JP2002323833A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing the undesired deterioration of the positional accuracy of a transfer roller and a resist roller with reference to a photoreceptor drum due to the undesired draw of a transfer belt unit. SOLUTION: In a jamming processing of the image forming device main body 30, in the case 1st and 2nd switches 44 and 45 are turned on, or in the case the 1st switch is turned off, but, the 2nd switch is turned on, the following possibility is increased that a toner image is transferred on the leading end side of the jammed paper, then, a locking mechanism 46 is released from being locked, and the jammed paper is removed while drawing out the transfer belt unit 7 in a right direction through a rocking frame 43. In another case, the rocking frame 43 is locked by the locking mechanism 46 so that the transfer belt unit 7 may not be drawn from the image forming device main body 30. Then, the transfer belt unit 7 is prevented from being undesirably drawn out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to an image forming apparatus having a structure in which a transfer belt unit can be pulled out from an image forming apparatus main body.

[0002]

2. Description of the Related Art For example, laser printers for forming a color image on a transfer body such as paper (hereinafter referred to as "sheet material") are generally classified into four types: a transfer drum system, an intermediate transfer system, a tandem system, and a multiple transfer system. Recording method.
Of these, in recent years, in response to a demand for high-speed recording, a tandem method that is superior to other methods in recording speed has been increasingly adopted. In this tandem laser printer, image forming units of black, cyan, magenta, and yellow are appropriately arranged as image forming units in a sheet material conveying direction (transfer belt moving direction). A toner image of each color is formed on the photosensitive drum, and these toner images are sequentially transferred and superimposed on a sheet material carried on the surface of the transfer belt, and then the toner images are fused and fixed by a fixing unit to obtain a desired toner image. The color image is fixed on the sheet material.

[0003]

In such a tandem laser printer, a color shift occurs unless a toner image of each color is transferred to a sheet material with high accuracy. Need to be aligned. In particular, the photosensitive drum on the image forming unit side,
It is necessary to maintain high parallelism between the transfer roller and the registration roller on the transfer belt unit side. Therefore, when the image forming unit and the transfer belt unit are separated and joined at the time of maintenance of the image forming unit or at the time of jam (paper jam) processing, the image forming unit and the transfer belt unit are accurately aligned. There is a need. Therefore,
It is preferable that the transfer belt unit is not separated from the image forming unit unless otherwise required.

When a jam occurs in an image forming apparatus, a cover to be opened and a unit to be pulled out for jam processing differ depending on where in the image forming apparatus main body the jam occurs. For example, if a paper jam occurs immediately after the paper is fed from the paper feed cassette, the paper feed cover near the paper feed cassette is opened to remove the jammed sheet material (hereinafter, appropriately referred to as “jam paper”). If a jam occurs when the sheet material is sandwiched between the photosensitive drum and the transfer belt, the transfer belt unit is pulled out from the image forming apparatus main body, and the transfer belt is separated from the photosensitive drum. Pull out the jam paper so that unfixed toner of the material does not adhere to the registration roller. further,
If it occurs near the fixing unit, the cover near the fixing unit is opened, and the jammed paper is removed. In such an image forming apparatus, in general, a jam portion is displayed on an operation panel, and a user performs a jam process by opening a cover or a unit corresponding to the display.

However, for example, in a small laser printer, a paper feed cover and a transfer belt unit are often arranged close to each other. If you open both the belt unit, you can deal with almost all jams. For this reason, the user may pull out the transfer belt unit at the same time as opening the sheet supply cover, even though the display on the operation panel is the sheet supply cover. In particular, in a configuration in which the paper feed cover is opened in conjunction with the operation of pulling out the transfer belt unit, it is expected that the user will easily pull out the transfer belt unit. When the transfer belt unit is frequently pulled out in this manner, there is a problem that the positional accuracy of the transfer roller and the registration roller on the transfer belt unit side with respect to the photosensitive drum on the image forming unit side tends to decrease.

Accordingly, it is an object of the present invention to provide an image forming apparatus in which the transfer belt unit is prevented from being pulled out from the main body of the image forming apparatus unless it is particularly necessary in a jam clearance or maintenance. Things.

