JPH09197917A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrifying device from being soiled by untransferred toner reaching it when such as a jamming occurs, in an image forming device provided with a developing device capable of serving as a cleaning device for removing the transfer residual toner on a photosensitive drum. SOLUTION: When the photosensitive drum 1 is stopped by such as a jamming and the untransferred toner remains in-between the developing device 3 and a transferring roller 4 (a), the untransferred toner on the photosensitive drum 1 is recovered on a developing sleeve 31, by making the photosensitive drum 1 reversely rotated in the direction of the arrow R12, while impressing the recovering bias on a developing sleeve 31 (b). At this time, carrier in the developer is stuck on the photosensitive drum 1 surface, however this can be recovered, by making the photosensitive drum 1 rotated forward in the direction of the arrow R11, impressing the developing bias on the developing sleeve 31 (c). Moreover, the toner on the developing sleeve 31 is unnecessarily shifted onto the photosensitive drum 1 by the developing bias, however the shift of the toner is minimized, by stopping the developing sleeve 31 from rotating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer which transfers a toner image formed on an image carrier onto a transfer material.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional image forming apparatus (copier).
The schematic configuration of is shown. The configuration and operation will be briefly described with reference to FIG.

First, the document G is placed on the document table 10 with the surface (image surface) to be copied facing downward. Next, copying is started by pressing the copy button.
A unit 11 in which a document irradiation lamp, a short focus lens array, a CCD sensor and the like are integrally incorporated is configured. This unit 11 moves (scans) in the direction of the arrow in the figure while illuminating the image surface of the document G from below by the document illuminating lamp, so that the reflected light of the illuminating scanning light from the document G has a short focal point. Imaged by lens array C
It is incident on the CD sensor. The CCD sensor is composed of a light receiving section, a transfer section, an output section and the like. A light signal of the CCD sensor converts an optical signal into an electric signal. The electrical signal is sequentially transferred to the output unit in synchronization with the clock pulse at the transfer unit, and the charge signal is converted into a voltage signal at the output unit, amplified, reduced in impedance, and output. The analog signal thus obtained is subjected to known image processing, converted into a digital signal (image signal), and sent to the printer section.

The printer section receives the above-mentioned image signal and forms an electrostatic latent image as follows. The photosensitive drum 1 has an arrow R1 at a predetermined process speed (peripheral speed).
It is driven to rotate in the direction, and its surface is uniformly charged with positive polarity or negative polarity by the charger 2 during the rotation process. An electrostatic latent image is formed by the image exposing means 12 on the surface of the photosensitive drum 1 after being charged. That is, the O
By scanning the light of the solid-state laser element that emits N / OFF with a rotating polygon mirror that rotates at a high speed, an electrostatic latent image corresponding to the image surface of the document G is sequentially formed on the surface of the photosensitive drum 1.

The developing process will be described below. Generally, there are four developing methods depending on whether the developer is one component or two components and whether the photosensitive drum and the developing sleeve are in contact or non-contact, that is, one-component contact development, one-component non-contact development, and two. It is roughly classified into component contact development and two-component non-contact development.

In FIG. 3, as one example of the two-component contact development which easily realizes high image quality and high stability among the above-mentioned four,
1 shows a schematic configuration of a developing device 3 for developing a component magnetic brush.

In the figure, 31 is a developing sleeve, 32 is a magnet roller fixedly arranged in the developing sleeve 31, and 3 is a roller.
Reference numerals 3 and 34 are stirring screws, 35 is a regulating blade for forming a thin layer of the developer on the surface of the developing sleeve 31, and 36 is a developing container for containing the developer.

Next, the developing process for developing the electrostatic latent image by the developing device 3 by the two-component magnetic brush method and the circulating system of the developer will be described. First, the developer carried on the developing sleeve 31 surface is pumped up by the magnetic pole N ₃ with the rotation of the arrow R31 direction of the developing sleeve 31 is in the process of being conveyed poles N _2, S _2, N ₁ and the developing sleeve Restriction blade 35 arranged perpendicular to 31
The layer thickness is regulated by, and a thin layer is formed on the developing sleeve 31. Here, the thin-layered developer is the main developing electrode S
_When it is conveyed to ₁ , the spikes are formed by the magnetic force. The photosensitive drum 1 is formed by the developer formed in the spike shape.
Develop the electrostatic latent image on top. After that, the developer on the developing sleeve 31 falls off from the surface of the developing sleeve 31 by the repulsive magnetic field of the magnetic poles N ₃ and N ₂ , and is collected in the developing container 36.

A DC bias and an AC bias are applied to the developing sleeve 31 by a power source (not shown). As the AC component at this time, for example, the peak-to-peak voltage V _PP =
2000V and frequency f = 2000Hz are applied. Generally, in the two-component developing method, when an AC bias is applied, the developing efficiency increases and the image becomes high quality, but conversely, fog tends to occur.

The toner image thus formed on the photosensitive drum 1 is transferred and separated by a transfer charger 4 as shown in FIG.
Is electrostatically transferred to a transfer material P such as paper, and the transfer material P after transfer is separated from the photosensitive drum 1. The transfer material P after the transfer of the toner image is conveyed to the fixing device 6, where it is heated and pressed to fix the toner image on the surface.

