JP2002055533A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an upper position of a belt in a circulating direction by a transmission type optical sensor without necessitating complicated wiring and a connector or the like connecting with a device main body even though a unit such as an intermediate transfer belt is freely attachably/detachably installed at the device main body. SOLUTION: A square hole 100 is provided in a reinforcing member 110 on a right side in the advancing direction of the intermediate transfer belt 5a, and a rocking flag 101 is provided at a belt frame so as to be capable of rocking by fitting in the rotary shafts of both ends, and the stopper part 101e of a sensor side flag 101b is pressed by a torsion coil spring 102 engaged with the belt side flag 101a of the rocking flag so as to butt against the wall of the belt frame. The flag 101b is slid to a circulating intermediate transfer belt, and is rocked by dropping in the square hole at the position of the square hole, and the square hole is detected because the flag 101a cuts the optical path of the transmission type optical sensor 103, so that the upper position of the belt in the circulating direction is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a color copying machine or a color printer using an electrophotographic system, and more particularly to an image forming apparatus using an intermediate transfer belt or a transfer material conveying belt. .

[0002]

2. Description of the Related Art Conventionally, a color image forming apparatus using an intermediate transfer belt has been disclosed in Japanese Patent Application Laid-Open Nos. 8-137168 and 8-1-1.
As described in Japanese Patent Application Laid-Open No. 46698/1999 and Japanese Patent Application Laid-Open No. H11-16047, in order to align the positions of the respective color toner images to be superimposed on the intermediate transfer belt, the position of the intermediate transfer belt in the circumferential direction is detected by position detection means. I have.

Normally, this position detecting means is composed of a light reflection type optical sensor (photo sensor), and a marker made of a light reflector is attached outside the image forming area of the intermediate transfer belt so as to face the marker. By arranging an optical sensor at a predetermined position and receiving the reflected light of the light emitted from the optical sensor by the marker, the image writing reference position is detected as the position in the rotation direction of the intermediate transfer belt. Then, by controlling the timing of writing the image data to the photoconductor by the exposure unit in synchronization with the detection signal,
Generally, the positions of the toner images of each color transferred from the photoreceptor onto the intermediate transfer belt are matched to prevent color misregistration.

However, the marker is stained with time due to scattered toner generated at the time of cleaning the residual toner on the intermediate transfer belt, and the amount of reflected light received by the optical sensor is reduced. There is a problem that the detection accuracy of the position of the belt in the circling direction becomes unstable and image deterioration such as color shift occurs.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
At 37168, a marker of a reflector having a different reflectance at the central portion and the outer peripheral portion is attached, and in synchronization with a signal when the optical sensor detects reflected light at a high reflectance portion at the central portion,
The writing of image data to the photoconductor by the laser writing means is started.

Japanese Patent Application Laid-Open No. H11-16047 has devised a method of removing fouling of a marker by providing flocked seal members at both ends of a cleaner of an intermediate transfer belt.

However, the use of a reflection type optical sensor still has the following problems. (1) The position detection accuracy may vary depending on the disturbance light of the reflection type optical sensor and the state of the background. (2) Variation in the distance between the reflector marker and the optical sensor causes variation in position detection accuracy. (3) There is variation in position detection accuracy due to variation in the mounting angle of the optical sensor. (4)
There is a problem of marker peeling. (5) It is costly to attach the reflector marker with high accuracy. (6) It is difficult to completely remove dirt on the reflector marker. (7) The reflection type optical sensor is expensive.

[0008]

On the other hand, conventionally, an end of the intermediate transfer belt is sandwiched by a transmission type optical sensor, and light from the light emitting element of the high sensor is transmitted through a hole provided at the end of the intermediate transfer belt. There is known a method of detecting the position of the intermediate transfer belt in the circumferential direction along the circumferential direction of the intermediate transfer belt by detecting the position of the intermediate transfer belt in the circumferential direction.

According to the transmission type optical sensor, there is no problem as in the reflection type optical sensor, but the transmission type optical sensor is mounted on the frame of the intermediate transfer belt unit incorporating the intermediate transfer belt. In the image forming apparatus in which the image forming apparatus is detachably mounted on the apparatus main body, wiring, a connector, and the like for transmitting a signal between the optical sensor and the image forming apparatus main body are required.

