JP2004252061A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent toner soil directly transferred by an accidental jamming of a transfer material from sticking to and consequently soiling the back of the transfer material, in the transfer material conveyance belt of an image forming apparatus that performs fixing before separation. <P>SOLUTION: The transfer material conveyance belt Bp makes the state that it is away from an intermediate transfer body 6a a home position. An image forming operation is performed such that after a state in which the transfer material P has been attracted to the surface of the conveyance belt Bp is detected by a transfer material detection means D with specific timing, the press contact of the conveyance belt Bp with the intermediate transfer belt 6 is performed at a secondary transfer nip N2. On the other hand, when the transfer material P is not detected with the specific timing, the image forming operation is forcibly ended, so that the press contact of the conveyance belt Bp with the intermediate transfer belt 6 is not performed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multicolor image forming apparatus that transfers an image of each color component onto a recording material by an electrophotographic method or an electrostatic recording method to obtain an image, and is applicable to a color copying machine, a color laser beam printer, and the like. Can be embodied.
[0002]
[Prior art]
For example, an apparatus as shown in FIG. 2 is used as an electrophotographic image forming apparatus.
[0003]
The photoconductor drum 1 is rotated at a predetermined driving speed (process speed), and the surface of the photoconductor drum 1 is uniformly charged by the primary charger 2. Next, a laser beam is exposed and scanned by the exposure device 3 which is ON / OFF controlled in accordance with image data of the yellow component as the first color, so that the electrostatic charge of the yellow component of the first color is formed on the photosensitive drum 1. Form a latent image.
[0004]
Reference numerals 4 and 5 denote developing means, and reference numeral 4 denotes fixed developing means containing a black toner developing device. On the other hand, reference numeral 5 denotes a rotary developing device for accommodating toner developing devices 5y, 5m, and 5c for color toners, that is, yellow, magenta, and cyan color components, which face the photosensitive drum 1 when developing the corresponding color components. It switches to the position where you do.
[0005]
The electrostatic latent image of the yellow component formed by the above process is developed and visualized by the yellow toner developing device 5y. The visualized first yellow toner image is transferred by a transfer unit 61 onto the surface of an intermediate transfer member (intermediate transfer drum) 6 which is rotated while being pressed against the photosensitive drum 1 with a predetermined pressing force. The primary transfer is electrostatically performed by applying a bias having a polarity opposite to that of the electric charge.
[0006]
The above-described primary transfer process on the intermediate transfer drum 6 is similarly repeated for other toners (magenta, cyan, and black), and the color image is visualized by being sequentially transferred and laminated on the intermediate transfer drum 6. Is formed.
[0007]
The stacked color images are conveyed to the secondary transfer portion N2, and are collectively and secondarily transferred onto the transfer material P conveyed at a predetermined timing.
[0008]
At this time, the toner is electrostatically attracted to the transfer material P by applying a bias having a polarity opposite to the charge of the toner to the secondary transfer outer roller 71.
[0009]
In the drawing, Bp denotes a transfer material transport belt, which is stretched by a secondary transfer inner roller 72, a stretching roller 502, a driving roller 503, and a tension roller 504, and is driven in the direction of the arrow in the drawing. The transfer material P is transported from the paper tray 301 to the transfer material transport belt Bp by the pickup roller 401 and the transport roller pairs 402 and 403, and is supplied onto the transfer material transport belt Bp by the registration rollers 501.
[0010]
The transfer material P on which the color visible image has been transferred is separated from the transfer material transfer belt Bp by curvature separation at the portion of the drive roller 503, transferred to the fixing device 9 by the pre-fixing guide 10, fixed, and fixed as a permanent image. Become.
[0011]
In the transfer method in which the toner is electrostatically attracted onto the transfer material as in the above configuration, it has been pointed out that image deterioration occurs when the transfer material peels off from the transport belt or after separation, Measures have been taken.
[0012]
First, there is an image defect called "crow" due to peeling discharge induced when the transfer material and the conveyor belt are separated.
[0013]
As shown in FIG. 3, a bias is applied to transfer the toner layer formed on the intermediate transfer drum 6 at the secondary transfer portion. Specifically, by applying a positive DC bias to the outer secondary transfer roller 71 and grounding the inner secondary transfer roller 72, the negatively charged toner is transferred onto the transfer material transport belt Bp. Is attracted onto the transfer material P carried on the sheet.
