JP2004252317A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain recording material folded center from being carried in a state where it is stuck to an image carrier. <P>SOLUTION: A rush-in preventing part 70 is provided on the downstream side of a secondary transfer part 20. The rush-in preventing part 70 is equipped with brackets 71 provided on both side parts of an intermediate transfer belt 15, a base part 72 whose both ends are respectively attached to the brackets 71, a reflection type POB sensor 73 disposed on the upper surface of the base part 72, a shaft 74 attached to the edge part of the base part 72, and a stopper 75 (75a to 75c) attached to freely rock on the shaft 74. The stopper 75 is lifted up by the center folded part Pb of the paper P and is rocked to abut on the belt 15, and the movement of the paper P stuck to the belt 15 is prevented. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as an electrophotographic copying machine, and more particularly, to an image forming apparatus that electrostatically transfers a toner image formed on an image carrier to a recording material.
[0002]
[Prior art]
2. Description of the Related Art As a conventional image forming apparatus, a plurality of image forming units having an image carrier (for example, a photosensitive drum) on which a toner image is formed and carried are arranged in parallel, and circulate and move along the arrangement direction of each image forming unit. An intermediate transfer belt is provided, and each color component (for example, yellow, magenta, cyan, black) image formed by each image forming unit is primary-transferred sequentially to the intermediate transfer belt by a primary transfer device, and then superimposed on the intermediate transfer belt. There has been known an image forming apparatus in which a superimposed image is batch-transferred (secondarily transferred) to a sheet by a secondary transfer device, and the image secondarily transferred to the sheet is fixed by a fixing device. Here, as the secondary transfer device, for example, a secondary transfer roll is disposed in pressure contact with the toner image bearing surface of the intermediate transfer belt, and a backup roll is disposed on the back side of the intermediate transfer belt facing the secondary transfer roll. Generally, a secondary transfer bias is applied between the secondary transfer roll and the backup roll to form a transfer electric field in which the toner on the intermediate transfer belt is transferred onto the paper.
[0003]
Further, in this type of image forming apparatus, a reflection type sensor for detecting the sticking of the sheet to the intermediate transfer belt after the secondary transfer is installed, and when the sticking of the sheet to the intermediate transfer belt is detected, the image forming apparatus is used. Has been proposed to stop the operation (see Patent Document 1).
Furthermore, in order to improve the paper detection performance when yellow toner is used by applying the technology described in Patent Document 1, detection is performed at a timing immediately before the leading end of the paper enters a portion facing the reflective sensor. It is effective to start the detection and end the detection at the timing immediately after the leading end of the sheet has passed the portion facing the reflection type sensor.
[0004]
[Patent Document 1]
JP 2000-162892 A
[Problems to be solved by the invention]
However, the above-described method of detecting at the leading end of the paper mainly assumes a situation in which the paper sticks to the intermediate transfer belt from the leading end in the transport direction. For this reason, if the sheet sticks to the intermediate transfer belt in the middle of the transport direction, it cannot be detected that the sheet has stuck to the intermediate transfer belt. Then, the sheet stuck to the intermediate transfer belt in a folded state enters the cleaner of the intermediate transfer belt, resulting in poor cleaning and resulting image formation failure.
[0006]
The present invention has been made in order to solve the above technical problem, and an object of the present invention is to prevent a folded medium from being conveyed in a state of being stuck to an image carrier. It is in.
Another object of the present invention is to make it possible to remove a recording material attached to an image carrier without damaging the image carrier.
[0007]
[Means for Solving the Problems]
According to the present invention, the recording material attached to the image carrier is swung with the image carrier by providing a swinging member that comes into contact with the image carrier such as the intermediate transfer belt when pressed by the folded recording material. It is proposed that damming is performed at a contact portion with the member so that the image carrier is not conveyed downstream from the contact portion in the moving direction of the image carrier.
That is, an image forming apparatus according to the present invention includes an image carrier rotatably disposed, and a transfer member that is disposed to face the image carrier and electrostatically transfers a toner image on the image carrier to a recording material. The image carrier and the transfer member are disposed downstream of the opposing portion of the image carrier in the moving direction of the image carrier, and are normally held at a position separated from the image carrier and pressed by the recording material passing through the opposing portion. And a swinging member that can swing to a position where it comes into contact with the image carrier.
