JP2763145B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an image forming apparatus using an electrophotographic recording technique, such as a copying machine and a laser printer, and more particularly to a corona transfer device. To an image forming apparatus.

(Prior Art) Generally, an image forming apparatus using an electrophotographic method uses a photoconductor having photoconductivity. A charging step of applying a corona charge to the photoreceptor, an exposure step of irradiating the photoreceptor with an optical signal such as a laser to form an electrostatic latent image, and a coloring powder (hereinafter referred to as toner) Is developed on the photoreceptor. As described above, the visualized image on the photoreceptor visualized by the toner overlaps the transfer material made of plain paper on the photoreceptor via the visualized image, and a corona discharge device, an electrode roller, etc. As a result, the visible image on the photosensitive member is transferred to the transfer material. The transfer material on which the developed image is recorded is then guided to heating and pressing means such as a heat roller or an oven heater, where the developed toner on the transfer material is melted and fixed on the transfer material. By the way, in such an image forming apparatus using plain paper as the transfer material, in the transfer step, how to efficiently transfer the visible toner of the photoconductor to the transfer material, that is, how to reduce the residual toner after the transfer. is important. These are affected by environmental conditions and deterioration of a developer composed of carrier (powder such as iron powder and ferrite) toner. The problem that the transfer actually occurs due to insufficient transfer is that the image quality is low, the image density is poor, the image transfer is poor, and the residual toner that has not been transferred is stored in the cleaning device, but the transfer is insufficient. Naturally, the amount of residual toner remaining in the cleaning device also increases, so that frequent replacement of the collection packs installed in the cleaning device and an increase in running costs become problems.

There is no problem as long as the residual toner can be sufficiently accommodated in the cleaning device. However, if the cleaning blade (urethane blade) of the cleaning device cannot be accommodated due to the increase in the residual toner and occurs in the form of toner scattering,
There is a possibility that secondary image defects may occur due to contamination inside the machine.

The above are various problems of the generally used image forming apparatus. Further, problems of the image forming and recording apparatus in the case of performing the simultaneous development and cleaning used in the present embodiment will be described.

In this recording apparatus, a memory removing brush is used as a substitute for the cleaning apparatus. As will be described in detail later, an image memory is generated depending on the polarity and the absolute amount of the residual toner after the transfer.

Such problems are mainly caused by a decrease in the surface resistance and internal resistance of the paper due to the moisture absorption state of the paper.

Therefore, how to maintain the normal state of the transfer becomes a problem. Conventionally, as a countermeasure against problems in the environment for plain paper, especially in high humidity, a method has been adopted in which the paper transport path is electrically floated or an appropriate bias voltage is applied to prevent leakage of electric charges through the paper. Or
In addition, there is a method of weakening the bonding force between the toner and the photoreceptor constituting the visual image before the transfer. The toner and the photoreceptor are linked by Coulomb force or other affinity. In order to weaken these, a method of reducing the photoreceptor potential by exposure before corona or corona discharge to weaken the cohesive force to weaken the Coulomb force before transfer, or adding an additive to the toner to increase the physical affinity with the photoreceptor Or a method of weakening.

However, in each case, a sufficient effect cannot be obtained and other adverse effects occur, so that it is insufficient to solve various transfer problems.

(Problem to be Solved by the Invention) With the simultaneous developing device, when the transfer efficiency is low, cleaning cannot be performed sufficiently, which causes deterioration of the next image. Accordingly, it is an object of the present invention to provide an image forming apparatus that performs image transfer with high transfer efficiency regardless of environmental conditions and types of transfer materials.

[Constitution of the Invention] (Means for Solving the Problems) The present invention has been made based on the above-mentioned problems, and includes a charging unit for charging a rotatable photoconductor to a specific polarity, Exposure means for forming an electrostatic latent image by exposing the charged photoreceptor, and the electrostatic latent image formed on the photoreceptor by the exposure means was charged to the same polarity as the specific polarity A developing and cleaning unit of a reversal developing method for supplying and developing a developer and removing a residual developer from an unexposed portion on the photoconductor, and formed on the photoconductor by the developing and cleaning unit. A transfer unit that electrostatically transfers the developer image from the photoconductor onto a transfer material by corona discharge, and downstream of the transfer unit along the rotation direction of the photoconductor, and of the charging unit. Provided in contact with the photoreceptor upstream A first disturbing unit configured to bundle a plurality of fibers and disturbing a residual developer remaining on the photoconductor after the transfer is performed by the transfer unit; and A residual developer that is provided downstream of the first disturbing means and upstream of the charging means in contact with the photoreceptor and is formed by bundling a plurality of fibers, and which has passed through the first disturbing means. And a voltage applying means for applying a voltage having a polarity opposite to the specific polarity to the first and second disturbing means, wherein the first and second disturbing means are provided. The fibers constituting the first disturbing means have an electric resistance of 10 ² to 10 ⁷ Ω · cm, and the fibers constituting the first disturbing means are thicker than the fibers constituting the second disturbing means. Or the thickness selected from 50 denier An image forming apparatus is provided.

(Operation) For example, in a transfer scorotron charger, the voltage applied to the grid portion is switched when the humidity environment changes. Suppose that in an environment with high humidity, the surface resistance of the paper and the internal resistance change due to the moisture absorption of the paper, and the potential rises near the contact portion of the paper with the photoreceptor. Problems such as avatars in the tone portion occur. At this time, the transfer voltage is improved by setting the applied voltage of the transfer grid portion to a lower voltage by the switch of the transformer so as to make the same potential state of the paper as in the normal normal humidity state and performing appropriate transfer.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows the appearance of an electrophotographic image forming apparatus using a semiconductor laser, and FIG. 3 shows the internal configuration thereof.
This image forming apparatus (laser printer) is a computer,
It is connected to a host system (not shown), which is an external output device such as a word processor, via a transmission controller such as an interface circuit. When a print start signal is received by the host system, an image recording operation is started, and the image is recorded on a sheet as a transfer material and output.

 This image forming apparatus has the following configuration.

That is, in the figure, reference numeral 1 denotes an apparatus main body.
The main control board 2 is arranged at the center of the inside. An electrophotographic process unit 3 for forming an image is arranged behind the main control board 2 (to the right in the state shown in FIG. 3), and a plurality of functions for additional functions are provided in the lower front part. A control board accommodating section 5 for accommodating a plurality of control boards 4 is provided, and a paper discharge section 6 is formed at an upper front portion.

Further, a lower part in the apparatus main body 1 is a cassette accommodating portion 8 for accommodating the paper feed cassette 7.

As shown in FIG. 2, the paper discharge unit 6 includes a recess formed on the upper surface of the front part of the apparatus main body 1,
A rotatable paper discharge tray 9 that can be folded on the paper discharge unit 6 or deployed as shown in the figure is provided. Further, a notch 9a is formed at the center of the front end of the sheet discharge tray 9, and a rotatable U-shaped auxiliary sheet discharger that can be accommodated in the notch 9a or developed as shown in the figure. A tray 10 is provided. Then, the size of the paper discharge unit 6 can be adjusted according to the size of the paper P as a recording medium to be discharged.

Further, a control panel 11 is disposed on the upper surface of the left frame 1a of the apparatus main body located on the left side of the paper discharge unit 6, and a manual feed tray 12 is mounted on the rear side of the apparatus main body 1. It is in a state of being left.

Next, the electrophotographic process unit 3 for performing an electrophotographic process such as charging, exposure, development, transfer, peeling, cleaning and fixing will be described with reference to FIGS. 3 and 4A.

An on-drum photoconductor 15 as an image carrier is disposed substantially at the center of the unit accommodating section.
A charging unit 16 composed of a scorotron, an exposure unit 17a of a laser exposure unit 17 as an exposure unit (an electrostatic latent image forming unit), a developing process and a cleaning (cleaning) process are simultaneously performed along the rotation direction. A magnetic brush type developing means 18, a transfer means 19 composed of a scorotron, a memory removing means 20 composed of a brush member, and a pre-exposure means 21 are sequentially arranged.

Further, in the apparatus main body 1, the sheet P fed from the sheet cassette 7 via the sheet feeding unit 22 and the sheet P manually fed from the manual tray 12 are transferred to the photosensitive member 15 and the transfer unit 19. A paper transport unit 24 is formed to guide the paper to a paper discharge unit 6 provided on the upper surface side of the apparatus main body 1 through an image transfer unit 23 between the image transfer unit 23 and the image transfer unit 23.

An aligning roller pair 25 and a transport roller pair 26 are arranged on the upstream side of the image transfer section 23 of the paper transport path 24, and a fixing unit 27 and a paper discharge roller pair 28 are arranged on the downstream side. Further, the transport roller pair 26 is disposed. Reference numeral 13 denotes an aligning switch.

When the printing start signal is received by the host system, the drum-shaped photoconductor 15 rotates and the photoconductor 15 is charged by the charging unit 16. Next, the laser beam a modulated by receiving the dot image data from the host system is supplied to a laser exposure unit 17 including a polygon mirror scanner 30.
Is used to perform operation exposure on the photoconductor 15 to form an electrostatic latent image on the photoconductor 15 corresponding to an image signal. The electrostatic latent image on the photoconductor 15 is developed and visualized by the toner t in the magnetic brush D 'of the developing means 18.

