Patent Grant
11345558
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application Nos. 2017-230434, filed on Nov. 30, 2017, and 2018-217148, filed on Nov. 20, 2018, in the Japan Patent Office, the entire disclosure of each of which is hereby incorporated by reference herein.
This disclosure relates to a sheet conveying device that feeds a conveyance target medium, an image forming apparatus including the sheet conveying device, a method of conveying a conveyance target medium, and a method of forming an image on a conveyance target medium using the method of conveying the conveyance target medium.
Various sheet conveying devices that convey a conveyance target medium are known to convey sheets such as papers and original documents in an image forming apparatus such as a copier and a printer.
In general, such sheet conveying devices are known that, when a sheet is conveyed to an image forming device or an image transfer device, the sheet under conveyance is abutted against a nip region of a pair of sheet conveying rollers that is stopped so as to correct an angular displacement of the sheet, and then the pair of sheet conveying rollers starts rotating at a predetermined timing to convey the sheet to a target position. However, a method of abutting the sheet to the nip region of the pair of sheet conveying rollers causes the sheet to stop temporarily, and therefore the productivity degrades (the image forming speed decreases).
In order to address this inconvenience and correct positional deviations of a sheet without degrading the productivity, a known sheet conveying device has been proposed that a pair of rollers is driven in a direction opposite to the direction of a positional deviation of the sheet while conveying the sheet so that the positional deviation of the sheet is corrected without stopping conveyance of the sheet.
However, when the positional deviation of a sheet is corrected while the sheet is being conveyed, the position of the leading end of the sheet changes, and therefore an amount of time that the leading end of the sheet reaches a predetermined target position varies. Consequently, if the sheet is conveyed at a predetermined conveying speed, the timing at which the sheet reaches the target position is shifted, which causes an inconvenience that the sheet cannot be conveyed with high accuracy.
In order to solve the shift of the timing caused by the correction of the positional deviation of the sheet, the known sheet conveying device calculates the position of the leading end of the sheet after the correction of the positional deviation of the sheet based on the positional deviation amount of the sheet, and the sheet conveying speed is adjusted based on the calculation result.
However, the known sheet conveying device detects the angular displacement of the sheet for one time, and therefore the correction of the angular and lateral displacements of the sheet is also performed for one time. Consequently, when the sheet further shifts after the correction of the positional deviation of the sheet the known sheet conveying device cannot convey the sheet with high accuracy.
At least one aspect of this disclosure provides a sheet conveying device including a position detector, a position adjuster, and circuitry. The position detector is configured to detect a position of a side end of a conveyance target medium. The position adjuster is configured to, based on a detection of the position of the side end of the conveyance target medium detected by the position detector, move in at least one of a width direction of the conveyance target medium and a rotation direction of the conveyance target medium within a plane of conveyance of the conveyance target medium and repeatedly adjust the position of the side end of the conveyance target medium, while the conveyance target medium is being conveyed. The circuitry is configured to change a conveying speed of the conveyance target medium, according to a change of the position of the side end of the conveyance target medium after adjusted by the position adjuster.
Further, at least one aspect of this disclosure provides an image forming apparatus including the above-described sheet conveying device.
Further, at least one aspect of this disclosure provides a sheet conveying device including a plurality of position sensors, a position adjuster, and circuitry. The plurality of position sensors are configured to detect a position of a side end of a conveyance target medium. The position adjuster is configured to, based on a detection of the position of the side end of the conveyance target medium detected by the plurality of position sensors, move in at least one of a width direction of the conveyance target medium and a rotation direction of the conveyance target medium within a plane of conveyance of the conveyance target medium and adjust the position of the side end of the conveyance target medium, while the conveyance target medium is being conveyed. The circuitry is configured to change a conveying speed of the conveyance target medium, according to a change of the position of the side end of the conveyance target medium after adjusted by the position adjuster.
Further, at least one aspect of this disclosure provides an image forming apparatus including the above-described sheet conveying device.
Further, at least one aspect of this disclosure provides a method of conveying a conveyance target medium including detecting a position of a side end of a conveyance target medium, moving in at least one of a width direction of the conveyance target medium and a rotation direction of the conveyance target medium within a plane of conveyance of the conveyance target medium while the conveyance target medium is being conveyed, based on a detection of the position of the conveyance target medium, adjusting the position of the side end of the conveyance target medium repeatedly while the conveyance target medium is being conveyed, based on the detection of the position of the conveyance target medium, and changing a conveying speed of the conveyance target medium, according to a change of the position of the side end of the conveyance target medium after adjusted by the adjusting.
Further, at least one aspect of this disclosure provides a method of forming an image on a conveyance target medium using the above-described method of conveying the conveyance target medium to convey the conveyance target medium and form an image on the conveyance target medium.
An exemplary embodiment of this disclosure will be described in detail based on the following figured, wherein:
It will be understood that if an element or layer is referred to as being “on”, “against”, “connected to” or “coupled to” another element or layer, then it can be directly on, against, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, if an element is referred to as being “directly on”, “directly connected to” or “directly coupled to” another element or layer, then there are no intervening elements or layers present. Like numbers referred to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements describes as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors herein interpreted accordingly.
Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that these elements, components, regions, layer and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure.
The terminology used herein is for describing particular embodiments and examples and is not intended to be limiting of exemplary embodiments of this disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Descriptions are given, with reference to the accompanying drawings, of examples, exemplary embodiments, modification of exemplary embodiments, etc., of an image forming apparatus according to exemplary embodiments of this disclosure. Elements having the same functions and shapes are denoted by the same reference numerals throughout the specification and redundant descriptions are omitted. Elements that do not demand descriptions may be omitted from the drawings as a matter of convenience. Reference numerals of elements extracted from the patent publications are in parentheses so as to be distinguished from those of exemplary embodiments of this disclosure.
