Information
-
Patent Grant
-
6539199
-
Patent Number
6,539,199
-
Date Filed
Wednesday, October 10, 200122 years ago
-
Date Issued
Tuesday, March 25, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 399 394
- 399 395
- 399 396
- 399 389
- 399 16
- 347 129
- 347 153
- 347 248
- 347 262
- 358 406
- 358 504
- 271 26501
- 271 26503
-
International Classifications
-
Abstract
A sheet feeding unit is provided with a feeding path, on which a cut sheet having a predetermined size is fed. A sheet edge sensor has sensor elements separately arranged at portions, at which the edge of the cut sheet can be detected, along a direction perpendicular to the feeding direction of the cut sheet. An image forming unit forms a predetermined image on the cut sheet. An image formation correcting unit corrects image formation according to lateral misalignment of the cut sheet based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus and, more particularly, to an image forming apparatus such as an electronic copying machine, a digital copying machine (PPC), a printer or a facsimile for forming an image of a document on a cut sheet serving as an image forming medium, in which the image of the document can be formed at a correct position by correcting lateral misalignment of the cut sheet serving as the image forming medium which is supplied and fed to an image forming unit, and a method for controlling the image forming apparatus.
As is well known, the image forming apparatus such as an electronic copying machine, a digital copying machine (PPC), a printer or a facsimile is designed such that an image of a document can be formed on a cut sheet serving as an image forming medium which is supplied and fed to an image forming unit provided with a laser printer.
In this case, if there is lateral misalignment of the cut sheet fed to the image forming unit, the image of the document cannot be formed at a correct position on the cut sheet.
Such lateral misalignment is liable to become large in the case where the cut sheet is fed in a direction perpendicular to the width direction of the cut sheet.
In view of this, in an electrophotographic printing apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-210285, there is provided a sheet edge sensor consisting of an array of light emitting elements and an array of light receiving elements arranged along the entire width in a direction perpendicular to a sheet feeding direction on a sheet feeding path, i.e., in a lateral direction of the sheet, for detecting misalignment in the direction of the width of the sheet, such that a laser printer in an image forming unit is controlled based on the detection result, thus correcting a position at which an electrostatic latent image is formed on a photosensitive drum.
In this manner, when the electrostatic latent image formed on the photosensitive drum is transferred onto a cut sheet serving as an image forming medium with a toner, a correct image of a document without any misalignment can be formed even on the cut sheet serving as the image forming medium having lateral misalignment.
However, since the sheet edge sensor consisting of the array of the light emitting elements and the array of the light receiving elements arranged along the entire width in the direction perpendicular to the sheet feeding direction on the sheet feeding path, i.e., in the lateral direction of the sheet is used as a sensor element in the above-described prior art, the sensor is redundantly configured such that the sensor elements are arranged even at portions where the cut sheet serving as the image forming medium having a size previously designated by a user is not actually fed.
There arise problems of much waste and an increase in cost by using the sheet edge sensor having the redundant configuration in which the sensor elements are arranged even at the portions where the cut sheet having the designated size is not actually fed.
Furthermore, if there is a smear caused by sheet leavings on the feeding path at the portion at which the sheet edge sensor is disposed, the conventional sheet edge sensor may erroneously detect the sheet at that portion.
Moreover, if a portion colored with a smear or the like is judged on a white-and-black criterion in the case where the conventional sheet edge sensor is a reflection type detecting sensor, the sensor may erroneously judge that a white sheet partly colored with a smear or the like is black as a whole.
Additionally, the image forming unit provided with the laser printer may over-correct the misalignment in the case where the conventional sheet edge sensor cannot detect a sheet edge for some accidental reasons, or the detection result differs greatly from the actual misalignment.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an image forming apparatus capable of correcting lateral misalignment in such a manner that a correct image of a document without any misalignment can be formed even on a cut sheet serving as an image forming medium having lateral misalignment, by means of an inexpensive and compact sheet edge sensor mechanism by detecting the edge of the cut sheet serving as the image forming medium by the use of sensor elements separately arranged at portions at which the sensor elements are actually used according to the size of the cut sheet serving as the image forming medium, and a method for controlling the image forming apparatus.
Another object of the present invention is to provide an image forming apparatus capable of correcting lateral misalignment in such a manner that a correct image of a document without any misalignment can be formed even on a cut sheet serving as an image forming medium having lateral misalignment, by means of an inexpensive and compact sheet edge sensor mechanism, by detecting the edge of the cut sheet serving as the image forming medium by the use of a sensor element movably arranged at a portion at which the sensor element is actually used according to the size of the cut sheet serving as the image forming medium, and a method for controlling the image forming apparatus.
In this case, it is to be understood that the sensor elements are arranged not only in the direction of the width of the sheet but also at portions requiring accuracy.
Furthermore, according to the present invention, a judgment criterion is previously corrected based on the current state of the sensor, thereby reducing erroneous detection.
Moreover, according to the present invention, a mechanism for removing a smear on the glass stage on which a document is placed can be eliminated, thereby achieving cost reduction as a whole.
Additionally, according to the present invention, information on the color of the sheet to be used is previously acquired, and thus, a judgment criterion corresponding to the color is used, thereby eliminating erroneous detection caused by a difference in color of the sheet.
In addition, according to the present invention, there is provided a limitation in the case where misalignment exceeds an estimated value, thereby minimizing over-correction.
In order to achieve the above-described objects, according to the present invention:
(1) There is provided an image forming apparatus comprising:
a sheet feeding unit provided with a feeding path, on which a cut sheet serving as an image forming medium having a predetermined size is fed;
a sheet edge sensor having sensor elements separately arranged at portions, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit;
an image forming unit for forming a predetermined image on the cut sheet serving as the image forming medium to be fed by the sheet feeding unit; and
an image formation correcting unit for correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit.
