JP2001249532A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device where feeding of developer to a developer carrier by a feeding roll, recovery of the developer after developing and exchange of the developer are carried out well. SOLUTION: In the developing device, the feeding roll is provided with a 1st foamed rubber layer with a volume resistivity that is <=105 Ω.cm and with a thickness of >=1 mm around a periphery of a conductive core metal and a 2nd foamed rubber layer with a volume resistivity that is >=106 Ω.cm with a thickness of <=0.5 mm outside the 1st foamed rubber layer and an oscillating electric field is formed between the developer carrier and the feeding roll.

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. 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 the developer is formed on the developing roller, and is conveyed to the developing area to develop the latent image on the image forming body. However, this method has a problem that a developing ghost remains on the developing roller after the development, and a ghost image is generated in a print image.

In order to solve the above-mentioned problems, the present inventors have applied a one-component developer (toner) uniformly to a developer carrier (developing roller) using a supply roller to prevent a ghost image. Has been proposed in Japanese Patent Application No. 11-131263.

[0004]

However, in the developing device according to the above proposal, the supply of the developer to the developer carrier by the supply roller and the collection of the developer after the development are performed.
There is a problem that the replacement of the developer is not performed well and a development ghost occurs.

The present invention solves the above-mentioned problems and provides a developing device which can exchange the developer between the supply of the developer to the developer carrier by the supply roller and the recovery of the developer after the development. The purpose is to do.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer carrier that holds and rotates a thin layer of a non-magnetic one-component developer, and a supply roller that supplies and recovers the developer to and from the developer carrier. A developing device having a developer regulating member that regulates an amount of developer on the developer carrying member, wherein the supply roller has a volume resistance around the conductive cored bar of 10 ⁵ Ω · cm or less and a thickness of 10 ⁵ Ω · cm or less. A first foamed rubber layer having a thickness of 1 mm or more, and a second foamed rubber layer having a volume resistance of 10 ⁶ Ω · cm or more and a thickness of 0.5 mm or less provided outside the first foamed rubber layer, A developing device for forming an oscillating electric field between a developer carrier and the supply roller (first invention)
Achieved by

Another object of the present invention is to provide a developer carrier that holds and rotates a thin layer of non-magnetic one-component developer, a supply roller that supplies and recovers the developer to and from the developer carrier, In a developing device having a developer regulating member that regulates the amount of developer on a carrier, the supply roller forms a foam rubber layer by attaching foam rubber to the outside of a conductive cored bar, and forms a foam rubber layer. This is achieved by a developing device (second invention), wherein the diameter of the cell is formed so as to increase from the conductive core portion to the surface layer.

[0008]

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 the claims 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, 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 charging means for each color, an exposure optical system 12 as an image writing means for each color, and a 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 photosensitive drum 10 at the developing position with or without contact with the surface.
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), and a DC voltage or an AC voltage with respect to the developing roller 131. By applying a developing bias voltage in which a DC voltage is superimposed on the photosensitive drum 10, contact or non-contact one-component inversion development is performed, and a toner image is formed on a latent image portion on the photosensitive drum 10. A supply roller 132 (or supply roller 132A), which is a toner supply member, is provided in contact with the development roller 131, and the supply roller 132 (or supply roller 132A) 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 a driving motor (not shown), and is disposed upstream of a transfer position for each color. The transfer belt 14a is pressed against the photosensitive drum 10 by the provided pressing elastic plate 14b, and the transfer belt 14a is rotated clockwise as indicated by an arrow in FIG. At this time, the photosensitive drum 10 is driven to rotate by receiving the driving force of the transfer belt 14a following the movement of the transfer belt 14a.

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 eliminator for each color, comprises:
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. By starting a photoconductor driving motor (not shown) at the start of image recording, the photoconductor drum 10 of the yellow (Y) image forming unit 100 is rotated in a counterclockwise direction indicated by an arrow in FIG. , The application of a potential to the Y photoconductor drum 10 is started.

After the Y photoreceptor drum 10 is applied with a potential, the Y exposure optical system 12 starts image writing with a first color signal, that is, an electrical signal corresponding to the Y image data, and the Y photoreceptor is exposed. The original image Y
An electrostatic latent image corresponding to the image is formed.

The latent image is reversely developed in a contact or non-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 an 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).
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
By the contact or non-contact reversal development by 31, the M toner image is transferred onto the M photoconductor drum 10 in the M transfer area (no symbol) by the M primary transfer device 14 c as the first transfer unit. An M toner image is superimposed on the Y toner image.

By a similar 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 cleaning means of 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 across the transfer belt 14a. .

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. 2 or FIG. FIG. 2 shows a first embodiment of the invention.
FIG. 3 is an enlarged cross-sectional configuration diagram of a developing device related to FIG.
FIG. 3 is a diagram illustrating a layer configuration of a supply roller provided in the developing device of FIG. 2.

