JPS63225271A - Developing device - Google Patents

Abstract

PURPOSE:To activate the movement of magnetic particles with respect to a sleeve and to increase the electric charge quantity of a toner on the sleeve by forming a magnetic field nearly covering the aperture surface on the inside of a developing container and forming a closed loop of magnetic force near the sleeve surface therein. CONSTITUTION:A magnetic field generating means 101 consists of 4 poles; 101a-101d and is set at the magnetic force smaller than the magnetic forces of magnetic poles 23a-23d. Magnetic lines 102 of force run mainly between the magnetic poles 23a and 23d on the aperture face of the developing container side and form the closed loop of the magnetic lines of force only near the surface of the developing sleeve 22 by the magnetic poles 101a-101d. On the other hand, the magnetic poles 101a-101d are set at the magnetic flux density slightly lower than the magnetic flux density of the magnetic pole 23a and the magnetic pole 23d. The electric charge quantity of the toner on a developer carrier is thereby increased and the electrostatic charge quantity of the toner adhered to the magnetic particles 27 is increased. The uniform development having no fogging, etc., is thus permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-component development type developing device that performs development using magnetic carrier particles and toner particles.

The present invention is a developing device that can be applied to various types of display devices for forming image records, printers, and facsimile electrophotographic devices.

[Background technology]

The applicant of the present application has provided an apparatus which performs development by supplying only one-component toner to the developing section, with a two-component toner inside the developing container and a one-inch difference in image power.

This is done by first putting magnetic particles into a developer supply container.
The particles are adsorbed and held as a magnetic particle layer (first layer) on the inner surface of the developer supply container of the rotationally driven developing sleeve.
Next, toner is added and stored outside the magnetic particle layer (
(2nd layer) and then developed (Japanese Unexamined Patent Application Publication No. 59/1989)
-204866, Japanese Unexamined Patent Publication No. 59-204867).

These devices bind magnetic particles in a developing container, and as the developing sleeve rotates, some of the trapped magnetic particles circulate on the sleeve. Through this circulation, replenishment toner is absorbed into the magnetic particles and a thin layer of toner is deposited on the sleeve. It formed a single layer. This is extremely important as it also discloses the basic structure of mixing and agitating magnetic particles and toner on a sleeve, and its effects were far superior to devices that did not employ this basic structure. In particular, it was unparalleled in terms of the simplicity and miniaturization of the device. However, even if a uniform thin layer of toner can be formed on the sleeve through this circulating action, if development is carried out over a long period of time or if some kind of impact is applied when the developing device is made removable from the image recording apparatus main body, It has been confirmed that this circulation becomes unstable, causing problems such as image deterioration. However, these inconveniences were minor drawbacks in light of the unique features and advantages mentioned above.

Through numerous experiments, the applicant was able to resolve these disadvantages and actively supply magnetic carrier particles to the developing section2.
A developing device that produces great effects in a component developing device is proposed in Japanese Patent Application No. 1983-204605 (filed on September 17, 1985) [Example] Figure 5 shows a cross section of such a developing device. It is a diagram.

The latent image carrier 1 is an insulated drum for electrostatic recording or α-3e.
, CdS, Zn0z, OPC, a-3i. The latent image carrier 1 is rotated in the direction of arrow a by a drive device (not shown). A developing sleeve 22 is in close proximity to or in contact with the latent image carrier 1, and is made of a non-magnetic material such as aluminum or 5O8316. The developing sleeve 22 has a right half-circumferential surface extending into the container 36 through a horizontally elongated opening formed in the lower left wall of the developing container 36 in the longitudinal direction of the container, and a left substantially half-circumferential surface exposed outside the container so as to be rotatably supported on a bearing. It is installed horizontally and is driven to rotate in the direction of the arrow.

Reference numeral 23 designates a fixed permanent magnet (magnet) as a fixed magnetic field generating means that is inserted into the developing sleeve 22 and positioned and maintained at the position and orientation shown in the figure. It remains fixed in its position.

This magnet 23 has an N-pole magnetic pole 23a, an S-pole magnetic pole 23b,
It has four magnetic poles: an N-pole magnetic pole 23c and an S-pole magnetic pole 23d. The magnet 23 may be an electromagnet instead of a permanent magnet.