This disclosure is applicable to any image forming apparatus and is implemented in the most effective manner in an electrophotographic image forming apparatus.
In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this disclosure is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes any and all technical equivalents that have the same function, operate in a similar manner, and achieve a similar result.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, preferred embodiments of this disclosure are described.
Descriptions are given of an example applicable to a sheet conveying device and an image forming apparatus incorporating the sheet conveying device.
It is to be noted that elements (for example, mechanical parts and components) having the same functions and shapes are denoted by the same reference numerals throughout the specification and redundant descriptions are omitted.
The image forming apparatus 100 may be a copier, a facsimile machine, a printer, a multifunction peripheral or a multifunction printer (MFP) having at least one of copying, printing, scanning, facsimile, and plotter functions, or the like. According to the present example, the image forming apparatus 100 is an inkjet printer that forms toner images on recording media with ink.
It is to be noted in the following examples that: the term “image forming apparatus” indicates an apparatus in which an image is formed on a recording medium such as paper, OHP (overhead projector) transparencies, OHP film sheet, thread, fiber, fabric, leather, metal, plastic, glass, wood, and/or ceramic by attracting developer or ink thereto; the term “image formation” indicates an action for providing (i.e., printing) not only an image having meanings such as texts and figures on a recording medium but also an image having no meaning such as patterns on a recording medium; and the term “sheet” is not limited to indicate a paper material but also includes the above-described plastic material (e.g., a OHP sheet), a fabric sheet and so forth, and is used to which the developer or ink is attracted. In addition, the “sheet” is not limited to a flexible sheet but is applicable to a rigid plate-shaped sheet and a relatively thick sheet. The term “sheet” also functions as a conveyance target medium.
Further, size (dimension), material, shape, and relative positions used to describe each of the components and units are examples, and the scope of this disclosure is not limited thereto unless otherwise specified.
Further, it is to be noted in the following examples that: the term “sheet conveying direction” indicates a direction in which a recording medium travels from an upstream side of a sheet conveying path to a downstream side thereof; the term “width direction” indicates a direction basically perpendicular to the sheet conveying direction.
Overall Configuration.
The inkjet type image forming apparatus 100 according to the present embodiment mainly includes a sheet feeding device 1, an image forming device 2, a drying device 3, and a sheet output device 4. In the inkjet type image forming apparatus 100, an image is formed by ink, which is a liquid for image formation, in the image forming device 2 on a sheet P as a sheet supplied from the sheet feeding device 1. Then, after the ink adhered on the sheet P is dried in the drying device 3, the sheet P is discharged from the sheet output device 4.
Further, when performing a duplex printing operation, after the image is formed on the front face of the sheet P in the image forming device 2, the sheet is dried by the drying device 3, and the sheet P is not discharged but is conveyed to a sheet reverse and conveyance passage 150. By passing through the sheet reverse and conveyance passage 150, the sheet P is reversed in the sheet reverse and conveyance passage 150 and conveyed to the image forming device 2 again. After an image is formed on a back face of the sheet P in the image forming device 2, the sheet P is dried in the drying device 3 and is discharged from the sheet output device 4.
Sheet Feeding Device.
The sheet feeding device 1 mainly includes a sheet feed tray 5, a sheet feeder 6 and a sheet conveying device 7. The sheet feed tray 5 is a sheet loader on which multiple sheets P are loaded thereon. The sheet feeder 6 separates and feeds the multiple sheets P one by one from the sheet feed tray 5. The sheet conveying device 7 conveys the sheet P to the image forming device 2. The sheet feeder 6 may be a sheet feeding unit that includes rollers, a sheet feeding unit employing an air suction method, and any other sheet feeding units. The sheet P fed from the sheet feed tray 5 by the sheet feeder 6 is conveyed to the image forming device 2 by the sheet conveying device 7.
Image Forming Device.
The image forming device 2 mainly includes a transfer cylinder 8, a sheet holding drum 9, an ink discharging device 10 and a transfer cylinder 11. The transfer cylinder 8 functions as a first conveyance rotary body to receive and transfer the fed sheet P to the sheet holding drum 9. The sheet holding drum 9 functions as a second conveyance rotary body to hold (grip) and convey the sheet P conveyed by the transfer cylinder 8 on an outer circumferential surface thereof. The ink discharging device 10 discharges ink toward the sheet P held by the sheet holding drum 9. The transfer cylinder 11 functions as a third conveyance rotary body to transfer the sheet P conveyed by the sheet holding drum 9 to the drying device 3.
After the sheet P is conveyed from the sheet feeding device 1 to the image forming device 2, a gripper 16 that is rotatable as a handle mounted on a surface of the transfer cylinder 8 grips the leading end of the sheet P, so that the sheet P is conveyed along with the surface movement of the transfer cylinder 8. The sheet P conveyed by the transfer cylinder 8 is transferred to the sheet holding drum 9 at an opposing position where the sheet P is brought to face the sheet holding drum 9.
A gripper similar to the gripper 16 on the transfer cylinder 8 is provided on the surface of the sheet holding drum 9, so that the leading end of the sheet P is gripped by the gripper on the sheet holding drum 9. Multiple air drawing openings are dispersedly formed on the surface of the sheet holding drum 9, and a suction airflow directing toward the inside of the sheet holding drum 9 by an air drawing device 12 is generated at each air drawing opening. The leading end of the sheet P that is transferred from the transfer cylinder 8 to the sheet holding drum 9 is gripped by the gripper. At the same time, the sheet P is sucked on the surface of the sheet holding drum 9 due to the suction airflow and is conveyed along with the surface movement of the sheet holding drum 9.
