JPH0584903B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device that supplies a powder developer to develop a latent image carrier.

INDUSTRIAL APPLICATION This invention is applicable to the recording of copying machines, printers, printing machines, etc. which use a developing device in general.

(Prior art) A developing container section, a rotary developing sleeve disposed in the developing container section facing the electrostatic latent image carrier and having a magnet therein, and a rotating developing sleeve disposed in the developing container section facing the electrostatic latent image carrier and having a magnet therein. The rotation of the developing sleeve causes the magnetic particles in the magnetic particle layer to move upwards, then reverse and move downwards in a circular motion, and the movement of the magnetic particles causes the toner layer outside the magnetic particle layer to In a developing device that takes toner into the magnetic particle layer, if a large amount of toner exists on the magnetic particle layer, the circulation movement of the magnetic particles becomes inactive due to the weight of the toner, causing the toner to enter the magnetic particle layer. The uptake of the toner becomes unstable, and the frictional charging of the toner within the magnetic particle layer becomes insufficient. Because of this, the quality of the developed image deteriorates.

(Objective of the Invention) An object of the present invention is to remove toner from the toner layer without inhibiting the circulation movement of the magnetic particles in the magnetic particle layer formed along the circumferential surface of the developing sleeve in the above-mentioned developing device. It is an object of the present invention to provide a developing device that can stabilize the uptake of toner into a magnetic particle layer, improve triboelectric charging of toner within the magnetic particle layer, and reduce the load of toner.

(Means for Achieving the Object) The developing device of the present invention includes a developing container portion, and a rotating developing sleeve disposed in the developing container portion facing the electrostatic latent image carrier and having a magnet therein. A magnetic particle layer is formed along a developing sleeve in the developing container, and by rotation of the developing sleeve, the magnetic particles in the magnetic particle layer are moved upwardly, then reversed and moved downwardly in a circular motion. In a developing device that takes toner from a toner layer outside the magnetic particle layer into the magnetic particle layer by movement, a toner storage container section disposed on the horizontal side of the developer container, this toner storage container section and the above-mentioned toner storage container section are provided. A slit-shaped toner passage section that communicates the developer container section at a position lower than the center of rotation of the development sleeve; A toner conveying member forming a toner accumulation portion rotates within the developer container portion such that a portion of its rotation locus passes through the toner accumulation portion, and does not eliminate the toner accumulation portion from the toner accumulation portion. and a toner supplying member that scrapes off the magnetic particles little by little and sends the toner to a lower part of the circulation movement area of the magnetic particles.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

The developing device in FIG. 1 is located diagonally above and to the right of a drum (not shown) serving as an electrostatic latent image carrier, and shows the state during development. l is a straight line representing the horizontal plane during development, and is a reference for the following height relationship.

The example in FIG. 1 is a method in which magnetic particles and non-magnetic toner are contained in the developer container 41, and development is carried out by adhering the toner and magnetic particles to the surface of a non-magnetic sleeve serving as a developer carrier (see FIG. 3). (described).

The latent image carrier 2 having the latent image to be developed may be an insulated drum for electrostatic recording or α-Se,
It is a photosensitive drum or photosensitive belt with a layer of photoconductive insulating material such as Cds, ZnO ₂ , OPC, α-Si. The developing sleeve 3 is in contact with or close to the latent image carrier 2. The developing sleeve 3 is a non-magnetic sleeve made of aluminum, for example, and the developing container 4
Insert approximately half the right side of the container 41 into the horizontally long opening of the left side wall of 1.
The container is inserted into the container, and approximately the left half circumferential surface is exposed to the outside of the container. The developing sleeve 3 may be a developer carrier in the form of an endless belt that is rotationally driven.

Reference numeral 36 denotes a fixed permanent magnet (magnet) as a fixed magnetic field generating means that is inserted into the developing sleeve 3 and held in the position and orientation shown in the figure.Even when the developing sleeve 3 is rotationally driven in the direction of the arrow, is fixedly held in the position and posture shown in the figure. Reference numeral 38 denotes a regulating blade made of a non-magnetic material, which controls the magnetic particles 7 into the container 4 due to its positional relationship with the magnet N located on the upstream side with respect to the rotational direction of the sleeve 3.
Constrain within 1. Therefore, the non-magnetic toner passes between the constrained magnetic particles and is formed as a thin toner layer on the surface of the sleeve 3. This toner thin layer reciprocates against the surface of the drum 2 under an alternating electric field (not shown) to develop the electrostatic latent image.

