JP2505814B2 - Development device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device of a two-component developing system for performing development using magnetic carrier particles and toner particles.

The present invention is a developing device applicable to various types of display devices for image recording, printers, and facsimile electrophotographic devices.

[Background technology]

In electrophotography using a two-component developer, toner particles as a visual material and magnetic carrier particles are mixed,
This two-component composition is supplied onto a developing sleeve in which a magnet is arranged to form a magnetic brush composed of this composition, and the electrophotographic photosensitive plate having an electrostatic latent image is rubbed or not rubbed with the magnetic brush. A toner image is formed on the photosensitive plate in close proximity.

The toner particles are charged in a direction opposite to the charge polarity of the electrostatic latent image on the photosensitive plate due to friction with the magnetic particles, and the toner particles on the magnetic brush adhere to the electrostatic latent image by an electric field, and the electrostatic latent image is charged. Image development takes place. The magnetic particles are attracted by the magnet in the sleeve and collected in the developing container.

By the way, the mixed state of the toner particles and the magnetic particles is related to the charge imparting to the toner particles, and as a result, the copy image quality is greatly affected. Therefore, in a two-component developing device, a control device (hereinafter referred to as ATR) which automatically detects the toner concentration so as to keep the toner concentration in the developer within a predetermined range and maintains the toner concentration according to this output. Called),
Further, the toner particles and the magnetic particles are sufficiently mixed and stirred by a member such as a screw.

[Problems to be solved]

In recent years, along with the downsizing of copying machines, there has been a demand for downsizing of the internal components of the copying machine as compared with the prior art.
In the developing device, the developing sleeve has been downsized, and accordingly, a small amount of the developer to be applied on the sleeve has been required and the layer thickness has to be reduced. However, the thinning of the coating layer means that the absolute amount of the developer supplied to the developing area decreases, and the ratio of the toner amount consumed by the development to the total toner amount supplied is large, and The toner concentration in the collected developer is extremely low as compared with the conventional large-volume developer coating system. Therefore, when exchanging used developer collected in the developing container and unused developer having a predetermined toner concentration,
It is necessary to replace and agitate more sufficiently than the conventional large amount developer coating system. Otherwise, uneven coating and uneven streaks will occur,
Image deterioration will occur. In addition, the thin layer tends to make the application of the developer on the sleeve non-uniform even against external vibration of the developing device. However, in a developing device using a small-diameter sleeve, there has been no proposal of a device configuration that is strong against external vibration and provides uniform coating, and the above problems have not been completely solved.

In addition to this, it is considered that the developer is magnetically restrained in a regulation region for regulating the magnetic developer to increase the charge amount of the magnetic developer to stabilize the developing ability. However, the premise of supplying a stable developer to the regulated area may be disturbed. The cause of this is that the developing device is rotated, the mechanical structure as in Japanese Patent Laid-Open No. 60-260073, the developer conveyance failure due to the aggregation of the developer when the toner having the pressure fixing property is used, and the toner of the magnetic developer are used. The present inventors have clarified that this is due to the developer conveyance failure depending on the density change.

Further, when the development is a solid full-color superimposing full-color development, the specific constitution for stabilizing the development characteristics and making the development density sufficient is unknown. No development structure is provided to stabilize the development under various severe conditions for the case of the rotary type developing device.

[Object of the Invention]

The present invention has a common object of favorably mixing a developer in a developer container.

[Outline of Invention]

The present invention that achieves the above-mentioned object is to provide a developer carrying body which is provided opposite to an electrostatic image carrying body carrying an electrostatic image and carries a developer having toner particles and magnetic particles, and a developer carrying body. A first magnetic pole, a second magnetic pole that is opposite in polarity to the first magnetic pole and is located first downstream of the first magnetic pole in the moving direction of the developer carrier, and a maximum magnetic flux density position of the first magnetic pole. A first stirring member which is provided on the downstream side in the moving direction of the developer carrying member and supplies the developer to the developer carrying member and conveys the developer in the generatrix direction of the developer carrying member; A second stirring member which is provided on the downstream side of the moving direction of the agent carrier and upstream of the maximum magnetic flux density position of the second magnetic pole, and which conveys the developer in a direction substantially opposite to the conveying direction of the first stirring member. Is a developing device.

〔Example〕

In the configuration of FIG. 1, the following common portions will be described.

The maximum stirring area referred to below is the portion of the locus drawn by the maximum radius of the stirring member (outside the concentric circles in the figure numbers 62 and 64 in the figure), M is the actual space, and 3 is the placement of Genzo-souchi. A mounting plate, and 4 indicates the center of rotation of the rotary development.

L1 is the maximum of the magnetic flux density on the sleeve of the magnetic pole 23a that forms a magnetic field in the regulation area and the straight line passing through the sleeve center, L2 is the straight line passing through the regulation end of the blade 24 and the sleeve center, and L3 is the regulation area side of the screw 64. A straight line passing through the sleeve center in contact with the maximum stirring area, L4 a straight line passing through the sleeve center in contact with the maximum stirring area on the developer recovery side of the screw 62, and L5 and L6 connecting the stirring center and sleeve center of the screws 64 and 62, respectively. A straight line passing through, L7 is a straight line passing through the maximum magnetic flux density on the sleeve of the magnetic pole 23d that forms a magnetic field in the developer recovery area and the center of the sleeve, L8
Is a straight line passing through the end of the magnetic field concentration surface of the magnetic member 50 and passing through the center of the sleeve. Further, θ1 is the angle between the straight lines L1 and L2, θ2 is the angle between the straight lines L1 and L4, θ3 is the angle between the straight lines L1 and L7, and θ4 is the angle between the straight lines L1 and L3.