The ink discharging device 10 according to the present embodiment includes liquid discharging heads 10C, 10M, 10Y and 10K having different colors of C (cyan), M (magenta), Y (yellow), and K (black), respectively, to form an image. The configuration of the liquid discharging heads 10C, 10M, 10Y and 10K is not limited thereto and any other configuration may be applied as long as each liquid discharging head ejects liquid. Another liquid discharging head that ejects special ink such as white, gold and silver may be added to the ink discharging device 10 or yet another liquid discharging head that ejects a surface coating liquid that does not form an image may be provided to the ink discharging device 10.
Respective discharging operations of the liquid discharging heads 10C, 10M, 10Y and 10K of the ink discharging device 10 are individually controlled by respective drive signals according to image data. When a sheet P held by the sheet holding drum 9 passes by an opposing region facing the ink discharging device 10, respective color inks are discharged from the liquid discharging heads 10C, 10M, 10Y and 10K, so that an image is formed according to the image data. It is to be noted that, in the present embodiment, the image forming device 2 is not limited thereto and any other configuration may be applied as long as the configuration is to form an image by supplying and adhering liquid onto the sheet P.
Drying Device.
The drying device 3 mainly includes a drying unit 13 and a sheet conveying unit 14. The drying unit 13 dries ink that is adhered on the sheet P in the image forming device 2. The sheet conveying unit 14 coveys the sheet P that is conveyed from the image forming device 2. The sheet P conveyed from the image forming device 2 is received by the sheet conveying unit 14. Then, the sheet P is conveyed to pass by the drying unit 13 and is transferred to the sheet output device 4. When passing through the drying unit 13, the ink on the sheet P is subjected to a drying process. By so doing, the liquid content such as moisture in the ink is evaporated, and therefore the ink is fixed onto the sheet P and curling of the sheet P is restrained.
Sheet Output Device.
The sheet output device 4 mainly includes a sheet output tray 15 onto which multiple sheets P are output and stacked. The sheets P that are sequentially conveyed from the drying device 3 are overlaid one after another and stacked. It is to be noted that the configuration of the sheet output device 4 according to the present embodiment is not limited thereto and any other configuration may be applied as long as the sheet output device discharges the sheet P or the multiple sheets P.
Other Additional Functional Devices.
As described above, the inkjet type image forming apparatus 100 according to the present embodiment includes the sheet feeding device 1, the image forming device 2, the drying device 3 and the sheet output device 4. However, other functional devices may be added appropriately. For example, the inkjet type image forming apparatus 100 may further include a pre-processing device between the sheet feeding device 1 and the image forming device 2 to perform pre-processing operations of image formation. The inkjet type image forming apparatus 100 may further include a post-processing device between the drying device 3 and the sheet output device 4 to perform post-processing operations of image formation.
An example of the pre-pre-processing device performs a processing liquid applying operation to apply processing liquid onto the sheet P so as to reduce bleeding by reacting with ink. However, the content of the pre-processing operation is not limited particularly. Further, an example of the post-processing device performs sheet reversing and conveying operations in the sheet reverse and conveyance passage 150 to reverse the sheet P having an image formed thereon in the image forming device 2 and convey the sheet P to the image forming device 2 again to form images on both sides of the sheet P or performs a binding operation to bind the multiple sheets P having respective images thereon. However, the content of the post-processing operation is not limited particularly.
It is to be noted that the term “image” to be formed on a sheet is not limited to visible significant images such as texts and figures but includes, for example, patterns that themselves have no meaning. In addition, the term “sheet” on which the image is formed is not limited to limited materials but may include any object to which liquid can be temporarily attached, for example, paper, thread, fiber, cloth, leather, metal, plastic, glass, wood and ceramics, or any object to be used for film products, cloth products such as clothing, building materials such as wallpaper and flooring materials and leather products, and functions as a conveyance target medium. The term “liquid” is not particularly limited as long as the liquid has a viscosity and a surface tension that can be discharged from the liquid discharging head. However, but it is preferable that the liquid has a viscosity of 30 mPa·s or less at normal temperature and normal pressure or by heating and cooling. More specifically, the liquid includes a solvent such as water or an organic solvent, a solution including a coloring agent such as a dye or a pigment, a functionalizing material such as a polymerizable compound, a resin or a surfactant, a biocompatible material such as DNA, amino acid, protein or calcium, edible materials such as natural pigments, or suspension or emulsion. These liquids can be used for ink for inkjet printing and surface treatment liquid, for example.
In addition, the term “inkjet type image forming apparatus” indicates an apparatus in which liquid discharging head(s) and a sheet material move relatively but is not limited thereto. An example of the inkjet type image forming apparatus includes a serial type image forming apparatus in which the liquid discharging head moves and a line type image forming apparatus in which the liquid discharging head does not move.
Further, the term “liquid discharging head” indicates a functional component that discharges and ejects liquid from liquid discharging holes (nozzles). As an energy generation source for discharging liquid, a discharging energy generating device, e.g., a piezoelectric actuator (stacked piezoelectric element and thin film piezoelectric element), a thermal actuator using an electrothermal transducer such as a heating resistor, and an electrostatic actuator including a diaphragm and a counter electrode, can be used. However, the discharging energy generating device to be used is not limited.
Next, a description is given of the sheet conveying device 7 included in the sheet feeding device 1 of the inkjet type image forming apparatus 100 according to the present embodiment of this disclosure.
