JPS6167060A - Developing device - Google Patents

Abstract

PURPOSE:To easily separate magnetic particles at a magnetic particle restraining member part and toner speed up the operation of an image forming device by using a magnetic means and a developer holding means, and arranging a magnetic means below a developer holding means. CONSTITUTION:A magnetic roller 8 consists of a rotatably nonmagnetic sleeve 9 and a magnet 10 fixed in the sleeve 9, and a magnetic brush is formed of a developer mixed body of nonmagnetic toner and magnetic particles, which are conveyed to a position facing a magnetic roller 11. The toner and magnetic particles conveyed by the magnetic roller 8 are napped where they contact or are close to the magnet roller, thereby forming the magnetic brush 12. The magnetic brush is attracted onto the magnetic roller with magnetic poles of a magnet 18, and part of the magnetic brush is passed from the magnetic roller to a developing roller. Magnetic particles in the developer mixed body sticking on the developing roller are restrained by a magnetic pole N3 and the magnetic particle restraining member 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The industrial application field of the invention relates to a developing device, and more specifically, to developing a latent image formed on a latent image carrier such as a photoreceptor in an image forming device such as an electrophotographic device. The present invention relates to a developing device.

Conventional technology Conventionally, as a developing method using a -component developer, there is a powder cloud method in which toner particles are sprayed, and a single layer of uniform toner is electrostatically formed on a developing roller such as a web or sheet. Contact development method, in which development is performed by bringing the toner into contact with the image holding surface I/C, and jumping development, in which the toner layer is not brought into direct contact with the electrostatic image holding surface, and the toner is selectively flown onto the holding surface by the electric field of the electrostatic image. Also known are the magneto-dry method, in which a magnetic brush is formed using conductive magnetic toner, and is brought into contact with an electrostatic image holding surface for development.

Among these, the jumping development method is known as unique. In this method, a developer is applied as a thin layer onto a developer carrier, and then the electrostatic latent image surface is opposed to the surface layer of the thin developer layer with a small gap therebetween. This is a method of developing by causing the developer to fly from the developer holding means to the electrostatic latent image surface using the electrostatic attraction (U.S. Pat. No. 2,839).
．． (See Specification No. 400, Specification No. 232.1/0)
. According to this method, not only is the developer not attracted to the non-image area where there is no latent image potential, but also the developer does not come into contact with the non-image area, resulting in good development with no background blur.

However, since the phenomenon of toner flight caused by the electric field of an electrostatic image is used for development, the resulting visible scratches generally lack sharpness and are unclear at the edges of the image area, and the development of line images In this case, the image is developed so that it appears thinner than the original image, and only an image with poor t-gradation characteristics with it gamma (gamma = slope of the characteristic curve of image density with respect to electrostatic image potential) is obtained.

The non-applicant had previously determined that the sharpness and gradation that were problems with the conventional jumping development method described above were good, and developed a new development method in Japanese Patent Application Laid-open No. 54-42141 and Japanese Patent Publication No. 5B-3.
It was proposed in No. 2375 and Japanese Patent Publication No. 5B-52577.

The development method described in % Kaisho of the former involves forming a uniform developer thin layer with a -component developer on a developer holding means, and preventing the surface layer of this developer thin layer from coming into contact with the surface on which an electrostatic latent image is formed. They are made to face each other with a small gap between them to form a T configuration. The electrostatic attraction causes the developer to extend toward the image area, thereby performing further development. Also, since development is carried out in a state where the developer does not come into contact with the non-image area, a sharp developed image with no background blur can be obtained.

The latter two developing methods described in Tokkosho have the same structure as the former, and furthermore, an alternating current bias voltage is applied as a developing bias voltage between the thin developer layer and the image forming surface of the electrostatic layer. Development is carried out by reciprocating and further by changing the gap between the electrostatic a image surface and the developer holding means over time. In this development method, in the early stage of development, the developer reaches the non-image area of the electrostatic latent image, thereby developing the halftone area, and over time, the developer reaches only the image area, and then the developer is developed. Do the following. This K is my friend because it produces sharp, fog-free development with extremely good halftone reproducibility.

By the way, in these developing methods, it is important to uniformly form a thin layer of developer on the developer holding means, and in the case of a -component magnetic developer, this thin layer of developer is formed by applying magnetic force. Although it is relatively easy to control and put into practical use by using a combination of means, it is difficult to stably obtain good results with -component nonmagnetic developers.