The latent image carrier 1 is an electrostatic recording insulating drum or AS
It is a photosensitive drum or photosensitive belt having a photoconductive insulating material layer such as e, Cds, ZnO ₂ , OPC and A-Si. The latent image carrier 1 is rotated in the direction of arrow a by a driving device (not shown). twenty two
Is a developing sleeve which is close to or in contact with the latent image carrier 1, and is made of a non-magnetic material such as aluminum or SUS316. The developing sleeve 22 has a laterally long opening formed in the lower left wall of the developing container 36 in a longitudinal direction of the container so that a substantially right half peripheral surface projects into the container 36, and a substantially left half peripheral surface is exposed outside the container and rotatably supported. It is installed horizontally and is driven to rotate in the direction of arrow b.

Reference numeral 23 denotes a fixed permanent magnet (magnet) as a fixed magnetic field generating means which is inserted into the developing sleeve 22 and is positioned and held in the position and orientation shown in the drawing. Even when the developing sleeve 22 is driven to rotate, the magnet 23 is at the position shown in the drawing. It is fixedly held as it is. The magnet 23 has four magnetic poles, an N-pole magnetic pole 23a, an S-pole magnetic pole 23b, an N-pole magnetic pole 23c, and an S-pole magnetic pole 23d. The magnet 23 may be an electromagnet instead of the permanent magnet.

Reference numeral 24 designates a base fixed to the side wall of the container on the upper edge side of the developer supply opening where the developing sleeve 2 is disposed, and the front end side protrudes outside the container 36 from the position of the upper edge of the opening to extend along the length of the upper edge of the opening. A non-magnetic blade as a developer regulating member
For example, SuS316 is bent into a cross-section road shape.

Reference numeral 26 is a magnetic particle limiting member whose upper surface is in contact with the lower surface side of the non-magnetic blade 24 and whose front end surface is the developer guide surface 261.
The portion formed by the non-magnetic blade 24, the magnetic particle limiting member 26, and the like is the restriction portion.

27 is a magnetic particle having a particle size of 30 to 100 μm, preferably 4 to
0 to 80 μm and the resistance value is 10 ⁷ Ωcm or more, preferably 10 ⁸ Ωcm
As described above, resin coated on ferrite particles (maximum magnetization of 60 emu / g) can be used.

 37 is a non-magnetic developer toner.

 38 are toner storage containers.

Reference numeral 40 denotes a seal member for sealing the toner accumulated in the lower portion of the developing container 36, which has elasticity and is bent in the rotation direction of the sleeve 22, and elastically presses the surface side of the sleeve 22.
The seal member 40 has an end portion on the downstream side in the sleeve rotation direction in the contact area with the sleeve so as to allow the developer to enter the inside of the container.

Reference numeral 30 denotes an anti-scattering electrode plate for applying a voltage of the same polarity as that of the floating developer generated in the developing step to adhere to the photoreceptor side to prevent scattering.

A toner replenishing roller 60 operates according to an output obtained by a toner concentration detection sensor (not shown).
As the sensor, a developer volume detection method, a piezoelectric element, an inductance change detection element, an antenna method using alternate bias, a method for detecting optical density, or the like can be used. The non-magnetic toner 37 is replenished by stopping the rotation of the roller. The flash developer supplied with the toner 37 is mixed and stirred while being conveyed by the screen 61. Therefore, tribo is applied to the replenished toner during the conveyance. 63 A cutout plate is cut out at both ends in the longitudinal direction of the developing device, and the screw is
The developer transferred by 61 is
Is delivered to.

The S magnetic pole 23d is a carrier pole. The collected developer after the development is collected in the container, and the developer in the container is conveyed to the regulation unit.

In the vicinity of 23d, the flash developer conveyed by the screw 62 provided close to the sleeve is replaced with the recovered developer after development.

This configuration is also effective when magnetic particles and non-magnetic or weakly magnetic toner are mixed in the developer container.

The distance d2 between the end of the non-magnetic blade 24 and the surface of the developing sleeve 22 is 50 to 900 μm, preferably 150 to 800 μm. If this distance is less than 50 μm, the magnetic particles described later are clogged in the meantime, and the developer layer tends to be uneven, and the developer required for good development cannot be applied, and the density of the developed image is low and uneven. There is a disadvantage that can only be obtained. d2 is 40 in order to prevent uneven coating (so-called blade clogging) due to unnecessary particles mixed in during development.
It is preferably 0 μm or more. On the other hand, if it is larger than 900 μm, the amount of the developer applied on the developing sleeve 22 increases, and the predetermined developer layer thickness cannot be regulated, so that the adhesion of magnetic particles to the latent image carrier increases and the circulation of the developer described later. , Developer limiting member 26
However, there is a drawback that the regulation of development is weakened, toner tribo is insufficient, and fogging easily occurs.