In order to achieve the above-described objects, according to the present invention:
(2) There is provided an image forming apparatus according to (1), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit adjusts a threshold as a judgment criterion of the presence of the sheet before actual detection of the sheet by the sheet edge sensor.
In order to achieve the above-described objects, according to the present invention:
(3) There is provided an image forming apparatus according to (2), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit previously designates the color of the sheet, and then, resets the threshold as the judgment criterion of the presence of the sheet in accordance with the designated color.
In order to achieve the above-described objects, according to the present invention:
(4) There is provided an image forming apparatus according to (1), wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit judges as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, gives a limitation to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value.
In order to achieve the above-described objects, according to the present invention:
(5) There is provided an image forming apparatus comprising:
a sheet feeding unit provided with a feeding path, on which a cut sheet serving as an image forming medium having a predetermined size is fed;
a sheet edge sensor having a sensor element movably arranged at a portion, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit;
an image forming unit for forming a predetermined image on the cut sheet serving as the image forming medium to be fed by the sheet feeding unit; and
an image formation correcting unit for correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit.
In order to achieve the above-described objects, according to the present invention:
(6) There is provided an image forming apparatus according to (5), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit adjusts a threshold as a judgment criterion of the presence of the sheet before actual detection of the presence of the sheet by the sheet edge sensor.
In order to achieve the above-described objects, according to the present invention:
(7) There is provided an image forming apparatus according to (6), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit previously designates the color of the sheet, and then, resets the threshold as the judgment criterion of the presence of the sheet in accordance with the designated color.
In order to achieve the above-described objects, according to the present invention:
(8) There is provided an image forming apparatus according to (5), wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit judges as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, gives a limitation to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value.
In order to achieve the above-described objects, according to the present invention:
(9) There is provided a method for controlling an image forming apparatus comprising the steps of:
feeding a cut sheet serving as an image forming medium having a predetermined size along a feeding path provided in a sheet feeding unit;
separately arranging sensor elements constituting a sheet edge sensor at portions, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit;
forming a predetermined image on the cut sheet serving as the image forming medium to be fed to an image forming unit by the sheet feeding unit; and
correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit.
In order to achieve the above-described objects, according to the present invention:
(10) There is provided a method for controlling an image forming apparatus according to (9), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, a threshold as a judgment criterion of the presence of the sheet is adjusted in the image formation correcting step before actual detection of the presence of the sheet by the sheet edge sensor.
In order to achieve the above-described objects, according to the present invention:
(11) There is provided a method for controlling an image forming apparatus according to (10), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the color of the sheet is previously designated, and then, the threshold as the judgment criterion of the presence of the sheet is reset in accordance with the designated color in the image formation correcting step.
In order to achieve the above-described objects, according to the present invention:
(12) There is provided a method for controlling an image forming apparatus according to (9), wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, it is judged as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, a limitation is given to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value in the image formation correcting step.
In order to achieve the above-described objects, according to the present invention:
(13) There is provided a method for controlling an image forming apparatus comprising the steps of:
feeding a cut sheet serving as an image forming medium having a predetermined size along a feeding path provided in a sheet feeding unit;
moving a sensor element constituting a sheet edge sensor at a portion, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit;
forming a predetermined image on the cut sheet serving as the image forming medium to be fed to an image forming unit by the sheet feeding unit; and
correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit.
In order to achieve the above-described objects, according to the present invention:
(14) There is provided a method for controlling an image forming apparatus according to (13), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, a threshold as a judgment criterion of the presence of the sheet is adjusted in the image formation correcting step before actual detection of the presence of the sheet by the sheet edge sensor.
In order to achieve the above-described objects, according to the present invention:
(15) There is provided a method for controlling an image forming apparatus according to (14), wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the color of the sheet is previously designated, and then, the threshold as the judgment criterion of the presence of the sheet is reset in accordance with the designated color in the image formation correcting step.
In order to achieve the above-described objects, according to the present invention:
(16) There is provided a method for controlling an image forming apparatus according to (13), wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, it is judged as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, a limitation is given to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value in the image formation correcting step.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiment of the invention and, together with the general description given above and the detailed description of the preferred embodiment given below, serve to explain the principles of the invention.
FIG. 1
is a view schematically showing the entire configuration of a digitally composite machine as one type of composite image forming apparatus which is used as an image forming apparatus according to the present invention;
FIG. 2
is a block diagram illustrating the schematic configuration of a control system in the digitally composite machine which is used as the image forming apparatus in a first embodiment according to the present invention;
FIG. 3
is a diagram illustrating the details of a console panel unit and a display unit illustrated in
FIG. 2
;
FIG. 4
is a diagram schematically illustrating the positional relationship between a sheet edge sensor
75
e
as an essential part according to the present invention and a sheet in the case where the sheet edge sensor
75
e
is disposed in a fixed or movable manner;
FIG. 5
is a diagram schematically illustrating the positional relationship between the sheet edge sensor
75
e
as the essential part according to the present invention and the sheet in the case where the sheet edge sensor
75
e
is disposed in the fixed manner in the first embodiment according to the present invention;
FIG. 6
is a diagram schematically illustrating the positional relationship between the sheet edge sensor
75
e
as the essential part according to the present invention and the sheet in the case where the sheet edge sensor
75
e
is disposed in the movable manner in a second embodiment according to the present invention;
FIG. 7
is a perspective view showing an example of a moving mechanism in the case where the sheet edge sensor
75
e
as the essential part according to the present invention is disposed in the movable manner;
FIG. 8
is a flowchart illustrating operation in the case where the sheet edge sensor
75
e
as the essential part according to the present invention is disposed in the movable manner;
FIG. 9
is a graph illustrating re-setting of a threshold as a judgment criterion of the presence of a sheet on the precondition for sheet edge detection in accordance with a smear on the sheet edge sensor as the essential part according to the present invention in a third embodiment according to the present invention;
FIG. 10
is a graph illustrating re-setting of a threshold as a judgment criterion of the presence of a sheet on the precondition for the sheet edge detection by the sheet edge sensor as the essential part according to the present invention in accordance with the color of the sheet in a fourth embodiment according to the present invention; and
FIG. 11
is a flowchart illustrating operation for limiting correction in forming an image based on a detection result by the sheet edge sensor as the essential part according to the present invention in a fifth embodiment according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the presently preferred embodiments of the invention as illustrated in the accompanying drawings, in which like reference numerals designate like or corresponding parts.