In each conventional development method, a one-component non-magnetic developer (toner) is normally supplied onto a developer holding means such as a developing roller, charged by a frictional charging member, and then placed opposite the electrostatic latent image surface. was. However, if the toner supplied to the developing roller is not constant, uneven coating tends to occur.The toner is abraded due to friction with the frictional charging member and the developing roller, and the surface of the frictional charging member and the developing roller is abraded. This causes fusion and aggregation, resulting in uneven toner application on the developing roller, and the amount of charge charged on the toner also becomes non-uniform. These factors appear in the copied image as development unevenness during development.

(9) In the following cases, when the surface of the developing roller is provided with unevenness for the purpose of retaining the toner particle layer, or when a toner-retaining surface layer consisting of a large number of micropores is provided, the toner that has entered the depressions and micropores is released. Such toner is not easily charged by the charging means, and does not contribute to development, resulting in poor development characteristics and only low-density copy images.

The present applicant further disclosed in Japanese Patent Application Laid-Open No. 56-40862 that a magnetic brush made of developer (toner) and magnetic particles (carrier) is formed on a magnetic roller, and the developing roller is brought into contact with this magnetic brush. A friend proposed a device that performs development by transferring only toner onto a developing roller. However, it is difficult to completely prevent the carrier from adhering to the developing roller. When the carrier attached to the developing roller reaches the developing position, there may be problems such as leakage of developing bias through the carrier between the developing roller and the photoreceptor, or damage to the surface of the photoreceptor due to carrier adhesion to the surface of the photoreceptor. will occur.

OBJECTS OF THE INVENTION In view of the above points, it is an object of the invention to provide a novel and superior comparative vision apparatus.

Another object of the invention is to confine the magnetic particles within the development device;
It is an object of the present invention to provide a developing device that performs development by applying only a developer onto a developer holding means.

A further object of the invention is to provide a developing device 1 that enables good development with a component non-magnetic developer.

Another object of the invention is to provide a developing device that can be used for color image formation.

Structure of the Invention The non-inventive feature is a magnetic field generating means provided inside a developer holding means for developing a latent image on a latent image holding member, and a magnetic field generating means provided inside a developer holding means for developing a latent image on a latent image holding member, and a magnetic field generating means provided within a developer holding means for developing a latent image on a latent image holding member, and A developing area, which has a developer holding means (a magnetic particle restraining member provided facing the opposite side) on the side thereof, and the magnetic particle restraining member allows all of the toner (lt=1m) to face the latent image holding member. This is a developing device that guides toner and develops a latent image.

Description of examples The present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram illustrating the configuration of an image forming apparatus to which a developing device based on the invention is applied. In FIG. 1, 1 is an electrostatic image carrier including a photoconductor layer, 2 is an electrostatic latent image forming device including a charging device and an exposure device, 3 is a developing device according to the invention, 4 is a transfer material, 5 is a transfer device, and 6 is an outer leaning device for an electrostatic image holder.

FIG. 2 shows the structure and components of a specific example of the developing device 3 according to the invention, in which 7 is a developer mixture containing non-magnetic toner and magnetic particles, of which T is a one-component non-magnetic toner and M is a developer mixture containing non-magnetic toner and magnetic particles. Represents magnetic particles. Reference numeral 8 denotes a magnetic roller, which is a magnetic means, and is composed of a rotating non-magnetic sleeve 9 and a fixed magnet 10. Of course, the sleeve fixed magnet may rotate, or both may rotate. 11 is a developing roller which is a developer holding means;
It has a sleeve 17 that rotates in the direction of the arrow and a fixed magnet 18. 12 is a magnetic brush formed on the magnetic row 2, and 13 is a scraper. 14ij A regulating member that regulates the amount of developer on the magnetic roller, 15ij A magnetic particle restraining member made of a magnetic material (magnet, iron, permalloy, etc.),
Within the range of the magnetic field of the magnetic pole Xs of the magnet 18, this magnetic pole N5
y) is also provided on the downstream side in the sleeve movement direction, facing the developing roller 11, and tilted toward the downstream side in the sleeve movement direction. 16 is a developing bias power supply. In this developing device, the non-magnetic toner TK is a powder of 7 to 15μ mainly composed of 10 parts of carbon and 90 parts of polystyrene, and a suitable charge control agent such as colloidal silica is mixed therein, and iron powder is used as the magnetic particles. friend. Iron powder whose surface has been oxidized or coated with resin may also be used.