[0010] The above-described problem is caused by the use of a transmissive optical sensor on the side of the conveyor belt in an image forming apparatus in which a conveyor belt unit incorporating a conveyor belt is detachably installed in the apparatus main body. This also occurs when detecting the position of the belt in the circling direction.

Accordingly, an object of the present invention is that even if the intermediate transfer belt unit and the transport belt unit are detachably mounted on the apparatus main body, complicated wiring and connectors to be connected to the apparatus main body by the transmission type optical sensor are required. An object of the present invention is to provide an image forming apparatus capable of detecting the position of these belts in the circling direction without having to use the belt.

[0012]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image forming apparatus comprising: an image carrier on which a visible image is formed; an intermediate transfer belt on which the visible image on the image carrier is transferred; and a detecting unit configured to detect a position of the intermediate transfer belt in a circumferential direction. The detection means includes an intermediate transfer body unit incorporating the intermediate transfer belt or a swing flag installed swingably on the image forming apparatus main body, and a transmission type optical sensor installed on the image forming apparatus main body. An image forming apparatus comprising:

According to the present invention, a detected portion is provided in a region outside the image transfer region at a predetermined position in the circumferential direction of the intermediate transfer belt, and the swing flag is swung by the detected portion, The transmission-type optical sensor detects the detected portion based on the swing of the swing flag, and detects a position of the intermediate transfer belt in a rotating direction. The transmission type optical sensor detects the detected portion by blocking the optical path between the light emitting element and the light receiving element of the transmission type optical sensor or canceling the blocking of the optical path by the swing of the swing flag. The detected portion is formed in a hole or a protrusion, and the swing flag has first and second flags, and swings when the first flag falls into the hole, or the first flag is swung. The flag swings by riding on the protrusion,
The second flag interrupts the optical path of the transmission type optical sensor or cancels the optical path means.

The swing flag is set at a position close to one of a plurality of rollers supporting the intermediate transfer belt on a side other than the image transfer portion side. The intermediate transfer body unit is detachably installed on the image forming apparatus main body. Alternatively, the image carrier and the intermediate transfer unit are integrated into an image forming unit that is detachable from the image forming apparatus main body. Visible images of a plurality of colors are sequentially formed on the image carrier. Alternatively, a plurality of image carriers are provided, and visible images of a plurality of colors are formed on the plurality of image carriers.

The present invention also provides an image carrier on which a visible image is formed, a transport belt for carrying and transporting a transfer material onto which the visible image is transferred on the image carrier, and a transport belt in a circumferential direction of the transport belt. And a detecting means for detecting the position of the image forming apparatus, the detecting means includes a conveyer belt unit incorporating the conveyer belt or a swing flag slidably mounted on an image forming apparatus main body; An image forming apparatus, comprising: a transmission type optical sensor installed in an apparatus main body.

According to the present invention, a detected portion is provided in a region outside the transfer material carrying region at a predetermined position in the circumferential direction of the transport belt, and the swing flag is swung by the detected portion, The transmission-type optical sensor detects the detected portion based on the swing of the swing flag, and detects a position of the transport belt in a rotating direction.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view showing an embodiment of an image forming apparatus according to the present invention. The image forming apparatus is configured as a four-color full-color laser beam printer.

The outline of the color image forming operation of the image forming apparatus will be described. In synchronization with the rotation of the intermediate transfer belt 5a of the intermediate transfer belt unit 5, the photosensitive drum 1 is moved in the arrow direction (counterclockwise) in FIG. The photosensitive drum 1 is rotated, and the surface of the photosensitive drum 1 is uniformly charged by the charging device 2, and the exposure unit 3 irradiates light of a yellow image to form a yellow electrostatic latent image on the photosensitive drum 1.

At the same time as the formation of the electrostatic latent image, the rotary developing device 4
Is driven to rotate the yellow developing device 4Y to the photosensitive drum 1
And is positioned at the developing position. Then, a voltage having the same polarity and substantially the same potential as the charging polarity of the photosensitive drum 1 is applied to the developing roller of the developing device 4Y, so that the yellow toner carried on the developing roller adheres to the electrostatic latent image on the photosensitive drum 1. To develop the latent image as a yellow toner image. Thereafter, a voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 5j also serving as a pressing roller of the intermediate transfer belt 5a, and the yellow toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a.

