JPS6314182A - Developing device - Google Patents

Abstract

PURPOSE:To enable fast development by extending a horizontal magnetic field which is produced by a magnetic field generating device for development to the closest part, and forming a developer reservoir on the upstream side of the closest part between a developer carrier member and a latent image carrier. CONSTITUTION:When a sleeve 22 is rotated as shown by an arrow, magnetic particles are elevated along the surface of the sleeve 22 from the lower part of a container 21 to reach the periphery of a blade 4. Some of the magnetic particles pass the gap between the tip of a blade 24 and the surface of the sleeve 22 together with toner and the remainder is turned over to fall by gravitation outside the elevation path of the magnetic particles and reach the lower part of the container 21 and then elevated again nearby the sleeve 22, thus repeating this operation. A developer formed on the surface of the sleeve 22 is sent through the rotation of the sleeve 22 and banked in front of the nearest part between a photosensitive drum 1 and sleeve 22 through the operation of a magnetic pole 23b, and the developer develops a latent image image on a photosensitive drum 1 while moving as shown by an arrow. Consequently, ground fogging is eliminated and a small-sized fast developing device is obtained.

Description

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

1] Various methods have been proposed and put into practical use as conventional dry developing methods. However, in the mainstream two-component magnetic brush abrasion development, abrasion marks occur in solid image areas, which increases the rotation speed of the sleeve.

It is necessary to increase the amount of developer applied to the sleeve. For this reason, the developing device configuration has become lower and more complex, and toner and
Carrier scattering became a problem. Therefore, in order to solve the above problem, a method has been proposed in which the amount of magnetic carrier applied to the sleeve is reduced, the ratio of toner to carrier is increased, and an alternating electric field is applied to achieve excellent image formation (particularly When performing even higher speed development, this proposal increases the toner to carrier ratio, which may result in insufficient friction between the toner and the carrier. At this time, some toner was not sufficiently charged, causing a problem of smudging of the image due to ground blur, and furthermore, there was a problem with toner scattering.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a developing device that can achieve high-speed development without increasing the size or complexity of the developing device. The purpose of this particularly special embodiment is to reduce the amount of magnetic carrier applied to developer carriers such as sleeves and belts, and to suppress the ratio of toner to carrier to a low level.
It is an object of the present invention to provide a developing device capable of preventing carrier scattering.

According to the present invention, there is provided a developing device for developing an electrostatic latent image on an electrostatic latent image carrier, and a developer container containing a developer having toner particles and magnetic particles. and forming a developing section facing the electrostatic latent image carrier for supplying toner particles to the electrostatic latent image carrier, and supplying toner particles and a small amount of magnetic particles from the container to the developing section. a developer supporting member that carries and conveys the developer; a developer regulating member that is located upstream of the developing section in the rotational direction of the developer carrier and has a regulating portion distal end spaced apart from the surface of the developer carrier; and the developer. Provided on the side of the supporting member opposite to the regulating member, and provided upstream of the closest portion with respect to the rotational direction of the developer carrier, avoiding the closest portion between the developer carrying member and the latent image carrier. between the developer carrying member and the latent image carrier and from the nearest part so that the horizontal magnetic field generated by the developing magnetic field generating means reaches the nearest part. Also provided is a developing device characterized in that a developer reservoir is formed on the upstream side. According to this, it is possible to provide a developing device that is compact and capable of achieving high-speed development without ground force blur.

View j FIG. 1 is a sectional view of a developing device according to an embodiment of the present invention.

In this figure, reference numeral 1 denotes an electrostatic latent 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.

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. It has a regulation blade 24 (hereinafter referred to as a blade) for controlling. Each configuration will be explained below.

Container 21 contains a developer having a mixture of magnetic particles 27 and toner particles 28 . 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. .

A developing section is configured between the sleeve 22 and the latent image carrier.

Toner and magnetic particles are conveyed to this developing section by a sleeve 22.

The magnet 23 is fixed statically inside the sleeve 22 and remains stationary even when the sleeve 22 rotates. The magnet 23 has an N magnetic pole 23a that cooperates with a blade 24 (to be described later) to control the amount of developer applied onto the sleeve 22, and a Sai pole 23 that is a developing magnetic pole.
b. It has an N magnetic pole 23c and an S magnetic pole 23d that transport the developer into the container 21 after passing through the developing section. The S and N poles may be reversed. Although this magnet is a permanent magnet in this example,
An electromagnet may be used instead.

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 a container 21, and its distal end is fixed to a sleeve 22.
facing the surface with a gap.

The power supply 34 applies a voltage between the latent image carrier 1 and the sleeve 22 to form an alternating electric field in the gap between them, thereby transferring the toner from the developer on the sleeve 22 to the latent image carrier 1. let 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.

The lower part of the container 21 extends in the direction of the latent image carrier 1 to form an extension, which prevents the developer (particularly toner particles) from leaking to the outside.

Here, the developing magnetic pole 23b, which is a feature of the present invention, will be explained in detail.

The developing magnetic pole 23b is set to be shifted by about 15 degrees upstream in the sleeve advancing direction from the closest point between the image carrier 1 and the sleeve 22. Further, the closest portion is set to be located within the magnetic flux density distribution 27 of the developing magnetic pole 23b. The distance fi (SD distance AI) between the image carrier l and the sleeve 22 is approximately 350
JLm (nearest part), and the height of the brush ears of magnetic particles was (nearest part) ~1.0 to 1.5 mm.

Amount of developer applied on the sleeve (5 to 10 particles after dispersion)
X 10-2g/ctrl. ) The height of the spike is 3 to 5 times the S-D distance, and by shifting the developing pole by 15 degrees to the upstream side, a sufficient developer pool (carrier pool) is created on the upstream side of the closest part. Furthermore, as the image carrier 1 and sleeve 22 move, active movement of the developer occurs as shown in FIG. 1.

Next, the operation of the developing device of this embodiment will be explained.

When the sleeve 22 is rotated in the direction of the arrow, the magnetic 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 magnetic particles are transferred to the blade 24 along with the toner.
passes through the gap between the tip of the magnetic particle and the surface of the sleeve 22, and the other part reverses and descends by gravity on the outside of the ascending path of the magnetic particles to reach the lower part of the container 21, and rises near the sleeve 22 again to form the above-mentioned The operation is repeated, during which the toner particles and magnetic particles are stirred by the stirring screw 25. By circulating and stirring in this way with the rotation of the sleeve 22, the toner is charged by friction with the magnetic particles and the surface of the sleeve 22. .

Near the front of the blade 24, the magnetic particles 27 near the surface of the sleeve 22 are attracted to the surface of the sleeve 22 by the magnetic pole 23a, and as the sleeve 22 rotates, the blade 2
4 and exits the container 21. At this time, the magnetic particles 27 carry out the toner attached to the surface thereof, and some of the charged toner particles 28 leave the container on the sleeve 22 while remaining attached to the surface of the sleeve 22 by reflection force. Blade 24 regulates the amount of developer applied onto sleeve 22.

The developer (mixture of magnetic particles 27 and toner 28) thus formed on the surface of the sleeve 22 is sent by the rotation of the sleeve 22, and is transferred to the photosensitive drum l and the sleeve 22.
In front of the nearest part of , due to the action of the magnetic pole 23b,
While forming a pool and moving as shown by the arrow, the photosensitive drum 1
Develop the upper latent image. Also, the latent image carrier l and the sleeve 22
The toner is transferred from the surface of the sleeve 22 and the surface of the magnetic particles onto the latent image by an alternating electric field applied between the
Develop the latent image.

As the sleeve 22 continues to rotate, the toner particles and magnetic particles that have not been consumed in development are collected into the container 21, and the process is repeated where they are coated on the sleeve 22 again by the above-mentioned circulation action. During the circulation, the magnetic particles take in toner from the toner layer at the top of the container 21, and are supplied with the amount of toner consumed in development.

Next, the operation of the device of this embodiment will be explained while comparing it with a known device.

In conventional magnetic brush development, a photosensitive drum 1 and a sleeve 2 are
2 Which distance (hereinafter referred to as the S-D distance) is 5ffI11
Since the height of the front and rear brush ears is around 10 m11 (the coat l on the sleeve is more than 10 times that of the present invention), the height is around twice the S-D distance, and developer pooling is unlikely to occur. Furthermore, even with the small amount of magnetic particle coating and development method disclosed in Japanese Patent Application No. 60-204605, the S-0 distance is approximately 350 ALa+, and the height of the brush tip is approximately 0°7II11, which is approximately twice the S-D distance. Moreover, since the closest point between the developing pole and S-D coincides with each other, no developer accumulation occurs.

In the present invention, this active flow in the developer reservoir generates a more active rubbing and mixing effect between the sleeve 22, the image bearing member l, and the toner and carrier, allowing not only magnetic brush development but also liquid development or It has a developing effect close to that of powder cloud, and these advantages can be used.

A small amount of magnetic particles referred to in the wood refers to a case where 50% or less of magnetic particles are present in the space defined in the developing section,
Preferably, it is 1.5% or more and 45% or less. This small amount of magnetic particles makes it possible to use the toner on the sleeve surface and its vicinity for development, thereby improving the density of the developed image.

This ratio is (M/h)X (1/ρ)X [(C/ (T+C)]
It can be found by Here, M is the application amount (g
/cm2), h is the height of the space in the developing section (cm), ρ is the true density of the magnetic particles in g/cm'', 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.

In the above-mentioned small amount magnetic particle coating and development method, by applying an alternating electric field, sufficient image density can be obtained even if the circumferential speeds of the gX rejector 1 and the sleeve 22 are the same, and there are no scratches caused by the magnetic brush. However, using only a DC electric field lowers the image density and causes scratches from the magnetic brush.

In contrast, in the development method of the present invention, by active movement in the developer reservoir and expansion of the development area, the rotation of the sleeve remains at the same speed as the image carrier even when a small amount of magnetic particles are used in the development section. Moreover, it was confirmed that sufficient image density could be obtained using only a DC electric field. At this time, it was confirmed that there were no scratch marks caused by the magnetic brush.

Next, the distance between S and 0 is reduced using conventional magnetic brush development, and the distance between S and 0 is reduced to I/3 to 1 with respect to the height of the brush ear.
When it was set to 15, carrier adhesion to the latent image carrier 1 suddenly increased. This is because the contact pressure between the latent image carrier 1 and the carrier at the closest point between the latent image carrier 1 and the sleeve 22 is large, and the repelling magnetic pole also exists on the downstream side of the latent image carrier 1 even after the development area. This is considered to be because the carrier brush comes into contact with the latent image carrier l. Therefore, with regard to carrier adhesion, it has been found that it is preferable that no magnetic pole exists downstream of the closest point between the latent image carrier and the sleeve. Furthermore, the developer knee lit of the sleeve is large, increasing the possibility of scratches on the image carrier l and the possibility of the developer being fused to the sleeve 22.

Furthermore, even in the small amount magnetic particle application system described above, when the height of the brush ears was increased to 3 to 5 times the distance between S and 0, an increase in carrier adhesion was observed that was several times greater than in the uninvented developing device. . This is also considered to be due to the large contact pressure between the latent image carrier and the carrier at the point where the latent image carrier l and the sleeve 22 are closest to each other. Furthermore, developer fusion to the sleeve 22 also occurred.

FIG. 3 shows the change in image density when the development pole position is changed in the configuration of this embodiment. It was confirmed that a developer pool occurred on the upstream side of the sleeve in the range of 5°≦θ≦30'', and the image density was also 1.0 or more.At other development pole positions, developer pools did not occur. As a result, rubbing marks became noticeable and the image density suddenly decreased.

At around 0 to 158, the developer pool becomes maximum and the image density also reaches its peak. At this time, the amount of spikes on the developing pole ~1.0
It was also found that the distance between the latent image carrier and the sleeve at the development pole position was approximately 1.5 mm.

FIG. 3 shows the amount of carrier attached to the latent image carrier 1 when the development pole position is changed in the configuration of this embodiment and in the case of conventional magnetic brush development. It has been found that the amount of carrier adhesion increases rapidly when the developing electrode is located downstream of the closest point in the traveling direction.

This can be understood as follows. Carrier sleeve 22
When considering the collection area to the side, the carrier collection force is Fm=
mH (Fm: force to collect, m: charge of carrier, H: strength of magnetic field 1/γ2)) and charge of 7, E: strength of electric field,
This can be roughly explained by the difference between oc(p2/γ2): reflection force). On the downstream side of the closest point, Fm (cc (1/γ2)) decreases rapidly, so the carrier collection force also decreases rapidly, resulting in Fm less FE. Therefore, when the development pole peak exists downstream of the closest point, It is thought that carrier adhesion increases.

This also holds true for the reversible magnetic poles of conventional magnetic brush development.

As explained above, it is possible to perform development with a low and stable T/C ratio, especially in an apparatus in which a small amount of magnetic particles are present in the developing section (the toner on the sleeve surface side rises to the tip area of the carrier ear). T
This is because even if the /C ratio is low, the amount of toner used for actual development can be increased. ), toner scattering (if you simply create a pool or simply create a magnetic brush, the toner will scatter on the second-stream side of the developing section, but even a small amount of carrier particles is strongly held at the developing pole shifted upstream, Since the toner that tends to scatter upstream from the developing section can be reliably held inside the reservoir, scattering and ground force blur can be prevented.), and ground force blur can be eliminated.

The present invention has the following advantages: By shifting the developing pole upstream from the point of closest contact,
By causing developer to accumulate, it is possible to obtain sufficient image density even with a DC electric field, and it is also possible to eliminate brush scratch marks. In addition, by locating the developing pole only on the first stream side, carrier adhesion can be prevented, and the circumferential speed of the sleeve can be made the same as that of the latent image carrier, making it possible to achieve compact size, light weight, low cost, and high reliability. It has the advantage of being able to handle higher speeds and higher speeds.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a developing device according to an embodiment of the present invention, Fig. 2 is a graph showing changes in image density when the position of the developing magnetic pole is changed, and Fig. 3 is a graph showing changes in image density when the position of the developing magnetic pole is changed. 3 is a graph showing the amount of carrier attached to an image carrier in the case of conventional magnetic brush development and in the case of conventional magnetic brush development. l...Latent image carrier 22...Developer holding member (sleeve) 23...Magnetic field generating means (magnet) 23b...Development magnetic pole 3rd [¥]

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 magnetic 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 toner particles and a small amount of magnetic particles 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 the regulating member of the developer carrying member. a developing magnetic field generating means provided on the opposite side and provided upstream of the closest portion with respect to the rotational direction of the developer carrier, avoiding the closest portion between the developer carrying member and the latent image carrier; , and a developer reservoir is formed between the developer carrying member and the latent image carrier and upstream of the nearest part so that the horizontal magnetic field generated by the developing magnetic field generating means reaches the nearest part. A developing device characterized by forming: