JP2014162638A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus provided with a configuration which prevents toner contamination of a sheet by using an existing reverse conveyance member without a special configuration and eliminates the possibility of damage of the reverse conveyance member.SOLUTION: An image formation apparatus is provided with a reverse discharge device which reverses a sheet transferred with a toner image from an image carrier and carries circularly again to the image carrier, and the reverse discharge device is provided with a conveyance roller 17 arranged on the entrance side of the reverse conveyance path and a reverse branch claw 18 which has a swinging end imparted with a behavior of coming in contact with the conveyance roller 17 and can switch the conveyance path. In the conveyance roller 17, a cleaning roller 100 smaller in diameter than the conveyance roller 17 is supported coaxially, and the reverse branch claw 18 is brought into elastic contact with the cleaning roller 100 while the swinging end is positioned in the downstream in the reverse conveyance direction of the sheet relative to the swinging base end.

Description

  The present invention relates to an image forming apparatus, and more particularly to a mechanism for preventing toner smearing on a sheet on which a conveyance mode such as reverse conveyance is selected.

In an image forming apparatus such as a printer or a printing machine, a toner image formed on a photoconductor used as a latent image carrier is transferred onto a sheet to obtain a copy output.
The paper on which the toner image has been transferred may be discharged as it is after being transferred, or may be recirculated and conveyed toward the photoconductor after being reversed in the conveyance path.
The reverse conveyance of the sheet is a conveyance form that can be selected for the purpose of image formation on both sides of the sheet (for example, Patent Document 1).

By the way, in the image forming apparatus, untransferred toner remaining on the photoconductor after image transfer is removed by a cleaning process.
It is known that the untransferred toner is scraped and removed by a blade that contacts the surface of the photosensitive member, because the untransferred toner causes contamination of the charging device due to soiling of the photosensitive member or scattering to the charging device.

On the other hand, as a member having a relationship in contact with the toner, there is a branching claw as a reverse branching member used in the reverse transport described above.
A branching claw, which is a reversing branching member, is a member that comes into contact with a toner image when a sheet having a toner image transferred on one side is reversed.
Since the branching claw, which is a reversal branching member disclosed in Patent Document 1, pressurizes the sheet toward the surface of the reversing conveyance roller, it comes into contact with the toner image with a pressure when nipping and conveying the sheet.
For this reason, when the tip of the branching claw comes into contact with the toner image, the toner image may be scraped off, and the scraped toner may remain attached to the tip of the branching claw. If the toner remains attached to the tip of the branching claw, the paper that will be transported next time will be contaminated with toner, leading to a reduction in image quality.

  Japanese Patent Application Laid-Open No. 2005-228561 only discloses a configuration for a photosensitive member with respect to toner removal, so-called cleaning, and does not discuss toner contamination during reverse conveyance.

  In view of the problems in the conventional image forming apparatus described above, an object of the present invention is to prevent the toner from being smudged on a sheet by using an existing reverse conveying member without causing a special configuration and to cause damage to the reverse conveying member. An object of the present invention is to provide an image forming apparatus having a configuration that does not occur.

  In order to achieve this object, the present invention provides an image forming apparatus including a reversal discharge device capable of reversing a sheet on which a toner image is transferred from an image carrier and circulatingly conveying the paper toward the image carrier again. The reverse discharge device includes a transfer roller disposed on the reverse transfer path entrance side and a transfer path switching claw having a swinging end imparted with a habit to abut on the transfer roller. A cleaning roller having a smaller diameter is supported on the same axis, and the conveyance path switching claw is positioned on the downstream side in the reverse conveyance direction of the sheet with respect to the rocking base end, and elastically moves to the cleaning roller. An image forming apparatus is characterized by being in contact with each other.

  According to the present invention, since the conveyance path switching claw can come into contact with the cleaning roller provided coaxially with the conveyance roller, the toner is removed from the conveyance path switching claw in contact with the paper. Become. As a result, the toner adhesion to the paper is eliminated by simply using the existing components, and the toner contamination of the paper is prevented.

