JPS6361272A - Developing device - Google Patents

Abstract

PURPOSE:To obtain a good development by setting the half-value width of magnetic force of a carrying magnetic pole to >=25 deg., setting a half-value width interval to 20 deg.-140 deg. in a container, and mixing and stirring sufficiently carrier grains and toner grains. CONSTITUTION:Carrier grains 27 are thrown into a container 21 and a carrier grain layer is formed on the surface of a sleeve 22 with a regulating magnetic pole 23a and a carrying magnetic pole 23d, and subsequently, a toner 28 is thrown in and a toner layer is formed on the outside of the carrier grain layer. When the sleeve 22 rotates, the carrier grains fetch the toner from the toner layer of the lower part of the container 21, and compensate for the consumed portion. In such a case, when a half-value width of the carrying magnetic pole 23d is set to >=25 deg., the carrying force for collecting the carrier grains can be secured enough, and also, when the half-value width interval BC of the carrying magnetic pole 23d and the control magnetic pole 23a is set to 20 deg.-140 deg., the carrying force can be weakened suitably, each grain of the carrier and the toner is mixed and stirred enough, the toner grains can be electrified enough, and a good developed image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Support ±j The present invention relates to a developing device for developing a latent image formed by electrophotography, electrostatic recording, or the like.

Applicant JLi first forms a thin layer of developer containing toner particles and carrier particles on a developer carrier, brings the thin layer of developer close to the latent image, and places the developer in this close portion. We have proposed a developing device that applies an alternating electric field and disposes a magnetic field generating means on the opposite side of the developer carrying member from the latent image, and performs development while bringing carrier particles into contact with the latent image in a developing section (specially Gansho 6
0-204605 specification).

This device ensures image density, and does not cause scratches caused by brushing, such as in the so-called two-component magnetic brush development method (for example, Japanese Patent Application Laid-open No. 53-93841), to appear on the developed image. Although it has been confirmed that this method is useful, further improvements are desired in terms of toner transport within the developer container.

Therefore, an object of the present invention is to be able to form a developed image with high image density and to ensure an appropriate conveyance force for toner particles within a developer container.

According to the present invention, there is provided a developing device for developing an electrostatic latent image on an electrostatic latent image carrier, the developer container containing a developer having toner particles and carrier particles; a developer carrying member that faces the electrostatic latent image carrier and forms a developing section that supplies toner particles to the electrostatic latent image carrier, and carries and conveys developer from the container to the developing section; , a developer regulating member having a regulating portion distal end located upstream of the developing section in the rotational direction of the developer carrying member and spaced apart from the surface of the developer carrying member, and opposite to the regulating member of the developer carrying member; a first magnetic field generating means provided on the side and located upstream of the developer regulating member with respect to the rotational direction of the developer carrier; and a first magnetic field generating means provided on the opposite side of the developer carrier from the regulating member, a second magnetic field generating means located upstream of the developer regulating member in the rotation direction of the developer carrier and corresponding to the inside of the developer container; and a half width of the magnetic force by the second magnetic field generating means. is 25° or more, and the opening in the container between the half-width and the half-width of the magnetic force by the second magnetic field generating means is 2O2 or more and 140° or less. According to this, a high-density developed image can be formed, and an appropriate conveyance force for the toner can be ensured in the developer container.

Figure 2 is a sectional view of a developing device according to an embodiment of the present invention.

In this figure, l is an electrostatic Hs image carrier that carries an electrostatic latent image to be imaged, and specifically, it is an endlessly movable photosensitive drum, a belt, a dielectric drum, a belt, or the like. The method of forming an electrostatic latent image thereon is not the gist of the present invention, and any known method may be used. In this embodiment, the electrostatic latent image carrier is a photosensitive drum on which an electrostatic latent image is formed by electrophotography. and is rotatable in the direction of arrow a.

The apparatus of this embodiment includes a developer container 21, a developing sleeve 22 (hereinafter simply referred to as a sleeve) that is a developer holding member, a magnet 23 that is a magnetic field generating means, and an amount of developer that is conveyed to the developing section on the sleeve 22. A regulation blade 24 (hereinafter simply referred to as a blade) that controls the
4 etc. Each configuration will be explained below.