The angle θ1 is -5 to 35 °, preferably 0 to 25 °.
When θ1 <−5, the thin developer layer formed by the magnetic force, mirroring force, cohesive force, etc. exerted on the developer becomes sparse and uneven, and when θ> 35 °, development is performed in the non-magnetic blade. The amount of developer applied increases, and it is difficult to obtain a predetermined amount of developer.

Even if the sleeve 22 is rotationally driven in the direction of arrow b, the magnetic particle layer slows its movement as it moves away from the sleeve surface due to the balance between the magnetic force, the restraining force based on gravity and the conveying force in the moving direction of the sleeve 2. . Of course, some fall under the influence of gravity.

Therefore, by appropriately selecting the arrangement positions of the magnetic poles 23a and 23d and the fluidity and magnetic characteristics of the magnetic particles 27, the magnetic particle layer is conveyed in the magnetic pole 23a direction as it is closer to the sleeve to form a moving layer.
Due to the movement of the magnetic particles, the sleeve 2 is rotated and conveyed to the developing area for development.

The movement of the magnetic particle layer is determined by the fluidity and magnetic force of the developer. When the toner content in the magnetic particles is low, the magnetic force carrying force of the developer is improved and the moving speed of the magnetic particle layer in the container is increased. The reason is that if the amount of toner interposed between the magnetic particles is small, the magnetic brush can be easily formed,
This is because the amount of the developer applied thereon increases, and the developer collected in the developing container again after the development stops moving the magnetic particle layer. Therefore, the collected developer is promoted to be exchanged with the fresh developer having a high toner concentration supplied from the screen 62, the stirring is promoted even on the sleeve in the conveying path, and the toner concentration becomes uniform.
Therefore, the toner concentration of the magnetic particle layer increases and reaches a predetermined concentration promptly.

Conversely, when the toner content of the magnetic particle layer is high, the magnetic transport force of the developer decreases, and the moving speed of the magnetic particle layer in the container decreases. This is because it is difficult to form a magnetic brush due to the large amount of toner interposed between the magnetic particles, and the amount of developer applied on the sleeve decreases,
This is because the moving speed of the magnetic particle layer in the container does not increase even if it is collected in the container. Therefore, the amount of the recovered developer exchanged with the developer having a relatively high toner concentration supplied from the screen 62 is reduced, the agitation is reduced even on the sleeve in the conveying path, and the developer having a high toner concentration is used. Mixing with is reduced.

The above-mentioned movement of the developer requires the arrangement position configuration described below.

The magnetizing interval between 23a and 23d is set to be wide because it is necessary to control the developer transporting force to be low and to sufficiently mix the developer.
Of course, if the carrying force is lowered too much, the collected developer does not enter the container and the developer is accumulated in the lower part of the developing device. According to the experiment, if a transporting electrode is provided between 23a and 23d, the transporting force is so strong that the developer reaches the regulation portion without sufficient stirring, resulting in uneven density. As a result, by expanding the exchange area between the flash developer and the collected developer, the developer on the sleeve is mixed and mixed in the subsequent transport path.
This means that the stirring area is narrowed.

As a developing device for a general commercial electrophotographic copying machine in which the outer dimension of the developing sleeve is about 10 to 30 mm, the magnetizing distance θ3 between the magnetic poles 23a and 23d must be 90 ° or more, preferably 100 ° or more. Further, in order to prevent the accumulation of the developer in the lower part of the container, it is preferably within 160 °, preferably within 150 °. In the embodiment of FIG. 1, θ3 = 130 ° was set. Also, the magnetic pole 23d
With respect to the installation relation between the screw 62 and the screw 62, it is preferable that the screw is provided on the downstream side of the magnetic pole 23d in the sleeve rotation direction.

When a screw is provided on the upstream side, a brush of magnetic particles is formed at the magnetic pole 23d, and the brush developer conveyed by the screw 62 is easily taken in from this portion. Therefore, the exchange area between the collected developer and the flash developer is substantially expanded, and the stirring / mixing area in the next conveying path is narrowed. Therefore, image unevenness is likely to occur in the copy image quality.

Further, the transportability of the agent between the magnetic poles 23d and 23c is deteriorated, and the collected developer is likely to accumulate in the lower portion of the developing device. This is because the transportability of the agent by 23d and 23a on the downstream side is set to be low, and the transportability of the agent on the upstream side of 23d is also affected and deteriorates. Therefore, if a member such as a screw is installed in the vicinity of the sleeve, the developer will be retained. Furthermore, when a screw is provided on the upstream side of the magnetic pole 23d, the brush developer of magnetic particles is taken in, so that a sleeve ghost is likely to occur in addition to the above-described image unevenness. However, the magnetic pole 23d
If a screw is installed on the downstream side of the sleeve, the collected developer and the fresh developer are mixed and agitated between the sleeve and the screw via the screw, and the developer moves in the sleeve axial direction. The developer is replaced sufficiently. Therefore, it is possible to prevent the occurrence of image unevenness and sleeve ghost.

Therefore, the rotation direction of the screw 62 is the magnetic pole 23d along the moving path of the flash developer in the direction of arrow C as in the embodiment of FIG.
It is preferable to provide it on the downstream side.

Further, the clearance between the screw 62 and the sleeve 22 is preferably about 1 to 5 mm, and if it is too far apart, the replacement of the agent will be deteriorated. In the embodiment, it is 3 mm.