[0008]
Here, the swing member may be made of metal or resin having a predetermined thickness. Further, a portion of the swinging member that comes into contact with the image carrier may have a predetermined curvature, and a rotatable roll member is provided on a free end side of the swinging member. It can be characterized by providing. Further, the swing member may be provided with a powder reservoir for receiving the powder dropped from the surface of the image carrier. In the image forming apparatus of the present invention, the image carrier is an intermediate transfer belt on which a toner image formed and carried on the image forming carrier is primarily transferred, and the transfer member is a toner primarily transferred on the intermediate transfer belt. The image forming apparatus can be characterized in that the image forming apparatus is a transfer and conveyance belt that transfers an image to a recording material by secondary transfer.
[0009]
From another viewpoint, an image forming apparatus according to the present invention includes an image carrier rotatably disposed, and a toner image on the image carrier, which is disposed to face the image carrier, and is used as a recording material. A transfer member that performs electrostatic transfer, a shaft member that extends in a direction perpendicular to the movement direction on the downstream side in the moving direction of the image carrier from a facing portion of the image carrier and the transfer member, and one end of the shaft member A plate-shaped member which is swingably attached to the member and whose other end is arranged in a direction facing the moving direction of the image carrier. The image forming apparatus further includes an urging member for urging the plate member in a direction away from the image carrier, or applies a bias having the same polarity as the toner constituting the toner image to the plate member. The device may further include a bias applying mechanism. Further, in the image forming apparatus of the present invention, the image carrier has an endless belt shape stretched over a plurality of rolls, and the transfer member has an endless belt shape stretched over a plurality of rolls. It can be a feature.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.
-Embodiment 1-
FIG. 1 is a diagram illustrating an image forming apparatus according to the first embodiment. The image forming apparatus shown in FIG. 1 is an image forming apparatus of a so-called tandem type, that is, a so-called intermediate transfer system, in which a plurality of image forming units 10 (10Y, 10M, 10C, 10K), an intermediate transfer belt 15 as an image carrier for sequentially transferring (primary transfer) and holding each color component toner image formed by each image forming unit 10, and a superimposed image transferred on the intermediate transfer belt 15 The secondary transfer unit 20 includes a secondary transfer unit 20 that collectively transfers (secondarily transfers) the toner image to a sheet P that is a recording material (transfer material), and a fixing unit 60 that fixes the secondary-transferred image on the sheet P. Further, a control unit 40 for controlling the operation of each device (each unit) is provided.
[0011]
In the present embodiment, each of the image forming units 10 (10Y, 10M, 10C, 10K) is charged around the photosensitive drum 11 as an image forming carrier rotating in the direction of arrow A. Charger 12, a laser exposure device 13 (an exposure beam is indicated by a symbol Bm in the figure) for writing an electrostatic latent image on the photosensitive drum 11, A developing device 14 for visualizing the electrostatic latent image with toner, a primary transfer roll 16 for transferring each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 15, and a residual toner on the photosensitive drum 11 Electrophotographic devices such as a drum cleaner 17 to be removed are sequentially arranged. These image forming units 10 are arranged substantially linearly in the order of yellow (Y color), magenta (M color), cyan (C color), and black (K color) from the upstream side of the intermediate transfer belt 15. I have.
[0012]
The intermediate transfer belt 15, which is an intermediate transfer member (toner image carrier), is an endless belt in which a resin such as polyimide or polyamide contains an appropriate amount of a conductive agent such as carbon black, and has a volume resistivity of 10 ⁶ to 10 ⁶ . It is formed to be 10 ¹⁴ Ω · cm, and is formed of a film-shaped endless belt having a thickness of, for example, about 0.1 mm. The intermediate transfer belt 15 is circulated (rotated) at a predetermined speed in a direction B shown in the figure by various rolls. The various rolls include a drive roll 31 driven by a motor (not shown) having an excellent constant speed to circulate and drive the intermediate transfer belt 15, and an intermediate roller extending substantially linearly along the direction in which the photosensitive drums 11 are arranged. A support roll 32 that supports the transfer belt 15, a tension roll 33 that applies a constant tension to the intermediate transfer belt 15 and functions as a correction roll that prevents the intermediate transfer belt 15 from meandering, and a backup provided in the secondary transfer unit 20. The cleaning unit includes a roll 25 and a cleaning backup roll 34 provided in a cleaning unit that scrapes residual toner on the intermediate transfer belt 15.
