed to a high humidity environment, only the surface of the uppermost paper S1 and the side edge of the paper bundle SA absorb moisture. When moisture is absorbed in this way, as shown in FIG. 6B, the surface of the uppermost paper S1 expands, and the side edges of the paper bundle SA swell.

  Here, in the uppermost paper S1, even if the front surface is extended, the back surface is less extended, so that a convex deformation phenomenon occurs in the uppermost paper S1 as shown in FIG. At this time, the coated paper has high smoothness and low air permeability, so that air hardly enters between the papers. For this reason, when a convex deformation phenomenon occurs in the uppermost paper S1, the volume between the uppermost paper S1 and the next paper S2 expands to generate a negative pressure, and the next paper S2 is adsorbed to the uppermost paper S1. (Hereinafter referred to as moisture absorption by uppermost paper) occurs.

  In addition, when the side end portion absorbs moisture in the paper bundle SA other than the uppermost paper, the side end portion swells, but even if the side end portion swells in this way, the central portion of the paper bundle SA does not swell, so the sheet thickness Volume expansion occurs in the direction, and this causes a phenomenon in which the space between the sheets is adsorbed with a negative pressure (hereinafter referred to as side edge moisture absorption adsorption).

  Further, as shown in FIG. 6D, when the second coated paper S2 also undergoes convex deformation due to the convex deformation of the uppermost sheet S1, the second coated paper S2 and the third coated paper S2 There is a case in which a negative pressure is applied between the coated sheets S3 (hereinafter referred to as chain deformation adsorption). In addition, this chain deformation adsorption may reach several dozens of sheets from the third sheet.

  As described above, there are three types of adsorption phenomena, namely, uppermost paper moisture absorption, side edge moisture absorption, and chain deformation adsorption as the mechanism of coated paper adsorption under high humidity. Here, these three types of adsorption phenomena are caused by the negative pressure generated when the coated paper absorbs moisture and swells or stretches. Therefore, the negative pressure is generated by flowing air between the coated papers. If it is eliminated, the adsorption phenomenon can be eliminated. Furthermore, by increasing the temperature of the air to flow in, the moisture-absorbed coated paper can be dehumidified and dried to suppress swelling, thereby suppressing the phenomenon that the coated paper is adsorbed again.

  Therefore, in the present embodiment, as shown in FIG. 2 and FIG. 3 described above, the back side in the width direction of the side regulating plates 1 and 2 so that air (air) flows in between the coated papers in this way. A plurality of (two in the present embodiment) air outlets 2a and 2b are provided in the side regulating plate 2 at a predetermined interval in the sheet conveying direction, and at least on the side surface of the sheet S at a position where it can be fed. The air ducts 2 and 2 are provided with ducts 9 and 12 in which fans 4 and 5 serving as air blowing means are attached, and the fans 4 and 5 pass the air through the air openings 2a and 2b. Air is blown to S.

  In addition, shutters 10 and 11 are provided between the fans 4 and 5 and the air outlets 2a and 2b so as to be lifted and lowered. The shutters 10 and 11 can be lifted and lowered by a swing motor 13 and a lifting mechanism (not shown). ing. When air is blown to the sheet S, the shutters 10 and 11 are gradually moved up and down to swing the air to be blown up and down, so that air is blown in sequence between the sheets, and the sheet curling effect is obtained. Can be raised.

  The fans 4 and 5 and the swing motor 13 are driven independently by signals from the controller 120 input via the fan driver circuits 4a and 5a and the swing motor driver circuit 13a shown in FIG. It has become.

  Further, as shown in FIG. 2, an air heating means 8 comprising a heater 6 and a heat sink 7 is provided in the vicinity of the air inlet 9a of the duct 9 provided in the air outlet 2a on the pickup roller side. By the air heating means 8 provided on the upstream side of the fan 5 in the air blowing direction, the air sucked in the direction of the arrow from the air inlet 9a can be heated before being blown out and blown out from the air outlet 2a.

  The thermistor 7a for detecting the temperature of the heat sink surface is attached to the heat sink 7, and the detection signal of the thermistor 7a is transmitted to the controller 120 as shown in FIG. Then, the controller 120 controls the temperature of the hot air from the air blowing port 2a by performing ON / OFF control of the heater 6 of the air heating means 8 through the driver circuit 6a according to the detection signal from the thermistor 7a. Can be done.