1 is a schematic diagram for explaining a configuration of an image forming apparatus according to an embodiment of the present invention. It is a schematic diagram for demonstrating the structure of the reverse discharge apparatus used for the image forming apparatus shown in FIG. It is a schematic diagram for demonstrating the relationship with the conveyance roller used for the reverse discharge apparatus shown in FIG. 2, and a conveyance path switching claw. It is a figure for demonstrating the characteristic of the structure used for the inversion discharge apparatus shown in FIG. In FIG. 4, it is an arrow view of the direction shown by a code | symbol (5). It is a block diagram for demonstrating the structure of the control part used for the reverse discharge apparatus shown in FIG. It is a timing chart for demonstrating an example of an effect | action of the control part shown in FIG.

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.
In FIG. 1, an image forming apparatus PR is a copying machine using an electrophotographic system, and includes the following apparatuses.
Image forming device (photosensitive member, charging device, developing device, transfer device, cleaning device, etc.) 1, transfer material (recording medium) reverse discharge device 2, reading device 3, writing device 4, paper feeding device 8, and fixing device 9 as a main part.

In the image forming apparatus PR, a document placed on a document placing table (not shown) of the reading device 3 is read. The read document image is converted into image information and used for image forming processing in the image forming apparatus 1 according to the image information.
In the image forming device 1, an electrostatic latent image is formed on the photoreceptor 6 by the writing device 4 based on the image information, and the electrostatic latent image is subjected to visible image processing by the developing device 7 to form a toner image.
The toner image is electrostatically transferred to the paper P supplied from the paper supply device 8 and fixed by the fixing device 9.
The paper P supplied from the paper supply device 8 is conveyed toward the image forming device 1 as indicated by an arrow 19, and the toner image is transferred by the transfer device after the registration timing for the photosensitive member 6 is set.

The paper P after the transfer is selected to be discharged to the paper discharge tray 11 after being fixed or to be conveyed to the reverse discharge device 2.
In the reverse discharge device 2, the paper P can be discharged out of the device as it is, or reversed and conveyed again to the photosensitive member 6 that is the image carrier on the image forming device 1 side.
When the sheet P is discharged straight (normally) outside the image forming apparatus PR, the sheet P passes through the sheet discharge roller 20 and is conveyed to the outside as it is. Further, when the paper P is transported to the reverse discharge device 2, the paper P is transported along a path indicated by an arrow 12.
When the paper P is reversed and discharged out of the apparatus, the paper P is conveyed from the reverse discharge apparatus 2 along the path indicated by the arrow 14. In addition, the paper P is reversed in the reverse discharge device 2 and is conveyed along the path indicated by the arrow 15 when re-supplied to the image forming device 1 for image formation on both sides of the paper P.

FIG. 2 is an enlarged view of a main part for explaining details and operation of the reverse discharge device 2 in FIG.
In FIG. 2, the reverse discharge device 2 includes a paper discharge branch claw 33, a reverse entrance upper guide plate 25a, a reverse entrance lower guide plate 25b, a paper detection sensor (hereinafter abbreviated as a sensor) on the upstream side in the transport direction of the paper P after fixing. 26).
Each of these members is disposed at a position to be introduced in order to reverse the sheet P after fixing.

On the other hand, the surface of the paper P introduced into the reverse discharge device 2 is reversed when it is passed through the peripheral surface of the transport roller 17 arranged on the reverse transport path entrance side. The sheet P whose surface is reversed can be recirculated and conveyed again toward the photoconductor as an image carrier.
A reverse branching claw 18 corresponding to a conveyance path switching claw having a swing end imparted with a habit of being brought into contact with the conveyance roller 17 is disposed opposite to the conveyance roller 17.
In the vicinity of the reverse branch claw 18 that can come into contact with the transport roller 17, a reverse transport guide plate 13 and a reverse drive roller 21 and a reverse driven roller 22 are disposed with the reverse transport guide plate 13 interposed therebetween.
A position regulating side fence (jogger) 29 is arranged on the reverse conveyance guide plate 13 so that the edges of the paper P can be aligned.
On one side in the longitudinal direction of the reverse conveyance guide plate 13, a double-sided drive roller 30 is disposed that rotates in a direction in which the paper P moving along the reverse conveyance guide plate 13 can be detoured and conveyed toward the reverse conveyance path 31. ing.
The double-sided drive roller 30 has a double-sided surface capable of switching the conveyance direction of the paper P from the reverse conveyance guide plate 13 side toward the reverse conveyance path 31 or the conveyance direction toward the paper discharge roller 20 as indicated by an arrow 14. The branching claw 28 is arranged to face each other.