[0013]
Each of the primary transfer rolls 16 provided inside the intermediate transfer belt 15 which is opposed to each of the photosensitive drums 11 and extends substantially linearly has a polarity opposite to the charging polarity (negative in this embodiment) of the toner (this embodiment). In this embodiment, a positive voltage is applied. As a result, the toner images on the respective photosensitive drums 11 are sequentially electrostatically attracted to the intermediate transfer belt 15, and a superimposed toner image is formed on the intermediate transfer belt 15.
[0014]
The secondary transfer unit 20 includes a secondary transfer / conveyance belt 21 as a transfer member disposed on the toner image bearing surface side of the intermediate transfer belt 15, a backup roll 25, and the like. The backup roll 25 is made of a tube of EPDM and NBR blended rubber in which carbon is dispersed on the surface, and is made of EPDM rubber. The surface of the backup roll 25 is formed to have a surface resistivity of 7 to 10 log Ω / □ and a roll diameter of 28 mm. Is set to, for example, 70 ° (Asuka C). The backup roll 25 is disposed on the back side of the intermediate transfer belt 15 and forms a counter electrode of the secondary transfer conveyance belt 21, and a metal power supply roll 26 to which a secondary transfer bias is stably applied is abutted. Have been. In the present embodiment, a secondary transfer bias having the same polarity (negative polarity) as the charged polarity of the toner is applied by the power supply roll 26.
[0015]
On the other hand, the secondary transfer transport belt 21 is a semiconductive endless belt stretched by a drive roll 22 and an idle roll 23 and having a volume resistivity of, for example, 10 ⁶ to 10 ¹⁰ Ω · cm. The drive roll 22 is disposed in pressure contact with the backup roll 25 with the secondary transfer conveyance belt 21 and the intermediate transfer belt 15 interposed therebetween, and performs a secondary transfer roll for performing secondary transfer on the paper P conveyed on the secondary transfer conveyance belt 21. Functioning as
A belt cleaner 35 that removes residual toner and paper dust on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15 is provided downstream of the secondary transfer unit 20 of the intermediate transfer belt 15. Are provided so as to be able to freely come and go. On the other hand, on the upstream side of the yellow image forming unit 10Y, a reference sensor (home position sensor) for generating a reference signal serving as a reference for setting an image forming timing in each image forming unit 10 (10Y, 10M, 10C, 10K). ) 42, and an image density sensor 43 for adjusting image quality is provided downstream of the black image forming unit 10K. The reference sensor 42 recognizes a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Each of the image forming units is controlled by an instruction from the control unit 40 based on the recognition of the reference signal. 10 (10Y, 10M, 10C, 10K) is configured to start image formation.
[0016]
Further, in the present embodiment, as a paper transport system, a paper tray 50 for storing the paper P, a paper feed roll 51 for taking out and transporting the paper P stacked on the paper tray 50 at a predetermined timing, a paper feed roll 51 The transport roll 52 transports the paper P fed by the transport roll 52, the transport chute 53 that transports the paper P transported by the transport roll 52 to the secondary transfer unit 20, and transports the paper P after the secondary transfer by the secondary transfer transport belt 21 And a transport belt 55 that transports the paper P to be fixed to the fixing unit 60.
[0017]
Further, on the paper P exit side of the secondary transfer unit 20, an intrusion prevention unit 70 for preventing the paper P after the secondary transfer from entering the belt cleaner 35 in a state where the paper P is stuck to the intermediate transfer belt 15 is provided. Have been.
