JPH11311929A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make image quality high by simultaneously preventing adverse influence exerted on recovered toner because toner is triboelectrified and adverse influence exerted on an image because of a foreign matter and flocculated toner in a screw pump and other spots and stably carrying the recovered toner in an image forming device equipped with a toner recycling mechanism using the screw pump. SOLUTION: This image forming device is provided with the toner recycling mechanism 500 for carrying the recovered toner recovered by a cleaning means to a developing device. In the device, the mechanism 500 is equipped with a stirring means 551 selecting and stirring the recovered toner, a powder pump 520, and an air pump for supplying air for fluidizing the recovered toner and carrying it to the pump 520. At least a part of the stirring means is made of conductive material and the stirring means electrifies the recovered toner coming in contact with the stirring means by supplying charge to the stirring means from a charge imparting means 700 connected to the stirring means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electrophotographic image forming apparatus such as a printer, a facsimile, a copying machine or the like using a two-component developer or a one-component developer. The present invention relates to an improvement in a toner recycling mechanism for transferring toner removed and collected by a cleaning device from a transfer conveyance body such as an image forming body or a transfer belt to a development device or the like.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus has a structure in which toner remaining on a photoreceptor after image formation is removed and collected by a cleaning device. A technique has been developed in which the toner recovered from the toner is returned to the developing device by a toner recycling mechanism provided separately from the cleaning device, and is reused. Techniques related to such a toner recycling mechanism include, for example, (1) a pipe is connected between a collected toner discharge portion of a cleaning device and a toner hopper of a developing device, and the collected toner is collected by a coil screw provided inside the pipe. Technology to transfer to developing device. (2) There is a technique using a screw pump (commonly called a mono pump) as a pump capable of transferring powder instead of the coil screw. The toner transfer technique using this screw pump has the advantage that the flexible tube is used as the toner transfer path, so that the piping is free and the layout flexibility is higher than the conventional technique shown in (1). Have.

[0003]

By the way, in the toner recycling mechanism using the above screw pump,
When the toner passes through a passage or the like between the movable part and the fixed part in the screw pump, electric charge is generated due to friction, and frictional charging occurs. The friction of the toner may cause reverse charging and deterioration of the toner. In addition, the recovered toner has lower chargeability and fluidity than the new toner and contains paper dust and agglomerated toner, so that an adverse effect on the image cannot be avoided. The present invention has been made in view of the above,
In an image forming apparatus equipped with a toner recycling mechanism using a screw pump, in the screw pump and other places, the adverse effect on the collected toner due to frictional charging of the toner and the adverse effect on the image due to foreign matter or agglomerated toner at the same time. An object of the present invention is to improve the image quality by preventing and stably transferring the collected toner.

[0004]

In order to achieve the above object,
According to the first aspect of the present invention, there is provided a developing device that supplies toner to an electrostatic latent image on a photoconductor to form a toner image, a cleaning device that removes and recovers residual toner on the photoconductor, and a recovery device that is recovered by the cleaning device. In the image forming apparatus having a toner recycling mechanism for transferring the toner to the developing device, the toner recycling mechanism is configured to select and agitate the collected toner collected by the cleaning device, and to collect the toner in the axial direction by rotating. A powder pump having a rotor for moving the toner, a fixed stator disposed so as to enclose the rotor and in contact with the outer periphery of the rotor on the inner wall, and supplying the air for fluidizing and transferring the collected toner to the powder. An air pump for supplying to the body pump, wherein the stirring member is at least partially made of a conductive material. By supplying a charge to the agitating member from the charge giving means connected to the agitating member, characterized in that charging the recovered toner in contact with the agitating member. According to a second aspect of the present invention, the stirring member has a cylindrical body formed of a mesh integrated with a horizontal stirring screw fixed to one end of the rotor, and a predetermined pitch in a circumferential direction on an outer peripheral surface of the cylindrical body. And protrudingly fixed blades.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. FIG. 1 shows a copying machine as an example of an image forming apparatus using the toner recycling mechanism of the present invention. The copier shown in FIG. 1 uses a well-known electrophotographic system, and includes a drum-shaped photosensitive member 131 inside a housing.
And a charging device 13 for performing an electrophotographic copying process along a rotation direction indicated by an arrow A around the photoconductor 131.
2. Exposure means (reading optical system and writing optical system) 120
The developing device 133, the transfer / transport device 600, and the cleaning device 200 are arranged. Exposure means 120 includes a light source 122 and a mirror 12 that constitute a reading optical system for reading a document placed on a document table 121 on the top of the copying machine.
3, 124, 125; image reading means (CCD, image processing section, etc.) 126; semiconductor lasers (not shown), polygon mirrors, mirror groups 128, 12 constituting a writing optical system
9 and so on. The developed image read by the reading optical system is converted into an electric signal by the image reading means 126, and the writing optical system sends the photosensitive member 13 based on the image signal.
1 to form an electrostatic latent image. The electrostatic latent image formed on the photoconductor 131 is formed into a toner image by the developing device 133, and the toner image is electrostatically transferred by the transfer / transport device 600 onto transfer paper fed from the paper feeding device 140. You. The transfer paper carrying the toner image is conveyed and fixed to the fixing device 135, discharged out of the copying machine by the discharge rollers 136, and stacked on the discharge tray 150.

