JP2750949B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring a visible image formed on an image carrier such as a photoreceptor, an insulator or a magnetic material to a transfer material conveyed by the transfer material carrier. With respect to the image forming apparatus adapted to transfer, for example, but not limited to, a plurality of images of different colors are respectively formed on a plurality of image carriers such as an electrophotographic photosensitive member, and these images are carried on a transfer material. The present invention is suitable for a color copying machine, a printer or the like of a system in which the transfer is sequentially performed on the same transfer material conveyed by the body.

2. Description of the Related Art Conventionally, a plurality of image forming units are provided, each image forming unit forms a developed image (toner image) having a different color, and these toner images are transferred by a transfer material carrier to the same transfer material. There have been proposed various image forming apparatuses that sequentially transfer images onto each other and collectively fix them to obtain a combined color image, that is, a so-called color image forming apparatus. Among them, an electrophotographic color copying machine is frequently used. It is.

An example of such an electrophotographic color copier is described in
Shown in the figure. The first, second, third and fourth four image forming units Pa, Pb, Pc and Pd are provided in the apparatus body of the color copying machine.
The image forming units Pa, Pb, Pc, and Pd have substantially the same configuration, and are dedicated image carriers that are driven to rotate in the direction of the arrow as shown in the drawing, in this example. It includes electrophotographic photosensitive drums 1a, 1b, 1c and 1d, respectively.
Around each of the photosensitive drums 1a to 1d, a dedicated image forming process means, for example, electrostatic latent image forming units 2a, 2b, 2c and 2d, developing units 3a, 3b, 3c and 3d, cleaning units 5a and 5
b, 5c, 5d, etc. are sequentially arranged in the drum rotation direction.

A transfer material carrier, in this example, a transfer material transport belt 8 is disposed below each of the image forming units Pa, Pb, Pc, and Pd. Inside the transport belt 8, each of the image forming units Pa to Pd is provided. Transfer units 4a, 4b, 4c and 4d are provided below the photosensitive drums 1a to 1d.

In the color copying machine having such a configuration, when the transfer material 6 is placed on the transfer belt 8 as a transfer material carrier from the transfer material cassette 60 via the registration roller pair 13, the transfer belt 8 is moved in the direction of the arrow in FIG. As a result, the image forming processes for the photosensitive drums 1a, 1b, 1c and 1d of the corresponding image forming units Pa to Pd are sequentially started. First, the first
The latent image forming section 2a forms a latent image of a black component color in the original image on the photosensitive drum 1a of the image forming section Pa. The latent image is made a visible image by a developer having a block toner in the developing unit 3a, and the black toner image is transferred to the transfer material 6 conveyed by the conveying belt 8 in the transfer unit 4a. While this black toner image is being transferred to the transfer material 6, a magenta component color latent image is formed on the photosensitive drum 1b of the second image forming portion Pb by the latent image forming portion 2b, and then the developing portion 3b To form a visible image with magenta toner,
The transfer material 6 that has been transferred at the first image forming unit Pa is the second transfer material.
Is transferred into the transfer section 4b below the photosensitive drum 1b of the image forming section Pb, the magenta toner image is transferred to a predetermined position on the transfer material 6.

Hereinafter, similarly, the third and fourth image forming units Pc and
The yellow toner image and the cyan toner image formed on the photoconductor drums 1c and 1d of Pd are respectively superimposed and transferred onto predetermined positions of the transfer material 6 that has been conveyed in the transfer units 4c and 4d below these photoconductor drums, respectively. Thus, the transfer material 6
The step of transferring the four full-color images upward is completed. When the transfer step is completed, the transfer material 6 is separated from the transport belt 8 by a separating unit (not shown) and sent to the fixing unit 7.
The color toner image weight-transferred by the fixing unit 7 is transferred to the transfer material 6.
After being fused and fixed to the sheet, the sheet is discharged to a discharge tray, whereby a desired full-color image is obtained.

On the other hand, each photoconductor drum 1a on which transfer has been completed. 1b, 1c and
In 1d, the residual toner is removed by the cleaning units 5a, 5b, 5c, and 5d to prepare for the subsequent latent image formation.