[0007]

According to a first aspect of the present invention, there is provided an image carrier which is disposed on an image forming apparatus main body side and has a toner image formed on a surface thereof, and which is detachably attached to the image forming apparatus main body. And an image forming apparatus for transferring a toner image on an image carrier to a sheet material carried and conveyed on a transfer belt disposed on the transfer belt unit side. is there. The image forming apparatus according to the present invention includes: a lock unit that takes a lock position that prohibits the transfer belt unit from being pulled out of the image forming device main body and a release position that allows the transfer belt unit to be drawn out; A sensor for determining whether or not the jam occurrence location is a location where the transfer belt unit needs to be pulled out when a jam due to a sheet material jam occurs, and The drawer is located at the release position only when it is determined that the drawer is necessary, and the rest is located at the lock position.

According to the present invention having the above-described structure, the transfer belt unit is not unexpectedly or unnecessarily pulled out during the jam processing. Therefore, for example, the positional accuracy of the transfer roller and the registration roller with respect to the image carrier is not required. A significant decrease can be prevented. Furthermore, it is possible to prevent such damage and contamination due to exposure of the image carrier and the transfer belt caused by unnecessary pulling out of the transfer belt unit.

According to a second aspect of the present invention, there is provided an image forming apparatus comprising:
A display means for displaying the judgment by the sensor is provided, and the lock means is manually arranged at the release position based on the display of the display means.

According to the present invention having such a configuration, for example, the user can know when it is really necessary to pull out the transfer belt unit based on the judgment of the sensor and the display of the judgment result on the display means. Only in this case, the transfer means can be pulled out by disposing the lock means at the release position. In other words,
In order to pull out the transfer belt unit, the user must positively release the locking means, so there is no possibility that the transfer belt unit will be pulled out by mistake.

According to a third aspect of the present invention, there is provided an image forming apparatus comprising:
An interlocking mechanism is provided for selectively arranging the lock means at a lock position and a release position based on the determination of the sensor.

According to the present invention having such a configuration, when the transfer belt unit needs to be pulled out, the lock of the locking means is automatically released by the interlocking mechanism.

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising:
The image forming apparatus includes a plurality of image carriers that are arranged on the main body side and toner images of different colors are formed on the respective surfaces, and the toner images of different colors formed on the plurality of image carriers are formed on the transfer belt. It is characterized by being sequentially transferred to a carried sheet material.

The present invention having such a structure is applied to a so-called tandem type image forming apparatus having a plurality of image carriers. The tandem type image forming apparatus has a plurality of image forming apparatuses and sequentially superposes toner images of different colors formed on the respective image carriers on a sheet material. High positional accuracy of the transfer roller and the like on the transfer belt unit side with respect to the carrier is required. Therefore, the present invention in which the positional accuracy is less reduced is particularly effective for such an image forming apparatus.

According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising:
A registration roller is provided on the transfer belt unit side to supply a sheet material to the transfer belt in a state where skew has been corrected.

When the registration roller is provided on the side of the transfer belt unit that is inserted into and removed from the main body of the image forming apparatus, frequent insertion and removal of the transfer belt unit deteriorates the positional accuracy of the registration roller with respect to the image carrier. According to the present invention having such a configuration, the frequency of transferring and removing the transfer belt unit is reduced, so that a decrease in the positional accuracy of the registration roller can be suppressed.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Schematic Configuration of Image Forming Apparatus) FIG. 1 shows a color printer (image forming apparatus) according to an embodiment of the present invention.
2 is a schematic configuration diagram of FIG.