The magnetic roller 8 is made up of a rotatable non-magnetic sleeve 9 and a friend magnet 10 fixed in the sleeve, forming a magnetic brush for a developer mixture consisting of non-magnetic toner and magnetic particles. It is transported to a position facing the developing roller 11. As shown in FIG. 2, the magnetic pole arrangement of the magnet fixed inside the rotatable non-magnetic sleeve 9 is such that one magnetic pole N1 is provided in the portion facing the developing roller 11, and a transport magnetic pole 8. is provided in the other portion. , N2,8. The establishment is a friend. In the figure, the magnetic pole arrangement of the silkworm is divided into 4 equal parts, and tKN poles and 8 poles are arranged alternately. Each magnetic pole is about 400 on the sleeve surface.
K was set so as to have a Gaussian surface magnetic flux density. However, the magnetic pole arrangement and magnetic flux density are not limited to the above embodiments, and may be equally divided into 2, 6, or 8 poles, and do not necessarily have to be equally divided. For example, a repelling magnetic pole may be provided in place of the position 1ca pole N1 facing the developing roller to facilitate the transfer of the developer mixture to the developing roller 11. In addition, the distance between the developing roller and the magnetic brush roller is 0.5 to 10
It is preferable to maintain a gap between the two, and in the example, it is set to 4m.

Low development? Regarding -11Jc, when developing by bringing the developing roller into contact with the electrostatic image holder as in the conventional case, it is preferable to use KFi and a material with a rubbery and flexible surface for the sleeve member 2. In this non-inventive embodiment, since development is carried out while keeping the toner layer on the sleeve 2 and the electrostatic image holder 1 out of contact, there is no need to use rubber or the like for the sleeve 17, but instead a non-magnetic material such as aluminum, etc. Stainless steel or the like can be used. The relative speed between the developing roller 11 and the electrostatic image holder 1 does not necessarily need to be zero, and it is possible to rotate both in the same direction or in opposite directions with a relative speed difference. In this embodiment, both are rotated in the same direction at close positions, and the sleeve 17 is rotated at approximately the same speed as the electrostatic image holder 1, or at 1~
- The toner and magnetic particles conveyed by the magnetic roller 8, which is rotating twice as fast, reach the magnetic pole N1 of the magnetic roller at a position in contact with or close to the developing roller.
The magnetic brush 12 is formed by standing up by the magnetic field.

This magnetic brush is attracted onto the developer roller by the magnetic pole $5 of magnet 18, and a portion of the magnetic brush is transferred from the magnetic roller to the developer roller. At this time, the strength of the magnetic field of each magnetic pole is preferably ss)N1. Further, the magnetic brush may be transferred by using only one magnetic pole N3 without providing the magnetic pole SS. In this case, the third
As shown in the figure as another embodiment, the magnetic pole f of the magnet 18,
It is preferable that B4 has a polarity opposite to that of the magnet 111N+ of the magnetic roller 8.

The magnetic roller may rotate either forward or backward relative to the developing roller, and rather than rotating at a constant speed, the amount of toner and carrier received by the developing roller may be varied depending on the amount of toner to be taken. In this embodiment, the sleeve 9 of the magnetic opening 7 is indicated by the arrow C.
The sleeve 17 is rotated in the opposite direction as shown in FIG.

Among the developer mixture adhering to the developing roller, the magnetic particles are at the magnetic pole N! and are restrained by the magnetic particle restraining member 15. Therefore, consider a circulation path in which the member 15 is magnetically bound on the passing side and falls onto the magnetic roller or below the developing unit.

As mentioned above, due to the contact of the magnetic pusher with the surface of the developing roller, the toner and υ magnetic particles move to the developing roller, and when they pass through the magnetic particle restraining member 15 provided opposite to the developing roller, 1 magnetic particles are transferred to the developing roller. The particles are magnetically restrained on the upstream side of the magnetic particle restraining member 15 in the sleeve movement direction, and a thin layer of only toner suitable for development is formed on the developing roller.

well formed. In this case, the toner in the toner layer formed on the developing roller is charged to a predetermined polarity due to friction with the developing roller surface or magnetic particles, and then adheres to the developing roller surface.

