JP2682988B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses magnetic carrier particles and toner particles.
A two-component developing system for developing, especially in the developing section.
And a developing device for applying an alternating electric field. The present invention provides a display device, a printer, and a printer for image recording formation.
With a developing device that can be applied to various types of Aximile electrophotographic devices
is there. [Prior Art] In a recording apparatus such as an electrophotographic copying apparatus, a magnetic carrier is used.
A two-component developer that is a mixture of particles and toner particles
The developer is supplied onto the surface of the carrier to convey the developer onto the surface of the carrier.
A layer is formed on the surface of the image carrier by the developer layer.
Development when developing latent images such as electric latent images or magnetic latent images
By applying an alternating electric field to the agent layer, delicate lines and
A clear high-quality image that faithfully reproduces points or shade differences
Has already been developed. Even in electrophotographic copying machines, the equipment is changing due to the trend of the times.
Is required to be smaller and lighter. Development method as described above
Even with a developing device that uses a
Carrier (hereinafter referred to as developing sleeve or simply sleeve
You. ) Is required to be smaller. In the conventional device, the diameter of the developing sleeve was φ20 or more.
Therefore, the magnets arranged inside the developing sleeve are relatively
It is possible to use a thicker diameter.
Also has a high degree of freedom in designing, and is sufficient even for the developing magnetic pole, for example.
Designed to cover the entire development area with magnetic flux density
It's easy to do. FIG. 2 shows the development of a conventional developing device having a relatively large diameter.
FIG. 2a) is a cross-sectional view of the region, showing the state of carrier particles.
2b) is a diagram showing a magnetic flux density distribution.
You. For a magnet with a large diameter, it is shown in Fig. 2.
As the developing magnetic pole maintains a sufficient magnetic flux density,
Easy to cover the body and in the development area
Carrier particles are sufficiently speared and the developer density is lowered.
Vibration of toner and carrier particles due to alternating electric field,
Flying is actively carried out, and extremely efficient development is possible.
You. In addition, sufficient magnetic force can be obtained on the downstream side of the development area.
To easily pull the carrier particles attached to the photoconductor with magnetic force.
It is possible to put it back. Therefore, it has good development characteristics and has carrier particles.
It was possible to provide a developing device without wear. [Problems to be Solved by the Invention] However, in the above-described embodiment, downsizing and extension of the developing device
However, there is a limit to the downsizing of electrophotographic copying machines,
The development sleeve should be made smaller in order to make it smaller and lighter.
is required. Inside when the developing sleeve diameter falls below φ20
The diameter of the magnet installed in the
Net volume is extremely small. Therefore, high magnetic flux density
It is difficult to make a wide and wide magnet.
Even if the sleeve diameter is larger, the cut magnetic pole
A magnet of a developing device including a plurality of magnetic poles such as a sending magnetic pole and a developing magnetic pole.
The Nettrol is designed according to the characteristics of each magnetic pole.
It is essential that only the developing magnetic pole be strong and wide as shown in Fig. 2.
It is almost impossible to set a wide range. If the magnetic force of the developing magnetic pole is dropped, carrier particles
It is difficult to prevent adhesion to the photoconductor, and as shown in FIG.
Even if the magnetic flux density is the same, the magnetic pole width is the same on the upstream and downstream sides.
Even if the taper is thinned, the magnetic force on the downstream side of the development area will be insufficient and the key
It is difficult to prevent the adhesion of the yaria particles to the photoconductor. Also, as shown in FIG. 4, the magnetic pole is tilted to the downstream side and
The one that increases the magnetic force of and prevents the adhesion of carrier particles
Carrier particles in the developing area do not rise sufficiently, and
From carrier particles near the sleeve surface or sleeve surface
It hinders the toner's flight, and its development efficiency declines.
I don't. (Object of the Invention) An object of the present invention is to solve the problem of a small-diameter developing sleeve.
At the same time, the quality of the developed image on the large diameter sleeve is improved.
