JP2511916B2 - Development device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device using a one-component magnetic toner, and more particularly to a developing device such as a copying device or a printing device using electrophotography.

2. Description of the Related Art Generally, as a method for developing an electrostatic latent image on an image bearing member, there are a two-component developing method in which a developer is composed of a toner and a carrier and a one-component developing method in which a developer is composed of a toner alone. In the two-component developing method, the toner forming a visible image has a charging polarity different from that of the carrier, and is relatively stably charged by being disturbed by the carrier in the developing device, and has a constant load amount. However, since the carrier has a limited life, it is necessary to replace the developer after a certain period of time, and the toner is consumed for each development but the carrier is hardly consumed. In order to obtain the toner, it is necessary to provide a large-sized disturbing device in the developing device, which takes charge of frictional charging between the newly supplied toner and the carrier.

In recent years, in order to solve this problem, the one-component developing method has been used in many developing devices. For example, by forming a magnetic brush using a low-resistance toner as shown in U.S. Pat.No. 3,909,258 and bringing the brush into contact with the electrostatic latent image on the image carrier, a load opposite to the electrostatic latent image is induced. The toner is injected into the toner by so-called magnetic dynamic method of developing by utilizing the above, or by physically agitating the toner as seen in British Patent No. 1,396,979 under a high electric field between the conductive members. A developing method utilizing the fact that charging is performed and US Pat. No. 4,102,305
As described in the specification, a developer whose resistance value sharply decreases when an electric field of a certain value or more is applied is used to generate an alternating electric field between the electrostatic latent image carrier and the toner holding member. A developing method for visualizing an electrostatic latent image and U.S. Pat. No. 4,259,42
No. 7, the method of developing an electrostatic latent image by charging the toner by friction between the toners as described in US Pat.
As described in US Pat. No. 4,292,427, the toner is charged by friction with a member that holds the toner or a member that controls the toner layer, and the toner layer is in a specific contact state without directly contacting the electrostatic latent image with the toner layer. Then, a so-called jumping developing method in which an alternating electric field is applied between the electrostatic latent image carrier and the toner holding member to selectively fly the toner can be used.

As described above, the charging of the toner in the developing device using the one-component developer is performed by the contact charging of the toner with the conductive member such as the developer holding member and the developer regulating member, the charge injection from these members, and the mutual mutual toner particle. Most of them are due to triboelectric charging.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention In the above-mentioned toner charging method using a low-resistance toner, it is possible to transfer the toner developed and attached to the image carrier to a transfer paper (plain paper) using an ordinary electric field. It is difficult to do it.

In the charging method by contact with a conductive member serving as a toner holding member or a toner regulating member, the amount of toner that can inevitably come into contact is limited by the conductive member, and the thickness of the toner layer needs to be thin. Further, since the electrostatic image is developed in a thin layer in a non-contact manner, sufficient image density cannot be obtained.

The method of injecting electric charges from the conductive member complicates the developing device and impairs the advantages of the developing device using a one-component developer. Furthermore, toner adhesion to non-image areas (so-called fog)
To prevent this, a constant bias is applied to the toner holding member to prevent this, but the electric field due to this bias causes the toner to be charged to the opposite polarity to the desired polarity, causing the toner to adhere to the non-image portion.

In the charging method based on friction between toner particles, since the same kind of particles are charged, the toners need to be relatively violently disturbed. Therefore, the magnetic roller contained in the toner holding member is rotated at a high speed to cause disturbance. Rotating the magnetic roller at a high speed has many disadvantages in that the toner is scattered from the toner holding member to contaminate the developing device or its periphery and shorten the maintenance cycle.

The present invention has been made in view of the above points, and the toner layer thickness and the toner are maintained while maintaining the layer thickness sufficient for the toner layer on the toner holding member to contact and rub against the electrostatic latent image. SUMMARY OF THE INVENTION It is an object of the present invention to propose a developing device capable of uniformly and stably obtaining the electrostatic charge of the above 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 is provided with a toner holding member that holds magnetic toner on its surface and rotates, and a rear surface side of the toner holding member. Magnetic field generating means, a regulating member arranged near the surface of the toner holding member for thinning the magnetic toner, and a range downstream of the regulating member and to which the magnetic field of the magnetic field generating means extends. And a magnetic rotating cylindrical member arranged near the surface of the toner holding member for expanding and disturbing the magnetic toner.

According to the present invention, with the above-described structure, the magnetic toner held by the holding member is generated by the high-density magnetic field formed between the magnetic field generating means disposed on the back side of the toner holding member and the magnetic cylindrical rotary charging member. In order to disperse the granulated and blocked toner by stretching and dispersing below, and stretching and disturbing by giving a turbulent flow by the rotation of the magnetic cylindrical rotary charging member, to cause sufficient triboelectric charging, A uniform thin toner layer that retains a stable charge for a long period of time is obtained, and the surface of the image carrier is rubbed by this thin magnetic toner layer, resulting in a uniform, high-density low fog. It is possible to obtain a high quality image.

Example Hereinafter, a specific example of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 is an internal structure diagram showing an example of a printing apparatus using an electrophotographic method to which the developing apparatus of the present invention is applied. In the figure, reference numeral 2 denotes a printer main body, and an image carrier, specifically, the photosensitive drum 1, is provided at a substantially central portion thereof so as to be rotationally driven in an arrow direction. Around the drum 1, the charging charger 3, the developing device 16 according to the present invention, the transfer charger 4, the separation charge-eliminating charger 5, and the cleaning device 6 are sequentially arranged in the rotation direction of the photosensitive drum 1. An image forming unit is provided which operates in accordance with the rotation of the drum 1 and transfers a toner image onto the transfer paper 7 which is conveyed in synchronization with the rotation of the drum 1.

This image forming unit uses the cleaning device 6 for cleaning the photosensitive drum 1.
After cleaning by, the battery is charged by the charging charger 3. The charged surface of the drum 1 is exposed by an exposure system 8 including, for example, a semiconductor laser diode, a polyhedral rotating body, and a lens optical system to form an electrostatic latent image. Next, this electrostatic latent image is developed with toner by the developing device 16 according to the present invention, and the toner image after development is transferred by the transfer charger 4 onto the transfer paper 7 sent in synchronization. Further, the transfer paper 7 after the transfer is separated from the surface of the drum 1 by the separation charge-eliminating charger 5. The cleaning device 6 scrapes off the residual toner on the surface of the drum 1 after transfer from which the transfer paper 7 has been separated, and returns to the initial state.

On the left side of the image forming unit, a transfer belt 9 that is charged by a belt charging charger 10 that conveys the transfer paper 7 and attracts the transfer paper 7 by electrostatic force, and a transfer toner image on the transfer paper 7 are heat-fused. The heat fixing device 11 is arranged to constitute a normal electrophotographic printing device. The paper feeding unit is mounted in a state where the paper feeding cassette 12 is projected to one side surface of the printing apparatus main body 2, and by driving the paper feeding roller 13, the transfer paper 7 is sent out from the paper feeding cassette 12 to the timing roller 14. Guided by the guide plate 15, the toner image is sent to the image forming unit in synchronism with the movement of the toner image on the photosensitive drum 1.

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

FIG. 1 is an internal structural diagram showing a developing device when applied to the above-described electrophotographic printing device of the present invention. In FIG. 1, the surface of the image carrier 1 is a high-resistance one-component magnetic material having an average particle size of about 10 μ, which is obtained by mixing and pulverizing a magnetic powder such as ferrite as a main component in a resin such as acrylic resin, styrene, and polyester. It is rubbed with a thin layer 23 of toner. This magnetic toner layer is held on the peripheral surface of a non-magnetic cylindrical toner holding member 24 that is rotatably supported and is driven to rotate in the arrow direction, and is conveyed to the surface of the image carrier 1. Toner holding member
A hopper 17 for storing magnetic toner near the outside of the peripheral surface of 24 and replenishing the peripheral surface of the toner holding member with a predetermined amount of toner.
Are arranged. Toner supply port at one end of hopper 17
18 is provided, and a regulating member 19 for thinning the magnetic toner is provided at the other end in the vicinity of the peripheral surface of the toner holding member 24. Regulation surface of regulation member 19 and toner holding member 24
The regulated gap from the peripheral surface of the toner varies depending on the required toner layer thickness, but is generally 0.2 to 0.5 mm. On the downstream side of the regulation member 19 to which the toner is conveyed, a rotary cylindrical member 20 is disposed in the vicinity of the peripheral surface of the toner holding member 24, like the regulation member 19. Toner holding member 24 of the rotating cylindrical member 20
The gap between the adjacent surface and the peripheral surface of the toner holding member 24 needs to be larger than the regulation gap in the regulation member 19 described above, and is preferably about 0.3 to 1.0 mm. These numerical values are, for example, when the amount of toner, which is regulated by the regulating member 19 and is conveyed to the image carrier 1 side, is 1,
The amount that can pass through the gap between the rotating cylindrical member 20 and the toner holding member 24 needs to be adjusted to 1 or more. The rotation direction of the rotating cylindrical member 20 is such that the circumferential moving direction of the rotating cylindrical member 20 is opposite to the circumferential moving direction of the toner holding member 24. It is desirable to forcibly disturb 23, and the peripheral speed thereof may be the same as the peripheral speed of the toner holding member 24. As a matter of course, the toner holding member 24 and the rotating cylindrical member 20 may have the same circumferential surface moving direction, but if the circumferential velocity difference between the respective members is small, a sufficient disturbing effect cannot be obtained. The member is rotated at a higher speed than necessary, which is not desirable in terms of toner scattering. A multi-pole permanent magnet 21 is internally fixed inside the cylindrical peripheral surface of the toner holding member 24 in order to brush the magnetic toner layer 23 held on the peripheral surface of the toner holding member 24 in a brush shape. The magnetic pole is located at a position where the brush-shaped toner layer can be rubbed against the image carrier 1 in the same manner as in a normal developing device of this type, and the toner layer is brushed in the position facing the regulating member 19. In addition to the position where the thickness of the toner layer 23 can be regulated by making a bristling shape, a magnetic field is exerted in the vicinity of the rotating cylindrical member 20 in the present invention in the vicinity of the rotating cylindrical member 20. At a position where the magnetic toner layer 23 held on the peripheral surface of the toner holding member 24 can be disturbed by raising, especially when the rotating cylindrical member 20 is a magnetic member.
A strong magnetic field is formed between them and the toner layer 23 is arranged at a position where the raised hair can be disturbed in this magnetic field. In the magnetic toner, the particles are usually piled up in a magnetic field along the lines of magnetic force, and the layer density becomes small.
It is easily disturbed that the toner particles are held by 24 and conveyed through the magnetic field because the toner particles are easily moved. At this time, the function of the rotating cylindrical member 20 is to rotate in the magnetic field formed by the multi-pole permanent magnet 21, so that the magnetic field oscillates and the toner layer 23 is mechanically and magnetically forcibly disturbed. As a result, triboelectrification is promoted. The above-mentioned disturbance is quantitatively performed on the regulated toner layer 23 having a sufficient thickness to rub the image carrier 1, so that the toner layer 23 and the toner holding member 24
Alternatively, it is possible to homogenize the triboelectrification with the rotating cylindrical member 20 and maintain the charge of the toner at a stable value for 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 portion of the hopper 17 in order to protect the rotating cylindrical member 20.

Next, the above embodiment will be further described by adding specific data. The image carrier 1 may be a selenium drum, an organic photosensitive drum, or an organic photosensitive belt as a photosensitive member, and here, an organic separation type organic photosensitive drum having a diameter of 80 mm was used. The surface charging voltage is −700 V and the peripheral speed is 14
It is 0 mm / Sec. As the magnetic toner, for example, an average particle size of 8 μ which was mixed and dispersed by a known method at a ratio of 64.5 parts of polyester resin, 30 parts of magnetite, 3 parts of charge control agent, 2 parts of carbon and 0.5 part of stearic acid was used. . The toner is not limited to the above composition. As the toner holding member, a non-magnetic stainless steel cylindrical material having a diameter of 30 mm is used in the state according to FIG. 1. The multi-pole permanent magnet contained in the toner holding member is 1000 gauss at each pole measured from the cylindrical surface. The surface magnetic flux density was used. A non-magnetic stainless steel plate having a thickness of 3 mm was used as the regulating member, and a magnetic stainless steel cylindrical member having a diameter of 12 mm was used as the rotating cylindrical member. The regulation gap was 0.2 mm, 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 photosensitive drum and the surface of the toner holding member is 0.4 mm. Under this condition, the thin toner layer is brushed and rubbed on the surface of the photosensitive member by the action of the magnetic field. . The peripheral speed of the toner holding member is constant in the same direction as the photosensitive member, and the peripheral speed of the rotating cylindrical member is constant in the direction opposite to the toner holding member. At this time, the charge amount of the toner reaching the developing position was measured and found to be -3.
It was 8 to −4.2 μC / g. Under these conditions, a bias of -600 V was applied to the toner holding member to form a latent image using the exposure system shown in FIG. 2, and reversal development was carried out to perform a print test. The resolution of the exposure system was 20 dots / mm, that is, the minimum line width of 50 μ was used for exposure, but the obtained print quality was a resolution that almost reproduced this. Further, under this condition, a continuous printing test was conducted by consuming 2 kg of magnetic toner,
The original print quality was maintained, high resolution and low fog images were obtained. Further, the entire surface of the photoconductor was exposed to obtain a solid black image on the transfer paper, and the black density was measured with a Macbeth RD914 densitometer. As a result, a stable black density of 1.4 or more was obtained.

As described above, the present invention is a developing device using a one-component high-resistance magnetic toner, which is magnetically magnetic after the toner is held by a toner holding member and the toner layer thickness is regulated by a regulating member. , Because the electric charge is obtained by rubbing with the surface of the toner holding member or the rotating cylindrical member while being mechanically disturbed, and the electric charge amount is stably maintained for a long period of time to rub the electrostatic latent image on the image carrier. Therefore, it is possible to provide a developed image with excellent print quality having a high black density level.

[Brief description of drawings]

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 diagram showing an example of a printing device using an electrophotographic method to which the developing device of the present invention is applied. It is a block diagram. 19 ... Regulating member, 20 ... Rotating cylindrical member, 21 ... Multi-pole permanent magnet, 22 ... Rotating cylindrical member protective cover, 24 ... Toner holding member.

Front page continued (72) Inventor Shinta Miyoshi Kadoma City, Kadoma 1006 No. 1006, Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-57-165865 (JP, A)

Claims (1)

(57) [Claims] 1. A developing device for supplying a thin layer of magnetic toner for rubbing the magnetic toner on the surface of an image carrier, which holds the toner on the surface for rubbing the magnetic toner. And a rotating toner holding member, a magnetic field generating means arranged on the back surface side of the toner holding member, and a regulating member arranged near the surface of the toner holding member for thinning the magnetic toner. A magnetic rotating cylindrical member disposed on the downstream side of the regulating member and near the surface of the toner holding member in the range of the magnetic field of the magnetic field generating means for extending and disturbing the magnetic toner. And developing device.