[0014]
Since a positive bias is applied to the outer secondary transfer roller 71, a transfer electric field E _2tr is generated in the secondary transfer portion as shown in FIG. At this time, the intermediate transfer drum 6, the transfer material P, and the transfer material transport belt Bp all have a volume resistivity of 10 ⁷ to 10 ¹⁶ Ω · cm, and behave as a dielectric (capacitor) because of medium resistance or high resistance. As a result, spontaneous polarizations P ₆ , P _p , and P _Bp are generated inside each of them, and charges are induced in each surface layer by these spontaneous polarizations. As shown in FIG. 4, the charge induced on the surface of the transfer material P on the image surface side (the side in contact with the toner) is a positive charge and the charge on the surface of the intermediate transfer drum 6 that contacts the toner. , A negatively charged toner is induced, so that the negatively charged toner electrostatically moves from the surface layer of the intermediate transfer drum 6 to the surface layer of the transfer material P.
[0015]
After the transfer of the toner onto the paper, the transfer material P is conveyed to the separation unit and separated. At this time, as shown in FIG. 5, a positive charge is induced on the rear surface of the peeled transfer material P, while a negative charge is induced on the surface of the belt on the conveying surface side. If an electric field is generated in the gap G and the electric field strength exceeds the Paschen discharge start condition, dielectric breakdown may occur in the gap.
[0016]
When a discharge is generated in the gap between the transfer material P and the belt, the charge induced at the place where the discharge is generated is locally extinguished. Occurs. This uneven charge induces a creeping discharge, which disturbs the toner electrostatically adsorbed on the surface. It is known that the discharge trace due to the creeping discharge is a direct cause of an image defect called “crow” in a halftone image.
[0017]
"Crows" are more frequent in low-humidity environments where the charge amount of the toner, the transfer material P, and the transport belt Bp is high, and several measures have been taken so far.
[0018]
One of them is a method of providing an auxiliary separation charger C as shown in FIG. The separation assisting charger C is a corona charger, and alleviates the electric charge induced in the transfer material P and the transport belt Bp by applying an AC bias to the discharge wire. This eliminates the electric field induced by the charge in the gap G between the back surface of the transfer material P and the front surface of the transport belt Bp, so that it is possible to avoid image deterioration due to discharge.
[0019]
However, such a method using the auxiliary separation charger also has a disadvantage. That is, since the charge of the toner is reduced in addition to the transfer material and the transport belt, the toner cannot be electrostatically attracted on the paper, and the unfixed toner image is disturbed.
[0020]
On the other hand, the drive roller is not directly grounded, but is grounded via a device Dr such as a resistor or a varistor, so that a minimum necessary charge for toner adsorption is secured. After the material P is separated, a method of charging the toner again using the post-charging device Cp may be used. However, in either case, there is a risk that the cost is increased or the configuration is complicated. Furthermore, when the process speed is increased to further improve the productivity, the charge may not be removed in time, and the charged charges may not be sufficiently removed. Therefore, the above measures may be insufficient.
[0021]
Next, as a second problem, there is a problem of an image defect caused by a transfer material in an unfixed state touching the pre-fixing guide.
[0022]
As shown in FIG. 8, the transfer material P on which the image has been transferred is separated from the conveyor belt Bp, passes through the pre-fixing guide 10, and is fixed by the fixing device 9. At this time, as shown in FIG. 8B, a rib 101 is provided on the pre-fixing guide 10 in order to ensure the transportability of the transfer material P. Since the conveyed transfer material P is rubbed by touching the rib 101, a contact portion between the rib 101 and the transfer material P is frictionally charged. Due to the frictional charging, toner scatters at a contact portion between the transfer material P and the rib 101 at a rear portion of the transfer material P, thereby causing a linear image defect in a halftone image called “rib trace”.
[0023]
The trace of the rib strongly depends on the type and shape of the resin constituting the rib 101, and the rib 101 is made of a material that is not easily triboelectrically charged. Countermeasures have been taken by reducing the area of the part and suppressing triboelectric charging. However, it is necessary to increase the process speed in order to further increase productivity in the future, and from the viewpoint of alleviating the suppression of triboelectric charging by dielectric relaxation, it can be said that increasing the speed is disadvantageous.
[0024]
On the other hand, as is known in Japanese Patent Application Laid-Open No. H11-163, as described below, this is avoided by a method of performing fixing at a stage before the transfer material is separated from the conveying means. This is a method of avoiding electrostatic image deterioration by fixing the image already at the time of separation, and image deterioration due to peeling discharge such as "crow" as described above, separation mark marks, etc. It has succeeded in avoiding image deterioration due to electrical and mechanical attack on the unfixed image after the transfer.
[0025]
[Patent Document 1]
JP-A-5-313531
[Problems to be solved by the invention]
However, when the fixing unit is disposed on the transport belt as described above, there is a possibility that toner contamination on the transport belt may be fixed on the transport belt by the fixing unit.
[0027]
For example, it is assumed that the transfer material is not transported to the secondary transfer unit at the intended timing. At this time, as shown in FIG. 9, in a place where there is no paper, that is, in a place where the conveyance belt Bp and the intermediate transfer body 6 on which the toner layer is formed are in direct contact, the toner layer on the intermediate transfer body 6 is conveyed. Secondary transfer is performed on the belt Bp. At this time, the toner layer T2 transferred onto the transport belt Bp is heated and fixed on the transport belt Bp in the fixing unit 9 formed by the fixing roller 901 and the pressure roller 902. The toner fixed on the conveyance belt Bp in this way is transferred to the back of the transfer material P conveyed for the next and subsequent image formation and to the back of the paper in the fixing unit 9. There is a risk that the back surface will be soiled.
[0028]
Specifically, as a case where the transfer material is not conveyed at an intended timing, a case where a jam occurs in the transfer material conveyance upstream of the registration roller 501 can be considered.
[0029]
Further, as a case where unintended toner stains are transferred onto the transport belt, there is a stain caused by fogging toner or the like. In this case, the drive is performed with the toner stain on the transport belt surface. There is a risk of soiling the back surface.
[0030]
As described above, the toner fixed on the belt in the separation and fixing unit 9 is difficult to remove by a known cleaning method such as blade cleaning or roller cleaning applying a cleaning bias, and does not transfer the toner onto the transport belt. It is necessary to take measures from the viewpoint of.
[0031]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problem, and toner dirt directly transferred due to unintended transfer material jam or the like adheres to a transfer material transport belt of an image forming apparatus that performs fixing before separation. It is another object of the present invention to provide an image forming apparatus that can prevent the back surface of a transfer material from being stained.
[0032]
[Means for Solving the Problems]
The present invention has the following configurations (1) and (2) in order to solve the above problems.
[0033]
(1) An image forming section, an intermediate transfer body that temporarily holds the image formed by the image forming section, a fixing section, and a transfer material to which the image carried on the intermediate transfer body is transferred. In an image forming apparatus having a transfer material conveying unit and a fixing unit,
The end portion of the transfer material conveying means is provided downstream of the exit of the fixing unit, wherein the transfer material after image fixing is separated from the transfer material conveying means downstream of the exit of the fixing unit,
The image forming apparatus is characterized in that the transfer material conveying means is set so as to be able to freely contact and separate from the intermediate transfer member, and a state where the transfer material is separated is a home position.
[0034]
(2) transfer material detecting means for confirming that the transfer material is carried on the transfer material transport means,
The image forming apparatus according to (1), wherein the detection unit is disposed upstream of a secondary transfer unit that transfers an image from an intermediate transfer member to a transfer material in a transfer material transport direction.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0036]
Embodiment 1
FIG. 1 is a schematic diagram of an electrophotographic color image forming apparatus (color laser printer) showing an embodiment of the present invention.
[0037]
In the present embodiment, the photosensitive drum 1 has an organic photoconductor (OPC) layer formed on the outer surface of an aluminum cylinder having a diameter of 60 mm, and is driven to rotate in a direction indicated by an arrow by a drive motor (not shown).
[0038]
The charging unit 2 is a conductive roller, and is brought into contact with the photosensitive drum 1 and applies a bias to the roller to uniformly charge the surface of the photosensitive drum 1 to a negative polarity.
[0039]
Exposure to the photosensitive drum 1 is performed by a laser exposure device 3. The laser exposure device 3 is ON / OFF controlled by a controller (not shown), and forms an electrostatic latent image by selectively exposing the photosensitive drum 1 to light.