Preferred embodiments in which an image forming apparatus according to the present invention is applied to a digitally composite machine will be described in reference to the accompanying drawings.
FIG. 1
is a view schematically showing the entire configuration of a digital copying machine
1
as one type of composite image forming apparatus which is used as an image forming apparatus according to the present invention (hereinafter referred to as the composite image forming apparatus, the image forming apparatus or the digitally composite machine case by case).
The digitally composite machine
1
is provided with a scanner
2
and a printer (a laser engine)
3
, and further, with an automatic document feeder (ADF)
4
at the upper portion thereof.
The automatic document feeder
4
is configured such that the rear edge of a cover body
21
serving as a casing is pivotably fixed to the rear edge of the upper surface of the feeder via a hinge, not shown, and further, the entire automatic document feeder
4
is turned and displaced, as required, to release the upper portion of a document stage
5
.
Slightly to the right of the cover body
21
is provided a document supplying tray
22
capable of holding therein a plurality of sheets of documents.
At one end of the feeder is disposed a supplier
23
for taking out the documents one by one and supplying them to one end (to a left end in
FIG. 1
) of the document stage
5
.
The supplier
23
includes a pick-up roller
27
for taking out the document, a weight plate
28
for pressing the document against the pick-up roller
27
, an empty sensor
29
serving as a document detecting sensor for detecting the set state of the document on the document supplying tray
22
, and the like.
Furthermore, a sheet supplying roller
32
is disposed in the document taking-out direction of the pick-up roller
27
, so as to securely supply and feed the documents one by one.
At the upper surface of the document stage
5
is stretched a document conveying belt
37
in such a manner as to cover the document stage
5
.
The document conveying belt
37
is a wide endless belt which has a white obverse surface and is stretched across a pair of belt rollers
40
and
40
, and is configured such that it can travel forward and reversely by means of a belt drive mechanism, not shown.
At the reverse surface at the inner circumference of the document conveying belt
37
are disposed a plurality of belt pressing rollers
41
. . . for pressing the belt surface on the document stage
5
and a set switch, not shown, for detecting the open/closed state of the automatic document feeder.
The document, which has been supplied and fed by the supplier
23
, is fed from one end (i.e., the left end) of the document stage
5
to the other end (i.e., a right end).
A sheet discharging device
38
disposed at a right portion of the feeder includes a feeding roller
44
, a pinch roller
45
for pressing the document against the feeding roller
44
, a sheet discharging sensor
46
serving as a document detector for detecting the rear end of the document which is fed in a sheet discharging direction, and the like.
Furthermore, a sheet discharging roller
48
is disposed downstream of a document discharging path.
Moreover, a gate
49
for leading the document upside down to the document stage
5
is provided on the document discharging path, thereby achieving double-sided copying of the document.
The scanner
2
serving as a reader comprises: an exposure lamp
6
serving as a light source, a first carriage
7
having a mirror
15
, a second carriage
9
having mirrors
8
a
and
8
b
for refracting an optical path, a lens
10
, a CCD sensor
11
for receiving reflected light, a drive system, not shown, for changing the positions of the above-described constituent parts, and an A/D converter, not shown, for converting an output from the CCD sensor
11
, i.e., analog image data (information) into digital image data.
The first and second carriages
7
and
9
are connected via a timing belt, not shown. The second carriage
9
is moved at a rate half of that of the first carriage
7
in the same direction as that of the first carriage
7
.
Consequently, scanning can be performed in such a manner that the length of the optical path up to the lens
10
becomes constant.
The lens
10
has a fixed focal distance, and is designed to be moved in a direction of an optical axis at the time of scaling.
One pixel of the document corresponds to one element of the CCD sensor
11
.
An output from the CCD sensor
11
is input into the A/D converter.
The first and second carriages
7
and
9
and the mirrors
12
a
and
12
b
are moved by stepping motors, not shown, respectively.
The first and second carriages
7
and
9
are configured to be moved in accordance with the operation of a timing belt, not shown, stretched between a drive pulley, not shown, connected to the rotary shaft of the stepping motor and an idle pulley, not shown.
When a spiral shaft, not shown, is rotated by a stepping motor, not shown, corresponding to the shaft, the lens
10
is moved in the direction of the optical axis in accordance with the movement of the spiral shaft.
A collimate lens
62
, a polygon mirror (a polygonal reflection mirror)
64
, a lens
66
, reflection mirrors
68
and
70
and a lens
72
are arranged in a manner corresponding to a laser diode
60
constituting a laser optical system
2
a
, so that a photosensitive drum
50
is irradiated with a laser beam emitted from an exposure device
52
.
An image forming unit
2
A, i.e., the printer
3
serving as an image forming means is configured by combining, for example, a laser optical system with an electrophotographic system capable of forming an image on a transfer sheet.
That is to say, the printer
3
includes the photosensitive drum
50
serving as an image carrier pivotably supported at substantially the center of the apparatus, and further, includes the exposure device
52
, a developer
54
, a transfer charger
55
, a separating charger
56
, a discharger
57
before cleaning, a cleaner
58
, a discharging lamp
59
and a charger
61
in this order located around the photosensitive drum
50
.
The photosensitive drum
50
is uniformly charged by the charger
61
.
In this manner, when the laser beam is emitted from the scanner
2
, an image of the document is focused on the photosensitive drum
50
, thereby forming an electrostatic latent image.