On the other hand, the paper P manually fed from the manual feed tray 12 taken out of the paper feed cassette 7 in synchronism with the toner image forming operation is fed through the aligning roller pair 25, and is fed onto the photoconductor 15 in advance. The toner image formed on the sheet P is transferred to the sheet P by the operation of the transfer unit 19. Then, paper P
Is sent to the fixing unit 27 through the paper transport path 24. The fixing unit 27 includes a heat roller 41 containing a heater lamp 40, and a pressure roller 42 pressed by the heat roller 41. The toner image is melted on the paper P by passing between the rollers 41 and 42. Be established. Thereafter, the sheet is discharged to the sheet discharge section 6 via the sheet discharge roller pair 28.

After the transfer of the toner image onto the paper P, the residual toner remaining on the photoreceptor 15 is removed by the memory removing means 7 composed of a conductive brush to remove the memory. Will be collected.

Further, in the present invention, in order to simplify the conventional electrophotographic process, a transfer development method of developing an exposed portion is adopted, and a method of removing transfer residual toner t simultaneously with development is adopted. did. At this time, the change of the surface potential of the photoconductor 15 and the state of the toner t on the photoconductor 15 are changed as shown in FIG.

That is, the photosensitive member 2 is charged to -500 V by the charging means 16 (see FIG. 5A). At this time, the toners t... At this time, it is clear from the experimental results that the surface potential is maintained at 80 to 90% or more even when the toner t is removed with a urethane blade or the like.

Next, the photosensitive member 15 receives the laser beam a scanned by the laser exposure unit 17 after receiving the dot image data from the host system as described above, and attenuates the surface potential to form an electrostatic latent image. "(B) of FIG. 5
reference]. At this time, the surface potential of the exposed portion becomes -50 V (room temperature). Here, the photoconductor 15, the charging means 16, and the laser exposure unit 17 are designed as follows.

The photoconductor 15 uses an OPC (organic photoconductor) photoconductor, and as shown in FIG. 6, a double-cut aluminum cylinder having an outer diameter of 30 mm.
A charge generation layer 51 and a charge transport layer 52 are applied in this order on a 50 (0.8 mm thick).

The charge generation layer 51 is formed by applying a γ-type phthalocyanine “manufactured by Toyo Ink Co., Ltd.” and a butyral resin at a weight ratio of 1: 1 to a thickness of 0.1 μm, and the charge transport layer 52 is formed of 9-ethylcarbazole-3-carboxy. Aldehyde-methylhydrofuzone (ECMP) [manufactured by Inu Yakuhin] and polyarylate (U-100)
It is a product of [Unitika] applied at a weight ratio of 0.65 to a thickness of 17 μm. The charge transport layer 52 is transparent to visible light and a semiconductor laser. Since the charge transport layer 52 is on the charge generation layer 52, even if toner particles t of 30 μm or less exist on the surface, as shown in FIG. When the photoconductor 15 is exposed 55,
Charge generation layer by diffraction light 56 and reflected scattered light 57 in the transport layer 52
In 51, the shadow of the toner particles t can be hardly formed, or can be formed only as thin as practically acceptable. However, when the diameter of the toner particles t is 30 μm or more, image defects occur as black spots on solid black. In addition, the transport layer 52 may be any material as long as it is translucent to the exposure light source and has a carrier transport function, for example, a material obtained by dispersing a pyrazoline derivative in a polycarbonate resin, or a material obtained by dispersing an oxadiazole derivative or an oxazole derivative in an acrylic resin. Or a dispersion of a triphenylmethane derivative in a polycarbonate resin. Further, if the thickness exceeds the average particle size of the toner t, it may cause an image defect. Further, as shown in FIG. 8, the thickness is preferably 30 μm or less in view of residual potential characteristics. The photoreceptor 15 basically only needs to have the charge transport layer 52 on the charge generation layer 51, and as shown in FIG. 9, the undercoat layer 59 and the transport layer 52 between the generation layer 51 and the substrate 58. There may be a protective layer 60 or the like on the surface. The photoreceptor 15 used in this embodiment has a half-reduction exposure amount of 6.2 erg.
/ cm ² (see FIG. 10). Here, the appropriate value of the laser light amount is determined based on the following grounds.

This process does not perform a dedicated cleaner or an independent step for cleaning, and performs electrostatic cleaning at the same time as development. Therefore, image exposure is performed from above the transfer residual toner t on the photoconductor 15. Therefore, in some cases, a portion where the transfer residual toner t exists may be exposed.

Normally, a photoconductor is used for a portion where there is no transfer residual toner t.
15 surface potential half-life exposure (6.2 erg / c in this embodiment)
If the exposure amount is about 3 to 4 times as large as m ² ), the light amount is sufficient as the latent image potential for the image (for example, 2 in FIG. 10).
4.8 erg / cm ² ), the toner t acts as a filter for the portion where the transfer residual toner is collected several times, and the photoreceptor 15 is underexposed to that portion, and the memory is generated and the image is defective. Become.

In other words, when the exposure amount is less than four times, a black and white pair line of one dot width as shown in FIG. 11B (a) or a checkered pattern by every other dot exposure as shown in FIG. 11A (a). In the case of a pattern like a pattern, as shown in (b) of FIGS. 11A and 11B, the developed portion is chipped according to the pattern of the transfer remaining toner t on the photoconductor 15, and the chipped portion of the image is 11
As shown by (c) in FIGS. A and B, it becomes visible as a negative pattern.

For this reason, the present invention, as described later,
To be surely taken.

Next, the main components of the electrophotographic process will be described in detail.

First, the charging means 3 is composed of a scorotron as shown in FIGS. 60 in shield case 70
The corona wire 71 having a diameter of μm is stretched. The corona wire 71 uses white tungsten on the surface so that the minus corona is not generated unevenly.

The corona wire 71 is fixed to a metal fitting 74 to which a power supply pin 73 as a charging unit power supply unit is screwed.
The power supply pin 72 and the metal fitting 74 are fixed in a power supply terminal 75.

On the other hand, the other end of the corona wire 71 is connected to a tension spring 72.
And is fixed to a terminal 77 by a plastic hook 76. The terminals 75 and 77 are covered with terminal covers 78 and 79, respectively, so that high-pressure parts are not exposed.

On the other hand, the shield case 70 is made of 0.3 mm thick stainless steel and has a mesh on the side facing the photoreceptor 15 as shown in FIG. 14, and has a simple structure that plays a role as the grid 70a of the scorotron charger. However, since the grid 70a is integrated with the side cases 70b and 70c, the grid 70a can maintain sufficient accuracy such as its flatness without using special parts.

In addition, since the same bias voltage is applied to both side cases 70b and 70c when corona discharge is performed (which will be described later), the corona current flowing through both side cases 70b and 70c also decreases, and the charger has a good current effect.

The shield case 70 is a 560v Zener diode
82 (see FIG. 18), and the charger guide 83 (18th
(See figure). On the other hand, the charger guide 83 is connected to a ground terminal of the main body.

Therefore, when a high voltage (−5 kv) is applied to the corona wire 71 from a high-voltage transformer (not shown) of the apparatus main body via the power supply pin 73, corona discharge occurs in the shield case 70 and current flows in the shield case 70. However, the potential of the shield case 70 is −
It rises to 560v and stays constant.

As a result, the grid 70a also has a potential of -560v, so that the surface potential of the photoconductor 15 2 mm away from the grid 70a is
Is kept constant at -500v, which is slightly lower than the potential of. 80,8 in the figure
1 is a process cartridge 105 to be described later for the charger 17.
(See FIG. 4B). When integrated into the process cartridge 105, the engaged portion 82 (FIG. 19 and FIG.
(See FIG. 0).

As shown in FIGS. 4 and 16, the laser exposure unit 17 scans a semiconductor laser oscillator (not shown), a polygon scanner 32 comprising a polygon mirror 30 and a mirror motor 31, a fθ lens 33, a correction lens 34, Reflection mirrors 35 and 3 for scanning the laser beam a to a predetermined position.
It is composed of 6 magnitudes. Below the position where the laser exposure unit 17 is provided, that is, the upper surface and the lower surface of the cassette accommodating portion 8 are open, and the paper cassette 7 is pulled out forward (in the direction of the arrow in FIG. 3). It is configured to be able to be taken out in the downward state (see Fig. 16).

Further, as described above, the developing means 18 adopts a reversal developing method and simplifies the process of the electrophotographic system, and adopts a method of removing the transfer residual toner t simultaneously with the development. I have. The developing means 18 includes a photosensitive member 15 and a developing roller opposed to the photosensitive member 15 in a casing 91 having a developer accommodating portion 90 as shown in FIGS. 4A and 7 in detail.
A two-component developer D including a toner (colored powder) t and a carrier (magnetic powder) c is stored in the developer storage section 90.

Further, the developer magnetic brush D ′ formed on the surface of the developing roller 92 is in sliding contact with the photoconductor 15, that is, the developer magnetic brush D ′ is located upstream of the developing position 93 in the rotation direction of the photoconductor 15. The doctor 94 for regulating the thickness is provided. Further, the developer accommodating section 90 accommodates first and second developer stirring bodies 95 and 96.