Next, the magnetic particle layers in the vicinity of the non-magnetic blade 24, which is a developer application amount regulating member, and in the vicinity of the limiting member 26 will be described. The limiting member does not only mechanically prevent unnecessary entry of the replenishment toner into the developer regulating portion. As described above, in the restriction region surrounded by the member 26 and the sleeve, the magnetic particles conveyed by the rotation of the sleeve by the magnetic pole N ₁ are packed along the guide surface 261 of the limiting member 26 and have a high density. Become. The space of the restriction portion area is narrowed in the sleeve rotation direction.
In this area, the magnetic particles that are conveyed and enter and the magnetic particles that flow out from the blade are exchanged dynamically, so that the magnetic particles collide with each other and are in a disturbed state. It is in a practical packing state. For this reason, tribo is imparted to the toner from the magnetic particles or the sleeve, and the small tribo imparting conner that has been attached to the magnetic particles or the sleeve with a weak force and conveyed is released from the magnetic particles or the sleeve. That is, toner selection and charging improvement are performed. Therefore, the toner to which tribo is sufficiently imparted can be used for development. Further, the non-uniform state during the transportation of the magnetic particles is also averaged in the space, so that the coating of the magnetic particle layer can be made uniform and stable. Therefore, when tribo is imparted to the toner newly replenished, it has been necessary to sufficiently mix it with a large amount of the carrier by a screw or the like. However, as described above, it is not necessary to sufficiently mix the toner with the carrier by the screwing or the like for imparting the toner to the toner and selecting the toner to which the toner is imparted by the regulating unit as in the conventional system. Therefore, the stirring section of the developing device can be simplified,
An image without density unevenness can be obtained even on a copy. Therefore, the guide surface 261 is essential for the limiting member 26, and the inclination of the slope and the volume of the space have a great influence on the packing state of the magnetic particles in the space.

On the other hand, the magnetic pole fixedly arranged in this area
23a rearranges the magnetic particles in the backing state along the lines of magnetic force. In the space, the packing state is unstable with respect to tribo application, and a constant backing state is always required for stabilization. This is to form a magnetic brush with magnetic particles that have been conveyed almost tangentially on the sleeve with a force that is perpendicular to that direction. And the uniformity and stabilization of the application of the tribo and the application of the magnetic particle layer are further promoted. At this time, if the developer concentrated by the peripheral configuration is subjected to a large pressure, there is a problem that the developer is clogged too much.
It is considered that the portion where the maximum magnetic force is generated faces the guide surface 261, thereby preventing excessive pressure concentration in the regulation region, and maintaining the concentration of the developer and the stable high-density magnetic particle existence ratio. .

Due to the above-described regulation region, a stable amount of magnetic particles and sufficiently charged toner particles can be formed as a thin developer layer on the surface of the developing sleeve. Therefore, the developing effect in the developing area 102 becomes stable. Further, there is provided an alternating electric field forming means for forming in the developing section an alternating electric field for transferring at least the toner particles carried on the surface of the developing carrying member among the developers conveyed to the developing section to the electrostatic latent image carrier. However, in the developing unit, the volume ratio of the magnetic particles of the developer conveyed to the developing unit to the volume of the space defined by the electrostatic latent image carrier and the developer carrying member is
It was confirmed that a great effect was obtained for the developing method and the apparatus of 1.5% to 30%.

FIG. 1 shows a case where the magnetic body 50 is installed on the non-magnetic blade side of the developer limiting member 26. In this case, it is not preferable to provide the magnetic body 50 at a position facing the magnetic pole 23a. This is because when they are opposed to each other, a strong concentrated magnetic field is generated between the magnetic poles 23a and the magnetic particles agitation and loosening effects by the magnetic poles 23a are reduced. However, it is effective to provide a magnetic body in the restricting portion to magnetically restrict the magnetic particles between the restricting portion and the magnet 23 inside the sleeve, because the gap tolerance between the restricting member and the sleeve is increased. Further, not only the tolerance, but also the gap length between the restricting member and the sleeve itself can be expanded, and it can be expanded by about 100 μ as compared with the case of only the non-magnetic blade. Further, the angle θ1 can be expanded by about 3 to 7 ° as compared with the case of only the non-magnetic blade. Also, when comparing the magnetic particles or the toner adhered on the sleeve, the charge amount of the toner adhered on the sleeve is smaller than that charged on the magnetic particles. The reason for this is that the magnetic particles are conveyed along with the movement of the sleeve, so that the toner on the sleeve is less likely to be rubbed by the magnetic particles. In order to raise the toner on the sleeve to a predetermined value, it is necessary to actively inspect the toner on the sleeve. That is, it is necessary to have magnetic particles in the vicinity of the sleeve surface that cause a relative velocity shift against the movement of the sleeve.

However, simply lowering the transportability of the magnetic particles is impossible in consideration of the transportability of the collected developer after the development described above. Further, as described above, it is also possible to arrange the magnetic body in the restriction portion so as to face the in-sleeve magnetic pole 23a and generate a concentrated magnetic field to improve the rubbing force of the magnetic particles on the sleeve.
The effect of disposing the maximum magnetic force generating portion of the magnetic pole in the space created by the developer circulation restricting member 26 is reduced.

