JP2758186B2 - Paper transport device for image forming apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device of an image forming apparatus, and more particularly, to a lateral registration control of a conveying roller.

(Prior art)

Conventionally, in an image forming apparatus such as a copying machine and a printer, after detecting the leading edge of a sheet of paper to be sent, by stopping and controlling the drive of a conveyance roller or adjusting the speed, the registration amount in the sheet conveyance direction, that is, It has been practiced to control the amount of blank space from the edge of the sheet to the image writing start position.

Conventionally, the amount of registration in the direction perpendicular to the paper transport direction,
That is, the lateral resist amount is not controlled but is set to a constant amount. However, the accuracy of the components of the apparatus, the error of the image writing system with respect to the image carrier, the error of the sheet setting position, and the like are accumulated to form an error.

As a countermeasure against this variation, a conventional method has been adopted in which the lateral resist amount is measured using a sample image and the image writing start position is adjusted stepwise using a dip switch or the like. However, performing such adjustments during the manufacturing process is labor and time consuming. In addition, since the dimension crossing of the paper is large and the dimensions change depending on the moisture absorption state, the gap between the paper cassette and the paper must be increased. In view of the above, it has been difficult to obtain an accurate lateral resist amount by simply adjusting the write start position.

[Problems to be solved by the invention]

An object of the present invention is to provide a sheet conveying device of an image forming apparatus for transferring an image on an image carrier to a sheet, wherein a pair of a sheet conveying roller for transfer formed so as to be movable in an axial direction and a sheet side end are provided. And a detection sensor for detecting the position of the conveyance roller based on a detection signal of the sensor. Are arranged at positions where both side edges of the largest size sheet can be detected, and the conveyance roller pair is in the axial direction of the conveyance roller pair while the sheet is being fed. The sheet is moved until one side end of the sheet is detected by one detection sensor of the sensor, and further, the one side end of the sheet is detected by the one detection sensor, and the axial direction of the transport roller pair is detected. of The sheet of the image forming apparatus, wherein after the movement is stopped, the conveyance roller pair is moved in the opposite direction until the other sensor detects the opposite side end of the sheet. Solved by the transport device.

[Action]

According to the present invention, the transport roller pair is movable in the axial direction, and the paper is moved in the horizontal direction by the movement of the transport roller pair.

The paper size and paper center position can be recognized by detecting the side edge of the paper with the paper side edge detection sensor, and the center position of the paper can be adjusted by calculating the movement amount in relation to the paper size, and any position Can be set.

The conveying roller pair includes a gear device driven by a motor,
It can be moved in the axial direction of the conveying roller by a cam device, for example, a spiral groove cam.

〔Example〕

 The details of the present invention will be described based on an embodiment shown in the drawings.

In the figure, a sheet 1 is nipped by a pair of conveying rollers 2 and 2 ′, fed and sent to an image carrier 3 that carries a toner image, and the sheet 1 contacts the image carrier 3 to form a toner image 4. The image is transferred to the sheet 1.

An annular groove 6 is formed on the shaft 5 of the transport roller 2 that transports the sheet, and one end of the arm 7 is engaged with the annular groove 6 so as not to hinder the rotation of the shaft 5 but to prevent relative movement in the axial direction. . The other end of the arm 7 is provided with a cam follower that engages with the cam groove of the spiral groove cam 8. According to the rotation of the spiral groove cam 8, the arm 7 is formed so as to be able to reciprocate in the axial direction without changing the posture. With the axial movement of the arm 7 by the helical cam 8, the transport roller pair 2,
2 'is moved in the directions of arrows A and A'.

A worm gear 10 is fixed to a shaft 9 of the helical cam 8, and the worm gear 10 is fixed to a shaft of a motor 11.
The spiral groove cam 8 is rotated by the motor 11 via the worm gear 10. The motor 11 is formed as a motor that can rotate forward and reverse.

Sensors 13 and 13 'are disposed at a position before the sheet 1 reaches the image carrier 3 to detect one or both side edges of the sheet 1.

In the case of an image forming apparatus such as a copying machine capable of feeding LT-sized (216 mm wide) paper, the paper side edge detection sensor
Reference numerals 13 and 13 'are formed as, for example, reflection type photointerrupter sensors, and are arranged so as to detect the sheet side edge at a position 108 mm from the center in the width direction with respect to the sheet conveyance direction.

The paper 1 is started to be transported by the transport roller pair 2, 2 ',
While the leading edge of the sheet 1 reaches the image carrier 3, the conveying roller pair 2, 2 'is moved in the axial direction B, B' by the drive of the motor 11, and a predetermined side edge detecting sensor, for example, as shown in FIG. When the side edge of the sheet 1 is detected by the sensor 13 on the left side, the motor
11 is stopped, and the positional relationship between the image carrier 3 and the image 4 in the horizontal direction is adjusted. As a result, highly accurate lateral registration control can be obtained.

