JPH09211970A - Developing device and color electrophotographic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent filming a developing roll with toner, in a developing device for attaining development by allowing the developing roll having a toner layer formed on the surface to contact with a photoreceptor and to prevent the fluctuation of an image density in each color, in a high-speed color electrophotographic device. SOLUTION: The developing device for attaining the development in such a manner that the developing roll 2 having the toner layer 12 formed on the surface comes into contact with the photoreceptor 1 is constituted to attain the carrying and coating of the toner with carriers attracted to a magnet (carrying roll 3) having multipole magnetization. Then, a bias voltage is applied to the elastic developing roll 2 constituted in such a manner that a rubber roll 2b is fitted into a metallic sleeve 2a and the magnet 3. Further, in the high-speed color electrophotographic device, at least one of the electric field or circumferential speed ratio between the developing roll and the magnet is controlled with a toner image after the development with the quantity of the toner with which the developing roll is coated is attained.

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 in an electrophotographic apparatus such as a copying machine, a printer, a facsimile, and a color electrophotographic apparatus using the developing apparatus.

[0002]

2. Description of the Related Art Conventional developing devices include a two-component developing device using a two-component developer containing a carrier and a toner and a one-component developing device using a one-component developer containing only toner.
The one-component developing device is advantageous in downsizing and cost reduction because it does not need to use a carrier and does not require a developer mixing ratio control mechanism, and also has an advantage that no carrier is attached to the photoconductor. , Is used in a color electrophotographic apparatus in which a plurality of developing devices are arranged. As shown in FIG. 2, a conventional one-component developing device 21 using a non-magnetic color toner used in a color electrophotographic apparatus includes a developing roll 2, a blade 18, a conveying roll 20, and a toner hopper 6 facing a photoconductor 1. The stirring blade 7 and the toner leakage prevention member 19 are provided, and the toner in the toner hopper 6 is supplied from the opening 13 to the vicinity of the conveying roll 20 by the stirring blade 7 and further conveyed to the vicinity of the developing roll 2 by the conveying roll 20. Then, the toner layer 1 is formed on the developing roll 2 by the blade 18.
2 is formed and is conveyed to a portion facing the photoconductor 1 by the rotation of the developing roll 2, and the toner layer 12 is brought into contact with the electrostatic latent image on the photoconductor 1 and a developing electric field is applied to the developing portion to form the toner. The image was formed.

Regarding such a non-magnetic one-component developing device, Japanese Patent Publication No. 7-43546 and Japanese Utility Model Publication No. 7-2068.
Those described in Japanese Laid-Open Patent Publication No. 3-9 are known. Regarding the magnetic one-component developing device, the one described in Japanese Patent Publication No. 2-48901 is known.

Further, as an example of using a magnet roll as a conveying roll in a non-magnetic one-component developing device that does not use magnetic toner, a sponge roll is used as a developing roll as described in JP-A-55-77764. Contact-developing, and as described in JP-A-3-59576 and JP-A-61-239266, non-contact development is performed by providing a space between the toner layer on the developing roll and the photoconductor. A method of performing the same is known.

[0005]

However, when a conventional non-magnetic one-component developing device is used to obtain a high-speed and high-definition color image, or to perform fixing by low-temperature fixing which requires power saving. There is a tendency that toner filming occurs on the developing roll, the image quality is deteriorated, and the replacement life of the developing device is shortened.

Further, in the method of performing contact development using a sponge roll as the developing roll, when used at a high speed, the developing sponge roll tends to be deformed and the replacement cycle tends to be shortened.

Further, in the method of performing non-contact development by providing a space between the toner layer on the developing roll and the photoconductor, the reproducibility of fine halftone dot images and gradation tends to be insufficient. .

The present invention has been made in view of the above-mentioned circumstances of the prior art. A first object of the present invention is to provide a developing device for applying only non-magnetic toner to a developing roll to perform development. Another object of the present invention is to provide a developing device capable of preventing toner filming from occurring and ensuring high-speed and high-quality image quality.

A second object of the present invention is to provide a developing device which can be applied to an electrophotographic apparatus which performs low temperature fixing which requires power saving.

