Image forming apparatus capable of adjusting print position of image on recording paper

Patent metadata

Field	Value
Publication number	US-10474086-B2
Application number	US-201213455289-A
Country	US
Kind code	B2
Filing date	Apr 25, 2012
Priority date	Apr 26, 2011
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

The image forming apparatus includes: a paper feed unit; a print unit; a registration roller; a sheet leading end sensor provided downstream, in a transport direction of the recording paper, of the registration roller; a time measuring unit for measuring a time from a start point of transportation of the recording paper by the registration roller to a point of detection of the leading end of the recording paper by the sheet leading end sensor; a memory unit for storing a reference image forming time and a reference time; a print control unit; and an arithmetic unit for obtaining a difference between the reference time and the time detected by the time measuring unit. The print control unit adjusts the length of the image forming period in accordance with the adjusted image forming time determined based on the difference obtained by the arithmetic unit and the reference image forming time.

First claim

What is claimed is:

1. An image forming apparatus, comprising:
a plurality of paper feed units;
a print unit for forming an image and printing the formed image on a recording paper;
a registration roller, arranged between the paper feed units and the print unit, for receiving a recording paper transported from one of the paper feed units and transporting the recording paper to the print unit;
a sheet leading end sensor provided downstream, in a transport direction of the recording paper, of the registration roller, for detecting a leading end of the recording paper;
a time measuring unit for measuring a time from a start point of transportation of the recording paper by the registration roller to a point of detection of the leading end of the recording paper by the sheet leading end sensor;
a memory unit for storing a reference image forming time, which is a reference value of a length of an image forming period from an image formation start point in the print unit to the start point of transportation of the recording paper by the registration roller and a reference time, which is a reference value of a time from the start point of transportation to the point of detection of the leading end of the recording paper by the sheet leading end sensor;
a print control unit for adjusting, when a recording paper is fed from an arbitrary paper feed unit among the paper feed units, a print position of an image on the recording paper by controlling the print unit and the registration roller to adjust the length of the image forming period; and
an arithmetic unit for obtaining, as a comparative time, a time detected by the time measuring unit when the leading end of the recording paper is detected by the sheet leading end sensor, obtaining a time difference between the obtained comparative time and the reference time stored in the memory unit every time a recording paper is fed from the paper feed unit, and storing the time difference in the memory unit in association with the paper feed unit from which the recording paper is fed,
wherein the print control unit adjusts, when the recording paper is fed from a specific paper feed unit among the paper feed units, the length of the image forming period in accordance with an adjusted image forming time obtained by subtracting the time difference, previously obtained by the arithmetic unit and stored in the memory unit in association with the specific paper feed unit from which the recording paper is fed before the recording paper is fed, from the reference image forming time stored in the memory unit.

2. The image forming apparatus according to claim 1 ,
wherein the print unit includes: an image carrier; a writing unit for writing an electrostatic latent image on the image carrier; a developing unit for developing the electrostatic latent image on the image carrier into a toner image; and a transfer unit for transferring the toner image on the image carrier onto the recording paper, and
the print control unit adjusts the length of the image forming period, which is a period from a start point of writing of the electrostatic latent image in a sub-scanning direction by the writing unit to the start point of transportation by the registration roller.

3. The image forming apparatus according to claim 1 , further comprising an input operation unit operated to adjust and set the reference image forming time.

4. The image forming apparatus according to claim 1 , wherein the print control unit adjusts, when a recording paper is fed from an arbitrary paper feed unit among the paper feed units, the length of the image forming period in accordance with an adjusted image forming time determined based on the reference image forming time stored in the memory unit and an average value of the differences obtained by the arithmetic unit and stored in the memory unit before the recording paper is fed and every time another recording paper was fed from the arbitrary paper feed unit.

5. An image forming apparatus, comprising:
a paper feed unit;
a print unit for forming an image and printing the formed image on a recording paper;
a registration roller, arranged between the paper feed unit and the print unit, for receiving a recording paper transported from the paper feed unit and transporting the recording paper to the print unit;
a sheet leading end sensor provided downstream, in a transport direction of the recording paper, of the registration roller, for detecting a leading end of the recording paper;
a time measuring unit for measuring a time from a start point of transportation of the recording paper by the registration roller to a point of detection of the leading end of the recording paper by the sheet leading end sensor;
a memory unit for storing a reference image forming time, which is a reference value of a length of an image forming period from an image formation start point in the print unit to the start point of transportation of the recording paper by the registration roller, and a reference time, which is a reference value of a time from the start point of transportation to the point of detection of the leading end of the recording paper by the sheet leading end sensor;
a print control unit for adjusting, when a recording paper of an arbitrary type is fed from the paper feed unit, a print position of an image on the recording paper by controlling the print unit and the registration roller to adjust the length of the image forming period; and
an arithmetic unit for obtaining, as a comparative time, a time detected by the time measuring unit when the leading end of the recording paper is detected by the sheet leading end sensor, obtaining a time difference between the obtained comparative time and the reference time stored in the memory unit every time a recording paper is fed from the paper feed unit, and storing the time difference in the memory unit in association with the type of the recording paper,
wherein the print control unit adjusts, when a recording paper of a specific type is fed from the paper feed unit, the length of the image forming period in accordance with an adjusted image forming time obtained by subtracting the time difference, previously obtained by the arithmetic unit and stored in the memory unit in association with the specific paper type before the recording paper is fed, from the reference image forming time stored in the memory unit.

6. The image forming apparatus according to claim 5 ,
wherein the print unit includes: an image carrier; a writing unit for writing an electrostatic latent image on the image carrier; a developing unit for developing the electrostatic latent image on the image carrier into a toner image; and a transfer unit for transferring the toner image on the image carrier onto the recording paper, and
the print control unit adjusts the length of the image forming period, which is a period from a start point of writing of the electrostatic latent image in a sub-scanning direction by the writing unit to the start point of transportation by the registration roller.

7. The image forming apparatus according to claim 5 , further comprising an input operation unit operated to adjust and set the reference image forming time.

8. The image forming apparatus according to claim 5 , wherein the print control unit adjusts, when a recording paper of an arbitrary type is fed from the paper feed unit, the length of the image forming period in accordance with an adjusted image forming time determined based on the reference image forming time stored in the memory unit and an average value of the differences obtained by the arithmetic unit and stored in the memory unit before the recording paper is fed and every time another recording paper of the arbitrary type was fed from the paper feed unit

Assignees

• Tomita Norio
• Fukada Yasuaki
• Atsumi Hidetoshi
• Wakamoto Koji
• Ogo Atsushi
• Sakai Ryosuke
• Sharp Kk

Inventors

• Tomita Norio
• Fukada Yasuaki
• Atsumi Hidetoshi
• Wakamoto Koji
• Ogo Atsushi
• Sakai Ryosuke

Classifications

• G03G15/235

  the image receiving member being preconditioned before transferring the second image, e.g. decurled, or the second image being formed with different operating parameters, e.g. a different fixing temperature · CPC title

• G03G2215/00742

  of sheet weight · CPC title

• G03G15/6561

  for sheet registration · CPC title

• G03G2215/00569

  Calibration, test runs, test prints · CPC title

• G03G15/6564 Primary

  with correct timing of sheet feeding · CPC title