The developing means 18 is provided with a toner replenishing device (not shown) so as to replenish the toner accommodating portion 90 with the toner t as needed.

Further, as shown in FIG.
It comprises a magnetic roller 103 having two magnetic pole portions 100, 101, and 102, and a non-magnetic sleeve 104 fitted around the magnetic roller 103 and rotating clockwise in FIG. Magnetic roll 103
Of the three magnetic pole portions 100, 101, 102, the magnetic pole portion 101 facing the developing position 93 is an N pole, and the other magnetic pole portions 100, 102 are S poles. The angle θ1 between the magnetic pole part 100 and the magnetic pole part 101 is 150 °, and the angle θ2 between the magnetic part 101 and the magnetic pole part 102 is
Is set to 120 °. Then, the electrostatic scraping force on the photoreceptor 15 due to the mechanical scraping force by the magnetic brush development using the two-component developer D and the potential difference between the charging potential due to the reversal phenomenon and the developing bias applied to the magnetic brush D ′. At the same time as the development of the latent image, the residual toner t is mechanically and electrically collected.

4B, 17 and 18
As shown in FIG. 19 and FIG. 19, the photoreceptor 15, the charging means 16, the memory removing means 20 and the like are integrally incorporated to constitute a process cartridge 105. Handle 110 (18th
(See FIG. 19 and FIG. 19). On the other end side, a developing means power supply section 111, a memory removing means power supply section 112, and a charging means power supply section 113 including a power supply pin 73 are provided in a protruding manner, and the process cartridge 105 is placed at a predetermined position in the apparatus main body 1. When pushed in, these power supply units 111, 112, 113 are inserted into a power supply connector provided in the apparatus main body 1.

On the upper surface side of the process cartridge 105, a folding handle 115 for carrying is provided, and a cleaning brush 116 for cleaning the lower roller 25a of the aligning roller pair 25 is attached.
Further, as shown in FIGS. 4B and 20, the developing sleeve 104, the first and second developer stirring members 95 and 96, and the photosensitive member protection sheet 120 are wound around the other end of the developing means 18. It is in a state of being connected to the take-up shaft 121 (see FIG. 17) and the like for taking up, and is in a state in which gear groups 122 that are interlocked with each other are provided.
The gear 122a meshes with a drive gear (not shown) provided on the apparatus main body 1 side. When the gear 122a is driven, each of the rotating members is rotated in a predetermined direction at a predetermined speed. Has become. The winding shaft 12
The photoreceptor protection sheet 120 wound up to 0 is accommodated in the guide cylinder 124 surrounding the winding shaft 120, and the end does not project outside.

Incidentally, 125 shown in FIG. 20 is a positioning groove of the charging means 19.

Reference numeral 126 shown in FIG. 18 is a rod that presses a switch (not shown) for detecting the presence or absence of the process cartridge 105.
Reference numeral 127 denotes a toner supply port shutter that opens when a toner supply hopper (not shown) is attached, and 128 denotes a shutter spring. Reference numeral 129 denotes a photosensitive drum fixing pin.

An auto toner sensor ring 140 made of a metal-plated cap is mounted on one end of the photoconductor 15 as shown in FIGS. 18 and 21, and has a configuration capable of detecting the developer concentration in this portion. Has become. This auto toner sensor ring 140 is connected to the doctor blade 94 via a conductive leaf spring 141 such as phosphor bronze as shown in FIG. 22, and further connected to the developing sleeve 104 via a conductive leaf spring 142. Auto toner ring 140, doctor blade 9
4, and the developing sleeve 104 have the same potential. In other words, power can be supplied to the automatic toner sensor ring 140 without using a dedicated power supply unit.

Also, the photoconductor 15 provided with the auto toner ring 140 is provided.
On the other end side, as shown in FIG.
When the process cartridge 105 is installed in the apparatus main body 1, a flange 145 provided with
The photosensitive member drive shaft 146 provided on the apparatus main body 1 side is to be inserted into the shaft insertion hole 145a of the flange 145. The engaging tongue pieces 143a of the leaf spring 143 are
The driving force of the photoconductor drive shaft 146 is transmitted to the photoconductor 15 by engaging with the engaged portion (not shown) of 46.

The transfer means 19 is composed of a scorotron as shown in FIGS. 23 to 26.

A corona wire 151 is stretched in a shield case 150, and one end of the corona wire 151 is connected to a metal fitting 153 spring-fixed to a power supply terminal 152 as shown in FIGS. 25 is connected to a shaft 155 of the power supply terminal 154 via a tension spring 156 as shown in FIG. The portion of the shield case 150 facing the photoconductor 15 is meshed as shown in FIG. 23, and forms a grid 150a.

On the power supply terminal 152 side, a grid voltage power supply section 157 and a wire high voltage power supply section 158 are provided as shown in FIGS. 23 and 26.

 Next, the memory removing means 20 will be described.

The memory removing unit 20 includes a brush member 160 and a holding member 204 that holds the brush member 160.

The brush member 160 is made of rayon, nylon, acrylic,
It is made of a resin such as polyester as the main component and carbonized carbon particles, metal powder, phenolic resin, etc., or a bundle of many conductive artificial fibers in which conductive materials such as stainless steel fibers are dispersed. . This artificial fiber is produced, for example, by extracting an appropriate amount of carbon particles dispersed in a liquid of the above resin through a nozzle-shaped extraction port. The volume resistance of the artificial fiber can be freely selected by changing the dispersion amount of the carbon particles. Further, the thickness and the cross-sectional shape of the artificial fiber can be appropriately changed according to the diameter and the shape of the extraction port of the nozzle.

The artificial fiber used as the brush member 102 of the present invention preferably has a volume resistance of 10 ² to 10 ⁷ Ωcm. When the deposition resistance is smaller than 10 ² Ωcm, when a voltage is applied to the brush member 102 to electrostatically attract residual toner as described later, a discharge phenomenon occurs between the brush member 102 and the photosensitive layer of the photosensitive member. Problems such as destruction. If the volume resistance is greater than 10 ⁷ Ωcm, even if a voltage is applied to the brush member 160, the untransferred toner on the photoreceptor cannot be electrostatically attracted, and the untransferred toner remains as it is. 16
Since it passes through 0, the operation and effect of the brush member 160 described later can be obtained.

The artificial fiber used as the brush member 160 of the present invention has a sectional shape as shown in FIG. That is, the artificial fiber has irregularities 160a on its peripheral surface, and the irregularities are substantially continuous in the length direction of the artificial fiber. Therefore, the artificial fiber used for the brush member 160 of the present invention has a large surface area and maintains linearity in the length direction. Therefore, when the brush member 160 is brought into contact with the photoreceptor 15, the brush member 160 can come into contact with more residual toner on the photoreceptor 15, and it does not bend, so that it will be described later. The function and effect of the brush member 160 can be further promoted, and the brush member 160 can withstand long-term use.

The thickness of the artificial fiber is desirably 1 to 50 denier. If the denier is less than 1 denier, the artificial fibers are likely to break or fall off the holding member 204, and cannot withstand long-term use as the brush member 160 of the present invention. If the denier is larger than 50 denier, the artificial fiber bundle becomes coarse even if the artificial fiber is brought into contact with the photoreceptor, causing a problem that the untransferred toner passes without sufficiently contacting the brush member 160. , Brush member described later
160 effects cannot be obtained.

The holding member 204 includes a holding bracket 162, a backing member 161 and an auxiliary metal plate 210. The holding metal member 162 is a plate made of a conductive metal, for example, an aluminum alloy. One end of the holding metal member 162 is bent in advance into a substantially L-shaped cross section, and extends long in the axial direction of the photoconductor.

Then, by taking into account the thickness a of the brush member 160 rather than the central portion of the holding member 162 in the short direction, the plate member is bent around the portion displaced to the other end side to sandwich the base of the brush member 160. , And supports the brush member 160. The brush member 160 is in a state of being bent in a substantially L shape between one end and the other end of the holding bracket 162. At this time, if the thickness b of the consideration a of the thickness a is smaller than the thickness a of the brush member 160, the brush member 160 may be cut off when the brush member 160 is sandwiched between the plate members.

The relationship between the thickness of the brush member 160 and the thickness c in a state where the holding fitting 162 is bent is such that the thickness a is 0.5 to 2 mm and the thickness c is desirably about 2.5 to 4 mm. When the plate is bent, the brush member 160
However, there is a problem in that the pieces are easily cut or come off.

In order to prevent the brush member 160 from coming off, a conductive adhesive may be poured between the brush member 160 and the plate member to reinforce the brush member 160.

The backing member 161 is provided along the surface of the brush member 160 opposite to the surface in contact with the photoconductor 15, and is for pressing the free end side of the brush member 160 against the photoconductor. The length of the backing member in the short direction is longer than the length of the free end side of the brush member 160, so that the brush member 160
This also has the effect of preventing the horn from being bent. Further, by making the length of the brush member 160 in the longitudinal direction longer than that of the brush member 102, it is possible to obtain an effect of preventing the toner once absorbed by the brush member from scattering.

