JPH09237022A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time necessary for toner recycling with simple constitution. SOLUTION: This device is operated in an image forming mode in which an electrostatic latent image is formed on an image carrier 1 and developed by a developing means 4 so that a toner image may be formed, and transferred on transfer material 9 by a transfer means 10, then residual toner after transfer is recovered by a cleaning means 13, and in a toner recovering mode in which the toner held by the cleaning means is stuck to the image carrier and recovered by the developing means. The cleaning means is composed of a cleaning roller 14a coming in contact with the image carrier, an auxiliary roller 14b coming in contact with the roller 14a, and a reflection density sensor 26 detecting reflection density on the roller 14b. The reflection density sensor 26 detects the reflection density on the roller 14b in specified timing in the image forming mode, and the toner recovering mode is executed in the case the detected density value is equal to or above a specified value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer or a facsimile which employs a dry process such as an electrophotographic method, and more particularly to an image forming apparatus having a toner reuse system.

[0002]

2. Description of the Related Art For example, the following techniques are related to toner recycling and cleaning in an image forming apparatus that employs a dry process such as an electrophotographic system. [A] Japanese Patent Application Laid-Open No. 3-89289: A toner recycling device equipped with a means for conveying cleaned toner to a toner storage means. [B] Japanese Patent Application Laid-Open No. 6-202529: A cleaning device equipped with a sensor for detecting the amount of cleaned toner. [C] Japanese Patent Laid-Open No. 6-308865: An image forming apparatus in which toner cleaned by magnetic brush cleaning is attached to a photoconductor and returned to a developing device.

[0003]

In an image forming apparatus such as a copying machine, a plain paper printer, and a facsimile using an electrophotographic method, for example, as shown in the prior art [B], the cleaned toner is used. It is necessary to confirm that the tank is full and to discard the toner in the tank, for example, by providing a sensor that detects when the tank that stores the toner is full. Therefore, from the viewpoint of reducing maintenance (toner collection work) and effectively using resources, toner reuse is socially required.

In such an image forming apparatus, the toner in the developing device adheres to the image carrier (photoconductor) during development, and most of it moves (transfers) to a transfer material such as paper. At this time, as a method of reusing the toner remaining on the image carrier without being transferred, (1) the toner is once collected by a cleaning device and then conveyed to a developing device by a conveyance path, and directly or mixed with replenishment toner. To be supplied to the developing device, (2) to hold the toner on the image carrier as it is and to be directly collected from the developing area to the developing device, and (3) to collect the toner once by the cleaning device and then carry the image. Reattaching to the body and collecting it directly from the development area to the developing device,
and so on. The above (1) and (2) are techniques well known to those skilled in the art, and (3) is the content filed by the applicant.

The above (1) is a reliable method as a toner recycling technique, but as shown in the above [A], a conveying means for conveying the cleaned toner is required and the apparatus is complicated and large. Turn into. In (2), if the length of one round of the image carrier is not larger than the length of the image, the developing device needs to collect the toner from the image carrier while developing, and the toner recovery is incomplete. There is a problem that unnecessary toner adheres to a part of the above, or on the contrary, sufficient image density cannot be obtained. On the other hand, in (3), as shown in [C] above, by separating the image forming operation and the toner collecting operation, the developing function of the developing device and the toner collecting function from the image carrier are optimized. It can be performed under the conditions. However. On the other hand, since the two operations are separated as described above, there is a problem that the time interval for continuous image formation becomes long and the apparent recording speed becomes slow.

The present invention has been made in view of the above circumstances, and its object (problem) is as follows. 1. An image forming apparatus that has a simple configuration and saves time for toner recycling is realized. 2. It improves the transfer rate and further shortens the time required for toner recycling. 3. (EN) Provided is a cleaning device which has a long life and does not generate a large driving torque.

