JP2004284746A - Sheet transport device and image forming device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet transport device and an image forming device capable of preventing a paper sheet from being damaged or a motor to drive transport rolls from causing loss of synchronism, etc., even in the case of jamming in which a sheet is pinched by transport rolls having different sheet feeding directions. <P>SOLUTION: The sheet transport device has at least two sets of transport rolls arranged along the sheet transport path and rotated in different directions from each other, and a control part is provided to make such control that either set of the transport rolls rotated in different directions are rotated as following at least for a certain time after the other transport rolls at least when the device is to be started. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sheet conveying apparatus used in an image forming apparatus such as a printer or a copier to which an electrophotographic method or an electrostatic recording method is applied, and an image forming apparatus using the same, and particularly to conveying a sheet having an image formed on one side. The present invention relates to a sheet conveying device suitably used for forming an image on both sides of a sheet by reversing the direction, and an image forming apparatus using the same.
[0002]
[Patent Document 1] JP-A-2000-72307 [Patent Document 2] JP-A-2001-158566 [Patent Document 3] JP-A-2002-87636 [0003]
[Prior art]
Conventionally, in an image forming apparatus such as a printer or a copying machine to which the above-described electrophotographic method or electrostatic recording method is applied, a sheet on which a toner image is transferred from a photosensitive drum is fixed by a fixing device, and an image is formed on one side of the sheet. After forming the sheet, the sheet is not directly discharged onto an external discharge tray by the discharge roller, and the discharge roller is nipped by the discharge roller at the rear end of the sheet on which an image is formed on one side. The image is formed on both sides of the sheet by reversing the direction, introducing the sheet into the sheet reversing path for both sides, and conveying the sheet again to the image forming unit of the photosensitive drum via the sheet reversing path for both sides. There is known a so-called switchback type sheet conveying apparatus that enables the sheet conveyance.
[0004]
Examples of the image forming apparatus using the switchback type sheet conveying apparatus include those disclosed in JP-A-2000-72307, JP-A-2001-158566, JP-A-2002-87636, and the like. is there.
[0005]
Further, in the image forming apparatus, a paper sensor for detecting a paper jam is provided on the upstream side of the registration roll for conveying the paper to the photosensitive drum, near the exit of the fixing device, or a paper reversing path for both sides. It is disposed in the vicinity of the downstream side of the transport roll provided near the section. In the image forming apparatus, when it is detected that a paper jam has occurred inside the image forming apparatus, if the paper sensor is detecting the paper, the apparatus is stopped or the paper sensor is detected. If not, discharge the paper remaining inside the paper transport path to the outside, or in order to be able to detect by the paper sensor, such as a discharge roll or a transport roll in the paper transport path for both sides, It is configured to be driven to rotate in a predetermined transport direction.
[0006]
[Problems to be solved by the invention]
However, the conventional technique has the following problems. That is, in the case of the above-described conventional image forming apparatus, as shown in FIG. 10, the apparatus is operated in a state where the paper 100 is sandwiched by both the discharge roll 101 and the transport roll 103 in the paper reversing path 102 for both sides. When stopping and restarting, the following problems occur. That is, when the paper sensor 104 does not detect the remaining paper, the discharge roll 101 is driven in the discharge direction of the paper 100, and the transport roll 103 in the paper reversing path 102 for both sides is driven in the paper reversal direction. The remaining paper 100 can be detected by the paper sensor 104 or the paper 100 can be discharged outside the apparatus.
[0007]
However, since the discharge roll 101 and the transport roll 103 in the paper reversing path 102 are set to rotate in opposite directions to each other, in the above-described case, the paper 100 is pulled and the paper 100 is damaged. Or the motor for driving the discharge roll 101 or the transport roll 103 may lose synchronism due to overload.
