Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-03-17
2002-01-29
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S248000, C399S394000
Reexamination Certificate
active
06342909
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a writing control method and an image forming apparatus, and particularly to the control by which an optimum image formation can be realized corresponding to a position of a transfer sheet in the primary scanning direction.
FIG. 9
is a plan view showing an outline structure of an image forming apparatus such as a laser printer. In
FIG. 9
, numeral
1
is a photoreceptor drum, numeral
3
is a semiconductor laser to generate the laser light corresponding to a writing signal, numeral
4
is a polygon mirror to conduct the deflection-scanning by using the laser light, and numerals
10
a
and
10
b
are transfer sheets.
Herein, the photoreceptor drum
1
is rotated at a constant speed, and an electrostatic latent image is formed by the laser light on the surface of the photoreceptor drum
1
. This electrostatic latent image is developed as a toner image by a developing unit, not shown, and the toner image is transferred onto the transfer sheet by a transfer unit, also not shown.
In this kind of image forming apparatus, when the transfer sheet is conveyed to quite the same position, the same image can be formed on the transfer sheet.
However, due to each kind of the slippage or sheet skew generated on a conveyance path from a sheet feed cassette to the photoreceptor drum, a slight slippage of position is caused.
When such the slippage or sheet skew occurs, in the conveyance direction, positioning can be conducted by a registration roller just before the transferring.
However, for the slippage or sheet skew in the direction perpendicular to the conveyance direction (primary scanning direction), it is necessary to detect the slippage of position and to change the scanning position of the laser light. In an example shown in
FIG. 9
, the situation of change from the state that the distance from a predetermined position is X in the transfer sheet
10
a
, to the state of X′ in the transfer sheet
10
b
, is typically shown.
For such the slippage of the transfer sheet in the direction perpendicular to the conveyance direction, conventionally, the correction is conducted by oscillating a conveyance roller in the axial direction, however, the sufficient accuracy can not be obtained.
Further, in Japanese Patent Publication No. 2550558, an image forming apparatus in which the relative slippage of the transfer sheet to its ideal reference position is detected, and the position of the image formation is corrected corresponding to the slippage, is shown. Incidentally, in the image forming apparatus shown in the patent publication, the slippage of the position of the transfer sheet is detected by a plurality of light receiving elements, the plurality of detection results from the light receiving elements are connected to a ROM, and are converted into the slippage amount in the ROM.
In such the image forming apparatus, there is a problem that a large number of wiring corresponding to the resolving power is necessary between sensors and the ROM. In the actual apparatus, the sensor section is arranged on the conveyance path, however, the ROM is located on a circuit board at the remote position, therefore, there is a problem of generation of radio noise or malfunction due to external noise.
Further, because the position of the transfer sheet is detected as the relative slippage from the reference value, when the size of the transfer sheet is changed, there is also a disadvantage that this system can not cope with it, or the treatment becomes very complicate.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to realize a writing control method and an image forming apparatus by which, when the position of the transfer sheet is detected, the radio noise is not generated, and further, the influence of the external noise is not affected, and the image forming position is determined corresponding to the position of passage of the transfer sheet and the stable image formation can be realized.
The above object can be attained by any one of the following structures (1) to (17).
(1) In a writing control method of an image forming apparatus using a digital method, having a photoreceptor and a writing means for writing an image onto the photoreceptor, the writing control method is characterized in that a position of passage of a transfer sheet in the primary scanning direction is detected by a position detection sensor as an absolute position, and according to the detection result, the writing position is determined.
In this structure, because the position of passage of the transfer sheet in the primary scanning direction is detected by the position detection sensor as the absolute position, and according to the detection result, the writing position is determined, thereby, without depending on the passage position of the transfer sheet or the size of the transfer sheet, the stable image formation can be carried out by the determination of the accurate writing position.
(2) A digital system image forming apparatus having: the photoreceptor; a memory means for storing the supplied image data; and the writing means for writing the stored image data onto the photoreceptor as an image, the image forming apparatus is characterized in that it is provided with the position detection sensor to detect the passage position of the transfer sheet in the primary scanning direction as the absolute position, and a writing control means for determining the writing position by the writing means according to the passage position information by the position detection sensor.
In this structure, because the position of passage of the transfer sheet in the primary scanning direction is detected by the position detection sensor as the absolute position, and according to the detection result, the writing position is determined, thereby, without depending on the passage position of the transfer sheet or the size of the transfer sheet, the stable image formation can be carried out by the determination of the accurate writing position.
(3) The image forming apparatus according to the structure (2), wherein the position detection sensor is a contact type line sensor using an LED light source.
In this structure, because the position of passage of the transfer sheet in the primary scanning direction is detected as the absolute position by the position detection sensor structured by the contact type line sensor, and according to the detection result, the writing position is determined, thereby, without depending on the passage position of the transfer sheet or the size of the transfer sheet, the stable image formation can be carried out by the determination of the accurate writing position.
(4) The image forming apparatus according to the structure (3), wherein the contact type line sensor is a clock operation type contact type line sensor.
In this structure, because the position of passage of the transfer sheet in the primary scanning direction is detected as the absolute position by the position detection sensor structured by the clock operation type contact type line sensor, and according to the detection result, the writing position is determined, thereby, by counting clocks, without depending on the passage position of the transfer sheet or the size of the transfer sheet, the stable image formation can be carried out by the determination of the accurate writing position.
(5) The image forming apparatus according to the structure (4), wherein the detection resolving power of the contact type line sensor is not smaller than 0.25 mm. In other words, the detection resolving power of the contact type line sensor has a detection error of not more than 0.25 mm.
In this structure, because the detection resolving power of the contact type line sensor is not smaller than 0.25 mm, the accuracy of about 100 dpi is obtained, thereby, the stable image formation can be carried out by the determination of the accurate writing position, without depending on the passage position of the transfer sheet or the size of the transfer sheet.
(6) The image forming appa
Haibara Fumio
Joichi Norio
Peng Youbao
Sakata Satoshi
Ui Makoto
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Konica Corporation
Pendegrass Joan
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