First, a schematic configuration of the color printer 2 will be described with reference to FIG. The color printer 2 feeds a sheet material 3 as a transfer body one by one, and conveys the sheet material 3 sent from the sheet feeding unit 4 to an image forming unit (image forming unit) 5 described later. A transport unit 6, an image forming unit 5 for creating a toner image to be transferred to the sheet material 3 transported by the transport unit 6, and a sheet material 3 transported by the transport unit 6; A transfer / transporting unit 7 that conveys the toner image formed by the image forming unit 5 onto the sheet material 3 while conveying the toner image on the sheet material 3; , A sheet discharging unit 10 for receiving the sheet material 3 discharged from the fixing unit 8, and an optical unit 11 for irradiating the image forming unit 5 with laser light for exposure.
And

The paper feed unit 4 feeds the sheet materials 3 stacked in the first paper feed tray 12 one by one by means of paper feed rollers 13a and 13b and a reverse roller 14.
And a second paper feed unit 18 for feeding a sheet material (not shown) on the manual feed tray 16 by a paper feed roller 17. In FIG. 1, the manual tray 16 is shown in a housed state, and when used, is rotated clockwise and pulled out for use.

The transport section 6 includes a transport path 20 for guiding the movement of the sheet material 3 sent from the paper feed section 4, a transport roller 21 disposed in the middle of the transport path 20, and a transport roller 21. A registration roller 22 that receives the sheet material 3, corrects the skew of the sheet material 3, and sends the sheet material 3 to the image forming unit 5;
A manual feed path 23 is connected to the feed path 20 upstream of the registration rollers 22 in the sheet feed direction.

Image forming unit (image forming unit) as an image forming unit
Reference numeral 5 denotes a first image forming unit 2 having black toner (hereinafter abbreviated as black) in order from the upstream side in the sheet conveying direction.
4. Second image forming unit 25 having toner containing cyan pigment (hereinafter abbreviated as cyan), and third image forming unit 2 having toner containing magenta pigment (hereinafter abbreviated as magenta)
6 and a fourth image forming unit 27 having a toner containing a yellow pigment (hereinafter abbreviated as yellow).
Each of the first to fourth image forming units 24 to 27 includes a cylindrical photosensitive drum (image carrier) 28, a developing device that forms a toner image on the outer peripheral surface of the photosensitive drum 28, A cleaning device including a fur brush and a cleaning blade for removing residual toner on the body drum 28; and a charging device (neither shown) for applying a charge to the photosensitive drum 28 to charge the photosensitive drum 28. Have. The image forming unit 5 can be pulled out of the image forming apparatus main body 30 integrally with the image forming frame (not shown).

The transfer conveying section (transfer belt unit) 7
An endless transfer belt 31 made of a fluororesin material, a driving roller 32 and a tension roller 33 around which the transfer belt 31 is wound, and transfer rollers 34a, 34b arranged at positions facing the respective photosensitive drums 28, respectively. 34
c and 34d, and also functions as a transfer body transporting device. These transfer rollers 34a to 34d
The transfer belt 3 has a predetermined pressing force and is
1 is sandwiched between them. Further, a belt guide roller 35 is disposed at an appropriate position on the inner peripheral side of the transfer belt 31.

The fixing section (fixing unit) 8 has a fixing roller 36 having a built-in heater and a pressure roller 37 pressed against the fixing roller 36.

The paper discharge section 10 guides the sheet material 3 discharged from the fixing section 8 to the upper portion of the image forming apparatus main body 30 through a discharge path 38, and the paper discharge tray 4 on which the image forming surface is stacked.
It has 0. The paper ejection cover 41 is pulled out of the image forming apparatus main body 30 when jam (sheet material jam) processing is performed, and is stored in the image forming apparatus main body 30 when jam processing is not performed.

The optical unit 11 has a polygon scanner mirror, an imaging lens, and a mirror arranged corresponding to each photosensitive drum 28, and irradiates the photosensitive drum 28 with laser light based on image information. It has become.

The color printer 2 thus formed
Is the sheet material 3 from the first paper supply unit 15 or the second paper supply unit 18.
Is transported, the sheet material 3 is transported by the transport unit 6 between the photosensitive drum 28 of the first image forming unit 24 and the transfer belt 31 of the transfer transport unit 7. The sheet material 3 is carried on the surface of the transfer belt 31 and is conveyed between the photosensitive drum 28 and the transfer rollers 34a to 34d. The formed toner images are sequentially transferred and overlapped. And a color image (a four-color toner image)
Is transferred between the fixing roller 36 and the pressure roller 37 of the fixing unit 8 by the transfer belt 31, where the sheet material 3 is heated and pressed to fix the color toner image. The sheet material 3 on which the fixing operation has been completed is discharged to the discharge tray 40. On the other hand, the residual toner of each color remaining on the surface of the photosensitive drum 28 without being transferred to the sheet material 3 is removed by the respective cleaning device, and used for the next image formation.

