JPS63104071A - Developing device - Google Patents

Abstract

PURPOSE:To homogenize and stabilize the thickness of a toner layer and an electrified charge of toner for a long period, by holding the toner by a toner holding member, allowing it pass through an intense magnetic field, while it is carried to a control member of thickness of the toner layer, stirring it and also, correcting the carrying quantity to the control member. CONSTITUTION:A magnetic toner which is held by a toner holding member 27 and reaches a control member 19 is stirred by allowing it to pass through the inside of a magnetic field in its upstream side, and prevented from being pelletized and converted to block. Subsequently, only the stirred toner is further stirred and converted to a thin layer by the control member 19, therefore, it prevents the block-shaped toner from being clogged in a control gap of the control member 19 and the toner holding member 27. Accordingly, a homogeneous toner thin layer 26 is obtained for a long period, and by this homogeneous magnetic toner thin layer, the surface of an image carrying 1 is rubbed. In such a way, an image high in quality uniform in density and less in ground fogging can be obtained.

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 Conventionally, methods using one-component magnetic toner, such as copying machines using electrophotography, are disclosed in, for example, U.S. Pat.
There are induction charging methods using low-resistance toner, as seen in British Patent No. 09,258, and injection charging methods, in which toner is rapidly physically disturbed under a high electric field, as shown in British Patent No. 1.396,979. However, in the former case, it is difficult to transfer toner developed and attached to the image carrier onto transfer paper (plain paper) using a method that uses a normal electric field, and in the latter case, the structure is complicated. There are few examples of this being put into practical use. More recently, for example, U.S. Pat.
259,427, a method in which the toner is charged by a member that holds the toner, a member that restricts the toner layer, or the friction between the toner and each other has come into practical use. A specific representative example is shown in FIG. In FIG. 3, a toner layer regulating member 28 made of a magnetic or elastic material regulates the layer thickness 26 of the toner supplied to the surface of the rotating toner holding member 27, and at this time, these regulating members 28 and toner This is a method in which the charge necessary for development is applied to the toner by friction between the holding member 27 and the toner particles. Although it is quite possible to obtain a uniform toner layer thickness 26 and a uniform charge using such a simple method, however, from the viewpoint of long-term reliability, the proximity of the toner regulating member 28 is insufficient. On the upstream side A, the toner blocks due to the granulation phenomenon, clogging the small regulating gap between the regulating member 28 and the toner holding member 27, and causing streak-like non-uniform unevenness in the thin toner layer 26. In addition, it is often seen that the above-mentioned toner granulated blocks slip through the regulation gap and reach the developing section B. This granulation phenomenon is particularly likely to occur when the toner particle size is reduced from the usual tens of microns to several microns in order to increase the image resolution.

Problems to be Solved by the Invention As mentioned above, such non-uniform streak-like unevenness in one layer of toner, or block-shaped toner particles that have slipped through the regulation gap, naturally lead to poor development results. It is clear that it gives The former results in striped white spots on the image, and the latter results in striped background fog.

The present invention has been made in view of the above points, and it is an object of the present invention to propose a developing device that can uniformly and stably obtain toner thickness and toner charge 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 first magnetic field generating means; a magnetic member for disturbing magnetic toner disposed near the surface of the toner holding member within a range covered by the magnetic field of the first magnetic field generating means; and a magnetic member disposed on the surface side of the toner holding member. A second magnetic field generating means disposed downstream of the magnetic member and within a range covered by the magnetic field of the second magnetic field generating means,
and a magnetic regulating member disposed close to the surface of the toner holding member for thinning the magnetic toner, and toner other than the disturbed magnetic toner entering from between the magnetic regulating member and the magnetic member. The structure includes a shielding member to prevent this from occurring.