Moreover, the electrostatic latent image formed on the photosensitive drum
50
is developed by the developer
54
, and then, the developed image is transferred, by the transfer charger
55
, onto a copying sheet (an image forming medium) P to be fed from a sheet supplying cassette
30
serving as a sheet supplier, described later, via a sheet supplying roller
20
and an aligning roller
25
.
The copying sheet P after being transferred by the transfer charger
55
is separated by the effect of an AC charge discharging by the separating charger
56
, and then, is conveyed to a fixing device
71
via the conveying belt.
The copying sheet P, on which the developed image is fused and fixed by the fixing device
71
, is discharged to a unit
74
having a sheet discharging tray
74
a
, by a pair of sheet discharging rollers
73
.
The unit
74
includes a pair of rollers
74
b
for allowing the copying sheet P, which is discharged by the pair of sheet discharging rollers
73
, to face down.
Additionally, the unit
74
is provided, at the upper portion thereof, with a stapler
74
c
for stapling one set of sheets in a staple-sort mode.
In the meantime, any developing agent remaining on the photosensitive drum
50
, after the developed image is transferred onto the copying sheet P and the copying sheet P is separated, is previously discharged by the discharger
57
before cleaning, followed by cleaning by the cleaner
58
, and then, a potential on the photo-sensitive drum
50
is adjusted to a predetermined level or lower by the discharging lamp
59
, thereby allowing the next copying operation.
Here, in the case of double-sided copying in which both sides of the copying sheet P are subjected to printing, the copying sheet P, on which the developed image is fused and fixed by the above-described fixing device
71
, is fed along a feeding path
75
a
, and then, is stacked on a tray
75
b.
The sheet P having only one side printed, stacked on the tray
75
b
is fed to the above-described transfer charger
55
along another feeding path
75
c
, and then, the developed image is transferred onto the other side of the sheet P, which has not been printed yet.
Under the tray
75
b
is disposed a sheet sensor
75
d
of a light reflection type, for detecting the presence of the sheet to be stacked on the tray
75
b.
The feeding path
75
a
, the tray
75
b
, the feeding path
75
c
and the sheet sensor
75
d
constitute an automatic double-sided device (ADD)
75
serving as an automatic double-sided reversing mechanism.
Furthermore, reference numeral
30
in
FIG. 1
designates the sheet supplying cassettes
30
serving as the sheet suppliers which are vertically disposed at a plurality of stages in such a manner so as to be detachably attached in front of the copying machine
1
.
The sheet supplying cassette
30
consists of a cassette case
31
serving as a casing containing therein the copying sheets P.
The cassette case
31
is configured such that its removal end is inclined toward a sheet taking-out direction.
The uppermost copying sheet P contained in the cassette case
31
of the sheet supplying cassette
30
is first picked up and taken out by a pick-up roller
81
.
The copying sheets P taken out by the pick-up roller
81
and fed to the removal end of the cassette case
31
are separated one by one at a sheet separating unit consisting of a sheet supplying roller
84
and a separating roller (or a separating pad)
85
disposed upward inside of the removal end of the cassette case
31
, and then, are fed to the printer
3
.
Moreover, at the right side of the copying machine are provided a sheet supplying cassette
43
and a large cassette feeder (LCF)
47
in a detachable manner.
The uppermost copying sheet P contained in the sheet supplying cassette
43
is first picked up and taken out by a pick-up roller
43
a.
The copying sheets P taken out by the pick-up roller
43
a
and fed to the removal end of the sheet supplying cassette
43
are separated one by one at a sheet separating unit consisting of a sheet supplying roller
43
b
and a separating roller
43
c
disposed upward inside of the removal end of the sheet supplying cassette
43
, and then, are fed to the printer
3
.
The uppermost copying sheet P contained in the LCF
47
is first picked up and taken out by a pick-up roller
47
a.
The copying sheets P taken out by the pick-up roller
47
a
and fed to the removal end of the LCF
47
are separated one by one at a sheet separating unit consisting of a sheet supplying roller
47
b
and a separating roller
47
c
disposed upward inside of the removal end of the LCF
47
, and then, are fed to the printer
3
.
In other words, the digital copying machine
1
as a composite image forming apparatus according to the present invention, as shown in
FIG. 1
, is constituted of the scanner
2
for reading the document and the image forming unit
2
A.
The scanner
2
optically scans the document, which has been taken in by the ADF (automatic document feeder)
4
or the like, by using the exposure lamp
6
as a light source, so that the reflection light enters the CCD sensor
11
, and then, is read as a digital image signal after A/D conversion.
The image forming unit
2
A comprises the photosensitive drum
50
, the laser optical system
2
a
, the LCF
47
serving as the sheet supplying tray, the printer
3
including the developing device
54
and the fixing device
5
, and the sheet discharging tray
74
a.
A semiconductor laser disposed inside the laser optical system
2
a
is switched on or off in response to the image signal read by the scanner
2
. The laser beam is reflected and scanned by the polygon mirror, and consequently, the electrostatic latent image is formed on the photosensitive drum
50
.
After the electrostatic latent image is developed by the developing device
54
, it is transferred onto the sheet which is supplied from any of the sheet supplying cassette
30
, the sheet supplying cassette
43
, the large cassette feeder (LCF)
47
and the tray
75
b
for the automatic double-sided device (ADD)
75
in accordance with the designation of a user, and then, is fixed by the fixing device
71
.
In this manner, a sheet having the image formed thereon is thereafter discharged onto the sheet discharging tray
74
a.
A sheet edge sensor
75
e
, described later, as an essential part according to the present invention is mounted in a fixed or movable manner on the tray
75
b
constituting the automatic double-sided device (ADD)
75
as one example according to the present invention, thereby detecting lateral misalignment of the sheet fed from the tray
75
b
along the feeding path.