In the above-described color printer 2, when a jam occurs during the image forming operation, the cover is opened or the unit is pulled out depending on the location where the jam occurs, to cope with the jam.

First, with respect to the jam near the fixing unit (fixing unit) 8, the discharge cover 41 which is normally stored in an upright posture (other than at the time of jam clearance or maintenance) is moved to the swing center of the lower end thereof. The fixing unit 8 is rotated substantially counterclockwise in FIG.
The jammed sheet material 3 (jam paper) is pulled out in a state where is exposed. After the jam clearance, the discharge cover 41 is returned to the normal upright posture. As for the jam near the fixing unit 8, the jammed paper may be automatically discharged as described later.

The jammed paper near the first paper supply unit 15 is
The paper feed cover 42, which is located substantially at the lower half of the image forming apparatus main body 30 on the right end side in FIG.
The paper feed cover 42 is swingably supported by the image forming apparatus main body 30 with reference to a swing center 42a at a lower end portion. The paper feed cover 42 is normally housed in the image forming apparatus main body 30 in an upright posture.
It swings clockwise (in the direction of the arrow) in the figure with reference to the swing center 42a, and exposes the vicinity of the first sheet feeding unit 15. Thereby, the jammed paper near the first paper supply unit 15 can be pulled out and removed. After clearing the jam, the paper feed cover 42
Returns to the normal upright position.

Further, the image forming unit 5 and the transfer belt unit 7
With respect to the jammed paper, the transfer belt unit 7 is pulled out to perform the jam processing. This will be described in detail below.

The entire transfer belt unit 7 is mounted on a movable frame 43. In this movable frame 43,
Further, the manual feed tray 16 and the paper feed roller 17 constituting the second paper feed unit 18 of the paper feed unit 4 and the transport path 20, the transport roller 21, the registration roller 22, and the manual feed path 23 constituting the transport unit 6 include Installed. Of these, the manual tray 16 is used when the sheet material 3 is not manually fed.
The upright posture shown in FIGS. 1 and 2 is assumed. Further, a first switch 44 is disposed on the movable frame 43 immediately upstream of the transport roller 21 along the transport path 20, and a second switch 45 is located immediately upstream of the registration roller 22.
Are arranged. The first and second switches 44 and 45 are
When there is no sheet material 3, levers 44a and 45a respectively
Is protruded into the transport path 20, and is in the OFF state at this time. On the other hand, when the levers 44a and 45a are retracted from the conveyance path 20 by the sheet material 3, the ON state occurs.
State.

The movable frame 43 is provided in the image forming apparatus main body 3.
1 and 2 so that it can be pulled out substantially horizontally along a rail member (not shown) in the left-right direction in FIGS. 1 and 2. That is, it can be moved substantially horizontally between the mounting position (leftward movement limit) shown in FIG. 1 and the pull-out position (rightward movement limit) shown in FIG. The transfer belt unit 7 moves diagonally downward (downward to the right in the drawing) for a short time immediately after the start of drawing, and thereafter moves rightward. This prevents sliding between the photosensitive drum 28 and the transfer belt 31 at the time of pulling out. Conversely, the transfer belt unit 7 moves diagonally upward immediately before the end of the mounting operation, and also at this time, the friction between the photosensitive drum 28 and the transfer belt 31 is similarly prevented. A notch 43a for engaging and disengaging a hook 47 of a lock mechanism (lock means) 46, which will be described below, is provided in a lower portion on the left end side of the movable frame 43.

The lock mechanism 46 has a hook 47 that swings substantially vertically with reference to a swing center 47a, and a drive unit 48 that swings the hook 47. The hook 47 is released by the drive unit 48 from the locked position shown in FIG. 1, that is, the position engaged with the notch 43 a of the movable frame 43, and the release position shown in FIG. 2, that is, the engagement with the notch described above is released. Take the position. Transfer belt unit 7 described above
The hook 47 is arranged at the lock position and engages with the movable frame 43 to thereby prevent the drawer from being pulled out, while the hook 47 is arranged at the release position and
By releasing the engagement with 3, the drawer is permitted.