Here, as shown in FIG. 2, the fans 4 and 5, the ducts 9 and 12, the air heating means 8, the shutters 10 and 11, etc. are all integrally attached to the side regulating plate 2 on the back side in the width direction. Thus, from those sheet S size shown in FIG. 2, also on behalf of the sheet S ₂ of small size illustrated in FIG. 7, which in conjunction with the widthwise direction inner side of the side regulating plate 2 fan 5 or the like is also integrally with since movement can always keep the positional relationship between the end portion of the sheet S _2.

As in the small size sheet S ₂ shown in FIG. 7, if the rear end position of the sheet S ₂ does not reach the sheet conveyance direction downstream of the air blowing port 2b, wasteful air blowing also by the fan 4 by driving the fan 4 become.

  For this reason, the controller 120 is provided in the cassette 100, and for example, sheet size information from the sheet size detection sensor 14 shown in FIG. 4 that detects the sheet size according to the positions of the side regulating plates 1 and 2 and the rear end regulating plate 3. When the signal S determines that the sheet S stored in the cassette 100 is a small size sheet, the driving of the fan 4 is stopped independently.

  In addition, air is introduced between the papers in this way to eliminate the negative pressure, and the coated paper that has absorbed moisture at a high air temperature is dehumidified and dried, so that swelling is suppressed and the phenomenon in which the coated papers are adsorbed is suppressed. can do.

  On the other hand, the present inventor has found by experiment that the coated paper has the highest adsorption power immediately after opening the coated paper from the wrapping paper.

  FIG. 8 is a diagram showing data obtained by measuring a change with time in the adsorbing force of the coated paper from the time of opening. In the figure, the vertical axis represents the adsorption force and the horizontal axis represents the time. The environment during this measurement is 30 ° C. and 80%.

  As is clear from the measurement results shown in the figure, the adsorbing force of the coated paper is highest immediately after opening, and gradually decreases with time. That is, the adsorption power of the coated paper is highest immediately after the user stores the coated paper in the cassette and stores the cassette 100 in the cassette storage unit 1005. Hereinafter, this adsorption phenomenon is referred to as adsorption immediately after opening.

  Next, the present inventor measured the time-dependent change in the adsorption force from the state where the adsorption force was released by flowing high-temperature air between the adsorbed coated paper sheets. FIG. 9 is a diagram showing data obtained by measuring the temporal change of the adsorption force from a state in which such an adsorption force is solved. In the figure, the vertical axis represents the adsorption force and the horizontal axis represents the time.

  Here, as is clear from the measurement results shown in the figure, the adsorbing force is canceled immediately after it is sown, but re-adsorption begins gradually over time, until the adsorbing force does not become large immediately after opening. However, considerable adsorption power is generated. Hereinafter, this adsorption phenomenon is referred to as re-adsorption after standing. And it has been found that such re-adsorption after standing and the adsorption immediately after opening as described above also cause double feed and misfeed.

  Furthermore, in order to investigate the influence on the image (transferability) due to partial drying of the coated paper by high-temperature air, the present inventor applied 45 ° C. hot air in an environment of 30 ° C. 80% and 5 ° C. 10%. The partial moisture content of the coated paper when sprayed for a minute was measured. As a result, it was found that the water content unevenness was hardly observed under the environment of 30 ° C. and 80%, and that the water content unevenness was significantly generated under the environment of 5 ° C. and 10%.

  Also, when images were transferred by the image forming unit 1003 using these coated papers, there was no problem with the coated paper at 30 ° C. and 80%, but the image at 5 ° C. and 10% was partially It was confirmed that the transfer was weak and the density did not come out at the low water content.

  In other words, the coated paper adsorbs remarkably in a high temperature and high humidity environment, but even if it is sprinkled with high temperature air, the image is not affected.On the contrary, the coated paper does not adsorb in a low humidity and low temperature environment. It has been found that there is no need to spray and no image defects occur when sprayed.

  It has also been found that image defects due to transfer defects in a low-humidity environment are correlated not only with air temperature but also with air blowing time and air blowing speed.

  Therefore, based on these clarification results, the present embodiment is configured as follows.

  That is, since the coated paper is adsorbed immediately after opening, when the paper surface of the coated paper is detected by the paper surface position sensor 14 after the cassette 100 is mounted in the cassette storage unit 1005, that is, the coated paper can be fed. At first, the air is blown for a predetermined time T1, and the operation is sufficiently carried out. This operation is hereinafter referred to as initial swing operation.