[0010]

In order to achieve the first object, a first means is to form a toner layer on a developing roll and bring the developing roll into contact with a photoconductor, and the toner is used to form the photoconductor. In the developing device that visualizes the latent image formed above, the developing roll is configured by fitting an elastic roll to a metal sleeve, and rotates a multi-pole magnetized magnet body in a position close to the developing roll. A restricting plate that restricts the layer thickness of the developer containing the carrier and the toner is provided on the outer periphery of the magnet body so that the developer layer controlled by the restricting plate is brought into contact with the developing roll while rotating. With
An electric field is applied between the magnet body and the developing roll to form a toner layer on the developing roll.

In this case, a guide plate for forming a toner pool for temporarily storing the toner supplied from the toner hopper and forming an opening portion for guiding the toner from the lower part of the toner pool to the magnet body side is provided on the upper part of the magnet body. It is preferable. At this time, a transport roll that supplies new toner to the magnet body side and that is mixed with the recirculating toner that is regulated by the regulation plate may be further provided in the opening portion. In addition, the transport roll may be composed of an agitating member, or a second roller may be provided below the transport roll.
It is also possible to provide a stirring member. The second agitating member may be composed of a pair of screw augers so that the toner can move along the axial direction of the magnet body.

The magnet body has 8 to 6 magnetic poles.
It is preferable that the magnetic pole has four poles and the magnetic force of the magnetic pole portion is in the range of 250 to 1000 gauss.

The absolute value of the difference between the first gap formed by the developing roll and the magnet body and the second gap formed by the regulation plate and the magnet body is 0 to 0.4 mm. It is preferable to set it in the range, and the ratio of the peripheral speed of the magnet body to the peripheral speed of the developing roll may be set in the range of 1.5 to 5.0.

The developer has a particle size of 20 to 8
The bias voltage applied to the developing roll is preferably a combination of a DC voltage and an AC voltage, which is composed of an iron powder carrier of 0 μm and a toner having a particle diameter of 5 to 8 μm.

Further, in order to achieve the second object,
A second means arranges a plurality of developing devices respectively accommodating developers corresponding to respective colors around a plurality of photoconductors, and the photoconductors form a plurality of latent images corresponding to the respective colors by one or a plurality of rotations. In the color electrophotographic apparatus having a step of developing latent images formed on the photoconductor with the plurality of developing devices together to form toner images of a plurality of colors on the photoconductor, the plurality of developing devices are described above. It consists of the developing device of
Based on the toner image of each color, at least one of the electric field or the peripheral speed ratio between the developing roll and the magnet body is controlled.

In the developing device having the above-mentioned structure, the blade contacting the developing roll is not provided, the magnet body is provided with a predetermined gap from the developing roll, and the developer (carrier And toner) to form a toner layer on the developing roll by contacting the developing roll with the developing roll. Since it is possible to scrape off the toner remaining on the developing roll after the image is developed, it is possible to prevent toner filming on the developing roll.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a schematic configuration diagram of a developing device according to a first embodiment of the present invention. In the figure, the developing device 8 is applied to the developing roller 2, the conveying roller 3, the regulating plate 4, the stirring blade 7 provided in the toner hopper 6, the developing roller 2 and the conveying roller 3 facing the photoconductor 1. The bias power sources 14 and 15 and the developer guide plate 5 are included.

The developing roll 2 has a thickness of about 20 to 60 μm.
m Ni electroformed sleeve 2a having a low hardness (for example, a rubber hardness of about 15 to 35 degrees (JIS-A)).
b is fitted into the developing roll 2 having elasticity. With this configuration, the Ni electroformed sleeve 2
By a, scratches and abrasion of the developing roll 2 are prevented, and the thickness is reduced so that the elasticity of the rubber roll 2b can be maintained. As a result, even if the developing roll 2 is brought into contact with the photoconductor 1, soft contact with the photoconductor 1 is obtained. Therefore, when the printing speed is fast, or the peripheral speed ratio k between the developing roll 2 and the photoconductor 1 is rather large (k = 1.5 to 2.
Even in the case of 0), the replacement cycle of the developing roll 2 and the photoconductor 1 can be lengthened. In this embodiment, the developing roll 2 has a diameter of 15 to 40 mm.