By the way, in the image forming apparatus as described above, generally, both ends of a dielectric resin film sheet such as a polyethylene terephthalate resin film sheet, a polyfukka vinylidene resin film sheet, or a polyurethane resin film sheet are overlapped with each other as a transfer material conveying belt. Those that are joined together and formed into an endless shape are often used. This is because a so-called seamless type belt having no seams is difficult to manufacture, becomes very expensive, and is very disadvantageous in cost.

In the case of using a belt having such a seam, if transfer is performed on a transfer material at a place corresponding to the seam portion, physical properties differ from the surrounding portion only at the seam portion. If it is convex, image defects such as image disturbance due to strong contact with the photoconductor will occur. Therefore, a mechanism for detecting this seam portion during preliminary rotation prior to image formation is provided, and this seam portion is detected, for example, immediately after the seam portion passes the portion where the transfer material is carried into the belt, the transfer material is detected. Heretofore, a method has been adopted in which the above-mentioned problem is avoided by carrying the paper into a belt.

However, in the conventional image forming apparatus having the above-described configuration, the actual image forming operation is started after the position of the seam portion on the conveyor belt is detected before the actual image forming. In the case of (1), the image forming operation is not performed while the conveyor belt makes substantially one round, and the rotation before image formation is prolonged, so that a so-called first copy time is prolonged. In addition, the conveyor belt, and devices, parts, members, and the like that operate simultaneously with the operation of the conveyor belt, such as a photoconductor drum and a fixing device, are additionally operated by rotation before image formation. There is also a disadvantage that the life of the device is shortened.

Therefore, an object of the present invention is to allow the transfer material to be quickly loaded into the transfer material carrier without causing the transfer material to fall on the joint portion of the transfer material carrier, and therefore, after the transfer material carrier starts rotating. The time required for the transfer material to be carried on the transfer material carrier can be shortened, the first copy time can be greatly reduced, and the reduction of the first copy time necessitates operation during rotation before image formation. An object of the present invention is to provide an image forming apparatus capable of extending the life of components, members, devices, and the like.

Means for Solving the Problems The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image carrier for carrying an image, a seam and a mark, a rotatable transfer material carrier capable of carrying a plurality of transfer materials, and the transfer material carrier on the transfer material carrier. Detecting means for detecting a mark, wherein a copying material is carried on the transfer material carrier so as to cross the seam according to a detection result by the detecting means, and the image on the image carrier is In the image forming apparatus which is transferred onto a transfer material carried on a material carrier, at least one of the mark and the detection unit is provided in a plurality in a rotation direction of the transfer material carrier, and the mark detected first is provided. The image forming apparatus is characterized in that the position at which the transfer material is first carried on the transfer material carrier is variable based on the detection means for detecting the mark.

According to one embodiment of the present invention, the transfer material carrier has a belt.

According to another embodiment of the present invention, the position at which the transfer material is first carried on the transfer material carrier is variable according to the length of the transfer material in the rotation direction of the transfer material carrier.

According to still another embodiment of the present invention, the transfer material carrier includes a plurality of the marks, and only one detection unit is provided.

According to still another embodiment of the present invention, the apparatus includes a transfer material supply unit that supplies a transfer material to the transfer material carrier, and when the mark detected first is detected by the detection unit. The position at which the transfer material is first carried on the transfer material carrier is variable depending on whether or not there is a transfer material in the transfer material supply means.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 6 is a sectional view schematically showing the overall configuration of a color image forming apparatus to which the present invention is applied, and shows a case where the present invention is applied to an electrophotographic color copying machine. Before describing the main parts of the present invention, first, the overall operation of the color copying machine shown in FIG. 6 will be described.

