JP3342217B2 - Image forming device - Google Patents

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 copying machine and a laser beam printer.

[0002]

2. Description of the Related Art In recent years, image forming apparatuses such as electrophotographic apparatuses have been reduced in size, enhanced in function and color, while improving reliability, system development, maintenance-free, and reducing human and environmental concerns. Demands for gentleness and the like are increasing, and various things have been proposed to satisfy these requirements.

Among these, in order to increase the speed of color image output, an apparatus for loading a plurality of photoconductors and successively multiplex transferring toner images while transferring a transfer material such as paper by a belt-like transfer means. A proposal has been made. As an example, FIG.
FIG. 1 shows an example of a color laser beam copying machine.

The copying machine shown in FIG. 1 has a plurality of image forming units, and a transfer belt serving as a transfer material conveying means is provided to extend through each image forming unit. In each of the image forming units M, C, Y, and Bk, a cylindrical photosensitive member (hereinafter, appropriately referred to as a “photosensitive drum”) 10M, 10C, 10Y, and 10Bk as an electrostatic latent image carrier is indicated by an arrow a (image). Only the forming unit M is supported so as to be rotatable in the same direction. 11M, 11C, 11Y,
11Bk is a primary charger, each of which is a photosensitive drum 10M,
They are installed at predetermined intervals from 10C, 10Y, and 10Bk. Reference numerals 14M, 14C, 14Y, and 14Bk denote laser exposure devices (laser scanners), which are provided to the primary chargers 11M, 11C, 11Y, and 11Bk, respectively, at the downstream side of the photosensitive drums 10M, 10C, 10Y, and 10Bk in the rotation direction. , 10C, 10Y and 10Bk are exposed. Reference numerals 16M, 16C, 16Y, and 16Bk denote developing units that store magenta, cyan, yellow, and black toners, respectively.
Further downstream from the exposure position of 10Bk, the photosensitive drum 1
0M, 10C, 10Y, and 10Bk.

Reference numeral 18 denotes a transfer material such as paper. Reference numeral 20 denotes a paper feeding unit which supplies the transfer material 18. Reference numeral 30 denotes a transfer belt, which is a photoconductor 10M, 10C, 10Y, or 10Bk.
And is driven in the direction of arrow b. Reference numeral 32 denotes a drive roller, and 31 denotes a separation roller, which drives the stretched transfer belt 30.

Reference numerals 24M, 24C, 24Y, and 24Bk denote transfer chargers, which are installed at respective transfer positions so as to sandwich the transfer belt 30 with respect to each photosensitive drum in order from the upstream side in the moving direction of the transfer belt 30. A fixing device 38 is disposed adjacent to the separation roller 31 of the transfer and conveyance belt 30.

Reference numerals 15M, 15C, 15Y, and 15Bk denote cleaners for the respective photosensitive drums.
M, 24C, 24Y, 24Bk
0M, 10C, 10Y, and 10Bk are installed downstream in the rotation direction. 13M, 13C, 13Y, and 13Bk are pre-exposure lamps, and each of the cleaners 15M, 15C, 15Y,
15Bk and each primary charger 11M, 11C, 11Y, 11
It is installed between Bk. Reference numeral 51 denotes a belt cleaner for cleaning the transfer belt 30.

The operation of the image forming apparatus configured as described above will be described by taking the image forming unit M as an example.
The same applies to the operation of the other image forming units.

First, the photosensitive drum 10M has an optical semiconductor layer on the surface of a conductive substrate such as aluminum, and rotates in the direction of arrow a. After the surface is uniformly negatively charged by the primary charger 11M, exposure is performed by the laser exposure device 14M to form an electrostatic latent image corresponding to the document. The developing unit 16M performs development using negatively charged toner, and forms a toner image corresponding to the electrostatic latent image on the surface of the photosensitive drum 10M. The toner image formed on the surface of the photosensitive drum 10M is transferred onto the transfer material 18 supplied from the paper supply unit 20 toward the transfer belt 30 in synchronization with the image formation by the rotation speed of the photosensitive drum 10M. .