As illustrated in
The “CIS” stands for a contact image sensor that contributes to a reduction in size of a device in recent years. The CIS uses small-size LEDs (light emitting diodes) as light sources to directly read an image by linear sensors via lenses. Each of the first CIS 101, the second CIS 102 and the third CIS 103 includes multiple line sensors aligned in the width direction of the sheet P so as to detect a side edge Pa of one end side in the width direction of the sheet P. Specifically, the first CIS 101 and the second CIS 102 are disposed at the upstream side from the pair of sheet holding rollers 31 and at the downstream side from the pair of sheet conveying rollers 44 that is disposed at one upstream position from the pair of sheet holding rollers 31. By contrast, the third CIS 103 is disposed at the downstream side from the pair of sheet holding rollers 31 and at the upstream side from the transfer cylinder 8. The first CIS 101, the second CIS 102 and the third CIS 103 are disposed parallel to each other relative to the width direction of the sheet P (i.e., a direction perpendicular to the sheet conveying direction).
Each of the downstream side leading end detection sensor 200 and the upstream side leading end detection sensor 220 includes a reflective optical sensor. The upstream side leading end detection sensor 220 is disposed upstream from the pair of sheet holding rollers 31 and downstream from the second CIS 102 in the sheet conveying direction. The downstream side leading end detection sensor 200 is disposed downstream from the pair of sheet holding rollers 31 and upstream from the third. CIS 103 in the sheet conveying direction. As the sheet P is conveyed, the leading end portion Pb of the sheet P is detected by the upstream side leading end detection sensor 220. Consequently, the sheet conveyance timing at which the leading end portion Pb of the sheet P reaches the upstream side leading end detection sensor 220 is detected. Further, as the leading end portion Pb of the sheet P reaches the position of the downstream side leading end detection sensor 200 after the sheet P is held by the pair of sheet holding rollers 31, the leading end portion Pb of the sheet P is detected by the downstream side leading end detection sensor 200. Then, the sheet conveyance timing at which the leading end portion Pb of the sheet P reaches the downstream side leading end detection sensor 200 is detected.
The pair of sheet holding rollers 31 moves in the width direction (i.e., in a direction indicated by arrow S in
As illustrated in
As illustrated in
Further, as illustrated in
As illustrated in
Further, as illustrated in
Further, the sheet conveying device 7 according to the present embodiment includes a lateral driving mechanism 38 and an angular driving mechanism 39. The lateral driving mechanism 38 causes the holder frame 72 and the pair of sheet holding rollers 31 to move in the width direction. The angular driving mechanism 39 causes the holder frame 72 and the pair of sheet holding rollers 31 to rotate within a plane of sheet conveyance.
As illustrated in
Further, as illustrated in
As illustrated in
Further, as illustrated in
Further, as illustrated in
As illustrated in
The controller 20 includes a positional deviation amount calculator 21, a target conveyance timing calculator 22 and a conveying speed controller 23. The positional deviation amount calculator 21 calculates an amount of positional deviation of a sheet based on the detection results of the first CIS 101, the second CIS 102 and the third CIS 103. The target conveyance timing calculator 22 calculates a target conveyance timing of a sheet to a predetermined target position based on the detection result of the downstream side leading end detection sensor 200 and the detection result of a home position sensor 80 (see
For example, the controller 20 may be implemented using hardware, a combination of hardware and software, or a non-transitory storage medium storing software that is executable to perform the functions of the same. For example, in some example embodiments, the controller 20 may include a memory and a processing circuitry. The memory may include a nonvolatile memory device, a volatile memory device, a non-transitory storage medium, or a combination of two or more of the above-mentioned devices.
The processing circuitry may be, but not limited to, a processor, Central Processing Unit (CPU), a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), an Application Specific Integrated Circuit (ASIC), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, or any other device capable of performing operations in a defined manner. The processing circuitry may be configured, through a layout design and/or execution of computer readable instructions stored in a memory, as a special purpose computer to perform the functions of the positional deviation amount calculator 21, the target conveyance timing calculator 22 and/or the conveying speed controller 23.
In other example embodiments, the controller 20 may include integrated circuit (IC) specially customized into special purpose processing circuitry (e.g., an ASIC) to perform the functions of the positional deviation amount calculator 21, the target conveyance timing calculator 22 and/or the conveying speed controller 23.
In the present embodiment, the sheet P is to reach a sheet gripping position A (see
Here, a description is given of a method of calculating angular and lateral displacement amounts of a sheet, with reference to
As illustrated in
Specifically, the lateral displacement amount α of the sheet P is calculated based on a position in the width direction of the sheet P detected by the second CIS 102 (i.e., a position of the side edge Pa of the sheet P). That is, the position in the width direction detected by the second CIS 102 is compared with the conveyance reference position K. Consequently, a distance K1 extending between the position of the sheet P and the conveyance reference position K is calculated as a lateral displacement amount α of the sheet P.
Further, the angular displacement amount β of the sheet P is calculated based on a difference of end positions in the width direction of the sheet P detected by the first CIS 101 and the second CIS 102. That is, as illustrated in
As described above, the lateral displacement amount α of the sheet P and the angular displacement amount β of the sheet P are calculated. It is to be noted that, as illustrated in
In order to address this inconvenience and correct positional deviations such as an angular displacement of a sheet without degrading the productivity, a comparative sheet conveying device corrects a positional deviation without stopping conveyance of the sheet by driving a pair of rollers in a direction opposite to the direction of the positional deviation of the sheet while conveying the sheet.
Specifically, as illustrated in
When the positional deviation of a sheet is corrected while the sheet is being conveyed, the position of the leading end of the sheet changes, and therefore an amount of time that the leading end of the sheet reaches a predetermined target position varies. Consequently, if the sheet is conveyed at a predetermined conveying speed, the timing at which the sheet reaches the target position is shifted, which causes an inconvenience that the sheet cannot be conveyed with high accuracy.
