JP2001249536A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device where developer is excellently replaced after development so as to prevent a situation that developing ghost is left on a developer carrier and a ghost image is caused on a printed image, and the electrified amount of toner before development is uniformized so as to prevent the filming of the toner from occurring on a developing roller. SOLUTION: A destaticizing roller is made to abut on the developer carrier after the development through the developer, and vibration electric field is formed between the developer carrier and the destaticizing roller. Then, the developer or the developer carrier is destaticized by discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for forming an electrophotographic image such as a copying machine, a printer, and a facsimile, and a developing device for an electrostatic image.

[0002]

2. Description of the Related Art As a developer, there is a one-component developer (hereinafter also simply referred to as a toner), which has various advantages. However, the developer is carried and conveyed to an image forming body (for example, a photosensitive material used for electrophotography). It is difficult to uniformly apply a proper amount to a developer carrying member (developing roller), which is a movable developer carrying means for supplying the developer to the body drum). ), A thin layer of developer is formed on the developing roller, and is conveyed to the developing area to develop the latent image on the photosensitive drum.

[0003]

However, in the developing device using the above method, the toner on the developing roller after development is not replaced well, and it appears as a ghost image at the next development. There is a point.

[0004] Further, the developing roller and the toner are charged by the frictional charging by the blade, but the charging is not uniform, which causes problems such as deterioration of the toner and filming of the toner on the developing roller. In order to solve this problem, the toner charge was made uniform by corona discharge.However, the amount of charge of the toner before development was likely to be excessive or non-uniform, and the occurrence of toner filming on the developing roller was completely prevented. Has not been resolved.

[0005] The present invention solves the above-mentioned problems, and the replacement of the developer after the development is carried out favorably, the development ghost remains on the developer carrier, and the ghost image is prevented from being generated in the print image. It is another object of the present invention to provide a developing device which makes the charge amount of toner before development uniform and prevents the occurrence of toner filming on a developing roller.

[0006]

The object of the present invention is to provide a developer holding member for holding a thin layer of a non-magnetic one-component developer in contact with an image forming member for carrying a latent image thereon. In a developing device that develops an image, an elimination roller is brought into contact with a developer carrier after development via a developer, and an oscillating electric field is formed between the developer carrier and the elimination roller. Thus, the present invention is achieved by a developing device (first invention) wherein the developer or the developer carrier is discharged by discharging.

Another object of the present invention is to provide a developing device having a developer carrier which holds and rotates a thin layer of non-magnetic one-component developer, and a developer regulating member which regulates the amount of developer on the developer carrier. In the apparatus, the developer on the developer carrying member contacts the image forming body carrying the latent image to develop the latent image on the image forming body, and removes the developer formed on the thin layer. This is achieved by a developing device (a second invention), wherein a charging roller is brought into contact with the developer carrier via the developing device.

Another object of the present invention is to provide a developing device having a developer carrier that holds and rotates a thin layer of non-magnetic one-component developer, and a developer regulating member that regulates the amount of developer on the developer carrier. In the device, a charging roller is brought into contact with the developer carrier via the developer formed in the thin layer, and an oscillating electric field is formed between the developer carrier and the charging roller. The oscillating electric field has a peak value 1 at which the developer on the developer carrier is attracted to the charging roller.
And a peak value 2 pressed against the developer carrier, wherein the time of the peak value 1 is shorter than the time of the peak value 2 (third invention). .

[0009]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Further, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning or technical scope of the terms of the present invention.

An image forming process and each mechanism of an embodiment of an image forming apparatus using a developing device according to each claim of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a main part of a color image forming apparatus showing an embodiment of an image forming apparatus using a developing device common to the claims of the present invention.

In FIG. 1, reference numeral 10 denotes a photosensitive drum as an image forming body for each color, 11 a scorotron charger as charging means for each color, 12 an exposure optical system as image writing means for each color, and 13 Denotes a developing device that is a developing unit for each color,
Reference numeral 4a denotes a transfer belt, and 14c denotes a transfer unit for each color.
A next transfer unit, 14m is a charge eliminator that is a charge elimination unit of the transfer belt, 14b is a pressing elastic plate that is a pressing unit of the transfer belt,
Reference numeral 17 denotes a fixing device as a fixing unit; 190, a cleaning device as a cleaning unit for an image forming body for each color;
Reference numeral 0a denotes a cleaning device which is a transfer belt cleaning unit.