Effect of the present invention With the above-described configuration, the magnetic toner held by the toner holding member and reaching the regulating member is disturbed by passing it through a magnetic field on its upstream side, thereby preventing it from forming into granulated blocks, and also preventing the disturbance from forming into granulated blocks. Since only the toner that has been removed is further agitated and thinned by the regulating member, it is possible to prevent block-shaped toner from clogging the regulating gap between the regulating member and the toner holding member, and to prevent the toner from colliding with each other over a long period of time. A homogeneous toner thin layer is obtained, and this homogeneous Cf
) Note: Since the surface of the image carrier is rubbed with a thin toner layer, it is possible to obtain a high-quality image with uniform density and less background fog.

EXAMPLE Hereinafter, a developing device according to an example of the present invention will be described in detail based on the attached drawings. FIG. 1 is an internal structural diagram showing an example of a printing device using electrophotography to which a 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 a developing device 16 according to the present invention, and the developed toner image is transferred by a transfer charger 4 onto a transfer paper 7 that is fed synchronously. Furthermore, the surface of the transfer paper 7 after the transfer is separated from the surface of the drum 1 by the charger 5 for separating and eliminating electricity. The surface of the drum 1 after the transfer from which the transfer paper 7 has been separated returns to its initial state after residual toner is scraped off by the cleaning device 6.

On the left side of the image forming section, there is a conveyor belt 9 which is charged by a belt charging charger 10 carrying 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. The paper feed section is installed with the paper feed cassette 2 protruding from one side of the printer main body 2, and the transfer paper 7 is transferred from the paper feed cassette 12 to the timing roller 14 by driving the paper feed roller 13. 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 in which the developing device according to the present invention can be used.

FIG. 2 is an internal structural diagram showing a developing device when the present invention is applied to the above-mentioned electrophotographic printing device.

In FIG. 2, the surface of the image carrier 1 has an average particle size of 10 mm, which is obtained by mixing and dispersing magnetic particles such as ferrite as a main component in a resin such as acrylic, styrene, or polyester.
It is rubbed with a thin layer 26 of high resistance component magnetic toner on the order of μ. This magnetic toner layer 26 is held on the circumferential surface of a non-magnetic cylindrical toner holding member 27 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 27 for storing magnetic toner and replenishing the circumferential surface of the toner holding member 27 with a predetermined amount of toner. A toner supply port 18 is provided at one end of the hopper 17, and a magnetic regulating member 19 for thinning the magnetic toner is provided at the other end close to the circumferential surface of the toner holding member 27. The regulating gap between the regulating surface of the magnetic regulating member 19 and the circumferential surface of the toner holding member 27 varies depending on the required toner thickness, but is generally 0.5 to 0.2 mm. On the upstream side of the magnetic regulating member 19 from which the toner is conveyed, a magnetic member 20 is disposed close to the circumferential surface of the toner holding member 27 in the same way as the magnetic regulating member 19 . The close surface of the magnetic member 20 to the toner holding member 27 and the toner holding member 27
The gap with the circumferential surface of the magnetic regulating member 19 needs to be larger than the regulation gap in the magnetic regulating member 19, and is preferably about 1 to 0.5 squares, and the width of the proximal surface is preferably at least 1 square or more.

These numbers are, for example, assuming that the amount of toner per unit time regulated by the magnetic regulating member 19 and conveyed to the image carrier 1 side is 1, and the amount of toner that passes through the gap between the magnetic member 20 and the toner holding member 27 is 1. The amount is preferably about 1.2 to 1.5, in other words, the amount of toner remaining under regulations is about 20 to 1.5.
It needs to be adjusted to 50%.