[0018]
Next, a basic image forming process of the image forming apparatus according to the present embodiment will be described. Image data output from an unillustrated image reading device (IIT) or an unillustrated personal computer (PC) is input to an image forming apparatus as illustrated in FIG. In the image forming apparatus, after an image processing device (IPS) (not shown) performs predetermined image processing, an image forming operation is performed by the image forming unit 10 or the like. The image processing apparatus (IPS) performs predetermined processing such as shading correction, positional deviation correction, brightness / color space conversion, gamma correction, various image editing such as frame erasing, color editing, and moving editing on the input reflectance data. Image processing is performed. The image data subjected to the image processing is converted into four color material gradation data of yellow (Y), magenta (M), cyan (C), and black (K), and is output to the laser exposure device 13. .
[0019]
The laser exposure device 13 irradiates, for example, an exposure beam Bm emitted from a semiconductor laser to each of the photosensitive drums 11 of the image forming units 10Y, 10M, 10C, and 10K according to the input color material gradation data. I have. In the photoconductor drums 11 of the image forming units 10Y, 10M, 10C, and 10K, after the surface is charged by the charger 12, the surface is scanned and exposed by the laser exposure device 13 to form an electrostatic latent image. The formed electrostatic latent image is developed as a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K) in each of the image forming units 10Y, 10M, 10C, and 10K. Is done.
[0020]
The toner images formed on the photosensitive drums 11 of the image forming units 10Y, 10M, 10C, and 10K are transferred onto the intermediate transfer belt 15 at a primary transfer section where the respective photosensitive drums 11 and the intermediate transfer belt 15 abut. Transcribed. More specifically, in the primary transfer section, a voltage having a polarity opposite to the charging polarity of the toner is applied to the base material of the intermediate transfer belt 15 by the primary transfer roll 16 so that the unfixed toner image is applied to the surface of the intermediate transfer belt 15. And the primary transfer is performed. The unfixed toner image primary-transferred in this way is conveyed to the secondary transfer unit 20 as the intermediate transfer belt 15 rotates.
[0021]
On the other hand, in the paper transport system, the paper supply roll 51 rotates in synchronization with the timing of image formation, and paper P of a predetermined size is supplied from the paper tray 50. The paper P supplied by the paper feed roll 51 is transported by the transport roll 52, and reaches the secondary transfer unit 20 via the transport chute 53. Before reaching the secondary transfer section 20, the sheet P is temporarily stopped, and the registration roll (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 15 carrying the toner image as described above. Thus, the position of the sheet P and the position of the toner image are aligned.
[0022]
In the secondary transfer section 20, the drive roll 22 is pressed against the backup roll 25 via the semiconductive secondary transfer conveyance belt 21 and the intermediate transfer belt 15. At this time, the sheet P conveyed in a timely manner is sandwiched between the intermediate transfer belt 15 and the secondary transfer conveyance belt 21. At this time, when a secondary transfer bias having the same polarity as the charging polarity of the toner is applied to the power supply roll 26, a transfer electric field is formed on the secondary transfer conveyance belt 21 as a counter electrode, and the transfer electric field is carried on the intermediate transfer belt 15. The unfixed toner image is electrostatically transferred to the sheet P at a secondary transfer position where the unfixed toner image is pressed by the drive roll 22 and the backup roll 25.
[0023]
Thereafter, the sheet P on which the toner image has been electrostatically transferred is conveyed as it is while being separated from the intermediate transfer belt 15 by the secondary transfer conveyance belt 21, and is provided downstream of the secondary transfer conveyance belt 21 in the sheet conveyance direction. Transport belt 55. The transport belt 55 transports the paper P to the fixing unit 60 in accordance with the optimal transport speed in the fixing unit 60. The unfixed toner image on the sheet P conveyed to the fixing unit 60 is fixed on the sheet P by being subjected to fixing processing by heat and pressure by the fixing unit 60, and the sheet P on which the fixed image is formed is discharged by a discharge roll. (Not shown) to be discharged outside the apparatus. On the other hand, after the transfer to the paper P is completed, the residual toner remaining on the intermediate transfer belt 15 is conveyed to the cleaning unit with the rotation of the intermediate transfer belt 15, and the intermediate toner is transferred by the cleaning backup roll 34 and the belt cleaner 35. It is removed from the transfer belt 15.
