JP7024325B2 - Image forming device and transfer control method - Google Patents

Description

The present invention relates to an image forming apparatus and a transport control method.

In general, an image forming apparatus (printer, copier, facsimile, etc.) using electrophotographic process technology irradiates (exposes) a charged photoconductor drum (image carrier) with laser light based on image data. Form an electrostatic latent image. Then, the image forming apparatus visualizes the electrostatic latent image and forms the toner image by supplying toner from the developing unit to the photoconductor drum on which the electrostatic latent image is formed. Further, in the image forming apparatus, the toner image is temporarily or secondarily transferred to the paper, and the paper is heated and pressed by the fixing nip of the fixing portion to fix the toner image on the paper. Further, in the image forming apparatus, a resist roller is provided on the upstream side of the transfer portion for transferring the image to the paper. The resist roller has a function of feeding the paper to the transfer unit by rotating so as to adjust the paper transport speed in order to align the tip side of the paper in the transport direction with the tip of the image.

Further, as a function of the conventional resist roller, a function of correcting the bending, that is, skewing (skew) of the tip side in the conveying direction of the paper by abutting the conveyed paper is provided (hereinafter referred to as bending correction). Have. Further, the resist roller has a function of correcting the misalignment in the width direction of the paper (hereinafter referred to as “position misalignment correction”) by swinging along the width direction of the paper after performing this bending correction. There is also (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-133634

By the way, in the image forming apparatus, as the transfer paper (recording material) for printing, generally, flat rectangular paper (standard paper such as A4) is most often used, but on the other hand, for example, an envelope, ultra-thin or Various shapes such as extra-thick sheet material, paper with rough cutting and non-rectangular edges, etc. may be used. Furthermore, the potential demand for printing images on various flat papers other than rectangles is considered to be high.

On the other hand, in the operation of the conventional resist roller that performs the above-mentioned bending correction and misalignment correction, in order to ensure the accuracy of the image position to be transferred (that is, to guarantee the image), the side on the tip side of the paper in the transport direction is a straight line. Moreover, it was necessary that the straight line and the side edge of the paper were at right angles. Specifically, when paper is used in which the sides on the tip side in the transport direction are not at right angles to each other, the bending (skew) state of the paper is further deteriorated during the above bending correction (so-called reverse correction). ) May. In such a case, even if the above misalignment correction is performed, there is a possibility that the bending of the paper cannot be completely corrected and the image reaches the transfer unit, so that the accuracy of the position of the image transferred by the transfer unit is ensured (that is,). Image cannot be guaranteed).

An object of the present invention is to provide an image forming apparatus and a transport control method capable of improving the position accuracy of a transferred image on paper having various shapes.

The image forming apparatus according to the present invention is
A transfer unit that transfers images to paper,
A resist roller provided on the upstream side of the transfer unit in the paper transport direction,
A control unit that controls the operation of the resist roller is provided.
Based on the paper shape information representing the shape of the paper, the control unit performs a resistless operation in which the tip of the paper in the transport direction does not abut against the resist roller and abuttes the tip of the paper against the resist roller. One of the resist operations is selectively performed, and after the resistless operation is executed, the side edge of the paper is aligned with the target position so that the position of the image transferred to the paper by the transfer unit is correct. The swing of the resist roller is controlled.
The image forming apparatus according to the present invention is
A transfer unit that transfers images to paper,
A resist roller provided on the upstream side of the transfer unit in the paper transport direction,
A control unit that controls the operation of the resist roller is provided.
Based on the paper shape information representing the shape of the paper, the control unit performs a resistless operation in which the tip of the paper in the transport direction does not abut against the resist roller, and the control unit abuts the tip of the paper against the resist roller. Any one of the resist operations is selectively performed, and after the resistless operation is executed, the position in the width direction of the paper is aligned with the position of the image transferred by the transfer unit, and the paper is transferred to the paper by the transfer unit. The rocking of the resist roller is controlled so that the position of the image is correct.

The transport control method according to the present invention is
A transfer control method for an image forming apparatus including a transfer unit for transferring an image to paper and a resist roller provided on the upstream side of the transfer unit in the paper transfer direction.
Either a resistless operation in which the tip of the paper is not abutted against the resist roller in the transport direction or a resist operation in which the tip of the paper is abutted against the resist roller based on the paper shape information representing the shape of the paper. After performing the resistless operation, the resist roller is swung so that the position of the image transferred to the paper by the transfer unit is correct.
The transport control method according to the present invention is
A transfer control method for an image forming apparatus including a transfer unit for transferring an image to paper and a resist roller provided on the upstream side of the transfer unit in the paper transfer direction.
Either a resistless operation in which the tip of the paper is not abutted against the resist roller in the transport direction or a resist operation in which the tip of the paper is abutted against the resist roller based on the paper shape information representing the shape of the paper. After performing the resistless operation, the position of the image transferred to the paper by the transfer unit is aligned with the position of the image transferred by the transfer unit in the width direction. Swing the resist roller so that it is correct.

According to the present invention, it is possible to improve the position accuracy of the transferred image on paper having various shapes.