On the other hand, the photosensitive drum 1 after the toner image transfer is
Adhesive contaminants such as transfer residual toner on the surface are removed as waste toner by the cleaner 5, and are provided for the next image formation.

It is possible to use a fur brush, a magnetic brush, or a charging roller instead of corona charging as the above-mentioned charging device 2 and a transfer roller as the transfer separation charging device 4. The basic image forming process is the same as that described above even when is used.

In recent years, there has been a demand for downsizing of image forming apparatuses, but there has been a limit only to downsizing process devices for charging, exposing, developing, transferring and cleaning. Further, the cleaner 5 collects the above-mentioned transfer residual toner waste toner. After that, the waste toner is discarded, but it is preferable that this waste toner is not generated from the viewpoint of environmental protection.

In order to further promote downsizing and to eliminate waste toner, a so-called cleanerless image forming apparatus in which the above-mentioned cleaner 5 is positively omitted and cleaning is performed at the same time by a developing device has appeared. Simultaneous development cleaning is a method in which toner that slightly remains on the photosensitive drum after transfer is collected by a fog removal bias during development in the subsequent steps. According to this method, the transfer residual toner is collected and used again after the next step, so that the waste toner is eliminated and maintenance is not required. Further, since a cleaner is not required, there is a great advantage in terms of space, and the image forming apparatus can be downsized as a whole.

In order to improve the cleaning efficiency in the simultaneous developing cleaning system, it is very effective to use a toner having an excellent releasability such as a toner produced by a polymerization method.

[0016]

In the above-described cleanerless image forming apparatus, as long as normal copying (image forming apparatus) is performed, the amount of transfer residual toner is determined by the chargeability in the next charging step. It does not hinder and does not contaminate the charging device. However, if a jam such as a paper jam occurs during the copying process and the copying process is interrupted, toner that has been developed on the photosensitive drum but has not entered the transfer process remains on the photosensitive drum. It may end up. The amount of residual toner at this time is much larger than the amount of toner remaining on the photosensitive drum after the normal transfer process. If a large amount of residual toner on the photosensitive drum passes through the charging section after the jam processing and attempts to restore it in this state, it contaminates the charging device, reducing the performance and durability of the charging device and causing image deterioration. Becomes Such defects are caused by a contact charging type charger, such as a charging roller, a fur brush,
This is remarkable when a magnetic brush or the like is used.

Therefore, it is an object of the present invention to provide an image forming apparatus of a cleanerless type, in which the above-mentioned contamination of the charger is prevented.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and includes a rotatable image carrier and a periphery of the image carrier along the forward rotation direction of the image carrier. Charging means for uniformly charging the surface of the image bearing body, image exposing means for exposing the charged surface of the image bearing body to form an electrostatic latent image, and a developer for the electrostatic latent image. And a transfer means for transferring the toner image onto a transfer material, and the developing means also functions as a cleaning means and remains on the surface of the image carrier after the toner image is transferred onto the transfer material. In the image forming apparatus for removing the transfer residual toner, a drive unit for selectively rotating the image carrier in the forward direction or the reverse direction, and a control unit for controlling the rotation direction of the image carrier via the drive unit. And the control means controls the undeveloped state after the development and before the transfer. When the image carrier is stopped with the transferred toner image remaining on the surface of the image carrier, a return operation including a reverse rotation operation of the image carrier is performed by the driving unit, and the return operation is performed during the return operation. A voltage is applied to the developing means, and the untransferred toner on the surface of the image carrier is collected by the developing means.

The developer contains toner and carrier 2
With the component developer, when the carrier is attached to the surface of the image carrier during the returning operation, the control unit applies a voltage to the developing unit during the returning operation to apply a voltage to the surface of the image carrier. The carrier can be recovered by the developing means.

The developing means has a developer carrier that carries and conveys the developer on the surface thereof to adhere to the electrostatic latent image on the surface of the image carrier, and during the returning operation, the developer carrier. While applying a recovery bias to the image carrier, the image carrier is rotated in the reverse direction to collect untransferred toner on the surface of the image carrier by the developing means, and then the developer carrier is stopped to apply a developing bias. The image carrier may be rotated in the forward direction and the carrier on the surface of the image carrier may be collected by the developing means.

It is also possible to have a discharging means for discharging the surface of the image carrier during the restoration operation.

The discharging means may be discharging exposing means arranged downstream of the developer carrier and upstream of the transfer means with reference to the forward rotation direction of the image carrier.

The image exposing means may also serve as the charge removing means, and the charging means may also serve as the charge removing means.

During the returning operation, while the image carrier is being rotated in reverse, the surface of the image carrier is exposed by the discharging exposure means, and a recovery bias is applied to the developer carrier to carry the image carrier. The untransferred toner on the body surface can be collected by the developing means.

During the returning operation, while the image carrier is rotated in the forward direction, the transfer area carrying the transfer toner on the surface of the image carrier is uniformly charged to a predetermined potential by the charging means, and then the developer is charged. The developing bias is applied to the carrier, the image carrier is rotated in the reverse direction, the untransferred area is neutralized by the image exposing unit, the image carrier is rotated in the forward direction, and the developing bias is applied. You may make it collect | recover the untransferred toner of the untransferred area | region on the said image carrier with an agent carrier.