The above operation is performed in each image forming unit, and the toner image formed on each photosensitive drum is sequentially transferred to the transfer material 18 held on the transfer belt 30. In the case of the full-color mode, M, C,
The transfer is performed in the order of Y and Bk. Similarly, in the case of the single color mode or the two- or three-color mode, the toner of the required color is similarly transferred in the order described above.
Is transcribed multiple times. Copy paper 18 to which the toner image has been transferred
Is supplied to the fixing device 38 by the transfer belt 30, and is heated and pressed to be fixed on the transfer material 18.

On the other hand, in the photosensitive drum 10M from which the toner image has disappeared due to the transfer, the residual toner adhering to the surface is removed by the cleaner 15M, and further, the charge is removed by the pre-exposure lamp 13M. Provided. Further, the surface of the transfer belt 30 that has finished supplying the transfer material 18 to the fixing device 38 is cleaned by a belt cleaner 51.

Although many such color image forming apparatuses have been proposed, recently, a simultaneous development type cleaning system has been adopted, particularly for miniaturization and ozone-less use, and for ecological measures without waste toner. In addition, copiers and prints employing a cleaner-less system for collecting and reusing transfer residual toner have been put to practical use. In particular, when such a method is adopted, the degree of practicality is further increased by using a spherical toner produced by a polymerization method as the toner.

Here, referring to FIG. 6, the reason why the toner recycling process by the cleanerless and simultaneous cleaning with development can be achieved by the spherical toner generated by the polymerization method will be described from the aspect of the adhesive force between the toner and the photoreceptor. explain.

When the toner adheres to the photoreceptor by the developing process (bias, latent image potential), the main forces acting on the toner in contact with the photoreceptor surface include a mirror force and a Van der Waals force. . The mirror power greatly depends on the amount of charge and its distance.

Since the surface of a pulverized toner produced by pulverization, which is a conventional toner, has irregularities, charges are concentrated on the convex portions during frictional charging. On the other hand, a spherical polymerized toner formed by the polymerization method has a spherical or nearly spherical surface, and therefore, the surface is uniformly charged.

In the pulverized toner, since the convex portions come into contact with each other and a lot of electric charges exist in a very close area, the reflection power increases. On the other hand, when the toner is spherical, as in the case of the polymerized toner, the contact state becomes almost dot-like, the amount of charge in the vicinity area is small, and the mirror power is smaller than that of the pulverized toner.

The van der Waals force is affected by the closest region, and becomes very large in a state where the contact is made in a plane. When the pulverized toner is used, a large number of toners are in contact with each other in a state shown in FIG. 6, and in this case, the van der Waals force is extremely large. On the other hand, since the surface of the polymerized toner is spherical, the toner contacts almost at points. Therefore, the polymerization toner also has a smaller van der Waals force.

For the above reasons, in the case of a polymer toner having a nearly spherical shape, the mirror image power, van der Waals force,
That is, the adhesive force is reduced, the transfer residual toner during transfer is reduced, and the toner collecting effect at the time of cleaning at the same time as the development is increased.

In the four-drum (four photosensitive drums) full-color printer having the structure shown in FIG.
For example, in the case of the two-color mode (magenta, cyan), the transfer material 18 supported on the transfer belt 30 is sequentially changed to magenta, cyan, yellow, and black image forming units M, C, Y, and Bk. Although the image forming unit passes the image forming unit, it is sufficient that only the desired unit, that is, only the image forming units M and C for magenta and cyan in the above-described case are operated.

[0020]

However, as described above, the transfer material 18 is sequentially provided with magenta, cyan, yellow, and black image forming units M, C, Y, and Bk.
To pass through the gap between the transfer belt 30 and each photosensitive drum. For this reason, when the operations of all the image forming processes of the undesired units, that is, the yellow and black image forming units Y and Bk are stopped, the transfer material 18 is stopped.
As described above, the magenta and cyan toner images already formed on the transfer material when passing through the gap between the transfer belt 30 and the photosensitive drums 10Y and 10Bk of the yellow and black image forming units Y and Bk as described above The black photosensitive drums 10 </ b> Y and 10 </ b> Bk are rubbed and disturbed, which causes a problem. In particular, when spherical toner is used as in this example, since the toner itself is likely to roll, damage due to printing is increased.

At this time, the magenta and cyan toners transferred onto the time transfer material 18 are electrostatically attracted to the transfer material 18, but the transfer material 18
When passing through the gaps between the black photosensitive drums 10Y and 10Bk and the transfer belt 30, these photosensitive drums 10Y and 10Bk
A part of the magenta and cyan toners may be reversely transferred to Y and 10Bk (transfer offset), and in this case, there is a problem that the image is deteriorated.