Container 21 contains a developer having a mixture of carrier particles 27 and toner particles 28 . In this embodiment, the toner particles are non-magnetic toner particles having a particle size of 7 to 20 pLra, and are formed mainly of, for example, 1 part carbon and 90 parts polystyrene. In this embodiment, the toner particles and carrier particles are stored in the container 21 as a uniform mixture, with the carrier particles having a high concentration near the sleeve 22 and a low concentration away from the sleeve 22. The container 21 has an opening at the lower left in FIG.

The sleeve 22 is made of a non-magnetic material such as aluminum, and is provided at the opening of the container 21, with a part of its surface exposed and the other surface protruding into the container 21. The sleeve 22 is rotatably supported around an axis perpendicular to the drawing, and is rotationally driven in the direction indicated by the arrow. In this embodiment, the sleeve 22 is a cylindrical sleeve, but it may also be an endless belt. .

The sleeve 22 opposes the photosensitive drum 1 with a small gap therebetween and constitutes a developing section. Toner and carrier particles are conveyed to this developing section by a sleeve 22, and carrier particles exist therein in a volume ratio (1.5 to 30%).

The magnet 23 is fixed statically inside the sleeve 22 and remains stationary even when the sleeve 22 rotates. The magnet 23 has an NFji pole 23a that cooperates with a blade 24 to be described later to regulate the amount of developer applied onto the sleeve 22, and an S magnetic pole 23 that is a developing magnetic pole.
b, an N magnetic pole 23c that transports the developer after passing through the developing section into the container 21, and an N magnetic pole 23c that takes toner and carrier that have not been developed in the developing section into the container, and further transports the carrier particles and toner into the container together with the regulating magnetic pole 23a; It has an S magnetic pole 23d that is conveyed by. The S and N poles may be reversed. Although this magnet is a permanent magnet in this embodiment, an electromagnet may be used instead.

FIG. 1 shows the distribution of magnetic force due to the regulating magnetic pole 23a and the carrier magnetic pole 23d. The maximum value of the magnetic field strength due to the carrier magnetic pole is X Gauss, and the maximum value of the magnetic field strength due to the regulating magnetic pole is Y Gauss. In the present invention, the width between two points A and B at half the value of the maximum magnetic field by the transport magnetic pole 23d, that is, the half width AB is at an angle α when viewed from the rotation center of the sleeve.
This half width α is 25° or more. Further, in the present invention, the interval BC between the half-width of the magnetic field by the regulating magnetic pole 23a and the half-width of the magnetic field by the transporting magnetic pole 23d is 20" or more and 140° or less, more preferably 30" or more and 120"
It is as follows.

In this embodiment, the blade 24 has at least its tip made of a non-magnetic material such as aluminum, and the blade 24 is made of a non-magnetic material such as aluminum.
extending in the longitudinal direction of the sleeve 22 near the top of the opening;
Its base is fixed to the easy 21, and the distal end is fixed to the sleeve 22.
facing the surface with a gap. The gap between the tip of the blade 24 and the surface of the sleeve 22 is 50 to 500 pm,
Preferably it is 100 to 350 p-ra, and in this example it is 250 p-ra. If this gap is smaller than 50 μl layer, carrier particles will easily clog this gap.

If it exceeds 5004 m, a large amount of carrier particles and toner will pass through the gap, making it impossible to form a developer layer with an appropriate thickness on the sleeve 22. In order to create a developer layer with such a thickness, which is smaller than the gap between the sleeve 22 and the sleeve 22 (however, the thickness of the developer at this time is the thickness on the sleeve 22 when no magnetic force is applied), The gap between the blade tip and the sleeve surface is preferably equal to or smaller than the gap between the sleeve surface and the photosensitive drum surface, but it is also possible to make it larger.

A carrier particle circulation limiting member 26 is provided on the inside of the container 21 of the blade 24, and this restricts the circulation area of carrier particles within the container 21, which will be described later.

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 voltage 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.The specific voltage value is 1. For example, for an electrostatic latent image with a dark potential of -600V and a light potential of -200V, a DC voltage of -300V is superimposed to increase the peak-to-peak voltage by 30V.
0 to 2000 Vpp, frequency 200 to 3000) 1z alternating voltage is applied to the sleeve 22 side.

The photosensitive drum l is held at ground potential.