The rubber roll 2b may be either insulating or conductive. However, when an insulating roll (for example, a resistance value of about 10 ¹³ to 10 ¹⁶ Ωcm) is used, electric power for applying a developing bias is supplied from the surface of the developing roll, whereas a conductive roll (for example, When the resistance value is about 10 ⁷ to 10 ⁸ Ωcm), there is an advantage that power can be supplied by using the shaft of the developing roll.

When the printing speed is relatively slow or the peripheral speeds of the developing roll 2 and the photosensitive member 1 are substantially equal to each other, the developing roll 2 does not use a metal sleeve and has a low hardness (for example,
A rubber roll having a rubber hardness of about 15 to 55 degrees (JIS-A) may be formed alone (or with a surface coating).

The transport roll 3 is composed of magnets of evenly-spaced multipole magnetism that are rotatably arranged through a gap (first gap) G ₁ with the developing roll 2. A second gap G _{2 is formed} between the outer circumference of the transport roll 3 and the outer circumference of the magnet body.
Is provided, and the layer thickness of the developer including the carrier and the toner held by the magnet body is regulated by the regulation plate 4. The developer layer 10 regulated by the regulation plate 4 is rotated in the counter direction (direction facing each other) by the transport roll 3 and comes into contact with the developing roll 2,
As described above, the toner layer 12 is formed on the developing roll 2 by the electric field acting between the transporting roll (magnet body) 3 and the developing roll 2. Further, it is desirable that the above electric field is formed between the magnet body and the developing roll 2 by superimposing a direct current and an alternating current of 1 to 10 KHz.

The magnet body is composed of only a magnet roll magnetized with a magnetic pole number of 8 to 64 poles, a magnetic force of the magnetic pole portion of 250 to 1000 gausses, preferably 32 poles or more and a magnetic force of 350 to 800 gausses. The magnetic developer attracted by the magnetic force of the magnet body is conveyed, and the developer layer 10
Is brought into contact with the developing roll 2 by rotating in the counter direction. That is, the transport roll (magnet roll) 3 and the developing roll 2 are both configured to rotate counterclockwise in FIG. 1, and the peripheral speed Ut of the transport roll (magnet body) 3 and the peripheral speed of the developing roll 2 are set. The ratio to Us is set in the range of 1.0 to 5.0, preferably 2.0 to 4.0.

In the developing device 8 having the developing roll 2 and the transport roll 3 as described above, the toner in the toner hopper 6 is supplied from the opening 13 to the vicinity of the upper portion of the transport roll 3 by the stirring blade 7. A developer guide plate 5 is provided on the upper portion of the transport roll 3 and regulates the movement of the toner dropped from the opening 13 to the transport roll 3 side so as to extend downward from a portion along the developer guide plate 5. Toner pool 9
Is formed, and the moving direction of the toner is regulated. The toner flows from below the toner reservoir 9, in other words, from the opening 9a on the lower end side of the developer guide plate 5 to the conveying roll 3
Move to the side. Further, the regulation plate 4 is provided in a portion which is continuous with the developer guide plate 5 on the downstream side in the rotation direction of the transport roll 3 and which contacts the upper portion of the transport roll 3.
The layer thickness of the developer layer 10 held by the transport roll 3 is regulated. As a result, the toner scraped into the toner reservoir 9 by the agitating blades 7 is prevented from coming into contact with the regulation plate 4.
The developer 11 containing the magnetic carrier and the non-magnetic toner, which is mixed with the developer 11 and is held by the transport roll 3 in association with the circulation of the developer 11 which is regulated and recirculated (U-turn), is transferred to the transport roll 3. The developer 11 held and moved in the direction of the regulation plate 4 moves to the side of the developing roll 2 where the developer 11 not regulated by the regulation plate 4 moves, and the regulated developer 11 follows the developer guide plate 5 to the lower part of the toner reservoir 9. Repeat the process of returning to the side.