It is to provide a developing device. The present invention can significantly prevent the loss of carrier particles, and
The development of a developing device that can form high quality images with high development efficiency
The purpose is to serve. (Summary of the Invention) In order to achieve the above object, the present invention provides an electrostatic image carrier and
Form a developing unit that develops an electrostatic image facing each other, and
A developer carrier that carries and moves a developer having a toner
The body and the current for forming the magnetic brush provided in the developing section.
An image magnetic pole, and the electrostatic image carrier and the developer carrier.
The electrostatic force is applied to the magnetic brush in an alternating electric field formed between the bodies.
In a developing device that develops by contacting the image carrier,
The magnetic flux density distribution curve formed by the developing magnetic pole is
The upstream side in the moving direction of the developer carrier is steeper than the downstream side.
The position of the peak of the magnetic flux density distribution and the position of the peak half value
Is characterized in that the downstream side is more than double the upstream side
It is assumed that. [Embodiment] FIG. 1 is a sectional view of a developing area of a developing device according to the present invention.
FIG. 5 is a sixth embodiment of the developing device according to the present invention.
The figure shows the magnetic flux density of the magnet used in the developing device of FIG.
It is a degree distribution chart. In FIG. 5, the latent image carrier 1 is an electrostatic recording insulating drum.
Or α-Se, Cds, ZnO _Two , OPC, α-Si like photoconductive insulation
A photosensitive drum or photosensitive belt having a material layer. Submarine
The image carrier 1 is moved in the direction of arrow a by a driving device (not shown).
Rotated. 2 is in proximity to or in contact with the latent image carrier 1
Developing sleeve, for example, aluminum, SUS3
It is composed of 16 non-magnetic materials. The developing sleeve 2
A horizontally long opening formed on the lower left wall of the developing container 11 in the longitudinal direction of the container.
Insert the right half-circle into the mouth into the container 11 and close the left half-circle.
It is exposed to the outside of the device, rotatably supported by a bearing, and installed horizontally.
And is driven to rotate in the direction of arrow b. 3 is positioned in the position and orientation shown in FIG.
A fixed permanent magnet as a fixed magnetic field generating means held in place.
It is a stone and the developing sleeve 2 is driven to rotate.
Even if this happens, keep the magnet 3 fixed in the position and orientation shown.
Be held. This magnet 3 has an N-pole magnetic pole 3a, an S-pole magnetic pole 3b,
It has four magnetic poles, an N-pole magnetic pole 3c and an S-pole magnetic pole 3d. Magnet 3
May be replaced with an electromagnet instead of the permanent magnet. 4 is on the opening of the developer feeder in which the developing sleeve 2 is arranged
On the edge side, the base is fixed to the side wall of the container, and the tip side is the upper edge position of the opening.
Along the length of the upper edge of the opening so that it protrudes to the outside of the container 11
With a non-magnetic blade as a developer control member,
For example, by bending SuS316 into a cross section,
is there. 5 is the front end of the non-magnetic blade 24 with its lower surface in contact with the upper surface.
This is a magnetic particle limiting member whose surface is the developer guide surface 51. 7 is a carrier particle having a particle size of 30 to 100 μm, preferably
More specifically, the resistance value is 40 to 80 μm and the average particle size is about 50 μm and the resistance value is 10
⁷ Ωcm or more, preferably 10 ⁸ Ferrite particles above Ωcm
Uses resin coated to (maximum magnetization 60emu / g)
You can be. Reference numeral 8 is a non-magnetic developer toner. 6 is from the lower part of the developing container 11 in which the developing sleeve 2 is arranged.
Prevents leakage of the carrier particles 7 or the non-magnetic toner particles 8.
Facing the developing sleeve 2 on the inner surface of the lower part of the developing container to stop
Is a magnetic material that is arranged in a
It was done. Magnetism between the magnetic body 6 and the magnetic pole 3d of S polarity
That achieves carrier particle 7 recovery and leakage prevention in the world
The effect is obtained. 9 is formed by the fixed magnetic pole 3 in the developing sleeve 2.