Next, FIG. 2 is an enlarged view of an example of the image forming section. The movement of the toner used in the image forming process will be described with reference to FIG. The developing device 133 is a two-component developing device, and includes a developer 302 including a carrier and a toner in a developing tank 301. When the developing device 133 supplies the toner onto the photoconductor 131 and converts the electrostatic latent image on the photoconductor into a toner image, the ratio (toner density) of the toner in the developer decreases. Therefore, in order to suppress a decrease in image density, when the toner density in the developer becomes equal to or less than a predetermined value, new toner is supplied from the toner hopper (new toner supply means) 310 to maintain the toner density in the developer. The toner concentration in the developer is measured by a magnetic permeability sensor 304 attached to a lower case of the developing device. The toner supplied from the toner hopper 310 is supplied to the developing device 13
The carrier is agitated and frictionally charged with the carrier by the stirring member 305 in 3. The developer including the carrier and the toner is jumped up to the developing roller 307a by the paddle wheel 306, and is attracted to the developing roller by the magnet in the developing roller 307a. The developer is transported by the sleeve around the developing roller, and the excess is scraped off by the developing doctor 308. The toner in the developer conveyed to the photoreceptor adheres to the electrostatic latent image due to the developing bias. The toner adhered on the photoconductor 131 is transferred to the transfer / transport device 60.
0, the toner is electrostatically transferred to the transfer paper, but about 10% of the toner is not transferred and remains on the photoreceptor. The untransferred toner is scraped off the photoconductor by the cleaning blade 211 and the brush roller 212 of the cleaning device 200. In the toner hopper 310, a supply roller 314a, a stirring member 314b, and the like, which rotate to transfer new toner in the hopper into the developing tank 301, are arranged. An empty space 320 (collected toner supply unit) is arranged, and the continuous space 320 is connected to an end of a transfer pipe 400 (tube). Reference numeral 321 denotes a degassing filter.

FIG. 3 is an external perspective view of a toner recycling mechanism (toner recycling unit). The toner recycling mechanism is a mechanism for recycling toner collected from a cleaning device to a developing device by a screw pump. . The toner collected by the cleaning device 200 for removing the attached toner from the photoconductor is
Collected toner discharge unit 2 provided at the lower part of the cleaning device
From the coil 10, the toner is transferred to the toner guide portion 510 which is a part of the toner recycling unit 500 engaged with the coil. The toner guide section 510 plays a role of a toner transfer path for sending toner from the cleaning device 200 to the toner transfer powder pump 520. The collected toner conveyed by the toner transfer powder pump 520 is supplied with air from the air pump 532 and becomes an air-fuel mixture.
The fluidized state is transferred inside the tube 400. Further, the toner is also transferred from the collected toner discharge unit 610 provided in the transfer belt device 600 as a transfer / conveyance device to the toner guide unit 510 which is a part of the toner recycling unit 500 engaged therewith. This toner recycle unit 500 is disposed on the rear side of the copying machine main body structure. A horizontal conveying screw 524 having a vibrating part 551 (a stirring member, FIG. 4) is provided in a case 525 located below the toner recycling unit 500, and collects the collected toner dropped from the toner guide part 510 to the powder pump 520. And send.