In this embodiment, a photosensitive drum 10 as an image forming body for each color, a scorotron charger 11 as a charging unit for each color, an exposure optical system 12 as an image writing unit for each color, and an The developing device 13 as a developing device and the cleaning device 190 as a cleaning device for an image forming body form a set of these as one set of yellow (Y), magenta (M), cyan (C), and black (K). Four sets of the image forming units 100 are provided. Under the transfer belt 14a with respect to the rotation direction of the transfer belt 14a rotated clockwise as indicated by the arrow in FIG. M, C, and K are arranged in this order.

A photosensitive drum 10 as an image forming body for each color
Is formed by forming an organic photoreceptor layer (OPC) having an overcoat layer (protective layer) on the outer periphery of a cylindrical metal substrate formed of, for example, an aluminum material on the outer periphery of the metal substrate. As will be described later, the transfer belt 14a in the contact state is rotated by receiving the driving force from the transfer belt 14a, and is rotated in a counterclockwise direction indicated by an arrow in FIG. The drum 10 is rotated.

The organic photoreceptor layer comprises a charge generating material (CGM)
And a charge transport layer (CTL) containing a charge transport material (CTM) as a main component. The organic photoreceptor layer comprises a charge generation material (CGM) and a charge transport material (C
(TM) in one layer, and the photosensitive layer having the single-layer structure or the two-layer structure usually contains a binder resin.

The scorotron charger 11, which is a charging means for each color, has the same polarity as the toner (toner at the time of development) used by the control grid and the corona discharge electrode maintained at a predetermined potential. The charging action (minus charging in the present embodiment) is performed by the corona discharge of (negative polarity), and a uniform potential is applied to the photosensitive drum 10. As the corona discharge electrode of the scorotron charger 11, a saw-tooth electrode or a needle electrode can also be used.

Exposure optical system 1 as image writing means for each color
2 indicates that the exposure position on the photosensitive drum 10 is the photosensitive drum 1 with respect to the scorotron charger 11 for each color described above.
It is arranged around the photosensitive drum 10 so as to be located on the downstream side in the rotation direction of 0. The exposure optical system 12 rotationally scans a laser beam emitted from a laser light source (not shown) with a rotary polygon mirror (not shown), and comprises an fθ lens (not shown), a reflection mirror (not shown), and the like, and is separate. In accordance with the image data of each color read by the image reading device and stored in the memory, the photosensitive layer of the photosensitive drum 10 is image-exposed to form an electrostatic latent image on the photosensitive drum 10 for each color.

The developing device 13, which is a developing means for each color,
In this embodiment, yellow (Y), magenta (M), cyan (C), and black (K) negatively charged non-magnetic one-component developers (toners) are accommodated in the present embodiment, and the peripheral portions of the photosensitive drum 10 are respectively charged. The surface of the photosensitive drum 10 rotates in the same direction as the rotation direction of the photoreceptor drum 10 at the developing position.
A developing roller 131 which is a developer carrier made of solid rubber such as urethane or silicon having a resistance of 10 ⁷ Ω · cm (JIS A) is provided, and a developing bias voltage of a DC voltage is applied to the developing roller 131. Thereby, the one-component reversal development of the contact is performed, and a toner image is formed on the latent image portion on the photosensitive drum 10. A supply roller 132, which is a toner supply member, is provided in contact with the development roller 131, and the supply roller 132 supplies and collects toner to the development roller 131. The charge amount of the toner used for development is preferably about 5 to 15 μC / g.

As the non-magnetic one-component developer (toner) used in the developing device 13, a spherical insulating toner obtained by the same method as the conventional toner can be used. Spherical toners are preferred for enhancing developability and obtaining high quality images. Preferable toners include polymerization of resins such as styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, and fatty acid wax such as palmitic acid and stearic acid. An average particle diameter of 20 μm or less, preferably 10 μm, which can be produced by a method similar to a conventionally known method for producing toner particles by adding a coloring component such as a color pigment and a charge controlling agent and the like, if necessary, to the agent. Hereinafter, it is particularly preferable that the particles be composed of particles of 1 to 7 μm. If necessary, a fluidizing agent for improving the fluidity of the particles and a cleaning agent useful for cleaning the surface of the image forming body are mixed. As a fluidizing agent, colloidal silica, silicone varnish, metal soap or a nonionic surfactant can be used, and as a cleaning agent,
Surface active agents such as fatty acid metal salts, organic group-substituted silicon, and fluoric acid can be used.