The lower part of the container 21 extends in the direction of the photosensitive drum 1 to form an extension, and prevents the developer (particularly toner particles) from leaking to the outside. Further, in order to further ensure the prevention of such leakage, a member 29 is provided on the upper surface of the extension portion to receive and restrain the leaked toner. Furthermore, a scattering prevention member 30 is fixed to the tip of the extension along the longitudinal direction of the sleeve 22 as shown. A voltage having the same polarity as that of the toner particles may be applied to this member 30, whereby the toner scattered from the development area can be pushed toward the photosensitive drum 3 by an electric field, thereby preventing toner scattering.

At both longitudinal ends of the sleeve 22, there are present agent blocking members 2.
5 are provided to prevent the developer from being applied to both ends of the sleeve 22.

Next, the operation of the developing device of this embodiment will be explained. First, carrier particles 27 are put into the container 21 . The introduced carrier particles are held on the sleeve 22 by the magnetic poles 23a and 23d, and the sleeve 2 facing into the container 21 is
The carrier particles adhere to the entire surface of the carrier particles 2 and constitute a carrier particle layer. Magnetic pole 23a and magnetic pole 23 of this carrier particle layer
In the part close to d, the carrier particles 27 constitute a magnetic brush. After that, the toner 28 is put into the container 21.

A toner layer is formed outside the carrier particle layer. It is preferable that the carrier particles 27 initially introduced include toner in an amount of 2 to 70% (by weight) of the carrier particles, but it is also possible to include only carrier particles. If the particles are adsorbed and held as a layer of carrier particles, substantial flow or inclination will not occur even if the device is vibrated or tilted considerably, and the state of covering the surface of the sleeve 22 will be maintained.

Next, when the sleeve 22 is rotated in the direction of the arrow, the carrier particles rise from the bottom of the container 21 in a direction along the surface of the sleeve 22 and reach the vicinity of the blade 24. Therefore, some of the carrier particles are pushed by the magnetic particles collected from the bottom of the container and pass through the gap between the tip of the blade 24 and the surface of the sleeve 22 together with the toner as the sleeve rotates, but a small portion of the carrier particles are pushed by the magnetic particles collected from the bottom of the container. After colliding with the carrier particles 26, the carrier particles may turn around and descend by gravity on the outside of the ascending path of the carrier particles, reach the lower part of the container 21, rise again near the sleeve 22, and repeat the above operation. Many of the magnetic particles then form a substantially immobile layer, being almost stationary or moving at a small speed compared to the magnetic particles in the sleeve surface area. This is formed because the moving direction is restricted by the member 26, and is particularly noticeable in carrier particles far from the surface of the sleeve 22. Due to this immobile layer, toner particle uptake is largely defined by the magnetic particles collected in the lower region of the container.

Furthermore, the carrier particles that turn around and fall near or in front of the blade 24 as described above take in toner particles from the toner layer on the outside.

By acting in this way together with the rotation of the sleeve 22, the toner 28 is charged by friction between the carrier particles 27 and the surface of the sleeve 22. When this passive layer of magnetic particles was replaced with a magnetic plate, sufficient toner charging could not be obtained and toner uptake failure also occurred, so this passive layer has a great effect. This is preferable because stable tripo application and toner uptake can be achieved with a slight movement.

Near the front side of the blade 24, the carrier particles 27 near the surface of the sleeve 22 are pushed into the sleeve 22 by the magnetic pole 23a.
It is attracted to the surface, and as the sleeve 22 rotates, it passes under the sleeve 24 and exits the container 21. At this time, the carrier particles 27 carry out the toner attached to the surface thereof, and some of the charged toner particles 28 are transferred to the sleeve 2.
It exits the container on the sleeve 22 while remaining attached to the surface of the sleeve 22 due to the reflection force. Blade 24 regulates the amount of developer applied onto sleeve 22.

The developer layer (mixture of carrier particles 27 and toner 28) thus formed on the surface of the sleeve 22 reaches a developing section facing the photosensitive drum 1 as the sleeve 22 rotates. Here, toner is transferred to the sleeve 22 by an alternating electric field applied between the photosensitive drum l and the sleeve 22.
and the surface of the carrier particles onto the Hs image, and the latent image is developed. In this example, the volume ratio of carrier particles in the developing section is 1.5 to 30%. This point will be explained in detail later.

As the sleeve 22 continues to rotate, the toner particles and carrier particles that have not been consumed in the development are collected into the container 21, and the process is repeated in which they are coated on the sleeve 22 again by the aforementioned action. At the time of recovery, the carrier particles take in toner from the toner layer at the bottom of the container 21 as shown by the arrow, and are supplied with the amount of toner consumed in development.

According to the present invention, since the above-mentioned half-width interval is 20' or more, the conveyance force that causes carrier particles and toner particles to rise within the container along the rotation of the sleeve can be appropriately weakened. When the angle is less than 20°, this conveying force becomes too strong, and toner is taken in between carrier particles excessively, resulting in an insufficient amount of charge on the toner particles and causing fogging. On the other hand, if the half-width interval is too large, the conveying force will be insufficient and the necessary conveyance will not be carried out.In the present invention, therefore, the half-width interval is set to 140° or less, thereby ensuring an appropriate conveying force.

If the angle exceeds 140@, the conveyance will be insufficient and the carrier particles and toner particles will stagnate in the container.

Further, since the half width of the transport pole 23d is set to 25° or more, further transport force can be ensured. If this half width is less than 25°, the conveying force will be insufficient. In particular, in the present invention, since the carrier particles once reach the developing section on the sleeve and then return to the container, it is preferable to ensure a relatively strong transport force near the transport magnetic pole 23d. In order to suppress the amount of carrier particles taken in, it is preferable to weaken the conveying force.According to the present invention, since the half width of the conveying magnetic pole 23d is 25° or more, a sufficient conveying force for collecting carrier particles is ensured. At the same time, in the container, the half-width interval BC is 20" or more and 140 degrees or less, so a sufficiently suppressed conveying force is maintained. Also, this allows the carrier particles and toner particles to be sufficiently mixed and agitated in the container. The toner particles can be sufficiently charged in a small space.Furthermore, these effects can be further ensured by setting the half-width interval to 30' or more and 120' or less.

Generally, in a developing device using a two-component developer, in order to stabilize the mixing ratio of toner particles and carrier particles,
Although an automatic density control device 4 (generally called ATR) is used, according to the present invention, for the above-mentioned reasons, an appropriate amount of toner can be taken in, so this automatic density control device is not necessary. In addition, the maximum magnetic field due to the regulating magnetic pole 23a is set to 800
When it is Gauss or higher, the developer layer to the developing area can be made more uniform, and the leakage amount of magnetic particles can also be made more uniform. Further, it is more preferable to set the maximum magnetic field by the transport magnetic pole 23d to 500 Gauss or more, since this allows the above-mentioned transport performance to be more stabilized.

Furthermore, the half-width due to the regulation magnetic pole 23a is changed to the transport magnetic pole 23d.
This is preferably larger than the half-width due to
This is because, in addition to the above-mentioned effects, it is possible to improve the conveyance property, so that the tripping of toner particles can be made more stable and appropriate.

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 tH1 between these by the power supply 34, and an alternating electric field is formed. On the other hand, inside the sleeve 22, there is a magnetic pole 23b of the magnet 23 corresponding to the closest portion between the photosensitive drum l and the sleeve 22.

In this space, there is a developer, which is a mixture of carrier particles 27 and toner 28, which have been conveyed by the rotation of the sleeve 22 as described above. The presence of the carrier particles 27 here is different from the development method using the so-called one-component non-magnetic developer thin layer described above (Japanese Patent Laid-Open Nos. 58-143360 and 59-101680). There is. In addition, due to the volume ratio of the carrier particles in this area (described later), the amount of carrier particles present is much smaller than in the normal so-called magnetic brush development method, and in this respect, it is also different from the magnetic brush development method. Different in wood quality. These few carrier particles 27 are the magnetic pole 23
By the action of a, the ears 51 connected in a chain form are formed in a coarse state, that is, in a sparse state.

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

In other words, these sparse ears of carrier particles form a uniform distribution in the direction of the magnetic field lines, and can open both the sleeve surface and the surface of the carrier particles, so that the toner adhering to the surface of the carrier particles is not obstructed by the ears. 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 carrier particles and the flight of toner particles will be explained.

As shown in FIG. 3, in this example h) the latent image is composed of negative charges (image dark areas);
The electric field due to the electrostatic PII 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, and therefore the ears 51 are in the maximum standing state as shown in the figure, and the long ears extend on the surface of the photosensitive drum 1.

On the other hand, since the toner 28 on the surfaces of the sleeve 22 and the carrier particles 27 is positively charged as described above,
The electric field formed in this space transfers the light to the photosensitive drum. At this time, since the ears 5 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 due to the electrostatic latent image (arrow a). 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 carrier particles 27 by the electric field formed in this space. In this way, the toner 28 reciprocates 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 complete.

