JP7435070B2 - Image reading device, image forming system - Google Patents

Description

The present invention relates to an image reading device and an image forming system.

In an electrophotographic image forming apparatus, a desired image forming result (printed material) may not be obtained due to various reasons. In order to deal with this, a technique is known that notifies the user of an abnormality in the image formation result.

As a conventional technology, information detected from an image formed on a sheet-like recording medium is compared with data used during image formation, and if an abnormality is detected in the formed image, the user is notified of the occurrence of the abnormality. A defect detection technique for preventing leakage of abnormal images is already known.

In addition, as a conventional technology, while the recording medium is being conveyed above the conveyance path of the recording medium, it is downstream in the conveyance direction from an image reading mechanism that reads an image formed on the recording medium, and upstream in the conveyance direction from the downstream conveyance roller. An image forming apparatus including a rotating member that contacts a recording medium has been disclosed (for example, Patent Document 1).

SUMMARY OF THE INVENTION An object of the present invention is to suppress deterioration in reading accuracy of images formed on a recording medium.

In order to solve the above problems, an image reading device includes a reading mechanism that reads an image formed on a sheet, and a first conveyor that is disposed upstream of the reading mechanism in the conveyance direction of the sheet and that conveys the sheet. a second conveying means disposed on the downstream side of the reading mechanism in the conveying direction and conveying the sheet; and a second conveying means disposed between the first conveying means and the second conveying means and extending along the conveying path. The reading mechanism includes a conveyance path switching member for switching, and a control means for controlling the conveyance operations of the first conveyance means and the second conveyance means , and the reading mechanism is located upstream of the conveyance path switching member in the conveyance direction. The control means transports the sheet in a state where the sheet transport speed by the second transport means is faster than the transport speed of the sheet by the first transport means, and the control means transports the sheet so that the sheet is read by the reading mechanism. reducing the difference between the conveying speed of the sheet by the first conveying means and the conveying speed of the sheet by the second conveying means when the trailing edge of the sheet passes a specified position , based on the image obtained by Features.

According to the present invention, it is possible to suppress a decrease in the accuracy of reading an image formed on a recording medium.

1 is a schematic configuration diagram showing an example of an image forming apparatus that is an embodiment of an image forming system according to the present invention. FIG. 2 is a peripheral schematic diagram showing an embodiment of a transport switching device included in the image forming apparatus. 3 is a flowchart illustrating an operation example of speed variable control according to the first embodiment of the image reading device according to the present invention. It is a figure showing an example of a standard pattern chart concerning a first embodiment. It is a flow chart which shows an example of operation of speed variable control in a second embodiment. It is a flow chart which shows an example of operation of speed variable control in a third embodiment. It is a figure showing an example of a standard pattern chart concerning a fourth embodiment.

Embodiments of an image reading device and an image forming system according to the present invention will be described below with reference to the drawings. The image reading device according to the present embodiment determines whether or not there is any abnormality in the formed image based on the result of reading the image. The image reading device is capable of controlling the image reading state so as to suppress a decrease in image reading accuracy when reading an image in an image reading mechanism.

In devices (e.g., image forming devices) equipped with conventional image defect detection technology by image reading, it is common practice to provide a mechanism for detecting image defects outside the device, but it is common practice to provide a mechanism for reading images inside the device. This may lead to cost reduction and downsizing.

Many conventionally known image forming apparatuses have a function of forming images on both sides of a sheet-like recording medium (hereinafter simply referred to as "recording medium"). Therefore, when an image reading mechanism is provided inside the image forming apparatus, it is necessary to read the front side image and the back side image. In this case, it is desirable to arrange a reading mechanism for reading the image between a fixing section that fixes the image on the recording medium and a path switching section that switches between the front and back sides of the recording medium in the transport direction. Note that depending on the mounting space inside the device, the reading mechanism may be placed immediately before the path switching section.

In conventionally known route switching units, a movable gate member is generally used as a mechanism for switching the conveyance route. In this case, it is necessary to secure a space (operating range) in which the route switching section (gate member) operates around the location where the gate member is arranged. In conventional path switching units, the conveyance path is generally wide in the direction perpendicular to the conveyance direction (vertical direction) in order to ensure the operating range of the path switching unit. That is, a portion of the recording medium conveyance space (conveyance path) includes a portion that extends in the vertical direction. When the print medium passes through this widened conveyance path, slack may occur in the print medium. When slack occurs, the recording medium passing through the path switching section may come into contact with the gate member. If a recording medium on which an image is formed comes into contact with the gate member, the recording medium or the image formed on the recording medium may be damaged, and streak-like uneven gloss may occur in the formed image. There is.

In order to prevent the recording medium from sagging, the sheet being conveyed may be pulled in the conveyance direction to make it "tensioned." Therefore, the rotational speed of the conveyance roller placed downstream of the path switching section is made faster than the rotational speed of the conveyance roller placed upstream of the path switching section, and the A configuration may be adopted in which tension is applied to the recording medium using rollers.

However, when the recording medium is placed in a tensioned state using two conveyance rollers, when the trailing edge of the recording medium passes through the upstream conveyance roller, the tension that was previously applied is lost, causing the trailing edge of the recording medium to become tensioned. The conveying speed at the edge accelerates, and the conveying speed of the entire recording medium is no longer in a steady state. This variation in conveyance speed causes conveyance unevenness. When conveyance unevenness occurs in the recording medium, it becomes a factor that deteriorates image reading accuracy in the sub-scanning direction (conveyance direction) in the reading mechanism.

In the prior art, no consideration has been given to improving the reading accuracy during image reading in consideration of the uneven conveyance that occurs as described above.