Here, toner supply as an example of development will be explained while explaining the configuration.

Reference numeral 61 denotes a toner storage container as a developer holding section, which holds fine particle toner throughout. A developing container 41 serves as a developer receiving section, and is arranged side by side with the toner storage container 61. A conveying member 8 rotates clockwise to convey the toner in the storage container 61, and a cloth sheet 81 is attached to the outside thereof. The conveyance member 8 has a plate shape that extends in the longitudinal direction of the container, and has a short width in the rotation radius direction. The sheet 81 moves while contacting the entire spherical bottom of the toner storage container. The member 8 and the sheet 81 function as a developer conveying member. 39
is an opening formed between the storage container 61 and the developer container 41, through which toner as a developer passes;
It is sealed with a sealing material (not shown) during transportation or before the start of use of the device. The opening 39 is opened by removing the sealing material. Reference numeral 30 denotes a flow dividing member as a developer guiding member provided in the toner storage container 61 above the opening 39;
A developer guiding surface 301 is provided which extends from the inside toward the opening 39 and is inclined in the direction of gravity. The guide surface 301 receives the toner conveyed by the conveying member 8 and the elastic sheet 81 and substantially divides the toner into the direction of arrow B on the opening 39 side and the direction of arrow C on the inside of the container 61. . The opening 39 has a flat part having a length L in the toner transport direction on the upper surface of the boundary part 100 that projects into the container, and the height H from this flat part is the actual toner passage permitting area of the opening 39. . This plane part is a pile-like accumulation part E of toner.
It is used as a lower surface.

Reference numeral 34 denotes the center of rotation of the developer conveying members 8 and 81, and its height from the horizontal plane is approximately equal to or lower than the guide surface 301, and is at the level of the opening 39.

A toner supply member 37 is located near the opening 39 and further conveys the toner supplied from the conveyance members 8 and 81 in the direction of the arrow of the developing sleeve 3. The toner supply member 37 has a cloth-like toner scraping plate 371 on the end side with respect to the rotation center 373 in the clockwise direction, and a rotation area 372 according to the rotation radius is within a circle in the figure. This rotation area 372
has a common area with the pile-shaped accumulation part E, and the pile-shaped accumulation part E is formed by rotation of the toner supply member.
toner is supplied to the magnetic member 40 side.

The rotation of the conveying members 8, 81 and the toner supplying member 37 is controlled so that a heap-shaped accumulation portion E is always formed between them. Specifically, their rotational speeds may be determined so that only a portion of the toner supply member is supplied to the magnetic particle circulation unit while maintaining the storage unit formed by the conveyance member.

If toner is supplied only by the conveying means in the toner container, such as the conveying members 8 and 81, not only will excessive supply occur, but also problems of toner fusion, increased load pressure, and excessive charging will occur. So I don't like it. From this point of view, it is preferable that the conveyance force be such that the heaped accumulation portion E can be maintained at a low speed of about 1 to 5 rpm.

When the rotation center of the toner conveying member is lower than the upper limit of the opening 39 as in this embodiment, the height of the heaped accumulation portion E is determined by the height H of the opening. In addition, the size of the lower surface L of the mountain-like accumulation portion E is as follows:
It is determined by the fluidity of the toner, the angle of repose, the transporting force of the toner transporting member, and the amount of toner remaining, but when the transporting force of the transporting member is small as in this example, it is determined mostly by the fluidity of the toner and the angle of repose. will be determined. In this case, there have been cases where there is no toner within the effective supply range of the rotational region of the toner supply member, and the pile-like accumulation portion E is formed in a small size. As a condition for solving such a problem, it is sufficient if the relationship L<2H is satisfied for the above-mentioned L and H. Thereby, a reliable amount of toner supply can be obtained, and a small amount of toner supply can be achieved. Therefore, in the development method described below, the circulation of the magnetic particle layer can be stably maintained with a reduced load and can be maintained for a long period of time, thereby improving the quality of the image formed.