It is a figure which shows schematic the whole structure of the image forming apparatus in this embodiment. The main part of the control system of the image forming apparatus in this embodiment is shown. It is a top view explaining the operation of the conventional resist roller pair, and shows the state which the side on the tip side in the paper transport direction was abutted against the resist roller pair. It is a top view explaining the 2nd operation (resistless operation) of a resist roller pair in this embodiment, and a state that a rocking operation is performed after transporting the paper without abutting the tip end side of the paper against the resist roller pair. Is shown. It is a top view which shows the structure which provided the tip detection sensor which detects the tip of the conveyed paper. It is a top view which shows the structure which provided two tip detection sensors. It is a figure explaining the case which made it possible to select the 1st operation and the 2nd operation of a resist roller pair, FIG. 7A is the outer shape of the paper which can be supported by the 1st operation, and FIG. An example of the outer shape of the paper is shown below. It is a flowchart which shows an example of the operation control of the resist roller pair in this embodiment.

Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing the overall configuration of the image forming apparatus 1 according to the present embodiment. FIG. 2 shows the main part of the control system of the image forming apparatus 1 in the present embodiment.

The image forming apparatus 1 of the present embodiment uses various special papers in addition to standard papers (standard papers) such as A4 size and A3 size, which are generally used as paper S, and images are printed on these papers S. Form.

In the present embodiment, the special paper is, for example, an envelope, a long paper having a longer length in the transport direction than the standard paper, an ultra-thin or extra-thick paper, a label paper, and a paper having a rough cut and not having a right end. Various embodiments may be included, such as trapezoidal or parallel quadrilateral paper, triangular or pentagonal or more polygonal paper, paper with curved sides, and materials other than paper (eg, made of resin).

As a whole, the paper S used in the image forming apparatus 1 of the present embodiment is along the transport direction so that it can be adjusted to a position in the width direction which is a reference or a target when controlling the resist swing described later. Anything having sides (preferably straight sides) may be used.

Hereinafter, when the term “paper S” or simply “paper” is used, both the above-mentioned standard paper (standard paper) and special paper may be included. Further, as an example of using the special paper, a case where an image is formed on a trapezoidal paper S (see FIGS. 4, 7B, etc.) will be mainly described.

The image forming apparatus 1 is an intermediate transfer type color image forming apparatus using an electrophotographic process technique. That is, the image forming apparatus 1 primary transfers the Y (yellow), M (magenta), C (cyan), and K (black) color toner images formed on the photoconductor drum 413 to the intermediate transfer belt 421. After superimposing the toner images of four colors on the intermediate transfer belt 421, the toner image is formed by secondary transfer to paper.

Further, in the image forming apparatus 1, the photoconductor drums 413 corresponding to the four colors of YMCK are arranged in series in the traveling direction of the intermediate transfer belt 421, and the toner images of each color are sequentially transferred to the intermediate transfer belt 421 in one procedure. The tandem method is adopted.

As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, a control unit 100, and the like.

The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads a program according to the processing content from the ROM 102, develops it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the expanded program. At this time, various data stored in the storage unit 72 are referred to. The storage unit 72 is composed of, for example, a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

The control unit 100 receives various data from an external device (for example, a personal computer (PC)) connected to a communication network such as a LAN (Local Area Network) or WAN (Wide Area Network) via the communication unit 71. Send and receive. The control unit 100 receives, for example, image data transmitted from an external device, and forms a toner image on paper based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card.

The image reading unit 10 includes an automatic document feeding device 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

The automatic document feeding device 11 conveys the document D placed on the document tray by the conveying mechanism and sends it out to the document image scanning device 12. The automatic document feeding device 11 can continuously read a large number of images (including both sides) of the document D placed on the document tray at once.

The document image scanning device 12 optically scans the document conveyed on the contact glass from the automatic document feeding device 11 or the document placed on the contact glass, and the reflected light from the document is a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and the original image is read. The image reading unit 10 generates input image data based on the reading result of the original image scanning device 12. Predetermined image processing is performed on the input image data by the image processing unit 30.

The operation display unit 20 is composed of, for example, a liquid crystal display (LCD: Liquid Crystal Display) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, an image status display, an operation status of each function, and the like according to a display control signal input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 100.

The image processing unit 30 includes a circuit or the like that performs digital image processing according to initial settings or user settings for input image data. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table LUT) in the storage unit 72 under the control of the control unit 100. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, compression processing, and the like, in addition to gradation correction, on the input image data. The image forming unit 40 is controlled based on the image data subjected to these processes.

The image forming unit 40 is an image forming unit 41Y, 41M, 41C, 41K, and an intermediate transfer unit 42 for forming an image with each colored toner of Y component, M component, C component, and K component based on the input image data. Etc. are provided.

The image forming units 41Y, 41M, 41C, 41K for the Y component, the M component, the C component, and the K component have the same configuration. For convenience of illustration and description, common components are indicated by the same reference numerals, and when distinguishing between them, the reference numerals are given with Y, M, C, or K. In FIG. 1, reference numerals are given only to the components of the image forming unit 41Y for the Y component, and the reference numerals are omitted for the other components of the image forming units 41M, 41C, and 41K.

The image forming unit 41 includes an exposure device 411, a developing device 412, a photoconductor drum 413, a charging device 414, a drum cleaning device 415, and the like.

The photoconductor drum 413 has, for example, an undercoat layer (UCL: Under Coat Layer), a charge generation layer (CGL: Charge Generation Layer), and a charge transport layer (CGL) on the peripheral surface of a conductive cylindrical body (aluminum raw tube) made of aluminum. It is a negatively charged organic photo-conductor (OPC) in which CTL: Charge Transport Layer) is sequentially laminated. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, a phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and a pair of positive charges and negative charges are generated by exposure by an exposure apparatus 411. The charge transport layer is composed of a hole transporting material (electron donating nitrogen-containing compound) dispersed in a resin binder (for example, a polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. do.

