JP3495600B2 - Paper skew transport correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper skew correction device provided in an image forming apparatus such as an electrostatographic copying machine, a printer or a facsimile. 2. Description of the Related Art Conventionally, in order to correct the oblique conveyance of a sheet conveyed to an image forming section, a pair of resists driven at a predetermined timing are conventionally provided in the middle of a sheet conveying path to the image forming section. A roller is arranged, and the leading end of the sheet conveyed by the feed roller is brought into contact with the nip portion of the registration roller, and the feed of the leading end of the sheet is momentarily stopped, thereby forming a loop at the leading end of the sheet. The skew of the leading edge of the sheet due to the skew conveyance is corrected, and the registration roller is driven to convey the skew-corrected sheet to the image forming unit. [0003] However, if the paper feed is stopped for a moment, the transport time per sheet becomes longer by the time of the stop, and the continuous image is not transferred. At the time of formation, the interval between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet becomes longer, and thus there is a problem in terms of high-speed processing of continuous images. SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and does not use a registration roller dedicated to skew correction, and therefore does not momentarily stop paper feeding, and obliquely transports paper. Device that can correct
In particular, it is an object of the present invention to provide a sheet skew conveyance correction device suitable for high-speed processing of continuous images. In order to achieve the above object, a feed roller for conveying a sheet to an image forming unit is provided in the present invention. A pair of rollers for correcting the skewed conveyance for nipping and conveying the sheet, and a pair of the skewed conveyance correction
Actuator for changing the position of a roller for rotation about an axis perpendicular to the paper surface of the transport paper, and the pair of oblique transport corrections
A sensor for detecting the degree of skew due to the oblique conveyance of the leading edge of the sheet nipped by the rollers for use, and further, based on the skew degree detection information from the sensor, until the sheet is nipped by the feed roller. In the meantime, the pair of skew conveyance
Roller to change the position, and, after the nip of the sheet by the feed roller, comprises a control means for returning the roller <br/> for the pair of oblique conveyance correction in the home position, or
Further, the peripheral speed of the pair of rollers for correcting the oblique conveyance is
The feature is that the speed is set higher than the peripheral speed of the feed roller . [0006] According to the above characteristic configuration, a pair of oblique conveyance.
When the sensor detects the skew of the leading end of the sheet nipped by the correction roller , a pair of skew is set so that the degree of skew becomes zero before the sheet is nipped by the downstream feed roller. The posture of the roller for correcting the skew conveyance is changed, so that the skew conveyance of the sheet is corrected without stopping the feeding of the sheet. [0007] When the sheet whose skew conveyance has been corrected is nipped by the downstream feed roller, thereafter, the pair of skew conveyance correction rollers whose postures have been changed once are changed .
The printer returns to the home position and prepares for the correction of the next skewed conveyance.Because the skewed conveyance of the paper is corrected while the conveyance of the paper is continued, the conveyance time per sheet Will be greatly reduced. Accordingly, when forming a continuous image, the interval between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet is shortened, so that high-speed processing of the continuous image can be performed. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an electrostatographic copier (an example of an image forming apparatus) configured to be capable of forming a double-sided image. A photoreceptor drum 3 is horizontally mounted on an apparatus main body 2 provided with a document holder 1 on the top. Around the photosensitive drum 3, a charging device 4, a developing device 5, a transfer device (image forming unit) 6, a paper separating device 7, and a cleaning device 8 are arranged in this order. An optical system movable exposure device 9 is disposed in the upper space of the main body 2. Further, a paper feeder 12 for transporting paper fed from a paper feed deck 11 provided with a plurality of paper feed cassettes 10 at upper and lower sides, and a paper feeder 12 for transferring paper after image formation. A suction-type paper feed path 14 for conveying the sheet to the fixing device 13 and a pair of discharge rollers 16 for discharging the fixing sheet to a discharge tray 15 outside the apparatus are provided. Tray 17, a stock feed path 18 for feeding fixing processing paper to the intermediate tray 17, and a refeed path for turning the stock paper upside down and feeding it again to the transfer device 6. 19 and
In addition, a path switching unit 20 is provided upstream of the discharge roller pair 16 so that the fixing processing paper can be switched between the discharge tray 15 and the stock paper supply path 18 and fed. As shown in FIGS. 2 to 4, the paper feeding and conveying device 12 first nips and conveys the paper a.