During the returning operation, the image carrier is rotated in the forward direction, the transfer area is uniformly charged to a predetermined potential by the charging means, and then the surface of the image carrier is neutralized by the image exposing means. The image carrier is rotated in the reverse direction, a recovery bias is applied to the developer carrier to recover the untransferred toner in the untransferred region on the image carrier to the developing means, and then to the developer carrier. It is also possible to rotate the image carrier in the forward direction while applying a bias.

[Operation] Based on the above configuration, when the unfixed toner remains on the transfer material due to a paper jam or the like, the unfixed toner reaches the charging unit by rotating the image carrier in the reverse direction. In addition, the unfixed toner on the image carrier can be recovered by the developing device by applying the recovery bias to the developing device (developer carrying member).

[0028]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> In Embodiment 1, in a cleanerless image forming apparatus, during a return operation (process) after a jam process or the like, a jam is generated while rotating the photosensitive drum in a direction opposite to a normal copying operation. It is characterized in that the untransferred toner on the photosensitive drum which is generated at times is collected by the developing device.

In the following description, "untransferred toner" means that the surface of the photosensitive drum is not transferred onto the transfer material due to a jam or the like after the development operation is normally completed and before the transfer operation is completed. The toner remaining on the transfer material is distinguished from the so-called transfer residual toner remaining on the photosensitive drum after the normal transfer operation on the transfer material is completed. Generally, the toner amount of untransferred toner is much larger than the toner amount of transfer residual toner.

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of the image forming apparatus according to the present embodiment. The configuration and operation of the image forming apparatus will be described with reference to the figure.

The image forming apparatus shown in FIG. 1 includes a drum type photosensitive member (hereinafter referred to as "photosensitive drum") 1 as an image bearing member. The photosensitive drum 1 includes a base formed in a cylindrical shape by a conductive member such as aluminum, and an O covering the surface thereof.
It has a photosensitive layer such as a PC and is rotatably supported by an image forming apparatus main body (hereinafter simply referred to as “apparatus main body”) M. The photosensitive drum 1 is driven by the drive unit 51 at the time of image formation (hereinafter appropriately referred to as “during copying”) in the direction of arrow R11 (hereinafter, rotation in the direction of arrow R11 is referred to as “forward rotation”, and rotation in the opposite direction). It is rotationally driven at a predetermined process speed (peripheral speed) in "reverse rotation". The photosensitive drum 1 may be reversed by the driving means 51 as described later. That is, the rotation direction and the rotation speed of the photosensitive drum 1 are appropriately controlled by the control means 52 connected to the driving means 51.

The surface of the photosensitive drum 1 which has been normally rotated during copying is -70 by a magnetic brush charger (charging means).
It is charged to 0V. The magnetic brush charger 2 will be described in detail later.

The surface of the photosensitive drum 1 after being charged is irradiated with a laser beam corresponding to an image signal from the image exposing means 12, and the potential of the irradiated portion is removed to form an electrostatic latent image. The part of the surface of the photosensitive drum 1 from which the charge has been removed is
Negatively charged toner is attached by the developing device (developing means) 3 and reverse development is performed as a toner image.

The toner image thus formed on the surface of the photosensitive drum 1 is transferred onto the surface of the transfer material P by the transfer roller (transfer means) 4. Transfer material P after toner image transfer
Is conveyed to the fixing device 6, where it is heated and pressed to fix the toner image, and then discharged to the outside of the apparatus main body M.

On the other hand, in the present invention, since there is no cleaner, the photosensitive drum 1 after the transfer of the toner image is not transferred to the transfer material P, and the transfer residual toner remaining on the surface is carried from the charging step. The next image forming process starts.

By the way, when the residual toner after transfer passes through the charging step, the exposure step, and the developing step as it is and is carried to the next transfer step, the toner is transferred onto a portion of the transfer material P which does not correspond to the image of the original G. Although the image becomes dirty, in reality, in the developing process, since the fog removing electric field (electric field for returning the toner particles to the developing device 3 direction) is applied to the white background portion, it can be collected by the developing device 3. .

The schematic structure of the developing device 3 used in the present embodiment is similar to that of the conventional example as shown in FIG. 3, and has a rotatable developing sleeve 31 including a fixed magnet roller 32. . The developer in the developing container 36 is carried on the surface of the developing sleeve 31, coated with a thin layer on the surface of the developing sleeve 31 by the regulating blade 35, and conveyed to the developing section. At this time, the developing sleeve 31
Rotates in the direction of arrow R31 at a process speed (peripheral speed) of 150 mm / sec. The developer is a two-component developer, which has a negative charging property of 8 μm and a positive charging property of 50 μm.
The magnetic carrier of μm is mixed with the superposed toner concentration of 5%. The toner used in the present embodiment is a toner manufactured by a polymerization method, and has a spherical shape and very good fluidity as compared with a toner manufactured by a pulverization method generally used in this type of apparatus. The toner concentration is detected by an optical toner concentration sensor (not shown), and the toner in the toner hopper 37 is replenished via the supply roller 37a based on the detection result. Developer container 36
The developer inside is stirred by the stirring members 33 and 34 so that the toner and the carrier become uniform. Developing sleeve 31
Has a peak-to-peak voltage V _PP of 2 kV from a power source (not shown),
AC (alternating current) voltage having a frequency f of 2 kHz and V _dc = -5
A voltage (hereinafter referred to as "developing bias") in which a DC (direct current) voltage of 50 V is superimposed is applied. The developer coated in a thin layer on the developing sleeve 31 and conveyed to the developing section develops the electrostatic latent image on the photosensitive drum 1 by the electric field generated by the above-described developing bias.