FIG. 4 is a sectional view of a toner recycling mechanism (toner recycling unit). A powder pump 520 uses a conventionally known screw pump called a so-called mono pump. It comprises a substantially spiral rotor 521, a hollow stator 522, and a stator holder 523. The rotor 521 is engaged with the horizontal transport screw 524 at one end in the axial direction, and rotates integrally. A stirring member 551 that stirs the toner dropped from the toner guide portion 510 is disposed in a cylindrical shape in the outer diameter direction of the horizontal transport screw 524, engages with the horizontal transport screw 524, and rotates integrally. The other end of the horizontal transport screw 524 is
26, a bearing 527, and a driven gear 528.
Reference numeral 700 denotes a charge applying unit.
Is a power supply 701, a switch 702, and a sliding electrode 703.
And a control unit (MPU) 704 for controlling a power supply and a switch
The control unit 704 also serves as control means for the drive motor 542. The control unit 704 may control the voltage from the power supply 701 or may control the current. The sliding electrode 703 slidably contacts, for example, the shaft end of the horizontal transport screw 524 to supply electric charges. By rotating the driven gear 528 by a driving gear 543 fixed to the output shaft of the driving motor 542, the horizontal conveying screw 524, the rotor 521, and the stirring member 551 are rotationally driven. Rotor 52
The control unit 704 operates the switch 702 simultaneously with the start of the rotation drive of the sliding electrode 703 from the power source 701.
To the rotor 521 and the stirring member 55 as a result.
A current flows through 1. At least a part of the rotor 521 and the stirring member 551 is made of a conductive material.
3 is configured to receive a current supply.

The stator 522 is made of an elastic material such as a rubber material and surrounds the rotor 521. Stator 5
There is a gap of about 1 mm between the outer peripheral surface of the holder 22 and the inner peripheral surface of the holder 523, and communicates with the collected toner passage 530. An air supply port 531 is provided so as to blow air into the collected toner passage 530 from the gap, and an air pump 532 is provided there.
Is supplied with air. Toner recycling unit 50
As for the collected toner in the toner container 0, only the selected toner drops due to the rotation of the stirring member 551, and is sent to the rotor 521 by the horizontal conveying screw 524, and the collected toner passage 5
Proceed to 30 side. At this time, the rotor 521, the stirring member 551
To control the charge generated in the toner by friction. Since the rotor 521 and the stirring member 551 are made of conductive metal, a controlled charge can be applied to the toner. In this case, the charge amount of the collected toner is higher by 1.5: 1 than when the voltage applied through the rotor 521 and the stirring member 551 is −550 V and when no voltage is applied. Become. Since the collected toner has a lower toner charge amount than the new toner, it is desirable that the toner electrostatic amount increases even slightly. In addition, the background stain on the image is improved by improving the electrostatic amount of the toner. Air pump 53
The recovered toner fluidized by the supply of the air from 2 is returned to the continuous space 320 on the near side of the hopper 310 of the developing device 133 through the tube 400. The new toner and the collected toner in the hopper 310 are supplied to the developing tank 301 of the developing device while traveling in the direction of arrow B in FIG.

FIG. 5 is a cross-sectional view of a portion for supplying new toner and collected toner. The collected toner is supplied through a continuous space 320 and the new toner is supplied through a new toner supply section 330. FIG. 6A is an enlarged perspective view showing the configuration of the stirring member 551, and FIG. 6B is an end view. Stirring member 551
Is a cylindrical mesh body around the axis of the horizontal transport screw 524. Specifically, a cylindrical body 554 made of a mesh is integrally held by two annular frame bodies 553 supported by a support rod 552 integrally extending from the lateral conveyance screw shaft in the outer diameter direction. Furthermore,
Blades 555 are integrated with the outer periphery of the cylindrical body 554 at a predetermined pitch. The blade 555 is disposed so as to cover the entire length of the cylindrical body 554 in the axial direction. The cylindrical body 554 is formed in a mesh shape, and the size of the holes of the mesh is set to be equal to the toner particle size, so that a toner mass having a large diameter and paper dust move to the screw pump side. Block. The diameter of the cylindrical body 554 is the spiral blade 5 of the horizontal conveying screw 524.
The outer diameter including the blade 555 on the surface of the cylindrical body is smaller than the shortest dimension inside the toner recycle unit 500. That is, the dimensions are set so as to rotate so as not to interfere with the inner wall of the case 525 accommodating the stirring member 551. The axial length of the cylindrical body 554 is the same as that of the case 52 of the toner recycling unit 500.
5 is set so as to secure a gap between the side wall 5 and the side wall 5 that does not hinder rotation. Blade 555 on cylindrical body surface
Are at equal intervals, and stir the collected toner during the rotation operation. The blades 555 are not meshed.
When the horizontal conveyance screw 524 starts rotating, the stirring member 551 is also operated, and the collected toner that has fallen into the case 525 is sorted while being stirred. Filters paper powder etc. and prevents movement to the screw pump side. Further, by supplying a voltage and a current from the power supply 701 to the stirring member 551 made of a conductive material, the charge amount of the toner whose charge amount has decreased can be increased, and the image quality can be improved.