As shown in the figure, the color copying machine is
In the first, second, third and fourth four image forming units Pa,
Pb, Pc and Pd are juxtaposed. Each image forming unit Pa, Pb,
Pc and Pd have substantially the same configuration, and include dedicated electrophotographic photosensitive drums 1a, 1b, 1c and 1d, which are image carriers that are driven to rotate in the direction of the arrow as shown. Around each photoconductor drum, for example, chargers 15a, 15b, 15c and 15d for uniformly charging the photoconductor drum, and developing devices 3a, 3b and 3c for developing an electrostatic latent image formed on the photoconductor drum And 3d, a transfer discharger 4 for transferring the developed color toner images to the recording material 6.
a, 4b, 4c and 4d, and cleaning means 5a, 5b, 5c and 5d for removing the toner remaining on the photosensitive drum are arranged sequentially in the drum rotation direction.

Laser beam scanners 16a, 16b, 16c and 16d are provided above the photosensitive drums 1a, 1b, 1c and 1d, respectively. These laser beam scanners 16a, 16b,
16c and 16d are composed of a semiconductor laser, a polygon mirror, an fθ lens, etc., receive an electric digital pixel signal, and develop a laser beam corresponding to this signal with the chargers 15a, 15b, 15c and 15d. The scanning is performed in the drum genera direction between the devices 3a, 3b, 3c and 3d to expose the drum surface.

On the other hand, below the photosensitive drums 1a, 1b, 1c and 1d, a transfer material carrier having a seam that rotates in the direction indicated by an arrow so as to cross each image forming unit Pa, Pb, Pc and Pd, in this example, is conveyed. A recording material conveying means having a belt 8 is disposed. The transport belt 8 having this seam is stretched between a drive roller 11 and an idler roller 12 via a tension adjusting roller 76, and is driven endlessly by the drive roller 11 in a direction indicated by an arrow in FIG. Transfer material 6 fed from cassette 60
And sequentially transports the image forming units Pa, Pb, Pc, and Pd to the respective transfer positions.

In the color image forming apparatus having the above configuration, when an image forming operation start signal is input to the image forming apparatus, the photosensitive drum 1a of the first image forming unit Pa starts to rotate in the direction of the arrow shown in the drawing, and the charger 15a The laser beam scanner 16a then writes a laser beam modulated by an image signal corresponding to the black component image of the original image, thereby forming a latent image. Next, the developing device 3a containing the black toner develops the latent image, and the photoconductor 1a
A black toner image is formed thereon.

On the other hand, the transfer material 6 in the transfer material cassette 60 is taken out by the pickup roller 9 and sent to the registration roller 13. The transfer material 6 once stopped by the registration roller 13 is fed by the registration roller 13 onto the transport belt 8 which has already started to rotate at a timing with the toner image formed on the photoreceptor 1a. The transfer material 6 sent on the conveyor belt at a proper timing is transferred to the transfer discharger while moving in the transfer section below the photosensitive drum 1a of the first image forming section Pa.
4a, a corona discharge for transfer is received from the back side of the conveyor belt 8, whereby the black toner image on the photosensitive drum 1a is transferred onto the transfer material 6. While this black toner image was being transferred to the transfer material 6, a visible image was formed by magenta toner on the photosensitive drum 1b of the second image forming portion Pb, and the transfer in the first image forming portion Pa was completed. Transfer material 6
Moves through the transfer section below the photosensitive drum 1b of the second image forming section Pb, the magenta toner image is transferred to a predetermined position on the transfer material 6 by the action of the transfer discharger 4b. .

Hereinafter, by the same process, the third and fourth image forming units
The transfer material 6 transported by the action of the transfer dischargers 4c and 4d at the transfer positions below the photosensitive drums, the yellow toner image and the cyan toner image formed on the photosensitive drums 1c and 1d of Pc and Pd, respectively. Thus, the step of transferring the four full-color images onto the transfer material 6 is completed. When the transfer process is completed, the transfer material 6
Almost immediately above the roller 12 at the left end of the transport belt 8, the toner is separated from the transport belt 8 while being subjected to AC neutralization by a separation charger 61, sent to the fixing unit 7, and transferred to the fixing unit 7 by the fixing unit 7. After the image is fused and fixed to the transfer material 6, the image is discharged from the discharge port 14 to the outside of the copying machine main body 10, thereby obtaining a desired full-color image.

The residual toner is removed from each of the photosensitive drums after the transfer by the cleaning means 5a, 5b, 5c, and 5d to prepare for the subsequent latent image formation.