Toner supply that supplies toner to the brush part of the carrier particles.
A rubber sheet is attached to a sheet metal that is a feeding member and rotatably bearings
Toner is conveyed as if sweeping the lower surface of the developing container. G
The toner feeding member 9 conveys the toner in the toner storage container 12.
The toner is supplied by the member 10. 12 and 13 are toner storage container and carrier particle storage, respectively
It is a container. 14 is a seal for sealing the toner accumulated in the lower part of the developing container 11.
The elastic member is elastic and bends in the direction of rotation of the sleeve 2.
Thus, the surface side of the sleeve 2 is elastically pressed.
The seal member 14 allows the developer to enter the inside of the container.
In the contact area with the sleeve, the sleeve rotation direction
It has an end on the downstream side. In addition, the S magnetic pole 3d is connected to the magnetic member 6 from one side to the other side.
A magnetic field generating means for magnetic seals for forming a magnetic field.
That is, one part faces the magnetic member 6. Magnetic member 6
At the substantial end of the developer container of the developer container.
It is located below the container and the magnetic properties collected around this container
Due to the movement of carrier particles, the developer on the sleeve surface
The toner particles located in the lower part of the container are taken in. Follow
The stable recovery of magnetic particles stabilizes the developing ability.
effective. The magnetic member 6 has a "K" or "L" shape and is made of iron.
A magnetic material that is not permanently magnetized such as is applicable.
When a magnet is used as the magnetic member 6, the plane 66 is magnetized.
Stone S _Two Must have an N polarity, which is opposite to the magnetic S of. In other words, the magnetic member 6 restrains the carrier particles while
Prevents the loss of carrier particles and
Toner particles in the developer container
It can be prevented from leaking from inside. Furthermore, by arranging the magnetic pole 3d as described above,
Thus, another preferable effect can be obtained in relation to the magnetic pole 3a. You
That is, according to the above relationship between the bottom of the container 11 and the magnetic pole 3d.
Then, in the magnetic brush 11 (compared to just stagnant state
Since it is not formed in a coarse state,
The amount of toner particles taken in is not excessive. excess
Incorporation causes insufficient toner charge and may cause fogging.
Become. Note that this structure is non-magnetic with magnetic particles in the developer container.
It is also effective when weak magnetic toner is mixed.
You. According to experiments, the distance between the developing sleeve and the magnetic member is 2.5m
At m, the magnetic carrier particles are completely recovered and the toner particles
No leakage was observed, and stable development could be achieved. This
The presence of the surface 66 in the area of indicates that the magnetic force of the magnetic pole 3d is
Disperse moderately to increase the magnetic force in this area.
As the magnetic field sealing effect is increasing,
Conceivable. The end of the non-magnetic blade 24 and the surface of the developing sleeve 2 are described above.
Distance d _Two Is 50 to 800 μm, preferably 150 to 500 μm
You. If this distance is less than 50 μm, magnetic particles described later
Clogged during this time, the developer layer is likely to be uneven and
You can apply the developer necessary for good development.
The disadvantage that only developed images with low density and large unevenness can be obtained
There is. If it is larger than 800 μm, it will be on the developing sleeve 2.
The amount of developer applied increases and the prescribed developer layer thickness is regulated.
If you can not do it, and the carrier particles adhere to the latent image carrier more
Both will be described later with the circulation of the developer and the developer limiting member 5.
Image regulation is weakened, toner tribo is insufficient, and fogging easily occurs.
Disadvantages. In this carrier particle layer, the sleeve 2 rotates in the direction of arrow b.