In the reverse discharge device 2 configured by each of such units, the conveyance of the paper P is performed according to the following procedure.
The paper P that has passed through the fixing device 9 and has an image fixed on one side is selected to be conveyed to the paper discharge roller 20 side or to the reverse discharge device 2 side by switching the paper discharge branch claw 33. That is, the paper P is conveyed to the reverse discharge device 2 by switching the paper discharge branching claw 33 in the direction shown by the solid line in FIG. 2, and the paper P is discharged straight by switching in the direction shown by the broken line in the figure. Is called.

When the paper discharge branch claw 33 is switched in the direction of the solid line, the paper P enters between the reverse entrance guide plate 25a and the reverse entrance lower guide plate 25b via the path indicated by the arrow 12.
A sensor 26 is provided on the reverse entrance guide plate 25a to detect the rear end of the sheet P in the traveling direction. The transport roller 17 is provided at a position close to the downstream side in the paper transport direction of the sensor 26 provided on the reverse entrance guide plate 25a.

The oscillating end of the reversing branch claw 18 is positioned below the conveying roller 17 on the downstream side in the reverse conveying direction in which the reversing branch claw 18 is reversed and conveyed by the conveying roller 17. Pressure is applied in the direction of the axis 16 of the roller 17.
As a result, the reversing branch claw 18 is given a habit of having its swing end abutted against the transport roller 17, and the paper P is sandwiched between the transport roller 17 and the reversing branch claw 18, thereby causing the transport roller. It is conveyed according to the rotational force of 17.

  A plurality of conveyance rollers 17 and reverse branching claws 18 are arranged side by side in a direction perpendicular to the paper surface in FIG. 2, and the leading ends of the reverse branching claws 18 alternately enter between the conveyance rollers 17 as described above. As a result, when the paper P enters between the transport roller 17 and the reverse branch claw 18, the paper P is pressed against the transport roller 17 by the pressure of the reverse branch claw 18, and a transport force is generated to move on the reverse transport guide plate 13. Be transported.

FIG. 3 is an enlarged conceptual view showing the periphery of the conveying roller 17 and the reversing branch claw 18 in the embodiment of the reversing device of FIG.
In FIG. 3, the arrow A indicates the carry-in state of the reverse branch claw 8, the arrow B indicates the reverse branch claw of the reverse branch claw, and the arrow G indicates the paper carry-in state.
As shown in these figures, at the time of carry-in, the paper P is sandwiched between the transport roller 17 and the reversing branch claw 18, and the tip of the reversing branch claw 18 is pressurized upward. 17, a conveying force is generated by the frictional force of the conveying roller 17 and is conveyed.
When the trailing edge of the paper P passes through the tip of the reverse branch claw 18, the reverse driven roller 22 descends (swings toward the reverse driving roller 21), and the paper P is fed to the reverse driven roller 22 and the reverse driving roller 21. The paper P is reversed and conveyed in the reverse direction.

The features of the present embodiment will be described below with the above configuration as an object.
The feature of this embodiment is that the conveyance roller 17 used as an existing component is provided with a toner contamination prevention mechanism for the reversing branch claw 18.
FIG. 4 is a diagram showing the positional relationship between the conveying roller 17 and the reversing branch claw 18. In FIG. 4, the conveying roller 17 has a cleaning roller 100 having a smaller diameter than the conveying roller 17 on the same axis as the rotation shaft 17 </ b> A. It is supported as a toner stain prevention mechanism.
The cleaning roller 100 is made of a material having an elastic body such as a sponge. When the sponge is used, the toner can be put into the bubbles, so that the dirt is less likely to be exposed on the surface than normal rubber and the collected toner can be easily stored.
As described above, the reversing branch claw 18 has a swinging end that comes into contact with the transport roller 17 by an urging means (not shown), and therefore, the swinging end has a relationship of elastically contacting the cleaning roller 100. Have.