 Next, the main part of the present invention will be described in detail.

FIG. 1 is a schematic sectional view showing a main part of an embodiment of an image forming apparatus according to the present invention. In this embodiment, when the distance from the image exposure position E of the photosensitive drum 1a to the transfer unit T along the rotation direction of the photosensitive drum 1a is ET, the transfer unit T
An optical sensor 17 as a detecting means for reading a mark provided on the conveyor belt 8 at a point S which is substantially backward by a distance ET to the upstream side in the movement direction of the conveyor belt 8, ie, a point S where ET ≒ TS. In the present embodiment, is installed at a position near the front end of the conveyor belt 8. Of course, the sensor 17 may be installed inside or outside the conveyor belt 8. On the other hand, near the seam 81 on the conveyor belt 8 and near the front end, a mark 18 indicating the seam 81 is provided.
The distance from the mark 18 on the downstream side in the moving direction of the transport belt 8 and substantially half the circumference L of the transport belt 8
A position on the conveyor belt separated by L / 2 indicates that the position is approximately L / 2 away from the seam portion 81. A mark 19 different from the mark 18 is provided. These marks 18, 19
When an optical sensor is used as in this embodiment,
For example, as shown in FIG. 2, the mark 18 is provided with one slit, and the mark 19 is provided with two slits.

Note that these marks are preferably provided outside the area on the conveyor belt 8 where the transfer material 6 is placed, that is, outside the image forming area.

Further, in the present embodiment, the marks 18 and 19 are slit, but anything may be used as long as the optical sensor 17 can be identified. For example, a paint having an optical reflectance different from that of the surrounding conveyor belt 8 is applied. Needless to say, such a method may be used.

Further, in this embodiment, an optical sensor is used as a sensor for reading a mark. However, sensors of different types, such as an electric sensor, a magnetic sensor, and a mechanical sensor, may be used. Needless to say, it is only necessary to use the one according to.

Now, in the image forming apparatus provided with such sensors and marks, when a signal indicating the start of image formation is input, the photosensitive drums 1a to 1d and the transport belt 8 are respectively driven in the directions of the arrows, and When the mechanism is activated, the transfer material 6
Is taken out of the transfer material cassette 60 and driven in the direction indicated by the arrow. After the transfer material 6 is conveyed to the registration roller 13, the transfer material 6 is temporarily stopped by the operation of the registration roller 13 and enters a standby state.

Next, the operation of the transport belt 8 will be described in the following two cases.

When the transport belt 8 starts operating, the transport belt 8
When the distance from the mark 18 provided in the vicinity of the seam portion 81 to the sensor 17 in the moving direction of the conveyor belt 8 is substantially L / 2 or less, that is, the mark 18 is earlier than the mark 19
When the mark 18 passes the sensor 17 when the transfer material 6 passes through the sensor 17, when the transfer material 6 is on standby at the position of the registration roller 13, the seam portion 81 on the transport belt 8 carries the transfer material 6 into the transport belt 8. In order to match the timing with the point (point A shown in FIG. 1), the synchronizing timing is calculated by a calculating means (not shown) based on a signal from the sensor 17, and the registration roller 13 is operated by a motor (not shown). The transfer material 6 is carried in immediately after the joint 81. On the other hand, on the photosensitive drum 1a, a point E on the photosensitive drum 1a is irradiated with a light image at almost the same time as the mark 18 passes through the sensor 17 in synchronization with the movement of the transfer material 6, and a latent image is formed. To start forming. At this time, since the distance ET ≒ TS as described above, when the leading end of the recording material 6 reaches the transfer position T of the photosensitive drum 1a, it is just synchronized with the leading end of the toner image on the photosensitive drum 1a. Thus, a lean operation can be performed.