The image reading device according to the present invention can improve image reading accuracy for detecting an abnormality in an image formed on a recording medium by suppressing conveyance unevenness during image reading. Specifically, by controlling the operations of transport mechanisms disposed upstream and downstream of a reading mechanism that reads images, uneven transport of the recording medium is suppressed. As a result, the posture of the medium on which the image is formed can be made suitable for reading the image, and the image reading accuracy can be improved. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus (image forming system) including an image reading device according to the present invention will be described below, and then details of the embodiment of the image reading device will be described.

<Configuration of image forming system>
First, the basic configuration of an image forming apparatus 100, which is an embodiment of an image forming system according to the present invention, will be described. The image forming apparatus 100 includes a reading mechanism that is an embodiment of an image reading apparatus according to the present invention, and also includes an image forming mechanism that forms an image on a sheet-shaped recording medium (sheet P). As will be described later, various types of recording media can be used, but in this embodiment, paper is assumed to be used. As shown in FIG. 1, the image forming apparatus 100 forms yellow (Y), magenta (M), cyan (C), and black (K) toner images with two optical writing units 1 (1a, 1b). It is equipped with four process units 2 (2Y, 2M, 2C, 2K) for processing. Also, a paper feed path 30, a pre-transfer transport path 31, a manual paper feed path 32, a manual feed tray 33, a pair of registration rollers 34, a transport belt unit 35, a fixing device 40, a transport switching device 50, a paper ejection path 51, and a paper ejection roller. It also includes a pair 52, a paper discharge tray 53, a paper feed device 7, a retransmission device, and the like.

The paper feeding device 7, which is a feeding means, includes two recording medium storage sections, each consisting of an upper paper feeding cassette 101 and a lower paper feeding cassette 102, which are stacking sections. The upper paper feed cassette 101 and the lower paper feed cassette 102 each accommodate therein a bundle of sheets P, which are sheet-shaped recording media. Then, by rotationally driving the upper paper feed roller 101a and the lower paper feed roller 102a, the top sheet P of the stack of sheets P is fed toward the paper feed path 30. This paper feed path 30 is followed by a pre-transfer transport path 31 for transporting the sheet P immediately before a secondary transfer nip, which will be described later. The sheet P sent out from the upper paper feed cassette 101 or the lower paper feed cassette 102 enters the pre-transfer conveyance path 31 via the paper feed path 30 . Note that the sheet P includes paper media, coated paper, label paper, OHP sheets, films, and the like.

A manual tray 33 is disposed on the side surface of the device housing of the image forming apparatus 100 so as to be openable and closable with respect to the housing, and a bundle of sheets P is manually fed onto the upper surface of the tray in an open state with respect to the housing. The top sheet P of the bundle of manually fed sheets P is sent out toward the pre-transfer conveyance path 31 by the sending roller of the manual feed tray 33.

The image forming apparatus 100 illustrated in FIG. 1 has a so-called tandem configuration, in which four process units 2Y, 2M, 2C, and 2K are arranged along the rotating direction of an intermediate transfer belt 61, which will be described later. have

Each of the process units 2 (2Y, 2M, 2C, 2K) has a drum-shaped photoreceptor 3 (3Y, 3M, 3C, 3K) as a latent image carrier. In addition, each of the process units 2 (2Y, 2M, 2C, 2K) supports various devices arranged around the photoreceptor 3 (3Y, 3M, 3C, 3K) as one unit on a common support. These can be attached to and detached from the main body of the image forming unit.

As the photoreceptor 3Y, a drum-shaped member is used, in which a photosensitive layer is formed by coating a photosensitive organic photosensitive material on a raw tube made of aluminum or the like. However, an endless belt-like one may also be used.

Each process unit 2 has the same configuration except that the toner colors used are different. For example, the Y process unit 2Y includes, in addition to the photoreceptor 3Y, a developing device 4Y for developing an electrostatic latent image formed on the surface of the photoreceptor 3Y as a Y toner image. In addition, it adheres to the charging device 5Y that performs a uniform charging process to uniformly charge the surface of the photoreceptor 3Y that is rotationally driven, and the surface of the photoreceptor 3Y after passing through a primary transfer nip for Y, which will be described later. It also includes a drum cleaning device 6Y for cleaning residual transfer toner.

The two optical writing units 1 (1a, 1b) each include a laser diode, a polygon mirror, various lenses, and the like. The laser diode is driven based on the image information read by a scanner outside the device or the image information sent from the personal computer, and the photoreceptor 3 (of the process unit 2 (2Y, 2M, 2C, 2K) is driven). 3Y, 3M, 3C, 3K) are optically scanned.

Each photoreceptor 3 of the process unit 2 is rotationally driven in the counterclockwise direction in the figure by a driving means. The optical writing unit 1a performs an optical scanning process by irradiating the photoreceptor 3Y and the photoreceptor 3M, which are being driven, with laser light while deflecting them in the rotational axis direction. As a result, electrostatic latent images based on the Y image information and the M image information are formed on the photoreceptor 3Y and the photoreceptor 3M, respectively. Further, the optical writing unit 1b performs optical scanning processing by irradiating the photoreceptor 3C and the photoreceptor 3K, which are being driven, with laser light while being deflected in the rotational axis direction. As a result, electrostatic latent images based on the C image information and the K image information are formed on the photoreceptor 3C and the photoreceptor 3K, respectively.

The developing device 4Y develops the latent image using a two-component developer (hereinafter simply referred to as "developer") containing a magnetic carrier and non-magnetic Y toner. As the developing device 4Y, a type that performs development with a one-component developer that does not contain a magnetic carrier may be used instead of a two-component developer. The developing device 4Y is appropriately replenished with the Y toner in the Y toner bottle 103Y by the Y toner replenishing device.