[0024]
Next, the intrusion prevention unit 70 will be described in detail. FIG. 2 is an enlarged view of a side surface of the secondary transfer unit 20 and the intrusion prevention unit 70, and FIG. 3 is a top view of the intrusion prevention unit 70 as viewed from a direction III in FIG. In FIG. 3, the intermediate transfer belt 15 is omitted. In the present embodiment, the intrusion prevention unit 70 includes brackets 71 provided on both sides of the intermediate transfer belt 15 for attachment to a frame (not shown), a base 72 having both ends attached to the bracket 71, and a base 72. A reflection-type POB (Paper On Belt) sensor 73 disposed on the upper surface, a shaft 74 as a shaft member attached to the tip of the base 72 (the side facing the secondary transfer unit 20), and the shaft 74. And a stopper 75 (75a to 75c) as a swinging member or a plate-like member, which is swingably attached to the shutter.
[0025]
Here, the stopper 75 is a plate-shaped member made of metal or resin having a thickness of 2 mm, and the tip end (oscillation end) of the stopper 75 is attached to the secondary transfer unit 20 so as to face the moving direction of the intermediate transfer belt 15. And has a round shape having a predetermined curvature. The stopper 75 is normally locked at a position shown by a solid line in FIG. 2, and is configured to be able to swing to a position shown by a broken line in FIG. 2 by being pressed from below. The width W of the base 72 is set to be larger than the sheet width of the sheet P of the maximum size usable in the image forming apparatus. Further, in the present embodiment, since a so-called side registration method is employed, the POB sensor 73 is provided on the side of the stopper 75a through which the paper P of all sizes passes. When the sheet P is detected by the POB sensor 73, the image forming operation is urgently stopped by an instruction from the control unit 40, and the sheet P can be prevented from entering the belt cleaner 35.
[0026]
Next, the operation of the rush prevention unit 70 will be described. FIG. 4A shows a normal state, that is, a state in which the sheet P is stably conveyed. In this state, the sheet P is conveyed while being attracted to the secondary transfer conveyance belt 21 and does not contact the stopper 75, and the stopper 75 is at a normal position.
[0027]
On the other hand, in FIG. 4B, when the leading end of the sheet P is discharged from the secondary transfer unit 20, an emergency of the fixing unit 60 (see FIG. 1) due to an abnormality (for example, occurrence of a paper jam in the fixing unit 60) occurs. This shows the state at the time of occurrence of the abnormality where the stop was performed. When such an emergency stop is performed, the transport belt 55 (see FIG. 1), the intermediate transfer belt 15, the secondary transfer transport belt 21, and the like may be stopped simultaneously with the fixing unit 60. If the carrier is suddenly stopped (see FIG. 1), the carrier is developed on the photosensitive drum 11 and the photosensitive drum 11 and the intermediate transfer belt 15 are damaged. Is stopped after a predetermined time has elapsed after the stoppage. For this reason, the sheet P stops in a state where the trailing edge is lifted, and a center folded portion Pb occurs. At this time, the stopper 75 is pressed by the middle bent portion Pb and swings upward, and stops in a state where the leading end portion thereof is in contact with the intermediate transfer belt 15. Therefore, in this state, the paper P cannot enter between the intermediate transfer belt 15 and the stopper 75, and the situation that the folded paper P enters the belt cleaner 35 does not occur. When the jammed sheet P is removed, the stopper 75 that is no longer pressed returns to the normal position (see FIG. 4A) due to the weight of the stopper 75.
[0028]
As described above, in the image forming apparatus according to the present embodiment, the sheet P after the secondary transfer cannot enter the belt cleaner 35 while being stuck to the intermediate transfer belt 15. As a result, it is possible to prevent breakage of the belt cleaner 35 and occurrence of cleaning failure in the intermediate transfer belt 15. Further, since a plate-shaped member that is swingably disposed is used as the stopper 75, the stopper 75 is not plastically deformed, and the intermediate transfer belt 15 can be prevented from being damaged by the stopper 75. . Further, in the present embodiment, since the tip of the stopper 75 is rounded, it is possible to avoid a situation in which the intermediate transfer belt 15 is damaged by the stopper 75 or untransferred toner is scraped off, thereby causing contamination inside the apparatus. As a result, even when the paper P stuck to the intermediate transfer belt 15 is removed, the situation where the intermediate transfer belt 15 is damaged by the stopper 75 does not occur.