In order to solve the shift of the timing at which the sheet reaches the target position caused by the correction of the positional deviation of the sheet, the comparative sheet conveying device calculates the position of the leading end of the sheet after the correction of the positional deviation of the sheet based on the positional deviation amount of the sheet, and the sheet conveying speed is adjusted based on the calculation result.
However, the comparative sheet conveying device cannot detect the angular displacement of the sheet after the leading end of the sheet has passed the angular displacement detection sensor. That is, the detection of the angular displacement of each sheet is performed for one time in total. Therefore, the correction of the angular and lateral displacements of the sheet is also performed for one time. Consequently, when the sheet further shifts after the correction of the positional deviation of the sheet the comparative sheet conveying device cannot convey the sheet with high accuracy.
Next, a description is given of the operations of the sheet conveying device 7 according to the present embodiment, with reference to the plan views and side views of
As illustrated in
Thereafter, as illustrated in
Then, the leading end portion Pb of the sheet P is detected by the upstream side leading end detection sensor 220, and based on the detection timing, the rollers of the pair of sheet holding rollers 31 come into contact with each other and start the conveying rotations. Thereafter, as illustrated in
Further, as illustrated in
Thereafter, as illustrated in
Further, as illustrated in
As described above, by detecting the angular and lateral displacements of the sheet P (i.e., the second position detection) even after the adjustment operation (i.e., the primary correction) and correcting the angular and lateral displacements of the sheet P based on the detection results (i.e., the secondary correction), the angular and lateral displacements of the sheet P that are generated while the sheet P is being conveyed by the pair of sheet holding rollers 31 is eliminated. Further, detection of the angular and lateral displacements of the sheet P after completion of the adjustment operation (i.e., the second position detection) may be performed multiple times at predetermined intervals during a period that the sheet P is passing by the second CIS 102 and the third CIS 103. Therefore, by performing the detection of the angular and lateral displacements of a sheet (i.e., the second position detection) for multiple times (repeatedly) and performing the correction of the angular and lateral displacements (i.e., the secondary correction) each time the above-described detection is performed, the sheet is conveyed with higher accuracy.
However, when the above-described correction of the angular and lateral displacements of the sheet (i.e., the secondary correction) is performed, the position of the sheet in the sheet conveying direction changes. Therefore, in a case in which the sheet having the change of the position in the sheet conveying direction is conveyed at the same conveying speed, the timing of arrival of the sheet to the target position B also changes. Therefore, in a case in which the sheet having the change of the position in the sheet conveying direction is conveyed at the same conveying speed, the timing of arrival of the sheet to the target position B also changes. In order to avoid this inconvenience, in the present embodiment, when the angular and lateral displacements of the sheet P are corrected after completion of the adjustment operation (i.e., the secondary correction), each time the correction of the angular and lateral displacements of the sheet P is performed, the conveying speed of the sheet P is changed (adjusted) based on the amount of correction of the angular and lateral displacements of the sheet P (a position after the change of the sheet P) (step S8 in the flowchart of
Hereinafter, a description is given of a method of controlling the conveying speed of a sheet with reference to a flowchart of
As illustrated in
The target rotation speed of the pair of sheet holding rollers 31 is calculated in accordance with the set target conveyance timing (step S14 in the flowchart of
Then, it is determined whether the sheet conveyance time has reached the target conveyance timing (step S16 in the flowchart of
In the present embodiment, the conveyance rotation speed of the pair of sheet holding rollers 31 is managed based on a signal from the rotary encoder 96 mounted on the pair of sheet holding rollers 31. Accordingly, in order to determine whether or not the conveyance rotation speed of the pair of sheet holding rollers 31 is faster or slower than the target rotation speed, the conveying speed controller 23 obtains the signal sent from the rotary encoder 96 (step S17 in the flowchart of
Further, when the correction of the angular and lateral displacements of the sheet P by the pair of sheet holding rollers 31 (i.e., the secondary correction) is performed after the setting of the target conveyance timing, the conveyance rotation speed of the pair of sheet holding rollers 31 is changed based on the amount of correction of the angular and lateral displacements of the sheet P along the secondary correction. The amount of correction of the angular and lateral displacements of the sheet P corresponds to the drive position (i.e., the drive amount and the drive direction) in which the pair of sheet holding rollers 31 moves in the width direction or rotates within a plane of sheet conveyance when correcting the angular and lateral displacements of the sheet. Accordingly, in the present embodiment, the conveying speed controller 23 obtains the signal sent from the rotary encoder 57 that detects the drive amount and the driving direction in the width direction of the pair of sheet holding rollers 31 and information from the rotary encoder 58 that detects the drive amount and the driving direction within a plane of sheet conveyance of the pair of sheet holding rollers 31 (step S18 in the flowchart of
Then, in step S14 in the flowchart of
Then, the control of the conveyance rotation speed of the pair of sheet holding rollers 31 as described above is performed until the sheet conveyance time reaches the target conveyance timing (step S16 in the flowchart of
Now, a description is given of a method of calculating the amount of position change of a sheet according to correction of the angular and lateral displacements of the sheet with reference to
In
As described above, in a case in which the position of the leading end of the sheet P changes along with the correction of angular and lateral displacements of the sheet P, the position coordinates (Qx, Qy) of a leading end position Q at the time t are calculated using the following equations, which are Equation 1 and Equation 2).
Qx=cos(Δθ)(Qx′−Zx)−sin(Δθ)(Qy′−Zy)+Zx+Xp Equation 1.
Qy=sin(Δθ)(Qx′−Zx)+cos(Δθ)(Qy′−Zy)+Zy+Yp+Ys Equation 2.