  Further, when the paper feeding is started, the air blowing operation is performed sufficiently for a predetermined time T2 before the paper feeding operation is started. This operation is hereinafter referred to as pre-job swing operation.

  Furthermore, in the case of coated paper, as described above, it is very strongly adsorbed in a high humidity environment, and no adsorption occurs in a low humidity environment. Therefore, the temperature control temperature of the heater 6 is set according to each environment. Yes.

  By the way, after the cassette 100 mounted in the cassette storage unit 1005 is moved up to a position where it can be fed, until the sheet feeding operation is started or after the sheet feeding operation is performed, the next sheet is received. If the predetermined waiting time until the feeding operation is started is long, there are cases where the sheets cannot be sufficiently rolled even if the pre-job swing is performed.

  Therefore, in the present embodiment, the standby operation interval T3 that is the operation interval time (standby time) of the standby swing operation is determined according to the detection result of the temperature / humidity sensor 108, and the standby operation interval T3 has elapsed. Then, the air is blown for the waiting swing operation time T4. This operation is hereinafter referred to as standby swing operation. By repeating such a standby swing operation until the sheet feeding operation is started, it is possible to eliminate post-leaving re-adsorption that occurs while the sheet feeding apparatus 1002 is on standby.

  10 to 13 show the optimum air blowing time (initial swing time T1 and pre-job swing time T2) formed by the inventor in consideration of the influence on transferability in each environment where the sheet feeding apparatus 1002 is used. ), Air temperature (temperature adjustment temperature of the heater 6), standby operation interval T3, standby swing operation time T4, and job swing operation stop time T5 described later.

  10 to 13, the blow time control table, the heating temperature control table, the standby swing operation control table that is the time control table, and the fan blow speed control table (not shown) in the initial swing and the pre-job swing are shown in FIG. 4 is stored in the storage means 30 shown in FIG.

  When the sheet set in the cassette 100 is set to be, for example, coated paper in the sheet type input unit 21 of the operation unit illustrated in FIG. 4, when the cassette 100 is loaded into the cassette storage unit 1005. The initial swing is performed for a predetermined time T1 according to the environmental conditions in the cassette storage unit 1005 or the cassette 100.

  In addition, since a sheet made of a resin material such as OHP or art film does not cause adsorption immediately after opening in a high-humidity environment or re-adsorption after standing, there is no need to perform initial swing, pre-job swing, and standby swing operations. . Further, since the adsorption mechanism is attached by charging, it is not necessary to warm the air with the heater 6. Thereby, the time until the heater 6 completes the temperature control can be reduced.

  In the case of plain paper, since it is not adsorbed from the beginning, there is no need for a whispering operation with air during the feeding operation. As described above, when it is not necessary, the FCOT is quickened by avoiding the initial swing, the pre-job swing, the standby swing operation, and the temperature control of the heater 6 as much as possible. Can be used.

  Next, the initial swing operation will be described with reference to the flowchart shown in FIG.

  When the cassette 100 is mounted in the cassette storage unit 1005 and the cassette attachment / detachment detection sensor 17 that detects this is turned on (Y in Step 1), the controller 120 drives the lifter motor 18 to rotate in the direction in which the lifter base 16 is raised. (Step 2). Thereafter, the paper surface position gradually rises together with the lifter base 16, and when the paper surface position detection sensor 15 detects the paper surface and is turned on (Y in Step 3), the lifter motor 18 is stopped (Step 4).

  Next, the temperature and humidity inside the cassette housing (cassette 100) is detected by the temperature and humidity sensor 108 (step 5), and the temperature of the heater 6 is adjusted from the control table shown in FIGS. 10 and 12 based on the detected temperature and humidity. The data of temperature and initial swing time T1 is called (step 6). Thereafter, the heater 6 is energized through the heater driver circuit 6a (see FIG. 4), and the temperature of the heater 6 is adjusted.

  Next, when the temperature control of the heater 6 is completed (Y in Step 7), the fans 4 and 5 and the swing motor 6 are turned on (Step 8). Thereafter, when the initial swing time T1 previously obtained from the control table has elapsed (Y in step 9), the fans 4, 5 and the swing motor 6 are turned off (stopped) (step 10).

  And just after opening in this way, the heated air is sprayed on the coated paper, so that the adsorption between the coated papers can be released and the coated paper can be spread reliably. Accordingly, it is possible to provide a highly reliable sheet feeding apparatus that is free from jamming and double feeding. In addition, the initial swing time T1 and the temperature control temperature use an optimum table that is required to achieve both the paper-sheet-spreading ability and the image quality by experiments, so that of course image degradation such as transfer failure does not occur.