The sheet edge sensor
75
e
as the essential part according to the present invention may be disposed not only on the tray
75
b
for the automatic double-sided device (ADD)
75
but also over or on a part of the feeding path, on which the sheet supplied from the above-described sheet supplying cassette
30
, sheet supplying cassette
43
, large cassette feeder (LCF)
47
or tray
75
b
for the automatic double-sided device
75
is fed to the image forming unit
2
A.
FIG. 2
is a block diagram illustrating the configuration of a control system in the above-described composite image forming apparatus.
The control system in the present composite image forming apparatus includes mainly a control panel unit
401
, a scanner unit
402
, a main controller unit
403
, a printer engine unit
404
, a memory editor unit
405
, a system unit
406
and a power source unit
407
.
The control panel unit
401
is composed of a control panel CPU
408
for controlling the entire control panel unit
401
, a RAM
409
, a ROM
410
, a control panel
411
and a priority card input port
452
.
The scanner unit
402
is composed of a scanner CPU
412
for controlling the entire scanner unit
402
, a CCD
413
for reading analog image data transmitted from the scanner, an A/D converting circuit
414
for performing A/D conversion, an SHD circuit
415
for performing shading correction, a line memory
416
for providing timing, a ROM
417
, a RAM
418
, a mechanic controller
419
, an ADF
420
and an editor
421
for a coordinate input device.
The main controller unit
403
is composed of a main CPU
422
for controlling the entire main controller unit
403
, a ROM
423
, a RAM
424
, a printer FONT ROM
425
, a display ROM
426
, a data switch/data buffer memory circuit
427
for switching where to transmit the data read by the scanner unit
402
or how to transmit the data to the printer engine, and performing buffering and an image processor
428
for performing image edition such as compression or extension.
The main CPU
422
controls also the respective CPUs in the units in addition to the above-described control.
The printer engine unit
404
comprises a mechanical controller or the like
430
, a sorter
431
, an LCF (a large cassette feeder)
432
, a laser modulating circuit
433
, a laser drive circuit
434
, a laser
435
, a ROM
436
, a RAM
437
, a multiple-stage sheet supplying tray
438
, a lateral misalignment correcting circuit
439
for giving a predetermined lateral misalignment correcting signal to the laser modulating circuit
433
or the laser drive circuit
434
based on a detection output transmitted from the above-described sheet edge sensor
75
e
as the essential part according to the present invention, and a sheet edge sensor drive circuit
440
.
The memory editor unit
405
is composed of an image editor
439
for editing the image data edited by the image processor
428
and image data transmitted from the system unit
406
, a compressor/extender
440
for compressing or extending the data, an enlarging/reducing/rotating portion
441
for performing enlargement, reduction or rotation, a page memory
444
for storing, per page, the image data processed by the above-described editor devices, an address controller
442
for managing a memory address, a memory management controller
443
for managing the data stored in the memory, a CPU controller
445
for linking a system CPU
446
in the system unit
406
to the main CPU
422
, and an interrupt controller
451
.
The above-described configuration achieves composition or the like per page.
The system unit
406
comprises the system CPU
446
for controlling the entire system unit and the memory editor unit
405
, a printer controller
447
for converting data transmitted from a personal computer or the like into image data, a facsimile (a FAX)
448
, a local area network (a LAN)
449
, and a hard disk drive (a HDD)
450
.
The composite image forming apparatus according to the present invention comprises the memory editor unit
405
, the printer controller
447
, the FAX
448
, the LAN
449
and the HDD
450
, in which electric power supply is controlled in accordance with an electric power mode, the system CPU (periphery)
446
for controlling the above-described optional devices, the main controller unit
403
for receiving a command in accordance with the electric power mode from the system CPU (periphery)
446
so as to control the power source unit
407
, and the power source unit
407
including an electric power system for supplying continuous electric power and another electric power system, which can be controlled by the system CPU (the periphery)
446
, in order to supply the electric power in accordance with the electric power mode.
FIG. 3
is a diagram illustrating the details of a console unit
217
and a display unit
214
.
In other words,
FIG. 3
illustrates the configuration of the console panel (control panel)
217
serving as an operating device.
Namely, the console panel
217
includes a finisher key
82
, a state display
83
, a cassette selecting key
86
for selecting the sheet supplying cassette
30
, a HELP key
87
, an automatic sheet selecting key
88
, an automatic magnification selecting key
89
, a zoom/100% key
90
, a document size key
91
, a sheet size key
92
, a message display
93
, an automatic density key
94
, a manual density key
95
, a preheating key
96
, an interrupt key
97
, an all-clear key
98
, a clear/stop key
99
, a start key
101
, a timer key
103
, a ten key
105
and a function switching key
120
.
The finisher key
82
is used in selecting a sort mode, a group mode or a staple mode.
The state display
83
is provided for displaying the state of the copying machine by flashing or displaying various pictorial characters.
The cassette selecting key
86
is depressed to select another cassette when the cassette for a desired size is not selected.
When the HELP key
87
is depressed as an operation guide key, a message representing operating procedures is displayed, and further, when it is depressed after a function is set, the set contents can be confirmed.
The automatic sheet selecting key
88
is normally set in an automatic sheet selecting mode. The size of the document placed on the document (glass) stage, not illustrated, is automatically detected, and then, a sheet having the same size as the detected size is automatically selected (only in copying under an equal magnification).
An automatic magnification selecting mode is selected by depressing the automatic magnification selecting key
89
and a desired sheet size is designated, the size of the document placed on the document (glass) stage
5
is detected, and then, a copying magnification is automatically calculated.
The copying magnification is decremented by 1% down to 50% by depressing a “50%<” key of the zoom/100% key
90
.
In contrast, the copying magnification is incremented by 1% up to 200% by depressing a “>200%” key of the zoom/100% key
90
.
Furthermore, the copying magnification is returned to an equal magnification (100%) by depressing a “100%” key of the zoom/100% key
90
.
The document size key
91
is used in setting the document size.