Even when driven to rotate, the binding force and sleeve based on magnetic force and gravity
2 The sleeve surface is balanced by the conveying force in the moving direction.
The movement becomes slower as the distance from the
Forms a stationary layer that can move somewhat but is almost immobile. Also
Of course, some fall due to the influence of gravity. Therefore, the positions of the magnetic poles 3a and 3d and the fluidity of the magnetic particles 7
The magnetic particle layer can be
The closer it is to the bulge, the more it is transported in the direction of the magnetic pole 3a to form the moving layer. this
Due to the movement of the magnetic particles, the magnetic particle layer (first layer) becomes a toner layer.
The toner is taken in from the (second layer) and the magnetic particles 7 or
The toner is triboelectrically charged due to the rubbing against the sleeve 2 and slips.
It is conveyed to the development area with the rotation of the probe 2 and provided for development.
You. The movement of the magnetic particle layer depends on the fluidity and magnetic force of the developer.
If the determined toner content in the magnetic particles is low, the
The static layer becomes smaller and most of the magnetic particle layers move faster.
Then, the toner is taken in from the toner layer. Also, the toner container
When the magnetic field is high, the static layer becomes large and the magnetic particle layer
The moving layer of the toner may come into contact with the toner layer covered by this stationary layer.
And the toner is not taken in.
You. Therefore, some toner content is naturally maintained
Is done. Next, the non-magnetic blade 4 which is the developer application amount regulating member
Description of the magnetic particle layer in the vicinity and in the vicinity of the limiting member 5
I do. The limited member does not require toner to be replenished to the developer control section.
It's not just mechanically blocking entry. As mentioned above,
In the regulation area surrounded by the sleeve, the recording member 5 has magnetic poles.
N ₁ The magnetic key carried by the pole as the sleeve rotates.
Yaria particles are packed along the guide surface 51 of the limiting member 5.
And the density increases. In this area, they are transported and enter
Carrier particles coming in and the carrier flowing out from the blade
Careful because the replacement with particles is dynamically occurring.
Even if the particles collide with each other and are in a disturbed state
It is in a practical packing state. Because of this
Tribo is applied to the toner from the particles or the sleeve.
Applied and weak on carrier particles or sleeve
Toner with small tribo imparted by force and conveyed
Detach from the carrier particles or sleeve. Toes
Therefore, the toner is sorted and the charging is made uniform. Therefore,
To provide toner with sufficient tribo donation for development
Can be. In addition, the non-uniform state when the carrier particles are conveyed is also
Uniform coating of the carrier particle layer, averaged in space
Stabilization and stabilization is also achieved. Therefore, the limiting member 5 is the above guide
The surface 51 is essential, and the slope of the slope and the volume of space are
Has a great effect on the packing state of carrier particles between
I can. On the other hand, the magnetic pole fixed to this area
3a shows the carrier particles in the packing state along the magnetic field lines.
Relocate. The packing state in the space is
There is some instability with respect to giving, in order to stabilize
Always requires a constant packing state. This is
Carrier particles transported almost tangentially on the leaves
To form a magnetic brush with a force directed directly in that direction.
Not only stirring effect on yaria particles, but also loosening effect
Also works, giving tribo to the above toner and carrier particle layer
The homogenization and stabilization of the application of is further promoted. At this time,
Due to the peripheral structure, the concentrated developer causes a large amount of pressure.
There is a problem that the developer gets too clogged if the force is kept applied.
However, the part of the magnetic pole 3a that generates the maximum magnetic force faces the guide surface 51.
To prevent excessive pressure collection in the regulated area.
Prevents inside, concentrates developer and stabilizes high-density carrier
It is considered that the particle existence ratio can be maintained. Due to the above regulated area, the surface of the developing sleeve is not
A fixed amount of carrier particles and fully charged toner particles
Can be formed as a thin layer of developer. Therefore, in the development area 102
The developing effect of is stable. And the development described above
At least the developer carrying member conveyed to the developing section
The toner particles carried on the surface are transferred to the electrostatic latent image carrier.
Alternating electric field forming means for forming an alternating electric field in the developing section
And, in the developing section, in front of the electrostatic latent image carrier.