The drum cleaning device 6Y uses a type in which a cleaning blade made of polyurethane rubber, which is a cleaning member, is pressed against the photoreceptor 3Y, but other types may be used. In order to improve cleaning performance, the image forming apparatus 100 employs a system in which a rotatable fur brush is brought into contact with the photoreceptor 3Y. This fur brush also has the role of scraping off the lubricant from the solid lubricant and applying it to the surface of the photoreceptor 3Y while turning it into fine powder.

A static elimination lamp is disposed above the photoreceptor 3Y, and this static elimination lamp is also a part of the process unit 2Y. The static elimination lamp eliminates static electricity from the surface of the photoreceptor 3Y after passing through the drum cleaning device 6Y by irradiating it with light. The surface of the photoreceptor 3Y from which electricity has been removed is uniformly charged by the charging device 5Y, and then optically scanned by the optical writing unit 1a. The charging device 5Y is rotatably driven while being supplied with a charging bias from a power source. Instead of this method, a scorotron charger method may be adopted in which the photoreceptor 3Y is charged in a non-contact manner.

The process unit 2Y for Y has been described above, but the process units 2M, 2C, and 2K for M, C, and K also have the same configuration as the process unit 2Y.

A transfer unit 60 is arranged below the four process units 2 (2Y, 2M, 2C, 2K). This transfer unit 60 is configured to bring an intermediate transfer belt 61, which is an endless belt stretched between a plurality of support rollers, into contact with the photoconductor 3 (3Y, 3M, 3C, 3K), and then press any one of the support rollers. It is caused to run (endless movement) in the clockwise direction in the figure by the rotational drive of. As a result, primary transfer nips for Y, M, C, and K are formed in which the photoreceptors 3 (3Y, 3M, 3C, and 3K) and the intermediate transfer belt 61 are in contact with each other.

In the vicinity of the primary transfer nip for Y, M, C, and K, primary transfer rollers 62 (62Y, 62M , 62C, 62K) to press the intermediate transfer belt 61 toward the photoreceptors 3 (3Y, 3M, 3C, 3K). A primary transfer bias is applied to each of these primary transfer rollers 62 (62Y, 62M, 62C, 62K) by a power source. As a result, a primary transfer electric field is created in the primary transfer nip for Y, M, C, and K to electrostatically move the toner images on the photoreceptors 3 (3Y, 3M, 3C, and 3K) toward the intermediate transfer belt 61. It is formed.

Toner images are sequentially superimposed at each primary transfer nip on the outer peripheral surface of the intermediate transfer belt 61, which sequentially passes through primary transfer nips for Y, M, C, and K as it moves endlessly clockwise in the figure. primary transfer is performed. By this primary transfer of overlapping, a four-color overlapping toner image (hereinafter referred to as a "four-color toner image") is formed on the outer peripheral surface of the intermediate transfer belt 61.

A secondary transfer roller 72 as a secondary transfer member is disposed below the intermediate transfer belt 61 in the figure. The secondary transfer roller 72 contacts from the belt outer peripheral surface a portion of the intermediate transfer belt 61 where it is wrapped around the secondary transfer backup roller 68 to form a secondary transfer nip. As a result, a secondary transfer nip is formed in which the outer peripheral surface of the intermediate transfer belt 61 and the secondary transfer roller 72 come into contact with each other.

A secondary transfer bias is applied to the secondary transfer roller 72 by a power source. On the other hand, the secondary transfer backup roller 68 in the belt loop is grounded. As a result, a secondary transfer electric field is formed within the secondary transfer nip.

The above-mentioned registration roller pair 34 is disposed on the right side of the secondary transfer nip in the figure, and is rotated at a timing that allows the sheet P sandwiched between the rollers to be synchronized with the four-color toner image on the intermediate transfer belt 61. Send it to the next transfer nip. In the secondary transfer nip, the four-color toner image on the intermediate transfer belt 61 is transferred all at once to the sheet P under the influence of the secondary transfer electric field and nip pressure, and together with the white color of the sheet P, a full-color image is formed.

Transfer residual toner that was not transferred to the sheet P in the secondary transfer nip is attached to the outer peripheral surface of the intermediate transfer belt 61 that has passed through the secondary transfer nip. This transfer residual toner is cleaned by a belt cleaning device 75 that comes into contact with the intermediate transfer belt 61.

The sheet P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 61 and delivered to the conveyor belt unit 35. This conveyor belt unit 35 moves an endless conveyor belt 36 in the counterclockwise direction in the figure by the rotation of the drive roller 37 while being stretched between a drive roller 37 and a driven roller 38 . Then, the sheet P transferred from the secondary transfer nip is held on the tension surface of the outer peripheral surface of the conveyor belt, and is conveyed along with the endless movement of the conveyor belt 36, and is transferred to a fixing device 40 as a fixing means.

In the image forming apparatus 100 according to the present embodiment, a reversing conveyance means is configured by the conveyance switching device 50, the refeed path 54, the switchback path 55, the post-switchback conveyance path 56, and the like. Specifically, the conveyance switching device 50 includes a path switching mechanism that switches the subsequent conveyance destination of the sheet P received from the fixing device 40 between the sheet discharge path 51 and the refeed path 54 . When executing a print job in single-sided mode in which an image is formed only on the first side of the sheet P, the conveyance destination of the sheet P is set to the paper discharge path 51. As a result, the sheet P on which the image is formed only on the first side is sent to the pair of paper discharge rollers 52 via the paper discharge path 51, and is discharged onto the paper discharge tray 53 outside the machine. Further, when executing a print job in duplex mode in which an image is also formed on the second side of the sheet P, when the sheet P with images fixed on both sides is received from the fixing device 40, the conveyance destination of the sheet P is is set in the paper discharge path 51. Thereby, the sheet P with images formed on both sides is discharged onto the paper discharge tray 53 outside the machine. On the other hand, when a sheet P with an image fixed only on the first side is received from the fixing device 40 during execution of a print job in the double-sided mode, the conveyance destination of the sheet P is set to the re-feed path 54.