If this amount is small, the toner thickness on the downstream side of the magnetic regulating member 19 tends to become unstable, and conversely, when it is large, the toner granulation block phenomenon occurs on the upstream side near the magnetic regulating member 19. It is from. In the cylindrical circumferential surface of the toner holding member 27, a first layer is provided in order to raise the magnetic toner layer 26 held on the circumferential surface of the toner holding member 27 in a brush shape.
A two-pole permanent magnet 21 is fixedly included as a magnetic field generating means. The magnetic pole faces the image carrier 1 at a position where the brush-like toner layer 26 can rub the image carrier 1, that is, the development position, and faces the magnetic member 20 at a position where the toner N26 stands up like a brush. A position where the toner layer 26 can be disturbed,
That is, in the present invention, the toner layer 26 is placed in a position where it can apply a magnetic field to the magnetic member 20 facing the magnetic member 20, form a strong magnetic field with the magnetic member 20, and stir the toner layer 26 in this magnetic field. There is. Normally, in a magnetic field, particles of magnetic toner are arranged in a feather-like manner along the lines of magnetic force, and the layer density becomes small. Because it is easy to move, it is easily disturbed and a phenomenon of unraveling of block-shaped toner occurs.

The function of the magnetic member 20 is the above-mentioned phenomenon in which block-shaped toner is loosened due to disturbance, and the above-described magnetic regulating member 1.
This is to prevent the toner from becoming blocked near the regulating member 19 by regulating the amount of toner sent to the regulating member 9 side. In the present invention, in addition to the two-pole permanent magnet 21, which is the first magnetic field generating means included on the back side of the toner holding member 27,
A permanent magnet 22 is also disposed at one end of the magnetic regulating member 19 as a second magnetic field generating means. The permanent magnet 22 is connected to the magnetic regulating member 1 provided within the range of its magnetic field.
A strong magnetic field is formed between the toner retaining member 27 and the internal magnetic member 23 disposed within the toner retaining member 27 by the lines of magnetic force leaking from the other end of the toner retaining member 27, thereby raising the toner on the toner retaining member 27 and regulating the toner layer thickness 26. It is also used to disturb the toner layer 26. In addition, in recent years, there has been a trend toward miniaturization of electrophotographic printing apparatus bodies, and along with this, there has been a desire for miniaturization of developing devices and toner holding members. The volume of the magnet 23 is becoming smaller, and it is becoming difficult to ensure a sufficient magnetic flux density and a necessary number of poles. According to the configuration shown here, the minimum required number of poles of the permanent magnet 23 contained in the toner holding member 27 is two, so it is possible to reduce the volume and ensure sufficient magnetic flux density. Therefore, it is possible to downsize the developing device without sacrificing the developing characteristics. In this embodiment, a shielding member 24 is provided at the lower end of the magnetic member 20 in the direction of the magnetic regulating member 19 . The shielding members 2 and 1 function to prevent toner other than those that have been raised and disturbed in the strong magnetic field from entering between the magnetic regulating member 19 and the magnetic member 20.

During this time, if more toner is mixed in than other toners, the amount of toner on the upstream side of the magnetic regulating member 19 cannot be regulated to an appropriate amount, resulting in toner blocking, which greatly impairs the effects of the present invention. Further, in this developing device, the remaining toner is removed from the magnetic member 2 on the upstream side near the magnetic regulating member 19.
Means for forwarding to the upstream side of 0 is added. That is, the toner holding member 27 is located below the magnetic regulating member 19.
The toner transported by the rotation of the magnetic regulating member 1
9, the excess toner is collected by the impeller 25 and transferred to the shielding member 24 and the hopper 1.
The magnetic member 20 is configured so that it can be sent to the upstream side of the magnetic member 20 through the bottom of the magnetic member 7.

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 a belt as a photoreceptor; here, a functionally separated organic photoreceptor drum is used. The surface charging voltage was -750V, and the circumferential speed was 90n/Sec. The magnetic toner is made of - for example polyester resin 57.5
The particles having an average particle size of 8 microns were mixed and dispersed and ground in a known method using a ratio of 35 parts of magnetite, 13 parts of Charge Control 7i, 4 parts of carbon, and 0.5 parts of stearic acid.