Therefore, in this embodiment, the magnetic body 50 is provided on the downstream side of the magnetic pole 23a in the sleeve rotation direction so that the magnetic lines of force on the blade side of the magnetic pole 23a are substantially concentrated in the tangential direction of the sleeve surface. As a result, only the magnetic particles near the sleeve surface form a magnetic brush along the sleeve surface,
The toner on the sleeve was rubbed, and the tribo-application of the toner on the sleeve could be increased.

It was found that when the magnetic developer was a mixed developer of magnetic carrier and toner, the initial development characteristics were significantly deteriorated during use. This was particularly remarkable in the toner concentration of the developer. FIG. 1 has a configuration for solving this problem.

Further, in an image forming apparatus such as that disclosed in Japanese Patent Laid-Open No. 60-260073, in which a developing device is rotated and used, a lump that is normally sunk in the dead space is raised due to the rotation and enters the conveyance path. Frequent clogging between the sleeve and the regular member has caused a problem that white streaks are generated more than in a normally fixed developing device. Further, in an image forming apparatus that supplies an appropriate amount of magnetic particles to the developing gap between the latent image carrier and the developing sleeve, the supply of the developer to the developing unit becomes unstable, and stable image formation may not be possible. .

In any case, it is important for the present invention to form a uniform and long-term stable developer layer of the magnetic developer, and thereby, image formation for forming various color images by superposing the developers. The image forming apparatus using the apparatus and the rotary developing device can be made excellent, which has not been obtained in the past.

The structure of FIG. 1 can be summarized. A developer layer that can form a stable magnetic developer layer and uses a magnetic member to form the developer layer of the magnetic developer on the surface of the developer carrier. In the forming device, a magnetic field generating portion fixedly arranged on the upstream side of the magnetic member in the developer conveying direction and on the side opposite to the developer carrying side of the developer carrying body, and on the downstream side of the magnetic member, the magnetic field A non-magnetic restricting member provided closer to the developer carrying member than the member, wherein the magnetic member is located on an end portion of the magnetic member closer to the developer carrying member and on the side of the magnetic field generating unit. The developer layer forming apparatus is characterized in that it has a magnetic field concentration surface as a side surface, and the length of the magnetic field concentration surface in the direction away from the developer carrier is 1 mm or more and 10 mm or less.

Unlike the conventional regulation of the magnetic developer by the magnetic member, this configuration eliminates the magnetic field concentration at the center of the edge, and makes it possible to form a uniform and strong magnetic field concentration. Can be achieved.

Here, the mechanism of forming the developer layer will be described.
The restriction region formed by the non-magnetic blade 24 and the magnetic blade 50 magnetic pole 23a forms a field for magnetically restraining the magnetic developer. The side surface of the magnetic blade having the length 1 concentrates the magnetic field lines from the magnetic pole 23a on the upstream side, but does not concentrate mainly on the blade end portion, but forms a concentrated magnetic field having a uniform distribution width over the entire surface. . Therefore, the disadvantage of giving the magnetic developer a very cooperative magnetic field constraint concentrated at one point is
The problem was solved fundamentally, it was possible to prevent the conventional generation of developer lumps, the developer layer was made uniform in a thin layer, and stable layer formation could be achieved for a long period of time.

In particular, as shown in FIG. 1, the magnetic member is substantially the same as the end of the magnetic member close to the developer carrying member and the vertical surface on the surface of the developer carrying member facing the end, or the magnetic field generating unit. When having a magnetic field concentration surface inclined to the side, it is possible to almost eliminate the difference between the magnetic field concentrated on the end of the magnetic member and the magnetic field concentrated on the entire magnetic field concentration surface,
As described above, strong magnetic field concentration due to the short surface length can be made uniform. This inclination angle is preferably larger than 0 degree and 60 degrees or less.

In this way, the developer layer forming device that concentrates the magnetic force on the upstream side of the magnetic developer on the side surface of the magnetic field concentration surface of the magnetic member and regulates it by the non-magnetic regulation blade intersects the developer transport direction of the magnetic member. The length in the direction is smaller than that of the conventional one and is preferably 1 mm or more and 10 mm or less. This is what the experiment has revealed. Further, if the length is 2.5 mm or more and 7 mm or less, uniform magnetic field concentration can be achieved on this surface of the magnetic member. The width of the magnetic body is 0.2 mm or more and 3 mm or less,
Preferably, it is 0.5 mm or more and 2.0 mm or less.

According to the inventor, in the structure of the present invention, the magnetic member not only causes the magnetic field concentration to occur uniformly, but in the related art, the influence of the magnetic field from the portion containing the developer to the outside is blocked by the long magnetic blade. However, in the present invention, on the contrary, the magnetic field is positively influenced via the magnetic member to the next magnetic field generation section, so that the developer carried out from the regulation section can be more stable, and the transportability of the regulated developer can be improved. Is believed to have been good too.

Also when considering the transportability of the developer on the magnetic poles 23d and 23a,
By installing the above-mentioned magnetic body, the latitude of the magnetic pole arrangement of 23a and 23d and the arrangement relation of the screw 62 can be expanded. That is, by installing the magnetic material in the regulation portion, the developer transportability in the regulation portion can be controlled to be low.
As a result of this, the regulation unit compensates for the functional load that makes the developer transportability lower in the transport path on the upstream side of the regulation unit. Therefore, the conveying path on the upstream side of the restriction portion can be made small, and the developing sleeve can be made small in diameter. Therefore, the developing device can be simplified and downsized.