In the case of OPC, for example, the photosensitive layer of the photosensitive drum 1 has a charge generation layer in which a diazo pigment is dispersed in a resin, and a charge transport layer in which a hydrazone is dispersed in a polycarbonate resin. Has a charge injection layer in which ultrafine SnO ₂ is dispersed in a photo-curable acrylic resin. During copying, the photosensitive drum 1 is rotationally driven in the direction of arrow R11 (see FIG. 1) at a process speed (peripheral speed) of 100 mm / sec.

The structure of the magnetic brush charger 2 is shown in FIG.
The magnetic brush charger 2 includes a rotatable charging sleeve 21 and
Magnet roller 22 fixed in charging sleeve 21
And a charging bias is applied to the charging sleeve 21 from a power source (not shown). The carrier 23 is carried on the surface of the charging sleeve 21 by the magnetic restraining force of the magnet roller 22, forms a magnetic brush, and contacts the surface of the photosensitive drum 1. The charging sleeve 21 rotates in the direction of arrow R21 at a peripheral speed of 200 mm / sec. In the nip portion (charging portion) where the surface of the photosensitive drum 1 and the surface of the charging sleeve 21 are closest to each other, the gap between them is 500 μm.
m, the magnetic flux density by the magnet on the developing sleeve 21 of the charging portion is 800 × 10 ⁻⁴ T. The average particle diameter of the carrier (magnetic particles) constituting the magnetic brush is 25μ.
m, resistance value 5 × 10 ⁶ Ω · cm, saturation magnetization 200 em
u / cm ² was used. The resistance value was measured by putting 2 g of the carrier in a metal cell (bottom area 228 mm ² ) to which a voltage can be applied, then applying 6.6 kg / cm ² and applying a voltage of 100 V.

The contact charging method such as magnetic brush charging generally produces less ozone than corona charging, and in particular, the magnetic brush is more sensitive to the photosensitive drum 1 than the elastic roller or the fur brush. It has the advantage that the contact is uniform and the shape does not change with time. Particularly when used in the cleanerless method as in the present embodiment, the transfer residual toner is dispersed to improve the recovery efficiency by the developing device 3, and the toner whose polarity is reversed by the discharge at the time of transfer is recharged. In addition, it also plays a role of preventing defective collection due to the reverse toner.

However, when a part of the toner that has entered the charging section is mixed into the carrier 23, the charging property may be deteriorated, and an increase in fog or image defects such as ghost may occur. Therefore, it is desirable that the transfer residual toner be made as small as possible. In this embodiment, a spherical toner produced by the suspension polymerization method is used, but this toner has a high transfer efficiency and is suitably used in such a cleanerless system. When this toner is used, the transfer residual toner amount is about 0.06 mg / cm ² even in the high density portion.
However, in the normal copying process, the toner that causes an image defect is not mixed into the carrier 23.

However, when the operation is interrupted due to a paper jam during the copying process, the photosensitive drum 1 has about 0.8 mg / cm ² of untransferred toner, that is, the photosensitive drum 1 in the developing section.
Toner that adheres to the surface and forms a toner image but does not reach the transfer portion may remain. Conventionally, when the recovery operation is started after handling a paper jam or the like, the untransferred toner remaining on the photosensitive drum 1 enters the charging section,
A large amount of toner may mix into the carrier 23 of the charger 2 and cause a defective image.

5 (a), 5 (b) and 5 (c) show the charging device 2, the developing device 3 and the transfer roller 4 in each step of this embodiment.
6A and 6B are schematic diagrams showing the operation of each device and the latent image potential of the untransferred area on the photosensitive drum 1 at this time.

The returning step in this embodiment will be described with reference to FIG. As shown in FIG. 6A, after the jam processing, the transfer residual toner is formed on the photosensitive drum 1 on the downstream side of the transfer roller 4 (referred to the rotating direction of the photosensitive drum 1 at the time of copying). Untransferred toner adheres to the upstream side. In the present embodiment, as shown in FIG. 7B, the photosensitive drum 1 is first rotated in the direction of arrow R12 in the reverse direction during the returning operation. The peripheral speed of the photosensitive drum 1 during reverse rotation is 10
It is 0 mm / sec. At this time, the developing sleeve 31 is rotating in the direction of arrow R31, and an AC voltage having a peak-to-peak voltage V _PP of 2 kV and a frequency of 2 kHz and a DC voltage of V _dc of +50 V are superposed by a power source (not shown). Voltage (hereinafter referred to as “recovery bias”) is applied.