When the primary transfer of the yellow toner image is completed in this manner, the next magenta-color developing device 4M rotates and moves to the developing position with the photosensitive drum 1, and in the same manner as in the case of yellow, The magenta electrostatic latent image formed on the photosensitive drum 1 is developed, and the obtained magenta toner image is primary-transferred onto the intermediate transfer belt 5a from above the yellow toner image.

Similarly, for each of the colors cyan and black, an electrostatic latent image is formed on the photosensitive drum 1 and the developing devices 4C, 4C
Bk Development, Intermediate Transfer Belt 5 of Obtained Toner Image
The primary transfer is sequentially performed on the intermediate transfer belt 5a, and a color image is formed on the intermediate transfer belt 5a by superimposing four color toner images of yellow, magenta, cyan, and black.

During this time, the secondary transfer roller 11 is not in contact with the intermediate transfer belt 5a, and the charging roller 5f for cleaning is also in non-contact with the intermediate transfer belt 5a.

After the completion of the formation of the four color images on the intermediate transfer belt 5a, as shown in FIG. 1, the secondary transfer roller 11 is pressed against the intermediate transfer belt 5a, and is further synchronized with the rotation of the intermediate transfer belt 5a. The transfer material, which is separated and fed one by one from the transfer material stacking means (sheet feeding cassette) 19 by the pickup roller 18 and stands by at a predetermined position near the registration roller pair 7d as the re-feeding means, is transferred to the intermediate transfer. The sheet is sent to the nip between the belt 5 a and the secondary transfer roller 11.

A pre-registration sensor 14 is provided immediately before the registration roller pair 7d. The sensor 14 detects the leading end of the transfer material and temporarily shuts off the rotational driving force of the registration roller pair 7d to remove the transfer material. Registration roller pair 17d
It is made to wait at a predetermined position in the vicinity.

A voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller 11 pressed against the intermediate transfer belt 5a. The four color toner images on the intermediate transfer belt 5a are The secondary transfer is collectively performed on the surface of the transfer material conveyed to the portion where the intermediate transfer belt 5a is in contact.

The transfer material on which the four-color toner images are secondarily transferred in this way reaches the fixing device 8 via the conveyor belt unit 12, where the four-color toner images are fixed. The sheet is conveyed along a sheet discharge guide 15 by a pair of sheet discharge rollers 13, and then discharged by a pair of discharge rollers 9 to a sheet discharge tray 10 above the image forming apparatus, thereby completing image formation.

On the other hand, after the secondary transfer, the cleaning charging roller 5f is pressed against the intermediate transfer belt 5a to apply a charge opposite to that at the time of transfer to the secondary transfer residual toner remaining on the intermediate transfer belt. The transfer residual toner provided with the opposite charge is conveyed by the intermediate transfer belt 5a, reaches the position of the photosensitive drum 1, electrostatically adheres to the photosensitive drum 1, and is removed from the intermediate transfer belt 5a. Photosensitive drum 1
Is collected by the cleaning blade 6 for the photosensitive drum 1, and the collected toner is accumulated in the waste toner box 16 along the transport path as waste toner.

Next, the means and method for detecting the position of the intermediate transfer belt, which is a feature of the present invention, will be described.

FIG. 2 is a sectional view of a process cartridge as an image forming unit in which the photosensitive drum and the intermediate transfer unit are integrally formed. The endless belt-shaped intermediate transfer belt 5a as an intermediate transfer member is made of a resin film such as polyvinylidene fluoride (PVDF) or polyimide (PI), and is stretched around two rollers of a driving roller 40 and a driven roller 41. Has been established. A compression spring 44 is provided on bearings 43 at both ends of the driven roller 41,
A predetermined tension is applied to the intermediate transfer belt 5a.

