JP2002189335A - Intermediate transfer body cleaning device and color electrophotographic device equipped therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make toner left after transfer on an intermediate transfer body even recyclingly usable when a color mixture is caused in a tandem indirect transfer type color electrophotographic device. SOLUTION: This color electrophotographic device where a color image is recorded on a sheet by forming a synthetic toner image on the intermediate transfer body 10 by using the tandem type image forming device 20 and transferring the toner image is equipped with the intermediate transfer body cleaning device 17. The cleaning device 17 is equipped with a cleaning means 90 for removing the toner left after transfer on the transfer body 10 and a toner restoring means 91 for restoring the toner left after transfer to a developing device 61BK used in a black image forming means 18BK in the tandem type image forming device. The toner restoring means is provided with a toner carrying member 96 such as a spring coil for carrying the toner removed by the cleaning means and a toner carrying path forming member 97 such as a recovery pipe and a recovery tube for guiding the toner carried by the member 96 to the developing device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, a facsimile,
In particular, using a two-component or one-component developer, charging, writing, development, transfer, cleaning, etc. are repeated to form toner images of different colors on a plurality of photoconductors, and the toner images are sequentially transferred. The present invention relates to a color electrophotographic apparatus that forms a synthetic toner image on an intermediate transfer member, transfers the toner image, and records a color image on a sheet. Also, the present invention relates to an intermediate transfer member cleaning device for removing transfer residual toner on the intermediate transfer member in such a color electrophotographic apparatus.

[0002]

2. Description of the Related Art In recent years, color electrophotographic apparatuses, such as color copiers and color printers, are increasing in number in response to market demands.

In a color electrophotographic apparatus, a plurality of color developing devices are provided around a single photoconductor, and toner is adhered by the developing devices to form a composite toner image on the photoconductor.
A so-called revolver type, which transfers the toner image to record a color image on a sheet, and a plurality of photoconductors 4 arranged side by side as shown in FIG. There is a so-called tandem type in which a single color toner image is formed on each of the above, and the single color toner images are sequentially transferred to record a composite color image on the sheet 2.

In recent years, even with this type of electrophotographic apparatus, it is recommended to return the toner collected from the sheet without being transferred to the developing apparatus again for recycling from the viewpoint of environmental problems and resource saving. Is done. However, in the case of the revolver type, it is difficult to recycle it because the collected toner causes color mixing. In tandem type,
There is almost no risk of color mixing.

However, in a tandem type electrophotographic apparatus,
When a single-color toner image is sequentially transferred from the photoconductor 4 to the sheet 2, reverse transfer occurs in which the toner already existing on the sheet 2 returns to the photoconductor 4 side, and some color mixing occurs. There was a problem.

Further, the sheet 2, in order to increase the whiteness, also to adjust the acidity of the sheet 2, calcium carbonate and talc _{(Mg 3 (Si 4 0 10} ) (OH) 2), kaolin (Al ₂ O
_{3 · 2SiO 2 · 2H 2 O} ) is added to paper additives such as. Also,
Paper dust is attached to the sheet 2.

Such paper deposits such as paper dust and paper additives are originally hardly charged to the positive electrode in consideration of the charging sequence, and almost all are charged to the negative electrode. However, the charge polarity depends on the contact person and the surrounding environment,
Not all paper deposits on the sheet 2 are charged to the negative electrode.

When the toner image on the photosensitive member 4 is brought into contact with the sheet 2 to be transferred onto the sheet 2, for example,
As shown in FIG. 3, the toner 1 charged on the negative electrode is transferred to the sheet 2 by receiving an electric attractive force. On the contrary, the toner 1 charged on the sheet 2 is charged on the positive electrode. The object 3 moves to the photoconductor 4 side so as to be replaced with toner.

The paper deposit 5 charged on the negative electrode is
The paper adhering substance 6 which remains on the sheet 2 but has a weak charge amount and is almost neutral physically adheres to the photoreceptor 4. The paper additive is an indispensable substance for maintaining the characteristics of the sheet 2, but has a problem that when it is attached to the photoreceptor 4, it causes filming and image flow.

In FIG. 13, reference numeral 7 denotes a conductive roller, which is an example of a transfer device, which applies a positive bias to the photosensitive member 4 to transfer a toner image on the photosensitive member 4 and transfer the toner image onto the sheet 2. The image is recorded on the. FIG.
In FIG. 4, reference numeral 8 denotes a sheet conveying belt for conveying the sheet 2.

In order to solve such a problem, a single-color toner image formed on each photosensitive member is sequentially transferred to form a composite toner image on an intermediate transfer member, and then the toner images are collectively transferred. Record a color image on the sheet
A so-called tandem type indirect transfer type color electrophotographic apparatus has been proposed.

According to this method, since the sheet does not directly contact the photoreceptor, the reverse transfer to the photoreceptor can be reduced, and the chance of adhering paper to the photoreceptor is greatly reduced. The possibility of reusing the transfer residual toner on the photoreceptor can be greatly increased.

[0013]

However, in such a tandem type indirect transfer type color electrophotographic apparatus,
It is desired that the transfer residual toner on the intermediate transfer member is recycled even if there is some adhering matter on the paper, and that the amount of waste toner is reduced to achieve environmental protection and resource saving.

However, when the transfer residual toner on the intermediate transfer member is collected, there is a problem that color mixing occurs. In addition, since transfer is performed from each photoreceptor to the intermediate transfer body and then from the intermediate transfer body to the sheet, stress is applied to the toner by repeating the transfer, and the polarity of the toner changes or the toner deteriorates Or there was a problem. For this reason, it is very difficult to recycle the transfer residual toner on the intermediate transfer member, and there has been no toner transfer device using an intermediate transfer member.

Accordingly, a first object of the present invention is to make it possible to recycle the transfer residual toner on the intermediate transfer member even in a tandem type indirect transfer type color electrophotographic apparatus, even if color mixing occurs. .

A second object of the present invention is to make it possible to recycle transfer residual toner on an intermediate transfer member with a simpler structure.

A third object of the present invention is to make it possible to recycle the transfer residual toner on the intermediate transfer member even if the polarity of the toner changes.