The transfer belt 14a has a volume resistance of 10 ¹² -1.
It is an endless belt of 0 ¹⁵ Ωcm, for example, a conductive material is dispersed in engineering plastics such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, nylon alloy, etc. This is a seamless belt having a two-layer structure in which a 1.0 mm semiconductive film substrate is coated with a fluorine coating having a thickness of 5 to 50 μm, preferably as a toner filming preventing layer. In addition, as the base of the transfer belt 14a, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber or urethane rubber can be used. Transfer belt 1
4a is stretched in contact with a driving roller 14d and a driven roller 14e. During image formation, the driving roller 14d is rotated by an intermediate transfer member driving motor (not shown), and is upstream of a transfer position for each color. The transfer belt 14a is pressed against the photosensitive drum 10 by the pressing elastic plate 14b disposed on the side, and the transfer belt 14a is rotated clockwise as indicated by an arrow in FIG. At this time, the photosensitive drum 1 receives the driving force of the transfer belt 14a following the movement of the transfer belt 14a.
0 is driven and rotated.

A primary transfer unit 14c as a transfer unit for each color
Is preferably constituted by a corona discharger, is provided opposite to the photosensitive drum 10 for each color with the transfer belt 14a interposed therebetween, and the transfer belt 14a and the photosensitive drum 1 for each color are provided.
A transfer area (no sign) is formed for each color between 0 and 0. A DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the primary transfer device 14c for each color, and a transfer electric field is formed in the transfer area. The toner image is transferred onto the transfer belt 14a.

The static eliminator 14m, which is a static elimination means for each color,
Preferably, the primary transfer unit 1 is constituted by a corona discharger.
The transfer belt 14a charged by 4c is neutralized.

Pressing elastic plate 1 as pressing means for the transfer belt
4b is formed by a rubber blade of urethane or the like, is disposed upstream of the transfer position for each color, presses the transfer belt 14a against the photosensitive drum 10 at the time of image formation, and follows the movement of the transfer belt 14a to move the photosensitive belt. The body drum 10 is rotated.

The fixing device 17 serving as a fixing means includes a fixing roller 17 having a heater inside at least one of the rollers.
a, and a pressure roller 17b. The toner image on the transfer material is fixed by applying heat and pressure between the fixing roller 17a and the pressure roller 17b.

The cleaning device 190, which is a cleaning device for the image forming body for each color, and the cleaning device 190a, which is a cleaning device for the transfer belt, have the same structure, and the cleaning devices 190 and 190a are provided respectively. The cleaning device 190 uses the cleaning blade 191 as a member to transfer residual toner on the photosensitive drum 10 for each color, and the cleaning device 190a uses the transfer belt 14a.
The transfer residual toner is cleaned.

Next, the image forming process (image forming step) will be described. The conveyance belt 14a is rotated by the start of an intermediate transfer member driving motor (not shown) at the start of image recording, and is brought into contact with the conveyance belt 14a.
4a, the photosensitive drum 10 of the yellow (Y) image forming unit 100 is rotated in the counterclockwise direction indicated by the arrow in FIG. 1, and at the same time, the Y scorotron charger 11 is rotated.
, The application of a potential to the Y photoconductor drum 10 is started.

After a potential is applied to the Y photosensitive drum 10, the Y exposure optical system 12 starts image writing with a first color signal, that is, an electric signal corresponding to the Y image data, and the Y photosensitive drum 10 starts writing. Y of the original image on the surface of the body drum 10
An electrostatic latent image corresponding to the image is formed.

The latent image is reversely developed in a contact state by a developing roller 131 of a Y developing device 13, and a yellow (Y) toner image is formed according to the rotation of the Y photosensitive drum 10.

The Y toner image formed on the Y photoreceptor drum 10 as the image forming body by the above-described image forming process is transferred to the Y transfer area (no symbol) in the Y transfer area (no symbol). The transfer belt 1 is moved by the primary transfer device 14c.
4a.

Next, the transfer belt 14a is synchronized with the Y toner image, and the image forming unit 1 of magenta (M) is formed.
00, an electric potential is applied by the charging action of the M scorotron charger 11, and the M exposure optical system 12 performs image writing using the second color signal, that is, an electric signal corresponding to M image data, and develops the M image. Developing roller 1 of device 13
M photosensitive drum 1 by reversal development of contact by 31
The M toner image is superimposed on the Y toner image from above the Y toner image by the M primary transfer unit 14c, which is the first transfer means, in the M transfer area (no symbol). It is formed together.