The control unit 100 rotates the photoconductor drum 413 at a constant peripheral speed (linear speed) by controlling the drive current supplied to the drive motor (not shown) that rotates the photoconductor drum 413.

The charging device 414 uniformly charges the surface of the photoconductor drum 413 having photoconductivity to a negative electrode property. The exposure apparatus 411 is composed of, for example, a semiconductor laser, and irradiates the photoconductor drum 413 with a laser beam corresponding to an image of each color component. As a result, an electrostatic latent image of each color component is formed on the surface of the photoconductor drum 413 due to the potential difference from the surroundings.

The developing device 412 is, for example, a developing device of a two-component developing method, and forms a toner image by visualizing an electrostatic latent image by adhering toner of each color component to the surface of the photoconductor drum 413.

The drum cleaning device 415 has a cleaning blade or the like that is slidably contacted with the surface of the photoconductor drum 413. The drum cleaning device 415 removes the transfer residual toner remaining on the surface of the photoconductor drum 413 after the primary transfer by the cleaning blade.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

The intermediate transfer belt 421 is composed of an endless belt and is stretched in a loop on a plurality of support rollers 423. At least one of the plurality of support rollers 423 is composed of a driving roller, and the other is composed of a driven roller. For example, it is preferable that the roller 423A arranged on the downstream side in the belt traveling direction with respect to the primary transfer roller 422 for the K component is the drive roller. This makes it easier to keep the running speed of the belt in the primary transfer unit constant. As the drive roller 423A rotates, the intermediate transfer belt 421 travels at a constant speed in the direction of arrow A.

The primary transfer roller 422 is arranged on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photoconductor drum 413 of each color component. The primary transfer roller 422 is pressed against the photoconductor drum 413 with the intermediate transfer belt 421 interposed therebetween, thereby forming a primary transfer nip for transferring the toner image from the photoconductor drum 413 to the intermediate transfer belt 421.

The secondary transfer roller 424 is arranged on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the backup roller 423B arranged on the downstream side in the belt traveling direction of the drive roller 423A. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the paper S.

The secondary transfer nip formed by the intermediate transfer belt 421, the backup roller 423B and the secondary transfer roller 424 corresponds to the "transfer portion" of the present invention.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner image on the photoconductor drum 413 is sequentially superimposed on the intermediate transfer belt 421 and the primary transfer is performed. Specifically, by applying a primary transfer bias to the primary transfer roller 422 and applying a charge having the opposite polarity to the toner on the side in contact with the primary transfer roller 422 of the intermediate transfer belt 421, the toner image is obtained by the intermediate transfer belt 421. Is electrostatically transferred to.

After that, when the paper S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the paper S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and a charge having a polarity opposite to that of the toner is applied to the side of the paper S in contact with the secondary transfer roller 424, whereby the toner image is transferred to the paper S. It is electrostatically transferred. The paper S on which the toner image is transferred is conveyed toward the fixing portion 60.

The belt cleaning device 426 has a belt cleaning blade or the like that is in sliding contact with the surface of the intermediate transfer belt 421, and removes the transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

The fixing portion 60 is an upper fixing portion 60A having a fixing surface side member arranged on the fixing surface side of the paper S, and a lower fixing portion having a back surface side support member arranged on the opposite surface side of the fixing surface of the paper S. It is provided with 60B, a heating source 60C, and the like. By pressing the back surface side support member against the fixing surface side member, a fixing nip that narrowly holds and conveys the paper S is formed.

The fixing unit 60 secondarily transfers the toner image and heats and pressurizes the conveyed paper S with the fixing nip to fix the toner image on the paper S. The fixing portion 60 is arranged as a unit in the fixing device F. Further, the fuser F is provided with an air separation unit 60D that separates the paper S from the fixing surface side member by blowing air.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. Paper S (standard paper, special paper) identified based on the basis weight (rigidity), size, etc. is set in the three paper feed tray units 51a to 51c constituting the paper feed unit 51 for each preset type. Be housed. The transport path unit 53 feeds a plurality of transport rollers such as a resist roller pair 53a and a loop roller 53b, a double-sided transport path for forming an image on both sides of the paper S, and the paper S from the outside of the apparatus (right side in FIG. 1). It has an external paper feed transfer path and the like for the purpose. The resist roller pair 53a corresponds to the "resist roller" of the present invention.

The resist roller pair 53a plays a role of correcting the bending of the paper S and a role of correcting the misalignment of the paper S under the control of the control unit 100. Further, the resist roller pair 53a has a function of adjusting the paper transport speed by rotating the resist roller pair 53a so as to align the position of the toner image secondarily transferred onto the paper under the control of the control unit 100.

Here, the bending correction is to correct the bending, that is, skew of the front end side of the paper S in the transport direction by abutting the conveyed paper S against the resist roller pair 53a. In the present embodiment, when the bending of the paper S is corrected, the rotation of the resist roller pair 53a is controlled by outputting a control signal from the control unit 100 to the drive source (motor or the like) of the resist roller pair 53a. .. The details of the control content of the bending correction of the paper S will be described later.

On the other hand, the misalignment correction corrects the position of the paper S in the width direction by swinging the resist roller pair 53a. That is, after the paper S is sandwiched between the nip of the resist roller pair 53a (hereinafter, also referred to as a resist nip), the resist roller pair 53a moves in the width direction to move the paper S (resist rocking). By controlling the above, the position of the paper S in the width direction is corrected. In the present embodiment, as the drive source for swinging the resist roller pair 53a, a motor (stepping motor or the like) different from the motor for rotating the resist roller pair 53a is used. The details of the control content of resist swing will be described later.

