Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
1999-12-06
2001-08-07
Brase, Sandra (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S233000
Reexamination Certificate
active
06271869
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multicolor image forming apparatus, and more particularly to a multicolor image forming apparatus such as a color laser printer and a color digital copying machine of a multi-photoreceptor system that obtains an image by scanning light beams onto a plurality of photoreceptors.
2. Description of the Related Art
As a conventional image forming apparatus of a multi-photoreceptor system, the one having a structure as shown in
FIG. 23
is proposed (see Japanese Published Unexamined Patent Application No. Hei 3-142412).
In such an image forming apparatus, generally, laser beams emitted from four laser light sources corresponding to cyan (C), magenta (M), yellow (Y), and black (K) are bidirectionally scanned by a polygon mirror
201
mounted in a light deflector. Thereafter, the laser beams pass through a scanning imaging optical system, are reflected in mirrors
202
to
213
, and scan on the photoreceptors
214
to
217
corresponding to the colors. Latent images formed on the photoreceptors are developed by a developing apparatus and successively transferred onto paper transported by a transporting belt
218
to form a color image.
Another conventional image forming apparatus will be described with reference to
FIGS. 25
to
27
. In these drawings, the reference numeral
250
designates an exposing apparatus;
252
K,
252
Y,
252
M, and
252
C, laser beams;
254
, a deflector;
256
K,
256
Y,
256
M, and
256
C, mirror assemblies;
258
K,
258
Y,
258
M, and
258
C, photoreceptors;
260
A and
260
B, registermarks; and
262
A and
262
B, detecting parts. In the exposing apparatus
250
, the four laser beams are scanned, by one deflector
254
, on the photoreceptors
258
K,
258
Y,
258
M, and
258
C corresponding to black (K), yellow (Y), magenta (M), and cyan (C), a transfer material (paper) not shown is transported by a belt
264
, and multiple images are transferred from the photoreceptors onto the transfer material, whereby a color image is formed. The exposing apparatus
250
scans and deflects, by the deflector
254
, laserbeams
252
K,
252
Y,
252
M, and
252
C containing information, emitted from light sources (not show), which are irradiated straightly onto the materials
258
K,
258
Y,
258
M, and
258
C to be scanned after passing through imaging lens systems (not shown) and mirror assemblies
256
K,
256
Y,
256
M, and
256
C into which reflecting mirrors are built. SOS (Start of Scan) is used to determine a write timing of the laser beams
252
K,
252
Y,
252
M, and
252
C, which are scanned and irradiated onto the photoreceptors
258
K,
258
Y,
258
M, and
258
C with a given delay after passing through a pickup mirror
266
and being detected by synchronous light detecting apparatuses
268
K,
268
Y,
268
M, and
268
C. To correct a skew of each color, the gradient of a scanning line (hereinafter referred to as a skew) is adjusted in this case. For example, the mirror assemblies
256
K,
256
Y,
256
M, and
256
C are provided at one end with a rotation center
270
and at the other with an actuator
272
, register marks
260
A and
260
B are formed on the belt
264
and are detected by the detecting parts
262
A and
262
B to detect skews of scanning lines, and based on the result, the actuator
272
is driven up and down in the E direction around the rotation center
270
, whereby skew adjustments are performed to form a color image free from color skews. Since the rotation center
270
is provided around an axis intersecting a light path of the above described SOS light, such a configuration prevents the SOS light from deviating from the synchronous light detecting apparatuses
268
K,
268
Y,
268
M, and
268
C due to the rotation of the mirror assemblies
256
K,
256
Y,
256
M, and
256
C during skew adjustments. Such an exposing apparatus
250
is disclosed in, e.g., Japanese Published Unexamined Patent Application No. Hei 3-150521.
Further, the configuration of another conventional exposing apparatus
450
will be described with reference to
FIGS. 28
to
30
. In the exposing apparatus
450
, a laser beam
454
is emitted from a light source
452
, passes through a light-gathering lens not assigned a reference numeral, is deflected by a deflector
456
, passes through an imaging lens system
458
, is reflected by a reflecting mirror
462
of a mirror assembly
460
, and is irradiated onto a photoreceptor
464
. The mirror assembly
460
is provided with a rotation center
466
in an upper portion near the central portion of scanning, and an adjusting part
468
and a spring
470
are provided at one end of the mirror assembly. In such a configuration, since the mirror assembly
460
rotates around the upper portion near the central portion of scanning during skew adjustments by moving the adjusting unit along the direction of the arrow D, skews can be adjusted. Such a mirror assembly configuration of an exposing apparatus is disclosed in, e.g., Japanese Published Unexamined Patent Application No. Sho 59-7331.
A disclosed method of correcting axis skews of photoreceptors due to a mounting error occurring when the photoreceptors
214
to
217
are mounted in such an image forming apparatus has problems of the complicated mechanism and high cost. In this method, a register mark
219
transferred onto a transporting belt
218
is sensed by a sensor such as CCD
220
, and mirrors
202
and
203
as shown in
FIG. 24
are moved by actuators
223
to
225
. Also, as technology to simplify mechanism, a method is proposed which corrects axis skews of photoreceptors by operating optical parts within an exposing apparatus from the outside. However, in an exposing apparatus that scans scanning beams on both photoreceptors and a polygon mirror, as shown in
FIG. 23
, since the directions of scanning lines
226
to
229
scanned in both of them are opposite such as the direction of the arrow A (scanning lines
226
and
227
) and the direction of the arrow B (scanning lines
228
and
229
), adjusting parts are placed separately in the front and rear parts of an image forming apparatus, posing a problem that a large number of man-hours are needed for adjustment operations. Also, for safety purposes and from a configuration viewpoint, adjustment results are not obtained until an image forming apparatus has been assembled, requiring repetitive operations such as many disassembling and assembling operations and confirmation of image color skew amounts.
Furthermore, since the exposing apparatus
250
shown in
FIGS. 25 and 26
is constructed to scan four laser beams by one deflector
254
, as shown in
FIG. 27
, the synchronous light detecting apparatuses
268
K,
268
Y,
268
M, and
268
C are placed in a staggered manner across the deflector
254
. In this example, a maintenance space need not be considered so seriously because the actuator
272
is small and skew adjustments are automatically performed. However, in order to reduce costs, if the actuator
272
is displaced so as to manually move relevant parts and skew dials
274
K,
274
Y,
276
M, and
274
C are provided as shown in
FIG. 27
, since a maintenance space (a space in which to manually move the dials) must be provided, there arises a problem that the size of a multicolor image forming apparatus increases by twice S.
A mirror assembly
460
of further another conventional exposing apparatus
450
as shown in
FIGS. 28 and 29
has a problem that, if skew adjustments are performed as shown in
FIG. 30
, a laser beam
454
C passing on the rotation center
466
is unchanged in light path length, but a laser beam
454
E passing through a scanning end portion changes by X′ in light path length, from X+Y to X+X′+Y.
SUMMARY OF THE INVENTION
In view of the above described facts, present invention provides a compact multicolor image forming apparatus that eases operations to correct skews of a plurality of images and provides an easy way to perform optical adjustments.
The present invention also provides a
Haginoya Yoshiaki
Tada Naoyuki
Brase Sandra
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
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