A fourth object of the present invention is to prevent the deterioration of the toner and to make it possible to recycle the transfer residual toner on the intermediate transfer member.

[0019]

In order to achieve the first object, the invention according to claim 1 forms a synthetic toner image on an intermediate transfer member using a tandem image forming apparatus. In a color electrophotographic apparatus that transfers the toner image and records a color image on a sheet, an intermediate transfer member cleaning device provided therein includes a transfer residual toner on the intermediate transfer member, and a black image in a tandem image forming apparatus. The image forming apparatus further includes a toner returning unit that returns the toner to the developing device used in the forming unit.

According to a second aspect of the present invention, there is provided an intermediate transfer body cleaning apparatus according to the first aspect, further comprising a cleaning unit for removing transfer residual toner on the intermediate transfer body. In addition, as a toner returning unit, a toner conveying member that conveys the toner removed by the cleaning unit, and a toner conveying path forming member that guides the toner conveyed by the toner conveying member to a developing device used in the black image forming unit. Is provided.

According to a third aspect of the present invention, there is provided an intermediate transfer member cleaning apparatus according to the first aspect, wherein the color electrophotographic apparatus is a black tandem type image forming apparatus. The forming unit is arranged at a position upstream of the image forming unit of another color in the conveying direction of the intermediate transfer body, and as a toner returning unit, the transfer residual toner on the intermediate transfer body is exposed by a developing device used in the black image forming unit. It is characterized in that charging means is provided to make the polarity opposite to that of the toner adhered to the body.

According to a fourth aspect of the present invention, there is provided an intermediate transfer member cleaning apparatus according to the first aspect, wherein the color electrophotographic apparatus is a black image in a tandem type image forming apparatus. The forming unit is disposed at an upstream position in the transport direction of the intermediate transfer member from the image forming units of the other colors, and the toner returning unit has a polarity opposite to that of the toner adhered on the photoconductor by the developing device used in the black image forming unit. And a cleaning member for removing transfer residual toner on the intermediate transfer body by applying

According to a fifth aspect of the present invention, there is provided a color electrophotographic apparatus including the intermediate transfer body cleaning apparatus according to any one of the first to fourth aspects, in order to achieve the first to third objects. It is characterized by that.

According to a sixth aspect of the present invention, there is provided a color electrophotographic apparatus according to the fifth aspect, wherein a toner containing a low softening point substance is used. Features.

According to a seventh aspect of the present invention, there is provided a color electrophotographic apparatus according to the fifth aspect, wherein the toner has a circularity of 90 or more.
It is characterized by the following.

According to an eighth aspect of the present invention, there is provided a color electrophotographic apparatus according to the fifth aspect, wherein a distribution curve of (toner charge amount) / (toner particle size) is achieved. It is characterized by using a toner having a half width of 2.2 [fC / 10 μm] or less.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention and is an overall schematic configuration diagram of a tandem-type indirect transfer type color copying machine.

In the figure, reference numeral 100 denotes a copying machine main body, 200 denotes a paper feed table on which the copying machine is mounted, 300 denotes a scanner mounted on the copying machine main body 100, and 400 denotes an automatic document feeder (ADF) further mounted thereon.

An endless belt-shaped intermediate transfer body 10 is provided at the center of the copying machine main body 100. In the intermediate transfer member 10, as shown in FIG. 2, the base layer 11 is made of a non-stretchable material such as fluororesin or canvas, and the elastic layer 1 is formed thereon.
2 is provided. The elastic layer 12 is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer 12 is coated with, for example, a fluorine-based resin and covered with a coat layer 13 having good smoothness.

Then, as shown in FIG.
The support rollers 14, 15, and 16 are wrapped around the support rollers 14, 15, and 16 so as to be rotatable clockwise in the drawing.

In the illustrated example, an intermediate transfer member cleaning device 17 for removing residual toner remaining on the intermediate transfer member 10 after image transfer is provided to the left of the second support roller 15 among the three.

The first support roller 14 of the three
Transfer member 10 stretched between the first support roller 15 and the second support roller 15
A tandem image forming apparatus 20 is formed by arranging four image forming units 18 of black, cyan, magenta, and yellow along the transport direction.

As shown in FIG. 1, an exposure device 21 is further provided on the tandem image forming device 20.

On the other hand, a secondary transfer device 22 is provided on the side opposite to the tandem image forming device 20 with the intermediate transfer member 10 interposed therebetween. In the illustrated example, the secondary transfer device 22 is configured by extending a secondary transfer belt 24, which is an endless belt, between two rollers 23, and presses the secondary transfer belt 24 against the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to a sheet.

A fixing device 25 for fixing a transferred image on a sheet is provided beside the secondary transfer device 22. Fixing device 25
Is a pressure roller 27 attached to a fixing belt 26 which is an endless belt.
Press to configure.

The above-mentioned secondary transfer device 22 has a sheet conveying function for conveying the sheet after image transfer to the fixing device 25. Of course, a non-contact charger may be provided as the secondary transfer device 22, and in such a case, it is difficult to additionally provide the sheet conveying function.

In the illustrated example, a sheet for reversing a sheet so as to record an image on both sides of the sheet is provided below the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming apparatus 20 described above. An inversion device 28 is provided.

When making a copy using this color copying machine, an original is set on the original table 30 of the automatic original transport device 400. Alternatively, the automatic document feeder 400 is opened and the contact glass 32 of the scanner 300 is opened.
The original is set on the upper part, and the automatic document feeder 400 is closed and pressed.

When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is conveyed and moved onto the contact glass 32, and then the document is placed on the contact glass 32. When set, the scanner 300 is immediately driven to travel on the first traveling body 33 and the second traveling body 34. And the first traveling body 3
3 emits light from the light source and further reflects the reflected light from the document surface to the second traveling body 34, where the second traveling body 3
The light is reflected by the mirror No. 4 and enters the reading sensor 36 through the imaging lens 35 to read the contents of the document.