The loop roller 53b is a pair of rollers arranged on the upstream side of the pair of resist rollers 53a in the transport direction. Under the control of the control unit 100, the loop roller 53b rotates so as to form a loop on the paper S with the resist roller pair 53a, thereby correcting the bending of the paper S in cooperation with the resist roller pair 53a. do.

A line sensor 54 is arranged on the downstream side of the resist roller pair 53a in the paper transport direction and on the upstream side of the secondary transfer nip. The line sensor 54 is a sensor in which photoelectric conversion elements are arranged in a line shape, detects one end of the paper S in the width direction (hereinafter referred to as a side end), and causes the paper S to be offset (reference or target position). It plays a role of detecting (positional deviation from (see the dotted line in FIG. 4)).

The paper S housed in the paper feed tray units 51a to 51c is sent out one by one from the uppermost portion, and is conveyed to the image forming unit 40 by the transfer path unit 53. Alternatively, the paper S is conveyed from the external paper feed tray or the paper feed device connected to the image forming device 1 (neither is shown) to the image forming unit 40 via the above-mentioned external paper feed transfer path. At this time, the side of the tip of the fed paper S in the transport direction is abutted against the resist roller pair 53a, and the side of the tip is made parallel to the axis of the resist roller pair 53a, so that the paper S is bent. Along with the correction (curving correction), the transfer timing of the paper S is adjusted.

Then, in the image forming unit 40, the toner image of the intermediate transfer belt 421 is collectively secondarily transferred to one surface of the paper S, and the fixing step is performed in the fixing unit 60. The image-formed paper S is discharged to the outside of the machine by the paper ejection unit 52 provided with the paper ejection roller 52a. At the time of double-sided printing, the paper S on which the image is formed on the first side is switched back and conveyed via the double-sided transfer path, so that the front and rear ends in the transfer direction are reversed and the front and back sides are reversed. After that, the toner image is secondarily transferred and fixed on the second surface, and is discharged to the outside of the machine by the paper ejection unit 52.

By the way, in the image forming apparatus, as the transfer paper (recording material) for printing, generally, flat rectangular paper (standard paper such as A4) is most often used, but on the other hand, for example, an envelope, ultra-thin or Various shapes such as extra-thick sheet material, paper with rough cutting and non-rectangular edges, etc. may be used. Furthermore, the potential demand for printing images on special paper having various flat shapes other than rectangles is considered to be high.

However, in the operation of the conventional resist roller pair 53a that performs the bending correction and the misalignment correction as described above, in order to secure the position accuracy (image guarantee) of the printed toner image, the tip of the paper in the transport direction is used. It was necessary that the side side was a straight line and that the straight line and the side edge of the paper were at right angles.

The above problem will be described more specifically with reference to FIG. 3 and the like. Here, FIG. 3 shows a state in which the tip of the rectangular paper S in the transport direction is abutted against the resist roller pair 53a, and the transport direction of the paper S is indicated by an arrow. For the sake of simplicity, the loop roller 53b is omitted in FIG. 3, and the same applies to FIGS. 4 to 6 described later.

As shown in FIG. 3, when the planar shape of the paper S is rectangular, the bending correction of the paper S can be normally performed by a normal resist operation. Here, the normal resist operation is performed by rotating the resist roller pair 53a as follows under the control of the control unit 100. That is, the resist roller pair 53a is stopped rotating (or rotated in the reverse feed direction) until the side of the tip of the paper S in the transport direction (hereinafter, simply referred to as the tip) abuts, and the tip of the paper S is a resist. When abutted against the roller pair 53a, it starts rotating in the forward feed direction (that is, the transport direction to the secondary transfer nip).

More specifically, the upstream side of the paper S is conveyed by the loop roller 53b, and when the tip of the paper S hits the resist roller pair 53a (in a state where the rotation is stopped or the like), the rotation of the loop roller 53b causes the paper S to rotate. Form a loop (paper deflection). At this time, the entire edge of the tip of the paper S abuts equally on the nip of the resist roller pair 53a to correct the bending (skew) of the paper S, and then when the resist roller pair 53a starts the progressive rotation, The paper S is conveyed toward the secondary transfer nip with the skew corrected.

In a normal resist operation, the rotation of the resist roller pair 53a is switched in this way, so that the paper S is conveyed toward the secondary transfer nip after the bending (skew) is corrected by the resist roller pair 53a. To.

On the other hand, when paper S having a trapezoidal planar shape as shown in FIG. 4, for example, the sides formed by the front end side and the side end side in the transport direction of the paper S are not at right angles (90 °). Therefore, in the above-mentioned normal resist operation, the bending correction of the paper S cannot be performed normally. That is, when a normal resist operation is performed on such a paper S, bending (skew) occurs when the paper S hits the resist roller pair 53a, so that the paper S is bent during the above-mentioned bending correction. The bending (oblique) state may be further aggravated (so-called reverse correction). In such a case, there is a possibility that the bending of the paper S cannot be completely corrected by the rocking motion of the resist roller pair 53a (that is, the control of the resist rocking) after the resisting operation, and the position of the image to be transferred by the secondary transfer nip may not be completely corrected. It is not possible to ensure accuracy (that is, image guarantee).

Further, in the image forming apparatus 1 that performs double-sided printing by switching back the paper S as in the present embodiment, when double-sided printing of the paper S is performed, the paper is printed on the first side and the second side. The side edge of S does not change, while the tip of the paper S abutted against the resist roller pair 53a is on the opposite side. Therefore, when the paper S having a planar shape other than the rectangular shape is conveyed in the direction shown in FIG. 4, the bending correction of the paper S is performed in the normal resist operation at the time of printing on either the first side or the second side. It cannot be done normally.

In general, in order to completely correct the bending of the paper S by the operation of the bending correction of the resist roller pair 53a or the like, the side of the tip of the paper S is completely perpendicular to the side of the side edge of the paper S (accurately). 90 °) is required. On the other hand, there is a paper S that does not have a perfect right angle as described above even if it is a standard paper, due to differences in machines (cutting machines and the like) at the time of manufacturing the paper S, manufacturing tolerances, and the like. Furthermore, it is not easy from the aspect of manufacturing technology to make the angle between the front edge side and the side edge side of the paper S a perfect right angle, and the angle is approximately 89 ° or 91 in the standard paper. In the case of ° (deviation of about 1 °), it can occur frequently.

Therefore, in the image forming apparatus 1 of the present embodiment, as an operation when the paper S is conveyed by the resist roller pair 53a, an operation (resistless operation) in which the tip of the paper S does not abut against the resist roller pair 53a is selected. It was configured to be able to be executed. That is, the control unit 100 has a normal resist operation (first operation) in which the tip of the paper S is abutted against the resist roller pair 53a and a resistless operation (second operation) in which the tip of the paper S is not abutted against the resist roller pair 53a. ) And the operation of the resist roller pair 53a is controlled so as to execute either of the above.

In the present embodiment, the normal resist operation (first operation) is the same as the conventional resist operation described above. On the other hand, the resistless operation (second operation) is an operation of rotating the resist roller pair 53a in the transport direction (forward feed direction) before the tip of the paper S reaches (rushes) the resist roller pair 53a. That is, when executing the resistless operation, the control unit 100 rotationally drives the resist roller pair 53a so that the resist roller pair 53a is rotated in the transport direction even before the tip of the paper S rushes into the resist roller pair 53a. Outputs a control signal to the motor.

In this example, from the viewpoint of improving productivity, the rotation speed of the resist roller pair 53a is controlled to be substantially the same as the rotation speed of the loop roller 53b when the resistless operation is executed. Therefore, when the resistless operation is executed, the loop of the paper S is not formed between the loop roller 53b and the resist roller pair 53a. On the other hand, the rotation speed of the resist roller pair 53a at the start of execution of the resistless operation can be adjusted to an arbitrary speed through a user setting screen (not shown) or the like.

When such a resistless operation is executed, the bending of the paper S is not corrected by the resist roller pair 53a, so that it is possible to prevent the situation in which the bending (skew state) of the paper S as described above is further deteriorated. be able to. On the other hand, since the bending (skew) of the paper S is not corrected by the resistless operation, in the present embodiment, after the resistless operation is executed, the resist roller pair 53a is swung to position the paper S. Performs bending (skew) correction as well as deviation correction.

In the present embodiment, the rocking operation of the resist roller pair 53a is performed even after the normal resist operation (first operation) is executed. That is, the control unit 100 controls the swing of the resist roller vs. 53a so that the paper S swings along the width direction of the paper after the normal resist operation or the resistless operation is executed.

FIG. 4 illustrates a case where the resist roller pair 53a is swung a plurality of times (three times) with respect to the trapezoidal paper S after the second operation is executed, and the swing timing and direction of each resist roller pair 53a are set to 3. It is indicated by the arrow in the book. FIG. 4 illustrates a case where the paper S is displaced to the right with respect to the target position indicated by the dotted line, and for the sake of simplicity, the resist roller pair 53a is swung to the left by the same amount and at the same interval three times. ing. On the other hand, in actual paper transport, bending (skew) of the paper S may occur, so that the movement of the resist roller vs. 53a (swing direction, number of swings, each swing amount, etc.) is It comes in various aspects.

Further, the control unit 100 aligns the tip end side of the paper S with the position in the paper transport direction in which the image (toner image) is transferred by the secondary transfer nip (transfer unit) after the normal resist operation or the resistless operation is executed. In addition, control is performed to adjust the rotation speed of the resist roller pair 53a (that is, the transport speed of the paper S). This control is called "tip timing adjustment", in which the transfer speed of the paper S is accelerated / decelerated by a known method and finally adjusted to the transfer speed of the secondary transfer nip, and the resist roller pair 53a It is performed in parallel with the swinging motion of.

In the present embodiment, the control of the tip timing adjustment after the execution of the resistless operation is started at a predetermined timing after the tip of the paper S is inserted into the resist roller pair 53a. For example, when the paper S has a trapezoidal planar shape as shown in FIG. 4, the timing at which the side (hypotenuse) on the tip side of the paper S passes through the nip of the resist roller pair 53a (the entire width of the paper S is sandwiched between the resist nips). At the time point), the control of tip timing adjustment is started. As another example, the control of the tip timing adjustment after the execution of the second operation starts at the timing when a part of the paper is detected by the line sensor 54.

