JP2008273673A - Sheet skew correcting device and image forming device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet skew correcting device having an excellent skew correction ability for the sheets burred or deformed at their ends and a reliability not lowered even if the device is operated at high speeds. <P>SOLUTION: A pair of resist rollers are formed of a pair of rollers disposed at two positions in the direction at right angle with respect to a sheet conveying direction. The pair of resist rollers disposed at the two positions are driven by drive devices independent of each other, respectively. The rotational speeds of the pair of resist rollers at the two positions are controlled according to sheet position information by a sheet detection sensor for detecting the arrival of the pair of sheets disposed at two positions in the direction at right angle with respect to the sheet conveying direction on the downstream side of the nip point of the pair of resist rollers and on the upstream side of a transfer device. Since the speed of the sheet so conveyed that the end of the sheet is parallel to the bus of a photosensitive member, the skew of the sheet can be corrected before the end of the sheet arrives at the transfer point on the photosensitive member. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus typified by a printer, a copying machine, and the like. In particular, a sheet conveyed one by one is corrected for skewing of the sheet upstream of an image forming unit, and a toner image on a photoreceptor. In particular, the present invention relates to a sheet skew correction device that feeds a sheet at a timing and an image forming apparatus using the sheet skew correction device.

  2. Description of the Related Art Conventionally, a conveyance device built in a printer or the like often has a sheet skew correction function for correcting a sheet oblique feeding phenomenon, generally called a skew (see, for example, Patent Documents 1 and 2). ).

  FIG. 3 is an explanatory diagram illustrating a sheet conveyance state in the sheet skew correction apparatus. As shown in the figure, the sheet skew correction device abuts the leading edge of the sheet conveyed on the sheet conveyance path provided upstream of the transfer device on the sheet conveyance path connecting the sheet feeding device and the transfer device. A drive side roller (hereinafter referred to as a resist drive roller 123) arranged to align the leading end of the sheet on the nip line of the roller, a driven side roller (hereinafter referred to as a resist idler roller 124), and further upstream A driving-side roller (hereinafter referred to as timing drive roller 121) for conveying a sheet on a sheet conveying path provided in the same, a driven-side roller (hereinafter referred to as timing idler roller 122), and a timing drive Detects that sheet 22 has passed through contact point 19 between roller 121 and timing idler roller 122 And a first sheet detection sensor 21 that.

  In the sheet skew correction device, in order to correct the skew of the sheet 22, the timing drive roller 121 and the timing idler roller 122 are rotated in the direction of the arrow shown in FIG. 3, and the sheet 22 fed from the sheet feeding device is stopped. The contact point 20 between the registration drive roller 123 and the registration idler roller 124 is brought into contact.

  Thereafter, the timing drive roller 121 and the timing idler roller 122 are rotated in the direction of the arrow shown in FIG. 4 to feed the sheet 22 by an arbitrary amount, and the registration drive roller 123, the registration idler roller 124, the timing drive roller 121, and the timing idler roller 122 are fed. The sheet 22 is bent in an S shape by a first bending portion 27 made of a buffer paper guide 16 having a spring reaction force in the closing direction and a second bending portion 28 made of a paper guide 18 between the two. The resist drive roller 123 and the resist are pressed while being pressed by the repulsive force of the sheet 22 curved in an S shape by the first curved portion 27 and the second curved portion 28 in the direction in which the tip of the sheet 22 follows the pair of contact points 19. The idler roller 124 can be rotated in the reverse direction of the arrow shown in FIG. In, and Narawase the leading edge of the sheet 22 to the contact point 20 to correct the skew of the sheet 22.

JP 2003-72982 A JP 2003-128300 A

  However, when there is a burr or deformation at the leading edge of the sheet, a phenomenon occurs in which the leading edge of the sheet is pulled back in the reverse rotation direction of the registration drive roller by the reverse rotation operation of the registration drive roller. As a result, if the leading edge of the sheet cannot be uniformly learned at the contact point of the registration roller pair, the necessary skew correction capability cannot be obtained, and there is a printing position defect or sheet skew detection device in which the sheet is inclined with respect to the printed image. Had the disadvantage of causing paper skew.

  In addition, when the printing speed of the image forming apparatus is increased, a stepping motor is used to drive the resist drive roller because it is necessary to perform the resist drive roller stop, reverse rotation, and restart processes in a short time. In the drive system, there is a disadvantage that the out-of-step phenomenon occurs due to insufficient time for the motor shaft to settle and the reliability of the apparatus is lowered.

  The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, have a good skew correction capability even for a sheet having burrs or deformation at the tip, and a sheet whose reliability does not deteriorate even when the apparatus is speeded up. An object of the present invention is to provide a skew correction device and an image forming apparatus using the same.

  The above-described object is a drive device in which the registration roller pair is composed of two roller pairs arranged at right angles to the sheet conveyance direction, and each of the registration roller pairs arranged at the two locations is driven independently. A sheet position of a sheet detection sensor configured to be able to drive and to detect the arrival of a pair of sheets disposed at two positions perpendicular to the sheet conveying direction downstream of the registration roller pair and upstream of the transfer device By controlling the rotational speed of each of the two registration roller pairs according to the information, the speed of the sheet conveyed so that the leading edge of the sheet is parallel to the bus of the photosensitive member is controlled. This is accomplished by correcting sheet skew before reaching the transfer point.

  According to a second aspect of the present invention, between the registration roller pair and the timing roller pair, the conveyance speed of the registration roller pair is made slower than the conveyance speed of the timing roller pair arranged upstream thereof. By making the sheet slack, the degree of freedom in twisting the sheet during skew correction is increased and skew correction is facilitated.

  According to a third aspect of the present invention, the detection accuracy of the skew amount of the paper is improved by not changing the paper conveyance speed until the paper passes through the sheet detection sensor. By making the conveyance speeds of the timing roller pair and the registration roller pair the same, it is possible to prevent an increase in sheet slack between both roller pairs, suppress an increase in sheet conveyance resistance, and improve skew correction accuracy. It is a feature.

  In a fourth aspect of the present invention, as a skew correction method, a control method is disclosed in which the conveying speed of the registration roller pair on the leading front side is substantially reduced to the process speed and the leading edge of the following is caught up. The sheet speed is easily matched with the process speed after skew correction.

  Further, according to the present invention, the correction value of the skew correction time t can be input and stored, thereby correcting the sheet arrival detection of the sensor and the variation in the conveyance speed of each roller from the printing result and improving the printing position accuracy. It is characterized by letting.

  According to the present invention, even when there is a burr or deformation at the leading edge of the sheet, a phenomenon that the leading edge of the sheet is pulled back in the reverse rotation direction of the registration drive roller due to the reverse rotation operation of the registration drive roller does not occur. It is possible to prevent a printing position defect and a sheet skew jam in which the sheet is inclined, and an effective skew correction can be performed. In addition, since the registration roller stop, reverse rotation, and restart processes are unnecessary, the printing speed can be increased without impairing the reliability.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 2, the image forming apparatus system includes an image forming apparatus 1 and a sheet handling apparatus 2. In this embodiment, the image forming apparatus 1 is exemplified by a laser printer that uses a photoreceptor and records and forms a toner image on a sheet material by a known electrophotographic process. Further, as the sheet handling device 2, a stacker that stacks and holds sheets discharged from the printer 1 on a tray is exemplified.

  In the printer 1, 3, 4, and 5 are sheet storage units that store sheets as sheet materials. Reference numeral 6 denotes a photosensitive drum, which starts rotating in the direction of an arrow based on a signal from a controller (not shown). When the photosensitive drum 6 starts rotating, the surface of the photosensitive drum 6 is uniformly charged by a corona charger (not shown). An electrostatic latent image is formed on the charged photosensitive drum 6 by a laser beam emitted from an exposure device (not shown). When the electrostatic latent image reaches the position of the developing device 7, the electrostatic latent image is developed with toner and visualized as a toner image on the photosensitive drum 6. Thus, the toner image formed by the well-known electrophotographic process is transferred by the transfer unit 8 to the sheet sent out from the sheet storage units 3, 4, 5 or the return path 14 described later. A fixing device 9 fixes the toner image transferred to the sheet. Reference numerals 10a and 10b denote gates having a function of switching the direction of the conveyed sheet. Reference numeral 13 denotes a reversing unit that switches back and reverses the sheet to be discharged, and has a function of changing the sheet discharge direction.

  Note that regarding the sheet conveyance path configured in the printer 1, in the following description, for convenience, (sheet storage units 3, 4, 5)-(image forming units 6, 7, 8)-(sheet discharge port 11). Is referred to as a “sheet feeding path”. 14 is referred to as a “return path” and is branched from the paper feed path 12 by the gate 10a, and the end of the branch is joined to the paper feed path 12 on the upstream side in the sheet conveying direction with respect to the image forming units 6, 7, and 8. It has been. Reference numeral 15 denotes a transport roller pair provided in front of the gates 10a and 10b.

  In FIG. 2, reference numerals 3a, 4a, and 5a denote pick rollers that feed out the sheets stored in the sheet storage portions 3, 4, and 5, and reference numerals 3b, 4b, and 5b denote sheet feeding rollers generally constituted by a feed roller and a retard roller. It is a pair. The pair of paper feed rollers 3b, 4b, and 5b supply the sheets one by one to the paper feed path 12 while preventing a plurality of sheets fed by the pick rollers 3a, 4a, and 5a from being conveyed in a stacked state. .

  Reference numerals 12a, 12b and 12c denote a pair of conveying rollers for conveying the paper in the paper feeding path 12, 12d is an upstream of the registration roller pair 12e, and a timing roller pair for supplying a sheet to the registration roller pair 12e. A pair of registration rollers that convey the sheet in synchronism with the timing at which the toner image formed on the drum 6 is transferred to the sheet paper. Reference numeral 26 denotes a second sheet detection sensor for detecting the arrival of the sheets disposed at two positions in the direction perpendicular to the sheet conveying direction downstream of the registration roller pair 12e. Reference numerals 14 a, 14 b, 14 c, 14 d, 14 e, and 14 f are conveyance roller pairs that convey the sheet in the return path 14.

  Next, a sheet conveyance state at the registration roller pair 12e will be described with reference to FIG. FIG. 1 is a schematic diagram showing a sheet paper conveyance state by the registration roller pair 12e and the second sheet detection sensor 26. FIG.

  The registration drive roller 123 is divided into 123a and 123b that can rotate independently of each other, and each roller is driven by an independent drive motor of 24a and 24b. The second sheet detection sensor 26 includes 26a and 26b arranged at two positions in the direction perpendicular to the sheet conveying direction corresponding to the registration drive rollers 123a and 123b. The sheet 221 shows a state in which the leading front edge P of the skewed sheet has reached the sheet detection sensor 26b.

  The sheet 222 shows a state in which the leading edge Q of the delayed sheet has reached the second sheet detection sensor 26a. The sheet 22 is conveyed at a speed αv (α> 1) with respect to the process speed v by a timing roller pair 12d (not shown), and βv (α> β> after reaching the registration roller pair 12e. It is conveyed at the speed of 1). The registration drive rollers 123a and 123b maintain their surface speeds at βv until the second sheet detection sensor 26a detects the leading edge Q of the delayed sheet.