In this embodiment, the rotation center 373 of clockwise rotation is
The sleeve center O and the rotation center 34 of the conveying member 8
is at a lower position level. The perpendicular distance from the reference plane l described above is determined by the center 34 being l ₁ and the center 3 being l 1 , respectively.
72 is l ₂ , sleeve center O is l _s , drum center is l _D
Then, l ₂ ≦l ₁ and l ₂ <l _s . Also, l _D is set as l _D < l ₂ .

This center positional relationship allows the toner supply member 37 to reliably supply the developed toner that has passed through the opening 39 to the entry area of the sleeve 3 present in the developer container, and also stabilizes the supply of toner from the toner storage container. It is possible to prevent toner from becoming insufficient in the entry area. And a stable amount of toner,
As the toner is transported to the surface of the sleeve that has entered the toner, a stable period of contact with the magnetic particle layer previously formed on the sleeve surface can be maintained, so that the toner is stably charged. The thin toner layer on the sleeve surface can maintain stable charging and layer thickness not only during the development process but also during the period of use of the developing device, and the resolution of the developed image can be improved.

In this example, the magnetic particles 7 are previously restrained by the magnetic poles N on the surface area of the developing sleeve and the magnetic blades 38
and the magnetic pole N to restrain the magnetic particles 7 in the container 41 and the particle reversing member 35 that helps circulate the magnetic particles 7.
Circulation is performed in a clockwise direction as indicated by arrow e. This circulation can be created by appropriately selecting the arrangement and number of magnetic poles in the sleeve, the fluidity of the particles 7, and the magnetic properties to balance magnetic force, gravity, and frictional force. Therefore, in this example, a toner intake part is formed at the point where the magnetic particles 7 start circulating with respect to the sleeve surface, and the toner supply member 37 actively supplies toner to this intake part, so that there is no problem in development. The above-mentioned unique effects are further ensured. In this example, further
Since the weight of the toner layer is not applied to the magnetic particle layer, stable toner uptake is possible without interfering with this circulation, allowing the use of light-pressure fixing toner, which previously could not be used due to problems of fusion and aggregation. enable.

In addition, by feeding the toner near the toner intake port, it is possible to effectively close the gap that occurs between the magnetic particle layer and the toner layer as the magnetic particles circulate, and the toner intake into the magnetic particle layer is stabilized. The developed image also becomes uniform.

In general, in a rotary type toner conveying member 8, as shown in FIG. Conveying force is F,
The horizontal conveying force is Fλ, and the vertical conveying force is Fy.
Then, since the force exerted on the toner by this toner conveying member 8 is directed in the tangential direction of the rotating circle of the conveying member, the conveying force Fx exerted on the toner in the horizontal direction is Fx
=Fxcos θ. That is, when θ=0°, the toner horizontal conveyance force Fx is maximum, and when θ=90°, it is minimum.

Therefore, returning to the developing device shown in FIG.
When the toner storage container 12 is installed approximately horizontally, the toner is transported from the toner storage container to the developer container mainly within the range of -90≦θ≦90 (particularly 0
≦θ≦90).

Because of this relationship, the position level of the above-mentioned configuration can bring the supply and conveyance relationship between the toner conveying members 8, 81, toner supply member 9, and sleeve 3 into a stable supply and conveyance state.

In this example, by further providing the guide member 30, the toner in the toner storage container can be supplied without waste, and the above-mentioned supply and conveyance state can be maintained even with a narrow opening.

The speed of each rotation is set for image formation, and is 120 mm/sec for the developing sleeve and drum, 13 rpm for the toner supply member 9, and 3 rpm for the toner transport member.
When normal development was carried out, the toner supply was stabilized, the toner charging state was also stabilized, and excellent images could be stably obtained even in a 2000-sheet durability test. In addition, in this experiment, the average particle size of the magnetic particles was
A 100 μm iron ball coated with a mixture of acrylic/futsuso resin is used, and an average particle system consisting of 100 parts of styrene/butadiene copolymer resin and 5 parts of copper phthalocyanine pigment is used as the non-magnetic developer.
A blue toner in which 1.0% colloidal silica was externally added to 12 μm toner powder was used, and the north pole was set to 800G.