Further, the developer on the sleeve in the developing container is difficult to separate from the sleeve due to the external vibration that is strongly retained magnetically by the above-mentioned configuration. Even if it was operated immediately, a stable and uniform coating state of the developer could be obtained.

The magnetic flux density of the magnetic pole 23a is 600 G or more, preferably 700 G
The above is preferable. This is because the application state of the developer tends to be more stable with respect to the change in the toner content of the magnetic particle layer as the magnetic flux density of the cut magnetic pole increases. In particular, in a developing device that does not have an automatic toner replenishing device for maintaining toner content, it is preferable that the magnetic flux density is 800 G or more.

However, since the transport force of the developer increases with an increase in the magnetic force of 23a, the amount of the developer applied on the sleeve increases,
It is necessary to select within an appropriate range according to the design specifications. According to the present inventors, a good result can be obtained by considering about 800 to 1200 G in view of other developing device configurations.

In FIG. 1, the magnetic pole 23c is a developing magnetic pole, but this developing magnetic pole is located almost at the developing portion and preferably has a magnetic flux density of 800 G or more in order to prevent magnetic particles from adhering to the latent image.

It goes without saying that the present invention includes any combination of the above-described configurations.

In any case, the present invention can provide a high image quality which cannot be obtained by the conventional developing method and apparatus, and has an excellent effect that the developing apparatus can be made compact.

The S magnetic pole 23b is a carrier magnetic pole provided to prevent the developer layer uniformly coated on the non-magnetic blade 4 from being disturbed due to the large gap between the cut magnetic pole 23a and the developing magnetic pole 23c. Since the S magnetic pole 23b does not disturb the developer layer, the strength of the magnetic pole is approximately equal to or slightly lower than that of the developing magnetic pole 23c. When using a developing sleeve with a diameter of 10 to 30φ, the distance between the cutting magnetic pole and the developing magnetic pole is 10 at the sleeve center angle.
Within about 0 °, the disturbance of the developer layer on the sleeve is small, but above 100 °, the disturbance of the developer layer is large, and it is preferable to provide a transport electrode in the middle.

Here, the volume ratio of the magnetic particles in the developing section will be described. "Developing section" means sleeve 22 to photosensitive drum 1
Where toner is transferred or supplied. The "volume ratio" is the percentage of the volume occupied by the magnetic particles present therein relative to the volume of the developing section. In the above-mentioned developing device, it is extremely preferable that this volume ratio has an important effect, and it is extremely preferable that this ratio be 1.5 to 30%, particularly 2.6 to 26%.

If it is less than 1.5%, a decrease in the density of the developed image is observed, a sleeve ghost is generated, a remarkable density difference occurs between a portion where the spike 51 is present and a portion where the spike 51 is not formed, This is not preferable in that the thickness of the developed developer image becomes non-uniform as a whole.

If it exceeds 30%, the degree to which the sleeve surface is closed increases and fogging occurs, which is not preferable.

In particular, the above-mentioned conditions mentioned as the preferred developing method for the present invention are such that the image quality does not monotonously deteriorate or increase as the volume ratio increases or decreases.
A sufficient image density can be obtained in the range of, and 30% even if it is less than 1.5%.
This is based on the fact that the image quality is deteriorated even when the value exceeds the above range, and neither sleeve ghost nor fogging occurs in the range of the above numerical value where the image quality is sufficient. The former image quality deterioration seems to be due to the negative characteristic, and in the latter, the amount of magnetic particles present becomes large and the surface of the sleeve 22 cannot be opened, and the toner supply amount from the magnetic particles 27 and the surface of the sleeve 22 is greatly reduced. It is thought to arise from things.

If it is less than 1.5%, the reproducibility of the line image is inferior and the image quality density is remarkably reduced. On the other hand, if it exceeds 30%, there is a problem that the magnetic particles damage the surface of the photosensitive drum, and there is a problem of transfer and fixation that occurs because they adhere as a part of the image.

And when the presence of magnetic particles is close to 1.5%, partial development unevenness called "Rabbi" occurs when reproducing a large area uniform high density image (solid black) (under special environment etc.). Therefore, it is preferable to set the volume ratio so that these are less likely to occur. This value is because the volume ratio of the magnetic particles to the developing portion is 2.6% or more, this range becomes a more preferable range, and when the presence of the magnetic particles is close to 30%, the spikes of the magnetic particles are There is a case where toner supply from the sleeve surface is delayed around the contacting portion (when the developing speed is high, etc.), and scaly density unevenness may occur during solid black reproduction. As a certain range for preventing this, the above volume ratio of the magnetic particles is more preferably 26% or less.