And the second feed rollers 21, 22, 23, 24,
A section for introducing paper from the paper feed deck 11 (see FIG. 1)
25 and the transfer device 6, and between the first and second feed rollers 21, 22, 23, and 24.
The skew conveyance correction device 26 for the sheet a is disposed, and the re-feeding path 19 is connected to the middle of the paper feeding path between the first feed rollers 21 and 22 and the skew conveyance correction device 26. The oblique conveyance correction device 26 for the sheet a is configured as follows. That is, a roller holding member 29 provided with a pair of oblique conveyance correcting rollers 27 and 28 for nipping and conveying the sheet a is moved around one end side of a support shaft 30 perpendicular to the sheet surface of the sheet to be conveyed. An actuator 31 for changing the attitude of the roller holding member 29 around the support shaft 30 is provided so as to be rotatable, and sensors 32a and 32b for detecting the degree of skew of the leading end of the sheet due to oblique conveyance are provided with correction rollers 27 and 32. 28, and a sensor 33 for detecting the leading and trailing ends of the sheet a is provided immediately upstream of the second feed rollers 23 and 24. The actuator 31 is driven, for example, by rotation of a cam 35 connected to a pulse motor 34, and
The roller holding member 29 is rotated around the support shaft 30 against the urging force of the spring 36. The roller holding member 29 includes, for example, a photo switch 37 and a light shielding plate 38 having a light projecting slit b. The position detecting means 39 is provided. The cam 35 and the light shielding plate 38 are rotated at a reduced speed by a gear G1 meshing with the gear G and gears G2 and G3. The reference position detecting means 39 determines the home position P of the correction rollers 27 and 28.
The number of pulses during which the correction rollers 27 and 28 return to the home position P from the reference point is set using the time when the photo switch 37 detects the light transmitted through the slit b of the light shielding plate 38 as a reference point. The pulse motor 34 is driven to rotate in the reverse direction by the number of pulses.
The operation of determining the home position P at 28 is performed every time the print switch is turned on. The peripheral speed of the second feed rollers 23, 24 is set to the process speed of image formation, and the peripheral speed of the correction rollers 27, 28 is set to a speed slightly higher than the process speed. And the first feed rollers 21 and 22
Is set to a speed slightly higher than the peripheral speed of the correction rollers 27 and 28. On the other hand, the sensors 32a and 32b detect the leading edge of two points in the width direction of the sheet a and detect the skew degree of the leading edge of the sheet due to the oblique transport based on the time difference between the leading edge detections. The actuator 31 is controlled by the control means 40 as follows based on information from the sensors 32a and 32b and the paper end detection sensor 33. That is, a mode in which a plurality of images are continuously formed will be described as an example. As is clear from the timing chart shown in FIG. 5, when the print switch is first turned on (step S1), As described above, the roller holding member 29 rotates around the support shaft 30 until the photo switch 37 detects the light shielding plate 38, and thereafter, the roller holding member 29 returns and rotates by a preset number of pulses. The home position P of the correction rollers 27 and 28 is determined (step S2). During this time, the conveyance of the paper a is started at a predetermined timing, and the paper a is fed to the correction rollers 27 and 28 through the first feed rollers 21 and 22.
At this time, sensors for detecting the oblique conveyance of the sheet a 32a, 32b
Detects the skew of the leading edge of the sheet nipped by the correction rollers 27 and 28 due to the oblique conveyance (step S3), the second feed rollers 23 and 24 feed the sheet a based on the skew degree detection information. Before the nip, the postures of the correction rollers 27 and 28 are changed in a direction to reduce the skew degree to zero (step S4). More specifically, based on the detection of the two leading edges of the paper a in the width direction, the control means 40 determines whether the oblique transport state of the paper a is rightward tilt or leftward tilt based on the time difference of the leading edge detection. Is determined, and the skew degree of the leading edge of the sheet is detected, and the roller holding member 29 is pulse-controlled in a direction to make the skew degree zero based on the skew direction and the skew degree. The number of control pulses at this time is stored in the control means 40. Here, since the peripheral speed of the first feed rollers 21 and 22 is set to be slightly higher than the peripheral speed of the correction rollers 27 and 28, the paper a nipped by the correction rollers 27 and 28 Are the first feed rollers 21 and 22
Therefore, the posture of the correction rollers 27 and 28 can be easily changed without causing the paper a to be torn. After the paper a whose skew has been corrected in this way is nipped by the second feed rollers 23 and 24, specifically, the paper end detection sensor 33 detects the rear end of the paper (step S5). In the meantime, the control unit 40 changes the attitude of the roller holding member 29 in the returning direction based on the number of pulses stored in the control unit 40 (step S6).
The correction rollers 27 and 28 are returned to the home position P, so that the correction rollers 27 and 28 prepare for the correction of the skewed conveyance of the next sheet a. Thereafter, the same control is repeatedly performed. When returning the correction rollers 27 and 28 to the home position P, the correction rollers 27 and 28
Is set to a speed slightly higher than the peripheral speed of the second feed rollers 23 and 24, so that the posture of the correction rollers 27 and 28 can be easily changed without the paper a being torn. You can do it. Correction roller 2 for correcting the above skewed conveyance
The change of the postures of 7, 28 is performed in consideration of the time until the sensors 32a and 32b detect the leading edge of the sheet (step S3) and the sensor 33 detects the leading edge of the sheet (step S7). The speed of the pulse motor 34 is controlled so that the attitude change of the correction rollers 27 and 28 is completed. The paper edge detection sensor 33 detects the leading edge of the paper (step S7), and the paper a is
Considering the time until the nip by 7, 28,
Thereafter, the correction rollers 27 and 28 are moved to the home position P.
, The return movement of the correction rollers 27 and 28 is started (step S8), and the paper end detection sensor 3
The pulse motor 34 is controlled so that the return movement of the correction rollers 27 and 28 to the home position P is completed by that time (step S9), taking into account the time required for the correction roller 27 to detect the trailing edge of the sheet (step S5). The speed is controlled. According to the above configuration, each time the print switch is turned on, the correction rollers 27 and 28 are returned to the reference points, and the home positions P of the correction rollers 27 and 28 are determined. The correction is achieved with high accuracy, and the home position P of the correction rollers 27 and 28 is accurately determined. Further, in addition to reliably correcting the oblique conveyance of the sheet a, the feeding of the sheet a is not stopped during that time.
Since the interval between the trailing edge of the following sheet and the leading edge of the succeeding sheet a1 can be reduced, high-speed processing of a continuous image can be performed. The feed roller 4 in the re-feeding path 19
It is needless to say that the skewed conveyance of the sheet is surely corrected based on the above-mentioned operation also for the sheet re-supplied to the sheet feeder 12 through the feed rollers 1 and 42. As described above, in the paper skew conveyance correction device according to the present invention, the paper feed is stopped without using the registration roller dedicated to skew correction, which stops the paper feed momentarily. By correcting the skew conveyance of the paper while the conveyance is continued, the conveyance time per sheet can be greatly reduced. Since the interval between the trailing edge and the leading edge of the succeeding sheet can be reduced, high-speed processing of a continuous image can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic longitudinal sectional view of an electrostatographic copying machine (an example of an image forming apparatus) shown together with a sheet feeding deck. FIG. 2 is a perspective view of a sheet feeding / conveying apparatus provided with a sheet skew conveyance correcting device. FIG. 3 is a side view of the sheet feeding device. FIG. 4 is a plan view of the paper feeder. FIG. 5 is a timing chart for correcting oblique conveyance of a sheet. [Description of References] 6 ... Image forming unit (transfer device), 23, 24 ... Feed roller, 27, 28 ... Correction roller, 31 ... Actuator, 32a, 32b ... Oblique conveyance detection sensor for paper, 4
0: control means, a: paper.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B65H 9/00 B41J 13/00 B41J 13/02 B41J 13/076 G03G 15/00 518

Claims (1)

(57) [Claim 1] An oblique conveyance correction device for a sheet conveyed to an image forming section, wherein the sheet is nipped upstream of a feed roller for conveying the sheet to the image forming section. And a pair of rollers for correcting skewed conveyance, and a pair of rollers for correcting skewed conveyance.
And an actuator for changing the position of the rollers around the axis perpendicular to the paper surface of the conveyance paper, and the pair of oblique conveyance correction
A sensor for detecting the degree of skew of the leading edge of the sheet nipped by the rollers in the oblique conveyance, and further comprising: In the meantime, the pair of skew conveyance correction
The attitude of the roller, and after the nip of the sheet by the feed roller, comprising a control means for returning the pair of oblique transport correction rollers to the home position ,
The peripheral speed of the pair of skew conveyance correction rollers is
An oblique conveyance correction device for paper, wherein the speed is set to be higher than the peripheral speed of the roller .