  When the second sheet detection sensor 26b detects the leading edge P of the preceding sheet, the counting means (not shown) starts counting until the second sheet detection sensor 26a detects the delayed leading edge Q of the sheet. Count time (Δt). After the second sheet detection sensor 26a detects the leading edge Q of the delayed sheet, the registration drive roller 123b on the side that coincides with the second sheet detection sensor 26b that has detected the leading edge of the preceding sheet detects the surface speed. Deceleration is controlled by speed control means (not shown) such that γv (α> β> γ≈1).

  Skew correction time t = (β · Δt) / (indexed from the time Δt counted by the counting means for the registration drive roller 123a that coincides with the second sheet detection sensor 26a that detects the leading edge of the delayed sheet. By maintaining the surface velocity βv by β−γ), the leading edge of the delayed sheet catches up with the leading edge of the preceding sheet. After the skew correction time t = (β · Δt) / (β−γ) has elapsed, the skew can be corrected by reducing the surface speed of the registration drive roller 123a to γv by a speed control means (not shown). The sheet 223 is in a state after the registration drive roller 123a reduces the surface speed to γv.

  By transporting the sheet as described above, effective skew correction is possible even in the case of a sheet having burrs or deformation at the tip, and the registration roller stop, reverse rotation, and restart processes are unnecessary. The printing speed can be increased without impairing the reliability. However, in order to improve the reproducibility of the skew correction capability, the mounting position accuracy of the second sheet detection sensors 26a and 26b and the registration drive rollers 123a and 123b are improved. It is necessary to maintain and manage the outer diameter dimensional accuracy of the product with high accuracy, which may lead to an increase in manufacturing cost. Therefore, an input means capable of inputting the correction value δ of the skew correction time t and a means for storing the same are provided so that the skew correction time can be corrected for each apparatus from the printing result, and the second sheet detection sensors 26a and 26b By absorbing variations in the mounting position accuracy and the outer diameter dimensional accuracy of the registration drive rollers 123a and 123b, an equivalent effect can be obtained even in an inexpensive configuration that does not perform strict accuracy control.

  Even when a low-quality sheet with burrs or deformation at the front end of the sheet is used, the printing position defect or sheet skew jam in which the sheet is inclined with respect to the printed image is reduced, and the reliability of the apparatus is not reduced. The speed of the printing apparatus can be increased.

It is explanatory drawing which shows the conveyance state of the registration roller counter part sheet which concerns on the Example of this invention. 1 is a schematic configuration diagram of an entire image forming apparatus of the present invention. It is explanatory drawing which shows the conveyance state of the sheet | seat of a sheet skew correction apparatus. It is explanatory drawing which shows the conveyance state of the sheet | seat of a sheet skew correction apparatus.

Explanation of symbols

  1 is an image forming apparatus (printer), 2 is a sheet handling apparatus (stacker), 3, 4 and 5 are sheet storage units, 3a, 4a and 5a are pick rollers, 3b, 4b and 5b are feed roller pairs, 6 Is a photoconductor, 7 is a developing device, 8 is a transfer device, 9 is a fixing device, 10a and 10b are gates, 11 is a discharge port, 12 is a paper feeding path, 12a, 12b, 12c, 14a, 14b, 14c, 14d, 14f and 15 are transport roller pairs, 12d is a timing roller pair, 12e is a registration roller pair, 121 is a timing drive roller, 122 is a timing idler roller, 123, 123a and 123b are registration drive rollers, 124 is a registration idler roller, 13 is Inversion path, 14 is a return path, 16 is a buffer paper guide, 17 and 18 are paper guides, 19 is a contact point of a timing roller pair, 2 Is a contact point of the registration roller pair, 21 is a first sheet detection sensor, 22, 221, 222, and 223 are sheets, 24a and 24b are registration drive roller drive motors, 26 is a second sheet detection sensor, and 26a is a registration drive. A sheet detection sensor provided in the vicinity of the roller 123a, 26b a sheet detection sensor provided in the vicinity of the registration drive roller 123b constituting the second sheet detection sensor, 27 a first bending portion, and 28 a second bending portion.