Further, as another example, the control of the tip timing adjustment after the execution of the resistless operation is performed by a sensor (tip) for detecting the tip of the paper S, as shown in FIG. 5 or FIG. 6, separately from the line sensor 54. The detection sensor 55) is arranged, and the start is performed at the timing when the tip of the paper S is detected by the sensor. Here, FIG. 5 shows the case where one tip detection sensor 55 is provided, and FIG. 6 shows a plurality of tip detection sensors 55 (two of 55A and 55B) along the axial direction of the resist roller pair 53a and the secondary transfer nip. The case where it is provided is shown. As shown in FIG. 6, when a plurality of tip detection sensors 55 are provided, the inclination of the tip of the paper S can be estimated, so that the tip timing and the image writing position on the tip side of the paper S can be more accurately written. Can be controlled. The tip detection sensors 55, 55A, 55B are not particularly limited as long as they can detect the tip of the paper, and may be, for example, either an optical method or a physical method.

In the present embodiment, the rocking operation of the resist roller pair 53a after the execution of the resistless operation is the bending correction of the paper S and the misalignment correction of the side edge of the paper S (hereinafter, simply referred to as the misalignment correction). It has both sides. In the present embodiment, for example, after the resistless operation (second operation) is executed, the resist roller pair 53a is swung a plurality of times or continuously so that the side edge of the paper S is always aligned with the target position. The operation of sequentially moving S in the width direction (direction orthogonal to the transport direction) is performed. Further, such a swinging operation, that is, swinging control of the resist roller pair 53a by the control unit 100 is continued (appropriately executed) even after the paper S reaches the secondary transfer nip. Due to such a swinging motion of the resist roller pair 53a, the paper S is bent (oblique) before the transfer of the toner image is started by the secondary transfer nip, regardless of the shape of the tip side of the paper S. And can correct misalignment. As a result, it is possible to improve the position accuracy of the transferred image with respect to various types of paper S.

It should be noted that it is possible to automatically or arbitrarily select whether to perform a normal resist operation (first operation) or a resistless operation (second operation) as an operation when the paper is conveyed by the resist roller pair 53a. It is good to have a configuration.

That is, when the shape of the paper S is trapezoidal as described above (see FIG. 7B), the angle of each corner of the paper S is greatly deviated from 90 °, and the resist operation (first operation) similar to the conventional one is performed. If this is done, there is a risk that the subsequent control of resist swing cannot be dealt with (image cannot be guaranteed).

On the other hand, depending on the shape of the paper S, typically, when the paper S is a standard paper and the angle of each corner is extremely close to 90 ° (see FIG. 7A), the resist operation similar to the conventional one (first). It is considered that there are cases where the control of the operation) and the resist swing can be sufficiently dealt with (that is, the image can be guaranteed).

From the above viewpoint, in the present embodiment, prior to the execution of the print job, the paper shape information representing the shape of the paper S is registered through the operation display unit 20 or the user setting screen (not shown) of the external device (PC or the like). (Store in memory etc.). Then, the control unit 100 determines whether to execute a normal resist operation (first operation) or a resistless operation (second operation) when the print job is executed, based on the paper shape information registered in advance. Perform the processing.

Here, the paper shape information can be set and registered by the user by manually inputting numerical values (vertical and horizontal lengths, angles of each corner, etc.) related to the outer shape of the paper S through the above-mentioned user setting screen.

Alternatively, in order to automatically register the paper shape information, for example, a reading device equipped with an optical sensor such as a scanner (not shown) is connected to the image forming apparatus 1 and the outer shape of the paper used in the image forming apparatus 1 is read in advance. Detect with the device. Then, the outer shape of the paper detected by the reading device is transmitted from the reading device to the image forming apparatus 1 as the paper shape information, and the control unit 100 stores the received paper shape information in the storage unit 72 or the RAM 103. .. By performing such processing, the shape of the paper (length of each side, angle of each corner, etc.) can be accurately detected and set as paper shape information.

It is considered that the outer shapes of the papers are the same or extremely close to each other if they are in the same lot. Therefore, it is advisable to register (that is, update) the paper shape information for each lot. On the other hand, from the viewpoint of image guarantee and the like, the paper shape information can be updated more frequently. For example, even in the same lot, the paper shape information may be updated every predetermined number of sheets (for example, several hundred sheets) or every print job.

As another example, the user may be able to set whether to execute the first operation or the second operation through the above-mentioned user setting screen. For example, when it is clear from the outer shape of the paper S that the resist operation (first operation) and the control of resist swing cannot be handled (image cannot be guaranteed) as in the conventional case, or as described in FIG. 7A. And the opposite is possible. Therefore, regardless of whether or not the paper shape information is registered, the user may be able to set in advance whether to execute the first operation or the second operation.

3 and 4 will be compared, and the first operation and the second operation of the present embodiment will be compared and described. As shown in FIG. 3, in the conventional resist operation (first operation of the present embodiment), the tip of the paper S in the transport direction is abutted against the resist roller pair 53a (that is, temporarily stopped), so that the paper S is stopped. The edge of the tip is corrected so as to be parallel to the axis of the resist roller pair 53a.

On the other hand, in the second operation (resistless operation) of the present embodiment, the resist roller pair 53a has already rotated in the transport direction at the time shown in FIG. 3, and therefore, the tip of the paper S is a resist. It is conveyed toward the secondary transfer nip without being abutted (temporarily stopped) by the roller pair 53a (see FIG. 4). Therefore, if the side side of the paper S is bent from the reference line parallel to the transport direction shown by the dotted line in FIG. 4, this bend is not corrected at the time of the second operation. Even in such a case, the resist roller pair 53a is swung in the width direction so that the side edge of the paper S is aligned with the target position (see the dotted line in FIG. 4) to reach the secondary transfer nip. The side edge of the paper S can be corrected in parallel with the transport direction to correct the bending.