That is, when the sheet size is selected and the document size is designated by depressing the document size key
91
, the copying magnification is automatically set.
The sheet size key
92
is used in selecting the sheet size.
The message display
93
as the display unit
214
displays, with characters and pictures, the state of the digital copying machine
1
, the operating procedures and various commands to a user.
The message display
93
as the display unit
214
may incorporate a touch panel therein so as to set functions.
When the automatic density key
94
is depressed, the digital copying machine
1
automatically detects the density of the document so as to select an optimum copying density.
A desired copying density can be selected by depressing the manual density key
95
.
The copying density can be reduced by five levels by depressing a “low” key; in contrast, the copying density can be increased by five levels by depressing a “high” key.
The copying machine is brought into a preheating state (a power saving state) by depressing the preheating key
96
, and therefore, all of display lamps are extinguished.
In order to restart the copying operation, the preheating key
96
is depressed again.
The interrupt key
97
is used when interrupt copying is intended to be performed during continuous copying.
When the all-clear key
98
is depressed, all of the selected modes are cleared, so that the copying machine is returned to a standard state.
The clear/stop key
99
is used to vary the number of sheets to be printed or stop the copying operation.
The start key
101
is depressed to start the copying operation.
The time when the power source of the digital copying machine
1
is turned on or off is displayed by depressing the timer key
103
(in the case where a weekly timer is set).
The ten key
105
is used to set the number of sheets to be printed, which can be set from 1 to 999.
The function switching key
120
is used to switch functions such as a facsimile function and a printer function, which are equipped in the composite digital copying machine.
First Embodiment
FIG. 4
is a diagram schematically illustrating the positional relationship between the sheet edge sensor
75
e
as the essential part according to the present invention and the sheet in the case where the sheet edge sensor
75
e is disposed in a fixed or movable manner.
Namely, it is assumed that a sheet having any one of sizes A3, B4, A4-R, B5-R and A5-R is fed along the feeding path while keeping a symmetric positional relationship with respect to a center line in a longitudinal direction, as illustrated in
FIG. 4
, and that a sheet having either one of sizes A4 and B5 is fed while keeping the symmetric positional relationship with respect to a center line in the direction of the width, as illustrated in FIG.
4
.
Consequently, in order to detect lateral misalignment of the sheet having any one of the above-described sizes to be fed in the above-described manner, the sheet edge sensor
75
e
is disposed in a fixed or movable manner at a position corresponding to substantially half of a distance from an edge to the center line in a direction perpendicular to the feeding path, as illustrated in
FIG. 4
, thereby detecting lateral misalignment of the sheet having any one of the above-described sizes.
Here, in
FIG. 4
, reference numeral
500
designates, for example, an ADU registration roller for feeding the sheet having any one of the above-described sizes (hereinafter the same).
FIG. 5
is a diagram schematically illustrating the positional relationship between the sheet edge sensor
75
e
as the essential part according to the present invention and the sheet in the case where the sheet edge sensor
75
e
is disposed in the fixed manner in a first embodiment according to the present invention.
In this case, the sheet edge sensor
75
e
of the fixed type includes a first sheet edge sensor
75
e
1
for detecting the edge of a sheet having a size A4 or A3, a second sheet edge sensor
75
e
2
for detecting the edge of a sheet having a size B4, a third sheet edge sensor
75
e
3
for detecting the edge of a sheet having a size A4-R, a fourth sheet edge sensor
75
e
4
for detecting the edge of a sheet having a size B5-R and a fifth sheet
25
edge sensor
75
e
5
for detecting the edge of a sheet having a size A5-R, each of which is sequentially disposed at the partly predetermined position corresponding to substantially half of the distance from the edge to the center line in the direction perpendicular to the feeding path.
Each of these first to fifth sheet edge sensors
75
e
1
to
75
e
5
is a light reflection type sensor with a size of about 10 mm, and consists of a light emitting diode serving as a light source and a photo diode serving as a light receiving element.
In the state in which the sheet having a predetermined size is fed along the feeding path, as described above, the edge of the sheet is detected by any one of the first to fifth sheet edge sensors
75
e
1
to
75
e
5
, and therefore, the amount of lateral misalignment of the sheet can be determined by the lateral misalignment correcting circuit
439
provided in the printer engine unit
404
illustrated in
FIG. 2
based on a regular edge position and the actually detected edge position.
That is to say, the lateral misalignment correcting circuit
439
provided in the printer engine unit
404
corrects the amount of lateral misalignment of the sheet determined based on a detection output transmitted from the sheet edge sensor
75
e
, and then, transmits a predetermined lateral misalignment correcting signal to the laser modulating circuit
433
, the laser drive circuit
434
or the like in such a manner as to correctly position the image formed on the sheet.
Thus, even if a lateral misalignment occurs of a sheet having a predetermined size fed along the feeding path, the lateral misalignment can be corrected, so that the image of the document can be correctly-positioned on the sheet.
Second Embodiment
FIG. 6
is a diagram schematically illustrating the positional relationship between the sheet edge sensor
75
e
as the essential part according to the present invention and the sheet, in the case where the sheet edge sensor
75
e
is disposed in the movable manner in a second embodiment according to the present invention.
In this case, the sheet edge sensor
75
e
of the movable type is a single sheet edge sensor
75
e
6
movably disposed at the position corresponding to substantially half of the distance from the edge to the center line in the direction perpendicular to the feeding path.
Like the above-described first to fifth sheet edge sensors
75
e
1
to
75
e
5
, the single sheet edge sensor
75
e
6
is a light reflection type sensor with a size of about 10 mm, and consists of a light emitting diode serving as a light source and a photo diode serving as a light receiving element.
Furthermore, the single sheet edge sensor
75
e
6
includes a sensor for starting the operation of the sheet edge sensor.
FIG. 7
is a perspective view showing an example of a moving mechanism in the case where the sheet edge sensor
75
e
as the essential part according to the present invention is disposed in the movable manner.