[0007]

In order to achieve the above object, an image forming apparatus according to claim 1 has an image carrier, an electrostatic latent image forming means arranged around the image carrier, and a developing device. Means, transfer means, and cleaning means, and an electrostatic latent image is formed on the image carrier by the electrostatic latent image forming means, and the electrostatic latent image is developed by the developing means to form a toner image. An image forming mode in which the toner image formed on the body is transferred to the transfer material by the transfer means, and the residual toner on the image carrier after the transfer is collected by the cleaning means, and the toner held in the cleaning means are set. It operates in a toner collecting mode in which the toner is attached to the image carrier and the developing means collects the toner. The cleaning unit includes a cleaning roller that contacts the image carrier, an auxiliary roller that contacts the cleaning roller, and a reflection density sensor that detects the reflection density on the auxiliary roller. In the formation mode, the reflection density on the auxiliary roller is detected at a predetermined timing, and when the density value is a predetermined value or more, the toner recovery mode is executed.

An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect.
In the image forming apparatus described above, the cleaning roller is a rubber roller containing carbon, and the auxiliary roller is made of metal.

The image forming apparatus according to claim 3 is the image forming apparatus according to claim 1.
In the image forming apparatus described above, the auxiliary roller is connected to a power supply that supplies voltage or current, and the cleaning roller is floated.

[0010] The image forming apparatus according to the fourth aspect is the first aspect.
In the image forming apparatus described above, a toner having a sphericity of 0.8 or more is used.

An image forming apparatus according to a fifth aspect of the present invention includes an image carrier and an electrostatic latent image forming means disposed around the image carrier.
A developing means, a transferring means, and a cleaning means, and an electrostatic latent image is formed on the image carrier by the electrostatic latent image forming means, and the electrostatic latent image is developed by the developing means to form a toner image,
An image forming mode in which the toner image formed on the image carrier is transferred to a transfer material by the transfer unit, and the residual toner on the image carrier after the transfer is collected by the cleaning unit,
It operates in a toner collecting mode in which the toner held by the cleaning unit is attached to the image carrier and the toner is collected by the developing unit. The cleaning unit includes a cleaning roller that contacts the image bearing member, an auxiliary roller that can contact and separate from the cleaning roller, and a reflection density sensor that detects the reflection density on the auxiliary roller.
During the execution of the image forming mode, the auxiliary roller comes into contact with the cleaning roller, the reflection density sensor detects the reflection density on the auxiliary roller, and when the density value is equal to or higher than a predetermined value, the toner collecting mode is executed. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment 1] First, an embodiment corresponding to claims 1, 2 and 3 will be described. FIG. 1 is a cross-sectional view of main parts schematically showing a configuration example of an image forming apparatus in which the present invention is implemented. This image forming apparatus includes a drum-shaped image bearing member (photoreceptor or the like) 1. Around the image bearing member 1, a charging roller 2, an image exposure system 3, a developing device 4, a transfer roller 10, a separation charger. 11, a pre-cleaning charger 12, a cleaning device 13, and a charge eliminating lamp 15 are arranged.
In this image forming apparatus, the image bearing member 1 is uniformly charged by the charging roller 2, and the electrostatic latent image is formed on the image bearing member 1 by the electrostatic latent image forming means including the image exposure system 3 such as a laser scanning device. And the electrostatic latent image is developed with toner by the developing device 4, the toner image formed on the image carrier is transferred to the transfer material 9 by the transfer roller 10, and remains on the image carrier after transfer. There are two modes, an image forming mode in which the toner is collected by the cleaning roller 14 of the cleaning device 13 and a toner collection mode in which the toner collected by the cleaning device 13 is attached to the image carrier 1 and collected by the developing device 4. It operates, and is controlled by the control part of FIG. 4 mentioned later.