As described above, in the second operation of the present embodiment, by correcting the sub-scanning side of the paper S, it is possible to correct the bending without depending on the shape of the tip side of the paper S in the transport direction. ..

Further, as can be seen by comparing FIGS. 3 and 4, in the resistless operation of the present embodiment, the operation of temporarily stopping the paper S by abutting the paper S against the resist roller pair 53a does not occur. The transport time to the secondary transfer nip can be shortened.

As described above, the control unit 100 basically shakes the resist roller pair 53a so as to align the side edge of the paper S conveyed by the resist roller pair 53a with the target position (see the dotted line in FIG. 4). Control the movement. By performing such control, the bending (skew) of the paper S is corrected before reaching the secondary transfer nip, and the side edge side of the paper S and the width direction of the toner image transferred by the secondary transfer nip. The writing position in is correct.

On the other hand, depending on the alignment between the resist roller pair 53a and the secondary transfer nip or the fixing nip, the paper S may bend from the middle even when the above control is performed. In particular, if the paper S bends after passing through the resist roller pair 53a, the position of the side edge of the paper S that has reached the secondary transfer nip may shift. Therefore, in such a case, the control unit 100 swings the resist roller pair 53a so as to align the position of the side edge of the paper S with the position of the toner image transferred by the secondary transfer nip. That is, the control unit 100 dares to shift the side end of the paper S, for example, from the target position (see the dotted line in FIG. 4) in consideration of the bending amount of the paper S after passing through the resist roller pair 53a. As such, the resist roller pair 53a is swung. By performing such control, it is possible to correct the bending and the misalignment of the paper more correctly and prevent the misalignment of the image from occurring.

From another point of view, the control unit 100 appropriately corrects the target position of the side edge of the paper S (that is, the position of the dotted line in FIG. 4) in the swing control after the execution of the first operation or the second operation. Shift appropriately) and swing the resist roller pair 53a so that the side edge of the paper comes to the corrected target position.

In order to control the swing of the resist roller pair 53a, for example, an image reading device (scanner or the like) (not shown) is provided after the image forming apparatus 1, and the image forming apparatus 1 performs trial printing of the paper S in advance. .. Then, the image position on the paper S on which the test printing has been performed is read by an image reading device to detect the degree of misalignment of the image, and the detection result is used as the target position of the side edge of the paper S at the time of main printing. It is reflected (feedback) in the correction value of.

By performing various processes related to the swing of the resist roller pair 53a in this way, the accuracy of the position of the toner image transferred to the paper S by the secondary transfer nip can be further improved.

Hereinafter, an example of the processing executed by the control unit 100 regarding the operation of the resist roller pair 53a in the image forming apparatus 1 and the transfer control of the paper S will be described with reference to the flowchart of FIG. In this example, it is assumed that the tip detection sensors 55A and 55B described above are provided in FIG. 6 and the trapezoidal paper S described above is used in FIG. 4 and the like.

When the print job is executed, the control unit 100 acquires various setting information in the print job (step S100). Here, as setting information, the control unit 100 includes, for example, information indicating the type of the paper S including the above-mentioned paper shape information (for example, the length of each side of the paper S, the angle of each corner, the basis weight, etc.). Acquire user settings regarding the orientation of the paper S, the operation selection of the resist roller vs. 53a, the presence / absence of double-sided printing, and the like.

In step S110, the control unit 100 refers to the acquired setting information to determine whether or not to perform the resist operation (paper tip abutting) described above, that is, to execute either the second operation or the first operation. Or decide. In this example, the control unit 100 determines to execute the second operation (resistless operation) based on the paper shape information (step S110, YES), and proceeds to step S130.

In step S130, the control unit 100 controls the drive source of the resist roller pair 53a so that the progressive rotation is started before the tip of the paper S reaches (rushes into) the resist roller pair 53a (execution of the second operation). .. By this control, the resist roller pair 53a conveys the paper S as it is toward the secondary transfer nip without performing the operation of abutting (temporarily stopping) the tip of the paper S (see FIG. 4). Therefore, when the paper S has a bend (skew), the bend is not corrected at this point, but the transport time to the secondary transfer nip can be shortened.

In step S140 following step S130, the control unit 100 monitors the detection signals of the tip detection sensors 55A and 55B to determine whether or not the paper S is detected by the sensors 55A and 55B. Then, while the control unit 100 determines that the paper S is not detected by the sensors 55A and 55B (step S140, NO), the control unit 100 considers that the tip of the paper S has not reached the positions of the sensors 55A and 55B. The determination in step S140 is repeated. On the other hand, when the control unit 100 determines that the paper S is detected by the sensors 55A and 55B (steps S140, YES), the control unit 100 proceeds to step S150.

In step S150, the control unit 100 controls the rotation and rocking of the resist roller pair 53a so as to perform the resist rocking (paper side edge alignment) operation together with the paper tip timing alignment operation described above. Regarding the operation of resist rocking, in this example, the control unit 100 sets the resist roller pair so that the position of the side edge of the paper S detected by the line sensor 54 matches the target position (see the dotted line in FIG. 4). Swing 53a in the width direction.

After executing the resist swing control in step S150, the control unit 100 ends the series of processes described above. The resist swing control in step S150 can be continued even after the paper S reaches the secondary transfer nip.

Further, when the double-sided printing job is executed, the control unit 100 returns to step S110 after step S150 to control the transfer of the second side of the paper S. In this example, since the paper S is trapezoidal and the tip of the second surface after the switchback transfer is also a hypotenuse, the control unit 100 determines to execute the second operation (resistless operation) (step S110). , YES), the process proceeds to step S130, and the same control as that of the first surface is executed.