The developer 11 regulated by the regulation plate 4 and having a predetermined layer thickness and moved to the developing roll 2 side rotates the conveying roll 3 in the counter direction with respect to the developing roll 2 to bring it into contact with the developing roll 2. An electric field is applied between the transport roll 3 and the developing roll 2 to transfer the toner onto the developing roll 2 to form the toner layer 12. The toner layer 12 has a toner charge amount of 5 to 30 μC / g (preferably 7 to 20 μC / g).
g), the toner adhesion amount is 0.4 to 1.5 mg / cm ² (preferably 0.6 to 1.2 mg / cm ² ). After that, the toner layer 12 is conveyed to a portion facing the photoconductor 1 by the rotation of the developing roll 2, and is brought into contact with the electrostatic latent image on the photoconductor 1, and a developing electric field is applied to the developing portion to cause the electrostatic charge. Toner is attached to the latent image to form a visible image, and a toner image is formed on the photoconductor 1.

The transport roll 3 having the magnet body as described above.
The developer (magnetic brush) 11 adsorbed on and conveyed by
It contacts the developing roll 2. As described above, the developer 11 is composed of the toner and the carrier, and is charged in the opposite directions by frictional charging associated with agitation and conveyance, so that an electric field (forward electric field) is applied between the conveyance roll 3 and the developing roll 2. When,
Only the toner is separated from the developer 11 held by the magnet body and moved onto the developing roll 2 to form a substantially uniform toner layer 12. Thereafter, the toner layer 12 on the developing roll 2 contacts the electrostatic latent image portion on the photoconductor 1 to transfer the toner, and development is performed.

As described above, in the present embodiment, unlike the conventional example shown in FIG. 2, the blade 18 that contacts the developing roller 2 is not provided, and the toner is charged and the developing roller 2 has a substantially uniform layer thickness. Since the toner layer 12 can be formed and development is performed using the substantially uniform toner layer 12, filming due to the toner does not occur on the developing roll 2.

Further, as in the second embodiment to be described later, when a control unit for controlling the rotation speed of the transport roll 3 and the bias voltage is provided, the rotation speed of the transport roll 3 is changed and the bias voltage of the transport roll 3 is changed. The thickness of the toner layer 12 adhered onto the developing roll 2 can be adjusted by adjusting the electric field strength applied between the transporting roll 3 and the developing roll 2. With this configuration, the stability of the image density can be improved, and the image quality of the color image can be kept constant for a long period of time.

The developing roll 2 and the photoconductor 1 may rotate in the same direction or in the counter direction, but the peripheral speed ratio k (= U _s / _UP ) is 2 or less. More preferably, the peripheral speed ratio k in the same direction a 1 ≦ k ≦ 1.5, the speed difference ΔV (= U _S -U _P) is 0 ≦ ΔV ≦ 5
What is necessary is just 0 mm. In particular, by superimposing a bias voltage of 1 to 10 KHz and an AC voltage of 100 to 1000 V in such a configuration, it is possible to achieve both image uniformity and photoconductor abrasion prevention.

The magnet body may be constructed by disposing a sleeve that can rotate concentrically with the magnet roll. In this case, the number of magnetic poles is 8 to 24 and the magnetic force of the magnetic pole portion is 400.
To a magnet roll magnetized in the range of 1000 Gauss, the developer roll 10 is rotated in the counter direction and brought into contact with the developer roll 10, so that the magnet roll is rotated clockwise and the sleeve is rotated counterclockwise. Let that time,
The ratio of the peripheral speed of the sleeve to the peripheral speed Us of the developing roll 2 is set in the range of 1.0 to 3.0, preferably 1.2 to 2.0. The rotation speed of the sleeve is preferably set in the range of 1.5 to 4.0.

In this embodiment, the first gap G ₁ formed by the developing roll 2 and the transport roll (magnet body) 3
Is set in the range of 0.5 mm to 1.0 mm, and the first
The absolute value of the difference between the second and the gap G ₂ is formed between the gap G ₁ between the regulating plate 4 and the transport roll (magnet) 3 | G ₁ -G
₂ | was set in the range of 0 mm to 0.4 mm. The developing roll 2 and the transport roll (magnet body) 3 are
Bias power supplies 14 and 15 are connected to each other, and a DC voltage or a voltage in which a DC voltage and an AC voltage are superimposed is applied.