[0029]
In the present embodiment, the stopper 75 is returned to the normal position by its own weight. However, as shown in FIG. 5, for example, a torsion spring as an urging member is wound around the shaft 74 as shown in FIG. If a configuration is adopted in which one end is hooked on a hook portion 71a attached to the bracket 71 and the other end is hooked on a hook portion 75d provided on the stopper 75, the forcible force of the torsion spring 76 is used. The stopper 75 can be returned to the normal position. However, the spring force of the torsion spring 76 needs to be set to be smaller than the pressing force due to the folded paper P.
[0030]
As shown in FIG. 6, a bias power supply 77 as a bias application mechanism is connected to the stopper 75, and the bias power supply 77 applies a bias having the same polarity as the toner (negative polarity in the present embodiment). Then, when the stopper 75 comes into contact with the intermediate transfer belt 15, the transfer of the toner attached to the intermediate transfer belt 15 can be suppressed.
[0031]
In the present embodiment, an image forming apparatus of a type that transfers a toner image to a sheet P via an intermediate transfer belt 15 as an image carrier has been described. However, the present invention is not limited to this. The present invention can be similarly applied to an image forming apparatus of a type in which a toner image is directly transferred to a sheet P from the printer. This case is particularly effective in an image forming apparatus using an endless photoreceptor belt.
Further, in the present embodiment, an example in which the secondary transfer conveyance belt 21 is used as the transfer member has been described. However, the present invention may be similarly applied to a case using a general transfer roll.
[0032]
-Embodiment 2-
The present embodiment is substantially the same as the first embodiment, except that a stopper 78 is provided with a toner reservoir (powder receiver) for storing the toner T, as shown in FIG. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the detailed description thereof will be omitted.
The stopper 78 is provided with a bearing portion 78a swingably attached to the shaft 74, a plate-shaped flat plate portion 78b attached to the bearing portion 78a, and a tip end of the flat plate portion 78b toward the intermediate transfer belt 15 side. And a curving curved portion 78c. The flat plate portion 78b and the curved portion 78c form a toner reservoir for receiving the toner T peeled off from the intermediate transfer belt 15.
[0033]
In the present embodiment, by configuring the stopper 78 as described above, it is possible to prevent the sheet P from entering the belt cleaner 35 when an abnormality occurs, as in the first embodiment. Further, since the curved portion 78c is provided at the tip of the stopper 78, the intermediate transfer belt 15 is not damaged even when the stopper 78 comes into contact with the intermediate transfer belt 15. Further, in the present embodiment, when the stopper 78 comes into contact with the intermediate transfer belt 15, the toner T detached from the intermediate transfer belt 15 can be stored on the upper side of the stopper 78, so that the inside of the apparatus becomes dirty. Can be prevented from occurring.
[0034]
-Embodiment 3-
This embodiment is substantially the same as the first embodiment, except that a roll 79b is attached to the tip of a stopper 79 as shown in FIG. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the detailed description thereof will be omitted.
[0035]
The stopper 79 is disposed so as to swing freely on the shaft 74, a roll 79b mounted on the tip side of the stopper body 79a, and a roll 79b inside the stopper body 79a so as to contact the roll 79b. And a scraper 79c. As described above, in the present embodiment, the toner reservoir is formed in the stopper main body 79a.
[0036]
In the present embodiment, by configuring the stopper 79 as described above, it is possible to prevent the sheet P from entering the belt cleaner 35 when an abnormality occurs, as in the first embodiment. Further, since the roll 79b is provided at the tip of the stopper 79, the intermediate transfer belt 15 is not damaged even when the stopper 79 comes into contact with the intermediate transfer belt 15. Further, in the present embodiment, when the stopper 79 comes into contact with the intermediate transfer belt 15, the toner T detached from the intermediate hand transfer belt 15 and adhered to the roll 79b is scraped off by the scraper 79c and stored in the stopper main body 79a. This makes it possible to prevent the occurrence of dirt inside the machine.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent the recording material that has been folded in the middle from being conveyed while being attached to the image carrier.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating an outline of an image forming apparatus according to a first embodiment;
FIG. 2 is a side view of a secondary transfer unit and a rush prevention unit according to the first embodiment.