In FIG. 2, an alternating current voltage is applied to the sleeve 17 of the developing roller by superimposing direct current from the bias power supply 16.
An alternating electric field is formed between the electrostatic image holder and the photoreceptor 1. However, the developing roller and the magnetic roller are kept at equal potential. In this case, an electric field is applied between the developing roller and the magnetic roller in a direction that promotes toner movement by a power source 20 as shown in FIG. (applying a bias voltage of It becomes easier to form a toner.

Furthermore, it is also effective to adjust the amount of toner movement from the magnetic roller to the developing roller by making the electric bias means 20 between the two rollers variable. in this case,
Providing an insulating layer on the surface of either the sleeve 9 or 17 to improve electrical insulation is effective in increasing the electric field strength between the developing roller and the magnetic roller.

As described above, the invention is based on the fact that the magnetic particles are restrained on the paper developing roller 2 by the magnetic particle restraining member, and the magnetic particles are circulated between the magnetic roller and the non-magnetic toner. The layer can be formed on the developer roller,
There are several desirable conditions for making this action more stable, and these will be explained in detail with reference to FIG. 4, which is a schematic enlarged view of FIG. TA2.

A magnetic material is used for the first restraining member 15 in order to stably restrain the brush made of magnetic particles by placing it close to the magnetic particle restraining member 15 and to make it circulate. In the embodiment shown in FIG. 4, a magnetic blade (iron plate) is used as the restraining member 15, and as shown in the figure, the cross section is bent into a dogleg shape and attached to the inner wall of the developing device 3. The center 0 of the sleeve 17 passes through the intersection 19 of the tip surface and the center line l of the blade.
The sleeve 17 is arranged so as to be inclined downstream 9RK in the moving direction of the sleeve 17 by an angle a with respect to the angle anlc. This angle δ is 0°≦
It is preferable that δ≦90′; if the thickness is less than 06, the magnetic particles tend to leak from the blade portion, and if it is more than 90 layers, there is a risk that the blade 15 will come into contact with the sleeve 17. In this example, δ=85'lC is set. The blade 15 is preferably arranged at an angle in accordance with the direction of the magnetic field vector of the magnetic pole Ns,
δ? O'i' (The closer the magnetic pole NsK is, the larger the horizontal component is than the vertical component of the magnetic field, and the magnetic particles are not pressed against the sleeve 17 surface mK by the vertical component of the magnetic field, so the effect of restraining the magnetic particles is Large. The gap between the blade 15 and the sleeve 17 is 100 to 1000μ,
Preferably it is 200 to 300μ. In this embodiment, the gap is set to 200μ, and the tip of the blade 15 and the magnetic pole N
The angle θFi20' or more with respect to the magnetic pole Ns is preferably set to d5G@ or more, within a range where the magnetic field by the magnetic pole Ns reaches the blade 15. In this embodiment, θ=so″ binding.

When the positional relationship between the magnetic blade 15 and the ON5 poles of the magnet 18 is selected to the above value, the state of the developer mixture at the bead 15 portion becomes as shown in FIG. That is, the toner T is transported in the direction of the arrow d and falls on the contact portion between the toner T, the magnetic particles M#i, and the developing roller 11, and a portion thereof is transferred in the direction e.

This developer mixture is released by the rotation of the sleeve 17 in the direction b).
, while being bound to the surface of the sleeve 17.

The magnetic particles M, which are restrained by the magnetic blade 15 and become excessive in front thereof, are released from the magnetic restraint and fall in the direction of the arrow g along with the excess non-magnetic toner. The conditions under which the magnetic particles are restrained by the magnetic blades at this time will be described in more detail. The restraining force increases as the amount of change in the magnetic field at the blade position increases, and also increases as the distance between the blade and the developing roller becomes narrower.

The greater the surface roughness of the toner and magnetic particles M#ni developing roller, the easier it is to be conveyed, and the greater the mirrored electric force with the secondary developing roller, the easier it is to be conveyed.