When the resistance value of the transport roll (magnet body) 3 is high, the regulation plate 4 is made of a conductive material and the regulation plate 4 is formed.
Also, the bias voltage is applied from the power source 15.
As a result, it is possible to prevent a decrease in the electric field strength in the first gap G ₁ .

As the developer held on the conveying roll (magnet body) 3, a developer containing a carrier having a particle size of 20 to 100 μm (preferably 40 to 80 μm) and a toner having a particle size of 5 to 8 μm was used. . In order to scrape off the toner remaining on the developing roll 2 after developing the electrostatic latent image on the photoconductor 1, an iron powder carrier having a particle size of 20 to 80 μm is most desirable, but the magnetic force of the transport roll (magnet body) 3 Alternatively, a resin carrier and a ferrite carrier can be used instead of the iron powder carrier by increasing the peripheral speed. The resin carrier has a bulk specific gravity of 1.0 to 1.6 g / cm ³ and a saturation magnetization of 60 to 80 emu / g, spherical or amorphous, and the ferrite carrier has a bulk specific gravity of 2.2 to 2.7 g / cm ³ . Saturation magnetization 20 to 70 emu /
It is possible to use a substantially spherical g.

For the toner, a binder resin having a glass transition point T _g of 55 to 65 ° C. is used for low-temperature fixing, and one or two kinds of silica of 10 to 100 nm or an inorganic oxide is used to improve fluidity. Used together. The developer used had a toner concentration of 5 to 20%.

As described above, the developer guide plate 5 is provided on the upper portion of the transport roll 3 to form the toner reservoir 9, and the developer 11 which is regulated by the regulation plate 4 and makes a U-turn.
When the image was directed downward, the image quality such as image density and fog was stable with time.

An organic photoconductor (OPC) is used as the photoconductor 1 by applying such a developing device to an electrophotographic printer device.
Is used to form an electrostatic latent image with a contrast potential of about 450 V on the photoconductor 1 having a peripheral speed of 100 to 400 mm / sec, and the peripheral speed U _s of the developing sleeve 2 is about 1 of the peripheral speed U _p of the photosensitive member.
The image density was 1.3 to 1.4 (OD) when reversal development was carried out by applying a developing bias of 250 to 350 V to the developing sleeve 2 and applying a developing bias of 250 to 350 V.

Even when long-term printing is performed,
Filming of the toner to the developing roll did not occur.

[Second Embodiment] This embodiment is an example in which the developing device of the present invention is applied to a color electrophotographic apparatus in which four image forming units corresponding to respective colors are arranged.

FIG. 3 is a schematic configuration diagram of the color electrophotographic apparatus according to this embodiment. In the figure, the color electrophotographic apparatus includes four developing devices 8-1, 8-2, 8-- which store developers corresponding to respective colors of Y, M, C and K.
3, 8-4 are four photoconductors 1-1, 1-corresponding to each color.
The photosensitive drums 1-1, 1-2, 1 are arranged around the peripheral portions 2, 1-3, 1-4, and the latent image writing timing by the exposure 24 is set in consideration of the transfer timing to the paper 22. −
3, a latent image corresponding to each color is formed on each of 1-4, and development is performed by the developing devices 8-1, 8-2, 8-3, 8-4 of each color to form a toner image of each color. Transfer device 25-
1, 25-2, 25-3, and 25-4 are sequentially transferred to the paper 22 and the toner images of the respective colors are overlapped to obtain a full-color image. In this embodiment, the developing devices 8-1, 8-of this color electrophotographic apparatus are used.
Of the second, 8-3, and 8-4, only the developing device 8-1 at the first stage will be described as an example. In this case, since it is full-color, although omitted in the other three developing units 8-2, 8-3, and 8-4, each unit described below is provided.

An example in which the developing device 8 of the first embodiment is applied to the developing device 8-1 will be described in detail below.