For the volume of the space formed with the developer carrying member,
Body occupied by carrier particles of the developer conveyed to the developing section
For developing method and equipment with a product ratio of 1.5% to 30%
It was confirmed that a great effect was given. FIG. 5 shows that the non-magnetic blade side of the developer limiting member 5 is magnetic.
The case where the body 50 is arranged is shown. In this case, the magnetic body 50
It is not preferable to provide it at a position facing the magnetic pole 3a. why
Then, if they are facing each other, a strong concentrated magnetic field is generated between the magnetic pole 3a.
Generated, stirring and loosening the carrier particles by the magnetic pole 3a
The effect is reduced. However, the magnetic material
Is provided between the inner magnet 3 of the sleeve and the magnetic regulation of magnetic particles.
The restriction is to increase the tolerance of the clearance between the restriction member and the sleeve.
And is effective. In addition, carrier particles or pickpockets
If you compare the toner adhered on the sleeve,
The amount of electrified charge of the deposited toner adheres to the carrier particles.
Less than. The reason for this is that as the sleeve moves,
Since the toner particles are also transported, the toner on the sleeve is
Opportunity to be rubbed by rear particles is reduced
It is. Set the toner on this sleeve to the specified charge amount.
The toner on the sleeve positively
It is necessary to rub it. That is, near the sleeve surface
A key that causes a deviation in relative speed against the movement of the leaves.
The presence of rear particles is required. However, simply reducing the transportability of the carrier particles
Is not possible considering the above-mentioned toner intake action.
is there. Also, the restriction section faces the sleeve magnetic pole 3a as described above.
The magnetic particles are arranged to generate a concentrated magnetic field, and carrier particles
It is also possible to improve the rubbing force of the
The maximum magnetic force of the magnetic poles is generated in the space created by the developer circulation regulating member 5.
The effect of placing the raw part is reduced. Therefore, in this embodiment, the sleeve is rotated more than the magnetic pole 3a.
The magnetic body 50 is provided on the downstream side with respect to the
The magnetic lines on the card side are concentrated almost in the tangential direction on the sleeve surface.
Configured as As a result, the key only near the sleeve surface
Yaria particles form a magnetic brush along the sleeve surface
The toner on the sleeve and rub it against the toner on the sleeve.
It was possible to increase the tribo endowment. The magnetic flux density of the magnetic pole 3a is 600 G or more, preferably 700 G or more.
Above is preferred. This is the toner content of the carrier particle layer.
When the developer is applied, the magnetic flux density of the cut magnetic pole is
This is because the higher the degree, the more stable it tends to be. Especially toner
No automatic toner replenishment device to maintain content
The developing device of the present invention has a magnetic flux density of 800 G or more.
And are preferred. In FIG. 5, the magnetic pole 3c is a developing magnetic pole, but it is shown in FIG.
As described above, the developing magnetic pole 3c is maximum in the portion facing the photoconductor.
Has a magnetic flux density of up to the upstream side in the rotation direction of the developing sleeve 2.
It suddenly weakens its magnetic force, and gradually slows down
Designed to fall into. Rotation of developing sleeve 2
The developer layer that was transported along with the
It rises sharply and is rubbed directly on the surface of the photoconductor, so development
Carrier particles 7 generated by the movement associated with the spike of the agent layer
The toner that separates from the transfer to the photoconductor 1 easily,
The detached toner becomes scattered toner and the inside of the electrophotographic apparatus is dirty.
It is preferable because it does not cause inconvenience. Also, in the developing area, the developer layer is in a spiked state.
The developing sleeve surface is released, and the
Toner flying from yaria particles is activated by an alternating electric field
Done. Therefore, most of the toner existing in the development area
All are provided for development, so development efficiency is extremely high and high quality
Images can be obtained. Also, there is almost no decrease in magnetic force on the downstream side of the development area.