[0040]
The developing means is for visualizing the electrostatic latent image, and includes an independent fixed developing device 4 containing a black developing device and a rotary developing device containing yellow, magenta, and cyan developing devices 5y, 5m, and 5c. It comprises a vessel 5. The black developing device 4 forms a visible image on the image carrier using black toner, and its developing sleeve is disposed at a position facing the photosensitive drum 1 with a small interval (about 300 μm). The black developing device 4 conveys the black toner to the developing sleeve by a toner conveying mechanism in the container, applies a thin layer of the toner to the outer periphery of the sleeve by a regulating blade pressed against the outer periphery of the developing sleeve, and applies a charge to the toner. By applying a developing bias in which an AC bias is superimposed on a DC bias to the sleeve, the electrostatic latent image formed on the photosensitive drum 1 is developed.
[0041]
On the other hand, the three color toner developing devices 5y, 5m, and 5c are detachably held in the rotatable rotary developing device 5, and are rotated while being held by the rotary developing device 5 during image formation. The yellow toner developing unit 5y stops at a position facing the photosensitive drum 1, for example, and the sleeve in the yellow toner developing unit 5y faces the photosensitive drum 1 at a minute interval (about 300 μm). Then, a visible image is formed on the photosensitive drum 1. When developing a toner image of a different color, for example, a cyan toner image or a magenta toner image, the rotation is similarly performed, and then stopped at a position facing the photosensitive drum 1 to perform the development.
[0042]
When the above-described developing operation is completed, the rotary developing device 5 is separated to a position where the sleeves in the developing devices of all colors in the rotary developing device 5 do not contact the photosensitive drum 1, and this position is defined as a home position. I do. Setting the home position in this manner prevents the toner in the rotary type developing device 5 from being carelessly attached to the surface of the photosensitive drum 1, and is stored in the other rotary type developing device 5. In the developing device of the same color. Furthermore, since the rotary developing device 5 is separated while the fixed developing device 4 is operating, it is not necessary to agitate the color toner when it is unnecessary, and it is possible to prevent unnecessary deterioration of the toner.
[0043]
The intermediate transfer member (intermediate transfer belt) 6 is a resin endless belt stretched by a primary transfer roller 61, a driving roller 62, a stretching roller 63, a tension roller 64, and a secondary transfer inner roller 72. In the present example, a polyimide (PI) resin having a thickness of 75 μm was used, and carbon black was added so that the volume resistivity was about 10 ⁹ Ω · cm. The peripheral length of the intermediate transfer belt 6 was 565.2 mm, and the driving speed (process speed) was 251.2 mm / sec.
[0044]
The cleaning blade 12 is for cleaning the residual toner on the intermediate transfer belt 6 after transferring the toner layer laminated on the intermediate transfer body to the transfer material P. The cleaning blade 12 is configured so as to be able to freely contact and separate from the intermediate transfer belt 6. When forming a full-color image, the intermediate transfer body is driven four times or more to form a visible image. After the image is collectively transferred to the transfer material P, the image is pressed against the intermediate transfer belt 6.
[0045]
The transfer material transport belt Bp is stretched by a stretching roller 502, a driving roller 503, and a tension roller 504. A registration roller 501 is opposed to the tension roller 502 with the transfer material conveyance belt Bp interposed therebetween. The transfer material P is transported from the paper tray 301 by the pickup roller 401 and the transport roller pairs 402 and 403, and is attracted and transported by the registration roller 501 to the transfer material transport belt Bp. In this example, a polyimide (PI) resin having a thickness of 75 μm was used, and carbon black was added so that the volume resistivity was about 10 ⁹ Ω · cm.
[0046]
As described above, in the image forming method in which fixing is performed before separation, the use of the transfer material transport belt has two advantages. The first purpose is to avoid the temperature rise of the image forming unit by sufficiently separating the image forming unit from the fixing units 901 and 902.
[0047]
There are several problems caused by too high a temperature inside the machine. For example, in the case of the OPC photoreceptor used in this example, when the temperature rises, the OPC photoreceptor does not charge properly but cannot form an electrostatic latent image. When the transfer bias applying roller used in the primary transfer nip N1 or the secondary transfer nip N2 is a rubber roller whose resistance is adjusted with an ion-conductive filler, the resistance of the roller increases with the temperature. Therefore, when the transfer bias is managed by the constant voltage control, an overcurrent occurs, which may cause image deterioration.