24 is the hot water JTIII in front of the developer supply device where the developing sleeve 2 is installed.
The non-magnetic blade as a developer regulating member is arranged along the length of the upper edge of the opening and protrudes outward from the upper edge of the container 36 than the upper edge of the opening. It is processed.

Reference numeral 26 denotes 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 a developer guide surface 261.

27 is a magnetic particle, which is a resin-coated ferrite particle (maximum magnetization 60 emu/g) having a particle size of 30 to 100 μm, preferably 40 to 80 μm, and a resistance value of 10 Ωcm or more, preferably 10' Ωcm or more. obtain.

37 is a non-magnetic developer toner.

Reference numeral 31 denotes a developing sleeve 22 on the inner surface of the lower part of the developing container in order to prevent leakage of magnetic particles 27 or non-magnetic toner particles 37 from the lower part of the developing container 36 in which the developing sleeve 22 is disposed.
A magnetic material placed opposite to the magnetic material, such as a plated iron plate. Magnetic body 31 and S polarity magnetic pole 23
A sealing effect that achieves collection of the magnetic particles 27 and prevention of leakage can be obtained by the magnetic field between the magnetic particles 27 and d.

Reference numeral 39 denotes a toner supply member that supplies toner to the brush portion of magnetic particles formed by the fixed magnetic pole 23 in the developing sleeve 22. A rubber sheet is pasted on a rotatably bearing plate, and a rubber sheet is attached to the bottom surface of the developing container. (Toner is transported.)

The toner supply member 39 includes a toner storage container 38 (not shown).
The toner is supplied by a toner conveying member inside.

38 and 35 are a toner storage container and a magnetic particle storage container, respectively.

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

Reference numeral 30 denotes a scattering prevention electrode plate that applies a voltage of the same polarity as the developer to cause the floating developer generated in the developing process to adhere to the photoreceptor side and prevent it from scattering.

Further, the S magnetic pole 23d is a magnetic field generating means for the magnetic sole for forming a magnetic field from one side to the other between the S magnetic pole 23d and the magnetic member 31, and a portion thereof faces the magnetic member 31. The magnetic member 31 is located below the developing device at the substantial end of the developer accommodating portion of the developer container, and around the inside of the container, the collected magnetic carrier particles move to cause the developer on the sleeve surface to Captures toner particles located lower inside the container.

Therefore, stable collection of magnetic particles has the effect of stabilizing the developing ability.

The magnetic member 31 has a "<" or "L" shape, and can be made of a magnetic material that is not permanently magnetized, such as iron, or a non-magnetic material that is made weakly magnetic by deforming it. In addition, when using a magnet as the magnetic member 31, the flat surface 6
6 must have an N polarity that is different from the magnetism S of the magnet S.

In other words, the magnetic member 31 restrains the magnetic particles while preventing loss of the magnetic particles, and also facilitates the recovery of the magnetic particles, thereby preventing the toner particles in the developer container from leaking out of the container.

Furthermore, by arranging the magnetic pole 23d as described above, another favorable effect can be obtained in relation to the magnetic pole 23a. That is, due to the above-mentioned relationship between the bottom of the container 36 and the magnetic pole 23d, the magnetic brush is not formed in an ffl state (compared to a merely stagnant state) within the container 21, so that toner particles do not enter the magnetic particles. The amount of intake will not become excessive. Excessive uptake leads to insufficient charging of the toner and causes fogging.

Note that this configuration is also effective when magnetic particles and non-magnetic or weakly magnetic toner coexist in the developer container.

According to experiments, the distance between the developing sleeve and the magnetic member 31 is 2.
．． At 5 mm, the magnetic carrier particles were completely recovered, no leakage of toner particles was observed, and stable development was achieved. The presence of the surface 66 in this region is considered to be because the surface 66 appropriately disperses the magnetic force of the magnetic pole 23d, thereby substantially increasing the magnetic force in this region.