On the other hand, when the transfer material 6 is not waiting at the position of the registration roller 13 when the mark 18 passes through the sensor 17, the timing is set longer than when the transfer material 6 arrives at the position of the registration roller 13. The transfer material 6 is carried in downstream of the seam portion 81 in the belt conveyance direction. further,
When the transfer material 6 is subsequently conveyed to the transport belt 8 from this state, that is, in the continuous image forming mode, the first transfer material 6 is generated using the signal generated when the mark 18 passes the sensor 17. The transfer is performed by the registration roller 13 while varying the distance between the transfer materials so that the transfer material does not always fall on the seam portion 81 in consideration of the position where the transfer material is carried into the transport belt 8, the size of the transfer material, and the like. Material 6 is transported to belt 8
It was also found that good results could be obtained by carrying them in.

Next, an example in which the mark 19 provided at a position approximately L / 2 away from the seam portion 81 of the conveyor belt 8 when the conveyor belt 8 starts operating passes the sensor 17 earlier than the mark 18. explain.

In this case also, the general operation is that the aforementioned mark 18 is the mark 19
This is the same as the case of passing the sensor 17 earlier than before. However, in this case, the peripheral length of the transport belt 8 is equal to the length in the transport direction of the transfer material to be carried in at this time.
In the case where the transfer material 6 is shorter than twice or when image formation is continuously performed, the transfer material 6 is preferably carried in using the signal when the mark 19 has passed the sensor 17 so that the transfer material 6 does not always reach the joint portion 81.

When an image was formed using an image forming apparatus having two marks indicating the distance from the seam portion 81 on the conveyor belt 8 as in the present embodiment, even when the first copy time was the worst, Of the maximum value of the first copy time was reduced to about half of the maximum value of the first copy time, and the life of the conveyor belt, the photosensitive drum, the fixing device and the like was prolonged.

Further, if the moving speed of the conveyor belt is higher before the mark on the conveyor belt passes through the sensor than after the mark passes, that is, after the actual image formation is started, a better effect can be obtained. Needless to say,

In the present embodiment, two marks indicating the seam are provided on the conveyor belt 8, but if three or more marks are provided, it goes without saying that better results can be obtained.

FIG. 3 is a schematic sectional view showing a main part of a second embodiment of the image forming apparatus according to the present invention. In this embodiment, when the distance from the image exposure position E of the photoconductor drum 1a to the transfer unit T along the rotation direction of the photoconductor drum 1a is ET, an upstream side in the moving direction of the transport belt 8 from the transfer unit T To the point S, which is almost the distance ET, that is, the point S where ET ≒ TS,
The first optical sensor 17 for reading the mark provided above is positioned at a position approximately L / 2 away from the point S, which is approximately half the circumference L of the conveyor belt 8. The two optical sensors 20 are respectively installed near the front side of the transport belt 8. Of course, the first and second optical sensors 17
And 20 may be installed inside or outside the conveyor belt 8. On the other hand, a mark 18 indicating the seam 81 is provided near the seam 81 on the conveyor belt 8 and near the front end.

When an image is formed using the image forming apparatus having the above-described configuration, when the mark 18 indicating the joint portion 81 passes through the first or second sensor 17 or 20, the same as that described in the first embodiment is performed. It is possible to start image formation in the operation procedure described above, and the same good results as in the first embodiment were obtained.
In other words, even if the first copy time is the worst, it is reduced to almost half of the conventional maximum value of the first copy time, and on average is reduced to almost half of the conventional value, and the life of the transport belt, the photosensitive drum, the fixing device, etc. is extended. became.

In the present embodiment, two sensors are installed to detect the mark 18 indicating the seam 81 provided on the conveyor belt 8, but if three or more sensors are provided, a better result is obtained. Needless to say, this is obtained.

Further, if the moving speed of the conveyor belt is increased before the mark on the conveyor belt passes the sensor, that is, after the mark is passed, that is, after the actual image formation is started, better results are obtained. Needless to say,