The area where the untransferred toner remains, that is, the area of the surface of the photosensitive drum 1 located between the developing portion (developing device 3) and the transfer portion (transfer roller 4) when the operation is stopped is entirely developed. The reverse rotation of the photosensitive drum 1 is stopped at the point when the photosensitive drum 1 passes through the section. The electric potential of the image portion on the photosensitive drum 1 is eliminated to a maximum of about −30 to −50 V. During this operation, an electric field generated toward the photosensitive drum 1 is present between the developing sleeve 31 and the photosensitive drum 1. The negatively charged toner is attracted to the developing sleeve 31 side, and the developing device 3
Collected inside. On the other hand, in the non-image portion on the surface of the photosensitive drum 1, since a large electric field is generated between the photosensitive drum 1 and the developing sleeve 31, a part of the positively charging magnetic carrier is the developing sleeve 31.
The magnetic force generated by the magnetic roller 32 included in the magnetic roller 32 overcomes the magnetic restraining force and adheres to the photosensitive drum 1 as shown in FIG. Next, as shown in FIG. 7C, a developing bias is applied to the developing sleeve 31 to stop the rotation of the developing sleeve 31. The photosensitive drum 1 is rotated in the direction of arrow R11 in the forward direction, and the magnetic carrier attached to the photosensitive drum 1 is removed from the photosensitive drum 1 and the developing sleeve 3.
It is collected on the surface of the developing sleeve 31 by the electrostatic force due to the alternating electric field between the developing sleeve 31 and the magnetic field generated by the magnet roller. As described above, the collection of the untransferred toner in the returning operation is completed. At this time, the rotation of the developing sleeve 31 is stopped in order to prevent the electrostatic latent image remaining on the photosensitive drum 1 from being redeveloped by the toner, and thus, the developing sleeve 31 is not necessary for the photosensitive drum 1. The toner that adheres is only the toner on the portion of the developing sleeve 31 that faces the photosensitive drum 1, and the charging ability of the charger 2 does not decrease.
Further, when the photosensitive drum 1 is rotated in the reverse direction, the carrier attached on the photosensitive drum 1 does not reach the charger 2.
It is preferable that the length from the charging portion to the developing portion in the forward rotation direction of the photosensitive drum 1 is longer than the length from the developing portion to the transfer portion.

The structure in this embodiment is an example, and the same effect can be obtained even if another structure having the same effect is used, for example, a corona charger is used for the transfer device and a fur brush is used for the charging device. . Further, in the present embodiment, the peripheral speed of the photosensitive drum 1 during the returning process is equal to the process speed during normal image formation, but by lowering the peripheral speed, a more reliable collection effect can be obtained. You can

By the above method, it is possible to effectively prevent the contamination of the charging device 2 due to the untransferred toner remaining on the photosensitive drum 1 when the copying operation is stopped and the accompanying image deterioration. <Second Embodiment> In the second embodiment, in the cleaner-less image forming apparatus, when the untransferred toner on the photosensitive drum generated at the time of jam is collected by the developing device while the photosensitive drum is rotated in the reverse operation at the time of the returning operation, It is characterized in that the charge eliminating exposure means provided on the downstream side of the developing device and on the upstream side of the transfer roller when the forward rotation is used as a reference is operated.

As shown in FIGS. 6 (a), 6 (b) and 6 (c), the apparatus configuration according to the present embodiment has a static elimination exposure lamp (static elimination exposure means) 7 between the developing device 3 and the transfer roller 4. Is the same as the first embodiment, except that is installed. The image forming process is also the same as that in the first embodiment, and therefore detailed description thereof will be omitted unless necessary.

In the first embodiment, the electrostatic latent image on the photosensitive drum 1 remains as it is when the copying operation is resumed after the copying operation is stopped.
Since the toner is collected by the collecting bias, the carrier adheres to the non-image portion on the photosensitive drum 1, and a step of collecting the adhered carrier again is necessary. In the present embodiment, the static elimination exposure lamp 7 is arranged between the developing device 3 and the transfer roller 4 to prevent the carrier from adhering.

FIGS. 6A, 6B and 6C show the operations of the charging device 2, the developing device 3, the transfer roller 4 and the discharging exposure lamp 7 in each step of this embodiment, and the photosensitive drum at that time. 3 is a schematic diagram showing the latent image potential of the untransferred area on FIG.

The returning process in this embodiment will be described with reference to FIG. As shown in FIG. 6A, the photosensitive drum 1 is stopped during the jam processing. After the jam processing, as shown in FIG. 7B, the charge elimination exposure lamp 7 is first turned on. Next, when the reverse rotation of the photosensitive drum 1 is started, a recovery bias is applied to the developing sleeve 31. The toner image on the photosensitive drum 1 is attracted onto the developing sleeve 31 by an electric field generated between the developing sleeve 31 and the photosensitive drum 1. In this way, the transfer residual portion is uniformly charged to -40V. In the non-image area on the photosensitive drum 1, the potential of the non-image area on the photosensitive drum 1 is equal to that of the image area due to the irradiation of the static elimination exposure lamp 7, and the carrier does not adhere. After all the toner in the untransferred area is collected in the developing container 36, the photosensitive drum 1
Are rotated forward as shown in FIG. At the same time when the area uniformly charged by the charger 2 reaches the developing section, a developing bias is applied to the developing sleeve 31, and the recovery of the untransferred toner in the returning operation is completed. At this time, it is desirable to dispose the charge elimination charging lamp 7 as close to the developing device 3 as possible. This is because the carrier adheres to the portion that is not irradiated with light in the untransferred area. Therefore, there is a region where light does not reach in the facing portion between the developing sleeve 31 and the photosensitive drum 1, and carrier adhesion occurs in that region, but the amount is not a problem.