Further, when the above-described transfer offset occurs, that is, when the magenta and cyan toners are reversely transferred to the yellow and black photosensitive drums, they are collected at the same time as the development without the drum cleaner. The problem of toner color mixing also occurs.

Further, in such a case, when the transfer material 18 passes through the gap between the photosensitive drum and the transfer belt 30, the transfer material may be easily jammed (jam).

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of forming a desired toner image on a transfer material.

[0025]

The invention according to claim 1 is
An image carrier movably supported, a latent image forming means for forming a latent image on the image carrier, and developing the toner image by attaching toner to the latent image , and simultaneously transferring residual toner after transfer. Simultaneous cleaning means for developing and toner
A transfer operation is performed in an image forming apparatus in which a plurality of image forming units each including a transfer unit that transfers an image from the image carrier to an image receiving member are arranged from upstream to downstream in the moving direction of the image receiving member. At least in the image forming unit disposed downstream from the image forming unit , the moving operation of the image carrier is continued and the operation of the simultaneous cleaning unit is stopped. It is characterized by the following.

According to a second aspect of the present invention, there is provided an image carrier movably supported, a latent image forming means for forming a latent image on the image carrier, and a method of attaching toner to the latent image to form a toner image. Developing, and an image forming unit including a developing simultaneous cleaning means for simultaneously cleaning the transfer residual toner after the transfer, and a transfer means for transferring the toner image from the image carrier to the image receiving member. in the image forming apparatus in which a plurality of arranged from the upstream side to the downstream side, the transfer movement
The image forming unit other than the image forming unit that is doing the work
At least, the operation of moving the image carrier is continued, and the operation of the simultaneous-developing cleaning unit is stopped.

[0027]

[0028]

In these image forming apparatuses, the image receiving member is a transfer material transporting means which moves while carrying a transfer material onto which the toner image on the image carrier is transferred, or a secondary transfer of the toner image to the transfer material. Prior to the transfer, the toner image on the image carrier may be an intermediate transfer member to which the toner image is primarily transferred.

[0030]

According to the above construction, for example, when an image is not formed in an image forming unit downstream of an image forming unit to which a toner image is currently transferred, in an image forming unit in which the image is not formed, a developing means is provided. Since it is stopped, no toner image is formed on the image carrier. Therefore, the toner image is not transferred to an image receiving member (for example, a transfer material or an intermediate transfer member) passing through the developing unit. Further, in this developing unit, since the image carrier is moving, the toner image transferred on the upstream side is not disturbed by rubbing or the like.

Such an operation can also be realized by selectively urging the image receiving member to the image carrier or selectively releasing the urging.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 shows a schematic configuration of an image forming apparatus according to the present invention. The same reference numerals are given to the members having the same configuration and operation as those of the image forming apparatus shown in FIG. 5 described above, and the description thereof will not be repeated.

The image forming apparatus shown in FIG. 1 is a four-drum full-color printer. In this embodiment, a cleaner-less device that eliminates a cleaner and performs simultaneous development and cleaning by a developing device is mounted. As image forming units, magenta, cyan, yellow, and black image forming units 10M, 10C, and 10Y are used. , 10Bk
Having. When the image forming unit of each image forming unit is described using the image forming unit M as an example, a photosensitive drum 10M as an image carrier and image forming means disposed around the photosensitive drum 10M, that is, a charging roller 12M, a laser exposure device 14M, A developing unit 16M and a pre-exposure lamp 13M are provided. Further, in this embodiment, a transfer material carrier (image receiving member) located at the transfer unit
, A transfer belt 30 is used. The transfer material 18 fed by the feed roller 20 is transferred to a transfer belt 30.
On each of the image forming units M, C, Y,
The transfer rollers 24M, 24
The toner images of the respective colors are transferred by C, 24Y, and 24Bk. Further, the transfer material 18 after the transfer process is separated from the transfer belt 30 and the toner image is fixed on the surface by the fixing device 38.

In the following description, for example, when there is no need to particularly distinguish the photosensitive drums 10M, 10C, 10Y, and 10Bk, they are simply referred to as "photosensitive drums 10".
The same applies to other members.