Also, the experimental development bias was 1.8KHz,
DC -260V was superimposed on an alternating electric field of 1.3KVpp, the image area was -680V, the non-image area -220V, and the distance between the sleeve and the drum was 400 μm.

This resulted in a good blue image.

In the above embodiment, development is performed using two-component particles during development, but the non-magnetic blade 38
Instead, a magnetic blade may be used to develop one component during development.

The magnetic particles have a resistance value of 10 ⁷ Ωcm or more, preferably
A magnetic material such as ferrite coated with resin and having a resistance of 10 ⁸ Ωcm or more is used. The magnetic particles 7 are first introduced into the developer container 41 from the magnetic particle storage section 5, so that the magnetic particles 7 are exposed to the area of the sleeve surface facing into the container 41 (i.e., the developer container in which the sleeve 3 is disposed). Member 4 for preventing magnetic particles or toner from leaking from 41
0 to the tip of the developer amount regulating blade 38).
It is attracted and held by the magnetic field. This forms a layer of magnetic particles that completely covers the sleeve surface area. At this time, it is preferable that the magnetic particle layer contains a predetermined amount of toner.

When sleeve 3 is rotated in the direction of arrow b, the magnetic pole
By appropriately selecting the arrangement positions of N ₁ and S ₂ and the fluidity and magnetic properties of the magnetic particles 7, the magnetic brush can be made into a magnetic pole.
It circulates in the direction of arrow e near _N1 , forming a circulation layer. Through the circulation of the magnetic particles, the surrounding toner is taken into the magnetic brush, and the toner is triboelectrically charged due to the friction between the magnetic particles and the sleeve, and as the sleeve rotates, the toner is transported to the development area together with the magnetic particles and subjected to development. Ru.

In this example, the peculiar point is that since the toner supply member 37 is located below the magnetic particle storage section 5, the opening area for the magnetic particles to fall is wide, making it easy to introduce the magnetic particles, and the developing sleeve 3 Magnetic particles that are not restrained by the fixed magnetic poles inside and have accumulated on the lower surface of the developer container 11 are also sent to the developer sleeve 3 side by the rotation of the toner supply member 9, eliminating unnecessary magnetic particles, resulting in extremely high efficiency.

In addition, in FIG. 1, the blade 38 in this embodiment is
At least its tip is made of a non-magnetic material such as aluminum and extends in the longitudinal direction of the sleeve 3 near the top of the opening of the container section 41, its base is fixed to the container section 41, and its tip side is made of a non-magnetic material such as aluminum. They face each other with a gap between the surfaces. The gap between the tip of the blade 24 and the surface of the sleeve 3 is 50 to 500 μm,
Preferably it is 100 to 350 μm, and in this example
It is 250μm. If this gap is smaller than 50μm,
Magnetic particles tend to clog this gap, and if the diameter exceeds 500 μm, a large amount of magnetic particles and toner will pass through the gap, making it impossible to form a developer layer of an appropriate thickness on the sleeve 3.

The development in the developing section of the apparatus shown in FIG. 1 will be explained below with reference to FIG. 3. In FIG.
The magnet is designated by the reference numeral 23.

The power supply 34 applies a voltage between the photosensitive drum 1 and the sleeve 22 to form an alternating electric field in the gap therebetween, thereby transferring the toner from the developer on the sleeve 22 to the photosensitive drum 1. The voltage from the power supply 34 may be a symmetrical alternating voltage in which the peak voltages on the positive side and the negative side are the same, or an asymmetrical alternating voltage in which a DC voltage is superimposed on such an alternating voltage. As a specific voltage value, for example, for an electrostatic latent image with a dark area potential of -600V and a bright area potential of -200V, for example,
A direct current voltage of -300 V is superimposed to apply a peak-to-peak voltage of 300 to 2000 Vpp and an alternating voltage of a frequency of 200 to 3000 Hz to the sleeve 22 side, and the photosensitive drum 1 is held at the ground potential.

