Image forming apparatus, and method thereof

• US 5,674,019 A
• Filed: 01/18/1996
• Issued: 10/07/1997
• Est. Priority Date: 11/02/1992
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Horikoshi, Jun, Munakata, Atsushi
• Primary Examiner(s): YAN, REN LUO
• Application Number:
  US08/588,284
• Time in Patent Office: 628 Days
• Field of Search: 400/545, 400/550, 400/551, 400/554, 400/568, 400/571, 400/703, 400/708
• US Class Current: 400/568
• CPC Class Codes: B41J 11/0085 Using suction for maintaining printing material flat on rotatable drums B41J13/226
• CPC Class Codes: B41J 11/42 Controlling printing material conveyance for accurate alignment of the printing material with the printhead; Print registering

Abstract

In a serial page printer for printing an image line by line by scanning a printing head, even if a motor for driving a roller for conveying a printing medium is rotated by a predetermined amount, the printing medium is not conveyed by a predetermined amount depending on decentering of the roller, the position of the printing medium, and the like, resulting in a printing error. In order to prevent this, a predetermined position of the roller is brought into contact with each line of a printing medium. For this purpose, an apparatus of the present invention detects that the position of the printing medium and the state of the roller are in a predetermined state. Therefore, a line subjected to printing and the state of the roller have a predetermined relationship on any page, and the printing medium can be conveyed by a predetermined amount for each line by adjusting the rotational amount of the roller for each line in advance.

Claims

1. An image forming apparatus for forming an image on a printing medium, which prints an area, by printing means, having predetermined length along the conveying direction of the printing medium and conveys the printing medium by a conveying distance corresponding to the predetermined length, repeatedly, comprising:

convey means, which includes rollers contactable with the printing medium and driving means to rotate the rollers, for conveying the printing medium by rotating the rollers;

setting means for setting each of an angular position of each roller and a position of the printing medium along the conveying direction to predetermined positions; and

storage means for storing predetermined drive-amount data of said driving means corresponding to each angular position of the rollers, so as to convey the printing medium by the conveying distance at each angular position of the rollers,

wherein said driving means rotate the rollers from the angular position set by said setting means to convey the printing medium by the conveying amount of the basis of the drive-amount data stored by said storage means.

2. An apparatus according to claim 1, wherein said driving means includes motors and said convey means includes transmitting means for transmitting a rotational force of said motors to said rollers, and the angular position of each roller indicates a position on a circumferential portion of each of said motors.

3. An apparatus according to claim 2, wherein a ratio of a rotational speed of said roller to that of said motor is an integer.

4. An apparatus according to claim 1, further comprising means for storing a predetermined image pattern, so that the predetermined image pattern is formed on the printing medium, and the drive amount data stored in said storage means is updated on the basis of the image.

5. An apparatus according to claim 1, wherein said convey means includes a pulse motor, said drive means includes a counter for counting drive pulses applied to said pulse motor in accordance with a rotation direction, and said setting means drives said pulse motor such that a count value of said counter becomes a predetermined value.

6. An apparatus according to claim 1, further comprising reading means for reading a document having a plurality of lines, so that an image printed by said printing means is read by said reading means to measure a convey amount for each line, and the drive amount data stored in said storage means is updated on the basis of the convey amount for each line.

7. An apparatus according to claim 1, wherein said printing means includes an ink-jet printing head for performing a printing operation by discharging an ink.

8. An apparatus according to claim 1, further comprising a printing head for discharging an ink by using thermal energy, wherein said printing head includes a thermal energy conversion member for generating thermal energy supplied to the ink.

9. An apparatus according to claim 1, wherein a total conveyed distance of the printing medium is n-times (n is an integer number) the conveying distance of a single rotation of the rollers.

10. An apparatus according to claim 9, wherein said storage means stores the drive-amount data corresponding to each of n-time-conveying distance of the printing medium conveyed from the position set by said setting means.

11. An apparatus according to claim 1, wherein said driving means includes pulse motors driven by electrical pulse, and said storage means stores a number of pulses to be inputted to the pulse motors as the drive-amount data.

12. An apparatus according to claim 11, wherein said conveying means includes pulleys and belts and the rollers are driven by the pulse motors via the pulleys and belts.

13. An apparatus according to claim 1, further comprising detection means for detecting angular positions of the rollers, wherein said setting means sets the positions of the rollers to the predetermined positions based on the detected position by said detection means.