The spikes 51 have frictional charges or mirror charges with the toner 28, static charges on the photosensitive drum l? ! ! There are latent image charges and charges injected by alternating electric fields between the photosensitive drum 1 and the sleeve 22, and their state changes depending on the charging/discharging time constant of the charges determined by the material of the carrier particles 27 and other factors.

As described above, the ears 51 of the carrier 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 carrier particles in the developing section at which the present invention can exhibit particularly effective effects will be explained. The "phenomenal part" is a part to which toner is transferred or supplied from the sleeve 22 to the photosensitive drum 1. "Volume ratio" is the percentage of the volume occupied by the carrier particles present in the developing section, and in order to effectively utilize the toner on the sleeve and improve the developing efficiency, this should be set to 1.5. ~
It is preferably 30%, particularly 2.6 to 26%.

If it is less than 1.5%, a decrease in the density of the developed image will be observed, a sleeve ghost will occur, a noticeable difference in density will occur between the area where the ears 51 are present and the area where the ears 51 are not present, and the concentration on the surface of the sleeve 22 will be reduced. This is undesirable because the thickness of the developer layer formed thereon tends to be non-uniform as a whole.

If it exceeds 30%, the degree of closure of the sleeve surface increases and fogging tends to occur, which is undesirable.

In particular, this is based on the fact that the inventor has found that sufficient image density can be obtained in the range of 1.5 to 30%, and neither sleeve ghost nor fog occurs within the above numerical range where the image quality is sufficient.

The former image quality deterioration is thought to be due to negative characteristics, and the latter is thought to occur because the amount of carrier particles present becomes large and the sleeve 22 surface cannot be opened, resulting in a significant decrease in the amount of toner supplied from the sleeve 22 surface. .

Further, if it is less than 1.5%, the reproducibility of line images is poor, and there is a noticeable tendency for the image quality and density to decrease.

When the presence of carrier particles is close to 1.5%, partial development unevenness called "roughness" occurs when reproducing a large-area uniform high-density image (solid black) (under special circumstances). etc.), so it is preferable to set a volume ratio where these are unlikely to occur.This value is a more preferable range since the volume ratio of carrier particles to the developing area is 2.6% or more. Become. Also, if the presence of carrier particles is close to 30%, there may be a delay in toner replenishment from the sleeve surface around the area where the ears of carrier 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 carrier particles is 26% or less.

If the volume ratio is in the range of 1.5 to 30%, sleeve 2
The spikes 51 are formed on the two surfaces in a sparse state to a preferable extent, and the toner on both the sleeve 22 and the spikes 51 is sufficiently opened to the photosensitive drum 1, and the toner on the sleeve is also transferred by flight due to the alternating electric field. Therefore, almost all of the toner is available for development, ensuring high development efficiency (ratio of toner that can be consumed for development out of the toner present in the development area) and high image density. . Preferably, a slight but strong vibration of the spike is generated, thereby loosening the carrier 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, the vibration of the ears activates the frictional contact between the carrier particles 27 and the toner 28, thereby improving the yi triboelectric charging of the toner 28 and preventing the occurrence of fogging. Note that high developing efficiency is suitable for downsizing of the developing device.

The volume ratio of the carrier particles 27 present in the developing section is (M/h)X (1/ρ)X [(C/ (T+c)]
It can be found by Here, M is the amount of developer applied per unit area of the sleeve (mixture...when not standing).
rI amount (g/cd), h is the height of the developing section space, Cl11
), ρ is the true density of carrier particles g/cd, C/(T+C
) is the weight percentage of carrier particles in the developer on the sleeve.

In addition, in the developing section defined above, the ratio of toner to carrier particles is preferably 4 to 40% by weight.

When the alternating electric field is strong (the rate of change is large or the VPP is large) as in the above embodiment, the ears 51 separate from the sleeve 22 or from its base, and the separated carrier particles 2
7 reciprocates in the space between the sleeve 22 and the photosensitive drum 1. 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 (newly manufactured by Hitachi) with an accuracy of 8000.
This was confirmed by taking pictures at 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.