[0048]
Therefore, by arranging the fixing device at the downstream position in the conveyance belt conveyance direction, the heat source is arranged at a position distant from the secondary transfer nip N2, so that the temperature rise of the image forming unit can be suppressed. Further, if necessary, a heat insulating member for appropriately shielding radiant heat is provided between the fixing roller 901 and the image forming unit in the drawing (for example, between the rotary developing device 5 and the intermediate transfer belt cleaning member 12). May be.
[0049]
The second purpose is to stabilize the behavior of the paper before and after the secondary transfer nip since the rotation is performed while the transfer material is being sucked.
[0050]
Image deterioration such as “crow” due to discharge before and after the transfer nip is caused by a gap between the intermediate transfer belt and the transfer material or between the transfer material (or the transfer material transport belt) and the transfer charger. When the transfer material is nipped directly between the intermediate transfer belt and the secondary transfer roller without using the transfer material transport belt, unintended gaps are formed due to slight skew of the transfer material or misalignment in front of the roller alignment. As a result, there is a risk of causing discharge deterioration, and a very severe design is required.
[0051]
By adsorbing the transfer material P on the belt at the upstream of the transfer nip by using the transfer material transport belt Bp, it is possible to avoid formation of an unintended gap before and after the nip, thereby reliably preventing image deterioration.
[0052]
In the figure, reference numeral D denotes a transfer material detecting means for detecting that the transfer material P has been sucked onto the conveyor belt Bp at a predetermined timing, and is disposed immediately downstream of the suction roller 501. In this embodiment, the transfer material detecting means D is an optical sensor in which a light emitting element and a light receiving element are combined.
[0053]
When an instruction to start image formation is given by a controller of an image forming apparatus (not shown), image writing in the image forming unit is started, and four color toner layers are stacked on the intermediate transfer belt 6. Next, the transfer material P is transported from the paper tray 301 and is attracted onto the transfer material transport belt Bp by the suction roller 501. At this time, the transfer material detecting means D detects whether or not the transfer material P is attracted and conveyed onto the transfer material conveying belt Bp at a predetermined timing.
[0054]
If it is confirmed that the transfer material P is being conveyed at a predetermined timing, the image forming operation is continued. That is, while the transfer material conveying belt Bp is being driven to rotate, the transfer material conveyance belt Bp is brought into contact with the intermediate transfer belt 6 which is being rotationally driven, and the image is collectively transferred onto the transfer material P at the secondary transfer nip N2.
[0055]
On the other hand, when it is detected that the sheet is not conveyed at a predetermined timing, the drive of the transfer material conveying belt Bp is stopped at that stage, and the pressure contact with the intermediate transfer belt 6 is not performed. In addition, the image forming unit also stops driving and performs a process of generating a jam error.
[0056]
In a state where the transfer material P is not suction-conveyed on the transfer material transport belt Bp, there is no contact with the intermediate transfer belt 6, so that any unfixed toner on the intermediate transfer body is transferred to the transfer material transport belt Bp. Absent.
[0057]
Further, the transfer material P is separated from the intermediate transfer belt 6 immediately after passing through the nip N2, that is, immediately after the completion of the secondary transfer. As a result, toner other than the intended image information can be isolated from the image forming unit without being transferred to the transfer material transport belt Bp.
[0058]
As described above, for the transfer material transport belt, the state in which the intermediate transfer belt on which the toner layer is stacked and the transfer material transport belt are separated is set as the home position, and during the image forming operation, the transfer material is attracted to the transfer material transport belt. By performing control so that the toner is brought into pressure contact with the intermediate transfer belt after confirming the above, it is possible to reliably avoid toner contamination fixed on the transfer material transport belt.
[0059]
Embodiment 2
By attaching the transfer material detection sensors D at a plurality of locations in the transport belt thrust direction, it is possible to more reliably avoid toner contamination of the transfer material transport belt Bp.
[0060]
As an unintended toner stain, the transfer material may be conveyed to the secondary transfer nip while being skewed. As shown in FIG. 10, when the transfer material P is conveyed on the transfer material conveyance belt Bp in a state in which the transfer material P is obliquely adsorbed, the transfer material P is transported from a part of the toner layer T, for example, from an intended position in the conveyance direction. At the point where the leading edge of the paper reaches the timing, the toner layer T is directly transferred onto the belt, so that the toner layer T is fixed as toner stain on the transfer material transport belt Bp.