[0008]
More specifically, as a conventionally used paper sensor 104, as shown in FIG. 11, when the paper 100 enters the paper reversing path 102, the actuator 105 rotates clockwise, One configured to open the optical path of the detection unit 106 may be mentioned. On the other hand, the actuator 105 is urged by a spring (not shown) in a counterclockwise direction. When the rear end of the sheet 100 passes, the actuator 105 rotates counterclockwise and stops at a standby position by a stopper to be detected. The optical path of the unit 106 is blocked. Also, when the paper 100 runs backward and the trailing edge of the paper collides with the actuator 105, the actuator 105 does not rotate counterclockwise from the standby position by the stopper, and as shown in FIG. It will damage the part.
[0009]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the related art, and an object of the present invention is to sandwich a sheet between transport rolls having different transport directions from each other when a paper jam occurs. It is an object of the present invention to provide an image forming apparatus capable of preventing damage to a sheet and occurrence of a step-out or the like of a motor for driving a conveying roll even when the sheet is damaged.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 is a sheet conveying apparatus having at least two sets of conveying rolls disposed along a sheet conveying path and driven to rotate in directions competing with each other. A control unit for controlling at least at the time of activation of the apparatus, such that one of the transport rolls rotationally driven in the competing direction is moved forward by the other transport roll for at least a fixed time. Is a sheet conveying apparatus characterized by the following.
[0011]
According to a second aspect of the present invention, there is provided a sheet conveying apparatus having at least one sheet detecting unit and at least two sets of conveying rolls that are driven to rotate in the competing directions. 2. The sheet conveying apparatus according to claim 1, further comprising: a control unit configured to control one of the conveying rolls to move forward at least for a predetermined time according to an output of the detecting unit. is there.
[0012]
Further, according to the invention described in claim 3, the sheet discharge unit provided with a discharge roll for discharging the sheet, and a sheet reversing path provided with a transport roll in which a transport direction of the discharge roll and the sheet are set in opposite directions. A sheet transporter that reverses the transport direction of the discharge roll while the rear end of the sheet is held by the discharge roll, and transports the sheet to a transport roll provided in the sheet reversing path. An apparatus according to claim 1, further comprising a control unit configured to control a transport roll in the sheet reversing path to move forward with respect to the discharge roll for a predetermined time at least when the apparatus is started. .
[0013]
According to a fourth aspect of the present invention, a sheet detecting unit capable of detecting a sheet regardless of the sheet conveying direction is provided at least upstream of the forwardly moving conveying roll in the sheet conveying direction. The sheet conveying device according to claim 1, wherein:
[0014]
Further, according to a fifth aspect of the present invention, the sheet detecting unit includes a sheet contact member that moves in a direction substantially orthogonal to the sheet conveying direction. Device.
[0015]
According to a sixth aspect of the present invention, there is provided a sheet conveyance unit for moving a sheet detection unit having a sheet contact member having a guide unit for guiding a sheet irrespective of the sheet advancing direction at least in the forward direction. The sheet conveying device according to claim 1, wherein the sheet conveying device is provided on an upstream side in the direction.
[0016]
Further, an invention according to a seventh aspect is an image forming apparatus including the sheet conveying device according to any one of the first to sixth aspects.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
[0018]
Embodiment 1
FIG. 1 shows a laser printer as an image forming apparatus to which the sheet conveying device according to the first embodiment of the present invention is applied.
[0019]
In FIG. 1, reference numeral 1 denotes a laser printer as a main body device. Inside the printer 1, an image processing unit 2 for performing predetermined image processing on image information input from the outside, An image output unit 3 that outputs an image based on image information on which predetermined image processing has been performed by the processing unit 2 is provided. The image processing unit 2 in the printer 1 reads image information sent from a host computer such as a personal computer (not shown), a communication line such as a telephone line or a LAN, or an image reading device (not shown). Image information and the like are input.
[0020]
An ROS 4 (Raster Output Scanner) that performs image exposure based on image information on which predetermined image processing has been performed by the image processing unit 2 is arranged in the image output unit 3 in the printer 1. Image exposure with laser light LB is performed according to the image information.
[0021]
In the ROS 4, as shown in FIG. 1, laser light LB is emitted from a semiconductor laser (not shown) in accordance with gradation data of image information. Laser light LB emitted from the semiconductor laser is deflected and scanned by a rotating polygon mirror (not shown), and is scanned on a photosensitive drum 5 as an electrostatic latent image carrier via a reflecting mirror (not shown).