A switchback path 55 is connected to the refeeding path 54, and the sheet P sent to the refeeding path 54 enters this switchback path 55. Then, when the entire area of the sheet P in the conveyance direction enters the switchback path 55, the conveyance direction of the sheet P is reversed and the sheet P is switched back. In addition to the refeed path 54, the switchback path 55 is connected to a post-switchback transport path 56, and the sheet P that has been switched back enters the post-switchback transport path 56. At this time, the sheet P is turned upside down. Then, the sheet P that has been turned upside down is sent again to the secondary transfer nip via the switchback transport path 56 and the paper feed path 30. The sheet P, on which the toner image has also been transferred to the second surface in the secondary transfer nip, passes through the fixing device 40 and the toner image is fixed on the second surface, and then the sheet P is connected to the conveyance switching device 50 and the paper discharge path 51. The paper is ejected onto a paper ejection tray 53 via a pair of paper rollers 52.

In the image forming apparatus 100, a purge tray 58 from which unnecessary sheets are ejected is provided at the lower left side of the apparatus in the figure. For example, when the apparatus is stopped due to a jam or the like, sheets existing in the apparatus are conveyed to the purge tray 58. Specifically, the refeed path 54 is connected to a tray conveyance path 57 that conveys the sheet to the purge tray 58, and when conveying the sheet to the purge tray 58, the conveyance destination of the sheet P is set to the tray conveyance path 57. . As a result, the sheet conveyed to the refeed path 54 is conveyed to the tray conveyance path 57 before the post-switchback conveyance path 56, and is discharged to the purge tray 58.

The image forming apparatus 100 also includes a control panel 8 that accepts job execution instructions from the user and displays the status of the image forming apparatus 100. Furthermore, in order to perform the above-mentioned operations and operations to be described later, a control section 150 (control means) is provided that controls each piece of hardware in an integrated manner. The control unit 150 has a configuration similar to that of a general computer, and includes, for example, an arithmetic processing unit such as a CPU (Central Processing Unit), a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory. have. In the control unit 150, the arithmetic processing unit executes the program stored in the storage device, thereby realizing a functional configuration that performs the above operations and the operations described below, and with this functional configuration, the sheet P It is possible to control the conveyance state of the

Also, among the above configurations, the configuration including the optical writing unit 1 (1a, 1b), the process unit 2 (2C, 2K, 2M, 2Y), the conveyance belt unit 35, the fixing device 40, and the transfer unit 60 is applied to the sheet. This corresponds to an image forming section (image forming means) that forms an image.

Next, the configuration of the transport switching device 50 and devices provided in its vicinity will be described with reference to FIG. 2.

In the image forming apparatus 100, the sheet P on which the image has been fixed by the fixing device 40 passes through a sheet cooling device 84 shown in FIG. Thereafter, when the sheet P passes through an image reading section 80 (reading mechanism) disposed on the downstream side in the transport direction with respect to the sheet cooling device 84, the image formed on the sheet P is read by the image reading section 80. The read image is subjected to defect detection in the control unit 150 to see if there is any abnormality. Here, the image reading section 80 is arranged upstream of the conveyance path switching member 85.

The conveyance path switching member 85 is a gate member that switches the conveyance path. By switching the conveyance path by the conveyance path switching member 85, the sheet P is conveyed to the paper discharge path 51 or the refeed path 54. When the sheet P is conveyed to the refeed path 54, the conveyance path switching member 85 rotates in the direction of the arrow 85b to switch the conveyance path.

By providing the image reading section 80 upstream of the conveyance path switching member 85, when executing the "single-sided print mode" which is an operation mode in which an image is formed only on one side of the sheet P, an image is formed on the first side of the sheet P. It is possible to detect defects in images. Furthermore, when executing the "double-sided print mode" which is an operation mode in which images are formed on both sides of the sheet P, images are formed on the first side of the sheet P and the reversed second side via the conveyance path 56 after switchback. Defects can be detected in the image.

Further, in the conveyance switching device 50, an upstream conveyance roller 81 (first conveyance means) is arranged on the upstream side in the conveyance direction of the sheet P with respect to the conveyance path switching member 85 and the image reading section 80. Further, a downstream conveyance roller 82 (second conveyance means) is arranged downstream of the conveyance path switching member 85 and the image reading section 80 in the conveyance direction of the sheet P.

<Issues with conventional technology>
Here, the problems in the prior art will be explained again along with the configuration of the transport switching device 50. As illustrated in FIG. 2, since the conveyance path switching member 85 rotates in the direction of the arrow 85b, in order to ensure the operating range of the conveyance path switching member 85, the direction perpendicular to the conveyance direction (in FIG. It becomes necessary to widen the conveyance path in the direction of arrow 85b). Referring to FIG. 2, the conveyance path provided with the conveyance path switching member 85 is wider than the conveyance paths of the paper discharge path 51 and the refeed path 54.

When the sheet P passes through this vertically expanding conveyance path, the sheet P may sag because the posture of the sheet P (the posture during conveyance) is not regulated by the conveyance path.