Next, in the image forming apparatus main body 30 shown in FIG. 1 and FIG. 2, the flow of the jam processing when the jam of the sheet material 3 occurs at a place other than the vicinity of the fixing unit 8 will be described. As shown in the flowchart of FIG. 3, the outline of the jam processing is as follows. When a jam (JAM) occurs, the leading end (sheet leading end) of the sheet material is transferred to the photosensitive drum 28 (hereinafter, appropriately referred to as “first drum”) on the most upstream side. The subsequent processing is changed depending on whether or not the arrival has been reached. If it has arrived, a later-described jam processing (+) is performed, and if it has not arrived, a later-described jam processing is performed. In this embodiment, as shown in FIG. 1 and FIG.
Since the upper end 42b of the second frame 42 is protruded into the drawing path of the movable frame 43, when the jam processing for pulling out the swing frame 43 is performed, the jam processing for opening the paper feed cover 42 is eventually performed. .

The flowchart of FIG. 4 and FIGS.
The jam processing flow will be described in more detail with reference to FIG.

In this embodiment, the position of the sheet material 3 is specified according to the ON / OFF of the first and second switches 44 and 45 described above. Specifically, the sheet material 3
It is determined whether there is a possibility that the leading end of the drum has reached the first drum. ON of the first and second switches 44 and 45
Consider four combinations of / OFF.

First, it is assumed that image formation on the sheet material 3 has started and a jam has occurred (step (S1)).
The first switch 44 is turned on ("YES" in step S2).
And the second switch 45 is ON (“YE” in step 3).
In the case of "S"), since the leading end of the sheet material 3 may reach the first drum, the lock by the lock mechanism 46 is released (step S4), and the jam processing (+
)I do. That is, by manually operating the drive unit 48 of the lock mechanism 46, the hook 47 is moved from the lock position shown in FIG. 1 to the release position shown in FIG. 2, and is engaged with the notch 43a of the movable frame 43. Hook 47
Is removed from the movable frame 43. Thus, the transfer belt unit 7 can be pulled out via the movable frame 43. The transfer belt unit 7 is moved rightward in FIG. 1 to be disposed at the position shown in FIG. 2, and a space is formed between the image forming apparatus main body 30 and the movable frame 43. At this time, the paper feed cover 42 is also opened at the same time. In this state,
From the space between the image forming apparatus main body 30 and the movable frame 43, it is confirmed whether or not the toner image has been transferred to the leading end of the sheet material 3. If it is confirmed that the image is not transferred, the user inserts his hand into the above-mentioned space and
Of the sheet material 3 protruding below the conveying roller 21 and being pulled out. On the other hand, if the toner image is transferred to the leading end of the sheet material 3, if the sheet material 3 is pulled out from the conveyance roller 21 side, the toner will adhere to the registration roller 22. Sheet material 3
To take out. Thereby, the jammed sheet material 3 can be removed. After the removal of the sheet material 3, the movable frame 43 is moved to the left, the transfer belt unit 7 is returned to the original position, the hook 47 of the lock mechanism 46 is arranged at the locked position, and the notch of the movable frame 43 is cut out. To be engaged. Also, the paper feed cover 42 is returned to the original position.

Next, the first switch 44 is ON ("YES" in step S2), and the second switch 45 is OFF.
In the case of ("NO" in step S3), the lock state is set to I (step S5). The lock state I refers to a case where only the jam processing is performed. That is, in this case, since there is no possibility that the leading end of the sheet material 3 has reached the first drum, the transfer belt unit 7 is unnecessarily pulled through the movable frame 43 while maintaining the locked state by the lock mechanism 46. In a state where the sheet is not ejected, the sheet feed cover 42 is opened, and the sheet material 3 protruding below the transport roller 21 is pulled out to perform a jam processing. After the jam clearance, the paper feed cover 42 is returned to the original position.