In addition, when using the carrier particles 27 having a relatively low resistance value, the alternating voltage applied between the photosensitive drum 1 and the sleeve 22 has a peak value when the voltage is applied to either the dark part or the bright part of the latent image. It is also necessary to make settings so that gap discharge does not occur. - On the other hand, when using ears 51 with a relatively high resistance value, the gap voltage should be prevented from reaching the discharge starting voltage by appropriately selecting the frequency of the alternating voltage and the charging/discharging time constant of @451. is preferred.

Taking these into consideration, the resistance of the entire ear 51 is as follows when the ear 51 is in contact with the photosensitive drum 1
It is preferable that the resistance in the height direction of
Approximately 2 to 10 6 Ωcm is preferable.

The carrier particles 27 have an average particle size of 30-100 l5, preferably 40-80 l.

In water development equipment, the two-component system 5
A carrier having a relatively high resistance of about 0 to loo# can be used.

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

As the material of the sleeve 22, in addition to aluminum, conductive materials such as brass and stainless steel, paper tubes, and synthetic resin cylinders can be used. Furthermore, if the surfaces of these cylinders are subjected to conductive treatment or made of a conductive material, they can function as developing electrodes. Furthermore, a core roll may be used and a conductive adhesive material, for example, a conductive sponge, may be wrapped around the circumferential surface of the core roll.

Regarding the magnetic pole 23b of the developing section, although the magnetic pole is arranged at the center of the developing section in the embodiment, it may be placed at a position shifted from the center, or the developing section may be arranged between the magnetic poles.

The toner may be externally supplemented with silica particles to improve fluidity or particles of a polishing agent for polishing the surface of the photosensitive drum 3, which is a latent image holding member in a transfer image forming method. However, a toner containing a small amount of carrier particles may be used. In other words, a magnetic toner may also be used as long as it has significantly weaker magnetism than the carrier particles and can be tribocharged.

In order to prevent the ghost image phenomenon, the sleeve 2 is not subjected to development from the surface of the sleeve 22 that has returned to the container 21 and has been rotated.
The developer layer remaining on the sleeve may be first scraped off by a scraper means (not shown), and the scraped sleeve surface may be brought into contact with the carrier particle layer to recoat the developer. .

A mechanism may be provided that detects the concentration of carrier particles and toner and automatically replenishes toner according to this output.

The developing device of the present invention can be used as a disposable type developing device that integrates a container 21, a sleeve 22, a blade 24, etc., or as a normal developing device fixed to an image forming apparatus.

As explained above, in the present invention, the conveyance, intake, and mixing of developer are greatly influenced by the half-width of the conveying magnetic pole and the interval between the half-width of the conveying magnetic pole and the half-width of the regulating magnetic pole. According to the present invention, it is possible to appropriately transport, take in, and mix the developer, and toner particles can be reliably charged in a small space, making it possible to perform good development.

[Brief explanation of drawings]

FIG. 1 shows the distribution of the magnetic field formed by the regulating magnetic pole and the carrying magnetic pole in polar coordinates. FIG. 2 is a sectional view of a developing device according to an embodiment of the present invention. 3 is an enlarged sectional view of the developing section of the developing device shown in FIG. 1. FIG. Explanation of symbols l...Latent image carrier (photosensitive drum) 21...Developer container (container) 22...Developer holding member (sleeve) 23b...First magnetic field generating means 23a...No. 2/〆23d...3rd 27...Carrier particles 28...Toner particles (toner) Figure 1 Figure 2

Claims (1)

[Scope of Claims] A developing device for developing an electrostatic latent image on an electrostatic latent image carrier, comprising: a developer container containing a developer having toner particles and carrier particles; and the electrostatic latent image. a developer carrying member that faces the carrier and forms a developing section that supplies toner particles to the electrostatic latent image carrier, and carries and conveys developer from the container to the developing section; a developer regulating member having a regulating portion distal end located upstream of the developing section in the rotational direction of the body and spaced apart from the surface of the developer carrying member; provided on the opposite side of the regulating member of the developer carrying member; a first magnetic field generating means located upstream of the developer regulating member with respect to the rotational direction of the developer carrier; and a first magnetic field generating means provided on a side of the developer carrier opposite to the regulating member;
a second magnetic field generating means located upstream of the developer regulating member in the rotation direction of the developer carrier and corresponding to the inside of the developer container; the half-width is 25° or more, and the distance within the container between the half-width and the half-width of the magnetic force by the second magnetic field generating means is 20° or more;
A developing device characterized in that the angle is 40° or less.