FIG. 3 is an enlarged sectional view for explaining the behavior in the developing section. The photosensitive drum 1 carries charges constituting a latent image. In this embodiment, the charges constituting the electrostatic latent image have a negative polarity, and the toner is charged to a positive polarity. Further, in this embodiment, the photosensitive drum 1 and the sleeve 22 rotate as shown by the arrows so as to move in the same circumferential direction. The above-mentioned alternating voltage is applied to the space between these by the power supply 34, and an alternating electric field is formed. On the other hand, photosensitive drum 1
There is a magnetic pole 23b of the magnet 23 inside the sleeve 22 corresponding to the closest portion between the sleeve 22 and the sleeve 22.

In this space, there is a developer, which is a mixture of magnetic particles 27 and toner 28, which have been conveyed by the rotation of the sleeve 22 as described above. In the case of the development method using the so-called one-component non-magnetic developer thin layer, the magnetic particles 27 are present here (Japanese Patent Application Laid-open Nos. 143360/1982 and 101680/1980).
It is essentially different. Furthermore, due to the relationship of the volume ratio of magnetic particles in this area (described later), the amount of magnetic particles present is much smaller than in the usual so-called magnetic brush development method, and in this respect, it is essentially different from the magnetic brush development method. different.
This small number of magnetic particles 27 is due to the action of the magnetic pole 23a,
The ears 51 connected in a chain are formed in a coarse state, that is, in a sparse state.

The behavior of the magnetic particles 27 in the developing section is special because the degree of freedom is increased.

In other words, these sparse spikes of magnetic particles form a uniform distribution in the direction of the magnetic field lines and can open both the sleeve surface and the magnetic particle surface, so that the toner adhering to the surface of the magnetic particles is not blocked by the spikes. By forming a uniform open surface on the sleeve surface, toner adhering to the sleeve surface can fly from the sleeve surface to the photosensitive drum surface by an alternating electric field.

Here, the behavior of magnetic particles and the flight of toner particles will be explained.

As shown in FIG. 1, in this embodiment, the electrostatic latent image is composed of negative charges (image dark areas), so the electric field due to the electrostatic latent image is in the direction indicated by arrow a. The direction of the electric field due to the alternating electric field changes alternately, but in the phase where the positive component is applied to the sleeve 22 side, the direction of the electric field due to this matches the direction of the electric field due to the latent image. At this time, the amount of charge injected into the ears 51 by the electric field becomes maximum, so the ears 51 are in the maximum standing state as shown in the figure, and the long ears extend over the surface of the photosensitive drum 1.

On the other hand, since the toner 28 on the surfaces of the sleeve 22 and the magnetic particles 27 is positively charged as described above, it is transferred to the photosensitive drum 1 by the electric field formed in this space. At this time, since the ears 51 stand up in a rough state, the surface of the sleeve 22 is exposed, and the toner 28 separates from both the sleeve 22 surface and the surface of the ears 51. In addition, since the spikes 51 are charged with the same polarity as the toner 28, the toner 28 on the surface of the spikes 51 is more likely to move due to electrical repulsion.

In the phase in which the negative component of the alternating voltage component is applied to the sleeve 22, the electric field due to the alternating voltage (arrow b)
is in the opposite direction to the electric field (arrow a) due to the electrostatic latent image. Therefore, the electric field in this space becomes strong in the opposite direction, the amount of charge injection becomes relatively small, and the ears 51 are brought into a contracted contact state in accordance with the amount of charge injection.

On the other hand, since the toner 28 on the photosensitive drum 1 is positively charged as described above, it is reversely transferred to the sleeve 22 or the magnetic particles 27 by the electric field formed in this space. In this way, the toner 28 moves back and forth between the photosensitive drum 1 and the surface of the sleeve 22 or the surface of the toner 28, and as the space between them expands due to the rotation of the photosensitive drum 1 and sleeve 22, the electric field becomes weaker. The developing action is completed at the same time.

There are charges injected into the spikes 51 by frictional charges or mirror charges with the toner 28, electrostatic latent image charges on the photosensitive drum 1, and alternating electric fields between the photosensitive drum 1 and the sleeve 22. , the state changes depending on the charging/discharging time constant of the charge determined by the material of the magnetic particles 27 and other factors.