  The reversing branch claw 18 has a swing end positioned on the downstream side in the reverse transport direction of the paper P with respect to the swing base end and can be in a trailing contact. Therefore, when the paper P enters, the paper P depends on its thickness. Open in a state that makes it easy to pass through. Further, since the contact state at the swing end is a state that flutters in accordance with the rotation of the cleaning roller 100, the frictional resistance can be reduced and the wear loss at the swing end can be reduced.

On the other hand, as shown in FIG. 5, a plurality of transport rollers 17 are provided along the width direction of the paper P corresponding to a direction perpendicular to the reverse transport direction of the paper P.
The cleaning roller 100 is arranged with the following relationship with respect to each transport roller 17.
That is, cleaning is performed on both sides of the conveyance roller 17B in the center of the sheet width direction and on one side in the sheet width direction of the conveyance roller 17C adjacent to the conveyance roller 17B at the center of the sheet width direction on the inner side of the outermost outer side of the sheet width direction. A roller 100 is provided.
The reason why the cleaning roller 100 is arranged in such a relationship is that the size of the paper P and the direction during conveyance are taken into consideration. In other words, at least the center in the width direction and the vicinity of the conveying roller 17 and the reversing branching claw 18 are in contact with the paper P corresponding to the direction at which the paper P is conveyed, thereby enabling the paper P to be reversed and conveyed.
The transport roller 17 located on the outermost side in the paper width direction is provided with cleaning rollers 100 on both sides in the paper width direction. As a result, it is possible to remove the toner adhering to the reversing branch claw 18 during the reversal separation with the maximum width of the paper P.

On the other hand, in this embodiment, a configuration for executing a cleaning mode for removing the toner adhering to the reversing branch claw 18 is used.
FIG. 6 is a block diagram illustrating a configuration of a control unit used when executing the cleaning mode.
In FIG. 6, the control unit 1000 is used to perform rotation drive control of the transport roller 17.
That is, the transport roller 17 is rotationally driven by the drive motor, and the drive motor is provided with a control unit 1000 that can control the rotation speed of the transport roller 17.
An operation panel 1001, a counter 1002, and an image information input unit 1003 are connected to the control unit 1000 on the input side, and a drive motor driver that forms a data output unit to the drive motor via a timer 1004 on the output side. 1005 is connected.
The operation panel 1001 is used as an input unit for paper type and thickness, the counter 1002 is used as a counting unit for the number of sheets to be passed, and the image information input unit 1003 is an input unit for data related to the number of pixels and the image area. Used.
The timer 1004 is used as a command unit for the drive time of the drive motor, and the drive motor driver 1005 drives the drive motor based on the drive time output from the timer 1004 and data relating to the drive speed set by the control unit 1000. Used to do.

The control unit 1000 is a member that can change the drive time or drive speed of the drive motor from the reverse conveyance initial condition to a different condition according to data from each input unit, and executes the cleaning mode after changing it.
The cleaning mode is executed when it is determined that there is a possibility that toner adheres to the reversing branch claw 18 and the paper is soiled. This determination time is determined in comparison with a threshold value (threshold value for determining the degree of contamination) in which data from each input unit is registered in advance through experiments or the like.
In the cleaning mode, the following conditions are used based on the timing chart shown in FIG.
(1) As the timing for changing the drive time or drive speed of the drive motor, a non-sheet passing period during which the sheet is not conveyed toward the reverse discharge device 2, in other words, a sheet interval is used.
(2) The drive time or drive speed of the drive motor is changed before the start of paper transport or after the transport of a predetermined number of sheets, in other words, before the start of a job (JOB) or after the end of a job (JOB). Use.
(3) The drive time of the drive motor in the cleaning mode is longer than the drive time in the steady state or faster than the drive speed in the steady state.
(4) When the drive speed is increased based on (3), the increase in speed and stop are combined.