FIG. 3 is a top view of the intrusion prevention unit shown in FIG. 2;
FIGS. 4A and 4B are diagrams illustrating an operation of a rush prevention unit at a normal time and at an abnormal time, respectively.
FIG. 5 is a side view of a secondary transfer unit and a rush prevention unit according to a modification of the first embodiment.
FIG. 6 is a side view of a secondary transfer unit and a rush prevention unit according to another modification of the first embodiment.
FIG. 7 is a side view of a secondary transfer unit and a rush prevention unit according to a second embodiment.
FIG. 8 is a side view of a secondary transfer unit and a rush prevention unit according to a third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Image forming unit, 15 ... Intermediate transfer belt, 20 ... Secondary transfer part, 21 ... Secondary transfer conveyance belt, 22 ... Drive roll, 23 ... Idle roll, 25 ... Backup roll, 26 ... Power supply roll, 31 ... Drive Roll, 32: Support roll, 33: Tension roll, 34: Cleaning backup roll, 35: Belt cleaner, 40: Control unit, 50: Paper tray, 60: Fixing unit, 70: Intrusion prevention unit, 71: Bracket, 71a ... Hook part, 72 ... Base part, 73 ... POB sensor, 74 ... Shaft, 75 ... Stopper, 75d ... Hook part, 76 ... Torsion spring, 77 ... Bias power supply, 78 ... Stopper, 78a ... Bearing part, 78b ... Flat plate part, 78c ... Bending part, 79 ... Stopper, 79a ... Stopper body, 79b ... Roll, 79c ... Scraper, P ... for , T ... toner

Claims (10)

An image carrier rotatably disposed;
A transfer member that is arranged to face the image carrier and electrostatically transfers the toner image on the image carrier to a recording material;
The recording device is disposed downstream of the opposing portion of the image carrier and the transfer member in the moving direction of the image carrier, and is normally held at a position separated from the image carrier, and passes through the opposing portion. An image forming apparatus comprising: a swinging member capable of swinging to a position where the member contacts the image carrier when pressed by a material. The image forming apparatus according to claim 1, wherein the swing member is made of metal or resin having a predetermined thickness. The image forming apparatus according to claim 1, wherein a portion of the swing member that contacts the image carrier has a predetermined curvature. The image forming apparatus according to claim 1, wherein a rotatable roll member is provided on a free end side of the swing member. 2. The image forming apparatus according to claim 1, wherein the swing member is provided with a powder reservoir for receiving powder dropped from the surface of the image carrier. The image carrier is an intermediate transfer belt on which a toner image formed and carried on the image forming carrier is primarily transferred,
2. The image forming apparatus according to claim 1, wherein the transfer member is a transfer conveyance belt that conveys the toner image primarily transferred onto the intermediate transfer belt by secondarily transferring the toner image onto the recording material. An image carrier rotatably disposed;
A transfer member that is arranged to face the image carrier and electrostatically transfers the toner image on the image carrier to a recording material;
A shaft member extending in a direction perpendicular to the moving direction on the downstream side in the moving direction of the image carrier from a facing portion of the image carrier and the transfer member;
An image forming apparatus comprising: a plate-shaped member having one end swingably attached to the shaft member and the other end arranged in a direction facing a moving direction of the image carrier. The image forming apparatus according to claim 7, further comprising an urging member that urges the plate member in a direction away from the image carrier. The image forming apparatus according to claim 7, further comprising a bias applying mechanism that applies a bias having the same polarity as the toner constituting the toner image to the plate member. The image carrier has an endless belt shape stretched over a plurality of rolls,
The image forming apparatus according to claim 7, wherein the transfer member has an endless belt shape stretched over a plurality of rolls.

Images