Namely, the moving mechanism is constituted of a spirally grooved rod
501
, which supports the above-described single sheet edge sensor
75
e
6
and extends in the direction perpendicular to the feeding path, a guide shaft
502
, and a belt mechanism
504
for transmitting the drive force from a stepping motor
503
to the spirally grooved rod
501
.
FIG. 8
is a flowchart illustrating operation in the case where the sheet edge sensor
75
e
as the essential part according to the present invention is disposed in the movable manner.
The sheet edge sensor
75
e
of the movable type is driven by the sheet edge sensor drive circuit
440
provided in the printer engine unit
404
illustrated in FIG.
2
.
When the user depresses the size key
91
on the console panel
217
illustrated in
FIG. 3
, the main CPU
422
illustrated in
FIG. 2
judges whether or not the size of the sheet is confirmed in the case where the size of the sheet is designated or the size of the sheet is automatically set (step S
1
).
When the size of the sheet is confirmed in the above-described manner, the single sheet edge sensor element
75
e
6
serving as the sheet edge sensor
75
e
of the movable type is moved to a position for the designated size of the sheet (for example, in
FIG. 6
, the partly predetermined position corresponding to substantially half of the distance from the edge to the center line in the direction perpendicular to the feeding path signifies any one of a first position at which the edge of the sheet having the size A4 or A3 is detected, a second position at which the edge of the sheet having the size B4 is detected, a third position at which the edge of the sheet having the size A4-R is detected, a fourth position at which the edge of the sheet having the size B5-R is detected, and a fifth position at which the edge of the sheet having the size A4-R is detected) by the sheet edge sensor drive circuit
440
provided in the printer engine unit
404
illustrated in FIG.
2
and the moving mechanism illustrated in
FIG. 7
(step S
2
).
When the user depresses the copy (start) key
101
on the console panel
217
illustrated in
FIG. 3
(step S
3
), a copying operation is started (step S
4
).
Subsequently, it is judged whether or not the sensor for starting the operation of the sheet edge sensor included in the single sheet edge sensor
75
e
6
is ON (step S
5
).
Here, if the sensor for starting the operation of the sheet edge sensor is ON, the single sheet edge sensor
75
e
6
which has been moved to the predetermined position, as described above, starts detecting the sheet edge (step S
6
).
When the single sheet edge sensor
75
e
6
detects the sheet edge in this manner, the amount of lateral misalignment of the sheet can be determined based on the difference between the regular edge position and the actually detected edge position in the lateral misalignment correcting circuit
439
provided in the printer engine unit
404
.
That is to say, the lateral misalignment correcting circuit
439
provided in the printer engine unit
404
corrects the amount of lateral misalignment of the sheet determined based on a detection output transmitted from the sheet edge sensor
75
e
, and then, transmits data for giving a predetermined lateral misalignment correcting signal to the laser modulating circuit
433
, the laser drive circuit
434
or the like in such a manner as to form the image of the document correctly-positioned on the sheet (step S
7
).
Thus, even if lateral misalignment occurs in a sheet having a predetermined size fed along the feeding path, lateral misalignment can be corrected, so that the image of the document can be correctly-positioned on the sheet (step S
8
).
Thereafter, it is judged whether or not the copying operation is completed (step S
9
).
Here, when it is judged that the copying operation is completed, the single sheet edge sensor
75
e
6
which has been moved to the predetermined position, as described above, is returned to its initial position (step S
10
).
Third Embodiment
FIG. 9
is a graph illustrating re-setting of a threshold as a judgment criterion of the presence of the sheet on the precondition for sheet edge detection in accordance with a smear on the sheet edge sensor as the essential part according to the present invention in a third embodiment according to the present invention.
As illustrated in
FIG. 9
, the readable intensity of light is reduced when the surface of the sensor is dirty. Therefore, if the sensor is used as the surface of the sensor is not cleared, a voltage cannot reach a threshold as a judgment criterion of the presence of the sheet on the precondition for the sheet edge detection, thereby resulting in the judgment that there is no sheet even if there is actually a sheet.
In view of this, in the third embodiment according to the present invention, the threshold as the judgment criterion of the presence of the sheet on the precondition for the sheet edge detection is adjusted to be lower than an initial value before the sheet is actually detected, as illustrated in
FIG. 9
, thus reducing erroneous detection of the presence of the sheet.
Accordingly, it becomes unnecessary to provide control or a mechanism for removing the smear from the surface of the sensor.
Moreover, in the case where a plurality of sheets are copied, the threshold is adjusted with respect to each of the plurality of sheets in the above-described manner, thus further increasing the accuracy.
Fourth Embodiment
FIG. 10
is a graph illustrating re-setting of a threshold as a judgment criterion of the presence of the sheet on the precondition for the sheet edge detection by the sheet edge sensor as the essential part according to the present invention in accordance with the color of the sheet in a fourth embodiment according to the present invention.
As illustrated in
FIG. 10
, the readable intensity of light is changed according to the brightness of the color of the sheet in the case of a reflection type sensor. If a sheet of a dark color is used, a detected voltage becomes low.
Consequently, an output from the sensor cannot reach a threshold voltage, thereby resulting in the judgment that there is no sheet even if there is actually a sheet.
In view of this, in the fourth embodiment according to the present invention, the color of the sheet is previously designated, and then, erroneous detection caused by the color of the sheet can be prevented by resetting the threshold as the judgment criterion of the presence of the sheet according to the color.
Moreover, in the case when a plurality of sheets are copied, the threshold is adjusted with respect to each of the plurality of sheets in the above-described manner, thus further increasing the accuracy.
Fifth Embodiment
FIG. 11
is a flowchart illustrating operation for limiting correction in forming an image based on the detection result by the sheet edge sensor as the essential part according to the present invention in a fifth embodiment according to the present invention.
