Image forming apparatus

• US 20070236528A1
• Filed: 04/06/2007
• Published: 10/11/2007
• Est. Priority Date: 04/07/2006
• Status: Abandoned Application

• Current Assignee: RISO Kagaku Corporation
• Original Assignee: RISO Kagaku Corporation
• Inventors: Oike, Hikaru
• Application Number:
  US11/783,222
• Publication Number:
  US 20070236528A1
• Time in Patent Office: Days
• US Class Current: 347/19
• CPC Class Codes: B41J 11/007 Conveyor belts or like feeding devices
• CPC Class Codes: B41J 11/008 Controlling printhead for accurately positioning print image on printing material, e.g. with the intention to control the width of margins
• CPC Class Codes: B41J 29/393 Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns
• CPC Class Codes: B41J 3/543 with multiple inkjet print heads B41J2/17503, B41J2/2103 take precedence

Abstract

An image-forming apparatus has: a transfer belt transferring a sheet; an encoder outputting a pulse signal in response to a rotational motion of the transfer belt; a bell reference sensor detecting a belt reference mark provided on the transfer belt; a first accumulator measuring a rotational position of the transfer belt against the reference mark by counting a pulse signal; a storage unit storing a table of printing timing correction values for one rotational cycle of the transfer belt; a second accumulator generating a printing timing signal by shifting a phase of the pulse signal by a printing timing correction value read from the table; and a image-forming unit controlling ink heads to eject inks on the sheet in synchronization with the printing timing signal, wherein an error in transfer amount of the sheet is calculated from a fluctuation in an interval of the inks ejected from the ink heads.

Claims

1. An image-forming apparatus comprising:

a transfer unit that transfers an image-formed medium by rotation thereof;

an image-forming unit that includes a first ink head and a second ink head arranged in a transfer direction of the image-formed medium at a predetermined interval and controls the first and second ink heads to eject first and second inks on the image-formed medium;

a transfer amount detecting unit that outputs a pulse signal in response to a rotational motion of the transfer unit;

a transfer reference position detecting unit that detects a reference position provided on the transfer unit;

an ink landing position calculating unit that calculates an ink landing position corresponding to the reference position on the image-formed medium by counting a pulse signal after detection of the reference position;

a storage unit that stores correction values for printing timing for one rotational cycle of the transfer unit as a correction table; and

a printing timing signal generating unit that reads out a correction value for printing timing, which corresponds to the ink landing position on the image-formed medium, from the correction table and generates a printing timing signal by shifting a phase of the pulse signal by the correction value for printing timing;

wherein the correction table includes a set of values, each value being calculated based on a measurement value of an interval between a first ink landing position by the first ink head and a second ink landing position by the second ink head in a predetermined image pattern formed on the predetermined image-formed media which are corresponding to a length longer than the one rotational cycle of the transfer unit, and canceling an error of a transfer amount of the predetermined image-formed media by the transfer unit, and

wherein the image-forming unit forms an image on the image-formed medium in transfer by controlling the first and second ink heads to eject the first and second inks in synchronization with the printing timing signal.

2. The image-forming apparatus of claim 1, wherein

the error of the transfer amount of the predetermined image-formed media is calculated by

$K$

( d ×

n ) = - ∑

i = 0 n 

KC 

( d ×

i )

from relationships KC(y)=K(y)·

C(y), C(y)=K(y+d) and a condition K(0)=0,

where “

d”

is an interval between the first ink head and the second ink head;

“

L”

a length of the one rotational cycle of the transfer unit;

“

K(y)”

a landing misalignment of the first ink ejected by the first ink head at a landing position in design “

y”

on the predetermined image-formed media;

“

C(y)”

a landing misalignment of the second ink ejected by the second ink head at the landing position in design “

y”

on the predetermined image-formed media;

“

KC(y)”

a relative landing misalignment between the first ink ejected by the first ink head and the second ink ejected by the second ink head at the landing position in design “

y”

on the predetermined image-formed media; and

“

n”

an integer which satisfies a relationship d×

n ≧

L.

3. The image-forming apparatus of claim 2, further comprising:

a register unit that registers and sends the predetermined image-formed media to the transfer unit so as to start ink-ejecting from the first ink head at a landing position in design y=0 on the predetermined image-formed media with satisfying the condition;

K(0)=0.

4. The image-forming apparatus of claim 1, wherein

the transfer unit includes a first transfer section that transfers an image-formed medium by rotation thereof, and a second transfer section that transfers the image-formed medium by rotation thereof,

the transfer reference position detecting unit includes a first transfer reference position detecting section that detects a first reference position provided on the first transfer section, and a second transfer reference position detecting section that detects a second reference position provided on the second transfer section,

the ink landing position calculating unit includes:

a first ink landing position calculating section that calculates an ink landing position corresponding to the first reference position on the image-formed media by counting the pulse signal after detection of the first reference position; and

a second ink landing position calculating section that calculates an ink landing position corresponding to the second reference position on the image-formed media by counting the pulse signal after detection of the second reference position,

the storage unit includes;

a first storage section that stores correction values for printing timing for one rotational cycle of the first transfer section as a first correction table; and

a second storage section that stores correction values for printing timing for one rotational cycle of the second transfer section as a second correction table, and

the correction table includes the first and second correction tables.