Next, the first switch 44 is turned off ("NO" in step S2) and the second switch 45 is turned on.
In the case of "YES" in step S6, since the leading end of the sheet material 3 has reached the first drum and the toner image is likely to be transferred to the sheet material 3, the first switch 44 is turned on. ("YES" in step S2) and the second
As in the case where the switch 45 is ON (“YES” in step 3), the lock is released (step S4) and the jam processing (+) is performed.

Finally, the first switch 44 is OFF ("NO" in step S2), and the second switch 45 is OFF.
If F (“NO” in step S6), the lock state II
(Step S7). The locked state II is a case where the jammed sheet material 3 is automatically discharged. Since the rear end of the sheet material 3 has already passed the second switch 45 and there is a high possibility that the toner image has been transferred to the sheet material 3, the sheet material 3 is automatically discharged in this case.

The above-mentioned "jam processing (+)"
“Jam clearing”, “unlocked”, “locked state I”, “locked state II”, and the like may be appropriately displayed on, for example, an operation panel (display unit) of the image forming apparatus main body.

By performing the above-described jam processing, it is possible to prevent the transfer belt unit 7 from being erroneously or unnecessarily pulled out. Therefore, the transfer roller unit 7 and the registration roller 22 can be prevented from lowering in position accuracy.

FIG. 5 is a flowchart according to another embodiment.

The difference from the above-described one shown in FIG. 4 is that step S8 is provided between step S3 and step S4. Steps S1 to S7 are the same as those described above, and will not be described.

In the embodiment shown in FIG. 4, when both the first and second switches 44 and 45 are ON, the sheet material 3
Is unlocked, and the transfer belt unit 7 is pulled out to perform a jam processing. However, like this,
Even when the second switches 44 and 45 are ON, the distance (hereinafter referred to as “distance Lm”) from the second switch 45 to the most upstream photosensitive drum 28 due to the arrangement position of the second switch 45.
m ”. ), The leading end of the sheet material 3 may not reach the most upstream photosensitive drum 28 in some cases. That is, this is a case where the leading end of the sheet material 3 is located between the second switch 45 and the photosensitive drum 28 on the most upstream side. In such a case, the transfer belt unit 7
In the embodiment of FIG. 3 described above, although it is not necessary to extract
The transfer belt unit 7 is unnecessarily pulled out. In the configuration shown in FIG. 4, such unnecessary drawers are eliminated by taking the above-mentioned distance L into consideration.

As described in the right box of FIG.
From the distance Lmm from the second switch 45 to the most upstream photosensitive drum 28 and the sheet material conveyance speed Vmm / sec,
The time required to convey the sheet material between them, Xsec, is given by the following equation:
Is calculated.

X (sec) = L (mm) ÷ V (mm / sec) Then, as shown in the flowchart of FIG. 10, the first switch 44 is turned on, the second switch 45 is turned on, and the sheet material is When a jam occurs, the second switch 45
Only when X seconds or more have elapsed from N (“YES” in step S8), the lock is released (step S4). That is, even if the first switch 44 is ON and the second switch 45 is ON, Xsec has not elapsed since the ON, that is, the leading end of the sheet material 3 is located between the second switch 45 and the first drum. In some cases, there is no need to pull out the transfer belt unit 7,
The locked state I (step S5) is maintained.

According to the embodiment shown in FIG. 5, FIG.
Unnecessary pulling out of the transfer belt unit 7, which has been performed in the embodiment, that is, pulling out of the transfer belt unit 7 when the leading end of the sheet material 3 is between the second switch 45 and the first drum is effectively prevented. be able to.

In the above embodiment, the lock release of the lock mechanism 46 was manually performed by the user by operating a lever, for example. However, the first and second switches 44 and 45 and the lock mechanism 46 are used. May be provided automatically by providing an interlocking mechanism (not shown) between them. For example, a solenoid is provided in the lock mechanism 46, and the solenoid is energized when the combination of ON / OFF of the first and second switches 44 and 45 is the above-described combination of unlocking, and the energization causes the hook 47 to be turned on. What is necessary is just to move from a lock position to a release position.