Note that the toner is not limited to the above composition. As the toner holding member, a non-magnetic stainless steel cylindrical material is used in the state shown in Fig. 2, and the two-pole permanent magnet contained therein has a surface magnetic flux density of 900 Gauss measured from the surface of the cylinder. did. On the other hand, the permanent magnet provided at one end of the magnetic regulation member had a magnetic flux density of 1100 Gauss at the end face of the magnetic pole.

Magnetic stainless steel was used for each of the magnetic regulation member and the magnetic member. The regulation gap was 0.4 mm, and the gap between the magnetic member and the toner holding member was selected to be 0.8 mm. At this time, the remaining toner on the upstream side of the regulating member is approximately 30% at the above ratio.
Met.

The gap between the image bearing member, that is, the organic photoreceptor drum, and the surface of the toner holding member is 0.4 mm, and under this condition, the thin toner layer is raised like a brush by the action of the magnetic field and can be rubbed on the surface of the photoreceptor. It is in. The circumferential speed of the toner holding member was set to be the same as that of the photoreceptor, and the amount of charge on the toner that had reached the development position at this time was measured, and the result was -5.0 to -5.9 μC/
It was g. Under these conditions, the toner holding member
A latent image was created using the exposure system shown in FIG. 1 with a bias of 0 V applied, and a printing test was performed by reversal development. The resolution of the exposure system was 20 dots/dragon, that is, a line width image of 50 μ was exposed, and the print quality obtained was at a resolution that could only reproduce this. Further, under these conditions, a continuous printing test was conducted using 2 kg of magnetic toner, but the original printing quality was maintained and an image with high resolution and less background blur was obtained.

Through the experiment described above, the regulation gap was kept constant and the gap between the surface of the toner holding member and the magnetic member was adjusted to eliminate striped backgrounds due to toner blocking, white spots due to streaks in the thin toner layer, and observed changes in the charge amount of the toner, and found that when the residual toner ratio mentioned above is about 10%, the toner thickness becomes unstable at some points, making it difficult to maintain uniform image density. On the other hand, if it exceeds 70%, block-like toner will be produced and the amount of charged charge will also fluctuate.

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 in a toner holding member until the toner is conveyed to a thicker regulating member. By configuring a strong magnetic field to pass through it, disturbing it, and optimizing the amount of conveyance relative to the regulating member, the phenomenon of toner granulation and blocking can be avoided and the amount of charged charge can be maintained stably while forming an image. It provides excellent printing quality without white spots, striped areas, or fringe, and also allows the printing device to be miniaturized because a two-pole magnet can be used as a permanent magnet.

[Brief explanation of the drawing]

FIG. 1 is an internal configuration diagram showing an example of a printing device using electrophotography to which the developing device of the present invention is applied, and FIG. 2 shows the developing device when it is applicable to the electrophotographic printing device of the present invention. The internal structure diagram, FIG. 3, is a specific representative example of a conventional developing device. 1... Image carrier, 2... Printing device main body, 3... Charging charger, 4... Transfer charger, 5...・Charger for separation static elimination, 6...Cleaning device, 7...Transfer paper, 8...Exposure system, 9...Transport belt, 10... ... Belt charging charger, 11.
... Heating fixing device, 12 ... Paper feed cassette, 13 ... Paper feed roller, 14 ... Swimming roller, 15 ... Guide Board, 16...
...Developing device.

Claims (1)

[Claims] 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, the toner rotating while holding the toner on the surface of the magnetic toner in order to rub the magnetic toner. A holding member, a first magnetic field generating means disposed on the back side of the toner holding member, and a magnetic toner disposed near the surface of the toner holding member within a range covered by the magnetic field by the first magnetic field generating means. a second magnetic field generating means disposed on the surface side of the toner holding member;
a magnetic regulating member for thinning the magnetic toner, disposed downstream of the magnetic member, within a range covered by the magnetic field of the second magnetic field generating means, and close to the surface of the toner holding member; A developing device comprising: a shielding member for preventing toner other than the disturbed magnetic toner from entering from between the magnetic regulating member and the magnetic member.