Therefore, in the conveyance switching device 50 included in the image forming apparatus 100, in order to prevent the sheet P from sagging, the rotation speed of the downstream conveyance roller 82 located on the downstream side of this widening conveyance path is changed to the upstream side. The control unit 150 controls the upstream conveying roller 81 to be faster than the upstream conveying roller 81 located at . By making the rotational speed of the downstream conveyance roller 82 faster than the rotational speed of the upstream conveyance roller 81, tension can be applied to the sheet P to put it in a "tensioned state" and sag can be prevented.

When performing defect detection processing using conventional defect detection technology, the rotational speed of each conveyance roller placed upstream and downstream of the reading mechanism is generally kept at a constant speed. It has a rotating configuration. In the case of such a constantly rotating conveyance roller, when the trailing edge of the sheet P in the conveyance direction passes through the upstream conveyance roller 81 and the "tensioned state" is released, the sheet P that had been stretched due to tension tries to return to its original position. A restoring force is generated by a change in the force applied to the sheet P. This restoring force accelerates the conveyance speed of the rear end portion of the sheet P in the conveyance direction. Therefore, in the conventional apparatus, the conveyance speed of the rear end of the sheet P relative to the reading mechanism temporarily increases. That is, during the conveyance by the rollers that were rotating steadily, the conveyance speed on the rear end side of the sheet P temporarily increases, causing conveyance unevenness. Since the sheet P passes through the image reading section 80 in a state where this conveyance unevenness has occurred, it becomes a factor that deteriorates the image reading accuracy in the sub-scanning direction (conveyance direction) when reading the image formed on the sheet P.

<First embodiment>
Embodiments of an image reading device according to the present invention will be described below. As an embodiment of the image reading device, the transport switching device 50 including the above-described image reading section 80, transport path switching member 85, upstream transport roller 81, and downstream transport roller 82 is used. The conveyance switching device 50 includes an image reading section 80 as a reading mechanism, a control section 150, and an upstream conveyance roller 81 and a downstream conveyance roller 82 whose operating conditions are changed by the control section 150 to control the conveyance speed of the sheet P. It is equipped with the following.

In order to solve the problems mentioned in the description of the conventional defect detection technology, in the first embodiment of the image reading device according to the present invention, the timing at which the conveyance timing sensor 83 provided at a specified position detects the trailing edge of the sheet P is determined. Taking this opportunity, the rotational speeds of the upstream conveyance roller 81 and the downstream conveyance roller 82 are changed. The rotational speed is changed by changing the set value of the rotational speed of the upstream conveyance roller 81 and the downstream conveyance roller 82 by the control unit 150. This makes the difference in rotational speed of the transport rollers, which are arranged at positions sandwiching the reading mechanism that reads the image formed on the sheet P, among the plurality of transport rollers that determine the transport speed of the sheet P, variable. By controlling this rotational speed difference, a decrease in the accuracy of reading an image formed on a recording medium is suppressed. Hereinafter, speed change control of the upstream conveyance roller 81 and the downstream conveyance roller 82 will be explained using FIGS. 3 and 4.

3(a) and 3(a) are flowcharts showing a first embodiment of speed change control that can be executed in the transport switching device 50. In the first embodiment, a speed change value is calculated using a reference pattern chart for speed adjustment.

First, a system administrator, maintenance person, etc. sets a sheet P in the upper paper cassette 101 or 102, and then changes the operation mode of the image forming apparatus 100 to the normal actual print mode (specified by the user) via the control panel 8. The mode is switched from a mode in which an image is formed on the sheet P to a mode in which an image is formed using a reference pattern for speed adjustment. Then, when the system administrator or the like presses the start button in the control panel 8, an arbitrary number of sheets P are fed from the upper paper feed cassette 101 or the lower paper feed cassette 102, and the image forming means forms the reference pattern chart. It is transferred onto the sheet P to form a reference pattern (S301).

FIG. 4A is an example of a reference pattern chart that is a chart image used in the first embodiment. FIG. 4(a) illustrates an ideally formed reference pattern chart. Therefore, a plurality of marks (referred to as a "reference pattern") are formed at equal intervals in the conveyance direction of the sheet P. The reference patterns are lines perpendicular to the transport direction, and a plurality of reference patterns are formed in parallel. The interval between these reference patterns is defined as an actual interval Lr. That is, the interval between the reference patterns ideally formed on the sheet P is defined as the actual interval Lr. Note that the example shown in FIG. 4A is just an example, and it is sufficient that a plurality of reference marks are provided at intervals based on a certain rule in the transport direction.

The sheet P on which the reference pattern chart is formed is conveyed to the image reading unit 80, which detects (images) it and outputs the detection result (imaging result) to the control unit 150 (S302).

Here, the difference between the reference pattern chart formed on the sheet P and the image detected by the image reading section 80 will be explained using FIG. 4(b). The reference pattern charts are provided at regular intervals Lr in the transport direction, and the reference patterns extracted from the actual intervals Lr of the reference patterns and the reference pattern chart detected by the image reading section 80 When compared with the interval (detection interval Ll shown by a broken line), they do not match, especially at the rear end of the sheet P, and a difference occurs. For example, when tension is applied to the sheet P by the upstream conveyance roller 81 and the downstream conveyance roller 82, the detected interval Ll is detected to be longer than the actual interval Lr, especially at the rear end of the sheet P. Ru. Furthermore, when the trailing edge of the sheet P passes the upstream conveyance roller 81, the tension that had been applied up to that point disappears, and the restoring force of the sheet P increases the advancing speed of the trailing edge of the sheet P, so that the actual distance Lr is reduced. On the other hand, the detection interval Ll is detected as being in a shorter state.