In the above configuration, according to the present invention, when in the single color mode, the two-color mode or the three-color mode, that is, when all four colors of magenta, cyan, yellow, and black are not used, Image forming means in the image forming unit, that is, photosensitive drum 10, charging roller 1
2, laser exposure device 14, developing device 16, transfer roller 2
4. Among the pre-exposure lamps 13, only the operation of the developing device 16 is stopped, and the other process devices are normally operated as in the full color mode.

The term "stopping the operation of the developing device 16" as used herein means that a bias for generating a developing electric field is not applied, or a bias that does not cause the developing is applied, or the photosensitive drum 10 and the developing device 16 are deactivated so that the developing cannot be performed. This means that the toner is not developed on the photosensitive drum 10 by, for example, separating the toner from the photosensitive drum 10, and the means may be a method suitable for the developing device and the developing method to be used.

At this time, the transfer roller 24 is an electric field applying means configured to apply an electric field having a polarity opposite to the charging polarity of the toner particles. In this embodiment, a roller charger as shown in FIG. 1 is used. However, other charging devices may be used as long as the above requirements can be satisfied.

Next, the operation of the image forming apparatus having the above configuration will be described with reference to the magenta single color mode as an example.

In the image forming apparatus, the magenta single-color mode is selected, so in the image forming units of the image forming units C, Y, and Bk for cyan, yellow, and black, the process devices other than the developing units 16C, 16Y, and 16Bk The operation is performed in the same manner as in the normal full-color mode. In the magenta image forming unit M, all the image forming units are operated as usual.

Transfer material 18 fed from paper feed roller 20
First passes through a magenta image forming unit M, at which time a magenta toner image is formed on the surface by a normal image forming process. Thereafter, the sheet passes through the gap between the photosensitive drum 10C of the cyan image forming unit C and the transfer belt 30. At this time, the photosensitive drum 10C, the charging roller 12C, the laser exposure device 14
C, the transfer roller 24C, and the pre-exposure lamp 13C are operating, but the developing device 16C is stopped.
Although a latent image may be formed on 0C, the latent image is not developed. Therefore, the cyan toner image is not transferred onto the passing transfer material 18.

Also, when the transfer material 18 carrying the magenta toner image passes through the gap between the photosensitive drum 10C of the cyan image forming unit C and the transfer belt 30, the surface of the photosensitive drum 10C contacts the transfer belt 30. Since the magenta toner image on the transfer material 18 is rubbed by the photosensitive drum 10C, the image is not damaged, and the transfer roller 24C generates an electric field having a polarity opposite to that of the toner. Since the transfer material 18 is applied to the transfer material 18, the suction force between the transfer material 18 and the toner is strongly maintained.
The magenta toner on 8 does not transfer back to the photosensitive drum 10C. Further, in this gap, the transfer material 18 and the transfer belt 30 generate an attraction force due to the action of the transfer electric field, so that the transfer material 18 and the transfer belt 30 adhere to each other, so that the transfer material 18 does not jam.

Hereinafter, when the transfer material 18 passes through the yellow and black image forming units Y and Bk, similarly to when the cyan material passes through the image forming unit C, the magenta toner image formed on the transfer material 18 is obtained. Does not impair. The transfer material 18 that has completed the transfer process for the four colors is separated from the transfer belt 30 and the toner image is fixed on the surface of the fixing device 38.

In the two-color mode and the three-color mode, an image of good quality can be obtained without disturbing the image on the transfer material as in the case of the single-color mode.

FIGS. 2 and 3 show the operating state of each process device. FIG. 2 shows a normal operation state of each process device at the time of full-color image formation, and an operation state of each process device of the image forming unit of a desired color in the single-color mode. FIG. The operation state of each process device in the image forming unit other than the desired one at the time is shown. <Embodiment 2> In Embodiment 1 described above, the transfer belt 3
The toner image is directly transferred by the image forming units M, C, Y, and Bk onto the transfer material 18 carried on the image forming unit 0. In this embodiment, an intermediate transfer member (image receiving member) may be used instead. As shown in FIG. 4, the intermediate transfer belt (intermediate transfer body) 26 is passed between each image forming unit and the transfer roller 24, and the toner formed by each image forming unit on the intermediate transfer belt is sequentially formed. Transfer the image. Then, the transfer material 18
To transfer the toner image collectively. <Embodiment 3> In recent years, digitalization of copying machines and printers has been advanced along with full colorization and systemization. For example,
2. Description of the Related Art Devices such as a laser beam printer that scans a laser beam, forms a latent image on a photosensitive drum by turning on and off the laser beam, and records a desired image have been widely known. A typical use is for binary recording of characters, figures, and the like. On the other hand, since the recording of characters, figures, and the like does not require halftone, the printer structure can be simplified.