14. An apparatus according to claim 1, wherein the drive-amount data stored by said storage means corresponds to the predetermined conveying distance of the printing medium so as to correct non-uniformity of conveying amount caused by eccentricity of the rollers, which corresponds to a predetermined rotating amount of the rollers.

15. A printing medium conveying method for an image forming apparatus which prints an area having predetermined length along the conveying direction of the printing medium and repeatedly conveys the printing medium by a conveying distance corresponding to the predetermined length by conveying means, wherein said convey means includes rollers contactable with the printing medium and driving means to rotate the rollers, and conveys the printing medium by rotating the rollers, comprising the steps of:

setting each of an angular position of each roller and a position of the printing medium along the conveying direction to predetermined positions; and

driving said driving means to rotate the rollers from an angular position set in said setting step to convey the printing medium by the predetermined conveying distance on the basis of the drive-amount data corresponding to conveying amount at each angular position of the rollers.

16. A method according to claim 15, wherein the drive-amount data is stored by the image forming apparatus.

17. A method according to claim 16, wherein a total conveyed distance of the printing medium is n-times (n is an integer number) the conveying distance of a single rotation of the rollers.

18. A method according to claim 17, wherein the image forming apparatus stores the drive-amount data corresponding to each of n-time-conveying distance of the printing medium conveyed from the position set in said setting step.

19. A method according to claim 15, wherein said driving means includes pulse motors driven by electrical pulse, and a storage means stores a number of pulses to be inputted to the pulse motors as the drive-amount data.

20. A method according to claim 19, wherein said convey means includes pulleys and belts and the rollers are driven by the pulse motors via the pulleys and belts.

21. A method according to claim 15, further comprising detecting step for detecting angular positions of the rollers, wherein the positions of the rollers are set to the predetermined positions in said setting step based on the detected position detected in said detecting step.

22. A method according to claim 15, wherein the drive-amount data corresponds to the predetermined conveying distance of the printing medium so as to correct non-uniformity of conveying amount caused by eccentricity of the rollers, which corresponds to a predetermined rotating amount of the rollers.

23. A method according to claim 15, wherein the image forming apparatus includes an ink-jet printing head for performing a printing operation by discharging an ink.

24. A method according to claim 15, wherein the image forming apparatus includes a printing head for discharging an ink by using thermal energy, and includes a thermal energy conversion member for generating thermal energy supplied to the ink.

25. A sheet conveying apparatus comprising:

convey means for conveying a sheet in a predetermined direction, said convey means comprising a first conveying roller and a second conveying roller, wherein the first and second conveying rollers are provided at a predetermined distance from each other in the predetermined direction, and each of which has contact with the sheet and conveys the sheet by rolling;

first and second drive means for rotating the first and second conveying rollers, respectively;

storage means for storing drive-amount data for said first and second driving means;

setting means for setting a position of the sheet along the conveying direction to a predetermined position and each of an angular position of the first and second conveying rollers to a predetermined position; and

control means for controlling a drive-amount, corresponding to a predetermined conveying amount, of the first and second driving means from each angular position of the first and second conveying rollers set by said setting means to convey the sheet on the basis of the drive-amount data stored by said storage means.

26. The sheet conveying apparatus according to claim 25, further comprising:

first detecting means for detecting an angular position of the first conveying roller; and

second detecting means for detecting an angular position of the second conveying roller,

wherein said control means controls the first and second conveying rollers to rotate to a predetermined angular position in advance of sheet conveyance.

27. The sheet conveying apparatus according to claim 25, wherein said control means controls respective rotational amounts, corresponding to a predetermined conveying amount, of the first and second conveying rollers, based on whether a sheet is conveyed by the first conveying roller or the second conveying roller.

28. The sheet conveying apparatus according to claim 27, wherein said control means controls respective rotational amounts of the first and second conveying rollers at a transmission stage from a state where a sheet is conveyed by the first and second conveying rollers to a state where a sheet is conveyed by the second conveying roller.

29. The sheet conveying apparatus according to claim 25, further comprising:

a first supporting roller, pressing the sheet against said first conveying roller, which rotates in accordance with rotation of said first conveying roller and with conveyance of the sheet; and

a second supporting roller, pressing the sheet against said second conveying roller, which rotates in accordance with rotation of said second conveying roller and with conveyance of the sheet.

30. The sheet conveying apparatus according to claim 29, wherein respective forces pressing the first and second supporting rollers against the first and second conveying rollers are different.