The distance d2 between the end of the non-magnetic blade 24 and the surface of the developing sleeve 22 is 50 to 800 μm, preferably 150 to 5 μm.
00 μm. If this distance is smaller than 50 μm, magnetic particles 27 (described later) will clog between this distance, causing unevenness and cracking in the developer layer, as well as making it impossible to apply the developer necessary for good development. The drawback is that only developed images with a large number of defects can be obtained. If the diameter is larger than 800 μm, the amount of developer applied onto the developing sleeve 22 increases, making it impossible to regulate the thickness of the developer layer to a predetermined value, increasing the amount of magnetic particles attached to the latent image carrier, and circulating the developer as described below. , the development regulation by the developer limiting member 26 is weakened), and the developer tribo is insufficient, resulting in easy fogging.

Even when the sleeve 22 is rotated in the direction indicated by the arrow, this magnetic particle layer maintains the magnetic force 9 and the restraining force based on gravity and the sleeve 22.
Due to the balance with the conveying force in the moving direction, the movement slows down as the distance from the sleeve surface increases, and above the magnetic particle layer, a stationary layer is formed that is mostly floating, although it can move to some extent. Of course, some things fall due to the influence of gravity.

Therefore, by appropriately selecting the arrangement positions of the magnetic poles 23a and 23d and the fluidity and magnetic properties of the magnetic particles 27, the closer the magnetic particle layer is to the sleeve, the more the magnetic particle layer is transported in the direction of the magnetic pole 23a, forming a moving layer. Due to this movement of the magnetic particles 27, the magnetic particle layer (first layer) takes in toner from the toner layer (second layer), and the toner receives frictional electrification due to the sliding friction with the magnetic particles 27 or the sleeve 22, and the rotation of the sleeve 22. Along with this, the image is transported to the development area and subjected to 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 stationary layer becomes small and most of the magnetic particle layer moves quickly, causing the toner to move from one layer to the other. Incorporate. Also, when the toner content is high, the static layer becomes large and the moving layer of magnetic particles cannot contact the toner layer covered by the static layer and hardly takes up toner. Therefore, some toner content is naturally maintained.

Next, the magnetic particle layer near the non-magnetic blade 24 and the limiting member 26, which are developer application amount regulating members, will be described. The limiting member not only mechanically prevents unnecessary entry of replenishment toner into the developer regulating section. As previously mentioned,
In the restriction area where the member 26 is surrounded by the sleeve, the magnetic particles transported by the magnetic pole N and the pole as the sleeve rotates are packed along the guide surface 261 of the restriction member 26 and become dense. In this region, the magnetic particles that are transported into the blade are dynamically replaced by the magnetic particles that flow out from the blade, causing the magnetic particles to collide with each other and create a state of disturbance. Therefore, triboelectricity is applied to the toner from the top of the magnetic particles or sleeve, and triboelectricity that has been attached to the magnetic particles or sleeve with a weak force and transported is in a substantial backing state. Small toner is separated from the magnetic particles or the sleeve. In other words, toner is sorted and charged uniformly. Therefore, toner with sufficient triboelectricity can be used for development. Also, the transport of magnetic particles The non-uniform state at the time is also averaged out in the space, and uniformity and stabilization of the coating of the magnetic particle layer can also be achieved.

Therefore, the guide surface 261 is essential for the limiting member 26,
The slope of the slope and the volume of the space have a large effect on the backing state of the magnetic particles in the space.

On the other hand, the magnetic pole 2 fixedly arranged with respect to this area
3a rearranges the magnetic particles in the backing state along the lines of magnetic force. The backing state in this space is unstable with respect to tribo-imposition, and a constant backing state is always required to stabilize it. This creates a magnetic brush by applying a force perpendicular to the direction of the magnetic particles conveyed on the sleeve in an almost tangential direction, which not only has a stirring effect on the magnetic particles but also has a stripping effect, and the toner particles are The uniformity and stabilization of the application of triboelectric particles and the application of the magnetic particle layer are further promoted. At this time, there is a problem that the developer is concentrated due to the surrounding structure, but by having the portion of the magnetic pole 23a that generates the maximum magnetic force facing the guide surface 261, excessive concentration of pressure in the regulated area is prevented. It is considered that the concentration of the developer and the stable high-density magnetic particle abundance ratio can be maintained.