“Xp” in Equation 1 is an X direction component of a conveyance distance of the sheet P in which the sheet P is conveyed until the one previous timing (i.e., the time t−1) before the time t. “Yp” in Equation 2 is a Y direction component of the conveyance distance of the sheet P. When a conveyance distance of the sheet P in which the sheet P is conveyed by the pair of sheet holding rollers 31 until the time t−1 (that is, a conveyance distance of the sheet P in a direction perpendicular to the roller shaft) is indicated as “Fp”, Xp and Yp are expressed by the following Equations 3 and 4. Further, “Ys” in Equation 2 is an amount of movement of the sheet P in the width direction from the point Q′ to the point Q (i.e., an amount of movement in a Y direction).
Xp=cos(θ′)Fp Equation 3.
Yp=sin(θ′)Fp Equation 4.
Therefore, by using the above Equations 1 to 4, the position coordinates (Qx, Qy) of the leading position Q at the time t is calculated.
Then, by subtracting an X coordinate Vx of the sheet leading end position after the time t has elapsed without the correction of the angular and lateral displacements of the sheet, from the calculated X coordinate Qx, the position change amount G of the leading end of the sheet according to the correction of the angular and lateral displacements of the sheet is calculated (see Equation 5 below). Then, by adjusting the conveying speed of the sheet to the target position based on the position change amount G that is calculated as described above, the sheet is conveyed to the target position at a predetermined sheet conveyance timing.
G=Qx−Vx Equation 5.
As described above, since the sheet conveying device according to the present embodiment of this disclosure includes a CIS or CISs to detect the position of the side end of a sheet as a position detector or occasionally a position sensor of a plurality of position sensors to detect the position of the sheet, the CIS(s) can detect the side end of the sheet repeatedly or for multiple times during the period of time in which the sheet is passing by the CIS(s), which is, for example, the correction of angular and lateral displacements of the sheet after the adjustment operation (i.e., the secondary correction). By employing the CIS(s) as described above, the position of the sheet can be detected repeatedly or for multiple times. Therefore, the angular and lateral displacements of the sheet that are continuously generated during the sheet conveyance can be detected, and therefore the correction of the angular and lateral displacements of the sheet can be performed with high accuracy. Further, even if the position of the sheet in the conveying direction changes along with the correction of the angular and lateral displacements of the sheet, each time the correction of the angular and lateral displacements of the sheet is performed, the conveying speed of the sheet is changed based on the correction amounts of the angular and lateral displacements of the sheet (that is, the amount of change of the sheet in the width direction and the amount of change of the sheet in the rotation direction within a plane of sheet conveyance). By so doing, the sheet is conveyed to the target position at a predetermined sheet conveyance timing. That is, not by collectively adjusting the position change of the sheet in the sheet conveying direction along with the multiple corrections of angular and lateral displacements of the sheet by one change of the conveying speed of the sheet but by adjusting the position change of the sheet in the sheet conveying direction each time the correction of angular and lateral displacements of the sheet is performed, the conveying speed of the sheet is adjusted with more time to spare. According to this configuration, the sheet is conveyed with accuracy to meet the target conveyance timing reliably. As a result, the positional deviation of the image to the sheet P is prevented with high accuracy, and therefore the print quality is enhanced. Further, when performing the duplex printing operation, the positional deviation of images to the front side and the rear side is corrected, and therefore a relative positional deviation of the image formed on the front face of the sheet P and the image formed on the back face of the sheet P is eliminated.
In the present embodiment, the correction of the angular and lateral displacements of the sheet and the change of the conveying speed of the sheet are performed each time the position of the sheet is detected. However, the method of correcting the displacements of the sheet and changing the conveying speed of the sheet is not limited thereto. For example, firstly the displacement of the sheet may be corrected based on some detection results (at least two times) of the position information of the sheet detected repeatedly or for multiple times, and then the conveying speed of the sheet may be changed. That is, the number of times to correct the angular and lateral displacements of the sheet and the number of times to change the conveying speed of the sheet may be less than the number of times to detect the position of the sheet.
In the present embodiment, the downstream side leading end detection sensor 200 is driven together (integrally) with the pair of sheet holding rollers 31 but the configuration of the downstream side leading end detection sensor 200 is not limited thereto. For example, the downstream side leading end detection sensor 200 may be driven separately from the pair of sheet holding rollers 31. However, in that case, the leading end detection position of the downstream side leading end detection sensor 200 may be different according to the degree of angular displacement of the sheet. Therefore, in a case in which the angular and lateral displacements of the sheet are corrected by the adjustment operation by the pair of sheet holding rollers 31 after the sheet leading end position is detected (i.e., the primary correction), the target conveyance timing varies according to the degree of movement of the adjustment operation (i.e., the degree of angular displacement amount of the sheet). Therefore, in order to address the influence of such operation of displacement correction (i.e., the primary correction), the sheet conveyance timing of the sheet is to be detected in a state in which adjustment operation is completed.
By contrast, in a case in which the downstream side leading end detection sensor 200 is driven together (integrally) with the pair of sheet holding rollers 31 as the present embodiment, the sheet can be detected each time while facing the downstream side leading end detection sensor 200 (each time the same posture). Consequently, the leading end detection position of the downstream side leading end detection sensor 200 may not vary according to the degree of angular displacement of the sheet. Therefore, the target conveyance timing may not be susceptible to the variation in the leading end detection position, in addition, the downstream side leading end detection sensor 200 is returned to the same position (i.e., the home position) each time along with the adjustment operation performed by the pair of sheet holding rollers 31. Therefore, the distance from the downstream side leading end detection sensor 200 to the target position B is the same distance each time. Accordingly, the target conveyance timing of the sheet is not susceptible to the change in the distance from the downstream side leading end detection sensor 200 to the target position B.
As described above, in the present embodiment, the downstream side leading end detection sensor 200 is driven together with the pair of sheet holding rollers 31. Therefore, there is no various adverse effects that are generated when the sensors are fixed, and therefore the conveying speed of the sheet according to the adjustment operation (i.e., the primary correction) may not be changed. Further, since the target conveying timing is not affected by the adjustment operation, the sheet conveyance timing of the sheet is detected before completion of the adjustment operation (in other words, before or during the adjustment operation). Therefore, the target conveyance timing can be set at an early stage, and sufficient control time of the conveying speed of the sheet to be performed later can be secured, and the accuracy in control is enhanced.
It is to be noted that, in the present embodiment, the downstream side leading end detection sensor 200 is disposed on the downstream side of the pair of sheet holding rollers 31. However, in order to obtain the effect by driving the downstream side leading end detection sensor 200 together with the pair of sheet holding rollers 31, the downstream side leading end detection sensor 200 may be disposed upstream from the pair of sheet holding rollers 31 in the sheet conveying direction.
Further, according to the present embodiment, the conveying speed of the sheet along with the adjustment operation may not need to be changed. Therefore, the conveying speed of the sheet may be changed corresponding to the correction of angular and lateral displacements of the sheet after the adjustment operation (i.e., the secondary correction). Moreover, the correction of angular and lateral displacements of the sheet after the adjustment operation (i.e., the secondary correction) is a fine correction of the displacements of the sheet to be performed after the angular and lateral displacements of the sheet have corrected once. Therefore, the change of the conveying speed of the sheet along with the correction of the displacements of the sheet (i.e., the secondary correction) is generally sufficient to be a fine change. Accordingly, even when the sheet is conveyed at high speed or even when the distance of conveyance of the sheet to the target position is short, the conveying speed of the sheet can be changed sufficiently.
Further, in the present embodiment, the correction amounts of angular and lateral displacements of the sheet are obtained indirectly from information of the rotary encoders 57 and 58 (that function as drive position detectors) that detect the amount of movement of the pair of sheet holding rollers 31 in the width direction and the amount of rotation of the pair of sheet holding rollers 31 within a plane of sheet conveyance (in other words, the magnitude that the pair of sheet holding rollers 31 adjusts the position of the sheet P). However, the correction amounts of angular and lateral displacements of the sheet may also be obtained by calculation based on the CIS(s) that directly detect the position of the sheet. However, the CIS (or the CISs) has a large amount of information and a large load such as communication and arithmetic processing. Therefore, the period from the time of detection of the position of the sheet to the time of the change of the conveying speed of the sheet may become longer. By contrast, when calculating the correction amount of angular and lateral displacements of the sheet indirectly based on the information from the rotary encoders (i.e., the rotary encoders 57 and 58), the amount of load such as communication and arithmetic processing is reduced. Therefore, the change of the conveying speed of the sheet is started at an earlier timing. Therefore, even in a configuration in which the conveying speed of the sheet is a relatively high speed or the distance of sheet conveyance to the target position is short, the control time of the conveying speed of the sheet is secured and the sheet is conveyed with high accuracy.
Now, a description is given of the sheet conveying device 7 according to another embodiment of this disclosure with reference to
The sheet conveying device 7 according to another embodiment illustrated in
Basically, the transfer cylinder 8 is controlled to rotate at a constant velocity. However, it is also conceivable that the conveyance rotation speed of the transfer cylinder 8 changes for some reasons. In that case, as described above, even if the conveyance rotation speed of the pair of sheet holding rollers 31 is changed based on the amounts of the angular and lateral displacement corrections of the sheet P, the timing of conveyance of the sheet P and the timing of arrival of the gripper 16 on the transfer cylinder 8 may not meet.
Therefore, in the present embodiment, the conveying speed controller 23 obtains a signal from the rotary encoder 17 of the transfer cylinder 8 in addition to the signal from the rotary encoder 96 that detects the conveyance rotation speed of the pair of sheet holding rollers 31 and the signal from the respective rotary encoders 57 and 58 that detect the amount of movement of the pair of sheet holding rollers 31 in the width direction and the amount of rotation of the pair of sheet holding rollers 31 within a plane of sheet conveyance, respectively (in other words, the magnitude that the pair of sheet holding rollers 31 adjusts the position of the sheet P) (steps S27 through S29 in the flowchart of
Next, a description is given of the sheet conveying device 7 according to yet another embodiment of this disclosure with reference to
The sheet conveying device 7 according to yet another embodiment illustrated in
Even without receiving the signal from the home position sensor 80, the position of the gripper 16 is checked based on the signal sent from the rotary encoder 17 of the transfer cylinder 8. Therefore, in the present embodiment, by (based on) receiving the signal from the downstream side leading end detection sensor 200 (step S11 in the flowchart of
Now, a description is given of the sheet conveying device 7 according to yet another embodiment of this disclosure with reference to
The sheet conveying device 7 according to yet another embodiment illustrated in
In the above-described embodiments, which are the sheet conveying device 7 illustrated in
Therefore, in the present embodiment, the sheet conveying device 7 according to this embodiment, the rotary encoder 96 that detects the conveyance rotation speed of the pair of sheet holding rollers 31 is replaced by the laser doppler velocimeter 18. By so doing, the conveyance rotation speed of the pair of sheet holding rollers 31 is controlled based on the conveying speed of the sheet P that is directly detected by the laser doppler velocimeter 18 (step S47 in
It is to be noted that, in the example of the configuration including the laser doppler velocimeter 18 in the embodiment, the conveying speed of the sheet P may be changed based on the conveyance rotation speed of the transfer cylinder 8 detected by the rotary encoder 17, as the example of the configuration illustrated in
Although the embodiments of this disclosure have been described above, this disclosure is not limited to the above-described embodiments, and it is obvious that various modifications can be made without departing from the gist of this disclosure.