In consideration of the estimated maximum amount of lateral misalignment of the sheet in the case where no sheet edge detecting sensor is provided, detection of the amount of misalignment in excess of the maximum amount of misalignment by the sheet edge detecting sensor seems to be a detection error by the sheet edge detecting sensor.
At this time, if the misalignment is corrected based on the detection result, an image to be formed differs largely.
In view of this, in the fifth embodiment according to the present invention, in the case where the maximum amount is set to, for example, 2 mm, a detection result is judged to be erroneous if the detection result exceeds 2 mm. There is provided a limitation such that only the amount of 2 mm or less is corrected, or only 50% to 70% of the detection result is corrected, thereby reducing an influence of erroneous operation caused by the detection error.
That is to say, as illustrated in
FIG. 11
, after the copying operation is started (step S
20
), the sheet edge sensor is started to be operated (step S
21
), and then, it is judged whether or not the detected amount of misalignment exceeds 2 mm based on the detection result (step S
22
).
Here, if the detected misalignment exceeds 2 mm, there is provided a limitation such that the misalignment is corrected by only the amount of 2 mm or less, or the misalignment is corrected by only 50% to 70% of the detection result (step S
23
).
In contrast, if the detected misalignment is less than 2 mm, the misalignment is corrected in accordance with the detection result (step S
24
).
The routine is ended when the completion of the copying operation is judged (step S
25
).
Incidentally, the present invention is featured also in that the threshold as the judgment criterion of the presence of the sheet on the precondition for the sheet edge detection can be effectively corrected, as described above, by using the photo diode of an analog output type as the sheet edge sensor.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Claims
- 1. An image forming apparatus comprising:a sheet feeding unit provided with a feeding path, on which a cut sheet serving as an image forming medium having a predetermined size is fed; a sheet edge sensor having sensor elements separately arranged at portions, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit; an image forming unit for forming a predetermined image on the cut sheet serving as the image forming medium to be fed by the sheet feeding unit; and an image formation correcting unit for correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit, wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit adjusts a threshold as a judgment criterion of the presence of the sheet before actual detection of the sheet by the sheet edge sensor, and when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit previously designates a color of the sheet, and then, resets the threshold as the judgment criterion of the presence of the sheet in accordance with the designated color.
- 2. An image forming apparatus according to claim 1, wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit judges as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, gives a limitation to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value.
- 3. An image forming apparatus comprising:a sheet feeding unit provided with a feeding path, on which a cut sheet serving as an image forming medium having a predetermined size is fed; a sheet edge sensor having a sensor element movably arranged at a portion, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit; an image forming unit for forming a predetermined image on the cut sheet serving as the image forming medium to be fed by the sheet feeding unit; and an image formation correcting unit for correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit, wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit adjusts a threshold as a judgment criterion of the presence of the sheet before actual detection of the presence of the sheet by the sheet edge sensor, and when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit previously designates a color of the sheet, and then, resets the threshold as the judgment criterion of the presence of the sheet in accordance with the designated color.
- 4. An image forming apparatus according to claim 3, wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, the image formation correcting unit judges as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, gives a limitation to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value.
- 5. A method for controlling an image forming apparatus comprising the steps of:feeding a cut sheet serving as an image forming medium having a predetermined size along a feeding path provided in a sheet feeding unit; separately arranging sensor elements constituting a sheet edge sensor at portions, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit; forming a predetermined image on the cut sheet serving as the image forming medium to be fed to an image forming unit by the sheet feeding unit; and correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit; wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, it is judged as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, a limitation is given to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value in the image formation correcting step.
- 6. A method for controlling an image forming apparatus according to claim 5, wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, a threshold as a judgment criterion of the presence of the sheet is adjusted in the image formation correcting step before actual detection of the presence of the sheet by the sheet edge sensor.
- 7. A method for controlling an image forming apparatus according to claim 6, wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, a color of the sheet is previously designated, and then, the threshold as the judgment criterion of the presence of the sheet is reset in accordance with the designated color in the image formation correcting step.
- 8. A method for controlling an image forming apparatus comprising the steps of:feeding a cut sheet serving as an image forming medium having a predetermined size along a feeding path provided in a sheet feeding unit; moving a sensor element constituting a sheet edge sensor at a portion, at which the edge of the cut sheet serving as the image forming medium having the predetermined size can be detected, along a direction perpendicular to the feeding direction of the cut sheet serving as the image forming medium on the feeding path in the sheet feeding unit; forming a predetermined image on the cut sheet serving as the image forming medium to be fed to an image forming unit by the sheet feeding unit; and correcting image formation according to lateral misalignment of the cut sheet serving as the image forming medium based on a detection result transmitted from the sheet edge sensor when a predetermined image is formed on the cut sheet serving as the image forming medium by the image forming unit, wherein when the amount of lateral misalignment of the sheet is corrected based on the detection result transmitted from the sheet edge sensor, it is judged as to whether or not the detected amount of misalignment exceeds a predetermined value, and then, a limitation is given to correction of the lateral misalignment of the sheet in the case where the detected amount of misalignment exceeds the predetermined value in the image formation correcting step.
- 9. A method for controlling an image forming apparatus according to claim 8, wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, a threshold as a judgment criterion of the presence of the sheet is adjusted in the image formation correcting step before actual detection of the presence of the sheet by the sheet edge sensor.
- 10. A method for controlling an image forming apparatus according to claim 9, wherein when the presence of the sheet is detected based on the detection result transmitted from the sheet edge sensor, a color of the sheet is previously designated, and then, the threshold as the judgment criterion of the presence of the sheet is reset in accordance with the designated color in the image formation correcting step.
US Referenced Citations (4)
Foreign Referenced Citations (4)
Number |
Date |
Country |
03-012668 |
Jan 1991 |
JP |
5-210285 |
Aug 1993 |
JP |
05-338859 |
Dec 1993 |
JP |
2000-034039 |
Feb 2000 |
JP |