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, 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 forward direction (counterclockwise in FIG. 2). Developing roller 131
A supply roller 132, which is a toner supply member, is provided in contact with the supply roller 132. 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 the developing roller 131
(The counterclockwise direction in FIG. 2). The charge amount of the toner used for development is preferably about 5 to 15 μC / g.

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.

Supply roller 132 as a toner supply member
As shown in FIG. 3, a volume resistance of 10 ⁴ Ω is formed on the peripheral surface of a conductive core bar 132a of stainless steel or the like having an outer diameter of about 5 mm.
The first foamed rubber layer 132b is formed of a foamed rubber such as urethane or silicon having a thickness of about 5 mm and a thickness of about 5 mm, and the volume resistance is 10 ⁹ outside (outer peripheral surface) of the first foamed rubber layer 132b.
The second foamed rubber layer 132c is formed of a solid rubber such as urethane or silicon having a thickness of about 0.1 mm and a thickness of about 0.1 mm.

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 operating 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 near the photosensitive drum 10 at a position upstream of the developing roller 131 in the developing area in the rotation direction. The charging roller 136 has a conductive sponge-like elastic body around a conductive shaft core, and its surface is covered with a thin protective layer having a high resistance (10 ⁶ to 10 ¹⁰ Ω / cm ² ). It is an elastic roller. The charging roller 136 is in contact with the developing roller 131 via the toner layer, and is driven to rotate. To the charging roller 136, a charging roller bias VT1 in which an AC voltage is superimposed on a DC voltage having the same polarity as the toner pole to be used (in this embodiment, a negative polarity) is applied. The one-component developer (toner) is charged by an oscillating electric field generated between the developing roller 131 and the charging roller 136 due to this.

At the time of development, the developing roller 131 is applied with a developing bias VB1 having the same polarity as the toner used (in the present embodiment, a minus polarity) and a DC voltage of about -250 V, thereby forming one component of contact. The reversal development is performed to form a toner image on a latent image portion on the photosensitive drum 10.

At the time of development, a bias voltage is applied to the supply roller 132. When a bias voltage is applied in a direction in which the developer moves from the development roller 131 to the supply roller 132 with only a DC voltage, the recovery is successful. Supply becomes worse. Conversely, if a bias voltage is applied in the direction in which the developer moves from the supply roller 132 to the development roller 131, the supply is successful but the collection is poor. Further, when an AC voltage is applied, the developer vibrates, and supply and recovery are relatively good. However, depending on the electric resistance of the supply roller 132, there is a case where the alternating current is disturbed and the developer does not vibrate well. Therefore, a DC voltage of the same polarity as the toner to be used (negative polarity in this embodiment) and about -500 V A supply roller bias VK1 superimposed with a rectangular wave AC voltage having a frequency of 1 kHz and a peak-to-peak voltage of 1 kV _pp is applied to generate an oscillating electric field between the developing roller 131 and the supply roller 132.

As described above, the layer configuration of the supply roller 132 and the oscillating electric field generated between the development roller 131 and the supply roller 132 due to the application of the supply roller bias VK1 cause the supply roller 132 to the development roller 131 to move from the supply roller 132 to the development roller 131. The supply of the one-component developer (toner) and the collection of the one-component developer (toner) from the developing roller 131 to the developing roller 131 are favorably performed.

As described above, the developer can be favorably exchanged between the supply of the developer to the developer carrier by the supply roller and the recovery of the developer after the development, and the development ghost can be prevented. Becomes possible.

Embodiment 2 A developing device according to claim 2 or 3 of the present invention will be described with reference to FIG. 4 or FIG. FIG. 4 is an enlarged cross-sectional configuration diagram of a developing device according to claim 2 or 3 of the present invention, and FIG. 5 is a diagram illustrating a layer configuration of a supply roller provided in the developing device of FIG.

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 is not in contact with the peripheral surface of the photosensitive drum 10, respectively, and rotates in the rotation direction (clockwise direction in FIG. 4) and the forward direction (FIG. 4 (counterclockwise direction of FIG. 4). A supply roller 132A, which is a toner supply member, is provided in contact with the developing roller 131, and supplies toner to the developing roller 131 and collects toner from the developing roller 131 by the supplying roller 132A. The supply roller 132A is provided in the supply section in parallel with the developing roller 131, and the developing roller 131
(In the counterclockwise direction in FIG. 4). The charge amount of the toner used for development is preferably about 5 to 15 μC / g.

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, a rectangular wave AC voltage having a frequency of 2 kHz and a peak-to-peak voltage of 2 kV _pp is applied to the developing roller 131 with a DC voltage of about -250 V having the same polarity (minus polarity in the present embodiment) as the toner polarity used. Is applied, and non-contact one-component reversal development is performed.
A toner image is formed on the latent image portion on 0.

Supply roller 132A as a toner supply member
As shown in FIG. 5, is formed by forming a foamed rubber layer 132d of a foamed rubber such as urethane or silicon on the outside (outer peripheral surface) of a conductive core bar 132a of stainless steel or the like having an outer diameter of about 5 mm. . Conductive core 13 of foamed rubber layer 132d
The diameter (cell diameter) of the cell SL closest to 2a is 50-1.
The diameter of the cell SL of the foamed rubber layer 132d is about
The cell SL is formed so as to increase as it goes to the surface layer (surface layer portion) of 2d, and the foam rubber layer 132d is formed so that the cell diameter of the cell SL in the surface layer portion of the foam rubber layer 132d is about 500 to 600 μm. At this time, the supply roller 13
2 is formed of a foamed rubber layer 132d and rubbed against the developing roller 131, so that both supply and recovery are relatively good. However, when the developer is clogged in the cell SL, the rubbing force changes and the function is reduced. However, in the present invention, since the cell diameter is large on the surface of the foamed rubber layer 132d, the developer is not easily clogged. Since the developer passes through the surface layer and is clogged inside the supply roller 132, the influence of the clogging of the developer is less likely to occur. During development, the supply roller 132A has the same polarity as the toner pole to be used (minus polarity in this embodiment), and
A supply roller bias VK2 of a DC voltage of about 00 V is applied.

With the configuration of the cell SL in the foamed rubber layer 132d of the supply roller 132A as described above, the supply roller 1
Supply of a one-component developer (toner) from the developing roller 131 to the developing roller 131;
The one-component developer (toner) is favorably collected.

Other components are the same as those described in the first embodiment, and will be described below. Reference numeral 133 denotes a blade serving as a developer regulating member provided for regulating the height and amount of the developer layer (toner layer). The blade 133 includes a belt-like elastic plate 133a made of, for example, a plate-like stainless steel or a rubber material. The end of the plate 133a is attached to a contact portion with the developing roller 131, and is composed of a band-shaped elastic body 133b made of, for example, a foaming agent of sponge or urethane rubber. 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. The blade 133 may be a so-called trail-type developer regulating member whose tip is disposed downstream in the rotation direction of the developing roller 131. By the blade 133, a thin developer layer of about one or two layers is 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 operating 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 unit 134 is frictionally charged between the developing roller 131, the blade 133, and the supply roller 132A.

Reference numeral 136 denotes a charging roller provided near the photosensitive drum 10 at a position upstream of the developing roller 131 in the developing area in the rotation direction. The charging roller 136 has a conductive sponge-like elastic body around a conductive shaft core, and its surface is covered with a thin protective layer having a high resistance (10 ⁶ to 10 ¹⁰ Ω / cm ² ). It is an elastic roller. The charging roller 136 is in contact with the developing roller 131 via the toner layer, and is driven to rotate. To the charging roller 136, a charging roller bias VT1 in which an AC voltage is superimposed on a DC voltage having the same polarity as the toner pole to be used (in this embodiment, a negative polarity) is applied. The one-component developer (toner) is charged by an oscillating electric field generated between the developing roller 131 and the charging roller 136 due to this.

As described above, the developer is switched between the supply of the developer to the developer carrier by the supply roller and the recovery of the developer after the development, and the development ghost is prevented. Becomes possible.

[0057]

According to the present invention, the replacement of the developer between the supply of the developer to the developer carrier by the supply roller and the recovery of the developer after the development is performed well, and the occurrence of the development ghost is reduced. A prevented developing device is 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 a diagram illustrating a layer configuration of a supply roller provided in the developing device of FIG. 2;

FIG. 4 is an enlarged cross-sectional configuration diagram of a developing device according to claim 2 or 3 of the present invention.

FIG. 5 is a diagram illustrating a layer configuration of a supply roller provided in the developing device of FIG. 4;

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14a transfer belt 131 developing roller 132, 132A supply roller 132a conductive core 132b first foamed rubber layer 132c second foamed rubber layer 132d foamed rubber layer 133 blade 134 Hopper section 138 Developing casing P Recording paper SL cell

Claims (3)

[Claims] 1. A developer carrier that holds and rotates a thin layer of a non-magnetic one-component developer, a supply roller that supplies and collects developer to and from the developer carrier, In the developing device having a developer regulating member for regulating a developer amount, the supply roller has a volume resistance around the conductive cored bar of 10%.
^A first foamed rubber layer having a thickness of not more than ⁵ Ω · cm and a thickness of not less than 1 mm; and a volume resistance of 10 ⁶ Ω · cm outside the first foamed rubber layer.
A developing device comprising: a second foamed rubber layer having a thickness of 0.5 mm or less as described above; and forming an oscillating electric field between the developer carrier and the supply roller. 2. A developer carrier that holds and rotates a thin layer of non-magnetic one-component developer, a supply roller that supplies and recovers developer to and from the developer carrier, In a developing device having a developer regulating member that regulates a developer amount, the supply roller adheres foam rubber to the outside of the conductive core to form a foam rubber layer, and the diameter of the foam rubber cell is reduced. A developing device formed so as to increase in size from the conductive core portion toward the surface layer. 3. The developing device according to claim 1, wherein the supply roller rotates in the same direction as the developer carrier.