FIG. 3 is a front view of the process cartridge 5A viewed from the front of the apparatus. As shown in FIG. 3, the width H of the intermediate transfer belt 5a is set at both ends in the width direction.
Is attached over the entire circumference of the belt, and the reinforcing member 110 on the right side in the traveling direction of the intermediate transfer belt 5a is attached to the intermediate transfer belt 5
a rectangular square hole 100 having a width h and a length L as a portion to be detected a
Is provided. The width h of the square hole 100 is determined by the swing flag 1
01 is set to be wider than the thickness t of the belt-side flag 101b, so that the intermediate transfer belt 5a can cope with any deviation within the deviation regulation width.

According to the present invention, the swing flag 101 is provided for the transmission type optical sensor 103 installed on the image forming apparatus main body side.
Together, they constitute a position detecting means of the intermediate transfer belt 5a. Although the swing flag 101 can be installed on the apparatus main body side, it is easier to obtain the positional accuracy with respect to the intermediate transfer belt 5a by providing the swing flag 101 on the intermediate transfer belt unit 5 side. Detection accuracy can be obtained.

The position of the swing flag 101 is determined so as not to affect the stable peripheral movement of the intermediate transfer belt 5a.
In the vicinity of the driving roller 40 and not on the primary transfer portion side of the image, that is, the photosensitive drum 1 and the intermediate transfer belt 5a
Is not located between the primary transfer position and the roller 40 in contact with each other, so that the belt is not affected at the time of transfer.

The swing flag 101 has a sensor-side flag (second flag) 101a in addition to the belt-side flag (first flag) 101b. , 101d are swingably fitted to the intermediate transfer belt frame 45,
1a, the torsion coil spring 102 engages the flag 10
The stopper portion 1e of 1b is biased so as to abut the wall of the intermediate transfer belt frame 45.

As shown by a solid line in FIG.
With the belt side flag 101b set to 0,
The length L of the square hole 100 in the circumferential direction of the intermediate transfer belt is set such that the belt-side flag 101b swings to a stopper position (a position where the stopper portion 101e abuts against the wall of the belt frame 45) as shown by a solid line in FIG. Must be long enough.

In FIG. 2, a two-dot chain line indicates a state in which the belt-side flag 101b slides on the surface of the intermediate transfer belt 5a, and the sensor-side flag 101a is located at a position away from the transmission type optical sensor 103.

Therefore, in this embodiment, the belt-side flag 101b slides on the surface of the rotating intermediate transfer belt 5a, and the square holes 100 of the intermediate transfer belt 5a
1b, the flag 101b falls into the square hole 100, the flag 101 swings, and the sensor-side flag 1
01a enters between the light emitting element 103a and the light receiving element 103b of the transmission type optical sensor 103 as shown in FIG.
The square hole 100 is detected by intercepting the optical path during this and changing the amount of received light, whereby the position on the intermediate transfer belt 5 along the circumferential direction of the intermediate transfer belt 5a, that is, the position on the circumferential direction is detected. .

According to this, an inexpensive and simple position detecting means can be constituted by using the transmission type optical sensor 103 without worrying about the mounting accuracy unlike the reflection type optical sensor. There is no variation in the position detection accuracy due to disturbance light, background state, the distance to the reflector marker, the variation in the mounting angle of the sensor, and the like, and the position detection accuracy can be improved. Further, even when the intermediate transfer body unit 5 is detachably installed in the image forming apparatus main body, the transmission type optical sensor 103 can be provided on the apparatus main body side, similarly to the reflection type optical sensor. Eliminates the need for complicated wiring and floating connectors connecting the units.

In the above description, the swing flag 101 is provided on the intermediate transfer belt unit 5, but may be provided on the image forming apparatus main body side. Further, although the square hole 100 is provided as a detected portion on the intermediate transfer belt 5a, a projection is provided as a detected portion, and the belt-side flag swings by riding on the protruding portion. The optical path may be blocked. In addition, the transmission type optical sensor 10
Although the detected portion is detected by blocking the optical path of No. 3 with the flag 101b, the detected portion may be detected by releasing the blocking of the optical path by the flag 101b.

Next, a description will be given of a method of synchronizing image writing and sheet feeding timing by detecting an intermediate transfer belt position in this embodiment.

Now, in the photosensitive drum 1 and the intermediate transfer belt 5a rotating at a predetermined peripheral speed, the square hole 100 of the intermediate transfer belt reaches a predetermined position, and the belt side flag 10
1b interrupts the transmission optical sensor 103 to generate a signal. In synchronization with this signal, a yellow image is formed on the surface of the photosensitive drum 1 uniformly charged by the charging device 2 by the laser scanner 3 as an exposure unit. Write an electrostatic latent image.

Simultaneously with the formation of the electrostatic latent image, the developing device 4 is driven to dispose the yellow developing device 4Y at the developing position, so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1. The electrostatic latent image is developed with yellow toner by applying a voltage having the same polarity as the charge polarity of No. 1 and substantially the same potential.
Thereafter, a voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 5j also serving as a pressing roller of the intermediate transfer belt unit 5, and the yellow toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a.

When the primary transfer of the yellow toner image is completed, the magenta, cyan, and black developing units sequentially rotate and move to the developing position opposed to the photosensitive drum 1, and, similarly to the case of yellow, For each of the colors magenta, cyan, and black, the square hole 100 of the intermediate transfer belt reaches a predetermined position, and the belt-side flag 101b is uniformly emitted by the charging device 2 in synchronization with a signal generated by blocking the transmission type optical sensor 103. The formation, development, and primary transfer of an electrostatic latent image are sequentially performed on the charged surface of the photosensitive drum 1, and four color toner images are superimposed on the intermediate transfer belt 5a without color shift.

During this time, the secondary transfer roller 11 is not in contact with the intermediate transfer belt 5a. At this time, the charging roller 5f as a cleaning unit is also in a non-contact state with the intermediate transfer belt 5a.

After the formation of the toner images of four colors on the intermediate transfer belt 5a, the secondary transfer roller 11 is pressed against the intermediate transfer belt 5a (the state shown in FIG. 1), and is synchronized with the rotation of the intermediate transfer belt 5a. The transfer material that has been separated and fed one by one from the paper feed cassette 19 by the pickup roller 18 and has been waiting at a predetermined position near the registration roller pair 7d as the re-feeding means is transferred to the intermediate transfer belt 5a and the secondary transfer belt. The toner is sent to the nip portion of the transfer roller 11.

The transmission optical sensor 1 triggered by the detection of the square hole 100 of the intermediate transfer belt 5a is also used for picking up the transfer material and refeeding it from the registration roller pair 7d.
03 can be performed in synchronism with the signal. It is also possible to provide another square hole different from the image writing, and extract and detect the detection signal.

The length of the signal from the transmission type optical sensor 103 is changed by dividing the number of square holes in the circumferential direction of the intermediate transfer belt and changing the length L of the square holes in the circumferential direction of the intermediate transfer belt. Accordingly, it is possible to determine and specify a plurality of positions in the circumferential direction of the intermediate transfer belt.

In this embodiment, as described above, the photosensitive drum 1 and the intermediate transfer belt unit 5 are integrated with the process cartridge 5A. A method of attaching and detaching the process cartridge 5A to and from the color image forming apparatus main body A and fixing the process cartridge 5A to a predetermined position will be described with reference to FIGS.

In FIG. 4, when the upper cover 60 of the image forming apparatus main body A is opened, the support portion 30 for supporting the photosensitive drum bearing is provided.
2, the intermediate transfer belt driving roller 4 provided on the support 303 for supporting the rotational driving force transmission coupling to the photosensitive drum 1 provided on the photosensitive drum 1 and the bearing portion of the intermediate transfer belt driving shaft.
The rotational driving force transmission coupling to zero is slid in the axial direction and retracted (disconnected state). Japanese Patent Laid-Open No. 11-109 describes the mechanism for retreating and connecting the coupling.
836 and the like, which are omitted in this embodiment.

A guide rail 300 for the photosensitive drum and a guide rail 301 for the intermediate transfer member are provided on both sides of the apparatus body with a step γ. The right bearing 206 and the left rotating shaft 202 of the photosensitive drum of the process cartridge 5A shown in FIG. 5 are moved to the guide line 300 for the photosensitive drum, and the right bearing 205 and the left bearing 2 of the intermediate transfer belt drive roller.
01, a projection 203 provided on the left and right side covers,
204 are respectively placed on the guide rails 301 for the intermediate transfer member and inserted while sliding.

Finally, the photosensitive drum right bearing 20
6. The left rotating shaft 202 falls into the support portion 302 that supports the photosensitive drum bearing, and the right bearing 205 and the left bearing 201 of the intermediate transfer belt drive roller fall into the support portion 303 that supports the bearing of the intermediate transfer belt drive shaft. The projections 203 and 204 provided on the left and right side covers respectively fall into the positioning grooves 304, and as shown in FIG. 4, are respectively pressed and fixed to the positioning portions of the apparatus body frame by torsion coil springs.

In this embodiment, the flag is swingably installed on the intermediate transfer body unit or the image forming apparatus main body in which the intermediate transfer belt is incorporated, and the swing flag and the image forming apparatus main body are installed. Combined with the installed transmissive optical sensor, the position detection means of the intermediate transfer belt is configured, so that the position detection means can be made inexpensive and simple, and the accuracy of detecting the position of the intermediate transfer belt in the circling direction is improved. Can also be improved. Further, even if the intermediate transfer belt unit is detachably installed in the apparatus main body, there is no need for complicated wiring or connectors for connecting the transmission type optical sensor and the apparatus main body.

Embodiment 2 FIG. 6 is a schematic diagram showing another embodiment of the image forming apparatus of the present invention.

The image forming apparatus of this embodiment has four photosensitive drums 1 and forms toner images one by one on each of the photosensitive drums 1 to form toner images of four colors on the four photosensitive drums. This is a four-drum tandem-type color image forming apparatus of an intermediate transfer system to be formed.

The image forming apparatus has four image forming stations 70Y to 70Bk along the intermediate transfer belt 5a suspended by the driving roller 40, the driven roller 43, and the secondary transfer opposing roller 52. Photosensitive drum 1 and charging roller 2 surrounding it, exposure means 3, developing device 4, primary transfer roller 50, and cleaning blade 6
And

A toner image of each color is formed on each photosensitive drum 1 through the steps of charging, exposure and development, and the toner images of each color are primary-transferred onto the intermediate transfer belt 5a by being superimposed by the transfer roller 50. Next, the intermediate transfer belt 5
The four color toner images on the sheet a are collectively and secondarily transferred by the secondary transfer roller 11 to the transfer material conveyed to the intermediate transfer belt 5a at a time by the registration roller 7d. The transfer material onto which the four color toner images have been transferred is conveyed to the fixing device 8 and the toner images are fixed, whereby a full-color fixed image is formed.

In this embodiment, as in the first embodiment, the swing flag 101 is attached to the frame of the intermediate transfer belt unit incorporating the intermediate transfer belt 5a or the image forming apparatus main body.
Is installed so as to be swingable, and constitutes a position detecting means together with the transmission type optical sensor 103 installed in the image forming apparatus main body.
By detecting a detected portion such as a square hole provided in the intermediate transfer belt 5a, the position of the intermediate transfer belt 5a in the circulating direction is detected, and has the same effect as in the first embodiment.

Embodiment 3 This embodiment is applied to a direct transfer type four-drum tandem type color image forming apparatus as shown in FIG.

The image forming apparatus according to the present embodiment includes a driving roller 4
0 and four image forming stations 70 </ b> Y to 70 </ b> Y along the transfer material conveying belt 54 suspended by the driven roller 43.
Each station has a photosensitive drum 1 and its surrounding charging roller 2, an exposing unit 3, a developing unit 4, a transfer roller 50, and a cleaning blade 6 as in the second embodiment.
And

A toner image of each color is formed on each photosensitive drum 1 through a charging, exposing and developing process, and is supplied from a paper feed cassette 19 to a conveyor belt 54 via a registration roller 7d. The toner image of each color is transferred by being superimposed by the transfer roller 50 onto the transfer material conveyed by being electro-adsorbed, and the transfer material onto which the four color toner images are transferred is conveyed to the fixing device 8 and transferred to the fixing device 8. Received,
A full-color fixed image is formed.

In the present embodiment, similarly to the first embodiment, a frame of a transport belt unit incorporating the transport belt 54,
Alternatively, a swing flag 101 is provided on the image forming apparatus main body so as to be swingable, and a position detecting unit is configured together with the transmission type optical sensor 103 provided on the image forming apparatus main body, such as a square hole provided on the intermediate transfer belt 5a. By detecting the detected portion, the position of the intermediate transfer belt 5a in the circulating direction is detected, and has the same effect as in the first embodiment.

In each of the first to third embodiments, a color image forming apparatus having a plurality of developing units for one photosensitive drum or the same number of developing units for a plurality of photosensitive drums has been described. The present invention can be applied to detecting the position of the intermediate transfer belt or the transfer material conveying belt in the circumferential direction even in a single-color image forming apparatus having one developing unit for the photosensitive drum.

[0063]

As described above, in the image forming apparatus of the present invention, the flag is swingably installed on the belt unit incorporating the intermediate transfer belt or the transfer material conveying belt, or on the image forming apparatus main body. A position detecting means is configured by combining with a transmission type optical sensor provided in the apparatus main body, and is detected in an area other than the image transfer area of the intermediate transfer belt or an area other than the transfer material carrying area of the transfer material transport belt. Detect holes and protrusions provided as parts,
Since the position of the belt in the circling direction is detected,
The position detecting means can be made simple and inexpensive, and the accuracy of detecting the position of the belt in the circumferential direction can be improved. Further, even if the belt unit is detachably mounted on the apparatus main body, there is no need for complicated wiring or connectors for connecting the transmission type optical sensor and the apparatus main body.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a cross-sectional view illustrating a process cartridge in which a photosensitive drum and an intermediate transfer unit provided in the image forming apparatus of FIG. 1 are integrated;

FIG. 3 is a front view of the process cartridge of FIG. 2 as viewed from the front side of the image forming apparatus.

FIG. 4 is a cross-sectional view illustrating a state where the process cartridge of FIG. 2 is attached to and detached from an image forming apparatus main body.

FIG. 5 is a plan view of the process cartridge of FIG. 2 as viewed from above.

FIG. 6 is a schematic configuration diagram showing another embodiment of the image forming apparatus of the present invention.

FIG. 7 is a schematic configuration diagram showing still another embodiment of the image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 4 Developing device 5 Intermediate transfer belt unit 5a Intermediate transfer belt 5A Process cartridge 45 Belt frame 54 Transfer material conveying belt 100 Square hole 101 Swing flag 101a Sensor side flag 101b Belt side flag 102 Torsion coil spring 103 Transmission type optical sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA02 BB15 BB27 FF02 LL30 2H027 DE02 DE07 ED24 EE02 EE03 2H030 AA01 AA05 AB02 AD05 BB24 BB42 BB56 2H032 AA05 AA15 BA09 BA18 BA23 CA01 2H071 BA09 DA09

Claims (26)

[Claims] An image carrier on which a visible image is formed, an intermediate transfer belt on which the visible image on the image carrier is transferred,
An image forming apparatus comprising: a detecting unit configured to detect a position of the intermediate transfer belt in a circumferential direction, wherein the detecting unit is swingably mounted on an intermediate transfer body unit or an image forming apparatus main body incorporating the intermediate transfer belt. An image forming apparatus, comprising: a swinging flag that has been set; and a transmission type optical sensor installed in the image forming apparatus main body. 2. A detection section is provided in an area outside an image transfer area at a predetermined position in a circumferential direction of the intermediate transfer belt, and in the transmission type optical sensor, the swing flag is caused to swing by the detection section. The image forming apparatus according to claim 1, wherein the detected portion is detected to detect a position of the intermediate transfer belt in a circumferential direction. 3. The transmission type optical sensor according to claim 2, wherein the optical path between the light emitting element and the light receiving element of the transmission type optical sensor is interrupted by the swing of the swing flag to detect the detected part. Image forming device. 4. The transmission type optical sensor detects the detected part by releasing the interruption of an optical path between a light emitting element and a light receiving element of the transmission type optical sensor by swinging the swing flag. 2 image forming apparatus. 5. The detected portion is formed in a hole, the swing flag has first and second flags, and the first flag swings by dropping into the hole, and 2
4. The image forming apparatus according to claim 3, wherein the flag interrupts an optical path of the transmission type optical sensor. 6. The detected portion is formed in a hole, the swing flag has first and second flags, and the first flag swings by dropping into the hole, and 2
5. The image forming apparatus according to claim 4, wherein the flag releases the interruption of the optical path of the transmission type optical sensor. 7. The detected portion is formed on a protrusion, and the swing flag has first and second flags.
4. The image forming apparatus according to claim 3, wherein the flag fluctuates by climbing on the protrusion, and the second flag interrupts an optical path of the transmission-type optical sensor. 5. 8. The detected portion is formed on a protrusion, and the swing flag has first and second flags, and
5. The image forming apparatus according to claim 4, wherein the flag swings by riding on the protrusion, and the second flag releases the interruption of the optical path of the transmission optical sensor. 6. 9. The image forming apparatus according to claim 1, wherein the swing flag is provided at a position close to one of a plurality of rollers supporting the intermediate transfer belt on a side other than the image transfer unit side. The image forming apparatus according to any one of the above items. 10. The image forming apparatus according to claim 1, wherein said intermediate transfer body unit is detachably mounted on said image forming apparatus main body. 11. The image forming apparatus according to claim 1, wherein the image carrier and the intermediate transfer unit are integrated into an image forming unit detachable from the image forming apparatus main body. Image forming apparatus. 12. The image forming apparatus according to claim 1, wherein visible images of a plurality of colors are sequentially formed on the image carrier. 13. The image forming apparatus according to claim 1, wherein a plurality of said image carriers are provided, and a plurality of color visible images are formed on said plurality of image carriers. 14. An image carrier on which a visible image is formed, a transport belt for carrying and transporting a transfer material onto which the visible image is transferred on the image carrier, and a position of the transport belt in a circumferential direction. In the image forming apparatus having a detecting unit for detecting, the detecting unit includes a conveying belt unit incorporating the conveying belt or a swing flag that is swingably installed on the image forming apparatus main body, and the image forming apparatus main body. An image forming apparatus, comprising: an installed transmission type optical sensor. 15. A detection portion is provided in a region outside a transfer material carrying region at a predetermined position in a circulating direction of the transport belt, and the transmission type optical sensor is configured such that the swing flag is swung by the detection portion. The image forming apparatus according to claim 14, wherein the detected portion is detected to detect a position of the transport belt in a circumferential direction. 16. The transmission type optical sensor according to claim 15, wherein the optical path between the light emitting element and the light receiving element of the transmission type optical sensor is interrupted by the swing of the swing flag to detect the detected part. Image forming device. 17. The transmission type optical sensor detects the detected part by releasing the interruption of an optical path between a light emitting element and a light receiving element of the transmission type optical sensor by swinging the swing flag. 15 image forming apparatuses. 18. The detection unit is formed in a hole, the swing flag has first and second flags, and the first flag swings by dropping into the hole, and 17. The image forming apparatus according to claim 16, wherein the second flag interrupts an optical path of the transmission type optical sensor. 19. The detected portion is formed in a hole, the swing flag has first and second flags, and the first flag swings by dropping into the hole, and 18. The image forming apparatus according to claim 17, wherein the second flag releases the interruption of the optical path of the transmission type optical sensor. 20. The detected portion is formed on a projection, the swing flag has first and second flags, and the first flag swings by riding on the projection, 16. The image forming apparatus according to claim 15, wherein the second flag interrupts an optical path of the transmission type optical sensor. 21. The detected portion is formed on a projection, the swing flag has first and second flags, and the first flag swings by riding on the projection, 17. The image forming apparatus according to claim 16, wherein the second flag cancels the interruption of the optical path of the transmission type optical sensor. 22. The image forming apparatus according to claim 14, wherein the swing flag is set at a position close to one of a plurality of rollers supporting the transport belt on a side other than the image transfer portion side. The image forming apparatus according to any one of the above items. 23. The image forming apparatus according to claim 14, wherein the transport belt is detachably mounted on the image forming apparatus main body. 24. The process cartridge according to claim 14, wherein said image bearing member and said conveyor belt unit are integrated into a process cartridge detachable from said image forming apparatus main body.
The image forming apparatus according to any one of the above items. 25. The image forming apparatus according to claim 14, wherein visible images of a plurality of colors are sequentially formed on the image carrier. 26. The image forming apparatus according to claim 14, wherein a plurality of said image carriers are provided, and visible images of a plurality of colors are formed on said plurality of image carriers.