As described above, the ears 51 of the magnetic particles 27 are brought into a state of slight but intense vibration due to the above-mentioned alternating electric field.

Here, the volume ratio of magnetic particles in the developing section will be explained. The "developing section" is a section where toner is transferred or supplied from the sleeve 22 to the photosensitive drum 1. The "volume ratio" is the percentage of the volume occupied by the magnetic particles present in the developing area relative to the volume of the developing area. As a result of various experiments and considerations, the inventor of the present invention has found that this volume ratio has an important influence on the above-mentioned developing device, and that this
It has been found that a content of 1.5 to 30%, particularly 2.6 to 26%, is extremely preferable.

If it is less than 1.5%, a decrease in the density of the developed image will be observed, sleeve ghost will occur, and panicle 5
This is preferable in that a noticeable difference in density occurs between the part where 1 is present and the part where it is not, and the thickness of the developer layer formed on the surface of the sleeve 22 becomes non-uniform as a whole. do not have.

If it exceeds 30%, the degree of closure of the sleeve surface increases, which is undesirable because fogging may occur.

In particular, in the present invention, the image quality does not monotonically deteriorate or increase as the volume ratio increases or decreases, but sufficient image density can be obtained in the range of 1.5 to 30%, and even if it is less than 1.5%, it can exceed 30%. This is based on the fact that the inventor has discovered that in the range of the above numerical values where the image quality is sufficient, neither sleeve ghost nor fogging occurs.
The deterioration in image quality in the former is thought to be due to the negative characteristic;
The latter is thought to occur because the amount of magnetic particles present becomes large and the surface of the sleeve 22 cannot be opened, resulting in a significant decrease in the amount of toner supplied from the surface of the sleeve 22.

Also, if it is less than 1.5%, the reproducibility of line images will be poor,
There is a noticeable decrease in image quality and density. On the other hand, if it exceeds 30%, the magnetic particles may damage the photosensitive drum surface.
There are transfer and fixing problems that occur because the image is attached as part of the image.

And if the presence of magnetic particles is close to 1.5%,
When reproducing large area uniform high density images (solid black),
Since partial development unevenness called "roughness" may occur (under special circumstances, etc.), it is preferable to set a volume ratio that makes it difficult for this to occur. This value indicates that the volume ratio of magnetic particles to the developing area is 2.6.
% or more, this range becomes a more preferable range. Also, if the presence of magnetic particles is close to 30%, there may be a delay in toner replenishment from the sleeve surface around the area where the ears of magnetic particles come into contact (such as when the development speed is high), and scales may appear when solid black is reproduced. This may result in uneven density. As a reliable range for preventing this, it is more preferable that the volume ratio of the magnetic particles is 26% or less.

If the volume ratio is in the range of 1.5 to 30%, the spikes 51 are formed on the surface of the sleeve 22 in a preferable sparse state, and the toner on both the sleeve 22 and the spikes 51 is sufficiently applied to the photosensitive drum 1. Since the toner on the sleeve is released and the toner on the sleeve is also transferred by flight due to the alternating electric field, almost all of the toner is in a state that can be consumed for development. ratio) and high image density. Preferably, slight but strong vibrations of the ears are generated, thereby loosening the magnetic particles and the toner adhering to the sleeve 22. In any case, it is possible to prevent uneven sweeping and ghost images that occur in the case of magnetic brushes. Furthermore, due to the vibration of the ears,
Since the frictional contact between the magnetic particles 27 and the toner 28 becomes active, the frictional electrification of the toner 28 can be improved and fogging can be prevented. Note that high developing efficiency is suitable for downsizing of the developing device.

The volume ratio of the magnetic particles 27 existing in the developing area can be determined as (M/h) x (1/ρ) x [(C/(T+C)]. Here, M is the volume ratio per unit area of the sleeve. Coating amount (g/cm ² ) of the developed image (mixture...when not standing), h is the height of the developing area space (cm),
ρ is the true density of the magnetic particles in g/cm ³ , and C/(T+C) is the weight ratio of the magnetic particles in the developer on the sleeve.