The magnetic carrier particles attached to the photoconductor 1 are
Holds enough magnetic force to pull it back to B2. in addition
Holds more than 70% of the magnetic force in the downstream area than the developing area
Is desirable. Also, the upstream and downstream sides of the magnetic pole center
Width to half value X ₁ , X _Two Is preferably 1: 2 or more
No. Therefore, it does not cause toner scattering and has good development characteristics, and
It is possible to provide a good image without adhesion of spear. In any case, the present invention cannot be obtained by the conventional developing device.
It is possible to provide excellent image quality and
It has an excellent effect that it can be made into a small type of discard type.
Is what you do. The toner supply member 9 is in the developing container 11 and is a magnetic particle layer.
To the toner by rotating in the direction of arrow d
8 is supplied to the carrier particle layer. Store the toner adjacent to the developing container 11 in a substantially horizontal direction.
In the toner storage container
Is provided with a toner conveying member 10 for feeding toner into the developing container 11.
Have been killed. In the S magnetic pole 3b, the cut magnetic pole 3a and the developing magnetic pole 3c are separated from each other.
Because it has a non-magnetic blade, it is uniformly coated with 44 parts
With a carrier pole provided to prevent the agent layer from being disturbed.
is there. The S magnetic pole 3b has the strength of the magnetic pole so as not to disturb the developer layer.
Then, it is similar to or slightly lower than the general developing magnetic pole 3c. Development
When using a 16φ reed, the cut magnetic pole and current
If the distance between the image magnetic poles is within 110 ° of the sleeve center angle,
Disturbance of the developer layer on the leaves was small, but exceeded 110 °
In this case, the developer layer is greatly disturbed and a carrier pole is provided in the middle.
Is preferred. The S magnetic pole 3d is a recovery magnetic pole for collecting the developer after development.
The direction of movement of the developing sleeve 2 from the tip of the magnetic seal 6.
It is located on the upstream side. The magnetic pole 3d is from the tip of the magnetic seal 6.
When placed on the downstream side, the toner removal on the bottom of the developer container 11
In the vicinity of the mouth, the spikes of carrier particles due to the magnetic pole 3d
Occurs, it becomes extremely easy to take in toner, and triboelectric charging is sufficient.
It is easy to cause fog etc. In Fig. 5, the sleeve 2 is made of aluminum with a diameter of 16 mm.
The surface of the sleeve is sanded with alundum abrasive
Use a blasted magnet and magnet 4 with 4 poles
Use the N pole and S pole alternately as shown in Fig. 6.
Was. The maximum value of the surface magnetic flux density by the magnet 3 is about 900 gau
It was The developing magnetic pole 3c has the maximum magnetic flux at the portion facing the photoconductor.
Density, the magnetic force sharply decreases on the upstream side, and the downstream side
Then, the decrease of the magnetic force is slow, and even after passing the development area
It has a sufficient magnetic force. 1.2 mm thick non-magnetic stainless steel is used for the blade 4.
The angle θ was 1.5 °. As the carrier particles, the surface is coated with silicone resin.
Ferrite with a particle size of 70 to 50μ (250/350 mesh)
Large magnetization 60emu / g) was used. Non-magnetic toners include styrene / butadiene copolymer
Consist of 100 parts of system resin and 5 parts of copper phthalocyanine pigment
1.0% of colloidal silica to toner powder with an average particle size of 10μ
When the blue toner added externally was used, the surface of the sleeve 2
Toner coating amount of about 10 ~ 30μm coating thickness is obtained,
Furthermore, a carrier particle layer of 200-300μ was obtained as the upper layer.
Was. The toner adheres to the surface of each carrier particle.
I have. Carrier particles are inside the sleeve 2 at and near the developing area.
The magnetic pole 3c causes the magnetic field to stand up and the maximum length is approximately 1.2 m.
It formed a brush of about m in height. The charge amount was measured by the blow-off method.
The amount of tribo charge of the toner on the carrier particles is +12 μC / g
Met. Assemble this developing device to FC-5 type copier manufactured by Canon Inc.