The configuration in this embodiment is an example, and the same effect can be obtained even if another configuration having the same effect is used, for example, a corona charger is used for the transfer device and a fur brush or the like is used for the charging device. . Further, in the present embodiment, the peripheral speed of the photosensitive drum 1 during the returning process is equal to the process speed during normal image formation, but by lowering the peripheral speed, a more reliable collection effect can be obtained. it can.

By the above method, it is possible to prevent the contamination of the charging device 2 due to the untransferred toner remaining on the photosensitive drum 1 when the copying operation is stopped, and the accompanying image deterioration. <Third Embodiment> In a third embodiment of the present invention, in a cleanerless image forming apparatus, at the time of a recovery operation after a jam process, the photosensitive drum is rotated in the forward direction, and transfer residual toner from the transfer portion to the charging portion on the photosensitive drum adheres. Area is uniformly charged to a predetermined potential by a charger, then while the photosensitive drum is rotated in the reverse direction, the untransferred portion is discharged by the image exposure means for forming an electrostatic latent image, and then collected in the developing sleeve. The photosensitive drum is normally rotated while applying a bias, and the toner remaining in the untransferred portion is collected in the developing device.

The structure of the image forming apparatus and the image forming process according to the present embodiment are the same as those in the first embodiment, and the description thereof will be omitted.

7 (a), (b), (c), and (d) are the photosensitive drum 1, the charger 2, and the charger 2 in each step of this embodiment.
3 is a schematic diagram showing the operation of each device of the developing device 3 and the image exposure means 12, and the latent image potential of the untransferred area on the photosensitive drum 1 at that time. FIG.

The return process in the present embodiment will be described with reference to these drawings. In the second embodiment, the charge is removed by the charge removing exposure lamp 7 arranged on the downstream side of the developing device 3 and on the upstream side of the transfer roller 4, but in the present embodiment, it is used when an electrostatic latent image is formed. Laser exposure (image exposure means) 1
2 is used for static elimination. However, since the image exposure by the image exposure unit 12 is performed upstream of the developing device 3 in the forward rotation direction of the photosensitive drum 1, when the charge is removed while rotating in the reverse direction, the charge is removed between the developing unit and the exposing unit. It is unavoidable that there are areas that are not protected. When the recovery bias is applied to the developing device 3 while rotating the photosensitive drum 1 in the forward direction with the electrostatic latent image remaining in this area, carrier adhesion occurs because the non-image area in that area is not neutralized. Will end up. In order to prevent this, the area between the developing section and the exposing section, which is not neutralized by the exposure at the time of reverse rotation, is previously made uniform to the same potential as the neutralizing potential of the image exposing means 12 in the non-image area. Need to be charged. In the present embodiment, the static elimination is performed using the magnetic brush charger 2. Normally, the peak voltage V _PP = 1.5 is applied to the magnetic brush charger 2 in order to uniformly charge the photosensitive drum 1 to −700V.
AC voltage of kV and frequency f = 1 kHz, and V _dc = -70
A charging bias in which a DC voltage of 0V is superimposed is applied, and the surface potential of the photosensitive drum 1 is DC of the charging bias.
Converge to the component. By the image exposure, the surface potential of the non-image portion of the photosensitive drum 1 is neutralized to about −40 V. However, in order to be charged to the same potential, the peak voltage V _PP = 1.5 kV is applied to the magnetic brush charger 2 at the frequency. A charging bias (hereinafter referred to as "static elimination bias") in which an alternating current voltage of f = 1 kHz and a direct current voltage of _Vdc- 40V are superposed is applied.

That is, first, as shown in FIG. 7B, while the photosensitive drum 1 is being rotated forward in the initial stage of the returning operation,
A static elimination bias is applied to the magnetic brush charger 2. After the photosensitive drum 1 is stopped when the boundary between the untransferred area and the transferred area on the photosensitive drum 1 reaches the charging section, the photosensitive drum 1 is rotated in the reverse direction in the direction indicated by arrow R12 in FIG. Let At the same time, the image exposure means 12 irradiates a laser beam to remove static electricity from the untransferred portion on the photosensitive drum 1. At this time, a developing bias is applied to the developing sleeve 31. When the boundary between the untransferred area and the transferred area reaches the exposed portion, the photosensitive drum 1 is stopped at the position shown in FIG. At this time, the area between the exposed portion and the developing portion is charged by the magnetic brush charger 2 to the same potential as the potential removed by the image exposing means 12, so that the toner is developed on the entire surface. Next, as shown in FIG. 3D, as the photosensitive drum 1 is rotated in the forward direction, a recovery bias is applied to the developing sleeve 31 to apply the developing sleeve 31 to the photosensitive drum 1.
The toner on the photosensitive drum 1 is collected in the developing container 36 by the electric field generated during the period. The bias applied to the magnetic brush charger 2 is switched from the static elimination bias to the charging bias when the static elimination of the untransferred portion is completed, and is applied to the developing sleeve 31 when the charged area reaches the developing portion. The bias is switched from the recovery bias to the development bias. As described above, the collection of the untransferred toner in the returning operation is completed.

In the steps described above, the length from the charging section to the exposing section in the forward rotation direction of the photosensitive drum 1 is transferred from the developing section so that the untransferred toner does not reach the charging device 2. It is preferably longer than the length of the part.

The structure in this embodiment is an example, and the same effect can be obtained even if another structure having the same effect is used, for example, a corona charger is used for the transfer device and a fur brush is used for the charging device. . Further, in the present embodiment, the peripheral speed of the photosensitive drum 1 during the returning process is equal to the process speed during normal image formation, but by lowering the peripheral speed, a more reliable collection effect can be obtained. it can.