FIG. 2 is a schematic sectional view showing a structural example of the developing device. The developing device 4 includes a developing sleeve 5, which is a developer transporting body, a doctor blade 6 that regulates the amount of the developer transported by the developing sleeve 5, stirring members 7, 8 and the like. The agitating members 7 and 8 mix and agitate the developer including the toner and the carrier. The developing sleeve 5 is made of a non-magnetic conductive member such as aluminum or stainless and has a permanent magnet that forms a plurality of magnetic poles inside. The developing sleeve 5 rotates in the direction of the arrow in the drawing to convey the developer, but the amount of the developer conveyed is restricted by the doctor blade 6. The doctor blade 6 and the developing sleeve 5 are connected to each other by a distance of 0.
A gap of about 2 to 1 mm is formed. Further, a bias different depending on the mode is applied to the developing sleeve 5 by the power supply 18. The developer used is a two-component developer composed of a non-magnetic toner and a magnetic carrier, and the toner is negatively charged. Although not shown, a roller-shaped or plate-shaped electrode member is arranged in the vicinity of the developing sleeve in the developing device, and a bias is applied to the electrode member to exchange toner with the developing sleeve 5. You can also
In this case, in the toner recovery mode, a bias that causes the toner to move from the developing sleeve to the electrode member is applied to the developing sleeve and the electrode member, and in the image forming mode, a bias that causes the toner to move from the electrode member to the developing sleeve is applied. To be done.

FIG. 3 is a schematic sectional view showing a structural example of the cleaning device. The cleaning device 13 includes a cleaning roller 14a and a cleaning roller 1 which rotate by rotating a rotation speed or a rotation direction by a drive source (not shown).
The auxiliary roller 14b is in contact with the auxiliary roller 4a, and the reflection density sensor 26 detects the reflection density on the auxiliary roller. The cleaning roller 14a electrostatically cleans the toner on the image carrier, or transfers the toner from the cleaning roller 14a to the image carrier 1. Therefore, the bias is applied directly or indirectly. As a method of indirectly applying the bias, the power source 18 and the auxiliary roller 14b are connected, the cleaning roller 14a is floated (electrically floated), and the auxiliary roller 14b and the image carrier 1 are connected. Take advantage of the voltage drop across. To that end, the cleaning roller 14a
Is required to be an elastic body having an appropriate resistance.
Therefore, the cleaning roller 14a is preferably a rubber roller containing carbon, for example. The auxiliary roller 14b is a metal roller and has a power source 1
A voltage or current is directly supplied from 8. The reflection density sensor 26 includes a light emitting element and a light receiving element. The light emitting element irradiates the auxiliary roller 14b with light and detects the amount of light reflected from the auxiliary roller 14b. The auxiliary roller 14
High reflectance is obtained when nothing is attached to b,
When toner adheres, the amount of reflected light decreases.

In the cleaning device 13, the toner stain on the cleaning roller 14a is detected as follows. The electric potential of the auxiliary roller 14b is set to a plus side by about 50 to 300 V with respect to the cleaning roller 14a, and the toner (here, negatively charged) is transferred to the auxiliary roller 14b. The controller detects the output of the reflection density sensor 26 at this time to judge the amount of toner adhesion. Then, the potential relationship between the two rollers 14a and 14b is reversed, and the toner is returned to the cleaning roller 14a.

FIG. 4 shows a block diagram of a control system in the image forming apparatus of the present invention. The control unit 20 includes a central processing unit (CPU) including a known microcomputer, and a memory (RO that stores control programs and control data.
M, RAM), various control circuits, clocks, input / output circuits (I / O), etc., and inputs a signal from the reflection density sensor 26 according to a preset program to apply a bias to each unit. High voltage power supply 18,
A laser control system 21 that controls the timing of image exposure, a mechanism 22 that brings the charging roller 10 into and out of contact with the image carrier 1, a paper feed mechanism 23 that supplies the transfer material 9, and a cleaning roller 14.
The cleaning roller rotating mechanism 24 and the like for controlling the rotation of a are controlled. Although not shown, the rotation mechanism of the image carrier 1, the rotation mechanism of the developing sleeve 5 and the stirring members 7 and 8,
Of course, the control unit 20 also controls the fixing roller rotating mechanism of the fixing device 16, the on / off state of the static elimination lamp 15, and the like. Further, key input information from the operation unit 25, signals from the reflection density sensor 26, and detection signals from various other sensors are input to the control unit 20.

FIG. 5 is a flow chart for explaining the basic operation of the control system. When the apparatus is started, the rotation of the image carrier 1, the discharge from the separation charger 11 and the pre-cleaning charger 12, and the lighting of the discharge lamp 15 are started.
Next, the toner collecting mode and subsequently the image forming mode are executed. If there is a next image and image formation is to be continued, the toner stains on the cleaning roller 14a are detected as described above when the previous image formation is completed,
When the stain of a predetermined value or more is detected, the toner collecting mode is executed and then the image forming mode is executed, and when the stain of the toner is less than the predetermined value, the image forming mode is executed. Further, the toner collecting mode is executed immediately before the image carrier 1 is stopped after a series of image formation is completed, and thereafter the operation of each unit is stopped.