Further, if the backing member is a particularly elastic or flexible resin member such as a polyester resin, it is possible to prevent the photosensitive member from being damaged even if the backing member touches the photosensitive member.

The auxiliary sheet metal 210 is provided in contact with the backing member on the side opposite to the photoconductor, and reinforces the backing member 161 and the brush member 160.

In this embodiment, the auxiliary sheet metal 210 and the backing member 161 are formed as separate members, but it is also possible for one member to serve as both. In this embodiment, the brush 160 is made of rayon containing carbon to have a specific resistance of 10 ⁶ Ω · cm and made into a fiber having a thickness of 6D (denier).
It has a satin weave with a density of ch, and is constructed by pulling out two double weft yarns. The brush 160 has a backing member 161 made of a polyester film having a thickness of tmm (about 0.1 mm) on one side as shown in FIGS.
The holding bracket 162 is attached in a state of protruding dmm (about 1.0 mm). Then, with respect to the photoconductor 15, θ (15 °)
The brush 160 is mounted upstream of the charging means 16 so that the brush surface is in contact with the brush 160 at a mounting angle of 3 mm from the tip of the brush 160.

The preferred shape of the memory removing means 20 is a fixed brush shape. That is, when the brush is rotated or moved left and right, the toner is not only scattered, but also the rotary type is increased in size and requires a drive system, which increases the cost.

Next, the principle, conditions, and the like of the simultaneous cleaning, transfer, image removal, and the like will be described, including experimental data.

This cleaning simultaneous development process (Cleaning & Deve
The point is that the loping process (CDP) is performed in transfer development. This is because the polarity of the toner is the same as the polarity of the toner, so that the polarity of the toner is not inverted by the charging unit 3.

On the other hand, as shown in FIG. 34, when the cleaning process is performed by the regular development, the following is performed.

In this case, if a negatively charged photoreceptor is used, the polarity of the toner will be positive, but first, in the charging step, the transfer residual toner will be negative with the opposite polarity. Exposure process
In FIG. 34B, the portion corresponding to the background (white background portion) is irradiated with light, but the light usually goes under the toner, and the potential of the background portion under the toner is attenuated. Next, when the unexposed area is developed using the toner of the positive polarity, the transfer residual toner in the unexposed area of the photoconductor is electrostatically removed, and the pattern to be developed comes off in a negative shape. The image becomes defective.

Further, the negative transfer residual toner in the exposed portion is not attracted to the developing device, and thus remains on the photosensitive member. Further, in some cases, a phenomenon occurs in which the positive polarity toner in the developer is sucked. In the transfer step (D), the transfer residual toner on the exposed portion remains on the photoreceptor without being transferred because of the same polarity as the transfer charger. Therefore, each time the process cycle is repeated, the transfer residual toner on the photoconductor increases. Further, since the positive polarity toner sucked by the transfer residual toner is transferred, an image before one rotation of the photosensitive drum appears on a white background portion of the transferred image. (White positive memory). That is, in the regular development method, the transfer residual toner on the photoconductor increases each time the process cycle is repeated, and the occurrence of black negative memory and white positive memory increases. In other words, this is why simultaneous development with cleaning is very difficult in regular development and easy in reversal development.

Further, in this method, since the photoconductor is cleaned by the developing device, paper waste attached to the photoconductor is taken into the developing device. One component such as a magnetic one-component system that requires the developer sleeve and doctor blade to be narrowed to several hundred microns to form a thin layer of developer on the developing sleeve, and a non-magnetic one-component system that slides the doctor blade on the sleeve In the method, when a large number of sheets are printed, paper waste enters between the doctor blade and the image sleeve, so that a uniform developer layer cannot be formed on the sleeve and image defects are likely to occur. (However, it is needless to say that the one-component developer can be sufficiently implemented with respect to the degree of the image and the frequency of use.) On the other hand, since the two-component developing method does not have such a problem, even if more than 50,000 sheets are printed, an image defect occurs Did not occur at all. In other words, the two-component developing method has a longer maintenance period of the developing device and is preferable for the present method.

However, in this CDP, certain process conditions are required to obtain good quality images. FIG. 35 is an explanatory diagram of the contents (terms) used herein. The potential when the photosensitive member 15 reaches the developing position 93 without being exposed by being charged by the charging means 16 is referred to as a charged potential V ₀ , The potential attenuated by the exposure is referred to as a post-exposure potential Ver, the potential applied to the developing roller 94 of the developing unit 18 is referred to as a developing bias Vb, and the difference between the post-exposure potential Ver and the developing bias Vb is referred to as a developing potential Vb = Vb−Ver. cleaning the difference between the charge potential V0 and the developing bias Vb potential VCL = V ₀ -Vb
Call.

In the present embodiment Vb in consideration of the photoconductor 15 was although positively charged type using OPC for negative charging, Ver, Vb-Ver, = V 0 -Vb is recommended to speak as absolute values.

The first quadrant in FIG. 36 is a plot of measured data with development potential Vb-Ver on the horizontal axis and image density on the vertical axis.
It can be seen that a developing potential of 100 V or more is required to obtain a good image density of 1.0 or more.

On the other hand, in the second quadrant, the horizontal axis represents the developing potential Vb, and the vertical axis represents the charging potential.
V ₀ is shown, and each plot point shows a state of generation of a memory by an image one rotation before the photoconductor 15 due to a cleaning failure in the image on the paper P.

Here, it has been found that when the developing potential is higher than 300 V, a memory of a black pattern is generated on a white background due to a cleaning failure (hereinafter referred to as a white background memory). This means that the image density does not increase even if the development potential exceeds 300 V,
It is considered that the actual amount of toner t attached is increasing, and the transfer residual toner t is also increasing at the same time.

Next, the third quadrant, in which the horizontal axis represents the cleaning potential V ₀ -Vb and the vertical axis represents the charging potential V ₀ , represents the state of generation of a memory image on the paper P.

Here, if the cleaning potential VCL = V ₀ −Vb is zero, a white background memory is definitely generated due to poor cleaning, and it has been found that at least 50 V or more is required.

However, when the cleaning potential is increased, a positive charge is reversely injected into the toner t from the developing roller 94 to the toner t, and the toner t which has changed from a negative polarity to a positive polarity is transferred to an unexposed portion (uncharged portion) of the photoconductor 15. ), And acts as a filter to reduce the exposure amount of the exposed portion 17a. This causes image defects such as blurred exposure images and the occurrence of an image of the photoreceptor 15 one round before in a dot pattern as a positive memory. Cause the cause. Therefore, it has been found that the maximum cleaning potential is somewhat affected by the toner t, the carrier c and the combination thereof, but is preferably at most 300 V or less.

Further, the resistance dependence of the memory removing means 20 was examined. Peripheral speed
The 30φ OPC photoconductor 15 rotating at 36 mm / sec is first subjected to pre-exposure by the pre-exposure device 21, and is charged to −500 V by a charging scorotron charger as the charging means 16, and the 30φ developing sleeve 104 is rotated at 140 rpm. The photoreceptor 15 is rotated at a rotation speed in a forward direction with respect to the rotation direction, and the electrostatic latent image formed by the exposure is simultaneously developed with the cleaning, and is transferred onto the paper P by a transfer charger as the transfer unit 19.

After the transfer, the image was passed through a brush 200 fixed to the process cartridge 105, and this was set as one cycle. Continuous printing was performed, and the transferred image was evaluated.

In the present embodiment, the development is a reversal development, and the surface potential of the photoconductor 15 after the transfer does not exceed the potential of the charge because the transfer charger as the transfer unit 19 has a polarity opposite to that of the charge.
Since the charging means 16 is a potential-controlled scorotron, there should be basically no potential fluctuation.However, when the same image is printed for a long period of time, as shown in FIG. Red LEDs were used for the purpose of forced fatigue because a difference occurred and the density became uneven when another image was printed.

The resistance dependence of the memory removing means 20 was examined, and the following results were obtained.

The brush used here is a single filament (fiber)
But 100 pieces of 3D (denier) are bundled into one thread and 10
Pile weave brush 170 at a density of 0,000 brushes / inch ² (Fig. 38
A, FIG. 38B, and FIG. 38C). In the figure, 171 is a base fabric weft, 172 is a base fabric warp, and 173 is a pile. Here 10 specific resistance under 20 ° C. 60% RH environment of the brush 170 is ⁰ Omega · cm to 10
Attempts to change the resistance to ¹⁵ Ω · cm showed that those having a specific resistance of 10 ⁶ Ω · cm or less were effective for black negative memories on halftone (dot) patterns as shown in Table 1. However, in practice, a resistor with a resistance of 10 ⁹ Ω · cm or less that can remove a white positive was sufficient.

If the resistance is less than 10 ³ Ω · cm, the photoconductor 15 may be damaged (dielectric breakdown of the photoconductor may occur).
, Leakage occurs, and when charging stops, it becomes solid black in the case of the reversal phenomenon. Therefore, preferably 10 ⁸ Ωcm to 10 ³ Ω
cm is good.

Also, it was necessary to apply a positive or negative bias to the black negative memory.

Here, when the transfer residue after passing through the brush 170 was transferred and sampled with a mending tape, the pattern of the transfer residual toner t was slightly changed even after passing through the brush 170 if the transfer residue was 0 V or float as shown in FIG. Although it becomes thin, memory is generated on the image almost unchanged.

However, with a negative bias having the same polarity as the toner t, the boundary of the character pattern becomes thinner, while the brush 170 develops the toner-free portion at the center of the line of the remaining transfer pattern, and the overall darker character becomes darker. It becomes a pattern.

However, this does not appear as a memory on the image.
If the positive bias is opposite to the polarity of the toner t, the boundary of the character pattern becomes thin, and no memory is generated on the image. The polarity of the toner t is a polarity obtained by frictional charging with the carrier c. Here, the memory removing brush 170 (160) does not diffuse the toner pattern of the character characteristics remaining after transfer, and the plush 170 (160) once attracts the toner t electrostatically, and then, to the photosensitive member 15. Photoconductor 15 extruded naturally
It was found that the position where the toner t was attached was changed. If only the toner position is changed, it is considered that a means for positively diffusing the toner t should be provided instead of the memory removal brush 170 (160). And problems such as toner scattering are undesirably caused. Further, as a result of the running test for outputting 20,000 sheets, the toner t hardly accumulated in the brush 170 (160).

On the other hand, for a white positive memory in which cleaning of untransferred toner was poor due to transfer omission caused by lifting, wrinkling, or folding of paper, no effect was obtained unless the voltage was 0 V or a float or positive voltage.

From these, it was found that the bias for the brush 170 (160) had to be positive. Therefore, the positive bias voltage is increased from 100V
The transfer residual toner t pattern and paper P changed to 1000V
When the effect of removing the above memory was examined, it was found that the effect was almost the same when the voltage was 100 V or more, and that a positive voltage was sufficient. But,
When +700 V or more is applied, the voltage leaks due to a slight defect (which seems to be a pinhole) in the OPC (organic, photoconductor) photoconductor 15, and as a result, it is found that a hole is made in the photoconductor 15. The voltage ranges from +100 to +700 V in a practically usable range.

In this embodiment, in order to reduce the size and cost of the apparatus, the photoconductor 15 is reduced in size to 30 mm, and the paper P is stiffened (rigidity).
The transfer means (transfer charger) 19 is applied to a portion through which the sheet P does not pass because only the peeling by the transfer is performed, and as shown in FIG. 40, the potential of the photoconductor 15 is +700 to +1 which is close to the transfer grid voltage.
Up to 200V, the part is positively charged.

Therefore, it has been found that the negatively charged toner t attached to the brush 170 (160) develops the positively charged portion where the paper P has not passed. In particular, the toner t adheres remarkably to the portion near the leading edge and the trailing edge of the paper P, and appears as a white positive and black negative memory in a streak shape on the image (see the paper interval mark in Table 1). To prevent this, a positive bias is applied to the brush 170 (160), and the transfer is performed only when the sheet P passes under the transfer means (transfer charger) 19 as shown in the flowchart of FIG. The problem was solved by turning on the power supply to the corona wire 151 of the means 19 so that the exposed portion of the photoconductor 15 before and after the transfer paper P was not positively charged.

Note that the apparatus of this embodiment can print up to A3 paper,
When printing narrower paper than A3 paper, for example, B5 paper,
Both sides of the sheet P of the photoreceptor 15 (because of the device that always feeds the center of the sheet P at the same position regardless of the size of the sheet P) are positively charged. There is no problem, so everything is not a problem.

In addition, as described later, it was also found that it is preferable that the brush shape be a satin weave.

Here, the bias power applied to the brush 170 (160) is turned on.
The timing of the operation will be described. Since a positive voltage (a voltage of the opposite polarity to the charging) is applied to the brush 170 (160),
Basically, the photoconductor 15 is positively charged. Therefore, the surface of the photoreceptor 15 that has passed the brush 170 (160) to which a voltage has been applied does not necessarily receive the charging corona by the charging unit 16, and if that portion passes through the developing unit 18, the toner (the negative electrode) of the developer in the developing unit 18 (Characteristics) t adheres and becomes solid black. Such solid black cannot be completely cleaned and poses a problem. Therefore, the negative charging by the brush 170 (160) is a charging means.
16 may be used to make the negative charge. The time required for the outer circumference of the photoconductor 15 to reach the charging position from the brush contact position is _TSM (see Fig. 32)
Then, the time for turning on the charging after turning on the brush bias power supply must be _TSM or less. In the present embodiment, as shown in FIG. 41, charging and brush bias ON are performed simultaneously.

Such a problem also occurs at the end of printing. For this reason, the discharging of the charging means 16 must not be stopped until the surface of the photoconductor 15 at the time of turning off passes the charging position. That is, the time for turning off the charging must be longer than _TSM .

Next, the effect on the memory by changing the thickness of the fiber of the brush 170 (160) was examined by examining the image and the transfer residual toner image on the photoconductor 15 after passing through the brush.
In particular, vertical line memory could not be removed. For 100D or less, no memory was generated, and the transfer residual toner image also had no dark portion at the boundary. In conclusion, the fiber thickness is preferably 100D or less.

In addition, the density of the brush 170 (160) is 1000 fibers / inch ² or more for piles and has no effect unless the thickness is 0.5 mm or more, and 10 to 1000 fibers for satin weave. It was found that non-brushed yarns were woven as warp yarns or weft yarns at a ratio of 10 bundles to inch or more as one bundle, resulting in unevenness in the memory removal effect. The memory removal effect is almost determined by the brush resistance, fiber thickness, density, etc. However, it has been found that toner actually drops (scatters) depending on the brush shape and contact method for practical use of the device. .

Here, a pile-woven brush 170 (see FIG. 38) and a bundle of 100 fibers each having a 3D thickness are 127 per inch.
The density of the bundle, the satin weave brush 170 (see Fig. 31) as warp, length l _A , thickness W (number of satin weaves), angle θ, contact position l _B (see Fig. 32), etc. Was changed, and 1000 sheets (A4 landscape) were printed, and the amount of toner t scattered or dropped on the charging means 16 composed of a scorotron was examined.

As a result, as shown in FIG.
Pile brush 170 shown in FIG. 42B.
The toner of the charging means 16 made of scorotron was stained completely black. In addition, there was a problem that hair loss sometimes occurred, short-circuited with the grid of the charging means 16, and a solid black image was generated. The brush 160 of the satin weave has the photoconductor 1 as shown in FIG.
The method of contacting with No. 5 is not preferable because toner is often dropped and a trace of the interval between sheets of paper P occurs occasionally.

On the other hand, as shown in FIG. 32, the use of the satin weave brush 160 instead of the tip of the stomach makes the toner drop significantly reduced. The optimal application condition is as shown in FIG. 32.
The brush 160 has no external force and the brush 160 is fully extended (the center line L to which pressure is applied once is
Assuming that a point P intersected with the outer diameter circle is P, and a tangent in the brush direction to the photoconductor 15 at the point P is M, the brush length l _A is 4 mm or more and the mounting angle θ is not less than 45 °. The effect diminished.

In addition, as shown in FIGS. 32 and 33, a backing film 161 is provided on the surface of the brush 160 on the side opposite to the surface in contact with the photoreceptor 15 to prevent the bristles of the brush 160 from spreading. No toner loss occurred even after printing 10,000 copies.

The backing film 161 is an insulating material, and may be made of any material such as polyester, urethane, high-density polyethylene, polypropylene, butadiene rubber, butyl rubber, silicon rubber, polyacetal, or fluororesin, which has an elasticity of 2 mm or less. However, the tip of the film 161 is the same as or larger than the tip of the brush 160 (1.5 in this embodiment).
It was necessary to protrude and was not effective if retracted.

This is because if the fiber is spread at the tip, the toner t adheres to each of several tens of micron-based fibers, and drops and scatters due to subtle changes in air flow and vibration.

The photoreceptor 15, the charging means 16, and the memory removing means 20 are integrated into the developing unit 18 (see FIGS. 4B and 18). Can be integrated into and out of the apparatus main body 1.

Therefore, even if the photoconductor 15 is removed from the apparatus main body 1, their relative positional relationship does not change, thereby making it possible to prevent scattering of the toner from the memory removing unit 20 and a reduction in the memory removing effect. Become.

In addition, since it is a simple fixed type, even if it is thrown away with the photoconductor 15, the cost does not change much.

Note that the electrostatic latent image on the photoconductor 15 is
Then, the image is transferred onto the sheet P by the transfer unit 19.

 Here, the following measures are taken.

The process speed (photoconductor peripheral speed) of this embodiment is 36 mm / s.
It is about 1/4 slower than ec and normal copiers (process speed is about 140mm / sec for A4 paper 15 sheets / min). In the case of such a low process speed, the following problem occurs when a corotron charger conventionally used as a transfer unit is used.

Since the corona current is small, the voltage applied to the corona wire is low, close to the discharge starting point, and unstable with respect to dirt and environmental changes.

The value of the applied voltage or the output current of the corona for performing good transfer of the character portion and the solid portion (the portion where the toner has a large area) is different, and it is difficult to obtain a good transfer image in both portions.

These causes are caused by a longer process time due to a lower process speed.

Basically, when the toner t is transferred, the potential of the sheet P is changed to the toner t.
It is sufficient to apply a charge to the paper P until the potential reaches a potential for electrostatically attracting the paper P.

Therefore, since the process speed is slow, a transfer current with a good degree of control is generated when the voltage applied to the corona wire is about 3.5 to 4 kv.
However, the voltage of 3.5 to 4 kv is almost the starting voltage of corona discharge as shown in FIG.
Discharge or not depending on the degree of adhesion of dirt, etc., resulting in poor stability and lack of stability.

In addition, in order to check the difference in the transfer conditions between the character portion and the solid portion image, solid or a large number of characters are printed in a fixed area, and a visible image is formed on the photoconductor 15 with the toner t.
In the case of non-transfer, the toner adhesion amount on the photoreceptor 15 after being transferred to the paper P is sampled on the tape with a fixed area cellophane tape (manufactured by Nichiban), and the sampled tape is dissolved with a certain amount of toluene to reduce the transmittance. From the measurement, the transfer efficiency was calculated by the following equation.

FIG. 45 shows a process speed of 36 mm / sec used in this embodiment.
The coronatron is used as the transfer means 19 of
The transfer effect of the character (line) image part and solid part when the voltage applied to 151 was changed was examined. There is no applied voltage that makes the transfer efficiency of the character part and solid part simultaneously 80% or more. Recognize. That is, as long as the corotron is used, it can be inevitable that the image density of either the character or the solid image decreases.

The reason for this is that, as shown in FIG. 46, the potential of the sheet P and the movement of the electric charge, the sheet P is separated from the photoconductor 15 in the solid portion because the toner t is interposed between the photoconductor 15 and the end portion. Since most of the charges except the transfer corona are kept,
The potential of the sheet P hardly decreases, and the toner t is transferred to the sheet P by an electric force.

On the other hand, in the character portion, since the width of the toner image is narrow, the charge on the paper P on the toner t is absorbed by the opposite charge of the unexposed portion of the photoconductor 15 beside the toner image, and the potential of the paper P does not increase. .

Therefore, if the transfer of the solid portion is appropriate, the potential of the paper P in the character portion is lowered, and the transfer efficiency is deteriorated. Conversely, when the potential of the character portion of the paper P is to be increased, the potential of the solid portion is too high, and the toner t of the solid portion receives a leak current from the paper P, the polarity is reversed, and the toner t is transferred from minus to plus. Become That is, the transfer becomes excessive.

In order to eliminate such a problem, a scorotron charger similar to the charging unit 16 was used for the transfer unit 19. By using the scorotron charger, a voltage of 5 kv or more can be used for the corona wire 151, which stabilizes the discharge and prevents the occurrence of charger unevenness due to dirt or the like. Further, since the potential of the transfer paper P in the solid portion and the character portion can be controlled to the same potential, a transfer image in which both the solid portion and the character portion are good can be obtained.

Fig. 47 shows that the transfer efficiency of the character part and the solid part when using a scotron was examined in the same way as when using a corotron, and the control was sufficient, and both solid and character simultaneously performed good transfer at the same time. (Transfer efficiency of 80% or more) indicates that the region can be widened. The shape of the scotron is almost the same as that of the charged one.

Here, the transfer scorotron is opened downward with respect to the photoreceptor 15, but since it is a positive corona, there is no problem unlike the negative charging, which generates almost no ozone. Here, the appropriate value of the grid voltage of the scorotron was examined by measuring the transfer efficiency.

Table 2 shows the results of determining the transfer efficiency of various transfer papers P by changing the grid voltage.

According to this, good transfer (efficient
It turned out that the area of the grid voltage was different.

Therefore, in order to perform good transfer on all types of paper, it is necessary to switch the voltage of the grid to at least two or more types of voltages according to the paper.

In this embodiment, as shown in FIG. 1, the grid transformer 350 is configured such that the output of the high-voltage output unit 351 is switched by a switching signal input to the switching SW 352 in accordance with the type of the paper P. I have. That is, the output of the high-voltage output unit 351 is switched to at least two stages of 1200 V when the paper P is an envelope and 700 V when another paper is used. Needless to say, the switching of the grid voltage may be performed in multiple stages according to various types of paper.

Here, as one of the considerations when the transfer means 19 is a scorotron, there is a measure against contamination of the grid of the scorotron. Normally, the transfer means 19 is attached to the lower side of the photoconductor 15. Therefore, the opening is directed upward, and the paper P passes above it. On this occasion,
Inevitably, the toner t on the photoreceptor 15 and the paper dust of the paper P will fall on the transfer and transfer unit 19. If the transfer means 19 is a scorotron, toner t or paper dust will inevitably fall and adhere on the grid 150a, and during the printing of several thousand to tens of thousands of sheets, the grid 150a becomes very dirty, It becomes jammed and transfer failure easily occurs.

Therefore, in this embodiment, the transfer position is above the photoconductor 15,
By providing the transfer means 19 of the scorotron above, the opening on the grid 150a side is directed downward, thereby preventing the grid 150a from being stained as described above (see FIG. 3).

The transfer property was examined by changing the Zener diode, varistor, resistance, voltage by a power source, and the like for the guide plate 180 and the conductive guide roller 25 in FIG. 4A. As a result, it was found that the transferability varies with the potential of the guide plate 181 and the roller 25 even in the scorotron.

 Table 3 is a table for evaluating the results.

It was found that when a voltage was applied to the guide members 181 and 180 in the case of using a scorotron, transfer failure due to excessive transfer was likely to occur.

For this reason, the guide member for the paper path of the paper P
Applying a self-bias to 181 and 180 with a voltage, resistance, or constant voltage element causes excessive transfer in scorotron transfer, which is a bad result. Rather, most preferred is ground (earth) or float (electrically insulated). Therefore, in this embodiment, the guide plate 181 and the roller 25 are connected to the ground, and the other contact portions are made of an insulating member (for example, ABS resin).

Here, the photoconductor 15 unique to simultaneous cleaning and cleaning (CDP)
A description will be given of the type of memory and the cause of the occurrence of the pattern developed one cycle before on the next image portion.

There are three types of memories: a black positive pattern (white positive) on a white background, a negative pattern (black negative) on a halftone made of an aggregate of dots or lines, and a halftone dot pattern made of an aggregate of dot patterns or lines. This is a positive pattern (black positive) on a halftone (see FIG. 48).

The cause of the white positive occurs when cleaning potential V _CL is the difference in cleaning is poor charging potential and the developing bias V _B is too small.

The black negative memory is caused by exposure failure due to the transfer residual toner image.

When the cleaning potential is too high, the black positive memory is caused by low toner resistance.

FIG. 49 shows the principle of generation of a black negative memory which is likely to appear on a halftone like a halftone dot pattern made of a group of dots or lines, with the vertical axis representing surface potential and the horizontal axis representing distance.

(A) shows that there is a small amount of transfer residual toner in the charging step (a).
3) shows the surface potential of the photoconductor 15 with some (b) and no (c, d) at all.

(B) shows the surface potential when a laser spot is irradiated on the photoreceptor 15 at intervals of every other dot. (C, d)
Since part (2) is a normal exposure, the potential is attenuated substantially equal to the laser exposure width. In part (a), since the amount of residual toner is small, the potential under the toner is considerably attenuated by transmitted light, diffraction light, and the like, and is close to the potential of the exposed portion where there is no toner. On the other hand, when the amount of the transfer residual toner is large (part b), the potential does not attenuate because it does not hit the photoreceptor part under the toner, so that the portion where the potential attenuates becomes narrower or completely absent.

(C) and (d) show the potential diagram when the exposure state of (b) is reversely developed and the pattern on the sheet P after heat fixing.
When there is no transfer residual toner (parts c and d), a toner image is formed in a pattern having the same diameter (width) as the exposure spot diameter (width). Since the portion that has been exposed is smaller than the exposure spot diameter (width), the pattern to be developed is small or completely absent. Then, the transfer residual toner is cleaned (collected to the developing device). Therefore, if a portion with a large amount of toner remaining after transfer forms a pattern of characters or numbers, it becomes a blank memory (a portion shown in FIG. 48).

On the other hand, in the case where the transfer residual toner is scattered (part a), the potential under the toner is attenuated or attenuated to some extent, so that the toner remains attached without being cleaned. Thus, a pattern image having substantially the same diameter (width) as the exposure spot is obtained. Even if the potential under the toner is not sufficiently attenuated, if the size of the toner particles is about one or two, the exposure spot diameter is the diameter of the toner particles (usually 8 to 12 μm).
m), which is as large as 60 μm (400 dots / inch) and the layer thickness of the developed toner is large, so that the toner is buried at the time of development or fixing and poses no substantial problem.

By the way, as described above, the cause of the black negative memory is due to the filter effect of the untransferred toner. However, the solid light image, the halftone image, and the laser light amount for lines of 5 dot lines or more (400 dots / inch or more) Black negative memory does not occur due to the configuration of the photoconductor, the transmittance of the toner, and the like. However, four or less dot lines are likely to occur. In particular, the edges of the lines are remarkable, and when represented by characters composed of 4 dot lines or less, they look like whitish outline characters.

Here, when the transfer remaining pattern of the character image on the photoreceptor 15 is adhesively transferred onto a mending tape (manufactured by 3M),
As shown in FIG. 50, there is much transfer residual toner at the boundary between the developed portion and the non-developed portion.

FIG. 51 is a cross section taken along the line XX of the transfer residual pattern in FIG. 50, and it can be seen that a large amount of the transfer residual toner at the boundary portion is left in a laminated state. Incidentally, reference numeral 190 shown in FIG. 51 is a tape. Therefore, almost no light passes through this boundary portion, which causes black negative memory.

The transfer residual toner laminated at the boundary of the character or the line pattern is broken to make a single layer without any memory. Alternatively, the black negative memory is obstructed by removing the laminated portion by electrostatic attraction.

Therefore, the memory removing member 20 acting as above is transferred to the transfer unit 19.
And upstream of the charging means 16.

FIG. 53 shows a state in which the memory removing means 20 is arranged in a non-contact state with respect to the photoconductor 15.

The brush member 160 constituting the memory removing means 20 and the photosensitive member 15
Does not need to be particularly in contact with each other, and the above-described effects can be sufficiently obtained as long as a gap having a predetermined distance is provided. In this case, the voltage is applied to the memory removing unit 20 as described above, and the toner remaining on the photoconductor 20 is electrostatically attracted by the memory removing unit 20.

In FIG. 56, a plurality (two in this embodiment) of memory removing means 20a and 20b are provided along the rotation direction of the photoconductor 15. The configurations of these memory removing units 20a and 20b are the same as those described above. Upstream memory removal means 20a
The thickness of the brush member may be the same as that of the downstream-side memory removing means 20b. However, it is preferable that the thickness of the brush member 20a is larger than that of the brush member 20b. However, the thickness is limited to the range described above. Also, the memory removal means 20 on the upstream side
In a, it is desirable that the electrical resistance of the brush member is larger than that of the memory removal brush 20b on the downstream side. However, in this case as well, the electric resistance of the brush member is limited to the above-mentioned range.
The material of the brush members of the memory removing brushes 20a and 20b may be different.

FIG. 54 shows an example of attachment of the control panel 11 to the apparatus main body. The control panel 11 is composed of a unit 11a, and a frame 1a of the apparatus main body.
And is rotatably attached to the support shaft 11b via a support shaft 11b. The pointing shaft 11b also has a role of an electric wire passage for enabling electrical contact between the unit 11a and the apparatus main body. With such a configuration, the control panel can be in a state of standing upright with respect to the apparatus main body, so that operability and visibility can be significantly improved. The method of attaching the control panel is not limited to the above-described point, and the same effect can be obtained by rotatably supporting the unit 11a with respect to the apparatus main body.

Next, the control panel 11 has a fluorescent display tube 11c and a key switch 11d for turning on and off the display of the fluorescent display tube. Regarding the fluorescent display tube 11c and the key switch 11d,
The operation will be described with reference to FIG. Fluorescent display tube
11c is in an on state when the power is turned on, and performs display. When an image forming start key (not shown) is turned on in this state, an image forming operation is started. On the other hand, when the start key is not turned on, the key switch 11d is turned off, so that the fluorescent display tube is turned off and the display is turned off. In this case, the operation of the cooling fan unit 29 is stopped or decelerated. The image forming operation is started only when the fluorescent display tube 11c is displayed.
Further, once the fluorescent display tube 11c, whose display has been turned off, is turned on by turning on the key switch 11d, the display control returns to the state when the power is turned on. With such a configuration, the power consumption of the entire apparatus can be reduced.

FIG. 57 shows an arrangement in which the cleaning blade 300 is combined with the above-described memory removal brush 20 # as the memory removal means. The cleaning blade 300 has a thickness
It is made of an elastic member (for example, a urethane sheet material) of about 0.1 mm to 3 mm, and is provided upstream of the position where the memory removing brush 20 is arranged in the rotation direction of the photoconductor 15. The cleaning blade 300 removes and removes residual toner from the photoconductor 15. A hole 300a is formed in the cleaning blade 300, and the residual toner separated and removed by the cleaning blade drops through the hole 300a downward in the figure. The falling residual toner is once sucked by the memory removing brush 20 and returned to the photoreceptor again, thereby achieving the same effect as the effect already described.

Next, a configuration for peeling and transferring the sheet P after transfer from the photoconductor 15 will be described.

As shown in FIG. 3, a memory removing brush 20 is provided between the photoconductor 15 and the fixing unit 27. In this embodiment, the polarity of the toner is negative. The transfer charger 19 performs a positive discharge, and the sheet P that has passed through the transfer charger 19 has a charge of a positive polarity. On the other hand, a holding metal member 162 which is a holding member of the memory removing brush 20 is located below the passing paper P in the drawing. This holding fixture is applied with a positive potential (for example, a bias voltage of about 500 V).
Therefore, the electric field generated from the holding bracket 162 and the positive charges of the paper repel each other, and the paper P is lifted upward in the figure. Therefore, the paper P after the transfer is peeled off from the photoconductor 15 and is smoothly transported to the fixing unit 27.
Note that a sheet metal member may be independently provided instead of the holding metal member 162, and a bias may be applied to this sheet metal member.

FIG. 58 shows the shape of the surface 7b of the paper feed cover 7a detachably provided on the paper feed cassette 7 and rubbing with the paper P. The surface 7b has an uneven shape, and the surface roughness is 10 μm or more. With such a configuration, the paper P is
It comes into contact with only the recess of 7b, so-called point contact state,
The area where the paper P contacts the paper feed cover 7a is greatly reduced. Therefore, the generation of triboelectricity between the paper P and the paper supply cover 7a is reduced, and the paper supply cover 7a and the paper P are not attracted to the static electricity, so that the paper can come out of the paper supply cassette 7 smoothly. .

FIG. 58 (a) shows an example in which the surface 7b is formed in a satin pattern, FIG. 58 (b) shows an example in which the surface 7b is formed in a hairline (one direction) shape,
FIG. 58 (c) shows an example in which the surface 7b is formed in a hairline shape, FIG. 58 (d) shows an example in which the surface 7b is formed in a hairline (blind) shape, and FIG. 58 (e) shows the surface 7b. 58 (f) is an example in which the surface 7b is formed in a tile shape, and the shape of the surface 7b may be any shape.

Next, details of the developing means 18 will be described with reference to FIG.

A member 18a such as a malt plate having a pressure contact property is provided on a casing 91 of the developing unit 18 which is adjacent to the optical system unit 34.
There is provided a cleaning member 18c having a double structure by attaching an elastic member 18b such as aelt to the cleaning member 18c. The cleaning member 18c is in contact with the light emitting surface of the optical system unit 34, and when the developing means 18 is taken out of the apparatus main body and when the developing means 18 is inserted into the apparatus main body, the light of the optical system unit 34 is The emission surface slides along the longitudinal direction. Therefore, the optical system unit 34 is periodically cleaned of dirt such as scattered toner when the developing unit 18 is replaced.

Next, transfer on plain paper of the same material and weight is considered.

Schaffert RM “Electrophotography” Focal Press
According to the document of (1965), the gap electric field strength E, which is the basic principle of the electrostatic transfer method, is expressed by the following equation.

dp; transfer material thickness dt; toner layer thickness dm; recording layer thickness εp; transfer material relative dielectric constant εr1; toner layer relative dielectric constant εm; recording layer relative dielectric constant VH; on developed toner layer Surface potential VPS; Surface potential on the transfer material g; Void width The state of the toner layer and the state of the recording layer are determined by the electrophotographic process other than the transfer process, so the change in the electric field strength due to the characteristics of the transfer material itself Is the thickness of the transfer material; dp
And the surface potential VPS on the transfer material and the relative dielectric constant εp of the transfer material exist as factors.

Considering these, the surface potential VPS on the transfer material is the same as that of the scorotron transfer charger used in this embodiment because of the aforementioned corona discharge control effect. Does not change significantly. That is, when the paper comes into contact with a part of the grounded airframe due to the decrease in the surface resistance of the paper, the leakage of electric charge occurs. Because of the supply, the charge leakage through the paper can be neglected. Therefore, factors relating to the transfer material include the thickness of the transfer material and the relative dielectric constant of the transfer material.

If the thickness of the transfer material is assumed to be constant, if the humidity environment is supposed to be under a high humidity condition, the dp / εp term becomes smaller due to the increase in the relative dielectric constant of the transfer material. Become.

Therefore, when a scorotron charger is used, transfer is excessive in a high humidity environment compared to a normal humidity environment. Actually, in the experiment according to the present embodiment, as shown in FIG. 59, the optimum value of the transfer grid voltage is the reflection density of the residual toner on the photosensitive drum after the transfer (in this experiment, the toner image after the transfer is collected by a tape and Macbeth The measurement by the densitometer changes with respect to the relative humidity, and the portion where the residual toner amount Mt ≦ 0.4 is shown by oblique lines in the figure.

It can be understood that the optimum transfer condition is shifted depending on the environment. That is, it is understood that the transfer voltage value in a humid environment is preferably lower than the normal voltage value.

Therefore, even for the same transfer material of the same material and weight, it is possible to reduce the amount of transfer residual toner by switching the transfer grid voltage according to a change in environment or the like.

In the present embodiment, Mode 1 is used for plain paper and Mode 2 is used for envelopes and OHP paper, and two stages of changeover switches 352 are used as switching means for different transfer materials. Further, even if the same material and weight are used, the transfer efficiency changes (appropriate voltage value shifts) under the influence of environmental conditions and deterioration of the developer, so that three contacts 353a and 353b as shown in FIG. , 35
By providing a changeover switch 353 as a switching means having 3c and switching between H, N, and L in three stages, it is devised to eliminate the influence. Table 4 shows this changeover switch.
Becomes

The condition for the normally used plain paper uses the transfer grid voltage value 800V of CH-N of Mode1. In a humid environment, as shown in FIG. 59, the transfer grid voltage shifts to the lower side, so that the switch is switched to CH-L to set an appropriate transfer condition. Similarly, in low quality or the like, CH-H is a preferable transfer grid voltage value.

Further, as shown in FIG. 60, the right side cover of the apparatus main body 1 is provided.
The charging means (charging charger) 16 can be pulled out or inserted by opening 1c, but a safety switch 400 for detecting opening and closing of the cover is provided at a position facing the end of the charging means 16. I have. When the charging means 16 is not inserted, the operation of the switch 400 is not performed, so that the presence or absence of the charging means 16 is simultaneously detected.

This configuration eliminates the need for a unique circuit as in the conventional case where the charging means 16 is actually operated and the presence or absence is detected based on the amount of current flowing through the circuit, thereby reducing costs and ensuring operation reliability. Can be improved.

[Effects of the Invention] As described above, the image forming apparatus of the present invention prevents paper dust on the photoconductor, which is a problem when using the developing and cleaning device, from being mixed with the developer in the developing and cleaning device. And a first and second disturbance means (memory removal brush) for disturbing the residual developer remaining on the photosensitive member. First
The disturbing means disperses the residual developer by disturbing the residual developer, and the second disturbing means disperses the residual toner which is loosened by the disturbance of the first disturbing means and is present on the photoreceptor randomly. Paper dust is removed from the paper dust. As a result, when the paper dust mixes with the developer in the developing and cleaning device, the characteristics of the developer are changed, and the toner mixed with the paper dust is repeatedly used for development, so that the toner should originally adhere. This prevents paper dust from adhering to the electrostatic latent image and causing white spots or poor transfer of the image. Therefore, image transfer can always be performed with high transfer efficiency, and even when various environmental conditions and types of transfer materials are different, simultaneous development and cleaning with less waste toner and excellent environmental performance can be performed. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. FIG. 1 is a circuit diagram of a main part of the present invention, FIG. 2 is an external perspective view of the entire image forming apparatus, and FIG. Similarly, FIG. 4A is a schematic vertical sectional front view showing the structure of a main part, FIG. 4B is a perspective view of a process unit, and FIG. FIG. 6 is an explanatory view schematically showing the state of toner on the body according to the process, FIG. 6 is a cross-sectional view of the photoreceptor, FIG. 7 is an explanatory view showing an irradiation state when toner is attached to the photoreceptor, and FIG. FIG. 9 is a diagram showing the relationship between environmental conditions and residual potential when the film thickness is changed, FIG. 9 is a schematic cross-sectional view of the photoconductor, FIG. 10 is a diagram showing the relationship between the exposure amount of the photoconductor and surface potential, and FIG. FIG. A is an explanatory diagram for explaining the effect of an insufficient amount of exposure when the exposure pattern is a pine pattern, and FIG. FIG. 12 is an explanatory diagram for explaining the effect of the insufficient exposure when the turn is one line, FIG. 12 is a plan view of the charging means as viewed from the grid side, FIG. 13 is a front view thereof, and FIG.
FIG. 15 is a cross-sectional view taken along the line AA, FIG. 15 is a side view in the direction of arrow B in FIG. 13, FIG. 16 is an explanatory view showing a state where the electrostatic latent image forming means is removed, and FIG. Schematic cross section,
FIG. 18 is also a plan view, FIG. 19 is a side view of one end side,
FIG. 20 is a side view of the other end showing a state in which only the developing unit is similarly provided, FIG. 21 is a cross-sectional view near the driving force transmission side of the photoconductor,
FIG. 22 is a diagram schematically showing a state of power supply to the auto toner ring, FIG. 23 is a partially cutaway plan view of the transfer means viewed from the grid side, and FIG. 24 is a part of arrow A in FIG. Notched front view, No.
25 is a sectional view taken along the line BB of FIG. 23, and FIG. 26 is a sectional view of FIG.
FIG. 27 is a plan view of the memory removing means, FIG. 28 is a front view thereof, FIG. 29 is a bottom view thereof,
FIG. 30 is a cross-sectional view taken along the line AA of FIG. 27, FIG. 31 is a perspective view of a satin brush constituting the memory removing member, FIG. 32 is a view showing the attached state, and FIG. FIG. 34 is a diagram showing the state of the backing film, FIG. 34 is a diagram schematically showing the change in surface potential and the state of the toner on the photoconductor in the case of performing simultaneous cleaning with regular development, according to the process,
FIG. 35 is an explanatory diagram showing the contents of the surface potential, FIG. 36 is an explanatory diagram showing the relationship between the developing potential and the image density, the developing potential and the charging potential, and the cleaning potential and the charging potential. FIG. 37 is the potential after the exposure. 38A is a perspective view of a pile weaving brush constituting a memory removing member, FIG. 38B is a partially enlarged view of the pile weaving brush, and FIG. 38C is a partial cross section of the pile weaving brush. FIG. 39 is an explanatory diagram showing a transfer residual pattern after passing through the brush disposing portion. FIG. 40 is a diagram showing a surface potential on the photoreceptor after transfer when the transfer corona is continuous.
FIG. 41 is a diagram showing the process timing during printing, and FIG.
FIG. A is an explanatory view when the tip of the pile weave brush is used in contact, FIG. 42B is an explanatory view when the belly of the pile weave brush is used in contact, and FIG. FIG. 44 shows the relationship between the applied voltage and the discharge current at the time of transfer, and FIG. 45 shows the relationship between the applied voltage of the character portion and the solid portion image by the corotron charger and the transfer efficiency. FIG. 46 is an explanatory diagram showing the state of the potential and charge leakage of the transfer paper, FIG. 47 is a diagram showing the relationship between the applied voltage by the scorotron charger and the transfer efficiency, and FIG. 48 is easy to appear on the transfer paper Explanatory diagram showing an example of a memory pattern,
FIG. 49 is a diagram showing the relationship between the potential of the photoconductor and the transfer residual toner when a black negative memory is generated, FIG. 50 is a diagram showing an example of a transfer residual pattern, and FIG. 52 is a cross-sectional view of the brush, FIG. 53 is an explanatory diagram when the tip of the brush is used in a non-contact state with the photoconductor,
54 is a partially cutaway view showing the operation unit, FIG. 55 is a flowchart showing the operation control of the display means, FIG. 56 is a cross-sectional view when a plurality of brushes are used, and FIG. FIG. 58 is a view showing the shape of the paper feed cover surface, FIG. 59 is a view showing the relationship between the transfer humidity and the transfer grid voltage, and FIG. 60 is a view showing a state in which the right side cover is opened. It is a perspective view. 15 ... image carrier, 19 ... transfer means (corona transfer device), 352,
353: switching means, P: recording medium.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Ohno 70, Yanagicho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Within Toshiba Intelligent Technology Co., Ltd. Technology Co., Ltd. (56) References JP-A-60-168184 (JP, A) JP-A-59-133573 (JP, A) JP-A-57-135965 (JP, A) JP-A-55-28081 (JP, A) , A) JP-A-53-149339 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 21/00 G03G 15/16

Claims (1)

(57) [Claims] A charging means for charging a rotatable photosensitive member to a specific polarity; an exposure means for forming an electrostatic latent image by exposing the photosensitive member charged by the charging means to light; Supplying a developer charged to the same polarity as the specific polarity to the electrostatic latent image formed on the photoreceptor by means to develop, and removing a residual developer from an unexposed portion on the photoreceptor A developing and cleaning unit of a reversal developing method, and a developer image formed on the photoconductor by the developing and cleaning unit is electrostatically transferred from the photoconductor to a transfer material by corona discharge. A transfer unit, provided in contact with the photoconductor downstream of the transfer unit and upstream of the charging unit along the rotation direction of the photoconductor, and configured by bundling a plurality of fibers; After the transfer is performed at First disturbing means for disturbing the residual developer remaining on the photoreceptor; and, along the rotation direction of the photoreceptor, downstream of the first disturbing means, and upstream of the charging means. A second fiber configured to bundle the plurality of fibers and to agitate the residual developer that has passed through the first agitation means;
And a voltage application means for applying a voltage having a polarity opposite to the specific polarity to the first and second disturbance means, wherein the fibers constituting the first and second disturbance means are ,
Each having a resistance of 10 ² to 10 ⁷ Ω · cm and 1 to 50 so that the fibers constituting the first disturbance means are thicker than the fibers constituting the second disturbance means.
An image forming apparatus having a thickness selected from denier.