By the above method, it is possible to prevent the contamination of the charging device 2 due to the untransferred toner remaining on the photosensitive drum 1 when the copying operation is stopped, and the image deterioration accompanying it. <Fourth Embodiment> In the fourth embodiment, the same device configuration as that of the third embodiment is used, but the recovery bias is applied to the developing device during the reverse rotation during the returning operation, and the development bias is applied during the next forward rotation. It is characterized by doing.

8 (a), (b), (c), and (d) show the photosensitive drum 1, the charger 2, and the charger 2 in each step of this embodiment.
FIG. 3 is a schematic diagram showing the operation of each device of the developing device 3 and the transfer roller 4 and the latent image potential of the untransferred area on the photosensitive drum 1 at that time.

As shown in FIGS. 7A and 7B, after the static elimination of the transfer portion on the photosensitive drum at the time of stop is completed in the same process as in the third embodiment, as shown in FIG. Then, the photosensitive drum 1 is rotated in the reverse direction. At this time, a collecting bias is applied to the developing sleeve 31 to collect the untransferred toner, and at the same time, the surface of the photosensitive drum 1 is discharged by the image exposing means 12.
At this time, the carrier adheres to the non-image area. When the boundary between the untransferred portion and the transferred portion reaches the exposed portion, the photosensitive drum 1 is stopped and the mode is switched to the forward rotation as shown in FIG. At this time, a collecting bias is continuously applied to the developing sleeve 31 to collect the carrier attached to the non-image portion in the developing container 36. In some cases, the charge may not be sufficiently removed by exposure in the area where the carriers are closely attached.
Most of the carrier is recovered by the magnetic force applied to the developing sleeve 31. The bias applied to the magnetic brush charger 2 is switched from the static elimination bias to the charging bias when the static elimination of the untransferred portion is completed, and is applied to the developing sleeve 31 when the charged area reaches the developing portion. The bias is switched from the recovery bias to the development bias. As described above, the collection of the untransferred toner in the returning operation is completed, but in the present embodiment as well, as in the third embodiment, the untransferred toner of the photosensitive drum 1 is prevented from reaching the charger 2. It is preferable that the length from the charging portion to the exposure portion in the forward rotation direction is longer than the length from the developing portion to the transfer portion. Further, the configuration in the present embodiment is an example, and the same effect can be obtained by using another configuration having the same effect, for example, a corona charger for the transfer device and a fur brush for the charging device. Further, in the present embodiment, the peripheral speed of the photosensitive drum 1 during the returning process is equal to the process speed during normal image formation, but by lowering the peripheral speed, a more reliable collection effect can be obtained. it can. <Fifth Embodiment> In the above-described first to fourth embodiments, the developing device 3 using a two-component developer as shown in FIG. 3 is used. It is characterized in that a one-component developing device 9 having a structure as shown in FIG. 9 is used. In the figure, 91 is a stainless steel support shaft 91a.
The surface of the developing roller 91 is covered with a conductive rubber 91b, and a metal blade 93 is brought into contact with the surface of the developing roller 91 to coat the surface of the developing roller 91 with non-magnetic toner. The developing roller 91 has a cleaning roller 92 made of urethane sponge.
Are in contact with each other and collect the residual toner remaining on the surface of the developing roller 91 and supply new toner 94 to the developing roller 91.

When the cleaning process is performed in the developing device 9 having the above-described structure, it is necessary to bring the conductive rubber 91b and the photosensitive drum 1 into contact with each other in order to improve the recovery effect of the developing device 9. In order to prevent discharge between the two, development is usually performed with a DC voltage (DC electric field). For example, if the charging potential (white background potential) of the photosensitive drum 1 is -700 V, a DC voltage of V _dc = -350 V is applied to the developing roller 91 as a developing bias, and a fog removal potential of -350 V is required. I am trying. This is because the number of toners that come into contact with the surface of the photosensitive drum 1 during the one-component contact development becomes larger than that during the two-component contact development, which is disadvantageous for fogging.

In the present embodiment, the configuration of the apparatus other than the developing device 9 is the same as that of the third embodiment, and the third embodiment is used.
The untransferred toner is collected by performing the same returning process as described in. The restoration process is simply repeated below.

At the time of the returning operation, the area on the photosensitive drum 1 where the transfer residual toner from the transfer portion to the charging portion adheres is uniformly charged to a predetermined potential by the charger 2, and then the photosensitive drum 1 is rotated in the reverse direction. Meanwhile, the untransferred portion is discharged by the image exposing means 12, and the photosensitive drum 1 is rotated in the forward direction while applying a collecting bias to the developing device 3 to collect the toner remaining in the untransferred portion into the developing container 36. It is a thing. However, the recovery bias applied to the support shaft 91a is + 300V.
DC voltage is used.

In the returning process in the first, second, and fourth embodiments, a large potential difference is generated between the developing sleeve 31 and the photosensitive drum 1 and discharge may occur, which is not applicable, but a latent image. Any low-potential development having a depth of about 400 V can be applied.

As described above, even in the one-component contact development, it is possible to effectively collect the untransferred toner that is generated during the jam processing.

[0068]

As described above, according to the present invention, in the image forming apparatus using the cleanerless system,
If the copying operation is interrupted due to a paper jam, etc., the untransferred toner remaining on the surface of the photosensitive drum is collected in the developing device by including the step of rotating the photosensitive drum in the direction opposite to that during the copying operation during the returning step. Therefore, it is possible to prevent the charging device from being contaminated by the untransferred toner and prevent the deterioration of the image quality due to the contamination.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a vertical sectional view showing a schematic configuration of a conventional image forming apparatus.

FIG. 3 is a vertical cross-sectional view showing the configuration of a developing device that uses a two-component developer.

FIG. 4 is a vertical cross-sectional view showing the configuration of a magnetic brush charger.

5A, 5B, and 5C are schematic diagrams illustrating a toner recovery process according to the first embodiment.

6A, 6B, and 6C are schematic diagrams illustrating a toner recovery process according to the second embodiment.

7A, 7B, 7C, and 7D are schematic diagrams illustrating a toner collecting process according to the third embodiment.

8A, 8B, 8C, and 8D are schematic diagrams illustrating a toner recovery process according to the fourth embodiment.

FIG. 9 is a vertical cross-sectional view showing the configuration of a developing device that uses a non-magnetic one-component developer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Charging means (charging device) 3 Developing means (developing device) 4 Transfer means (transfer roller) 6 Fixing means (fixing device) 7 Discharge exposing means (discharging exposure lamp) 21 Charging sleeve 22 Magnet Roller 31 Developer-carrying member (developing sleeve) 32 Magnet roller 51 Drive means 52 Control means P Transfer material

Claims (10)

[Claims] 1. A rotatable image bearing member, a charging means disposed around the image bearing member in order along the forward rotation direction of the image bearing member, for uniformly charging the surface of the image bearing member, and after charging. Image exposing means for exposing the surface of the image bearing member to form an electrostatic latent image, developing means for adhering the toner of the developer to the electrostatic latent image for development, and transferring the toner image onto a transfer material. An image forming apparatus, comprising: a transfer unit, wherein the developing unit also serves as a cleaning unit to remove transfer residual toner remaining on the surface of the image carrier after the transfer of the toner image onto the transfer material. Drive means for selectively rotating in the opposite direction, control means for controlling the rotation direction of the image carrier via the drive means, and the control means is the untransferred toner image after the development and before transfer. The image carrier is stopped while remaining on the surface of the carrier. In this case, the driving unit performs a returning operation including a reverse rotation operation of the image carrier, and a voltage is applied to the developing unit during the returning operation to remove the untransferred toner on the surface of the image carrier. An image forming apparatus characterized in that the image is collected by a developing means. 2. When the developer is a two-component developer containing a toner and a carrier, and the carrier is attached to the surface of the image carrier during the returning operation, the control means controls during the returning operation. The image forming apparatus according to claim 1, wherein a voltage is applied to the developing unit to collect the carrier on the surface of the image carrier by the developing unit. 3. The developing means has a developer carrier for carrying and transporting a developer on the surface thereof to adhere to the electrostatic latent image on the surface of the image carrier, and the developer during the returning operation. While applying a recovery bias to the carrier, the image carrier is rotated in the reverse direction to collect untransferred toner on the surface of the image carrier by the developing means, and then the developer carrier is stopped to apply a developing bias. 3. The image forming apparatus according to claim 2, wherein the image carrier is rotated in the forward direction while the carrier on the surface of the image carrier is collected by the developing means. 4. A static eliminator for static eliminating the surface of the image carrier during the returning operation, according to any one of claims 1 to 3.
An image forming apparatus according to any one of the preceding claims. 5. The static elimination means is static elimination exposure means arranged on the downstream side of the developer carrying body and on the upstream side of the transfer means with reference to the forward rotation direction of the image carrying body. The image forming apparatus according to claim 4, which is characterized in that. 6. The image forming apparatus according to claim 4, wherein the image exposing unit also serves as the charge removing unit. 7. The image forming apparatus according to claim 4, wherein the charging unit also serves as the charge removing unit. 8. During the returning operation, while the image carrier is being rotated in reverse, the surface of the image carrier is exposed by the charge eliminating exposure means, and a recovery bias is applied to the developer carrier. The image forming apparatus according to claim 5, wherein the untransferred toner on the surface of the image carrier is collected by a developing unit. 9. During the returning operation, while the image carrier is rotated in a forward direction, the transfer area carrying the transfer toner on the surface of the image carrier is uniformly charged to a predetermined potential by the charging means, A developing bias is applied to the developer bearing member, the image bearing member is rotated in the reverse direction, the untransferred area is neutralized by the image exposing unit, the image bearing member is rotated in the forward direction, and a recovery bias is applied. The image forming apparatus according to claim 6 or 7, wherein the developer carrying member collects untransferred toner in an untransferred region on the image carrying member. 10. The image carrier is rotated in the forward direction during the returning operation, the transfer area is uniformly charged to a predetermined potential by the charging means, and then the surface of the image carrier is neutralized by the image exposing means. While rotating the image carrier in reverse,
A recovery bias is applied to the developer carrying member to collect the untransferred toner in the untransferred region on the image carrying member by the developing means, and then the recovery member bias is applied to the image carrying member. The image forming apparatus according to claim 6 or 7, wherein the body is rotated forward.