When a start switch (not shown) is pressed, the support rollers 14, 15, 16 are driven by a drive motor (not shown).
Is rotationally driven to rotate the other two support rollers, and the intermediate transfer member 10 is rotationally conveyed. At the same time, the photoreceptor 40 is rotated by the individual image
A single color image of black, yellow, magenta, and cyan is formed on 0, respectively. Then, as the intermediate transfer body 10 is transported, the single-color images are sequentially transferred to form a composite toner image on the intermediate transfer body 10.

On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated to feed out a sheet from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. The sheet is separated one by one by a separation roller 45 and put into a sheet feeding path 46, conveyed by a conveying roller 47, guided to a sheet feeding path 48 in the copying machine main body 100, and stopped against a registration roller 49.

Alternatively, the sheet on the manual feed tray 51 is fed out by rotating the paper feed roller 50 and
The sheets are separated one by one and put into the manual sheet feeding path 53, and are similarly stopped against the registration rollers 49.

Then, the registration roller 49 is rotated in synchronization with the synthesized toner image on the intermediate transfer body 10, and a sheet is fed between the intermediate transfer body 10 and the secondary transfer device 22, and Transfer and record a color image on the sheet.

The sheet after image transfer is transferred to a secondary transfer device 22.
The fixing device 25 applies heat and pressure to fix the transferred image, and then the switching claw 55
And the sheet is discharged by the discharge roller 56 and the discharge tray 57
Stack on top. Alternatively, the sheet is switched by the switching claw 55 to enter the sheet reversing device 28, where it is reversed and guided again to the transfer position, the image is also recorded on the back surface, and then the discharge roller 56
To discharge onto the discharge tray 57.

On the other hand, the intermediate transfer member 10 after the image transfer is removed by an intermediate transfer member cleaning device 17 to remove the residual toner remaining on the intermediate transfer member 10 after the image transfer, and the image is again formed by the tandem image forming device 20. Prepare for.

Here, a bias is applied to the resist roller 49 using a conductive rubber roller. With diameter φ18,
The surface is made of conductive NBR rubber having a thickness of 1 mm. The electric resistance is about 10E9 Ωcm as the volume resistance of the rubber material, and the applied voltage is about −850 V on the side (front side) where the toner is transferred.

A voltage of about +200 V is applied to the back side of the sheet, but may be grounded especially when it is not necessary to consider the transfer of paper powder on the back side. Although a DC bias is applied as an applied voltage, this may be an AC voltage having a DC offset component.

The AC superimposed DC bias can more uniformly charge the sheet surface. The sheet surface after passing through the registration roller 49 is slightly negatively charged. Therefore, in the transfer from the intermediate transfer body 10 to the sheet,
It should be noted that the transfer condition may be changed as compared with the case where no voltage is applied to the registration roller 49.

The tandem image forming apparatus 20 described above
In detail, each of the image forming units 18 includes, for example, a charging device 60, a developing device 61, a primary transfer device 62,
A photoconductor cleaning device 63, a neutralization device 64, and the like are provided. In the illustrated example, the photoreceptor 40 has a drum shape in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a base tube made of aluminum or the like, but may have an endless belt shape.

Although not shown, at least the photosensitive member 40 is provided, and a process cartridge is formed by all or a part of the portion constituting the image forming means 18.
May be made detachable collectively to improve maintainability.

Of the parts constituting the image forming means 18,
The charging device 60 is formed in a roller shape in the illustrated example, and contacts the photoreceptor 40 to apply a voltage to the photoreceptor 4.
0 is charged.

The developing device 61 may use a one-component developer, but in the illustrated example, a two-component developer composed of a magnetic carrier and a non-magnetic toner is used. Then, the agitating section 66 which transports the two-component developer while agitating it and adheres to the developing sleeve 65, and the developing section 67 which transfers the toner of the two-component developer adhered to the developing sleeve 65 to the photoconductor 40. And the agitating section 66 is positioned lower than the developing section 67.

The stirring unit 66 has two parallel screws 6.
8 is provided. The two screws 68 are partitioned by a partition plate 69 except for both ends (see FIG. 6). Further, a toner concentration sensor 71 is attached to the developing case 70.

On the other hand, a developing sleeve 65 is provided in the developing section 67 so as to face the photoconductor 40 through the opening of the developing case 70, and a magnet 72 is fixedly provided in the developing sleeve 65. In addition, a doctor blade 73 is provided with the tip approaching the developing sleeve 65. In the illustrated example, the interval at the closest part between the doctor blade 73 and the developing sleeve 65 is set to 500 μm.

Then, the two-component developer is supplied to two screws 6
The toner is conveyed and circulated while being stirred at 8, and supplied to the developing sleeve 65. The developer supplied to the developing sleeve 65 is pumped up and held by the magnet 72 to form a magnetic brush on the developing sleeve 65. The magnetic brush is cut into an appropriate amount by the doctor blade 73 as the developing sleeve 65 rotates. The cut-off developer is supplied to the stirring unit 6.
Returned to 6.

On the other hand, the toner in the developer on the developing sleeve 65 is transferred to the photosensitive member 40 by the developing bias voltage applied to the developing sleeve 65, and the electrostatic latent image on the photosensitive member 40 is visualized. . After the visualization, the developer remaining on the developing sleeve 65 separates from the developing sleeve 65 and returns to the agitating section 66 where there is no magnetic force of the magnet 72. As a result of this repetition, when the toner concentration in the stirring section 66 becomes low, the toner density is detected by the toner concentration sensor 71 and the stirring section 66 is detected.
Replenish the toner.

In the illustrated example, the linear velocity of the photosensitive member 40 is 200 mm / s, and the linear velocity of the developing sleeve 65 is 240 mm / s. The development process is performed with the diameter of the photoconductor 40 being 50 mm and the diameter of the developing sleeve 65 being 18 mm. The toner charge amount on the developing sleeve 65 is -10 to -30 μm.
It is in the range of C / g. The developing gap _GP, which is the gap between the photoconductor 40 and the developing sleeve 65, can be set in the range of 0.8 mm to 0.4 mm in the related art, and it is possible to improve the developing efficiency by reducing the value.

The thickness of the photosensitive member 40 is set to 30 μm and the optical system
Beam spot diameter of 50 × 60 μm and light amount of 0.47
mW. Further, the charging (before exposure) of the photoconductor 40 is performed.
Rank V ₀Is -700 V, the post-exposure potential V_LIs -120V
To a developing bias voltage of -470 V, that is, a developing potential.
The developing process is performed at 350 V.

Next, the primary transfer device 62 is provided in the form of a roller and pressed against the photosensitive member 40 with the intermediate transfer member 10 interposed therebetween. Separately, the present invention is not limited to the roller shape, and may be a non-contact corona charger or the like.

The photosensitive member cleaning device 63 is provided with a cleaning blade 75 made of, for example, polyurethane rubber with its tip pressed against the photosensitive member 40, and has an outer periphery in contact with the photosensitive member 40 to indicate a conductive fur brush 76. Provide rotatable in the direction. Further, a metal electric field roller 77 for applying a bias to the fur brush 76 is rotatably provided in the direction of the arrow, and the tip of the scraper 78 is pressed against the electric field roller 77. Further, a collecting screw 79 for collecting the removed toner is provided.

Then, the residual toner on the photoconductor 40 is removed by the fur brush 76 that rotates in the counter direction with respect to the photoconductor 40. The toner adhering to the fur brush 76 is removed by an electric field roller 77 that rotates in the counter direction with respect to the fur brush 76 and applies a bias. The electric field roller 77 is cleaned by a scraper 78. The toner collected by the photoconductor cleaning device 63 is brought to one side of the photoconductor cleaning device 63 by a collection screw 79,
For details, the toner is returned to the developing device 61 by the toner recycling device 80 described later and reused.

The static eliminator 64 is, for example, a lamp, and irradiates light to initialize the surface potential of the photoconductor 40.

Then, as the photosensitive member 40 rotates, first, the surface of the photosensitive member 40 is uniformly charged by the charging device 60, and then written by the above-described exposure device 21 using a laser, LED, or the like in accordance with the contents read by the scanner 300. Irradiation of light L forms an electrostatic latent image on photoconductor 40.

Thereafter, the electrostatic latent image is visualized by attaching toner with the developing device 61, and the visible image is transferred onto the intermediate transfer body 10 by the primary transfer device 62. The surface of the photoreceptor 40 after the image transfer is cleaned by removing the residual toner by the photoreceptor cleaning device 63, and the charge is removed by the charge removing device 64 to prepare for the image formation again.

FIG. 4 is an enlarged view of a main part of the color copying machine shown in FIG. In the figure, a tandem image forming apparatus 2
0, each photoconductor 40 of the image forming unit 18, each developing device 61, each photoconductor cleaning device 63, and each primary unit provided to face the photoconductor 40 of each image forming unit 18. After each symbol of the transfer device 62,
BK for black, Y for yellow
, M for magenta, and C for cyan.

FIGS. 5 and 6 show a toner recycling apparatus 80. FIG. As shown in FIG. 5, a roller 82 having a pin 81 is provided at one end of the collection screw 79 of the photoconductor cleaning device 63. And the roller portion 8
2 is placed on one side of the belt-shaped collected toner conveying member 83 of the toner recycling device 80, and the collected toner conveying member 8
The pin 81 is inserted into the third long hole 84. Blades 85 are provided at regular intervals on the outer periphery of the collected toner conveying member 83,
The other side is hung on the roller portion 87 of the rotating shaft 86.

The collected toner conveying member 83 is put in a conveying path case 88 shown in FIG. The transport path case 88 is formed integrally with the cartridge case 89, and one of the two screws 68 of the developing device 61 described above is inserted into the end of the developing device 61 on the side thereof.

Then, the driving force is transmitted from the outside to rotate the collecting screw 79 and the collected toner conveying member 8
3, the toner collected by the photoconductor cleaning device 63 is conveyed to the developing device 61 through the conveying path case 88, and is put into the developing device 61 by the rotation of the screw 68. Thereafter, as described above, the toner is conveyed and circulated while being stirred by the two screws 68 together with the developer already in the developing device 61, supplied to the developing sleeve 65 and cut off by the doctor blade 73, and then cut off by the photoconductor 40. And the latent image on the photoreceptor 40 is developed.

The toner has a charge characteristic by mixing a charge control agent (CCA) and a colorant with a resin such as polyester, polyol or styrene acrylic, and then externally adding a substance such as silica or titanium oxide. , Increasing liquidity. The particle size of the additive is usually in the range of 0.1 to 1.5 [μm]. Coloring agents include carbon black, phthalocyanine blue, quinacridone, carmine and the like.
The charging polarity is negative charging in the illustrated example.

As the toner, a toner obtained by externally adding the above type of additives to a base toner in which wax or the like is dispersed and mixed can be used. In the above description, the toner is prepared by a pulverization method, but a toner prepared by a polymerization method or the like can also be used. Generally, a toner formed by a polymerization method, a heating method, or the like can have a shape factor of 90% or more, and further has a very high additive coverage depending on the shape.

Here, the shape factor is originally sphericity and is defined as “surface area of sphere having the same volume as particle / surface area of actual particle * 100%”. However, since measurement becomes considerably difficult, , The degree of circularity. The definition is “perimeter of a circle having the same projected area as a particle / projected contour length of a real particle * 100”.
% ". Then, the closer the projected circle is to a perfect circle, the closer to 100%.

The volume average particle diameter of the toner ranges from 3 to 12
μm is preferred. In the illustrated example, it is 6 μm and 1200 μm.
It is possible to sufficiently cope with high-resolution images of dpi or more.

The magnetic particles contain a magnetic material such as ferrite with a metal or resin as a core, and the surface layer is coated with a silicon resin or the like. The particle size is preferably in the range of 20 to 50 μm. The optimum resistance is a dynamic resistance in the range of 10 ⁴ to 10 ⁶ Ω. However, the measuring method is a roller with a magnet inside (φ20; 600 RPM)
An electrode having an area of 65 mm in width and 1 mm in length is brought into contact with a gap of 0.9 mm, and an applied voltage of an upper limit level of withstand voltage (400 V for high-resistance silicon-coated carrier to several V for iron powder carrier) is applied. This is the measured value when the measurement is performed.