[0061]
Therefore, as shown in FIG. 11, three transfer material detection sensors Df, Dc, and Dr are provided in parallel to the transport belt Bp driving direction. At this time, the distance W between the sensors at both ends (Df and Dr in the figure) is set to a width capable of detecting the smallest size among transfer materials usable as transfer materials in the image forming apparatus. In this embodiment, the distance W is set to 100 mm because a government-made postcard can be used as the transfer material having the smallest size.
[0062]
The control of pressing the transfer belt Bp against the intermediate transfer belt 6 is started based on signals from the transfer material detection sensors Df, Dc, and Dr. In other words, the difference between the timings of the transfer material leading edge detection signals of the sensors Df and Dr at both ends is within a predetermined time, and the timing of the transfer material leading edge detection signal of Dc is different from that in the image forming as shown in the first embodiment. If it is within the allowable range, the transfer material P is adsorbed onto the transfer material transport belt Bp without delay, and it is determined that there is no skew, and the image forming operation is continued.
[0063]
As described above, by attaching the transfer material detection sensor to a plurality of locations in the thrust direction of the transport belt, it is possible to detect that the transfer material is attracted to the belt at a predetermined timing, and to determine whether the paper is skewed. Verification can also be performed, and toner contamination of the transfer material transport belt can be avoided more reliably.
[0064]
【The invention's effect】
As is apparent from the above, according to the present invention, there is provided an image forming apparatus capable of preventing toner stains fixed on a transfer material transport belt and avoiding toner stains on the back surface of the transfer material accompanying the toner stains. be able to.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of the present invention; FIG. 2 is a diagram for explaining an example of a conventional technique; FIG. 3 is a diagram for explaining a conventional problem; FIG. FIG. 5 is a diagram for explaining a problem. FIG. 5 is a diagram for explaining image deterioration due to peeling discharge at the time of transfer material separation. FIG. 6 is a diagram for explaining an example of a conventional technique. FIG. 8 is a diagram for explaining an image deterioration called “rib trace” of an unfixed image. FIG. 9 is a diagram for explaining a conventional problem. FIG. FIG. 11 is a diagram for explaining an embodiment of the present invention. FIG. 11 is a diagram for explaining an embodiment of the present invention.
Reference Signs List 1 photoreceptor drum 2 primary charger (charging means)
3 Exposure equipment (laser exposure equipment)
4 Developing means (independent fixed developing device, black developing device)
5 Developing means (rotary developing device)
5y, 5m, 5c Developing device 6 Intermediate transfer member (intermediate transfer belt, intermediate transfer drum)
9 Fixing device 10 Pre-fixing guide 12 Intermediate transfer belt cleaning member (cleaning blade)
61 Primary transfer roller (transfer means)
62 Intermediate Transfer Belt Drive Roller 63 Tension Roller 64 Tension Roller 71 Secondary Transfer Charger 72 Secondary Transfer Inner Roller 301 Paper Tray 401 Pickup Rollers 402 and 403 Transport Roller Pair 501 Suction Roller (Register Roller)
502 Long roller 503 Transfer material transport belt drive roller 504 Tension roller 901 Fixing roller 902 Pressure roller Bp Transfer material transport belt C Separation auxiliary charger Cp Post chargers D, Df, Dc, Dr Transfer material detection means (transfer material detection sensor )
P Transfer material T Unfixed toner layer N1 Primary transfer nip N2 Secondary transfer nip

Claims (2)

An image forming unit, an intermediate transfer body that temporarily holds an image formed by the image forming unit, a fixing unit, and a transfer material conveyance that conveys a transfer material onto which the image carried on the intermediate transfer body is transferred. Means, and an image forming apparatus having a fixing unit,
The end portion of the transfer material conveying means is provided downstream of the exit of the fixing unit, wherein the transfer material after image fixing is separated from the transfer material conveying means downstream of the exit of the fixing unit,
The image forming apparatus is characterized in that the transfer material conveying means is set so as to be able to freely contact and separate from the intermediate transfer member, and a state where the transfer material is separated is a home position. Having a transfer material detecting means for confirming that the transfer material is carried by the transfer material transport means,
2. The image forming apparatus according to claim 1, wherein the detection unit is disposed upstream of a secondary transfer unit that transfers an image from an intermediate transfer member to a transfer material in a transfer material transport direction.

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