As another printing example, as described with reference to FIG. 7A or the like, when the angle of each corner of the paper S is extremely close to 90 °, the control unit 100 controls both the first side and the second side of the paper S. , It is determined to execute the normal resist operation (first operation) (step S110, NO), and the process proceeds to step S150 described above through step S120. By controlling the first operation in step S120, the resist roller pair 53a continues to stop rotating or reverse feed rotation until the tip of the paper S abuts, and the tip of the paper S abuts against the resist roller pair 53a. , Start forward rotation. By this first operation, the paper S is conveyed to the secondary transfer nip in a posture in which the bending is corrected by the resist roller pair 53a and the skew state is corrected.

According to the image forming apparatus 1 that performs the above control, it is possible to improve the position accuracy of the transferred image with respect to the paper having various shapes.

In the above-described embodiment, the case where the registrationless operation is executed on the trapezoidal paper S as the special paper has been illustrated and described. On the other hand, the resistless operation of the present embodiment can be applied to papers having various outer shapes as described above, and can be similarly applied to papers S having a perfect rectangular shape.

As a whole, according to the image forming apparatus 1 of the present embodiment that performs the conveying control as described above, the accuracy of the image position to be formed is ensured regardless of the shape and angle of the tip side in the conveying direction of the paper S. As a result, the image can be guaranteed).

In the above-described embodiment, a case where a sheet of paper is used as the paper has been described. On the other hand, the above embodiment can be similarly applied to roll paper.

In the above-described embodiment, an example of an image forming apparatus including a transfer unit for secondarily transferring an image to be printed using the intermediate transfer belt 421 to paper S has been described. On the other hand, the above-described embodiment can be similarly applied to a transfer-type image forming apparatus (for example, a monochrome printer, an inkjet printer, etc.) that temporarily transfers an image to be printed onto paper S.

In addition, the above embodiments are merely examples of embodiment of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. That is, the present invention can be implemented in various forms without departing from its gist or its main features.

1 Image forming device 20 Operation display unit 30 Image processing unit 40 Image forming unit 50 Paper transport unit 53a Resist roller pair 54 Line sensor 55, 55A, 55B Tip detection sensor 100 Control unit 421 Intermediate transfer belt 423B Backup roller 424 Secondary transfer roller S paper

Claims (10)

A transfer unit that transfers images to paper,
A resist roller provided on the upstream side of the transfer unit in the paper transport direction,
A control unit that controls the operation of the resist roller is provided.
Based on the paper shape information representing the shape of the paper, the control unit performs a resistless operation in which the tip of the paper in the transport direction does not abut against the resist roller and abuttes the tip of the paper against the resist roller. One of the resist operations is selectively performed, and after the resistless operation is executed, the side edge of the paper is aligned with the target position so that the position of the image transferred to the paper by the transfer unit is correct. Controlling the swing of the resist roller,
Image forming device. A transfer unit that transfers images to paper,
A resist roller provided on the upstream side of the transfer unit in the paper transport direction,
A control unit that controls the operation of the resist roller is provided.
Based on the paper shape information representing the shape of the paper, the control unit performs a resistless operation in which the tip of the paper in the transport direction does not abut against the resist roller, and the control unit abuts the tip of the paper against the resist roller. Any one of the resist operations is selectively performed, and after the resistless operation is executed, the position in the width direction of the paper is aligned with the position of the image transferred by the transfer unit, and the paper is transferred to the paper by the transfer unit. The rocking of the resist roller is controlled so that the position of the image is correct.
Image forming device. In the resistless operation, the control unit controls to rotate the resist roller in the transport direction even before the tip of the paper rushes into the resist roller.
The image forming apparatus according to claim 1 or 2 . After executing the resistless operation, the control unit controls to adjust the rotation speed of the resist roller so as to match the position in the paper transport direction in which the image is transferred by the transfer unit.
The image forming apparatus according to any one of claims 1 to 3 . The control unit continues to control the swing of the resist roller even after the paper reaches the transfer unit.
The image forming apparatus according to claim 1 . The paper shape information is configured to be preset.
The image forming apparatus according to claim 1. The control unit executes either the resistless operation or the resist operation based on the paper shape information set through the operation input unit.
The image forming apparatus according to claim 6 . The control unit executes either the resistless operation or the resist operation based on the paper shape information acquired by the sensor that reads the outer shape of the paper.
The image forming apparatus according to claim 6 . A transfer control method for an image forming apparatus including a transfer unit for transferring an image to paper and a resist roller provided on the upstream side of the transfer unit in the paper transfer direction.
Either a resistless operation in which the tip of the paper is not abutted against the resist roller in the transport direction or a resist operation in which the tip of the paper is abutted against the resist roller based on the paper shape information representing the shape of the paper. After performing the resistless operation, the resist roller is shaken so that the side edge of the paper is aligned with the target position and the position of the image transferred to the paper by the transfer unit is correct. Move,
Transport control method. A transfer control method for an image forming apparatus including a transfer unit for transferring an image to paper and a resist roller provided on the upstream side of the transfer unit in the paper transfer direction.
Either a resistless operation in which the tip of the paper is not abutted against the resist roller in the transport direction or a resist operation in which the tip of the paper is abutted against the resist roller based on the paper shape information representing the shape of the paper. After performing the resistless operation, the position of the image transferred to the paper by the transfer unit is aligned with the position of the image transferred by the transfer unit in the width direction. Swing the resist roller so that it is correct.
Transport control method.

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