If the volume ratio is in the range of 1.5 to 30%, as shown in FIG. 3, the ears 51 are formed on the surface of the sleeve 22 in a sparse manner to a preferable degree, and the toner on both the sleeve 22 and the ears is formed on the photosensitive drum 1. Since the toner 100 on the sleeve is fly-transferred by the alternating electric field, almost all of the toner can be consumed for development, and thus high development efficiency (of the toner existing in the developing section % Of toner that can be consumed for high density) and high image density. Preferably, a slight but severe spike vibration is generated, which loosens the toner 100 adhering to the magnetic particles 27 and the sleeve 22. In any case, it is possible to prevent the generation of uneven sweep and ghost image as in the case of a magnetic brush. Further, due to the vibration of the spikes, the frictional contact between the magnetic particles 27 and the toner 28 becomes active, so that the triboelectrification of the toner 28 is improved and the occurrence of fogging can be prevented. The high developing efficiency is suitable for downsizing of the developing device. Further, it becomes possible to use a fine particle toner having a high cohesiveness and an average particle size of 10 μm or less.

The volume ratio of the magnetic particles 27 present in the developing section is (M /
h) × (1 / ρ) × [(C / (T + C)], where M is the coating amount (g / cm) of the developer (mixture... ² ), h is the height (cm) of the developing space, ρ is the true density of magnetic particles g / cm ³ , C / (T
+ C) is the weight percentage of magnetic particles in the developer on the sleeve.

The ratio of the toner to the magnetic particles in the developing section defined above is preferably 4 to 40% by weight. When the alternating electric field is strong (the rate of change is large or Vpp is large) as in the above embodiment, the ears are separated from the sleeve 22 or the base thereof, and the separated magnetic particles 27 are separated between the sleeve 22 and the photosensitive drum 1. Reciprocates in the space. Since the energy of the reciprocating motion is large, the effect of the above-described vibration is further promoted.

The above behavior was confirmed by shooting 8000 frames / sec with a high-speed camera (manufactured by Hitachi, Ltd.). Even when the gap between the surface of the photosensitive drum 1 and the surface of the sleeve 22 is reduced to increase the contact pressure between the photosensitive drum 1 and the spikes and reduce the vibration, the gap is large at the entrance and exit sides of the developing unit. Vibration occurs, and the above-described effects are achieved.

Conversely, it is preferable to increase the gap between the photosensitive drum 1 and the sleeve 22 so that the ears do not contact the photosensitive drum 1 in a state where no magnetic field is applied, but it is preferable that the ears be in contact with the photosensitive drum 1 when the magnetic field is applied.

In Fig. 1, each screw has an outer diameter of 12 mm by spirally winding an aluminum plate around an aluminum core with an outer diameter of 6 mm.
The diameter. The pitch gap between aluminum plates is
61 is 10 mm, 62 is 20 mm, and 64 is 5 mm. The rotation direction of the developer was determined so that the screw 61 was conveyed above the paper surface, 62 was conveyed to the back of the paper surface, and 64 was conveyed above the paper surface.

The rotation speed of the screw 61 is 250 γ pm, 62 is 320 γ pm, 64 is 17
It was set to 0γpm.

The peripheral speed of the sleeve is 210 mm / sec, the peripheral speed of the photosensitive drum is 160
mm / sec.

In the figure, the surface of a stainless steel (SuS316) sleeve with a diameter of 20 mm is used as the sleeve 22, and the magnet is made by atypical sandblasting with No. 400 alundum abrasive grains.
As 23, a 4-pole magnet having N-pole and S-pole alternately shown in FIG. 1 was used. The gap between the sleeve 22 and the tip of the blade 24 was set to 650 μ.

As the blade 24, 1.2 mm thick non-magnetic stainless steel was used, and as the magnetic body 50, a 1.0 mm thick iron plate was used. The magnetic particles have a particle size of 60 to 50μ with a silicone resin coating on the surface.
Ferrite (maximum magnetization of 60 emu / g) was used.

As the non-magnetic toner, 100 parts of polyester resin and 5 parts of copper phthalocyanine pigment as the main component have an average particle size of 11
When blue toner was used by externally adding 0.4% of colloidal silica to toner powder of μ, a toner coating layer having a coating thickness of about 10 to 30 μm was obtained on the surface of the sleeve 22 and further 300 to 500 μ of magnetic particles as the upper layer. Layers were obtained. The toner adheres to the surface of each magnetic particle.

The magnetic particles stand up by the magnetic field by the magnetic pole 23b in the sleeve 22 in the developing unit and its vicinity, and the maximum length is about 0.8 to 1.
A magnetic particle layer composed of a brush for brushing about 3 mm was formed. As starting developer, 270 g of magnetic particles and 30 g of toner were mixed and used.

This developing device was incorporated into a modified NP-150Z copying machine manufactured by Canon Inc., and the distance between the photosensitive drum 3 (made of an organic photosensitive material) and the surface of the sleeve 22 was set to 450 μm. The peripheral speed difference between the photosensitive drum and the developing sleeve is 1: 1.3. The photosensitive drum used had an outer diameter of 60 mm. An OPC drum was used as the photosensitive drum, and a charging latent image potential of -600V was used. Development was performed using a bias power source 4 having a frequency of 1700 Hz and an AC voltage of peak-to-peak value of 1500 V superposed with a DC voltage of -300 V.

 A description of the configuration of FIG. 1 will be given below.