The control unit 150 performs arithmetic processing based on the difference between the detection interval Ll and the actual interval Lr, thereby determining a suitable upstream rotational speed change value Vc1 of the upstream conveyance roller 81 and a suitable downstream rotational speed change of the downstream conveyance roller 82. A value Vc2 is calculated (S303). The upstream rotational speed change value Vc1 and the downstream rotational speed change value Vc2 are the rotational speeds (roller rotational speeds) of the upstream conveyance roller 81 and the downstream conveyance roller 82 in order to reduce the difference between the actual interval Lr and the detected interval Ll. be. The upstream rotational speed change value Vc1 and the downstream rotational speed change value Vc2 are values such that the difference in rotational speed between the upstream conveyance roller 81 and the downstream conveyance roller 82 is smaller than during steady rotation. Further, the upstream conveyance roller 81 and the downstream conveyance roller 82 change the upstream rotational speed change value Vc1 from the previous speed (rotational speed of steady rotation) to the timing when the conveyance timing sensor 83 detects the trailing edge of the sheet P. The rotation speed is switched to the rotation speed based on the downstream rotation speed change value Vc2. Therefore, the timing for controlling changes in the rotational speeds of the upstream conveyance roller 81 and the downstream conveyance roller 82 also depends on the relative positions of the image reading section 80 and the conveyance timing sensor 83. Therefore, the conveyance distance from the conveyance timing sensor 83 to the upstream conveyance roller 81, the distance between the upstream conveyance roller 81 and the image reading section 80, the distance between the upstream conveyance roller 81 and the downstream conveyance roller 82, etc. are also determined by the upstream rotation speed change value. It is included in the parameters related to calculation of Vc1 and downstream rotational speed change value Vc2. Then, the control unit 150 stores the upstream rotation speed change value Vc1 and the downstream rotation speed change value Vc2, which are the calculation results, in the storage device, and ends the process of FIG. 3(a).

Next, the speed change control in the actual print mode after the upstream rotational speed change value Vc1 and the downstream rotational speed change value Vc2 are calculated will be described using the flowchart of FIG. 3(b).

When the sheet P is supplied from the upper paper feed cassette 101 or the lower paper feed cassette 102, the image forming unit forms an image specified by the user on the sheet P (S310). Thereafter, triggered by the timing at which the conveyance timing sensor 83 detects the trailing edge of the sheet P (S311), the control unit 150 changes the rotation speed of the upstream conveyance roller 81 to the upstream rotation speed change value Vc1, and also changes the rotation speed of the upstream conveyance roller 81 to the downstream rotation speed change value Vc1. The rotation speed of the conveyance roller 82 is changed to the downstream rotation speed change value Vc2 (S312). With this speed change control, uneven conveyance of the sheet P can be suppressed, and a decrease in image reading accuracy in the sub-scanning direction (conveyance direction) in the image reading section 80 can be suppressed.

<Second embodiment>
Next, a second embodiment of speed change control that can be executed in the transport switching device 50 will be described. The extent to which the sheet P sag at the location where the transportation path switching member 85 is provided, that is, the location where the transportation path becomes wide, also depends on the thickness of the sheet P (the stiffness of the sheet P). do. In the second embodiment, the rotational speed of the upstream conveyance roller 81 and the rotational speed of the downstream conveyance roller 82 are changed in consideration of the thickness of the sheet P (referred to as sheet thickness). FIG. 5 is a flowchart of speed change control according to the second embodiment.

In the second embodiment, the control unit 150 stores table data in which the sheet thickness is associated with the rotational speed of the downstream conveyance roller 82 (second downstream rotational speed change value Vc3) that is changed in consideration of the sheet thickness. It is assumed that the information is stored in advance in the storage means of the computer.

The control unit 150 according to the second embodiment acquires and sets the sheet thickness of the sheet P on which image formation is performed (S501). This sheet thickness information is based on a value specified by the user when executing an image forming job via the control panel 8, for example. For example, when the type of sheet P on which the image is to be formed is specified, if the sheet thickness specified by the type is stored in the storage unit of the control unit 150, the thickness is determined by the type of the sheet P. Alternatively, it may be determined by the size of the sheet P. Alternatively, it may be set in advance as an initial value. Note that the conveyance switching device 50 may be provided with a detection means for detecting the sheet thickness, and the sheet thickness may be acquired from the detection means.

Once the sheet thickness is acquired, the control unit 150 starts an image forming job (S502). Triggered by the timing at which the conveyance timing sensor 83 detects the rear end of the sheet P (S503), the control unit 150 refers to the table data stored in the storage means based on the sheet thickness acquired in S501, and A second rotational speed change value Vc3 is obtained. Note that the operation for obtaining the second downstream rotational speed change value Vc3 may be performed before S503. Then, the control unit 150 changes the rotation speed of the downstream conveyance roller 82 based on the second downstream rotation speed change value Vc3 (S504). Note that the second downstream rotational speed change value Vc3 is a value that reduces the difference in rotational speed between the upstream conveyance roller 81 and the downstream conveyance roller 82.

According to the second embodiment, it is possible to suppress uneven conveyance of the sheet P depending on the sheet thickness, and it is possible to suppress a decrease in image reading accuracy in the sub-scanning direction (conveyance direction) in the image reading section 80. . Although the example of implementation here takes into consideration the sheet thickness, the amount of slack also depends on the type and material of the sheet, such as paper, coated paper, label paper, OHP sheet, film, etc. Therefore, table data in which an identifier that uniquely identifies the type, material, etc. is associated with the downstream rotation speed second change value Vc3 is provided in advance in the control unit 150, and table data is provided in advance in which the identifier that uniquely identifies the type, material, etc. is associated with the downstream rotation speed second change value Vc3. Accordingly, the rotation speed of the downstream conveyance roller 82 may be changed by performing an operation similar to the above process.

Furthermore, according to the second embodiment, compared to the first embodiment, there is no need to form a reference pattern chart or the like on the sheet P and read it. Therefore, the consumption of paper and toner for forming the reference pattern chart etc. can be suppressed, and the time required for reading the chart can be saved.

<Third embodiment>
In the first embodiment, an image (reference pattern chart) in which a specific mark (reference pattern) is formed at a constant actual interval Lr in the transport direction is read, and a detection interval Ll of marks extracted from the read reference pattern chart is read. Based on this, changes in conveyance speed were controlled. In the third embodiment, instead of using images formed at regular intervals like a reference pattern chart, changes in the conveyance speed are controlled by reading specific images formed at irregular intervals.

FIGS. 6A and 6A are flowcharts showing a third embodiment of speed change control that can be executed in the transport switching device 50. FIG. In the third embodiment, instead of using a standard pattern chart for speed adjustment, as illustrated in FIG. The speed change value shall be calculated.

In the third embodiment, since a dedicated reference pattern for calculating the speed change value is not used, there is no need to switch the operation mode of the image forming apparatus 100 as in the first embodiment. However, if the already calculated speed change value is not stored in the storage device of the control unit 150, the operation mode is changed once during the first operation, and the image forming process of the image to be formed specified by the user is performed. It is sufficient to operate so as to calculate the speed change value while executing the program. If the speed change value has already been calculated, it is not necessary to execute the process related to the flowchart of FIG. 6(a) described below.

First, the flow of processing when calculating a speed change value will be explained. As shown in FIG. 6A, a user, a system administrator, or the like executes an image forming job (S601). An example of the image formed at this time is illustrated in FIG. 7(a). FIG. 7(a) includes a plurality of images. Among the multiple locations included in this image, the location suitable for calculating the speed change value is the image on the upstream side in the transport direction. Therefore, the control unit 150 designates, as a "judgment area", an area where feature points are easily detected, from among the original data (image forming data) of the image to be formed, on the upstream side in the transport direction. Then, an area used for calculating the speed change value is specified as a characteristic area in the image included in the specified determination area. The interval between adjacent ones of the plurality of identified characteristic regions is calculated (S602).

The control unit 150 automatically extracts and specifies the characteristic region. This automatic extraction process is executed by searching and extracting from the image, for example, locations where density, brightness, etc. change significantly among pixels included in the original data (image data) of the image to be formed.

Here, the determination area, feature area, and feature point will be explained. As illustrated in FIG. 7A, among a plurality of locations included in the image to be formed on the sheet P, three locations on the upstream side in the conveyance direction are defined as determination areas. Then, a region (feature region) serving as a feature point in the image included in the determination region is specified. In the example of FIG. 7, the lower left edge of the character "A" in the determination area, the lower left edge of the character "B" in the determination area, and the lower right edge of the character "C" in the determination area Let each part be a feature region.

Then, the distance between adjacent feature regions in the transport direction is calculated by the calculation process of the control unit 150. Here, the calculated intervals are defined as "first actual interval Lr'" and "second actual interval Lr'', as shown in FIG. 7(b).

The sheet P on which the image to be formed is formed is conveyed to the image reading unit 80, which detects (images) this and outputs the detection result (imaging result) to the control unit 150 (S603).

Here, the difference between the formed image formed on the sheet P and the image detected by the image reading section 80 will be explained using FIG. 7(b). The image to be formed includes a predetermined interval (first actual interval Lr', second actual interval Lr'') with respect to the conveyance direction. If the same interval is extracted from the non-formed image detected by the image reading unit 80, the interval (first detection interval Ll' and second detection interval Ll'') can be specified from the original data. They are different from the intervals (first actual interval Lr', second actual interval Lr''). In particular, the rear end portion of the sheet P (upstream side in the conveyance direction) does not match, and a difference occurs.

This is because when the state in which tension is applied to the sheet P by the upstream conveyance roller 81 and the downstream conveyance roller 82 changes to the state in which the tension disappears, the traveling speed of the rear end of the sheet P increases, causing slack. Become. Therefore, immediately after the tension disappears, the first detection interval Ll' is longer than the first actual interval Lr', and the second detection interval Ll'' is longer than the second actual interval Lr''. It's growing.

The control unit 150 identifies a characteristic region included in the determination region used for extracting the actual interval (S604), and calculates a first detection interval Ll' and a second detection interval Ll'' (S605).

Next, an upstream rotational speed change value Vc4, which is a preferred rotational speed setting value of the upstream conveyance roller 81, and a downstream rotational speed change value Vc5, which is a suitable rotational speed setting value of the downstream conveyance roller 82, are calculated ( S606). The upstream rotation speed change value Vc4 and the downstream rotation speed change value Vc5 are the difference between the first actual interval Lr' and the first detection interval Ll', and the difference between the second actual interval Lr'' and the second detection interval Ll''. This is the rotational speed of the upstream conveyance roller 81 and the downstream conveyance roller 82 (roller rotational speed) for reducing the .

The upstream rotational speed change value Vc4 and the downstream rotational speed change value Vc5 are also values such that the difference in rotational speed between the upstream conveyance roller 81 and the downstream conveyance roller 82 is smaller than during steady rotation. Further, the upstream conveyance roller 81 and the downstream conveyance roller 82 change the upstream rotational speed change value Vc1 from the previous speed (rotational speed of steady rotation) to the timing when the conveyance timing sensor 83 detects the trailing edge of the sheet P. The rotation speed is switched to the rotation speed based on the downstream rotation speed change value Vc2. Therefore, the timing for controlling changes in the rotational speeds of the upstream conveyance roller 81 and the downstream conveyance roller 82 also depends on the relative positions of the image reading section 80 and the conveyance timing sensor 83. Therefore, the conveyance distance from the conveyance timing sensor 83 to the upstream conveyance roller 81, the distance between the upstream conveyance roller 81 and the image reading section 80, the distance between the upstream conveyance roller 81 and the downstream conveyance roller 82, etc. are also determined by the upstream rotation speed change value. It is included in the parameters related to the calculation of Vc4 and the downstream rotation speed change value Vc5. Then, the control unit 150 stores the upstream rotation speed change value Vc4 and the downstream rotation speed change value Vc5, which are the calculation results, in the storage device, and ends the process of FIG. 6(a).

Next, speed change control in the actual print mode after the upstream rotation speed change value Vc4 and the downstream rotation speed change value Vc5 are calculated will be described. This control, as shown in FIG. 6(b), is similar to the control in the first embodiment already described, so detailed explanation will be omitted (see FIG. 3(b)).

With this speed change control, uneven conveyance of the sheet P can be suppressed, and a decrease in image reading accuracy in the sub-scanning direction (conveyance direction) in the image reading section 80 can be suppressed.

Note that the aspects of the first embodiment, second embodiment, and third embodiment described above may be combined with each other. For example, the user may be able to select which mode to control the conveyance operation of each roller.

The image reading device includes an upstream conveyance roller 81 , a downstream conveyance roller 82 , an image reading section 80 , and a control section 150 . Further, in each of the above embodiments, the image reading device is described as being for detecting image defects, but the application is not limited to this. For example, the image reading device of this embodiment may be applied to detect the density or position of an image.

The image forming means may be of an inkjet type, and a belt-shaped conveyance belt may be used instead of the conveyance roller.

As a method of changing the speed difference between the upstream and downstream roller pairs, a method of changing the rotational speed of both the upstream conveyance roller 81 and the downstream conveyance roller 82 as in the first embodiment may be adopted, or A method of changing only the rotation speed of the downstream conveyance roller 82 may be adopted as in the embodiment. Alternatively, a method of changing only the rotational speed of the upstream conveyance roller 81 may be adopted. That is, the control unit 150 may be configured to control the conveyance operation of each roller so as to change the difference in conveyance speed between the upstream conveyance roller 81 and the downstream conveyance roller 82.

As described above, according to the present embodiment, it is possible to suppress a decrease in image reading accuracy when reading an image formed on a sheet.

1: Optical writing unit 1a: Optical writing unit 1b: Optical writing unit 2: Process unit 3: Photoconductor 3C: Photoconductor 4Y: Developing device 5Y: Charging device 6Y: Drum cleaning device 7: Paper feeding device 8: Control panel 30 : Paper feed path 31 : Pre-transfer conveyance path 32 : Manual feed path 33 : Manual feed tray 34 : Registration roller pair 35 : Conveyance belt unit 36 : Conveyance belt 37 : Drive roller 38 : Followed roller 40 : Fixing device 50 : Conveyance switching device 51 : Paper discharge path 52 : Paper discharge roller pair 53 : Paper discharge tray 54 : Refeed path 55 : Switchback path 56 : Post-switchback conveyance path 57 : Tray conveyance path 58 : Purge tray 60 : Transfer unit 61 : Intermediate transfer belt 62 : Primary transfer roller 68 : Secondary transfer backup roller 72 : Secondary transfer roller 75 : Belt cleaning device 80 : Image reading section 81 : Upstream conveyance roller 82 : Downstream conveyance roller 83 : Conveyance timing sensor 84 : Sheet cooling Device 85: Conveyance path switching member 85b: Arrow 100: Image forming device 101: Upper paper feed cassette 101a: Upper paper feed roller 102: Lower paper feed cassette 102a: Lower paper feed roller 150: Control unit

Japanese Patent Application Publication No. 2015-220471

Claims (6)

a reading mechanism that reads images formed on the sheet;
a first conveyance means that is disposed upstream of the reading mechanism in the conveyance direction of the sheet and conveys the sheet;
a second conveyance means that is arranged downstream of the reading mechanism in the conveyance direction and conveys the sheet;
a conveyance path switching member that is arranged between the first conveyance means and the second conveyance means and switches the conveyance path;
a control means for controlling the conveyance operations of the first conveyance means and the second conveyance means;
including;
The reading mechanism is arranged upstream of the transport path switching member in the transport direction,
The control means transports the sheet in a state where the speed at which the sheet is transported by the second transport means is higher than the speed at which the sheet is transported by the first transport means, and the controller transports the sheet based on the image read by the reading mechanism. reducing the difference between the conveyance speed of the sheet by the first conveyance means and the conveyance speed of the sheet by the second conveyance means when the trailing edge of the sheet passes a prescribed position ;
An image reading device characterized by: The control means changes the difference based on reading results at a plurality of locations included in the image read by the reading mechanism and corresponding to mutually different positions in the transport direction. The image reading device according to claim 1. The image formed on the sheet is a chart image in which marks are arranged in the transport direction,
The image reading device according to claim 2, wherein the control means changes the difference based on a result of reading the chart image by the reading mechanism. The marks are formed at regular intervals in the transport direction,
4. The image reading apparatus according to claim 3, wherein the control means changes the difference based on an interval between the marks read by the reading mechanism. 3. The control means changes the difference based on the reading results of characteristic regions at mutually different positions in the transport direction among a plurality of locations included in the image read by the reading mechanism. 2. The image reading device according to 2. an image forming means for forming an image on the sheet;
An image forming system comprising: an image reading device according to any one of claims 1 to 5 , which reads a sheet on which an image is formed by the image forming means.