By the same process, the image is synchronized with the superposed toner images of Y and M, and is formed by the third color signal formed on the photosensitive drum 10 of C by the image forming unit 100 of cyan (C). The C toner image corresponding to the C image data is transferred from the top of the Y and M toner images by the C primary transfer unit 14c, which is the first transfer unit, in the C transfer area (no symbol). A toner image of C is formed on the photosensitive drum 10 of K by the black (K) image forming unit 100 in synchronism with the toner image of Y, M, and C. The K toner image corresponding to the K image data based on the fourth color signal is transferred by the K primary transfer unit 14c as the first transfer unit in the K transfer area (no sign). From the top of the C toner image Over image is formed by overlapping, Y, M, color toner image overlay C and K are formed on the transfer belt 14a.

The transfer residual toner remaining on the peripheral surface of the photosensitive drum 10 for each color after the transfer is cleaned by a cleaning device 190 which is a means for cleaning the image forming body for each color.

In synchronization with the formation of the superimposed color toner image on the transfer belt 14a, recording paper is fed from a paper feed cassette (not shown) as a transfer material storage means via a timing roller (not shown) as a transfer material feeding means. P is conveyed to a transfer area (no sign) of a secondary transfer device 14g, which is a second transfer unit, and a secondary transfer device to which a DC voltage having the opposite polarity (positive polarity in the present embodiment) to the toner is applied. By 14g,
The superimposed color toner images on the transfer belt 14a are collectively transferred onto the recording paper P.

The recording paper P on which the color toner image has been transferred is
The charge is removed by a charge removing electrode 16b, which is a separating means formed of a sawtooth electrode plate, conveyed to the fixing device 17, and heat and pressure are applied between the fixing roller 17a and the pressure roller 17b, so that the recording paper P After the toner image is fixed,
The sheet is discharged to a tray (not shown) outside the apparatus.

The transfer residual toner remaining on the peripheral surface of the transfer belt 14a after the transfer is cleaned by a cleaning device 190a which is a transfer belt cleaning means provided opposite to the driven roller 14e with the transfer belt 14a interposed therebetween. .

In the above, the transfer material is transferred to the transfer belt 14a.
The toner image formed by the image forming unit 100 for each color is sequentially transferred onto a transfer material by a first transfer unit for each color, and a color toner image is formed on the transfer material. , May be fixed. In this case, transfer by the second transfer unit is unnecessary.

Embodiment 1 A developing device according to claim 1 of the present invention will be described with reference to FIG. FIG. 2 is an enlarged cross-sectional configuration diagram of the developing device according to claim 1 of the present invention.

According to FIG. 2, the developing device 13 which is a developing means for each color includes yellow (Y), magenta (M), cyan (C) and black (K). A non-magnetic one-component developer (toner) is accommodated, respectively, and comes into contact with (contacts) the peripheral surface of the photosensitive drum 10. The developing roller 131 rotates in the direction (counterclockwise in FIG. 2). A supply roller 132, which is a toner supply member, is provided in contact with the developing roller 131. The supply roller 132 supplies toner to the developing roller 131 and collects toner from the developing roller 131. The supply roller 132 is provided in the supply section in parallel with the developing roller 131, and is rotated in the same direction as the developing roller 131 (counterclockwise in FIG. 2).

The developing roller 131, which is a developer carrier,
For example, a hardness of 45 ° (JIS)
In A), it is formed of a solid rubber such as urethane or silicon having a volume resistance of 10 ⁷ Ω · cm. At the time of development, the developing roller 131 is applied with a developing bias VB1 having the same polarity as the toner polarity to be used (minus polarity in the present embodiment) and a DC voltage of about -250 V to perform one-component inversion development of contact. Then, a toner image is formed on the latent image portion on the photosensitive drum 10.

Supply roller 132 as a toner supply member
Is formed by forming a foamed rubber layer with a foamed rubber such as urethane or silicone on the outer side (outer peripheral surface) of a conductive metal core (no symbol) such as stainless steel. During development, the supply roller 13
2, a supply roller bias VK1 of the same polarity as the toner pole to be used (minus polarity in the present embodiment) and a DC voltage of about -500 V is applied.

Reference numeral 133 denotes a blade which is a developer regulating member provided for regulating the height and amount of the developer layer (toner layer). For example, a belt-like elastic plate 133a made of plate-like stainless steel or rubber material is used. And a belt-like elastic body 1 made of, for example, a sponge or a foaming agent of urethane rubber, which is attached to a contact portion with the developing roller 131 at a tip end of the elastic plate 133a.
33b. The blade 133 is a so-called counter-type developer regulating member that is disposed with its tip facing upstream in the rotation direction of the developing roller 131. In addition,
The blade 133 may also use a so-called trail-type developer regulating member whose tip is arranged downstream of the developing roller 131 in the rotation direction. This blade 133
As a result, one or two thin developer layers are formed on the developing roller 131.

Reference numeral 134 denotes a hopper section containing a developer, which is surrounded by a developing casing 138. Hopper section 134
Inside, there is a lever-shaped stirring member 134a that rotates counterclockwise in the figure, and the stirring member 134
A rotates and the developer in the hopper 134 is agitated and carried out, and the developer is supplied.

Reference numeral 138 denotes a developing casing. The developing casing 138 is formed along the operation area of the stirring member 134a in the hopper 134, but has a protruding portion 138a protruding outward near the developing roller 131. The blade 133 is attached to and supported by the protrusion 138a. The developer discharged from the hopper 134 is frictionally charged between the developing roller 131, the blade 133, and the supply roller 132.

Reference numeral 135 denotes a discharging roller provided in the present embodiment. The discharging roller 135 is a developing roller 131.
And is provided near the entrance of the developing casing 138 on the downstream side in the rotation direction of the developing roller 131 in the developing area.
The static elimination roller 135 has a conductive sponge-like elastic body in which conductive carbon powder is dispersed around a conductive core metal,
The elastic roller has a surface covered with a thin protective layer having a high resistance (10 ⁶ to 10 ¹⁰ Ω / cm ² ). Static elimination roller 135
Abuts on the developing roller 131 via the toner layer collected after the development, and is driven to rotate. The static elimination roller 135 includes
It has the same polarity as the toner pole to be used (negative polarity in this embodiment), a DC voltage of about -100 V, and a frequency of 1
kHz, the discharging roller bias VJ1 obtained by superimposing an AC voltage of peak-to-peak voltage 1 kV _pp is applied, the developing roller 131
An oscillating electric field is generated between the discharge roller 135 and the discharge roller 135. The developing roller 131 and the one-component developer (toner) are discharged by AC discharge of an oscillating electric field generated between the developing roller 131 and the discharging roller 135, and the one-component developer (toner) from the supply roller 132 to the developing roller 131 is discharged. ) And the recovery of the one-component developer (toner) from the developing roller 131 to the supply roller 132 is performed satisfactorily.

The potential difference between the DC voltage applied to the developing roller 131 and the DC voltage applied to the charge eliminating roller 135 is constant, and a negative polarity DC voltage having a higher absolute value than the DC voltage applied to the developing roller 131 is applied to the charge eliminating roller 135. Is preferred. However, when the developing roller 131 and the one-component developer (toner) are set to the same potential, the toner is removed from the discharging roller 135.
Therefore, it is necessary to reduce the charge amount of the toner to have the same polarity and maintain the condition that a ghost image does not appear. From this, the static elimination roller 1
The DC voltage to 35 is preferably higher than the DC voltage to developing roller 131.

As described above, the charge of the developer carrier after the development and the residual toner after the development are removed, and the developer on the developer carrier after the development is exchanged favorably. Is removed, and a developing device that prevents generation of a developing ghost can be realized.

Second Embodiment A developing device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is an enlarged cross-sectional configuration diagram of a developing device according to a second aspect of the present invention.

According to FIG. 3, the developing device 13 which is a developing means for each color includes yellow (Y), magenta (M), cyan (C) and black (K). A non-magnetic one-component developer (toner) is accommodated, respectively, and comes into contact with (contacts) the peripheral surface of the photosensitive drum 10. The developing roller 131 rotates in the direction (counterclockwise in FIG. 3). A supply roller 132, which is a toner supply member, is provided in contact with the developing roller 131. The supply roller 132 supplies toner to the developing roller 131 and collects toner from the developing roller 131. The supply roller 132 is provided in the supply section in parallel with the developing roller 131, and is rotated in the same direction as the developing roller 131 (counterclockwise in FIG. 3).

The developing roller 131, which is a developer carrier,
For example, a hardness of 45 ° (JIS)
In A), it is formed of a solid rubber such as urethane or silicon having a volume resistance of 10 ⁷ Ω · cm. At the time of development, the developing roller 131 is applied with a developing bias VB1 having the same polarity as the toner polarity to be used (minus polarity in the present embodiment) and a DC voltage of about -250 V to perform one-component inversion development of contact. Then, a toner image is formed on the latent image portion on the photosensitive drum 10.

Supply roller 132 as a toner supply member
Is formed by forming a foamed rubber layer with a foamed rubber such as urethane or silicone on the outer side (outer peripheral surface) of a conductive metal core (no symbol) such as stainless steel. During development, the supply roller 13
2, a supply roller bias VK1 of the same polarity as the toner pole to be used (minus polarity in the present embodiment) and a DC voltage of about -500 V is applied.

Reference numeral 133 denotes a blade which is a developer regulating member provided for regulating the height and amount of the developer layer (toner layer). For example, a belt-like elastic plate 133a made of plate-like stainless steel or rubber material is used. And a belt-like elastic body 1 made of, for example, a sponge or a foaming agent of urethane rubber, which is attached to a contact portion with the developing roller 131 at a tip end of the elastic plate 133a.
33b. The blade 133 is a so-called counter-type developer regulating member that is disposed with its tip facing upstream in the rotation direction of the developing roller 131. In addition,
The blade 133 may also use a so-called trail-type developer regulating member whose tip is arranged downstream of the developing roller 131 in the rotation direction. This blade 133
As a result, one or two thin developer layers are formed on the developing roller 131.

Reference numeral 134 denotes a hopper section containing a developer, which is surrounded by a developing casing 138. Hopper section 134
Inside, there is a lever-shaped stirring member 134a that rotates counterclockwise in the figure, and the stirring member 134
By rotating a, the developer in the hopper 134 is agitated and carried out, and the developer is supplied.

Reference numeral 138 denotes a developing casing. The developing casing 138 is formed along the operation range of the stirring member 134a in the hopper 134, but has a protruding portion 138a protruding outward near the developing roller 131. The blade 133 is attached to and supported by the protrusion 138a. The developer discharged from the hopper 134 is frictionally charged between the developing roller 131, the blade 133, and the supply roller 132.

Reference numeral 136 denotes a charging roller provided in this embodiment, and the charging roller 136 is a developing roller 131.
And is provided in the vicinity of the photosensitive drum 10 on the upstream side in the rotation direction of the developing roller 131 in the developing area. The charging roller 136 has a conductive sponge-like elastic body around a conductive core, and has a high resistance (10 ⁶ to 10 ¹⁰ Ω / c) on the surface.
m ² ) is an elastic roller covered with a thin protective layer. The charging roller 136 is in contact with the developing roller 131 carrying the toner layer before development via the toner layer, and is driven to rotate. The charging roller 136 has the same polarity (minus polarity in this embodiment) as the toner pole to be used, and has a voltage of -100 V
A charging roller bias VT1 of about DC voltage is applied. The one-component developer (toner) is charged by an electric field generated between the developing roller 131 and the charging roller 136 due to this.

The one-component developer (toner) is uniformly charged to 30 to 300 V by the output voltage difference between the DC voltage of the developing roller 131 and the DC voltage of the charging roller 136. Since this DC voltage difference is related to the image density, after adjusting the density,
The settings are made constant.

In this case, it is preferable to apply a negative polarity DC voltage, which is higher in absolute value than the DC voltage to the developing roller 131, to the charging roller 136, and the difference between the two is set to be 500 to 200V. It is preferable to make the one-component developer (toner) on the developing roller 131 have a uniform toner charge amount.

According to the above, it is possible to form a developer layer having a uniform toner charge amount on the developer carrying member before development, thereby enabling a developing device capable of preventing filming on the developer carrying member and deterioration of the toner. In addition, a change in the amount of charge of the developer due to an environmental change is prevented, a ghost image is prevented from being generated, an image having extremely excellent image quality is obtained, and a developing device capable of high-speed development can be realized.

Embodiment 3 A developing device according to claim 3 or 4 of the present invention will be described with reference to FIGS. FIG. 4 is an enlarged sectional view of the structure of the developing device according to the third or fourth aspect of the present invention, and FIG. 5 is a diagram showing a waveform of a charging roller bias.

According to FIG. 4, the developing device 13 which is a developing means for each color includes yellow (Y), magenta (M), cyan (C), and black (K), and in this embodiment, negatively charged. A non-magnetic one-component developer (toner) is accommodated, and each of the non-magnetic one-component developers (toner) is brought into contact (contact) with the peripheral surface of the photosensitive drum 10. The developing roller 131 rotates in the direction (counterclockwise in FIG. 4). A supply roller 132, which is a toner supply member, is provided in contact with the developing roller 131. The supply roller 132 supplies toner to the developing roller 131 and collects toner from the developing roller 131. The supply roller 132 is provided in the supply unit in parallel with the developing roller 131, and is rotated in the same direction as the developing roller 131 (counterclockwise in FIG. 4).

The developing roller 131, which is a developer carrier,
For example, a hardness of 45 ° (JIS)
In A), it is formed of a solid rubber such as urethane or silicon having a volume resistance of 10 ⁷ Ω · cm. At the time of development, the developing roller 131 is applied with a developing bias VB1 having the same polarity as the toner polarity to be used (minus polarity in the present embodiment) and a DC voltage of about -250 V to perform one-component inversion development of contact. Then, a toner image is formed on the latent image portion on the photosensitive drum 10.

Supply roller 132 as a toner supply member
Is formed by forming a foamed rubber layer with a foamed rubber such as urethane or silicone on the outer side (outer peripheral surface) of a conductive metal core (no symbol) such as stainless steel. During development, the supply roller 13
2, a supply roller bias VK1 of the same polarity as the toner pole to be used (minus polarity in the present embodiment) and a DC voltage of about -500 V is applied.

Reference numeral 133 denotes a blade which is a developer regulating member provided for regulating the height and amount of the developer layer (toner layer). For example, a belt-like elastic plate 133a made of plate-like stainless steel or rubber material is used. And a belt-like elastic body 1 made of, for example, a sponge or a foaming agent of urethane rubber, which is attached to a contact portion with the developing roller 131 at a tip end of the elastic plate 133a.
33b. The blade 133 is a so-called counter-type developer regulating member that is disposed with its tip facing upstream in the rotation direction of the developing roller 131. In addition,
The blade 133 may also use a so-called trail-type developer regulating member whose tip is arranged downstream of the developing roller 131 in the rotation direction. This blade 133
As a result, one or two thin developer layers are formed on the developing roller 131.

Reference numeral 134 denotes a hopper section containing a developer, which is surrounded by a developing casing 138. Hopper section 134
Inside, there is a lever-shaped stirring member 134a that rotates counterclockwise in the figure, and the stirring member 134
By rotating a, the developer in the hopper 134 is agitated and carried out, and the developer is supplied.

Reference numeral 138 denotes a developing casing. The developing casing 138 is formed along the operation area of the stirring member 134a in the hopper 134, but has a protruding portion 138a protruding outward near the developing roller 131. The blade 133 is attached to and supported by the protrusion 138a. The developer discharged from the hopper 134 is frictionally charged between the developing roller 131, the blade 133, and the supply roller 132.

Reference numeral 136 denotes a charging roller provided in this embodiment, and the charging roller 136 is a developing roller 131.
And is provided in the vicinity of the photosensitive drum 10 on the upstream side in the rotation direction of the developing roller 131 in the developing area. The charging roller 136 is made of a conductive sponge-like elastic body around a conductive cored bar, and has a volume resistance of 10 ⁵ Ω · cm or less.
The layer and the surface (outer peripheral surface) of the first layer have a volume resistance of 10 ⁶ Ω
-An elastic roller composed of a second layer as a thin protective layer of not less than cm. The charging roller 136 is in contact with the developing roller 131 carrying the toner layer before development via the toner layer, and is driven to rotate. As shown in FIG. 5, the charging roller 136 has a DC voltage of about -500 V, an alternating current of a frequency of 1 kHz and a peak-to-peak voltage of 1 kV _pp having the same polarity as the toner pole to be used (minus polarity in the present embodiment). An oscillating electric field is generated between the developing roller 131 and the charging roller 136 by applying the charging roller bias VT2 on which the voltage is superimposed. A one-component developer (toner) is generated by an oscillating electric field generated between the developing roller 131 and the charging roller 136.
Charge. As described above, during development, the developing roller 13
The DC voltage applied to the developing bias VB1 is -250 V, which has the same polarity (minus polarity in the present embodiment) as the toner pole used.

The oscillating electric field of the charging roller bias VT2 for forming an oscillating electric field between the developing roller 131 and the charging roller 136 is, for example, a one-component developer (toner) on the developing roller 131 as shown by a rectangular wave in FIG. ) Is charging roller 1
The peak value 1 indicated by the voltage value V1 (V: volts) (shown by a solid line arrow in FIG. 5) attracted to the side 36 and the one-component developer (toner) on the developing roller 131 are
And a peak value 2 indicated by a voltage value V2 (V: volts) (indicated by a chain line arrow in FIG. 5), and the time T1 (msec) of the peak value 1 is the time T2 of the peak value 2
(Msec). As a result, the one-component developer (toner) on the developing roller 131 is attracted to the charging roller 136 side rather than the developing roller 1.
A large amount of force acts on the developing roller 1
A good toner layer is formed on the base 31.

As described above, uniform charging of the toner can be obtained by combining the DC voltage and the AC voltage of the charging roller bias. In addition, it also has an effect of eliminating charge accumulation on the developing roller and a change in the amount of charge of the toner generated after the development, thereby eliminating the development ghost.

The one-component developer (toner) is uniformly charged to 30 to 300 V by the output voltage difference between the DC voltage of the developing roller 131 and the DC voltage of the charging roller 136. Since this DC voltage difference is related to the image density, after adjusting the density,
The settings are made constant.

In this case, it is preferable to apply a negative polarity DC voltage having an absolute value higher than the DC voltage to the developing roller 131 to the charging roller 136, and the difference between the absolute values of the two is set to 500 V to 2 kV. It is preferable to make the one-component developer (toner) on the developing roller 131 have a uniform toner charge amount.

According to the above, it is possible to form a developer layer having a uniform toner charge amount on the developer carrying member before development, thereby enabling a developing device which prevents filming on the developer carrying member and deterioration of the toner. In addition, a change in the amount of charge of the developer due to an environmental change is prevented, a ghost image is prevented from being generated, an image having extremely excellent image quality is obtained, and a developing device capable of high-speed development can be realized.

[0070]

According to the first aspect, static electricity is removed from the developer carrier after development and the residual toner after development, so that the developer on the developer carrier after development is exchanged favorably. In addition, the development pattern on the developer carrier is removed, and a development device that prevents generation of a development ghost can be provided.

According to the second to fourth aspects, it is possible to form a developer layer having a uniform toner charge amount on the developer carrying member before the development, so that filming on the developer carrying member and deterioration of the toner can be prevented. A developing device that can prevent the occurrence of ghost images by preventing a change in the amount of charge of the developer due to environmental changes, obtains an image with extremely excellent image quality, and is capable of high-speed development. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a color image forming apparatus showing an embodiment of an image forming apparatus using a developing device common to the claims of the present invention.

FIG. 2 is an enlarged cross-sectional configuration diagram of a developing device according to claim 1 of the present invention.

FIG. 3 is an enlarged cross-sectional configuration diagram of a developing device according to a second embodiment of the present invention.

FIG. 4 is an enlarged cross-sectional configuration diagram of a developing device according to claim 3 or 4 of the present invention.

FIG. 5 is a diagram illustrating a waveform of a charging roller bias.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14 a transfer belt 131 developing roller 132 supply roller 133 blade 134 hopper unit 135 static elimination roller 136 charging roller 138 developing casing P recording paper

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H073 AA09 BA03 BA06 BA15 BA45 CA02 2H077 AD06 AD13 AD17 AD31 AD36 AD37 CA09 CA10 EA14 EA15 FA25

Claims (4)

[Claims] 1. A developing device for developing a latent image on an image forming body by bringing a developer carrying body holding a thin layer of a non-magnetic one-component developer into contact with an image forming body carrying a latent image. A developing roller is brought into contact with the developer carrier after development via a developer, and an oscillating electric field is formed between the developer carrier and the discharging roller to form the developer or the developing agent. A developing device for discharging a developer carrier by discharging. 2. A developing device comprising: a developer carrier that holds and rotates a thin layer of a non-magnetic one-component developer; and a developer regulating member that regulates the amount of developer on the developer carrier. The developer on the developer carrier contacts the image forming body that carries the latent image to develop the latent image on the image forming body, and develops the developer via the developer formed on the thin layer. A developing device wherein a charging roller is brought into contact with an agent carrier. 3. A developing device comprising: a developer carrier that holds and rotates a thin layer of a non-magnetic one-component developer; and a developer regulating member that regulates an amount of developer on the developer carrier. A charging roller is brought into contact with the developer carrier via a developer formed in a thin layer, and an oscillating electric field is formed between the developer carrier and the charging roller. A peak value 1 at which the developer on the developer carrier is attracted to the charging roller, and a peak value 2 at which the developer is pressed toward the developer carrier, and the time of the peak value 1 is equal to the peak value 2. A developing device that is shorter than the time. 4. The charging roller includes a first layer having a volume resistance of 10 ⁵ Ω · cm or less around a conductive core metal, and a second layer having a volume resistance of 10 ⁶ Ω · cm or more outside the first layer. 4. The developing device according to claim 3, comprising: