JPS63163476A - Developing device - Google Patents

Abstract

PURPOSE:To homogenize and stabilize the thickness of a toner layer and the electrification charge of a toner extending over a long period by providing a rotary cylindrical member for stirring up a laminated magnetic toner, at the downstream side of a control member, and also, in the vicinity of the surface of a toner holding member of a range covered by the magnetic field of a magnetic field generating means. CONSTITUTION:A toner layer 23 is placed at a position for raising and stirring up a magnetic toner layer 23 held on the peripheral surface of a toner holding member 24 in the vicinity of a rotary cylindrical member 20. As for a magnetic toner, usually each grain is connected plumosely along the line of magnetic force in a magnetic field, and its layer density becomes small, therefore, when the toner is held by the toner holding member 24 in this state and allowed to pass through and carried in the magnetic field, it is stirred up easily since the toner grain moves easily. In this case, the rotary cylindrical member 20 rotates in the magnetic field formed by a multipolar permanent magnet 21, therefore, the magnetic field oscillates, the toner layer 23 is stirred up forcibly, mechanically and magnetically, and a frictional electrification is accelerated. In such a way, while being stirred up magnetically and mechanically, the toner layer is rubbed against the toner holding member or the surface of the rotary cylindrical member and the charge is obtained, therefore, the electrification charge quantity can be maintained stably extending over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a developing device using -component magnetic toner.
In particular, the present invention relates to a developing device such as a copying device or a printing device using electrophotography.

2. Description of the Related Art In general, methods for developing an electrostatic latent image on an image carrier include a two-component development method in which the developer is composed of toner and a carrier, and a one-component development method in which the developer is composed of toner alone. In the two-component development method, the toner forming the visible image has a charging polarity different from that of the carrier, and is agitated with the carrier in the developing device, resulting in relatively stable charging and a constant load. However, because the carrier has a limited lifespan, the developer must be replaced after a certain period of time, and while the toner is consumed with each development, the carrier is almost never consumed, so stable images are always produced. In order to obtain this, it is necessary to provide a large-sized disturbance device in the developing device that is responsible for frictionally charging the newly replenished toner and carrier.

In recent years, in order to solve this problem, a one-component developing method has been used in many developing devices.

For example, by forming a magnetic brush using a low-resistance toner, as seen in U.S. Pat. No. 3,909,258, and bringing it into contact with the electrostatic latent image on the image carrier, The so-called Magnedynamink method, which performs development by utilizing the induced load, or the British Patent No. L
396,979, which utilizes injection charging of the toner by physically rapidly agitating the toner under a high electric field between conductive members, and U.S. Pat. No. 4,102. , No. 305, an alternating electric field is applied between the electrostatic latent image bearing member and the toner holding member using a developer whose resistance value rapidly decreases when an electric field of a certain value or more is applied. A developing method that generates an electrostatic latent image and develops an electrostatic latent image, a method that develops an electrostatic latent image by charging toners by friction between the toners as seen in U.S. Pat. No. 4,259,427, U.S. Patent No. 4,29
As described in the specification of No. 2,427, the toner is charged by friction with a member that holds the toner or a member that regulates the toner layer, and the toner layer is not brought into direct contact with the electrostatic latent image. Examples include a so-called jumping development method in which an alternating electric field is applied between the electrostatic latent image carrier and the toner holding member in this state to cause the toner to fly selectively.

In this way, toner charging in a developing device using a -component developer is caused by contact charging of the toner with conductive members such as a developer holding member and a developer regulating member, charge injection from these members, and furthermore, toner particle mutual charging. The majority of this is due to frictional electrification.

Problems to be Solved by the Invention In the toner charging method described above, the method using low-resistance toner uses a normal electric field to transfer the toner developed and attached to the image carrier onto transfer paper (plain paper). This method is difficult.

In the charging method through contact with a conductive member or a toner regulating member, which serves as a toner holding member, the amount of toner that can come into contact with the toner is inevitably limited by the conductive member, and the thickness of each toner layer must be thin. Furthermore, since non-contact development is performed on an electrostatic image using a thin layer, sufficient image density cannot be obtained.

The method of injecting charge from a conductive member complicates the developing device, and the advantages of the developing device using a one-component developer are lost.

Furthermore, in order to prevent toner from adhering to non-image areas (so-called fogging), a certain bias is applied to the toner holding member to prevent this, but the electric field caused by this bias can cause the toner to be charged to a polarity opposite to the desired one. This causes toner to adhere to non-image areas.