FIG. 7 is a flowchart of charge control for the rotor 521 in the toner recycle unit 500 at the time of toner supply. When the “toner-less level” is detected when the remaining amount of toner in the developing tank 301 is detected by the toner sensor 304, the control unit starts a toner supply operation (step 1). In the toner supply operation, first, the toner bottle unit operates (step 2,
3) After the new toner supply amount reaches the “toner present level” (Step 4 Yes), the drive motor 542 and the air pump 532 of the toner recycling unit 500 start operating (Steps 5 and 6). At the same time rotor 5
An electric current flows through 21 and the stirring member 551 (step 7).
The collected toner is supplied in accordance with the new toner supply amount, and when the supply amount is satisfied (YES in step 8), the drive motor 54
2 stops and the current flowing through the rotor 521 and the stirring member 551 stops, so that the applied voltage is also turned off (steps 9 and 10). In step 8, the operation time of the toner bottle unit relating to the new toner supply amount and the operation time of the toner recycle unit relating to the recovered toner supply amount are counted, respectively. Is stopped, but this is an example, and various stop timings may be set arbitrarily. In the above example, the voltage is controlled, but the same effect can be obtained by controlling the flowing current.

[0012]

As described above, according to the present invention, in an image forming apparatus provided with a toner recycling mechanism using a screw pump, an adverse effect on collected toner due to frictional charging of the toner inside the screw pump and other places. In addition, the image quality can be improved by simultaneously preventing adverse effects on the image due to foreign matter and agglomerated toner, and stably transferring the collected toner. That is, by providing the rotor and the stirring member of the toner recycling mechanism of the present invention with charge applying means, it is possible to prevent reverse charging and toner deterioration of the recovered toner due to frictional charging, and to remove foreign matter and agglomerated toner, thereby obtaining a uniform and beautiful toner. A recovered toner can be obtained. Also, the toner charge amount can be kept constant,
Since stable and clean collected toner can be transferred, high quality on an image can be achieved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is an enlarged view of an image forming unit.

FIG. 3 is a configuration diagram of a toner recycling mechanism and its periphery.

FIG. 4 is a sectional view of a toner recycling mechanism of the present invention.

FIG. 5 is a sectional view of a hopper.

6A is a perspective view showing a configuration of a stirring member, and FIG. 6B is an end view.

FIG. 7 is a flowchart showing the operation of the embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 120 Exposure unit, 131 Photoconductor, 132 Charging device, 132, 133 Developing device, 200 Cleaning device, 210 Collected toner discharge unit, 301 Developing tank, 302 Developer, 304 Magnetic permeability sensor, 310
Hopper (new toner supply means), 400 tubes,
500 toner recycling unit, 510 toner guide section, 520 powder pump for transferring toner, 521 rotor, 522 stator, 523 holder, 524 horizontal conveying screw, 525 case, 532 air pump, 551
Stirring member, 552 support rod, 553 frame, 554
Cylindrical body, 555 blades, 600 transfer belt device, 61
9 Collection toner discharge section, 700 charge applying means, 701
Power supply, 702 switch, 703 sliding electrode, 704
Control unit,

Claims (2)

[Claims] A developing device that supplies toner to an electrostatic latent image on a photoconductor to form a toner image; a cleaning device that removes and collects residual toner on the photoconductor; and a collection device that collects toner collected by the cleaning device. A toner recycling mechanism for transferring the toner to the developing device, wherein the toner recycling mechanism sorts and agitates the collected toner collected by the cleaning device;
A powder pump having a rotor that moves the collected toner in the axial direction by rotating the rotor, a powder pump having a fixed stator that is arranged to wrap the rotor and that is in contact with the outer periphery of the rotor on the inner wall, and fluidizes and transfers the collected toner An air pump for supplying air to the powder pump for causing
The stirrer is at least partially made of a conductive material, and supplies a charge to the stirrer from a charge applying unit connected to the stirrer, thereby charging the collected toner in contact with the stirrer. Characteristic image forming apparatus. 2. The agitating member has a cylindrical body made of a mesh integrated with a horizontal stirring screw fixed to one end of the rotor, and protrudes from an outer peripheral surface of the cylindrical body at a predetermined pitch in a circumferential direction. 2. The image forming apparatus according to claim 1, comprising fixed blades.