[0022]
As the photosensitive drum 5 on which the laser beam LB is scanned and exposed by the ROS 4, for example, a photosensitive body using an organic photoconductive substance (OPC) is used. Is driven to rotate at a predetermined speed in the direction of the arrow. The surface of the photosensitive drum 5 is previously charged to a predetermined potential by a charging roll 6 serving as a charging unit, and is then scanned and exposed to laser light LB in accordance with image information to form an electrostatic latent image. . The electrostatic latent image formed on the photosensitive drum 5 is developed by a developing roll 8 as a developer carrier of a developing device 7 to become a toner image.
[0023]
The toner image formed on the photosensitive drum 5 is transferred onto a transfer sheet 10 as a sheet by a transfer roll 9 arranged so as to come into contact with the photosensitive drum 5, and the toner image is transferred. The transferred transfer paper 10 is separated from the photosensitive drum 5. As shown in FIG. 1, the transfer paper 10 is separated one by one from a paper feed cassette 12 of a paper feeder 11 arranged at a lower portion of the printer main body 1 by a nager roll 13, a feed roll 14, and a retard roll 15. And fed. The transfer paper 10 fed from the paper cassette 12 is transported to the transfer position of the photosensitive drum 5 by the registration roll 17 via the transport roll 16 and the paper transport path 16a. In the illustrated embodiment, the paper feeder 11 is built in two stages in advance in the lower part of the printer 1.
[0024]
Further, as shown in FIG. 2, the printer main body 1 is provided with a manual feed tray (not shown) in place of the uppermost sheet feeding device, so that transfer of materials and sizes such as OHP sheets and postcards from the manual feed tray is performed. Media can be fed.
[0025]
The transfer paper 10 on which the toner image has been transferred from the photosensitive drum 5 is separated from the surface of the photosensitive drum 5 and then conveyed to the fixing device 21 as described above. After the toner image is fixed on the transfer paper 10 by heat and pressure by the heating roll 22 and the pressure roll 23 of the fixing device 21, the transfer paper 10 separated from the surface is switched via the switching levers 24a and 24b. The sheet is discharged onto the discharge tray 26 provided on the upper portion of the printer main body 1 by the discharge roll 25, and the image forming process is completed.
[0026]
Further, when images are printed on both sides of the transfer sheet 10, as shown in FIG. 1, the transfer sheet 10 having the image printed on one side is not discharged onto the discharge tray 26 as it is, The transfer direction of the transfer paper 10 is switched by switching levers 24a and 24b provided at the outlet of the printer, and guided to a double-sided printing unit 29 provided with a plurality of transfer rolls 28a, 28b and 28c by a discharge roll 25 that rotates in reverse. The sheet 10 is configured to be transported to the transfer position of the photosensitive drum 5 again in a state where the sheet 10 is turned upside down.
[0027]
After the transfer of the toner image is completed, the surface of the photosensitive drum 5 is cleaned of residual toner and paper dust by a cleaning device having a cleaner blade 30, as shown in FIG. It is prepared for the forming process.
[0028]
Further, in the laser printer 1, the photosensitive drum 5 and the image forming member around the photosensitive drum 5 are integrally formed as an image forming unit 31, and when the toner in the developing device 7 runs out, or when the photosensitive drum 5 Is reached, the entire image forming unit 31 is replaced with a new one.
[0029]
Further, the laser printer 1 is provided with a post-processing device 52 that functions as a sorter that discharges the paper while appropriately offsetting the paper. The post-processing device 52, which functions as a sorter, transfers the transfer paper 10 on which an image is formed on one or both sides and has been subjected to the fixing process by the fixing device 21 to the inside of the post-processing device 52 by the switching lever 24 and the discharge roll 53. The sheet is introduced into the provided paper transport path 54, and is discharged onto the offset catch tray 57 by the transport roll 55 and the discharge roll 56 provided in the paper transport path 54.