In the above-described embodiment, during normal image formation, the second switch 45 is also used as a sensor for detecting whether or not the sheet material 3 has reached the registration roller 22. However, it is more preferable to provide a dedicated sensor for detecting the presence / absence of the sheet material 3 immediately before the first drum and to change the subsequent jam processing instead of using the dual purpose as described above. Jam processing can be performed.

[0052]

As described above, according to the image forming apparatus of the present invention, the transfer belt unit is not unexpectedly or unnecessarily pulled out during the jam processing. Unnecessary decrease in the position accuracy of the registration roller can be prevented. Furthermore, it is possible to effectively prevent such damage and contamination due to exposure of the image bearing member and the transfer belt caused by unnecessary pulling out of the transfer belt unit.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a state in which a transfer belt unit is mounted on an image forming apparatus main body in an image forming apparatus according to the present invention.

FIG. 2 is a schematic longitudinal sectional view showing a state in which a transfer belt unit is pulled out of an image forming apparatus main body in the image forming apparatus according to the present invention.

FIG. 3 is a flowchart illustrating an outline of a jam process.

FIG. 4 is a flowchart illustrating the flow of a jam process according to the present invention.

FIG. 5 is a flowchart illustrating the flow of a jam process according to another embodiment of the present invention.

[Explanation of symbols]

2 ... color printer (image forming apparatus), 3 ... sheet material, 5 ... image forming unit (image forming unit), 7 ... transfer belt unit, 22 ... registration roller, 28 ... photosensitive drum (image) Carrier), 30 ... Image forming apparatus main body, 31 ...
Transfer belt, 44... 1st switch (sensor), 45.
... Second switch (sensor), 46 ... Lock mechanism (Lock means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/00 550 G03G 15/00 550 3F048 15/01 15/01 Y 3F102 114 114B 15/16 15/16 F-term (reference) 2H027 DA21 DA28 DC04 DC14 DE01 DE07 DE10 ED16 EE07 GA30 GB06 GB08 HB18 2H030 AA01 AB02 AD05 AD16 BB44 BB46 BB53 BB56 2H071 AA39 BA03 BA14 BA33 DA09 DA22 DA23 DA32 2H072 AA02 AA12 GAA GA44 GA47 HA01 HB12 JA01 JB06 JB10 JB15 JB20 JB49 JB50 LA01 PA27 PB26 3F048 AA02 AA04 AA05 AB01 BA14 BB02 BD07 CA08 CB03 CC01 DA06 DA07 DB02 DC05 EA11 EB24 EB33 3F102 AA02 AA01 BB01 BA01 CB02

Claims (5)

[Claims] An image bearing member provided on the image forming apparatus main body side and having a toner image formed on a surface thereof; and a transfer belt unit detachably attached to the image forming apparatus main body. An image forming apparatus for transferring a toner image on the image carrier to a sheet material carried and conveyed on a transfer belt provided on a belt unit side, wherein the transfer from the image forming apparatus main body is performed. A lock unit that takes a lock position that prohibits the belt unit from being pulled out and a release position that allows the transfer belt unit to be pulled out; and when a jam that is a sheet material jam occurs in the image forming apparatus main body, A sensor for determining whether or not the occurrence location is a location where the transfer belt unit needs to be pulled out. The image forming apparatus is arranged at the release position only when it is determined that it is necessary to pull out the belt unit, and is arranged at the lock position otherwise. 2. The apparatus according to claim 1, further comprising a display unit for displaying a determination by the sensor, wherein the lock unit is manually arranged at the release position based on a display on the display unit. Image forming device. 3. The image forming apparatus according to claim 1, further comprising an interlocking mechanism for selectively arranging the lock unit at the lock position and the release position based on the determination of the sensor. 4. A plurality of image carriers which are arranged on the image forming apparatus main body side and on which toner images of different colors are formed on the surface, respectively, wherein different colors formed on the plurality of image carriers, respectively. 4. The image forming apparatus according to claim 1, wherein the toner images are sequentially transferred to a sheet material carried on the transfer belt. 5. A registration roller for supplying a sheet material to the transfer belt in a state where skew has been corrected is provided on the transfer belt unit side. An image forming apparatus according to claim 1.