In addition, in the developing section defined above, the ratio of toner to magnetic particles 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 spikes 51 separate from the sleeve 22 or from its base, and the separated magnetic particles 27 are attached to the sleeve 22 and the photosensitive drum 1.
It moves back and forth in the space between. Since the energy of this reciprocating motion is large, the effect of the vibration described above is further promoted.

The above behavior was observed using a high-speed camera (manufactured by Hitachi).
This was confirmed by shooting at 8000 frames per second.

Even if 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 brush 51 and to reduce vibration, the gap is large at the entrance and exit sides of the developing section. Sufficient vibration occurs to produce the above-mentioned effects.

Conversely, it is preferable to increase the gap between the photosensitive drum 1 and the sleeve 22 so that the ears 51 do not contact the photosensitive drum 1 when no magnetic field is applied, but do come into contact when a magnetic field is applied.

Note that the magnetic particles 27 having a relatively low resistance value
When using an alternating voltage applied between the photosensitive drum 1 and the sleeve 22, it is necessary to set the alternating voltage applied between the photosensitive drum 1 and the sleeve 22 so that no gap discharge occurs in either the dark or bright areas of the latent image when the voltage reaches its peak value. . On the other hand, when using ears 51 with a relatively high resistance value, the gap voltage does not reach the discharge starting voltage by appropriately selecting the frequency of the alternating voltage and the charging/discharging time constant of the ears 51. It is preferable.

Taking these into consideration, the resistance of the entire spike 51 in the height direction of the spike 51 with the developing brush in contact with the photosensitive drum 1 is preferably in the range of 10 ¹⁵ to 10 ⁶ Ωcm, and a developing electrode effect is expected. If you do
Approximately 10 ¹⁰ to 10 ⁶ Ωcm is preferable.

The magnetic particles 27 have an average particle size of 30 to 100 microns, preferably 40 to 80 microns. In general, the smaller the average particle size, the better the triboelectric charging characteristics of the toner on the sleeve 22, and the sleeve ghost (a phenomenon in which the density decreases due to the rotation of the sleeve immediately after developing a solid black original, or every rotation of the sleeve). (which appears as a phenomenon in which the developing density decreases) will no longer occur. However, if the particle size is small, there is a tendency for the magnetic particles to adhere to the electrostatic holder. The position of this adhesion differs depending on the resistance value of the magnetic particles; for example, those with relatively low resistance will adhere to the image area, and those with high resistance will adhere to the non-image area. This is a general tendency, and in reality, the magnetic properties of the magnetic particles, the surface shape, and the surface treatment material (including resin coating) also have some influence.

In commercial electrophotographic development equipment where the magnetic field on the sleeve of the developer section is 600 to 900 G, adhesion of magnetic particles increases when the particle size is less than 30 microns. Also, sleeve ghosts are noticeable at 100μ or more. Therefore, the above range is preferable.

In this developing device, a conventional two-component carrier having a relatively high resistance of about 50 to 100 μm can be used.

Each magnetic particle may consist only of magnetic material,
The magnetic particles may be a combination of a magnetic material and a non-magnetic material, or the magnetic particles as a whole may be a mixture of two or more types of magnetic particles.

Next, when the angle θ is in a range of θ<2°, agglomerates of the magnetic particles 27 occur or the developer is not formed as a uniform layer on the sleeve. This is thought to be due to the fact that the magnetic particles are arranged in a coarse manner along the lines of magnetic force in the vicinity of the blade 24, and only after a certain number of magnetic particles have accumulated here do they leave. On the other hand, when θ>40°, the effect of regulating the amount of magnetic particles 27 is significantly inferior. Therefore, 2°≦θ≦
It has been found that 40° is preferred and 5°≦θ≦20° is particularly preferred.

Regarding the relationship between the angle θ and the amount of developer passing through, as θ is decreased, the amount of developer passing through decreases, and therefore the volume ratio in the developing section decreases, and as θ is increased, the opposite tendency occurs. The amount of toner applied onto the surface of the sleeve 22 is not affected by θ and remains approximately constant.

Next, a specific example using the developing device shown in FIG. 1 will be described. In Fig. 1, the sleeve 22 is an aluminum sleeve with a diameter of 20 mm, the surface of which has been subjected to irregular sandblasting with Alundum abrasive grains, and the magnet 23 is 4-pole magnetized with N and S poles alternately shown in Fig. 1. I used something like the one shown in . The maximum value of the surface magnetic flux density due to the magnet 23 was about 900 Gauss.