In a device capable of switching and using sheets of various sizes, it is one method to provide a detection sensor at a side end position corresponding to each sheet size in order to perform high-precision horizontal registration control on sheets of each size. Alternatively, the control can be performed only by the detection sensor arranged at the end of the sheet of the maximum size. That is, the amount of deviation in the horizontal direction from the side end position of the maximum size is stored for paper of various sizes, and for example, the deviation amount of 3 mm is stored for an A4 size (210 mm width) with respect to an LT size (216 mm width). When a support signal indicating the A4 size is given, after detecting the paper side edge by the side edge detection sensor 13, the transport roller pair 2, 2 'is moved by 3 mm with the paper 1 facing the center. It may be moved by a minute and stopped. The movement amount control of the pair of conveying rollers 2, 2 'after the detection of the paper side end is performed by controlling the paper side end to the side end detection sensor 13
After the detection, the drive time of the motor 11 is calculated according to the amount to be moved, and the control method of stopping the motor 11 at the calculated time, or a stepping motor is used as the motor 11 according to the amount to be moved. There is a control method for stopping at the position of the rotation amount calculated by the above.

The above control is one sensor that detects one paper side edge
It can be done simply by providing 13. On the other hand, by providing two sensors 13 and 13 'so as to be able to detect both sheet side edges, the same pair of transport rollers 2, 2' as described above are provided.
In addition to the control of the movement amount, the detection of the size of the sheet in the width direction and the recognition of the center of the sheet can be performed, and the position of the sheet can be freely set.

For example, when an A4 size (210 mm width) sheet 1 is passed through an apparatus in which the side edge detection sensors 13 and 13 ′ are arranged corresponding to an LT size (216 mm width), the motor 11 drives the sheet 1 so that the conveyance roller The sheet is moved in the direction of arrow B (or arrow B ') in the lateral direction (the direction of the axis of the conveying roller) while feeding by pairs 2, 2', and the sheet side end is detected by the side end detection sensor 13 (or 1).
3 '), the motor 11 is driven in the reverse direction. The sheet is moved in the direction of B '(or arrow B) by the reverse rotation of the motor 11, and the movement amount until the opposite side end of the sheet 1 is detected by the side end detection sensor 13' (or 13) is 6 mm. Is detected from the time or the amount of rotation of the motor 11 to determine that the sheet 1 is an A4 size sheet.

If it is determined that the size of paper 1 is A4 size,
In order to adjust the center of the sheet to the reference position, the motor 11 is driven to rotate forward after the detection by the side edge detection sensor 13 '(or 13), and moves the sheet in the B direction by the calculated distance of 3 mm.

With the method described above, once the sheet 1 is once adjusted to the center reference position, the sheet 11 can be moved and set to an arbitrary horizontal setting position by driving the motor 11 again as needed.

The center of the paper is recognized in the same manner as above, not only for standard-size paper such as A4 size, but also for irregular-size paper. Can be set to position.

〔effect〕

According to the present invention, positioning in the width direction can be performed for each sheet conveyed, and the lateral registration amount can be maintained with high accuracy with little variation. Since the amount of the lateral resist can be kept constant with high accuracy, it is possible to improve the image quality of multi-color prints and color prints obtained by performing printing a plurality of times.

The present invention eliminates the need for resist adjustment in the manufacturing process and eliminates variations in the amount of lateral resist between machines. In addition, the dimensional tolerance from the writing system to the paper setting section, which had conventionally required strict accuracy, Can be made rough, and a jig or the like used for increasing accuracy is not required, so that costs are reduced.

According to the present invention, it is possible to determine the size of each sheet individually, and it becomes unnecessary to prepare a large number of cassette cases according to the sheet size in order to determine the sheet size.
Further, it is no longer necessary to link the variable portion of the variable cassette with the paper size detecting means.

According to the present invention, paper can be set at an arbitrary position in the horizontal direction. Further, even for paper of an irregular size, a special switch or the like is not provided, and a special cassette is not prepared. The center reference position can be adjusted and the paper position can be set to an arbitrary position, as in the case of size paper.

[Brief description of the drawings]

FIG. 2 is a perspective view of a sheet conveying device of the image forming apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Paper, 2 and 2 '... Conveying roller 3 ... Image carrier 4, ... Toner image 6 ... Annular groove, 7 ... Lever 8 ... Spiral groove cam, 10 ... Worm gear 11 ... Motor, 12: Worm 13, 13 ': Side end detection sensor

Claims (1)

(57) [Claims] An image forming apparatus for transferring an image on an image carrier to a sheet is a sheet conveying device, and a transfer sheet conveying roller pair movably formed in an axial direction and a sheet side end portion are detected. A sheet conveyance device of an image forming apparatus that adjusts a sheet position by controlling an axial movement amount of the conveyance roller based on a detection signal of the sensor, wherein the detection sensor has a maximum usable size. One side of each of the detection sensors is disposed at a position where both side end portions of the sheet can be detected, and the conveying roller pair is in the axial direction of the conveying roller pair in a state where the sheet is being fed. The sheet is moved until one side edge of the sheet is detected by the detection sensor, and further, the one side edge of the sheet is detected by the one detection sensor, and the axial movement of the transport roller pair is stopped. Sa The sheet conveying device of the image forming apparatus, further comprising: moving the pair of conveying rollers in the opposite direction until the other sensor detects the opposite side edge of the sheet.