FIG. 6 is a flow chart for explaining an operation example in the image forming mode. In the following, a series of image forming processes will be described as a negative / positive process.
In the image forming mode, first, the charging roller 2 is brought into contact and a bias is applied to the charging roller 2, so that the image carrier 1 which is a photoconductor (OPC) having an organic photoconductive layer is uniformly made negative. It is charged (-700V). Next, −500 V is applied to the developing sleeve 5 of the developing device 4 (when the electrode member is arranged in the developing device, −8 V is applied to the electrode member).
00V is applied), a bias of + 200V is applied to the cleaning roller 14a of the cleaning device 13, and the cleaning roller 14a rotates at a low speed. Next, the image carrier 1 is irradiated with laser light whose intensity is modulated by the image exposure system 3 according to the image signal, so that an electrostatic latent image is formed. At this time, the lowest solid black potential is -100V.

The latent image thus formed is developed by the magnetic brush formed on the developing sleeve 5 of the developing device 4 when passing through the developing area to form a toner image. On the other hand, a transfer paper (transfer material) 9 is fed from a paper feed mechanism (not shown), and a pair of upper and lower registration rollers (not shown) are provided between the image carrier 1 and the transfer roller 10 in synchronization with the leading edge of the image. And the toner image is transferred. The transfer roller 10 is +2 to match the timing.
A constant current of about 0 μA is supplied. After that, the transfer paper 9 is separated from the image carrier 1 and then the image is fixed through the fixing device 16 and discharged as a copy.

Although the toner developed by the developing sleeve 5 is almost all negatively charged, the transfer roller 10
Then, since the positive charge is supplied, the charge is injected from the transfer roller 10 into a part of the transfer residual toner to become the positive polarity toner. The pre-cleaning charger 12 (hereinafter referred to as PCC) supplies a negative corona to these toners, and the toners are recharged to the negative side. Since the positive bias is applied to the cleaning roller 14a while rotating, the transfer residual toner negatively charged by the PCC is collected by the cleaning roller 14a. Further, the charge eliminating lamp 15 is turned on to erase the negative charge on the image carrier 1. Further, the image exposure is stopped after the exposure of one image is completed.

Next, FIG. 7 is a flow chart for explaining an operation example in the toner collecting mode. When the image formation is completed, the charging roller 2 is separated from the image carrier 1, the bias application is stopped, and −20 μA is supplied to the transfer roller 10. Further, + 300V is applied to the developing sleeve 5 (+ 600V is applied to the electrode member when the electrode member is arranged in the developing device), -10 μA is supplied to the cleaning roller 14a, and cleaning is performed. The roller 14a rotates at high speed. Then, this mode ends when the cleaning roller 14a makes almost one rotation.

When the rotation speed and bias of the cleaning roller 14a are switched, the cleaning roller 14a
The toner collected by a is discharged to the image carrier 1. The discharged toner is conveyed to the developing area as the image carrier 1 rotates. At this time, the charging roller 2 is separated from the image carrier 1 so that the discharged toner does not adhere, and the surface potential of the image carrier 1 becomes about 0V. Also, the developing sleeve 5 has a +3
Since 00V is applied, the electrostatic force from the image carrier 1 toward the developing sleeve 5 acts on the toner on the image carrier in the developing area, and the impact force of the magnetic brush is also applied to remove the toner on the image carrier from the developing sleeve. Collect on the magnetic brush formed above. When the electrode member is arranged in the developing device, the electric field from the developing sleeve 5 to the electrode member acts on the toner attached to the tip of the magnetic brush, and a part of the toner moves to the electrode member side. Therefore, the amount of toner at the tip of the magnetic brush is reduced, and the toner can be reliably collected from the image carrier 1.