By the way, there is a printer which can form a half tone even in such a binary recording system. As such a printer, a printer employing a dither method, a density pattern or the like is well known. However, as is well known, high resolution cannot be obtained with a printer employing the dither method and the density pattern method.

Therefore, in recent years, a method of forming a halftone pixel in each pixel without reducing the recording density has been proposed. In this method, halftone is formed by pulse width modulation (PWM) of a laser beam with an image signal. According to this method, a high-resolution and high-gradation image can be formed.

In this embodiment, for the purpose of downsizing the apparatus and eliminating waste toner, a cleaner-less apparatus for eliminating the cleaner and performing simultaneous development and cleaning by the developing apparatus is mounted. The simultaneous cleaning with development is a method of recovering the transfer residual toner slightly remaining on the photosensitive drum after the transfer by using a fog removing bias at the time of development after the next step. According to this method, since the transfer residual toner is collected and used in the subsequent steps, waste toner can be eliminated. In addition, there is a great advantage in terms of space, and the size can be significantly reduced.

Embodiment 3 will be described with reference to FIGS.

First, as shown in FIG. 7, an original 2 is set on an original table 3 with the surface to be copied facing downward. Next, copying is started by pressing the copy button. The document 2 is illuminated by the document illumination lamp 4 and the reflected light is input to the CCD sensor 7.

The CCD sensor 7 comprises a light receiving section, a transfer section, and an output section. The light signal is converted to an electric signal in the CCD light receiving unit, and is sequentially transferred to the output unit in synchronization with the clock pulse in the transfer unit. The output unit converts the charge signal into a voltage signal, and amplifies and lowers the impedance to output. . The unlog signal thus obtained is subjected to well-known image processing, converted into a digital signal, and sent to a printer unit.

The printer section receives the image signal and forms an electrostatic latent image as follows.

The photosensitive drum 10M is driven to rotate in a direction indicated by an arrow at a predetermined peripheral speed about a central support shaft, and receives a uniform negative polarity charging process by a charging roller 12M during the rotation process.
The light of the semiconductor laser element 102 (see FIG. 8) which emits ON and OFF light corresponding to the image signal on the uniformly charged surface is scanned by a rotating polygon mirror 104 rotating at high speed, so that the surface of the photosensitive drum 10 is An electrostatic latent image corresponding to a document image is sequentially formed.

FIG. 2 shows a schematic configuration of a laser scanning section 100 for scanning a laser beam in the above-mentioned apparatus. When a laser beam is scanned by the laser scanning section 100, first, the semiconductor laser element 102 is caused to blink at a predetermined timing by the light emission signal generator 101 based on the input image signal.

The laser beam emitted from the semiconductor laser element 102 is converted into a substantially parallel light beam by a collimator lens system 103, and further scanned in a direction of an arrow K by a rotating polygon mirror 104 rotating in a direction of an arrow c. The lens groups 105a, 105b, and 105c form a spot image on the surface to be scanned 106 such as a photosensitive drum.

By the scanning of the laser beam, an exposure distribution for one scan of the image is formed on the surface to be scanned 106, and the surface to be scanned 106 is scrolled by a predetermined amount perpendicular to the scanning direction for each scan. By doing so, an exposure distribution according to the image signal is obtained on the scanned surface 106. The electrostatic latent image formed as described above is developed by a developing device described below.

FIG. 9 is a schematic view of the developing device 16 for two-component magnetic brush development used in this embodiment. In this figure, the developing device 16M containing magenta toner will be described, but the other developing devices 16C, 16Y and 16Bk have the same configuration and operate similarly. In the figure, 161 is a developing sleeve,
162 is a magnet roller fixedly arranged in the developing sleeve, 163 and 164 are stirring screws, 165 is a regulating blade arranged to form a thin layer of developer on the surface of the developing sleeve, and 166 is a developing container.