[0030]
By the way, in the printer 1 configured as described above, as shown in FIG. 1, the paper feed rolls 13 to 15 are arranged at the most upstream in the paper transport direction, and A registration roll 17 is provided in the row, and a registration sensor 61 is provided in front of the registration roll 17. An image forming unit, that is, a transfer roll 9 that comes into contact with the photosensitive drum 5 and a fixing unit 21 are provided at a stage subsequent to the registration roll 17. A sensor 62 is provided. Further, a discharge roll 25 is provided at the most downstream in the paper transport direction.
[0031]
The discharge roll 25 is driven to rotate by a discharge motor 63. The rotation direction of the discharge roll 25 is reversed by rotating the discharge motor 63 in a state where the rear end of the paper 10 is sandwiched during double-sided printing, and the rear end of the paper 10 is introduced into the paper reversing path 29a. You. A first transport roll 28a, a second transport roll 28b, and a third transport roll 28c are provided in the sheet reversing path 29a, and are disposed between the first transport roll 28a and the second transport roll 28b. The reversing sensor 64 is arranged near the first transport roll 28a. The first to third transport rolls 28a to 28c in the sheet reversing path 29a are configured to be driven by a reversing motor 65. The image forming units such as the paper feed rolls 13 to 15, the registration roll 17, and the photosensitive drum 15 are driven by a main motor (not shown).
[0032]
The printer 1 can display an error message and prompt the operator to remove the paper 10 when the paper 10 is detected by any of the sensors 61, 62, and 64 when the apparatus is started. In a state where the paper 10 is not detected by any of the sensors 6162 and 64, the printer 1 cannot determine whether or not there is any remaining paper. The motors 63, 65, etc. are driven for a certain period of time to execute the paper feeding operation, and if there is any remaining paper, the remaining paper is detected by any of the sensors 61, 62, 64. .
[0033]
FIG. 2 is a configuration diagram showing the reversing sensor.
[0034]
As shown in FIG. 2, the reversing sensor 64 has an actuator 66 rotatably mounted only in a clockwise direction. An arcuate guide surface is also provided in the direction. The reversing sensor 64 is configured to detect a paper jam by causing the actuator 66 to rotate clockwise when a paper jam occurs and blocking the detection unit 67 of the sensor.
[0035]
Since the reversing sensor 64 is provided with the guide surface 66a also in the reverse feeding direction of the paper 10, even if the paper 10 runs backward and collides with the actuator 66, it may damage the edge of the paper 10. Absent.
[0036]
In this embodiment, as shown in FIG. 1, the motors 63 and 65, a main motor (not shown), and the like are rotationally driven at a predetermined timing by a CPU 68 as a control unit. The CPU 68 receives detection signals from the sensors 61, 62, and 64.
[0037]
In the above-described configuration, in the image forming apparatus to which the sheet conveying device according to the present embodiment is applied, as described below, when a paper jam occurs, a sheet is sandwiched between conveying rolls having different conveying directions. Even in such a case, it is possible to prevent the paper from being damaged and the motor for driving the transport roll from falling out of synchronization.
[0038]
That is, in the printer 1 according to this embodiment, when the activation state is instructed to the CPU 68, the CPU 68 starts driving the main motor, as shown in FIG. , A predetermined bias voltage is applied to start preparation for a printing operation.
[0039]
More specifically, as shown in FIG. 4, when the CPU 68 detects that a start command has been issued by turning on a power switch or an interlock switch (step 101), any of the paper sensors 61, 62, It is confirmed whether or not 64 is in the ON state (step 102). Then, if any of the paper sensors 61, 62, and 64 is in the ON state, the CPU 68 determines that there is remaining paper, and displays a message such as "Please remove the paper" (step 103). Is encouraged to remove remaining paper.
[0040]
On the other hand, if all the sheet sensors 61, 62, 64 are in the OFF state, the CPU 68 starts a start-up sequence (ERASE CYCLE) for driving all the sheet conveying motors 63, 65 (step 104). Then, if any of the paper sensors 61, 62, and 64 is turned ON after the start sequence is started (step 105), it is determined that there is remaining paper, and the start sequence is stopped (step 106). Is displayed, prompting the operator to remove the remaining paper (step 103).