Photosensitive drum 1 (made of organic photosensitive material) and sleeve 2
Was 350 μm. Bias power supply (not shown
AC) with frequency 1600Hz and peak-to-peak value 1300V
Develop using a voltage with a -300V DC voltage superimposed
Then, a good blue color image was obtained. Develop the solid black image, and develop the sleeve.
Observation of the surface revealed that toner and
The toner on the leave is almost consumed and the developing effect is almost 100%
Was being developed at a rate. There is no fog in the development characteristics, and good development characteristics
I was able to get it. Further, the magnetic particles having good effects of the magnetic member 6 are also available.
To prevent ingress, leakage, and good circulation.
It has been certified. As described above, according to this embodiment, high image density,
High development efficiency, fogging, ghost images, uneven swaths, negative characteristics
It is possible to carry out development without properties. The material of the sleeve 2 is aluminum as well as brass.
Conductors such as stainless steel, paper cylinders, and synthetic resin cylinders
Can be used. The surfaces of these cylinders are conductively treated.
Or if it is made of a conductor, it functions as a developing electrode
You can also. In addition, a core roll is used to guide
It is constructed by winding an electrically conductive elastic body, for example, a conductive sponge.
You may. Toner has silica particles to improve fluidity,
For example, in a transfer type image forming method, a photosensitive image
For polishing the surface of the drum 1, externally add abrasive particles, etc.
Is also good. Use a small amount of magnetic particles in the toner
May be. In other words, it is significantly weaker than magnetic particles.
Yes, use magnetic toner if tribo chargeable
Can be. To prevent the ghost image phenomenon, return to the container 11
On the sleeve 2 that has not been subjected to development from the surface of the moved sleeve 2
The remaining developer layer is temporarily removed with a scraper (not shown).
After scraping off the sleeve surface, the magnetic particle layer
To re-coat the developer by contacting
May be. Detects the concentration of magnetic particles and toner and responds to this output.
A mechanism for automatically replenishing toner may be provided. The developing device of the present invention includes a container 11, a sleeve 2 and a breaker.
Use as a developer type developing device that integrates the D4 etc.
Also used as a normal developing unit fixed to the image forming apparatus
It is possible. In this embodiment, a developing sleeve with a diameter of 16φ is used.
However, the present invention not only has a small diameter, but also has a large diameter of 20φ or more.
Anything can be applied. <Embodiment II> In the above-mentioned embodiment, the developing magnetic pole 3c is a single pole on the upstream side.
That the magnetic force of is significantly attenuated and the attenuation on the downstream side is slow
Was used, but a pole and carrier particles that improve the development efficiency were used.
The electrodes to be collected may be independent from each other. A cross-sectional view of the developing area of the developing device of the general embodiment is shown in FIG.
It shows in FIG. In FIG. 7, the developing magnetic pole 3c is the photosensitive drum 1
N facing ₁ Magnetic pole and N directed downstream of development area _Two Magnetic
It consists of repulsive magnetic poles. N ₁ Development of magnetic pole in the development area
The development of the agent is perfected and good development characteristics are obtained.
N _Two The magnetic pole ensures that the carrier attached to the photoconductor 1 is rotated.
It becomes possible to collect. Also, by using a repulsive magnetic pole, N ₁ , N _Two Magnetic force between magnetic poles
A weak part of the magnetic field is created, and the binding force of the magnetic field is weak in this part,
Carrier particles vibrate and fly extremely easily due to alternating electric fields
The toner from the carrier and sleeve.
Is easily performed, and the fog toner on the drum can be removed.
There is also a more reliable effect. In addition, toner is a kind of powder cloud in this weak area.
The edge-like shape promotes the edge development effect. Therefore, the sharpness of the line and the solid density are sufficient.
Images can be obtained. <Embodiment III> FIG. 8 shows a magnetic plate between the developing magnetic pole 3c and the upstream magnetic pole 3d.