Here, a description will be given of a developing step of visualizing the electrostatic latent image by the two-component magnetic brush method using the developing device 16 and a circulating system of the developer. First, the developer pumped at the N2 pole with the rotation of the developing sleeve 161 is:
In the process of being transported from the S2 pole to the N1 pole, the regulating blade 165 disposed perpendicular to the developing sleeve 161
And a thin layer is formed on the developing sleeve 161.

Here, when the developer formed in a thin layer is conveyed to the developing main pole S1, a spike is formed by the magnetic force. The electrostatic latent image is developed by the spike-shaped developer, and then the developer on the developing sleeve 161 is returned into the developing container 166 by the repulsive magnetic field of the N3 pole and the N2 pole.

A DC and AC developing bias is applied to the developing sleeve 161 from a power supply, and the photosensitive drum 10M
A toner image is formed thereon. The toner image thus formed by the developing unit 16M is transferred by a transfer device as described below, while the surface of the photosensitive drum 10 after the toner transfer is repeatedly subjected to image formation with the transfer residual toner remaining. You.

The transferred toner is charged to the charging roller 1
The charge is adjusted to a negative regular charge polarity by the action of 2M, transported to the development area, and collected in the development container 166 by the action of the fogging bias potential of the development bias.

The transfer device includes a drive roller 32, a separation roller 31, a transfer belt 30 stretched by transfer rollers 24M, 24C, 24Y, and 24Bk, and a belt cleaner 51 for cleaning the transfer belt 30, and a belt cleaner 51 for cleaning the transfer belt 30. Suction roller 5 for adsorbing transfer material 18 to transfer belt 30
a and an electrode roller 5b which is a counter electrode thereof.

The transfer roller 24M disposed opposite to each photosensitive drum 10M (in this description, a representative image forming unit M of magenta) is provided with a side plate 40 as shown in FIG. Both ends in a locking groove 41 provided in the up-down direction are supported, and are urged upward by magenta urging means (image receiving member urging means) 37, respectively.

Thus, the transfer belt 30 is in contact with the opposing surface of the photosensitive drum 10M. The magenta urging means 37 is a compression spring 37 mounted between the base 370 formed below the locking groove 41 and the base 370 and the end of the magenta transfer roller 35M to urge the transfer roller 24M upward.
And 2.

The transfer device 3 includes a magenta urging means 3
7 has a magenta releasing means 39 for releasing the contact between the transfer belt 30 and the magenta photosensitive drum 10M. As shown in FIGS. 11 and 13, the magenta releasing means 39 includes a pair of swing levers 393 having one ends connected by a connecting lever 391, and a connecting bar 3 via a hook 395.
And a magenta solenoid 397 that is locked to the base 91 and swings the swing lever 393. Swing lever 39
Reference numeral 3 designates a substantially central portion pivotally supported by the side plate 40 by a pin 399, and the lower end of the other end is disposed so as to face the upper side of the magenta transfer roller 24M.

As shown in FIG. 10, the magenta solenoid 397 is turned on / off under the control of the CPU by operating a color mode selection key on an operation panel (not shown) or by a signal based on data read by a reader. Occasionally, by swinging the swing lever 393, the other end of the swing lever 393 pushes down the magenta transfer roller 24M downward against the urging force of the compression spring 372 (see FIGS. 12 and 14). ).

The magenta operation stopping means 5 for stopping the operation of the magenta photosensitive drum 10M whose contact has been released.
0 is provided in combination with the magenta canceling means 39.

That is, as shown in FIG. 13, the magenta operation stopping means 50 of this embodiment is provided with one swing lever 39.
3 has a release lever 500 which is provided integrally with the swing lever 393 and extends from the other end of the magenta release means 39.
Swing lever 393, magenta solenoid 397, and the like.

The release lever 500 is disposed such that its tip is in contact with a swing bearing 18 that bears a pair of idle gears 17a and 17b that mesh with each other. The swing bearing 18 is provided so as to be able to swing around the shaft of one idle gear 17b, and a tension spring 19 attached to the shaft of the other idle gear 17a.
And the other idle gear 17a is meshed with the drive gear of the magenta photosensitive drum 10M. Thus, when the magenta solenoid 397 is on, the engagement between the drive gear and the idle gear 17a is released (see FIG. 14).

Hereinafter, the image forming units C, Y, and Bk for cyan, yellow, and black are similarly configured.