The blade 24 was made of nonmagnetic stainless steel with a thickness of 1.2 mm, and the angle θ was 15°.

As the magnetic particles, ferrite (maximum magnetization 60 emu/g) with a particle size of 70 to 50 μm (250/300 mesh) whose surface was coated with silicone resin was used.

As a non-magnetic toner, blue toner was used, which was made by externally adding 0.6% of colloidal silica to toner powder with an average particle size of 10μ, which was made of 100 parts of styrene/butadiene copolymer resin and 5 parts of copper phthalocyanine pigment. A toner coating layer with a coating thickness of about 20 to 30 μm was obtained on the surface, and a magnetic particle layer with a thickness of 100 to 200 μm was obtained as an upper layer. The toner is attached to the surface of each magnetic particle.

At this time, the total weight of the magnetic particles and all the toner on the sleeve 22 was approximately 2.43×10 ⁻² g/cm ² .

The magnetic particles are placed in the sleeve 2 in the developing area and its vicinity.
The brushes were raised by the magnetic field generated by the magnetic pole 23b in the brush 2, forming a raised brush with a maximum length of about 0.9 mm.

When the amount of charge was measured using the blow-off method, the amount of triboelectric charge of the toner on the sleeve and on the magnetic particles was +
It was 10μC/g.

This developing device was installed in a PC-10 type copying machine manufactured by Canon Inc., and the gap between the photosensitive drum 3 (made of an organic photosensitive material) and the surface of the sleeve 22 was set to 350 μm. When the volume ratio was calculated under these conditions, it was approximately 10% (h = 350 μm, M = 2.43 × 10 ^-2 g/cm ² , ρ = 5.5
g/cm ³ , T/(T+C)=20.4%). Frequency 1600Hz as bias power supply 34, peak-to-peak value
When development was carried out using an AC voltage of 1300V superimposed with a DC voltage of -300V, a good blue image was obtained.

Further, when a solid black image was developed and the sleeve surface after development was observed, it was found that most of the toner attached to the magnetic particles and the toner on the sleeve were consumed, and development was performed with nearly 100% development efficiency.

(Effects) The present invention achieves stabilization of developer supply from the developer accommodating section to the developer receiving section and onto the developer carrier, and forms a stable charging state of the developer, thereby improving reproduced image quality. make it good. It also has the effect of widening the range of development conditions and selection of materials used.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of essential parts of an embodiment of the present invention, FIG. 2 is an explanatory diagram of movement of the toner conveying member in FIG. 1, and FIG. 3 is a schematic explanatory diagram of a developing device to which the present invention is applied. 8 is a conveyance member, 30 is a guide member, 41 is a developer container, 39 is an opening, 61 is a storage container, 81 is a sheet, l ₁ , l ₂ , l _s , l _D , L ₁ , L ₂ , L _s , L _D is distance.

Claims (1)

[Claims] 1. A developing container section, and a rotating developing sleeve disposed in the developing container section facing the electrostatic latent image carrier and having a magnet therein, and magnetic particles are distributed along the developing sleeve within the developing container section. The rotation of the developing sleeve causes the magnetic particles in the magnetic particle layer to move upwards, then reverse and move downwards in a circular motion, and the movement of the magnetic particles causes the magnetic particles to move from the toner layer outside the magnetic particle layer to the magnetic particle layer. In a developing device that takes toner into the developing device, a toner storage container portion disposed on the horizontal side of the developer container, and the toner storage container portion and the developer container portion communicate with each other at a position lower than the center of rotation of the developer sleeve. a slit-shaped toner passage section; a toner conveying member that rotates within the toner storage container section to feed the toner in the toner storage container section to the toner passage section to form a toner accumulation section in the toner passage section; and a rotation locus. The magnetic particles rotate in the developing container so that a part of the toner particles pass through the toner accumulation area, and are scraped off from the toner accumulation area little by little to the extent that the toner accumulation area does not disappear. A developing device comprising: a toner supply member that supplies toner to a lower portion of the area.