  If there is a possibility that the coated paper is not sufficiently produced in the initial swing operation, the job start may not be accepted until the initial swing operation is completed, or after accepting the job start, The job may be started after the initial swing operation is completed.

  Next, a pre-job swing operation that is performed prior to the start of the feeding operation in order to eliminate re-adsorption after being left will be described with reference to the flowchart shown in FIG.

  When the user presses the job start button, the temperature / humidity sensor 108 first detects the temperature / humidity inside the cassette housing (cassette 100) (step 21), and based on the detected temperature / humidity, FIG. 11 and FIG. Each data of the pre-job swing time T2 and the temperature control temperature of the heater 6 is called from the control table (step 22).

  Thereafter, the controller 120 energizes the heater 6 to control the temperature of the heater 6, and when the temperature adjustment of the heater 6 is completed (Y in step 23), the fans 4 and 5 and the swing motor 6 are turned on to perform the job. A front swing is performed (step 24). When the pre-job swing time T2 previously obtained from the control table elapses (Y in step 25), the feeding operation is started (step 26). When the predetermined job is completed, that is, when the final sheet of the job is fed (Y in Step 27), the fans 4 and 5 and the swing motor 6 are turned off (stopped) (Step 28).

  And after leaving in this way, before starting feeding operation, by blowing the heated air on the coated paper, it is possible to release the re-adsorption and to spread the coated paper reliably.

  Next, a standby swing operation performed when the sheet feeding standby time is long will be described with reference to a flowchart shown in FIG. FIG. 16 shows a swing operation during standby when the standby time from when the cassette 100 mounted in the cassette storage unit 1005 reaches the feedable position to when the sheet feeding operation is performed is long.

  When the initial swing control shown in FIG. 14 is completed, the controller 120 starts a standby swing operation according to the temperature and humidity from the time control table shown in FIG. 13 based on the temperature and humidity detected by the temperature and humidity sensor 108. A predetermined standby operation interval T3 and a standby swing operation time T4 that is a predetermined time for performing the standby swing operation are called (step 31). Then, first, the controller 120 energizes the heater 6 through the heater driver circuit 6a to adjust the temperature of the heater 6.

  Next, the timer 109 (see FIG. 4) is actuated (step 32), and thereafter, it waits for the start of the sheet feeding operation (step 33). Specifically, it waits for the user to press the job start button. Thereafter, the sheet feeding operation is not started (N in Step 33), and when the standby operation interval T3 elapses in this state (Y in Step 34), the fans 4 and 5 and the swing motor 6 are turned on ( Step 35). After that, when the standby swing operation time T4 previously obtained in the time control table has elapsed (Y in step 36), the fans 4, 5 and the swing motor 6 are turned off (stopped) (step 37).

  Even when the standby time from the sheet feeding operation to the next sheet feeding operation is long, the feeding of the final job sheet shown in step 27 of FIG. After turning off 4, 5 and the swing motor 6, the controller 120 performs the same processing as in FIG. Such a standby swing operation is repeatedly performed until the sheet feeding operation is started.

  Further, the pre-job swing control and the sheet feeding control may be performed as in the flowchart shown in FIG. The processing from step 41 to step 47 shown in the figure is the same as the processing from step 21 to step 27 in FIG.

  In the flowchart shown in FIG. 17, after a predetermined job is completed, that is, after the final sheet of the job is fed, after the swing operation stop time T5 during the job obtained from the time control table in step 48 has elapsed (step 48), the fans 4 and 5 and the swing motor 6 are turned off (step 49).

  Then, after the in-job swing operation stop time T5 elapses, the fans 4, 5 and the swing motor 6 are stopped, so that the coated paper can be more reliably and smoothly sprinkled in the next pre-job swing operation. Can be done.

  As described above, when the sheet has not reached the position where the sheet can be fed or after the sheet feeding operation is performed, the sheet feeding operation is not performed even after a predetermined waiting time has elapsed. In this case, by performing a blowing operation for a predetermined time and eliminating sheet adsorption that occurs during standby of the sheet feeding operation, image defects such as transfer defects do not occur, and coated paper, OHP, and art film are reliably produced. Various sheets such as ultra-thick paper can be separated and fed. Further, the next sheet feeding operation can be performed smoothly. Note that each swing operation may be performed only by blowing air by stopping the vertical movement of the shutters 10 and 12.

  In addition, by setting the temperature control temperature of the heater 6 based on a signal from the temperature / humidity sensor 108 provided in the vicinity of the cassette 100, it is possible to provide a high-quality image free from image defects such as transfer failure as well as feeding performance. it can.

  In the present embodiment, the control when coated paper is used has been described in detail. However, the present invention is not limited to this, and OHP, art film, super-thick paper, and others other than coated paper that have different characteristics depending on the environment. A control table may be created for each plain paper.

  For example, as described above, in the case of an OHP film or art film, adsorption due to charging occurs in a low humidity environment, so the air is blown at a high wind speed in a low humidity environment, and the adsorption due to the above charging hardly occurs in a high humidity environment, so it is low It is only necessary to blow at the wind speed. Further, since sheets made of these resin materials do not absorb moisture, there is no need for warm air, and therefore the heater may be turned off. Further, since these paper types do not cause re-adsorption after being left, no standby swing operation is required.

  In addition, in the case of ultra-thick paper, the conveyance resistance increases due to its own weight and pickup failure occurs, so that there is no environmental dependency in this case. Therefore, it is only necessary to blow air in the entire environment. Also, as with OHP and the like, adsorption due to moisture absorption does not occur, so there is no need for warm air, the heater only needs to be turned off, and no re-adsorption occurs after standing, so no standby swing operation is required. is there.

  In this way, the control table of the optimum heater temperature control temperature, wind speed, blowing time, etc. for each material is created, and a sheet type input unit 21 is provided as a sheet type input means as shown in FIG. An optimum time control table may be selected from a plurality of time control tables according to the sheet type information from the sheet type input unit 21 and used. Further, since the adsorption characteristics and transferability characteristics vary depending on the type and brand of the coated paper, an optimum control table may be provided for each type and brand of the coated paper. As a result, a more reliable sheet feeding apparatus can be provided.

  Further, in order to rewrite data in a table such as time control and temperature control, and to add a table, a data input unit 22 is provided as shown in FIG. 4, and a user or a service person via the data input unit 22, respectively, Each control table described above can be created freely according to the application, and can be stored.

  In the above-described embodiment, the fans 4 and 5 and the air outlets 2a and 2b are arranged on the side (one end in the width direction of the sheet) of the sheet bundle stacked on the lifter table 16 so that the side edge of the sheet bundle. However, the present invention is not limited to this, and the present invention is not limited to this. A blower opening is provided on the front side in the feeding direction of the stacked sheets, and air is supplied to the front end of the sheet bundle. You may apply this invention to the structure made to spray.

  Further, by performing the above-described initial swing, pre-job swing, and standby swing for the sheet deck, image defects such as transfer defects do not occur, and the sheets can be reliably separated and fed.

  In this embodiment, the retard method is used as an example of the sheet feeding / separating unit, but it goes without saying that this may be a separation pad method or an air feeding method.

1 is a cross-sectional view of a printer that is an example of an image forming apparatus that includes a sheet feeding apparatus according to an embodiment of the present invention. The top view which shows the structure of the said sheet | seat feeding apparatus. Side surface sectional drawing of the said sheet feeding apparatus. FIG. 2 is a block diagram of the printer. The chart which shows the relationship between adsorption power and relative humidity. The figure explaining the adsorption | suction mechanism of a coated paper. The top view which shows a state when the small size sheet | seat of the said sheet feeding apparatus is accommodated. The chart which shows a time-dependent change immediately after opening of adsorption power. The graph which shows the time-dependent change after the adsorption force has spread. A control table for controlling an initial swing time of the sheet feeding apparatus. A control table for controlling a pre-job swing time of the sheet feeding apparatus. The control table for controlling the heater temperature control temperature of the said sheet feeding apparatus. A time control table for controlling a standby swing operation of the sheet feeding device. 6 is a flowchart illustrating an initial swing operation of the sheet feeding device. 7 is a flowchart illustrating a pre-job swing operation of the sheet feeding apparatus. 7 is a flowchart illustrating a standby swing operation of the sheet feeding device. 6 is a flowchart illustrating a pre-job swing operation when a standby swing operation of the sheet feeding apparatus is performed. The figure explaining the structure of the conventional sheet feeding apparatus.

Explanation of symbols

1, 2 Side restriction plates 2a, 2b Blower 4, 5 Fan 6 Heater 7a Thermistor 8 Air heating means 9, 12 Duct 15 Paper surface position detection sensor 16 Lifter base 100 Cassette 101 Pickup roller 108 Temperature / humidity sensor 109 Timer 120 Controller 1000 Printer 1001 Printer Main Body 1002 Sheet Feeding Device 1003 Image Forming Unit 1005 Cassette Storage Unit 1010 Paper Deck S Sheet

Claims (10)

In a sheet feeding apparatus that feeds sheets stacked on a sheet stacking means that can be moved up and down by a sheet feeding means,
An air blowing means for blowing air to an end of a sheet bundle supported by the sheet stacking means;
Sheet position detecting means for detecting that the upper surface of the sheet bundle has reached a position where the sheet can be fed by the sheet feeding means;
With
A predetermined waiting time elapses after the sheet position detecting means detects that the upper surface of the sheet bundle has reached a position where it can be fed, or after the sheet feeding operation by the sheet feeding means is performed. when the sheet feeding operation by the sheet feeding means also is not performed, have rows blowing operation by the blowing means at the predetermined blowing time, and a certain time the blowing operation by the blowing means after job termination sheet feeding apparatus according to claim rows Ukoto. A time control table in which data of the waiting time corresponding to the environment in the device is stored;
Control means for controlling the operation of the blowing means;
With
2. The control unit according to claim 1, wherein waiting time data is called from the time control table based on an environment in the apparatus, and the operation of the blowing unit is started based on the waiting time data. The sheet feeding apparatus described in 1. Humidity detecting means for detecting humidity in the vicinity of the sheet stacking means;
A time control table in which data of standby time corresponding to humidity is stored;
Control means for controlling the operation of the blowing means;
With
The control means calls standby time data from the time control table based on humidity information from the humidity detection means, and starts the operation of the blowing means based on the standby time data. The sheet feeding apparatus according to claim 1. A time control table in which data of the blowing time corresponding to the environment in the apparatus is stored;
Control means for controlling the operation of the blowing means;
With
The said control means calls the data of ventilation time from the said time control table based on the environment in the said apparatus, and makes the said ventilation means operate | move based on this ventilation time data. The sheet feeding apparatus according to the description. Humidity detecting means for detecting humidity in the vicinity of the sheet stacking means;
A time control table in which data of the blowing time corresponding to humidity is stored;
Control means for controlling the operation of the blowing means;
With
The said control means calls the data of the ventilation time from the said time control table based on the humidity information from the said humidity detection means, and operates the said ventilation means based on this ventilation time data. The sheet feeding device according to 1.   6. The control device according to claim 2, wherein the control unit causes the blowing unit to perform a blowing operation for the predetermined blowing time each time the predetermined waiting time elapses. Sheet feeding device. A lifter base on which a bundle of sheets is loaded;
A pick-up roller for feeding the sheet from the lifter table;
An air outlet arranged to face the end of the sheet bundle on the lifter table;
A fan for blowing out air from the air outlet;
A paper surface position detection sensor that raises the lifter base and detects that the upper surface of the sheet bundle has reached a position capable of feeding;
With
Even if a predetermined waiting time has elapsed after the sheet surface detection sensor detects that the upper surface of the sheet bundle has reached a position where it can be fed, or after the sheet feeding operation by the pickup roller is performed. when the sheet feeding operation is not performed, it has rows blowing operation by the fan at a predetermined blowing time, and after the job completion sheet feeding and said fixed time line Ukoto the blowing operation by the fan apparatus. A humidity sensor for detecting the humidity in the vicinity of the lifter base;
A time control table in which data of the waiting time is stored corresponding to humidity;
A controller for controlling the operation of the fan;
With
The said controller calls the data of standby time from the said time control table based on the humidity information from the said humidity sensor, The operation | movement of the said fan is started based on this data of standby time. The sheet feeding apparatus described in 1. A humidity sensor for detecting the humidity in the vicinity of the lifter base;
A time control table in which data of the air blowing time corresponding to humidity is stored;
A controller for controlling the operation of the fan;
With
The said controller calls the data of ventilation time from the said time control table based on the humidity information from the said humidity sensor, and operates the said fan based on this ventilation time data. Sheet feeding device.   An image forming unit that forms an image on a sheet, and the sheet feeding device according to any one of claims 1 to 9 that feeds the sheet to the image forming unit. Image forming apparatus.

Images