As can be seen from FIG. 3, bias power sources 14-1 and 15-1 are connected to the developing roll 2-1 and the conveying roll 3-1 of the developing unit 8-1, and the roll 2
-1, 3-1 are respectively rotary drive units 16-1, 17-
It is driven to rotate by 1. On the other hand, the color image sensor 27-1 for detecting the toner image of the developed color is the photosensitive member 1-
1, the detection output of the color image sensor 27-1 is input to the image controller 28-1. The bias power sources 14-1 and 15-1 are controlled by a bias control unit 30-, and the bias control unit 30-
-1 sets the aforementioned bias voltage and bias frequency according to the control output from the image control unit 28-1.
The rotation drive units 16-1 and 17-1 are rotation control units 29-
The rotation speed is controlled by 1, and the rotation control unit 29-1 similarly sets the speed according to the control output from the image control unit 28-1.

A transfer device 25-is provided around the photosensitive member 1.
Cleaners 26-1, 26-2 for cleaning the toner remaining on the photoconductors 1-1, 1-2, 1-3, 1-4 after the transfer by 1, 25-2, 25-3, 25-4. 26-3, 26
-4 is arranged, and further, the fixing device 31 for melting and fixing the unfixed image on the paper 22 is arranged behind the transfer device 25-4 at the final stage.

In such a structure, when a color toner image is formed on the photoconductor 1 and color printing is performed, at least the electric field between the developing roll 2 and the transporting roll 3 or the circumference is determined based on the toner image after development. Since at least one of the speed ratios can be controlled, a desired amount of toner development on the photoconductor 1 can be secured, and even in long-term printing, the image density does not drop or fluctuate and the color image does not deteriorate.

In this embodiment, fan hold paper is used to continuously form a color image, but the same applies to cut paper, and
For example, even when a color image of two colors is formed, the same configuration and the same operation are performed only by providing a device such as a photoconductor and a developing device for two colors.

[Third Embodiment] FIG. 4 is a schematic configuration diagram of a developing device according to a third embodiment. The same reference numerals are given to the same parts as those in the first embodiment. The description will be omitted and only different components will be described.

In this embodiment, as can be seen from FIG. 4, the second carrying roll 32 is provided in the opening 9a between the carrying roller 3 and the toner reservoir 9 in the first embodiment, and other parts are provided. Are all configured in the same manner as in the first embodiment.

In this embodiment, the second transfer roll 32 is made of a sponge roll or a rotating brush and is in contact with or close to the developer guide plate 5. As a result, the toner pool 9 is collected on the second transport roll 32.
4 forms a toner layer 12 containing new toner from the above, and contacts the developer 11 regulated by the regulation plate 4 in the direction of the arrow in FIG. 4 or the developer 11 adsorbed by the transport roll 3 and moving. It is supposed to do.

With this structure, the effect of reducing fog was observed as compared with the first embodiment.

[Fourth Embodiment] FIG. 5 is a schematic diagram of the development according to the fourth embodiment. The same reference numerals are attached to the same units as those in the first and third embodiments. The description will be omitted and only different components will be described.

In this embodiment, a second stirring member 33 is provided in place of the second transport roll 32 in the third embodiment, and the toner in the toner reservoir 9 and the developer 11 are mixed. The other parts are configured in the same manner as in the first and third embodiments described above.
As the stirring member, for example, a stirring blade or a screw auger is used.

According to the above-mentioned structure, the effect that the image density unevenness does not occur even in the long-term printing and the fog is reduced can be seen.

As can be seen from FIG. 5, in addition to the second stirring member 33, stirring members 34 and 35 may be provided below the stirring member 33. Stirring member 34,
In this case, as the reference numeral 35, for example, two screw augers having different transport directions (in the axial direction) are arranged. It is preferable that these stirring members 34 and 35 have not only the mixing and stirring ability in the rotating direction but also the ability to move the developer in the direction parallel to the transport roll 3. Specifically, it is preferable to use a screw-shaped member or an inclined fin member which can change the moving direction of the developer 11 by switching the rotating directions of the stirring members 34 and 35.

According to this structure, in long-term printing, the image density unevenness does not occur in the axial direction, and the fog is further reduced as compared with the case where only the second stirring member 33 is used.

[0054]

As is apparent from the above description, according to the developing device of the present invention, toner filming does not occur on the developing roll even in long-term printing using low-temperature fixing toner, and the high developing property is obtained. A developing device capable of forming a high quality image can be provided.