It should be noted that the numerical values shown in this embodiment are not limited, and are appropriately set so that the above-described operation occurs. For example, in the case of forming an image by regular development (positive / positive process) using positively charged toner, the bias value is naturally commensurate with that, and the bias applied to the cleaning roller 14a, the developing sleeve 5 and the like is also image formation. In the mode, the toner is set to move from the developing sleeve 5 (from the electrode member to the developing sleeve) to the image bearing member 1 and from the image bearing member 1 to the cleaning roller 14a. In the toner collecting mode, the toner is moved to the cleaning roller 14a. To the image carrier 1 and from the image carrier 1 to the developing sleeve 5 (from the developing sleeve to the electrode member).

[Embodiment 2] Next, an embodiment corresponding to claim 4 will be described. In this embodiment, the toner used in the image forming apparatus of the first embodiment is spherical. As means for spheroidizing toner, a method in which particles obtained by a suspension polymerization method, a dispersion polymerization method or an emulsion polymerization method is used as a toner (a coloring agent or a charge control agent is externally added if necessary), and a pulverized toner There is a method of spheroidizing by applying thermal and mechanical action.

In the image forming mode, the toner that has not been transferred to the transfer material 9 is cleaned. Under normal conditions, the transfer rate (ratio of the transfer toner amount to the developing toner amount) is at least about 80%, and the cleaning device 13 cleans a small amount of toner in one image formation. It is also known that the transferability varies greatly depending on the toner. Therefore, by further using the toner having a high transfer rate, it is possible to reduce the number of times of executing the toner collecting mode and improve the recording speed.

As a result of the experiments conducted by the present inventors, it has been clarified that the transfer rate is improved by making the toner spherical. In particular, the effect was clear when the sphericity was 0.8 or more. Therefore, by using such toner in the image forming apparatus according to the first exemplary embodiment, it is possible to further reduce the number of times the toner collecting mode is executed and to improve the recording speed without deteriorating the quality.

[Embodiment 3] Next, an embodiment corresponding to claim 5 will be described. In the image forming apparatus according to the first embodiment, the auxiliary roller 14b and the cleaning roller 14a may not be in constant contact with each other, but may be in contact with each other only when toner stain is detected during execution of the image forming mode. As a result, the adverse effect of the constant contact between the cleaning roller 14a and the auxiliary roller 14b (cleaning roller 14a
Of the toner, the increase of the rotation torque, the sticking of the toner to the cleaning roller 14a and the auxiliary roller 14b, etc.) can be eliminated.

[0029]

As described above, in the image forming apparatus according to the first aspect of the present invention, the cleaning means has the cleaning roller in contact with the image carrier, the auxiliary roller in contact with the cleaning roller, and the reflection on the auxiliary roller. It consists of a reflection density sensor that detects the density.The reflection density sensor detects the reflection density on the auxiliary roller at a predetermined timing during the image forming mode, and executes the toner collection mode when the density value is above the predetermined value. With this configuration, it is possible to save the time required for the cleaning device to collect the cleaned toner and to improve the recording speed by detecting the toner stains on the cleaning roller and executing the toner recovery mode accordingly. You can

In the image forming apparatus according to claim 2,
In addition to the structure of claim 1, since the cleaning roller is a rubber roller containing carbon and the auxiliary roller is made of metal, it is possible to apply a proper bias without damaging the image bearing member with which the cleaning roller contacts. By temporarily transferring the adhered toner to the auxiliary roller, it is possible to reliably detect the toner stain.

In the image forming apparatus according to claim 3,
In addition to the configuration of claim 1, since the auxiliary roller is connected to a power source that supplies voltage or current and the cleaning roller is floated, the bias power source required for cleaning and toner stain detection can be shared. it can.

In the image forming apparatus according to claim 4,
In addition to the configuration of claim 1, since the toner having the sphericity of 0.8 or more is used, the transfer residual toner can be reduced, thereby reducing the toner collecting operation and further improving the recording speed. be able to.

In the image forming apparatus according to claim 5,
The cleaning unit includes a cleaning roller that contacts the image carrier, an auxiliary roller that can be brought into contact with and separated from the cleaning roller, and a reflection density sensor that detects the reflection density on the auxiliary roller. Comes into contact with the cleaning roller, the reflection density sensor detects the reflection density on the auxiliary roller, and if the density value is equal to or higher than a predetermined value, the toner recovery mode is executed.
It is possible to prevent the deformation of the cleaning roller and the adhesion of the toner to extend the life of the cleaning device and reduce the driving force of the roller.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part schematically showing a configuration example of an image forming apparatus in which the present invention is implemented.

FIG. 2 is a schematic cross-sectional view showing a configuration example of a developing device of the image forming apparatus shown in FIG.

FIG. 3 is a schematic cross-sectional view showing a configuration example of a cleaning device of the image forming apparatus shown in FIG.

4 is a block diagram showing a configuration example of a control system of the image forming apparatus shown in FIG.

FIG. 5 is a flowchart illustrating a basic operation example of a control system.

FIG. 6 is a flowchart illustrating an operation example in an image forming mode.

FIG. 7 is a flowchart illustrating an operation example in a toner recovery mode.

[Explanation of symbols]

 1: image carrier (photoreceptor) 2: charging roller 3: image exposure system (electrostatic latent image forming means) 4: developing device (developing means) 5: developing sleeve (developer carrier) 6: doctor blade ( Developer regulating member) 7, 8: Stirring member 9: Transfer material 10: Transfer roller (transfer means) 11: Separation charger 12: Pre-cleaning charger 13: Cleaning device (cleaning means) 14a: Cleaning roller 14b: Auxiliary roller 15: Static erasing lamp 16: Fixing device 18: High-voltage power supply 20: Control unit 21: Laser control system 22: Charging / separating mechanism 23: Paper feeding mechanism 24: Cleaning roller rotating mechanism 25: Operation unit 26: Reflection density sensor

Claims (5)

[Claims] 1. An image carrier and an electrostatic latent image forming unit, a developing unit, a transfer unit and a cleaning unit arranged around the image carrier, the electrostatic latent image forming unit being provided on the image carrier. An electrostatic latent image is formed, the electrostatic latent image is developed by the developing unit to form a toner image, the toner image formed on the image carrier is transferred to a transfer material by the transfer unit, and the cleaning is performed. An image forming mode for collecting the residual toner on the image carrier after transfer by the means, and a toner collecting mode for adhering the toner held by the cleaning means to the image carrier and collecting the toner on the developing means. In the image forming apparatus that operates, the cleaning unit includes a cleaning roller that contacts the image carrier, an auxiliary roller that contacts the cleaning roller, and a reflection density sensor that detects the reflection density on the auxiliary roller. The reflection density sensor detects the reflection density on the auxiliary roller at a predetermined timing during the image forming mode, and executes the toner collection mode when the density is a predetermined value or more. A characteristic image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the cleaning roller is a rubber roller containing carbon, and the auxiliary roller is made of metal. 3. The image forming apparatus according to claim 1, wherein the auxiliary roller is connected to a power source that supplies voltage or current, and the cleaning roller is floated. 4. The image forming apparatus according to claim 1, wherein a toner having a sphericity of 0.8 or more is used. 5. An image carrier and an electrostatic latent image forming unit, a developing unit, a transfer unit and a cleaning unit arranged around the image carrier, the electrostatic latent image forming unit being provided on the image carrier. An electrostatic latent image is formed, the electrostatic latent image is developed by the developing unit to form a toner image, the toner image formed on the image carrier is transferred to a transfer material by the transfer unit, and the cleaning is performed. An image forming mode for collecting the residual toner on the image carrier after transfer by the means, and a toner collecting mode for adhering the toner held by the cleaning means to the image carrier and collecting the toner on the developing means. In the image forming apparatus that operates, the cleaning means includes a cleaning roller that is in contact with the image carrier, an auxiliary roller that can be brought into contact with and separated from the cleaning roller, and a reflection density sensor that detects the reflection density on the auxiliary roller. The auxiliary roller comes into contact with the cleaning roller during execution of the image forming mode, the reflection density sensor detects the reflection density on the auxiliary roller, and when the density value is equal to or higher than a predetermined value, the toner recovery mode is set. An image forming apparatus characterized by executing.