The color image forming apparatus of this embodiment is configured as described above.

In order to form a single-color image of only one color by this color image forming apparatus, first, a color mode selection key on the operation panel is operated, or an image is formed by a signal based on original reading data by a reader. An image forming unit of a desired color used for forming is selected.

When the magenta image forming unit M is selected, for example, the solenoids 397 of the cyan, yellow, and black image forming units are turned on, and the swing lever 393 swings about the pin 399. I do.
As a result, the other end of the swing lever 393 moves downward against the urging force of the compression spring 372, and pushes down the transfer rollers 24C, 24Y, and 24Bk of cyan, yellow, and black downward to transfer the transfer belt 30 and the cyan, The contact with the yellow and black photosensitive drums 10C, 10Y, and 10Bk is released.

At the same time, as shown in FIG. 14, the release lever 500 provided integrally with the swing lever 393 moves downward to push the swing bearing 18 downward. As a result, the oscillating bearing 18 is connected to one drive gear and the idle gear 17.
Release the engagement with a.

Therefore, the photosensitive drums 10C, 10Y, and 10Bk of cyan, yellow, and black receive no drive transmission from the drive motor and are in a non-contact state with the transfer belt 30. When the cyan, yellow, and black photosensitive drums 10C, 10Y, and 10Bk do not operate, the CPU is controlled so that the entire cyan, yellow, and black image forming units do not operate.

When the start switch is turned on in this state, first, an electrostatic latent image corresponding to the original image is formed on the surface of the magenta image forming unit M, and this electrostatic latent image is visualized by the developing unit 16M. Thus, a toner image is formed.

On the other hand, the transfer belt 30 rotates at the same speed as the rotation speed of the magenta photosensitive drum 10M. Then, the transfer material 18 is sent out by the registration roller 20 in synchronization with the electrostatic latent image formed on the surface of the magenta photosensitive drum 10M, and is suction-transported onto the transfer belt 30 by the action of the suction roller 5a and the counter electrode roller 5b. Is done.

The transfer material 18 is used for the magenta photosensitive drum 1
The toner image on the magenta photosensitive drum 10 is transferred by the transfer electric field applied by the magenta transfer roller 24M while being sandwiched between the transfer belt 30 and the transfer belt 30 pushed up by the magenta transfer roller 24M.

Thereafter, the transfer material 18 on the transfer belt 30
Is separated from the magenta photosensitive drum 24M, is conveyed without contact with the cyan, yellow, and black photosensitive drums as the transfer belt 30 moves, and is separated from the transfer belt 30 by the separation roller 31 to fix the fixing device. 38
Then, the toner on the transfer material 18 is fixed by the heat and pressure action of the fixing device 38 to output an image.

On the other hand, on the surface of the magenta photosensitive drum 10M after the transfer of the toner image, the toner is repeatedly used for image formation with the transfer residual toner remaining. The transfer residual toner is collected in the developing device 166 by the fogging potential of the developing bias at the time of image formation development after the next step.

When the cyan image forming unit Y is selected by the selection key, or according to a signal based on image reading by the reader, the solenoids of the magenta, yellow, and black image forming units M, Y, and Bk are used. Turns on, and the solenoid of the cyan image forming unit C turns off. This allows magenta, yellow,
The black photosensitive drums 10M, 10Y, and 10Bk receive no drive transmission from the drive motor, and the transfer belt 30
, And the image is formed only by the cyan image forming unit C.

When all the image forming units are selected by the selection key, or when the signal based on the image reading by the reader turns on the solenoids of all the image forming units, all the image forming units are turned off. The toner images formed by the units are sequentially multiplex-transferred onto the transfer material 18 to form a full-color image.

As described above, in the full-color image forming apparatus of this embodiment, when an image is formed without using all the image forming units such as in the case of a single black color, the unused photosensitive drum and the transfer belt 30 on the transfer belt 30 are not used. Since the transfer material is not in contact, the toner already transferred on the transfer material to the unused photosensitive drum does not reversely transfer, so that color mixing of the toner due to the simultaneous recovery of development can be prevented.

Further, since the unused image forming units are controlled so as not to operate, useless operations can be omitted, and as a result, running costs can be reduced. Furthermore, the toner image on the transfer material is not disturbed,
The occurrence of jam can be prevented.