FIG. 4 is a schematic sectional view showing a main part of a third embodiment of the image forming apparatus according to the present invention. In this embodiment, when the distance from the image exposure position E of the photoconductor drum 1a to the transfer unit T along the rotation direction of the photoconductor drum 1a is ET, an upstream side in the moving direction of the transport belt 8 from the transfer unit T To the point S, which is almost the distance ET, that is, the point S where ET ≒ TS,
The first optical sensor 17 for reading the mark provided above is placed at a position separated from the point S by a distance approximately L / 2, which is approximately half the circumference L of the conveyor belt 8, and the second optical sensor 17. Are installed near the front side of the conveyor belt 8 respectively. Of course, the first and second optical sensors 17
And 20 may be installed inside or outside the conveyor belt 8. On the other hand, near the seam 81 on the conveyor belt 8 and near the front end, a mark 18 indicating the seam 81 is provided, and further from the position of the mark 18 on the downstream side in the moving direction of the conveyor belt 8 and Almost 1/4 of the circumference L of the conveyor belt 8
The mark 21 is provided at a position on the conveyor belt at a distance of approximately L / 4, which is the length of the joint, to indicate that the position is approximately L / 4 away from the seam portion 81. In the present embodiment, the mark 21 is located substantially downstream of the mark 18 in the conveying belt signal direction.
Although provided at a position on the conveyor belt separated by L / 4, it is needless to say that it may be provided at a position on the conveyor belt approximately L / 4 upstream.

When an image is formed using the image forming apparatus having the above configuration, when the mark 18 or the mark 21 indicating the joint portion 81 passes through the first or second sensor 17 or 20, the first and second embodiments are performed. Image formation can be started in the same operation procedure as shown in the example, and good results similar to those of the first and second embodiments can be obtained. In other words, even if the first copy time is the worst, it is reduced to almost 1/4 of the conventional maximum value of the first copy time, and even to about 1/4 of the conventional average, and the transport belt, the photosensitive drum, the fixing device, etc. Has a longer lifespan.

In this embodiment, two marks indicating the seam portion 81 of the conveyor belt 8 are provided, and these marks are detected by two sensors. However, if three or more marks and sensors are provided, respectively, Needless to say, even if three or more are provided, even better results can be obtained.

Further, if the moving speed of the conveyor belt is increased before the mark on the conveyor belt passes the sensor, that is, after the mark is passed, that is, after the actual image formation is started, better results are obtained. Needless to say,

FIG. 5 is a schematic sectional view showing a main part of a fourth embodiment of the image forming apparatus according to the present invention. In this embodiment, when the distance from the image exposure position E of the photoconductor drum 1a to the transfer unit T along the rotation direction of the photoconductor drum 1a is ET, an upstream side in the moving direction of the transport belt 8 from the transfer unit T To the point S, which is almost the distance ET, that is, the point S where ET ≒ TS,
The first optical sensor 17 for reading the mark provided above is provided at a position downstream of the point S in the moving direction of the conveyor belt 8 and substantially 1/4 of the circumferential length L of the conveyor belt 8. The second optical sensor 22 is located at a position approximately L / 4 away from a certain distance,
Each is installed near the front side of the conveyor belt 8. These first and second optical sensors 17 and 22 may be installed inside or outside the conveyor belt 8. On the other hand, near the seam portion 81 on the conveyor belt 8 and near the front end,
A mark 18 indicating the seam portion 81 is provided, and further, at a position on the conveyor belt that is separated from the position of the mark 18 by a distance substantially L / 2, which is substantially half the circumference L of the conveyor belt 8,
A mark 19 indicating that the position is approximately L / 2 away from the seam portion 81 is provided. In the present embodiment, the sensor 22 is provided at a position substantially L / 4 on the downstream side in the transport belt traveling direction from the sensor 17, but it is needless to say that the sensor 22 may be provided at a position substantially L / 4 on the upstream side. .

When an image was formed using the image forming apparatus having the above configuration, when the mark 18 or the mark 19 indicating the joint portion 81 passed the first or second sensor 17 or 22, the first to third
The image formation can be started in the same operation procedure as shown in the embodiment, and the same good results as those in the first to third embodiments can be obtained. In other words, even if the first copy time is the worst, it is reduced to almost 1/4 of the conventional maximum value of the first copy time, and even to about 1/4 of the conventional average, and the transport belt, the photosensitive drum, the fixing device, etc. Has a longer lifespan.