In the charging method using friction between toner particles, since particles of the same type are charged, relatively severe disturbance of toner particles is required. For this reason, a magnetic roller included in the toner holding member is rotated at high speed to generate disturbance. Rotating this magnetic roller at high speed has many disadvantages in that it causes toner to scatter from the toner holding member, contaminating the developing device or its surroundings, and shortening the maintenance cycle.

The present invention has been made in view of the above points, and the present invention has been made to increase the toner layer thickness while maintaining a sufficient layer thickness so that the toner layer on the toner holding member can contact and rub against the electrostatic latent image. The object of the present invention is to propose a developing device that can uniformly and stably obtain a charge of 100% over a long period of time.

Means for Solving the Problems In order to solve the above problems, the developing device of the present invention includes a toner holding member which rotates while holding magnetic toner on its surface, and a toner holding member disposed on the back side of the toner holding member. a regulating member disposed close to the surface of the toner holding member for thinning the magnetic toner, and a range downstream of the regulating member and covered by the magnetic field of the magnetic field generating means; and a rotating cylindrical member for forcibly agitating the layered magnetic toner disposed near the surface of the toner holding member.

According to the above-described structure, the present invention allows a single layer of magnetic toner, which is held by a toner holding member, reaches a regulating member, and is regulated and layered, to be forced by a rotating cylindrical member while passing through a magnetic field on the downstream side of the regulating member. In order to achieve sufficient frictional electrification with the toner holding member or rotating cylindrical member, a homogeneous toner thin layer that retains a stable charge for a long period of time is obtained, and this magnetic toner thin layer Since the layer rubs the surface of the image carrier, it is possible to obtain a uniform, high-density, high-quality image with little background fog.

EXAMPLE Hereinafter, a specific example of the present invention will be described in detail with reference to the attached drawings. FIG. 2 is an internal structural diagram showing an example of a printing device using electrophotography to which the developing device of the present invention is applied. In the figure, reference numeral 2 denotes a main body of the printing apparatus, and an image carrier, specifically a photosensitive drum 1, is provided approximately at the center thereof so as to be driven to rotate in the direction of the arrow.

Around the drum 1, a charging charger 3, a developing device 16 according to the present invention, a transfer charger 4, a separation charger 5, and a cleaning device 6 are arranged in order in the rotational direction of the photosensitive drum 1 as shown by the arrow. The image forming section is arranged to operate as the drum 1 rotates, and to transfer a toner image onto the transfer paper 7 that is conveyed in synchronization with the rotation of the drum 1.

In this image forming section, after the photosensitive drum 1 is cleaned by a cleaning device 6, it is charged by a charging charger 3. This charged surface of the drum 1 is exposed to light by an exposure system 8 comprising, for example, a semiconductor laser diode, a polygonal rotating body, and a lens optical system, and an electrostatic latent image is formed.

Next, this electrostatic latent image is developed with toner by the developing device 16 according to the present invention, and the developed toner image is transferred by the transfer charger 4 onto the transfer paper 7 that is sent in synchronization. Further, the transfer paper 7 after the transfer is separated from the surface of the drum 1 by the separation charger 5. The cleaning device 6 scrapes off the residual toner on the surface of the drum 1 after the transfer, from which the transfer paper 7 has been separated, and returns to the initial state.

On the left side of the image forming section, there is a conveying heald 9 that is charged by a belt charging charger 10 that carries the transfer paper 7, attracts the transfer paper 7 by electrostatic force, and heat-fuses the transferred toner image on the transfer paper 7. A heating fixing device 11 is provided to constitute a normal electrophotographic printing device. In the paper feeding section, a paper feeding cassette 12 is attached to one side of the printer main body 2 so as to protrude from one side, and by driving the paper feeding roller 3, the transfer paper 7 is transferred from the paper feeding cassette 12 to the timing roller 4.
The toner image is guided by the guide plate 15 and sent to the image forming section in synchronization with the movement of the toner image on the photosensitive drum 1.

The above is an example of a printing device to which a developing device according to the present invention is applied.

FIG. 1 is an internal structural diagram showing a developing device when the present invention is applied to the above-mentioned electrophotographic printing device.

In FIG. 1, the surface of the image carrier 1 has an average particle diameter of 10 mm, which is obtained by mixing and dispersing magnetic powder such as ferrite as a main component in a resin such as acrylic, styrene, or polyester, and pulverizing the mixture.
It is rubbed with a thin layer 23 of high resistance component magnetic toner of about μ. This single layer of magnetic toner is held on the circumferential surface of a non-magnetic cylindrical toner holding member 24 that is rotatably supported and rotationally driven in the direction of the arrow, and is conveyed to the surface of the image carrier 1. A hopper 17 is disposed near the outside of the circumferential surface of the toner holding member 24 for storing magnetic toner and replenishing the circumferential surface of the toner holding member with a predetermined amount of toner. A toner supply port 18 is provided at one end of the hopper 7, and a regulating member 19 for thinning the magnetic toner is provided at the other end close to the circumferential surface of the toner holding member 24. . The regulating gap between the regulating surface of the regulating member 19 and the circumferential surface of the toner holding member 24 varies depending on the required thickness of the toner and whether the regulating member 19 is magnetic or non-magnetic, but is generally 0.2 to 0.5 i.
It is n. On the downstream side of the regulating member 19 where the toner is transported, a rotating cylindrical member 20 is disposed close to the circumferential surface of the toner holding member 24 in the same manner as the regulating member 19 . The gap between the surface of the rotating cylindrical member 20 adjacent to the toner holding member 24 and the circumferential surface of the toner holding member 24 needs to be larger than the regulating gap in the regulating member 19, and the material of the rotating cylindrical member 20 is magnetic. Alternatively, it is preferably about 0.3 to 1.0 mm, depending on whether it is non-magnetic. For example, if the amount of toner regulated by the regulating member 19 and conveyed to the image carrier 1 side per unit time is 1, then the amount of toner passing through the gap between the rotating cylindrical member 20 and the toner holding member 24 is calculated as follows. The amount that can be done needs to be adjusted to 1 or more.

The direction of rotation of the rotating cylindrical member 20 is such that the direction of movement of the circumferential surface of the rotating cylindrical member 20 is opposite to the direction of movement of the circumferential surface of the toner holding member 24. It is preferable to forcibly disturb the toner, and its circumferential speed may be approximately the same as the circumferential speed of the toner holding member 24. Of course, it is possible for the circumferential surfaces of the toner holding member 24 and the rotating cylindrical member 20 to move in the same direction, but if the difference in circumferential surface speed between each member is small, a sufficient disturbance effect cannot be obtained. This is not desirable from the standpoint of toner scattering, since the members rotate at a higher speed than necessary. A multipolar permanent magnet 21 is internally fixed within the cylindrical circumferential surface of the toner holding member 240 in order to raise the magnetic toner layer 23 held on the circumferential surface of the toner holding member 24 in a brush shape. As in a normal developing device of this kind, the magnetic pole is located at a position facing the image bearing member 1 where a single layer of brush-like toner can be rubbed against the image bearing member 1, and facing a regulating member 19 at a position where a single layer of toner can be brushed. In addition to the position where the thickness of the toner layer 23 can be controlled by making the toner stand up in a shape, in the present invention, a magnetic field is applied to the vicinity of the rotating cylindrical member 20 facing the rotating cylindrical member 20, and this magnetic field is In particular, when the rotating cylindrical member 20 is a magnetic member, a strong magnetic field is applied between the rotating cylindrical member 20 and the member 20 at a position where the magnetic toner layer 23 held on the circumferential surface of the toner holding member 24 can be fluffed and disturbed. The toner layer 23 is formed at a position where the toner layer 23 can be fluffed and disturbed in this magnetic field. Normally, in a magnetic field, magnetic toner particles are arranged like feathers along the lines of magnetic force, and the layer density becomes small.
4 and transported through a magnetic field, the toner particles are easily disturbed because they are mobile.

At this time, the function of the rotating cylindrical member 20 is that of the multipolar permanent magnet 2.
Since the toner 1 rotates within the magnetic field formed by the toner 1, the magnetic field oscillates, and the toner layer 23 is forcibly disturbed both mechanically and magnetically, thereby promoting frictional electrification.

Since the above-mentioned disturbance is performed quantitatively on the regulated toner layer 23 having a thickness sufficient to rub the image carrier 1, the toner layer 23 and the toner holding member 24 or the rotating cylindrical member This makes it possible to homogenize the frictional charge between the toner and the toner and maintain the charge on the toner at a stable value over a long period of time. In the developing device of the present invention, a cover 22 is attached around the rotating cylindrical member 20 so as to extend from the lower part of the hopper 17 in order to additionally protect the rotating cylindrical member 20.

Next, the above embodiment will be further explained with the addition of specific data. The image carrier 1 may be a selenium drum, an organic photoreceptor drum, or an organic photoreceptor belt as a photoreceptor, and here a functionally separated organic photoreceptor drum with a diameter of 80 mm was used. The surface charging voltage was -700 cm, and the circumferential speed was 140 f/sec. The magnetic toner includes - for example, 64.5 parts of polyester resin, 30 parts of magnetite,
A mixture having an average particle size of 8 μm was used, which was prepared by mixing and dispersing and pulverizing a mixture of 3 parts of charge control agent, 2 parts of carbon, and 0.5 part of stearic acid using a well-known method. Note that the toner is not limited to the above composition. As a toner holding member,
In the state shown in Fig. 1, a non-magnetic stainless steel cylindrical material with a diameter of 30 mm is used.
One with a Gaussian surface magnetic flux density was used. A nonmagnetic stainless steel plate with a thickness of 3 m was used as the regulating member, and a magnetic stainless steel cylindrical material with a diameter of 12 m was used as the rotating cylindrical member. The regulation gap was on the order of 0.2, and the gap between the rotating cylindrical member and the toner holding member was selected to be 0.75 mm. The gap between the image carrier, that is, the organic photoreceptor drum and the surface of the toner holding member is
0.4, and under these conditions, the thin toner layer is brush-like and can be rubbed on the surface of the photoreceptor by the action of the magnetic field. The circumferential speed of the toner holding member is constant in the same direction as the photoreceptor, and the circumferential speed of the rotating cylindrical member is constant in the opposite direction to the toner holding member.

At this time, the amount of charge on the toner that had reached the development position was measured, and the result was -3.8 to -4.2 μC/g. Under these conditions, a bias of -600 V was applied to the toner holding member, a latent image was created using the exposure system shown in FIG. 2, and a printing test was performed by reverse development. The resolution of the exposure system was 20 dots/IIN, that is, the minimum line width of 50 μ was used for exposure, and the print quality obtained was at a resolution that could roughly reproduce this. Furthermore, under these conditions, 2 kg of magnetic toner
We conducted a continuous printing test using 300 yen, but the original printing quality was maintained and images with high resolution and less background blur were obtained.

In addition, the entire surface of the photoreceptor is exposed to light to obtain a solid black image on transfer paper.
Is that black density Makhess RD914? As a result of measurement using a jtff meter, a stable black density of 1.4 or higher was obtained.

Effects of the Invention As described above, the present invention provides a developing device using -component high-resistance magnetic toner, in which the toner is held by a toner holding member and the thickness of the toner is regulated by a regulating member, and then magnetically developed. , obtains electric charge by friction with the surface of the toner holding member or rotating cylindrical member while being mechanically disturbed, thereby maintaining the amount of charged charge stably over a long period of time and rubbing the electrostatic latent image on the image carrier. Therefore, it provides a developed image with a high black density level and excellent print quality.

[Brief explanation of the drawing]

FIG. 1 is an internal structure diagram showing a developing device when the present invention is applied to an electrophotographic printing device, and FIG. 2 is an internal structure diagram showing an example of a printing device using an electrophotographic method to which the developing device of the present invention is applied. FIG. Work 9...Restriction member, 20...Rotating cylindrical member, 21...Multi-polar permanent magnet, 22...
... Rotating cylindrical member protection cover, 24 ... Toner holding member. Name of agent: Patent attorney Toshio Nakao and 1 other person / -m-
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Claims (2)

[Claims] (1) A developing device that supplies a thin layer of magnetic toner in order to rub the magnetic toner on the surface of an image carrier, which holds the toner on the surface and rotates it in order to rub the magnetic toner. a moving toner holding member; a magnetic field generating means disposed on the back side of the toner holding member; a regulating member disposed close to the surface of the toner holding member for thinning the magnetic toner; A rotating cylindrical member for disturbing the layered magnetic toner, which is disposed downstream of the regulating member and near the surface of the toner holding member within the range covered by the magnetic field of the magnetic field generating means. developing device. (2) The developing device according to claim (1), wherein the direction of movement of the surface of the toner holding member and the direction of movement of the surface of the rotating cylindrical member are opposite directions.