Reference numeral 64 is a transport screen for equalizing the amount of developer in the axial direction of the developing sleeve. The developer is conveyed in the direction opposite to that of the screen 62. The screen 64 makes the amount of the developer conveyed to the regulating section uniform in the longitudinal direction of the developing sleeve immediately before the entrance of the regulating section. The action is to stabilize the pressurizing state of the developer in this restriction portion, and the developer supplied is leveled in the axial direction of the sleeve and forcedly fed, and at the same time, the gap between the curved guide surface 262 is formed. Excessive developer is discharged to the space M to pass the pressure condition in the regulation section to a constant level.
FIG. 2 shows a developing device which does not have the conveying screw 64, which is a reference example for comparison with the present invention. As shown in FIG. 2, if the conveying screw 64 is not provided, the amount of the developer conveyed to the regulating portion varies greatly, and the layer thickness of the developer layer on the regulated sleeve becomes uneven, resulting in a copy image quality. As a result, uneven density occurs. The position of the screw 64 is good on the upstream side of the magnetic pole 23a with respect to the sleeve rotation direction, and is preferably provided in the latter half of the transport path from 23a to 23d. If provided in the first half, the homogenizing effect in the axial direction may be slightly reduced. θ
₄ is 0 ° to 40 °. When the influence of the magnetic force of the magnetic pole 23a disappears, the developer is conveyed in the axial direction of the sleeve poorly. Therefore, it is necessary to provide the developer within the range of the magnetic force of the magnetic pole 23a. The screw 64 controls the amount of charge of the toner in a direction to stabilize it.

If the magnetic force of the magnetic pole 23d is too strong, the amount of the developer present on the sleeve from the screw 64 to the restriction portion decreases, and the effect and effect of the developer restriction in this area are not expected, so that uniform coating becomes difficult to perform. Further, the screw 64 is also poorly conveyed in the axial direction, and the uniformizing action of the screw 64 in the axial direction of the sleeve is also reduced. Therefore, it is preferable that the magnetic force of 23d be made weaker than the magnetic force of 23a so that the existing amount of the developer in the above-mentioned region is set to be large.

As described above, according to this embodiment, high image density,
It is possible to perform development with high development efficiency, such as fog, ghost image, unevenness of sweep.

As the material of the sleeve 22, in addition to stainless steel, a conductor such as brass or aluminum, a paper cylinder or a cylinder of synthetic resin can be used. In addition, when the surfaces of these cylinders are subjected to conductive treatment or are made of a conductor, they can also function as developing electrodes. Further, it may be used as a core roll and a conductive elastic body such as a conductive sponge may be wound around the peripheral surface of the core roll.

Regarding the magnetic pole 23b of the developing unit, the magnetic pole is arranged at the center of the developing unit in the embodiment, but it may be displaced from the center, or the developing unit between the magnetic poles may be arranged. FIG. 4 shows another embodiment.

To the toner, silica particles may be externally added in order to improve fluidity, and abrasive particles or the like may be externally added for polishing the surface of the photosensitive drum 1 which is a latent image holding member in the transfer type image forming method. You may use what added a small amount of magnetic particles to the toner. That is, magnetic toners can be used as long as they are significantly weaker than magnetic particles and can be tribocharged.

In order to prevent the ghost image phenomenon, the developer layer remaining on the sleeve 22 that has not been used for development from the surface of the sleeve 22 that has returned to the inside of the container 21 and rotated, is scraped off once by a scraper means (not shown), and The scraped sleeve surface may be brought into contact with the magnetic particle layer to recoat the developer.

The developing device of the present invention can be used as a single-use type developing device in which the container 21, the sleeve 22, the blade 24 and the like are integrated, or as a normal developing device fixed to an image forming apparatus.

〔The invention's effect〕

The present invention can perform stable two-component development without image deterioration such as density unevenness and streaks even if a small-diameter sleeve having an outer diameter of 9 to 25φ is used, and the developing device can be downsized.

Further, the developer in the developing container can be used at a fraction of that of the conventional two-component developing device, and the developer on the sleeve is less likely to be biased against external vibration. I was able to.

[Brief description of drawings]

1 and 4 are explanatory views of another embodiment of the developing device according to the present invention, FIG. 2 is an explanatory view of a reference developing device according to the present invention, and FIG. 3 is a preferred developing configuration of FIG. FIG. 1 ... Photosensitive drum 22 ... Development sleeve 23 ... Magnet 27 ... Magnetic particles 37 ... Toner particles 36 ... Development container 50 ... Magnetic material 61, 62, 64 ... Transport screen

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-138879 (JP, A) JP 57-136671 (JP, A) JP 62-116974 (JP, A)

Claims (1)

(57) [Claims] 1. A developer carrying member, which is provided opposite to an electrostatic image carrying member carrying an electrostatic image and carries a developer having toner particles and magnetic particles, and a developer carrying member provided inside the developer carrying member. The first magnetic pole and the second magnetic pole which is opposite in polarity to the first magnetic pole and is located first downstream of the first magnetic pole in the moving direction of the developer carrying member.
A first magnetic pole is provided downstream of the maximum magnetic flux density position of the first magnetic pole in the moving direction of the developer carrier, and supplies the developer to the developer carrier and conveys the developer in the generatrix direction of the developer carrier. The stirring member and the first stirring member are provided on the downstream side in the moving direction of the developer carrying member and on the upstream side of the maximum magnetic flux density position of the second magnetic pole, and the developer is transferred in a direction substantially opposite to the conveying direction of the first stirring member. And a second stirring member that conveys the developing device.