In the above-described embodiments, CISs are used as position detectors or occasionally a plurality of position sensors to detect the position of the side end of a sheet. However, the position detector (or the position sensor of the plurality of position sensors) is not limited to a CIS and may be any detector such as multiple photosensors disposed along the width direction of the sheet as long as the detector detects the side edge of a sheet.
Further, in the above-described embodiments, both the angular displacement and the lateral displacement of a sheet are corrected. However, the sheet conveying device 7 according to this disclosure may be applied when correcting either one of the angular displacement and the lateral displacement of the sheet. Even in the configuration in which the lateral displacement alone is corrected, when the sheet has the angular displacement, the timing at which the leading end of the sheet reaches the downstream side leading end detection sensor varies by correcting the lateral displacement of the sheet. Therefore, the sheet conveyance timing of the sheet to the target value also varies.
Further, in the above-described embodiments, the conveying speed of a sheet is adjusted by changing the conveyance rotation speed of the pair of sheet holding rollers 31. However, without changing the conveying rotation speed of the pair of sheet holding rollers 31, a pair of sheet conveying rollers may be added to adjust the conveying speed of the sheet on the downstream side of the pair of sheet holding rollers 31.
Further, in the above-described embodiments, the sheet conveying device according to this disclosure is applied to an inkjet type image forming apparatus but is not limited thereto. For example, the sheet conveying device according to this disclosure may also be applicable to an electrophotographic image forming apparatus.
In
The document reading device 302 optically reads image data of an original document D. The exposure device 303 emits an exposure light L based on the image data read by the document reading device 302 to the photoconductor drum 305. The developing device 304 forms a toner image on the surface of the photoconductor drum 305. The transfer unit 307 transfers the toner image formed on the surface of the photoconductor drum 305 onto a sheet P. The document conveying device 310 functions as a document feeder that conveys the original document D set on a document tray or a document loader to the document reading device 302. Each of the first sheet feed tray 312, the second sheet feed tray 313 and the third sheet feed tray 314 contains the sheet P therein.
The fixing device 320 fixes an unfixed image formed on the sheet P to the sheet P by application of heat and pressure. The sheet conveying device 330 conveys the sheet P fed by any one of the first sheet feed tray 312, the second sheet feed tray 313 and the third sheet feed tray 314.
A description is given of the basic operations of the electrophotographic image forming apparatus 300.
When the document D is conveyed by the document conveying device 310 in the direction indicated by arrow in
In such an electrophotographic image forming apparatus 300, the conveying speed of the sheet P is to be adjusted such that the sheet P reaches the transfer unit 307 at a timing synchronized with movement of the toner image formed on the photoconductor drum 305. Therefore, by applying a sheet conveying device conveying device similar to the above-described embodiment as the sheet conveying device 330 that conveys the sheet P to the transfer unit 307, the sheet conveyance timing of the sheet P is controlled with high accuracy while the positional deviation of the sheet P is corrected, so as to convey the sheet P to the transfer unit 307.
Further, the sheet conveying device according to this disclosure is also applicable to a post processing device that performs stapling and folding to the sheet after an image has been transferred onto the sheet.
Now, a description is given of a post processing device 400 to which this disclosure is applied, with reference to
The post processing device 400 illustrated in
The punching device 410 performs a punching process to a sheet. The stapling device 420 performs a binding process to the sheet. The sheet folding device 430 performs a center folding process. The first sheet tray 441, the second sheet tray 442, and the third sheet tray 443 function as multiple sheet loaders. The sheet conveying device 450 conveys the sheet from the image forming apparatus 100 to the punching device 410.
Further, the post processing device 400 performs different post processing processes by conveying the sheet conveyed from the image forming apparatus 100 to any one of three sheet conveyance passages, which are a first sheet conveyance passage J1, a second sheet conveyance passage J2 and a third sheet conveyance passage J3.
The first sheet conveyance passage J1 is a sheet conveyance passage to convey the sheet P to the first sheet tray 441 after the punching process is performed by the punching device 410 or without the punching process. The second sheet conveyance passage J2 is a sheet conveyance passage to convey the sheet P to the second sheet tray 442 after the stapling process is performed by the stapling device 420. The third sheet conveyance passage J3 is a sheet conveyance passage to convey the sheet P to the third sheet tray 443 after the center folding process is performed by the sheet folding device 430.
By applying a sheet conveying device similar to the sheet conveying device according to the above-described embodiments as the sheet conveying device 450 provided to the post processing device 400, the sheet is conveyed at a predetermined timing while the positional deviation of the sheet is being corrected. Therefore, the punching process, the accuracy of the binding process or the center folding process to be performed when the sheet is conveyed is enhanced.
Further, the sheet conveying device according to this disclosure is not limited to a sheet conveying device to convey sheets. The sheet conveying device according to this disclosure can be applied to a sheet conveying device that conveys recording media such as overhead projector (OHP) sheets and OHP films on which an image is formed or sheets such as original documents, as well as sheets including plain papers, thick papers, thin papers, coated papers, label papers and envelopes. Further, the sheet conveying device according to this disclosure can be employed to not only a sheet conveying device that conveys a recording median and a sheet such as an original document, but also a sheet conveying device that conveys a conveyance target medium such as a printed circuit board.
The above-described embodiments are illustrative and do not limit this disclosure. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements at least one of features of different illustrative and exemplary embodiments herein may be combined with each other at least one of substituted for each other within the scope of this disclosure and appended claims. Further, features of components of the embodiments, such as the number, the position, and the shape are not limited the embodiments and thus may be preferably set. It is therefore to be understood that within the scope of the appended claims, the disclosure of this disclosure may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
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| JP2017-230434 | Nov 2017 | JP | national |
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