Electrophotography – Control of electrophotography process – Having temperature or humidity detection
Reexamination Certificate
2002-07-22
2004-10-05
Ngo, Hoang (Department: 2852)
Electrophotography
Control of electrophotography process
Having temperature or humidity detection
C399S398000, C399S400000
Reexamination Certificate
active
06801726
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an image forming apparatus, which can optimize the rising sequence of a fan and shorten the time from the start of a copy job to the delivery of the first sheet out of the apparatus.
2. Description of Related Art
An example of the image forming apparatus according to the prior art will hereinafter be described with reference to
FIGS. 6 and 7
of the accompanying drawings.
FIG. 6
is a typical cross-sectional view of a photosensitive member, a transferring device, a stripping device, a transport device and a fixing device in an image forming portion contained in the image forming apparatus (not shown).
FIG. 7
simply shows the relation between the time from the standby state through the copying operation to the stop of the copying operation of the image forming apparatus and the operation sequence of a fan.
As shown in
FIG. 6
, a sheet P transported to registration rollers
501
as sheet supplying means by feeding and transporting means (not shown) comes into between a photosensitive drum
502
which is a photosensitive member bearing thereon a toner image formed by electrophotography and being rotated and transferring means
503
and stripping means
504
disposed in proximity to and opposed relationship with the photosensitive drum
502
.
In a transferring area, the sheet P begins to contact with the photosensitive drum
502
which is an image bearing member, passes through the transferring area and arrives at the corona discharge area of the stripping means
504
, whereupon the sheet P which has so far been in contact with the photosensitive drum
502
is stripped from the photosensitive drum
502
.
The sheet P thus stripped is completely stripped from the photosensitive drum
502
by suction means
505
playing the auxiliary role of the stripping means
504
, and is sent to transporting means
506
along a guide
507
provided on the sheet passing surface of the stripping means
504
. The suction means
505
is comprised of a duct
508
and a stripping fan
509
.
Further, the transporting means
506
is comprised of a driving runner
510
, a driven runner
511
and a transport belt
513
looped around and driven by the driving runner
510
and the driven runner
511
. The transported sheet P is transported to fixing means
514
by the transport belt
513
.
Here, the stripping fan
509
assumes the starting sequence as shown in FIG.
7
. In a graph as shown in
FIG. 7
, a section up to time T1 of a line designated by “a” represents the standby state of the image forming apparatus. In the standby state, a user performs a series of operations in preparation for the copying operation, and when he depresses a copy start button at T1, the stripping fan
509
is started. The stripping fan
509
rises to a use, rotating speed at T1-T3. T2 and T2′ indicate the time when the leading edge of the sheet P arrives at the registration rollers
501
.
If the leading edge of the sheet P has already arrived at the registration rollers
501
at T2 (T2<T3), the sheet P stands by at the position of the registration rollers
501
until T3 when the stripping fan
509
rises. Or if the leading edge of the sheet P has arrived at the registration rollers
501
at T2′ (T2′>T3) whereat the stripping fan
509
is already in its rising state, the sheet P does not stand by at the registration rollers
501
but shift is made to the image forming operation.
Thereafter, the image forming operation is started and at T4, the last sheet P is delivered out of the image forming apparatus, whereupon the stripping fan
509
performs the stopping operation.
Also, if as previously described, in the line designated by “a” in the graph, the leading edge of the sheet P arrives at the registration rollers
501
at T2, as a measure for shortening the time for which the sheet P stands by at the position of the registration rollers
501
, use has been made of a sequence as shown by a line designated by “b” in the graph for pre-starting the stripping fan
509
in the standby state.
In recent years, as seen in an image forming apparatus such as a copying machine or a printer for forming an image which is provided with a post-processing apparatus having the functions of sorting, stapling, punching and binding sheets on which images have been formed, the complication of the apparatus system has been advanced while on the other hand, the higher speed of the apparatus has also been advanced to improve productivity. Further, with the advance of the higher speed of the apparatus on the one hand, the trend for energy saving has become popular as the consideration for environmental problems. So, the above-described prior art has suffered from such problems as will be shown below.
In the prior-art image forming apparatuses of low and medium speeds, a method of corona-discharging to a sheet has been popular as a method of stripping a sheet from a photosensitive member. In recent years, however, the higher speed of the image forming apparatuses have been advanced to improve productivity and it has become difficult to strip a sheet from the photosensitive member by the aforedescribed stripping method alone. For example, as the image forming apparatus becomes higher in speed, the rotating speed of the photosensitive member increases and therefore, sufficient discharge is not done to the sheet and bad stripping may result and jam may sometimes be caused.
So, a solution to these problems has been attempted by a countermeasure such as strengthening the discharge current or sucking the sheet by a fan through a duct in the stripping portion. Also, in order that the sheet stripped from the photosensitive member may be standby transported to the fixing means even if the higher speed is advanced, use has often been made of a fan in the transporting means to suck the sheet by the fan through a duct to thereby suck the sheet onto the transporting means as well as to satisfy stable transportability.
However, when the higher speed is further advanced, suction means greater in suction force becomes necessary in order to improve the aforementioned separability and transportability. Consequently, the fan necessarily becomes bulky and this has led to such a problem as will be described below.
A bulky fan, as compared with the fan heretofore used, becomes long in its rising time and therefore, if for example, the fan is started from a point of time at which the user has operated a copy button to thereby start a copy job, a certain extent of time is required until the rotation of the fan becomes stable and thus, even a sheet started to be transported stops at a predetermined position for the time until the rotation of the fan becomes stable. This leads to the problem that the time until the first sheet after the start of the copy job is delivered out of the apparatus becomes long, and this is against the aforedescribed improvement in the productivity of the image forming apparatus.
Therefore, in the prior art, the shortening of the rising time has been contrived by operating the fan at a half of the ordinary use rotating speed or keeping the fan at the ordinary use rotating speed in the standby state of the image forming apparatus. However, depending on the installation environment (temperature and humidity) of the image forming apparatus or the type of paper great in rigidity such as thick paper good in separability, there is a case where the rotating speed of the fan is excessive. In such case, the fan is operated even during a time when the suction of a sheet is not required and thus, consumes extra electric power, and this is against the above-described trend for energy saving.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the above-noted problems peculiar to the prior art and the object thereof is to provide an image forming apparatus in which the rising sequence of a fan made bulkier with the higher speed of the image forming apparatus is reconsidered and the time from the start of a copy job until the first sheet
Shimizu Akihiro
Watanabe Koki
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Ngo Hoang
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