31. The sheet conveying apparatus according to claim 25, wherein said convey means comprises a first pulse motor for driving said first conveying roller and a second pulse motor for driving said second conveying roller.

32. The sheet conveying apparatus according to claim 31, wherein said first and second conveying rollers are driven by rotational motion of said first and second pulse motors, and where the motion is transmitted via belts.

33. The sheet conveying apparatus according to claim 32, further comprising belt position detecting means for detecting a position of the belt.

34. The sheet conveying apparatus according to claim 33, wherein said control means drives said first and second pulse motors until the belts reach predetermined positions in advance of sheet conveyance.

35. The sheet conveying apparatus according to claim 33, further comprising count means for counting numbers of pulses for driving said first and second pulse motors, wherein said control means controls said first and second pulse motors to rotate in reverse direction of conveying direction of the sheet until numbers counted by said count means become zeros in advance of sheet conveyance.

36. A sheet conveying method for conveying a sheet by convey means having a first conveying roller and a second conveying roller driven by first and second driving means respectively, where the first and second conveying rollers are provided at a distance from each other and convey a sheet by rolling contact with the sheet, comprising the steps of:

setting a position of the sheet along the conveying direction to a predetermined position and each of an angular position of the first and second conveying rollers to predetermined positions; and

controlling a drive-amount, corresponding to a predetermined conveying amount, of the first and second driving means on the basis of a predetermined drive-amount and each of the predetermined positions set by said setting step.

37. The sheet conveying method according to claim 36, further comprising the step of storing rotational amount data for the first and second conveying rollers, wherein said control means controls the rotational amounts of the first and second conveying rollers on the basis of the rotational amount data stored by said storage means.

38. The sheet conveying method according to claim 36, further comprising the step of:

detecting an angular position of the first conveying roller; and

detecting an angular position of the second conveying roller,

wherein said control means controls the first and second conveying rollers to rotate to predetermined angular position in advance of sheet conveyance.

39. The sheet conveying method according to claim 36, wherein the control of respective rotational amounts, corresponding to a predetermined conveying amount, of the first and second conveying rollers, is based on whether a sheet is conveyed by the first conveying roller or the second conveying roller.

40. The sheet conveying method according to claim 39, wherein the control of respective rotational amounts of the first and second conveying rollers is at a transmission stage from a state where a sheet is conveyed by the first and second conveying rollers to a state where a sheet is conveyed by the second conveying roller.

41. The sheet conveying method according to claim 36, further comprising:

rotating a first supporting roller, pressing the sheet against said first conveying roller, in accordance with rotation of said first conveying roller and with conveyance of the sheet; and

rotating a second supporting roller, pressing the sheet against said second conveying roller, in accordance with rotation of said second conveying roller and with conveyance of the sheet.

42. The sheet conveying method according to claim 41, wherein respective forces pressing the first and second supporting rollers against the first and second conveying rollers are different.

43. The sheet conveying method according to claim 36, wherein the convey means comprises a first pulse motor for driving said first conveying roller and a second pulse motor for driving said second conveying roller.

44. The sheet conveying method according to claim 43, wherein the first and second conveying rollers are driven by rotational motion of said first and second pulse motors, and where the motion is transmitted via belts.

45. The sheet conveying method according to claim 44, further comprising the step of detecting a position of the belt.

46. The sheet conveying method according to claim 45, wherein rotational amounts are controlled by driving the first and second pulse motors until the belts reach predetermined positions in advance of sheet conveyance.

47. The sheet conveying method according to claim 45, further comprising the step of counting numbers of pulses for driving said first and second pulse motors, wherein rotational amounts are controlled by driving the first and second pulse motors to rotate in reverse direction of conveying direction of the sheet until numbers counted during said counting steps become zeros in advance of sheet conveyance.

48. The sheet conveying method according to claim 36, wherein said control step comprises the steps of:

conveying the sheet by controlling the first conveying roller to rotate until a top edge of the sheet reaches the second conveying roller;

controlling both the first and second conveying rollers to rotate after the top edge of the sheet reaches the second conveying roller until a rear edge of the sheet leaves the first conveying roller, and conveying a sheet by rotation of the first conveying roller; and

conveying the sheet by controlling the second conveying roller to rotate after the rear edge of the sheet leaves the first conveying roller,

wherein at least one conveying roller of the first and second conveying rollers which is conveying the sheet is controlled so that its rotational amount corresponds to the predetermined conveying amount.