[0041]
If any of the paper sensors 61, 62, and 64 does not change to ON and the startup sequence ends (step 107), the host system is notified that the preparation for printing is completed and printing is possible (step 107). Step 108).
[0042]
By the way, the case where the above-described control is performed and the paper 10 stays without being detected by any of the sensors 6162 and 64 will be specifically described.
[0043]
FIG. 5 shows a case where the rear end of the paper 10 stays in a state where it passes through the discharge sensor 62 and is nipped by the discharge roll 25. FIG. 6 shows a case where the rear end of the paper 10 passes through the reversing sensor 64 and the front end of the paper 10 stays in front of the registration sensor 61. FIG. 7 shows a case where the sheet 10 is sandwiched between the discharge roll 25 and the first transport roller 28 a, and the leading end of the sheet 10 stays in front of the reversing sensor 64. FIG. 8 shows a case where the paper 10 stays between the registration sensor 61 and the discharge sensor 62.
[0044]
The problem here is the case of FIG. When the discharge motor 63 and the reversing motor 65 rotate in the paper discharging direction (forward rotation), the paper 10 may be pulled and damaged, or the paper 10 may be damaged, or the discharge motor 63 and the reversing motor 65 may be overloaded. And step out.
[0045]
Therefore, in this embodiment, assuming the above case, as shown in FIG. 3, the discharge motor 63 is rotated forward and the reverse motor 65 is rotated reversely.
[0046]
However, the problem here is the case of FIG. That is, if the reverse rotation amount of the reverse motor 65 is large, the rear end of the paper 10 may collide with the actuator 66 of the reverse sensor 64 and damage the paper 10.
[0047]
Therefore, in this embodiment, the reverse rotation amount of the reversing motor 65 is set to the distance L from the detection position of the reversing sensor 64 to the first transport roll 28a, and thereafter the reversing motor 65 is rotated forward. Is configured. By doing so, in the case shown in FIG. 7, the rear end of the paper 10 surely passes through the first transport roll 28a, so that the paper 10 is transported only by the discharge roll 25 and discharged to the outside of the machine. 10 can be reliably discharged out of the machine without generating tension.
Note that the case has been described in which, when the presence of remaining paper is detected during the startup sequence, the operation is performed so as to stop the startup sequence. However, control may be performed so that the remaining paper is discharged out of the apparatus without stopping the apparatus.
[0049]
As described above, in the above-described embodiment, even when there are transport rolls rotating in directions competing with each other, one transport roll 28a is configured to move forward to the other transport roll 25 for a certain period of time. Thus, it is possible to prevent the paper 10 from being out of step without damaging the paper 10 and overloading the motor.
[0050]
Further, according to the above-described embodiment, even if the paper 10 is not detected by any of the sensors 61, 62, and 64 and stays in the apparatus, the paper 10 is not damaged and the motor 10 is not damaged. The remaining paper can be discharged outside the machine or detected by any of the sensors 61, 62, 64 without overloading the 63, 65 and causing a step out. Therefore, since the number of detection units for the paper 10 is not increased unnecessarily, it is possible to contribute to cost reduction of the apparatus.
[0051]
Further, according to the above-described embodiment, in the image forming apparatus including the switchback type double-sided printing unit 29, even if the image forming apparatus is started with the sheet 10 sandwiched between the discharge roll 25 and the transport roll 28a, The remaining paper can be discharged out of the machine or detected by any of the sensors 61, 62, and 64 without damaging the paper 10 and without causing the motors 63 and 65 to overload and lose synchronism. Therefore, the number of detection units is not unnecessarily increased, which contributes to cost reduction of the apparatus.
[0052]
Still further, according to the above-described embodiment, the sheet 10 can be detected even in the case where the sheet 10 is reversely run, so that the remaining sheet can be reliably detected, and an inadvertent paper jam can be generated. Absent. The paper sensor includes, for example, a reflection type photo sensor having no actuator.
[0053]
According to the above-described embodiment, as shown in FIG. 2, the distal end 66 a of the actuator 66 of the sensor 64 is formed in an arc shape in the transport direction and the reverse direction of the paper 10, so that at least the paper 10 is formed. This is preferable since no damage is caused.
[0054]
Further, as shown in FIG. 9, by configuring the actuator 66 to move in a direction substantially orthogonal to the sheet conveying direction, it is possible to inexpensively configure a sheet detecting unit capable of performing bidirectional detection.
[0055]
【The invention's effect】
As described above, according to the present invention, even when paper is sandwiched between transport rolls having different transport directions, the paper may be damaged or the transport roll may be moved. It is possible to provide a sheet conveying apparatus capable of preventing a stepping out of a driving motor and the like, and an image forming apparatus using the same.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a printer as an image forming apparatus to which a sheet conveyance device according to a first embodiment of the present invention is applied;
FIG. 2 is a configuration diagram illustrating a paper sensor.
FIG. 3 is a timing chart illustrating an operation of a printer as an image forming apparatus to which the sheet conveying device according to the first embodiment of the present invention is applied;
FIG. 4 is a flowchart illustrating an operation of a printer as an image forming apparatus to which the sheet conveying device according to the first embodiment of the present invention is applied;
FIG. 5 is a configuration diagram illustrating an operation of a printer as an image forming apparatus to which the sheet conveying device according to the first embodiment of the present invention is applied;
FIG. 6 is a configuration diagram illustrating an operation of a printer as an image forming apparatus to which the sheet conveyance device according to the first embodiment of the present invention is applied;
FIG. 7 is a configuration diagram illustrating an operation of a printer as an image forming apparatus to which the sheet conveyance device according to the first embodiment of the present invention is applied;
FIG. 8 is a configuration diagram illustrating an operation of a printer as an image forming apparatus to which the sheet conveying device according to the first embodiment of the present invention is applied;
FIG. 9 is a configuration diagram illustrating another sheet sensor.
FIG. 10 is a configuration diagram showing a conventional sheet conveying device.
FIG. 11 is a configuration diagram showing a conventional paper sensor.
[Explanation of symbols]
25: discharge roll, 28a: transport roll, 29a: sheet reverse path, 63: discharge motor, 65: reverse motor, 68: CPU (control unit).

Claims (7)

In a sheet conveying apparatus having at least two sets of conveying rolls arranged along a sheet conveying path and rotated in directions competing with each other,
At least at the time of starting the apparatus, a control unit that controls so that one of the transport rolls rotationally driven in the competing direction is moved forward by the other transport roll for at least a predetermined time is provided. Characteristic sheet conveying device. At least one sheet detection unit and a sheet conveyance device having at least two sets of conveyance rolls driven to rotate in the competing direction, at least at the time of starting the device, according to an output of the sheet detection unit, 2. The sheet conveying device according to claim 1, further comprising a control unit that controls the other conveying roll to move forward at least for a predetermined time. A sheet discharge unit having a discharge roll for discharging the sheet, and a sheet reversing path having a transport roll in which a transport direction of the discharge roll and the sheet is set in a reverse direction, and a trailing end of the sheet by the discharge roll While holding the portion, in the sheet conveying device that reverses the conveying direction of the discharge roll, and conveys the sheet to the conveying roll provided in the sheet reversing path,
A sheet transport device comprising: a control unit that controls a transport roll in the sheet reversing path to move forward with respect to the discharge roll for a predetermined time at least when the apparatus is started. 4. The sheet detecting unit according to claim 1, wherein a sheet detecting unit capable of detecting the sheet regardless of the sheet conveying direction is provided at least on an upstream side of the forwardly moving conveying roll in the sheet conveying direction. 3. The sheet conveying device according to 1. The sheet conveyance device according to claim 4, wherein the sheet detection unit includes a sheet contact member that moves in a direction substantially orthogonal to a sheet conveyance direction. A sheet detection unit provided with a sheet contact member having a guide unit for guiding the sheet regardless of the sheet traveling direction is provided at least on the upstream side in the sheet transport direction of the forwardly moving transport roll. Item 4. The sheet conveying device according to any one of Items 1 to 3. An image forming apparatus, comprising: the sheet conveying device according to claim 1.

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