Due to the above-mentioned regulation area, a stable amount of magnetic particles and sufficiently charged toner particles can be formed as a thin layer of developer on the surface of the developing sleeve. Therefore, the development effect in the development area 111 becomes stable. And an alternating electric field forming means for forming an alternating electric field in the developing section that causes at least the toner particles carried on the surface of the developer carrying member to be transferred to the electrostatic latent image carrying member. in the developing section, the volume occupied by the magnetic particles of the developer conveyed to the developing section with respect to the volume of the space defined by the electrostatic latent image carrier and the developer carrying member; It was confirmed that the developing method and apparatus having a ratio of 1.5% to 30% have a great effect.

IVII + field to the flute! This figure shows a case where a magnetic body 50 is installed on the side of a non-recorded book on the 9th day.

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 face each other, a strong concentrated magnetic field is generated between the magnetic pole 23a and the magnetic pole 23a.
This is because the effect of stirring and loosening the magnetic particles is reduced. However, it is effective to provide a magnetic material in the regulating portion and to magnetically regulate the magnetic particles between the regulating member and the sleeve internal magnet 23, since this increases the gap between the regulating member and the sleeve. In addition, I/I attached to the magnetic particles or sleeve
Comparing toners, the amount of charge on the toner deposited on the sleeve is smaller than that on the magnetic particles. The reason for this is that as the sleeve moves, the magnetic particles are also transported, which reduces the chance that the toner on the sleeve will be rubbed by the magnetic particles. In order to lift the toner on the sleeve to a predetermined amount of charge, it is necessary to actively rub the toner on the sleeve.

That is, it is necessary to have magnetic particles near the sleeve surface that cause a shift in relative velocity against the movement of the sleeve.

However, it is impossible to simply reduce the transportability of magnetic particles when considering the above-mentioned toner uptake effect.

Furthermore, as described above, it is also possible to dispose a magnetic material in the regulating section facing the magnetic pole 23a in the sleeve to generate a concentrated magnetic field and to direct the sliding force of the magnetic particles onto the sleeve. The effect of arranging the maximum magnetic force generating portion of the magnetic pole in the space created by the agent circulation regulating member 26 is reduced.

[Purpose of the invention]

However, when the device described above, in which only one magnetic field generating magnetic pole is provided in the opening area of the developer container, is miniaturized, the contact area between the mixing of toner particles and carrier particles and the contact area of the toner particles with the sleeve surface becomes smaller. becomes small, and the amount of charge on the toner particles as a whole decreases, which may lead to poor development.

An object of the present invention is to increase the amount of charge of toner on a developer carrier and to increase the charge 1 of toner attached to magnetic particles, thereby performing uniform development without fogging or the like.

[Summary of the invention]

The present invention is characterized in that a small closed loop is formed within the container, creating an environment that provides a sufficient charge to the mixed developer. That is, the present invention provides a developing device that develops a latent image using a developer having carrier particles and toner particles in a developing section, and a developer container containing a developer having toner particles and magnetic particles; a developer carrying member that faces the latent image carrying member and forms a developing section that supplies toner particles to the latent image carrying member, and carries and conveys the developer from the container to the developing section; The developer carrier has a magnetic field generating means made of a plurality of magnetic poles inside the developer carrier, and a means for regulating the amount of developer applied on the surface of the developer carrier, and the regulation with respect to the rotational direction of the developer carrier. A magnetic field is formed between a magnetic pole immediately upstream of the means and a magnetic pole immediately upstream of the wall surface of the developer container further upstream, and a closed loop of minute magnetic lines of force is formed on the surface of the developer carrier between the two magnetic poles. According to
Since the movement of the magnetic particles on the sleeve surface is activated and the amount of charge of the toner adhering to the sleeve surface and the magnetic particles can be set to a predetermined value, a good image without fogging etc. can be obtained.

〔Example〕

FIG. 1 shows a hot water level that best represents the features of the present invention, and since the same reference numerals as those of the developing device shown in FIG. 5 are used, a detailed explanation of the same reference numerals will be omitted.

In FIG. 1, reference numeral 101 denotes a magnetic field generating means that is located within the developing sleeve 22 and forms a loop of magnetic lines of force near the circumferential surface of the developing sleeve 22 at the opening on the side of the container 36. In this embodiment, the magnetic field generating means 01 is a magnet having a plurality of magnetic poles facing the surface of the sleeve 22. Magnetic field generating means 10
FIG. 2 shows the state of the magnetic field in the vicinity of the developing sleeve 22 according to No. 1. In this embodiment, the magnetic field generating means 101 includes 101 a, 10 l b, 101 c,
Consists of 4 poles of 101 d, magnetic poles 23a, 23b, 2
3c.

23d, and as shown in FIG. ~101d forms a closed loop of magnetic lines of force. The magnetic flux density of the magnetic poles 23a and 23d is preferably 500G or more, preferably 600G or more.

On the other hand, magnetic pole 101 a, magnetic pole 10 l b, magnetic pole 10 I
c. The magnetic flux density of the magnetic pole 101d is set to be lower than that of the magnetic poles 23a and 23d. For example, it is preferably 500G or less, preferably 400G or less.

Returning to the developing device shown in FIG. 1, the magnetic particle layer in the developing container 36 is mainly formed along the lines of magnetic force caused by the magnetic poles 23a and 23d, so the magnetic particle stationary layer is formed by the magnetic poles 23a and 23d.
The spikes of magnetic particles formed between the magnetic poles 101a to 101d are covered with a stationary layer and do not come into direct contact with the toner. Excess toner is not supplied from the area (where the density of magnetic particles is lower than in areas where this is not the case).

The toner taken in from the most upstream side of the magnetic particle layer moves along with the magnetic particles near the surface of the sleeve 22 toward the regulating section. At this time, each time the magnetic particles pass through the magnetic poles 101d to 101a, they rotate on the developing sleeve 22, causing a deviation in relative motion against the movement of the sleeve, so that the toner adhering to the sleeve surface is actively rubbed. This makes it possible to increase the amount of charge of the toner on the sleeve to a predetermined value. Furthermore, the toner on the magnetic particles also has more uniform tribo due to the rotation of the magnetic particles. As a result, the toner adhering to the sleeve and the toner adhering to the magnetic particles become uniform in tripod, providing good development characteristics and making it possible to obtain stable images.

In this embodiment, the magnet 101 that faces the opening on the side of the developer container and forms a closed loop of magnetic lines of force near the circumferential surface of the sleeve has four magnets.
Although the magnet is composed of poles, it is not limited thereto, and may have four or less poles, for example, two poles, or four or more poles.

It is preferable that the magnet 101 covers a range of 10 to 60% of the inner opening of the container 36 with the center of the opening as the center. If the magnet 101 extends to the most upstream side of the opening, if a small magnetic pole exists near the toner intake port of the magnetic particle layer, toner will be taken in excessively, which is undesirable; This is not preferable because the state of application of the developer is unstable, and the range is preferably 10 to 60%, more preferably 20 to 50%, with the center of the dowel opening as the center.

The magnetic flux density of the magnetic pole 23a is preferably 500G or more, preferably 700G or more. This is because the state of application of the developer tends to be more stable with respect to changes in the toner content of the magnetic particle layer as the magnetic flux density of the cut magnetic pole is higher. In particular, in the developing device of the present invention which does not have an automatic toner replenishing device to maintain toner content, it is preferable that the magnetic flux density be 800 G or more.

In FIG. 1, the magnetic pole 23c is a developing magnetic pole, and this developing magnetic pole is located in the developing area, 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 also includes a method for controlling the floating amount of each soot layer as described above.

In any case, the present invention can provide high image quality that could not be obtained with conventional developing methods and devices, and has the excellent effect of making the developing device small and disposable.

The toner supply member 39 is located in the developer container 36 and is driven to rotate in the direction of arrow d while being close to or in contact with the magnetic particle layer to supply toner 37 to the magnetic particle layer.

A toner storage container 38 for storing toner is arranged approximately horizontally adjacent to the developer container 36, and a toner transporting member (
(not shown) is provided.

The S magnetic pole 23b is a transport magnetic pole provided to prevent the developer layer uniformly applied by the non-magnetic blade 24 from being disturbed due to the large distance between the cut magnetic pole 23a and the developing magnetic pole 23c. The strength of the S magnetic pole 23b is approximately equal to that of the developing magnetic pole 23c in order not to disturb the developer layer.
A little low is good. When a 20φ developing sleeve is used, if the distance between the cut magnetic pole and the developing magnetic pole is within 100° at the center angle of the sleeve, the developer layer on the sleeve will not be disturbed, but if it exceeds 1000°, the developer layer will be disturbed. Since the disturbance is large, it is preferable to provide a transport pole in the middle.

The S magnetic pole 23d is a collection magnetic pole that collects the developer after development, and is arranged upstream of the tip of the magnetic seal 31 in the moving direction of the developing sleeve 22. The magnetic pole 23d is the magnetic seal 31
When placed on the downstream side from the tip, a spike of magnetic particles is generated by the magnetic pole 23d near the toner intake port at the bottom of the developer container 36, which makes it extremely easy to take in toner, resulting in insufficient frictional electrification and fogging. easy to become.

Here, the volume ratio of magnetic particles in the developing section will be explained. The "developing section" refers to the area from the sleeve 22 to the photosensitive drum 1.
This is the part to which toner is transferred or supplied. 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. In the above-mentioned developing device, this volume ratio has an important influence, and it is highly preferred that it be between 1.5 and 30%, particularly between 2.6 and 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 in that the thickness of the developer layer formed is non-uniform throughout.

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

In particular, the above-mentioned conditions listed as a preferable developing method for the present invention are such that the image quality does not monotonically deteriorate or increase as the volume ratio increases or decreases (1,5-30
The fact is that sufficient image density can be obtained in the range of 1.5%, image quality will deteriorate if it is less than 1.5% or more than 30%, and neither sleeve ghost nor fogging will occur in the range of the above values where image quality is sufficient. It is based on The former image quality deterioration is thought to be due to negative characteristics, and the latter is thought to occur because the amount of magnetic particles present increases and the sleeve 22 surface cannot be opened, resulting in a significant decrease in toner supply 1 from the sleeve 22 surface. It will be done.

Further, if it is less than 1.5%, the reproducibility of line images is poor and the image quality and density are significantly lowered. On the other hand, if it exceeds 30%, there will be problems with the magnetic particles damaging the photosensitive drum surface and problems with transfer and fixing caused by the magnetic particles adhering as part of the image.

When the presence of magnetic particles is close to 1.5%, when reproducing a large-area uniform high-density image (solid black),
Since there are cases where partial development unevenness called ``developing unevenness'' occurs (under special circumstances, etc.), it is preferable to set a volume ratio that makes it difficult for these 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. In addition, if the presence of magnetic particles is close to 30%, a film is applied around the area where the ears of magnetic particles come into contact.
, -^ L Fu - T Mouth Buddha Koi 3 Also 1 Kendanmu r old 1 can speed is high), which may cause scale-like density unevenness when reproducing solid black. As a reliable range to prevent this, the above volume ratio of magnetic particles is 26
% or less is more preferable.

If the volume ratio is in the range of 1.5 to 30% (set to 4% in the example), the ears 51 are formed on the surface of the sleeve 22 in a preferable sparse state as shown in FIG.
The toner of both the sleeve 22 and the planting soil is on the photosensitive drum 1.
Since the toner 100 on the sleeve is also transferred by flight due to the alternating electric field, almost all the toner is in a state where it can be consumed for development, resulting in high development efficiency (
The proportion of toner present in the development section that can be consumed for development) and high image density can be obtained. Preferably,
A slight but strong vibration of the spike is caused, thereby causing magnetic particles and the toner 10 attached to the sleeve 22.
0 is loosened.

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 magnetic particles 27 and the toner 37, thereby improving the frictional charging of the toner 37 and preventing the occurrence of fogging. Note that a high developing efficiency is suitable for downsizing the developing device. The magnetic pole in FIG. 6 is an S pole 23b, which is different from the developing pole 23c in FIG. 5, but either one may be used in this example.

The volume ratio of the magnetic particles 27 existing in the developing section is (M/
h)X (1/ρ) crtr
), h is the height of the developing section space (cm), ρ is the true density of the magnetic particles g/crd, and C/(T+C) is the weight ratio of the magnetic particles in the developer on the sleeve.

Note that 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 ears separate from the sleeve 22 or from its base, and the separated magnetic particles 27 are placed between the sleeve 22 and the photosensitive drum 1. make a reciprocating motion in the space of 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 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 ears and reduce vibration,
Since the gaps are large on the inlet and outlet sides of the developing section, sufficient vibration occurs to produce the above-mentioned effect.

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

In Fig. 6, the sleeve 22 is an aluminum sleeve with a diameter of 20 mm whose surface has been subjected to irregular sandblasting using Alundum abrasive grains, and the magnet 23 is a 4-pole magnet with alternating north and south poles. there was. 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.

The non-magnetic toner is a toner powder with an average particle size of 10μ consisting of 100 parts of styrene/butadiene copolymer resin and 5 parts of copper phthalocyanine pigment, and 0.6 parts of colloidal silica.
When using blue toner with external addition of %, sleeve 2
A toner coating layer with a thickness of 10 to 30 .mu.m was obtained on the 2 surface, and a magnetic particle layer of 200 to 300 .mu.m was further formed as an upper layer thereon. 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 about 2.43×10 −2 g/Crtr.

At this time, the weight ratio of the toner attached to the magnetic particles and the toner attached to the sleeve was about 2:1.

The magnetic particles are raised by the magnetic field generated by the magnetic pole 23c in the sleeve 22 in the developing section and its vicinity, and the maximum summary 1.
It formed a standing brush about 2 mm in diameter.

The amount of charge on the toner was measured using the following method for the toner on the sleeve and on the magnetic particles. The magnetic particles in the development area of the development sleeve were collected using another magnet, and the toner on the magnetic particles and the sleeve were collected. The remaining toner was measured using a suction type Faraday gauge.

As a result, in the developing device shown in Figure 5, the triboelectricity on the magnetic particles was +13μC/g, while the triboelectricity on the toner on the sleeve was +10μC/g, and the overall average was 12μC/g. On the other hand, in the developing device of this embodiment, the toner on the sleeve was 14 μC/g compared to +16 μC/g on the magnetic particles.
The average tribo was +15 μC/g, and tribo UP of the toner on the sleeve was confirmed.

This developing device was installed in a Canon PC-10 copier (manufactured by Kiki), and photosensitive drum 1 (made of organic photosensitive material) and sleeve 2 were installed.
The distance from the surface of No. 2 was 350 μm. When the volume ratio was determined under these conditions, it was approximately 10%. (h=350μm
, M=2.43×10-2g/crt? , ρ=5.5
g/crrr. T/(T+C)=20.4%). When development was carried out using a bias power supply 4 with a frequency of 1600 Hz and a peak-to-peak value of 1300 V AC voltage superimposed with a DC voltage of -300 V, 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 l-toner attached to the magnetic particles and the toner on the sleeve were consumed, and development was performed with nearly 100% development efficiency.

As for development characteristics, there was no fog, and good development characteristics could be obtained.

Furthermore, regarding the effects of the magnetic member 31, it was confirmed that good penetration of magnetic particles, prevention of leakage, and good circulation were achieved.

As explained above, according to this embodiment, high image density,
High development efficiency eliminates fogging and ghost images.

Development can be performed without uneven sweeping or negative characteristics.

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 elastic body, for example, a conductive sponge, may be wound around the circumferential surface of the core roll.

Regarding the magnetic pole 23c 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.

Silica particles may be externally added to the toner to improve fluidity, and abrasive particles may be added to the toner to polish the surface of a photosensitive drum, which is a latent image holding member in a transfer image forming method, for example. A toner containing a small amount of magnetic particles may also be used. That is, magnetic toner can also be used as long as it has significantly weaker magnetism than magnetic particles and can be tribocharged.

In order to prevent the ghost image phenomenon, the surface of the sleeve 22 that has returned to the container 36 and has been rotated is removed from the sleeve 22 without being subjected to development.
The developer layer remaining on the magnetic particle layer 2 may be once scraped off 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.

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

The developing device of the present invention includes a container 36. It can be used as a single-use type developer in which the sleeve 22, blade 24, etc. are integrated, or as a regular developer fixed to an image forming apparatus.

It is also possible to use toner with a particle size of about 1 to 10 μm in order to improve the image quality of the developed image.
A magnetic field generating member (magnet) is used as a member that forms a closed loop of lines of magnetic force near the circumferential surface of the developing sleeve, and the lines of magnetic force formed by the magnetic poles 23a and 23d in FIG. 5 are bent to form a closed loop of lines of magnetic force near the circumferential surface of the developing sleeve. may be formed. FIG. 3 shows a magnetic body 103 attached to a magnet roll 23, and lines of magnetic force 10 near the circumferential surface of the developing sleeve.
2 is once drawn into the magnetic body 103 in the developing sleeve to form a closed loop of magnetic lines of force near the circumferential surface of the developing sleeve.

FIG. 4 is a cross-sectional view of a developing device equipped with the magnet roll shown in FIG. 3. Components equivalent to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

As the magnetic body 103, materials such as iron, nickel, permalloy, etc. can be used. As for the size of the magnetic body, a mass is required to draw in the lines of magnetic force near the circumferential surface of the sleeve, and in this example, the material is iron, and the material is 1.2 mm thick and 5 mm long. Rotational motion of the magnetic particles is observed near the groove provided at approximately the center of the sleeve, and the tribo on the sleeve is made uniform.

Furthermore, in this embodiment, since a magnetic material is used as the magnetic force line closed loop forming member, deterioration such as demagnetization of the magnetic force line closed loop forming member itself does not occur, which is preferable.

Further, in this embodiment, the number of magnetic bodies 103 attached to the magnet roller 23 is one, but it is of course possible to use a plurality of magnetic bodies 103.

〔Effect of the invention〕

As explained above, by forming a magnetic field that almost covers the inner opening surface of the developer container and forming a magnetic closed loop near the sleeve surface within the magnetic field, the movement of the magnetic particles relative to the sleeve can be activated, and It becomes possible to sufficiently increase the amount of charge of the toner, and it is possible to obtain good development characteristics and provide high-quality images.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a developing device embodying the present invention.
2 and 3 are respectively magnetic field line diagrams of the magnet roll used in the present invention, FIG. 4 is a schematic diagram of a developing device using the magnet roll of FIG. 3, and FIG. 5 is an explanatory diagram of the background art. FIG. 6 is a diagram showing the state of the developer in the developing section. ■...Latent image bearing pair, 22...Developing sleeve,
23... Magnet roll, 24... Regulating member, 2
7... Magnetic particles, 37... Toner particles,
38... Toner storage container, 39... Toner supply member, 40... Seal member,
31...Magnetic seal, 101...Magnetic field generating means (closed loop forming member), 10
3 magnetic material (closed loop forming member).

Claims (3)

[Claims] (1) In a developing device that develops a latent image using a developer having carrier particles and toner particles in a developing section, a developer container containing a developer having toner particles and magnetic particles and a latent image carrying the latent image. A developing section that faces the carrier and supplies toner particles to the latent image carrier is formed, and a developer carrier that carries and conveys the developer from the container to the developing section, and a plurality of developer carriers inside the developer carrier. and a means for regulating the amount of developer applied on the surface of the developer carrier, wherein the magnetic field generating means is configured to control the amount of developer applied to the surface of the developer carrier with respect to the rotating direction of the developer carrier. It has a magnetic pole 1 immediately upstream and another magnetic pole 2 further upstream on the wall surface of the developer container, forming a magnetic field between both magnetic poles, and creating a closed loop of minute magnetic lines of force near the surface of the developer carrier between the two magnetic poles. A developing device characterized by having a closed loop forming member that forms a closed loop. (2) The developing device according to claim 1, wherein the closed loop forming member is a magnet. (3) The developing device according to claim 1, wherein the closed loop forming member is made of a magnetic material.