Further, in the high-speed color electrophotographic apparatus to which the developing device of the present invention is applied, fluctuations in image density can be prevented, so that clear color images can be stably secured.

[Brief description of drawings]

FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional developing device.

FIG. 3 is a schematic configuration diagram of a color electrophotographic apparatus according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a main part of a developing device according to still another embodiment of the present invention.

FIG. 5 is a cross-sectional view of essential parts of a developing device according to still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing roll 2a Sleeve 2b Rubber roll 3 Conveying roll 4 Regulation plate 5 Developer guide plate 6 Toner hopper 7 Stirring blades 8,21 Developing device 9 Toner reservoir 9a Opening part 10 Developer layer 11 Developer 12 Toner layer 13 Opening 14 -1,15-1 Bias power supply 16-1,17-1 Rotation drive part 28-1 Image control part 29-1 Rotation control part 30-1 Bias control part 32 2nd conveyance roll 33 2nd stirring member 34,35 Screw auger G ₁ , G ₂ gap

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location G03G 15/06 101 G03G 15/06 101 15/09 15/09 A (72) Inventor Masayasu Anzai Hitachinaka City, Ibaraki Prefecture 1060 Takeda, Katsuta Research Laboratory, Hitachi Koki Co., Ltd.

Claims (12)

[Claims] 1. A developing device for forming a toner layer on a developing roll, bringing the developing roll into contact with a photoconductor, and visualizing the latent image formed on the photoconductor by the toner, wherein the developing roll is A developer including a metal sleeve and an elastic roll fitted therein, rotatably arranging a multi-pole magnetized magnet at a position close to the developing roll, and a developer containing a carrier and toner on the outer periphery of the magnet. A regulating plate for regulating the layer thickness of the developing roller is provided, and the developer layer regulated by the regulating plate is brought into contact with the developing roll while being rotated, and an electric field is applied between the magnet body and the developing roll, A developing device, wherein a toner layer is formed on the developing device. 2. A guide plate, which forms a toner pool for temporarily storing the toner supplied from the toner hopper and which forms an opening portion for guiding the toner from the lower part of the toner pool to the magnet body side, is provided at the upper part of the magnet body. The developing device according to claim 1, wherein: 3. The transport roller, which supplies new toner to the magnet body side and is mixed by the toner which is regulated by the regulation plate and recirculates, is further provided in the opening portion. Developing device. 4. The developing device according to claim 3, wherein the transport roll comprises a stirring member. 5. The third stirring member according to claim 3, further comprising a second stirring member below the conveying roll.
The developing device described. 6. The developing device according to claim 5, wherein the second stirring member includes a pair of screw augers, and the toner is movable along the axial direction of the magnet body. 7. The developing device according to claim 1, wherein the magnet body has 8 to 64 magnetic poles, and the magnetic force of the magnetic pole portion is set in the range of 250 to 1000 gauss. 8. The absolute value of the difference between the first gap formed by the developing roll and the magnet body and the second gap formed by the regulation plate and the magnet body is 0 to 0.
The developing device according to claim 1, wherein the developing device is set in a range of 4 mm. 9. The developing device according to claim 1, wherein the ratio of the peripheral speed of the magnet body to the peripheral speed of the developing roll is set in the range of 1.5 to 5.0. 10. The developer has a particle size of 20 to 80.
2. The developing device according to claim 1, further comprising an iron powder carrier of .mu.m and a toner having a particle size of 5 to 8 .mu.m. 11. The developing device according to claim 1, wherein the bias voltage applied to the developing roll is a superposition of a DC voltage and an AC voltage. 12. A plurality of developing devices respectively accommodating developers corresponding to respective colors are arranged around a plurality of photoconductors, and the photoconductors form a plurality of latent images corresponding to the respective colors by one or a plurality of rotations. A color electrophotographic apparatus comprising a step of developing latent images formed on the photoconductor by the plurality of developing devices to form toner images of a plurality of colors on the photoconductor, wherein the plurality of developing devices are The developing device according to any one of 1 to 11, wherein at least one of an electric field or a peripheral speed ratio between the developing roll and the magnet body is controlled based on a toner image of each color. Color electrophotographic device.