Patent Application
20070267803
An exemplary embodiment for embodying the invention will be described in detail hereinbelow with reference to the drawings.
In
A photosensitive drum 111, a developing unit 112, a laser scanner unit 130, and the like are provided in the image forming unit 300. The sheet feeding apparatus 400 has: first and second paper decks 401 and 451 having a common sheet feeding mechanism; and the attracting and conveying belt 101 for feeding the sheets enclosed in the first and second paper decks 401 and 451.
Further, the sheet feeding apparatus 400 has an air blowing unit 406 for blowing the air from the front edge side of the sheet bundle. The air blowing unit 406 is provided on the side of the sheet feeding direction of the sheet bundle stacked on a tray 403 which has been provided for each of the first and second paper decks 401 and 451 and which will be described hereinafter. The first paper deck 401 can enclose 1500 sheets S. The second paper deck 451 can enclose 2000 sheets S.
The image forming operation of the printer 1000 with such a construction will now be described.
When a start button (not shown) is pressed, the ADF 150 feeds the originals set on a document tray 152 so as to face upward one by one to the left in order from the top page. The ADF 150 conveys the originals through a curved path from the left to the right through a flow-reading position on the platen glass 151. When the original passes through the flow-reading position on the platen glass 151 from the left to the right in this manner, the image reading unit 200 reads an image of the original.
The image read by the image reading unit 200 in this manner is converted into image data by an image sensor 153 and transmitted to the laser scanner unit 130 of the image forming unit 300.
Subsequently, in the image forming unit 300, when the image data is transmitted from the image reading unit 200 to the laser scanner unit 130, a laser beam based on the image data is irradiated from the laser scanner unit 130 onto the photosensitive drum 111. At this time, the photosensitive drum 111 has previously been charged. By irradiating the light onto the drum surface, an electrostatic latent image is formed thereon. Subsequently, by developing the electrostatic latent image by the developing unit 112, a toner image is formed on the photosensitive drum 111.
When a sheet feeding signal is output from the control unit (not shown) to the sheet feeding apparatus 400, the sheets S enclosed in one of the first and second paper decks 401 and 451 are attracted to the attracting and conveying belt 101 and fed. The sheet fed as mentioned above is conveyed to a registration roller 115 through a sheet conveying unit 409, so that its skew feeding is corrected. After that, the sheet is further sent to a transfer unit constructed by the photosensitive drum 111 and a transfer roller 116 so as to be synchronized with the timing of the toner image on the photosensitive drum 111 by the registration roller 115.
Subsequently, the toner image is transferred onto the sheet sent to the transfer unit and, thereafter, the sheet is conveyed to a fixing unit 117. Further, after that, the sheet is heated and pressed by the fixing unit 117, so that a non-fixed transfer image is permanently fixed onto the sheet. The sheet to which the image has been fixed as mentioned above is ejected from the printer main body 1001 to one of discharge trays 119 and 121 by ejecting rollers 118 and 120.
The first paper deck 401 has the tray 403 (refer to
The air blowing unit 406 has the pre-separating nozzle 110 as a loosening air blowing unit. The pre-separating nozzle 110 blows the air to the front edge side surfaces of the sheets S stacked on the tray and allows the sheets S to be floated, thereby loosening the sheets S.
The air blowing unit 406 also has the separating nozzle 109 as an air blowing unit. In order to prevent the double feeding, the separating nozzle 109 blows the air to the downstream side in the sheet conveying direction of the attracting and conveying belt 101 and supplies the separating air for separating the next sheet Sn from the top sheet St attracted to the attracting and conveying belt 101. An attracting and conveying unit 405 is constructed by the attracting and conveying belt 101 and the sucking duct 103.
In
An environment sensor 9 detects an atmospheric temperature and an atmospheric humidity in the first paper deck 401. Information showing the temperature and humidity from the environment sensor 9 is input to a control unit 15 as a controller provided at a predetermined position in the printer main body 1001 illustrated in
As shown in
The control unit 15 controls a rotational speed of a driving motor M for driving the driving roller 101a to circle the attracting and conveying belt 101, thereby controlling a speed of the attracting and conveying belt 101. As will be described hereinafter, if a steam generating apparatus 11 is provided for the first paper deck 401, the control unit 15 controls the on/off operation of the steam generating apparatus 11.
The sheet feeding operation in the first paper deck 401 with such a construction will now be described.
When the air is sucked into the duct 107 by the fan 106, the sucked air passes through the air heater 108 controlled based on one of the external (environmental) temperature and the external (environmental) humidity detected by the environment sensor 9. At this time, if the air heater 108 is ON, the air is heated when passing through the air heater 108.
After that, the duct 107 branches into the separating air duct 4 as a second duct and the pre-separating air duct 105 as a third duct. The air is blown out to the outside as one of the separating air As and the pre-separating air Ap from one of the separating nozzle 109 and the pre-separating nozzle 110.
Subsequently, when the sucking fan 102 is driven, the top sheet St among a plurality of sheets S in the loosened state as illustrated in
When the sheet is conveyed by the attracting and conveying belt 101 as mentioned above, the separating air As is blown out from the separating nozzle 109 toward the downstream side in the rotating direction of the attracting and conveying belt 101. The next sheet Sn of the top sheet St is separated by the separating air As.
When the separating air As is blown from the separating nozzle 109 as mentioned above, the control unit 15 allows the separating air As to be further heated by the separating air heater 8 based on the external temperature and humidity detected by the environment sensor 9.
The top sheet St is conveyed passes over the separating nozzle 109 and is fed. Therefore, when the separating air heater 8 is turned on, the separated sheet is sent in the state where the heated separating air As has been blown to the lower surface and almost the whole sheet area is heated. Thus, the moisture content of the whole sheet area can be adjusted.
Specifically speaking, since a variation in drying state is liable to occur in the high humidity environment, in the high humidity environment, by turning on the separating air heater 8 and raising the temperature of the separating air As, the whole area of the top sheet St is uniformly dried by the separating air As.
In the embodiment, the condition for turning on the separating air heater 8 and the air heater 108 is determined as follows.
Discrimination value Jp=(atmospheric temperature (° C.)−25)+(atmospheric humidity (%)−60)
Discrimination value Jp≧0: air heater (On)
Discrimination value Jp≧20: air heater and separating air heater (On)
The following Table shows the conditions for turning on the separating air heater 8 and the air heater 108 at the atmospheric temperature and the atmospheric humidity. In this Table, an axis of ordinate indicates the atmospheric temperature and an axis of abscissa indicates the atmospheric humidity. In this Table, 1 indicates that only the air heater 108 is turned on, and 2 indicates that the air heater 108 and the separating air heater 8 are turned on.
By uniformly drying the whole sheet area of the top sheet St by the separating air As as mentioned above, the drying variation can be reduced. Since calculating methods of the discrimination value Jp to make control as mentioned above differ depending on the construction of the apparatus, the invention is not limited to the numerical values shown in the embodiment.
As described above, by controlling the heating operation of only the air heater 108 or the heating operations of the separating air heater 8 and the air heater 108 based on the temperature and humidity information from the environment sensor 9, the sheets S can be uniformly dried.
That is, by heating not only the pre-separating air Ap to attract the top sheet St but also the separating air As based on the moisture content which is supposed to be contained in the sheets S, the moisture content of the sheets S can be optimally adjusted according to the environment. Thus, the sheet can be stably fed. A drying variation in the sheet surface can be also prevented. Consequently, the occurrence of image defects can be prevented while suppressing a transfer variation. Thus, various types of sheets can be fed without causing a deterioration of the image quality.
The second embodiment of the invention will now be described.
In
By blowing out the steam toward the sheet St in this manner, the drying variation can be prevented and the moisture content of the sheet St can be adjusted. However, if the pre-separating air Ap is humidified, since the sheets are mutually attracted, only the separating air As is humidified and the sheet St which is fed is humidified.
In the embodiment, in a manner similar to the air heater 108 and the separating air heater 8, the steam generating apparatus 11 is controlled by the control unit 15 as illustrated in
In the embodiment, the condition for turning on the separating air heater 8, the air heater 108, and the steam generating apparatus 11 are determined as follows.
Discrimination value Jp=(atmospheric temperature (° C.)−25)+(atmospheric humidity (%)−60)
Discrimination value Jp≧0: air heater (On)
Discrimination value Jp≧20: air heater and separating air heater (On)
Discrimination value Jp<−40: steam generating apparatus (On)
As mentioned above, in the embodiment, the moisture content of the sheet St is adjusted by using the steam generating apparatus 11 in addition to the separating air heater 8 and the air heater 108. Since the calculating methods of the discrimination value Jp to make control as mentioned above differ depending on the construction of the apparatus, the invention is not limited to the numerical values shown in the embodiment.
In the case where, particularly, a thick sheet is used and the drying variation of the sheet St cannot be sufficiently eliminated by the separating air heater 8, it is desirable to turn on the steam generating apparatus 11 and the separating air heater 8 and set the temperature of the separating air As to 170° C. or higher. The steam of 170° C. or higher is what is called a superheated steam and since dehumidification performance is higher than that of the ordinary air as disclosed in Japanese Patent Application Laid-Open No. 2002-333275, the drying variation of the sheet St can be easily eliminated.
Further, it is also possible to construct the apparatus in such a manner that by controlling the rotational speed of the driving motor M (refer to
By changing the sheet conveying speed as mentioned above, a time (total volume) which is necessary for the separating air As to be blown to the top sheet St can be changed. The dehumidifying/humidifying effects by the separating air As can be adjusted.
For example, in the high temperature and high humidity environment, by rotating the driving roller 101a at a speed lower than that in the ordinary state, the conveying speed of the top sheet St is reduced. Thus, even if the moisture content of the sheet on the tray 403 is large, a time during which the top sheet St is buffeted with the separating air As becomes long. Consequently, the sheet is dried by the separating air As for a longer time, and dehumidification performance of the whole sheet area can be improved.
Although the temperature of the air has been adjusted by controlling the on/off operations of the separating air heater 8 and the air heater 108 in each of the foregoing embodiments, it is also possible to properly heat the air by adjusting the heating temperature by using the heaters whose temperatures can be adjusted. In such a case, the optimum air heating temperature according to the moisture content of the sheet which is presumed by the external temperature and humidity is preliminarily obtained by experiments or the like, and the heating temperature of each heater is adjusted based on the detection results of the environment sensor 9.
Although the moisture content of the sheets S has been presumed based on the external temperature and humidity detected by the environment sensor 9 and the separating air heater 8 and the air heater 108 have been controlled based on the presumed moisture content in the embodiments, the invention is not limited to such a construction. For example, the moisture content of the sheet stacked on the tray can be also directly detected by a moisture content detecting sensor Sm (shown in
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2006-140887, filed May 19, 2006, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-140887 | May 2006 | JP | national |