81 is provided to sharply reduce the magnetic flux density on the upstream side of the developing magnetic pole 3c.
It's a downed one. By providing the magnetic plate 81 as in this embodiment, development
The magnetic field on the upstream side of the part can be controlled.
It is possible to easily control the starting point of the ear of the baby
It is possible to prevent spikes from developing at a distance in the developing area.
it can. As a result, the detached toner that accompanies the rising motion of the developer is removed.
The toner does not become scattered toner and is effectively used for development.
Therefore, a good developing device with less scattering can be provided.
You. Further, the developing magnetic pole 3c has the opposite polarity as shown in the second embodiment.
It may be a magnetic pole. <Embodiment IV> FIG. 9 shows the magnetic brush tip of the embodiment used in FIG.
This is an example in which the leveling member 15 is applied. The member is upstream of the developing pole N pole (not limited to FIG. 1)
It is preferably provided near the side inclined portion. As a shape property
Is a flexible polymer material such as Mylar
(Name) A sheet having a thickness of 25 μm was used in contact with the sleeve. Magnetic bra coated on sleeve by application of said member
Can form fine ears in the development area
You. Therefore, the toner is easily released from the carrier, and
Rash marks are less likely to appear on the image, and due to the downstream magnetic force
And easy to hold or suck carrier particles on the sleeve
Effectively prevents carrier adhesion to the photoconductor
I can. In addition, during transportation from the regulation blade to the developing area
Toner scattering can also be prevented. [Effect of the Invention] As described above, according to the present invention
The developer is fully sprung up and the developing sleeve surface
Open, so that you can develop efficiently
It is also important to prevent carrier particles from sticking to the photoreceptor.
And the effect of reducing toner scattering that accompanies the spike of developer
There is. Especially when using a small-diameter sleeve with an outer diameter of 6 to 20 mm,
A good image can be obtained by applying the present invention. Also, when using a fine particle toner of 10 μm or less,
A good image is obtained by applying light.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) (b) is an enlarged view of a developing area of a developing device embodying the present invention, and FIG. 2 (a) (b) to FIG. 4 (a) (b). FIG. 5 is an explanatory view of a conventional developing unit, FIG. 5 is a sectional view of a developing device embodying the present invention, FIG. 6 is a magnetic flux pattern diagram used in the developing device of FIG. 5, and FIGS. 7 (a) and 7 (b). , FIG. 8 and FIG. 9 are enlarged views of the developing area of another embodiment of the present invention. 1 ... Latent image carrier 2 ... Developing sleeve 3 ... Magnetic field generating means 4 ... Developer amount regulating member 5 ... Developer circulation area limiting member 6 ... Magnetic seal 7 ... Carrier particles 8 ... Toner 9 ...... Toner supply member 10 …… Toner transport member 11 …… Developer container 12 …… Toner storage container 13 …… Magnetic particle storage container 14 …… Lower scattering prevention film 15 …… Pressing leveling member

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Rehisa Hoshika               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Hiroshi Taka               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Masahide Kinoshita               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc.                (56) References JP-A-54-143237 (JP, A)                 JP-A-58-72972 (JP, A)                 Japanese Patent Laid-Open No. Sho 50-110642 (JP, A)

Claims (1)

(57) [Claims] A developing unit that develops an electrostatic image is formed facing the electrostatic image carrier, and a developer carrier that carries and moves a developer having a carrier and toner, and a magnetic brush provided in the developing unit are formed. And a developing magnetic pole for carrying out development, in which a magnetic brush is brought into contact with the electrostatic image carrier in an alternating electric field formed between the electrostatic image carrier and the developer carrier to perform development. In the device, the magnetic flux density distribution curve formed by the developing magnetic pole is steeper on the upstream side in the moving direction of the developer carrying member than on the downstream side, and the distance between the peak position of the magnetic flux density distribution and the half-value position of the peak is A developing device characterized in that the downstream side is more than twice as large as the upstream side.