The developing sleeve 65 has a non-magnetic rotatable sleeve-like shape, and has a plurality of magnets 7 therein.
2 are arranged. Since the magnet 72 is fixed, a magnetic force can be applied when the developer passes through a predetermined place. In the illustrated example, the diameter of the developing sleeve 65 is φ18, and the surface is subjected to sandblasting or a process of forming a plurality of grooves having a depth of 1 to several mm so as to be within a range of 10 to 30 μm RZ.

The magnet 72 moves N ₁ , S ₁ , N ₁ from the doctor blade 73 in the rotation direction of the developing sleeve 65.
₂ , S ₂ , and S ₃ . The (toner + magnetic particles) formed by the magnet 72 is carried on the developing sleeve 65 as a developer, and the toner obtains a prescribed charge amount by being mixed with the magnetic particles. In the illustrated example, -10 to
A range of −30 [μC / g] is preferable. Developing sleeve 6
5 is a magnet 72 formed with a magnetic brush of developer.
In the area on the S1 side of the photoconductor 40, the photoconductor 40 is disposed.

As shown in FIG. 7, the cleaning device 90 for removing the transfer residual toner on the intermediate transfer member 10 and the transfer residual toner on the intermediate transfer member 10 are provided in the intermediate transfer member cleaning device 17 in detail. And a toner returning means 91 for returning to the developing device 61BK used in the black image forming means 18BK in the tandem type image forming apparatus 20.

In the cleaning means 90, a fur brush 93 and a cleaning blade 94 as cleaning members are provided in a cleaning case 92, and a recovery screw 95 is provided. The fur brush 93 has its outer periphery in contact with the intermediate transfer member 10 and transmits rotation from a driving source (not shown) to be rotatable in the direction of the arrow in the figure. On the other hand, the cleaning blade 94 is made of, for example, polyurethane and has its tip pressed against the intermediate transfer body 10. The collection screw 95 brings the toner removed by the cleaning members to one side of the cleaning case 92.

The toner returning means 91 carries a toner conveying member 96 such as a spring coil, for example, which conveys the toner removed by the cleaning means 90, and a toner conveyed by the toner conveying member 96 into a black image forming means. To the developing device 61BK used in 18BK,
Toner conveying path forming member 9 such as a collecting pipe and a collecting tube
7 is provided.

Then, the fur brush 93 is rotated while the intermediate transfer body 10 is conveyed in the direction of the arrow in the figure, and the transfer residual toner on the intermediate transfer body 10 is removed by the fur brush 93 and the cleaning blade 94 as the cleaning members. . The removed toner is brought to one side in the longitudinal direction of the cleaning case 92 by the collecting screw 95 and is put into the toner conveying path forming member 97. The toner contained in the toner conveying path forming member 97 is conveyed by the toner conveying member 96 while being guided by the toner conveying path forming member 97, and is returned to the black developing device 61BK for recycling.

As the toner conveying member 96, besides a spring coil, a screw belt or the like can be used, and a pump can also be used. When a pump is used as the toner conveying member 96, for example, the developing device 61
It is installed on the BK side and sucks the collected toner from the cleaning means 90 side. Alternatively, the collected toner is sent to the developing device 61BK by installing the cleaning device 90 using an air pump.

In the above-described example, the intermediate transfer body cleaning device 17 is constituted by the cleaning means 90 and the toner return means 91. However, for example, in FIG.
As shown in FIG. 6, the developing device 61B uses the transfer residual toner on the intermediate transfer body 10 in the black image forming unit 18BK.
A charging means 102 for adjusting the polarity to the opposite polarity to the toner adhered on the photoconductor 40BK by K may be provided.

As the charging means 102, for example, as shown in FIG. 8, a conductive roller is provided in contact with the intermediate transfer member 10, and a bias is applied to the conductive roller to inject a charge, for example, as shown in FIG. As described above, a corona charger is provided, and a charge is applied by a discharge phenomenon. Although not shown, charged particles are generated by a charge generation device such as a conductive brush or a scorotron charger, and the charged particles are attached to the toner to apply a charge. Then, the transfer residual toner on the intermediate transfer body 10 is transferred to the photoconductor 40 by the developing device 61BK used in the black image forming unit 18BK.
The polarity is made opposite to the polarity of the toner adhered on the BK.

That is, in the developing device 61BK, the toner is negatively charged and adheres to the photosensitive member 40BK. In the primary transfer device 62BK, a bias is applied and the photoconductor 40BK is applied.
The upper toner is transferred onto the intermediate transfer member 10. In the secondary transfer device 22, a bias is applied to transfer the toner on the intermediate transfer body 10 onto the sheet.

However, in the secondary transfer device 22, since a strong electric field having a positive polarity opposite to that of the negative toner is applied, the transfer residual toner on the intermediate transfer member 10 has a positive polarity, that is, the photoconductor 40BK is developed by the developing device 61BK. In many cases, the toner is charged in a polarity opposite to that of the toner adhered on the toner. However, not all of the transfer residual toner is charged to the opposite polarity, and there are also those which are partially neutralized and have no charge, and those which maintain the negative polarity as before. .

In the charging means 102, the transfer residual toner having various polarities on the intermediate transfer member 10 is transferred to the developing device 61B.
With K, the polarity is adjusted to the positive polarity which is the reverse polarity of the toner attached to the photoconductor 40BK.

As described above, in the tandem image forming apparatus 20, the black image forming means 18BK is
The image forming units 18Y, 18M, and 18C for the other colors are arranged at an upstream position in the intermediate transfer body conveying direction. Therefore, when the transfer residual toner on the intermediate transfer body 10 reaches the black primary transfer position while the intermediate transfer body 10 is being transported, the toner (negative polarity) on the photoconductor 40BK is biased by the primary transfer device 62BK. Is transferred onto the intermediate transfer member 10, the transfer residual toner (positive polarity) on the intermediate transfer member 10 is transferred to the photoconductor 40BK side. And the photoconductor 40BK
The toner transferred to the upper side is the photoconductor cleaning device 63B.
K, and the developing device 61 is removed by the toner recycling device 80.
Return to BK.

Here, since the negative polarity toner on the photoconductor 40BK and the positive polarity transfer residual toner on the intermediate transfer body 10 only come into contact for a short time, their charges are not canceled out.

In the example shown in FIG. 8, a conductive support 105 is provided at the center of the conductive roller, and a rubber support is provided around the conductive support.
An elastic layer 106 made of resin or the like is provided, and a coating layer 107 is provided therearound. As the conductive support 105, a metal such as aluminum, iron, copper, stainless steel, or an alloy thereof, or a conductive resin in which carbon, metal particles, or the like are dispersed is used.

The elastic layer 106 only needs to have such a hardness that it can be brought into contact with the intermediate transfer member 10 without any gap, and that it has a certain electric breakdown voltage against an applied bias.
Specifically, acrylonitrile-butadiene (NB
R), styrene butadiene rubber, butadiene rubber, ethylene propylene rubber, chloroprene rubber, chlorosulfonated polyethylene rubber, chlorinated polyethylene rubber, acrylic rubber, fluorine rubber, urethane rubber and the like.
The resistance value is 10E7 to 10E11Ω in volume resistivity.
Cm (when 1 kV is applied) is desirable.

As the toner returning means 91, although not shown, the developing device 61BK used in the black image forming means 18BK applies a polarity opposite to that of the toner adhered on the photoreceptor 40BK to the intermediate transfer body 10, A cleaning member for removing transfer residual toner may be provided.

Then, for example, a positive bias is applied to the cleaning member to remove the negatively charged toner among the transfer residual toner on the intermediate transfer body 10. On the other hand, the positively charged toner is left on the intermediate transfer body 10 as it is, and when it reaches the black primary transfer position, the toner is replaced with the toner on the photosensitive body 40BK by the bias of the primary transfer device 62BK. The toner is transferred to the body 40BK side, removed by the photoconductor cleaning device 63BK, and returned to the developing device 61BK by the toner recycling device 80.

The toner developed on the photoreceptor 40 by the developing device 61 has a solid portion of 0.65 mg / c.
It was m ^2. PVDF (polyvinyldene fluoride) or E
TFE (ethylene tetrafluoroethylene copolymer),
When the intermediate transfer member 10 made of PET (polyethylene terephthalate) or the like is used, the primary transfer rate from the photosensitive member 40 to the intermediate transfer member 10 is approximately 95%, and the secondary transfer from the intermediate transfer member 10 to a sheet is performed. The ratio is approximately 90%. At this time, the primary transfer residual toner is returned from the photoconductor cleaning device 63 to each of the developing devices 61 for use.

The residual toner that has not been subjected to the secondary transfer is 0.062 mg / cm ² per color. For example, when a color image is composed of four color (black, yellow, magenta and cyan) toners, About 0.185 mg / cm ^{2 of} color toner is collected for up to three colors.

When the recovered toner is mixed and returned to the black developing device 61BK for reuse, the maximum possible value is (0.185) / (0.185+
0.65) = approximately 22% of the black toner is reused color toner.

At this time, what is most worrisome is the optical density and color of the black toner on the sheet. In this example, the A4 size color chart having an image area ratio of 7% for each color is printed on 1,000 sheets. When the optical density of the black toner image on the sheet was measured, the first sheet had an image density of 1.65 and the 1000th sheet had an image density of about 1.61, and no appreciable decrease in the image density was observed. . Although the color was also a concern, the fluctuation was almost within the range of the measurement error.

However, the above-described experiment is performed under ideal conditions in which the image area ratios of the color toners are the same. In actual use, for example, a large amount of cyan-only images may be printed. In such a case, the image area ratio is measured by counting pixel data or the like, and magenta and yellow toners, which are complementary colors of cyan, are positively supplied to the black developing device 61BK for color adjustment. Work is also important in maintaining color.

Next, the toner used in the above-described color electrophotographic apparatus of the illustrated example will be described.

In the illustrated electrophotographic apparatus, a toner containing a substance having a low softening point, so-called wax, is used. Waxes include natural and synthetic waxes. A typical example of the former is carnauba wax, and a typical example of the latter is polypropylene. These substances are present alone without ever reacting with the toner resin.

The presence of the wax outside the toner resin functions as a lubricant, so to speak. Due to this effect, the toner resin itself is not crushed even if it comes into contact with the cleaning member without pain. By the way, when we performed a quality test over time with or without wax,
In the case of the toner without wax, the toner deteriorates at 190K sheets, the degree of aggregation increases, the developing ability decreases, and the image quality deteriorates. However, the toner containing 3% by weight of carnauba wax deteriorates up to 250K sheets. It was possible to maintain image quality by continuing recycling without recycling.

As the toner, those prepared by a pulverization method and a polymerization method can be used. The surface of the toner produced by this method can be smoothed, and a toner having a shape factor, that is, a circularity of 90% or more can be produced. Spherical toner generally has an index represented by sphericity. With the true sphere being 1, the sphericity decreases as the pulverized toner becomes.

Assuming that the circularity of the projected image of the sphericity is SR, SR = (perimeter of a circle having the same area as the projected area of the particle /
It can be defined as (perimeter of a particle projected image) × 100%, and the closer the toner is to a true sphere, the closer to 100%.

The effect of toner spheroidization will be described in comparison with a conventional pulverized (irregular) toner. Similarly, the toner B (this embodiment) has 0.5% by weight of silica and 0.7% by weight of titanium oxide with respect to the conventional toner A (0.2% by weight of silica and 0.3% by weight of titanium oxide). One of the main functions of the additive is to reduce the cohesive force of the toners to prevent the toners from forming agglomerated masses, and to make them as “unraveled” as possible for uniform development,
The purpose is to obtain transfer characteristics. At this time, considering the ratio of the toner B adhering around the mother toner in terms of the coverage, the toner B has a small surface area compared to the conventional toner A because the toner B is nearly spherical. To that extent, the coverage of the toner B with the additive is increased, and the fluidity is improved, so that the toner B can easily move on the developing sleeve 65 and the developing ability is increased. When a toner having a circularity of 90 or more is used, the transfer rate is improved by smoothing the surface, and a value of 92% is obtained for the transfer rate of 88% with the conventional pulverized toner. As a result, the amount of recycled toner is reduced and the image is not deteriorated because it is less susceptible to toner crushing during recycling.

Next, the distribution curve of (toner charge amount) / (toner particle size) will be described below.

The particle size and charge distribution of the toner on the developing sleeve 65 are measured. For measurement, E-SPART ANALYZER manufactured by Hosokawa Micron Corporation was used. Although a detailed description of the E-SPART ANALYZER is omitted, air of the toner on the developing sleeve 65 is blown off to catch the movement in the electric field, thereby obtaining data of the particle size and charge amount of each toner. . Incidentally, in this confirmation experiment, 3000 toners were sampled, and the difference in distribution was observed. Here, the distribution of q / d is mainly compared by dividing the charge amount of the toner by the toner particle size. This is because the charge amount depends on the particle size of the toner.

The toner used in the examples is most preferably a dry toner containing the modified polyester at least as a toner binder and a toner prepared by a polymerization method.
The case using the former toner will be described. The shape factor of the toner is SF = 95%. Therefore, when the particle size and the charge amount distribution of the toner on the developing sleeve were measured initially, the charge amount distribution became sharp as shown in FIG. The half width is 1.1 [fC / 10 μm].
Met.

An index relating to sharpness is generally represented by a half-value width, and the smaller the value, the sharper. Generally, when the distribution is sharp, there are many toners having q / d values close to each other, and uniform development can be achieved because the developing ability is the same. Conversely, when the distribution is broad, the range of the toner charge amount existing is widened and the range of the developing ability is also widened, so that the development amount fluctuates, and when the low charge amount side increases, background fouling is likely to occur. .

Next, the same half width after recycling was found to be 1.7 [fC / 10 μm]. Further, when the value after recycling was measured by a system using a general pulverized toner, it was 2.7 [fC / 10 μm].

FIG. 11 shows the relationship between the above-mentioned half width and background contamination.
It is known that the difference between the reflection densities with respect to the undeveloped transfer paper is used as ΔID. As a result, in the case of the conventional pulverized toner, the background fouling property after recycling is reduced. However, when a toner having a half width of 2.2 or less is used, a sufficient amount of charge is maintained and image quality is not deteriorated even if recycling is performed.

Next, the elasticity of the intermediate transfer member 10 will be described.
This will be described below.

The range of the hardness HS of the intermediate transfer member 10 is preferably set to 10 ≦ HS ≦ 60 ° (JIS-A). When a belt is used, the hardness is sufficiently low, but there is a possibility that the belt will slip at the drive transmission unit. On the other hand, when a rigid roller is used, unevenness in rotation, that is, running, can be extremely reduced. However, if the hardness is too high, the margin due to accuracy is narrowed, and there is a possibility that the photoconductor 40 does not adhere well. Therefore, the intermediate transfer member 1
By providing the elastic layer 12 at 0, the hardness is reduced, the flexibility is given, the degree of close contact with the photoreceptor 40 is improved, the transfer rate is improved, and the image quality is reduced by reducing the amount of recycled toner. This is to avoid and maintain image quality.

If the hardness is lower than 10 ° JIS-A, it is very difficult to mold with high dimensional accuracy. this is,
This is due to the fact that they tend to contract and expand during molding. Also,
In the case of softening, it is a general method to contain an oil component in the base material, but it has a drawback that when it is operated continuously in a pressurized state, it oozes out. Thereby, the toner carried on the surface of the intermediate transfer body 10 is contaminated,
It was found that the transfer rate was significantly reduced.

On the other hand, those having a hardness of 60 ° JIS-A or more can be molded with high accuracy due to the increased hardness.
Since the oil content can be kept low, the contamination of the toner can be reduced. However, since the usable range in consideration of the contact pressure is narrowed, it is necessary to set the biting amount or the contact pressure accurately.

FIG. 12 shows the relationship between the hardness of the intermediate transfer member 10 and the amount of biting into the photoreceptor 40 using the contact pressure as a parameter. 3 to 8 gf / mm for A, 3 to 12 gf for intermediate transfer roller B
/ Mm, the bite widths are 0.02 mm and 0.05 mm, respectively. The intermediate transfer roller A has a dimensional accuracy of about 2. That would have to be increased by a factor of five.

Therefore, the type of the intermediate transfer roller B has a wider margin. Compared with the conventional intermediate transfer roller A (hardness of 61 JIS-A) having relatively high hardness, the transfer ratio of the intermediate transfer roller B (hardness of 40 JIS-A) of the present invention is measured. With the intermediate transfer roller B of the present invention, a value of 94% is obtained with respect to 90%, and the amount of recycled toner is reduced, and the image is deteriorated because it is less susceptible to toner pulverization at the time of recycling. do not do.

[0115]

As described above, according to the first aspect of the present invention, there is provided a toner return means for returning the transfer residual toner on the intermediate transfer member to the black developing device in the tandem type image forming apparatus. In a color indirect transfer type color electrophotographic apparatus, even if a color mixture occurs in the collected toner, it is possible to reuse the transfer residual toner on the intermediate transfer body without impairing the optical density and color by returning to the black developing device. Can be possible. In addition, the generation of waste toner can be reduced, environmental protection and resource saving can be realized, and maintenance cost can be reduced.

According to the second aspect of the present invention, a cleaning means is provided, and as a toner returning means, a toner conveying member for conveying the toner removed by the cleaning means and the toner conveyed by the toner conveying means are guided to the black developing device. Since the toner transfer path forming member is provided, the transfer residual toner on the intermediate transfer body can be recycled and used with a simpler configuration.

According to the third aspect of the present invention, as the toner returning means, there is provided a charging means for aligning the transfer residual toner on the intermediate transfer member with a polarity opposite to that of the toner adhered on the photoreceptor by the black developing device. In addition, even if the polarity of the toner changes, the charging means aligns the polarity to improve the recycling efficiency, enables the use of the transfer residual toner on the intermediate transfer body to be recycled, and reduces the generation of waste toner. be able to. Further, since no mechanical load is applied, the life of the intermediate transfer member can be prolonged, and the deterioration of the toner can be reduced.

According to the fourth aspect of the present invention, as the toner returning means, a cleaning member for removing the transfer residual toner on the intermediate transfer member by applying a polarity opposite to that of the toner adhered on the photosensitive member by the black developing device. Therefore, in addition to the mechanical cleaning by the cleaning member, even if the polarity of the toner changes, the charging efficiency also makes the polarity uniform to improve the recycling efficiency and recycle the residual toner on the intermediate transfer body. And waste toner can be further reduced. Further, since the mechanical load is reduced, the life of the intermediate transfer member can be prolonged, and the deterioration of the toner can be reduced.

According to the fifth aspect of the present invention, since the intermediate transfer body cleaning device according to any one of the first to fourth aspects is provided, a color electrophotographic apparatus having the above-described effects can be obtained.

According to the sixth aspect of the invention, in such a color electrophotographic apparatus, a toner containing a low softening point substance is used. Deterioration can be prevented, and a decrease in image quality can be prevented.

According to the seventh aspect of the present invention, in the above-described color electrophotographic apparatus, the toner having a circularity of 90 or more is used. As a result, the amount of recycled toner can be reduced, the deterioration of the toner can be prevented, and the deterioration of the image quality can be prevented.

According to the eighth aspect of the present invention, in the above-described color electrophotographic apparatus, (the charge amount of the toner) /
In the distribution curve of (toner particle size), the half width is 2.2 [f].
C / 10 μm] or less, and in addition, the distribution curve is kept sharp, the toner component ratio does not fluctuate at the time of toner recycling, toner deterioration is prevented, and image quality is prevented from deteriorating. be able to.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention and is an overall schematic configuration diagram of a tandem-type indirect transfer type color copying machine.

FIG. 2 is a partially enlarged sectional view showing a sectional structure of an intermediate transfer member used in the color copying machine.

FIG. 3 is a partially enlarged configuration diagram of a dandem image forming apparatus used in the color copying machine.

FIG. 4 is an enlarged configuration diagram of a main part of the color copying machine.

FIG. 5 is an exploded perspective view illustrating a toner recycling device used in the color copying machine.

FIG. 6 is a cutaway perspective view on the developing device side of the toner recycling device.

FIG. 7 is an enlarged configuration diagram around an intermediate transfer body cleaning device in the color copying machine.

FIG. 8 is an enlarged configuration diagram around another intermediate transfer body cleaning device.

FIG. 9 is an enlarged configuration diagram around another intermediate transfer body cleaning device.

FIG. 10 is a distribution curve diagram of (toner charge amount) / (toner particle size).

FIG. 11 is a diagram showing the relationship between the half-width of the distribution curve and background contamination.

FIG. 12 is a relationship diagram between the hardness of the intermediate transfer member and the amount of bite into the image carrier.

FIG. 13 is a state explanatory view showing a state of a change in toner and paper adhering matter in a conventional color electrophotographic apparatus.

FIG. 14 is a main part configuration diagram of a tandem type direct transfer type electrophotographic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Intermediate transfer body 12 Elastic layer 17 Intermediate transfer body cleaning device 18 Image forming means 18BK Black image forming means 20 Tandem image forming apparatus 40 Photoconductor 61 Developing device 61BK Black developing device 63 Photoconductor cleaning device 80 Toner recycling device 90 Cleaning Means 91 Toner Return Means 92 Cleaning Case 93 Fur Brush (Cleaning Member) 94 Cleaning Blade (Cleaning Member) 95 Collection Screw 96 Toner Conveying Member 97 Toner Conveying Path Forming Member 102 Charging Means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/08 365 G03G 15/16 15/08 507 9/08 361 15/16 15/08 507D 21/10 21/00 310 F term (reference) 2H005 AA06 AA15 AA21 CA14 CB18 DA01 DA07 EA05 2H030 AA04 AB02 AD01 AD02 AD03 AD16 BB22 BB42 BB46 BB63 BB71 2H032 AA05 AA15 BA01 BA02 BA05 BA09 BA23 BA30 2H016 AA01 AC02 JB01 KB11 KB12 KG01 KG03 KG04 KG07 KH17 KJ02

Claims (8)

[Claims] 1. A color electrophotographic apparatus for forming a synthetic toner image on an intermediate transfer member using a tandem image forming apparatus and transferring the toner image to record a color image on a sheet, wherein the intermediate transfer member is provided. A toner return unit that returns the upper transfer residual toner to a developing device used in a black image forming unit in the tandem image forming apparatus;
Intermediate transfer member cleaning device. 2. A toner conveying member for removing toner remaining after transfer on the intermediate transfer member, and as the toner returning unit, a toner conveying member for conveying the toner removed by the cleaning unit, and a toner conveying member for conveying the toner. 2. The intermediate transfer member cleaning device according to claim 1, further comprising a toner conveying path forming member that guides the toner to be transferred to a developing device used in the black image forming unit. 3. The color electrophotographic apparatus, wherein the black image forming means in the tandem type image forming apparatus is arranged at a position upstream of the other color image forming means in the transport direction of the intermediate transfer member, and the toner is As a return means,
2. The intermediate transfer body according to claim 1, further comprising a charging unit that aligns the transfer residual toner on the intermediate transfer body with a polarity opposite to that of the toner attached on the photoconductor by a developing device used in the black image forming unit. 3. Cleaning device. 4. The color electrophotographic apparatus according to claim 1, wherein the black image forming unit in the tandem type image forming apparatus is arranged at an upstream position in a conveying direction of the intermediate transfer member from another color image forming unit. A cleaning member for removing toner remaining after transfer on the intermediate transfer body by applying a polarity opposite to that of the toner adhered on the photoconductor by a developing device used in the black image forming means as the toner return means. Item 2. An intermediate transfer member cleaning device according to Item 1. 5. A color electrophotographic apparatus comprising the intermediate transfer member cleaning device according to claim 1. Description: 6. The color electrophotographic apparatus according to claim 5, wherein a toner containing a low softening point substance is used. 7. The color electrophotographic apparatus according to claim 5, wherein a toner having a circularity of 90 or more is used. 8. The color electronic device according to claim 5, wherein a toner having a half width of 2.2 [fC / 10 μm] or less in a distribution curve of (toner charge amount) / (toner particle size) is used. Photo equipment.