Also, place the tip of the blade below the horizontal line passing through the center 0 of the magnetic blade 15ij current row 2-.
Rumor J--Extrusion of the Spear H-M Last Name Go 1 When the node is below the horizontal line, gravity acts on the magnetic particles y in the opposite direction to the conveyance force due to the movement of the sleeve 17, so the restraint of the magnetic particles is This is because the magnetic particles are more likely to fall in the direction of the arrow g, and the toner and the magnetic particles can be easily separated by the blade section. That is, even if the N pole of the magnet 18 is set to be relatively weak, there is an advantage that magnetic particles can be prevented from leaking from the blade portion toward the downstream side in the sleeve movement direction. In this embodiment, when there is no blade ν, the magnetic flux density of the Is pole is
I set it to 5 so that it would be 500 Gauss on 7.

7'jj6KrIi with magnetic blade provided in the above position
It is desirable to install the magnetic roller below the developing roller as well, and in this embodiment, as described above, the magnetic roller 2-
The developing roller is also placed below. Another advantage of this configuration is that gravity acts on the magnetic particles on the developing roller in a direction opposite to the magnetic binding force, which reduces the pressure on the developing roller, which reduces the deterioration of the toner magnetic particles and the surface of the developing roller. In addition, when it is necessary to arrange a plurality of developing devices around the photosensitive drum, such as in a color electrophotographic copying machine, the magnetic roller can be placed at T1 of the developing roller. K has the advantage that the arrangement of each developing device is facilitated. Of course, if sufficient space is provided, the magnetic roller can also be installed on the side or above the developing roller.

Although the surface of the sleeve 170 of the developing roller 11 may be mirror-finished, it is desirable that the sleeve surface be rough in order to coat the sleeve surface with enough toner for development. When the surface roughness of the sleeve 170 is set to 0.2 to 8 μm in JIS ten point average roughness Rst, if the distance between the sleeve 17 and the magnetic particle restraining member 15 is about 20 times or less than the average particle diameter of the magnetic particles, it is magnetic. It was confirmed through experiments that the particles could be sufficiently restrained by the restraining member.

The magnetic particles preferably have an average particle size of 1 to 30 times the average particle size of the toner particles, more specifically a particle size of 30 to 200 μm, preferably Fi 70 to 150 μm. If the particle size of the magnetic particles is significantly smaller than that of the toner particles, the toner and magnetic particles tend to adhere to each other and pass over the magnetic particle restraining member onto the developing roller.On the other hand, if the magnetic particles are significantly larger than the toner particles, the toner If the amount is small, stirring of the toner and magnetic particles becomes poor, and streaks are likely to occur in the resulting toner coating. As magnetic particles, those widely known as carriers in two-component development methods, including steel frames and ferrite particles, can be used. The non-magnetic toner is about 2 to 70 wt% based on the magnetic particles, more preferably from the viewpoint of maintaining fluidity of the developer mixture.
K to contain 2-20 vt%.

In order to keep the toner concentration in the developer mixture constant, a bottle is used to store replenishment toner T' as shown in FIG. par 1
01, and a supply roller 102 such as a sponge roller.
The toner for replenishment may be sequentially supplied into the developing device 3 by the following steps. Further, a sensor 105 for detecting toner concentration is provided in the developing device 3, and a driving means 105 such as a motor is operated via a control means 104 (based on a signal detected by this sensor) to rotate the replenishment roller 102. Alternatively, the toner T' may be replenished. For the sensor 103, five conventionally known detection means such as optical detection, magnetic detection, resistance detection, or leakage current detection can be used.

Further, in order to make the developer mixture uniform in the axial direction of the sleeve 9, a stirring member such as a screw may be provided. In order to recover the magnetic particles that have leaked a small amount of +lC from the magnetic blade 15 (especially when the sleeve 17 is rotated at high speed, leakage of magnetic particles may occur), a magnetic pole for transporting the magnetic particles has been installed. am-s5-15 may be provided. The same applies to the embodiment shown in FIG.

The invention has been explained above using non-magnetic toner as an example of a developer, but even if it is a magnetic toner that contains a magnetic material, the content of the magnetic material is small or the particle size is considerably smaller than the magnetic particles. Therefore, those with weak magnetic binding force can be used as toner.

In the developing section shown in FIG. 2, an AC bias voltage is applied between the developing roller 11 and the electrostatic image holder 1 to cause the toner particles to reciprocate. The frequency of the alternating current bias is determined by the developing speed, and in commercial copying machines, good images without uneven development can be obtained even when the frequency is as low as several tens of hertz.

The AC waveform may be not only a sine wave but also a rectangular wave or a triangular wave, and does not necessarily have to be an equal waveform.

Further, when the above AC bias is applied, toner adhesion occurs even on the non-image surface, resulting in blurring. In this case, it is preferable to apply a DC voltage higher than the potential of the non-image area to the AC bias. According to the embodiment, when developing by rotating the developing roller 11 in the forward direction at a constant speed in the developing section with respect to the electrostatic image holder 1 moving at a speed of 120111/sec,
The gap between the developing roller and the electrostatic image carrier is maintained at 300 μm, and the gap between the developing roller and the magnetic particle restraining member 15 is maintained at 20 μm.
The toner layer was maintained at 0μ to form a toner layer of approximately 80μ on the developer roller. As an AC waveform, frequency 1600Hz, voltage peak-to-peak value 1300Vi'C DC component +250
Added v.

When this alternating bias voltage was applied to the sleeve 17 from the power supply 16, a surface image with good gradation and no image fog was obtained.

Regarding the relationship between image density and toner layer thickness, for toner particles with an average particle size of around 4 to 20 μm used by Honor, the developed image density has a large effect on fluctuations in toner layer thickness until the toner layer thickness is around 30 μm. On the other hand, the concentration tends to be saturated at 30μ or more. Therefore, if the toner layer thickness is less than 30μ, the image density will be unstable, and it is essential to control the toner layer so as to maintain its uniform distribution.
The above is preferable because a good density can be obtained in the partial layer.

-1. When the toner layer thickness is 100μ or more, it has almost reached the saturation state, so there is no problem with the density. Therefore, when adjusting the gap with the electrostatic image carrier surface, toner layer thickness in this range Any thickness can be used. However, the increase in toner thickness is -1
Therefore, from the viewpoint of economy and ease of operation, it is preferable to develop with a thickness of 100 μm or less.

The developing roller surface rMII' that completed development in this way
i. The residual toner is removed by the scraper 13. Although this is not always necessary, by removing the toner on the developing roller after development in this way, the next time the toner is applied with the magnetic brush, it will be applied uniformly.
Furthermore, it is possible to completely prevent the occurrence of ghosts on the developing roller, which sometimes appear in the next developed image (depending on the presence or absence of residual toner from the previous time). As the scraper member, a metal piece, such as a phosphor bronze plate of about 0.1 to Q, 2xx, or a rubber plate, such as urethane rubber with a rubber hardness of 60 to 9σ, is suitably used.

FIG. 5 shows a concrete example of the construction of a Kyuriki 2-image forming apparatus to which a developing device based on the 8AK is applied.

The photoreceptor drum 21 has a photoreceptor on its surface that does not include a conductive layer, a photoconductive layer, and an insulating layer.

A document table places an original to be copied on the lath 22, and illuminates it with an illumination lamp 25fC. Scanning mirrors 24 and 25 for scanning the original scan the original in synchronization with the rotation of the drum 21, and move to positions 24' and 25'. At this time, the illumination lamp 23 also moves to the position 23'.

The light image of the scanned original is exposed to the photoreceptor surface through the lens 26, mirror 27, color separation means 28, and mirror 29, and further through the exposure-simultaneous static eliminator 50. Color separation means 2
8Fi, t281, green 282, red 28 according to each separation color
3 and 1 (D 284).

-1. The surface of the photosensitive drum 210 is cleaned in advance with a blade cleaner 31, and then the influence of the previous latent image is removed by the pre-exposure tube 32 and the pre-static eliminator 331C. Further, the surface of the photoreceptor drum 210 is uniformly charged by a primary charger 34, and then a KN light simultaneous static eliminator 3 is used to expose the original to a light image.
Static electricity is removed by °K. Subsequently, the entire surface of the photoreceptor is uniformly exposed by the entire surface exposure light source 35, and a high-contrast electrostatic latent image is formed on the surface of the photoreceptor.

Then yellow 361, magenta 36 based on the invention
2, a developing device 3 having a plurality of developing units that supply non-magnetic toner of each color of cyan 363 and black 364;
Development is performed by a predetermined unit 60. Each of these developing units 361-'364K is applied with the uninvented developing device 3 shown in FIG. 2 or 3 described above, and each unit is equipped with a developing roller 11 and a magnetic roller 8.