Claims (6)

A registration roller pair provided upstream of the transfer device and a registration roller pair on a conveyance path connecting the sheet feeding device and the transfer device for transferring the toner image on the photosensitive member to the sheet conveyed from the sheet feeding device. A pair of timing rollers, a paper guide that forms a conveyance path connecting the registration roller pair and the timing roller pair, and a direction perpendicular to the sheet conveyance direction downstream of the registration roller pair and upstream of the transfer device. And a sheet detection sensor for detecting the arrival of the paper placed in two places,
By controlling the rotation speed of the registration roller based on the sheet position information of the sheet detection sensor, the speed of the conveyed sheet can be controlled so that the toner image on the photoconductor can be transferred to a predetermined position on the sheet. In the sheet skew correction device for
The registration roller pair is composed of two roller pairs arranged at right angles to the sheet conveyance direction, and the registration roller pair arranged at the two locations is configured to be independently rotatable, and A driving device that independently drives each of the registration rollers arranged at two locations, and a control for independently controlling the rotation of each of the registration rollers arranged at two locations based on the sheet position information of the sheet detection sensor pair. An apparatus for correcting the skew of a sheet, comprising:   Until the sheet passes through the registration roller pair and reaches the sheet detection sensor pair, the surface speed of the timing roller pair is driven at a speed of αv (α> 1) with respect to the process speed v. The surface speed of the registration roller pair is driven at a speed of βv (α> β> 1) after the sheet reaches the registration roller pair until it reaches the sheet detection sensor pair. The sheet skew correcting device according to claim 1.   After the sheet reaches one of the sheet detection sensors, the timing roller pair is driven at a surface speed βv with respect to the process speed v until the sheet passes through both of the sheet detection sensors. 3. The sheet skew correcting device according to claim 1, wherein the registration roller pair is driven at a surface speed of βv (α> β> 1).   After the sheet has passed through both of the pair of sheet detection sensors, the surface speed of the registration roller on the sensor side that has detected the arrival of the sheet first in the pair of sheet detection sensors is approximately γv ( Difference in detection time between a control unit that drives at a speed of α> β> γ≈1), a sensor that detects the arrival of a sheet first of the pair of sheet detection sensors, and a sensor that detects the arrival of a sheet later The counting means for counting (Δt) and the surface speed of the registration roller on the sensor side that detects the arrival of the sheet from the rear of the pair of sheet detection sensors are counted by the counting means while maintaining the speed of βv. The time t = (until the difference in the arrival distance of the leading edge of the sheet calculated from the difference in the arrival time of the sheet to the sheet detection sensor pair disappears. 4. The apparatus according to any one of claims 1 to 3, further comprising a control unit that drives by Δt) / (β−γ) and drives the speeds of both registration roller pairs equally after time t has elapsed. The sheet skew correction apparatus as described.   After the sheet has passed through both of the pair of sheet detection sensors, the surface speed of the registration roller on the sensor side that has detected the arrival of the sheet first in the pair of sheet detection sensors is approximately γv ( Detection of a control unit that drives at a speed of α> β> γ≈1), a sensor that detects the arrival of the sheet first of the first sheet detection sensor pair, and a sensor that detects the arrival of the sheet later Counting means for counting a time difference (Δt), input means capable of inputting a correction value δ of a skew correction time t, which will be described later, means for storing this, and a sheet from the rear of the sheet detection sensor pair The difference in the arrival time of the sheet to the pair of sheet detection sensors counted by the counting means while the surface speed of the registration roller on the sensor side that has detected the arrival of The driving is performed for a time obtained by combining the time t until the difference in the arrival distance of the indexed sheet leading edge to the sheet detection sensor pair and the correction value δ of the skew correction time, and after the time (t + δ) has elapsed, 4. The sheet skew correcting device according to claim 1, further comprising a control unit that drives the speeds of the pair of registration rollers equally.   An image forming apparatus using the sheet skew correcting device according to claim 1.

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