By using the above conditions, it is possible to prevent the paper from being soiled by the reversing and branching claw used in the paper transport unit by using the existing configuration as it is without using a special cleaning mechanism. it can.
In particular, with regard to a configuration in which a member for cleaning is provided, a configuration has been proposed in which the operating condition of the cleaning member is determined according to the image forming conditions for the charging roller (for example, reference: Japanese Patent No. 4158373). However, the configuration disclosed in the reference document does not use the existing configuration as in the present embodiment.
Accordingly, it can be said that the configuration is completely different from the configuration in which the toner contamination of the members related to the sheet conveyance is eliminated only by using the existing configuration.

Further, in this embodiment, when the cleaning mode is executed, only the rotation speed of the drive motor of the conveyance roller is adjusted, so that the reversal branch claw is worn by optimizing the adjustment time. It becomes possible to clean while suppressing.
Further, the toner that could not be removed in the cleaning between sheets is almost completely removed by executing the cleaning mode again before the job starts or after the job ends.
In addition, when the drive speed of the drive motor is increased, the high speed and the stop are combined to enhance the friction between the two by utilizing the inertia generated between the reverse branch claw and the cleaning roller. Removal efficiency can be increased.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus as image forming apparatus 2 Reverse discharge apparatus 17 Conveyance roller 18 Reverse branch claw 100 Cleaning roller 1000 Control part 1001 Operation panel 1002 Counter 1003 Image information input part 1004 Timer 1005 Drive motor driver P Paper

Japanese Patent No. 3926639

Claims (8)

An image forming apparatus including a reversing discharge device capable of reversing a sheet onto which a toner image has been transferred from an image bearing member and circulating and feeding the sheet toward the image bearing member again.
The reversing discharge device is provided with a reversing branching claw having a conveying roller disposed on the reversing conveying path inlet side and a conveying path switching reversing claw having a swinging end imparted with a habit to contact the conveying roller.
A cleaning roller having a smaller diameter than that of the conveying roller is supported on the same axis,
The reversing branch claw is characterized in that the swing end is positioned downstream of the swing base end in the reverse transport direction of the paper and is elastically brought into contact with the cleaning roller. .   A plurality of the transport rollers are provided along a paper width direction corresponding to a direction perpendicular to the reverse transport direction of the paper, and at least both sides in the paper width direction and the outermost side in the paper width direction of the transport rollers located at the center in the paper width direction The image forming apparatus according to claim 1, wherein the cleaning roller is provided on one side in the paper width direction of a transport roller adjacent to a transport roller in the center in the paper width direction inside.   3. The image forming apparatus according to claim 1, wherein the cleaning roller is provided on both sides of the transport roller in the paper width direction on the transport roller located on the outermost side in the paper width direction. The transport roller is rotationally driven by a drive motor, and the drive motor is provided with a control unit capable of controlling the rotation speed of the transport roller,
The control unit is connected to an input side of a paper type, a thickness input unit, and a data input unit relating to the number of sheets to be passed and an image area, and a data output unit relating to the drive time and drive speed of the drive motor is connected to the output side. Connected to
4. The control unit according to claim 1, wherein the drive time or drive speed of the drive motor can be changed from a reverse conveyance initial condition to a different condition according to data from the input unit. 5. The image forming apparatus according to claim 1.   5. The image forming apparatus according to claim 4, wherein the control unit uses a non-sheet passing period during which the sheet is not conveyed toward the reversal discharge device as a timing for changing a driving time or a driving speed of the driving motor. .   5. The image forming apparatus according to claim 4, wherein the control unit uses the time before the start of transporting the paper or after the end of transporting a predetermined number of sheets as the time for changing the drive time or drive speed of the drive motor.   7. The control unit according to claim 4, wherein, as a condition for changing a drive time or a drive speed of the drive motor, the control unit is longer than the drive time in a steady state or faster than the drive speed. The image forming apparatus according to any one of the above.   7. The control unit according to claim 4, wherein, as a condition for changing a drive time or a drive speed of the drive motor, a combination of higher speed and stop than the drive speed in a steady state is combined. The image forming apparatus according to any one of the above.

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