In this embodiment, a plurality of image forming units are juxtaposed, and the transfer belt 30 is arranged so as to penetrate the image forming units. For example, instead of the transfer belt 30, An image may be formed using a transfer drum, an intermediate transfer member, or the like, or a one-component development method may be used in the simultaneous recovery of development without being limited to the two-component magnetic brush development method.

The latent image forming method and the transfer method are not restricted by the description of this embodiment.
As in the present embodiment, the contact and release mechanism of 0 and the photosensitive drum is not limited to the method using the up and down transfer electric field applying means.
The contact and release means may be provided separately, and the control method of contact and release is not limited to this.

[0086]

As described above, according to the present invention,
The image carrier of the downstream developing unit, which is not used for image formation, prevents the image carrier transferred onto the transfer material on the upstream side from being rubbed and disturbed. Also, the jam of the transfer material is reduced.

Further, it is possible to prevent the toner transferred on the transfer material on the upstream side from being re-transferred to the image carrier on the downstream side. It is possible to prevent color mixture of the toner in the developing device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

FIG. 2 is a timing chart illustrating an operation state of the image forming apparatus according to the first exemplary embodiment.

FIG. 3 is a timing chart illustrating an operation state of the image forming apparatus according to the first exemplary embodiment.

FIG. 4 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 5 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 6 is a view for explaining the relationship between the toner shape and the mirroring power and Van der Waals force.

FIG. 7 is a schematic configuration diagram of an image forming apparatus according to a third embodiment.

FIG. 8 is a configuration diagram of a laser scanning unit according to a third embodiment.

FIG. 9 is a configuration diagram of a developing device according to a third embodiment.

FIG. 10 is a block diagram of control mainly using a CPU.

FIG. 11 is a side view showing the urging means and the releasing means.

FIG. 12 is a side view showing a state in which the release means is operated.

FIG. 13 is a side view showing the operation stopping means.

FIG. 14 is a side view showing a state in which the operation stopping means is operated.

[Explanation of symbols]

10, 10M, 10C, 10Y, 10Bk image carrier (photosensitive drum) 12, 12M, 12C, 12Y, 12Bk charging device (charging roller) 16, 16M, 16C, 16Y, 16Bk developing device (developing device) 24M, 24C 24Y, 24Bk transfer means (transfer roller) 26 image receiving member (intermediate transfer body) 30 image receiving member (transfer material carrier, transfer belt) 37 image receiving member urging means (transfer belt urging means) 39 image receiving member releasing means (transfer belt) Release means) M, C, Y, Bk image forming unit

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/01-15/01 117

Claims (4)

(57) [Claims] And 1. A movably supported image bearing member, a latent image forming means for forming a latent image on the image bearing member, by adhering toner to the latent image is developed as a toner image, after transfer An image forming unit including a developing simultaneous cleaning unit that simultaneously cleans transfer residual toner and a transfer unit that transfers a toner image from the image bearing member to an image receiving member is provided from an upstream side to a downstream side in the moving direction of the image receiving member. In the image forming apparatus provided with a plurality of image forming units, at least in the image forming unit disposed downstream of the image forming unit performing the transfer operation , at least the moving operation of the image carrier is continued.
An image forming apparatus, wherein the operation of the simultaneous cleaning unit is stopped. 2. An image carrier movably supported, a latent image forming means for forming a latent image on the image carrier, a toner attached to the latent image and developed as a toner image, and An image forming unit including a developing simultaneous cleaning unit that simultaneously cleans transfer residual toner and a transfer unit that transfers a toner image from the image bearing member to an image receiving member is provided from an upstream side to a downstream side in the moving direction of the image receiving member. In a plurality of image forming apparatuses, image forming units other than the image forming unit performing the transfer operation
In the unit , at least the moving operation of the image carrier is continued and the developing simultaneous cleaning means is provided.
Stopping the operation of the image forming apparatus. Wherein said image receiving member is a transfer material conveying means for the toner image on the image bearing member moves while carrying the transfer material to be transferred, according to claim 1 or 2, characterized in that Image forming device. Wherein said image receiving member is an intermediate transfer member the toner image on said image bearing member prior to the secondary transfer of the toner image is primarily transferred onto the transfer material, according to claim 1 or, characterized in that 3. The image forming apparatus according to 2.