-1. The transfer material 37 to which the developed images are transferred is sent to the transfer unit 39 by the delivery roller 381C. Transcription Units)! S9t: has a t gripper 40 and transfer material 3
The transfer material is held by gripping the tip of 7. The transfer material 37 is transferred to a transfer corona discharger 411 in the transfer unit 39.
A corona discharge is applied from the back surface of C, and the developed images on the photoreceptor surface are transferred. In the case of monochrome copying, the transfer material 37 is immediately separated from the transfer unit by the operation of the separation claw 42. - In the case of multicolor reproduction, the transfer unit 39C) gripper 40 does not open and the separation claw 42 does not operate until the transfer of the two or three colors to be reproduced is completed. hold the material.

In either case, the transfer material 37 after separation is transferred to the conveyor belt 45
1C) is guided to a heat fixing row 7-44, where the transferred raw image is heat fixed. After the fixing is completed, the transfer material is discharged onto the paper discharge tray 45. On the other hand, the toner remaining on the surface of the photoreceptor drum 21 after completion of the transfer is cleaned by a blade cleaner 31 and is used for the next copying cycle.

The yellow, magenta, and cyan color nonmagnetic toners used in the above-mentioned development units 561, 362, and 363 were prepared with the following compositions.

Cyan toner polyester resin 94 parts Phthalocyanine blue 5 parts Charge control agent 1 part Magenta toner polyester resin 94 parts Rhodamine lake pigment 5 parts Charge control agent
1 part yellow toner polyester resin 94 parts Hansa Yellow 5 parts charge control agent
1 part The average particle size of each of the above toners was 10 microns.

These are mixed together with iron powder as magnetic particles, and a magnetic brush is formed by the magnetic roller of each developing unit.
Be sure to apply non-magnetic toner to the developing roller to perform development.

In this way, the color image forming apparatus to which the developing device according to the invention is applied uses non-magnetic toner, so that images with good color reproducibility can be obtained.

On the other hand, in conventional developing devices using magnetic toner,
The toner has a dark taste due to the magnetic substance contained in the toner! Beauty,
As a color developer, it has low sharpness and is difficult to use.As mentioned above, the invention uses a magnetic means and a developer holding means, so the conveyance path for the magnetic particles can be sufficiently long. Therefore, the toner and the magnetic particles are sufficiently stirred, and a sufficient triboelectric charge can be imparted to the non-magnetic toner by friction with the developer holding means or the magnetic particles. In addition, by arranging the magnetic means below the developer holding means, the magnetic particles and toner can be completely separated at the magnetic particle restraining member, and the magnetic particles are released from the restraining member. Can prevent leakage. Similarly,
The pressure of the magnetic particles on the surface of the developer holding means can be reduced, and this has the effect of preventing abrasion of the surface of the developer holding member and deterioration of the developer. Therefore, according to the inventive structure, it is possible to increase the speed of the image forming apparatus. Further, in the first invention, development is carried out using the above-mentioned developing method using non-magnetic toner, so good images without fogging can be obtained, and the reproduction of color images in particular is excellent, so it can be effectively applied to color image forming apparatuses. be able to.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an image forming apparatus, FIG. 2 is a sectional view of a developing device according to the invention, FIG. 3 is a sectional view of another embodiment of the invention, and FIG. 4 is a schematic diagram of FIG. 2. The enlarged explanatory view, FIG. 5, is a configuration diagram of a force 2-image forming apparatus to which the developing device of the invention is applied. In the figure, 1... Electrostatic image holder 3... Developing device 7... Developer 8... Magnetic roller 9... Sleeve 10... Magnet 11... Developing roller 12... Magnetic brush 15...Magnetic particle restraining member 16...Bias power supply 17...Sleeve 18...Magnet T...Nonmagnetic toner M...Represents magnetic particles.

Claims (1)

[Scope of Claims] A developing device for developing a latent image on a latent image carrier, comprising: a magnetic means for forming a magnetic brush of a developer mixture having toner and magnetic particles on the surface; A developer holding means that receives a developer mixture from a magnetic brush, a magnetic field generating means provided inside the developer holding means, and a downstream side with respect to the moving direction of the developer holding means from a region in contact with the magnetic brush. and a magnetic particle restraining member provided opposite to the developer holding means,
A developing device characterized in that the magnetic particle restraining member applies toner onto a developer holding means, guides the toner to a developing area facing the latent image holding member, and develops the latent image.