In this embodiment, two marks indicating the seam portion 81 of the conveyor belt 8 are provided, and these marks are detected by two sensors. However, if three or more marks and sensors are provided, respectively, It goes without saying that even if three or more are provided, even better results can be obtained.

Further, if the moving speed of the conveyor belt is increased before the mark on the conveyor belt passes the sensor, that is, after the mark is passed, that is, after the actual image formation is started, better results are obtained. Needless to say,

In the above embodiment, the present invention is applied to an electrophotographic color image forming apparatus. However, the present invention is not limited to the above embodiments, but may be applied to various other copiers, printers, etc. This can be equally applied to the image forming apparatus. Needless to say, various modifications and changes can be made as needed.

As is apparent from the above description, in the image forming apparatus according to the present invention, the transfer material is first carried on the transfer material carrier based on the mark detected first and the detecting means for detecting the mark. Is variable, so that the time from when the transfer material carrier starts rotating until the transfer material is carried on the transfer material carrier can be shortened, and the worst case is the first copy time. However, it can be reduced to approximately half or less of the conventional maximum value of the first copy time, and even to an average of approximately 1/2 or less of the conventional first copy time. Therefore, the first copy time can be significantly reduced, and the life of parts, members, devices, and the like, such as a conveyor belt, a photosensitive drum, and a fixing device, which are forced to operate during rotation before image formation due to the reduction of the first copy time, are reduced. Has a remarkable effect that it can be lengthened.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a main part of a first embodiment of the image forming apparatus according to the present invention. FIG. 2 is an enlarged plan view showing a part of the conveyor belt used in the image forming apparatus shown in FIG. FIG. 3 is a schematic sectional view showing a main part of a second embodiment of the image forming apparatus according to the present invention. FIG. 4 is a schematic sectional view showing a main part of a third embodiment of the image forming apparatus according to the present invention. FIG. 5 is a schematic sectional view showing a main part of a fourth embodiment of the image forming apparatus according to the present invention. FIG. 6 is a sectional view schematically showing the overall configuration of a color image forming apparatus to which the present invention is applied. FIG. 7 is a schematic sectional view showing an example of a conventional color image forming apparatus. 1a to 1d: Photoreceptor drum 6: Transfer material 8: Transfer material transport belt with seams 17, 20, 22: Sensors 18, 19, 21: Mark 81: Seam

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G03G 15/16 G03G 15/16 (56) References JP-A-61-158344 (JP, A) JP-A-63-279279 (JP) JP-A-60-84563 (JP, A) JP-A-54-86344 (JP, A) JP-A-58-46353 (JP, A) JP-A-60-218670 (JP, A) Patent 2633077 (JP, A) JP, B2)

Claims (5)

(57) [Claims] An image carrier for carrying an image; a seam and a mark; a rotatable transfer material carrier capable of carrying a plurality of transfer materials; and detecting the mark on the transfer material carrier. A copy material is carried on the transfer material carrier so as to cross the seam according to a detection result by the detection device, and an image on the image carrier is the transfer material carrier. In the image forming apparatus which is transferred to a transfer material carried on the image forming apparatus, at least one of the mark and the detection unit is provided in a plurality in a rotation direction of the transfer material carrier, and the mark detected first and the mark An image forming apparatus, wherein a position at which a transfer material is first carried on the transfer material carrier is variable based on the detection means for detecting. 2. An image forming apparatus according to claim 1, wherein said transfer material carrier has a belt. 3. The transfer material according to claim 1, wherein a position at which the transfer material is first carried on the transfer material carrier is variable according to a length of the transfer material in a rotation direction of the transfer material carrier.
Or the image forming apparatus of 2. 4. An image forming apparatus according to claim 1, wherein said transfer material carrier comprises a plurality of said marks, and only one said detecting means is provided. 5. The apparatus according to claim 1, further comprising a transfer material supply means for supplying a transfer material to the transfer material carrier, wherein when the mark detected first is detected by the detection means, the transfer material supply means is supplied to the transfer material supply means. The image forming apparatus according to any one of claims 1 to 4, wherein a position where the transfer material is first carried on the transfer material carrier is variable depending on whether or not there is a transfer material. .